WorldWideScience

Sample records for calderas

  1. PREFACE: Collapse Calderas Workshop

    Science.gov (United States)

    Gottsmann, Jo; Aguirre-Diaz, Gerardo

    2008-10-01

    Caldera-formation is one of the most awe-inspiring and powerful displays of nature's force. Resultant deposits may cover vast areas and significantly alter the immediate topography. Post-collapse activity may include resurgence, unrest, intra-caldera volcanism and potentially the start of a new magmatic cycle, perhaps eventually leading to renewed collapse. Since volcanoes and their eruptions are the surface manifestation of magmatic processes, calderas provide key insights into the generation and evolution of large-volume silicic magma bodies in the Earth's crust. Despite their potentially ferocious nature, calderas play a crucial role in modern society's life. Collapse calderas host essential economic deposits and supply power for many via the exploitation of geothermal reservoirs, and thus receive considerable scientific, economic and industrial attention. Calderas also attract millions of visitors world-wide with their spectacular scenic displays. To build on the outcomes of the 2005 calderas workshop in Tenerife (Spain) and to assess the most recent advances on caldera research, a follow-up meeting was proposed to be held in Mexico in 2008. This abstract volume presents contributions to the 2nd Calderas Workshop held at Hotel Misión La Muralla, Querétaro, Mexico, 19-25 October 2008. The title of the workshop `Reconstructing the evolution of collapse calderas: Magma storage, mobilisation and eruption' set the theme for five days of presentations and discussions, both at the venue as well as during visits to the surrounding calderas of Amealco, Amazcala and Huichapan. The multi-disciplinary workshop was attended by more than 40 scientist from North, Central and South America, Europe, Australia and Asia. Contributions covered five thematic topics: geology, geochemistry/petrology, structural analysis/modelling, geophysics, and hazards. The workshop was generously supported by the International Association of Volcanology and the Chemistry of The Earth's Interior

  2. Nonstatistical dynamics on the caldera

    CERN Document Server

    Collins, Peter; Carpenter, Barry K; Ezra, Gregory S; Wiggins, Stephen

    2014-01-01

    We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the `dynamical matching' phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a `stretched' version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quan...

  3. Nonstatistical dynamics on the caldera

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Peter; Wiggins, Stephen, E-mail: stephen.wiggins@mac.com [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Kramer, Zeb C., E-mail: zck3@cornell.edu; Ezra, Gregory S., E-mail: gse1@cornell.edu [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States); Carpenter, Barry K., E-mail: CarpenterB1@cardiff.ac.uk [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom)

    2014-07-21

    We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the “dynamical matching” phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a “stretched” version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quantum wave packets on the caldera potential (stretched and unstretched). These computations reveal a quantum mechanical analogue of the “dynamical matching” phenomenon, where the initial expectation value of the momentum direction for the wave packet determines the exit channel through which most of the probability density passes to product.

  4. Nonstatistical dynamics on the caldera.

    Science.gov (United States)

    Collins, Peter; Kramer, Zeb C; Carpenter, Barry K; Ezra, Gregory S; Wiggins, Stephen

    2014-07-21

    We explore both classical and quantum dynamics of a model potential exhibiting a caldera: that is, a shallow potential well with two pairs of symmetry related index one saddles associated with entrance/exit channels. Classical trajectory simulations at several different energies confirm the existence of the "dynamical matching" phenomenon originally proposed by Carpenter, where the momentum direction associated with an incoming trajectory initiated at a high energy saddle point determines to a considerable extent the outcome of the reaction (passage through the diametrically opposing exit channel). By studying a "stretched" version of the caldera model, we have uncovered a generalized dynamical matching: bundles of trajectories can reflect off a hard potential wall so as to end up exiting predominantly through the transition state opposite the reflection point. We also investigate the effects of dissipation on the classical dynamics. In addition to classical trajectory studies, we examine the dynamics of quantum wave packets on the caldera potential (stretched and unstretched). These computations reveal a quantum mechanical analogue of the "dynamical matching" phenomenon, where the initial expectation value of the momentum direction for the wave packet determines the exit channel through which most of the probability density passes to product.

  5. Stratigraphy of the Volcanic Products Around Nemrut Caldera: Implications for Reconstruction of the Caldera Formation

    OpenAIRE

    KARAOĞLU, Özgür; ÖZDEMİR, Yavuz; TOLLUOĞLU, A. ÜMİT

    2005-01-01

    The volcanological development of the Nemrut stratovolcano, located near the southwestern tip of Lake Van in eastern Turkey, is subdivided into three stages: pre-caldera, post-caldera and late stages. Two ignimbrite flows have been recognized in the pre-caldera stage. The earlier of the two occurred after basaltic lavas formed along extensional fissures. The latter, which forms the main subject of this paper, was a major flow associated with the development of the Nemrut caldera. The pyroclas...

  6. Subsidence of ash-flow calderas: Relation to caldera size and magma-chamber geometry

    Science.gov (United States)

    Lipman, P.W.

    1997-01-01

    Diverse subsidence geometries and collapse processes for ash-flow calderas are inferred to reflect varying sizes, roof geometries, and depths of the source magma chambers, in combination with prior volcanic and regional tectonic influences. Based largely on a review of features at eroded pre-Quaternary calderas, a continuum of geometries and subsidence styles is inferred to exist, in both island-arc and continental settings, between small funnel calderas and larger plate (piston) subsidences bounded by arcuate faults. Within most ring-fault calderas, the subsided block is variably disrupted, due to differential movement during ash-flow eruptions and postcollapse magmatism, but highly chaotic piecemeal subsidence appears to be uncommon for large-diameter calderas. Small-scale downsag structures and accompanying extensional fractures develop along margins of most calderas during early stages of subsidence, but downsag is dominant only at calderas that have not subsided deeply. Calderas that are loci for multicyclic ash-flow eruption and subsidence cycles have the most complex internal structures. Large calderas have flared inner topographic walls due to landsliding of unstable slopes, and the resulting slide debris can constitute large proportions of caldera fill. Because the slide debris is concentrated near caldera walls, models from geophysical data can suggest a funnel geometry, even for large plate-subsidence calderas bounded by ring faults. Simple geometric models indicate that many large calderas have subsided 3-5 km, greater than the depth of most naturally exposed sections of intracaldera deposits. Many ring-fault platesubsidence calderas and intrusive ring complexes have been recognized in the western U.S., Japan, and elsewhere, but no well-documented examples of exposed eroded calderas have large-scale funnel geometry or chaotically disrupted caldera floors. Reported ignimbrite "shields" in the central Andes, where large-volume ash-flows are inferred to

  7. The future of volcanism at Yellowstone caldera

    Science.gov (United States)

    Girard, G.; Stix, J.

    2009-12-01

    Yellowstone caldera has produced three very large Pliocene and Pleistocene ignimbrite eruptions, the 2500 km3 Huckleberry Ridge Tuff, 280 km3 Mesa Falls Tuff, and 1000 km3 Lava Creek Tuff, at 2.05, 1.29 and 0.639 Ma, respectively. Today, Yellowstone caldera is seismically active, and its degassing rate is among the highest of Earth’s volcanoes. Whether, when and how this restless rhyolitic caldera will erupt again is of utmost importance. We analyzed trace elements in whole rock, glass and crystals of intra-caldera and extra-caldera Yellowstone rhyolites erupted during the last 0.5 Ma, in order to decipher their petrogenesis and shed light on future volcanism at Yellowstone. Based on these data, together with published mapping, hydrothermal activity, seismicity, seismic tomography, ground deformation and neotectonic data, we identify six areas within or near the caldera where eruptions may potentially occur in the future. Among these areas are two NNW-trending eruptive vent lineaments, which (1) cut through the caldera between the two resurgent domes, and (2) define the western caldera rim. These eruptive vents are those of the 173-70 ka Central Plateau Member (CPM) rhyolites, the youngest intra-caldera rhyolites, which total ~ 600 km3 in volume. These lineaments, despite being seismically and hydrothermally less active than other regions of the caldera, thus appear the most likely foci of future eruptions related to CPM magmatism. The volume of such effusive rhyolitic eruptions may reach several cubic kilometers. (3) Much of the seismicity, ground deformation, hydrothermal activity and degassing is observed in the northeastern part of the caldera. Despite this current unrest, no volcanism has occurred in this area in the last 0.48 Ma, and the upper crust (composed of older ignimbrite material as elsewhere beneath the caldera) may be more fertile and more likely to melt subsequent to deep heat inputs than the crust beneath the CPM lineaments, where ~ 600 km3 of

  8. Calderas and mineralization: volcanic geology and mineralization in the Chianti caldera complex, Trans-Pecos Texas

    Energy Technology Data Exchange (ETDEWEB)

    Duex, T.W.; Henry, C.D.

    1981-01-01

    This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some and denied by others. Steven and others have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, postsubsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chianti caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas.

  9. Hydrothermal system of Long Valley caldera, California

    Energy Technology Data Exchange (ETDEWEB)

    Sorey, M.L.; Lewis, R.E.; Olmsted, F.H.

    1978-01-01

    The geologic and hydrologic setting of the hydrothermal system are described. The geochemical and thermal characteristics of the system are presented. A mathematical model of the Long Valley caldera is analyzed. (MHR)

  10. Post-supereruption recovery at Toba Caldera

    National Research Council Canada - National Science Library

    Adonara E Mucek; Martin Danisík; Shanaka L De Silva; Axel K Schmitt; Indyo Pratomo; Matthew A Coble

    2017-01-01

    ..., limiting our ability to understand how supervolcanoes work and address their hazards. Toba Caldera, Indonesia, caused the greatest volcanic catastrophe of the last 100 kyr, climactically erupting ∼74 ka...

  11. Post-supereruption recovery at Toba Caldera

    National Research Council Canada - National Science Library

    Adonara E Mucek; Martin Danisík; Shanaka L De Silva; Axel K Schmitt; Indyo Pratomo; Matthew A Coble

    2017-01-01

      Large calderas, or supervolcanoes, are sites of the most catastrophic and hazardous events on Earth, yet the temporal details of post-supereruption activity, or resurgence, remain largely unknown...

  12. Intracaldera volcanism and sedimentation - Creede Caldera, Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.; Krier, D.; Snow, M.G. [and others

    1997-06-01

    Within the Creede caldera, Colorado, many of the answers to its postcaldera volcanic and sedimentary history lie within the sequence of tuffaceous elastic sedimentary rocks and tuffs known as the Creede Formation. The Creede Formation and its interbedded ash deposits were sampled by research coreholes Creede 1 and 2, drilled during the fall of 1991. In an earlier study of the Creede Formation, based on surface outcrops and shallow mining company coreholes, Heiken and Krier concluded that the process of caldera structural resurgence was rapid and that a caldera lake had developed in an annulus ({open_quotes}moat{close_quotes}) located between the resurgent dome and caldera wall. So far we have a picture of intracaldera activity consisting of intermittent hydrovolcanic eruptions within a caldera lake for the lower third of the Creede Formation, and both magmatic and hydrovolcanic ash eruptions throughout the top two-thirds. Most of the ash deposits interbedded with the moat sedimentary rocks are extremely fine-grained. Ash fallout into the moat lake and unconsolidated ash eroded from caldera walls and the slopes of the resurgent dome were deposited over stream delta distributaries within relatively shallow water in the northwestern moat, and in deeper waters of the northern moat, where the caldera was intersected by a graben. Interbedded with ash beds and tuffaceous siltstones are coarse-grained turbidites from adjacent steep slopes and travertine from fissure ridges adjacent to the moat. Sedimentation rates and provenance for elastic sediments are linked to the frequent volcanic activity in and near the caldera; nearly all of the Creede Formation sedimentary rocks are tuffaceous.

  13. CALDERA ACTIVITIES IN NORTH BALI, INDONESIA

    OpenAIRE

    -, K. Watanabe; -, T. Yamanaka; -, A. Harijoko; -, C. Saitra; -, I W. Warmada

    2015-01-01

    One of the most serious natural hazards is largescaled Plinian eruption that forms caldera. Although the probability to have such large-scaled eruption is very low, the result will be catastrophic if it happens. Thus, it is important to clarify features of caldera system including eruption timing, scale of eruption, precursor activity, etc. With enough scientific information, we may be able to mitigate such very rare but extremely large-scaled geohazard. In Bali Island, Indonesia, there are t...

  14. Origin of calderas: discriminating between collapses and explosions

    Directory of Open Access Journals (Sweden)

    Izumi Yokoyama

    2017-01-01

    Full Text Available Origins of calderas may differ according to their subsurface structure that may be characterized by high or low density deposits that may be observed as high or low gravity anomalies, respectively. In the Introduction, the pioneering work of Fouqué[1879] on Santorini caldera is referred to in relation to definition of calderas. First, our discussion is focused on four calderas that were seen forming during the period from 1815 (the Tambora eruption to 1991 (the Pinatubo eruption. Coincidently, these four calderas are all low-gravity-anomaly type. Their formation processes and subsurface structure are summarized by the existing data analyzed by various authors. These results are confirmed by results of drillings at some other calderas. Then, caldera formation of both types is discussed: High-gravity-anomaly-type calderas are expected to originate from subsidence of high-density ejecta into the summit magma reservoir. On the calderas of this type, the genetic eruptions believed to be accompanied by subsidences were not actually observed, and consequently three examples are mentioned only briefly. The low-gravity-anomaly-type calderas are discussed from standpoint of both the models of collapses and explosions. It is also emphasized that dynamic pressure ofexplosions is an important factor in the caldera formation, not only volume of the ejecta. To confirm the possibility that volcanic ejecta and edifices collapse into magma reservoirs, we discuss stress propagation from a depleted reservoir upward towards the Earth surface. Formation mechanisms of large calderas of this type are speculated; large calderas measuring about 20 km across may develop by successive merging of component calderas over a long period of times. A Kamchatka caldera under enlargement during the Holocene period is interpreted by successive merging of five component calderas.

  15. Caldera resurgence driven by magma viscosity contrasts.

    Science.gov (United States)

    Galetto, Federico; Acocella, Valerio; Caricchi, Luca

    2017-11-24

    Calderas are impressive volcanic depressions commonly produced by major eruptions. Equally impressive is the uplift of the caldera floor that may follow, dubbed caldera resurgence, resulting from magma accumulation and accompanied by minor eruptions. Why magma accumulates, driving resurgence instead of feeding large eruptions, is one of the least understood processes in volcanology. Here we use thermal and experimental models to define the conditions promoting resurgence. Thermal modelling suggests that a magma reservoir develops a growing transition zone with relatively low viscosity contrast with respect to any newly injected magma. Experiments show that this viscosity contrast provides a rheological barrier, impeding the propagation through dikes of the new injected magma, which stagnates and promotes resurgence. In explaining resurgence and its related features, we provide the theoretical background to account for the transition from magma eruption to accumulation, which is essential not only to develop resurgence, but also large magma reservoirs.

  16. Ground deformations in collapsed caldera structures

    Science.gov (United States)

    De Natale, Giuseppe; Pingue, Folco

    1993-09-01

    A method is presented to analyze the effect of stress-strain discontinuities on the ground deformations generated by a pressure source. This is meant to simulate the effects due to caldera structures, likely to present fractured zones at the borders of the collapsed area. A method originally developed by Crouch (1976) to solve plane-strain problems has been used to simulate deformation curves for several source and discontinuity geometries. The main result is that the location of the discontinuities controls the extension of the deformed zone, and always reduces it with respect to a continuous medium. With respect to a homogeneous medium the presence of lateral discontinuities also acts towards lowering the overpressure required to produce a given amount of deformation. These results indicate that, when analyzing ground deformations in calderas, the use of classical methods involving continuous media should be avoided, or at least taken with caution. These methods, in fact, assume that the extension of the deformed zone is only linked to the source depth. Some examples of ground deformations in active calderas have been analyzed in the framework of the results obtained from theoretical modeling. Four calderas recently affected by ground deformations have been considered: Rabaul (New Guinea), Campi Flegrei (Italy), Long Valley and Yellowstone (U.S.A.). The effects of collapsed structures on the deformation field are possibly evidenced for all the four calderas. At Rabaul and Campi Flegrei, the fracture systems mainly affecting the ground deformations probably represent younger, innermost collapses and are well evidenced by seismicity studies. Ground deformations are here concentrated in an area much smaller than the one enclosed by geologically visible caldera rims. In particular, at Rabaul, the effect of the innermost collapse can explain the high concentration of the uplift in the period 1971-1985, previously modeled by a very shallow source (1-3 km) in terms of

  17. Post-supereruption recovery at Toba Caldera.

    Science.gov (United States)

    Mucek, Adonara E; Danišík, Martin; de Silva, Shanaka L; Schmitt, Axel K; Pratomo, Indyo; Coble, Matthew A

    2017-05-16

    Large calderas, or supervolcanoes, are sites of the most catastrophic and hazardous events on Earth, yet the temporal details of post-supereruption activity, or resurgence, remain largely unknown, limiting our ability to understand how supervolcanoes work and address their hazards. Toba Caldera, Indonesia, caused the greatest volcanic catastrophe of the last 100 kyr, climactically erupting ∼74 ka. Since the supereruption, Toba has been in a state of resurgence but its magmatic and uplift history has remained unclear. Here we reveal that new (14)C, zircon U-Th crystallization and (U-Th)/He ages show resurgence commenced at 69.7±4.5 ka and continued until at least ∼2.7 ka, progressing westward across the caldera, as reflected by post-caldera effusive lava eruptions and uplifted lake sediment. The major stratovolcano north of Toba, Sinabung, shows strong geochemical kinship with Toba, and zircons from recent eruption products suggest Toba's climactic magma reservoir extends beneath Sinabung and is being tapped during eruptions.

  18. Valles Caldera, New Mexico Microearthquakes: Improved Detection and Location with Expanded Caldera Station Coverage

    Science.gov (United States)

    House, L. S.; Roberts, P. M.; Ten Cate, J. A.

    2016-12-01

    The Los Alamos Seismic Network (LASN) has operated for 44 years, providing data to locate more than 2,500 earthquakes in north-central New Mexico. Roughly 1-2 earthquakes are detected and located per month within about 150 km of Los Alamos, a total of over 900 from 1973 to present. LASN's primary purpose is to monitor seismicity close to the Los Alamos National Laboratory (LANL) for seismic hazards; monitoring seismicity associated with the nearby Valles Caldera is secondary. Until 2010 the network comprised only 7 stations, all near LANL or in the nearby Jemez Mountains. Just one station (PER, installed in 1998) was close enough to Valles Caldera to be able to detect microearthquakes located in or near the caldera. An initial study of the data from station PER between 1998 and 2002 identified and located 13 events with magnitudes less than 0.5 using the single-station hodogram technique. Those events were all located south of the caldera within a few kilometers of PER. Recently, two new digital broadband stations were installed inside the caldera, one on a northeastern ring-fracture dome, station CDAB, and the other on a northwestern dome, station SAMT. Also, station PER was upgraded with digital broadband instrumentation. Thus, LASN now can detect and record microearthquakes as small as magnitude -1.5 near the caldera, and they can be located using arrival times at multiple stations. Several recent events located near station SAMT on the caldera's ring fracture are the first that have been seen in that area. Additional events were recorded (by all three stations) and located in the area south of the caldera where the earlier hodogram-only events were located. These new multi-station event recordings allow a more quantitative assessment of the uncertainties in the initial single-station hodogram locations. Each event is located using multiple arrival times as well as the hodogram method at as many as three stations. Thus, improvements can be made to the

  19. California's restless giant: the Long Valley Caldera

    Science.gov (United States)

    Hill, David P.; Bailey, Roy A.; Hendley, James W.; Stauffer, Peter H.; Marcaida, Mae

    2014-01-01

    Scientists have monitored geologic unrest in the Long Valley, California, area since 1980. In that year, following a swarm of strong earthquakes, they discovered that the central part of the Long Valley Caldera had begun actively rising. Unrest in the area persists today. The U.S. Geological Survey (USGS) continues to provide the public and civil authorities with current information on the volcanic hazard at Long Valley and is prepared to give timely warnings of any impending eruption.

  20. Core lithology, Valles caldera No. 1, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, J.N.; Goff, F.; Goff, S.; Maassen, L.; Mathews, K.; Wachs, D.; Wilson, D.

    1987-04-01

    Vallas caldera No. 1 (VC-1) is the first Continental Scientific Drilling Program research core hole in the Vallas caldera and the first continuously cored hole in the region. The hole penetrated 298 m of moat volcanics and caldera-fill ignimbrites, 35 m of volcaniclastic breccia, and 523 m of Paleozoic carbonates, sandstones, and shales with over 95% core recovery. The primary research objectives included coring through the youngest rhyolite flow within the caldera; obtaining structural and stratigraphic information near the intersection of the ring-fracture zone and the pre-caldera Jemez fault zone; and penetrating a high-temperature hydrothermal outflow plume near its source. This report presents a compilation of lithologic and geophysical logs and photographs of core that were collected while drilling VC-1. It is intended to be a reference tool for researchers interested in caldera processes and associated geologic phenomena.

  1. Magnetic study of the Furnas caldera (Azores

    Directory of Open Access Journals (Sweden)

    J. M. Torta

    1997-06-01

    Full Text Available A local ground magnetic study of the Furnas caldera (S. Miguel Island, Azores has provided new insight into the magnetic structure of this volcano. Analysis of the data comprised removal of the IGRF, reduction to the pole, pseudogravity integration and upward continuation. Also, a spectral method was applied to estimate the depth to the magnetic sources, as well as a 2.5D forward modelling technique. Magnetic properties obtained at the laboratory for some representative sample rocks were considered in the modelling process. The most relevant features are the existence of an important negative anomaly inside the caldera and of an intense positive anomaly to the south of the coast. The former points out a decrease in the magnetization of the caldera filling materials with respect to the surrounding rocks, which could be explained as the result of post-eruption processes such as hydrothermal alteration. This is expected as Furnas has an active hydrothermal system probably related with a magmatic reservoir at high temperature. The positive anomaly suggests the existence of a strongly-magnetized body beneath the south coast.

  2. Caldera-Fill Sediments at Toba Caldera, Sumatra, Indonesia: A Field Reconnaissance Report

    Science.gov (United States)

    Chesner, C. A.; Barbee, O. A.; Lesmana, Z.; Nasution, A.

    2013-12-01

    The 74 ka Toba Caldera in northern Sumatra offers a unique opportunity to study caldera-fill sedimentation and its implications on the dynamic post-collapse history of Earth's largest Quaternary resurgent caldera. Although the complete 74,000 year sedimentation record is hidden beneath Lake Toba, a significant portion (~20-74 ka) of the post-caldera sedimentary sequence has been uplifted above lake level and is exposed on the 45 x 18 km Samosir Island resurgent dome. This extensive sedimentary record, over 100 m thick in places, is exposed by stream incision, and in resurgent dome fault scarps. Reconnaissance mapping and sampling of the sedimentary veneer covering Samosir Island was conducted in 2012-2013 to supplement recent sub-bottom seismic reflection profiling (chirp sonar) of the younger sediments and provide the basis for a more detailed caldera-fill sedimentation study at Toba. Our preliminary mapping indicates that distinct lacustrine and fluvial sedimentary sequences occur on Samosir Island. The lacustrine sequence dominates the surface exposures across the island and consists of interbedded clays, silts, sands, and diatomites. Different depositional environments and processes are suggested by regional variations in the componentry (i.e. abundance of diatoms, pumice clasts, reworked lake sediment clasts, rafted pumice blocks, etc.), but no significant ash-beds have been identified. An underlying coarse-grained indurated fluvial sequence is exposed in deeply incised drainages and fault scarps. This sequence consists mostly of coarse oxidized sands in eastern Samosir (approximately in the center of the caldera) that thicken and become coarser in western Samosir towards the caldera wall, where breccias and debris flows are also common. Blocks and boulders up to several meters in diameter derived from the basement rocks in the western caldera walls suggest a wedge of alluvial sediments formed before the lake reached its maximum level. Samples have been

  3. Caldera processes and magma-hydrothermal systems continental scientific drilling program: thermal regimes, Valles caldera research, scientific and management plan

    Energy Technology Data Exchange (ETDEWEB)

    Goff, F.; Nielson, D.L. (eds.)

    1986-05-01

    Long-range core-drilling operations and initial scientific investigations are described for four sites in the Valles caldera, New Mexico. The plan concentrates on the period 1986 to 1993 and has six primary objectives: (1) study the origin, evolution, physical/chemical dynamics of the vapor-dominated portion of the Valles geothermal system; (2) investigate the characteristics of caldera fill and mechanisms of caldera collapse and resurgence; (3) determine the physical/chemical conditions in the heat transfer zone between crystallizing plutons and the hydrothermal system; (4) study the mechanism of ore deposition in the caldera environment; (5) develop and test high-temperature drilling techniques and logging tools; and (6) evaluate the geothermal resource within a large silicic caldera. Core holes VC-2a (500 m) and VC-2b (2000 m) are planned in the Sulphur Springs area; these core holes will probe the vapor-dominated zone, the underlying hot-water-dominated zone, the boiling interface and probable ore deposition between the two zones, and the deep structure and stratigraphy along the western part of the Valles caldera fracture zone and resurgent dome. Core hole VC-3 will involve reopening existing well Baca number12 and deepening it from 3.2 km (present total depth) to 5.5 km, this core hole will penetrate the deep-crystallized silicic pluton, investigate conductive heat transfer in that zone, and study the evolution of the central resurgent dome. Core hole VC-4 is designed to penetrate deep into the presumably thick caldera fill in eastern Valles caldera and examine the relationship between caldera formation, sedimentation, tectonics, and volcanism. Core hole VC-5 is to test structure, stratigraphy, and magmatic evolution of pre-Valles caldera rocks, their relations to Valles caldera, and the influences of regional structure on volcanism and caldera formation.

  4. Yellowstone and Long Valley - A Comparison of Two Restless Calderas

    Science.gov (United States)

    Hill, D. P.; Smith, R. B.

    2007-12-01

    Three large, silicic calderas in the conterminous United States have explosively erupted volumes > 300 km3 within in the last 2 million years -- Yellowstone caldera (Wyoming) Long Valley caldera (California) and the Vallez caldera (New Mexico) all located in extensional tectonic environments. All have shown varying levels of historic unrest. Pronounced unrest episodes at Yellowstone and Long Valley calderas over the past three decades stimulated extensive research on these two closely monitored calderas, and we explore some emerging similarities and differences. Yellowstone caldera is underlain by a long-lived (> 17 my) upper-mantle hot-spot that has fed a series of caldera-forming, extending to the southwest across southern Idaho to central Oregon including three caldera-forming eruptions from the Yellowstone caldera system in the last 2 my, the most recent at 600,000 ybp. It is marked by relatively low density and low seismic velocities extending to depths of at least 400 km and a regional topographic swell with elevations exceeding 2000 m. The extensive Yellowstone hydrothermal system has a thermal output of 5 GW. The most recent magmatic eruption dated at 70,000 ybp. By comparison, Long Valley caldera is underlain by a relatively modest "hot-spot", the locus of which appears to be influenced by a dilatational jog between the dextral Eastern California Shear Zone and the Walker Lane and westward delamination of the dense lithospheric root of the adjacent Sierra Nevada. The Long Valley system has fed multiple eruptions of over the past 4 my and a single caldera-forming eruption at 760,000 ybp. It is marked by a limited topographic swell but with the elevation of the caldera floor and adjacent basins comparable to the 2000-plus m elevation of the Yellowstone swell. Long Valley caldera hydrothermal system has a thermal output of 0.3 GW (including a 40 MW geothermal power plant). The most recent eruptions from the Long Valley Caldera- Mono Domes volcanic field

  5. Chapter 1. Valles Caldera National Preserve land use history

    Science.gov (United States)

    Kurt F. Anschuetz

    2007-01-01

    The land use history of the Valles Caldera National Preserve (VCNP) extends back over thousands of years. Few known archaeological properties in the Valles Caldera date to the Paleoindian period (10000/9500–5500 B.C.). These finds include the recent discovery, during ongoing archaeological studies (Dr. Bob Parmeter, personal communication, VCNP, Los Alamos, 2005), of...

  6. Setting A Stopwatch for Post-Caldera Effusive Rhyolite Eruptions at Yellowstone caldera, Wyoming

    Science.gov (United States)

    Till, C. B.; Vazquez, J. A.; Boyce, J. W.

    2015-12-01

    Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone caldera (Wyoming), Long Valley caldera (California), and Valles caldera (New Mexico) in the United States. Although orders of magnitude smaller in volume than rare caldera-forming supereruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear, particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses trace element diffusion in sanidine crystals measured at nanometer-scale with NanoSIMS to reveal that rejuvenation of a near-solidus or subsolidus silicic intrusion occurred within ~10 months following a protracted period (220 k.y.) of volcanic repose, and resulted in effusion of ~3 km3 of high-silica rhyolite lava at the onset of Yellowstone's last volcanic interval. In addition we find that the frequently made assumption in geospeedometry of a step-function initial condition can be inaccurate despite petrographic evidence for resorption, and can be addressed by interrogating diffusion time scale concordance between multiple trace elements that are geochemically similar. The results of this study reveal that a sufficiently energetic rejuvenation of Yellowstone's shallow crystal-melt mush and/or hydrothermally altered wall rock could lead to an effusive eruption within months. Fortunately, any significant rejuvenation of the reservoir is likely to be associated with deformation or seismicity and identifiable by geophysical monitoring.

  7. How piecemeal is your caldera? Going beyond modelling to investigate the structural evolution of explosive caldera volcanoes

    Energy Technology Data Exchange (ETDEWEB)

    Willcox, Chris; Branney, Mike [University of Leicester, UK, LE1 7RH (United Kingdom); Carrasco-Nunez, Gerardo [Centro de Geociencias Campus Juraquilla, UNAM, Apdo. Postal 1-742 Queretaro, Qro. 76001 (Mexico)], E-mail: cpw14@le.ac.uk

    2008-10-01

    Despite a profusion of analogue models relatively little is known about the internal structure and temporal evolution of explosive caldera volcanoes. So how can modellers test their predictions given that the internal structures of many young calderas are concealed? Mapping ancient exhumed calderas has proven advantageous, yet this requires a large investment of time and expertise to constrain the structural evolution in sufficient detail. We aim to investigate the interplay between the structural evolution and eruption style over time at a modern caldera. We have selected Los Humeros (Mexico) because it is thought to be an example of a caldera with some piecemeal development, and it also has a well-exposed pyroclastic succession and abundant borehole data.

  8. Central San Juan caldera cluster: Regional volcanic framework

    Science.gov (United States)

    Lipman, Peter W.

    2000-01-01

    Eruption of at least 8800 km3 of dacitic-rhyolitic magma as 9 major ash-slow sheets (individually 150-5000 km3) was accompanied by recurrent caldera subsidence between 28.3 and about 26.5 Ma in the central San Juan Mountains, Colorado. Voluminous andesitic-decitic lavas and breccias were erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of explosive volcanism, making the central San Juan caldera cluster an exceptional site for study of caldera-related volcanic processes. Exposed calderas vary in size from 10 to 75 km in maximum diameter, the largest calderas being associated with the most voluminous eruptions. After collapse of the giant La Garita caldera during eruption if the Fish Canyon Tuff at 17.6 Ma, seven additional explosive eruptions and calderas formed inside the La Garita depression within about 1 m.y. Because of the nested geometry, maximum loci of recurrently overlapping collapse events are inferred to have subsided as much as 10-17 km, far deeper than the roof of the composite subvolcanic batholith defined by gravity data, which represents solidified caldera-related magma bodies. Erosional dissection to depths of as much as 1.5 km, although insufficient to reach the subvolcanic batholith, has exposed diverse features of intracaldera ash-flow tuff and interleaved caldera-collapse landslide deposits that accumulated to multikilometer thickness within concurrently subsiding caldera structures. The calderas display a variety of postcollapse resurgent uplift structures, and caldera-forming events produced complex fault geometries that localized late mineralization, including the epithermal base- and precious-metal veins of the well-known Creede mining district. Most of the central San Juan calderas have been deeply eroded, and their identification is dependent on detailed geologic mapping. In contrast, the primary volcanic morphology of the

  9. Stratigraphy of Reforma Caldera, Baja California Sur, Mexico

    Science.gov (United States)

    García Sánchez, L.; Macias, J. L.; Osorio, L. S.; Pola, A.; Avellán, D. R.; Arce, J. L.; Saucedo, R.; Sánchez, J. M.; García-Tenorio, F.; Cisneros, G.; Reyes-Agustín, G.; Cardona, S.; Jimenez, A.

    2015-12-01

    The Reforma caldera is located at ~35 km to the northwest of Santa Rosalía in the central part of the Baja California peninsula. It has 10 km in diameter and a maximum height of 1200 masl in the center and between 100 and 500 masl in its slopes. Reforma is within a tectonic zone affected by two fault systems: A NW-SE normal fault system linked to the opening of the Gulf of California, and a NNW-SSE and NW-SE strike-slip fault system associated with an active Riedel system. Reforma was built upon Cretaceous granites that outcrop at the caldera center, Miocene to Pliocene volcano-sedimentary rocks of the Comondú group, and Miocene marine sediments of the Santa Rosalía basin. On top of these rocks outcrop at least four submarine to subaerial ignimbrites interbedded with marine fossiliferous beds and the lower Pleistocene deposits associated to the Reforma caldera. These deposits are formed by a ignimbrite that shifts to different lithofacies that change gradually their welding, here dubbed basal, transitional, intermediate, and upper (all of then enriched in black fiammes), followed by a pumice-rich, white fiammes, and vitrophyre lithofacies, which are distributed around the 9 km wide caldera and have been associated to the caldera formation episode. Deposits related to post-caldera volcanism are andesite-basaltic lava flows erupted along the caldera rim through localized feeding dikes and andesitic and rhyolitic domes, and scoria cinder cones exposed inside and outside the caldera. On top of these deposits rest the middle Pleistocene Aguajito caldera deposits.

  10. Magma storage in a strike-slip caldera.

    Science.gov (United States)

    Saxby, J; Gottsmann, J; Cashman, K; Gutiérrez, E

    2016-07-22

    Silicic calderas form during explosive volcanic eruptions when magma withdrawal triggers collapse along bounding faults. The nature of specific interactions between magmatism and tectonism in caldera-forming systems is, however, unclear. Regional stress patterns may control the location and geometry of magma reservoirs, which in turn may control the spatial and temporal development of faults. Here we provide new insight into strike-slip volcano-tectonic relations by analysing Bouguer gravity data from Ilopango caldera, El Salvador, which has a long history of catastrophic explosive eruptions. The observed low gravity beneath the caldera is aligned along the principal horizontal stress orientations of the El Salvador Fault Zone. Data inversion shows that the causative low-density structure extends to ca. 6 km depth, which we interpret as a shallow plumbing system comprising a fractured hydrothermal reservoir overlying a magmatic reservoir with vol% exsolved vapour. Fault-controlled localization of magma constrains potential vent locations for future eruptions.

  11. New Seismic Monitoring Station at Mohawk Ridge, Valles Caldera

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Peter Morse [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-20

    Two new broadband digital seismic stations were installed in the Valles Caldera in 2011 and 2012. The first is located on the summit of Cerros del Abrigo (station code CDAB) and the second is located on the flanks of San Antonio Mountain (station code SAMT). Seismic monitoring stations in the caldera serve multiple purposes. These stations augment and expand the current coverage of the Los Alamos Seismic Network (LASN), which is operated to support seismic and volcanic hazards studies for LANL and northern New Mexico (Figure 1). They also provide unique continuous seismic data within the caldera that can be used for scientific studies of the caldera’s substructure and detection of very small seismic signals that may indicate changes in the current and evolving state of remnant magma that is known to exist beneath the caldera. Since the installation of CDAB and SAMT, several very small earthquakes have already been detected near San Antonio Mountain just west of SAMT (Figure 2). These are the first events to be seen in that area. Caldera stations also improve the detection and epicenter determination quality for larger local earthquakes on the Pajarito Fault System east of the Preserve and the Nacimiento Uplift to the west. These larger earthquakes are a concern to LANL Seismic Hazards assessments and seismic monitoring of the Los Alamos region, including the VCNP, is a DOE requirement. Currently the next closest seismic stations to the caldera are on Pipeline Road (PPR) just west of Los Alamos, and Peralta Ridge (PER) south of the caldera. There is no station coverage near the resurgent dome, Redondo Peak, in the center of the caldera. Filling this “hole” is the highest priority for the next new LASN station. We propose to install this station in 2018 on Mohawk Ridge just east of Redondito, in the same area already occupied by other scientific installations, such as the MCON flux tower operated by UNM.

  12. Intracaldera volcanism and sedimentation-Creede caldera, Colorado

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G.; Krier, D.; Snow, M.G. [Los Alamos National Lab., NM (United States); McCormick, T. [Colorado Univ., Boulder, CO (United States). Dept. of Geological Sciences

    1994-12-31

    Within the Creede caldera, Colorado, many of the answers to its postcaldera volcanic and sedimentary history lie within the sequence of tuffaceous clastic sedimentary rocks and tuffs known as the Creede Formation. The Creede Formation and its interbedded ash deposits were sampled by research coreholes Creede 1 and 2, drilled during the fall of 1991. In an earlier study of the Creede Formation, based on surface outcrops and shallow mining company coreholes, Heiken and Krier (1987) concluded that the process of caldera structural resurgence was rapid and that a caldera lake had developed in an annulus (``moat``) located between the resurgent dome and caldera wall. So far we have a picture of intracaldera activity consisting of intermittent hydrovoleanic eruptions within a caldera lake for the lower third of the Creede Formation, and both magmatic and hydrovolcanic ash eruptions throughout the top two-thirds. Most of the ash deposits interbedded with the moat sedimentary rocks are extremely fine-grained. Ash fallout into the moat lake and unconsolidated ash eroded from caldera walls and the slopes of the resurgent dome were deposited over stream delta distributaries within relatively shallow water in the northwestern moat, and in deeper waters of the northern moat, where the caldera was intersected by a graben. Interbedded with ash beds and tuffaceous siltstones are coarse-grained turbidites from adjacent steep slopes and travertine from fissure ridges adjacent to the moat. Sedimentation rates and provenance for clastic sediments are linked to the frequent volcanic activity in and near the caldera; nearly all of the Creede Formation sedimentary rocks are tuffaceous.

  13. Caldera ring-fault intrusion through repeated sheet capture

    Science.gov (United States)

    Browning, J.; Gudmundsson, A.

    2014-12-01

    The subsurface structure of caldera-bounding ring faults remains a contentious issue, with geometries often inferred from numerical and analogue models as well as from geophysical studies. All of these inferred structures need to be compared with actual ring-faults so as to test the model implications. Here we present field observations of a deeply eroded and uniquely well exposed section of caldera ring fault in a Tertiary central volcano in south-western Iceland. The Hafnarfjall ring fault represents the outermost fault complex of an elliptical caldera with an original diameter of approximately 5 km. Vertical displacement is estimated to be > 200 m on the steeply inward-dipping ring fault. Several thin (software COMSOL, we offer a mechanical explanation for the deflection of inclined sheets into sub-vertical dikes at a mechanically stratified fault damage zone and core. A model is proposed whereby ring faults can act as a barrier for the propagation of inclined sheets away from a magma chamber within the caldera. Our findings provide an alternative mechanical explanation for magma channelling along caldera ring-faults, which is a process likely to be fundamental in controlling the location of post-caldera volcanism.

  14. Geology and structure of the Malpaso caldera and El Ocote ignimbrite, Aguascalientes, Mexico

    Science.gov (United States)

    Nieto-Obregón, Jorge; Aguirre-Díaz, Gerardo

    2008-10-01

    A new caldera, named Malpaso, is reported west of the city of Aguascalientes, Mexico. The Malpaso caldera is a volcano-tectonic depression, highly fractured and faulted, and was filled by voluminous pyroclastic products related to the caldera collapse. Due to these characteristics it as a graben caldera. It is truncated by younger normal faults of the Calvillo and Aguascalientes grabens. In this work we present a summary of the geologic and structural observations on this caldera, as well as a description of the main caldera product, the high-grade El Ocote ignimbrite.

  15. Science guide for the Long Valley Caldera deep hole

    Energy Technology Data Exchange (ETDEWEB)

    Rundle, J.B.; Eichelberger, J.C. (eds.)

    1989-05-01

    The Magma Energy Program of the US Department of Energy, Geothermal Technology Division, is planning to begin drilling a deep (6 km) exploration well in Long Valley Caldera, California, in September 1988. The location of the well is in the central part of the caldera, coincident with a large number of shallow (5-7 km) geophysical anomalies identified through many independent investigations. Results from the hole will permit the following: direct investigation of the geophysical anomalies interpreted to be magma; investigation of the patterns and conditions of deep fluid circulation and heat transport below the caldera floor; determination of the amount of collapse and subsequent resurgence of the central portion of Long Valley caldera; and determination of the intrusion history of the central plutonic complex beneath the caldera, and establishment of the relationship of intrusive to eruptive events. The hole will thus provide a stringent test of the hypothesis that magma is still present within the central plutonic complex. If the interpretation of geophysical anomalies is confirmed, the hole will provide the first observations of the environment near a large silicic magma chamber. 80 refs., 7 figs., 2 tabs.

  16. Carbonatite ring-complexes explained by caldera-style volcanism.

    Science.gov (United States)

    Andersson, Magnus; Malehmir, Alireza; Troll, Valentin R; Dehghannejad, Mahdieh; Juhlin, Christopher; Ask, Maria

    2013-01-01

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alnö carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at ~3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas.

  17. Temperature data from wells in Long Valley Caldera, California

    Science.gov (United States)

    Farrar, Christopher; DeAngelo, Jacob; Williams, Colin; Grubb, Frederick; Hurwitz, Shaul

    2010-01-01

    The 30-by-20-km Long Valley Caldera (LVC) in eastern California (fig.1) formed at 0.76 Ma in a cataclysmic eruption that resulted in the deposition of 600 km? of Bishop Tuff outside the caldera rim (Bailey, 1989). By approximately 0.6 Ma, uplift of the central part of the caldera floor and eruption of rhyolitic lava formed the resurgent dome. The most recent eruptive activity in the area occurred approximately 600 yr ago along the Mono-Inyo craters volcanic chain (Bailey, 2004; Hildreth, 2004). LVC hosts an active hydrothermal system that includes hot springs, fumaroles, mineral deposits, and an active geothermal well field and power plant at Casa Diablo along the southwestern boundary of the resurgent dome (Sorey and Lewis, 1976; Sorey and others, 1978; Sorey and others, 1991). Electric power generation began in 1985 with about 10 Mwe net capacity and was expanded to about 40 Mwe (net) in 1991 (Campbell, 2000; Suemnicht and others, 2007). Plans for further expansion are focused mainly on targets in the caldera?s western moat (Sass and Priest, 2002) where the most recent volcanic activity has occurred (Hildreth, 2004). LVC has been the site of extensive research on geothermal resources and volcanic hazards (Bailey and others, 1976; Muffler and Williams, 1976; Miller and others, 1982; Hill and others 2002). The first geothermal exploratory drilling was done in the shallow (cold groundwater recharge that occurs mostly around the caldera margin and beneath the resurgent dome. Reservoir temperatures at Casa Diablo (fig.1) are about 170?C (for example, MBP-3 and Mammoth-1), decreasing to about 100 degrees C in wells near Hot Creek Gorge (for example, MW-4 and CH-10B), and are generally less than 50?C in thermal springs near Lake

  18. Evolution of Eastern Upper Basin Member Rhyolites, Yellowstone Caldera, WY

    Science.gov (United States)

    Pritchard, C. J.; Larson, P. B.

    2008-12-01

    Cyclic recharging of the large magmatic system underneath Yellowstone Caldera, Yellowstone National Park (YNP), Wyoming, is key to understanding source contributions to these rhyolitic magmas. To better understand recharging of the Caldera magmatic system we focus on the eastern Upper Basin Member Rhyolites (EUBM), which erupted at 480 ka following the collapse of the Yellowstone Caldera at 640 ka. The EUBM outcrops in the northeast corner of the Caldera ring fracture. Genesis of the high silica EUBM could have feasibly included assimilation of an array of bedrock lithologies: Precambrian gneiss, Paleozoic and Mesozoic sediments, Eocene Absaroka Volcanics, and Pliocene and Quaternary volcanics of the Yellowstone Caldera. The most reasonable heat source for assimilation is from basaltic injections. Preliminary geochemical data agree well with previous studies and show that although the intercaldera rhyolites are geochemically homogeneous (e.g., silica in the range 72.1-78.2 weight percent), the EUBM exhibits distinctive signatures. EUBM major and trace element concentrations generally show higher weight percents of TiO2 as well as higher ppms of Ba, Sc, and Sr when compared to other intercaldera rhyolites. EUBM are also generally depleted in O isotope ratios and enriched in 87/86Sr, 207/204Pb, and 208/204Pb when compared to other intercaldera rhyolites. The variation in geochemistry in the EUBM is not easily explained if their magma supply was entirely remelted shallow instrusives. Although the significant decrease in EUBM O istotope ratios strongly suggests hydrothermal alteration of the magma's source rock, major and trace element data and isotope ratios suggest contributions from a less evolved source. Our preliminary data show that, of the possible magma sources, the Precambrian gneiss and Pliocene/Quaternary Caldera volcanics exhibit a geochemical signature closest to that of the EUBM. Therefore, we propose that the EUBM is a product of partial melting of

  19. Workshop on recent research in the Valles caldera

    Energy Technology Data Exchange (ETDEWEB)

    Heiken, G. (comp.)

    1985-02-01

    Over the last 5 years, there has been increased interest in the geology of the Jemez Mountains volcanic field, New Mexico. Of special interest is the Toledo-Valles caldera complex, which is targeted for research coring as part of the Continental Scientific Drilling Program. The general topics covered in this workshop were (1) hydrothermal systems and rock-water interactions, (2) volcanology and structural framework of the Jemez volcanic field, (3) determining the presence or absence of melt below the Valles caldera, and (4) deep coring and drilling technology. Separate abstracts were prepared for each presentation.

  20. Application of the Gauss theorem to the study of silicic calderas: The calderas of La Primavera, Los Azufres, and Los Humeros (Mexico)

    Science.gov (United States)

    Campos-Enríquez, J. O.; Domínguez-Méndez, F.; Lozada-Zumaeta, M.; Morales-Rodríguez, H. F.; Andaverde-Arredondo, J. A.

    2005-10-01

    We explored applications (including limitations) of Gauss's theorem to the study of silicic calderas. First it enables us to determine the mass deficiency from calderas. Mass deficiency itself has also other potential applications. It enables to make qualitative comparisons between calderas. We can use the mass deficiency to test, in a quick way and as a preliminary step to a formal gravity inversion, for the feasibility of caldera types of simple geometry (i.e., piston subsidence and funnel models). This application can be done in a straightforward way, once the mass deficiency has been determined. For this purpose the mass deficiency is converted to the volume of material missing at the caldera. Subsequently, for example, this volume and the respective caldera diameter enable us to estimate the height of the cylinder fitting the piston subsidence model. If the obtained parameters are congruent with the known geology and geophysical information then the model may be considered further in the inversion of the gravity data for the detailed structure. Other simple models (i.e., the funnel model) can also be analyzed in this way. In particular, when working with a piston subsidence caldera type, the Gauss theorem enables us to estimate the caldera collapse (very difficult to obtain based on geologic information alone). These possible uses of Gauss's theorem are illustrated with the calderas of La Primavera, Los Azufres, and Los Humeros caldera (Mexico). The obtained mass deficiency from these calderas follow the linear mass deficiency-diameter trend observed for other calderas. In particular, because of their diameters and mass deficiencies, La Primavera and Krakatau calderas can be considered equiparable. This comparison is of the most importance considering that La Primavera is located in the neighbourhood of a metropolis (Guadalajara City). Since geophysical studies have already established a piston subsidence model for these calderas, we assessed Gauss's theorem

  1. Igneous evolution of a complex laccolith-caldera, the Solitario, Trans-Pecos Texas: Implications for calderas and subjacent plutons

    Science.gov (United States)

    Henry, C.D.; Kunk, M.J.; Muehlberger, W.R.; McIntosh, W.C.

    1997-01-01

    The Solitario is a large, combination laccolith and caldera (herein termed "laccocaldera"), with a 16-km-diameter dome over which developed a 6 x 2 km caldera. This laccocaldera underwent a complex sequence of predoming sill, laccolith, and dike intrusion and concurrent volcanism; doming with emplacement of a main laccolith; ash-flow eruption and caldera collapse; intracaldera sedimentation and volcanism; and late intrusion. Detailed geologic mapping and 40Ar/39Ar dating reveal that the Solitario evolved over an interval of approximately 1 m.y. in three distinct pulses at 36.0, 35.4, and 35.0 Ma. The size, duration, and episodicity of Solitario magmatism are more typical of large ash-flow calderas than of most previously described laccoliths. Small volumes of magma intruded as abundant rhyolitic to trachytic sills and small laccoliths and extruded as lavas and tuffs during the first pulse at 36.0 Ma. Emplacement of the main laccolith, doming, ash-flow eruption, and caldera collapse occurred at 35.4 Ma during the most voluminous pulse. A complex sequence of debris-flow and debris-avalanche deposits, megabreccia, trachyte lava, and minor ash-flow tuff subsequently filled the caldera. The final magmatic pulse at 35.0 Ma consisted of several small laccoliths or stocks and numerous dikes in caldera fill and along the ring fracture. Solitario rocks appear to be part of a broadly cogenetic, metaluminous suite. Peralkaline rhyolite lava domes were emplaced north and west of the Solitario at approximately 35.4 Ma, contemporaneous with laccolith emplacement and the main pulse in the Solitario. The spatial and temporal relation along with sparse geochemical data suggest that the peralkaline rhyolites are crustal melts related to the magmatic-thermal flux represented by the main pulse of Solitario magmatism. Current models of laccolith emplacement and evolution suggest a continuum from initial sill emplacement through growth of the main laccolith. Although the Solitario

  2. An ion microprobe study of individual zircon phenocrysts from voluminous post-caldera rhyolites of the Yellowstone caldera

    Science.gov (United States)

    Watts, K. E.; Bindeman, I. N.; Schmitt, A. K.

    2010-12-01

    Following the formation of the Yellowstone caldera from the 640 ka supereruption of the Lava Creek Tuff (LCT), a voluminous episode of post-caldera volcanism filled the caldera with >600 km3 of low-δ18O rhyolite. Such low-δ18O signatures require remelting of 100s of km3 of hydrothermally altered (18O-depleted) rock in the shallow crust. We present a high resolution oxygen isotope and geochronology (U-Th and U-Pb) study of individual zircon crystals from seven of these voluminous post-caldera rhyolites in order to elucidate their genesis. Oxygen isotope and geochronology analyses of zircon were performed with an ion microprobe that enabled us to doubly fingerprint 25-30 µm diameter spots. Host groundmass glasses and coexisting quartz were analyzed in bulk for oxygen isotopes by laser fluorination. We find that zircons from the youngest (200-80 ka) post-caldera rhyolites have oxygen isotopic compositions that are in equilibrium with low-δ18O host groundmass glasses and quartz and are unzoned in oxygen and U-Th age. This finding is in contrast to prior work on older (500-250 ka) post-caldera rhyolites, which exhibit isotopic disequilibria and age zoning, including the presence of clearly inherited zircon cores. Average U-Th crystallization ages and δ18O zircon values for Pitchstone Plateau flow (81±7 ka, 2.8±0.2‰), West Yellowstone flow (118±8 ka, 2.8±0.1‰), Elephant Back flow (175±22 ka, 2.7±0.2‰) and Tuff of Bluff Point (176±20 ka, 2.7±0.1‰) are overlapping or nearly overlapping in age and identical in oxygen isotope composition within uncertainty (2 SE). New U-Pb geochronology and oxygen isotope data for the North Biscuit Basin flow establish that it has an age (188±33 ka) and δ18O signature (2.8±0.2‰) that is distinctive of the youngest post-caldera rhyolites. Conversely, the South Biscuit Basin flow has a heterogeneous zircon population with ages that range from 550-250 ka. In this unit, older and larger (200-400 µm) zircons have more

  3. GPS time series at Campi Flegrei caldera (2000-2013

    Directory of Open Access Journals (Sweden)

    Prospero De Martino

    2014-05-01

    Full Text Available The Campi Flegrei caldera is an active volcanic system associated to a high volcanic risk, and represents a well known and peculiar example of ground deformations (bradyseism, characterized by intense uplift periods, followed by subsidence phases with some episodic superimposed mini-uplifts. Ground deformation is an important volcanic precursor, and, its continuous monitoring, is one of the main tool for short time forecast of eruptive activity. This paper provides an overview of the continuous GPS monitoring of the Campi Flegrei caldera from January 2000 to July 2013, including network operations, data recording and processing, and data products. In this period the GPS time series allowed continuous and accurate tracking of ground deformation of the area. Seven main uplift episodes were detected, and during each uplift period, the recurrent horizontal displacement pattern, radial from the “caldera center”, suggests no significant change in deformation source geometry and location occurs. The complete archive of GPS time series at Campi Flegrei area is reported in the Supplementary materials. These data can be usefull for the scientific community in improving the research on Campi Flegrei caldera dynamic and hazard assessment.

  4. Vesuvius, the Tengger Mountains and the problem of calderas

    NARCIS (Netherlands)

    Escher, B.G.

    1926-01-01

    Until recently there was no good general map of the Tengger Mountains, so that in 1914 F. von Wolff (bibl. 1) in his work „Der Vulkanismus”, vol. I, p. 510—511, gives a reproduction of Pr. Junghuhn's map of 1844. For a volcanic district that has frequently been used as an example of a caldera and

  5. The Salma Caldera complex, northeastern Arabian Shield, Kingdom of Saudi Arabia

    Science.gov (United States)

    Kellogg, K.S.

    1985-01-01

    The upper Proterozoic Salma caldera is genetically part of an elongate alkali granitic massif, Jabal Salma. Comenditic ash-flow tuffs, the oldest recognized rocks of the caldera complex, were erupted during caldera collapse associated with the rapid evacuation of the upper, mildly peralkaline part of a zoned magma reservoir. Within the tuff sequence, a massive, lithic-rich intracaldera tuff containing megabreccia blocks is overlain by a layered ash-flow sequence. Later peralkaline granite intruded the caldera ring fracture zone. Metaluminous to peraluminous magma rose beneath the caldera approximately 580 Ma ago and solidified as biotite alkali-feldspar granite, syenogranite, and granophyre. No apparent structural doming of the exposed volcanic rocks along the east side of the caldera took place, and post- emplacement deformation and metamorphism of the caldera are minimal.

  6. Hollow volcanic tumulus caves of Kilauea Caldera, Hawaii County, Hawaii

    Directory of Open Access Journals (Sweden)

    William R. Halliday

    1998-01-01

    Full Text Available In addition to lava tube caves with commonly noted features, sizable subcrustal spaces of several types exist on the floor of Kilauea Caldera. Most of these are formed by drainage of partially stabilized volcanic structures enlarged or formed by injection of very fluid lava beneath a plastic crust. Most conspicuous are hollow tumuli, possibly first described by Walker in 1991. Walker mapped and described the outer chamber of Tumulus E-I Cave. Further exploration has revealed that it has a hyperthermic inner room beneath an adjoining tumulus with no connection evident on the surface. Two lengthy, sinuous hollow tumuli also are present in this part of the caldera. These findings support Walkers conclusions that hollow tumuli provide valuable insights into tumulus-forming mechanisms, and provide information about the processes of emplacement of pahoehoe sheet flows.

  7. Long Valley Caldera Lake and reincision of Owens River Gorge

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2016-12-16

    Owens River Gorge, today rimmed exclusively in 767-ka Bishop Tuff, was first cut during the Neogene through a ridge of Triassic granodiorite to a depth as great as its present-day floor and was then filled to its rim by a small basaltic shield at 3.3 Ma. The gorge-filling basalt, 200 m thick, blocked a 5-km-long reach of the upper gorge, diverting the Owens River southward around the shield into Rock Creek where another 200-m-deep gorge was cut through the same basement ridge. Much later, during Marine Isotope Stage (MIS) 22 (~900–866 ka), a piedmont glacier buried the diversion and deposited a thick sheet of Sherwin Till atop the basalt on both sides of the original gorge, showing that the basalt-filled reach had not, by then, been reexcavated. At 767 ka, eruption of the Bishop Tuff blanketed the landscape with welded ignimbrite, deeply covering the till, basalt, and granodiorite and completely filling all additional reaches of both Rock Creek canyon and Owens River Gorge. The ignimbrite rests directly on the basalt and till along the walls of Owens Gorge, but nowhere was it inset against either, showing that the basalt-blocked reach had still not been reexcavated. Subsidence of Long Valley Caldera at 767 ka produced a steep-walled depression at least 700 m deeper than the precaldera floor of Owens Gorge, which was beheaded at the caldera’s southeast rim. Caldera collapse reoriented proximal drainages that had formerly joined east-flowing Owens River, abruptly reversing flow westward into the caldera. It took 600,000 years of sedimentation in the 26-km-long, usually shallow, caldera lake to fill the deep basin and raise lake level to its threshold for overflow. Not until then did reestablishment of Owens River Gorge begin, by incision of the gorge-filling ignimbrite.

  8. Uplift, thermal unrest and magma intrusion at Yellowstone caldera.

    Science.gov (United States)

    Wicks, Charles W; Thatcher, Wayne; Dzurisin, Daniel; Svarc, Jerry

    2006-03-02

    The Yellowstone caldera, in the western United States, formed approximately 640,000 years ago when an explosive eruption ejected approximately 1,000 km3 of material. It is the youngest of a series of large calderas that formed during sequential cataclysmic eruptions that began approximately 16 million years ago in eastern Oregon and northern Nevada. The Yellowstone caldera was largely buried by rhyolite lava flows during eruptions that occurred from approximately 150,000 to approximately 70,000 years ago. Since the last eruption, Yellowstone has remained restless, with high seismicity, continuing uplift/subsidence episodes with movements of approximately 70 cm historically to several metres since the Pleistocene epoch, and intense hydrothermal activity. Here we present observations of a new mode of surface deformation in Yellowstone, based on radar interferometry observations from the European Space Agency ERS-2 satellite. We infer that the observed pattern of uplift and subsidence results from variations in the movement of molten basalt into and out of the Yellowstone volcanic system.

  9. Uplift, thermal unrest and magma intrusion at Yellowstone caldera

    Science.gov (United States)

    Wicks, Charles W.; Thatcher, Wayne; Dzurisin, Daniel; Svarc, Jerry

    2006-03-01

    The Yellowstone caldera, in the western United States, formed ~640,000years ago when an explosive eruption ejected ~1,000km3 of material. It is the youngest of a series of large calderas that formed during sequential cataclysmic eruptions that began ~16 million years ago in eastern Oregon and northern Nevada. The Yellowstone caldera was largely buried by rhyolite lava flows during eruptions that occurred from ~150,000 to ~70,000years ago. Since the last eruption, Yellowstone has remained restless, with high seismicity, continuing uplift/subsidence episodes with movements of ~70cm historically to several metres since the Pleistocene epoch, and intense hydrothermal activity. Here we present observations of a new mode of surface deformation in Yellowstone, based on radar interferometry observations from the European Space Agency ERS-2 satellite. We infer that the observed pattern of uplift and subsidence results from variations in the movement of molten basalt into and out of the Yellowstone volcanic system.

  10. Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

    Science.gov (United States)

    Bacon, Charles R.

    2008-01-01

    Crater Lake partly fills one of the most spectacular calderas of the world, an 8-by-10-km basin more than 1 km deep formed by collapse of the volcano known as Mount Mazama (fig. 1) during a rapid series of explosive eruptions about 7,700 years ago. Having a maximum depth of 594 m, Crater Lake is the deepest lake in the United States. Crater Lake National Park, dedicated in 1902, encompasses 645 km2 of pristine forested and alpine terrain, including the lake itself, virtually all of Mount Mazama, and most of the area of the geologic map. The geology of the area was first described in detail by Diller and Patton (1902) and later by Williams (1942), whose vivid account led to international recognition of Crater Lake as the classic collapse caldera. Because of excellent preservation and access, Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. For example, the climactic ejecta are renowned among volcanologists as evidence for systematic compositional zonation within a subterranean magma chamber. Mount Mazama's climactic eruption also is important as the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore. A detailed bathymetric survey of the floor of Crater Lake in 2000 (Bacon and others, 2002) provides a unique record of postcaldera eruptions, the interplay between volcanism and filling of the lake, and sediment transport within this closed basin. Knowledge of the geology and eruptive history of the Mount Mazama edifice, greatly enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve. Lastly, the many smaller volcanoes of the High Cascades beyond the limits of Mount Mazama are a source of information on the flux of mantle-derived magma through the region. General principles of magmatic and eruptive

  11. Implications of a Caldera Origin of the Lunar Crater Copernicus

    Science.gov (United States)

    Green, J.

    2007-12-01

    The forthcoming renaissance in lunar exploration will focus on many objectives such as Copernicus. Copernicus appears to be a caldera for at least 8 reasons. If a caldera we see (1) transient activity (2) no overturned impact flap at the crater margins (3) internal sinuous leveed lava flow channels (4) a lava covered floor (5) terraces of different ages (6) multiple central volcanoes, one showing a directed volcanic blast (7) olivine-rich komatiitic lavas on central volcanoes and (8) magmatic inflation/deflation on caldera flanks localizing craterlets and extinct fumaroles in "loop" patterns. Regarding (6), directed volcanic blasts can remove a segment of the volcano wall as evidenced in terrestrial analogs at Mt. St. Helens and Bezymianny. Impact mechanisms to produce this feature in Copernicus are contrived. For (7) Clementine spectral data show a high olivine content of the central mountains on Copernicus which I interpret as forsteritic spinifex mineralization in komatiitic lavas and not as impact rebound of olivine-rich deep seated rocks. (8) MacDonald (1956) documented loop patterns on the flank of Halemaumau in Hawaii defining arcuate fractures localizing fumaroles and craterlets. Inflation/deflation of subjacent magma bodies are interpreted as the cause for these loops. Inflation/deflation mechanisms on caldera flanks are common around terrestrial calderas. "Loop" patterns on the flank of Copernicus localizing "gouge" craterlets have been interpreted as ballistic features resulting from the meteorite impact of this crater. Questioned is the logic of a linear N26E trending array of fragments within Copernicus to serve as a source of ballistic projectiles to form the loops localizing conjugate craterlets. The fused craterlet axes on the lunar loops do not point back to a presumed impact center in Copernicus. The axes are oriented parallel to a regional northwest (N35-60W) fracture zone. Implications for an endogenic origin of Copernicus would involve

  12. Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption.

    Science.gov (United States)

    Di Vito, Mauro A; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

    2016-08-25

    Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

  13. An ignimbrite caldera from the bottom up: Exhumed floor and fill of the resurgent Bonanza caldera, Southern Rocky Mountain volcanic field, Colorado

    Science.gov (United States)

    Lipman, Peter W.; Zimmerer, Matthew J.; McIntosh, William C.

    2015-01-01

    Among large ignimbrites, the Bonanza Tuff and its source caldera in the Southern Rocky Mountain volcanic field display diverse depositional and structural features that provide special insights concerning eruptive processes and caldera development. In contrast to the nested loci for successive ignimbrite eruptions at many large multicyclic calderas elsewhere, Bonanza caldera is an areally isolated structure that formed in response to a single ignimbrite eruption. The adjacent Marshall caldera, the nonresurgent lava-filled source for the 33.9-Ma Thorn Ranch Tuff, is the immediate precursor for Bonanza, but projected structural boundaries of two calderas are largely or entirely separate even though the western topographic rim of Bonanza impinges on the older caldera. Bonanza, source of a compositionally complex regional ignimbrite sheet erupted at 33.12 ± 0.03 Ma, is a much larger caldera system than previously recognized. It is a subequant structure ∼20 km in diameter that subsided at least 3.5 km during explosive eruption of ∼1000 km3 of magma, then resurgently domed its floor a similar distance vertically. Among its features: (1) varied exposure levels of an intact caldera due to rugged present-day topography—from Paleozoic and Precambrian basement rocks that are intruded by resurgent plutons, upward through precaldera volcanic floor, to a single thickly ponded intracaldera ignimbrite (Bonanza Tuff), interleaved landslide breccia, and overlying postcollapse lavas; (2) large compositional gradients in the Bonanza ignimbrite (silicic andesite to rhyolite ignimbrite; 60%–76% SiO2); (3) multiple alternations of mafic and silicic zones within a single ignimbrite, rather than simple upward gradation to more mafic compositions; (4) compositional contrasts between outflow sectors of the ignimbrite (mainly crystal-poor rhyolite to east, crystal-rich dacite to west); (5) similarly large compositional diversity among postcollapse caldera-fill lavas and resurgent

  14. Seismic constraints on caldera dynamics from the 2015 Axial Seamount eruption.

    Science.gov (United States)

    Wilcock, William S D; Tolstoy, Maya; Waldhauser, Felix; Garcia, Charles; Tan, Yen Joe; Bohnenstiehl, DelWayne R; Caplan-Auerbach, Jacqueline; Dziak, Robert P; Arnulf, Adrien F; Mann, M Everett

    2016-12-16

    Seismic observations in volcanically active calderas are challenging. A new cabled observatory atop Axial Seamount on the Juan de Fuca ridge allows unprecedented real-time monitoring of a submarine caldera. Beginning on 24 April 2015, the seismic network captured an eruption that culminated in explosive acoustic signals where lava erupted on the seafloor. Extensive seismic activity preceding the eruption shows that inflation is accommodated by the reactivation of an outward-dipping caldera ring fault, with strong tidal triggering indicating a critically stressed system. The ring fault accommodated deflation during the eruption and provided a pathway for a dike that propagated south and north beneath the caldera's east wall. Once north of the caldera, the eruption stepped westward, and a dike propagated along the extensional north rift. Copyright © 2016, American Association for the Advancement of Science.

  15. Long Valley Caldera 2003 through 2014: overview of low level unrest in the past decade

    Science.gov (United States)

    Wilkinson, Stuart K.; Hill, David P.; Langbein, John O.; Lisowski, Michael; Mangan, Margaret T.

    2014-01-01

    Long Valley Caldera is located in California along the eastern escarpment of the Sierra Nevada Range. The caldera formed about 760,000 years ago as the eruption of 600 km3 of rhyolite magma (Bishop Tuff) resulted in collapse of the partially evacuated magma chamber. Resurgent doming in the central part of the caldera occurred shortly afterwards, and the most recent eruptions inside the caldera occurred about 50,000 years ago. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation and seismicity since at least 1978. Periods of intense unrest in the 1980s to early 2000s are well documented in the literature (Hill and others, 2002; Ewert and others, 2010). In this poster, we extend the timeline forward, documenting seismicity and deformation over the past decade.

  16. Preliminary geologic studies of Sierra El Aguajito (Baja California, Mexico): a resurgent-type caldera

    Science.gov (United States)

    Garduño-Monroy, V. H.; Vargas-Ledezma, H.; Campos-Enriquez, J. O.

    1993-12-01

    Geologic field studies conducted in the Quaternary volcanic field of Tres Virgenes (State of Baja California Sur, Mexico) revealed the existence of a resurgent caldera. The caldera's eruptive products, the Aguajito sequence, overlie the products of the nearby Reforma caldera (Reforma sequence) whose youngest products have already been dated as Quaternary. The rim of the Aguajito caldera is inferred by the existence of an arcuate alignment of rhyolitic domes. The mean diameter of this subcircular feature is 10 km. The volume of its mapped acidic products is a minimum of 10 km 3. Several horizons within the sequence contain shells. K/Ar dates of the ignimbrites and domes of El Aguajito formation confirm that the unit are Pleistocene. The detailed stratigraphy also shows the evolution of a marine regression partly related to the caldera.

  17. Renewed inflation of Long Valley Caldera, California (2011 to 2014)

    Science.gov (United States)

    Montgomery-Brown, Emily; Wicks, Chuck; Cervelli, Peter F.; Langbein, John O.; Svarc, Jerry L.; Shelly, David R.; Hill, David P.; Lisowski, Michael

    2015-01-01

    Slow inflation began at Long Valley Caldera in late 2011, coinciding with renewed swarm seismicity. Ongoing deformation is concentrated within the caldera. We analyze this deformation using a combination of GPS and InSAR (TerraSAR-X) data processed with a persistent scatterer technique. The extension rate of the dome-crossing baseline during this episode (CA99 to KRAC) is 1 cm/yr, similar to past inflation episodes (1990–1995 and 2002–2003), and about a tenth of the peak rate observed during the 1997 unrest. The current deformation is well modeled by the inflation of a prolate spheroidal magma reservoir ∼7 km beneath the resurgent dome, with a volume change of ∼6 × 106 m3/yr from 2011.7 through the end of 2014. The current data cannot resolve a second source, which was required to model the 1997 episode. This source appears to be in the same region as previous inflation episodes, suggesting a persistent reservoir.

  18. The hydrothermal system of Long Valley Caldera, California

    Science.gov (United States)

    Sorey, M.L.; Lewis, Robert Edward; Olmsted, F.H.

    1978-01-01

    Long Valley caldera, an elliptical depression covering 450 km 2 on the eastern front of the Sierra Nevada in east-central California, contains a hot-water convection system with numerous hot springs and measured and estimated aquifer temperatures at depths of 180?C to 280?C. In this study we have synthesized the results of previous geologic, geophysical, geochemical, and hydrologic investigations of the Long Valley area to develop a generalized conceptual and mathematical model which describes the gross features of heat and fluid flow in the hydrothermal system. Cenozoic volcanism in the Long Valley region began about 3.2 m.y. (million years) ago and has continued intermittently until the present time. The major event that resulted in the formation of the Long Valley caldera took place about 0.7 m.y. ago with the eruption of 600 km 3 or more of Bishop Tuff of Pleistocene age, a rhyolitic ash flow, and subsequent collapse of the roof of the magma chamber along one or more steeply inclined ring fractures. Subsequent intracaldera volcanism and uplift of the west-central part of the caldera floor formed a subcircular resurgent dome about 10 km in diameter surrounded by a moat containing rhyolitic, rhyodacitic, and basaltic rocks ranging in age from 0.5 to 0.05 m.y. On the basis of gravity and seismic studies, we estimate an aver- age thickness of fill of 2.4 km above the precaldera granitic and metamorphic basement rocks. A continuous layer of densely welded Bishop Tuff overlies the basement rocks, with an average thickness of 1.4 km; the fill above the welded Bishop Tuff consists of intercalated volcanic flows and tuffs and fluvial and lacustrine deposits. Assuming the average grain density of the fill is between 2.45 and 2.65 g/cm 3 , we calculate the average bulk porosity of the total fill as from 0.11 to 0.21. Comparison of published values of porosity of the welded Bishop Tuff exposed southeast of the caldera with calculated values indicates average bulk porosity

  19. Months between rejuvenation and volcanic eruption at Yellowstone caldera, Wyoming

    Science.gov (United States)

    Till, Christy B.; Vazquez, Jorge A.; Boyce, Jeremy W

    2015-01-01

    Rejuvenation of previously intruded silicic magma is an important process leading to effusive rhyolite, which is the most common product of volcanism at calderas with protracted histories of eruption and unrest such as Yellowstone, Long Valley, and Valles, USA. Although orders of magnitude smaller in volume than rare caldera-forming super-eruptions, these relatively frequent effusions of rhyolite are comparable to the largest eruptions of the 20th century and pose a considerable volcanic hazard. However, the physical pathway from rejuvenation to eruption of silicic magma is unclear particularly because the time between reheating of a subvolcanic intrusion and eruption is poorly quantified. This study uses geospeedometry of trace element profiles with nanometer resolution in sanidine crystals to reveal that Yellowstone’s most recent volcanic cycle began when remobilization of a near- or sub-solidus silicic magma occurred less than 10 months prior to eruption, following a 220,000 year period of volcanic repose. Our results reveal a geologically rapid timescale for rejuvenation and effusion of ~3 km3 of high-silica rhyolite lava even after protracted cooling of the subvolcanic system, which is consistent with recent physical modeling that predict a timescale of several years or less. Future renewal of rhyolitic volcanism at Yellowstone is likely to require an energetic intrusion of mafic or silicic magma into the shallow subvolcanic reservoir and could rapidly generate an eruptible rhyolite on timescales similar to those documented here.

  20. Sheet flow caves of Kilauea Caldera, Hawaii County, Hawaii

    Directory of Open Access Journals (Sweden)

    William R. Halliday

    1998-01-01

    Full Text Available Terminal lobes of sheet flows of pahoehoe lava sometimes form three-dimensional nests, initially separated by partitions consisting of accreted ‘skins” of each lobe. Melting breaks down these partitions, forming a uniform flow unit. In Kilauea Caldera we have found and mapped sizable drained cavities in low-slope sheet flows. Their general pattern includes three-dimensional nests, with partially melted septa evident in some examples. Christmas Cave is the most extensive found to date, with 632 meters surveyed on two levels. It is located at the lower end of an inflated sheet flow tongue which underwent local deflation as a result of drainage through the cave after its parameters were partially fixed. Small conduit remnants persist in its boundary ridges. The major part of the cave consists of wide, low nestled chambers. Meltdown of such partitions is one of the few emplacement mechanisms of thermal erosion which may not involve any mechanical element. Additional caves in this caldera are being identified and studied.

  1. Changes in magma storage conditions following caldera collapse at Okataina Volcanic Center, New Zealand

    Science.gov (United States)

    Rubin, Allison; Cooper, Kari M.; Leever, Marissa; Wimpenny, Josh; Deering, Chad; Rooney, Tyrone; Gravley, Darren; Yin, Qing-zhu

    2016-01-01

    Large silicic volcanic centers produce both small rhyolitic eruptions and catastrophic caldera-forming eruptions. Although changes in trace element and isotopic compositions within eruptions following caldera collapse have been observed at rhyolitic volcanic centers such as Yellowstone and Long Valley, much still remains unknown about the ways in which magma reservoirs are affected by caldera collapse. We present 238U-230Th age, trace element, and Hf isotopic data from individual zircon crystals from four eruptions from the Okataina Volcanic Center, Taupo Volcanic Zone, New Zealand, in order to assess changes in trace element and isotopic composition of the reservoir following the 45-ka caldera-forming Rotoiti eruption. Our data indicate that (1) mixing of magmas derived from crustal melts and mantle melts takes place within the shallow reservoir; (2) while the basic processes of melt generation likely did not change significantly between pre- and post-caldera rhyolites, post-caldera zircons show increased trace element and isotopic heterogeneity that suggests a decrease in the degree of interconnectedness of the liquid within the reservoir following collapse; and (3) post-caldera eruptions from different vents indicate different storage times of the amalgamated melt prior to eruption. These data further suggest that the timescales needed to generate large volumes of eruptible melt may depend on the timescales needed to increase interconnectedness and achieve widespread homogenization throughout the reservoir.

  2. Limited Boron Isotopic Variation Between Caldera-Forming and Post-Caldera Low-δ 18O Rhyolites from Yellowstone Caldera

    Science.gov (United States)

    Schmitt, A. K.

    2004-12-01

    Post-collapse rhyolites from within Yellowstone caldera show prominent excursions to δ 18O values (VSMOW) as low as ˜0 ‰ that provide strong evidence for significant non-lithospheric oxygen input into magmas, presumably via infiltration of meteoric waters (1). Very little, however, is known about the behavior of other stable isotope systems, such as boron, in low δ 18O rhyolites and their potential for unraveling the mechanisms by which brines and magmas interact. Ion microprobe measurements of quartz-hosted melt inclusions from two low-δ 18O rhyolite flows (South Biscuit Basin SBB and Middle Biscuit Basin MBB) yielded average δ 11B values (NIST SRM 951) of -1.5 and -0.9 ‰ , respectively. These values overlap within error with those for glassy obsidian matrix from SBB and MBB. Melt inclusions from two caldera-forming tuff eruptions (Lava Creek Tuff LCT and Huckleberry Ridge Tuff HRT), known to have 'normal' oxygen isotopic compositions, also yielded indistinguishable δ 11B values of -1.8 ‰ . Recent petrologic studies (1) suggested that bulk remelting of hydrothermally altered volcanic rocks, specifically HRT, in the down-dropped roof of the magma chamber produced the low-δ 18O magmas. The lack of strong boron isotopic variations (within ±2‰ ) between 'normal' and low-δ 18O rhyolites, however, contrasts with published evidence for strong 11B-depletion in hydrothermal altered rhyolite encountered in Yellowstone drill-wells (δ 11B = -9.7 ‰ ; 2). This implies that boron isotopic fractionation due to interaction with hydrothermal fluids was either absent in the source region of the SBB and MBB magmas, or became masked due to subsequent processes. From preliminary mixing calculations it is concluded that assimilation of 11B- and 18O-depleted rocks by fresh rhyolite recharge could be a compositionally and thermally viable alterative to bulk remelting. (1) I. N. Bindeman and J. W. Valley (2001) J Petrol 42, 1491-1517; (2) M. R. Palmer and N. C. Sturchio

  3. Caldera volcanoes of the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Wilson, C. J. N.; Rogan, A. M.; Smith, I. E. M.; Northey, D. J.; Nairn, I. A.; Houghton, B. F.

    1984-09-01

    The Taupo volcanic zone (TVZ) has been active since 2 Ma and has erupted >104 km3 of dominantly rhyolitic magma during the last 1 m.y. Most of the volcanism is concentrated in a 125×60 km area forming the central TVZ and is expressed largely as six major caldera volcanoes, Rotorua, Okataina, Kapenga, Mangakino, Maroa, and Taupo, marked by localized collapse of the underlying basement and clustering of known or inferred vent sites. These centers have activity spans from 150 to 600 ka and have each erupted at least 300 to 1000 km3 of magma. All centers except Rotorua are known or inferred to have had complex histories of multiple caldera collapse, which have occurred alongside general basement collapse within the TVZ accompanying regional extension. Deep-seated NE trending basement lineations and/or faults have influenced vent sites at Okataina, Maroa, and Taupo. Welded ignimbrites are prominent in the pre-140 ka record; their absence since then is attributed to the effects of surface water on eruption styles rather than to a change in eruptive behavior. Volcanism from the centers has been overwhelmingly rhyolitic (>97% SiO2 69-77 wt%) with minor high-A1 basalt and dacite and traces of andesite, mostly as lithic fragments in ignimbrites from Okataina and Mangakino. Although insignificant in volume, the basalt is important as a low-Si end-member in mixing relationships with the rhyolite (at one extreme generating the dacites) and occasionally as a trigger for the rhyolitic eruptions. The current average rhyolite magma eruption rate from the central TVZ is ˜0.27 m3 s-1, equally divided between Okataina and Taupo, a figure close to the long-term average for the last 1.1 Ma. However, geothermal heat flow data imply that a further 1.4-1.8 m3 s-1 of magma may be intruded within the crust. The ratio of inferred intruded material to erupted material is higher at centers where lava extrusions are volumetrically significant (Okataina, Maroa), and this is correlated with

  4. Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event

    OpenAIRE

    Alexey Piskarev; Daria Elkina

    2017-01-01

    A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80?km long, 40?km wide and 1.2?km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km3 placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimate...

  5. Volcano-tectonic architecture of a Caldera Complex, Karthala volcano, Grande Comore: new field observations

    Science.gov (United States)

    Poppe, S.; Kervyn, M.; Soulé, H.; Cnudde, V.; De Kock, T.; Jacobs, P.

    2012-04-01

    Karthala volcano on the oceanic island of Grande Comore, West-Indian Ocean, is one of worlds' largest active alkaline basalt shield volcanoes, with 5 eruptions since 1991. In the last century the volcanic activity mainly concentrated within the 3.5 x 2.8 km large area of the summit caldera complex. Limited study has so far been carried out to unravel the structure and geometry of the summit caldera complex, the collapse chronology and the recent changes caused by the 2005 - 2007 eruption phases. Two exploratory missions to the Karthala summit in July 2011 led to an updated overview of the volcano-tectonic structures, evidence of the local orientation of the principle stresses and a preliminary stratigraphy of the 400 m deep rock sequence exposed in the caldera walls. Three overlapping caldera's build the main structure of the complex, with vertically-subsided blocks forming intermediate terraces along the caldera structures. Within these blocks, several graben-like structures with N-S and N135°E orientations are evidencing a secondary influence of extension during or after the overall vertical collapse. One of the southwestern caldera blocks shows a 'tilted block' morphology, with a caldera-inward rotation. 'Choungou Changouméni', a nested pit crater in the Northern caldera, was 30 m deep in 1965 and has now been almost completely filled with pyroclastic deposits and lava flows. Caldera walls in the whole complex consist of massif meter-thick alkali-basalt flows with decimetric intercalations of weathered pyroclastic layers, and are topped by scoria and tuff cones. The caldera floor itself is covered by volcanic ash, lapilli, and massif scoriaceous surfaces of ancient flows. At the intersection of the 3 main caldera structures two deep explosion craters are located, together named 'Choungou Chahalé'. These were the centres of recent phreatic activity. Their vertical walls show a sequence of thick alkali basalt flows and hold numerous cross-cutting dykes which

  6. Volcanology. A large magmatic sill complex beneath the Toba caldera.

    Science.gov (United States)

    Jaxybulatov, K; Shapiro, N M; Koulakov, I; Mordret, A; Landès, M; Sens-Schönfelder, C

    2014-10-31

    An understanding of the formation of large magmatic reservoirs is a key issue for the evaluation of possible strong volcanic eruptions in the future. We estimated the size and level of maturity of one of the largest volcanic reservoirs, based on radial seismic anisotropy. We used ambient-noise seismic tomography below the Toba caldera (in northern Sumatra) to observe the anisotropy that we interpret as the expression of a fine-scale layering caused by the presence of many partially molten sills in the crust below 7 kilometers. This result demonstrates that the magmatic reservoirs of present (non-eroded) supervolcanoes can be formed as large sill complexes and supports the concept of the long-term incremental evolution of magma bodies that lead to the largest volcanic eruptions. Copyright © 2014, American Association for the Advancement of Science.

  7. Geologic field-trip guide to Long Valley Caldera, California

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2017-07-26

    This guide to the geology of Long Valley Caldera is presented in four parts: (1) An overview of the volcanic geology; (2) a chronological summary of the principal geologic events; (3) a road log with directions and descriptions for 38 field-trip stops; and (4) a summary of the geophysical unrest since 1978 and discussion of its causes. The sequence of stops is arranged as a four-day excursion for the quadrennial General Assembly of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), centered in Portland, Oregon, in August 2017. Most stops, however, are written freestanding, with directions that allow each one to be visited independently, in any order selected.

  8. Monitoring a supervolcano in repose: Heat and volatile flux at the yellostone caldera

    Science.gov (United States)

    Lowenstern, J. B.; Hurwitz, S.

    2008-01-01

    Although giant calderas ("supervolcanoes") may slumber for tens of thousands of years between eruptions, their abundant earthquakes and crustal deformation reveal the potential for future upheaval. Any eventual supereruption could devastate global human populations, so these systems must be carefully scrutinized. Insight into dormant but restless calderas can be gained by monitoring their output of heat and gas. At Yellowstone, the large thermal and CO2 fluxes require massive input of basaltic magma, which continues to invade the lower to mid-crust, sustains the overlying high-silica magma reservoir, and may result in volcanic hazard for millennia to come. The high flux of CO2 may contribute to the measured deformation of the caldera floor and can also modify the pressure, thermal, and chemical signals emitted from the magma. In order to recognize precursors to eruption, we must scrutinize the varied signals emerging from restless calderas with the goal of discriminating magmatic, hydrothermal, and hybrid phenomena.

  9. Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event

    Science.gov (United States)

    Piskarev, Alexey; Elkina, Daria

    2017-01-01

    A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80 km long, 40 km wide and 1.2 km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km3 placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge. The Gakkel Ridge Caldera is the single example of a supervolcano in the rift zone of the Mid-Oceanic Ridge System. PMID:28393928

  10. Steady subsidence of a repeatedly erupting caldera through InSAR observations: Aso, Japan

    KAUST Repository

    Nobile, Adriano

    2017-04-05

    The relation between unrest and eruption at calderas is still poorly understood. Aso caldera, Japan, shows minor episodic phreatomagmatic eruptions associated with steady subsidence. We analyse the deformation of Aso using SAR images from 1993 to 2011 and compare it with the eruptive activity. Although the dataset suffers from limitations (e.g. atmospheric effects, coherence loss, low signal-to-noise ratio), we observe a steady subsidence signal from 1996 to 1998, which suggests an overall contraction of a magmatic source below the caldera centre, from 4 to 5 km depth. We propose that the observed contraction may have been induced by the release of the magmatic fluids feeding the eruptions. If confirmed by further data, this hypothesis suggests that degassing processes play a crucial role in triggering minor eruptions within open conduit calderas, such as at Aso. Our study underlines the importance of defining any eruptive potential also from deflating magmatic systems with open conduit.

  11. Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event.

    Science.gov (United States)

    Piskarev, Alexey; Elkina, Daria

    2017-04-10

    A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80 km long, 40 km wide and 1.2 km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km(3) placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge. The Gakkel Ridge Caldera is the single example of a supervolcano in the rift zone of the Mid-Oceanic Ridge System.

  12. Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event

    Science.gov (United States)

    Piskarev, Alexey; Elkina, Daria

    2017-04-01

    A giant caldera located in the eastern segment of the Gakkel Ridge could be firstly seen on the bathymetric map of the Arctic Ocean published in 1999. In 2014, seismic and multibeam echosounding data were acquired at the location. The caldera is 80 km long, 40 km wide and 1.2 km deep. The total volume of ejected volcanic material is estimated as no less than 3000 km3 placing it into the same category with the largest Quaternary calderas (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge. The Gakkel Ridge Caldera is the single example of a supervolcano in the rift zone of the Mid-Oceanic Ridge System.

  13. Field trip guide to the Valles Caldera and its geothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Goff, F.E.; Bolivar, S.L.

    1983-12-01

    This field trip guide has been compiled from extensive field trips led at Los Alamos National Laboratory during the past six years. The original version of this guide was designed to augment a workshop on the Valles Caldera for the Continental Scientific Drilling Program (CSDP). This workshop was held at Los Alamos, New Mexico, 5-7 October 1982. More stops were added to this guide to display the volcanic and geothermal features at the Valles Caldera. The trip covers about 90 miles (one way) and takes two days to complete; however, those who wish to compress the trip into one day are advised to use the designated stops listed in the Introduction. Valles Caldera and vicinity comprise both one of the most exciting geothermal areas in the United States and one of the best preserved Quaternary caldera complexes in the world.

  14. Patterns of Fluid Circulation and Steam Generation in Caldera-Hosted Hydrothermal Systems

    Science.gov (United States)

    Barnard, M. E.; Cook, S. J.

    2009-05-01

    Steam formation is an important mechanism powering near surface phenomena in active hydrothermal systems (e.g., Yellowstone) and an established ore deposition mechanism in ancient equivalents (e.g., Creede). To gain insights into factors controlling steam formation and distribution in these systems, a series of steady-state numerical models were run on a hypothetical caldera-hosted system based on characteristics of a representative suite of calderas (e.g., Yellowstone, Valles, Creede). Base model conditions consisted of (1) a 10 km-wide caldera with a flat floor and rim height of 800 m; (2) a 500 C intrusion 1.5 km below the caldera centre; (3) a regional conductive heat flux twice continental average (0.10 W/m2); (4) host rock thermal conductivity of 2.5 W/m C, density 2650 kg/m3 and pore fraction 0.05. An impermeable intrusion was modeled with a 500 m wide surrounding region with a permeability (k) 10-3 m2 less than the system meant to represent a ductile region produced by elevated temperature (T > 350 C). The remainder of the system was given homogenous permeability. Cylindrical coordinates were used to represent caldera geometry. For these conditions, a minimum k = 10-15 m2 was required to achieve the target thermal condition of T approximately 220 C at 300 m below ground surface observed in active systems (e.g., Yellowstone). This model also resulted in a continuous steam plume originating at the intrusive contact that reached within 300 m of the surface along the edges of the caldera ~2 km from caldera centre. Models with k caldera centre and reduced its volume, but still achieved target conditions. Increasing intrusion temperature by 10% produced a second distinct plume at the caldera centre that also achieved target conditions. Increasing the rim height for these conditions produced the base (i.e., single plume) conditions. Resurgent doming up to 300 m was also modeled for the caldera floor. Increasing dome height shifted steam towards the caldera centre

  15. Inner structure of La Pacana Caldera (Central Andes, Chile) using gravimetry data

    Science.gov (United States)

    Delgado, F.; Pavez Alvarado, A.

    2010-12-01

    La Pacana caldera is located in the Altiplano Puna Volcanic Complex in the Chilean Andes and is a 60 by 35 km NS elongated body. It is one of the largest resurgent calderas in the world, comparable to the supervolcanoes of La Garita, Toba and Yellowstone. It has been described as being formed 4 My ago during an eruption with a VEI of 8,7, which makes it the fifth largest eruption ever in the geological record. This eruption was followed by a subsidence of 0,9 up to 2 km according to previous studies. Different models for this caldera formation were proposed but with a lack of sub surface information. We hence carried a gravimetry study to investigate its inner structure and to better off constrains on these proposed models. The residual Bouguer anomaly (figure 1) is asymetric with multiple high and low gravity, with an average amplitude of -14 mGal, which reaches -24 mGal near the resurgent dome, interpreted as the deepest part of the caldera. Based on this, we propose that the main collapse zone is not related to the topographic border, but to resurgent dome edges. This is compatible with a piecemeal collapse geometry. There are several gravity highs below strato-volcanoes and postcaldera domes within La Pacana caldera, which are interpreted as magmatic reservoirs. Our data combined with previous geological studies allowed us to separate La Pacana in two nested calderas and to trace its NNW, N and NNE borders, previously unrecognized features. The 2,5 D forward modelling cross sections constrained with geological data showed that the maximum caldera depth is 1,3 km with a minimum of 0,6 km in its southern part. We finally suggest that caldera rims are surrounded by paleozoic basement uplifted by thrust fault systems. La Pacana's residual Bouguer anomaly is small (1/2) when compared with the ones associated to other supervolcanoes (Toba, Yellowstone). La Pacana caldera constitutes then an anomaly for supervolcanoes internal structure due to its interpreted low

  16. Post-eruptive flooding of Santorini caldera and implications for tsunami generation

    Science.gov (United States)

    Nomikou, Paraskevi; Druitt, Tim; Hübscher, Christian; Mather, Tamsin; Paulatto, Michele; Kalnins, Lara; Kelfoun, Karim; Papanikolaou, Dimitris; Bejelou, Konstantina; Lampridou, Danai; Pyle, David; Carey, Steven; Watts, Anthony; Weiß, Benedikt; Parks, Michelle

    2017-04-01

    Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The eruption of Santorini 3600 years ago was one of the largest of eruptions known worldwide from the past 10,000 years - and was at least 3 times larger than the catastrophic eruption of Krakatoa. This huge eruption evacuated large volumes of magma, causing collapse of the large caldera, which is now filled with seawater. Tsunamis from this eruption have been proposed to have played a role in the demise of the Minoan culture across the southern Aegean, through damage to coastal towns, harbors, shipping and maritime trade. Before the eruption, there was an older caldera in the northern part of Santorini, partly filled with a shallow lagoon. In our study, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Following subsidence of the caldera floor, rapid inflow of seawater and landslides cut a deep 2.0-2.5 km3 submarine channel into the northern flank of the caldera wall. Hydrodynamic modelling indicates that the caldera was flooded through this breach in less than a couple of days. It was previously proposed that collapse of the caldera could have led to the formation of a major tsunami; but this is ruled out by our new evidence. Any tsunami's generated were most likely caused by entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations. This idea is consistent with previous assertions that pyroclastic flows were the main cause of tsunamis at Krakatau.

  17. Investigation of the groundwater system at Masaya Caldera, Nicaragua, using transient electromagnetics and numerical simulation

    Science.gov (United States)

    MacNeil, R.E.; Sanford, W.E.; Connor, C.B.; Sandberg, S.K.; Diez, M.

    2007-01-01

    The distribution of groundwater beneath Masaya Volcano, in Nicaragua, and its surrounding caldera was characterized using the transient electromagnetic method (TEM). Multiple soundings were conducted at 30 sites. Models of the TEM data consistently indicate a resistive layer that is underlain by one or more conductive layers. These two layers represent the unsaturated and saturated zones, respectively, with the boundary between them indicating the water-table elevation. A map of the TEM data shows that the water table in the caldera is a subdued replica of the topography, with higher elevations beneath the edifice in the south-central caldera and lower elevations in the eastern caldera, coinciding with the elevation of Laguna de Masaya. These TEM data, combined with regional hydrologic data, indicate that the caldera in hydrologically isolated from the surrounding region, with as much as 60??m of difference in elevation of the groundwater table across caldera-bounding faults. The water-table information and estimates of fluxes of water through the system were used to constrain a numerical simulation of groundwater flow. The simulation results indicate that basalt flows in the outer parts of the caldera have a relatively high transmissivity, whereas the central edifice has a substantially lower transmissivity. A layer of relatively high transmissivity must be present at depth within the edifice in order to deliver the observed flux of water and steam to the active vent. This hydrologic information about the caldera provides a baseline for assessing the response of this isolated groundwater system to future changes in magmatic activity. ?? 2007.

  18. Long Valley Caldera-Mammoth Mountain unrest: The knowns and unknowns

    Science.gov (United States)

    Hill, David P.

    2017-01-01

    This perspective is based largely on my study of the Long Valley Caldera (California, USA) over the past 40 years. Here, I’ll examine the “knowns” and the “known unknowns” of the complex tectonic–magmatic system of the Long Valley Caldera volcanic complex. I will also offer a few brief thoughts on the “unknown unknowns” of this system.

  19. Catastrophic isotopic modification of rhyolitic magma at times of caldera subsidence, Yellowstone plateau volcanic field.

    Science.gov (United States)

    Hildreth, W.; Christiansen, R.L.; O'Neil, J.R.

    1984-01-01

    This Wyoming volcanic field has undergone repeated eruption of rhyolitic magma strongly depleted in 18O. Large calderas subsided 2.0, 1.3 and 0.6 m.y. ago on eruption of ash-flow sheets. More than 60 other rhyolite lavas and tuffs permit reconstruction of the long-term chemical and isotopic evolution of the silicic system. Narrow delta 18O ranges in the ash-flow sheets contrast with wide delta 18O variation in post-caldera lavas. The earliest post-collapse lavas are 3-6per mille lighter than the preceding ash-flow sheets. The 18O depletions were short-lived events that immediately followed caldera subsidence and sequences of post-caldera lavas record partial recovery toward pre-caldera delta 18O values. Contemporaneous extra-caldera rhyolites show no effects of the repeated depletions. Although some contamination by foundering roof rocks seems to be required, water was probably the predominant contaminant.-W.H.B.

  20. Hydrothermal activity in the Tulancingo-Acoculco Caldera Complex, central Mexico. Exploratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Hernandez, Aida [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico); Garcia-Estrada, Gerardo; Palma-Guzman, Hugo; Quijano-Leon, Jose L. [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Aguirre-Diaz, Gerardo; Gonzalez-Partida, Eduardo [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico)

    2009-09-15

    Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo-Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He{sup 3}/He{sup 4} ratios. (author)

  1. Post-eruptive flooding of Santorini caldera and implications for tsunami generation.

    Science.gov (United States)

    Nomikou, P; Druitt, T H; Hübscher, C; Mather, T A; Paulatto, M; Kalnins, L M; Kelfoun, K; Papanikolaou, D; Bejelou, K; Lampridou, D; Pyle, D M; Carey, S; Watts, A B; Weiß, B; Parks, M M

    2016-11-08

    Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km(3), submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

  2. Effect of stress fields on magma chamber stability and the formation of collapse calderas

    Science.gov (United States)

    Bosworth, William; Burke, Kevin; Strecker, Manfred

    2003-08-01

    The summits of many of the Earth's and other planets' larger volcanoes are occupied by calderas that formed by collapse into an evacuating, underlying magma chamber. These collapse calderas are typically several tens of square kilometers in area and are commonly elliptical in shape. We show that the long axes of late Quaternary collapse calderas in the Kenya rift valley, the western Basin and Range province, the Snake River-Yellowstone Plateau, and the Iceland rift zone are parallel to the upper crustal minimum horizontal stress direction (Sh) as determined by independent criteria. We suggest that circular magma chambers beneath these volcanoes became elliptical by stress-induced spalling of their chamber walls, by a mechanism that is analogous to the formation of breakouts in boreholes and tunnels. In breakouts, the hole becomes elongate parallel to the far-field minimum stress. In the Kenya rift, Late Pleistocene caldera collapse was accompanied by a 45° rotation of Sh and an increase in the magnitude of the maximum horizontal stress (SH). The breakout model predicts increasingly unstable caldera walls under these conditions, a possible explanation for the sudden appearance of so many collapse events in a volcanic setting that had never experienced them before. This mechanism of stress change-induced collapse may have played a role in other caldera settings.

  3. Peralkaline ash flow tuffs and calderas of the McDermitt volcanic field, southeast Oregon and north central Nevada.

    Science.gov (United States)

    Rytuba, J.J.; McKee, E.H.

    1984-01-01

    This volcanic field covers an area of 20 000 km2 and consists of seven large-volume ash-flow sheets that vented 16.1-15 m.y. ago. The volcanic field is characterized by peralkaline, high-silica rhyolite, and all but one of the sheets are comendites. Each ash-flow sheet resulted in the formation of a large collapse caldera. Thickening of the ash-flow sheets, monoclinal warping outside the caldera ring-fault and tilting-in towards the caldera of blocks bounded by curvilinear faults all indicate regional subsidence prior to caldera collapse. The McDermitt caldera complex is highly mineralized; it contains ore deposits of Hg, Sb, Cs, Li and U. The peralkaline tuffs have high contents of these elements and were the source rocks from which metals were leached by hydrothermal systems developed during the last stage of caldera-related volcanism. (Following abstract) -W.H.B.

  4. The confirmation of a work hypothesis: a new caldera in the center of the Mexican Volcanic Belt; La confirmacion de una hipotesis de trabajo: una nueva caldera en el centro del Cinturon Volcanico Mexicano

    Energy Technology Data Exchange (ETDEWEB)

    Anguita Virella, Francisco; Pal Verma, Surendra; Milan, Marcos; Garcia Cacho, Luis; Samaniego M, Daniel [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1991-12-31

    After synthesizing the most relevant aspects of the current volcanology and the genesis process of the collapse calderas, a process is described on the location and confirmation of a new caldera (the Mazahua) in the central part of the Mexican Volcanic Belt (MVB). [Espanol] Tras sintetizar los aspectos mas destacados de la vulcanologia actual y el proceso de genesis de las calderas de colapso, se describe el proceso de localizacion y confirmacion de una nueva caldera (la Mazahua) en la parte central del Cinturon Volcanico Mexicano (CVM).

  5. Seismic and gravity signature of the Ischia Island Caldera (Italy)

    Science.gov (United States)

    Capuano, P.; de Matteis, R.; Russo, G.

    2009-04-01

    The Campania (Italy) coasts are characterized by the presence of several volcanoes. The island of Ischia, located at the northwestern end of the Gulf of Naples, belongs to the Neapolitan Volcanic District together with Phlegrean Fields and Vesuvius, having all these Pleistocene volcanoes erupted in historical times, and it is characterized by diffuse hydrothermal phenomena The island represents the emergent part of a more extensive volcanic area developed mainly westward of the island, with underwater volcanoes aligned along regional fault patterns. The activity of Ischia volcano is testified by the occurrence of eruptions in historical times, the presence of intense hydrothermal phenomena, and by seismic activity (e.g. the 1883 Casamicciola earthquake). Ischia is populated by about 50,000 inhabitants increasing, mainly in the summer, due to thriving tourism business, partially due to its active volcanic state. Hazard assessment at active, densely populated volcanoes is critically based on knowledge of the volcanoes past behavior and the definition of its present state. As a contribution to the definition of the present state of the Ischia island volcano, we obtain a model of the shallow crust using geophysical observables through seismic tomography and 3D gravity inversion. In particular we use travel times collected during the Serapis experiment on the island and its surroundings and free air anomaly. A new 3D gravity inversion procedure has been developed to take better into account the shape and the effects of topography approximating it by a triangular mesh. Below each triangle, a sequence of triangular prisms is built, the uppermost prism having the upper face coincident with the triangle following the topography. The inversion is performed searching for a regularized solution using the minimum norm stabilizer. The main results inferable from the 3D seismic and gravity images are the definition of the caldera rims hypothesize by many authors along the

  6. Geochemical and geochronologic data from the Hall Creek caldera, Toiyabe Range, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.

    2017-01-01

    The magmatic, tectonic, and topographic evolution of what is now the northern Great Basin remains controversial, notably the temporal and spatial relation between magmatism and extensional faulting. This controversy is exemplified in the northern Toiyabe Range of central Nevada, where previous geologic mapping suggested the presence of a caldera that sourced the late Eocene (34.0 mega-annum [Ma]) tuff of Hall Creek. This region was also inferred to be the locus of large-magnitude middle Tertiary extension (more than 100 percent strain) localized along the Bernd Canyon detachment fault, and to be the approximate location of a middle Tertiary paleodivide that separated east and west-draining paleovalleys. Geologic mapping, 40Ar/39Ar dating, and geochemical analyses document the geologic history and extent of the Hall Creek caldera, define the regional paleotopography at the time it formed, and clarify the timing and kinematics of post-caldera extensional faulting. During and after late Eocene volcanism, the northern Toiyabe Range was characterized by an east-west trending ridge in the area of present-day Mount Callaghan, probably localized along a Mesozoic anticline. Andesite lava flows erupted around 35–34 Ma ponded hundreds of meters thick in the erosional low areas surrounding this structural high, particularly in the Simpson Park Mountains. The Hall Creek caldera formed ca. 34.0 Ma during eruption of the approximately 400 cubic kilometers (km3) tuff of Hall Creek, a moderately crystal-rich rhyolite (71–77 percent SiO2) ash-flow tuff. Caldera collapse was piston-like with an intact floor block, and the caldera filled with thick (approximately 2,600 meters) intracaldera tuff and interbedded breccia lenses shed from the caldera walls. The most extensive exposed megabreccia deposits are concentrated on or close to the caldera floor in the southwestern part of the caldera. Both silicic and intermediate post-caldera lavas were locally erupted within 400 thousand

  7. Stress field control during large caldera-forming eruptions

    Directory of Open Access Journals (Sweden)

    Antonio Costa

    2016-10-01

    Full Text Available Crustal stress field can have a significant influence on the way magma is channelled through the crust and erupted explosively at the surface. Large Caldera Forming Eruptions (LCFEs can erupt hundreds to thousands of cubic kilometres of magma in a relatively short time along fissures under the control of a far-field extensional stress. The associated eruption intensities are estimated in the range 109 - 1011 kg/s. We analyse syn-eruptive dynamics of LCFEs, by simulating numerically explosive flow of magma through a shallow dyke conduit connected to a magma chamber that in turn is fed by a deeper magma reservoir, both under the action of an extensional far-field stress. Results indicate that huge amounts of high viscosity silicic magma can be erupted over timescales of a few to several hours. Our study provides answers to outstanding questions relating to the intensity and duration of catastrophic volcanic eruptions in the past. In addition, it presents far-reaching implications for the understanding of dynamics and intensity of large-magnitude volcanic eruptions on Earth and to highlight the necessity of a future research to advance our knowledge of these rare catastrophic events.

  8. Tourism Development Based on Geopark in Bakkara Caldera Toba, Indonesia

    Science.gov (United States)

    Ginting, N.; Vinky Rahman, N.; Sembiring, G.

    2017-03-01

    Bakkara Caldera Toba is an outstanding product of natural phenomena of Toba Supervolcano which has fascinating nature and culture. Bakkara has a great potential to develop world tourism further. It requires a model of sustainable planning Geopark to develop Bakkara. This sustainable concept helps to improve the local community and tourist’s quality of life and also still maintain the quality of the environment. through field observation and depth interview. The Collected data with a triangulation method. Development tourism destination such as attractions and environment; facilities and services; accessibility; image; and price to consume. It associated based on Geopark aspects there are; geological heritage; geo-conservation activities; sustainable tourism activities; educational; activities; community involvement products; strong management structure; and secure basis, infrastructure, and activities. The results of this study indicate that the Bakkara has the potential to become a tourist destination by applying the concept of Geotourism which accentuate its natural side, by optimizing the management of its destination attractions, its facilities and services, and its accessibilities.

  9. Scientific core hole VC-2A, Valles Caldera, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Musgrave, J.; Goff, S. (Los Alamos National Lab., NM (USA)); Turner, T. (Turner (Tom), Salt Lake City, UT (USA))

    1990-10-01

    This report details the remedial action activities that were necessary to complete scientific core hole Valles caldera {number sign}2A (VC-2A) before it was relinquished to the landowners. Sandia National Laboratories, acting as the Geoscience Research Drilling Office (GRDO), managed the coring operations. Los Alamos National Laboratory (Los Alamos) obtained the proper drilling permits with the New Mexico State Engineers Office (SEO). A legal agreement between Los Alamos and the landowners states that the Laboratory will give the landowners the completed core hold with casing, well head, and other hardware at the end of May 1991, or earlier if scientific investigations were completed. By May 1988, the Science Team completed the planned scientific investigations in the VC-2A core hole. Upon the insistence of the GRDO, the New Mexico Oil Conservation Division (OCD) inspected the core hole, declared jurisdiction, and required that the 11.43- by 11.43-cm annular cement job be repaired to comply with OCD regulations. These regulations state that there must be a return to surface of cement in all cementing operations. We successfully completed a squeeze cementing operation and relinquished the core hold to the landowners in November 1988 to the satisfaction of the OCD, SEO, the landowners, and Los Alamos. 7 refs., 4 figs., 1 tab.

  10. Calderas produced by hydromagmatic eruptions through permafrost in northwest Alaska

    Science.gov (United States)

    Beget, J. E.

    1993-01-01

    Most hydromagmatic eruptions on Earth are generated by interactions of lava and ground or surface water. This eruptive process typically produces craters 0.1-1 km in diameter, although a few as large as 1-2 km were described. In contrast, a series of Pleistocene hydromagmatic eruptions through 80-100-m-thick permafrost on the Seward Peninsula of Alaska produced four craters 3-8 km in diameter. These craters, called the Espenberg maars, are the four largest maars known on Earth. The thermodynamic properties of ground ice influence the rate and amount of water melted during the course of the eruption. Large quantities of water are present, but only small amounts can be melted at any time to interact with magma. This would tend to produce sustained and highly explosive low water/magma (fuel-coolant) ratios during the eruptions. An area of 400 km(sub 2) around the Alaskan maars shows strong reductions in the density of thaw lakes, ground ice, and other surface manifestations of permafrost because of deep burial by coeval tephra falls. The unusually large Espenberg maars are the first examples of calderas produced by hydromagmatic eruptions. These distinctive landforms can apparently be used as an indicator of the presence of permafrost at the time of eruption.

  11. Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO

    Science.gov (United States)

    Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.

    2015-12-01

    El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

  12. Eruptive and noneruptive calderas, northeastern San Juan Mountains, Colorado: Where did the ignimbrites come from?

    Science.gov (United States)

    Lipman, P.W.; McIntosh, W.C.

    2008-01-01

    The northeastern San Juan Mountains, the least studied portion of this well-known segment of the Southern Rocky Mountains Volcanic Field are the site of several newly identified and reinterpreted ignimbrite calderas. These calderas document some unique eruptive features not described before from large volcanic systems elsewhere, as based on recent mapping, petrologic data, and a large array of newly determined high-precision, laser-fusion 40Ar/39Ar ages (140 samples). Tightly grouped sanidine ages document exceptionally brief durations of 50-100 k.y. or less for individual Oligocene caldera cycles; biotite ages are more variable and commonly as much as several hundred k.y. older than sanidine from the same volcanic unit. A previously unknown ignimbrite caldera at North Pass, along the Continental Divide in the Cochetopa Hills, was the source of the newly distinguished 32.25-Ma Saguache Creek Tuff (???400-500 km3). This regionally, distinctive crystal-poor alkalic rhyolite helps fill an apparent gap in the southwestward migration from older explosive activity, from calderas along the N-S Sawatch locus in central Colorado (youngest, Bonanza Tuff at 33.2 Ma), to the culmination of Tertiary volcanism in the San Juan region, where large-volume ignimbrite eruptions started at ca. 29.5 Ma and peaked with the enormous Fish Canyon Tuff (5000 km3) at 28.0 Ma. The entire North Pass cycle, including caldera-forming Saguache Creek Tuff, thick caldera-filling lavas, and a smaller volume late tuff sheet, is tightly bracketed at 32.25-32.17 Ma. No large ignimbrites were erupted in the interval 32-29 Ma, but a previously unmapped cluster of dacite-rhyolite lava flows and small tuffs, areally associated with a newly recognized intermediate-composition intrusion 5 ?? 10 km across (largest subvolcanic intrusion in San Juan region) centered 15 km north of the North Pass caldera, marks a near-caldera-size silicic system active at 29.8 Ma. In contrast to the completely filled North Pass

  13. Magma Storage, Recharge and the Caldera Cycle at Rabaul, Papua New Guinea

    Science.gov (United States)

    Fabbro, G.; Bouvet de Maisonneuve, C.; Sindang, M.

    2015-12-01

    Many calderas have a history of repeated caldera-forming eruptions, interspersed with periods of more minor activity. Rabaul, for instance, has had at least 11 ignimbrite-forming eruptions over the last 200 ky. The most recent of these was the '1400 BP' eruption, which led to caldera collapse. Since then, there has been multiple smaller eruptions, including the ongoing activity from Tavurvur and Vulcan. An important question facing volcanology today is what controls the size of eruptions at calderas such as Rabaul.Detailed stratigraphic sampling of the 1400BP eruption reveals that prior to eruption, the magma reservoir below Rabaul contained a well-mixed dacite with whole-rock SiO2 contents of 65.0-66.4 wt%. The dacite contains a single phenocryst assemblage of plag (An44-52), cpx (En43-46Fs13-15Wo40-41), opx (En69-71Fs25-28Wo3) and magnetite, along with minor apatite. The homogeneity of the dacite is underscored by the narrow range of compositions of both the matrix glass and the melt inclusions (67.8-69.0 wt% SiO2). The only exception to this is at the top of the ignimbrite, representing some of the last magma to have been withdrawn. Dispersed throughout the dacitic pumices are darker, more mafic blebs. Streaks of mingled magma with a range of SiO2 contents, down to 59.9 wt% SiO2 are also found in the pumice, suggesting that a mafic recharge magma was intruded into the base of the reservoir shortly before eruption. High TiO2 contents rule out the direct involvement of basalt, and instead imply the magma that intruded into the reservoir was an andesite with at least 56 wt% SiO2. Phenocrysts related to this recharge magma are rare, and the crystals found in the dark blebs are identical in composition to those found in the dacite, indicating that the recharge was aphyric. The present-day, post-caldera recharge magma is different to the pre-1400 BP recharge magma: it is basaltic. This suggests that the plumbing system of Rabaul is different during the pre-caldera and

  14. Long Valley caldera and the UCERF depiction of Sierra Nevada range-front faults

    Science.gov (United States)

    Hill, David P.; Montgomery-Brown, Emily K.

    2015-01-01

    Long Valley caldera lies within a left-stepping offset in the north-northwest-striking Sierra Nevada range-front normal faults with the Hilton Creek fault to the south and Hartley Springs fault to the north. Both Uniform California Earthquake Rupture Forecast (UCERF) 2 and its update, UCERF3, depict slip on these major range-front normal faults as extending well into the caldera, with significant normal slip on overlapping, subparallel segments separated by ∼10  km. This depiction is countered by (1) geologic evidence that normal faulting within the caldera consists of a series of graben structures associated with postcaldera magmatism (intrusion and tumescence) and not systematic down-to-the-east displacements consistent with distributed range-front faulting and (2) the lack of kinematic evidence for an evolving, postcaldera relay ramp structure between overlapping strands of the two range-front normal faults. The modifications to the UCERF depiction described here reduce the predicted shaking intensity within the caldera, and they are in accord with the tectonic influence that underlapped offset range-front faults have on seismicity patterns within the caldera associated with ongoing volcanic unrest.

  15. Caldera of Godean, Sleman, Yogyakarta: A Volcanic Geomorphology Review

    Directory of Open Access Journals (Sweden)

    Hill Gendoet Hartono

    2017-07-01

    Full Text Available Godean hills is located approximately 10 km westward from the Yogyakarta City. The landscape of Godean hills and plains is affected by various factors, such as lithology, geological structure, and sub-aerial process. The purpose of this study was to reveal the landscape of Godean. The method consisted of field study, morphological variables assessment, rock sampling, and laboratory analysis. The results of field mapping indicated that the landscape of Godean  is an isolated hill with a steep slope of >40° and an elevation of +231 m a.s.l, passed by the rivers flows from northeast to southwest that disembogue into the west part of Kulon Progo. The morphologhy of Godean hills varies including G. (Gunung/Mountain So (+173 m amsl, G. Gede (+218 m a.s.l, G. Wungkal (+187 m a.s.l, G. Butak (+154 m a.s.l, and G. Berjo ( + 175 m a.s.l, dominated by the lithology of igneous rock, which is composed of porphyry andesite-microdiorite, pumice lapilli, and quartz rich lapilli-tuff. In addition, most of the igneous rocks have weathered and have been altered to clays, while the deposition from Merapi volcano formed a landscape with an altitude between +100–+150 m a.s.l surrounding Godean hills. Sentolo Formation was found in Kembang, Bantul, which is located approximately ±5km in the south of the study area N93ºE/12º,  while the distribution in the southwest and northeast relatively covers the Godean hills in curve shape. The results of the analysis provide information related with Godean landscape that it is the remains of the volcanic caldera, with various igneous rock types and volcaniclastics deposits, as well as endured the occurrences of hydrothermal alteration and mineralization. Further geophysical research is required to determine the configuration of igneous rocks under the earth's surface.

  16. The El Cajete Series, Valles Caldera, New Mexico

    Science.gov (United States)

    Self, S.; Kircher, D. E.; Wolff, J. A.

    1988-06-01

    Three rhyolite eruptive units totaling 3 km3 dense rock equivalent volume are the youngest products from the Valles caldera, New Mexico. These pyroclastic and effusive units, herein called the El Cajete Series, were erupted over an appreciable time period with Plinian and ignimbrite-forming activity preceding an effusive phase by a lengthy but indeterminable interval. New U-Th disequilibrium and published fission track dates support an age for the event between 170 and 130 ka. The explosive phases formed the El Cajete Plinian deposit (about 1.3 km3), minor dry pyroclastic surges, and the Battleship Rock tuff (about 1.0 km3), a valley-confined welded ignimbrite. The Plinian eruption column is estimated to have been 28 km high during deposition of the most widely dispersed pumice fall unit. Slow effusion of the Banco Bonito obsidian lava flow (<1.0 km3) onto a dissected surface cut into the El Cajete and Battleship Rock pyroclastic deposits, accompanied by minor explosive activity, terminated the event. Twenty-four bulk-rock samples from all three eruptive stages exhibit little significant compositional variation, and the three units are petrographically identical apart from differences arising from contrasting eruption styles. Very few phenocrysts appear to have been in equilibrium with their enclosing high-silica rhyolitic liquid. Plagioclase grains are typically strongly resorbed, while biotite and hornblende frequently occur in aggregate grains in which textures characteristic of plutonic rocks can be discerned. These features result from partial melting of preexisting crustal igneous rock, probably of dioritic to granodioritic composition, and subsequent eruption of the resulting liquid plus restite crystals. Rapid generation and eruption of rhyolitic magma during this most recent phase of activity in the Jemez Mountains may imply that the Valles magma system is presently in a state where small magma bodies are transient phenomena.

  17. Public views and attitudes concerning fire and fuels reduction strategies in the Valles Caldera National Preserve (VCNP) New Mexico

    Science.gov (United States)

    Kurt Anschuetz; Carol Raish

    2010-01-01

    The Valles Caldera National Preserve (VCNP), located in the heart of the Jemez Mountains in northcentral New Mexico, is a special place for many residents of the region. The large volcanic caldera, formerly the privately owned Baca Ranch, is an 89,000-acre property known for its scenic meadows and abundant wildlife, including herds of elk. The U.S. purchased the...

  18. Doubly stochastic models for volcanic hazard assessment at Campi Flegrei caldera

    CERN Document Server

    Bevilacqua, Andrea

    2016-01-01

    This study provides innovative mathematical models for assessing the eruption probability and associated volcanic hazards, and applies them to the Campi Flegrei caldera in Italy. Throughout the book, significant attention is devoted to quantifying the sources of uncertainty affecting the forecast estimates. The Campi Flegrei caldera is certainly one of the world’s highest-risk volcanoes, with more than 70 eruptions over the last 15,000 years, prevalently explosive ones of varying magnitude, intensity and vent location. In the second half of the twentieth century the volcano apparently once again entered a phase of unrest that continues to the present. Hundreds of thousands of people live inside the caldera and over a million more in the nearby city of Naples, making a future eruption of Campi Flegrei an event with potentially catastrophic consequences at the national and European levels.

  19. Progressive approach to eruption at Campi Flegrei caldera in southern Italy

    Science.gov (United States)

    Kilburn, Christopher R. J.; de Natale, Giuseppe; Carlino, Stefano

    2017-05-01

    Unrest at large calderas rarely ends in eruption, encouraging vulnerable communities to perceive emergency warnings of volcanic activity as false alarms. A classic example is the Campi Flegrei caldera in southern Italy, where three episodes of major uplift since 1950 have raised its central district by about 3 m without an eruption. Individual episodes have conventionally been treated as independent events, so that only data from an ongoing episode are considered pertinent to evaluating eruptive potential. An implicit assumption is that the crust relaxes accumulated stress after each episode. Here we apply a new model of elastic-brittle failure to test the alternative view that successive episodes promote a long-term accumulation of stress in the crust. The results provide the first quantitative evidence that Campi Flegrei is evolving towards conditions more favourable to eruption and identify field tests for predictions on how the caldera will behave during future unrest.

  20. Graben calderas of the Sierra Madre Occidental: The case of Guanajuato, central Mexico

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Tristán-González, M.; Labarthe-Hernández, G.; Marti, J.

    2013-12-01

    The Sierra Madre Occidental (SMO) volcanic province is characterized by voluminous silicic ignimbrites that reach an accumulated thickness of 500 to 1500 m. A single ignimbrite can reach up to 350 m thick in its outflow facies. This ignimbrite sequence formed mostly within 38-23 Ma, building up a total estimated volume of ca. 580,000 km3 making the SMO the largest ignimbrite province of the world. We have showed that several and probably most of the SMO ignimbrites were erupted from fissures associated to Basin and Range fault systems or grabens (Geology, 2003), thus naming these volcano-tectonic structures as graben calderas (Caldera Volcanism book, Elsevier, 2008). Generally, the sequence observed in graben calderas include, from oldest to youngest, alluvial fan deposits combined with lacustrine deposits, pyroclastic surge deposits and minor volume ignimbrites, a large-volume ignimbrite that could be massive or made of successive layers, and sometimes silicic lava domes and/or mafic fissural lavas both with vents aligned with the graben trend. Fallout deposits, plinian or non-plinian, are not observed in the sequence. Thus, onset of caldera collapse represented by the major ignimbrite must occur just after deposition of continental sediments within the graben domain. A similar volcano-tectonic development is observed in pull-apart grabens. Therefore, extensional or transtensional tectonics, before and during caldera collapse, and the emplacement of a subgraben shallow silicic magma chamber are the necessary conditions for the development of graben calderas. We describe here the case of the Guanajuato graben caldera, located in the central part of Mexico and in the southeastern portion of the SMO volcanic province. The caldera is part of the economically important mining district of Guanajuato, with 28 silver mines, some active since the 16th century. The caldera structure, a rectangle of 10 x 16 km, was controlled by NW and NE regional fault systems. Most ore

  1. Progressive approach to eruption at Campi Flegrei caldera in southern Italy.

    Science.gov (United States)

    Kilburn, Christopher R J; De Natale, Giuseppe; Carlino, Stefano

    2017-05-15

    Unrest at large calderas rarely ends in eruption, encouraging vulnerable communities to perceive emergency warnings of volcanic activity as false alarms. A classic example is the Campi Flegrei caldera in southern Italy, where three episodes of major uplift since 1950 have raised its central district by about 3 m without an eruption. Individual episodes have conventionally been treated as independent events, so that only data from an ongoing episode are considered pertinent to evaluating eruptive potential. An implicit assumption is that the crust relaxes accumulated stress after each episode. Here we apply a new model of elastic-brittle failure to test the alternative view that successive episodes promote a long-term accumulation of stress in the crust. The results provide the first quantitative evidence that Campi Flegrei is evolving towards conditions more favourable to eruption and identify field tests for predictions on how the caldera will behave during future unrest.

  2. Clues on the origin of post-2000 earthquakes at Campi Flegrei caldera (Italy).

    Science.gov (United States)

    Chiodini, G; Selva, J; Del Pezzo, E; Marsan, D; De Siena, L; D'Auria, L; Bianco, F; Caliro, S; De Martino, P; Ricciolino, P; Petrillo, Z

    2017-06-30

    The inter-arrival times of the post 2000 seismicity at Campi Flegrei caldera are statistically distributed into different populations. The low inter-arrival times population represents swarm events, while the high inter-arrival times population marks background seismicity. Here, we show that the background seismicity is increasing at the same rate of (1) the ground uplift and (2) the concentration of the fumarolic gas specie more sensitive to temperature. The seismic temporal increase is strongly correlated with the results of recent simulations, modelling injection of magmatic fluids in the Campi Flegrei hydrothermal system. These concurrent variations point to a unique process of temperature-pressure increase of the hydrothermal system controlling geophysical and geochemical signals at the caldera. Our results thus show that the occurrence of background seismicity is an excellent parameter to monitor the current unrest of the caldera.

  3. Accelerated uplift and magmatic intrusion of the Yellowstone caldera, 2004 to 2006.

    Science.gov (United States)

    Chang, Wu-Lung; Smith, Robert B; Wicks, Charles; Farrell, Jamie M; Puskas, Christine M

    2007-11-09

    The Yellowstone caldera began a rapid episode of ground uplift in mid-2004, revealed by Global Positioning System and interferometric synthetic aperture radar measurements, at rates up to 7 centimeters per year, which is over three times faster than previously observed inflation rates. Source modeling of the deformation data suggests an expanding volcanic sill of approximately 1200 square kilometers at a 10-kilometer depth beneath the caldera, coincident with the top of a seismically imaged crustal magma chamber. The modeled rate of source volume increase is 0.1 cubic kilometer per year, similar to the amount of magma intrusion required to supply the observed high heat flow of the caldera. This evidence suggests magma recharge as the main mechanism for the accelerated uplift, although pressurization of magmatic fluids cannot be ruled out.

  4. Formation of low-δ18O rhyolites after caldera collapse at Yellowstone, Wyoming, USA

    Science.gov (United States)

    Bindeman, Ilya N.; Valley, John W.

    2000-08-01

    We present a new model for the genesis of low-δ18O rhyolites of the Yellowstone caldera based on analyses of zircons and individual quartz phenocrysts. Low-δ18O rhyolites were erupted soon after the massive caldera-forming Lava Creek Tuff eruption (602 ka, ˜1000 km3) and contain xenocrysts of quartz and zircon inherited from precaldera rhyolites. These zircons are isotopically zoned and out of equilibrium with their host low-δ18O melts and quartz. Diffusion modeling predicts that magmatic disequilibria of oxygen isotopes persists for as much as tens of thousands of years following nearly total remelting of the hydrothermally altered igneous roots of the depressed cauldron, in which the alteration-resistant quartz and zircon initially retained their δ18O values. These results link melting to caldera collapse, rule out rapid or catastrophic magma meteoric water interaction, and indicate wholesale melting rather than assimilation or partial melting.

  5. Electrical structure of Plaine des Sables caldera, Piton de la Fournaise volcano (Reunion Island

    Directory of Open Access Journals (Sweden)

    P. A. Schnegg

    1997-06-01

    Full Text Available An Audio Magnetotelluric (AMT profile has been carried out across the Plaine des Sables, a former caldera of the active Piton de la Fournaise volcano, Reunion Island. Located in the Western Indian Ocean, between the Mascarene and Madagascar basins, this basaltic shield volcano originates from the activity of a hot spot. Our aim was to determine the internal structure of the volcano, in particular the shallow electrical properties of an area extending between the old and the new caldera rims. Although several teams had already conducted AMT work in this region a few years ago, there was a need for more a detailed, in depth survey. Our final model displays a noticeable slope of the Plaine des Sables basement oriented toward the present Fournaise summit. This slope is interpreted as resulting from successive landslides toward the ocean. We conclude that this dipping, electrically good conducting layer, probably belongs to the flat layering of an older caldera.

  6. Characterizing analogue caldera collapse with computerized X-ray micro-tomography

    Science.gov (United States)

    Poppe, Sam; Holohan, Eoghan; Boone, Matthieu; Pauwels, Elin; Cnudde, Veerle; Kervyn, Matthieu

    2013-04-01

    Analogue models in the past mainly explored caldera collapse structures by documenting 2D model cross-sections. Kinematic aspects and 3D structures of caldera collapse are less well understood, although they are essential to interpret recent field and monitoring data. We applied high resolution radiography and computerized X-ray micro-tomography (µCT) to image the deformation during analogue fluid withdrawal in small-scale caldera collapse models. The models test and highlight the possibilities and limitations of µCT-scanning to qualitatively image and quantitatively analyse deformation of analogue volcano-tectonic experiments. High resolution interval radiography sequences document '2.5D' surface and internal model geometry, and subsidence kinematics of a collapsing caldera block into an emptying fluid body in an unprecedented way. During the whole drainage process, all subsidence was bound by caldera ring faults. Subsidence was associated with dilatation of the analogue granular material within the collapsing column. The temporal subsidence rate pattern within the subsiding volume comprised three phases: 1) Upward ring fault propagation, 2) Rapid subsidence with the highest subsidence rates within the uppermost subsiding volume, 3) Relatively slower subsidence rates over the whole column with intermittent subsidence rate acceleration. Such acceleration did almost never affect the whole column. By using radiography sequences it is possible in a non-destructive manner to obtain a continuous observation of fault propagation, down sag mechanisms and the subsequent development of collapse structures. Multi-angle µCT scans of the collapse result allow for a full virtual 3D reconstruction of the model. This leads to an unprecedented 3D view on fault geometries. The developed method is a step towards the quantitative documentation of volcano-tectonic models that would render data interpretations immediately comparable to monitoring data available from recent

  7. Reconstruction of the most recent volcanic eruptions from the Valles caldera, New Mexico

    Science.gov (United States)

    Wolff, J. A.; Brunstad, K. A.; Gardner, J. N.

    2011-01-01

    Products of the latest eruptions from the Valles caldera, New Mexico, consist of the El Cajete Pyroclastic Beds and Battleship Rock Ignimbrite, a sequence of pyroclastic fall and density current deposits erupted at ~ 55 ka, capped by the later Banco Bonito Flow erupted at ~ 40 ka, and collectively named the East Fork Member of the Valles Rhyolite. The stratigraphy of the East Fork Member has been the subject of conflicting interpretations in the past; a long-running investigation of short-lived exposures over a period of many years enables us to present a more complete event stratigraphy for these eruptions than has hitherto been possible. The volume of rhyolitic magma erupted during the 55 ka event may have been more than 10 km 3, and for the 40 ka event can be estimated with rather more confidence at 4 km 3. During the earlier event, plinian eruptions dispersed fallout pumice over much of the Valles caldera, the southern Jemez Mountains, and the Rio Grande rift. We infer a fallout thickness of several decimeters at the site of the city of Santa Fe, and significant ash fall in eastern New Mexico. In contrast, pyroclastic density currents were channeled within the caldera moat and southwestward into the head of Cañon de San Diego, the principal drainage from the caldera. Simultaneous (or rapidly alternating) pyroclastic fallout and density current activity characterized the ~ 55 ka event, with density currents becoming more frequent as the eruption progressed through two distinct stages separated by a brief hiatus. One early pyroclastic surge razed a forest in the southern caldera moat, in a similar manner to the initial blast of the May 18, 1980 eruption of Mt. St. Helens. Ignimbrite outflow from the caldera through the drainage notch may have been restricted in runout distance due to steep, rugged topography in this vicinity promoting mixing between flows and air, and the formation of phoenix clouds. Lavas erupted during both the ~ 55 and ~ 40 ka events were

  8. There's more than one way to build a caldera magma chamber: Evidence from volcanic-plutonic relationships at three faulted Rio-Grande-rift calderas

    Science.gov (United States)

    Zimmerer, M. J.; McIntosh, W. C.

    2011-12-01

    The temporal and chemical relationships of volcanic and plutonic rocks of the Questa (NM), Mt. Aetna (CO), and Organ caldera (NM) complexes were investigated to establish the origin of these silicic magmas. Rio Grande Rift faulting at these systems has exposed both intracaldera sequences and subvolcanic plutons. Ar/Ar and U/Pb ages reveal the timing of volcanic activity and pluton emplacement and cooling. We observe a link between ignimbrite zoning patterns and the temporal-chemical relationship of volcanic and plutonic rocks. The Questa caldera erupted the high-SiO2 peralkaline Amalia Tuff (AT) at 25.4 Ma. Volumetrically minor phases of two resurgent plutons and a ring dike are compositionally similar to the AT. The age of the ring dike (25.4 Ma) is indistinguishable to AT, suggesting that the peralkaline intrusions are nonerupted AT. The remaining pluton ages are 100 ka to 6.1 Ma younger than AT and are too young to be the AT residual crystal mush. The Mt. Princeton batholith and nested Mt. Aetna caldera are interpreted to be the sources for the 37.3 Ma, low-SiO2 rhyolitic Wall Mountain Tuff (WMT) and the 34.3 Ma, dacitic Badger Creek Tuff (BCT). U/Pb and Ar/Ar ages of Mt. Princeton batholith (36.5 to 35.1 Ma) indicate that it was emplaced and rapidly cooled during the interval between the WMT and BCT eruptions, and that any WMT age intrusions are now eroded. During the eruption of the BCT, the fully crystallized Mt. Princeton batholith collapsed into the Mt. Aetna caldera. Intrusions along the margins of the Mt. Aetna caldera are compositionally identical the BCT and contain zircons 100 to 500 ka older than the tuff, suggesting that the BCT magma chamber was incrementally emplaced prior to caldera eruption. The Organ caldera complex erupted three ignimbrites: a basal high-silica 36.5 Ma rhyolite, a middle intermediate-silica 36.2 Ma rhyolite, and an upper 36.0 Ma low-silica rhyolite. The intracaldera sequence is intruded by the Organ Needle pluton. U/Pb zircon

  9. Application of electric and electromagnetic methods to the definition of the Campi Flegrei caldera (Italy)

    Energy Technology Data Exchange (ETDEWEB)

    Di Maio, R.; Patella, D.; Cecere, G. [Naples Univ. Federico II, Naples (Italy). Dipt. di Scienze Fisiche; Petrillo, Z.; De Martino, P. [Osservatorio Vesuviano, Ercolano, NA (Italy); Siniscalchi, A. [Bari Univ., Bari (Italy). Dipt. di Geologia e Geofisica

    2000-04-01

    The results of an analysis of dipolar geoelectrical (DG), magnetotelluric (MT) and self-potential (SP) data collected over the emerged portion of the Campi Flegrei (CF) caldera (Southern Italy) are presented. The DG and MT data are from previous surveys, while the SP data have been recently collected during a survey consisting of 265 pickup land sites. Although the emerged part of the CF caldera appears as a highly inhomogeneous structure, a few simple features have been highlighted through an integrated analysis of subsets of consistent data. A well resolved feature is the structural pattern of the caldera depression along a roughly E-W- profile, deduced from a 2D combined interpretation of the MT and DG soundings. Resistivity dispersion effects have also been observed at both ends of this profile. They have been ascribed to the presence of hydrothermally altered zones related to the main fracture systems bordering the caldera. A pressure-temperature source body at a mean depth of about 5 km bsl under Pozzuoli bay (Italy) has been inferred from the analysis of the 3D SP tomography imaging.

  10. Modeling surface deformation observed with synthetic aperture radar interferometry at Campi Flegrei caldera

    NARCIS (Netherlands)

    Lundgren, P.; Usai, S.; Sansosti, E.; Lanari, R.; Tesauro, M.; Fornaro, G.; Berardino, P.

    2001-01-01

    Satellite radar interferometry of Campi Flegrei caldera, Italy, reveals a pattern of subsidence during the period 1993–1998. Interferograms spanning the first half of the observation period (1993–1995) have a lower amplitude and average rate of subsidence than those spanning either the second half

  11. Galileo's Last Fly-Bys of Io: NIMS Observations of Loki, Tupan, and Emakong Calderas

    Science.gov (United States)

    Lopes, Rosaly M. C.; Kamp, L. W.; Davies, A. G.; Smythe, W. D.; Carlson, R. W.; Doute, S.; McEwen, A.; Turtle, E. P.; Leader, F.; Mehlman, R.

    2002-01-01

    NIMS results from the 2001 Galileo fly-bys of Io will be presented, focusing on three calderas that may contain lava lakes. Preliminary results from the January 2002 Io fly-by will be presented. Additional information is contained in the original extended abstract.

  12. Monitoring super-volcanoes: geophysical and geochemical signals at Yellowstone and other large caldera systems.

    Science.gov (United States)

    Lowenstern, Jacob B; Smith, Robert B; Hill, David P

    2006-08-15

    Earth's largest calderas form as the ground collapses during immense volcanic eruptions, when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the Earth's crust over a period of days to weeks. Continuing long after such great eruptions, the resulting calderas often exhibit pronounced unrest, with frequent earthquakes, alternating uplift and subsidence of the ground, and considerable heat and mass flux. Because many active and extinct calderas show evidence for repetition of large eruptions, such systems demand detailed scientific study and monitoring. Two calderas in North America, Yellowstone (Wyoming) and Long Valley (California), are in areas of youthful tectonic complexity. Scientists strive to understand the signals generated when tectonic, volcanic and hydrothermal (hot ground water) processes intersect. One obstacle to accurate forecasting of large volcanic events is humanity's lack of familiarity with the signals leading up to the largest class of volcanic eruptions. Accordingly, it may be difficult to recognize the difference between smaller and larger eruptions. To prepare ourselves and society, scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption.

  13. Geology and ore deposits of the McDermitt Caldera, Nevada-Oregon

    Science.gov (United States)

    Rytuba, James J.

    1976-01-01

    The McDermitt caldera is a Miocene collapse structure along the Nevada-Oregon border. The oval-shaped caldera is bounded by arcuate normal faults on the north and south and by rhyolite ring domes on the west. Precollapse ash-flow tuffs exposed within the south caldera rim consist of three cooling units and are peralkaline in composition. Refractive indexes of nonhydrated glasses from basal vitrophyres of the. units range from 1.493 to 1.503 and are typical of comendites. Post-collapse intracaldera rocks consist of tuffaceous lake sediments, rhyolite flows and domes, and ash-flow tuffs. Within the caldera are the mercury mines of Bretz, Cordero, McDermitt, Opalite, and Ruja and the Moonlight uranium mine. The mercury mines are adjacent to ring fracture faults, and the uranium mine and other uranium occurrences are located within rhyolite ring domes. Fluid inclusions in quartz indicate a deposition temperature of 340?C for the uranium deposit and 200?C for the mercury deposits. The mercury deposits formed at shallow depth by replacement of lakebed sediments and volcanic rocks.

  14. Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins.

    Science.gov (United States)

    Benson, Thomas R; Coble, Matthew A; Rytuba, James J; Mahood, Gail A

    2017-08-16

    The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of tectonic settings using in situ trace-element measurements of quartz-hosted melt inclusions to demonstrate that moderate to extreme lithium enrichment occurs in magmas that incorporate felsic continental crust. Cenozoic calderas in western North America and in other intracontinental settings that generated such magmas are promising new targets for lithium exploration because lithium leached from the eruptive products by meteoric and hydrothermal fluids becomes concentrated in clays within caldera lake sediments to potentially economically extractable levels.Lithium is increasingly being utilized for modern technology in the form of lithium-ion batteries. Here, using in situ measurements of quartz-hosted melt inclusions, the authors demonstrate that preserved lake sediments within rhyolitic calderas have the potential to host large lithium-rich clay deposits.

  15. More than a scenic mountain landscape: Valles Caldera National Preserve land use history

    Science.gov (United States)

    Kurt F. Anschuetz; Thomas Merlan

    2007-01-01

    This study focuses on the cultural-historical environment of the 88,900-acre (35,560-ha) Valles Caldera National Preserve (VCNP) over the past four centuries of Spanish, Mexican, and U.S. governance. It includes a review and synthesis of available published and unpublished historical, ethnohistorical, and ethnographic literature about the human occupation of the area...

  16. Applying hydrology to land management on the Valles Caldera National Preserve

    Science.gov (United States)

    Robert R. Parmenter

    2009-01-01

    Since 2004, the Valles Caldera National Preserve (VCNP) in the Jemez Mountains of northern New Mexico has hosted extensive field hydrology research by scientists from the Center for Sustainability of semi- Arid Hydrology and Riparian Areas (SAHRA) at the University of Arizona. With the development of a detailed hydrologic understanding of VCNP's climate, geology,...

  17. Chapter 9. The Valles Caldera National Preserve as a multi-layered ethnographic landscape

    Science.gov (United States)

    Kurt F. Anschuetz

    2007-01-01

    The land use history of the Valles Caldera National Preserve (VCNP), as represented in the documentary record maintained in various archives and libraries, focuses primarily on the Hispanic and Anglo-American occupation of the locale subsequent to 1860. In an act of June 21, 1860, the U.S. Congress authorized the Baca Land Grant heirs to choose as many as five square...

  18. Modeling surface deformation observed with synthetic aperture radar interferometry at Campi Flegrei caldera

    NARCIS (Netherlands)

    Lundgren, P.; Usai, S.; Sansosti, E.; Lanari, R.; Tesauro, M.; Fornaro, G.; Berardino, P.

    Satellite radar interferometry of Campi Flegrei caldera, Italy, reveals a pattern of subsidence during the period 1993–1998. Interferograms spanning the first half of the observation period (1993–1995) have a lower amplitude and average rate of subsidence than those spanning either the second half

  19. The first report of the aphids of the Valles Caldera National Preserve, New Mexico, USA

    Science.gov (United States)

    We report 50 species, belonging to 26 genera of aphids (Hemiptera: Aphididae), collected within and near the boundary of the Valles Caldera National Preserve in the Jemez Mountains of northern New Mexico, USA. Of these, 35 (70%) represent new distribution records for New Mexico. Plant genera/species...

  20. Monitoring super-volcanoes: Geophysical and geochemical signals at Yellowstone and other large caldera systems

    Science.gov (United States)

    Lowenstern, Jacob B.; Smith, Robert B.; Hill, David P.

    2006-01-01

    Earth's largest calderas form as the ground collapses during immense volcanic eruptions, when hundreds to thousands of cubic kilometres of magma are explosively withdrawn from the Earth's crust over a period of days to weeks. Continuing long after such great eruptions, the resulting calderas often exhibit pronounced unrest, with frequent earthquakes, alternating uplift and subsidence of the ground, and considerable heat and mass flux. Because many active and extinct calderas show evidence for repetition of large eruptions, such systems demand detailed scientific study and monitoring. Two calderas in North America, Yellowstone (Wyoming) and Long Valley (California), are in areas of youthful tectonic complexity. Scientists strive to understand the signals generated when tectonic, volcanic and hydrothermal (hot ground water) processes intersect. One obstacle to accurate forecasting of large volcanic events is humanity's lack of familiarity with the signals leading up to the largest class of volcanic eruptions. Accordingly, it may be difficult to recognize the difference between smaller and larger eruptions. To prepare ourselves and society, scientists must scrutinize a spectrum of volcanic signals and assess the many factors contributing to unrest and toward diverse modes of eruption. ?? 2006 The Royal Society.

  1. Application of electric and electromagnetic methods to the definition of the Campi Flegrei caldera (Italy

    Directory of Open Access Journals (Sweden)

    G. Cecere

    2000-06-01

    Full Text Available The results of an analysis of Dipolar Geoelectrical (DG, Magnetotelluric (MT and Self-Potential (SP data collected over the emerged portion of the Campi Flegrei (CF caldera (South Italy are presented. The DG and MT data are from previous surveys, while the SP data have been recently collected during a survey consisting of 265 pickup land sites. Although the emerged part of the CF caldera appears as a highly inhomogeneous structure, a few simple features have been highlighted through an integrated analysis of subsets of consistent data. A well resolved feature is the structural pattern of the caldera depression along a roughly E-W profile, deduced from a 2D combined interpretation of the MT and DG soundings. Resistivity dispersion effects have also been observed at both ends of this profile. They have been ascribed to the presence of hydrothermally altered zones related to the main fracture systems bordering the caldera. A pressure/temperature source body at a mean depth of about 5 km bsl under the Bay of Pozzuoli has been inferred from the analysis of the 3D SP tomography imaging.

  2. A three-dimensional gravity model of the geologic structure of Long Valley caldera

    Energy Technology Data Exchange (ETDEWEB)

    Carle, S.F.; Goldstein, N.E.

    1987-03-01

    Several attempts to define and interpret this anomaly have been made in the past using 2-D and 3-D models. None of the previous interpretations have yielded definitive results, but in fairness, the interpretation here has benefited from a larger gravity data base and more subsurface control than available to previous workers. All published 3-D models simplistically assumed constant density of fill. All 2-D models suffered from the inherent three-dimensionality of the complicated density structure of Long Valley caldera. In addition, previous interpreters have lacked access to geological data, such as well lithologies and density logs, seismic refraction interpretations, suface geology, and structural geology interpretations. The purpose of this study is to use all available gravity data and geological information to constrain a multi-unit, 3-D density model based on the geology of Long Valley caldera and its vicinity. Insights on the geologic structure of the caldera fill can help other geophysical interpretations in determining near-surface effects so that deeper structure may be resolved. With adequate control on the structure of the caldera fill, we are able to examine the gravity data for the presence of deeper density anomalies in the crust. 20 refs., 7 figs.

  3. Magnetic fabrics in sub-caldera plutons recording magma ascent and fault-caldera interactions, the Etiavnica volcano-plutonic complex, Western Carpathians

    Science.gov (United States)

    Tomek, Filip; Žák, Jiří

    2013-04-01

    The Štiavnica volcano-plutonic complex in the Western Carpatians exposes a spectacular section through middle Miocene stratovolcano (50 km in diameter) built on Variscan basement and late Paleozoic to Cretaceous sedimentary rocks. The stratovolcano consists of early andesite lava flows, extrusive domes, and pyroclastic flow deposits intruded by andesite and andesite porphyry sills and laccoliths. At around 14.5-15.5 Ma, the pre-volcanic basement beneath the central portion of the stratovolcano was intruded by a diorite stock and a voluminous bell-jar granodiorite pluton followed by quartz diorite to granodiorite porphyry dikes and stocks. The pluton emplacement led to the development of a 20 km wide collapse caldera associated with late andesite and dacite extrusive domes, dome flows, pyroclastic deposits, and quartz-diorite porphyry dikes and sills. Subsequently, the central domain underwent resurgence accompanied by intrusion of small rhyolitic and granite porphyry bodies. The present-day exposure with significant vertical relief cuts through all these units including the sub-caldera plutons and their flat roof which represents the volcano basement. The sub-caldera plutons exhibit contrasting magnetic fabrics as revealed by anisotropy of magnetic susceptibility (AMS). The diorite is characterized by very low degree of magnetic anisotropy (less than 10 %) and both prolate and oblate AMS ellipsoids. Magnetic foliations are mostly sub-parallel to the nearby pluton roof margin and are associated with steep lineations. In contrast, the younger granodiorite shows slightly higher degree of magnetic anisotropy (up to 12 %) and chiefly oblate susceptibility ellipsoids for the same magnetic mineralogy (both plutons are ferromagnetic, with the AMS carried predominantly by magnetite). Unlike fabric in the diorite, magnetic foliations are homogeneously oriented and dip moderately to the W to WNW whereas magnetic lineations vary from down-dip to subhorizontal. We interpret

  4. Plio-pleistocene volcano-tectonic evolution of la Reforma Caldera, Baja California, Mexico

    Science.gov (United States)

    Demant, Alain; Ortlieb, Luc

    1981-01-01

    La Reforma volcanic complex, in east-central Baja California, shows a characteristic caldera structure, 10 km in diameter. The first eruptive stage, during the Pliocene, was manifested by ash and pumice falls and by subaqueous pumitic flows. In a second stage basic flows were deposited in a near-shore environment (subaerial and pillow lavas). During the early Pleistocene a large ignimbritic eruption, producing mainly pantelleritic tuffs, immediately predated the formation of the caldera itself. Afterwards, along marginal fractures of the caldera, some rhyolitic domes and flows partially covered the thick ignimbritic sheet. A block of Miocene substratum, in the center of the caldera, has been uplifted, nearly 1 km, by "resurgent doming". Small outcrops of diorite might constitute the top of coarse-grained crystallized magmatic bodies, and thus support the "resurgent doming" interpretation. A few basaltic cones were finally built on the flanks of the caldera complex; the latter are not related to the caldera history but to the extension tectonics of the Gulf of California which are also responsible for the Tortuga Island and the Holocene Tres Virgenes tholeiitic cones. South of la Reforma are found the highest (+300 m) Pleistocene marine deposits of the Gulf coast of Baja California. The uplift of this area is due in part to the positive epeirogenic movements of the whole peninsular crustal block, and also to the late doming of the caldera. On the coastal (eastern) flank of La Reforma complex up to seven stepped wave-cut terraces have been preserved, the highest reaching more than +150 m and the lowest ones +25 m. Lateral correlations of the marine terraces along the whole Gulf of California suggest that this volcano-tectonic uplift, that is still active, is of the order of 240 mm/10 3 y. The set of terraces is interpreted to be Middle (700-125 × 10 3y) to Upper (125-80 × 10 3y) Pleistocene, and is tentatively correlated with the paleoclimatic chronology of deep

  5. A short review of our current understanding of the development of ring faults during collapse caldera formation

    Directory of Open Access Journals (Sweden)

    Adelina eGeyer

    2014-09-01

    Full Text Available The term collapse caldera refers to those volcanic depressions resulting from the sinking of the chamber roof due to the rapid withdrawal of magma during the course of an eruption. During the last three decades, collapse caldera dynamics has been the focus of attention of numerous, theoretical, numerical and experimental studies. Nonetheless, even if there is a tendency to go for a general and comprehensive caldera dynamics model, some key aspects remain unclear, controversial or completely unsolved. This is the case of ring fault nucleation points and propagation and dip direction. Since direct information on calderas’ deeper structure comes mainly from partially eroded calderas or few witnessed collapses, ring faults layout at depth remains still uncertain. This has generated a strong debate over the detailed internal fault and fracture configuration of a caldera collapse and, in more detail, how ring faults initiate and propagate. We offer here a very short description of the main results obtained by those analogue and theoretical/mathematical models applied to the study of collapse caldera formation. We place special attention on those observations related to the nucleation and propagation of the collapse-controlling ring faults. This summary is relevant to understand the current state-of-the-art of this topic and it should be taken under consideration in future works dealing with collapse caldera dynamics.

  6. A short review of our current understanding of the development of ring faults during collapse caldera formation

    Science.gov (United States)

    Geyer, Adelina; Marti, Joan

    2014-09-01

    The term collapse caldera refers to those volcanic depressions resulting from the sinking of the chamber roof due to the rapid withdrawal of magma during the course of an eruption. During the last three decades, collapse caldera dynamics has been the focus of attention of numerous, theoretical, numerical and experimental studies. Nonetheless, even if there is a tendency to go for a general and comprehensive caldera dynamics model, some key aspects remain unclear, controversial or completely unsolved. This is the case of ring fault nucleation points and propagation and dip direction. Since direct information on calderas’ deeper structure comes mainly from partially eroded calderas or few witnessed collapses, ring faults layout at depth remains still uncertain. This has generated a strong debate over the detailed internal fault and fracture configuration of a caldera collapse and, in more detail, how ring faults initiate and propagate. We offer here a very short description of the main results obtained by those analogue and theoretical/mathematical models applied to the study of collapse caldera formation. We place special attention on those observations related to the nucleation and propagation of the collapse-controlling ring faults. This summary is relevant to understand the current state-of-the-art of this topic and it should be taken under consideration in future works dealing with collapse caldera dynamics.

  7. Probing the source and timing of rejuvenation and hybridization in post-caldera rhyolite magmas at Yellowstone Caldera

    Science.gov (United States)

    Till, C.; Vazquez, J. A.; Boyce, J. W.; Stelton, M. E.

    2013-12-01

    We find petrographic, isotopic and geochemical evidence for rejuvenation and recycling of subvolcanic intrusions within low δ18O intracaldera rhyolite lavas erupted following the formation of Yellowstone Caldera. In order to resolve the timing and compositional end-members involved in rejuvenation and hybridization of Yellowstone's subvolcanic magma reservoir, we have analyzed the Pb isotopic composition of clinopyroxene and sanidine phenocrysts and performed U-Pb dating of zircons from the South Biscuit Basin (SBB) and Scaup Lake (SCL) rhyolite lava flows. Both SBB and SCL erupted ca. 260 ka based on indistinguishable 40Ar/39Ar ages [1,2] and represent a renewed episode of postcaldera volcanism after a hiatus of ~200 kyr. Zoned phenocrysts of quartz, clinopyroxene, orthopyroxene, plagioclase, and sanidine and accessory zircon and Fe-Ti oxides characterize both SBB and SCL. SCL and SBB clinopyroxene have identical compositions and core-to-rim zoning patterns in Fe, Mg, and trace elements and commonly exhibit exsolution lamellae in their cores, suggesting that subsolidus conditions were attained during the early evolution of these rhyolites. The exsolution-bearing cores are mantled by a zone of relatively high Mg/Fe and low HREE & Rb, which is in turn overgrown by a rim with slightly lower Mg/Fe, and higher HREE & Rb. This zoning pattern suggests rejuvenation of subsolidus rhyolite by the influx of at least two less evolved, hotter silicic magmas. Diffusion modeling of Fe-Mg concentration profiles in clinopyroxene suggests that these events occurred on the order of 103 yrs prior to eruption. To identify the source of the rejuvenated rhyolite and delimit intra-grain variability, we analyzed the Pb-isotopic compositions of the SBB and SCL clinopyroxene zones via LA-MC-ICPMS. The different zones within SBB and SCL clinopyroxene yield indistinguishable Pb-isotope compositions with 208Pb/206Pb=2.165-2.185 and 207Pb/206Pb=0.882-0.890, which matches the Pb

  8. Fluid-driven uplift at Long Valley Caldera, California: Geologic perspectives

    Science.gov (United States)

    Hildreth, Wes

    2017-07-01

    Since persistent seismicity began in the Sierra Nevada adjacent to Long Valley caldera in 1978-1980, intracaldera unrest has been marked by (1) episodes of uplift totaling 83 cm, centered on the middle Pleistocene resurgent dome, and (2) recurrent earthquake swarms along a 12-km-long segment of the caldera's ring-fault zone that is contiguous with both the dome and the Sierran seismogenic domain. Others have attributed the recent unrest to magmatic intrusion(s), but it is argued here that evidence for new magma is lacking and that ongoing uplift and ring-fault-zone seismicity are both promoted by ascent of aqueous fluid released by second boiling of the residue of the enormous Pleistocene rhyolitic reservoir terminally crystallizing at depths ≥ 10 km. For 2 Myr, eruptive vent clusters migrated southwestward from Glass Mountain to Mammoth Mountain. There has been no eruption on the resurgent dome since 500 ka, and since 230 ka volcanism has been restricted to the caldera's west moat and contiguous Sierran terrain, both outside the structural caldera. High-temperature hydrothermal activity in the central caldera waned after 300 ka, cooling the Pleistocene rhyolitic focus to the extent that drilling on the resurgent dome found mid-caldera temperature to be only 100 °C and isothermal at depths of 2-3 km. Beneath most of the resurgent dome, there is little seismicity at any depth, no emission of magmatic CO2 or other magmatic gases, no elevated 3He/4He ratios, and only normal to below-normal heat flow. Most of the 75-km-long ring-fault zone is likewise aseismic, excepting only the 12-km segment contiguous with the extracaldera seismogenic domain in the Sierra. Since 1980, the Sierran seismicity has released 3.6 times more cumulative seismic energy than have intracaldera earthquakes. The caldera seismicity is not driven by stresses associated with the adjacent uplift but, instead, by the extracaldera tectonic stressfield. Sierran seismicity activated the directly

  9. Geothermal hydrology of Valles Caldera and the southwestern Jemez Mountains, New Mexico

    Science.gov (United States)

    Trainer, Frank W.; Rogers, Robert J.; Sorey, M.L.

    2000-01-01

    The Jemez Mountains in north-central New Mexico are volcanic in origin and have a large central caldera known as Valles Caldera. The mountains contain the Valles geothermal system, which was investigated during 1970-82 as a source of geothermal energy. This report describes the geothermal hydrology of the Jemez Mountains and presents results of an earlier 1972-75 U.S. Geological Survey study of the area in light of more recent information. Several distinct types of thermal and nonthermal ground water are recognized in the Jemez Mountains. Two types of near-surface thermal water are in the caldera: thermal meteoric water and acid sulfate water. The principal reservoir of geothermal fluids is at depth under the central and western parts of the caldera. Nonthermal ground water in Valles Caldera occurs in diverse perched aquifers and deeper valley-fill aquifers. The geothermal reservoir is recharged by meteorically derived water that moves downward from the aquifers in the caldera fill to depths of 6,500 feet or more and at temperatures reaching about 330 degrees Celsius. The heated geothermal water rises convectively to depths of 2,000 feet or less and mixes with other ground water as it flows away from the geothermal reservoir. A vapor zone containing steam, carbon dioxide, and other gases exists above parts of the liquid-dominated geothermal zone. Two subsystems are generally recognized within the larger geothermal system: the Redondo Creek subsystem and the Sulphur Creek subsystem. The permeability in the Redondo Creek subsystem is controlled by stratigraphy and fault-related structures. Most of the permeability is in the high-angle, normal faults and associated fractures that form the Redondo Creek Graben. Faults and related fractures control the flow of thermal fluids in the subsystem, which is bounded by high-angle faults. The Redondo Creek subsystem has been more extensively studied than other parts of the system. The Sulphur Springs subsystem is not as well

  10. Hydrogeochemical data for thermal and nonthermal waters and gases of the Valles Caldera- southern Jemez Mountains region, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Shevenell, L.; Goff, F.; Vuataz, F.; Trujillo, P.E. Jr.; Counce, D.; Janik, C.J.; Evans, W.

    1987-03-01

    This report presents field, chemical, gas, and isotopic data for thermal and nonthermal waters of the southern Jemez Mountains, New Mexico. This region includes all thermal and mineral waters associated with Valles Caldera and many of those located near the Nacimiento Uplift, north of San Ysidro. Waters of the region can be categorized into five general types: (1) surface and near-surface meteoric waters; (2) acid-sulfate waters at Sulphur Springs (Valles Caldera); (3) thermal meteoric waters in the ring fracture zone (Valles Caldera); (4) deep geothermal waters of the Baca geothermal field and derivative waters in the Soda Dam and Jemez Springs area (Valles Caldera); and (5) mineralized waters near San Ysidro. Some waters display chemical and isotopic characteristics intermediate between the types listed. Data in this report will help in interpreting the geothermal potential of the Jemez Mountains region and will provide background for investigating problems in hydrology, structural geology, hydrothermal alterations, and hydrothermal solution chemistry.

  11. Evolution of the Creede Caldera and its relation to mineralization in the Creede mining district, Colorado

    Science.gov (United States)

    Barton, Paul B.; Rye, Robert O.; Bethke, Philip M.

    2000-01-01

    At 25 Ma a major epithermal silver and base metal deposit formed in rhyolitic welded tuff near Creede, Colorado. Nearly 24000 metric tons of silver, appreciable lead, and small amounts of zinc, copper, and gold, have been produced from large, crustified veins under Bachelor and Bulldog Mountains north and northwest of Creede. Prior geologic, hydrologic, and stable-isotope studies showed that ore deposition was associated with the mixing and boiling of waters from diverse sources and suggester that a critical part of the ore-forming fluid may have originated within the ancient lake and sediments of the lacustrine Creede Formation that filled the Creede caldera. Two drill holes that sampled the heretofore hidden lower half of the Creede Formation are the focus of this book. The Creede caldera formed at 26.9 Ma within a high constructional plateau of silicic ashflows that covered and were sporadically interlayed with, intermediate lavas and lahars from large stratovolcanoes. The Creede caldera lake had an inflow evaporation balance that did not permit rapid filling to create a brim-full deep lake. Thus salts were evaporatively concentrated; but, with the exception of possible gypsum, no evaporite minerals preserved. Cool springs deposited travertine as mounds and contributed to limestone interlaminations within the sediment. The lake bottom was anoxic, and bacterial reduction of sulfate led to extreme sulfur isotopic fractionation in diagenetic pyrite. The caldera gradually resurged, converting the initial equant lake into an arcuate moat. Resurgent doming, alluvial fans, lacustrine sediments, ashfalls, and lava domes displaced water, lifted the lake so that it overlapped what later became the southern edge of the mineralized are, and eventually filled the basin. At 25.1 Ma an unseen pluton intruded beneath the northen part of the Creede district and created a convecting olume that drew in brine from the Creede caldera fill, meteotic water from highlands to the north

  12. Aeromagnetic evidence for a volcanic caldera(?) complex beneath the divide of the West Antarctic Ice Sheet

    Science.gov (United States)

    Behrendt, John C.; Finn, C.A.; Blankenship, D.; Bell, R.E.

    1998-01-01

    A 1995-96 aeromagnetic survey over part of the Sinuous Ridge (SR) beneath the West Antarctic Ice Sheet (WAIS) divide shows a 70-km diameter circular pattern of 400-1200-nT anomalies suggesting one of the largest volcanic caldera(?) complexes on earth. Radar-ice-sounding (RIS) shows the northern part of this pattern overlies the SR, and extends south over the Bentley Subglacial Trench (BST). Modeled sources of all but one the caldera(?) anomalies are at the base of <1-2-km thick ice and their volcanic edifices have been glacially removed. The exception is a 700-m high, 15-km wide 'volcano' producing an 800-nT anomaly over the BST. 'Intrusion' of this 'volcano' beneath 3 km of ice probably resulted in pillow basalt rather than easily removed hyaloclastite erupted beneath thinner ice. The background area (-300 to -500-nT) surrounding the caldera(?) is possibly caused by a shallow Curie isotherm. We suggest uplift of the SR forced the advance of the WAIS.A 1995-96 aeromagnetic survey over part of the Sinuous Ridge (SR) beneath the West Antarctic Ice Sheet (WAIS) divide shows a 70-km diameter circular pattern of 400-1200-nT anomalies suggesting one of the largest volcanic caldera(?) complexes on earth. Radar-ice-sounding (RIS) shows the northern part of this pattern overlies the SR, and extends south over the Bentley Subglacial Trench (BST). Modeled sources of all but one the caldera(?) anomalies are at the base of < 1-2-km thick ice and their volcanic edifices have been glacially removed. The exception is a 700-m high, 15-km wide 'volcano' producing an 800-nT anomaly over the BST. 'Intrusion' of this 'volcano' beneath 3 km of ice probably resulted in pillow basalt rather than easily removed hyaloclastite erupted beneath thinner ice. The background area (-300 to -500-nT) surrounding the caldera(?) is possibly caused by a shallow Curie isotherm. We suggest uplift of the SR forced the advance of the WAIS.

  13. Geologic field trip guide to Mount Mazama and Crater Lake Caldera, Oregon

    Science.gov (United States)

    Bacon, Charles R.; Wright, Heather M.

    2017-08-08

    Crater Lake partly fills one of the most spectacular calderas of the world—an 8 by 10 kilometer (km) basin more than 1 km deep formed by collapse of the Mount Mazama volcano during a rapid series of explosive eruptions ~7,700 years ago. Having a maximum depth of 594 meters (m), Crater Lake is the deepest lake in the United States. Crater Lake National Park, dedicated in 1902, encompasses 645 square kilometers (km2) of pristine forested and alpine terrain, including the lake itself, and virtually all of Mount Mazama. The geology of the area was first described in detail by Diller and Patton (1902) and later by Williams (1942), whose vivid account led to international recognition of Crater Lake as the classic collapse caldera. Because of excellent preservation and access, Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. For example, the climactic ejecta are renowned among volcanologists as evidence for systematic compositional zonation within a subterranean magma chamber. Mount Mazama’s climactic eruption also is important as the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest United States, adjacent Canada, and offshore. A detailed bathymetric survey of the floor of Crater Lake in 2000 (Bacon and others, 2002) provides a unique record of postcaldera eruptions, the interplay between volcanism and filling of the lake, and sediment transport within this closed basin. Knowledge of the geology and eruptive history of the Mount Mazama edifice, enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve. In addition, many smaller volcanoes of the High Cascades beyond the limits of Mount Mazama provide information on the flux of mantle-derived magma through the region. General principles of magmatic and eruptive processes revealed by

  14. Conductive heat flux in VC-1 and the thermal regime of Valles Caldera, Jemez Mountains, New Mexico

    Science.gov (United States)

    Sass, J. H.; Morgan, Paul

    1988-06-01

    Over 5% of heat in the western United States is lost through Quaternary silicic volcanic centers, including the Valles caldera in north central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. We present new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the southwestern margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247±16 mW m-2. The only deep temperature information available is from an uncalibrated commercial log made 19 months after drilling. Gradients, derived from uncalibrated temperature logs, and conductivities are inversely correlated between 335 and 737 m, indicating a conductive thermal regime, and component heat fluxes over three depth intervals (335-539 m, 549-628 m, and 628-737 m) are in excellent agreement with each other with an average of 504±15 mW m-2. Temperature logs to 518 m depth with well-calibrated temperature sensors result in a revised heat flow of 463±15 mW m. We use shallow thermal gradient data from 75 other sites in and around the caldera to interpret the thermal regime at the VC-1 site. A critical review of published thermal conductivity data from the Valles caldera yields an average thermal conductivity of ≥1 W m-1 K-1 for the near-surface tuffaceous material, and we assume that shallow gradient values (°C km-1) are approximately numerically equal to heat flow (mW m-2). Heat loss from the caldera is asymmetrically distributed, with higher values (400 mW m-2 or higher) concentrated in the west-southwestern quadrant of the caldera. This quadrant also contains the main drainage from the caldera and the youngest volcanism associated with the caldera. We

  15. Pyroclastic deposits as a guide for reconstructing the multi-stage evolution of the Somma-Vesuvius Caldera

    Science.gov (United States)

    Cioni, Raffaello; Santacroce, Roberto; Sbrana, Alessandro

    The evolution of the Somma-Vesuvius caldera has been reconstructed based on geomorphic observations, detailed stratigraphic studies, and the distribution and facies variations of pyroclastic and epiclastic deposits produced by the past 20,000years of volcanic activity. The present caldera is a multicyclic, nested structure related to the emptying of large, shallow reservoirs during Plinian eruptions. The caldera cuts a stratovolcano whose original summit was at 1600-1900m elevation, approximately 500m north of the present crater. Four caldera-forming events have been recognized, each occurring during major Plinian eruptions (18,300 BP "Pomici di Base", 8000 BP "Mercato Pumice", 3400 BP "Avellino Pumice" and AD 79 "Pompeii Pumice"). The timing of each caldera collapse is defined by peculiar "collapse-marking" deposits, characterized by large amounts of lithic clasts from the outer margins of the magma chamber and its apophysis as well as from the shallow volcanic and sedimentary units. In proximal sites the deposits consist of coarse breccias resulting from emplacement of either dense pyroclastic flows (Pomici di Base and Pompeii eruptions) or fall layers (Avellino eruption). During each caldera collapse, the destabilization of the shallow magmatic system induced decompression of hydrothermal-magmatic and hydrothermal fluids hosted in the wall rocks. This process, and the magma-ground water interaction triggered by the fracturing of the thick Mesozoic carbonate basement hosting the aquifer system, strongly enhanced the explosivity of the eruptions.

  16. Time scales of magma storage and differentiation of voluminous high-silica rhyolites at Yellowstone caldera, Wyoming

    Science.gov (United States)

    Vazquez, Jorge; Reid, Mary

    2002-09-01

    Ion microprobe dating of zircons from post-collapse rhyolites at Yellowstone caldera reveals the time scales of crystallization and storage of silicic magma in a differentiating magma reservoir, the role of recycling of crystals from the caldera-forming magmatism, and the timing and efficacy of crystal-melt separation. Zircons in the voluminous ( 900 km3) Central Plateau Member lavas, which progressively erupted between 70 to 160 ka, yield 238U-230Th disequilibrium ages dominantly spanning the range from those of their respective eruptions to 200 ka mean zircon ages range to ca. 60,000 years before eruption. When considered together with the trace element and Sr- and Nd-isotope compositions of their host melts, the age distributions of the CPM zircons show that the rhyolites are cogenetic and differentiated tens of thousands of years prior to eruption from an evolving magma reservoir. Thus, the post-caldera CPM rhyolites were not erupted from a long-standing body of rhyolitic magma left over from the caldera-forming eruption, nor do they represent significant remobilization of the plutonic roots of the caldera. Rather, the CPM magma was generated and differentiated by episodes of effective crystal-melt separation at 200 and 125 ka and, sustained by thermal inputs, stored for timescales on par with estimates for other voluminous caldera-related rhyolites.

  17. Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow.

    Science.gov (United States)

    Gudmundsson, Magnús T; Jónsdóttir, Kristín; Hooper, Andrew; Holohan, Eoghan P; Halldórsson, Sæmundur A; Ófeigsson, Benedikt G; Cesca, Simone; Vogfjörd, Kristín S; Sigmundsson, Freysteinn; Högnadóttir, Thórdís; Einarsson, Páll; Sigmarsson, Olgeir; Jarosch, Alexander H; Jónasson, Kristján; Magnússon, Eyjólfur; Hreinsdóttir, Sigrún; Bagnardi, Marco; Parks, Michelle M; Hjörleifsdóttir, Vala; Pálsson, Finnur; Walter, Thomas R; Schöpfer, Martin P J; Heimann, Sebastian; Reynolds, Hannah I; Dumont, Stéphanie; Bali, Eniko; Gudfinnsson, Gudmundur H; Dahm, Torsten; Roberts, Matthew J; Hensch, Martin; Belart, Joaquín M C; Spaans, Karsten; Jakobsson, Sigurdur; Gudmundsson, Gunnar B; Fridriksdóttir, Hildur M; Drouin, Vincent; Dürig, Tobias; Aðalgeirsdóttir, Guðfinna; Riishuus, Morten S; Pedersen, Gro B M; van Boeckel, Tayo; Oddsson, Björn; Pfeffer, Melissa A; Barsotti, Sara; Bergsson, Baldur; Donovan, Amy; Burton, Mike R; Aiuppa, Alessandro

    2016-07-15

    Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption. We use multiparameter geophysical and geochemical data to show that the 110-square-kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, near-exponential decline of both collapse rate and the intensity of the 180-day-long eruption. Copyright © 2016, American Association for the Advancement of Science.

  18. Interpreting compositional zonation of the Zaragoza ignimbrite from Los Humeros caldera, Central Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco-Nunez, Gerardo [Centro de Geociencias, UNAM, Campus Juriquilla, Queretaro, Qro. (Mexico); McCurry, Michael [Department of Geology, Idaho State University, Pocatello, ID (United States); Branney, Michael J [Department of Geology, University of Leicester, Leicester (United Kingdom)

    2008-10-01

    Compositional zonation in ignimbrites is relatively common, and is often inferred to record gradual withdrawal by an eruption of a density-stratified magma chamber (with silicic magma towards the top and more dense, mafic magma at the bottom). We show that this model does not match observations at the ca. 0.1 Ma Zaragoza ignimbrite from Los Humeros caldera in central Mexico. Detailed petrologic studies reveal a more complex scenario: the ignimbrite exhibits a 'double' vertical zonation based on the compositions of pumice lapilli. We present evidence for mingling and limited mixing occurred during or immediately before the caldera-forming eruption. One possibility to explain the observations is that the ignimbrite eruption occurred in response to intrusion of a hybridized andesitic magma into a rhyodacitic magma chamber.

  19. The timescales of magmatic processes prior to a caldera-forming eruption

    OpenAIRE

    Fabbro, Gareth Nicholas

    2014-01-01

    Large, explosive, caldera-forming eruptions are amongst the most destructive phenomena on the planet, but the processes that allow the large bodies of crystal-poor silicic magma that feed them to assemble in the shallow crust are still poorly understood. Of particular interest is the timescales over which these reservoirs exist prior to eruption. Long storage times—up to 105 y—have previously been estimated using the repose times between eruptions and radiometric dating of crystals found with...

  20. Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.

    Science.gov (United States)

    Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

    2012-02-01

    Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.

  1. Lithium enrichment in intracontinental rhyolite magmas leads to Li deposits in caldera basins

    OpenAIRE

    Benson, Thomas R.; Coble, Matthew A.; Rytuba, James J.; Mahood, Gail A.

    2017-01-01

    The omnipresence of lithium-ion batteries in mobile electronics, and hybrid and electric vehicles necessitates discovery of new lithium resources to meet rising demand and to diversify the global lithium supply chain. Here we demonstrate that lake sediments preserved within intracontinental rhyolitic calderas formed on eruption and weathering of lithium-enriched magmas have the potential to host large lithium clay deposits. We compare lithium concentrations of magmas formed in a variety of te...

  2. The hydrothermal outflow plume of Valles Caldera, New Mexico, and a comparison with other outflow plumes

    Science.gov (United States)

    Goff, Fraser; Shevenell, Lisa; Gardner, Jamie N.; Vuataz, Francois-D.; Grigsby, Charles O.

    1988-06-01

    Stratigraphic, temperature gradient, hydrogeochemical, and hydrologic data have been integrated with geologic data from previous studies to show the structural configuration of the Valles caldera hydrothermal ouflow plume. Hydrologic data suggest that 25-50% of the discharge of the Valles outflow is confined to the Jemez fault zone, which predates caldera formation. Thermal gradient data from bores penetrating the plume show that shallow gradients are highest in the vicinity of the Jemez fault zone (up to 190°C/km). Shallow heat flow above the hydrothermal plume is as high as 500 mW m-2 near core hole VC-1 (Jemez fault zone) to 200 mW m-2 at Fenton Hill (Jemez Plateau). Chemical and isotopic data indicate that two source reservoirs within the caldera (Redondo Creek and Sulphur Springs reservoirs) are parents to mixed fluids flowing in the hydrothermal plume. However, isotopic data, borehole data, basic geology, and inverse relations between temperature and chloride content at major hot springs indicate that no single reservoir fluid and no single diluting fluid are involved in mixing. The Valles caldera hydrothermal plume is structurally dominated by lateral flow through a belt of vertical conduits (Jemez fault zone) that strike away from the source reservoir. Stratigraphically confined flow is present but dispersed over a wide area in relatively impermeable rocks. The Valles configuration is contrasted with the configuration of the hydrothermal plume at Roosevelt Hot Springs, which is dominated by lateral flow through a near-surface, widespread, permeable aquifer. Data from 12 other representative geothermal systems show that outflow plumes occur in a variety of magmatic and tectonic settings, have varying reservoir compositions, and have different flow characteristics. Although temperature reversals are commonly observed in wells penetrating outflow plumes, reversals are not observed in all plumes. Less information is available on the absolute age of

  3. Ecology of Coyotes on the Valles Caldera National Preserve, New Mexico: Implications for Elk Calf Recruitment

    OpenAIRE

    Gifford, Suzanne J.

    2013-01-01

    Valles Caldera National Preserve (VCNP) managers were concerned about low elk recruitment observed at the same time as an apparent increase in sightings of coyotes and observations of coyote predation on elk calves. The goal of this study was to describe coyotes’ ecological interactions with elk, particularly coyote diet and movements on the Valle Grande, a large grassland meadow in the southeastern portion of the VCNP. We examined coyote diet by quantifying undigested remains of food item...

  4. Post-caldera volcanism: In situ measurement of U-Pb age and oxygen isotope ratio in Pleistocene zircons from Yellowstone caldera

    Science.gov (United States)

    Bindeman, I.N.; Valley, J.W.; Wooden, J.L.; Persing, H.M.

    2001-01-01

    The Yellowstone Plateau volcanic field, the site of some of the largest known silicic volcanic eruptions, is the present location of NE-migrating hotspot volcanic activity. Most volcanic rocks in the Yellowstone caldera (0.6 Ma), which formed in response to the climactic eruption of 1000 km3 of Lava Creek Tuff (LCT), have unusually low oxygen isotope ratios. Ion microprobe analysis of both U-Pb age and ??18O in zircons from these low-??18O lavas reveals evidence of complex inheritance and remelting. A majority of analyzed zircons from low-??18O lavas erupted inside the Yellowstone caldera have cores that range in age from 2.4 to 0.7 Ma, significantly older than their eruption ages (0.5-0.4 Ma). These ages and the high-??18O cores indicate that these lavas are largely derived from nearly total remelting of normal-??18O Huckleberry Ridge Tuff (HRT) and other pre-LCT volcanic rocks. A post-HRT low-??18O lava shows similar inheritance of HRT-age zircons. The recycling of volcanic rocks by shallow remelting can change the water content and eruptive potential of magma. This newly proposed mechanism of intracaldera volcanism is best studied by combining in situ analysis of oxygen and U-Pb isotope ratios of individual crystals. ?? 2001 Elsevier Science B.V. All rights reserved.

  5. Post-caldera volcanism: in situ measurement of U-Pb age and oxygen isotope ratio in Pleistocene zircons from Yellowstone caldera

    Science.gov (United States)

    Bindeman, Ilya N.; Valley, John W.; Wooden, J. L.; Persing, Harold M.

    2001-07-01

    The Yellowstone Plateau volcanic field, the site of some of the largest known silicic volcanic eruptions, is the present location of NE-migrating hotspot volcanic activity. Most volcanic rocks in the Yellowstone caldera (0.6 Ma), which formed in response to the climactic eruption of 1000 km3 of Lava Creek Tuff (LCT), have unusually low oxygen isotope ratios. Ion microprobe analysis of both U-Pb age and δ18O in zircons from these low-δ18O lavas reveals evidence of complex inheritance and remelting. A majority of analyzed zircons from low-δ18O lavas erupted inside the Yellowstone caldera have cores that range in age from 2.4 to 0.7 Ma, significantly older than their eruption ages (0.5-0.4 Ma). These ages and the high-δ18O cores indicate that these lavas are largely derived from nearly total remelting of normal-δ18O Huckleberry Ridge Tuff (HRT) and other pre-LCT volcanic rocks. A post-HRT low-δ18O lava shows similar inheritance of HRT-age zircons. The recycling of volcanic rocks by shallow remelting can change the water content and eruptive potential of magma. This newly proposed mechanism of intracaldera volcanism is best studied by combining in situ analysis of oxygen and U-Pb isotope ratios of individual crystals.

  6. Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

    Science.gov (United States)

    Hutnak, M.; Hurwitz, S.; Ingebritsen, S.E.; Hsieh, P.A.

    2009-01-01

    Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2O-CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

  7. Source and dynamics of a volcanic caldera unrest: Campi Flegrei, 1983-84.

    Science.gov (United States)

    De Siena, Luca; Chiodini, Giovanni; Vilardo, Giuseppe; Del Pezzo, Edoardo; Castellano, Mario; Colombelli, Simona; Tisato, Nicola; Ventura, Guido

    2017-08-14

    Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi Flegrei area (Southern Italy) during the 1983-1984 unrest have revealed a 4-4.5 km deep NW-SE striking aseismic zone of high attenuation offshore Pozzuoli. The lateral features and the principal axis of the attenuation anomaly correspond to the main source of ground uplift during the unrest. Seismic swarms correlate in space and time with fluid injections from a deep hot source, inferred to represent geochemical and temperature variations at Solfatara. These swarms struck a high-attenuation 3-4 km deep reservoir of supercritical fluids under Pozzuoli and migrated towards a shallower aseismic deformation source under Solfatara. The reservoir became aseismic for two months just after the main seismic swarm (April 1, 1984) due to a SE-to-NW directed input from the high-attenuation domain, possibly a dyke emplacement. The unrest ended after fluids migrated from Pozzuoli to the location of the last caldera eruption (Mt. Nuovo, 1538 AD). The results show that the high attenuation domain controls the largest monitored seismic, deformation, and geochemical unrest at the caldera.

  8. Modelling ground movements at Campi Flegrei caldera (Italy): the role of the shallow geothermal system

    Science.gov (United States)

    Troiano, Antonio; Giulia di Giuseppe, Maria; Petrillo, Zaccaria; Troise, Claudia; de Natale, Giuseppe

    2010-05-01

    Campi Flegrei caldera is characterized by large ground movements, well known since Roman times. Superimposed to a general secular subsidence occurring at a rate of 1.5-2.0 cm/year, an episode of sharp uplift is in progress since 1969, with peak rates up to 1 m/year (in 1982-1984), similar to another episode which culminated with the 1538 eruption. Peak uplift episodes are often followed by some amount of subsidence, which prevent a simple interpretation in terms of purely magmatic inflation phenomena. Such up and down episodes of ground deformations are rather common at large calderas, like in Yellowstone (USA), Long Valley (USA), etc. Here we propose an interpretation based on a mixed mechanical-fluid-dynamical model, in which part of the uplift is generated by increase of water pressure in the shallow geothermal system, as a response to rapid inflow of magmatic fluids exsolved from a deeper magma chamber. We use the program THOUGH2 to model the changes of temperature and pressure in the geothermal system due to the magmatic fluids inflow. Changes in pressure in the caldera volume are then used to compute ground deformations. This way, a theoretical time evolution of ground deformation has been obtained, which compares well with the observed one, if appropriate values of permeability are used. We discuss the implication of such a model for eruption forecast purposes, and the extent at which the required values of permeability can be really representative of the real medium.

  9. Radon and helium in soil gases at Cañadas caldera, Tenerife, Canary Islands, Spain

    Science.gov (United States)

    Hernández, Pedro; Pérez, Nemesio; Salazar, José; Reimer, Mike; Notsu, Kenji; Wakita, Hiroshi

    2004-03-01

    The spatial distribution of soil radon was investigated at Cañadas caldera, Tenerife, in two surveys carried out in the summers of 1992 and 1995 by using α-particle-sensitive cellulose nitrate films (Track-Etch) and emanometry, respectively. Soil helium was studied at several transects crossing different structural features of the area. Radon concentration measured by Track-Etch ranged from 1.0 to 1990 pCi/l while that measured by emanometry ranged from 0.1 to 618 pCi/l. Soil helium concentration varied from 5250 to 15 560 ppb with an average value of 6197 ppb. The spatial distribution of soil radon correlates quite closely with structural features (fractures, emission centers, etc.), where the main geothermal manifestations (fumaroles, steam ground and high subsurface temperature and gas contents) also occur. Areas showing high soil Rn concentrations occur at the summit of Teide, Roques de Garcı´a, caldera rim and south and east off side of the caldera. High soil helium anomalies correlate well spatially with those of radon, especially at the summit of Teide where relatively high 3He/ 4He isotopic ratios occur, suggesting a deep contribution for these emanations. Data indicate that radon and helium are supplied mostly from a deep source, with a minor contribution from U- and Th-rich shallow rocks and soils.

  10. Petrologic evolution of divergent peralkaline magmas from the Silent Canyon caldera complex, southwestern Nevada volcanic field

    Science.gov (United States)

    Sawyer, D.A.; Sargent, K.A.

    1989-01-01

    The Silent Canyon volcanic center consists of a buried Miocene peralkaline caldera complex and outlying peralkaline lava domes. Two widespread ash flow sheets, the Tub Spring and overlying Grouse Canyon members of the Miocene Belted Range Tuff, were erupted from the caldera complex and have volumes of 60-100 km3 and 200 km3, respectively. Eruption of the ash flows was preceded by widespread extrusion of precaldera comendite domes and was followed by extrusion of postcollapse peralkaline lavas and tuffs within and outside the caldera complex. Lava flows and tuffs were also deposited between the two major ash flow sheets. Rocks of the Silent Canyon center vary significantly in silica content and peralkalinity. Weakly peralkaline silicic comendites (PI 1.0-1.1) are the most abundant precaldera lavas. Postcollapse lavas range from trachyte to silicic comendite; some have anomalous light rare earth element (LREE) enrichments. Silent Canyon rocks follow a common petrologic evolution from trachyte to low-silica comendite; above 73% SiO2, compositions of the moderately peralkaline comendites diverge from those of the weakly peralkaline silicic comendites. The development of divergent peralkaline magmas, toward both pantelleritic and weakly peralkaline compositions, is unusual in a single volcanic center. -from Authors

  11. Proceedings of the symposium on the Long Valley Caldera: A pre-drilling data review

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, N.E. (ed.)

    1987-09-01

    This proceedings volume contains papers or abstracts of papers presented at a two-day symposium held at the Lawrence Berkeley Laboratory (LBL) on 17 and 18 March 1987. Speakers presented a large body of new scientific results and geologic-hydrogeoloic interpretations for the Long Valley caldera. The talks and the discussions that followed focused on concepts and models for the present-day magmatic-hydrothermal system. Speakers at the symposium also addressed the topic of where to site future scientific drill holes in the caldera. Deep scientific drilling projects such as those being contemplated by the DOE Division of Geothermal Technology (DGT), under the Magma Energy Program, and by the DOE Office of Energy Research, Division of Engineering and Geosciences (DEG), along with the USGS and NSE, under the Continental Scientific Drilling Program (CSDP), will be major and expensive national undertakings. DOE/DEG is sponsoring a program of relatively shallow coreholes in the caldera, and DOE/DGT is considering the initiation of a multiphase program to drill a deep hole for geophysical observations and sampling of the ''near magmatic'' environment as early as FY 1988, depending on the DOE budget. Separate abstracts have been prepared for the individual papers.

  12. Mechanisms of crustal uplift and subsidence at the Yellowstone caldera, Wyoming

    Science.gov (United States)

    Dzurisin, D.; Yamashita, K.M.; Kleinman, J.W.

    1994-01-01

    Leveling surveys in 1923, 1976, and each year from 1983 to 1993 have shown that the east-central part of the Yellowstone caldera, near the base of the Sour Creek resurgent dome, rose at an average rate of 14??1 mm/year from 1923 to 1976 and 22??1 mm/year from 1976 to 1984. In contrast, no detectable movement occurred in the same area from 1984 to 1985 (-2??5 mm/year), and from 1985 to 1993 the area subsided at an average rate of 19??1 mm/year. We conclude that uplift from 1923 to 1984 was caused by: (1) pressurization of the deep hydrothermal system by fluids released from a crystallizing body of rhyolite magma beneath the caldera, then trapped beneath a self-sealed zone near the base of the hydrothermal system; and (2) aseismic intrusions of magma into the lower part of the sub-caldera magma body. Subsidence since 1985 is attributed to: (1) depressurization and fluid loss from the deep hydrothermal system, and (2) sagging of the caldera floor in response to regional crustal extension. Future intrusions might trigger renewed eruptive activity at Yellowstone, but most intrusions at large silicic calderas seem to be accommodated without eruptions. Overpressurization of the deep hydrothermal system could conceivably result in a phreatic or phreatomagmatic eruption, but this hazard is mitigated by episodic rupturing of the self-sealed zone during shallow earthquake swarms. Historical ground movements, although rapid by most geologic standards, seem to be typical of inter-eruption periods at large, mature, silicic magma systems like Yellowstone. The greatest short-term hazards posed by continuing unrest in the Yellowstone region are: (1) moderate to large earthquakes (magnitude 5.5-7.5), with a recurrence interval of a few decdes; and (2) small hydrothermal explosions, most of which affect only a small area (<0.01 km2), with a recurrence interval of a few years. ?? 1994 Springer-Verlag.

  13. Imaging hydrothermal systems at Furnas caldera (Azores, Portugal): Insights from Audio-Magnetotelluric data

    Science.gov (United States)

    Hogg, Colin; Kiyan, Duygu; Rath, Volker; Byrdina, Svetlana; Vandemeulebrouck, Jean; Silva, Catarina; Viveiros, Maria FB; Ferreira, Teresa

    2016-04-01

    The Furnas volcano is the eastern-most of the three active central volcanoes of Sao Miguel Island. The main caldera formed about 30 ka BP, followed by a younger eruption at 10-12 ka BP, which forms the steep topography of more than 200 m in the measuring area. It contains several very young eruptive centers, and a shallow caldera lake. Tectonic features of varying directions have been identified in the Caldera and its vicinity. In the northern part of the caldera, containing the fumarole field of Caldeiras das Furnas, a detailed map of surface CO2 emissions was recently made available. In 2015, a pilot survey of 13 AudioMagnetoTelluric soundings (AMT) and Electrical Resistivity Tomography (ERT) data were collected along two profiles in the eastern part of Furnas caldera in order to image the electrical conductivity of the subsurface. The data quality achieved by both techniques is extraordinary and first results indicate a general correlation between regions of elevated conductivity and the mapped surface CO2 emissions, suggesting that they may both be caused by the presence hydrothermal fluids. Tensor decomposition analysis using the Groom-Bailey approach produce a generalised geo-electric strike direction, 72deg East of North, for the AMT data compared to the surface geological strike derived from the major mapped fault crossing the profiles of 105deg. An analysis of the real induction arrows at certain frequencies (at depths greater than 350 m) infer that an extended conductor at depth does not exactly correspond to the degassing structures at the surface and extends outside the area of investigation. The geometry of the most conductive regions with electrical conductivities less then1 Ώm found at various depths differ from what was expected from earlier geologic and tectonic studies and possibly may not be directly related to the mapped fault systems at the surface. On the eastern profile, which seemed to be more appropriate for 2-D modelling with 72deg strike

  14. Geochemical constraints on the link between volcanism and plutonism at the Yunshan caldera complex, SE China

    Science.gov (United States)

    Yan, Lili; He, Zhenyu; Beier, Christoph; Klemd, Reiner

    2018-01-01

    The Yunshan caldera complex is part of a larger scale, ca. 2000-km-long volcanic-plutonic complex belt in the coastal region of SE China. The volcanic rocks in the caldera complex are characterized by high-silica peraluminous and peralkaline rhyolites associated with an intracaldera porphyritic quartz monzonite pluton. In this study, we present zircon U-Pb, Hf and stable O isotopes along with geochemical data of both volcanic and plutonic rocks to evaluate the potential petrogenetic link between volcanism and plutonism in the Yunshan caldera complex. SHRIMP zircon U-Pb geochronology of both volcanic and plutonic rocks yields almost identical ages ranging from 95.6 to 93.1 Ma. The peraluminous and peralkaline rhyolites show negative anomalies of Sr, P, Ti and Ba and to a lesser extent negative Nb and Ta anomalies, along with positive Rb anomalies and `seagull-like' rare earth element (REE) patterns with negative Eu anomalies and low (La/Yb)N ratios. The intracaldera porphyritic quartz monzonite displays minor negative Rb, Nb, Ta, Sr, P and Ti anomalies and a positive Ba anomaly with REE patterns characterized by relatively high (La/Yb)N ratios and lack significant Eu anomalies. The peraluminous and peralkaline rhyolites and the porphyritic quartz monzonite exhibit consistent ɛ Nd( t) of - 3.7 to - 2.2 and display zircon ɛ Hf( t) values of - 2.1 to 3.7. They further have similar, mantle-like, zircon oxygen isotopic compositions (δ18OVSMOW mainly = 4.63 to 5.76‰). We interpret these observations to be in agreement with a crystal mush model in which the parental magma of the volcanic and plutonic rocks of the Yunshan caldera complex was likely produced by interaction of asthenosphere melts with subduction-influenced enriched mantle wedge. The peralkaline rhyolites are interpreted to represent the most differentiated magma that has subsequently experienced significant fluid-melt interactions, whereas the porphyritic quartz monzonite may be representative of the

  15. Eruptive history, geochronology, and post-eruption structural evolution of the late Eocene Hall Creek Caldera, Toiyabe Range, Nevada

    Science.gov (United States)

    Colgan, Joseph P.; Henry, Christopher D.

    2017-02-24

    The magmatic, tectonic, and topographic evolution of what is now the northern Great Basin remains controversial, notably the temporal and spatial relation between magmatism and extensional faulting. This controversy is exemplified in the northern Toiyabe Range of central Nevada, where previous geologic mapping suggested the presence of a caldera that sourced the late Eocene (34.0 mega-annum [Ma]) tuff of Hall Creek. This region was also inferred to be the locus of large-magnitude middle Tertiary extension (more than 100 percent strain) localized along the Bernd Canyon detachment fault, and to be the approximate location of a middle Tertiary paleodivide that separated east and west-draining paleovalleys. Geologic mapping, 40Ar/39Ar dating, and geochemical analyses document the geologic history and extent of the Hall Creek caldera, define the regional paleotopography at the time it formed, and clarify the timing and kinematics of post-caldera extensional faulting. During and after late Eocene volcanism, the northern Toiyabe Range was characterized by an east-west trending ridge in the area of present-day Mount Callaghan, probably localized along a Mesozoic anticline. Andesite lava flows erupted around 35–34 Ma ponded hundreds of meters thick in the erosional low areas surrounding this structural high, particularly in the Simpson Park Mountains. The Hall Creek caldera formed ca. 34.0 Ma during eruption of the approximately 400 cubic kilometers (km3) tuff of Hall Creek, a moderately crystal-rich rhyolite (71–77 percent SiO2) ash-flow tuff. Caldera collapse was piston-like with an intact floor block, and the caldera filled with thick (approximately 2,600 meters) intracaldera tuff and interbedded breccia lenses shed from the caldera walls. The most extensive exposed megabreccia deposits are concentrated on or close to the caldera floor in the southwestern part of the caldera. Both silicic and intermediate post-caldera lavas were locally erupted within 400 thousand

  16. Conductive heat flux in VC-1 and the thermal regime of Valles caldera, Jemez Mountains, New Mexico ( USA).

    Science.gov (United States)

    Sass, J.H.; Morgan, P.

    1988-01-01

    Over 5% of heat in the western USA is lost through Quaternary silicic volcanic centers, including the Valles caldera in N central New Mexico. These centers are the sites of major hydrothermal activity and upper crustal metamorphism, metasomatism, and mineralization, producing associated geothermal resources. Presents new heat flow data from Valles caldera core hole 1 (VC-1), drilled in the SW margin of the Valles caldera. Thermal conductivities were measured on 55 segments of core from VC-1, waxed and wrapped to preserve fluids. These values were combined with temperature gradient data to calculate heat flow. Above 335 m, which is probably unsaturated, heat flow is 247 + or - 16 mW m-2. Inteprets the shallow thermal gradient data and the thermal regime at VC-1 to indicate a long-lived hydrothermal (and magmatic) system in the southwestern Valles caldera that has been maintained through the generation of shallow magma bodies during the long postcollapse history of the caldera. High heat flow at the VC-1 site is interpreted to result from hot water circulating below the base of the core hole, and we attribute the lower heat flow in the unsaturated zone is attributed to hydrologic recharge. -from Authors

  17. Electromagnetic imaging of the deep Campi Flegrei caldera structure (Southern Italy)

    Science.gov (United States)

    Giulia Di Giuseppe, Maria; Isaia, Roberto; Patella, Domenico; Piochi, Monica; Troiano, Antonio

    2017-04-01

    The Campi Flegrei caldera (CFc) is the most hazardous volcano in Europe. Enormous investigative efforts have been done aimed to share its inner structure and to understand its unrest dynamics, making the CFc one of the main subjects of interest of modern volcanology. Due to the destructive potential and the active geothermal system, the CFc geological structures have been investigated through many different methodologies. A key role belongs to the applied geophysics that allows to gain knowledge about the volcanic setting and consequently to understand the dynamics of this active caldera system. So far, the main CFc structures have been not yet clearly defined. The strong heterogeneity of the territory associated to the composite coastal morphology and the extreme urbanization represent a major obstacle to apply the geophysical techniques. Therefore the geometry and configuration of the CFc plumbing system are still largely undefined, although seismic surveys nowadays detected findings of melt-bearing rocks, at least locally. Here a deep electromagnetic (EM) imaging the CFc is presented. A Magnetotelluric (MT) profile has been carried out across a 12 km-long transect, ideally intersecting the main recent volcano-tectonic structures. The peculiar sensitivity to subsurface fluids and melts, associated with huge electric conductivity contrasts, make the MT particularly well suited to be applied in active volcanic settings. The obtained results highlight the buried structures down to 10 km of depth providing an interpretative key into the overall caldera dynamics. In particular, the deep magmatic source is revealed, as well as the main ascent pathway of magmatic fluids and the related structures which critically contributing to the shallower-level of deformation at CFc.

  18. Ignimbrite Analyses of Batur Caldera, Bali, based on 14C Dating

    Directory of Open Access Journals (Sweden)

    Igan S. Sutawidjaja

    2014-06-01

    Full Text Available http://dx.doi.org/10.17014/ijog.vol4no3.20094The Batur Caldera, in the northeastern part of Bali Island, is an elliptical collapse structure 13.8 by 10 km in size and another circular composite collapse structure with a diameter of 7.5 km in its centre. Two stages of the collapse were interrupted by silicic andesite lavas and domes. The first collapse was initiated by the eruption of about 84 km3 of the dacitic "Ubud Ignimbrite", about 29,300 years B.P., which caused a steep-walled depression about 1 km deep. The second ignimbrite was erupted from a large crater about the present lake, and it  produced about 19 km3 of a similar voluminous dacitic ignimbrite, called the "Gunungkawi Ignimbrite" about 20,150 years B.P. This second eruption trig- gered a second collapse, which created the central circular caldera, and formed a basin structure. Both the Ubud and Gunungkawi Ignimbrites consist of a similar dacitic composition, white to red (the most abundant nearly 90 % and dark grey to black dacitic pumice clasts. The large clasts, up to 20 cm in diameter, are in the non-welded ignimbrite, particularly in the upper part of the Gunungkawi Ignimbrite. The intracaldera ignimbrite, called the "Batur Ignimbrite" about 5 km3  in volume is a densely welded ignimbrite and generally shows typical welded features. The ignimbrite comprises at least five different flow units, separated by thin (15 - 40 cm welded pumiceous airfall deposits, with flattened pumice clasts. Another large eruption occurred about 5,500 years B.P., producing around 0.09 km3  andesitic ignimbrite. This was initiated by phreatomagmatic eruptions, indicated by thick phreatomagmatic and surge deposits, underlying the ignimbrite. The caldera and its vicinity are partly filled, and variably mantled by later eruptive products of dacitic and andesitic phreatomagmatic and airfall deposits.  

  19. The lifecycle of caldera-forming volcanoes in the Main Ethiopian Rift: insights from Aluto volcano

    Science.gov (United States)

    Mather, T. A.; Hutchison, W.; Yirgu, G.; Biggs, J.; Cohen, B. E.; Barfod, D. N.; Lewi, E.; Pyle, D. M.

    2015-12-01

    The silicic peralkaline volcanoes of the East African Rift are some of the least studied and yet potentially most dangerous volcanoes in the world. We present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in the Main Ethiopian Rift, using new constraints from fieldwork, remote sensing, 40Ar/39Ar geochronology and geochemistry. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at ca. 300 ka developing a ~42 km2 collapse structure. After a hiatus of ~250 kyr, a phase of post-caldera volcanism began. Since ca. 60 ka, highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. The age of the youngest volcanism is not well known. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (>80 %) of typical 'rift basalt'. Based on the field stratigraphy and the number, style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes between 1-100 × 106 m3. Comparisons with other caldera volcanoes in this section of the rift suggest that there may be parallels between Aluto's behaviour and that of other volcanic centres, both in terms of the volcanic 'lifecycle', and broad timings of caldera collapse events.

  20. New proximal tephras at Somma-Vesuvius: evidences of a pre-caldera, large (?) explosive eruption

    Science.gov (United States)

    Sparice, Domenico; Scarpati, Claudio; Mazzeo, Fabio Carmine; Petrosino, Paola; Arienzo, Ilenia; Gisbert, Guillem; Petrelli, Maurizio

    2017-04-01

    A 5 m thick pyroclastic and volcaniclastic sequence, never reported before, comprising a pumice fall deposit has been recognized in a disused quarry near Pollena Trocchia, on the NW slope of Somma-Vesuvius. It is composed of three stratigraphic units: a pumice fall deposit that underlies a pyroclastic density current deposit; they are overlain by a volcaniclastic unit emplaced during a quiescent period of the volcano. The pyroclastic deposits are separated by a horizon of reworked material indicating the emplacement from two distinct eruptive events. The pumice fall deposit has been subject of a detailed investigation. It consists of an ash bed overlaid by a roughly stratified pumice fall layer. The presence of ballistic clasts indicates the proximal nature of this deposit and its stratigraphic position below the Pomici di Base (22 ka) Plinian deposit allows constraining its age to the pre-caldera period (22-39 ky) of activity of Somma-Vesuvius. Samples have been collected in order to perform sedimentological (grain size and componentry), geochemical and isotopic analyses. Samples range from moderately to poorly sorted and show a trachytic composition. The comparison with literature data of compatible deposits vented from Somma-Vesuvius (Schiava, Taurano and Codola eruptions as well as borehole data) allows excluding any correlation with already known Vesuvian products suggesting that the analysed products are ascribable to a new, pre-caldera, explosive eruption. We name this new event ;Carcavone eruption;. Based on thickness, maximum lithic clasts and orientation of impact sags, showing a provenance from SE, we envisage the emplacement from a Plinian style eruption vented in the northern sector of the current caldera.

  1. Quartz phenocrysts preserve volcanic stresses at Long Valley and Yellowstone calderas

    Science.gov (United States)

    Befus, K. S.; Leonhardi, T. C.; Manga, M.; Tamura, N.; Stan, C. V.

    2016-12-01

    Magmatic processes and eruptions are the consequence of stresses active in volcanic environments. Few techniques are presently available to quantify those stresses because they operate in subsurface and/or hazardous environments, and thus new techniques are needed to advance our understanding of key processes. Here, we provide a dataset of volcanic stresses that were imparted to quartz crystals that traveled through, and were hosted within, pyroclastic and effusive eruptions from Long Valley and Yellowstone calderas. We measured crystal lattice deformation with submicron spatial resolution using the synchrotron X-ray microdiffraction beamline (12.3.2) at the Advanced Light Source, Lawrence Berkeley National Laboratory. Quartz from all units produces diffraction patterns with residual strains locked in the crystal lattice. We used Hooke's Law and the stiffness constants of quartz to calculate the stresses that caused the preserved residual strains. At Long Valley caldera, quartz preserves stresses of 187±80 MPa within pumice clasts in the F1 fall unit of the Bishop Tuff, and preserves stresses of 120±45 MPa from the Bishop Tuff welded ignimbrite. At Yellowstone caldera quartz preserves stresses of 115±30 and 140±60 MPa within pumices from the basal fall units of the Mesa Falls Tuff and the Tuff of Bluff Point, respectively. Quartz from near-vent and flow-front samples from Summit Lake lava flow preserves stresses up to 130 MPa, and show no variation with distance travelled. We believe that subsurface processes cause the measured residual stresses, but it remains unclear if they are relicts of fragmentation or from the magma chamber. The residual stresses from both Long Valley and Yellowstone samples roughly correlate to lithostatic pressures estimated for the respective pre-eruption magma storage depths. It is possible that residual stress in quartz provides a new geobarometer for crystallization pressure. Moving forward, we will continue to perform analyses and

  2. A fluid-driven earthquake swarm on the margin of the Yellowstone caldera

    Science.gov (United States)

    Shelly, David R.; Hill, David P.; Massin, Frederick; Farrell, Jamie; Smith, Robert B.; Taira, Taka'aki

    2013-01-01

    Over the past several decades, the Yellowstone caldera has experienced frequent earthquake swarms and repeated cycles of uplift and subsidence, reflecting dynamic volcanic and tectonic processes. Here, we examine the detailed spatial-temporal evolution of the 2010 Madison Plateau swarm, which occurred near the northwest boundary of the Yellowstone caldera. To fully explore the evolution of the swarm, we integrated procedures for seismic waveform-based earthquake detection with precise double-difference relative relocation. Using cross-correlation of continuous seismic data and waveform templates constructed from cataloged events, we detected and precisely located 8710 earthquakes during the three-week swarm, nearly four times the number of events included in the standard catalog. This high-resolution analysis reveals distinct migration of earthquake activity over the course of the swarm. The swarm initiated abruptly on January 17, 2010 at about 10 km depth and expanded dramatically outward (both shallower and deeper) over time, primarily along a NNW-striking, ~55º ENE-dipping structure. To explain these characteristics, we hypothesize that the swarm was triggered by the rupture of a zone of confined high-pressure aqueous fluids into a pre-existing crustal fault system, prompting release of accumulated stress. The high-pressure fluid injection may have been accommodated by hybrid shear and dilatational failure, as is commonly observed in exhumed hydrothermally affected fault zones. This process has likely occurred repeatedly in Yellowstone as aqueous fluids exsolved from magma migrate into the brittle crust, and it may be a key element in the observed cycles of caldera uplift and subsidence.

  3. Survey and assessment of post volcanic activities of a young caldera lake, Lake Cuicocha, Ecuador

    Directory of Open Access Journals (Sweden)

    G. Gunkel

    2009-05-01

    Full Text Available Cuicocha is a young volcano adjacent to the inactive Pleistocene Cotacachi volcano complex, located in the western cordilleras of the Ecuadorian Andes. A series of eruptions with intensive ash emission and collapse of the caldera occurred around 4500–3000 y BP. A crater 3.2 km in diameter and a maximum depth of 450 m was formed. Further eruptions of the volcano occurred 1300 y BP and formed four smaller domes within the caldera. Over the last few hundred years, a caldera lake has developed, with a maximum depth of 148 m. The lake water is characterized by sodium carbonate with elevated concentrations of manganese, calcium and chloride. Nowadays, an emission of gases, mainly CO2, and an input of warm spring water occur in Lake Cuicocha. The zone of high activity is in the western basin of the lake at a depth of 78 m, and continuous gas emissions with sediment resuspension were observed using sonar. In the hypolimnion of the lake, CO2 accumulation occurs up to 0.2% saturation, but the risk of a limnic eruption can be excluded at present. The lake possesses monomictic stratification behaviour, and during overturn an intensive gas exchange with the atmosphere occurs. Investigations concerning the sedimentation processes of the lake suggest only a thin sediment layer of up to 10–20 cm in the deeper lake basin; in the western bay, in the area of gas emissions, the lake bottom is partly depleted of sediment in the form of holes, and no lake colmation exists. Decreases in the lake water level of about 30 cm y−1 indicate a percolation of water into fractures and fissures of the volcano, triggered by a nearby earthquake in 1987.

  4. Menes caldera, a highly active site of brine seepage in the Eastern Mediterranean Sea: "In situ" observations from the NAUTINIL expedition

    NARCIS (Netherlands)

    Huguen, C.; Foucher, J.-P.; Mascle, J.; Ondreas, H.; Thouement, M.; Gontharet, S.; Stadnitskaia, A.; Pierre, C; Bayon, G.; Loncke, L; Boetius, A.; Bouloubassi, I.; de Lange, G.; Caprais, J.-C.; Fouquet, Y.; Woodside, J.M.; Dupre, S.

    2009-01-01

    This paper reports the first "in situ" seafloor observations of fluid escape structures in a fault-controlled caldera-type depression of about 8 km diameter, named the Menes caldera, in the Eastern Mediterranean sea off Egypt (western province of the Nile Deep Sea Fan). A detailed analysis of seven

  5. The Laramide Mesa formation and the Ojo de Agua caldera, southeast of the Cananea copper mining district, Sonora, Mexico

    Science.gov (United States)

    Cox, Dennis P.; Miller, Robert J.; Woodbourne, Keith L.

    2006-01-01

    The Mesa Formation extends from Cananea, Mexico, southeast to the Sonora River and is the main host rock of Laramide porphyry copper deposits in the Cananea District and at the Alacran porphyry prospect to the east. The Mesa consists of two members-a lower andesite and an upper dacite. The lowest part of the dacite member is a crystal tuff about 100 m thick. This tuff is the outfall of a caldera centered near the village of Ojo de Agua, dated by 40Ar/39Ar at 65.8 Ma ?0.4. The Ojo de Agua Caldera is about 9 km in diameter and is filled by a light gray biotite dacite tuff with abundant flattened pumice fragments. The volume of the caldera is estimated to be 24 km3.

  6. Aprovechamiento del recurso biomasa a partir de los desechos de madera para una caldera de vapor

    OpenAIRE

    Arroyo Vinueza, Juan Sebastián; Reina Guzmán, Washington Salvatore

    2016-01-01

    Este artículo describe el potencial energético de la biomasa residual que proviene de la madera al ser utilizado en una caldera de vapor como combustible sustitutivo; esto con el fin de proporcionar una alternativa de energía limpia diferente a la actual dependencia del petróleo usado en estos dispositivos. Además, la información detalla la industria que proporciona los desechos de madera y sus diferentes formas de presentación, sus propiedades físicas y energéticas; t...

  7. Las cocinas del infierno. La visualidad de las mujeres en las calderas de Pedro Botero

    OpenAIRE

    Zuriaga Senent, Vicente Francesc

    2013-01-01

    Casi todas las religiones nos hablan del infierno como lugar en el que las almas son torturadas eternamente. El judaísmo lo llama Gehena, la mitología clásica Tártaro y Hades, las religiones paganas Inframundo, y la tradición cristiana castellana Las calderas de Pedro Botero. Los profetas del Antiguo Testamento narran con claridad los tormentos del infierno y Dante en La Divina Comedia nos lo relata con una visión particular. La literatura y el arte nos ofrecen abundancia de imáge...

  8. Micro kinematic indicators in the Green Tuff Ignimbrite: can they tell us about caldera collapse?

    OpenAIRE

    Williams, Rebecca; Dyble, Jodie

    2014-01-01

    This poster presents the results from a 4 week research placement through the Nuffield Foundation scheme. Jodie created this poster as part of the assessment for a Gold CREST Award from the British Science Association. We are also presenting this poster at the VMSG conference, Norwich, 2015. It should be cited as: Dyble, J.A., Williams, R., 2015. Micro kinematic indicators in the Green Tuff Ignimbrite: can they tell us about caldera collapse? VMSG Meeting, Norwch, 5th-7th January 2015. htt...

  9. Hydrothermal alteration in the Baca Geothermal System, Redondo Dome, Valles Caldera, New Mexico

    Science.gov (United States)

    Hulen, Jeffrey B.; Nielson, Dennis L.

    1986-02-01

    Thermal fluids circulating in the active hydrothermal system of the resurgent Redondo dome of the Valles caldera have interacted with their diverse host rocks to produce well-zoned alteration assemblages, which not only help locate permeable fluid channels but also provide insight into the system's thermal history. The alteration shows that fluid flow has been confined principally to steeply dipping normal faults and subsidiary fractures as well as thin stratigraphic aquifers. Permeability along many of these channels has been reduced or locally eliminated by hydrothermal self-sealing. Alteration from the surface through the base of the Miocene Paliza Canyon Formation is of three distinctive types: argillic, propylitic, and phyllic. Argillic alteration forms a blanket above the deep water table in formerly permeable nonwelded tuffs. Beneath the argillic zone, pervasive propylitic alteration is weakly developed in felsic host rocks but locally intense in deep intermediate composition volcanics. Strong phyllic alteration is commonly but not invariably associated with major active thermal fluid channels. Phyllic zones yielding no fluid were clearly once permeable but now are hydrothermally sealed. High-temperature alteration phases at Baca are presently found at much lower temperatures. We suggest either that isotherms have collapsed due to gradual cooling of the system, that they have retreated without overall heat loss due to uplift of the Redondo dome, that the system has shifted laterally, or that it has contracted due to a drop in the water table. The deepest Well (B-12, 3423 m) in the dome may have penetrated through the base of the active hydrothermal system. Below a depth of 2440 m in this well, hydrothermal veining largely disappears, and the rocks resemble those developed by isochemical thermal metamorphism. The transition is reflected by temperature logs, which show a conductive thermal gradient below 2440 m. This depth may mark the dome's neutral plane

  10. Insights From the Kilgore Tuff: Surprising Homogeneity of Supervolcanic Magmas in Yellowstone Hotspot Calderas

    Science.gov (United States)

    Watts, K. E.; Bindeman, I. N.; Schmitt, A. K.; Morgan, L. A.

    2008-12-01

    Supervolcanic eruptions in the late Miocene Heise volcanic field in eastern Idaho concluded ~4.5Ma with the eruption of the Kilgore Tuff, an extremely voluminous (1,800km3) caldera-forming ignimbrite. The Heise volcanic field represents the most recently extinct phase of volcanism over the Yellowstone hotspot and is the most immediate predecessor to the active Yellowstone Plateau volcanic field in western Wyoming. Thus, the climactic Kilgore Tuff of the Heise field is an important example of silicic magma genesis in the Yellowstone hotspot track, and may serve as an analog to large volume, late-stage magmatism in the Yellowstone Plateau volcanic field. We present major and trace element analyses, oxygen isotope ratios of bulk and individual phenocrysts, strontium isotope ratios of whole rock powders, and uranium-lead zircon crystallization ages of five geographically discrete and compositionally diverse samples of the Kilgore Tuff. Despite the presence of both high and low-silica rhyolites, with and without quartz phenocrysts, our isotopic and geochronologic data indicate that the Kilgore Tuff was erupted from a remarkably homogeneous silicic magma chamber with a constant and low δ18O value of 3.32±0.02‰, a 87Sr/86Sr ratio of 0.7105±0.0001, and a 238U-206Pb crystallization age of 4.64±0.05Ma (uncertainties are 1σ). Our new data support a shallow crustal recycling model of magma genesis for the Kilgore Tuff, in which low-δ18O intracaldera fill, consisting of hydrothermally altered and buried volcanic rocks from three previous caldera-forming eruptions, is remelted in batches and rapidly assembled into one voluminous, well-mixed magma chamber. Following isotopic homogenization by convection, fractional crystallization resulted in low and high-silica magma types in the parental Kilgore batholith. Similar processes may also explain effusive, large volume silicic magma genesis of the low-δ18O Central Plateau Member rhyolites (0.25-0.07Ma, 700km3) in the

  11. Initial results from VC-1, First Continental Scientific Drilling Program Core Hole in Valles Caldera, New Mexico

    Science.gov (United States)

    Goff, Fraser; Rowley, John; Gardner, Jamie N.; Hawkins, Ward; Goff, Sue; Charles, Robert; Wachs, Daniel; Maassen, Larry; Heiken, Grant

    1986-02-01

    Valles Caldera 1 (VC-1) is the first Continental Scientific Drilling Program (CSDP) core hole drilled in the Valles caldera and the first continuously cored well in the caldera region. The objectives of VC-1 were to penetrate a hydrothermal outflow plume near its source, to obtain structural and stratigraphie information near the intersection of the ring fracture zone and the precaldera Jemez fault zone, arid to core the youngest volcanic unit inside the caldera (Banco Bonito obsidian). Coring of the 856-m well took only 35 days to finish, during which all objectives were attained and core recovery exceeded 95%. VC-1 penetrates 298 m of moat volcanics and caldera fill ignimbrites, 35 m of precaldera volcaniclastic breccia, and 523 m of Paleozoic carbonates, sandstones, and shales. A previously unknown obsidian flow was encountered at 160 m depth underlying the Battleship Rock Tuff in the caldera moat zone. Hydrothermal alteration is concentrated in sheared, brecciated, and fractured zones from the volcaniclastic breccia to total depth with both the intensity and rank of alterations increasing with depth. Alteration assemblages consist primarily of clays, calcite, pyrite, quartz, and chlorite, but chalcopyrite and sphalerite have been identified as high as 450 m and molybdenite has been identified in a fractured zone at 847 m. Carbon 13 and oxygen 18 analyses of core show that the most intense zones of hydrothermal alteration occur in the Madera Limestone above 550 m and in the Madera and Sandia formations below 700 m. This corresponds with zones of most intense calcite and quartz veining. Thermal aquifers were penetrated at the 480-, 540-, and 845-m intervals. Although these intervals are associated with alteration, brecciation, and veining, they are also intervals where clastic layers occur in the Paleozoic sedimentary rocks.

  12. The High Rock caldera complex, NW Nevada: Geologic mapping, volcanology, geochemistry, and ultra-high precision 40Ar/39Ar dating of early Yellowstone hotspot magmatism

    Science.gov (United States)

    Hausback, B.; Smith, J.; Henry, C. D.; Hilton, R. P.; McIntosh, W. C.; Heizler, M. T.; Noble, D. C.

    2012-12-01

    Our new work reveals a complex evolution of the High Rock caldera, one of the oldest calderas related to initiation of the Yellowstone hotspot. The caldera formed at 16.43±0.01 Ma (n=2, Fish Canyon sanidine = 28.201 Ma; all ages reported here agree with stratigraphy) during eruption of the zoned (metaluminous, high-silica dacite to slightly peralkaline, low-silica rhyolite), abundantly porphyritic Summit Lake Tuff. The only exposed precaldera rocks are a suite of intermediate lavas along the western margin. They are undated but compositionally similar to 30 Ma rocks in the region, so probably unrelated to the caldera. The caldera margin is entirely buried by moat domes and post-collapse lavas and tuff. Sparsely porphyritic rhyolite lavas erupted at 16.30±0.01 Ma (n=1) north of the caldera, possibly along the ring fracture. A large suite of petrographically and compositionally nearly indistinguishable, abundantly porphyritic, peralkaline rhyolite lavas and tuffs, the Soldier Meadow (SM) rock type, erupted from vents around the entire caldera margin in two pulses at 16.14±0.01 and 16.09±0.01 Ma (n=6 and 3). The first pulse includes lavas along the western and eastern margin; the Soldier Meadow Tuff (SMT, a moderately peralkaline, crystal-rich welded ignimbrite that is thinly-layered with coarse lag breccias in the proximal area and massive in distal locations), which erupted along the eastern caldera margin; and accidental blocks (up to 3m) of SMT brought up in the interior of the caldera by later eruptions. The second pulse includes several more lavas and associated small-volume flow, fall, and surge(?) tuffs along the northeastern and southwestern margin. Distribution of the SM rock type suggests that its magma chamber underlay the entire caldera. Rocks of the second pulse are distinguished only by higher incompatible element concentrations (Rb, Zr, Nb, Th), which suggests the magma body continued to differentiate between pulses. The tuffs of Alkali Flat and

  13. Source parameter inversion for earthquakes in the Bardarbunga caldera (August 2014-February 2015) based on high-rate GPS data

    Science.gov (United States)

    Rodríguez Cardozo, Félix; Hjörleifsdóttir, Vala; Jónsdóttir, Kristín; Geirsson, Halldor; Iglesias, Arturo

    2017-04-01

    In August 2014 a sequence of earthquakes took place in the Bardarbunga caldera (7x11 km) and a laterally propagating dike that connected the caldera with the Holuhraun lava field. The caldera earthquakes were coincident in time with the caldera subsidence ( 70 m) and the propagation of a dike, which ended in a fissural eruption in Holuhraun (Guðmundsson et al., 2016). The volcanic seismic sources represented by the moment tensor, commonly have a large non-double couple component, which implies that the source can not be described as a slip on a planar fault. However, encountering an apropiate physical mechanism that explain the non double couple component is a challenging task since there are several phenomena that could explain it, such as intrusive processes like dikes or sills (Kanamori et al 1993, Riel et al 2014) as well as geometric effects due slip on a curved fault (Nettles & Ekström, 1998). The earthquakes in the Bardarbunga caldera are quite interesting not only due to the magnitudes (around seventy events between 5.0non double couple components; for some of them, the seismic waves were registered by a GPS high-rate station and for one (18th september 2014 Mw. 5.3), a ring fault model was built based on interferometric synthetic aperture radar (InSAR) also (Guðmundsson et al., 2016). Taking into account that the Bardarbunga caldera is covered by glacier (which makes difficult detecting changes in the surface using InSAR) and detecting waveforms in GPS stations is common only for large tectonics earthquakes (above Mw.7); observing a volcanic earthquakes simultaneously by InSAR and GPS is a rare and outstanding opportunity for constrain the volcanic seismic source . Likewise, if we assume that all the subsidence earthquakes in Bardarbunga have a common seismic source, we can use the same fault plane costrained for the 18th september earthquake, for inverting the seismic source of all the events in the caldera, only variying some parameters such as half

  14. A physical model of sill expansion to explain the dynamics of unrest at calderas with application to Campi Flegrei

    Science.gov (United States)

    Giudicepietro, Flora; Macedonio, Giovanni; Martini, Marcello

    2017-07-01

    Many calderas show remarkable unrests, which often do not culminate in eruptions (non-eruptive unrest). In this context the interpretation of the geophysical data collected by the monitoring networks is difficult. When the unrest is eruptive, a vent opening process occurs, which leads to an eruption. In volcanic calderas, vent locations typically are scattered over a large area and monogenic cones form. The resulting pattern is characterized by a wide dispersion of eruptive vents, therefore, the location of the future vent in calderas is not easily predictable. We propose an interpretation of the deformation associated to unrest and vent pattern commonly observed at volcanic calderas, based on a physical model that simulates the intrusion and the expansion of a sill. The model can explain both the uplift and the subsequent subsidence, through a single geological process. In particular, we simulate the vertical displacement that occurred at the central area of Campi Flegrei caldera during the last decades, and we obtain good agreement with the data of a leveling benchmark near the center of the caldera. Considering that the stress mainly controls the vent opening process, we try to gain insight on the vent opening in calderas through the study of the stress field produced by the intrusion of an expanding sill. We find that the tensile stress in the rock above the sill is concentrated in a ring-shaped area with radius depending on the physical properties of magma and rock, the feeding rate and the magma cooling rate. This stress field is consistent with widely dispersed eruptive vents and monogenic cone formation, which are often observed in the calderas. However, considering the mechanical properties of the elastic plate and the rheology of magma, we show that remarkable deformations may be associated with low values of stress in the rock at the top of the intrusion, thereby resulting in non-eruptive unrests. Moreover, we have found that, under the assumption of

  15. Resurgent Toba – field, chronologic, and model constraints on time scales and mechanisms of resurgence at large calderas

    Directory of Open Access Journals (Sweden)

    Shanaka L De Silva

    2015-06-01

    Full Text Available New data reveal details of the post-caldera history at the Earth’s youngest resurgent supervolcano, Toba caldera in Sumatra. Resurgence after the caldera-forming ~74 ka Youngest Toba Tuff eruption uplifted the caldera floor as a resurgent dome, Samosir Island, capped with 100m of lake sediments. 14C age data from the uppermost datable sediments reveal that Samosir Island was submerged beneath lake level (~900m a.s.l ~33.7 ky. Since then, Samosir experienced 700m of uplift as a tilted block dipping to the west. Using 14C ages and elevations of sediment along a transect of Samosir reveal that minimum uplift rates were ~4.9 cm/yr from ~33.7 to 22.5 ka, but diminished to ~0.7 cm/yr after 22.5ka. Thermo-mechanical models informed by these rates reveal that detumescence does not produce the uplift nor the uplift rates estimated for Samosir. However, models calculating the effect of volume change of the magma reservoir within a temperature-dependent viscoelastic host rock reveal that a single pulse of ~475 km3 of magma produces a better fit to the uplift data than a constant flux. Reproducing the uplift rates require more sophisticated models. Motivation for resurgent uplift of the caldera floor is rebound of remnant magma as the system re-established magmastatic and isostatic equilibrium after the caldera collapse. Previous assertions that the caldera floor was apparently at 400m a.s.l or lower requires that uplift must have initiated between sometime between 33.7 ka and 74 ka at a minimum average uplift rate of ~1.1 cm/ year. The change in uplift rate from pre-33.7 ka to immediately post-33.7 ka suggests a role for deep recharge augmenting rebound. Average minimum rates of resurgent uplift at Toba are at least an order of magnitude slower than net rates of restlessness at currently active calderas. This connotes a distinction between resurgence and restlessness controlled by different processes, scales of process, and controlling variables.

  16. Pyroclastic flow dynamics and hazard in a caldera setting: Application to Phlegrean Fields (Italy)

    Science.gov (United States)

    Todesco, Micol; Neri, Augusto; Esposti Ongaro, Tomaso; Papale, Paolo; Rosi, Mauro

    2006-11-01

    Numerical simulation of pyroclastic density currents has developed significantly in recent years and is increasingly applied to volcanological research. Results from physical modeling are commonly taken into account in volcanic hazard assessment and in the definition of hazard mitigation strategies. In this work, we modeled pyroclastic density currents in the Phlegrean Fields caldera, where flows propagating along the flat ground could be confined by the old crater rims that separate downtown Naples from the caldera. The different eruptive scenarios (mass eruption rates, magma compositions, and water contents) were based on available knowledge of this volcanic system, and appropriate vent conditions were calculated for each scenario. Simulations were performed along different topographic profiles to evaluate the effects of topographic barriers on flow propagation. Simulations highlighted interesting features associated with the presence of obstacles such as the development of backflows. Complex interaction between outward moving fronts and backflows can affect flow propagation; if backflows reach the vent, they can even interfere with fountain dynamics and induce a more collapsing behavior. Results show that in the case of large events (≥108 kg/s), obstacles affect flow propagation by reducing flow velocity and hence dynamic pressure in distal regions, but they cannot stop the advancement of flows. Deadly conditions (in terms of temperature and ash concentration) characterize the entire region invaded by pyroclastic flows. In the case of small events (2.5 × 107 kg/s), flows are confined by distal topographic barriers which provide valuable protection to the region beyond.

  17. Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan.

    Science.gov (United States)

    Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

    2016-09-13

    Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

  18. Discovery of a flank caldera and very young glacial activity at Hecates Tholus, Mars.

    Science.gov (United States)

    Hauber, Ernst; van Gasselt, Stephan; Ivanov, Boris; Werner, Stephanie; Head, James W; Neukum, Gerhard; Jaumann, Ralf; Greeley, Ronald; Mitchell, Karl L; Muller, Peter

    2005-03-17

    The majority of volcanic products on Mars are thought to be mafic and effusive. Explosive eruptions of basic to ultrabasic chemistry are expected to be common, but evidence for them is rare and mostly confined to very old surface features. Here we present new image and topographic data from the High Resolution Stereo Camera that reveal previously unknown traces of an explosive eruption at 30 degrees N and 149 degrees E on the northwestern flank of the shield volcano Hecates Tholus. The eruption created a large, 10-km-diameter caldera approximately 350 million years ago. We interpret these observations to mean that large-scale explosive volcanism on Mars was not confined to the planet's early evolution. We also show that glacial deposits partly fill the caldera and an adjacent depression. Their age, derived from crater counts, is about 5 to 24 million years. Climate models predict that near-surface ice is not stable at mid-latitudes today, assuming a thermo-dynamic steady state. Therefore, the discovery of very young glacial features at Hecates Tholus suggests recent climate changes. We show that the absolute ages of these very recent glacial deposits correspond very well to a period of increased obliquity of the planet's rotational axis.

  19. Molecular analysis of the benthos microbial community in Zavarzin thermal spring (Uzon Caldera, Kamchatka, Russia).

    Science.gov (United States)

    Rozanov, Alexey S; Bryanskaya, Alla V; Malup, Tatiana K; Meshcheryakova, Irina A; Lazareva, Elena V; Taran, Oksana P; Ivanisenko, Timofey V; Ivanisenko, Vladimir A; Zhmodik, Sergey M; Kolchanov, Nikolay A; Peltek, Sergey E

    2014-01-01

    Geothermal areas are of great interest for the study of microbial communities. The results of such investigations can be used in a variety of fields (ecology, microbiology, medicine) to answer fundamental questions, as well as those with practical benefits. Uzon caldera is located in the Uzon-Geyser depression that is situated in the centre of the Karym-Semyachin region of the East Kamchatka graben-synclinorium. The microbial communities of Zavarzin spring are well studied; however, its benthic microbial mat has not been previously described. Pyrosequencing of the V3 region of the 16S rRNA gene was used to study the benthic microbial community of the Zavarzin thermal spring (Uzon Caldera, Kamchatka). The community is dominated by bacteria (>95% of all sequences), including thermophilic, chemoorganotrophic Caldiserica (33.0%) and Dictyoglomi (24.8%). The benthic community and the previously examined planktonic community of Zavarzin spring have qualitatively similar, but quantitatively different, compositions. In this study, we performed a metagenomic analysis of the benthic microbial mat of Zavarzin spring. We compared this benthic community to microbial communities found in the water and of an integral probe consisting of water and bottom sediments. Various phylogenetic groups of microorganisms, including potentially new ones, represent the full-fledged trophic system of Zavarzin. A thorough geochemical study of the spring was performed.

  20. Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A.

    Science.gov (United States)

    Bacon, C.R.

    1983-01-01

    New investigations of the geology of Crater Lake National Park necessitate a reinterpretation of the eruptive history of Mount Mazama and of the formation of Crater Lake caldera. Mount Mazama consisted of a glaciated complex of overlapping shields and stratovolcanoes, each of which was probably active for a comparatively short interval. All the Mazama magmas apparently evolved within thermally and compositionally zoned crustal magma reservoirs, which reached their maximum volume and degree of differentiation in the climactic magma chamber ??? 7000 yr B.P. The history displayed in the caldera walls begins with construction of the andesitic Phantom Cone ??? 400,000 yr B.P. Subsequently, at least 6 major centers erupted combinations of mafic andesite, andesite, or dacite before initiation of the Wisconsin Glaciation ??? 75,000 yr B.P. Eruption of andesitic and dacitic lavas from 5 or more discrete centers, as well as an episode of dacitic pyroclastic activity, occurred until ??? 50,000 yr B.P.; by that time, intermediate lava had been erupted at several short-lived vents. Concurrently, and probably during much of the Pleistocene, basaltic to mafic andesitic monogenetic vents built cinder cones and erupted local lava flows low on the flanks of Mount Mazama. Basaltic magma from one of these vents, Forgotten Crater, intercepted the margin of the zoned intermediate to silicic magmatic system and caused eruption of commingled andesitic and dacitic lava along a radial trend sometime between ??? 22,000 and ??? 30,000 yr B.P. Dacitic deposits between 22,000 and 50,000 yr old appear to record emplacement of domes high on the south slope. A line of silicic domes that may be between 22,000 and 30,000 yr old, northeast of and radial to the caldera, and a single dome on the north wall were probably fed by the same developing magma chamber as the dacitic lavas of the Forgotten Crater complex. The dacitic Palisade flow on the northeast wall is ??? 25,000 yr old. These relatively

  1. Caldera-scale inflation of the Lazufre volcanic area, South America: Evidence from InSAR

    Science.gov (United States)

    Ruch, J.; Anderssohn, J.; Walter, T. R.; Motagh, M.

    2008-07-01

    Collapsed calderas are the structural surface expression of the largest volcanic eruptions on Earth and may reach diameters of tens of kilometres while erupting volumes larger than 1000 km 3. Remnants of collapse calderas can be found along the South American volcanic arc and are thought to be inactive. However, this study shows that systems of such dimension may become active in a relatively short period of time without attracting much attention. Using satellite-based InSAR data, a 45 km wide elongated area of ground deformation was observed in the Lazufre volcanic region (Chile), where no deformation was detected 10 years ago. The deformation signal shows an uplift of up to ~ 3 cm yr - 1 during 2003-2006, affecting an area of about 1100 km 2, comparable in size to super-volcanoes such as Yellowstone or Long Valley. This deformation signal can be explained by an inflating magma body at about 10 km depth, expanding and propagating laterally at a velocity of up to 4 km per year. Although it is not clear whether this intrusion will lead to an eruption, its dimensions and the rapid deformation rate insinuate that a potentially large volcanic system is forming.

  2. Bibliography of literature pertaining to Long Valley Caldera and associated volcanic fields

    Science.gov (United States)

    Ewert, John W.; Harpel, Christopher J.; Brooks, Suzanna K.; Marcaida, Mae

    2011-01-01

    On May 25-27, 1980, Long Valley caldera was rocked by four M=6 earthquakes that heralded the onset of a wave of seismic activity within the caldera which has continued through the present. Unrest has taken the form of seismic swarms, uplift of the resurgent dome, and areas of vegetation killed by increased CO2 emissions, all interpreted as resulting from magma injection into different levels beneath the caldera, as well as beneath Mammoth Mountain along the southwest rim of the caldera. Continuing economic development in the Mammoth Lakes area has swelled the local population, increasing the risk to people and property if an eruption were to occur. The U.S. Geological Survey (USGS) has been monitoring geophysical activity in the Long Valley area since the mid-1970s and continues to track the unrest in real time with a sophisticated network of geophysical sensors. Hazards information obtained by this monitoring is provided to local, State, and Federal officials and to the public through the Long Valley Observatory. The Long Valley area also was scientifically important before the onset of current unrest. Lying at the eastern foot of the Sierra Nevada, the deposits from this active volcanic system have provided fertile ground for research into Neogene tectonics, Quaternary geology and geomorphology, regional stratigraphy, and volcanology. In the early 1970s, intensive studies of the area began through the USGS Geothermal Investigations Program, owing to the presence of a large young silicic volcanic system. The paroxysmal eruption of Long Valley caldera about 760,000 years ago produced the Bishop Tuff and associated Bishop ash. The Bishop Tuff is a well-preserved ignimbrite deposit that has continued to provide new and developing insights into the dynamics of ignimbrite-forming eruptions. Another extremely important aspect of the Bishop Tuff is that it is the oldest known normally magnetized unit of the Brunhes Chron. Thus, the age of the Bishop Tuff is used to

  3. Phreatomagmatic explosive eruptions along fissures on the top of mafic stratovolcanoes with overlapping compound calderas

    Science.gov (United States)

    Nemeth, Karoly; Geshi, Nobuo

    2017-04-01

    On near summit flank eruptions on stratovolcanoes it is commonly inferred that external water to have little or no influence on the course of the eruptions. Hence eruptions are typicaly "dry" that form spatter-dominated fissures and scoria cones. This assumption is based on that in elevated regions - especially on steep slopes - the hydrogeological conditions are not favourable to store large volume of ground water that can have effect on the eruptions. However there is some controversial trend of eruption progression from an early dry eruption below the summit that later turn to be phreatomagmatic as the eruption locus migrates toward the summit. The Suoana Ccrater on top of Miyakejima Island's mafic stratovolcano is a fine example to demonstrate such process. Suona Crater is the topmost crater of the 3 km long fissure aligned chain of small-volume volcanoes that formed in the 7th century flank of the summit region of the Miyakejima mafic stratovolcano. The oval shape crater of Suona (400 x 300 m) is surrounded by a tuff ring that developed over lava flows and epiclastic deposits accumulated in an older caldera forming about a tuff ring that is about 25 m in its thickest section with a basal consistent lava spatter dominated unit gradually transforming into a more scoria-dominated middle unit. A caldera-forming eruption in AD 2000 half-sectioned the Suona Crater exposing of its internal diatreme - crater in-fill - tephra rim succession providing a unique opportunity to understand the 3D architecture of the volcano. Toward the top of the preserved and exposed tuff ring section a clear gradual transition can be seen toward more abundance of chilled dark juvenile particles providing a matrix of a coarse ash that commonly hold cauliflower lapilli and bomb. This transition indicates that the eruption progressed from an early dry explosive phase such as lava fountaining to be a more Strombolian style explosive eruption that later on turned to be heavily influenced by

  4. Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

    Science.gov (United States)

    Benson, Thomas R.; Mahood, Gail A.

    2016-01-01

    The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at ~ 15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of low-temperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre- and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single ~ 20 × 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins ~ 300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are

  5. Tensor controlled-source audiomagnetotelluric survey over the Sulphur Springs Thermal area, Valles Caldera, New Mexico, U.S.A.; Implication for structure of the western Caldera and for CSAMT methodology

    Energy Technology Data Exchange (ETDEWEB)

    Wannamaker, P.E.

    1994-06-01

    We have carried Out an extensive tensor CSAMT survey of the Sulphur Springs geothermal area, Valles Caldera, New Mexico. This survey, consisting of 45 high-quality sites, has been acquired by in support of Continental Scientific Drilling Program (CSDP) drillholes VC-2A and VC-2B. Two independent transmitter dipoles were energized for tensor measurements using a 30 kW generator placed approximately 13 km south of the VC-2B wellhead. The soundings in the Sulphur Springs area were arranged in four profiles to cross major structural features. The electric bipoles parallel to each profile were deployed contiguously to ensure against spatial aliasing of the impedance response corresponding to current flow across structural trends. The frequency range of acquisition was 4096 Hz down to 1 Hz for the central line, but only down to 4 Hz for most sites of the other lines. Data quality is high overall and is established by repeatability of measurements. Agreement between the CSAMT and available natural field MT data is very good over almost all the period range of overlap indicating that we are free of calibration problems and that far-field results are generally being obtained. Non plane-wave effects in the CSAMT around Sulphur Springs are apparent at 1 to 2 Hz, and perhaps slightly even at 4 Hz, however, which is near the bottom of our frequency range. CSAMT and MT data taken outside the Valles Caldera to the west were modeled in an attempt to compare resistivity structure exterior to the caldera to that within. With the availability of tensor CSAMT and MT data both inside and outside Valles Caldera, assumptions and methods of CSAMT are tested. In the Sulphur Springs area, near-coincident CSAMT and MT data near well VC -2B indicate that non-lane-wave effects in the apparent resistivity and impedance phase occure at a frequency near to that predicted from the resistivity structure local to the wester caldera.

  6. Quantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 2. Pyroclastic density current invasion maps

    Science.gov (United States)

    Neri, Augusto; Bevilacqua, Andrea; Esposti Ongaro, Tomaso; Isaia, Roberto; Aspinall, Willy P.; Bisson, Marina; Flandoli, Franco; Baxter, Peter J.; Bertagnini, Antonella; Iannuzzi, Enrico; Orsucci, Simone; Pistolesi, Marco; Rosi, Mauro; Vitale, Stefano

    2015-04-01

    Campi Flegrei (CF) is an example of an active caldera containing densely populated settlements at very high risk of pyroclastic density currents (PDCs). We present here an innovative method for assessing background spatial PDC hazard in a caldera setting with probabilistic invasion maps conditional on the occurrence of an explosive event. The method encompasses the probabilistic assessment of potential vent opening positions, derived in the companion paper, combined with inferences about the spatial density distribution of PDC invasion areas from a simplified flow model, informed by reconstruction of deposits from eruptions in the last 15 ka. The flow model describes the PDC kinematics and accounts for main effects of topography on flow propagation. Structured expert elicitation is used to incorporate certain sources of epistemic uncertainty, and a Monte Carlo approach is adopted to produce a set of probabilistic hazard maps for the whole CF area. Our findings show that, in case of eruption, almost the entire caldera is exposed to invasion with a mean probability of at least 5%, with peaks greater than 50% in some central areas. Some areas outside the caldera are also exposed to this danger, with mean probabilities of invasion of the order of 5-10%. Our analysis suggests that these probability estimates have location-specific uncertainties which can be substantial. The results prove to be robust with respect to alternative elicitation models and allow the influence on hazard mapping of different sources of uncertainty, and of theoretical and numerical assumptions, to be quantified.

  7. The McDermitt Caldera, NV-OR, USA: Geologic mapping, volcanology, mineralization, and high precision 40Ar/39Ar dating of early Yellowstone hotspot magmatism

    Science.gov (United States)

    Henry, C. D.; Castor, S. B.; Starkel, W. A.; Ellis, B. S.; Wolff, J. A.; Heizler, M. T.; McIntosh, W. C.

    2012-12-01

    The irregularly keyhole-shaped, 40x30 to 22 km, McDermitt caldera formed at 16.35±0.03 Ma (n=4; Fish Canyon sanidine = 28.201 Ma) during eruption of a zoned, aphyric, mildly peralkaline rhyolite to abundantly anorthoclase-phyric, metaluminous dacite (McDermitt Tuff, MDT). Intracaldera MDT is locally strongly rheomorphic and, where MDT and caldera floor are well-exposed along the western margin, contains abundant megabreccia but is a maximum of ~450 m thick. If this thickness is representative of the caldera, intracaldera MDT has a volume of ~400 km3. Outflow MDT is currently known up to 13 km south of the caldera but only 3 km north of the caldera. Maximum outflow thickness is ~100 m, and outflow volume is probably no more than about 10% that of intracaldera MDT. The thickness and volume relations indicate collapse began very early during eruption, and most tuff ponded within the caldera. Outflow is strongly rheomorphic where draped over paleotopography. Late, undated icelandite lavas and domes are probably residual magma from the caldera chamber. Resurgence is expressed as both a broad, symmetrical dome in the north part and a fault-bound uplift in the south part of the caldera. Mineralization associated with the caldera includes Zr-rich U deposits that are indistinguishable in age with the McDermitt Tuff, Hg, Au, Ga, and Li-rich intracaldera tuffaceous sediments. Although formed during probable regional extension, the caldera is flat-lying and cut only at its west and east margins by much younger, high-angle normal faults. The caldera formed in an area of highly diverse Cenozoic volcanic rocks. The oldest are 39 and 46 Ma metaluminous dacite lavas along the northwest margin. Coarsely plagioclase-phyric to aphyric Steens Basalt lavas crop out around the west, northwest, and northeast margin. An anorthoclase-phyric, low-Si rhyolite lava (16.69±0.02 Ma) that is interbedded with probable Steens lavas northeast of the caldera and a biotite rhyolite lava dome (16.62

  8. Volcanic flood simulation of magma effusion using FLO-2D for drainage of a caldera lake at the Mt. Baekdusan

    Science.gov (United States)

    Lee, Khil-Ha; Kim, Sung-Wook; Kim, Sang-Hyun

    2014-05-01

    Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. Sudden release of huge volume of water stored in temporarily elevated caldera lakes are a recurrent feature of volcanic environments, due to the case with which outlet channels are blocked by and re-cut through, unwelded pyroclastic deposits. The volcano is showing signs of waking from a century-long slumber recently. Volcanic floods, including breakouts from volcanic lakes, can affect communities beyond the areas immediately affected by a volcanic eruption and cause significant hydrological hazards because floods from lake-filled calderas may be particularly large and high. Although a number of case studies have been presented in the literature, investigation of the underlying physical processes is required as well as a method for interpreting the process of the rapid release of water stored in a caldera lake. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. This study focuses on constructing a flood hazard map triggered by the magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by examples at other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic

  9. Bonded 2D-DEM Models of Pit Craters and Collapse Calderas

    Science.gov (United States)

    Holohan, E. P.; Schöpfer, M. P. J.; Walsh, J. J.

    2010-05-01

    Subsidence of the roof of a magma reservoir commonly produces volcanic depressions, which, depending on scale, are termed pit craters or collapse calderas. To identify what geometric and mechanical factors influence the structural evolution of this subsidence, we used Distinct Element Method (DEM) numerical models. The models comprise an assemblage of gravitationally-loaded circular particles that interact at their contacts according to elastic-frictional laws. Cohesion is provided by inter-particle bonds that break once their shear or tensile strength is exceeded. Varying particle and bond micro-properties yields assemblage macro-properties characteristic of natural rock masses (e.g. elasticity, failure, and strain softening), with fracture localization simulated by bond breakage. The magma reservoir is represented as a region of non-bonded, low-fiction particles. Withdrawal of magma is simulated by incrementally reducing the area of the reservoir particles. The resultant gravity-driven failure and subsidence of the overlying reservoir roof is explicitly replicated. We investigated the effect on subsidence of several initial mechanical and geometric properties. Of these, the strength (cohesion) and thickness/diameter ratio (T/D) of the roof exerted strongest influences, whilst the roof's Young's Modulus and the reservoir's ceiling curvature imparted secondary influences. These properties interacted to produce four ‘end-member' subsidence styles, although elements of several styles tended to occur in any one model realization: (1) Predominantly central sagging at low T/D and low strength; (2) hitherto unrecognized ‘central snapping' at low T/D and high strength; (3) predominantly single central block subsidence at low to intermediate strength and at intermediate T/D ratios; (4) multiple central block subsidence at high strength and high T/D ratios. The critical T/D ratio, at which subsidence changes from single central block to multiple central block, was

  10. Quilotoa volcano — Ecuador: An overview of young dacitic volcanism in a lake-filled caldera

    Science.gov (United States)

    Hall, Minard L.; Mothes, Patricia A.

    2008-09-01

    Quilotoa volcano, an example of young dacitic volcanism in a lake-filled caldera, is found at the southwest end of the Ecuador's volcanic front. It has had a long series of powerful plinian eruptions of moderate to large size (VEI = 4-6), at repetitive intervals of roughly 10-15 thousand years. At least eight eruptive cycles (labeled Q-I to Q-VIII with increasing age) over the past 200 ka are recognized, often beginning with a phreatomagmatic onset and followed by a pumice-rich lapilli fall, and then a sequence of pumice, crystal, and lithic-rich deposits belonging to surges and ash flows. These unwelded pyroclastic flows left veneers on hillsides as well as very thick accumulations in the surrounding valleys, the farthest ash flow having traveled about 17 km down the Toachi valley. The bulk volumes of the youngest flow deposits are on the order of 5 km 3, but that of Q-I's 800 yr BP ash-fall unit is about 18 km 3. In the last two eruption cycles water has had a more important role. Upon Quilotoa's low-relief volcanic edifice, three calderas are recognized; the formation of the oldest one predates the Q-IV cycle and the others occurred during the Q-II and Q-I cycles. Dacite lava domes are common along the present caldera rim and most were emplaced at the end of the Q-II cycle; older domes of dark dacite belong to the Q-III and IV cycles. The explosive onset of the Q-I cycle expulsed as much as 250 million m 3 of the lake's water, resulting in large debris flows that scoured the eastern flanks of the edifice and descended the Toachi river. Little variation in the mineralogy and chemistry of Quilotoa's eruptive products is observed, suggesting that the source is a homogeneous magma body at shallow depth. Both the pyroclastic material and the domes are composed chiefly of gray porphyritic dacites carrying large phenocrysts of plagioclase, amphibole, biotite, and occasionally quartz.

  11. Using Laser Altimetry to Detect Topographic Change in Long Valley Caldera, California

    Science.gov (United States)

    Hofton, M. A.; Minster, J.-B.; Ridgway, J. R.; Blair, J. B.

    1997-01-01

    Long Valley caldera California, is a site of extensive volcanism, persistent seismicity, and uplift of a resurgent dome, currently at a rate of about 3 cm/year. Airborne laser altimetry was used to determine the surface topography of the region in 1993. A repeat mission occurred in 1995. Three different laser altimeters were flown, dubbed ATLAS, SLICER and RASCAL. Data processing consists of the combination of the aircraft trajectory and attitude data with the laser range, the determination of an atmospheric delay, laser pulse timing errors, laser system biases, and data geolocation to obtain the position of the laser spot on the ground. Results showed that using the ATLAS and SLICER instruments, the elevation of an overflown lake is determined to precisions of 3.3 cm and 2.9 cm from altitudes of 500 m and 3 km above the ground, and about 10 cm using the RASCAL instrument from 500 m above ground. Comparison with tide gauge data showed the laser measurements are able to resolve centimeter-level changes in the lake elevation over time. Repeat pass analysis of tracks over flat surfaces indicate no systematic biases affect the measurement procedure of the ATLAS and SLICER instruments. Comparison of GPS and laser-derived elevations of easily-identifiable features in the caldera confirm the horizontal accuracy of the measurement is within the diameter of the laser footprint, and vertical accuracy is within the error inherent in the measurement. Crossover analysis shows that the standard error of the means at track intersection points within the caldera, and dome (i.e., where zero and close to the maximum amount of uplift is expected) are about I cm, indicating elevation change at the 3 cm/year level should be detectable. We demonstrate one of the powerful advantages of scanning laser altimetry over other remote sensing techniques; the straightforward creation of precise digital elevation maps of overflown terrain. Initial comparison of the 1993-1995 data indicates uplift

  12. Using Laser Altimetry to Detect Topographic Change at Long Valley Caldera, California

    Science.gov (United States)

    Hofton, M. A.; Minster, J.-B.; Ridgway, J. R.; Blair, J. B.; Rabine, D. L.; Bufton, J. L.; Williams, N. P.

    1997-01-01

    Long Valley caldera, California, is a site of extensive volcanism, persistent seismicity, and uplift of a resurgent dome, currently at a rate of approximately 3 cm/year. Airborne laser altimetry was used to determine the surface topography of the region in 1993. A repeat mission occurred in 1995. Three different laser altimeters were flown, dubbed ATLAS, SLICER and RASCAL. Data processing consists of the combination of the aircraft trajectory and attitude data with the laser range, the determination of an atmospheric delay, laser pulse timing errors, laser system biases, and data geolocation to obtain the position of the laser spot on the ground. Results showed that using the ATLAS and SLICER instruments, the elevation of an overflown lake is determined to precisions of 3.3 cm and 2.9 cm from altitudes of 500 m and 3 km above the ground, and approximately 10 cm using the RASCAL instrument from 500 m above ground. Comparison with tide gauge data showed the laser measurements are able to resolve centimeter-level changes in the lake elevation over time. Repeat pass analysis of tracks over flat surfaces indicate no systematic biases affect the measurement procedure of the ATLAS and SLICER instruments. Comparison of GPS and laser-derived elevations of easily-identifiable features in the caldera confirm the horizontal accuracy of the measurement is within the diameter of the laser footprint, and vertical accuracy is within the error inherent in the measurement. Crossover analysis shows that the standard error of the means at track intersection points within the caldera and dome (i.e., where zero and close to the maximum amount of uplift is expected) are about 1 cm, indicating elevation change at the 3 cm/year level should be detectable. We demonstrate one of the powerful advantages of scanning laser altimetry over other remote sensing techniques; the straightforward creation of precise digital elevation maps of overflown terrain. Initial comparison of the 1993-1995 data

  13. Reticulite‐producing fountains from ring fractures in Kīlauea Caldera ca. 1500 CE: Chapter 16

    Science.gov (United States)

    May, Michael; Carey, Rebecca J.; Swanson, Don; Houghton, Bruce F.; Carey, Rebecca; Cayol, Valérie; Poland, Michael P.; Weis, Dominique

    2015-01-01

    A widely dispersed reticulite bed occurs close to the base of the Keanakākoʻi Tephra at Kīlauea Volcano. It can be divided into six subunits in the northern sector of the volcano; the reticulite also occurs in the southern sector, but outcrops are sparse owing to penecontemporaneous erosion and burial. Multilobate isopachs for each subunit and the total deposit suggest that multiple fountaining vents were distributed in the northern half of the caldera, possibly along ring fractures for the newly formed caldera. Isopach maps also show a sharp decline in thickness along the dispersal axis of each lobe, which could be explained by remobilization of tephra and/or inclined fountains. Despite such isopach characteristics, thinning rates calculated from the isopach data indicate that the fountains were among the most intense and powerful of all studied Kīlauea fountains. Density analyses of the pyroclasts suggest that fountaining was high (>600m) yet complex, possibly due to lava ponding and reentrainment. The calculated volume of the reticulite deposited around the caldera rim is approximately 0.2km3, more voluminous than the deposits of the 1959 Kīlauea Iki eruption; this volume is a minimum, however, as the low-density tephra is easily remobilized, and 600m high caldera walls probably trapped tephra within the caldera, which is deeply buried today and not accounted for in the volume calculations. The duration of this eruption was most likely at least a few days to weeks, based on the calculated volume and estimated discharge rates as seen during the Kīlauea Iki 1959 eruption.

  14. Determining the physical processes behind four large eruptions in rapid sequence in the San Juan caldera cluster (Colorado, USA)

    Science.gov (United States)

    Curry, Adam; Caricchi, Luca; Lipman, Peter

    2017-04-01

    Large, explosive volcanic eruptions can have both immediate and long-term negative effects on human societies. Statistical analyses of volcanic eruptions show that the frequency of the largest eruptions on Earth (> ˜450 km3) differs from that observed for smaller eruptions, suggesting different physical processes leading to eruption. This project will characterize the petrography, whole-rock geochemistry, mineral chemistry, and zircon geochronology of four caldera-forming ignimbrites from the San Juan caldera cluster, Colorado, to determine the physical processes leading to eruption. We collected outflow samples along stratigraphy of the three caldera-forming ignimbrites of the San Luis caldera complex: the Nelson Mountain Tuff (>500 km3), Cebolla Creek Tuff (˜250 km3), and Rat Creek Tuff (˜150 km3); and we collected samples of both outflow and intracaldera facies of the Snowshoe Mountain Tuff (>500 km3), which formed the Creede caldera. Single-crystal sanidine 40Ar/39Ar ages show that these eruptions occurred in rapid succession between 26.91 ± 0.02 Ma (Rat Creek) and 26.87 ± 0.02 Ma (Snowshoe Mountain), providing a unique opportunity to investigate the physical processes leading to a rapid sequence of large, explosive volcanic eruptions. Recent studies show that the average flux of magma is an important parameter in determining the frequency and magnitude of volcanic eruptions. High-precision isotope-dilution thermal ionization mass spectrometry (ID-TIMS) zircon geochronology will be performed to determine magma fluxes, and cross-correlation of chemical profiles in minerals will be performed to determine the periodicity of magma recharge that preceded these eruptions. Our project intends to combine these findings with similar data from other volcanic regions around the world to identify physical processes controlling the regional and global frequency-magnitude relationships of volcanic eruptions.

  15. The 1817 Eruption of Okmok Caldera, Umnak Island, Alaska: New Insights Into a Complex Historical Eruption in the Eastern Aleutians

    Science.gov (United States)

    Neal, C. A.; Beget, J.; Grey, D.; Wolfe, B.

    2003-12-01

    Okmok is a 10-km-diameter, late-Holocene caldera on Umnak Island in the eastern Aleutians, 1400 km southwest of Anchorage. The most recent eruption in 1997 was strombolian in character, producing a basaltic-andesite lava flow within the caldera and localized ash fall. Since caldera-formation approximately 2050 14C yrs BP, however, more violent eruptions from vents within the caldera have impacted all flanks of the volcano with tephra fall, ballistics, pyroclastic surges and flows, and lahars. An example of these more violent intracaldera events is the 1817 eruption. Reevaluation of historical accounts of activity at Okmok combined with new geologic mapping and tephra studies suggest that an 1817 eruption included (1) early, largely hydrovolcanic, explosive activity and the production of significant pyroclastic fall and surge deposits extending down the north and east flanks of the volcano; (2) generation of a flood that reached the Bering Sea; (3) late-stage strombolian fountaining and lava flow production. Vents from the 1817 eruption form a 4-km-long arc that parallels the base of the north caldera wall and include a 50-70-m-deep, elongate maar crater erupted through pre-existing tuff cone deposits. Terrace morphology and flood deposits less than 200 14C yrs BP indicate a flooding event down Crater Creek consistent with historical accounts of Aleut village inundation at the coastline in 1817. The later part of the eruption produced a 120-m high cinder and spatter cone and a blocky a'a lava flow field that fills a shallow basin near the outlet of Crater Creek. These preliminary results indicate that Okmok is capable of eruptions far more violent than the largely effusive events of the last century.

  16. Isotopic modeling and the formation of the post-caldera eastern Upper Basin Member rhyolites, Yellowstone, WY

    Science.gov (United States)

    Pritchard, C. J.; Larson, P. B.

    2010-12-01

    An array of samples from the eastern Upper Basin Member of the Plateau Rhyolites in the Yellowstone Plateau were collected and analyzed to evaluate styles of deposition, geochemical variation, and plausible sources for these low δ18O rhyolites. The eastern Upper Basin Member is comprised of the Tuff of Sulphur Creek, Canyon flow, and Dunraven Road flow, all high silica rhyolites that were thought to have erupted from within the present Yellowstone Caldera between the northeastern resurgent dome and the northeastern portion of the ring fracture. These eruptions are some of the earliest intracaldera rhyolites and followed the last caldera collapse by approximately 160ka, and generally differ from most other intra-caldera rhyolites by low δ18O values (1.5 to 4.5 per mil) , higher radiogenic isotope ratios, increased plagioclase abundance, and less depleted/ more primitive geochemistry, e.g., higher Sc, Ti, Ba, and Sr. Petrologic textures, higher radiogenic 87Sr/86Sr values in plagioclase phenocrysts (0.7134 to 0.7185) than surrounding melt (0.7099 to 0.7161), whole rock radiogenic values, and δ18O depletions on the order of 5 per mil found in the Tuff of Sulphur Creek and Canyon flow indicate at least a two-stage petrogenesis. Assimilation and fractional crystallization processes may have occurred while the magmatic system was younger leaving un-erupted material at the margins. This magmatic rind may have been hydrothermally altered after cooling, subsided during caldera collapses, and then assimilated/melted to form the Tuff of Sulphur Creek and the Canyon flow. The youngest flow from the eastern Upper Basin Member, the Dunraven Road flow, is geochemically more similar to the extra-caldera Roaring Mountain Member and can be modeled using assimilation of hydrothermally altered wall rock from the ring fracture followed by fractional crystallization.

  17. A preliminary study of older hot spring alteration in Sevenmile Hole, Grand Canyon of the Yellowstone River, Yellowstone Caldera, Wyoming

    Science.gov (United States)

    Larson, Peter B.; Phillips, Allison; John, David; Cosca, Michael; Pritchard, Chad; Andersen, Allen; Manion, Jennifer

    2009-11-01

    Erosion in the Grand Canyon of the Yellowstone River, Yellowstone Caldera (640 ka), Wyoming, has exposed a cross section of older hydrothermal alteration in the canyon walls. The altered outcrops of the post-collapse tuff of Sulphur Creek (480 ka) extend from the canyon rim to more than 300 m beneath it. The hydrothermal minerals are zoned, with an advanced argillic alteration consisting of an association of quartz (opal) + kaolinite ± alunite ± dickite, and an argillic or potassic alteration association with quartz + illite ± adularia. Disseminated fine-grained pyrite or marcasite is ubiquitous in both alteration types. These alteration associations are characteristic products of shallow volcanic epithermal environments. The contact between the two alteration types is about 100 m beneath the rim. By analogy to other active geothermal systems including active hydrothermal springs in the Yellowstone Caldera, the transition from kaolinite to illite occurred at temperatures in the range 150 to 170 °C. An 40Ar/ 39Ar age on alunite of 154,000 ± 16,000 years suggests that hydrothermal activity has been ongoing since at least that time. A northwest-trending linear array of extinct and active hot spring centers in the Sevenmile Hole area implies a deeper structural control for the upflowing hydrothermal fluids. We interpret this deeper structure to be the Yellowstone Caldera ring fault that is covered by the younger tuff of Sulphur Creek. The Sevenmile Hole altered area lies at the eastern end of a band of hydrothermal centers that may mark the buried extension of the Yellowstone Caldera ring fault across the northern part of the Caldera.

  18. Post 19 ka B.P. eruptive history of Ulleung Island, Korea, inferred from an intra-caldera pyroclastic sequence

    Science.gov (United States)

    Kim, G. B.; Cronin, S. J.; Yoon, W. S.; Sohn, Y. K.

    2014-04-01

    Ulleung Island is a Quaternary volcanic island located in the mid-western part of the East Sea (Sea of Japan) back-arc basin, which has erupted from the Pliocene until the late Holocene. This study focuses on reconstructing the latest eruptive history of the island by describing the sedimentological and stratigraphic characteristics of the most recent, trachytic/phonolitic pyroclastic sequence, named the Nari Tephra Formation. This formation is preserved as a succession of unwelded pyroclastic and epiclastic deposits within an embayed margin of the Nari Caldera. The embayment acted as a topographic trap for proximal pyroclastic deposits, and contains a complete record of the past 19,000 years of eruption history. The formation includes evidence for five separate eruptive episodes (Member N-1 to N-5), with intervening weathered and/or soil horizons indicating hundreds to thousands of years of repose between each eruption. Eruption styles and depositional mechanisms varied between and during individual episodes, reflecting changing dynamics of the magma plumbing system, magmatic gas coupling, and a variable role of external water. Extra-caldera sequences show that only a few of these eruptions generated sustained eruption columns or pyroclastic density currents (PDCs) large enough to overtop the caldera wall. Thus tephra sequences outside the caldera provide an underestimate of eruption frequency, and care needs to be taken in the interpretation and correlation to distal tephra sequences recognized in marine and terrestrial records. In addition, topographic effects of caldera structures should be considered for the assessment of PDC-related hazards in such moderately sized pyroclastic eruptions.

  19. Interplay Between Tectonics And Volcanic Processes Active In The Yellowstone Caldera Detected Via DInSAR And GPS Time-Series

    Science.gov (United States)

    Tizzani, Pietro; Battaglia, Maurizio; Castaldo, Raffaele; Pepe, Antonio; Zeni, Giovanni; Lanari, Riccardo

    2014-05-01

    We discriminate and quantify the effects of different stress sources that are active in the Yellowstone volcanic region. In particular, the use of long-term deformation time series allows us to separate the spatial and temporal contributions of the regional tectonic field due to North American (NA) plate motion from the dynamic of magmatic/hydrothermal sources beneath the caldera area. Yellowstone volcano was formed by three major caldera forming eruptions that occurred around 2.0, 1.3 and 0.64 Ma, the most recent one responsible for the 60 km-wide and 40 km-long Yellowstone caldera. Two structural resurgent domes emerged after the last caldera forming eruption: the Mallard Lake (ML) resurgent dome in the southwestern region of Yellowstone caldera, and the Sour Creek (SC) resurgent dome in the northeast part of the caldera. In this work, we extensively exploit DInSAR and GPS measurements to investigate surface deformation at Yellowstone caldera over the last 18 years. We start by analyzing the 1992-2010 deformation time series retrieved by applying the Small BAseline Subset (SBAS) DInSAR technique. This allows us identifying three macro-areas: i) Norris Geyser Basin (NGB), ii) ML and SC resurgent domes and iii) Snake River Plain (SRP), characterized by unique deformation behaviors. In particular, SRP shows a signal related to tectonic deformation, while the other two regions are influenced by the caldera unrest. To isolate the deformation signals related to different stress sources in the Yellowstone caldera, we also remove from the retrieved mean deformation velocity maps the mean displacement rate associated to the northern sector of the Snake River Plain. This latter is the result of tectonic processes controlled by complex interactions between the NA plate, moving in the ENE - WSW direction with a rate of about 2 cm/yr, and the flow of the asthenosphere plume beneath the Yellowstone volcanic region. These de-trended data allow recognizing four major deformation

  20. Workshop on hydrologic and geochemical monitoring in the Long Valley Caldera: proceedings

    Energy Technology Data Exchange (ETDEWEB)

    Sorey, M.L.; Farrar, C.D.; Wollenberg, H.A.

    1984-10-01

    A workshop reviewed the results of hydrologic and geochemical monitoring in the Long Valley caldera. Such monitoring is being done to detect changes in the hydrothermal system induced by ongoing magmatic and tectonic processes. Workshop participants discussed the need to instrument sites for continuous measurements of several parameters and to obtain additional hydrologic and chemical information from intermediate and deep drill holes. In addition to seismic and deformation monitoring, programs are currently in progress to monitor changes in the discharge characteristics of hot springs, fumaroles, and soil gases, as well as pressures and temperatures in wells. Some hydrochemical parameters are measured continuously, others are measured monthly or at longer intervals. This report summarizes the information presented at the hydrologic monitoring workshop, following the workshop agenda which was divided into four sessions: (1) overview of the hydrothermal system; (2) monitoring springs, fumaroles, and wells; (3) monitoring gas emissions; and (4) conclusions and recommendations.

  1. Petrogenesis of Rinjani Post-1257-Caldera-Forming-Eruption Lava Flows

    Directory of Open Access Journals (Sweden)

    Heryadi Rachmat

    2016-06-01

    Full Text Available DOI:10.17014/ijog.3.2.107-126After the catastrophic 1257 caldera-forming eruption, a new chapter of Old Rinjani volcanic activity beganwith the appearance of Rombongan and Barujari Volcanoes within the caldera. However, no published petrogeneticstudy focuses mainly on these products. The Rombongan eruption in 1944 and Barujari eruptions in pre-1944, 1966,1994, 2004, and 2009 produced basaltic andesite pyroclastic materials and lava flows. A total of thirty-one sampleswere analyzed, including six samples for each period of eruption except from 2004 (only one sample. The sampleswere used for petrography, whole-rock geochemistry, and trace and rare earth element analyses. The Rombonganand Barujari lavas are composed of calc-alkaline and high K calc-alkaline porphyritic basaltic andesite. The magmashows narrow variation of SiO2 content that implies small changes during its generation. The magma that formedRombongan and Barujari lavas is island-arc alkaline basalt. Generally, data show that the rocks are enriched in LargeIon Lithophile Elements (LILE: K, Rb, Ba, Sr, and Ba and depleted in High Field Strength Elements (HFSE: Y, Ti,and Nb which are typically a suite from a subduction zone. The pattern shows a medium enrichment in Light REEand relatively depleted in Heavy REE. The processes are dominantly controlled by fractional crystallization andmagma mixing. All of the Barujari and Rombongan lavas would have been produced by the same source of magmawith little variation in composition caused by host rock filter process. New flux of magma would likely have occurredfrom pre-1944 until 2009 period that indicates slightly decrease and increase of SiO2 content. The Rombongan andBarujari lava generations show an arc magma differentiation trend.

  2. Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera

    Science.gov (United States)

    Befus, Kenneth S.; Gardner, James E.

    2016-04-01

    Between 70 and 175 ka, over 350 km3 of high-silica rhyolite magma erupted both effusively and explosively from within the Yellowstone Caldera. Phenocrysts in all studied lavas and tuffs are remarkably homogenous at the crystal, eruption, and caldera-scale, and yield QUILF temperatures of 750 ± 25 °C. Phase equilibrium experiments replicate the observed phenocryst assemblage at those temperatures and suggest that the magmas were all stored in the upper crust. Quartz-hosted glass inclusions contain 1.0-2.5 % H2O and 50-600 ppm CO2, but some units are relatively rich in CO2 (300-600 ppm) and some are CO2-poor (50-200 ppm). The CO2-rich magmas were stored at 90-150 MPa and contained a fluid that was 60-75 mol% CO2. CO2-poor magmas were stored at 50-70 MPa, with a more H2O-rich fluid (X_{{{text{CO}}2 }} = 40-60 %). Storage pressures and volatiles do not correlate with eruption age, volume, or style. Trace-element contents in glass inclusions and host matrix glass preserve a systematic evolution produced by crystal fractionation, estimated to range from 36 ± 12 to 52 ± 12 wt%. Because the erupted products contain eruption. In the Tuffs of Bluff Point and Cold Mountain Creek, matrix glass is less evolved than most inclusions, which may indicate that more primitive rhyolite was injected into the reservoir just before those eruptions. The presence and dissolution of granophyre in one flow may record evidence for heating prior to eruption and also demonstrate that the Yellowstone magmatic system may undergo rapid changes. The variations in depth suggest the magmas were sourced from multiple chambers that follow similar evolutionary paths in the upper crust.

  3. Modeling the Interaction between Fluid Pressure and Faulting in an Earthquake Swarm at Long Valley Caldera

    Science.gov (United States)

    Hsieh, P. A.; Shelly, D. R.; Hill, D. P.

    2016-12-01

    Rapid migration of hypocenters during the 2014 Long Valley Caldera, California, earthquake swarm suggests that the activity was initiated and sustained by fluids, composed primarily of water and carbon dioxide, exsolved from underlying magma (Shelly et al., 2016, JGR, doi:10.1002/2015JB012719). To investigate how fluid pressure and faulting may co-evolve, we develop a simulation model that couples fluid flow with mechanical stress, while treating earthquakes with the "static/dynamic friction" approach developed by McClure and Horne (2010, Geotherm. Resour. Counc. Trans., 34, 381-396). We set up the model to represent a vertical, permeable fault (divided into a grid of elements) bounded by impermeable rock in a strike-slip tectonic environment. At the start of the simulation, a high-pressure source is introduced at depth to represent the injection of magmatic-derived fluids along the fault. The fluid flow component of the model simulates diffusion of the source pressure into the fault, and halts when the pressure increase at a fault element is sufficient to cause failure (slip). Next, the mechanical stress component of the model calculates the stress changes that result from the slip. Because these stress changes could induce surrounding elements to slip, the model iterates through this chain-reaction process until a stable configuration is achieved (i.e., slipped elements do not induce further slips).The patch of slipped elements represents an earthquake in the model. The permeability of the patch is increased to represent the effect of shear displacement, and the pressure diffusion simulation resumes. Although this model implements a simplified representation of the earthquake mechanism, it is able to mimic (using reasonable rock properties) the overall character of a local swarm of approximately 1000 earthquakes (-0.9 < M < 2.8) that occurred during 7 July 2014 in Long Valley Caldera.

  4. Low- δ18O tephra from a compositionally zoned magma body: Fisher Caldera, Unimak Island, Aleutians

    Science.gov (United States)

    Bindeman, Ilya N.; Fournelle, John H.; Valley, John W.

    2001-11-01

    We present the results of an oxygen isotope study of phenocrysts in pumice clasts and ash layers produced by the 9100 yr BP composite dacite-basaltic andesite climactic eruption that formed Fisher Caldera in the eastern Aleutians. Products of the eruption represent a low-δ18O magma with δ18O plagioclase (+4.79±0.24‰) and clinopyroxene (3.81±0.23‰) corresponding to equilibrium at magmatic temperatures. Dacitic and overlying basaltic-andesitic tephra of the climactic eruption, subsequent intracaldera basaltic to andesitic lavas, and a cumulate inclusion, are similarly low in δ18O. Other analyzed lavas and pyroclastics of Unimak island and the lower Alaska peninsula, as well as precaldera Fisher basalt, have normal δ18O magmatic values (>+5.5‰). We propose a model in which prior to 9100 yr BP, normal mantle-derived basaltic magma coalesced in a large shallow precaldera magma chamber during Late Wisconsin glaciation. Lowering of magmatic δ18O resulted then from long-term assimilation of ∼5-10% of syn-glacial hydrothermally-altered country rocks. Differentiation of basaltic magma was concurrent with this assimilation and produced low-δ18O Fisher dacites, cumulates, and post-caldera crystal-richer lavas. We propose the use of δ18O values of phenocrysts (especially alteration-resistant pyroxene) in tephra as a tool for tephrochronological and tephrostratigraphic correlation. Distinctly low-δ18O values are useful in identification of the Fisher ash in the eastern Aleutians and in the lower Alaska Peninsula.

  5. Constraints on tree seedling establishment in montane grasslands of the Valles Caldera, New Mexico.

    Science.gov (United States)

    Coop, Jonathan D; Givnish, Thomas J

    2008-04-01

    Montane and subalpine grasslands are prominent, but poorly understood, features of the Rocky Mountains. These communities frequently occur below reversed tree lines on valley floors, where nightly cold air accumulation is spatially coupled with fine soil texture. We used field experiments to assess the roles of minimum temperature, soil texture, grass competition, and ungulate browsing on the growth, photosynthetic performance, and survival of transplanted ponderosa pine (Pinus ponderosa) seedlings at 32 sites straddling such reversed tree lines in the Valles Caldera National Preserve (VCNP) of the Jemez Mountains, New Mexico (USA). Seedling growth increased most strongly with increasing nighttime minimum temperatures away from the valley bottoms; seedlings experiencing the coldest temperatures on the caldera floor exhibited stunted needles and often no measurable height growth. Based on the chlorophyll fluorescence ratios PhiPSII and Fv/Fm, we found that low minimum temperatures, low soil moisture, and fine soil texture all contributed to photoinhibition. Neighboring herbs had only minor negative effects on seedlings. We found no effect of ungulates, but golden-mantled ground squirrels (Spermophilus lateralis) caused substantial seedling mortality. Second-year seedling survival was highest on sandy soils, and third-year survival was highest at sites with higher minimum temperatures. We conclude that differential tree seedling establishment driven by low minimum temperatures in the valley bottoms is the primary factor maintaining montane grasslands of the VCNP, although this process probably operated historically in combination with frequent surface fire to set the position of the tree line ecotone. As at alpine tree lines, reversed tree lines bordering montane and subalpine grasslands can represent temperature-sensitive boundaries of the tree life form.

  6. Microbiology and geochemistry of Little Hot Creek, a hot spring environment in the Long Valley Caldera.

    Science.gov (United States)

    Vick, T J; Dodsworth, J A; Costa, K C; Shock, E L; Hedlund, B P

    2010-03-01

    A culture-independent community census was combined with chemical and thermodynamic analyses of three springs located within the Long Valley Caldera, Little Hot Creek (LHC) 1, 3, and 4. All three springs were approximately 80 degrees C, circumneutral, apparently anaerobic and had similar water chemistries. 16S rRNA gene libraries constructed from DNA isolated from spring sediment revealed moderately diverse but highly novel microbial communities. Over half of the phylotypes could not be grouped into known taxonomic classes. Bacterial libraries from LHC1 and LHC3 were predominantly species within the phyla Aquificae and Thermodesulfobacteria, while those from LHC4 were dominated by candidate phyla, including OP1 and OP9. Archaeal libraries from LHC3 contained large numbers of Archaeoglobales and Desulfurococcales, while LHC1 and LHC4 were dominated by Crenarchaeota unaffiliated with known orders. The heterogeneity in microbial populations could not easily be attributed to measurable differences in water chemistry, but may be determined by availability of trace amounts of oxygen to the spring sediments. Thermodynamic modeling predicted the most favorable reactions to be sulfur and nitrate respirations, yielding 40-70 kJ mol(-1) e(-) transferred; however, levels of oxygen at or below our detection limit could result in aerobic respirations yielding up to 100 kJ mol(-1) e(-) transferred. Important electron donors are predicted to be H(2), H(2)S, S(0), Fe(2+) and CH(4), all of which yield similar energies when coupled to a given electron acceptor. The results indicate that springs associated with the Long Valley Caldera contain microbial populations that show some similarities both to springs in Yellowstone and springs in the Great Basin.

  7. The Jurassic Bupyeong caldera in South Korea and its tectonic implication

    Science.gov (United States)

    Hwang, J.; Kwon, S.; Kim, T.

    2015-12-01

    The Bupyeong circular structure with ~10 km in diameter, near to the west of Seoul in middle Korea, has been considered as the remnant of a Mesozoic caldera, and consists of felsic volcanic and plutonic rocks. However, the ages of the magmatism have not been well constrained. We measured in situ U-Pb zircon ages using LA-ICP-MS technique. Two welded tuffs at the western part of the structure gave 171.3 ± 2.6 (95% confidence level hereafter) Ma (n=18) and 173.4 ± 4.6 Ma (n=3). Four granitic rocks within the structure gave 170.5 ± 5.2 Ma (n=8), 171.3 ± 2.6 Ma (n=18), 172.3 ± 1.9 Ma (n=19) and 172.3 ± 3.7 Ma (n=10). The age data indicate coeval volcanism and plutonism of early Middle Jurassic, supporting the caldera interpretation. The early Middle Jurassic granitic plutons are widespread in South Korea and form NE-SW or NNE-SSW belts. Only those in the Bupyeong structure are associated with volcanic rocks, indicating that they are shallow level intrusions, while others are deeper level ones. This observation is well supported by aluminum-in-hornblende geobarometric data of previous works, in that granites near the Bupyeong structure have lower emplacement pressure (<4 kb), compared with those in other areas (5-8 kb). In summary, the Bupyeong structure may have formed outside of main orogenic zone during the Daebo (Jurassic) orogeny.

  8. Jurassic ash-flow sheets, calderas, and related intrusions of the Cordilleran volcanic arc in southeastern Arizona: implications for regional tectonics and ore deposits

    Science.gov (United States)

    Lipman, P.W.; Hagstrum, J.T.

    1992-01-01

    Volcanologic, petrologic, and paleomagnetic studies of widespread Jurassic ash-flow sheets in the Huachuca-southern Dragoon Mountains area have led to identification of four large source calderas and associated comagnetic intracaldera intrusions. Stratigraphic, facies, and contact features of the caldera-related tuffs also provide constraints on the locations, lateral displacements, and very existence for some major northwest-trending faults and inferred regional thrusts in southeastern Arizona. Silicic alkalic compositions of the Jurassic caldera-related, ash-flow tuffs; bimodal associated mafic magmatism; and interstratified coarse sedimentary deposits provide evidence for synvolcanic extension and rifting within the Cordilleran magmatic arc. Gold-copper mineralization is associated with subvolcanic intrusions at several of the Jurassic calderas. -from Authors

  9. How Frequently Can a "Supervolcano" Erupt? Rapid Emplacement of Voluminous Compositionally Diverse Ignimbrites, Central San Juan Calderas, Colorado

    Science.gov (United States)

    Lipman, P. W.; McIntosh, W. C.

    2006-12-01

    High-resolution single-crystal laser-fusion 40Ar/39Ar age determinations on sanidine phenocrysts document sequential eruption of four multi-hundred cubic-kilometer ignimbrites and associated lavas flows from calderas in the central San Juan Mountains, Colorado within a cumulative time interval of less than 50-100 ka. The tight recurrence interval was not evident from previous incremental-heating 40Ar/39Ar plateau ages, which were stratigraphically inconsistent on time scales beyond analytical precision. The new single- crystal results show that three tuff sheets, Rat Creek (>150 km3), Cebolla Creek (>250 km3), and Nelson Mountain Tuffs Creek (>500 km3) from spatially overlapping sources in the San Luis- Cochetopa caldera complex, erupted between 26.92±0.05 and 26.91±0.03 Ma (9 separate samples). A sequence of four postcollapse lavas at Cochetopa erupted at 26.86±0.04 Ma (6 samples) while an andesitic stratocone grew within San Luis caldera complex. Concurrently, Snowshoe Mountain Tuff (>500 km3) erupted from the Creede caldera, 20 km to the south, at 26.87±0.05 Ma (5 samples). Within this limited time interval, eruptive compositions fluctuated widely. Rat Creek and Nelson Mountain Tuffs are compositionally zoned from crystal-poor low-Si rhyolite to cpx-bearing dacite, while the intervening Cebolla Creek Tuff is uniform mafic hbl-rich dacite. Cochetopa Dome lavas are nearly aphyric high-Si rhyolite, while Snowshoe Mountain Tuff is crystal-rich low-Si cpx-bearing dacite. For comparison, four ignimbrites from Aso caldera in southern Japan, with a cumulative volume of ~300 km3, erupted at 270, 140, 120, and 90 ka (Nakada et al., 2003); four overlapping caldera collapses at Santorini in the Aegean were each associated with silicic tuff with volumes of several tens of kilometers, at 203, ~100, 21, and 3.6 ka (Druitt, 1999). In contrast, larger "supervolcano" systems, such as Yellowstone, commonly have repose periods of 0.5- 1x106 m.y., even when eruptive compositions

  10. Crystal scale anatomy of a dying supervolcano: an isotope and geochronology study of individual phenocrysts from voluminous rhyolites of the Yellowstone caldera

    Science.gov (United States)

    Watts, Kathryn E.; Bindeman, Ilya N.; Schmitt, Axel K.

    2012-07-01

    A voluminous (>600 km3) and long-lived (~520-75 ka) phase of rhyolitic eruptions followed collapse of the Yellowstone caldera 640 ka. Whether these eruptions represent a dying cycle, or the growth of a new magma chamber, remains an important question. We use new U-Th zircon ages and δ18O values determined by ion microprobe, and sanidine Pb isotope ratios determined by laser ablation, to investigate the genesis of voluminous post-caldera rhyolites. The oldest post-caldera rhyolites, erupted between ~520 and 470 ka, exhibit extreme age and oxygen isotopic heterogeneity, requiring derivation from individual parcels of low-δ18O melts. We find a progressive increase in zircon homogeneity for rhyolite eruptions from ~260 to 75 ka, with homogeneous low-δ18O zircon values of 2.7-2.8‰ that are in equilibrium with low-δ18O host melts for the majority of the youngest eruptions. New sanidine Pb isotope data define separate arrays for post-caldera rhyolites and the caldera-forming tuffs that preceded them, indicating that they were not sourced from a mushy Lava Creek Tuff batholith that remained after caldera collapse. Rather, our new age and isotopic data indicate that the post-caldera rhyolites were generated by remelting of a variety of intracaldera source rocks, consisting of pre-Lava Creek Tuff volcanic and plutonic rocks and earlier erupted post-Lava Creek Tuff rhyolites. Batch assembly of low-δ18O melts starting at ~260 ka resulted in progressive homogenization, followed by differentiation and cooling up until the last rhyolite eruption ~75 ka, a trend that we interpret to be characteristic of a dying magma reservoir beneath the Yellowstone caldera.

  11. Deep-sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu-Ogasawara arc, Japan

    Science.gov (United States)

    Honsho, Chie; Ura, Tamaki; Kim, Kangsoo

    2013-10-01

    We conducted deep-sea magnetic measurements using autonomous underwater vehicles in the Bayonnaise knoll caldera, the Izu-Ogasawara island arc, which hosts the large Hakurei hydrothermal field. We improved the conventional correction method applied for removing the effect of vehicle magnetization, thus greatly enhancing the precision of the resulting vector anomalies. The magnetization distribution obtained from the vector anomaly data shows a ˜2 km wide belt of high magnetization, trending NNW-SSE going through the caldera, and a low-magnetization zone ˜300 m by ˜500 m in area, extending over the Hakurei site. Comparison between the results obtained using the vector anomaly and the total intensity anomaly shows that the magnetic field is determined more accurately, especially in areas of sparse data distribution, when the vector anomaly rather than the total intensity anomaly is used. We suggest a geologically motivated model that basaltic volcanism associated with the back-arc rifting occurred after the formation of the caldera, resulting in the formation of the high-magnetization belt underneath the silicic caldera. The Hakurei hydrothermal field lies in the intersection of the basaltic volcanism belt and the caldera wall fault, suggesting a mechanism that hot water generated by the heat of the volcanic activity has been spouting out through the caldera wall fault. The deposit apparently extends beyond the low-magnetization zone, climbing up the caldera wall. This may indicate that hot water rising from the deep through the alteration zone is transported laterally when it comes near the seafloor along fissures and fractures in the caldera wall.

  12. New geologic evidence for additional 16.5-15.5 Ma silicic calderas in northwest Nevada related to initial impingement of the Yellowstone hot spot

    Energy Technology Data Exchange (ETDEWEB)

    Coble, Matthew A; Mahood, Gail A [Department Geological and Environmental Sciences, 450 Serra Mall, Bldg 320, Stanford University, Stanford, CA 94305-3115 (United States)

    2008-10-01

    Three silicic calderas have been newly identified in northwest Nevada west of McDermitt caldera. This volcanism is interpreted to have formed during a short interval at 16.5-15.5 Ma, during the waning stage of Steens flood basalt volcanism after the initial impingement of the Yellowstone hot spot. New mapping demonstrates that the area affected by this mid-Miocene silicic volcanism is significantly larger than previously appreciated in the western U.S.

  13. Overview for geologic field-trip guides to Mount Mazama, Crater Lake Caldera, and Newberry Volcano, Oregon

    Science.gov (United States)

    Bacon, Charles R.; Donnelly-Nolan, Julie M.; Jensen, Robert A.; Wright, Heather M.

    2017-08-16

    These field-trip guides were written for the occasion of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) quadrennial scientific assembly in Portland, Oregon, in August 2017. The guide to Mount Mazama and Crater Lake caldera is an updated and expanded version of the guide (Bacon, 1989) for part of an earlier IAVCEI trip to the southern Cascade Range. The guide to Newberry Volcano describes the stops included in the 2017 field trip. Crater Lake and Newberry are the two best-preserved and most recent calderas in the Cascades Volcanic Arc. Although located in different settings in the arc, with Crater Lake on the arc axis and Newberry in the rear-arc, both volcanoes are located at the intersection of the arc and the northwest corner region of the extensional Basin and Range Province.

  14. Rapid differentiation in a sill-like magma reservoir: a case study from the campi flegrei caldera.

    Science.gov (United States)

    Pappalardo, Lucia; Mastrolorenzo, Giuseppe

    2012-01-01

    In recent decades, geophysical investigations have detected wide magma reservoirs beneath quiescent calderas. However, the discovery of partially melted horizons inside the crust is not sufficient to put constraints on capability of reservoirs to supply cataclysmic eruptions, which strictly depends on the chemical-physical properties of magmas (composition, viscosity, gas content etc.), and thus on their differentiation histories. In this study, by using geochemical, isotopic and textural records of rocks erupted from the high-risk Campi Flegrei caldera, we show that the alkaline magmas have evolved toward a critical state of explosive behaviour over a time span shorter than the repose time of most volcanic systems and that these magmas have risen rapidly toward the surface. Moreover, similar results on the depth and timescale of magma storage were previously obtained for the neighbouring Somma-Vesuvius volcano. This consistency suggests that there might be a unique long-lived magma pool beneath the whole Neapolitan area.

  15. Caldera collapse: Perspectives from comparing Galápagos volcanoes, nuclear-test sinks, sandbox models, and volcanoes on Mars

    Science.gov (United States)

    Howard, K.A.

    2010-01-01

    The 1968 trapdoor collapse (1.5 km3) of Fernandina caldera in the Galapágos Islands developed the same kinds of structures as found in small sandbox-collapse models and in concentrically zoned sinks formed in desert alluvium by fault subsidence into underground nuclear-explosion cavities. Fernandina’s collapse developed through shear failure in which the roof above the evacuating chamber was lowered mostly intact. This coherent subsidence contrasts to chaotic piecemeal collapse at small, rocky pit craters, underscoring the role of rock strength relative to subsidence size. The zoning at Fernandina implies that the deflated magma chamber underlay a central basin and a bordering inward-dipping monocline, which separates a blind inner reverse fault from an outer zone of normal faulting. Similar concentric zoning patterns can be recognized in coherent subsidence structures ranging over 16 orders of magnitude in size, from sandbox experiments to the giant Olympus Mons caldera on Mars.

  16. Measuring Variable Scales of Surface Deformation in and around the Yellowstone Caldera with TerraSAR-X Interferometry

    Science.gov (United States)

    Wicks, C. W., Jr.; Dzurisin, D.

    2014-12-01

    Utilizing three years of TerraSAR-X (TSX) Stripmap data covering the Yellowstone Caldera, Wyoming, we identify several examples showing the benefits of the high spatial and temporal resolution TSX data. Although the Stripmap footprints are small, compared to those of past SAR satellites, we are nonetheless able to track subsidence/uplift cycles of the ~50 x 80 km Yellowstone caldera using multiple strips. The Stripmap data are also useful for measuring deformation associated with the area of the North Rim anomaly, an area of repeated uplift and subsidence, ~30 km in diameter near the intersection of the north caldera rim, north-trending Mammoth-Norris Corridor, and west-northwest trending seismic belt east of Hebgen Lake. We measured ~45 mm of uplift associated with an episode that occurred mostly during the winter of 2013-2014 (as verified by GPS), and ~15 mm of subsequent subsidence in the early summer of 2014. The TSX Stripmap data have also proven effective at measuring small-scale deformation features. Because of the high-resolution of the TSX Stripmap data, we have also been able to measure many small-scale deforming features in Yellowstone National Park that are associated with apparent aquifer discharge/recharge cycles, unstable slope movement, geyser basin deformation, and deformation related to other hydrothermal features. We present an example of ~3 cm of seasonal deformation likely resulting from water movement in and out of an aquifer along the southwest caldera rim. We also document subsidence of ~1 cm/yr in a circular area nearly 0.5 km across near the vent from the Pitchstone Plateau, a thick rhyolite flow that erupted nearly 70 ka. TSX data are instrumental in identifying the seasonal variation found in some of these features, and in measuring the small spatial areas of deformation associated with other features.

  17. The Late Cretaceous Middle Fork caldera, its resurgent intrusion, and enduring landscape stability in east-central Alaska

    Science.gov (United States)

    Bacon, Charles R.; Dusel-Bacon, Cynthia; Aleinikoff, John N.; Slack, John F.

    2014-01-01

    Dissected caldera structures expose thick intracaldera tuff and, uncommonly, cogenetic shallow plutons, while remnants of correlative outflow tuffs deposited on the pre-eruption ground surface record elements of ancient landscapes. The Middle Fork caldera encompasses a 10 km × 20 km area of rhyolite welded tuff and granite porphyry in east-central Alaska, ∼100 km west of the Yukon border. Intracaldera tuff is at least 850 m thick. The K-feldspar megacrystic granite porphyry is exposed over much of a 7 km × 12 km area having 650 m of relief within the western part of the caldera fill. Sensitive high-resolution ion microprobe with reverse geometry (SHRIMP-RG) analyses of zircon from intracaldera tuff, granite porphyry, and outflow tuff yield U-Pb ages of 70.0 ± 1.2, 69.7 ± 1.2, and 71.1 ± 0.5 Ma (95% confidence), respectively. An aeromagnetic survey indicates that the tuff is reversely magnetized, and, therefore, that the caldera-forming eruption occurred in the C31r geomagnetic polarity chron. The tuff and porphyry have arc geochemical signatures and a limited range in SiO2 of 69 to 72 wt%. Although their phenocrysts differ in size and abundance, similar quartz + K-feldspar + plagioclase + biotite mineralogy, whole-rock geochemistry, and analytically indistinguishable ages indicate that the tuff and porphyry were comagmatic. Resorption of phenocrysts in tuff and porphyry suggests that these magmas formed by thermal rejuvenation of near-solidus or solidified crystal mush. A rare magmatic enclave (54% SiO2, arc geochemical signature) in the porphyry may be similar to parental magma and provides evidence of mafic magma and thermal input.

  18. Magnetotelluric imaging of the resurgent caldera on the island of Ischia (southern Italy): inferences for its structure and activity

    Science.gov (United States)

    Di Giuseppe, M. G.; Troiano, A.; Carlino, S.

    2017-12-01

    The island of Ischia (located in the Bay of Naples, Italy) represents a peculiar case of a well-exposed caldera that has experienced a large (>800 m) and rapid resurgence, accompanied by volcanic activity. What drives the resurgence of calderas is a crucial issue to investigate, because this process is associated with potential eruptions and high risk to people living within and around such large active volcanic systems. To improve the knowledge of volcano-tectonic processes affecting the caldera of Ischia, electromagnetic imaging of the structures associated with its resurgence was performed and integrated with available geological information. A magnetotelluric (MT) survey of the island was carried out along two main profiles through the central-western sector, providing an electrical resistivity map to a depth of 3 km. These resistivity cross sections allowed us to identify the presence of a very shallow magmatic intrusion, possibly a laccolith, at a depth of about 1 km, which was responsible for both the resurgence and the volcanic activity. Furthermore, the tectonic structures bordering the resurgent area and the occurrence of a large thermal anomaly in the western sector of the caldera also provided a signature in the resistivity cross sections, with the magma intrusion producing advection of hot fluids with high geothermal gradients (>150 °C km-1) in the southern and western sectors. All of these data are fundamental for the assessment of the island's volcano-tectonic dynamics and their associated hazards. The structure and activity of the island have been controlled by the process of resurgence associated with the arrival of new magma and the progressive intrusion of a laccolith at a shallow depth. The reactivation of such a shallow system may imply imminent eruption which would pose a major volcanic hazard.

  19. Low-velocity zones in the crust beneath Aso caldera, Kyushu, Japan, derived from receiver function analyses

    Science.gov (United States)

    Abe, Yuki; Ohkura, Takahiro; Shibutani, Takuo; Hirahara, Kazuro; Yoshikawa, Shin; Inoue, Hiroyuki

    2017-03-01

    Aso volcano, in central Kyushu Island in southwest Japan, has a large caldera (18 × 25 km) that formed by the ejection of more than 600 km3 of deposits 89 thousand years ago. We calculated receiver functions from teleseismic waveform data obtained from densely distributed stations in and around the caldera. We estimated the crustal S wave velocity structure from the receiver functions by using genetic algorithm inversion. We detected a low-velocity zone (Vs > 2.2 km/s) at a depth of 8-15 km beneath the eastern flank of the central cones. A sill-like deformation source has been detected at a depth of 15.5 km by analyses of GPS data, and a swarm of low-frequency earthquakes exists at depths of 15-25 km just beneath this low-velocity zone. Magma may be newly generated and accumulated in this low-velocity zone as a result of hot intrusions coming from beneath it. Except for the region beneath the eastern flank of the central cones, a second low-velocity zone (Vs > 1.9 km/s) extends in and around the caldera at a depth of 15-23 km, although phenomena representing intrusions have not been detected below it. From the estimated velocity structure, these low-velocity zones are interpreted to contain a maximum of 15% melt or 30% water.

  20. Evidence for water influx from a caldera lake during the explosive hydromagmatic eruption of 1790, Kilauea volcano, Hawaii

    Science.gov (United States)

    Mastin, L.G.

    1997-01-01

    In 1790 a major hydromagmatic eruption at the summit of Kilauea volcano, Hawaii, deposited up to 10 m of pyroclastic fall and surge deposits and killed several dozen Hawaiian natives who were crossing the island. Previous studies have hypothesized that the explosivity of this eruption was due to the influx of groundwater into the conduit and mixing of the groundwater with ascending magma. This study proposes that surface water, not groundwater, was the agent responsible for the explosiveness of the eruption. That is, a lake or pond may have existed in the caldera in 1790 and explosions may have taken place when magma ascended into the lake from below. That assertion is based on two lines of evidence: (1) high vesicularity (averaging 73% of more than 3000 lapilli) and high vesicle number density (105-107 cm-3 melt) of pumice clasts suggest that some phases of the eruption involved vigorous, sustained magma ascent; and (2) numerical calculations suggest that under most circumstances, hydrostatic pressure would not be sufficient to drive water into the eruptive conduit during vigorous magma ascent unless the water table were above the ground surface. These results are supported by historical data on the rate of infilling of the caldera floor during the early 1800s. When extrapolated back to 1790, they suggest that the caldera floor was below the water table.

  1. A novel thermophilic methane-oxidizing bacteria from thermal springs of Uzon volcano caldera, Kamchatka

    Science.gov (United States)

    Dvorianchikova, E.; Kizilova, A.; Kravchenko, I.; Galchenko, V.

    2012-04-01

    Methane is a radiatively active trace gas, contributing significantly to the greenhouse effect. It is 26 times more efficient in absorbing and re-emitting infrared radiation than carbon dioxide. Methanotrophs play an essential role in the global carbon cycle by oxidizing 50-75% of the biologically produced methane in situ, before it reaches the atmosphere. Methane-oxidizing bacteria are isolated from the various ecosystems and described at present. Their biology, processes of methane oxidation in fresh-water, marsh, soil and marine habitats are investigated quite well. Processes of methane oxidation in places with extreme physical and chemical conditions (high or low , salinity and temperature values) are studied in much smaller degree. Such ecosystems occupy a considerable part of the Earth's surface. The existence of aerobic methanotrophs inhabiting extreme environments has been verified so far by cultivation experiments and direct detection of methane monooxygenase genes specific to almost all aerobic methanotrophs. Thermophilic and thermotolerant methanotrophs have been isolated from such extreme environments and consist of the gammaproteobacterial (type I) genera Methylothermus, Methylocaldum, Methylococcus and the verrucomicrobial genus Methylacidiphilum. Uzon volcano caldera is a unique area, where volcanic processes still happen today. Hydrothermal springs of the area are extreme ecosystems which microbial communities represent considerable scientific interest of fundamental and applied character. A thermophilic aerobic methane-oxidising bacterium was isolated from a sediment sample from a hot spring (56.1; 5.3) of Uzon caldera. Strain S21 was isolated using mineral low salt medium. The headspace gas was composed of CH4, Ar, CO2, and O2 (40:40:15:5). The temperature of cultivation was 50, pH 5.5. Cells of strain S21 in exponential and early-stationary phase were coccoid bacilli, about 1 μm in diameter, and motile with a single polar flagellum. PCR and

  2. Reservoir processes and fluid origins in the Baca Geothermal System, Valles Caldera, New Mexico

    Science.gov (United States)

    Truesdell, Alfred H.; Janik, Cathy J.

    1986-02-01

    At the Baca geothermal field in the Valles caldera, New Mexico, 19 deep wells were drilled in an attempt to develop a 50-MWe (megawatts electric) power plant. The chemical and isotopic compositions of steam and water samples have been used to indicate uniquely the origin of reservoir fluids and natural reservoir processes. Two distinct reservoir fluids exist at Baca. These fluids originate from the same deep, high-temperature (335°C), saline (2500 mg/kg Cl) parent water but have had different histories during upflow. One fluid (from wells 4 and 13) is isotopically light, high in radiogenic noble gases, CO2 and HCO3, and low in Ca. It has a temperature of 290°-295°C and a reservoir chloride near 1900 mg/kg. This fluid resulted from rapid upward flow through 1.1- to 1.4-m.y.-old Bandelier Tuff reservoir rocks after long residence in pre-Bandelier (>7 m.y.) sediments and Precambrian basement rocks and 25% dilution with high-altitude cold groundwater from Redondo Peak. The other water (from wells 15, 19, and 24) moved slowly through the Bandelier Tuff and cooled conductively (with minor steam loss for well 19) from 335°C to 280°-260°C. Apparently, short residence in old basement rocks has left this water with low radiogenic gases. Conductive cooling without mixing has kept the original chloride and relatively heavy isotope composition of the deep water. The recharge to the deep parent water is not well understood but may be from lower elevation precipitation outside the Valles caldera area. Gases are in equilibrium in all-liquid reservoir fluids at near reservoir temperatures, and the concentrations of atmospheric gases are similar to those of air-saturated water, indicating little boiling and steam loss. All water, solutes, and gases in the reservoir fluids originate from air-saturated meteoric recharge water, watermineral reactions, and rock leaching, with the possible exception of excess 3He that must have an ultimate mantle source. This gas could originate

  3. Volatile Release and Eruption Dynamics of a Basaltic Plinian Eruption From Masaya Caldera, Nicaragua

    Science.gov (United States)

    Wehrmann, H.; Freundt, A.; Kutterolf, S.; Schmincke, H.; Strauch, W.

    2003-12-01

    Our project is part of SFB 574 "Volatiles and Fluids in subduction zones", and focusses on degassing dynamics of highly-explosive arc volcanoes. Masaya Caldera in west-central Nicaragua is part of the Central American volcanic arc at the convergent boundary of the Cocos and Carribean plates. A basaltic plinian eruption of VEI 6 occurred at Masaya Caldera in the Late-Pleistocene, depositing a widespread fan of scoria lapilli, named Fontana Tephra. We have constrained parameters of the Fontana eruption by extensive isopach and isopleth mapping. Total erupted tephra volume is >0.83 km3 (about 1012 kg DRE). The eruption columns reached 30 to 35 km height at an average discharge rate of 1.3*108 kg/s. This violent eruption was not continuous but proceeded in distinct pulses evident by the well-bedded deposit. An initial sequence of numerous highly explosive but short pulses formed a well-bedded layer of very highly vesicular, hawaiian-type lapilli, possibly representing a gas-enriched top zone of the magma reservoir. The following series of longer-duration plinian events, interupted by weak phases of ash emission, formed beds of highly vesicular scoria lapilli. The eruption ceased with abundant short-lived pulses of lower-energy subplinian activity. We estimate volatile emissions during the eruption from the differences in volatile concentration between matrix glass and glass inclusions in minerals, considered to represent degassed and undegassed melt, respectively. Concentrations of fluorine of about 7000 ppm are about equal in matrix glass and glass inclusions, indicating little degassing of fluorine during eruption. Chlorine contents amount to 1200 ppm in the inclusions, and to about 1000 ppm in matrix glass. The concentration difference, multiplied by erupted magma mass, suggests a total chlorine emission of 16 Mt. Apparently only little chlorine exsolved in the initial eruption phase, but degassing strongly increased during the plinian phase. Sulphur concentrations

  4. Historical Earthquakes and Expected Seismic Damage at Ischia Island, Resurgent Caldera (Southern Italy)

    Science.gov (United States)

    Carlino, S.; Cubellis, E.

    2005-05-01

    Information on the seismicity of the Ischia island spans about eight centuries, starting from 1228. This is characterized by the occurence of earthquakes with low energy and high intensity. The most recent earthquake of 1883 caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island, specially at Casamicciola town. This event (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed. After the 1883 earthquake there was a period of seismic quiescence except for some isolated events felt at beginning of the last century and the very occasional micro-earthquakes recorded in the last 20 years in the northern part of the island. The epicenter of all known earthquakes are on the northern slope of Mt. Epomeo (787 m a. s.l.) resurgent block, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. The Mt. Epomeo is a resurgent structure in the central sector of the island, whose uplift is correlated to the caldera resurgence process, for the increase of pressure of shallow magma reservoir. The caldera was formed after a large explosive eruption that deposited the Mt. Epomeo Green Tuff, about 55 ka B.P. The uplift, which started about 30 ka B.P., was of about 900 meters. The resurgent structure is bordered by a system of faults and fractures, with NW-SE, NE-SW and N-S strike and along these faults, in the northern sector, the seismicity has been localized. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such

  5. Perspectives on managing multi-cultural landscapes: Use, access, and fire/fuels management attitudes and preferences of user groups concerning the Valles Caldera National Preserve (VCNP) and adjacent areas

    Science.gov (United States)

    Kurt F. Anschuetz

    2014-01-01

    The Valles Caldera National Preserve (VCNP), which consists of a large, 1.2- to 1.6-million-year-old volcanic caldera, forms the heart of the Jemez Mountains in north-central New Mexico (Figure 1). Known as the Valles Caldera, this bowl-shaped hollow is an especially treasured place within this beloved mountainous landscape for many residents of the region. Its valles...

  6. Seismic Signals reveal Precursors, Force History and Runout Dynamics of the Tsunami-creating Askja Caldera Landslide, July 21, 2014

    Science.gov (United States)

    Schöpa, A.; Chao, W. A.; Burtin, A.; Hovius, N.

    2016-12-01

    We have analysed signals from a network of 52 seismic stations that recorded a large landslide at the steep-sided Askja caldera, Central Iceland, on 21 July 2014. As no direct observations where made, the seismic signals are a very valuable record not only to describe the landslide dynamics in great detail but also to identify triggers and precursors of the slide useful for early warning purposes. This study is motivated by the high hazard potential of the side as the landslide created a tsunami in the caldera lake with waves up to 60 m high reaching famous tourist spots at the northern lake shore. Analysis of the high frequencies reveals that the main slope failure started at 23.24UTC. The relatively long rise time of 40 s until the maximum peak ground velocity was reached points towards cascading failure of the caldera wall. The high seismic energies recorded during the first two minutes of the slide are the result of colliding and impacting blocks. Velocity peaks in the seismic signals following the main failure are indicative for subsequent slope failures that occur less frequent, with shorter duration and lower amplitude during the twelve hours after the main event. The high frequency records of the stations up to 30 km away from the landslide source area show that the background noise level started to increase 20 min before the main failure, with amplitudes up to three times the background level about seven minutes before the main slide. Five minutes before the main failure, amplitudes decreased back to the background level. The characteristic increase and decrease in ground velocities before the main landslide could be implemented in a monitoring and early warning system of the caldera walls at Askjas. Inversion of the long-period signals (0.025-0.05 Hz) enables us to describe the history of the forces acting on the Earth during the landslide. The maximum acceleration of the moving mass was reached 40 s after the start of the slide with unloading forces

  7. Mega-rings Surrounding Timber Mountain Nested Calderas, Geophysical Anomalies: Rethinking Structure and Volcanism Near Yucca Mountain (YM), Nevada

    Science.gov (United States)

    Tynan, M. C.; Smith, K. D.; Savino, J. M.; Vogt, T. J.

    2004-12-01

    Observed regional mega-rings define a zone ˜80-100 km in diameter centered on Timber Mountain (TM). The mega-rings encompass known smaller rhyolitic nested Miocene calderas ( ˜11-15 my, calderas cluster within the central area and on the outer margin of the interpreted larger mega-ring complex. The mega-ring interpretation is consistent with observations of regional physiography, tomographic images, seismicity patterns, and structural relationships. Mega-rings consist of arcuate faulted blocks with deformation (some remain active structures) patterns showing a genetic relationship to the TM volcanic system; they appear to be spatially associated and temporally correlated with Miocene volcanism and two geophysically identified crustal/upper mantle features. A 50+ km diameter pipe-like high velocity anomaly extends from crustal depth to over 200 km beneath TM (evidence for 400km depth to NE). The pipe is located between two ˜100 km sub-parallel N/S linear trends of small-magnitude earthquake activity, one extending through the central NV Test Site, and a second located near Beatty, NV. Neither the kinematics nor relational mechanism of 100km seismically active N/S linear zones, pipe, and mega-rings are understood. Interpreted mega-rings are: 1) Similar in size to larger terrestrial volcanic complexes (e.g., Yellowstone, Indonesia's Toba system); 2) Located in the region of structural transition from the Mohave block to the south, N/S Basin and Range features to the north, Walker Lane to the NW, and the Las Vegas Valley shear zone to the SE; 3) Associated with the two seismically active zones (similar to other caldera fault-bounded sags), the mantle high velocity feature, and possibly a regional bouguer gravity anomaly; 4) Nearly coincident with area hydrologic basins and sub-basins; 5) Similar to features described from terrestrial and planetary caldera-collapse studies, and as modeled in laboratory scaled investigations (ice melt, balloon/sand). Post Mid

  8. High-Resolution Seismic Identification of the Caldera System and Dynamics of the Haakon Mosby Mud Volcano, Barents Sea Slope.

    Science.gov (United States)

    Perez-Garcia, C.; Feseker, T.; Mienert, J.; Berndt, C.

    2007-12-01

    The Haakon Mosby Mud Volcano (HMMV) is an active 1 km wide cold seep structure located at 1250 m deep in the Bear Island Slide, southwestern Barents Sea. The HMMV is one of the few examples of mud volcanoes in non-compressional tectonic settings. Previous studies defined the deeper structure of the HMMV as an approximately 3 km deep seismic disturbance in Plio-Pleistocene deposits. Two-dimensional 3.5 kHz Sediment Echosounder Profiler data combined with Chirp seismic data collected during two cruises in 2005 and 2006 show the HMMV as an inverted-conical-shaped structure composed by five seismic units (U5-U1 from older to younger) and characterized by pull-down of reflections towards its geometrical centre as well as by a vertically oriented central area of poor seismic image quality. The lack of coherent reflectivity or "blanking" is likely due to the presence of gas in the section. Several studies have interpreted this lack of reflectivity as a "caldera" for mud volcanoes which constitutes the main pathway for fluid and gas in such structures. Isopach maps of the identified seismic units show that U5-U2 distribution is regional, but the youngest unit U1 is confined to the surroundings of the HMMV. The seismic signature of U5-U3 is mainly parallel or absent while unit U1 follows a hummocky trend, interpreted as mud flow deposits. Although the seismic unit U2 is mainly parallel, hummocky reflections as those in U1 have been identified westward of the geometrical centre of the volcano. Detailed analysis of the blanking effect over the seismic units reveals spatially overlapping calderas indicating different ages. Both size and position change, being circular and centrically located in U5-U3 units and oval and northeasterly displaced in both U2 and U1. The shallow structure of the HMMV can be described as a caldera complex in which five overlapping calderas have been identified. They record the migration dynamics of the HMMV over the time. Three years of in

  9. The shallow-water chitons (Mollusca, Polyplacophora of Caldera, Region of Atacama, northern Chile

    Directory of Open Access Journals (Sweden)

    Juan Francisco Araya

    2015-03-01

    Full Text Available The Molluscan species of the northern littoral of Chile have been sparsely studied. This work reviews for the first time the diversity of polyplacophoran molluscs around the port of Caldera, in the Region of Atacama (26°45’49”S; 70°45’17”W to 27°20’23”S; 70°56’46”W, northern Chile. Eleven species were found in this study: Acanthopleura echinata (Barnes, 1824; Callistochiton pulchellus (Gray, 1828; Calloplax vivipara (Plate, 1899, Chaetopleura peruviana (Lamarck, 1819; Chiton cumingsii Frembly, 1827; Chiton granosus Frembly, 1827; Chiton magnificus Deshayes, 1827; Enoplochiton niger (Barnes, 1824, Radsia barnesii (Gray, 1828, Tonicia atrata (G. B. Sowerby II, 1840 and Tonicia chilensis (Frembly, 1827. All of the species occurring in the area have distributions in the southeastern Pacific Ocean, from Ecuador to central Chile, and three of them are species endemic to the Chilean coasts (Calloplax vivipara, Radsia barnesii, and Tonicia atrata. This diversity of species is comparable to that of better surveyed faunas of central and southern Chile or Patagonia. Of the eleven species recorded, the geographic distribution records for Callistochiton pulchellus, Radsia barnesii and Tonicia atrata are extended, and Calloplax vivipara is found alive again after 40 years, filling a gap in its known distribution. Illustrations of living specimens in their habitat, distribution records and a taxonomic key for all the studied taxa are also provided.

  10. Microbial diversity in acidic thermal pools in the Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Mardanov, Andrey V; Gumerov, Vadim M; Beletsky, Alexey V; Ravin, Nikolai V

    2017-08-16

    Microbial communities of four acidic thermal pools in the Uzon Caldera, Kamchatka, Russia, were studied using amplification and pyrosequencing of 16S rRNA gene fragments. The sites differed in temperature and pH: 1805 (60 °C, pH 3.7), 1810 (90 °C, pH 4.1), 1818 (80 °C, pH 3.5), and 1807 (86 °C, pH 5.6). Archaea of the order Sulfolobales were present among the dominant groups in all four pools. Acidilobales dominated in pool 1818 but were a minor fraction at the higher temperature in pool 1810. Uncultivated Archaea of the Hot Thaumarchaeota-related clade were present in significant quantities in pools 1805 and 1807, but they were not abundant in pools 1810 and 1818, where high temperatures were combined with low pH. Nanoarchaeota were present in all pools, but were more abundant in pools 1810 and 1818. A similar abundance pattern was observed for Halobacteriales. Thermophilic Bacteria were less diverse and were mostly represented by aerobic hydrogen- and sulfur-oxidizers of the phylum Aquificae and sulfur-oxidising Proteobacteria of the genus Acidithiobacillus. Thus we showed that extremely acidic hot pools contain diverse microbial communities comprising different metabolic groups of prokaryotes, including putative lithoautotrophs using energy sources of volcanic origin, and various facultative and obligate heterotrophs.

  11. Biodiversity of thermophilic prokaryotes with hydrolytic activities in hot springs of Uzon Caldera, Kamchatka (Russia).

    Science.gov (United States)

    Kublanov, Ilya V; Perevalova, Anna A; Slobodkina, Galina B; Lebedinsky, Aleksander V; Bidzhieva, Salima K; Kolganova, Tatyana V; Kaliberda, Elena N; Rumsh, Lev D; Haertlé, Thomas; Bonch-Osmolovskaya, Elizaveta A

    2009-01-01

    Samples of water from the hot springs of Uzon Caldera with temperatures from 68 to 87 degrees C and pHs of 4.1 to 7.0, supplemented with proteinaceous (albumin, casein, or alpha- or beta-keratin) or carbohydrate (cellulose, carboxymethyl cellulose, chitin, or agarose) biological polymers, were filled with thermal water and incubated at the same sites, with the contents of the tubes freely accessible to the hydrothermal fluid. As a result, several enrichment cultures growing in situ on different polymeric substrates were obtained. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments obtained after PCR with Bacteria-specific primers showed that the bacterial communities developing on carbohydrates included the genera Caldicellulosiruptor and Dictyoglomus and that those developing on proteins contained members of the Thermotogales order. DGGE analysis performed after PCR with Archaea- and Crenarchaeota-specific primers showed that archaea related to uncultured environmental clones, particularly those of the Crenarchaeota phylum, were present in both carbohydrate- and protein-degrading communities. Five isolates obtained from in situ enrichments or corresponding natural samples of water and sediments represented the bacterial genera Dictyoglomus and Caldanaerobacter as well as new archaea of the Crenarchaeota phylum. Thus, in situ enrichment and consequent isolation showed the diversity of thermophilic prokaryotes competing for biopolymers in microbial communities of terrestrial hot springs.

  12. Uncultured archaea dominate in the thermal groundwater of Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Mardanov, Andrey V; Gumerov, Vadim M; Beletsky, Alexey V; Perevalova, Anna A; Karpov, Gennady A; Bonch-Osmolovskaya, Elizaveta A; Ravin, Nikolai V

    2011-05-01

    The thermoacidophilic microbial community inhabiting the groundwater with pH 4.0 and temperature 50°C at the East Thermal Field of Uzon Caldera, Kamchatka, was examined using pyrosequencing of the V3 region of the 16S rRNA gene. Bacteria comprise about 30% of microorganisms and are represented primarily by aerobic lithoautotrophs using the energy sources of volcanic origin--thermoacidophilic methanotrophs of the phylum Verrucomicrobia and Acidithiobacillus spp. oxidising metals and reduced sulfur compounds. More than 70% of microbial population in this habitat were represented by archaea, in majority affiliated with "uncultured" lineages. The most numerous group (39% of all archaea) represented a novel division in the phylum Euryarchaeota related to the order Thermoplasmatales. Another abundant group (33% of all archaea) was related to MCG1 lineage of the phylum Crenarchaeota, originally detected in the Yellowstone hot spring as the environmental clone pJP89. The organisms belonging to these two groups are widely spread in hydrothermal environments worldwide. These data indicate an important environmental role of these two archaeal groups and should stimulate the investigation of their metabolism by cultivation or metagenomic approaches.

  13. Change in Magma Dynamics at Okataina Rhyolite Caldera revealed by Plagioclase Textures and Geochemistry

    Science.gov (United States)

    Shane, P. A. R.

    2015-12-01

    A fundamental reorganization of magma dynamics at Okataina volcano, New Zealand, occurred at 26 ka involving a change from smaller volume, high-temperature rhyodacite magmas to a lower eruptive tempo of larger volume, low-temperature, rhyolite magmas. Zircon studies demonstrate the presence of a periodically active, long-lived (100,000 yr) magmatic reservoir. However, there is little correlation between periods of zircon crystallization and eruption events. In contrast, the changing magmatic dynamics is revealed in plagioclase growth histories. Crystals from the ~0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular-texture of high-An (>40) zones partially replaced by low-An (cellular texture of variable An content (An 40-50). The crystals display step-wise re-growth of successively higher An, Fe, Mg and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry indicating growth in separate melts and co-occurrence via magma-mingling. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent re-development of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations, resulting in simpler growth histories of the Kaharoa crystals. The plagioclase lack features associated with rapid decompression events that are common in andesite systems.

  14. Duration of the Banco Bonito Rhyolite Eruption, Vales Caldera, New Mexico based on magma transport modeling

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Benjamin R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baldridge, W. Scott [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Gable, Carl W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sicilian, James M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2007-03-05

    Finite volume calculations of the flow of rhyolite are presented to investigate the fate of viscous magmas flowing in planar fractures with realistic length to width ratios of up to 2500:1. Heat and mass transfer for a melt with a temperature dependent viscosity and the potential to undergo phase change are considered. Magma driving pressures and dike widths are chosen to satisfy simple elastic considerations. These models are applied within a parameter space relevant to the Banco Bonito rhyolite flow, Valles caldera, New Mexico. We estimate a maximum eruption duration for the event of ~200 days, realized at a minimum possible dike width of 5-6 m and driving pressure of 7-8 MPa. Simplifications in the current model may warrant scaling of these results. However, we demonstrate the applicability of our model to magma dynamics issues and suggest that such models may be used to infer information about both the timing of an eruption and the evolution of the associated magma source.

  15. A three-dimensional QP imaging of the shallowest subsurface of Campi Flegrei offshore caldera, southern Italy

    Science.gov (United States)

    Serlenga, Vincenzo; de Lorenzo, Salvatore; Russo, Guido; Amoroso, Ortensia; Virieux, Jean; Garambois, Stephane; Zollo, Aldo

    2017-04-01

    We build a three-dimensional attenuation image of the shallowest subsurface of Campi Flegrei caldera, a resurgent caldera located 15 km west of Naples, southern Italy. Extracting tstar (t*) measurements from an active seismic dataset can be achieved by a spectral ratio method which has been intensively used for earthquakes. The applicability of such measurement has to be validated for active seismic datasets which have a narrower frequency band compared to frequency band of quakes. The validation, as well as the robustness, of such extraction for narrow Ricker source wavelet has been checked through many synthetic and realistic tests. These tests allow us to conclude that this measurement is valid as long as 1) short signal time window are chosen to perform the spectral analysis; 2) the effects caused by heterogeneities of the sampled medium on the seismic spectra have to be taken into account in the description of elastic Green's function. Through such a deconvolution strategy, contributions of the fine velocity structure on signal amplitudes have been significantly removed: in case of suspicious behavior of the spectrum ratio, the measurement is disregarded. This procedure, a kind of deconvolution of the phase propagation imprint, is expected to leave nearly untouched the attenuation signature of seismic traces we are interested in. Such refined measurement approach based on the spectral ratio method has been applied to the real active seismic SERAPIS database providing us a reasonable dataset of 11,873 differential t* measurements (dt*). These data are used for imaging anelastic properties of Campi Flegrei caldera through a linearized, iterative, damped attenuation tomography. Based on configuration of sources and receivers, an attenuating volume as large as 13 x 13 x 1.5 km3 has been imaged. The tomography, with a resolution of 1 km in the horizontal directions and 0.5 km in the vertical direction, allowed to image important features whose reliability has been

  16. Voluminous low δ18O magmas in the late Miocene Heise volcanic field, Idaho: Implications for the fate of Yellowstone hotspot calderas

    Science.gov (United States)

    Bindeman, I.N.; Watts, K.E.; Schmitt, A.K.; Morgan, L.A.; Shanks, P.W.C.

    2007-01-01

    We report oxygen isotope compositions of phenocrysts and U-Pb ages of zircons in four large caldera-forming ignimbrites and post-caldera lavas of the Heise volcanic field, a nested caldera complex in the Snake River Plain, that preceded volcanism in Yellowstone. Early eruption of three normal δ18O voluminous ignimbrites with δ18Oquartz = 6.4‰ and δ18Ozircon = 4.8‰ started at Heise at 6.6 Ma, and was followed by a 2‰–3‰ δ18O depletion in the subsequent 4.45 Ma Kilgore caldera cycle that includes the 1800 km3 Kilgore ignimbrite, and post-Kilgore intracaldera lavas with δ18Oquartz = 4.3‰ and δ18Ozircon = 1.5‰. The Kilgore ignimbrite represents the largest known low-δ18O magma in the Snake River Plain and worldwide. The post-Kilgore low δ18O volcanism likely represents the waning stages of silicic magmatism at Heise, prior to the reinitiation of normal δ18O silicic volcanism 100 km to the northeast at Yellowstone. The occurrence of low δ18O magmas at Heise and Yellowstone hallmarks a mature stage of individual volcanic cycles in each caldera complex. Sudden shifts in δ18O of silicic magmas erupted from the same nested caldera complexes argue against any inheritance of the low δ18O signature from mantle or crustal sources. Instead, δ18O age trends indicate progressive remelting of low δ18O hydrothermally altered intracaldera rocks of previous eruptions. This trend may be generally applicable to older caldera complexes in the Snake River Plain that are poorly exposed.

  17. Strengths and strain energies of volcanic edifices: implications for eruptions, collapse calderas, and landslides

    Science.gov (United States)

    Gudmundsson, A.

    2012-07-01

    Natural hazards associated with volcanic edifices depend partly on how fracture resistant the edifices are, i.e. on their strengths. Observations worldwide indicate that large fluid-driven extension fractures (dikes, inclined sheets), shear fractures (landslides), and mixed-mode fractures (ring dikes and ring faults) normally propagate more easily in a basaltic edifice (shield volcano) than in a stratovolcano. For example, dike-fed eruptions occur once every few years in many basaltic edifices but once every 102-3 yr in many stratovolcanoes. Large landslides and caldera collapses also appear to be more common in a typical basaltic edifice/shield volcano than in a typical stratovolcano. In contrast to a basaltic edifice, a stratovolcano is composed of mechanically dissimilar rock layers, i.e. layers with mismatching elastic properties (primarily Young's modulus). Elastic mismatch encourages fracture deflection and arrest at contacts and increases the amount of energy needed for a large-scale edifice failure. Fracture-related hazards depend on the potential energy available to propagate the fractures which, in turn, depends on the boundary conditions during fracture propagation. Here there are two possible scenarios: one in which the outer boundary of the volcanic edifice or rift zone does not move during the fracture propagation (constant displacement); the other in which the boundary moves (constant load). In the former, the total potential energy is the strain energy stored in the volcano before fracture formation; in the latter, the total potential energy is the strain energy plus the work done by the forces moving the boundary. Constant-displacement boundary conditions favor small eruptions, landslides, and caldera collapses, whereas constant-load conditions favor comparatively large eruptions, landslides, and collapses. For a typical magma chamber (sill-like with a diameter of 8 km), the strain energy change due to magma-chamber inflation is estimated at the

  18. Strengths and strain energies of volcanic edifices: implications for eruptions, collapse calderas, and landslides

    Directory of Open Access Journals (Sweden)

    A. Gudmundsson

    2012-07-01

    Full Text Available Natural hazards associated with volcanic edifices depend partly on how fracture resistant the edifices are, i.e. on their strengths. Observations worldwide indicate that large fluid-driven extension fractures (dikes, inclined sheets, shear fractures (landslides, and mixed-mode fractures (ring dikes and ring faults normally propagate more easily in a basaltic edifice (shield volcano than in a stratovolcano. For example, dike-fed eruptions occur once every few years in many basaltic edifices but once every 102-3 yr in many stratovolcanoes. Large landslides and caldera collapses also appear to be more common in a typical basaltic edifice/shield volcano than in a typical stratovolcano. In contrast to a basaltic edifice, a stratovolcano is composed of mechanically dissimilar rock layers, i.e. layers with mismatching elastic properties (primarily Young's modulus. Elastic mismatch encourages fracture deflection and arrest at contacts and increases the amount of energy needed for a large-scale edifice failure. Fracture-related hazards depend on the potential energy available to propagate the fractures which, in turn, depends on the boundary conditions during fracture propagation. Here there are two possible scenarios: one in which the outer boundary of the volcanic edifice or rift zone does not move during the fracture propagation (constant displacement; the other in which the boundary moves (constant load. In the former, the total potential energy is the strain energy stored in the volcano before fracture formation; in the latter, the total potential energy is the strain energy plus the work done by the forces moving the boundary. Constant-displacement boundary conditions favor small eruptions, landslides, and caldera collapses, whereas constant-load conditions favor comparatively large eruptions, landslides, and collapses. For a typical magma chamber (sill-like with a diameter of 8 km, the strain energy change due to magma-chamber inflation

  19. Audiomagnetotellurics-Magnetotelluric (AMT-MT) survey of the Campi Flegrei inner caldera

    Science.gov (United States)

    Siniscalchi, Agata; Tripaldi, Simona; Romano, Gerardo; D'Auria, Luca; Improta, Luigi; Petrillo, Zaccaria

    2017-04-01

    In the framework of the EU project MED-SUV, an audiomagnetotellurics-magnetotelluric (AMT-MT) survey in the frequency band 0.1-100kHz was performed in the eastern border of the Campi Flegrei inner caldera comprising the area where seismicity is concentred in the last decade. This survey was aimed to provide new insights on the electrical resistivity structure of the subsoil. Among all the collected MT soundings, twenty-two, on a total of forty-three, were selected along a WSW-ENE alignment that crosses the main fumarole emissions (Solfatara, Pisciarelli and Agnano) and used for 2D regularized inversion. The obtained model is characterized by a quite narrow resistivity range that well matches typical range of enhanced geothermal environment as largely documented in the international literature. In particular focusing on the Solfatara and Pisciarelli districts the resistivity distribution clearly calls to mind the behavior of a high temperature geothermal system with a very conductive cap in the shallower part. Here the presence of gaps in this conductor just in correspondence of the main superficial emissions describes the inflow and outflow pathway of the shallow fluids circulation. A high resistive reservoir appearing at a depth of about 500 m b.s.l.. WithinWithin this region we selected a vertical resistivity profile just in correspondence of a Vp/Vs profile versus depth coming from a passive seismic tomography (Vanorio et al., 2005). The comparison of the two behaviors shows a clear anti-correlation between the two physical parameters (high resistivity and low Vp/Vs) in the depth range 500-1000 m supporting the interpretation that an over-pressurized gas bearing rocks under supercritical conditions constituting the reservoir of the enhanced geothermal system. On the eastern side of this resistive plume up to 2.5 km of depth is present a local relative conductive unit underneath the Pisciarelli area. In the same volume most of the recent (from 2005 up to date

  20. Optimum geometry for boiler soot blowers nozzles; Geometria optima de toberas para deshollinadores de caldera

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza Garza, Jesus; Garcia Tinoco, Guillermo J.; Martinez Flores, Jose Oscar [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1989-12-31

    For boiler soot blowing converging-diverging nozzles are employed, whose function is to convert thermal energy of a gas into kinetic energy to remove the deposits that adhere to the heat exchanger surfaces. In this paper are described the experimental equipment and the methods for flow, dynamic pressure, discharge velocity and air expansion factor calculation in each nozzle, as a function of its design geometry, utilizing air from a five stage centrifugal compressor. The graphic analysis of the results, concludes that the most efficient nozzles are not the ones than develop the greatest velocity, but the ones of highest dynamic pressure at the outlet. The nozzle geometry that allows obtaining the maximum dynamic air pressure at the discharge is A{sub 2}/A{sub g}=1.3676 [Espanol] Para el deshollinado de calderas se utilizan las toberas convergentes-divergentes, cuya funcion es convertir la energia termica de un gas en energia cinetica para remover los depositos que se adhieren a las superficies de intercambio de calor. En este trabajo se describen el equipo experimental y los metodos de calculo para flujo, presion dinamica, velocidad a la descarga y factor de expansion del aire en cada tobera, como funcion de su geometria de diseno. Durante la experimentacion se evaluaron siete disenos diferentes de toberas, empleando aire de un compresor centrifugo de cinco etapas. Del analisis grafico de los resultados, se concluye que las toberas mas eficientes no son las que desarrollan mayor velocidad sino las de mayor presion dinamica de la salida. La geometria de tobera que permite obtener la maxima presion dinamica del aire a la descarga es A{sub 2}/A{sub g} = 1.3676.

  1. Comparative geochemical and microbiological characterization of two thermal pools in the Uzon Caldera, Kamchatka, Russia.

    Science.gov (United States)

    Burgess, Elizabeth A; Unrine, Jason M; Mills, Gary L; Romanek, Christopher S; Wiegel, Juergen

    2012-04-01

    Arkashin Schurf (Arkashin) and Zavarzin Spring (Zavarzin), two active thermal pools in the Uzon Caldera, Kamchatka, Russia, were studied for geochemical and microbiological characterization. Arkashin, the smaller of the two pools, had broader temperature and pH ranges, and the sediments had higher concentrations of total As (4,250 mg/kg) relative to Zavarzin (48.9 mg/kg). Glycerol dialkyl glycerol tetraether profiles represented distinct archaeal communities in each pool and agreed well with previous studies of these pools. Although no archaeal 16S rRNA sequences were recovered from Arkashin, sequences recovered from Zavarzin were mostly representatives of the Crenarchaeota and "Korarchaeota," and 13% of the sequences were unclassifiable. The bacterial community in Arkashin was dominated by uncultured "Bacteroidetes," Hydrogenobaculum of the Aquificales and Variovorax of the Betaproteobacteria, and 19% of the sequences remained unclassified. These results were consistent with other studies of As-rich features. The most abundant members of the Zavarzin bacterial community included the Chloroflexi, as well as members of the classes Deltaproteobacteria and Clostridia. In addition, 24% of the sequences were unclassified and at least 5% of those represent new groups among the established Bacterial phyla. Ecological structure in each pool was inferred from taxonomic classifications and bulk stable isotope δ values of C, N, and S. Hydrogenobaculum was responsible for primary production in Arkashin. However, in Zavarzin, the carbon source appeared to be allochthonous to the identified bacterial community members. Additionally, sequences related to organisms expected to participate in N and S cycles were identified from both pools.

  2. Microbial life in Bourlyashchy, the hottest thermal pool of Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Chernyh, Nikolay A; Mardanov, Andrey V; Gumerov, Vadim M; Miroshnichenko, Margarita L; Lebedinsky, Alexander V; Merkel, Alexander Y; Crowe, Douglas; Pimenov, Nikolay V; Rusanov, Igor I; Ravin, Nikolay V; Moran, Mary Ann; Bonch-Osmolovskaya, Elizaveta A

    2015-11-01

    Bourlyashchy is the largest and hottest pool in the Uzon Caldera, located in the territory of Kronotsky Nature Reserve, Kamchatka, Russia, with sediment surface temperatures at the margins ranging from 86 to 97 °C, and pH from 6.0 to 7.0. The microbial communities of the pool water and sediments were studied comprehensively from 2005 to 2014. Radioisotopic tracer studies revealed the processes of inorganic carbon assimilation, sulfate reduction, lithotrophic methanogenesis and potentially very active process of acetate oxidation to CO2. The total number of microbial cells in water was different in different years ranging from 5.2 to 7.0 × 10(6); in sediments, it changed from year to year between 6.3 × 10(6) and 1.75 × 10(8), increasing with a decrease in temperature. FISH with Archaea- and Bacteria-specific probes showed that the share of Bacteria differed with year, changing from 34 to 71%. According to 16S rRNA gene pyrosequencing data, lithoautotrophs (Aquificales and Thermoproteales) predominated in water samples, while in sediments they shared the niche with organotrophic Crenarchaeota, Korarchaeota, and bacteria of the genus Caldimicrobium (phylum Thermodesulfobacteria). The majority of organisms in water belonged to cultivated orders of prokaryotes; the only large uncultured group was that representing a novel order in class Thermoprotei. In sediments, unclassified Aquificeae comprised a significant part of the bacterial population. Thus, we showed that the hottest of the terrestrial hot pools studied contains numerous and active microbial populations where Bacteria represent a significant part of the microbial community, and planktonic and sediment populations differ in both composition and function.

  3. The Life and Times of Supervolcanoes: Inferences from Long Valley Caldera

    Science.gov (United States)

    Simon, Justin

    2014-01-01

    Cataclysmic eruptions of silicic magma from "supervolcanoes" are among the most awe-inspiring natural phenomena found in the geologic record, in terms of size, power, and potential hazard. Based on the repose intervals between eruptions of this magnitude, the magmas responsible for them could accumulate gradually in the shallow crust over time scales that may be in excess of a million years (Smith, 1979; Spera and Crisp, 1981; Shaw, 1985). Pre-eruption magma residence time scales can also be inferred from the age difference between eruption (i.e., using 40Ar/39Ar dating to determine the time when hot erupted material cools to below its Ar closure temperature, 200 to 600 degC) and early pre-eruption crystallization (i.e., zircon saturation temperatures; Reid et al., 1997). I will discuss observations from Long Valley a Quaternary volcanic center in California. Long Valley is a voluminous, dominantly silicic caldera system. Based on extensive dating of accessory minerals (e.g., U-Th-Pb dating of zircon and allanite) along with geochemical and isotopic data we find that silicic magmas begin to crystallize 10's to 100's of thousands of years prior to their eruption and that rhyolites record episodes of punctuated and independent evolution rather than the periodic tapping of a long-lived magma. The more punctuated versus more gradual magma accumulation rates required by the absolute and model ages, respectively, imply important differences in the mass and heat fluxes associated with the generation, differentiation, and storage of voluminous rhyolites and emphasize the need to reconcile the magmatic age differences.

  4. Renewed Volcano-Stratigraphc Studies of Calderas with Geothermal Potential in Mexico

    Science.gov (United States)

    Macias, J. L.; Arce, J. L.; García-Tenorio, F.; Layer, P. W.; Saucedo, R.; Castro, R.; Garduño, V. H.; Jimenez, A.; Pérez, H.; Valdez, G.; Meriggi, L.

    2014-12-01

    During the past six years we have carried out volcanologic fieldwork either in active geothermal fields in Mexico (Los Azufres, Tres Vírgenes, and Cerro Prieto) or in potential sites in which some geothermal exploration studied had been done by the National Power Company (CFE). These studies have been very successful in reassessing the location of the geothermal reservoirs within the volcanic successions through detailed mapping of the volcanic units using high resolution topography and satellite imagery to produce 3-D imagery in conjunction with field work to produce preliminary geologic maps. Detailed stratigraphy of volcanic units, assisted with 40Ar/39Ar and radiocarbon geochronology have redefined the evolution of some of these complexes. For example, our studies at Los Azufres geothermal field located in the State of Michoacán indicate that the volcanic complex of the same name sits upon a structural high transected by E-W faults related to the youngest structures of the Trans-Mexican Volcanic Belt. The volcanic complex has been emplaced during the past ~1.5 Ma. During this time, magmas evolved from basaltic to rhyolitic in composition with the emplacement of circa 100 vents. Several landforms have undergone intense hydrothermal alteration and, in some cases, generated debris avalanches. The revised stratigraphy based on drill holes and new dates of cores suggested that the geothermal reservoir is hosted in Miocene rocks bracketed between the Miocene Sierra de Mil Cumbres volcanics (17-22 Ma) and the products of the volcanic field itself. Similar studies will be carried out at four other Pleistocene calderas (Acoculco, La Primavera, Aguajito and Reforma) attempting to refine their volcanic stratigraphy, evolution, and the location of the geothermal system, and those results will help in the design of exploration strategies for geothermal sources.

  5. Estudio vulcanológico y qeoquímico del maar de la Caldera del Rey. Tenerife (Canarias

    Directory of Open Access Journals (Sweden)

    Paradas Herrero, A.

    1984-12-01

    Full Text Available In this study a cartographic, morphological, geochemical and petrographic study is made of the ''Caldera del Rey". The "Caldera del Rey" is a volcanic structure formed by two overlapping maars, The second one (maar that was formed is of greaten dimensions and destroyed part of the first one, Both maars erupted throught a possible fracture N 35 E, which is one of the directions with regional importance in the Archipelago. The eruption, which was very explosive, has been thought to be due in part to the great importance of the gaseous phase of the salic magma and also to the steam produced during the interaction of the magma with underground water. This explosivity can be clearly seen in the cleaf resalte cul out in the "Serie Basáltica Antigua" to some extent penetrated and fragmented by the eruption, The phreatomagmatic character of the eruption is evident because of the existence of accretionary lapilli. The materials emitted are exc1usively of aerial projection: agglomerates, tuffs cinerites. There was no flow of lava. ' Some of the fragments of tuffs as cinerites and pumice are comagmatic. These correspond to salic trachytic phonolitic rocks, which represent one of the last stages of differentiation of the alkaline oceanic magmas. The geochemical character of the materials of the "Caldera del Rey" is characteristic and can be easily distinguished from other nearly salic deposits formed in different cycles.

    En este trabajo se hace el estudio cartográfico, morfológico, petrográfico y geoquímico de la Caldera del Rey. La Caldera del Reyes un edificio volcánico formado por dos maars imbricados. El que se formó en segundo lugar es de mayores dimensiones y destruyó en parte el primero. Ambos aprovecharon para hacer erupción una posible fractura de dirección N 35'"E, de importancia regional en el Archipiélago. La erupción fue de una gran explosividad, que se supone debida, en parte, a la gran importancia de la fase gaseosa del

  6. Real-time monitoring of seismicity and deformation during the Bárdarbunga rifting event and associated caldera subsidence

    Science.gov (United States)

    Jónsdóttir, Kristín; Ófeigsson, Benedikt; Vogfjörd, Kristín; Roberts, Matthew; Barsotti, Sara; Gudmundsson, Gunnar; Hensch, Martin; Bergsson, Bergur; Kjartansson, vilhjálmur; Erlendsson, Pálmi; Friðriksdóttir, Hildur; Hreinsdóttir, Sigrún; Guðmundsson, Magnús; Sigmundsson, Freysteinn; Árnadóttir, Thóra; Heimisson, Elías; Hjorleifsdóttir, Vala; Soring, Jón; Björnsson, Bogi; Oddsson, Björn

    2015-04-01

    We present a monitoring overview of a rifting event and associated caldera subsidence in a glaciated environment during the Bárðarbunga volcanic crisis. Following a slight increase in seismicity and a weak deformation signal, noticed a few months before the unrest by the SIL monitoring team, an intense seismic swarm began in the subglacial Bárðarbunga caldera on August 16 2014. During the following two weeks, a dyke intruded into the crust beneath the Vatnajökull ice cap, propagating 48 km from the caldera to the east-north-east and north of the glacier where an effusive eruption started in Holuhraun. The eruption is still ongoing at the time of writing and has become the largest eruption in over 200 years in Iceland. The dyke propagation was episodic with a variable rate and on several occasions low frequency seismic tremor was observed. Four ice cauldrons, manifestations of small subglacial eruptions, were detected. Soon after the swarm began the 7x11 km wide caldera started to subside and is still subsiding (although at slower rates) and has in total subsided over 60 meters. Unrest in subglacial volcanoes always calls for interdisciplinary efforts and teamwork plays a key role for efficient monitoring. Iceland has experienced six subglacial volcanic crises since modern digital monitoring started in the early 90s. With every crisis the monitoring capabilities, data interpretations, communication and information dissemination procedures have improved. The Civil Protection calls for a board of experts and scientists (Civil Protection Science Board, CPSB) to share their knowledge and provide up-to-date information on the current status of the volcano, the relevant hazards and most likely scenarios. The evolution of the rifting was monitored in real-time by the joint interpretation of seismic and cGPS data. The dyke propagation could be tracked and new, updated models of the dyke volume were presented at the CPSB meetings, often daily. In addition, deformation

  7. Scenario earthquake hazards for the Long Valley Caldera-Mono Lake area, east-central California

    Science.gov (United States)

    Chen, Rui; Branum, David M.; Wills, Chris J.; Hill, David P.

    2014-01-01

    As part of the U.S. Geological Survey’s (USGS) multi-hazards project in the Long Valley Caldera-Mono Lake area, the California Geological Survey (CGS) developed several earthquake scenarios and evaluated potential seismic hazards, including ground shaking, surface fault rupture, liquefaction, and landslide hazards associated with these earthquake scenarios. The results of these analyses can be useful in estimating the extent of potential damage and economic losses because of potential earthquakes and in preparing emergency response plans. The Long Valley Caldera-Mono Lake area has numerous active faults. Five of these faults or fault zones are considered capable of producing magnitude ≥6.7 earthquakes according to the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) developed by the 2007 Working Group of California Earthquake Probabilities (WGCEP) and the USGS National Seismic Hazard Mapping (NSHM) Program. These five faults are the Fish Slough, Hartley Springs, Hilton Creek, Mono Lake, and Round Valley Faults. CGS developed earthquake scenarios for these five faults in the study area and for the White Mountains Fault to the east of the study area. Earthquake scenarios are intended to depict the potential consequences of significant earthquakes. They are not necessarily the largest or most damaging earthquakes possible. Earthquake scenarios are both large enough and likely enough that emergency planners should consider them in regional emergency response plans. Earthquake scenarios presented here are based on fault geometry and activity data developed by the WGCEP, and are consistent with the 2008 Update of the United States National Seismic Hazard Maps (NSHM).For the Hilton Creek Fault, two alternative scenarios were developed in addition to the NSHM scenario to account for different opinions in how far north the fault extends into the Long Valley Caldera. For each scenario, ground motions were calculated using the current standard practice

  8. Zeolite-clay mineral zonation of volcaniclastic sediments within the McDermitt caldera complex of Nevada and Oregon

    Science.gov (United States)

    Glanzman, Richard K.; Rytuba, James J.

    1979-01-01

    Volcaniclastic sediments deposited in the moat of the collapsed McDermitt caldera complex have been altered chiefly to zeolites and potassium feldspar. The original rhyolitic and peralkaline ash-flow tuffs are included in conglomerates at the caldera rims and grade into a lacustrine series near the center of the collapse. The tuffs show a lateral zeolitic alteration from almost fresh glass to clinoptilolite, clinoptilolite-mordenite, and erionite; to analcime-potassium feldspar; and finally to potassium feldspar. Vertical zonation is in approximately the same order. Clay minerals in associated mudstones, on the other hand, show little lateral variation but a distinct vertical zonation, having a basal dioctahedral smectite, a medial trioctahedral smectite, and an upper dioctahedral smectite. The medial trioctahedral smectite is enriched in lithium (as much as 6,800 ppm Li). Hydrothermal alteration of the volcaniclastic sediments, forming both mercury and uranium deposits, caused a distinct zeolite and clay-mineral zonation within the general lateral zonation. The center of alteration is generally potassium feldspar, commonly associated with alunite. Potassium feldspar grades laterally and vertically to either clinoptilolite or clinoptilolite-mordenite, generally associated with gypsum. This zone then grades vertically and laterally into fresh glass. The clay minerals are a dioctahedral smectite, a mixed-layer clay mineral, and a 7-A clay mineral. The mixed-layer and 7-A clay minerals are associated with the potassium feldspar-alunite zone of alteration, and the dioctahedral smectite is associated with clinoptilolite. This mineralogical zonation may be an exploration guide for mercury and uranium mineralization in the caldera complex environment.

  9. The initiation and development of a caldera-forming Plinian eruption (172 ka Lower Pumice 2 eruption, Santorini, Greece)

    Science.gov (United States)

    Simmons, J. M.; Cas, R. A. F.; Druitt, T. H.; Carey, R. J.

    2017-07-01

    The rhyodacitic 172 ka Lower Pumice 2 (LP2) eruption terminated the first magmatic cycle at Santorini (Greece), producing a proximal short-lived precursory eruption column, depositing a column (LP2-A2, A3). The progressive increase in maximum vesicle number density (NVF) in rhyodacitic pumice, from 3.2 × 109 cm- 3 in the basal fall unit of LP2-A2-1 to 9.2 × 109 cm- 3 in LP2-A3, translates to an increase in magma decompression rate from 18 to 29 MPa s- 1 over the course of the initial Plinian phase. This is interpreted to be a consequence of progressive vent widening and a deepening of the fragmentation surface. Such interpretations are supported by the increase in lithic clast abundance vertically through LP2-A, and the occurrence of basement-derived (deep) lithic components in LP2-A3. The increasing lithic clast content and the inability to effectively entrain air into the eruption column, due to vent widening, resulted in column collapse and the development of pyroclastic density currents (PDCs; LP2-B). A major vent excavation event or the opening of new vents, possibly associated with incipient caldera collapse, facilitated the ingress of water into the magmatic system, the development of widespread PDCs and the deposition of a < 20m thick massive phreatomagmatic tuff (LP2-C). The eruption cumulated in catastrophic caldera collapse, the enlargement of a pre-existing flooded caldera and the discharge of lithic-rich PDCs, depositing proximal < 9 m thick lithic lag breccias (LP2-D).

  10. The volcanic history of Mars: High-resolution crater-based studies of the calderas of 20 volcanoes

    Science.gov (United States)

    Robbins, Stuart J.; di Achille, Gaetano; Hynek, Brian M.

    2011-02-01

    Determining absolute surface ages for bodies in the Solar System is, at present, only possible for Earth and Moon with radiometric dating for both bodies and biologic proxies such as fossils for Earth. Relative ages through cratering statistics are recognized as one of the most reliable proxies for relative ages, calibrated by lunar geologic mapping and Apollo program sample returns. In this work, we have utilized the Mars Reconnaissance Orbiter's ConTeXt Camera's images which provide the highest resolution wide-scale coverage of Mars to systematically crater-age-date the calderas of 20 of Mars' largest volcanoes in order to constrain the length of time over which these volcanoes - and major volcanic activity on the planet, by extension - were active. This constitutes the largest uniform and comprehensive research on these features to date, eliminating unknown uncertainties by multiple researchers analyzing different volcanoes with varied data and methods. We confirm previous results that Mars has had active volcanism throughout most of its history although it varied spatially and temporally, with the latest large-scale caldera activity ending approximately 150 ma in the Tharsis region. We find a transition from explosive to effusive eruption style occurring in the Hesperian, at approximately 3.5 Ga ago, though different regions of the planet transitioned at different times. Since we were statistically complete in our crater counts to sizes as small as ˜60 m in most cases, we also used our results to study the importance of secondary cratering and its effects on crater size-frequency distributions within the small regions of volcanic calderas. We found that there is no "golden rule" for the diameters secondaries become important in crater counts of martian surfaces, with one volcano showing a classic field of secondaries ˜2 crater diameters from the center of its primary but not affecting the size-frequency distribution, and another clearly showing an influence

  11. 2.8-Ma ash-flow caldera at Chegem River in the northern Caucasus Mountains (Russia), contemporaneous granites, and associated ore deposits

    Science.gov (United States)

    Lipman, P.W.; Bogatikov, O.A.; Tsvetkov, A.A.; Gazis, C.; Gurbanov, A.G.; Hon, K.; Koronovsky, N.V.; Kovalenko, V.I.; Marchev, P.

    1993-01-01

    Diverse latest Pliocene volcanic and plutonic rocks in the north-central Caucasus Mountains of southern Russia are newly interpreted as components of a large caldera system that erupted a compositionally zoned rhyolite-dacite ash-flow sheet at 2.83 ?? 0.02 Ma (sanidine and biotite 40Ar/39Ar). Despite its location within a cratonic collision zone, the Chegem system is structurally and petrologically similar to typical calderas of continental-margin volcanic arcs. Erosional remnants of the outflow Chegem Tuff sheet extend at least 50 km north from the source caldera in the upper Chegem River. These outflow remnants were previously interpreted by others as erupted from several local vents, but petrologic similarities indicate a common origin and correlation with thick intracaldera Chegem Tuff. The 11 ?? 15 km caldera and associated intrusions are superbly exposed over a vertical range of 2,300 m in deep canyons above treeline (elev. to 3,800 m). Densely welded intracaldera Chegem Tuff, previously described by others as a rhyolite lava plateau, forms a single cooling unit, is > 2 km thick, and contains large slide blocks from the caldera walls. Caldera subsidence was accommodated along several concentric ring fractures. No prevolcanic floor is exposed within the central core of the caldera. The caldera-filling tuff is overlain by andesitic lavas and cut by a 2.84 ?? 0.03-Ma porphyritic granodiorite intrusion that has a cooling age analytically indistinguishable from that of the tuffs. The Eldjurta Granite, a pluton exposed low in the next large canyon (Baksan River) 10 km to the northwest of the caldera, yields variable K-feldspar and biotite ages (2.8 to 1.0 Ma) through a 5-km vertical range in surface and drill-hole samples. These variable dates appear to record a prolonged complex cooling history within upper parts of another caldera-related pluton. Major W-Mo ore deposits at the Tirniauz mine are hosted in skarns and hornfels along the roof of the Eldjurta Granite

  12. Persistent inflation at Aira caldera accompanying explosive activity at Sakurajima volcano: Constraining deformation source parameters from Finite Element inversions

    Science.gov (United States)

    Hickey, James; Gottsmann, Jo; Iguchi, Masato; Nakamichi, Haruhisa

    2015-04-01

    Aira caldera is located within Kagoshima Bay at the southern end of Kyushu, Japan. Sakurajima is an active post-caldera andesitic stratovolcano that sits on the caldera's southern rim. Despite frequent Vulcanian-type explosive activity, the area is experiencing continued uplift at a maximum rate of approximately 1.5 cm/yr with a footprint of 40 km, indicating that magma is being supplied faster than it is erupted. This is of particular concern as the amplitude of deformation is approaching the level inferred prior to the 1914 VEI 4 eruption. Using GPS data from 1996 - 2007 we explore causes for the uplift. To solve for the optimum deformation source parameters we use an inverse Finite Element method accounting for three-dimensional material heterogeneity (inferred from seismic tomography) and the surrounding topography of the region. The same inversions are also carried out using Finite Element models that incorporate simplified homogeneous or one-dimensional subsurface material properties, with and without topography. Results from the comparison of the six different models show statistically significant differences in the inferred deformation sources. This indicates that both subsurface heterogeneity and surface topography are essential in geodetic modelling to extract the most realistic deformation source parameters. The current best-fit source sits within a seismic low-velocity zone in the north-east of the caldera at a depth of approximately 14 km with a volume increase of 1.2 x 108 m3. The source location underlies a region of active underwater fumaroles within the Wakamiko crater and differs significantly from previous analytical modelling results. Seismic data further highlights areas of high seismic attenuation as well as large aseismic zones, both of which could allude to inelastic behaviour and a significant heat source at depth. To integrate these observations, subsequent forward Finite Element models will quantify the importance of rheology and

  13. A 2-D FEM thermal model to simulate water flow in a porous media: Campi Flegrei caldera case study

    Directory of Open Access Journals (Sweden)

    V. Romano

    2012-05-01

    Full Text Available Volcanic and geothermal aspects both exist in many geologically young areas. In these areas the heat transfer process is of fundamental importance, so that the thermal and fluid-dynamic processes characterizing a viscous fluid in a porous medium are very important to understand the complex dynamics of the these areas. The Campi Flegrei caldera, located west of the city of Naples, within the central-southern sector of the large graben of Campanian plain, is a region where both volcanic and geothermal phenomena are present. The upper part of the geothermal system can be considered roughly as a succession of volcanic porous material (tuff saturated by a mixture formed mainly by water and carbon dioxide. We have implemented a finite elements approach in transient conditions to simulate water flow in a 2-D porous medium to model the changes of temperature in the geothermal system due to magmatic fluid inflow, accounting for a transient phase, not considered in the analytical solutions and fluid compressibility. The thermal model is described by means of conductive/convective equations, in which we propose a thermal source represented by a parabolic shape function to better simulate an increase of temperature in the central part (magma chamber of a box, simulating the Campi Flegrei caldera and using more recent evaluations, from literature, for the medium's parameters (specific heat capacity, density, thermal conductivity, permeability. A best-fit velocity for the permeant is evaluated by comparing the simulated temperatures with those measured in wells drilled by Agip (Italian Oil Agency in the 1980s in the framework of geothermal exploration. A few tens of days are enough to reach the thermal steady state, showing the quick response of the system to heat injection. The increase in the pressure due to the heat transport is then used to compute ground deformation, in particular the vertical displacements characteristics of the Campi Flegrei caldera

  14. Crystallization and eruption ages of Breccia Museo (Campi Flegrei caldera, Italy) plutonic clasts and their relation to the Campanian ignimbrite

    Science.gov (United States)

    Gebauer, Samantha K.; Schmitt, Axel K.; Pappalardo, Lucia; Stockli, Daniel F.; Lovera, Oscar M.

    2014-01-01

    The Campi Flegrei volcanic district (Naples region, Italy) is a 12-km-wide, restless caldera system that has erupted at least six voluminous ignimbrites during the late Pleistocene, including the >300 km3 Campanian ignimbrite (CI) which originated from the largest known volcanic event of the Mediterranean region. The Breccia Museo (BM), a petrologically heterogeneous and stratigraphically complex volcanic deposit extending over 200 km2 in close proximity to Campi Flegrei, has long remained contentious regarding its age and stratigraphic relation to the CI. Here, we present crystallization and eruption ages for BM plutonic ejecta clasts that were determined via uranium decay series and (U-Th)/He dating of zircon, respectively. Despite mineralogical and textural heterogeneity of these syenitic clasts, their U-Th zircon rim crystallization ages are indistinguishable with an average age of 49.7 ± 2.5 ka (2σ errors; mean square of weighted deviates MSWD = 1.2; n = 34). A subset of these crystals was used to obtain disequilibrium-corrected (U-Th)/He zircon ages which average 41.7 ± 1.8 ka (probability of fit P = 0.54; n = 15). This age closely overlaps with published CI 40Ar/39Ar eruption ages (40.6 ± 0.1 ka) after recalibration to recently revised flux monitor ages. Concordant eruption ages for BM and CI agree with previous chemostratigraphic and paleomagnetic correlations, suggesting their origin from the same eruption. However, they are at variance with recalibrated 40Ar/39Ar ages which have BM postdate CI by 3 ± 1 ka. BM syenites show similar geochemical and Sr-Nd isotopical features of pre-caldera rocks erupted between 58 and 46 ka, but are distinctive from subsequent caldera-forming magmas. Energy-constrained assimilation and fractional crystallization modeling of Nd-Sr isotopic data suggests that pre-caldera magmas formed a carapace of BM-type intrusions in a mid-crust magma chamber (≥8 km depth) shielding the younger CI magma from contamination by

  15. [Interactions between larvae of the hoverfly Eristalinus sepulchralis and microorganisms in the hydrothermal springs of the Uzon caldera, Kamchatka].

    Science.gov (United States)

    Lobkova, L E; Barinova, E S; Dulov, L E; Gal'chenko, V F

    2007-01-01

    The physicochemical and microbial characteristics of some medium-temperature hydrotherms of Kamchatka Peninsula (Uzon caldera), habitats of the hoverfly Eristalinus sepulchralis larvae, were studied. In these hydrothermal vents, the larvae were found to use various prokaryotic and eukaryotic microorganisms as a nutrient substrate. The rates of chemo- and photosynthetic activity of the suspended microbial communities inhabiting the hydrotherms and supporting the existence of larvae were measured. By light and electron microscopy, exo- and endosymbiotic prokaryotic microorganisms were revealed in the digestive and respiratory systems of larvae.

  16. Selected data fron continental scientific drilling core holes VC-1 and VC-2a, Valles Caldera, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Musgrave, J.A.; Goff, F.; Shevenell, L.; Trujillo, P.E. Jr.; Counce, D.; Luedemann, G.; Garcia, S.; Dennis, B.; Hulen, J.B.; Janik, C.; Tomei, F.A.

    1989-02-01

    This report presents geochemical and isotopic data on rocks and water and wellbore geophysical data from the Continental Scientific Drilling Program core holes VC-1 and VC-2a, Valles Caldera, New Mexico. These core holes were drilled as a portion of a broader program that seeks to answer fundamental questions about magma, water/rock interactions, ore deposits, and volcanology. The data in this report will assist the interpretation of the hydrothermal system in the Jemez Mountains and will stimulate further research in magmatic processes, hydrothermal alteration, ore deposits, hydrology, structural geology, and hydrothermal solution chemistry. 37 refs., 36 figs., 28 tabs.

  17. El Morro caldera (33° 10‧ S, 66° 24‧ W), San Luis, Argentina: An exceptional case of fossil pre-collapse updoming

    Science.gov (United States)

    Sruoga, P.; Ibañes, O. D.; Japas, M. S.; Urbina, N. E.

    2017-05-01

    Volcanism at Sierra del Morro represents the final stages of the flat-slab related magmatism in the easternmost San Luis Neogene Volcanic Belt. This 80 km-long NW-WNW-trending belt tracks the episodic inland migration of both magmatism and tectonic deformation since 18 Ma. The Sierra del Morro stands out in the Eastern Sierras Pampeanas as a metamorphic block uplifted during the Late Miocene-Pleistocene by a combination of magma injection and tectonic deformation. Although sequences that preserve stages of basement updoming are not often preserved, exposures in Sierra del Morro are exception in providing key evidence and insight into the involved processes. Based on the comprehensive study of volcanic stratigraphy and structures, the reconstruction of the volcanic architecture has been carried out. We infer a three stage evolution of the El Morro caldera as follows: 1) pre-collapse updoming and volcanism, 2) collapse caldera formation and 3) post-caldera volcanism. The ascent of magma is recorded in small tumescence sites, strongly controlled by oblique transtensional WNW-NW and ENE-striking brittle-ductile megashear zones. Even though the area affected by tumescence was large, magma injection progressed only locally. At Cerros Guanaco and Pampa, metamorphic rocks were updomed and strongly brecciated, whereas at Sierra del Morro magma was emplaced as pre-collapse domes with associated block-and-ash flows, ignimbrite caldera-forming eruptions and post-caldera lava domes and dykes. The caldera is located in the intersection of two major oblique transtensional WNW-NW and ENE-trending brittle-ductile megashear zones, where the highest positive dilatation occurred.

  18. A probability tomography approach to the analysis of potential field data in the Campi Flegrei caldera (Italy

    Directory of Open Access Journals (Sweden)

    D. Patella

    2001-06-01

    Full Text Available The results of the application of the 3D probability tomography imaging approach to the study of the Campi Flegrei (CF caldera are presented and discussed. The tomography approach has been applied to gravity, magnetic and ground deformation data already available in literature. The analysis of the 3D tomographic images is preceded by a brief qualitative interpretation of the original survey maps and by an outline of the probability tomography approach for each geophysical prospecting method. The results derived from the 3D tomographic images are the high occurrence probabilities of both gravity and ground deformation source centres in the CF caldera under the town of Pozzuoli. A Bouguer negative anomaly source centre is highlighted in the depth range 1.6-2 km b.s.l., whereas a positive ground deformation point source, responsible for the bradyseismic crisis of 1982-1984, is estimated at a mean depth of 3-4 km b.s.l. These inferences, combined with the results of a previous analysis of magnetotelluric, dipolar geoelectrical and self-potential data, corroborate the hypothesis that the bradyseismic events in the CF area may be explained by hot fluids vertical advection and subsequent lateral diffusion within a trapped reservoir overlying a magma chamber.

  19. A GIS-based volcanic hazard and risk assessment of eruptions sourced within Valles Caldera, New Mexico

    Science.gov (United States)

    Alcorn, Rebecca; Panter, Kurt S.; Gorsevski, Pece V.

    2013-11-01

    The objective of this study is to evaluate the spatial extent of a possible future eruption using a GIS-based volcanic hazard tool designed to simulate pyroclastic fallout and density currents (PDCs) as well as lava flows and to assess the social and economic vulnerabilities of the area at risk. Simulated pyroclastic fallout deposits originating from the El Cajete crater within the Valles Caldera, Jemez Mountains volcanic field, New Mexico, are calibrated to isopach and lithic isopleth maps of the Lower and Upper El Cajete as constructed by Wolff et al. (2011). The change in the axial orientation of fallout deposits between the Lower and Upper El Cajete is best matched using seasonal variations in wind speed and direction based on modern atmospheric records. The calibration of PDCs is based on the distribution and run-out of the Battleship Rock Ignimbrite. Once calibrated, hazards are simulated at a second vent location determined from probability distributions of structural features. The resulting hazard simulation maps show the potential distribution of pyroclastic fallout, PDCs and lava flows, indicating areas to the S/SE of Valles Caldera to be at greatest risk.

  20. Clinopyroxene Diffusion Chronometry of the Scaup Lake Rhyolite, Yellowstone Caldera, WY

    Science.gov (United States)

    Brugman, K. K.; Till, C. B.; Bose, M.

    2016-12-01

    Eruption of the Scaup Lake flow (SCL) ended 220,000 years of dormancy and began the youngest sequence of eruptions at Yellowstone caldera [Christiansen et al., USGS, 2007]. Quantification of the time intervals between magmatic events and eruption recorded in SCL is critical to interpreting signs of unrest at modern-day Yellowstone. SCL rhyolite includes zoned phenocrysts and accessory phases that indicate multiple rejuvenation events occurred shortly before eruption; previous studies focused on feldspar and zircon crystal records [e.g. Bindeman et al., J.Pet, 2008; Till et al., Geology, 2015]. Here we exploit zoned clinopyroxene (cpx)—one of the earliest-crystalized minerals in SCL as indicated by petrographic relationships—as a diffusion dating tool and utilize elements with different diffusivities to more precisely resolve rejuvenation-eruption timescales. Using NanoSIMS concentration profiles with 300-900 nanometer spacing, we employ the slower-diffusing REE Ce as a proxy for the initial profile shape of faster-diffusing Fe to calculate diffusive timescales. The outermost resolvable zone boundary in SCL cpx yields a rejuvenation-eruption timescale of 166 ± 80 yrs (1 SD). In comparison, modeling relaxation of Fe from a step function initial condition at the same temperature (920°C) yields a less precise timescale of 488 +9000 -300 yrs. Examination of our results, in concert with observed petrographic relationships, indicates SCL cpx may record an older, separate rejuvenation event than those recorded in feldspar rims at eruption [Till et al., Geology, 2015]. The difference in the youngest recorded event between feldspar and cpx may be due to different crystallization intervals for these phases and/or slower crystal growth rates for cpx relative to feldspar. Our diffusion modeling results reinforce that intracrystalline zoning timescales modeled using a step function initial condition should be considered maxima, especially in viscous rhyolitic magmas, and

  1. The Askja rockslide and the associated tsunami in the caldera lake

    Science.gov (United States)

    Vogfjörd, Kristin; Kristinn Helgason, Jon; Jonsdottir, Kristin; Brynjolfsson, Sveinn; Grimsdottir, Harpa; Johannesson, Tomas; Hensch, Martin; Ripepe, Maurizio

    2015-04-01

    A large rockslide was released in Askja, central Iceland, on the evening of 21 July 2014 and descended into the caldera lake. It is one of the largest known rockslides since the settlement of Iceland. The release area of the slide is approximately 900 m wide and 350 m above the lake. The front of the landslide travelled at least 2000 m along the lake bottom where it reached the depth of 150 m. The total run-out is approximatly 3100 m and the fall height 500 m. The estimated volume of the slide is estimated as 15-50 million m3. The rockslide appeared as shallow tremor on IMO seismographs near Askja and the data show that the slide was released at 23:24. The slide created seismic waves that travelled over most of Iceland in roughly one minute. In addition, it triggered atmospheric pressure waves that were detected on an infrasound array some 210 km southwest of the event. The infrasound waves travelled this distance in 11 minutes and were reflected in the stratosphere. Photographs from the rockslide area indicate that considerable movement had started a few years before the slide was released. Slow movement in the bedrock seems to have accelerated in the summer of 2014. There was deep snow in the mountains and fairly warm weather before the slide occurred. Percolating water from the melting snow might, thus, have increased the rate of movement. Seismic data indicate that a creeping movement started around 40 minutes before the slide, but at 23:24 the failure point was reached and the rockslide was released. The slide triggered a tsunami in the lake that washed up on the lakeshores all around the lake, reaching up to 20-30 m elevation above the water level and even higher in some places. The wave travelled farthest around 400 m (horizontally) into the flatland SE of the crater Víti. It was fortunate that the rockslide occurred late at night when nobody was close to the water, otherwise it would have been extremely hazardous. A few hours earlier, dozens of people were

  2. Geochemical exploration of a promissory Enhanced Geothermal System (EGS): the Acoculco caldera, Mexico.

    Science.gov (United States)

    Peiffer, Loic; Romero, Ruben Bernard; Pérez-Zarate, Daniel; Guevara, Mirna; Santoyo Gutiérrez, Edgar

    2014-05-01

    The Acoculco caldera (Puebla, Mexico) has been identified by the Mexican Federal Electricity Company (in Spanish 'Comisión Federal de Electricidad', CFE) as a potential Enhanced Geothermal System (EGS) candidate. Two exploration wells were drilled and promising temperatures of ~300° C have been measured at a depth of 2000 m with a geothermal gradient of 11oC/100m, which is three times higher than the baseline gradient measured within the Trans-Mexican Volcanic Belt. As usually observed in Hot Dry Rock systems, thermal manifestations in surface are scarce and consist in low-temperature bubbling springs and soil degassing. The goals of this study were to identify the origin of these fluids, to estimate the soil degassing rate and to explore new areas for a future detailed exploration and drilling activities. Water and gas samples were collected for chemical and isotopic analysis (δ18O, δD, 3He/4He, 13C, 15N) and a multi-gas (CO2, CH4, H2S) soil survey was carried out using the accumulation chamber method. Springs' compositions indicate a meteoric origin and the dissolution of CO2 and H2S-rich gases, while gas compositions reveal a MORB-type origin mixed with some arc-type contribution. Gas geothermometry results are similar to temperatures measured during well drilling (260° C-300° C). Amongst all measured CO2 fluxes, only 5% (mean: 5543 g m-2 day-1) show typical geothermal values, while the remaining fluxes are low and correspond to biogenic degassing (mean: 18 g m-2 day-1). The low degassing rate of the geothermal system is a consequence of the intense hydrothermal alteration observed in the upper 800 m of the system which acts as an impermeable caprock. Highest measured CO2 fluxes (above > 600 g m-2 day-1) have corresponding CH4/CO2 flux ratios similar to mass ratios of sampled gases, which suggest an advective fluid transport. To represent field conditions, a numerical model was also applied to simulate the migration of CO2 towards the surface through a

  3. Environmental Magnetism of mid-Pleistocene Lacustrine Sediments of the Valles Caldera, New Mexico

    Science.gov (United States)

    Hurley, L. L.; Geissman, J. W.; Fawcett, P.; Tim, W.; Goff, F.

    2007-12-01

    Rock magnetic measurements are applied to almost 80 m of lacustrine sediment (VC-3) to augment independent means of interpreting the environmental conditions of a mid-Pleistocene lake in the Valle Grande of the Valles Caldera, northern New Mexico. An age model for the core is pinned to an Ar/Ar age determination of 552 ± 3 ka for a sanidine bearing ash layer at 78 m depth and major transitions in the organic carbon record at 53 m, 40 m, 27 m, and 17 m; these data suggest that deposition of VC-3 spans MIS 14 to MIS 10, including glacial terminations VI (531 ka) and V (426 ka). AF demagnetization resolves positive inclination magnetizations from most of the core, consistent with Brunhes normal polarity. Three thin (Big Lost excursion (~580 ± 8 ka). Data from an array of rock magnetic investigations indicate magnetite, titanomagnetite, and pyrhotite characterize VC-3 sediments. Susceptibility and frequency dependent susceptibility experiments at low temperature reveal an abundance of paramagnetic and super-paramagnetic material. Scanning electron microscopy of magnetic separates show an array of Fe-oxide and Fe-sulfide grains, including titanomagnetites with trellis ilmenite intergrowths. NRM intensities of sediment deposited during glacial periods typically range from 0.04 mA/m to values as high as 1.6 mA/m; interglacial sediment NRM intensities range from 0.05 mA/m to 0.2 mA/m. NRM values increase to 3.3 mA/m, between 48 m to 43 m, where the sediment exhibits shallow mud crack, bioturbation, and oxidation. Overall, trends in susceptibility, ARM, and SIRM are similar to those in NRM intensity. Bivariate plot of susceptibility/ARM shows little variation in concentration of low coercivity minerals (i.e. magnetite) in VC-3 sediments. Also, the concentration of high coercivity minerals (i.e. hematite) indicated by the IRM/susceptibility curve show similar variation between sediments deposited during glacial and interglacial times as the remanence data sets but the

  4. Lithologic Control on Secondary Clay Mineral Formation in the Valles Caldera, New Mexico

    Science.gov (United States)

    Caylor, E.; Rasmussen, C.; Dhakal, P.

    2015-12-01

    Understanding the transformation of rock to soil is central to landscape evolution and ecosystem function. The objective of this study was to examine controls on secondary mineral formation in a forested catchment in the Catalina-Jemez CZO. We hypothesized landscape position controls the type of secondary minerals formed in that well-drained hillslopes favor Si-poor secondary phases such as kaolinite, whereas poorly drained portions of the landscape that collect solutes from surrounding areas favor formation of Si-rich secondary phases such as smectite. The study focused on a catchment in Valles Caldera in northern New Mexico where soils are derived from a mix of rhyolitic volcanic material, vegetation includes a mixed conifer forest, and climate is characterized by a mean annual precipitation of ~800 mm yr-1 and mean annual temperature of 4.5°C. Soils were collected at the soil-saprolite boundary from three landscape positions, classified as well drained hillslope, poorly drained convergent area, and poorly drained hill slope. Clay fractions were isolated and analyzed using a combination of quantitative and qualitative x-ray diffraction (XRD) analyses and thermal analysis. Quantitative XRD of random powder mounts indicated the presence of both primary phases such as quartz, and alkali and plagioclase feldspars, and secondary phases that include illite, Fe-oxyhydroxides including both goethite and hematite, kaolinite, and smectite. The clay fractions were dominated by smectite ranging from 36-42%, illite ranging from 21-35%, and kaolinite ranging from 1-8%. Qualitative XRD of oriented mounts confirmed the presence of smectite in all samples, with varying degrees of interlayering and interstratification. In contrast to our hypothesis, results indicated that secondary mineral assemblage was not strongly controlled by landscape position, but rather varied with underlying variation in lithology. The catchment is underlain by a combination of porphorytic rhyolite and

  5. MULTISCALE THERMAL-INFRARED MEASUREMENTS OF THE MAUNA LOA CALDERA, HAWAII

    Energy Technology Data Exchange (ETDEWEB)

    L. BALICK; A. GILLESPIE; ET AL

    2001-03-01

    Until recently, most thermal infrared measurements of natural scenes have been made at disparate scales, typically 10{sup {minus}3}-10{sup {minus}2} m (spectra) and 10{sup 2}-10{sup 3} m (satellite images), with occasional airborne images (10{sup 1} m) filling the gap. Temperature and emissivity fields are spatially heterogeneous over a similar range of scales, depending on scene composition. A common problem for the land surface, therefore, has been relating field spectral and temperature measurements to satellite data, yet in many cases this is necessary if satellite data are to be interpreted to yield meaningful information about the land surface. Recently, three new satellites with thermal imaging capability at the 10{sup 1}-10{sup 2} m scale have been launched: MTI, TERRA, and Landsat 7. MTI acquires multispectral images in the mid-infrared (3-5{micro}m) and longwave infrared (8-10{micro}m) with 20m resolution. ASTER and MODIS aboard TERRA acquire multispectral longwave images at 90m and 500-1000m, respectively, and MODIS also acquires multispectral mid-infrared images. Landsat 7 acquires broadband longwave images at 60m. As part of an experiment to validate the temperature and thermal emissivity values calculated from MTI and ASTER images, we have targeted the summit region of Mauna Loa for field characterization and near-simultaneous satellite imaging, both on daytime and nighttime overpasses, and compare the results to previously acquired 10{sup {minus}1} m airborne images, ground-level multispectral FLIR images, and the field spectra. Mauna Loa was chosen in large part because the 4x6km summit caldera, flooded with fresh basalt in 1984, appears to be spectrally homogeneous at scales between 10{sup {minus}1} and 10{sup 2} m, facilitating the comparison of sensed temperature. The validation results suggest that, with careful atmospheric compensation, it is possible to match ground measurements with measurements from space, and to use the Mauna Loa validation

  6. Constraining the Carbon Cycle through Tree Rings: A Case Study of the Valles Caldera, NM

    Science.gov (United States)

    Alexander, M. R.; Babst, F.; Moore, D. J.; Trouet, V.

    2013-12-01

    and the derived biomass increments illustrate that the forests at the Valles Caldera are considerably less productive during years of extreme drought and warmer than average temperatures. With future projections calling for consecutive years of extreme conditions in the American Southwest, this could have a substantial effect on the overall productivity of these forests.

  7. The Natural and Political Caldera-lake crisis of Mount Pinatubo, Philippines, 2001

    Science.gov (United States)

    Rodolfo, K. S.; Rodolfo, K. S.

    2001-12-01

    In 1991 Mount Pinatubo's eruptions produced a caldera with a 5.4 km2 catchment that ever since has gathered a lake with a surface that has risen roughly 10 m every rainy season. The rim is lowest at 960+ masl in the northwest, at the Maraunot notch, named after the stream into which overtopping lake water would drain, thence along the Balin Baquero and Bucao to the town of Botolan and the South China Sea 40 km downstream. In December 2000, with only 10 m of remaining notch freeboard, Philippine government geologists and American colleagues were aware of the potential for catastrophic breaching, because the surface 20 m of rock beneath the rim is highly erodible breccia. A breakout of as much as 60 x 106 m3 is considered possible. Easily eroded eruption debris is abundant in the path of the flood, which could "bulk up" into worst-case lahars with a volume of 3 x 108 m3. Government engineers discussed lowering the lake with siphons or a tunnel, or scraping down and strengthening the notch, but did nothing. Only in August, three months into a very wet monsoon season, when only about 5 m of freeboard remained, did the government inform the 46,000 Botolan inhabitants of the danger. It did so only after Oxfam GB, a humanitarian organization, issued a report written by private geological consultants familiar with Pinatubo and its lahars. The crisis, still evolving, unfortunately is pitting government attitudes and policies -- strict control of information and decisions regarding hazards -- against those of academic science, and of some NGOs concerned with community development and empowerment. In August, the government abruptly abandoned its initial denials of a serious threat, and decided to build a canal with which to induce a breach at a propitious time. Poorly paid and supervised aborigine labor has inadvertently reduced the freeboard to only 2 m, and the government is announcing that it will evacuate Botolan and induce the breach as early as September 5. Spontaneous

  8. High Resolution Magnetotelluric Imaging of the Nisyros Caldera and Geothermal Resource (Greece)

    Science.gov (United States)

    Tzanis, Andreas; Sakkas, Vassilis; Lagios, Evangelos

    2017-04-01

    This work reports the qualitative and quantitative re-examination of legacy magnetotelluric soundings data obtained in the caldera of Nisyros, a small island volcano at the eastern end of the Hellenic Volcanic Arc (HVA), Greece, in an attempt to explore the high temperature geothermal resource of the area. The data set comprises 39 single-site soundings and is re-examined with improved data processing methods, new hypothetical event analysis techniques to study the spatial configuration of the telluric field and two-dimensional inversion tools. Iteratively reweighted least squares have been implemented to compute stable and smooth Earth response functions, which were found to exhibit 2-D to weakly 3-D attributes as a result of induction in low-contrast local geoelectric inhomogeneities, superimposed on a dominantly 2-D background structure. The transfer functions appear to be free of coastal and island induction effects due to the low offshore/onshore resistivity contrast at, and below sea level. The spatial properties of the telluric field are studied with hypothetical event analysis based on 3-D decompositions of the impedance tensor [1]. The results indicate that convection and hydrothermal circulation is controlled by a system of antithetic NE-SW oriented active normal faults which form a graben-like structure and define the 2-D background, as well as a conjugate system of NNW-SSE normal faults which is particularly active at the SW quadrant of the island and define the main convection path. It was determined that under these conditions the data can be interpreted with 2-D inversion, which was carried out with [2]. The inversion has successfully reconstructed detailed images of the structural and functional elements of the hydrothermal system. The structural elements include a number of shallow hot water reservoirs in the argillic and phyllic alteration zones and a laterally extended deep (approx. 1km) circulation zone, all embedded in a low-resistivity matrix

  9. Analysis of vector magnetic anomalies over the Bayonnaise Knoll caldera obtained from a deep-sea magnetic exploration by AUV

    Science.gov (United States)

    Sayanagi, K.; Isezaki, N.; Matsuo, J.; Harada, M.; Kasaya, T.

    2011-12-01

    Bayonnaise Knoll is a submarine caldera with an outer rim of 2.5-3 km and a floor of 840-920 m, which is located in the Izu-Ogasawara arc. A large hydrothermal deposit, Hakurei deposit, lies in the southeast part of the caldera. In the R/V Bosei-maru cruise, we observed three components of magnetic anomalies at depths of 400-570 m along SE-NW and WE tracks across the caldera. In the R/V Yokosuka YK10-17 cruise, we observed three components and total intensity of magnetic anomalies at altitudes of 60-100 m around the Hakurei deposit and at depth of 500 m above the caldera. The analysis of these data is now energetically pushed forward. A 3D gridded data set of the vector magnetic anomaly in the latter cruise was made by solving the Laplace's equation in the areas where observation data were not available, which is the unique procedure for analysis of the vector anomalies. Several magnetization solutions have been so far obtained by successive approximation and inversion methods. We will here present the measurement of the geomagnetic field and analysis of magnetization structure in Bayonnaise Knoll caldera. Note that this study has been supported by the Ministry of Education, Culture, Sports, Science & Technology (MEXT).

  10. The Project Serapis: High Resolution Seismic Imagingof The Campi Flegrei Caldera Structure

    Science.gov (United States)

    Zollo, A.; Virieux, J.; Capuano, P.; Chiarabba, C.; de Franco, R.; Makris, J.; Michelini, A.; Musacchio, G.; Serapis Group

    expected NE-SW and SE-NW structural trends and it has been designed to get 2D/3D images of the crustal structure at a regional scale. A denser 2D network of 35 OBSs has been deployed in the bay of Pozzuoli aimed at detecting and modeling reflected/converted waves from 1 the possible shallow to deep discontinuities beneath the Campi Flegrei caldera. The main target of this particular receiver lay-out is the detailed imaging of the magma chamber top, expected at 4-5 km depth, according to temperature measurements in wells and sparse seismic observations. About 5000 shots have been performed dur- ing the SERAPIS experiment, at an average spatial spacing of 125 m, for a total ship travel path of 620 km. All of the seismic lines have been re-sampled at least twice, using a staggered configuration, which results in a smaller source spacing (less than 65m). In the gulf of Pozzuoli the source array had a geometry of a 5x5 km grid, slightly shifted south with respect to the OBS array. Seismic signals produced by air- guns have been well detected up to 50-60 km distance and the whole Campi Flegrei, Ischia and Procida on-land networks have recorded high quality seismograms pro- duced by the gridded source array in the bay of Pozzuoli. Due to the extended and very dense source and receiver arrays used for SERAPIS, this campaign can provide an innovative contribution to the accurate reconstruction of the Campi Flegrei caldera structure and to the definition of its feeding system at depth. *SERAPIS group: Auger Emmanuel, Bernard Marie-Lise, Bobbio Antonella, Bonagura Mariateresa, Cantore Luciana, Convertito Vincenzo, D'Auria Luca, De Matteis Raffaella, Emolo Anto- nio, Festa Gaetano, Gasparini Paolo, Giberti Grazia, Herrero Andre, Improta Luigi, Lancieri Maria Flora, Nielsen Stefan, Nisii Vincenzo, Russo Guido, Satriano Clau- dio, Simini Mariella, Vassallo Maurizio, Bruno Pier Paolo, Buonocunto Ciro, Capello Marco, Del Pezzo Edoardo, Galluzzo Danilo, Gaudiosi Germana, Giuliana Alessio

  11. The earliest low and high δ18O caldera-forming eruptions of the Yellowstone plume: Implications for the 30–40 Ma Oregon calderas and speculations on plume-triggered delaminations

    Directory of Open Access Journals (Sweden)

    Angela Nicole Seligman

    2014-11-01

    Full Text Available We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma, Crooked River (32–28 Ma, Tower Mountain (32 Ma, and Mohawk River (32 Ma. The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (δ18O and εHf values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 x 27 km have δ18Ozircon values that include seven low δ18Ozircon units (1.8–4.5 ‰, one high δ18Ozircon unit (7.4–8.8 ‰, and two units with heterogeneous zircons (2.0–9.0 ‰, similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low δ18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high δ18Ozircon values (6.4–7.9 ‰ and normal to low εHfi values (5.2–12.6, indicating crustal melting of high-δ18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32–28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created

  12. Evaluación de la calidad ambiental de los sedimentos marinos en el sistema de bahías de Caldera (27°S), Chile

    National Research Council Canada - National Science Library

    Jorge Valdés; Alexis Castillo

    2014-01-01

    ... (Caldera, Calderilla, Inglesa y Salada) de la Región de Atacama, Chile. Las concentraciones medias globales fueron 76,8 mg kg-1 de Cu, 90,4 mg kg-1 de Zn, 39 mg kg-1 de Pb, 23,4 mg kg-1 de Ni, 118,5 mg kg-1 de V, 0,09...

  13. Progress Report Phase I: Use, access, and fire/fuels management attitudes and preferences of user groups concerning the Valles Caldera National Preserve (VCNP) and adjacent areas

    Science.gov (United States)

    Kurt F. Anschuetz; Carol B. Raish

    2010-01-01

    This document represents a progress report of activities completed during Phase I of the study titled, Use, Access, and Fire/Fuels Management Attitudes and Preferences of User Groups Concerning the Valles Caldera National Preserve (VCNP) and Adjacent Areas, and the preliminary findings of this work.

  14. Revisions to the stratigraphy and volcanology of the post-0.5 Ma units and the volcanic section of VC-1 core hole, Valles Caldera, New Mexico

    Science.gov (United States)

    Self, S.; Wolff, J. A.; Spell, T. L.; Skuba, C. E.; Morrissey, M. M.

    1991-03-01

    Reexamination of the Continental Scientific Drilling Project VC-1 core, new field data, and new isotopic ages necessitate revision of the previously described geology of the youngest eruptive units from the Valles caldera. The Banco Bonito rhyolite lava flow and minor attendant pyroclastic, autoclastic, and reworked deposits about 0.9 km3 dense rock equivalent volume (DRE), are recognized as the product of the youngest eruption from the caldera. The best estimate of the age of this event is 170-240 ka (1σ). A slightly earlier eruption produced the El Cajete pumice fall deposit, followed by the Battleship Rock ignimbrite and the VC-1 Rhyolite, totalling about 1.8 km3 DRE. We suggest that the VC-1 Tuffs, ignimbrites recognized only in the VC-1 core hole, are not a separate unit as previously proposed but are, in fact, the Battleship Rock ignimbrite. A complex volcaniclastic breccia dating from about the time of the South Mountain Rhyolite lava flow (529 ka) is the lowermost volcanic unit in the VC-1 core. The young, post-500 ka eruption products from the SW part of the Valles caldera are all composed of very similar low-silica rhyolite and are thus distinct from earlier, postcaldera high-silica rhyolites included in the Valles Rhyolite Formation. This distinction marks a major change in the magmatic evolution of the Valles caldera. We propose that recognition of this change necessitates revisions to the stratigraphy of the upper part of the Tewa Group.

  15. Post-glacial inflation-deflation cycles, tilting, and faulting in the Yellowstone Caldera based on Yellowstone Lake shorelines

    Science.gov (United States)

    Pierce, Kenneth L.; Cannon, Kenneth P.; Meyer, Grant A.; Trebesch, Matthew J.; Watts, Raymond D.

    2002-01-01

    The Yellowstone caldera, like many other later Quaternary calderas of the world, exhibits dramatic unrest. Between 1923 and 1985, the center of the Yellowstone caldera rose nearly one meter along an axis between its two resurgent domes (Pelton and Smith, 1979, Dzurisin and Yamashita, 1987). From 1985 until 1995-6, it subsided at about two cm/yr (Dzurisin and others, 1990). More recent radar interferometry studies show renewed inflation of the northeastern resurgent dome between 1995 and 1996; this inflation migrated to the southwestern resurgent dome from 1996 to 1997 (Wicks and others, 1998). We extend this record back in time using dated geomorphic evidence of postglacial Yellowstone Lake shorelines around the northern shore, and Yellowstone River levels in the outlet area. We date these shorelines using carbon isotopic and archeological methods. Following Meyer and Locke (1986) and Locke and Meyer (1994), we identify the modern shoreline as S1 (1.9 ? 0.3 m above the lake gage datum), map paleoshoreline terraces S2 to S6, and infer that the prominent shorelines were cut during intracaldera uplift episodes that produced rising water levels. Doming along the caldera axis reduces the gradient of the Yellowstone River from Le Hardys Rapids to the Yellowstone Lake outlet and ultimately causes an increase in lake level. The 1923-1985 doming is part of a longer uplift episode that has reduced the Yellowstone River gradient to a ?pool? with a drop of only 0.25 m over most of this 5 km reach. We also present new evidence that doming has caused submergence of some Holocene lake and river levels. Shoreline S5 is about 14 m above datum and estimated to be ~12.6 ka, because it post-dates a large hydrothermal explosion deposit from the Mary Bay area (MB-II) that occurred ~13 ka. S4 formed about 8 m above datum ~10.7 ka as dated by archeology and 14C, and was accompanied by offset on the Fishing Bridge fault. About 9.7 ka, the Yellowstone River eroded the ?S-meander?, followed

  16. Keanakākoʻi Tephra produced by 300 years of explosive eruptions following collapse of Kīlauea's caldera in about 1500 CE

    Science.gov (United States)

    Swanson, Donald A.; Rose, Timothy R.; Fiske, Richard S.; McGeehin, John P.

    2012-01-01

    The Keanakākoʻi Tephra at Kīlauea Volcano has previously been interpreted by some as the product of a caldera-forming eruption in 1790 CE. Our study, however, finds stratigraphic and 14C evidence that the tephra instead results from numerous eruptions throughout a 300-year period between about 1500 and 1800. The stratigraphic evidence includes: (1) as many as six pure lithic ash beds interleaved in sand dunes made of earlier Keanakākoʻi vitric ash, (2) three lava flows from Kīlauea and Mauna Loa interbedded with the tephra, (3) buried syneruptive cultural structures, (4) numerous intraformational water-cut gullies, and (5) abundant organic layers rich in charcoal within the tephra section. Interpretation of 97 new accelerator mass spectrometry (AMS) 14C ages and 4 previous conventional ages suggests that explosive eruptions began in 1470–1510 CE, and that explosive activity continued episodically until the early 1800s, probably with two periods of quiescence lasting several decades. Kīlauea's caldera, rather than forming in 1790, predates the first eruption of the Keanakākoʻi and collapsed in 1470–1510, immediately following, and perhaps causing, the end of the 60-year-long, 4–6 km3 ʻAilāʻau eruption from the east side of Kīlauea's summit area. The caldera was several hundred meters deep when the Keanakākoʻi began erupting, consistent with oral tradition, and probably had a volume of 4–6 km3. The caldera formed by collapse, but no eruption of lava coincided with its formation. A large volume of magma may have quickly drained from the summit reservoir and intruded into the east rift zone, perhaps in response to a major south-flank slip event, leading to summit collapse. Alternatively, magma may have slowly drained from the reservoir during the prolonged ʻAilāʻau eruption, causing episodic collapses before the final, largest downdrop took place. Two prolonged periods of episodic explosive eruptions are known at Kīlauea, the Keanak

  17. A Tale of Two Swarms: Mapping Of Calderas And 40Ar/39Ar Geochronology Of Rhyolite Ignimbrites Delineate Two Distinct Steens Basalt Fissure Systems

    Science.gov (United States)

    Benson, T. R.; Mahood, G. A.

    2016-12-01

    Giant radiating dike swarms are associated with most flood basalt provinces, and their orientations have been used to elucidate the physical processes involved during flood basalt emplacement. In the Mid-Miocene Columbia River flood basalt province, three major dike swarms have been identified: the NNW-trending Chief Joseph dike swarm, the source for the Imnaha, Grande Ronde, Wanapum, and Saddle Mountain members; the NNW-trending Monument dike swarm, the source for the Picture Gorge member; and the Steens dike swarm, the source for the oldest member, the Steens Basalt. A relatively limited number of Steens feeder dikes have been identified in southern Oregon and northern Nevada due to cover by Miocene volcanic strata. Exposed dikes at Steens Mountain trend NNE, and all other Steens dikes exposed in the region trend NNW. As a result, most interpretations of the mechanisms involved in Steens Basalt emplacement have relied on these few dikes and the curvilinear aeromagnetic anomaly of the Northern Nevada Rift. Newly defined Mid-Miocene calderas genetically related to Steens Basalt provide additional data for understanding the orientation and propagation rate of the Steens Basalt swarm, as the progression of the first silicic magma chambers to form in a given area is a proxy for the progression of maximum flood basalt intrusion. We identify two distinct trends of caldera volcanism associated with Steens Basalt: (1) the NNE High Rock swarm, with five calderas on strike with NNE-trending Steens dikes exposed in Steens Mountain, and (2) the NNW McDermitt swarm, with five calderas on strike with NNW-trending Steens dikes in the Trout Creek and Santa Rosa Mountains and the trend of the Northern Nevada Rift. New high-precision 40Ar/39Ar ages on the ignimbrites associated with these calderas demonstrate that within both the High Rock and McDermitt swarms, initiation of caldera volcanism occurred in the vicinity of Steens Mountain at 16.5 Ma and propagated southward at a rate

  18. The 1996-2009 borehole dilatometer installations, operation, and maintenance at sites in Long Valley Caldera, CA

    Science.gov (United States)

    Myren, Glenn; Johnston, Malcolm; Mueller, Robert

    2011-01-01

    High seismicity levels with accelerating uplift (under the resurgent dome) in Long Valley caldera in the eastern Sierra Nevada from 1989 to 1997, triggered upgrades to dilational strainmeters and other instrumentation installed in the early 1980's following a series of magnitude 6 earthquakes. This included two additional high-resolution borehole strainmeters and replacement of the failed strainmeter at Devil's Postpile. The purpose of the borehole-monitoring network is to monitor crustal deformation and other geophysical parameters associated with volcanic intrusions and earthquakes in the Long Valley Caldera. Additional instrumentation was added at these sites to improve the capability of providing continuous monitoring of the magma source under the resurgent dome. Sites were selected in regions of hard crystalline rock, where the expected signals from magmatic activity were calculated to be a maximum and the probability of an earthquake of magnitude 4 or greater is large. For the most part, the dilatometers were installed near existing arrays of surface tiltmeters, seismometers, level line, and GPS arrays. At each site, attempts are made to separate tectonic and volcanic signals from known noise sources in each instrument type. Each of these sites was planned to be a multi-parameter monitoring site, which included measurements of 3-component seismic velocity and acceleration, borehole strain, tilt, pore pressure and magnetic field. Using seismicity, geophysical knowledge, geologic and topographic maps, and geologists recommendations, lists of preliminary sites were chosen. Additional requirements were access, and telemetry constraints. When the final site choice was made, a permit was obtained from the U.S. Forest Service. Following this selection process, two new borehole sites were installed on the north and south side of the Long Valley Caldera in June of 1999. One site was located near Big Spring Campground to the east of Crestview. The second site was

  19. Application of 2-D Inversion, to Magnetotelluric data on the Newberry Caldera, Oregon, for Potential Geothermal Power

    Science.gov (United States)

    Martin, T. P.; Schultz, A.

    2012-12-01

    Newberry Volcano lies immediately to the east of the Cascades volcanic arc in Oregon. However, Newberry differs from the main Cascadia arc, both chemically and in its physical setting. Newberry was formed by a combination of a shallow mantle source hot spot and subduction melts. This conclusion is suggested by depleted 3He/4He ratios and enriched Ba, Sr and Pb, which together indicate an oceanic crust subduction melt. As a result Newberry cannot be only formed from a stationary deep mantle source, or any other fixed source. Newberry also lies at the westernmost extent of an E-W oriented volcanic belt that appears to terminate in the east with the hot spot trace of the Snake River Plain/Yellowstone. Newberry's complex structure is also attributed to its proximity to the northernmost end of the Brothers Fault Zone (BFZ), related to regional tectonic fabric attributable to the transition to the Basin and Range province. The most recent volcanism at the caldera is a large obsidian flow, which erupted approximately 1,300 years ago. The United States Geological Survey considers Newberry to be a very high threat and to be "Central Oregon's Sleeping Giant." The western outer flank of the caldera is the site of an Enhanced Geothermal System (EGS) demonstration project being carried out by AltaRock Energy, Inc. and Davenport Newberry Holdings, LLC. EGS injection well stimulation is planned to open up a fracture network in a hot but dry series of altered basaltic/andesitic formations 2000-3000 m below ground level. Under Department of Energy funding, a collaboration between Oregon State University, the Department of Energy's National Energy Technology Laboratory, and Zonge International, Inc., seeks to image changes in fluid infiltration and migration, changes in porosity and permeability, and ultimately changes in the geothermal reservoir's capacity to produce thermal energy for sustained periods in response to changes in reservoir pressurization and injection rates. To

  20. Composition of Magmas, Minerals, and Melts of Tuffs and Lavas from the San Luis Caldera Complex, Colorado: Framework for Crystal Recycling and Melt Extraction Processes

    Science.gov (United States)

    Streck, M. J.; Lipman, P. W.

    2007-12-01

    The stratigraphy of the Oligocene San Luis Caldera Complex comprises three voluminous tuffs issued from overlapping calderas and numerous, compositionally diverse pre- and post-caldera lavas. The entire complex was erupted over an amazingly short period of 50-100 k.y. From oldest to youngest, the tuffs are the Rat Creek Tuff (>150 km3) that ranges in bulk composition from dacite to rhyolite to high-silica rhyolite, the dacitic Cebolla Creek Tuff (>250 km3), and the Nelson Mountain Tuff (>500 km3) that is again compositionally zoned from dacite to high-silica rhyolite. Pre- and post-caldera lavas range in composition from andesite to high-silica rhyolite. Phenocryst contents of most units range from 15 to 25%; only high-silica rhyolites are notably crystal-poorer (?5%) and tuffs can reach crystal contents of 35-45%. The compositional and lithological framework of the San Luis Caldera complex combined with the tight temporal and spatial control provide an ideal field laboratory for investigating whether minerals in younger volcanic units may be in part derived from recycling crystals of non-erupted magma of older units and for investigating generation processes of crystal-poor high-silica rhyolites. Many eruptive units are distinct on the level of bulk rock in terms of major and trace elemental composition and/or mineral proportions. For example, the dacitic to rhyolitic Rat Creek and Nelson Mountain Tuffs are dominated by pyroxene with only minor amphibole while the intervening dacitic Cebolla Creek Tuff contains abundant amphibole with subordinate pyroxene. When glass and mineral compositions are considered, eruptive units are less distinctive and observed compositions of individual units may cluster tightly or spread over most of the observed range for all units but in either case individual units typically follow broad compositional trends defined by all units. Interstitial melts of andesites to rhyolite are rhyodacitic to high-silca rhyolite.

  1. The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy

    Directory of Open Access Journals (Sweden)

    Andrea Bevilacqua

    2017-09-01

    Full Text Available This study presents a new method for producing long-term hazard maps for pyroclastic density currents (PDC originating at Campi Flegrei caldera. Such method is based on a doubly stochastic approach and is able to combine the uncertainty assessments on the spatial location of the volcanic vent, the size of the flow and the expected time of such an event. The results are obtained by using a Monte Carlo approach and adopting a simplified invasion model based on the box model integral approximation. Temporal assessments are modeled through a Cox-type process including self-excitement effects, based on the eruptive record of the last 15 kyr. Mean and percentile maps of PDC invasion probability are produced, exploring their sensitivity to some sources of uncertainty and to the effects of the dependence between PDC scales and the caldera sector where they originated. Conditional maps representative of PDC originating inside limited zones of the caldera, or of PDC with a limited range of scales are also produced. Finally, the effect of assuming different time windows for the hazard estimates is explored, also including the potential occurrence of a sequence of multiple events. Assuming that the last eruption of Monte Nuovo (A.D. 1538 marked the beginning of a new epoch of activity similar to the previous ones, results of the statistical analysis indicate a mean probability of PDC invasion above 5% in the next 50 years on almost the entire caldera (with a probability peak of ~25% in the central part of the caldera. In contrast, probability values reduce by a factor of about 3 if the entire eruptive record is considered over the last 15 kyr, i.e., including both eruptive epochs and quiescent periods.

  2. The effects of vent location, event scale and time forecasts on pyroclastic density current hazard maps at Campi Flegrei caldera (Italy)

    Science.gov (United States)

    Bevilacqua, Andrea; Neri, Augusto; Bisson, Marina; Esposti Ongaro, Tomaso; Flandoli, Franco; Isaia, Roberto; Rosi, Mauro; Vitale, Stefano

    2017-09-01

    This study presents a new method for producing long-term hazard maps for pyroclastic density currents (PDC) originating at Campi Flegrei caldera. Such method is based on a doubly stochastic approach and is able to combine the uncertainty assessments on the spatial location of the volcanic vent, the size of the flow and the expected time of such an event. The results are obtained by using a Monte Carlo approach and adopting a simplified invasion model based on the box model integral approximation. Temporal assessments are modelled through a Cox-type process including self-excitement effects, based on the eruptive record of the last 15 kyr. Mean and percentile maps of PDC invasion probability are produced, exploring their sensitivity to some sources of uncertainty and to the effects of the dependence between PDC scales and the caldera sector where they originated. Conditional maps representative of PDC originating inside limited zones of the caldera, or of PDC with a limited range of scales are also produced. Finally, the effect of assuming different time windows for the hazard estimates is explored, also including the potential occurrence of a sequence of multiple events. Assuming that the last eruption of Monte Nuovo (A.D. 1538) marked the beginning of a new epoch of activity similar to the previous ones, results of the statistical analysis indicate a mean probability of PDC invasion above 5% in the next 50 years on almost the entire caldera (with a probability peak of 25% in the central part of the caldera). In contrast, probability values reduce by a factor of about 3 if the entire eruptive record is considered over the last 15 kyr, i.e. including both eruptive epochs and quiescent periods.

  3. The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Karlstrom, Leif; Wright, Heather M.; Bacon, Charles R.

    2015-01-01

    The pattern of eruptions at long-lived volcanic centers provides a window into the co-evolution of crustal magma transport, tectonic stresses, and unsteady magma generation at depth. Mount Mazama in the Oregon Cascades has seen variable activity over the last 400 ky, including the 50 km3 climactic eruption at ca. 7.7 ka that produced Crater Lake caldera. The physical mechanisms responsible for the assembly of silicic magma reservoirs that are the precursors to caldera-forming eruptions are poorly understood. Here we argue that the spatial and temporal distribution of geographically clustered volcanic vents near Mazama reflects the development of a centralized magma chamber that fed the climactic eruption. Time-averaged eruption rates at Mount Mazama imply an order of magnitude increase in deep magma influx prior to the caldera-forming event, suggesting that unsteady mantle melting triggered a chamber growth episode that culminated in caldera formation. We model magma chamber–dike interactions over ∼50 ky preceding the climactic eruption to fit the observed distribution of surface eruptive vents in space and time, as well as petrologically estimated deep influx rates. Best fitting models predict an expanding zone of dike capture caused by a growing, oblate spheroidal magma chamber with 10–30 MPa of overpressure. This growing zone of chamber influence causes closest approaching regional mafic vent locations as well as more compositionally evolved Mazama eruptions to migrate away from the climactic eruptive center, returning as observed to the center after the chamber drains during the caldera-forming eruption.

  4. The effect of pressurized magma chamber growth on melt migration and pre-caldera vent locations through time at Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Karlstrom, Leif; Wright, Heather M.; Bacon, Charles R.

    2015-02-01

    The pattern of eruptions at long-lived volcanic centers provides a window into the co-evolution of crustal magma transport, tectonic stresses, and unsteady magma generation at depth. Mount Mazama in the Oregon Cascades has seen variable activity over the last 400 ky, including the 50 km3 climactic eruption at ca. 7.7 ka that produced Crater Lake caldera. The physical mechanisms responsible for the assembly of silicic magma reservoirs that are the precursors to caldera-forming eruptions are poorly understood. Here we argue that the spatial and temporal distribution of geographically clustered volcanic vents near Mazama reflects the development of a centralized magma chamber that fed the climactic eruption. Time-averaged eruption rates at Mount Mazama imply an order of magnitude increase in deep magma influx prior to the caldera-forming event, suggesting that unsteady mantle melting triggered a chamber growth episode that culminated in caldera formation. We model magma chamber-dike interactions over ∼50 ky preceding the climactic eruption to fit the observed distribution of surface eruptive vents in space and time, as well as petrologically estimated deep influx rates. Best fitting models predict an expanding zone of dike capture caused by a growing, oblate spheroidal magma chamber with 10-30 MPa of overpressure. This growing zone of chamber influence causes closest approaching regional mafic vent locations as well as more compositionally evolved Mazama eruptions to migrate away from the climactic eruptive center, returning as observed to the center after the chamber drains during the caldera-forming eruption.

  5. Hydrothermal activity and subsoil complexity: implication for degassing processes at Solfatara crater, Campi Flegrei caldera

    Science.gov (United States)

    Montanaro, Cristian; Mayer, Klaus; Isaia, Roberto; Gresse, Marceau; Scheu, Bettina; Yilmaz, Tim I.; Vandemeulebrouck, Jean; Ricci, Tullio; Dingwell, Donald B.

    2017-12-01

    The Solfatara area and its fumaroles are the main surface expression of the vigorous hydrothermal activity within the active Campi Flegrei caldera system. At depth, a range of volcanic and structural processes dictate the actual state of the hydrothermal system below the crater. The presence of a large variety of volcanic products at shallow depth (including pyroclastic fallout ash beds, pyroclastic density current deposits, breccias, and lavas), and the existence of a maar-related fault system appears to exert major controls on the degassing and alteration behavior. Adding further to the complexity of this environment, variations in permeability and porosity, due to subsoil lithology and alteration effects, may further influence fluid flow towards the surface. Here, we report results from a field campaign conducted in July 2015 that was designed to characterize the in situ physical (temperature, humidity) and mechanical (permeability, strength, stiffness) properties of the Solfatara crater subsoil. The survey also included a mapping of the surficial hydrothermal features and their distributions. Finally, laboratory measurements (porosity, granulometry) of selected samples were performed. Our results enable the discrimination of four main subsoils around the crater: (1) the Fangaia domain located in a topographic low in the southwestern sector, (2) the silica flat domain on the western altered side, (3) the new crust domain in the central area, and (4) the crusted hummocks domain that dominates the north, east, and south parts. These domains are surrounded by encrusted areas, reworked material, and vegetated soil. The distribution of these heterogeneous subsoils suggests that their formation is mostly related to (i) the presence of the Fangaia domain within the crater and (ii) a system of ring faults bordering it. The subsoils show an alternation between very high and very low permeabilities, a fact which seems to affect both the temperature distribution and

  6. Older Hydrothermal Activity along the Northern Yellowstone Caldera Margin at Sulphur Creek, Yellowstone Park, Wyoming

    Science.gov (United States)

    Manion, J. L.; Larson, P.

    2008-12-01

    The Tuff of Sulphur Creek (480 ka) is well exposed in the Seven Mile Hole area of the Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming. The rhyolitic tuff erupted after the collapse of the Yellowstone Caldera (640 ka) and hosts more than 350 vertical meters of hydrothermal alteration. Two epithermal alteration assemblages with different mineral associations have been identified in the area: an illite-silica-pyrite phase and a kaolinite-alunite-silica-pyrite phase. Kaolinite and opal occur along the canyon rim, montmorillonite and other smectites are found at intermediate depths, and illite and sulfides (pyrite) are found deepest in the section. Our work on the north side of the Sevenmile Hole altered area has found a complex system of veining. The veins are concentrated in the eastern portion of the canyon and are less frequent to the west. Brecciated cross-cutting veins ranging from 2 to 30cm wide are found at the base of the canyon. Moving vertically up the canyons walls, the veining style becomes less complex. These veins are about 1 to 1.5cm wide and are not brecciated, occurring less frequently than the brecciated veins. The canyon walls and the canyon rim mainly contain millimeter-scale cross-cutting silica veinlets. These stockwork-like veinlets are the most abundant fracture filling that we find throughout the canyon walls. Veins at the base of the system, found in the stream bed, contain abundant sulfides (mainly pyrite). Sulfides are present in three forms: disseminated in a silica matrix, as massive pyrite in healed fractures, and encrusting clays and silica. The latter is the least common. Disseminated and massive sulfides are typically associated with the matrix in the brecciated veins. Breccias include angular clasts of altered tuff with argillized feldspar phenocrysts and fragments of earlier vein-filling opal. Sulfides are most abundant in the bottom of the canyon and in the western part of the field area. Hydrothermal

  7. The Oldest Known Caldera Associated with the Yellowstone Hotspot: New Geologic Mapping, Geochemistry, and 40Ar/39Ar Geochronology for the Northern McDermitt Volcanic Field, Northern Nevada and Southeastern Oregon

    Science.gov (United States)

    Benson, T. R.; Mahood, G. A.

    2015-12-01

    McDermitt Volcanic Field (MVF) of Nevada and Oregon is one of three major caldera centers associated with Mid-Miocene Steens/Columbia River flood basalts. Pioneering geologic mapping of MVF by Rytuba and McKee (1984) and subsequent work established four main ignimbrites within the field. Our new 40Ar/39Ar ages (FCT=28.02 Ma) are 16.41±0.02 (±2σ) Ma for Tuff of Oregon Canyon, 16.35±0.04 Ma for Tuff of Trout Creek Mountains, 16.30±0.04 Ma for Tuff of Long Ridge, and 15.56±0.08 Ma for Tuff of Whitehorse Creek. We have mapped two previously unrecognized overlapping calderas that we interpret as sources for Tuff of Oregon Canyon and Tuff of Trout Creek. These ~20-km diameter calderas lie north of the well-known McDermitt Caldera; a smaller 7-km caldera that formed on eruption of the Tuff of Whitehorse Creek is nested within them. Argon ages and geochemistry of alkali rhyolite lava domes in the northern MVF define two populations: ~16.6-16.3 Ma associated with the newly recognized calderas, and ~15.5-15.3 Ma outlining the margins of the younger Whitehorse Caldera. Consistent with both ignimbrites erupting from the same evolving magma system, the high-silica alkali rhyolite Tuff of Oregon Canyon lies on compositional trends defined by the Tuff of Trout Creek, which is zoned from a moderately crystal-rich high-silica alkali rhyolite to a strongly porphyritic low-silica alkali rhyolite. They both are distinguished from the Tuff of Long Ridge from McDermitt Caldera by their higher Zr/Rb, and relatively high FeO* concentrations distinguish all MVF ignimbrites from ignimbrites from the nearby High Rock Caldera Complex, where the oldest caldera formed on eruption of the Idaho Canyon Tuff at 16.38±0.02 Ma (Coble and Mahood, in review). The Tuff of Trout Creek rests conformably on the Tuff of Oregon Canyon west and southwest of the calderas, where they overlie a thick stack of Steens Basalt lavas. To the east and southeast the two ignimbrites are separated by as much as

  8. Possible structures of the old Urcunina Caldera, revealed by high precision relocation of VT earthquakes at Galeras volcano

    Science.gov (United States)

    Lizarazo C, M. J.; Alvarado, H.; Sanchez, J. J.

    2013-12-01

    Volcano-Tectonic earthquakes at Galeras Volcano were relocated using the waveform catalog waveform and preliminary phase arrival data compiled by the monitoring network at Observatorio Volcanológico y Sismológico de Pasto. Several routines were developed in MATLAB, mainly to prepare waveforms, calculate differential travel times, and identifying seismic families; and the HypoDD program was implemented, which allowed performing the relocations. The procedure resulted in the detection of 10 swarm-type families and 4 spatial-type families of earthquakes, which reveal a fault of 1.6 km bounding the Urcunina Caldera, and a ring fault of 1.8 km in diameter, adjacent to the crater. Reductions in the range 56.84% - 87.48% were achieved in the hypocentral parameters uncertainties as compared to uncertainties in traditional locations, to finally obtain an alternative image of the Volcano-Tectonic earthquakes distribution Galeras Volcano VG with a significantly lower uncertainty.

  9. Advisory expert system for energy analysis in industrial boilers; Sistema experto asesor en el analisis energetico de calderas industriales

    Energy Technology Data Exchange (ETDEWEB)

    Kemper Valverde, Nicolas; Lara Rosano, Felipe; Vazquez Nava, Rodolfo [Laboratorio de Inteligencia Artificial, Instituto de Ingenieria UNAM, Mexico, D. F. (Mexico)

    1994-12-31

    This paper presents an expert system for the operational analysis of industrial boilers, estimating the potential of heat recovery, in the small and medium size industry. The package is friendly, practical, flexible easy to maintain and expandable to take into consideration the user`s specific requirements and allows the analysis of the energy losses in the combustion, feed water, drains, and insulation, identifying the enhancements and estimating the saving potential, in energy as well as economical. [Espanol] En este trabajo se presenta un sistema experto para analizar la operacion de calderas industriales estimando el potencial de recuperacion de calor, en la pequena y mediana industria. El paquete es amigable, practico, flexible, facil en su mantenimiento y expandible para tomar en consideracion los requerimientos especificos de los usuarios y permite el analisis de las perdidas de energia en la combustion, agua de alimentacion, purgas y aislamientos, identificando las mejoras y estimando ahorros potenciales, tanto energeticos como economicos.

  10. Study of the 2011-2013 unrest at Campi Flegrei caldera (Italy) through InSAR and 3D modelling

    Science.gov (United States)

    Trasatti, Elisa; Polcari, Marco; Bignami, Christian; Bonafede, Maurizio; Buongiorno, Fabrizia; Stramondo, Salvatore

    2014-05-01

    Campi Flegrei is a nested caldera in Italy, at the western edge of the Bay of Naples. Together with Vesuvius and Mt Etna, it is one of the Italian GeoHazard Supersites. The area is characterized by one of the highest volcanic hazard in the world, due to the very high density of inhabitants (1800/km2), the persistent activity of the system and the explosive character of volcanism. A major unrest episode took place in 1982-84, when the town of Pozzuoli, located at the caldera center, was uplifted by 1.80 m (~1 m/yr). Minor uplifts of few cm, seismic swarms and degassing episodes took place in 1989, 2000 and 2004-06. Since 2005 Campi Flegrei is uplifting, reaching a ground velocity of 9 cm/yr in 2012, showing that the caldera is in a critical state on the verge of instability. In the present work we consider InSAR time series of the recent activity (2010-2013) detected by COSMO SkyMed satellite. In particular, the time series show a progressive velocity increase of ground deformation during 2012, while it slowed down in 2013 approaching zero. The cumulative displacement from COSMO SkyMed descending orbit (March 2011 - March 2013) show a semicircular pattern centered in Pozzuoli with a maximum LoS (Line of Sight) displacement of 11 cm and maximum velocity 9 cm/yr reached along the coastline. The spatial distribution of the cumulative displacement from COSMO SkyMed ascending orbit show a similar behavior, confirming the bell-shaped pattern of the deformation at least inside the inner rim of the caldera. The cumulative ascending LoS displacement between March 2013 - September 2013 is 1-2 cm, confirming the stall of the unrest after the first few months of 2013 as observed by GPS. Initially, several source geometries are adopted (sphere, spheroid, sill) to model the cumulative deformation between 2011 and 2013. All the sources are located offshore Pozzuoli at a depth of about 2 km. The sphere and spheroid result to dilate at an annual volume variation rate of the order of

  11. Evaluation of minderal resource potential, Caldera geology, and volcano-tectonic framework at and near Yucca Mountain, Task 3

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1993-09-30

    This report summarizes the results of Task 3 work that was initially discussed in our monthly reports for the period October 1, 1992 through September 30, 1993, and contained in our various papers and abstracts, both published and currently in press or in review. Our work during this period was involved (a) the continuation of studies begun prior to October, 1992, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern and Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill hole samples obtained in 1991 and 1992, and (b) new studies of veins and siliceous rocks cropping out in northwestern Yucca Mountain that provide evidence for previously unrecognized hydrothermal activity during the Crater Flat Tuff period of volcanism.

  12. ROCK PHYSICS. Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera.

    Science.gov (United States)

    Vanorio, Tiziana; Kanitpanyacharoen, Waruntorn

    2015-08-07

    Uplifts in the Campi Flegrei caldera reach values unsurpassed anywhere in the world (~2 meters). Despite the marked deformation, the release of strain appears delayed. The rock physics analysis of well cores highlights the presence of two horizons, above and below the seismogenic area, underlying a coupled process. The basement is a calc-silicate rock housing hydrothermal decarbonation reactions, which provide lime-rich fluids. The caprock above the seismogenic area has a pozzolanic composition and a fibril-rich matrix that results from lime-pozzolanic reactions. These findings provide evidence for a natural process reflecting that characterizing the cementitious pastes in modern and Roman concrete. The formation of fibrous minerals by intertwining filaments confers shear and tensile strength to the caprock, contributing to its ductility and increased resistance to fracture. Copyright © 2015, American Association for the Advancement of Science.

  13. Evaluation of mineral resource potential, caldera geology, and volcano-tectonic framework at and near Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1992-09-30

    This report summarizes the result of Task 3 work initially discussed in our monthly reports for the period October 1, 1991 through September 30, 1992, and contained in our various papers and abstracts, both published and currently in press or review. Our work during this period has involved (a) the continuation of studies begun prior to October, 1991, focussed mainly on aspects of the caldera geology, volcanic stratigraphy, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and northwestern parts of the southwestern Nevada volcanic field (SWNVF), and (b) new studies of the alteration and trace-metal geochemistry of subsurface rocks at Yucca Mountain utilizing drill hole samples obtained in late 1991 and early 1992.

  14. State of stress and relationship of mechanical properties to hydrothermal alteration at Valles Caldera core hole 1, New Mexico

    Science.gov (United States)

    Dey, Thomas N.; Kranz, Robert L.

    1988-06-01

    We measured the densities, total and microcrack porosities, and ultrasonic velocities of a number of core samples from an 856-m-deep core hole near the Banco Bonito vent at Valles Caldera, New Mexico. Reductions in porosity with depth define a zone from about 600 m down where hydrothermal mineralization and recrystallization have been most active. This zone is also reflected in a large decrease in the anisotropy of acoustic velocities. Stress orientation estimates based on microcrack orientations at the 812-m depth as determined by differential strain curve analysis, as well as anelastic strain recovery measurements on a sample from 472-m depth, show a horizontal E-W minimum compression direction and a maximum compression inclined about 30° from vertical.

  15. A GIS-based volcanic hazard and risk assessment of eruptions sourced within Valles Caldera, New Mexico

    Science.gov (United States)

    Alcorn, R.; Panter, K. S.; Gorsevski, P.; Ye, X.

    2013-05-01

    The Jemez Volcanic field in New Mexico is best known for the two cataclysmic eruptions that formed the Valles Caldera and deposited the Bandelier tuff at 1.61 and 1.25 Ma. This was followed by a period of small-scale activity limited to within the moat until ~ 55 ka when plinian eruptions sourced from the El Cajete crater dispersed tephra well beyond the caldera wall. These deposits include the El Cajete pyroclastic beds and the Battleship Rock Ignimbrite. Following the eruption of the Banco Bonito lava flow at ~40 ka, the Valles caldera has lain dormant. However, there is potential for future activity and it is prudent to assess the risk to the surrounding area and consider possible mitigation strategies well before a disaster strikes. The objective of this study is to evaluate the spatial extent of a possible future eruption using a GIS-based volcanic hazards tool designed to simulate pyroclastic fallout and density currents (PDCs) as well as lava flows [1] and to assess the social and economic vulnerability of the area at risk. Simulated pyroclastic fall deposits originating from the El Cajete crater are calibrated to isopach and lithic isopleth maps of the Lower and Upper El Cajete as constructed by [2]. The change in the axial orientation of fall deposits between the Lower and Upper El Cajete is best matched using seasonal variations in wind speed and direction based on modern atmospheric records. The calibration of PDCs is based on the distribution and run-out of the Battleship Rock Ignimbrite. Once calibrated, hazards are simulated at two other vent locations determined from probability distributions of structural features. The resulting hazard maps show the potential distribution of pyroclastic fall, PDCs and lava flows, indicating areas to the S/SE of Valles Caldera to be at greatest risk. To assess hazard preparedness, social vulnerability is evaluated for all census-designated places (CDP) within the study site. Based on methods by [3], twenty

  16. Regulatory, Land Ownership, and Water Availability Factors for a Magma Well: Long Valley Caldera and Coso Hot Springs, California

    Energy Technology Data Exchange (ETDEWEB)

    Blackett, Robert

    1985-09-01

    The U.S. Department of Energy is currently engaged in a program to demonstrate the engineering feasibility of extracting thermal energy from high-level molten magma bodies. The program is being carried out under the direction of Sandia National Laboratories where a number of individual projects support the overall program. The existing program elements include (1) high-temperature materials compatibility testing; (2) studies of properties of melts of various compositions; and (3) the investigation of the economics of a magma energy extraction system. Another element of the program is being conducted with the cooperation of the U.S. Geological Survey, and involves locating and outlining magma bodies at selected sites using various geophysical techniques. The ultimate goal here will be to define the limits of a magma body as a drilling target. During an earlier phase of the program, more than twenty candidate study sites considered were evaluated based upon: (1) the likelihood of the presence of a shallow magma chamber, (2) the accessibility of the site, and (3) physical and institutional constraints associated with each site with respect to performing long-term experiments. From these early phase activities, the number of candidate sites were eventually narrowed to just 2. The sites currently under consideration are Coso Hot Springs and the Long Valley caldera (Figure 1). This report describes certain attributes of these sites in order to help identify potential problems related to: (1) state and federal regulations pertaining to geothermal development; (2) land ownership; and (3) water resource availability. The information sources used in this study were mainly maps, publications, and informative documents gathered from the California Division of Oil and Gas and the U.S. Department of the Interior. Environmental studies completed for the entire Long Valley caldera study area, and for portions of the Coso Hot Springs study area were also used for reference.

  17. A geochemical and geophysical reappraisal to the significance of the recent unrest at Campi Flegrei caldera (Southern Italy)

    Science.gov (United States)

    Moretti, Roberto; De Natale, Giuseppe; Troise, Claudia

    2017-04-01

    Volcanic unrest at calderas involve complex interaction between magma, hydrothermal fluids and crustal stress and strain. Campi Flegrei caldera (CFc), located in the Naples (Italy) area and characterised by the highest volcanic risk on Earth for the extreme urbanisation, undergoes unrest phenomena involving several meters of uplift and intense shallow micro-seismicity since several decades. Despite unrest episodes display in the last decade only moderate ground deformation and seismicity, current interpretations of geochemical data point to a highly pressurized hydrothermal system. We show that at CFc, the usual assumption of vapour-liquid coexistence in the fumarole plumes leads to largely overestimated hydrothermal pressures and, accordingly, interpretations of elevated unrest. By relaxing unconstrained geochemical assumptions, we infer an alternative model yielding better agreement between geophysical and geochemical observations. The model reconciles discrepancies between what observed 1) for two decades since the 1982-84 large unrest, when shallow magma was supplying heat and fluids to the hydrothermal system, and 2) in the last decade. Compared to the 1980's unrest, the post-2005 phenomena are characterized by much lower aquifers overpressure and magmatic involvement, as indicated by geophysical data and despite large changes in geochemical indicators. Our interpretation points out a model in which shallow sills, intruded during 1969-1984, have completely cooled, so that fumarole emissions are affected now by deeper, CO2-richer, magmatic gases producing a relatively modest heating and overpressure of the hydrothermal system. Our results do have important implications on the short-term eruption hazard assessment and on the best strategies for monitoring and interpreting geochemical data.

  18. 238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

    Science.gov (United States)

    Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

    2014-01-01

    Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

  19. Regional earthquakes followed by delayed ground uplifts at Campi Flegrei Caldera, Italy: Arguments for a causal link

    Science.gov (United States)

    Lupi, Matteo; Frehner, Marcel; Weis, Philipp; Skelton, Alasdair; Saenger, Erik H.; Tisato, Nicola; Geiger, Sebastian; Chiodini, Giovanni; Driesner, Thomas

    2017-09-01

    Earthquake-triggered volcanic activity promoted by dynamic and static stresses are considered rare and difficult-to-capture geological processes. Calderas are ideal natural laboratories to investigate earthquake-volcano interactions due to their sensitivity to incoming seismic energy. The Campi Flegrei caldera, Italy, is one of the most monitored volcanic systems worldwide. We compare ground elevation time series at Campi Flegrei with earthquake catalogues showing that uplift events at Campi Flegrei are associated with large regional earthquakes. Such association is supported by (yet non-definitive) binomial tests. Over a 70-year time window we identify 14 uplift events, 12 of them were preceded by an earthquake, and for 8 of them the earthquake-to-uplift timespan ranges from immediate responses to 1.2 yr. Such variability in the response delay may be due to the preparedness of the system with faster responses probably occurring in periods during which the Campi Flegrei system was already in a critical state. To investigate the process that may be responsible for the proposed association we simulate the propagation of elastic waves and show that passing body waves impose high dynamic strains at the roof of the magmatic reservoir of the Campi Flegrei at about 7 km depth. This may promote a short-lived embrittlement of the magma reservoir's carapace otherwise marked by a ductile behaviour. Such failure allows magma and exsolved volatiles to be released from the magmatic reservoir. The fluids, namely exsolved volatiles and/or melts, ascend through a nominally plastic zone above the magmatic reservoir. This mechanism and the associated inherent uncertainties require further investigations but the new concept already implies that geological processes triggered by passing seismic waves may become apparent several months after passage of the seismic waves.

  20. DYNAMIC MIXING MODEL OF THE CHIGNAHUAPAN THERMAL SPRING IN THE GEOTHERMAL ZONE OF THE ACOCULCO CALDERA, PUEBLA, MEXICO

    Science.gov (United States)

    Gutierrez-Cirlos, A.; Torres-Rodriguez, V.

    2009-12-01

    The Acoculco Caldera, of Pliocenic age, is located within the limits of the Transmexican Volcanic Belt (CVT) and the Sierra Madre Oriental (SMOr). The Acoculco geothermal zone consists of a 790m thick igneous sequence, related to a volcanic complex formed by andesites and rhyolitic domes emplaced in an 18 Km diameter annular fracture. It unconformably overlies a 5000 m thick section of folded and faulted Jurassic-Cretaceous carbonate rocks. The Chignahuapan Spring, located in the extreme eastern part of the Geothermal Zone of the Acoculco Caldera, yields temperatures of 49°C and discharges an estimated of 98 lps from the karstified Lower Cretaceous limestone. Both major and trace element geochemical analysis were carried out, and results were interpreted using Piper and Stiff diagrams, as well as geothermometry. The results indicate that water belongs to the calcium-bicarbonate type and yield temperatures in a range of 70-80°C at depth, which suggest an extensive lateral flow from the main reservoir and mixing with shallow groundwaters. The spring suffers significant variations in its temperature throughout the year, especially during the rainy season, when water temperature decreases up to 10°C. Analyzing the hot spring water temperature data from of the last 10 years and comparing it with the precipitation and air temperature curves of the region, we expect to develop a dynamic mixing model which depicts the relation between these factors and the importance of each one in the water temperature variation. We also look forward to be able to forecast water temperature trends for the next several years and correlate it with climate change in the area.

  1. Contrasting plagioclase textures and geochemistry in response to magma dynamics in an intra-caldera rhyolite system, Okataina volcano

    Science.gov (United States)

    Shane, Phil

    2015-05-01

    The changing magmatic dynamics of the rhyolite caldera volcano, Okataina Volcanic Centre, New Zealand, is revealed in plagioclase growth histories. Crystals from the ~ 0.7 ka Kaharoa eruption are characterized by resorbed cores displaying a cellular texture of high-An (> 40) zones partially replaced by low-An (cellular texture of variable An content (An40-50). The crystals display step-wise regrowth of successively higher An, Fe, Mg, and Ti content, consistent with progressive mafic recharge. Two crystal groups are distinguished by trace element chemistry, indicating growth in separate melts and co-occurrence via magma mingling. For plagioclase in both eruption deposits, partition coefficients (D) estimated from crystal rim-groundmass glass analyses, produce melt compositions similar to the array of rock and glass compositions erupted and are consistent with the processes of fractional crystallization and recharge. However, D values estimated from some published formulations based on An content and temperature produce unrealistic melts. The contrasting zoning patterns in plagioclase correspond to the evolutionary history of magmatism at Okataina. Emptying of the magma reservoir following caldera eruption at 46 ka reduced barriers to mafic magma ascent. This is recorded by the frequent resorption and recharge episodes in Hauparu crystals. Subsequent redevelopment of a more silicic reservoir zone (post-26 ka) dampened thermal and mass perturbations, resulting in simpler growth histories of the Kaharoa crystals. The plagioclase lack features associated with rapid decompression events that are common in andesite systems. This reflects the rapid ascent of the rhyolite magmas and lack of precursory eruptions that could decompressed the system.

  2. Geology of the Vilama caldera: A new interpretation of a large-scale explosive event in the Central Andean plateau during the Upper Miocene

    Science.gov (United States)

    Soler, M. M.; Caffe, P. J.; Coira, B. L.; Onoe, A. T.; Kay, S. Mahlburg

    2007-07-01

    The Vilama caldera is one of the very large-volume volcanic structures that formed during the ignimbrite flare-up that lasted from 10 Ma to 4 Ma on the central Andean plateau. Formerly, the Vilama structure was interpreted as a 65 × 40 km wide caldera with a two stage evolution. New field correlations, petrographical, geochemical and geochronological data lead to a substantially larger reinterpreted Vilama ignimbrite, whose outcrops cover more than 4000 km 2. New and existing K/Ar and Ar/Ar dating shows that the dacitic Vilama ignimbrite erupted from the Vilama caldera at 8.4-8.5 Ma. The ignimbrite can be divided into extracaldera outflow and intracaldera deposits. The outflow has a mean thickness of ˜ 40 m and is separated into a restricted valley-ponded lower cooling unit, and a laterally extensive low aspect ratio upper cooling unit. The Vilama caldera, which is roughly rectangular (35-40 km × 15-18 km) in shape and has central coordinates of 22°24' S and 66°57' W, is considered to have formed in a single-stage collapse event. As the topographic rim is only seen on the western side, the extent of collapse and geometry of the caldera are incompletely known and inferred from indirect data. Possible collapse geometries include a slightly asymmetric single-block subsidence and non-chaotic multiple-block collapse. Estimated erupted volumes range from ˜ 1800 to 1200 km 3, or 1400 to 1000 km 3 in dense rock equivalents. The properties of the Vilama ignimbrite which include a crystal-rich and pumice-poor nature, a high degree of welding and induration and a prodigious volume, suggest that an external drive, rather than volatile overpressures, controlled and maintained the eruption. The best candidate is caldera subsidence triggered by the instability of a magma chamber roof above a batholith-scale magma body. Transtensive/distensive tectonic stresses resulted in the northwest elongation of the magma chamber and/or influenced the roughly rectangular

  3. The link between volcanism and plutonism in epizonal magma systems; high-precision U-Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    Science.gov (United States)

    Rioux, Matthew; Farmer, G. Lang; Bowring, Samuel A.; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-02-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U-Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the final eruption. Calculated magmatic

  4. Geochemical and Isotopic Data for Oligocene Ignimbrites, Calderas, and Granitic Plutons, Southern Stillwater Range and Clan Alpine Mountains: Insights into the Volcanic-Plutonic Connection and Crustal Evolution in Western Nevada

    Science.gov (United States)

    John, D. A.; Colgan, J. P.; Watts, K. E.; Henry, C.; Cousens, B.

    2015-12-01

    Oligocene calderas and underlying plutons in the southern Stillwater Range (SSR) and Clan Alpine Mountains (CAM) in western Nevada were tilted (40->90°) by large-magnitude Miocene extension and unconformably overlain by 15-13 Ma intermediate and mafic lava flows. New geologic mapping, geochemistry, and Ar-Ar and U-Pb dating document 2 brief periods of magmatism resulting in 5 nested calderas and related plutons in sections locally ≥9 km thick. Early magmatism at ~29 Ma included the Deep Canyon caldera in CAM, and in the SSR, pre-caldera rhyolites, ~5 km of pre- and post-collapse intermediate lavas and rhyolite tuff that filled Job Canyon caldera (JC, ~29.4 to 28.8 Ma), and the >4-5 km thick IXL pluton (~28.5 Ma) that intruded JC and is compositionally similar to the tuff and lava flows. The second period included 3 ignimbrite units in 3 calderas: small-volume tuff of Louderback Mountains (LM, low-silica rhyolite; ≥600 m thick; ~25.3 Ma); multiple cooling units of tuff of Poco Canyon (PC, high-silica rhyolite; ≤4.5 km thick; ~25.3 Ma); and ≥2500 km3 of tuff of Elevenmile Canyon (EC, trachydacite to rhyolite; ≤4.5 km thick; 25.1 Ma) that covers ~1600 km2 and extends east from SSR to the northern Desatoya Mountains. The composite Freeman Creek pluton (granodiorite, ~25.0 Ma; granite, ~24.8 Ma) and Chalk Mountain rhyolite porphyry (~25.2 Ma) and granite (~24.8 Ma) plutons intruded LM, PC and EC calderas. Radiogenic isotopes in all caldera units are similar (Sri~0.7050, ΕNd~0.0), while oxygen isotope compositions are variable (δ18Oquartz=5.7-8.4‰, δ18Ozircon=4.1-6.3‰), corresponding to a magmatic range of 5.6-7.6‰, including 2-5 km) underlie compositionally and temporally related caldera-filling ignimbrites, (2) caldera-forming cycles are isotopically variable, requiring temporally and spatially distinct magma sources, and (3) caldera magmas have a strong mantle affinity and overlap isotopically (Sr, Nd, and O) with regional Late Cenozoic basalts.

  5. Tomography from 26 years of seismicity revealing that the spatial extent of the Yellowstone crustal magma reservoir extends well beyond the Yellowstone caldera

    Science.gov (United States)

    Farrell, Jamie; Smith, Robert B.; Husen, Stephan; Diehl, Tobias

    2014-05-01

    The Yellowstone volcanic field has experienced three of Earth's most explosive volcanic eruptions in the last 2.1 Ma. The most recent eruption occurred 0.64 Ma forming the 60 km long Yellowstone caldera. We have compiled earthquake data from the Yellowstone Seismic Network from 1984 to 2011 and tomographically imaged the three-dimensional P wave velocity (Vp) structure of the Yellowstone volcanic system. The resulting model reveals a large, low Vp body, interpreted to be the crustal magma reservoir that has fueled Yellowstone's youthful volcanism. Our imaged magma body is 90 km long, 5-17 km deep, and 2.5 times larger than previously imaged. The magma body extends ~15 km NE of the caldera and correlates with the location of the largest negative gravity anomaly, a -80 mGal gravity low. This new seismic image provides important constraints on the dynamics of the Yellowstone magma system and its potential for future volcanic eruptions and earthquakes.

  6. 3D image of Brittle/Ductile transition in active volcanic area and its implication on seismicity: The Campi Flegrei caldera case study

    Science.gov (United States)

    Castaldo, Raffaele; Luca, D'auria; Susi, Pepe; Giuseppe, Solaro; Pietro, Tizzani

    2015-04-01

    The thermo-rheology of the rocks is a crucial aspect to understand the mechanical behavior of the crust in young and tectonically active area. As a consequence, several studies have been performed since last decades in order to understand the role of thermic state in the evolution of volcanic environments. In this context, we analyze the upper crust rheology of the Campi Flegrei active caldera (Southern Italy). Our target is the evaluation of the 3D geometry of the Brittle-Ductile transition beneath the resurgent caldera, by integrating the available geological, geochemical, and geophysical data. We first performed a numerical thermal model by using the a priori geological and geophysical information; than we employ the retrieved isothermal distribution to image the rheological stratification of the shallow crust beneath caldera. In particular, considering both the thermal proprieties and the mechanical heterogeneities of the upper crust, we performed, in a Finite Element environment, a 3D conductive time dependent thermal model through an numerical of solution of the Fourier equation. The dataset consist in temperature measurements recorded in several deep wells. More specifically, the geothermal gradients were measured in seven deep geothermal boreholes, located in three main distinct areas: Mofete, Licola, and San Vito. In addition, we take into account also the heat flow density map at the caldera surface calculated by considering the thermal measurements carried out in 30 shallow water wells. We estimate the isothermal distribution of the crust calibrating two model parameters: the heat production [W], associated to the magma injection episodes in the last 60 kyears within the magma chamber and the heat flow coefficient [W/m2*K] at the external surface. In particular, the optimization procedure has been performed using an exhaustive grid search, to minimize the differences between model and experimental measurements. The achieved results allowed us to

  7. Fault Networks in the Northwestern Albuquerque Basin and Their Potential Role in Controlling Mantle CO2 Degassing and Fluid Migration from the Valles Caldera

    Science.gov (United States)

    Smith, J. R.; Crossey, L. J.; Karlstrom, K. E.; Fischer, T. P.; Lee, H.; McGibbon, C. J.

    2015-12-01

    The Rio Grande rift (RGR) has Quaternary and active volcanism and faulting that provide a field laboratory for examining links between mantle degassing and faults as fluid conduits. Diffuse and spring CO2 flux measurements were taken at 6 sites in the northwestern Albuquerque Basin (NWAB) and Valles caldera geothermal system. All sites progress to the southwest from the 1.25 Ma Valles caldera, down the rift-related Jemez fault network, to intersect with the Nacimiento fault system. Mantle CO2 and He degassing are well documented at 5 of 6 sites, with decreasing 3He/4He ratios away from the caldera. The instrument used to measure CO2 flux was an EGM-4 CO2 gas analyzer (PP systems) with an accumulation chamber. Carbonic springs at Penasco Springs (PS) and San Ysidro (SY), and the carbonate-cemented Sand Hill Fault (SHF) were targeted, all near the western border of the RGR. The SHF has no spring activity, had the smallest maximum flux of all the sites (8 g/m2d), but carbonate along the fault zone (Dam (1,882 g/m2d) at Valles caldera geothermal sites are comparable to Yellowstone geothermal systems. We use geospatial analysis and local geologic mapping to examine relationships of CO2 flux to structure. Travertine mounds can create impermeable barriers that modify near-surface degassing patterns, making it difficult to decipher where CO2 and fluids preferentially migrate up the damage zones in the hanging-wall or footwall. Future work will utilize grids to more accurately assess the localized affect fault zones have on CO2 flux rates.

  8. Isotopic and geochemical constraints on the origin and evolution of postcollapse rhyolites in the Valles Caldera, New Mexico

    Science.gov (United States)

    Spell, Terry L.; Kyle, Philip R.; Thirlwall, Matthew F.; Campbell, Andrew R.

    1993-11-01

    Ring-fracture rhyolites of the Valles Caldera (VC) were examined to determine the evolution of the magma system following eruption of the upper Bandelier Tuff (UBT) and subsequent caldera collapse. Volcanism began with eruption of Deer Canyon (DC), Redondo Creek, and Del Medio (DM) rhyolites during the interval 1140-1133 ka. Quartz delta O-18 for the UBT, (average +8.3 %), DC (+7.9 %), and DM (+8.7 %) rhyolites indicate no significant lowering of delta O-18 following caldera collapse. In contrast, DM rhyolites record low epsilon(sub Nd) of -3.6 to -3.8 relative to the UBT (-2.7) and variable initial 87-Sr/86-Sr (0.70923-0.71307). Del Abrigo (DA) and Santa Rosa I rhyolites (973-915 ka) exhibit lower epsilon(Sub Nd) (-4.4 to -4.6) and initial 87-Sr/86-Sr (0.70707-0.71009), as well as shifts in compatible and incompatible trace element ratios. Seco, San Luis, and Santa Rosa II rhyolites (800-787 ka) have epsilon(Sub Nd) (-4.0 to -4.3) similar to the 973 to 915 ka rhyolites but lower initial 87-Sr/86-Sr (0.70616-0.70747). After a hiatus of 230 ka, San Antonio (SA), South Mountain (SM), and La Jara (LJ) rhyolites (557-521 ka) were erupted with epsilon(Sub Nd) of -3.7 to 4.3, distinctly lower initial 87-Sr/86-Sr of 0.70513-0.70553 and less evolved trace element compositions. The youngest rhyolites, the El Cajete-Banco Bonito group (EC-BB) (300-170 ka) are petrographically and geochemically distinct with the highest epsilon(Sub Nd) (-2.7 to -3.0) and the lowest initial 87-Sr/86-Sr (0.70464-0.70478) of postcollapse rhyolites. The isotopic data indicate that Valles rhyolites are not direct melts of Proterozoic basement (epsilon(Sub Nd) of -10 to -15) and indicate a significant mantle-derived (basaltic) component. Elevated initial 87-Sr/86-Sr is restricted to rhyolites depleted in Sr (less than 10 ppm) and probably reflects minor upper crustal assimilation. Calculated magma delta 0-18 values (+6.6 to +7.0 %) indicate no substantial supracrustal sediment in the source region

  9. Evaluation of the thermal regime of the Valles Caldera, New Mexico, U.S.A., by downward continuation of temperature data

    Science.gov (United States)

    Tomczyk, Ted; Morgan, Paul

    1987-03-01

    Downward continuation of temperature data from 73 wells extending to depths of 250 ft (76 m) provides constraints on the thermal regime of the Valles Caldera. Surface-temperature gradient data and bottom-hole temperatures were used as constraints in the downward continuation. Three factors were found to control the shallow thermal regime: (1) heat associated with the main geothermal source; (2) local topography; and (3) west-southwest groundwater flow. Although the well density is relatively high, comparison with the topography shows that the wells are not randomly distributed and tend to be clustered in valleys. Many details in the thermal regime appear to be related to groundwater drainage in these valleys. Temperature gradients and temperatures generally increase in the same direction as the regional drainage of the caldera suggesting a long-wavelength, shallow component to this regional gradient trend. Inversion of gradient and temperature data show additional deep heat input in the west-southwest sector of the caldera which appears to be spatially associated to the youngest volcanism. A previously reported northeast displacement of the main heat source from the surface anomaly has not been confirmed.

  10. The dynamics of post-collapse magmatism at rhyolitic calderas: Analogue experiments and geochemistry of Yellowstone lavas

    Science.gov (United States)

    Girard, Guillaume

    The dynamics of magma replenishment in silicic magma reservoirs are not well understood. This is an important issue, since replenishment may lead to the rapid accumulation of large volumes of crystal-poor magma, a condition potentially leading to cataclysmic caldera-forming eruptions. To shed light on this process, I have undertaken a combined experimental---geochemical approach designed to provide an integrated and synthetic view of magma replenishment processes. Scaled analogue experiments show that in silicic systems, buoyant injections rise through a magma reservoir without significant mixing with resident material, forming a layered reservoir. When a crystal mush is present at the base of the reservoir, its presence does not hinder buoyant injections to ascend. Indeed, such injections entrain crystals from the mush and transport them to the uppermost layers of the reservoir, resulting in the accumulation of a mix of replenishing magma and mush crystals. This process may have played a significant role in the generation of early post-collapse rhyolites of Yellowstone caldera, the Upper Basin Member rhyolites. In these lavas, I observe the coexistence of large, isolated, sieved plagioclase crystals with small, fresh, more calcic plagioclase crystals occurring as aggregates with pyroxenes and oxides. This unusual mineral assemblage suggests that a higher-temperature, more primitive silicic replenishing magma mixed with crystals from a mush shortly before eruption. In this scenario, the aggregates crystallized from the replenishing magma while the sieved crystals were extracted from the mush. Unlike the Upper Basin Member rhyolites, the younger voluminous Central Plateau Member rhyolites define a cogenetic series in which younger lavas exhibit more evolved mineralogy and trace element signatures, while crystal geochemistry suggests crystallization from progressively cooler melts. At the same time, the crystals also exhibit dissolution textures, suggesting a

  11. Fluid geochemistry and soil gas fluxes (CO2-CH4-H2S) at a promissory Hot Dry Rock Geothermal System: The Acoculco caldera, Mexico

    Science.gov (United States)

    Peiffer, L.; Bernard-Romero, R.; Mazot, A.; Taran, Y. A.; Guevara, M.; Santoyo, E.

    2014-09-01

    The Acoculco caldera has been recognized by the Mexican Federal Electricity Company (CFE) as a Hot Dry Rock Geothermal System (HDR) and could be a potential candidate for developing an Enhanced Geothermal System (EGS). Apart from hydrothermally altered rocks, geothermal manifestations within the Acoculco caldera are scarce. Close to ambient temperature bubbling springs and soil degassing are reported inside the caldera while a few springs discharge warm water on the periphery of the caldera. In this study, we infer the origin of fluids and we characterize for the first time the soil degassing dynamic. Chemical and isotopic (δ18O-δD) analyses of spring waters indicate a meteoric origin and the dissolution of CO2 and H2S gases, while gas chemical and isotopic compositions (N2/He, 3He/4He, 13C, 15N) reveal a magmatic contribution with both MORB- and arc-type signatures which could be explained by an extension regime created by local and regional fault systems. Gas geothermometry results are in agreement with temperature measured during well drilling (260 °C-300 °C). Absence of well-developed water reservoir at depth impedes re-equilibration of gases upon surface. A multi-gas flux survey including CO2, CH4 and H2S measurements was performed within the caldera. Using the graphical statistical analysis (GSA) approach, CO2 flux measurements were classified in two populations. Population A, representing 95% of measured fluxes is characterized by low values (mean: 18 g m- 2 day- 1) while the remaining 5% fluxes belonging to Population B are much higher (mean: 5543 g m- 2 day- 1). This low degassing rate probably reflects the low permeability of the system, a consequence of the intense hydrothermal alteration observed in the upper 800 m of volcanic rocks. An attempt to interpret the origin and transport mechanism of these fluxes is proposed by means of flux ratios as well as by numerical modeling. Measurements with CO2/CH4 and CO2/H2S flux ratios similar to mass ratios

  12. Task 3: Evaluation of mineral resource potential, caldera geology, and volcano-tectonic framework at and near Yucca Mountain

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Larson, L.T. [Univ. of Nevada, Reno, NV (United States)

    1994-12-31

    This report summarizes the work of Task 3 that was initially discussed in our monthly reports for the period October 1, 1993 through September 30, 1994, and is contained in our various papers and abstracts, both published and in press or currently in review. Our efforts during this period have involved the continuation of studies begun prior to October, 1993, focussed mainly on aspects of the caldera geology, magmatic activity, hydrothermal mineralization and extensional tectonics of the western and central parts of the southwestern Nevada volcanic field (SWNVF), studies of the subsurface rocks of Yucca Mountain utilizing drill-hole sampled obtained in 1991 and 1992, and studies of veins and siliceous ledges cropping out in northwestern Yucca Mountain. These veins and ledges provide evidence for near-surface hydrothermal activity in northwestern Yucca Mountain during the Crater Flat Tuff period of volcanism. During the period of this report we have concentrated our efforts on the production and publication of documents summarizing many of the data, interpretations and conclusions of Task 3 studies pertaining to hydrothermal activity and mineralization in the Yucca Mountain region and their relations to volcanism and tectonic activity. The resulting two manuscripts for journal publication and a compilation of radiometric age and trace-element geochemical data are appended to this report.

  13. Lower Pliensbachian caldera volcanism in high-obliquity rift systems in the western North Patagonian Massif, Argentina

    Science.gov (United States)

    Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.

    2014-12-01

    In the Cerro Carro Quebrado and Cerro Catri Cura area, located at the border between the Neuquén Basin and the North Patagonian Massif, the Garamilla Formation is composed of four volcanic stages: 1) andesitic lava-flows related to the beginning of the volcanic system; 2) basal massive lithic breccias that represent the caldera collapse; 3) voluminous, coarse-crystal rich massive lava-like ignimbrites related to multiple, steady eruptions that represent the principal infill of the system; and, finally 4) domes, dykes, lava flows, and lava domes of rhyolitic composition indicative of a post-collapse stage. The analysis of the regional and local structures, as well as, the architectures of the volcanic facies, indicates the existence of a highly oblique rift, with its principal extensional strain in an NNE-SSW direction (˜N10°). The analyzed rocks are mainly high-potassium dacites and rhyolites with trace and RE elements contents of an intraplate signature. The age of these rocks (189 ± 0.76 Ma) agree well with other volcanic sequences of the western North Patagonian Massif, as well as, the Neuquén Basin, indicating that Pliensbachian magmatism was widespread in both regions. The age is also coincident with phase 1 of volcanism of the eastern North Patagonia Massif (188-178 Ma) represented by ignimbrites, domes, and pyroclastic rocks of the Marifil Complex, related to intraplate magmatism.

  14. Spatiotemporal analysis of changes in lode mining claims around the McDermitt Caldera, northern Nevada and southern Oregon

    Science.gov (United States)

    Coyan, Joshua; Zientek, Michael L.; Mihalasky, Mark J.

    2017-01-01

    Resource managers and agencies involved with planning for future federal land needs are required to complete an assessment of and forecast for future land use every ten years. Predicting mining activities on federal lands is difficult as current regulations do not require disclosure of exploration results. In these cases, historic mining claims may serve as a useful proxy for determining where mining-related activities may occur. We assess the utility of using a space–time cube (STC) and associated analyses to evaluate and characterize mining claim activities around the McDermitt Caldera in northern Nevada and southern Oregon. The most significant advantage of arranging the mining claim data into a STC is the ability to visualize and compare the data, which allows scientists to better understand patterns and results. Additional analyses of the STC (i.e., Trend, Emerging Hot Spot, Hot Spot, and Cluster and Outlier Analyses) provide extra insights into the data and may aid in predicting future mining claim activities.

  15. Near real-time monitoring of volcanic surface deformation from GPS measurements at Long Valley Caldera, California

    Science.gov (United States)

    Ji, Kang Hyeun; Herring, Thomas A.; Llenos, Andrea L.

    2013-01-01

    Long Valley Caldera in eastern California is an active volcanic area and has shown continued unrest in the last three decades. We have monitored surface deformation from Global Positioning System (GPS) data by using a projection method that we call Targeted Projection Operator (TPO). TPO projects residual time series with secular rates and periodic terms removed onto a predefined spatial pattern. We used the 2009–2010 slow deflation as a target spatial pattern. The resulting TPO time series shows a detailed deformation history including the 2007–2009 inflation, the 2009–2010 deflation, and a recent inflation that started in late-2011 and is continuing at the present time (November 2012). The recent inflation event is about four times faster than the previous 2007–2009 event. A Mogi source of the recent event is located beneath the resurgent dome at about 6.6 km depth at a rate of 0.009 km3/yr volume change. TPO is simple and fast and can provide a near real-time continuous monitoring tool without directly looking at all the data from many GPS sites in this potentially eruptive volcanic system.

  16. Three-dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

    Science.gov (United States)

    Peacock, Jared R.; Mangan, Margaret T.; McPhee, Darcy K.; Wannamaker, Phil E.

    2016-01-01

    Though shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3-D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east-west elongated body 4 km below the west moat. The heat source could be a zone of 2–5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5–10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5–10% basaltic partial melt.

  17. Caldimicrobium rimae gen. nov., sp. nov., an extremely thermophilic, facultatively lithoautotrophic, anaerobic bacterium from the Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Miroshnichenko, Margarita L; Lebedinsky, Alexander V; Chernyh, N A; Tourova, Tatyana P; Kolganova, Tatyana V; Spring, Stefan; Bonch-Osmolovskaya, Elizaveta A

    2009-05-01

    An extremely thermophilic, strictly anaerobic, facultatively chemolithoautotrophic bacterium designated strain DS(T) was isolated from Treshchinnyi Spring, one of the hottest springs of the Uzon Caldera (Kamchatka, Russia). Cells of the novel organism were Gram-negative rods, about 1.0-1.2 microm long and 0.5 microm wide. The temperature range for growth was 52-82 degrees C, with an optimum at 75 degrees C. Growth was observed at pH 6.8-7.4, and the optimum pH was 7.0-7.2. Strain DS(T) was able to grow lithoautotrophically with hydrogen in the presence of CO(2) as a carbon source and thiosulfate or elemental sulfur as an electron acceptor. It also grew well with ethanol, fumarate, succinate or malate in the presence of thiosulfate. Yeast extract was not required for growth and did not stimulate growth. The genomic DNA G+C content was 35.2 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that the novel organism was a member of the family Thermodesulfobacteriaceae. On the basis of phylogenetic and physiological considerations, it is proposed that strain DS(T) represents a new genus and species, Caldimicrobium rimae gen. nov., sp. nov. The type strain of Caldimicrobium rimae is DS(T) (=DSM 19393(T) =VKM B-2460(T)).

  18. Aquifer Recharge Estimation through Atmospheric Chloride Mass Balance at Las Cañadas Caldera, Tenerife, Canary Islands, Spain

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    Rayco Marrero-Diaz

    2015-05-01

    Full Text Available The atmospheric chloride mass balance (CMB method was used to estimate net aquifer recharge in Las Cañadas Caldera, an endorheic summit aquifer area about 2000 m a.s.l. with negligible surface runoff, which hosts the largest freshwater reserve in Tenerife Island, Canary Islands, Spain. The wet hydrological year 2005–2006 was selected to compare yearly atmospheric chloride bulk deposition and average chloride content in recharge water just above the water table, both deduced from periodical sampling. The potential contribution of chloride to groundwater from endogenous HCl gas may invalidate the CMB method. The chloride-to-bromide molar ratio was an efficient tracer used to select recharge water samples having atmospheric origin of chloride. Yearly net aquifer recharge was 631 mm year−1, i.e., 69% of yearly precipitation. This result is in agreement with potential aquifer recharge estimated through an independent lumped-parameter rainfall-runoff model operated by the Insular Water Council of Tenerife. This paper illustrates basic procedures and routines to use the CMB method for aquifer recharge in active volcanic oceanic islands having sparse-data coverage and groundwater receiving contribution of endogenous halides.

  19. Continuous Hidden Markov Models: Application to automatic earthquake detection and classification at Las Canãdas caldera, Tenerife

    Science.gov (United States)

    Beyreuther, Moritz; Carniel, Roberto; Wassermann, Joachim

    2008-10-01

    A possible interaction of (volcano-) tectonic earthquakes with the continuous seismic noise recorded in the volcanic island of Tenerife was recently suggested. Also recently the zone close to Las Canadas caldera shows unusual high number of near (speech recognition where statistical models, called Hidden Markov Models (HMMs), are widely used for spotting words in continuous audio data. In this study HMMs are used to detect and classify volcano-tectonic and/or tectonic earthquakes in continuous seismic data. Further the HMM detection and classification is evaluated and discussed for a one month period of continuous seismic data at a single seismic station. Being a stochastic process, HMMs provide the possibility to add a confidence measure to each classification made, basically evaluating how "sure" the algorithm is when classifying a certain earthquake. Moreover, this provides helpful information for the seismological analyst when cataloguing earthquakes. Combined with the confidence measure the HMM detection and classification can provide precise enough earthquake statistics, both for further evidence on the interaction between seismic noise and (volcano-) tectonic earthquakes as well as for incorporation in an automatic early warning system.

  20. Usos del suelo y capacidad de carga territorial: el caso de la Caldera del Rey (Tenerife, Islas Canarias

    Directory of Open Access Journals (Sweden)

    José Iván Bolaños González

    2002-01-01

    Full Text Available Adeje, municipio suroccidental de la isla de Tenerife, ha experimentado un importante crecimiento turístico en las últimas décadas, concentrándose las urbanizaciones destinadas a dicha actividad en el ámbito costero colmatándolo progresivamente. Como consecuencia, la superficie ocupada por uno de los principales cultivos de exportación de Canarias, el plátano, se ha reducido notablemente, pues este uso del suelo compite con la expansión turística en detrimento del platanal. La Caldera del Rey se ha convertido en uno de los «refugios» de este cultivo, aunque se deberá conocer la capacidad de carga territorial de este ámbito con el fin de averiguar el grado de compatibilidad de la actividad agraria con la declaración de Monumento Natural. Así, se propone en este artículo un procedimiento para su cálculo, basado en la aptitud, la vulnerabilidad y la calidad ambiental, aunque será el análisis de la dinámica de usos del suelo el punto de partida del mismo.

  1. Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry

    Science.gov (United States)

    Stelten, Mark; Cooper, Kari M.; Vazquez, Jorge A.; Calvert, Andrew T.; Glessner, Justin G

    2015-01-01

    We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircon crystals from each rhyolite. We compare these zircon data to 238U- 230Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150 – 250 kyr) and genetically related to the preceding episode of magmatism, which occurred ca. 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e., are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e., are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238U-230Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all CPM sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to

  2. Magma chamber rejuvenation associated with Yellowstone 516-70 ka post-caldera rhyolitic lava flows : results from crystal geochemistry

    Science.gov (United States)

    Girard, G.; Stix, J.

    2007-12-01

    After Yellowstone caldera collapsed at 640 ka, it has been the focus of many voluminous rhyolite effusions. Over 900 km3 of magma have been erupted during relatively short periods, at 516 ka, 486-479 ka, 198 ka, and principally from 165 to 70 ka when the largest lava flows were emplaced. The last period itself consists of three episodes, from 165 to 147 ka, 117 to 102 ka, and 72 to 70 ka (Christiansen, 2001). The first-erupted lavas contain mainly plagioclase and sanidine. Quartz becomes increasingly abundant in younger flows, and clearly dominates over plagioclase in the 165 ka and younger rocks. Plagioclase is not present in the 117-102 ka and 72-70 ka lavas. Recent micro-analytical techniques have led to a better understanding of pre-eruptive conditions in magmatic systems by studying trace element concentrations and zoning in volcanic crystals. We analyzed plagioclase by electron microprobe and Ti in quartz by laser ablation-ICP-MS in order to assess changes in crystallization conditions from one period to the next, and also to reconstruct the pre-eruptive history of individual lava flows, by searching for potential dissolution, overgrowth or zoning features. Plagioclase in the lavas shifts progressively from a median value of An28 at 516 ka to An21 at ~ 160 ka. The plagioclase also contains decreasing amounts of K over time for a given level of Ca; for example, K2O at An22 declines from ~ 1.9 wt % in the oldest lavas to ~ 1.4 wt % in the 160 ka episode lavas, suggesting a reduced ability of plagioclase to incorporate K. This may translate into crystallization in a progressively cooler or shallower environment. Average Ti contents in quartz rims decrease from ~ 150- 200 ppm in the older lavas to ~ 100-125 ppm at ~ 160 ka and ~ 75-90 ppm at 70 ka. Zoned quartzes are found in most flows. They show higher Ti contents in the cores, with up to 240 ppm in the older lavas, 150 ppm at ~ 160 ka and 120 ppm at 70 ka. The temporal Ti decline in quartz rims and the normal

  3. Residence of silver in mineral deposits of the Thunder Mountain caldera complex, Central Idaho, U.S.A.

    Science.gov (United States)

    Leonard, B.F.; Christian, R.P.

    1987-01-01

    Silver is an accessory element in gold, antimony, and tungsten deposits of the caldera complex. Most of the deposits are economically of low grade and genetically of xenothermal or epithermal character. Their gold- and silver-bearing minerals are usually disseminated, fine grained, and difficult to study. Sparsely disseminated pyrite and arsenoprite are common associates. Identified silver minerals are: native silver and electrum; the sulfides acanthite, argentite (the latter always inverted to acanthite), and members of the Silberkies group; the sulfosalts matildite, miargyrite, pyrargyrite, argentian tetrahedrite, and unnamed Ag-Sb-S and Ag-Fe-Sb-S minerals; the telluride hessite and the selenide naumannite; halides of the cerargyrite group; and the antimonate stetefeldtite. Suspected silver minerals include the sulfide uytenbogaardtite and the sulfosalts andorite, diaphorite, and polybasite. Electrum, acanthite, and argentian tetrahedrite are common, though nowhere abundant. The other silver minerals are rare. Silver is present as a minor element in the structure of some varieties of other minerals. These include arsenopyrite, chalcopyrite, chalcostibite, covelline, digenite, galena, sphalerite, and stibnite. The search for adventitious Ag in most of these minerals has been cursory. The results merely indicate that elemental silver is not confined to discrete silver minerals and is, therefore, an additional complication for the recovery of silver-bearing material from some deposits. Silver occurs cryptically in some plants of the region. At Red Mountain, for example, the ashed sapwood of Douglas-fir (Pseudotsuga menziesii) contains 2 to 300 ppm Ag. Silver in the ashed wood is roughly 100 times as abundant as it is in soil. The phenomenon, useful in biogeochemical exploration, deserves the attention of mineralogists. ?? 1987 Springer-Verlag.

  4. Control of Volume and Porosity on Pumice Floatation Time: A Case Study with Pumice from the Havre Submarine Caldera Volcano

    Science.gov (United States)

    Hosseini, B.; Fauria, K.; Manga, M.; Carey, R.; Soule, S. A.

    2016-12-01

    During the 2015 MESH (Mapping, Exploration, and Sampling at Havre) expedition to the submarine Havre caldera volcano, we collected pumice from the 2012 eruption. Here, we report pumice volume, porosity, and floatation time from measurements on 32 clasts (0.2-16 g) that provide insight into the eruption dynamics and mechanisms that deposited these clasts on the seafloor. We measured pumice volume using photogrammetry, capturing 100-180 images per sample. We used a series of open-source software—VisualSFM and MeshLab—to process the images and construct volume models. Combined with measurements of mass, we can determine pumice porosity. We calculated a mean porosity of 0.86+/-0.03 for the 32 samples. The lowest measured porosity of 0.78 was from a fragment of a giant 1.5-m diameter pumice clast. In addition to quantifying pumice volume and porosity, we conducted floatation experiments in which we cleaned, dried, and set the 32 samples on water and measured the time required for each clast to sink. Pumice floatation times varied from 0.8-226 days. We found that pumice floatation time scales with both pumice volume and porosity. These trends are consistent with a gas trapping mechanism for cold pumice floatation and suggest that pumice porosity, in addition to pumice volume, exerts an important control on the floatation time and fate of floating pumice. Despite the wide range of floatation times for these clasts, the proximal to vent collection suggests that these pumice (with the possible exception of the giant pumice fragment) were deposited on the seafloor soon after the 2012 eruption and never reached the ocean surface.

  5. Multilocus sequence analysis of Thermoanaerobacter isolates reveals recombining, but differentiated, populations from geothermal springs of the Uzon Caldera, Kamchatka, Russia.

    Science.gov (United States)

    Wagner, Isaac D; Varghese, Litty B; Hemme, Christopher L; Wiegel, Juergen

    2013-01-01

    Thermal environments have island-like characteristics and provide a unique opportunity to study population structure and diversity patterns of microbial taxa inhabiting these sites. Strains having ≥98% 16S rRNA gene sequence similarity to the obligately anaerobic Firmicutes Thermoanaerobacter uzonensis were isolated from seven geothermal springs, separated by up to 1600 m, within the Uzon Caldera (Kamchatka, Russian Far East). The intraspecies variation and spatial patterns of diversity for this taxon were assessed by multilocus sequence analysis (MLSA) of 106 strains. Analysis of eight protein-coding loci (gyrB, lepA, leuS, pyrG, recA, recG, rplB, and rpoB) revealed that all loci were polymorphic and that nucleotide substitutions were mostly synonymous. There were 148 variable nucleotide sites across 8003 bp concatenates of the protein-coding loci. While pairwise F ST values indicated a small but significant level of genetic differentiation between most subpopulations, there was a negligible relationship between genetic divergence and spatial separation. Strains with the same allelic profile were only isolated from the same hot spring, occasionally from consecutive years, and single locus variant (SLV) sequence types were usually derived from the same spring. While recombination occurred, there was an "epidemic" population structure in which a particular T. uzonensis sequence type rose in frequency relative to the rest of the population. These results demonstrate spatial diversity patterns for an anaerobic bacterial species in a relative small geographic location and reinforce the view that terrestrial geothermal springs are excellent places to look for biogeographic diversity patterns regardless of the involved distances.

  6. A Photogrammetric Approach to Measuring Temporal Change in Tree Kill Areas at Mammoth Mountain and Long Valley Caldera, California

    Science.gov (United States)

    Clor, L. E.; Barefoot, J. D.; Hurwitz, S.; Diefenbach, A. K.

    2015-12-01

    A zone of dead trees and bare ground near Horseshoe Lake on the southeast flank of Mammoth Mountain in California is attributed to high emissions of volcanic CO2 and has been characterized and studied since the 1990s. Measurements of diffuse CO2 emissions have been made since 1994, but tree kills occurred following a large earthquake swarm in 1989 and before these first measurements. In order to track vegetation changes over time, fifteen aerial images of the Horseshoe Lake tree kill from 1951 to 2014 were analyzed using photogrammetric techniques which allow us to quantify the extent of bare ground and provide an indirect analysis of tree mortality, possibly related to CO2 emissions. The aerial images were assigned a uniform spatial reference, then image pixels were classified into two main categories, trees or bare ground, and the aerial extent quantified using the GIS software ArcMap. Between 1951 and 1987, there was little change in area of bare ground or tree density near Horseshoe Lake. The tree kill area appeared in 1992 and expanded rapidly to about 0.20 km2 by 1998, which is similar to its present extent. In images from 2012 and onward, a large increase in bare ground was identified and correlated with a powerful windstorm that occurred in 2011. Overlaying CO2 flux maps on the GIS classified images shows that the area of diffuse emission generally correlates with the tree kill area. This method was applied to imagery of thermal tree kill areas within Long Valley Caldera as well. Tree kill near Shady Rest Park in Mammoth Lakes expanded incrementally to the east, southeast and west between 1993 and 2014 to its present extent of about 0.053 km2, but this area also includes significant tree thinning by the city. In Basalt Canyon, southeast of Shady Rest, tree kill area has slowly expanded since 1995 to its present extent of about 0.041 km2.

  7. The link between volcanism and plutonism in epizonal magma systems; high-precision U–Pb zircon geochronology from the Organ Mountains caldera and batholith, New Mexico

    Science.gov (United States)

    Rioux, Matthew; Farmer, Lang; Bowring, Samuel; Wooton, Kathleen M.; Amato, Jeffrey M.; Coleman, Drew S.; Verplanck, Philip L.

    2016-01-01

    The Organ Mountains caldera and batholith expose the volcanic and epizonal plutonic record of an Eocene caldera complex. The caldera and batholith are well exposed, and extensive previous mapping and geochemical analyses have suggested a clear link between the volcanic and plutonic sections, making this an ideal location to study magmatic processes associated with caldera volcanism. Here we present high-precision thermal ionization mass spectrometry U–Pb zircon dates from throughout the caldera and batholith, and use these dates to test and improve existing petrogenetic models. The new dates indicate that Eocene volcanic and plutonic rocks in the Organ Mountains formed from ~44 to 34 Ma. The three largest caldera-related tuff units yielded weighted mean 206Pb/238U dates of 36.441 ± 0.020 Ma (Cueva Tuff), 36.259 ± 0.016 Ma (Achenback Park tuff), and 36.215 ± 0.016 Ma (Squaw Mountain tuff). An alkali feldspar granite, which is chemically similar to the erupted tuffs, yielded a synchronous weighted mean 206Pb/238U date of 36.259 ± 0.021 Ma. Weighted mean 206Pb/238U dates from the larger volume syenitic phase of the underlying Organ Needle pluton range from 36.130 ± 0.031 to 36.071 ± 0.012 Ma, and the youngest sample is 144 ± 20 to 188 ± 20 ka younger than the Squaw Mountain and Achenback Park tuffs, respectively. Younger plutonism in the batholith continued through at least 34.051 ± 0.029 Ma. We propose that the Achenback Park tuff, Squaw Mountain tuff, alkali feldspar granite and Organ Needle pluton formed from a single, long-lived magma chamber/mush zone. Early silicic magmas generated by partial melting of the lower crust rose to form an epizonal magma chamber. Underplating of the resulting mush zone led to partial melting and generation of a high-silica alkali feldspar granite cap, which erupted to form the tuffs. The deeper parts of the chamber underwent continued recharge and crystallization for 144 ± 20 ka after the

  8. Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification

    Science.gov (United States)

    Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

    2017-01-01

    Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The ~7,700 calendar year B.P. climactic eruption of Mount Mazama, USA vented ~50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Mazama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ±1 m lateral and ±4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow- parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of pit craters caused by phreatic explosions, fractures and cracks caused by extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented

  9. 40Ar/(39Ar) geochronology of rhyolites erupted following collapse of the Yellowstone caldera, Yellowstone Plateau volcanic field: implications for crustal contamination

    Science.gov (United States)

    Gansecki, C. A.; Mahood, G. A.; McWilliams, M. O.

    1996-07-01

    Single-crystal laser-probe 40Ar 39Ar dating of 133 grains of sanidine and plagioclase has enabled us to resolve the eruption ages of the Upper Basin Member rhyolites — the lava flows and related tuffs that erupted within the Yellowstone Caldera shortly after its collapse 630 ky ago on eruption of the Lava Creek Tuff. Two lavas and a tuff that erupted from the eastern ring-fracture zone yield an eruptive age of 481 ± 8 ka, whereas two flows from the western ring-fracture zone yield eruptive ages of 516 ± 7 and 198 ± 8 ka. Most of the units contain old xenocrysts, explaining why previous attempts at dating these earliest post-caldera units by the conventional K sbnd Ar method yielded poorly resolved and, in some cases, anomalous ages. The tuff shows the most severe contamination. Grains from a single pumice lapilli in the tuff show as large an age range as those from bulk vitrophyre, indicating that the xenocrysts were incorporated in the magma prior to its near-surface explosive fragmentation. Diffusion calculations indicate that the xenocrysts could not have remained in the magma for more than a few years without degassing and giving ages indistinguishable from the phenocrysts. Thus, the contamination represented by the xenocrysts probably occurred during fracturing and conduit propagation, rather than during caldera collapse, which took place more than 100 ky earlier. The apparent ages of xenocrysts and their compositions as determined by electron microprobe suggest that the Eocene Absaroka volcanics are the main contaminant, with a single xenocryst probably coming from Precambrian basement rocks. Most of the xenocrysts are difficult to distinguish optically or chemically from feldspar phenocrysts, illustrating the necessity of single-crystal to date many young volcanic rocks accurately.

  10. Genesis of the post-caldera eastern Upper Basin Member rhyolites, Yellowstone, WY: from volcanic stratigraphy, geochemistry, and radiogenic isotope modeling

    Science.gov (United States)

    Pritchard, Chad J.; Larson, Peter B.

    2012-08-01

    An array of samples from the eastern Upper Basin Member of the Plateau Rhyolite (EUBM) in the Yellowstone Plateau, Wyoming, were collected and analyzed to evaluate styles of deposition, geochemical variation, and plausible sources for low δ18O rhyolites. Similar depositional styles and geochemistry suggest that the Tuff of Sulphur Creek and Tuff of Uncle Tom's Trail were both deposited from pyroclastic density currents and are most likely part of the same unit. The middle unit of the EUBM, the Canyon flow, may be composed of multiple flows based on a wide range of Pb isotopic ratios (e.g., 206Pb/204Pb ranges from 17.54 to 17.86). The youngest EUBM, the Dunraven Road flow, appears to be a ring fracture dome and contains isotopic ratios and sparse phenocrysts that are similar to extra-caldera rhyolites of the younger Roaring Mountain Member. Petrologic textures, more radiogenic 87Sr/86Sr in plagioclase phenocrysts (0.7134-0.7185) than groundmass and whole-rock ratios (0.7099-0.7161), and δ18O depletions on the order of 5‰ found in the Tuff of Sulphur Creek and Canyon flow indicate at least a two-stage petrogenesis involving an initial source rock formed by assimilation and fractional crystallization processes, which cooled and was hydrothermally altered. The source rock was then lowered to melting depth by caldera collapse and remelted and erupted. The presence of a low δ18O extra-caldera rhyolite indicates that country rock may have been hydrothermally altered at depth and then assimilated to form the Dunraven Road flow.

  11. 40Ar/39Ar and U-Pb Ages and Isotopic Data for Oligocene Ignimbrites, Calderas, and Granitic Plutons, Southern Stillwater Range and Clan Alpine Mountains: Insights into the Volcanic-Plutonic Connection and Crustal Evolution in Western Nevada

    Science.gov (United States)

    John, D. A.; Watts, K. E.; Henry, C.; Colgan, J. P.; Cousens, B.

    2014-12-01

    Calderas in the southern Stillwater Range (SSR) and Clan Alpine Mountains (CAM) were formed during the mid-Tertiary ignimbrite flareup and subsequently tilted (40->90°) by large-magnitude extension. New geologic mapping, geochemistry, and 40Ar/39Ar and SHRIMP U-Pb zircon dating document 2 periods of magmatism resulting in 4 nested calderas and related granitoid plutons in sections up to 10 km thick. The first period included pre-caldera rhyolite lava domes (30(?) Ma), ~5 km of pre- and post-collapse intermediate lavas and rhyolite tuff that filled the Job Canyon caldera (~29.4 to 28.8 Ma), and the >4-5 km thick, geochemically similar IXL pluton (28.9±0.4 Ma) that intruded the Job Canyon caldera. The second period included pre-caldera rhyolite lava domes and dikes (~25.5 Ma) and 3 ignimbrite units in 3 calderas: tuff of the Louderback Mountains (low-silica rhyolite; ≥600 m thick; ~25.2 Ma); tuff of Poco Canyon (high-silica rhyolite; up to 4.3 km thick; 25.27±0.05 Ma); and ≥2000 km3 tuff of Elevenmile Canyon (trachydacite to rhyolite; up to 4.5 km thick; 25.12±0.01 Ma). The composite Freeman Creek pluton (granite, 24.8±0.4 Ma; granodiorite, 25.0±0.2 Ma) and Chalk Mountain rhyolite porphyry (25.2±0.2 Ma) and granite (24.8±0.3 Ma) plutons intruded the Poco Canyon and Elevenmile Canyon calderas. Early (30 Ma) rhyolites have the least radiogenic compositions (Sri~0.7040), whereas other units are relatively homogeneous (Sri~0.7050, ENd~0.0). Oxygen isotope compositions for SSR and CAM calderas are highly variable (d18Oquartz=5.6-8.2‰, d18Osanidine=5.5-7.0‰, d18Ozircon= 4.1-6.3‰), corresponding to a magmatic range of 5.7-7.9‰. U-Pb dating of zircons indicates homogeneous age populations and few/no xenocrysts and antecrysts. These data show that (1) thick plutons (>2-5 km) underlie compositionally and temporally related caldera-filling ignimbrites, (2) caldera-forming cycles are isotopically variable, requiring divergent magmatic sources in relatively

  12. Rendimiento térmico de calderas bagaceras modernas en Tucumán, R. Argentina Thermal efficiency of modern bagasse boilers in Tucumán, Argentina

    Directory of Open Access Journals (Sweden)

    Federico J. Franck Colombres

    2011-12-01

    Full Text Available Se evaluaron tres calderas de vapor modernas instaladas en ingenios azucareros de Tucumán, R. Argentina, equipos que se encuadran dentro de las tecnologías de producción más limpia. Tomando como base la metodología de cálculo de la eficiencia térmica de generadores de vapor desarrollada en 2008 por la Sección Ingeniería y Proyectos Agroindustriales de la Estación Experimental Agroindustrial Obispo Colombres, y a partir de los datos recolectados por medio de mediciones y balances de materia y energía, se determinaron sus principales variables características de operación. Las eficiencias energéticas determinadas para cada una fueron del 73,5%; 75,2% y 77,3%. Se realizó además una comparación con las calderas de vapor convencionales y se determinó el ahorro de bagazo que puede obtenerse con las calderas modernas, el cual resultó ser de un 27,6%. Como una ventaja adicional, se hace mención a la posibilidad de mejora del rendimiento térmico del ciclo motriz de la planta, que viene acompañada con el aumento de la presión de trabajo de la caldera.Three modern steam boilers, installed in sugar mills in Tucumán, R. Argentina, to attain a cleaner production, were evaluated. Their major operating variables were determined using the methodology for calculating thermal efficiency of steam generators developed by Sección Ingeniería y Proyectos Agroindustriales of Estación Experimental Agroindustrial Obispo Colombres in 2008, and data obtained from measurements and material and energy balances. Energy efficiency values determined for each boiler were 73.5%, 75.2% and 77.3%, respectively. A comparison with conventional steam boilers was drawn and it was found that bagasse savings amounted to about 27.6% when modern boilers were used. The possibility of improving the thermal efficiency of the plant cycle by increasing boiler pressure is mentioned as an additional advantage.

  13. Shallow sub-surface structure of the central volcanic complex of Tenerife, Canary Islands: implications for the evolution and the recent reactivation of the Las Canadas caldera

    Energy Technology Data Exchange (ETDEWEB)

    Gottsmann, J [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ (United Kingdom); Camacho, A G; Fernandez, J [Instituto de Astronomia y Geodesia (CSIC-UCM), Ciudad Universitaria, Pza. de Ciencias, 3, 28040 Madrid (Spain); MartI, J [Institute of Earth Sciences ' Jaume Almera' , CSIC, Lluis Sole SabarIs s/n, Barcelona 08028 (Spain); Wooller, L; Rymer, H [Department of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); GarcIa, A [Department of Volcanology, Museo Nacional de Ciencias Naturales, CSIC, C/ Jose Gutierrez Abascal, 2, 28006 Madrid (Spain)], E-mail: j.gottsmann@bristol.ac.uk

    2008-10-01

    We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain. The high-density core of the CVC and the pronounced gravity low centred in the Las Canadas caldera (LCC) in greater detail than previously available. Mathematical construction of a subsurface model from the local anomaly data, employing a 3-D inversion enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture of the complex, and shedding light on its evolution.

  14. Incorporating surface indicators of reservoir permeability into reservoir volume calculations: Application to the Colli Albani caldera and the Central Italy Geothermal Province

    Science.gov (United States)

    Giordano, Guido; De Benedetti, Arnaldo Angelo; Bonamico, Andrea; Ramazzotti, Paolo; Mattei, Massimo

    2014-01-01

    The Quaternary Roman Volcanic Province extends for over 200 km along the Tyrrhenian margin of the Italian peninsula and is composed of several caldera complexes with significant associated geothermal potential. In spite of the massive programs of explorations conducted by the then state-owned ENEL and AGIP companies between the 1970s and 1990s, and the identification of several high enthalpy fields, this resource remains so far unexploited, although it occurs right below the densely populated metropolitan area of Roma capital city. The main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks, the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain. As a consequence, almost half of the many exploration deep bore-holes drilled in the area reached a dry target. This work reviews available data and re-assesses the geothermal potential of caldera-related systems in Central Italy, by analysing in detail the case of the Colli Albani caldera system, the closest to Roma capital city. A GIS based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential. The approach is based on a three dimensional matrix of georeferenced spatial data; the A axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data; the B axis accounts for the thermal modelling of the crust (i.e. T with depth) based on measured thermal gradients. Both A and B data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs. We discuss the implementation of a C axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation. We consider datasets on: i

  15. Application of HydroGeoSphere to model the response to anthropogenic climate change of three-dimensional hydrological processes in the geologically, geothermally, and topographically complex Valles Caldera super volcano, New Mexico: Preliminary results

    Science.gov (United States)

    Wine, M.; Cadol, D. D.

    2014-12-01

    Anthropogenic climate change is expected to reduce streamflow in the southwestern USA due to reduction in precipitation and increases in evaporative demand. Understanding the effects of climate change in this region is particularly important for mountainous areas since these are primary sources of recharge in arid and semi-arid environments. Therefore we undertook to model effects of climate change on the hydrological processes in Valles Caldera (448 km2), located in the Jemez Mountains of northern New Mexico. In Valles Caldera modeling the surficial, hydrogeological, and geothermal processes that influence hydrologic fluxes each present challenges. The surficial dynamics of evaporative demand and snowmelt both serve to control recharge dynamics, but are complicated by the complex topography and spatiotemporal vegetation dynamics. Complex factors affecting evaporative demand include leaf area index, temperature, albedo, and radiation affected by topographic shading; all of these factors vary in space and time. Snowmelt processes interact with evaporative demand and geology to serve as an important control on streamflow generation, but modeling the effects of spatiotemporal snow distributions on streamflow generation remains a challenge. The complexity of Valles Caldera's geology—and its associated hydraulic properties—rivals that of its surficial hydrologic forcings. Hydrologically important geologic features that have formed in the Valles Caldera are three-dimensionally intricate and include a dense system of faults, alluvium, landslides, lake deposits, and features associated with the eruption and collapse of this super volcano. Coupling geothermally-driven convection to the hydrologic cycle in this still-active geothermal system presents yet an additional challenge in modeling Valles Caldera. Preliminary results from applying the three-dimensional distributed hydrologic finite element model HydroGeoSphere to a sub-catchment of Valles Caldera will be

  16. U-Pb isochron age and Pb isotope systematics of the Golden Fleece vein - implications for the relationship of mineralization to the Lake City caldera, western San Juan Mountains, Colorado.

    Science.gov (United States)

    Hon, K.; Ludwig, K. R.; Simmons, K.R.; Slack, J.F.; Grauch, R.I.

    1985-01-01

    A U/Pb isochron age of 27.5 + or - 0.5 m.y. is determined for the Golden Fleece vein, an age which is identical with the age of the quartz latite lavas that the vein cuts. Within the Lake City area, only the Golden Fleece vein contains pitchblende and Au-Ag tellurides and has Pb isotope ratios that together define it as unique within the area. The 27.5 m.y. age relates this vein to the waning stages of the Uncompahgre caldera (27-29) rather than to the Lake City caldera (23.1 m.y.). -G.J.N.

  17. [Dominant phylotypes in the 16S rRNA gene clone libraries from bacterial mats of the Uzon caldera (Kamchatka, Russia) hydrothermal springs].

    Science.gov (United States)

    Akimov, V N; Podosokorskaia, O A; Shliapnikov, M G; Gal'chenko, V F

    2013-01-01

    In situ analysis of the 16S rRNA genes form bacterial mats of five hydrothermal springs (36-58 degrees C) in the Uzon caldera (Kamchatka, Russia) was carried out using clone libraries. Eight clone libraries contained 18 dominant phylotypes (over 4-5%). In most clone libraries, the phylotype of the green sulfur bacterium Chlorobaculum sp. was among the dominant ones. The phylotypes of the green nonsulfur bacteria Chloroflexus and Roseiflexus and of purple nonsulfur bacteria Rhodoblastus, Rhodopseudomonas, and Rhodoferax were also among the dominant ones. Cyanobacteria were represented by one dominant phylotype in a single spring. Among nonphototrophic bacteria, the dominant phylotypes belonged to Sulfyrihydrogenibium sp., Geothrixsp., Acidobacterium sp., Meiothermus sp., Thiomonas sp., Thiofaba sp., and Spirochaeta sp. Three phylotypes were not identified at the genus level. Most genera of phototrophic and nonphototrophic organisms corresponding to the phylotypes from Uzon hydrotherms have been previously revealed in the hydrotherms of volcanically active regions of America, Asia, and Europe. These results indicate predominance of bacterial mats carrying out anaerobic photosynthesis in the hydrotherms of the Uzon caldera.

  18. Geomicrobiological exploration and characterization of a novel deep-sea hydrothermal system at the TOTO caldera in the Mariana Volcanic Arc.

    Science.gov (United States)

    Nakagawa, Tatsunori; Takai, Ken; Suzuki, Yohey; Hirayama, Hisako; Konno, Uta; Tsunogai, Urumu; Horikoshi, Koki

    2006-01-01

    Novel hydrothermal activities accompanying effluent white smokers and elemental sulfur chimney structures at the north-east lava dome of the TOTO caldera depression in the Mariana Volcanic Arc have been explored and characterized by geochemical and microbiological surveys. White smoker hydrothermal fluids were observed in the potential hydrothermal activity centre of the field and represented the maximal temperature of 170 degrees C and the lowest pH of 1.6. The chimney structures, all consisting of elemental sulfur (sulfur chimney), were also unique to the TOTO caldera hydrothermal field. Microbial community structures in a sulfur chimney and its formation hydrothermal fluid with a high concentration of hydrogen sulfide (15 mM) have been investigated by culture-dependent and -independent analyses. 16S rRNA gene clone analysis and fluorescence in situ hybridization (FISH) analysis revealed that epsilon-Proteobacteria dominated the microbial communities in the sulfur chimney structure and formed a dense microbial mat covering the sulfur chimney surface. Archaeal phylotypes were consistently minor components in the communities and related to the genera Thermococcus, Pyrodictium, Aeropyrum, and the uncultivated archaeal group of 'deep-sea hydrothermal vent euryarchaeotal group'. Cultivation analysis suggested that the chemolithoautotrophs might play a significant ecological role as primary producers utilizing gas and sulfur compounds provided from hydrothermal fluids.

  19. Late Quaternary eruption of the Ranau Caldera and new geological slip rates of the Sumatran Fault Zone in Southern Sumatra, Indonesia

    Science.gov (United States)

    Natawidjaja, Danny Hilman; Bradley, Kyle; Daryono, Mudrik R.; Aribowo, Sonny; Herrin, Jason

    2017-12-01

    Over the last decade, studies of natural hazards in Sumatra have focused primarily on great earthquakes and associated tsunamis produced by rupture of the Sunda megathrust. However, the Sumatran Fault and the active volcanic arc present proximal hazards to populations on mainland Sumatra. At present, there is little reliable information on the maximum magnitudes and recurrence intervals of Sumatran Fault earthquakes, or the frequency of paroxysmal caldera-forming (VEI 7-8) eruptions. Here, we present new radiocarbon dates of paleosols buried under the voluminous Ranau Tuff that constrain the large caldera-forming eruption to around 33,830-33,450 calender year BP (95% probability). We use the lateral displacement of river channels incised into the Ranau Tuff to constrain the long-term slip rate of two segments of the Sumatran Fault. South of Ranau Lake, the Kumering segment preserves isochronous right-lateral channel offsets of approximately 350 ± 50 m, yielding a minimum slip rate of 10.4 ± 1.5 mm/year for the primary active fault trace. South of Suoh pull-apart depression, the West Semangko segment offsets the Semangko River by 230 ± 60 m, yielding an inferred slip rate of 6.8 ± 1.8 mm/year. Compared with previous studies, these results indicate more recent high-volume volcanism in South Sumatra and increased seismic potency of the southernmost segments of the Sumatran Fault Zone.

  20. Variability of the planktonic foraminifera community across the Eocene/Oligocene boundary, Fuente Caldera Section, Baetic Ranges (Spain)

    Science.gov (United States)

    Legarda-Lisarri, A.

    2013-12-01

    During the Eocene/Oligocene transition, in a massive extinction event that took place about 33.7 million years ago, the current high resolution study analyzes qualitatively and quantitatively the community structure of the planktonic foraminifera that were preserved in the hemipelagic sediments of the Tethys Sea. The sampled section of the Fuente Caldera column, located in the Baetic mountain ranges, spans a register of 396,551.7 years. Based in the identification of 27 species, that belong to 13 genera and 2 families of foraminifera, there have been found three biozones of Gonzalvo Zonation (Gonzalvo, 2002) in the studied stratigraphic interval: Turborotalia cocoaensis and Cribrohantkenina lazzarii Biozones (Rupelian), and Paragloborotalia increbescens (Priabonian). The planktonic foraminifera associations variability patterns are defined by paleoecologic indexes (diversity index, high and low latitude species index and planktonic and benthic foraminifera index), by geochemical proxies: δ18O and δ13C and by 'Q' Mode Factor Analysis. They prove that the deposition environment is outer platform and also, they suggest that the studied area in the Tethys Sea underwent many thermal pulses, during which some species extinct or appear. In the first extinction event the species Turborotalia cocoaensis and Turborotalia cunialensis became extinct. In the second one, Hantkenina alabamensis, Hantkenina brevispina, Cribrohantkenina lazzarii and Pseudohastigerina micra became extinct while a succession occured; Globigerina officinalis, Globoturborotalita anguliofficinalis and Tenuitellinata angustiumbilicata appeared. The cooling event that finished in the Lower Oligocene was the biggest of these pulses, which was extremely abrupt and corresponds to the Oi-1 event that was described by Miller (Miller, 1991). All this evidences that the planktonic foraminifera extinction in the Upper Eocene was a gradual and fast event, what is supported by the Factor Analysis application. Key

  1. Magma Chamber Model of Batur Caldera, Bali, Indonesia: Compositional Variation of Two Facies, Large-Volume Dacitic Ignimbrites

    Directory of Open Access Journals (Sweden)

    Igan S. Sutawidjaja

    2015-05-01

    Full Text Available DOI:10.17014/ijog.2.2.111-124Batur is one of the finest known calderas on Earth, and is the source of at least two major ignimbrite eruptions with a combined volume of some 84 km3 and 19 km3. These ignimbrites have a similar compositions, raising the question of whether they are geneticaly related. The Batur Ignimbrite-1 (BI-1 is crystal poor, containing rhyodacitic (68 - 70wt % SiO2, white to grey pumices and partly welded and unwelded. The overlying Batur Ignimbrite-2 (BI-2 is a homogeneous grey to black dacitic pumices (64 - 66 wt % SiO2, unwelded and densely welded (40 - 60% vesicularity, crystal and lithic rich. Phase equilibria indicate that the Batur magma equilibrated at temperatures of 1100 - 1300oC with melt water contents of 3 - 6 wt%. The post-eruptive Batur magma was cooler (<1100oC and it is melt more water rich (> 6 wt % H2O. A pressure of 20 kbar is infered from mineral barometry for the Batur magma chamber. Magmatic chamber model is one in which crystals and melt separate from a convecting Batur magma by density differences, resulting in a stratified magma chamber with a homogeneous central zone, a crystal-rich accumulation zone near the walls or base, and a buoyant, melt-rich zone near the top. This is consistent with the estimated magma temperatures and densities: the pre-eruptive BI-1 magma was hoter (1300oC and more volatile rich (6 wt % H2O with density 2.25 g/cm3 than the BI-2 magma (1200oC; 4 wt % H2O in density was higher (2.50 g/cm3. Batur melt characteristics and intensive parameters are consistent with a volatile oversaturation-driven eruption. However, the higher H2O content, high viscosity and low crystal content of the BI-1 magma imply an external eruption trigger.

  2. Petrologic Insights into the Triggering Mechanism for the Lava Creek Tuff Super-Eruption, Yellowstone Caldera, WY

    Science.gov (United States)

    Shamloo, H. I.; Till, C. B.

    2016-12-01

    Yellowstone's most recent caldera-forming eruption occurred 631,000 years ago and was responsible for producing the >1000 km3 Lava Creek Tuff (LCT), which was deposited over most of contiguous United States. The LCT contains zoned sanidine (55 vol. %) and quartz (35%) phenocrysts, along with minor plagioclase and clinopyroxene (8%), magnetite and ilmenite (2%). This study takes two approaches to interrogate the mechanisms leading to eruption recorded in the LCT: 1) the application of feldspar thermometry to chemically zoned sanidine from LCT Member B ash analyzed via electron probe, and 2) modeling the phase equilibria for the LCT using rhyolite-MELTS. Sanidine-liquid thermometry yields average temperatures of 820-840°C (±22°C) for the sanidine rims, and suggests a slight heating trend from core to rim. The major element composition of the outermost sanidine rims reveals two distinct drops in orthoclase content that coincide with sharp increases in barium content. When compared to the feldspar compositions predicted by MELTS, these sharp changes in composition each require temperature increases of ≥25°C and are interpreted to reflect two magmatic rejuvenation events shortly before eruption. MELTS models best align with the feldspar thermometry at relatively low water contents (e.g., 1-2 wt.% H2O) and suggest the LCT may be drier than previously thought (Gansecki et al., Geology, 1998). The crystallization sequence predicted by MELTS for the LCT at 3 kbar includes quartz as the liquidus phase at 1000°C, precipitation of the first feldspar at 950°C, followed by precipitation of two feldspar phases (sanidine and albite) below the feldspar solvus at 850°C, with the ternary minimum and water exsolution occurring at 740°C. Despite the uncertainty in the absolute temperatures of the phase boundaries predicted by MELTS, the phase proportions and feldspar compositions in the LCT suggest that the last feldspar crystallization prior to eruption occurred well above

  3. The Dynamics of the Post-Caldera Magmatic System at Yellowstone: Insights from Age, Trace Element, and Isotopic Data of Zircon and Sanidine

    Science.gov (United States)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Calvert, A. T.; Glessner, J. J.; Wimpenny, J.; Yin, Q. Z.

    2014-12-01

    Yellowstone hosts a voluminous magmatic system that produced three silicic caldera-forming eruptions over the past 2.1 My. Following the most recent of these (the Lava Creek Tuff at 639 ka), the magma system at Yellowstone underwent two episodes of intracaldera eruptions, the latest of which produced the Central Plateau Member (CPM) rhyolites. The CPM rhyolites erupted intermittently from ca. 170 ka to ca. 70 ka and can be viewed as snapshots of the magma system through time, which provides a unique opportunity to study the dynamics of an evolving caldera system. To constrain the nature and timescales of magmatic processes at Yellowstone we examine four CPM rhyolites that erupted from ca. 116 ka to ca. 74 ka and present a comprehensive data set that integrates (1) 238U-230Th ages, trace-elements, and Hf isotope compositions of the surfaces and interiors of single zircons, (2) bulk 238U-230Th ages and in situ Ba and Pb isotope compositions of sanidines, (3) sanidine 40Ar-39Ar ages, and (4) trace-element and isotopic compositions of the CPM glasses. Zircon 238U-230Th ages and Hf isotope data demonstrate that isotopically juvenile magmas, derived from Yellowstone basalts, were added to the Yellowstone magma reservoir over time and were fundamental to its post-caldera isotopic evolution. We use zircon Hf isotope data along with new Hf isotope data (and existing O isotope data) for the Yellowstone basalts (whole-rocks), older Yellowstone rhyolites (glasses), and local crustal sources to quantify the role of isotopically juvenile magma in the evolution of the magmatic system. Additionally, linking age, trace-element, and isotopic data from zircon and sanidine demonstrates that eruptible CPM rhyolites were generated by extracting melt and antecrystic zircon from a long-lived (>200 ky) crystal mush, while sanidine remained trapped in the crystal network. The extracted melts amalgamated and then crystallized new sanidines and rims on the antecrystic zircons that were in

  4. Preliminary report, between seismic swarms, the constant cycles of inflation/ deflation in some volcanic calderas in the world and the minimum and/or solar maximum years

    Science.gov (United States)

    Casati, Michele

    2014-05-01

    The global communication network and GPS satellites have enabled us to monitor for more than a decade, some of the more sensitive, well-known and highly urbanized volcanic areas around the world. The possibility of electromagnetic coupling between the dynamics of the Earth-Sun and major geophysical events is a topic of research. However the majority of researchers are orienting their research in one direction. They are attempting to demonstrate a significant EM coupling between the solar dynamics and terrestrial seismicity ignoring a possible relationship between solar dynamics and the dynamics inherent in volcanic calderas. The scientific references are scarce, however, a study conducted by the Vesuvius Observatory of Naples, notes that the seismic activity on the volcano is closely related to changes in solar activity and the Earth's magnetic field. We decided to extend the study to many other volcanic calderas in the world in order to generalise the relationship between solar activity and caldera activity and/or deformation of the ground. The list of Northern Hemisphere volcanoes examined is as follows: Long Valley, Yellowstone, Three sisters, Kilauea Hawaii, Axial seamount (United States); Augustine ( Alaska), Sakurajima (Japan); Hammarinn, Krisuvik; Askja (Iceland) and Campi Flegrei (Italy). We note that the deformation of volcanoes recorded in GPS logs varies in long, slow geodynamic processes related to the two well-known time periods within the eleven-year cycle of solar magnetic activity: the solar minimum and maximum. We find that the years of minimum (maximum), are coincident with the years in which transition between a phase of deflation (inflation) occurs. Additionally, the seismicity recorded in such areas reaches its peak in the years of solar minimum or maximum. However, the total number and magnitude of seismic events is greater during deep solar minima, than maxima, evidenced by increased seismic activity occurring between 2006 and 2010. This

  5. Millennial-Scale Climate Variability During a mid-Pleistocene Glacial (MIS 12) from a Terrestrial Lacustrine Record in the Valles Caldera, New Mexico

    Science.gov (United States)

    Fawcett, P. J.; Brown, E. T.; Werne, J. P.; Contreras, S.; Anderson, R. S.; Dodd, J. P.; Sharp, Z. D.; Heikoop, J. M.; Allen, C. D.

    2011-12-01

    We present a high-resolution terrestrial climate record from the Valles Caldera, New Mexico which spans some 200,000 years from mid MIS 14 to early MIS 10. The glacial periods represented in the record exhibit millennial-scale Dansgaard-Oeschger like variability, especially in MIS 12, one of the coldest glacials in the Pleistocene. High resolution proxies from core VC-3 including scanning XRF data, sediment density, color, and magnetic susceptibility show approximately 23 millennial-scale oscillations in MIS 12 with an average duration of 2,300 years. Many of these oscillations are characterized by relatively slow coolings followed by abrupt warmings, similar to D-O events in the Greenland ice core record. MBT/CBT MAT estimates in the MIS 12 portion of the core show stadial to interstadial warmings of up to 6 °C. The VC-3 stadials correlate with high percentages of boreal taxa pollen ( Picea, Abies ) (up to 25%) while interstadials have lower boreal pollen percentages (~5%) and many correlate with local maxima in Juniperus> and Quercus> . Significant changes in the hydrologic cycle also occur at these millennial timescales. Oxygen isotope data from diatom silica record changes of up to 10 per mil from stadial to interstadial, probably reflecting a combination of changes in moisture source (Pacific vs. Gulf of Mexico), moisture transport pathway, and the seasonality of precipitation. Several interstadials correlate with increases in Cyperaceae (sedge) pollen suggesting a shallower lake with a broad marshy zone around its margin. This zone was minimized during stadials when the lake was deeper. Interstadial shallowing probably resulted from higher evaporation rates and/or a reduction in winter precipitation. This combination of proxies from the Valles Caldera suggests that glacial stage millennial-scale climate variability in the American southwest was strongly driven by changes in the strength and location of the winter polar jet, which in turn affected the local

  6. Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Wright, Heather M.; Bacon, Charles R.; Vazquez, Jorge A.; Sisson, Thomas W.

    2012-01-01

    The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic–rhyodacitic eruptive deposits (71–7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe–Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918–968 to ~950 to 845–895 °C). Oxygen fugacity began at nickel–nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite–rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3–4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and

  7. Deformation near the Casa Diablo geothermal well field and related processes Long Valley caldera, Eastern California, 1993-2000

    Science.gov (United States)

    Howle, J.F.; Langbein, J.O.; Farrar, C.D.; Wilkinson, S.K.

    2003-01-01

    Regional first-order leveling lines, which extend from Lee Vining, CA, to Tom's Place, CA, have been surveyed periodically since 1957 by the U.S. Geological Survey (USGS), the National Geodetic Survey (NGS), and Caltrans. Two of the regional survey lines, or leveling networks, intersect at the Casa Diablo geothermal well field. These leveling networks, referenced to a distant bench mark (C916) near Lee Vining, provide time-series vertical control data of land-surface deformation that began around 1980. These data are also useful for delineating localized subsidence at Casa Diablo related to reservoir pressure and temperature changes owing to geothermal development that began in 1985. A comparison of differences in bench-mark elevations for five time periods between 1983 and 1997 shows the development and expansion of a subsidence bowl at Casa Diablo. The subsidence coincides spatially with the geothermal well field and temporally with the increased production rates and the deepening of injection wells in 1991, which resulted in an increase in the rate of pressure decline. The subsidence, superimposed on a broad area of uplift, totaled about 310 mm by 1997. The USGS established orthogonal tilt arrays in 1983 to better monitor deformation across the caldera. One tilt array (DBR) was established near what would later become the Casa Diablo geothermal well field. This array responded to magmatic intrusions prior to geothermal development, tilting away from the well field. With the start of geothermal fluid extraction in 1985, tilt at the DBR array reversed direction and began tilting into the well field. In 1991, geothermal power production was increased by a factor of four, and reservoir pressures began a period of steep decline. These changes caused a temporary three-fold increase in the tilt rate. The tilt rate became stable in 1993 and was about 40% lower than that measured in 1991-1992, but still greater than the rates measured during 1985-1990. Data from the

  8. Geophysical imaging of the lacustrine sediments deposited in the La Calderilla Volcanic Caldera (Gran Canaria Island, Spain) for paleoclimate research

    Science.gov (United States)

    Himi, Mahjoub; Rodríguez-González, Alejandro; Criado, Constantino; Tapias, Josefina C.; Ravazzi, Cesare; Pérez-Torrado, Francisco; Casas, Albert

    2016-04-01

    The discovery of well-preserved maar structures is important not only for studying the eruptive activity and formation of volcanoes, but also for paleoclimate research, since laminated maar lake sediments may contain very detailed archives of climate and environmental history. Maars are a singular type of volcanic structure generated by explosive phreatomagmatic eruptions as a result of interaction between rising magma and groundwater. This kind of structures are characterised by circular craters, often filled with water and/or lacustrine sediments and surrounded by a ring of pyroclastic deposits.Recently a borehole was drilled at the bottom of La Calderilla volcanic complex which penetrated about 8.7 m in its sedimentary sequence and paleobotanical study has supplied the first evidence of paleoenvironmental evolution during the Holocene on the Gran Canaria Island. This survey, however, did not penetrate into the substrate because the total thickness of the sedimentary fill was unknown. Since the age of formation of La Calderilla volcanic complex based on K/Ar dating is about 85,000 years (Upper Pleistocene), the possibility of its sedimentary fill extends beyond of the Holocene is extremely attractive, since, for example, there are few paleoenvironmental data regarding how much the last glaciation that affected the Canary Islands. In these circumstances, the knowledge of the total thickness of the lacustrine sediments is crucial to design a deeper borehole in the next future. Therefore, the subsurface characterisation provided by geophysics is essential for determining thickness and geometry of the sedimentary filling. Multielectrode ERT method was used to obtain five 2-D resistivity cross-sections into La Calderilla volcanic caldera. An Iris Syscal Pro resistivity system with 48 electrodes connected to a 94 m long cable (2m electrode spacing) in Wenner-Schlumberger configuration for an investigation depth of about 20 m. Data quality (q heterogeneous can be

  9. Chemical abrasion-SIMS (CA-SIMS) U-Pb dating of zircon from the late Eocene Caetano caldera, Nevada

    Science.gov (United States)

    Watts, Kathryn E.; Coble, Matthew A.; Vazquez, Jorge A.; Henry, Christopher D.; Colgan, Joseph P.; John, David A.

    2016-01-01

    Zircon geochronology is a critical tool for establishing geologic ages and time scales of processes in the Earth's crust. However, for zircons compromised by open system behavior, achieving robust dates can be difficult. Chemical abrasion (CA) is a routine step prior to thermal ionization mass spectrometry (TIMS) dating of zircon to remove radiation-damaged parts of grains that may have experienced open system behavior and loss of radiogenic Pb. While this technique has been shown to improve the accuracy and precision of TIMS dating, its application to high-spatial resolution dating methods, such as secondary ion mass spectrometry (SIMS), is relatively uncommon. In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry), some grains yielded anomalously young U-Pb ages that implicated Pb-loss and motivated us to investigate with a comparative CA and non-CA dating study. We present CA and non-CA 206Pb/238U ages and trace elements determined by SHRIMP-RG for zircons from three Caetano samples (Caetano Tuff, Redrock Canyon porphyry, and a silicic ring-fracture intrusion) and for R33 and TEMORA-2 reference zircons. We find that non-CA Caetano zircons have weighted mean or bimodal U-Pb ages that are 2–4% younger than CA zircons for the same samples. CA Caetano zircons have mean U-Pb ages that are 0.4–0.6 Myr older than the 40Ar/39Ar sanidine eruption age (34.00 ± 0.03 Ma; error-weighted mean, 2σ), whereas non-CA zircons have ages that are 0.7–1.3 Myr younger. U-Pb ages do not correlate with U (~ 100–800 ppm), Th (~ 50–300 ppm) or any other measured zircon trace elements (Y, Hf, REE), and CA and non-CA Caetano zircons define identical trace element ranges. No statistically significant difference in U-Pb age is observed for CA versus non-CA R33 or TEMORA-2 zircons. Optical profiler measurements of ion microprobe pits demonstrate consistent depths of ~ 1.6

  10. Sixty thousand years of magmatic volatile history before the caldera-forming eruption of Mount Mazama, Crater Lake, Oregon

    Science.gov (United States)

    Wright, Heather Michelle; Bacon, Charles R.; Vazquez, Jorge A.; Sisson, Thomas W.

    2012-12-01

    The well-documented eruptive history of Mount Mazama, Oregon, provides an excellent opportunity to use pre-eruptive volatile concentrations to study the growth of an explosive silicic magmatic system. Melt inclusions (MI) hosted in pyroxene and plagioclase crystals from eight dacitic-rhyodacitic eruptive deposits (71-7.7 ka) were analyzed to determine variations in volatile-element concentrations and changes in magma storage conditions leading up to and including the climactic eruption of Crater Lake caldera. Temperatures (Fe-Ti oxides) increased through the series of dacites, then decreased, and increased again through the rhyodacites (918-968 to ~950 to 845-895 °C). Oxygen fugacity began at nickel-nickel-oxide buffer (NNO) +0.8 (71 ka), dropped slightly to NNO +0.3, and then climbed to its highest value with the climactic eruption (7.7 ka) at NNO +1.1 log units. In parallel with oxidation state, maximum MI sulfur concentrations were high early in the eruptive sequence (~500 ppm), decreased (to ~200 ppm), and then increased again with the climactic eruption (~500 ppm). Maximum MI sulfur correlates with the Sr content (as a proxy for LREE, Ba, Rb, P2O5) of recharge magmas, represented by basaltic andesitic to andesitic enclaves and similar-aged lavas. These results suggest that oxidized Sr-rich recharge magmas dominated early and late in the development of the pre-climactic dacite-rhyodacite system. Dissolved H2O concentrations in MI do not, however, correlate with these changes in dominant recharge magma, instead recording vapor solubility relations in the developing shallow magma storage and conduit region. Dissolved H2O concentrations form two populations through time: the first at 3-4.6 wt% (with a few extreme values up to 6.1 wt%) and the second at ≤2.4 wt%. CO2 concentrations measured in a subset of these inclusions reach up to 240 ppm in early-erupted deposits (71 ka) and are below detection in climactic deposits (7.7 ka). Combined H2O and CO2

  11. Geomorfología de la región de los lagos Moquehue y Aluminé: consideraciones acerca de las propuestas Calderas Meseta del Arco y Nacimientos del Aluminé (Neuquén) Geomorphology of the Moquehue and Aluminé Lakes: Considerations about the Meseta del Arco and Nacimientos del Aluminé calderas

    OpenAIRE

    Emilio F. González Díaz; Inés Di Tommaso

    2010-01-01

    Se exponen elementos de juicio geomórficos y estructurales, que avalan la morfogénesis glaciaria de la depresión en artesa que aloja la cuenca lacustre Moquehue-Aluminé, ubicada en la cordillera neuquina (38°30´S), adyacente al límite internacional. Trabajos anteriores distinguen en la región dos calderas de un gran complejo volcánico plio-cuaternario, situado al este del frente volcánico actual e integrado por nueve depresiones caldéricas y cuerpos dómicos asociados. En el área de estudio só...

  12. Magma injection beneath the urban area of Naples: a new mechanism for the 2012-2013 volcanic unrest at Campi Flegrei caldera.

    Science.gov (United States)

    D'Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

    2015-08-17

    We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km(3) of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area.

  13. Hydrothermal alteration products and stable isotope ratios of the Sulfur Creek Tuff; a window into the subsurface environment of the Yellowstone caldera in Yellowstone National Park, WY

    Science.gov (United States)

    Lonero, A.; Larson, P. B.

    2013-12-01

    The Yellowstone Caldera in northwest Wyoming is the site of active hydrothermal alteration. Hydrothermal activity relating to the Yellowstone hotspot has resulted in the alteration of rhyolites within the caldera. Specifically, the Seven Mile Hole area of the Grand Canyon of Yellowstone River provides an ideal location and opportunity to investigate the nature of the ongoing hydrothermal alteration. Here, erosion by the river has exposed a sequence of rocks which are host to hydrothermal fluids and are themselves significantly altered. Analyses of clay minerals and other alteration products, such as opal, has been undertaken in order to characterize and distinguish different zones of alteration. Hydrogen isotope ratios have been measured for the altered rock units within the Seven-Mile Hole area, and they range from -84.6 ‰ to -185.1 ‰ (VSMOW). Samples from this area commonly contain minerals such as kaolinite, illite, alunite, or buddingtonite, and the deuterium / hydrogen (D/H) ratios of these mineral phases are shown to vary considerably with respect to their location and elevation in the canyon. Additionally, oxygen isotope ratios have been measured on some samples in order to compare the samples' isotope values to the local meteoric water line. Plotting these samples in δD - δ18O space has shown that some values lie in a region trending away from the meteoric water line and along a "kaolinite line." This area is parallel to the array of Yellowstone hot spring fluids and a broad range of values are possible here depending on temperature of alteration. Furthermore, these data support a model where hydrothermal fluids flow upward through faults related to caldera collapse that are present in the sulfur creek tuff. This research may also show that the unique coloration patterns visible on the slopes of the Grand Canyon of Yellowstone can be, in part, explained as the result of both surface oxidation and hydrothermal alteration processes. Major element XRF

  14. Insights into the 3D architecture of an active caldera ring-fault at Tendürek volcano through modeling of geodetic data

    KAUST Repository

    Vasyura-Bathke, Hannes

    2015-04-28

    The three-dimensional assessment of ring-fault geometries and kinematics at active caldera volcanoes is typically limited by sparse field, geodetic or seismological data, or by only partial ring-fault rupture or slip. Here we use a novel combination of spatially dense InSAR time-series data, numerical models and sand-box experiments to determine the three-dimensional geometry and kinematics of a sub-surface ring-fault at Tendürek volcano in Turkey. The InSAR data reveal that the area within the ring-fault not only subsides, but also shows substantial westward-directed lateral movement. The models and experiments explain this as a consequence of a ‘sliding-trapdoor’ ring-fault architecture that is mostly composed of outward-inclined reverse segments, most markedly so on the volcano\\'s western flanks but includes inward-inclined normal segments on its eastern flanks. Furthermore, the model ring-fault exhibits dextral and sinistral strike-slip components that are roughly bilaterally distributed onto its northern and southern segments, respectively. Our more complex numerical model describes the deformation at Tendürek better than an analytical solution for a single rectangular dislocation in a half-space. Comparison to ring-faults defined at Glen Coe, Fernandina and Bárðarbunga calderas suggests that ‘sliding-trapdoor’ ring-fault geometries may be common in nature and should therefore be considered in geological and geophysical interpretations of ring-faults at different scales worldwide.

  15. NeMO-Net: A System for Near Real-Time Remote Sensing of Hydrothermal and Biological Activity in the Caldera of an Active Submarine Volcano

    Science.gov (United States)

    Hammond, S. R.; Butterfield, D.; Embley, R. W.; Meinig, C.; Stalin, S.

    2001-12-01

    In July of 2000, a camera and three temperature sensors were placed on the seafloor near a hydrothermal vent located in the caldera of an active submarine volcano. The volcano's summit lies at a depth of about 1500 m and is located at 46° N, 130° W, approximately 250 nautical miles off the Oregon coast. The volcano is the site of a long-term interdisciplinary study focused in part on discovering relationships between submarine volcanic and hydrothermal activity and a microbial biosphere which exists beneath the sea floor within the volcano's summit caldera. NeMO-Net utilizes an acoustic modem to communicate with a surface mooring anchored nearby. The mooring, in turn, is linked from the ocean surface to the Pacific Marine Environmental Laboratory by means of satellite systems. A unique feature of NeMO-Net is that it enables shore-based investigators to interrogate and command the system to perform specific tasks, the results of which are then reported back typically within several minutes . In the initial year-long deployment, photographic images, along with hourly readings from the three temperature probes, were available on a website which was updated every 24 hours. During the year, the camera documented a dynamic vent biological community as well as water temperature variations due to the influence of tides, and possibly with changing vent fluid temperatures The NeMO-Net system is under continuing development with particular emphasis on linking it to multiple sea floor instruments including near-real-time chemical and water samplers. Near-future plans also call for NeMO Net to be linked to a resident sea floor AUV.

  16. Fluid-faulting evolution in high definition: Connecting fault structure and frequency-magnitude variations during the 2014 Long Valley Caldera, California earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Ellsworth, William L.; Hill, David P.

    2016-01-01

    An extended earthquake swarm occurred beneath southeastern Long Valley Caldera between May and November 2014, culminating in three magnitude 3.5 earthquakes and 1145 cataloged events on 26 September alone. The swarm produced the most prolific seismicity in the caldera since a major unrest episode in 1997-1998. To gain insight into the physics controlling swarm evolution, we used large-scale cross-correlation between waveforms of cataloged earthquakes and continuous data, producing precise locations for 8494 events, more than 2.5 times the routine catalog. We also estimated magnitudes for 18,634 events (~5.5 times the routine catalog), using a principal component fit to measure waveform amplitudes relative to cataloged events. This expanded and relocated catalog reveals multiple episodes of pronounced hypocenter expansion and migration on a collection of neighboring faults. Given the rapid migration and alignment of hypocenters on narrow faults, we infer that activity was initiated and sustained by an evolving fluid pressure transient with a low-viscosity fluid, likely composed primarily of water and CO2 exsolved from underlying magma. Although both updip and downdip migration were observed within the swarm, downdip activity ceased shortly after activation, while updip activity persisted for weeks at moderate levels. Strongly migrating, single-fault episodes within the larger swarm exhibited a higher proportion of larger earthquakes (lower Gutenberg-Richter b value), which may have been facilitated by fluid pressure confined in two dimensions within the fault zone. In contrast, the later swarm activity occurred on an increasingly diffuse collection of smaller faults, with a much higher b value.

  17. Heat flow in vapor dominated areas of the Yellowstone Plateau volcanic field: implications for the thermal budget of the Yellowstone Caldera

    Science.gov (United States)

    Hurwitz, Shaul; Harris, Robert; Werner, Cynthia Anne; Murphy, Fred

    2012-01-01

    Characterizing the vigor of magmatic activity in Yellowstone requires knowledge of the mechanisms and rates of heat transport between magma and the ground surface. We present results from a heat flow study in two vapor dominated, acid-sulfate thermal areas in the Yellowstone Caldera, the 0.11 km2 Obsidian Pool Thermal Area (OPTA) and the 0.25 km2 Solfatara Plateau Thermal Area (SPTA). Conductive heat flux through a low permeability layer capping large vapor reservoirs is calculated from soil temperature measurements at >600 locations and from laboratory measurements of soil properties. The conductive heat output is 3.6 ± 0.4 MW and 7.5 ± 0.4 MW from the OPTA and the SPTA, respectively. The advective heat output from soils is 1.3 ± 0.3 MW and 1.2 ± 0.3 MW from the OPTA and the SPTA, respectively and the heat output from thermal pools in the OPTA is 6.8 ± 1.4 MW. These estimates result in a total heat output of 11.8 ± 1.4 MW and 8.8 ± 0.4 MW from OPTA and SPTA, respectively. Focused zones of high heat flux in both thermal areas are roughly aligned with regional faults suggesting that faults in both areas serve as conduits for the rising acid vapor. Extrapolation of the average heat flux from the OPTA (103 ± 2 W·m−2) and SPTA (35 ± 3 W·m−2) to the ~35 km2 of vapor dominated areas in Yellowstone yields 3.6 and 1.2 GW, respectively, which is less than the total heat output transported by steam from the Yellowstone Caldera as estimated by the chloride inventory method (4.0 to 8.0 GW).

  18. Assessing future vent opening locations at the Somma-Vesuvio volcanic complex: 2. Probability maps of the caldera for a future Plinian/sub-Plinian event with uncertainty quantification

    Science.gov (United States)

    Tadini, A.; Bevilacqua, A.; Neri, A.; Cioni, R.; Aspinall, W. P.; Bisson, M.; Isaia, R.; Mazzarini, F.; Valentine, G. A.; Vitale, S.; Baxter, P. J.; Bertagnini, A.; Cerminara, M.; de Michieli Vitturi, M.; Di Roberto, A.; Engwell, S.; Esposti Ongaro, T.; Flandoli, F.; Pistolesi, M.

    2017-06-01

    In this study, we combine reconstructions of volcanological data sets and inputs from a structured expert judgment to produce a first long-term probability map for vent opening location for the next Plinian or sub-Plinian eruption of Somma-Vesuvio. In the past, the volcano has exhibited significant spatial variability in vent location; this can exert a significant control on where hazards materialize (particularly of pyroclastic density currents). The new vent opening probability mapping has been performed through (i) development of spatial probability density maps with Gaussian kernel functions for different data sets and (ii) weighted linear combination of these spatial density maps. The epistemic uncertainties affecting these data sets were quantified explicitly with expert judgments and implemented following a doubly stochastic approach. Various elicitation pooling metrics and subgroupings of experts and target questions were tested to evaluate the robustness of outcomes. Our findings indicate that (a) Somma-Vesuvio vent opening probabilities are distributed inside the whole caldera, with a peak corresponding to the area of the present crater, but with more than 50% probability that the next vent could open elsewhere within the caldera; (b) there is a mean probability of about 30% that the next vent will open west of the present edifice; (c) there is a mean probability of about 9.5% that the next medium-large eruption will enlarge the present Somma-Vesuvio caldera, and (d) there is a nonnegligible probability (mean value of 6-10%) that the next Plinian or sub-Plinian eruption will have its initial vent opening outside the present Somma-Vesuvio caldera.

  19. Magma mixing and the generation of isotopically juvenile silicic magma at Yellowstone caldera inferred from coupling 238U–230Th ages with trace elements and Hf and O isotopes in zircon and Pb isotopes in sanidine

    Science.gov (United States)

    Stelten, Mark E.; Cooper, Kari M.; Vazquez, Jorge A.; Reid, Mary R.; Barfod, Gry H.; Wimpenny, Josh; Yin, Qing-Zhu

    2013-01-01

    The nature of compositional heterogeneity within large silicic magma bodies has important implications for how silicic reservoirs are assembled and evolve through time. We examine compositional heterogeneity in the youngest (~170 to 70 ka) post-caldera volcanism at Yellowstone caldera, the Central Plateau Member (CPM) rhyolites, as a case study. We compare 238U–230Th age, trace-element, and Hf isotopic data from zircons, and major-element, Ba, and Pb isotopic data from sanidines hosted in two CPM rhyolites (Hayden Valley and Solfatara Plateau flows) and one extracaldera rhyolite (Gibbon River flow), all of which erupted near the caldera margin ca. 100 ka. The Hayden Valley flow hosts two zircon populations and one sanidine population that are consistent with residence in the CPM reservoir. The Gibbon River flow hosts one zircon population that is compositionally distinct from Hayden Valley flow zircons. The Solfatara Plateau flow contains multiple sanidine populations and all three zircon populations found in the Hayden Valley and Gibbon River flows, demonstrating that the Solfatara Plateau flow formed by mixing extracaldera magma with the margin of the CPM reservoir. This process highlights the dynamic nature of magmatic interactions at the margins of large silicic reservoirs. More generally, Hf isotopic data from the CPM zircons provide the first direct evidence for isotopically juvenile magmas contributing mass to the youngest post-caldera magmatic system and demonstrate that the sources contributing magma to the CPM reservoir were heterogeneous in 176Hf/177Hf at ca. 100 ka. Thus, the limited compositional variability of CPM glasses reflects homogenization occurring within the CPM reservoir, not a homogeneous source.

  20. Differentiation and thermal history of the post-collapse magma reservoir at Yellowstone caldera as revealed by combining the temperature-age-compositional history of zircons

    Science.gov (United States)

    Vazquez, J. A.; Reid, M. R.; Kyriazis, S. F.

    2006-12-01

    Coupling the age and compositional history recorded between and within single accessory minerals, such as zircon or allanite, may provide a high-resolution perspective on the thermochemical evolution of voluminous magma reservoirs in the prelude to eruption. At Yellowstone caldera, USA, more than 900km3 of high- silica rhyolite erupted sequentially in the aftermath of caldera collapse from an evolving magma reservoir. At least 21 lavas and tuffs comprise the voluminous Central Plateau Member (CPM) of the Plateau Rhyolite which erupted between 160 ka and 70 ka. 238U-230Th disequilibrium and U-Pb dating reveal that CPM zircons crystallized approximately 0 to 60 thousand years prior to their respective K-Ar eruption ages, and contain little inheritance from the caldera-forming magma. To obtain a temperature-time-compositional history for CPM zircons and evaluate the applicability of the zircon thermometry to high-silica rhyolites, we performed ion microprobe analyses of trace element concentrations in >65 of the dated zircons from four lavas representing early, middle, and late tapping of the CPM reservoir. Most CPM zircons contain typical REE patterns with chondrite-normalized Lu/La of up to 30,000, and with Eu/Eu* as low as 0.03. A subset of the results (~45%) yield elevated light REE, Ti, and Fe concentrations where sampled zircon domains included small inclusions of Fe-Ti oxides, chevkinite, and/or monazite. Application of Ti-in-zircon thermometry to dated zircons that are unaffected by inclusions yield temperatures that have a range of approximately 70 degrees. Calculated temperatures would largely fall within the range of 800°-840°C for CPM magmas obtained by Zr-glass, zircon saturation, and QUILF thermometry if an essentially fixed melt aTiO2 of 0.3 due to ilmenite saturation is assumed. Where analyzed, the rims of single zircons yield temperatures that are 10°-20° lower than their cores. Our combination of zircon thermometry, age, and composition reveals

  1. Characterizing Volcanic Processes using Near-bottom, High Resolution Magnetic Mapping of the Caldera and Inner Crater of the Kick'em Jenny Submarine Volcano

    Science.gov (United States)

    Ruchala, T. L.; Chen, M.; Tominaga, M.; Carey, S.

    2016-12-01

    Kick'em Jenny (KEJ) is an active submarine volcano located in the Lesser Antilles subduction zone, 7.5 km north of the Caribbean island Grenada. KEJ, known as one of the most explosive volcanoes in Caribbean, erupted 12 times since 1939 with recent eruptions in 2001 and possibly in 2015. Multiple generations of submarine landslides and canyons have been observed in which some of them can be attributed to past eruptions. The structure of KEJ can be characterized as a 1300 m high conical profile with its summit crater located around 180 m in depth. Active hydrothermal venting and dominantly CO2 composition gas seepage take place inside this 250m diameter crater, with the most activity occurring primarily within a small ( 70 x 110 m) depression zone (inner crater). In order to characterize the subsurface structure and decipher the processes of this volcanic system, the Nautilus NA054 expedition in 2014 deployed the underwater Remotely Operated Vehicle (ROV) Hercules to conduct near-bottom geological observations and magnetometry surveys transecting KEJ's caldera. Raw magnetic data was corrected for vehicle induced magnetic noise, then merged with ROV to ship navigation at 1 HZ. To extract crustal magnetic signatures, the reduced magnetic data was further corrected for external variations such as the International Geomagnetic Reference Field and diurnal variations using data from the nearby San Juan Observatory. We produced a preliminary magnetic anomaly map of KEJ's caldera for subsequent inversion and forward modeling to delineate in situ magnetic source distribution in understanding volcanic processes. We integrated the magnetic characterization of the KEJ craters with shipboard multibeam, ROV visual descriptions, and photomosaics. Initial observations show the distribution of short wavelength scale highly magnetized source centered at the north western part of the inner crater. Although locations of gas seeps are ubiquitous over the inner crater area along ROV

  2. Kinematic GPS Analysis Gives New Insights on the Origin of the Very-Long-Period Seismic Signals at Miyake-Jima Volcano during the Caldera Formation

    Science.gov (United States)

    Munekane, H.; Oikawa, J.; Kobayashi, T.

    2014-12-01

    Miyake-jima is an active basaltic stratovolcano that is located 200km south of Tokyo, Japan. Its eruption event in 2000 was remarkable in that the large caldera was formed at the summit in approximately one month. During the caldera forming stage, very-long-period (VLP) seismic pulse waves with a duration of about 50-s that were accompanied by the step-like inflation were repeatedly recorded. Based on the broadband seismometer data, the piston model is proposed in which a vertical piston of solid materials in the conduit is intermittently sucked into the magma chamber located 3-5 km beneath the edific. In this study, we used the kinematic displacements from the continuous GPS observation to obtain additonal insights on the source mechanism of the pulse waves.  We calculated the kinematic displacements of 15 GPS stations on Miyake-jima that were in operation at that time at 30 sec interval. Then we extracted the displacements associated with each event using 20-hour time window centered at the occurrence of the event, and stacked the whole time series to obtain mean displacement time series. The obtained time series contain: 1) step-like displacements associated with the pulse waves, 2) exponential decay following the events with time constant of approximately half-day, and 3) steady linear displacements indicating continuous contraction of the edifice. The type one displacements can be attributed to the simultaneous inflation of an mogi-type spherical pressure source located at the depth of 3.6 km under the edifice, and the opening of the nearby vertical dike whose top is at the depth of 2.3 km. The type two displacements can be interpreted as the pressure adjustment at the type one source by the outflow of the magma driven by the pressure difference between the type one source and surrounding area. The type three displacements can be interpreted as the steady outflow of the magma from the type one source. The above results support the ``piston model'' for the

  3. Eruption-triggered mixing of extra-caldera basalt and rhyolite complexes along the East Gallatin-Washburn fault zone, Yellowstone National Park, WY, USA

    Science.gov (United States)

    Pritchard, C. J.; Larson, P. B.; Spell, T. L.; Tarbert, K. D.

    2013-08-01

    weakened zones of the upper crust. The decompression induced mixing was facilitated by coeval extensional tectonics and structures in the Norris-Mammoth Corridor. Extra-caldera rhyolites are some of the first volcanics following the collapse of the current caldera and also some of the youngest volcanics in the Yellowstone Plateau and require further understanding of volcanism in the Yellowstone Plateau.

  4. Monitoring the hydrologic system for potential effects of geothermal and ground-water development in the Long Valley caldera, Mono County, California, U.S.A.

    Science.gov (United States)

    Farrar, C.D.; Lyster, D. L.

    1990-01-01

    In the early 1980's, renewed interest in the geothermal potential of the Long Valley caldera, California, highlighted the need to balance the benefits of energy development with the established recreational activities of the area. The Long Valley Hydrologic Advisory Committee, formed in 1987, instituted a monitoring program to collect data during the early stages of resource utilization to evaluate potential effects on the hydrologic system. Early data show declines in streamflow, spring flow, and ground-water levels caused by 6 years of below-average precipitation. Springs in the Hot Creek State Fish Hatchery area discharge water that is a mixture of nonthermal and hydrothermal components. Possible sources of nonthermal water have been identified by comparing deuterium concentrations in streams and springs. The equivalent amount of undiluted thermal water discharged from the springs was calculated on the basis of boron and chloride concentrations. Quantifying the thermal and nonthermal fractions of the total flow may allow researchers to assess changes in flow volume or temperature of the springs caused by groundwater or geothermal development.

  5. Corrosión en caliente de un acero inoxidable 304h para calderas en presencia de sales fundidas de vanadatos y sulfatos

    Directory of Open Access Journals (Sweden)

    Sonia Rincón

    2003-01-01

    Full Text Available El presente trabajo busca indagar y establecer el tipo de mecanismo de daño que sufre el acero inoxidable 304H en contacto con depósitos de sal fundida, junto con un estudio preliminar de la cinética de la corrosión. Para ello, se analizarán los depósitos fundidos, la composición química de éstos y se medirá la pérdida de material luego de ser sometido a períodos continuos de ataque, con el uso de la técnica gravimétrica en crisol. Con esto se pretende conocer las variables que influyen directamente sobre el deterioro del acero 304H, para en un futuro, adoptar medidas predictivas y/o preventivas que incrementen su vida útil, aumentando de ésta manera la eficiencia de las calderas y disminuyendo el tiempo entre paradas programadas.

  6. Pterópodos thecosomados en el Pacífico suroriental frente a Caldera, Chile (Mollusca, Opistobranchiata: Euthecostomata y Pseudothecostomata

    Directory of Open Access Journals (Sweden)

    Mónica Labrín

    2015-03-01

    Full Text Available Se analizaron los pterópodos thecosomados colectados en una transecta oceanógrafica efectuada entre Caldera, Chile (~27°S y los alrededores de Isla de Pascua e Isla Salas y Gómez, Pacífico suroriental. Se registró un total de 2021 individuos, agrupados en 18 especies, siendo Clio pyramidata y Styliola subula especies dominantes a lo largo del transecto, las más frecuentes y representadas en 18 de las 23 estaciones analizadas. Las especies más abundantes fueron S. subula (35%, C. pyramidata (28% y Cavolinia inflexa (13%. Las siguientes especies constituyen nuevos registros para el Pacífico suroriental: Cavolinia labiata, Cavolinia uncinata, Cavolinia gibosa, Cuvierina columnella, Clio cuspidata, Clio chaptali, Diacria trispinosa, D. quadridentata, D. major, Cymbulia sp. y Peracle reticulata. La clasificación permite reconocer tres conjuntos de estaciones caracterizadas por sus especies, abundancia total, riqueza de especies y diversidad, que incluyen un conjunto nerítico (71-79°W, un conjunto oceánico (82-105°W y un conjunto de estaciones talasoepipelágicas asociadas a las islas oceánicas.

  7. Calcification and Silicification: Fossilization Potential of Cyanobacteria from Stromatolites of Niuafo‘ou's Caldera Lakes (Tonga) and Implications for the Early Fossil Record

    Science.gov (United States)

    Kazmierczak, Józef; Łukomska-Kowalczyk, Maja; Kempe, Stephan

    2012-01-01

    Abstract Calcification and silicification processes of cyanobacterial mats that form stromatolites in two caldera lakes of Niuafo‘ou Island (Vai Lahi and Vai Si‘i) were evaluated, and their importance as analogues for interpreting the early fossil record are discussed. It has been shown that the potential for morphological preservation of Niuafo‘ou cyanobacteria is highly dependent on the timing and type of mineral phase involved in the fossilization process. Four main modes of mineralization of cyanobacteria organic parts have been recognized: (i) primary early postmortem calcification by aragonite nanograins that transform quickly into larger needle-like crystals and almost totally destroy the cellular structures, (ii) primary early postmortem silicification of almost intact cyanobacterial cells that leave a record of spectacularly well-preserved cellular structures, (iii) replacement by silica of primary aragonite that has already recrystallized and obliterated the cellular structures, (iv) occasional replacement of primary aragonite precipitated in the mucopolysaccharide sheaths and extracellular polymeric substances by Al-Mg-Fe silicates. These observations suggest that the extremely scarce earliest fossil record may, in part, be the result of (a) secondary replacement by silica of primary carbonate minerals (aragonite, calcite, siderite), which, due to recrystallization, had already annihilated the cellular morphology of the mineralized microbiota or (b) relatively late primary silicification of already highly degraded and no longer morphologically identifiable microbial remains. Key Words: Stromatolites—Cyanobacteria—Calcification—Silicification—Niuafo‘ou (Tonga)—Archean. Astrobiology 12, 535–548. PMID:22794297

  8. Calcification and silicification: fossilization potential of cyanobacteria from stromatolites of Niuafo'ou's Caldera Lakes (Tonga) and implications for the early fossil record.

    Science.gov (United States)

    Kremer, Barbara; Kazmierczak, Józef; Lukomska-Kowalczyk, Maja; Kempe, Stephan

    2012-06-01

    Calcification and silicification processes of cyanobacterial mats that form stromatolites in two caldera lakes of Niuafo'ou Island (Vai Lahi and Vai Si'i) were evaluated, and their importance as analogues for interpreting the early fossil record are discussed. It has been shown that the potential for morphological preservation of Niuafo'ou cyanobacteria is highly dependent on the timing and type of mineral phase involved in the fossilization process. Four main modes of mineralization of cyanobacteria organic parts have been recognized: (i) primary early postmortem calcification by aragonite nanograins that transform quickly into larger needle-like crystals and almost totally destroy the cellular structures, (ii) primary early postmortem silicification of almost intact cyanobacterial cells that leave a record of spectacularly well-preserved cellular structures, (iii) replacement by silica of primary aragonite that has already recrystallized and obliterated the cellular structures, (iv) occasional replacement of primary aragonite precipitated in the mucopolysaccharide sheaths and extracellular polymeric substances by Al-Mg-Fe silicates. These observations suggest that the extremely scarce earliest fossil record may, in part, be the result of (a) secondary replacement by silica of primary carbonate minerals (aragonite, calcite, siderite), which, due to recrystallization, had already annihilated the cellular morphology of the mineralized microbiota or (b) relatively late primary silicification of already highly degraded and no longer morphologically identifiable microbial remains.

  9. The Somma-Vesuvius complex and the Phlaegrean Fields caldera: New chronological data of several eruptions of the Copper-Middle Bronze Age period

    Science.gov (United States)

    Passariello, Isabella; Lubritto, Carmine; D'Onofrio, Antonio; Guan, Yongjing; Terrasi, Filippo

    2010-04-01

    Radiocarbon dating of short-lived sample materials is a useful tool applied to date deposits of volcanic eruptions. Several archaeological sites discovered and excavated in Campania witnessed important volcanic eruptions, which occurred in the Copper and Middle Bronze Ages. These eruptions come from the Somma-Vesuvius complex and the Phlaegrean Fields caldera. At least four Plinian eruptions have been identified in the eruptive history of Somma-Vesuvius, interspersed by interplinian events, called protohistoric, which occurred between Avellino and Pompeii. At S. Paolo Belsito a stratigraphic sequence below Avellino and above the first two protohistoric events after Avellino were highlighted; while Nola (Naples) gives new information on the chronology of Avellino. Sites like Caivano and Gricignano D'Aversa, involved by the Agnano 3, Paleoastroni 2 and Agnano Monte Spina eruptions were highlighted and investigated. In this work, we want to clarify the chronology of some eruptions by comparing our results with previous data. Charcoal, bone and seed samples were collected, treated and measured at the CIRCE laboratory in Caserta.

  10. Quaternary erosion and cosmic-ray-exposure history derived from 10Be and 26Al produced in situ—An example from Pajarito plateau, Valles caldera region

    Science.gov (United States)

    Albrecht, Achim; Herzog, Gregory F.; Klein, Jeffrey; Dezfouly-Arjomandy, Bijan; Goff, Fraser

    1993-06-01

    10Be and 26Al concentrations measured by accelerator mass spectrometry in 20 samples of quartz separated from rhyolitic volcanic ash-flow tuffs collected on the Pajarito plateau of the Valles caldera, New Mexico, were used to model time-integrated erosion rates and cosmic ray-exposure histories. The model erosion rates determined for different stratigraphic units within the Tshirege member, upper Bandelier Tuff, vary from 0.1 cm/ka for the resistant unit to 1.1 cm/ka for the softer unit. Intermediate erosion rates are thought to indicate earlier age cover by post-tuff lithologies of different hardness. The geographic distribution of these intermediate rates allows an approximate determination of the extent of material now gone (stratigraphic ghosts). Periods of burial can be determined from 26Al/10Be ratios. For the Pajarito plateau, burial most likely resulted from cover by soil and sediment held in place by vegetation. Our data allow us to model the duration and extent of thick forest cover, which today exists only at higher altitudes.

  11. Control Robusto de Orden Fraccionario de la Presión del Vapor en el Domo Superior de una Caldera Bagacera

    Directory of Open Access Journals (Sweden)

    R. Rivas-Perez

    2014-01-01

    Full Text Available Resumen: En el presente trabajo se desarrolla un controlador de orden fraccionario del tipo IDα-1 para el control robusto de la presión de vapor en el domo superior de una caldera bagacera, el cual posibilita aumentar la efectividad en el control, así como la eficiencia energética de estos equipos. La aplicación de un controlador de orden fraccionario se justifica por el hecho de que la dinámica del proceso objeto de estudio puede cambiar de forma drástica con la variación del calor especifico de combustión (I. Se obtiene un modelo matemático nominal de la variación de la presión de vapor en el domo superior de la caldera bagacera. Los resultados de validación del modelo matemático obtenido muestran un elevado grado de adecuación. Mediante estudios experimentales se estimó el rango de variación de los parámetros dinámicos del modelo matemático obtenido cuando el calor específico de combustión varía en el rango de operación [Imin,-1Imax]. El diseño del controlador IDα se realiza en base a especificaciones en el dominio de la frecuencia. Se muestran los resultados comparativos de simulación del sistema de control desarrollado con controladores IDα-1 vs PI e IDα-1 vs PID, en el sentido de exhibir el mismo comportamiento dinámico en lazo cerrado para las especificaciones de la planta nominal y en presencia de perturbaciones. Estos resultados demuestran que cuando la ganancia de la presión del vapor en el domo superior de la caldera bagacera presenta variaciones en-1el rango [Kmin, Kmax] el controlador IDα diseñado exhibe mejores prestaciones, así como una mayor robustez. Abstract: This paper presents a fractional order controller of the class IDα-1 for robust control of the steam pressure in the steam drum of a bagasse boiler. The proposed controller improves the effectiveness on the control, and likewise the energy efficiency of this plant. The

  12. Hydrothermal brecciation in the Jemez Fault zone, Valles Caldera, New Mexico: Results from CSDP (Continental Scientific Drilling Program) corehole VC-1

    Energy Technology Data Exchange (ETDEWEB)

    Hulen, J.B.; Nielson, D.L.

    1987-06-01

    Paleozoic and Precambrian rocks intersected deep in Continental Scientific Drilling Program corehole VC-1, adjacent to the late Cenozoic Valles caldera complex, have been disrupted to form a spectacular breccia sequence. The breccias are of both tectonic and hydrothermal origin, and probably formed in the Jemez fault zone, a major regional structure with only normal displacement since mid-Miocene. Tectonic breccias are contorted, crushed, sheared, and granulated; slickensides are commmon. Hydrothermal breccias, by contrast, lack these frictional textures, but arej commonly characterized by fluidized matrix foliation and prominent clast rounding. Fluid inclusions in the hydrothermal breccias are dominantly two-phase, liquid-rich at room temperature, principally secondary, and form two distinctly different compositional groups. Older inclusions, unrelated to brecciation, are highly saline and homogenize to the liquid phase in the temperature range 189 to 246/sup 0/C. Younger inclusions, in part of interbreccia origin, are low-salinity and homogenize (also to liquid) in the range 230 to 283/sup 0/C. Vapor-rich inclusions locally trapped along with these dilute liquid-rich inclusions document periodic boiling. These fluid-inclusion data, together with alteration assemblages and textures as well as the local geologic history, have been combined to model hydrothermal brecciation at the VC-1 site.

  13. The Somma-Vesuvius complex and the Phlaegrean Fields caldera: New chronological data of several eruptions of the Copper-Middle Bronze Age period

    Energy Technology Data Exchange (ETDEWEB)

    Passariello, Isabella, E-mail: isabella.passariello@unina2.i [CIRCE - Dipartimento di Scienze Ambientali, II Universita di Napoli and INNOVA, via Vivaldi 43, Caserta 81100 (Italy); Lubritto, Carmine; D' Onofrio, Antonio [CIRCE - Dipartimento di Scienze Ambientali, II Universita di Napoli and INNOVA, via Vivaldi 43, Caserta 81100 (Italy); Guan, Yongjing [CIRCE - Dipartimento di Scienze Ambientali, II Universita di Napoli and INNOVA, via Vivaldi 43, Caserta 81100 (Italy); ICTP, Trieste (Italy); Terrasi, Filippo [CIRCE - Dipartimento di Scienze Ambientali, II Universita di Napoli and INNOVA, via Vivaldi 43, Caserta 81100 (Italy)

    2010-04-15

    Radiocarbon dating of short-lived sample materials is a useful tool applied to date deposits of volcanic eruptions. Several archaeological sites discovered and excavated in Campania witnessed important volcanic eruptions, which occurred in the Copper and Middle Bronze Ages. These eruptions come from the Somma-Vesuvius complex and the Phlaegrean Fields caldera. At least four Plinian eruptions have been identified in the eruptive history of Somma-Vesuvius, interspersed by interplinian events, called protohistoric, which occurred between Avellino and Pompeii. At S. Paolo Belsito a stratigraphic sequence below Avellino and above the first two protohistoric events after Avellino were highlighted; while Nola (Naples) gives new information on the chronology of Avellino. Sites like Caivano and Gricignano D'Aversa, involved by the Agnano 3, Paleoastroni 2 and Agnano Monte Spina eruptions were highlighted and investigated. In this work, we want to clarify the chronology of some eruptions by comparing our results with previous data. Charcoal, bone and seed samples were collected, treated and measured at the CIRCE laboratory in Caserta.

  14. Monitoreo de un sistema de secado de bagazo acoplado a una caldera en un ingenio de México Monitoring of a bagasse drying system attached to a boiler in a sugar mill in Mexico

    Directory of Open Access Journals (Sweden)

    Federico J. Franck Colombres

    Full Text Available Se evaluó el desempeño de un secador de bagazo diseñado por la Estación Experimental Agroindustrial Obispo Colombres, acoplado a una caldera bagacera convencional en un ingenio de México (caldera Nº 5. Para ello, se realizaron ensayos de mediciones y balances de materia y energía, para la caldera operando con el secador y sin él en funcionamiento. La caldera Nº 5, de una producción nominal de 60 t/h de vapor y una presión máxima de trabajo de 29 bar, cuando fue alimentada únicamente con bagazo húmedo pudo generar como máximo 33 t/h de vapor a 19 bar y 269ºC, con un rendimiento energético de 60,4% y un índice de generación de 1,6 kg de vapor/ kg de bagazo. Con la adición del secador, se logró secar 28,6 toneladas de bagazo de 50,2% a 30,4% de humedad. Aproximadamente un 72% de este bagazo presecado se mezcló con bagazo húmedo y se utilizó para alimentar la caldera, produciéndose así 58,4 t/h de vapor; es decir, 77% más de vapor que sin secador. El rendimiento energético del sistema caldera-secador fue de 73,6%, un 21,8% superior al de la caldera sin secador, mientras que el índice de generación fue de 2,0 kg de vapor/ kg de bagazo, 25% mayor que el de la caldera original. Este aumento en la producción de vapor permitió sacar de servicio a la caldera Nº 6, que producía aproximadamente 20 t/h de vapor, con un rendimiento similar al de la caldera Nº 5 sin secador. Estas mejoras dieron como resultado, un ahorro de energía de 45,4 MJ/h, aproximadamente un 18% respecto a la energía consumida por ambas calderas (Nº 5 y Nº 6 cuando no funcionaba el secador. Este ahorro equivale a 1103 l/h de "fuel oil", es decir, alrededor de 1,5 millones de dólares por zafra.A bagasse dryer designed by Estación Experimental Agroindustrial Obispo Colombres was attached to a conventional bagasse boiler (Boiler No. 5 in a sugar mill in Mexico for evaluation. Measurement tests and material and energy balances for the boiler operating

  15. Volcanic and tectonic processes coinciding with glaciation and crustal rebound: an early Holocene rhyolitic eruption in the Dyngjufjöll volcanic centre and the formation of the Askja caldera, north Iceland

    Science.gov (United States)

    Sigvaldason, Guðmundur

    2002-03-01

    A pronounced volcanic production maximum on the rift zones through Iceland coincided with rapid crustal rebound during and after glacier melting at the Pleistocene/Holocene boundary. At peak glaciation, ice thickness over central Iceland may have reached 1,500-2,000 m, causing 400-500-m depression of the crust. Rapid climatic improvement caused glacier melting and removal of the ice load within about 1,000 years. Low mantle viscosity resulted in rapid crustal rebound which was completed in about 1,000 years, with an average rate of uplift on the order of nearly half a metre per year over central Iceland. High volcanic production rate is documented by tephrachronological dating and volume estimates of several large-volume monogenetic lava shields and polygenetic volcanic centres along the plate boundary. A Plinian rhyolitic eruption, dated at about 10 ka within the Askja caldera in the Dyngjufjöll volcanic centre, left a pumice deposit which serves as a marker horizon during this remarkable, high-intensity period in the history of the volcano. At the time of the eruption, glaciers had retreated from the coastal areas of the country but the central, elevated parts were covered with a thinning glacier. The Plinian eruption (1-2 km3 dense rock equivalent) was triggered by pressure release caused by glacier melting and volatile supersaturation. Distal deposits of rhyolitic pumice are found in soil sections in coastal areas of eastern and northern Iceland where the pumice occurs between tephra layers from other sources which have been dated by independent methods. A few proximal deposits are preserved within the Dyngjufjöll centre. These provide age constraints on major tectonic and volcanic events during the period of crustal rebound, before and after complete glacier removal. The rhyolitic pumice is sandwiched between thick layers of phreatomagmatic basaltic tephra formed in an open melt-water lake. Sharp contacts between the deposits suggest quick succession of

  16. Inventariando la biodiversidad en el Parque Nacional de La Caldera de Taburiente (La Palma, Islas Canarias, España: novedades científicas

    Directory of Open Access Journals (Sweden)

    Domingo-Quero, Teresa

    2003-12-01

    Full Text Available This paper is the first result of an agreement between the Organismo Autónomo Parques Nacionales and the Consejo Superior de Investigaciones Científicas, entitled “Inventory and study of the Invertebrate Fauna of the National Park of La Caldera de Taburiente”. A detailed account of the faunistic novelties found up to now among the specimens of terrestrial and freshwater invertebrates collected along the two years of sampling (July 1999 to July 2001, whose number is estimated in ca. 500,000, is given. A brief description of planning and of methodology applied to the inventory of the invertebrate fauna is made and a tabulated summary of novelties is presented. The list shows at present 284 families, 594 genera and 739 species. For the Canary Islands, the present record of new taxa is 29 families, 115 genera (1 of them confirmed as new to Science and 3 awaiting confirmation and 187 species (24 new to Science. Moreover, 242 genera and 338 species are new to the fauna of La Palma I., being known from other islands of the archipelago. Other 47 taxa, still being studied, could be new to Science as well. These results have been reached with the study of just a minimal part of the whole material, which underlines the need for systematic, continued sampling to evaluate the faunistic richness of poorly explored areas and its possible necessity for protection. Therefore, one should expect more novelties and the inventory may increase significantly when all the material is revised.

    El presente artículo es el primer resultado de un convenio entre el Organismo Autónomo Parques Nacionales y el Consejo Superior de Investigaciones Científicas, denominado “Inventario y estudio de la Fauna Invertebrada del Parque Nacional de La Caldera de Taburiente”. Se detallan las novedades faunísticas encontradas hasta el momento entre los ejemplares de invertebrados terrestres y dulceacuícolas recogidos durante los dos años de muestreo (julio de 1999 a

  17. MED SUV TASK 6.3 Capacity building and interaction with decision makers: Improving volcanic risk communication through volcanic hazard tools evaluation, Campi Flegrei Caldera case study (Italy)

    Science.gov (United States)

    Nave, Rosella; Isaia, Roberto; Sandri, Laura; Cristiani, Chiara

    2016-04-01

    In the communication chain between scientists and decision makers (end users), scientific outputs, as maps, are a fundamental source of information on hazards zoning and the related at risk areas definition. Anyway the relationship between volcanic phenomena, their probability and potential impact can be complex and the geospatial information not easily decoded or understood by not experts even if decision makers. Focusing on volcanic hazard the goal of MED SUV WP6 Task 3 is to improve the communication efficacy of scientific outputs, to contribute in filling the gap between scientists and decision-makers. Campi Flegrei caldera, in Neapolitan area has been chosen as the pilot research area where to apply an evaluation/validation procedure to provide a robust evaluation of the volcanic maps and its validation resulting from end users response. The selected sample involved are decision makers and officials from Campanian Region Civil Protection and municipalities included in Campi Flegrei RED ZONE, the area exposed to risk from to pyroclastic currents hazard. Semi-structured interviews, with a sample of decision makers and civil protection officials have been conducted to acquire both quantitative and qualitative data. The tested maps have been: the official Campi Flegrei Caldera RED ZONE map, three maps produced by overlapping the Red Zone limit on Orthophoto, DTM and Contour map, as well as other maps included a probabilistic one, showing volcanological data used to border the Red Zone. The outcomes' analysis have assessed level of respondents' understanding of content as displayed, and their needs in representing the complex information embedded in volcanic hazard. The final output has been the development of a leaflet as "guidelines" that can support decision makers and officials in understanding volcanic hazard and risk maps, and also in using them as a communication tool in information program for the population at risk. The same evaluation /validation process

  18. The Baia-Fondi di Baia eruption at Campi Flegrei: stratigraphy and dynamics of a multi-stage caldera reactivation event

    Science.gov (United States)

    Pistolesi, Marco; Bertagnini, Antonella; Di Roberto, Alessio; Isaia, Roberto; Vona, Alessandro; Cioni, Raffaello; Giordano, Guido

    2017-09-01

    The Baia-Fondi di Baia eruption is one of the sporadic events that have occurred in the western sector of the Campi Flegrei caldera. It dates back to 9525-9696 bp and opened Epoch 2 of the caldera activity after a 1000-year-long period of quiescence. Although relatively small in terms of erupted volume with respect to most of the events of the past 15 ka, the Baia-Fondi di Baia eruption was characterized by a complex series of events, which have led to different interpretations in the literature. We present a detailed stratigraphic study of 40 outcrops in a sector of about 90 km2, coupled with sedimentological (grain size, componentry), physical (density, vesicularity), textural, and compositional analyses of the erupted deposits. Based on these data, we interpret the stratigraphic succession as being related to two distinct eruptive episodes (Baia and Fondi di Baia). These were separated by a short time interval, and each was characterized by different eruptive phases. The Baia eruptive episode started in a shallow-water environment with an explosive vent-opening phase that formed a breccia deposit (Unit I), rapidly followed by alternating fallout activity and dense, pyroclastic density current deposits generation (Unit II). Sedimentological features and pumice textural analyses suggest that deposition of Unit II coincided with the intensity peak of the eruption, with the fallout deposit being characterized by a volume of 0.06 ± 0.008 km3 (corresponding to a total erupted mass of 4.06 ± 0.5 × 1010 kg), a column height of 17 km, and a corresponding mass flow rate of 1.8 × 107 kg s-1. The associated tephra also shows the highest vesicularity (up to 81 vol.%) the highest vesicle number density (1.01 × 108 cm-3) and decompression rate (0.69 MPa s-1). This peak phase waned to turbulent, surge-like activity possibly associated with Vulcanian explosions and characterized by progressively lower intensity, as shown by density/vesicularity and textural properties of

  19. Shallow geothermal investigations into the existence of the Valles Caldera outflow plume near Ponderosa and Jemez Pueblo, north-central, New Mexico

    Science.gov (United States)

    Salaz, Robert Ezekiel

    Geothermal research within the Jemez Mountains spans several decades and is documented in many papers. This study serves to extend the research boundary to the south and east outside of Valles caldera and Canon de San Diego, where the main occurrences of geothermal activity are located. The focus of this investigation is to test for a deep ~900 m, stratigraphically-bound thermal aquifer within the Madera Limestone along the western margin of the Santo Domingo basin transition zone near Ponderosa and Jemez Pueblo, in north-central New Mexico. Numerous springs were sampled for aqueous geochemistry to identify leakage of a deeper geothermal aquifer into shallow aquifers. Wells were sampled for temperature anomalies. In addition, two travertine deposits were analyzed for stable isotope composition and one deposit was dated using U-Series techniques to assess the timing and origin of deposition. This study is important because researchers in other extensional basins have identified reasonably good geothermal reservoirs in deep carbonate aquifers that are similar in geologic setting to the Madera Limestone aquifer of this study. The existence of a deep geothermal aquifer near Ponderosa and Jemez Pueblo, New Mexico could prove to be another prospect for geothermal exploration in the Jemez Mountains. Aqueous geochemistry of springs are plotted on ternary Piper diagrams to help classify similar geochemical trends and group these trends into recognizable patterns. These data indicate calcium carbonate rich waters in the north that may gradationally change to alkaline type waters as they flow south through the study area. Contrasting this data, SiO2 and TDS concentrations show two separate systems that may indicate separate confined aquifers. Two distinct TDS regions are observed, one with higher concentrations (>1000 ppm) shows a decrease from N-S and one with lower concentrations (geothermal mixing was observed in any of the samples. Temperature data taken from shallow

  20. New Temperature and H2O estimates for Post Caldera Yellowstone Rhyolite Lavas from Feldspar Geothermometry and Rhyolite-MELTS Modeling

    Science.gov (United States)

    Shaffer, J. S.; Till, C. B.

    2016-12-01

    Determination of the thermal histories of previously erupted silicic magma bodies at Yellowstone, specifically the effusive eruptions that have characterized the system since ca. 260 ka, is critical to understanding the future behavior of the system. Post-caldera Yellowstone rhyolite flows have been extensively studied using Fe-Ti oxides, QUILF, titaniQ, and zircon saturation geothermometry. In this study, we add two-feldspar and liquid-feldspar thermometry of five rhyolitic Upper Basin Member flows (Scaup Lake, South, North, East, and Middle Biscuit Basin) and one Central Plateau Member (Hayden Valley). The feldspar rims record temperatures between 780 to 880°C using the plagioclase-liquid and sanidine-liquid thermometers of Putirka (2008) and the SOLVCALC two feldspar thermometer. Additionally, rhyolite-MELTS modeling was performed at varying water contents assuming a pressure of 3 kbar, similar to the modern day reservoir. We find the modeling best reproduces the overall phase proportions, feldspar compositions, and feldspar thermometry at ≤1.5 H2O wt. % for all flows. In general, the location of the feldspar solvus predicted by rhyolite-MELTS is in excellent agreement with two feldspar thermometry (e.g., for the Scaup Lake flow, MELTS solvus=826°C vs. two feldspar thermometry=819±20°C), whereas the plagioclase-liquid thermometry records higher temperatures. The rhyolite-MELTS models also suggest that quartz, rather than feldspar, is the first silicic phase to crystallize in all the lava compositions. When compared to the location of vapor saturation as predicted by rhyolite-MELTS ( 730-735°C), the thermometry of the feldspar rims suggests they crystallized at temperatures significantly above vapor saturation. This work sheds light on the calibration and interpretation of rhyolite-MELTS models in conjunction with detailed feldspar thermometry.

  1. New Approaches for Identifying the P-T-X-t Histories and Eruption Triggers for Silicic Magmas; An Example Examining the Scaup Lake Rhyolite, Yellowstone Caldera, WY

    Science.gov (United States)

    Till, C. B.; Boyce, J. W.

    2016-12-01

    The crystal cargoes from past eruptions provide petrologic records of the pressure, temperature and composition of a magma body preceding eruption. Recent advances in diffusion chronometry also now enable us to reconstruct the timing of magmatic events shortly before eruption. Here these techniques are combined to unlock detailed P-T-X-t histories of silicic magma bodies leading to eruption, using the 260 ka Scaup Lake rhyolite lava (SCL) from Yellowstone caldera as an example. The SCL contains 30% phenocrysts of reversely zoned quartz, clinopyroxene, orthopyroxene, plagioclase and sanidine. SCL sanidine and plagioclase reveal ubiquitous bright rims that are enriched in Ba, Sr, Ca and in some cases Mg and Ti relative to the grain interior. Major element transects across the full width of the sanidine rims reveal two pronounced changes in composition that can be equated to heating events (older +25°C, younger +100°C) using sanidine-liquid thermometry and compositional relationships predicted by Rhyolite-MELTS. Renewed precipitation of sanidine at higher temperatures could reflect magma ascent and concomitant exsolution of dissolved H2O, the addition of CO2 by new magma, and/or the addition of K-Na-enriched melt derived from melting sanidine-rich cumulates. The increase in magmaphile elements associated with the 25°C heating event indicate this episode of feldspar growth resulted from the injection of a hotter, less evolved magma 10-40 yrs prior to eruption based on diffusion chronometry (Till et al., Geology, 2015). Estimates using natural and experimental crystal growth rates suggest the second heating event of 100°C recorded in the outermost sanidine rims occurred within 1.5-2 yrs of eruption. This is consistent with a subset of the diffusion chronometry results that indicate rejuvenation-eruption timescales of eruption. Instead it appears the necessary overpressure was provided by a second intrusion in the prior several years to months.

  2. Fuel oil-water emulsions to reduce unburned particle emissions from boilers; Emulsiones agua en combustoleo para reducir las emisiones de particulas inquemadas en calderas

    Energy Technology Data Exchange (ETDEWEB)

    Diego Marin, Antonio; Ocampo Barrera, Rene; Martinez Flores, Marco Antonio; Tamayo Flores, Gustavo Adolfo; Alarcon Quiroz, Ernesto [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1997-12-31

    To diminish the problems caused by fuels in boilers such as abnormal soiling of heat interchange surfaces, decrease of thermal and combustion efficiencies and increment of pollutants it is proposed the utilization of fuel oil water emulsions. This technology process is described, its development and application in other countries is shown and mention is made of the experiences in this regard at the Instituto de Investigaciones Electricas (IIE), as well as the perspectives this technology has in Mexico. In conclusion, the fuel oil water emulsion is an alternative that can help burning efficiently the fuel oil and so to contribute to fulfill with the limits established by the environmental regulations on pollutant emissions. The development of this technology is economical and of simple application, compared with others, such as the installation of new burners, the utilization of a commercial technology for flue gas conditioning, etcetera [Espanol] Para disminuir los problemas ocacionados por el combustoleo en las calderas como: ensuciamientos anormales de las superficies de intercambio de calor, disminucion de eficiencias termicas y de combustion e incremento de las emisiones, se propone la utilizacion de la emulsion de agua en combustoleo. Se describe el proceso de esta tecnologia, se muestra su desarrollo y aplicacion en otros paises y se mencionan las experiencias a este respecto en el Instituto de Investigaciones Electricas (IIE), asi como las perspectivas que tiene esta tecnologia en Mexico. En conclusion, la emulsion de agua en combustoleo es una alternativa que puede ayudar a quemar eficientemente al combustoleo y asi contribuir a cumplir con los limites de emisiones que establecen normas ambientales. El desarrollo de esta tecnologia es economica y de aplicacion sencilla, comparada con otras como: la instalacion de nuevos quemadores, la utilizacion de una tecnologia comercial para acondicionar los gases de combustion, etcetera

  3. Rock magnetic evidence of non-random raw material selection criteria in Cerro Toledo Obsidian Artifacts from Valles Caldera, New Mexico

    Science.gov (United States)

    Gregovich, A.; Feinberg, J. M.; Steffen, A.; Sternberg, R. S.

    2014-12-01

    Stone tools are one of the most enduring forms of ancient human behavior available to anthropologists. The geologic materials that comprise stone tools are a reflection of the rocks that were available locally or through trade, as are the intended use of the tools and the knapping technology needed to produce them. Investigation of the rock magnetic and geochemical characteristics of the artifacts and the geological source materials provides a baseline to explore these past behaviors. This study uses rock magnetic properties to explore the raw material selection criteria involved in the production of obsidian tools in the region around Valles Caldera in northern New Mexico. Obsidian is locally abundant and was traded by tribes across the central United States. Here we compare the rock magnetic properties of a sample of obsidian projectile points (N =25) that have been geochemically sourced to the Cerro Toledo obsidian flow with geological samples collected from four sites within the same flow (N =135). This collection of archaeological artifacts, albeit small, contains representatives of at least 8 different point styles that were used over 6000 years from the Archaic into the Late Prehistoric. Bulk rock hysteresis parameters (Mr, Ms, Bc, and Bcr) and low-field susceptibility (Χ) measurements show that the projectile points generally contain a lower concentration of magnetic minerals than the geologic samples. For example, the artifacts' median Ms value is 2.9 x 10-3 Am2kg-1, while that of the geological samples is 6.5 x 10-3 Am2kg-1. The concentration of magnetic minerals in obsidian is a proxy for the concentration of microlites in general, and this relationship suggests that although obsidian was locally abundant, toolmakers employed non-random selection criteria resulting in generally lower concentrations of microlites in their obsidian tools.

  4. Evidences for disruption of a crystallizing front in a magma chamber during caldera collapse: an example from the Breccia Museo unit (Campanian Ignimbrite eruption, Italy)

    Science.gov (United States)

    Fulignati, P.; Marianelli, P.; Proto, M.; Sbrana, A.

    2004-05-01

    This work is focused on juvenile components and some cognate xenoliths of the Breccia Museo (BM) unit. The BM is a coarse-grained proximal unit of the caldera-forming phase of the Ignimbrite Campana (IC) eruption, southern Italy. The BM products show some peculiar characteristics that distinguish them from the other IC deposits. In particular, different types of pumice fragments constitute the juvenile fraction and their crystal contents are remarkably higher than the other IC units. Slightly porphyritic and highly porphyritic trachytic to phonolitic pumices were distinguished in each sample and investigated separately for mineralogy, matrix glass composition, melt and fluid inclusion studies. Most feldspar crystals may have formed at the margins of the magma chamber and the crystal content of both types of pumice fragments can be ascribed to variable entrainment of these crystals (from the solidification front) by the melt. Variably porphyritic (<5 to 30 vol% phenocrysts) pumice and completely crystallized nodules may represent samples of progressively crystallized magma at the chamber walls. Crystallization temperatures of magmas and xenoliths were estimated using two independent methods: a two-feldspar geothermometer and the homogenization temperatures of melt and fluid inclusions in clinopyroxene and K-feldspar. The decrease in the estimated crystallization temperatures from the melt (980-850°C) to the nodules (840-820°C) is consistent with a model of decreasing temperature at a magma chamber solidification front. The study of xenoliths revealed that exsolution of a hypersaline aqueous fluid phase occurred at the peripheral parts of the magma chamber.

  5. Cultivation and complete genome sequencing of Gloeobacter kilaueensis sp. nov., from a lava cave in Kīlauea Caldera, Hawai'i.

    Science.gov (United States)

    Saw, Jimmy H W; Schatz, Michael; Brown, Mark V; Kunkel, Dennis D; Foster, Jamie S; Shick, Harry; Christensen, Stephanie; Hou, Shaobin; Wan, Xuehua; Donachie, Stuart P

    2013-01-01

    The ancestor of Gloeobacter violaceus PCC 7421(T) is believed to have diverged from that of all known cyanobacteria before the evolution of thylakoid membranes and plant plastids. The long and largely independent evolutionary history of G. violaceus presents an organism retaining ancestral features of early oxygenic photoautotrophs, and in whom cyanobacteria evolution can be investigated. No other Gloeobacter species has been described since the genus was established in 1974 (Rippka et al., Arch Microbiol 100:435). Gloeobacter affiliated ribosomal gene sequences have been reported in environmental DNA libraries, but only the type strain's genome has been sequenced. However, we report here the cultivation of a new Gloeobacter species, G. kilaueensis JS1(T), from an epilithic biofilm in a lava cave in Kīlauea Caldera, Hawai'i. The strain's genome was sequenced from an enriched culture resembling a low-complexity metagenomic sample, using 9 kb paired-end 454 pyrosequences and 400 bp paired-end Illumina reads. The JS1(T) and G. violaceus PCC 7421(T) genomes have little gene synteny despite sharing 2842 orthologous genes; comparing the genomes shows they do not belong to the same species. Our results support establishing a new species to accommodate JS1(T), for which we propose the name Gloeobacter kilaueensis sp. nov. Strain JS1(T) has been deposited in the American Type Culture Collection (BAA-2537), the Scottish Marine Institute's Culture Collection of Algae and Protozoa (CCAP 1431/1), and the Belgian Coordinated Collections of Microorganisms (ULC0316). The G. kilaueensis holotype has been deposited in the Algal Collection of the US National Herbarium (US# 217948). The JS1(T) genome sequence has been deposited in GenBank under accession number CP003587. The G+C content of the genome is 60.54 mol%. The complete genome sequence of G. kilaueensis JS1(T) may further understanding of cyanobacteria evolution, and the shift from anoxygenic to oxygenic photosynthesis.

  6. Sulfurihydrogenibium rodmanii sp. nov., a sulfur-oxidizing chemolithoautotroph from the Uzon Caldera, Kamchatka Peninsula, Russia, and emended description of the genus Sulfurihydrogenibium.

    Science.gov (United States)

    O'Neill, Andrew H; Liu, Yitai; Ferrera, Isabel; Beveridge, Terry J; Reysenbach, Anna-Louise

    2008-05-01

    Four thermophilic, sulfur-oxidizing, chemolithoautotrophic strains with >99 % 16S rRNA gene sequence similarity were isolated from terrestrial hot springs in the Geyser Valley and the Uzon Caldera, Kamchatka, Russia. One strain, designated UZ3-5T, was characterized fully. Cells of UZ3-5T were Gram-negative, motile, slightly oval rods (about 0.7 microm wide and 1.0 microm long) with multiple polar flagella. All four strains were obligately microaerophilic chemolithoautotrophs and could use elemental sulfur or thiosulfate as electron donors and oxygen (1-14 %, v/v) as the electron acceptor. Strain UZ3-5T grew at temperatures between 55 and 80 degrees C (optimally at 75 degrees C; 1.1 h doubling time), at pH 5.0-7.2 (optimally at pH 6.0-6.3) and at 0-0.9 % NaCl (optimally in the absence of NaCl). The G+C content of the genomic DNA of strain UZ3-5T was 35 mol%. Phylogenetic analysis revealed that strain UZ3-5T was a member of the genus Sulfurihydrogenibium, its closest relative in culture being Sulfurihydrogenibium azorense Az-Fu1T (98.3 % 16S rRNA gene sequence similarity). On the basis of its physiological and molecular characteristics, strain UZ3-5T represents a novel species of the genus Sulfurihydrogenibium, for which the name Sulfurihydrogenibium rodmanii sp. nov. is proposed. The type strain is UZ3-5T (=OCM 900T =ATCC BAA-1536T =DSM 19533T).

  7. Dissulfurimicrobium hydrothermale gen. nov., sp. nov., a thermophilic, autotrophic, sulfur-disproportionating deltaproteobacterium isolated from a hydrothermal pond of Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Slobodkin, A I; Slobodkina, G B; Panteleeva, A N; Chernyh, N A; Novikov, A A; Bonch-Osmolovskaya, E A

    2015-12-08

    A thermophilic, anaerobic, chemolithoautotrophic bacterium (strain Sh68T) was isolated from a hydrothermal pond at Uzon Caldera, Kamchatka, Russia using anoxic medium with elemental sulfur as the only energy source. Cells of strain Sh68T were Gram-negative rods, 0.5 to 0.8 μm in diameter and 1.2 to 2.0 μm in length, motile with flagella. The temperature range for growth was 30-65oC, with an optimum at 50-52oC. The pH range for growth was 5.2-7.5, with an optimum growth at 6.0-6.2. Growth of strain Sh68T was observed at NaCl concentrations ranging from 0 to 2.3% (w/v). Strain Sh68T grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. The growth was enhanced in the presence of poorly crystalline Fe(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain Sh68T was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor neither with H2 nor organic electron donors. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the class Deltaproteobacteria and it most closely related to Dissulfuribacter thermophilus (90.0% sequence similarity). On the basis of its physiological properties and results of phylogenetic analyses, strain Sh68T is considered to represent a novel species of a new genus, for which the name Dissulfurimicrobium hydrothermale gen. nov., sp. nov. is proposed. The type strain of Dissulfurimicrobium hydrothermale is Sh68T (=JCM 19990T =VKM B-2854T). This is the first description of sulfur-disproportionating thermophile from a terrestrial ecosystem.

  8. A thermophilic, hydrogenogenic and carboxydotrophic bacterium, Calderihabitans maritimus gen. nov., sp. nov., from a marine sediment core of an undersea caldera.

    Science.gov (United States)

    Yoneda, Yasuko; Yoshida, Takashi; Yasuda, Hisato; Imada, Chiaki; Sako, Yoshihiko

    2013-10-01

    A hydrogenogenic, carboxydotrophic marine bacterium, strain KKC1(T), was isolated from a sediment core sample taken from a submerged marine caldera. Cells were non-motile, Gram-stain-negative, 1.0-3.0 µm straight rods, often observed with round endospores. Strain KKC1(T) grew at 55-68 °C, pH 5.2-9.2 and 0.8-14 % (w/v) salinity. Optimum growth occurred at 65 °C, pH 7.0-7.5 and 2.46 % salinity with a doubling time of 3.7 h. The isolate grew chemolithotrophically, producing H2 from carbon monoxide (CO) oxidation with reduction of various electron acceptors, e.g. sulfite, thiosulfate, fumarate, ferric iron and AQDS (9,10-anthraquinone 2,6-disulfonate). KKC1(T) grew heterotrophically on pyruvate, lactate, fumarate, glucose, fructose and mannose with thiosulfate as an electron acceptor. When grown mixotrophically on CO and pyruvate, C16 : 0 constituted almost half of the total cellular fatty acids. The DNA G+C content was 50.6 mol%. The 16S rRNA gene sequence of KKC1(T) was most closely related to those of members of the genus Moorella with similarity ranging from 91 to 89 %. Based on physiological and phylogenetic novelty, we propose the isolate as a representative of a new genus and novel species with the name Calderihabitans maritimus gen. nov., sp. nov.; the type strain of the type species is KKC1(T) ( = DSM 26464(T) = NBRC 109353(T)).

  9. Scenario earthquake hazards for the Long Valley Caldera-Mono Lake area, east-central California (ver. 2.0, January 2018)

    Science.gov (United States)

    Chen, Rui; Branum, David M.; Wills, Chris J.; Hill, David P.

    2014-06-30

    As part of the U.S. Geological Survey’s (USGS) multi-hazards project in the Long Valley Caldera-Mono Lake area, the California Geological Survey (CGS) developed several earthquake scenarios and evaluated potential seismic hazards, including ground shaking, surface fault rupture, liquefaction, and landslide hazards associated with these earthquake scenarios. The results of these analyses can be useful in estimating the extent of potential damage and economic losses because of potential earthquakes and also for preparing emergency response plans.The Long Valley Caldera-Mono Lake area has numerous active faults. Five of these faults or fault zones are considered capable of producing magnitude ≥6.7 earthquakes according to the Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) developed by the 2007 Working Group on California Earthquake Probabilities (WGCEP) and the USGS National Seismic Hazard Mapping Program. These five faults are the Fish Slough, Hartley Springs, Hilton Creek, Mono Lake, and Round Valley Faults. CGS developed earthquake scenarios for these five faults in the study area and for the White Mountains Fault Zone to the east of the study area.In this report, an earthquake scenario is intended to depict the potential consequences of significant earthquakes. A scenario earthquake is not necessarily the largest or most damaging earthquake possible on a recognized fault. Rather it is both large enough and likely enough that emergency planners should consider it in regional emergency response plans. In particular, the ground motion predicted for a given scenario earthquake does not represent a full probabilistic hazard assessment, and thus it does not provide the basis for hazard zoning and earthquake-resistant building design.Earthquake scenarios presented here are based on fault geometry and activity data developed by the WGCEP, and are consistent with the 2008 Update of the United States National Seismic Hazard Maps (NSHM). Alternatives

  10. Timescales of magmatic processes prior to the ˜4.7 ka Agnano-Monte Spina eruption (Campi Flegrei caldera, Southern Italy) based on diffusion chronometry from sanidine phenocrysts

    Science.gov (United States)

    Iovine, Raffaella Silvia; Fedele, Lorenzo; Mazzeo, Fabio Carmine; Arienzo, Ilenia; Cavallo, Andrea; Wörner, Gerhard; Orsi, Giovanni; Civetta, Lucia; D'Antonio, Massimo

    2017-02-01

    Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (˜4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera.

  11. Dynamics of an open basaltic magma system: The 2008 activity of the Halema‘uma‘u Overlook vent, Kīlauea Caldera

    Science.gov (United States)

    Eychenne, Julia; Houghton, Bruce F.; Swanson, Don; Carey, Rebecca; Swavely, Lauren

    2015-01-01

    On March 19, 2008 a small explosive event accompanied the opening of a 35-m-wide vent (Overlook vent) on the southeast wall of Halema‘uma‘u Crater in Kīlauea Caldera, initiating an eruptive period that extends to the time of writing. The peak of activity, in 2008, consisted of alternating background open-system outgassing and spattering punctuated by sudden, short-lived weak explosions, triggered by collapses of the walls of the vent and conduit. Near-daily sampling of the tephra from this open system, along with exceptionally detailed observations, allow us to study the dynamics of the activity during two eruptive sequences in late 2008. Each sequence includes background activity preceding and following one or more explosions in September and October 2008 respectively. Componentry analyses were performed for daily samples to characterise the diversity of the ejecta. Nine categories of pyroclasts were identified in all the samples, including wall-rock fragments. The six categories of juvenile clasts can be grouped in three classes based on vesicularity: (1) poorly, (2) uniformly highly to extremely, and (3) heterogeneously highly vesicular. The wall-rock and juvenile clasts show dissimilar grainsize distributions, reflecting different fragmentation mechanisms. The wall-rock particles formed by failure of the vent and conduit walls above the magma free surface and were then passively entrained in the eruptive plume. The juvenile componentry reveals consistent contrasts in degassing and fragmentation processes before, during and after the explosive events. We infer a crude ‘layering’ developed in the shallow melt, in terms of both rheology and bubble and volatile contents, beneath a convecting free surface during background activity. A tens-of-centimetres thick viscoelastic surface layer was effectively outgassed and relatively cool, while at depths of less than 100 m, the melt remained slightly supersaturated in volatiles and actively vesiculating

  12. Thermalkalibacillus uzonensis gen. nov. sp. nov, a novel aerobic alkali-tolerant thermophilic bacterium isolated from a hot spring in Uzon Caldera, Kamchatka.

    Science.gov (United States)

    Zhao, Weidong; Weber, Carolyn; Zhang, Chuanlun L; Romanek, Christopher S; King, Gary M; Mills, Gary; Sokolova, Tatyana; Wiegel, Juergen

    2006-08-01

    A novel thermophilic, alkali-tolerant, and CO-tolerant strain JW/WZ-YB58(T) was isolated from green mat samples obtained from the Zarvarzin II hot spring in the Uzon Caldera, Kamchatka (Far East Russia). Cells were Gram-type and Gram stain-positive, strictly aerobic, 0.7-0.8 mum in width and 5.5-12 mum in length and produced terminal spherical spores of 1.2-1.6 mum in diameter with the mother cell swelling around 2 mum in diameter (drumstick-type morphology). Cells grew optimally at pH(25 degrees C) 8.2-8.4 and temperature 50-52 degrees C and tolerated maximally 6% (w/v) NaCl. They were strict heterotrophs and could not use either CO or CO(2 )(both with or without H(2)) as sole carbon source, but tolerated up to 90% (v/v) CO in the headspace. The isolate grew on various complex substrates such as yeast extract, on carbohydrates, and organic acids, which included starch, D: -galactose, D: -mannose, glutamate, fumarate and acetate. Catalase reaction was negative. The membrane polar lipids were dominated by branched saturated fatty acids, which included iso-15:0 (24.5%), anteiso-15:0 (18.3%), iso-16:0 (9.9%), iso-17:0 (17.5%) and anteiso-17:0 (9.7%) as major constituents. The DNA G+C content of the strain is 45 mol%. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain JW/WZ-YB58(T) is distantly (<93% similarity) related to members of Bacillaceae. On the basis of 16S rRNA gene sequence, physiological and phenotypic characteristics, the isolate JW/WZ-YB58(T) (ATCC BAA-1258; DSM 17740) is proposed to be the type strain for the type species of the new taxa within the family Bacillaceae, Thermalkalibacillus uzoniensis gen. nov. sp. nov. The Genbank accession number for the 16S rRNA gene sequence is DQ221694.

  13. The Black-tailed Antechinus, Antechinus arktos sp. nov.: a new species of carnivorous marsupial from montane regions of the Tweed Volcano caldera, eastern Australia.

    Science.gov (United States)

    Baker, Andrew M; Mutton, Thomas Y; Hines, Harry B; Dyck, Steve Van

    2014-02-17

    We describe a new species of dasyurid marsupial within the genus Antechinus that was previously known as a northern outlier of Dusky Antechinus (A. swainsonii). The Black-tailed Antechinus, Antechinus arktos sp. nov., is known only from areas of high altitude and high rainfall on the Tweed Volcano caldera of far south-east Queensland and north-east New South Wales, Australia. Antechinus arktos formerly sheltered under the taxonomic umbrella of A. swainsonii mimetes, the widespread mainland form of Dusky Antechinus. With the benefit of genetic hindsight, some striking morphological differences are herein resolved: A. s. mimetes is more uniformly deep brown-black to grizzled grey-brown from head to rump, with brownish (clove brown-raw umber) hair on the upper surface of the hindfoot and tail, whereas A. arktos is more vibrantly coloured, with a marked change from greyish-brown head to orange-brown rump, fuscous black on the upper surface of the hindfoot and dense, short fur on the evenly black tail. Further, A. arktos has marked orange-brown fur on the upper and lower eyelid, cheek and in front of the ear and very long guard hairs all over the body; these characters are more subtle in A. s. mimetes. There are striking genetic differences between the two species: at mtDNA, A. s. mimetes from north-east New South Wales is 10% divergent to A. arktos from its type locality at Springbrook NP, Queensland. In contrast, the Ebor A. s. mimetes clades closely with conspecifics from ACT and Victoria. A. arktos skulls are strikingly different to all subspecies of A. swainsonii. A. arktos are markedly larger than A. s. mimetes and A. s. swainsonii (Tasmania) for a range of craniodental measures. Antechinus arktos were historically found at a few proximate mountainous sites in south-east Queensland, and have only recently been recorded from or near the type locality. Even there, the species is likely in low abundance. The Black-tailed Antechinus has plausibly been detrimentally

  14. Discovery of a Plains Caldera Complex and Extinct Lava Lake in Arabia Terra, Mars: Implications for the Discovery of Additional Highland Volcanic Source Regions

    Science.gov (United States)

    Bleacher, Jacob; Michalski, Joseph

    2012-01-01

    Several irregularly shaped topographic depressions occur near the dichotomy boundary in northern Arabia Terra, Mars. The geomorphology of these features suggests that they formed by collapse, opposed to meteor impact. At least one depression (approx.55 by 85 km) displays geologic features indicating a complex, multi-stage collapse history. Features within and around the collapse structure indicate volcanic processes. The complex occurs within Hesperian ridged plains of likely volcanic origin and displays no crater rim or evidence for ejecta. Instead the depression consists of a series of circumferential graben and down-dropped blocks which also display upper surfaces similar to ridged plain lavas. Large blocks within the depression are tilted towards the crater center, and display graben that appear to have originally been linked with circumferential graben outside of the complex related to earlier collapse events. A nearly 700 m high mound exists along a graben within the complex that might be a vent. The deepest depression displays two sets of nearly continuous terraces, which we interpret as high-stands of a drained lava lake. These features appear similar to the black ledge described during the Kilauea Iki eruption in 1959. A lacustrine origin for the terraces seems unlikely because of the paucity of channels found in or around the depression that could be linked to aqueous surface processes. In addition, there is no obvious evidence for lacustrine sediments within the basin. Together with the presence of significant faulting that is indicative of collapse we conclude that this crater complex represents a large caldera formed in the Late Noachian to Early Hesperian. Other linear and irregular depressions in the region also might be linked to ancient volcanism. If that hypothesis is correct, it suggests that northern Arabia Terra could contain a large, previously unrecognized highland igneous province. Evacuation of magma via explosive and effusive activity

  15. Crustal-scale recycling in caldera complexes and rift zones along the Yellowstone hotspot track: O and Hf isotopic evidence in diverse zircons from voluminous rhyolites of the Picabo volcanic field, Idaho

    Science.gov (United States)

    Drew, Dana L.; Bindeman, Ilya N.; Watts, Kathryn E.; Schmitt, Axel K.; Fu, Bin; McCurry, Michael

    2013-11-01

    Rhyolites of the Picabo volcanic field (10.4-6.6 Ma) in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain (SRP), and within a deep (>3 km) borehole near the central axis of the Yellowstone hotspot track. In this study we present new O and Hf isotope data and U-Pb geochronology for individual zircons, O isotope data for major phenocrysts (quartz, plagioclase, and pyroxene), whole rock Sr and Nd isotope ratios, and whole rock geochemistry for a suite of Picabo rhyolites. We synthesize our new datasets with published Ar-Ar geochronology to establish the eruptive framework of the Picabo volcanic field, and interpret its petrogenetic history in the context of other well-studied caldera complexes in the SRP. Caldera complex evolution at Picabo began with eruption of the 10.44±0.27 Ma (U-Pb) Tuff of Arbon Valley (TAV), a chemically zoned and normal-δ18O (δ18O magma=7.9‰) unit with high, zoned 87Sr/86Sri (0.71488-0.72520), and low-ɛNd(0) (-18) and ɛHf(0) (-28). The TAV and an associated post caldera lava flow possess the lowest ɛNd(0) (-23), indicating ˜40-60% derivation from the Archean upper crust. Normal-δ18O rhyolites were followed by a series of lower-δ18O eruptions with more typical (lower crustal) Sr-Nd-Hf isotope ratios and whole rock chemistry. The voluminous 8.25±0.26 Ma West Pocatello rhyolite has the lowest δ18O value (δ18Omelt=3.3‰), and we correlate it to a 1,000 m thick intracaldera tuff present in the INEL-1 borehole (with published zircon ages 8.04-8.35 Ma, and similarly low-δ18O zircon values). The significant (4-5‰) decrease in magmatic-δ18O values in Picabo rhyolites is accompanied by an increase in zircon δ18O heterogeneity from ˜1‰ variation in the TAV to >5‰ variation in the late-stage low-δ18O rhyolites, a trend similar to what is characteristic of Heise and Yellowstone, and which indicates remelting of variably hydrothermally altered tuffs followed by rapid batch

  16. Establishment and Evolution of a new Silicic Magma System North of Yellowstone Caldera: Geochronology, Geochemistry and Petrographic Relationships of Extracaldera Basalts and Rhyolites in the Norris-Mammoth Corridor

    Science.gov (United States)

    Spell, T. L.; Smith, E. I.; Nastanski, N. M.; Bennett, K.

    2004-12-01

    Basalts and rhyolites erupted north of the Yellowstone Caldera following collapse at 640 ka. The geochronology, petrographic relationships and geochemistry of these rocks record the development of a new rhyolitic magma system in the Yellowstone Plateau Volcanic Field. Basaltic lavas were erupted from at least seven shield volcanoes and a cinder cone between 358 ka to 209 ka (40Ar/39Ar eruption ages). Lavas for each center are associated with separate magma batches derived by melting of asthenospheric mantle and incorporating differing amounts of lithospheric mantle. For example, the Swan Lake Flat basalt erupted from four centers and displays decreasing 87Sr/86Sr and increasing ɛ Nd with decreasing age (87Sr/86Sr from 0.7062 to 0.7053, ɛ Nd from -2.5 to +0.18). Trace-element concentrations decrease (e.g., Ba decreases from OIB levels to 0.1 OIB). This change is modeled by a larger MORB and a smaller lithospheric component in the younger lavas. These patterns are similar to those seen prior to previous caldera-forming eruptions at Yellowstone. For example, just before the eruption of the Huckleberry Ridge tuff at 2.2 Ma, the Hepburn Mesa basalt evolved from ɛ Nd -6 to -1 signifying an increased input of asthenospheric mantle derived basalt just prior to caldera formation. Aside from two older rhyolite lavas erupted at 358 ka and 526 ka which are spatially and chemically distinct, all extracaldera rhyolites have characteristics which suggest they are derived from an evolving silicic magma system of substantial longevity (>326 ka to 80 ka). Eruptions occurred in an area ~5-7 km wide by 22 km long (north-south). Mingled lavas consisting of andesite enclaves in rhyolite characterize the early magma system from 316 ka to 263 ka, contemporaneous with Swan Lake Flat basaltic volcanism. Andesite enclave chemistry can be modeled as mixing of Swan Lake Flat basalt with rhyolite from mingled lavas. 206Pb/238U zircon ages from these early rhyolites indicate mean magma

  17. Crustal-scale recycling in caldera complexes and rift zones along the Yellowstone hotspot track: O and Hf isotopic evidence in diverse zircons from voluminous rhyolites of the Picabo volcanic field, Idaho

    Science.gov (United States)

    Drew, Dana L.; Bindeman, Ilya N.; Watts, Kathryn E.; Schmitt, Axel K.; Fu, Bin; McCurry, Michael

    2013-01-01

    Rhyolites of the Picabo volcanic field (10.4–6.6 Ma) in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain (SRP), and within a deep (>3 km) borehole near the central axis of the Yellowstone hotspot track. In this study we present new O and Hf isotope data and U–Pb geochronology for individual zircons, O isotope data for major phenocrysts (quartz, plagioclase, and pyroxene), whole rock Sr and Nd isotope ratios, and whole rock geochemistry for a suite of Picabo rhyolites. We synthesize our new datasets with published Ar–Ar geochronology to establish the eruptive framework of the Picabo volcanic field, and interpret its petrogenetic history in the context of other well-studied caldera complexes in the SRP. Caldera complex evolution at Picabo began with eruption of the 10.44±0.27 Ma (U–Pb) Tuff of Arbon Valley (TAV), a chemically zoned and normal-δ18O (δ18O magma=7.9‰) unit with high, zoned 87Sr/86Sri (0.71488–0.72520), and low-εNd(0) (−18) and εHf(0) (−28). The TAV and an associated post caldera lava flow possess the lowest εNd(0) (−23), indicating ∼40–60% derivation from the Archean upper crust. Normal-δ18O rhyolites were followed by a series of lower-δ18O eruptions with more typical (lower crustal) Sr–Nd–Hf isotope ratios and whole rock chemistry. The voluminous 8.25±0.26 Ma West Pocatello rhyolite has the lowest δ18O value (δ18Omelt=3.3‰), and we correlate it to a 1,000 m thick intracaldera tuff present in the INEL-1 borehole (with published zircon ages 8.04–8.35 Ma, and similarly low-δ18O zircon values). The significant (4–5‰) decrease in magmatic-δ18O values in Picabo rhyolites is accompanied by an increase in zircon δ18O heterogeneity from ∼1‰ variation in the TAV to >5‰ variation in the late-stage low-δ18O rhyolites, a trend similar to what is characteristic of Heise and Yellowstone, and which indicates remelting of variably hydrothermally altered tuffs

  18. Paleomagnetism and rock magnetism of Quaternary volcanic rocks and Late Paleozoic strata, VC-1 core hole, Valles Caldera, New Mexico, with emphasis on remagnetization of Late Paleozoic strata

    Science.gov (United States)

    Geissman, John W.

    1988-06-01

    Paleomagnetic and rock magnetic data obtained from azimuthally unoriented core samples, collected at approximately 1- to 3-m intervals, of Continental Scientific Drilling Program core hole VC-1 have prompted reinterpretations of the Quaternary volcanic stratigraphy intersected by the bore and have aided in evaluating the thermal regime within late Paleozoic strata attending fluid circulation and mineral deposition during and after development of the Toledo and Valles calderas. The results from Quaternary units (Banco Bonito Obsidian: I = +35.4°, a95 = 2.8° (inclination only determinations), n = 33; Battleship Rock Tuff: D = 359.6°, I = +42.4°, a95 = 2.8°, n = 5 site means (surface sites); VC-1 Rhyolite: I = +39.2°, a95 = 12.8°, n = 7; Upper VC-1 Tuff: I = +37.2°, a95 = 10.7°, n = 13; Middle VC-1 Tuff: I = +42.1°, a95 = 2.1°, n = 39; South Mountain Rhyolite: D = 350.9°, I = +49.9°, a95 = 3.4°, n = 10 (one surface site)) are consistent with isotopic age data, indicating that the entire moat volcanic sequence intersected is less than 650 kyr. Monitoring of natural remanent magnetization (NRM) intensity, NRM directions, directions of magnetizations isolated during progressive demagnetization, median destructive forces, and rock magnetization parameters has identified systematic variations within the thick Banco Bonito Obsidian and VC-1 Tuff units. The Permian Abo Formation, Pennsylvanian to earliest Permian Madera Limestone, and Pennsylvanian Sandia Formation typically contain a moderate positive inclination magnetization component (Abo Formation: I = +52.2°, a95 = 7.4°, n = 16; Madera Limestone: I = +58.4°, a95 = 2.8°, n = 105; Sandia Formation: I = +53.9°, a95 = 4.8°, n = 21); when residing in magnetite, it is usually unblocked in the laboratory by 350°C; when carried by hematite it is unblocked by 550°C. A moderate negative inclination (e.g., Madera and Abo strata: D = 173.1°, I = -46.6°, a95 = 5.5°; n = 47 samples; assuming a north seeking

  19. Inyección de aire secundario caliente en calderas de vapor bagaceras y su influencia en el rendimiento térmico Injection of heated secondary air in steam bagasse boilers and its influence on thermal efficiency

    Directory of Open Access Journals (Sweden)

    Marcos A. Golato

    2005-12-01

    Full Text Available Como alternativa para aumentar la eficiencia térmica de calderas bagaceras productoras de vapor, se evalúa la inyección de aire secundario al hogar, previamente calentado. Además, se reúne información sobre la combustión y los factores que influyen en dicho fenómeno. Se calculó el rendimiento térmico en una caldera bagacera con inyección de aire secundario frío, mediante el empleo de balances de masa y energía con datos de ensayos experimentales. Se planteó luego un modelo teórico para el caso de calentar todo este aire secundario, y se determinó el nuevo rendimiento térmico. Finalmente se realizó un análisis técnico-económico para evaluar la rentabilidad del uso de esta tecnología, teniendo en cuenta el ahorro de bagazo y su equivalente en gas natural. Para el caso analizado, los resultados mostraron: aumento del rendimiento térmico de la caldera (1,62 puntos; mejora del índice de generación de vapor (2,27%; reducción del consumo de bagazo (2,45%; aceptable periodo de repago de la inversión (114 días de zafra.Previously heated secondary air injection is evaluated as an alternative to increase thermal efficiency of bagasse steam boilers. Aspects regarding the combustion process and the factors affecting it are also described. Tests were made in a bagasse boiler of a sugar mill. Thermal efficiency of the bagasse boiler with cold secondary air injection was determined by solving mass and energy balances. A new thermal efficiency for the case in which all secondary air is pre-heated with hot gases was determined afterwards. Finally, a technical-economic analysis was made to evaluate the yield of this technology, taking into account bagasse saving and its equivalent in natural gas. For the analyzed case, the results showed: an increase in the thermal efficiency of the boiler (1,62 points; a higher steam production index (2,27%; a reduction in bagasse consumption (2,45%; an acceptable payback period of the investment (114

  20. A combined morphostructural/fluid migration model of Pisciarelli area (Campi Flegrei caldera - CFc) through structural and integrated Terrestrial Laser Scanner (TLS) and Electrical Resistivity Tomography (ERT) analysis.

    Science.gov (United States)

    Caputo, Teresa; Di Giuseppe, Maria Guilia; Troiano, Antonio; Somma, Renato; Isaia, Roberto; Vitale, Stefano; Troise, Claudia; De Natale, Giuseppe

    2014-05-01

    The Solfatara-Pisciarelli (S-P) area was characterized by an intense eruptive activity during the last 5 ka and is presently the highly distributed degassing zones inside the CFC, worldwide well-known for its bradyseismic phenomenon. The last two main crises occurred during the 1970-72 and 1982-84, associated with an overall 3.5 m of ground uplift and an elevate rate of low magnitude seismicity. A strong direct relationship has always been observed between the increase of hydrothermal activity in the S-P area and ground uplift of the CFc. More recently starting from the 2005 a new gradual increase of the hydrothermal activity and ground uplift has been observed, with a steep growth of these effects from 2012, accompanied by seismic events with highest magnitude of 1.8. The Pisciarelli area has been the site of a significant morphological changes of its hydrothermal field including new fumarolic vents and a wide enlargement of a mud pool. Monitoring either landscape deformation than fluids migration of the S-P activity can be considered a good indicator of the volcanic dynamics taking place in the whole CFc caldera. This study shows a first attempt to integrate multidisciplinary approach including volcanological and structural field surveys and studies such us TLS and ERT signals applied to this highly dynamic areas. A detailed geo-structural survey allow us to characterize the complex pattern of fractures and faults recorded in the volcanic rocks in different times of the polyphasic CFc volcanic history. In order to statistically record data about fault and fracture (i) attitudes and (ii) spacing, the scan line method was applied. The whole planar structure is the locus of the well-known fumaroles and mud pools of Pisciarelli. A first time detailed Digital Terrestrial Model DTM of the area with an accuracy of 5cm obtained through TLS has been integrated combining the ERT of the lower part of the area, characterized by a widespread fumarolic activity and soil

  1. Individual magma batches related to the origin of Yellowstone 516-70 ka post-caldera rhyolitic lava flows : results from glass geochemistry.

    Science.gov (United States)

    Stix, J.; Girard, G.

    2007-12-01

    Since its last collapse at 640 ka, Yellowstone caldera has been filled by at least 25 voluminous rhyolitic lava flows totalling more than 900 km3. The oldest identified flows have been erupted at 516 ka, 486-479 ka and 198 ka around the two resurgent domes. Most of the known effusions occurred during relatively short episodes from 165 to 147 ka, 117 to 102 ka, and 72 to 70 ka (Christiansen, 2001), erupting along 2 NNW-trending lineaments which are parallel to regional faults and do not intersect the resurgent domes. The intermittent nature of the volcanism and its spatial distribution remain largely unresolved questions. We used a combination of XRF whole rock major and trace element analyses, electron microprobe and laser ablation-ICP-MS major and trace element glass micro-analyses to examine the temporal and spatial links among the eruptions. Petrologically, we observe a broad-scale differentiation of the lavas over time. Lavas dated at 516 ka have SiO2 contents of 71-72 wt% for bulk rock and 76-76.5 wt% in glass, while 165 ka and younger lavas exhibit SiO2 contents of 76.5-77.5 wt% for both the bulk rock and glass. Mineralogically, the lavas evolve from plagioclase-dominated to sanidine and quartz with no plagioclase. These observations suggest an origin from a common source undergoing slow differentiation. Temporal changes of certain trace elements such as Sr and Ba also suggest a similar evolution. For instance, Sr evolves from 115 ppm in bulk rock in the most primitive lavas of the 516 ka group, to 60 ppm at 198 ka, declining to 2.5 ppm at 70 ka. A simultaneous increasingly negative Eu anomaly is observed in the glass. Such behavior is expected from feldspar fractionation in a long-lived reservoir. Elements such as Y, Th and REE also behave compatibly in the Yellowstone lavas, their concentrations being systematically higher in bulk rock compared to glass. Should the system be a long-lived magma chamber undergoing fractionation, their concentrations over time

  2. Magma mixing and crystal exchange at Yellowstone caldera revealed though sub-crystal-scale age, trace-element, and Hf-isotopic analyses of zircons

    Science.gov (United States)

    Stelten, M. E.; Cooper, K. M.; Vazquez, J. A.; Wimpenny, J.; Yin, Q.

    2011-12-01

    We examine magma mixing and crystal exchange in a young magma reservoir by correlating sub-crystal-scale SIMS age, SIMS trace element, and LA-MC-ICPMS Hf-isotopic data from zircons in the coeval ca. 100ka, yet compositionally distinct rhyolites of the Solfatara Plateau flow (SPF) and Hayden Valley flow (HVF) at Yellowstone Caldera. The SPF and HVF lavas are part of the Central Plateau Member (CPM) of the Plateau Rhyolite that is composed of the youngest intracaldera rhyolite flows at Yellowstone, erupted between ca. 170-70ka. We compare these data to age and trace element data from zircons in 1) the Pitchstone Plateau Flow, West Yellowstone Flow, and Dry Creek Flow of the CPM as representative of main reservoir zircons, 2) the ca. 118ka extracaldera Gibbon River Flow rhyolite (GRF), and 3) the ca. 260ka Scaup Lake Flow of the Upper Basin Member rhyolites. Additionally, we compare the zircon data to new MC-ICPMS Hf-isotopic data from CPM glasses. Correlating age, trace element, and Hf-isotopic data from zircons in the HVF and SPF reveals the presence of four zircon populations. Main reservoir-like (MR-like) zircons have trace element compositions similar to main CPM reservoir zircons, young ages (Lastly, a population of zircons (which we interpret to be inherited) have cores with older ages (>350ka), a range in trace element compositions, and high ɛHf (-5.8 to -3.6) whereas the rims have restricted MR-like trace element compositions and ɛHf within error of CPM glasses. The sense of core to rim zoning specific to each population suggests that each population has its own unique history. The core to rim zoning in MR-like and inherited zircons, from cores with a range of Hf-isotopic compositions to rims similar to CPM glasses, suggests that MR-like and inherited zircons in the SPF and HVF came from distinct high ɛHf magmas and were incorporated into the CPM reservoir. For mixed zircons, the zoning from MR-like or EC-like cores to intermediate rim compositions

  3. Thermoanaerobacter uzonensis sp. nov., an anaerobic thermophilic bacterium isolated from a hot spring within the Uzon Caldera, Kamchatka, Far East Russia.

    Science.gov (United States)

    Wagner, Isaac D; Zhao, Weidong; Zhang, Chuanlun L; Romanek, Christopher S; Rohde, Manfred; Wiegel, Juergen

    2008-11-01

    Several strains of heterotrophic, anaerobic thermophilic bacteria were isolated from hot springs of the Uzon Caldera, Kamchatka, Far East Russia. Strain JW/IW010(T) was isolated from a hot spring within the West sector of the Eastern Thermal field, near Pulsating Spring in the Winding Creek area. Cells of strain JW/IW010(T) were straight to slightly curved rods, 0.5 mum in width and variable in length from 2 to 5 mum and occasionally up to 15 mum, and formed oval subterminal spores. Cells stained Gram-negative, but were Gram-type positive. Growth was observed between 32.5 and 69 degrees C with an optimum around 61 degrees C (no growth occurred at or below 30 degrees C, or at or above 72 degrees C). The pH(60 degrees C) range for growth was 4.2-8.9 with an optimum at 7.1 (no growth occurred at or below pH(60 degrees C) 3.9, or at 9.2 or above). The shortest observed doubling-time at pH(60 degrees C) 6.9 and 61 degrees C was 30 min. Strain JW/IW010(T) was chemo-organotrophic; yeast extract, peptone, Casamino acids and tryptone supported growth. Yeast extract was necessary for the utilization of non-proteinaceous substrates, and growth was observed with inulin, cellobiose, maltose, sucrose, glucose, fructose, galactose, mannose, xylose, trehalose, mannitol, pyruvate and crotonate. The G+C content of the genomic DNA of strain JW/IW010(T) was 33.6 mol% (HPLC method). The major phospholipid fatty acids were iso-15 : 0 (53.5 %), 15 : 0 (11.8 %), 16 : 0 (7.3 %), 10-methyl 16 : 0 (7.3 %) and anteiso-15 : 0 (5.3 %). 16S rRNA gene sequence analysis placed strain JW/IW010(T) in the genus Thermoanaerobacter of the family 'Thermoanaerobacteriaceae' (Firmicutes), with Thermoanaerobacter sulfurigignens JW/SL-NZ826(T) (97 % 16S rRNA gene sequence similarity) and Thermoanaerobacter kivui DSM 2030(T) (94.5 %) as the closest phylogenetic relatives with validly published names. The level of DNA-DNA relatedness between strain JW/IW010(T) and Thermoanaerobacter sulfurigignens JW/SL-NZ826

  4. Why does the Size of the Laacher See Magma Chamber and its Caldera Size not go together? - New Findings with regard to Active Tectonics in the East Eifel Volcanic Field

    Science.gov (United States)

    Schreiber, Ulrich; Berberich, Gabriele

    2013-04-01

    The East Eifel's early Cenozoic tectonic development is characterized by a main stress field trending in NW-SE direction, causing a re-organisation of postvariscan dextral strike-slip faults in approximately 105° direction, the formation of the tectonic depression of the Neuwieder Basin and small-scale transtension zones. The 105° trending strike-slip faults are staggered in equidistant intervals of several kilometers. This system continues from the Eifel to the North into the Ruhr Carboniferous, where it has been recognized due to the extensive underground coal mining first (Loos et al. 1999). Our recent research on analyses of tectonics in quarries, quartz/ore-dykes, mapping of minerals springs and gas analyses, has revealed a prominent 105° trending strike-slip fault cutting the South of Laacher See ("Laacher See Strike-slip Fault"). Within the Laacher See caldera, the "Laacher See Strike-slip Fault" can be tracked by a wide mofette zone that was mapped with a self-propelled submarine. At present, the "Laacher See Strike-slip Fault" can be tracked from Holzmühlheim in the West, Spessart, Wehrer Kessel, Laacher See, Plaidt to Bad Ems and furthermore to the South-East. Along this direction five intersections points of the "Laacher See Strike-slip Fault" with the Lahn River are documented, creating small-scale mofette fields in the Lahn River. In the Neuwied Basin, near Plaidt, the "Laacher See Strike-slip Fault" is intersected by the NW-SE-trending Ochtendung Fault. Regional strike-slip faults in combination with block rotation and uplift could have provided the voids for the magma chambers of the Wehrer Kessel and the Laacher See Caldera. Holohan et al. (2005) showed in analogue models that regional strike-slip regimes (including Riedel shears, chamber-localised graben fault, and a partial Y-shear) play a decisive role for caldera formation. In the East Eifel tectonic movement rates of active faults are approx. 1 mm/year (Meyer & Stets 2002, Cambell et al

  5. Diseño de una caldera híbrida (energía solar y leña) para la obtención de aceite esencial de Hierba Luisa utilizando un concentrador Scheffler de 8 m2

    OpenAIRE

    Vidal Porta, Nicolás

    2014-01-01

    La presente tesis comprende el diseño de una caldera híbrida que utilice como fuente de energía la leña y la energía solar concentrada. Ésta deberá suministrar vapor a un equipo de destilación ya existente en las instalaciones del GRUPO de apoyo al sector rural de la Pontificia Universidad Católica del Perú. La caldera utilizará la potencia térmica entregada por un concentrador Scheffler de 8m2 de superficie también perteneciente al GRUPO de la PUCP que se encuentra en la localidad de Huyro, ...

  6. Boiler model of a 300 Mw fossil fuel power plant for the turbine turning simulator; Modelo de caldera de una planta termoelectrica de 300 Mw para el simulador de rodado de turbina

    Energy Technology Data Exchange (ETDEWEB)

    Rossano Roman, Miguel [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1993-07-01

    The objective of the model is to reproduce the behavior of a boiler of a 300 Mw fossil fuel unit, in the training turbine turning simulator. This simulator was designed to be used in the training that is performed in the control rooms or training centers of the fossil fuel power plants of the Comision Federal de Electricidad (CFE). In this article the equations of the model for a 300 Mw thermal plant are described, based in balances and physical relationships. The basic considerations and simplifications are shown. The model considers the combustion in the furnace, the dome, the downcomers, the recirculation pumps, the water walls, the superheater and the reheater. The mass and energy balances take into account the sensible heat of all the constituents involved, as well as the combustion heat. Heat transference zones by convection or by a combined mechanism convective-radiant, in the boiler furnace, are considered. The dome pressure is modeled with basis in the mass and energy balance, considering all the existing sources and sinks. The simulation also reflects the pressure transients due to thermal variations, combustion variations, and steam demand variations. The heat transference by convection is considered for all the tube banks along the combustion gases path to the stack. Comparisons were made with the design and operation data of the power station, using a selection of transient states to demonstrate de model fidelity. This selection was focussed of transients states, at the unit start up, since in this operation stage the turning and the heating of the turbine is accomplished. [Espanol] El objetivo del modelo es reproducir el comportamiento de una caldera de una unidad termoelectrica de 300 Mw, en el simulador para entrenamiento en rodado de turbina. Este simulador se diseno para ser utilizado en el entrenamiento que se realiza en los cuartos de control o centros de entrenamiento de las plantas termoelectricas de la Comision Federal de Electricidad (CFE

  7. Modelación energética y operacional del sistema de agua de alimentar caldera de una central termoeléctrica; Modeling energetic and operational of the boiler feed water system of a power plant

    Directory of Open Access Journals (Sweden)

    Ernesto Miguel Solís Alemán

    2015-09-01

    Full Text Available Se propone un modelo combinado basado en la implementación paralela de dos aproximadores funcionales, utilizando una red neuronal del tipo (MLP y una regresión estadística, para la obtención de las características energéticas y de operación actual del Sistema de Agua de Alimentar Caldera (SAAC en una Central Termoeléctrica (CTE, en la cual se regula el flujo de agua a la caldera por variación de velocidad. La respuesta del modelo combinado se obtiene a partir de la suma ponderada de cada aproximador funcional. Dicho modelo es utilizado para relacionar el consumo de corriente y la posición del variador de velocidad, en función de la presión de descarga y el flujo entregado por cada bomba del SAAC. Para el ajuste de los modelos se utilizan mediciones almacenadas en el archivo histórico del sistema SCADA, donde se aplica un método de procesamiento de datos para eliminar ruidos que pueden afectar el ajuste de los modelos propuestos.Is proposed a combined model based on the parallel implementation of two functional approximators, using a neural network of the type (MLP and a statistical regression to obtain the actual energetic and operation characteristics of the Boiler Feed Water System (BFWS in a Power Plant, in which the water flow to the boiler is controlled by variation speed. The response of the combined model is obtained from the weighted sum of each functional approximator. This model is used to relate the current consumption and the position of the speed variator, in function of the discharge pressure and flow delivered by each pump of the BFWS. For the fit of the models is used save measurements of the historical file of the SCADA system, where is applied a data processing method to eliminating noise that can affect the fit of the models proposed.

  8. NEAR AND FAR-FIELD EFFECTS OF TSUNAMIS GENERATED BY THE PAROXYSMAL ERUPTIONS, EXPLOSIONS, CALDERA COLLAPSES AND MASSIVE SLOPE FAILURES OF THE KRAKATAU VOLCANO IN INDONESIA ON AUGUST 26-27, 1883

    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis

    2003-01-01

    Full Text Available The paroxysmal phases of Krakatau's volcanic activity on August 26-27, 1883, included numerous submarine Surtsean (phreatomagmatic eruptions, three sub air Plinian eruptions from the three main craters of Krakatau on Rakata island, followed by a fourth gigantic, sub air, Ultra-Plinian explosion. Landslides, flank failures, subsidences and a multiphase massive caldera collapse of the volcano - beginning near the Perbowetan crater on the northern portion of Rakata and followed by a collapse of the Danan crater - occurred over a period of at least 10 hours. The first of the three violent explosions occurred at 17: 07 Greenwich time (GMT on August 26.The second and third eruptions occurred at 05:30 GMT and at 06:44 GMT on August 27. Each of these events, as well as expanding gases from the submarine phreatomagmatic eruptions, lifted the water surrounding the island into domes or truncated cones that must have been about 100 meters or more in height. The height of the resulting waves attenuated rapidly away from the source because of their short periods and wavelengths. It was the fourth colossal explosion (VEI=6 and the subsequent massive f lank failure and caldera collapse of two thirds of Rakata Island, at 10:02 a.m., on August 27 that generated the most formidable of the destructive tsunami waves. A smaller fifth explosion, which occurred at 10:52 a.m., must have generated another large water cone and sizable waves. The final collapse of a still standing wall of Krakatau - which occurred several hours later at 16:38, generated additional waves.The near field effects of the main tsunami along the Sunda Strait in Western Java and Southern Sumatra, were devastating. Within an hour after the fourth explosion/caldera collapse, waves reaching heights of up to 37 m (120 feet destroyed 295 towns and villages and drowned a total of 36,417 people. Because of their short period and wavelength, the wave heights attenuated rapidly with distance away from the

  9. Estudio de modificaciones geométricas en boquillas de calderas piro y acuotubulares para la combustión eficiente de crudos pesados // Study of geometric modifications in pyro and aquatubular mouthpieces of boilers for the efficient combustion of heavy oil

    Directory of Open Access Journals (Sweden)

    E. Lincheta Mesa

    2000-07-01

    Full Text Available Se presenta un estudio de boquillas de quemadores de calderas piro y acuotubulares. Se analizan diferentes variantes en lasdimensiones, forma y posición de los conductos de atomizador que dan paso al combustible y al fluido auxiliar en el casode quemadores con atomización por vapor.En todos los casos se evalúa el cono de pulverización y la calidad del spray, analizando la influencia de la presión deatomización y de la configuración geométrica en la eficiencia de atomización.Se determina la eficiencia de la combustión con varios tipos de boquillas, demostrándose la efectividad de lasmodificaciones introducidas cuando se queman combustibles de menor calidad.Se concluye que es posible sustituir algunas boquillas de importación y elevar la eficiencia en la combustión de crudospesados y sus mezclas, con un significativo efecto económico y como un paso más en el perfeccionamiento de las CentralesEléctricas del país para el aprovechamiento del crudo nacional.Palabras claves: quemador, atomizador, fuel oil, caldera, generación de vapor, combustibles, combustión._____________________________________________________________________Abstract :It is presented a study of mouthpieces of pyro and aquatubular burners of boilers. Different variants are analyzed indimensions, forms and position of the atomizer conduits that open the way to the fuel and auxiliary fluid in case of burnerswith steam atomization.In all cases, it is evaluated the pulverization cone and the quality of spray, analyzing the influence of atomization pressureand geometric configuration in the atomization efficiency.Estudio de modificaciones geométricas en boquillas de calderas piro y acuotubulares para la combustión eficiente decrudos pesadosThe efficiency of combustion is determined with several types of mouthpieces. The effectiveness of the introducedmodifications in connection with the import mouthpieces is demonstrated when fuels of smaller quality burns.It is

  10. Influencia de la composición y tratamiento térmico sobre el comportamiento a fluencia de aceros ferrítico-martensíticos del tipo 9Cr1MoVNb utilizados en calderas supercríticas

    Directory of Open Access Journals (Sweden)

    Gutiérrez Urrutia, I.

    2000-06-01

    Full Text Available In the present investigation, creep behaviour on various ferritic-martensitic steels (type 9Cr1MoVNb from last generation were studied. They’re amply used as high pressure and temperature tubes in supercritical boilers for advanced thermoelectric plant. The material used was produced with vacuum high frecuency induction furnace hot-rolling followed by normalizing plus and tempering heat treatments. Creep testing carry out with different stress (also constant lower than yield strength (σ < Re and temperatures at 600±50ºC. Influence by variation of some chemical elements (B, Ti, V, Nb, V, C, as well assessment Larson-Miller, Manson-Haferd and Orr-Sherby-Dorn parameters, they’re likewise studied.

    Se estudia el comportamiento a fluencia de varios aceros ferrítico-martensíticos de última generación, del tipo 9Cr1MoVNb, que son ampliamente utilizados como tubos presurizados de alta temperatura en calderas supercríticas para centrales térmicas avanzadas de producción de energía eléctrica. El material utilizado fue fabricado en hornos de inducción de alta frecuencia y al vacío, laminado en caliente y posteriormente aplicado diferentes tratamientos térmicos de Normalizado y Revenido. En los ensayos de fluencia se aplicaron diferentes y ctes. σ < Re y temperaturas de 550, 600 y 650º C. La influencia de la variación de determinados elementos (C, N, V, Nb, Ti, B de su composición química así como observar los valores que toman los parámetros de Larson-Miller, Manson-Haferd y Orr-Sherby-Dorn, son asimismo contemplados.

  11. Influencia de la temperatura de austenización y tiempo de permanencia sobre el tamaño de grano en aceros ferrítico-martensíticos del tipo 9Cr1MoVNb utilizados en calderas supercríticas

    Directory of Open Access Journals (Sweden)

    Gutiérrez-Urrutia, L.

    2001-04-01

    Full Text Available The aim of the present work is to determine the influence of austenitizing temperature holding time and heating velocity on grain size of ferritic-martensitic type 9CrlMoVNb steels developed for Oak Ridge National Laboratories & Combustion Engineering, T91/P91[1] Steels (USA and X10CrMoVNb 9.1 (Europe. The potential benefits of this material, in term of high resistance, good ductily and oxidation resistance, weldability and in particular good high temperature creep strength, are now widely acknowledged, particulary by supercritical boilers (P = 300 bar, T = 550±50 °C. The studied steels have been produced in, high frecuency induction vacum furnaces and hot-rolled.

    Se estudia la influencia de la temperatura de austenización, tiempo de permanencia a esta temperatura y velocidad de calentamiento sobre el tamaño de grano de varios aceros ferrítico-martensíticos de última generación del tipo 9CrlMoVNb, desarrollados por Oak Ridge National Laboratories (ORNL conjuntamente con Combustion Enginering en USA, conocidos por ASME/ASTM por las designaciones T91/P91[1] y en Europa como X10CrMoVNb9.1. Son aceros ductiles y tenaces que presentan muy buenas propiedades de resistencia a fluencia, soldabilidad y conductividad térmica. Son cada vez más utilizados como tubos de alta temperatura (550±50 °C y presión (300 bar en calderas supercríticas para centrales térmicas avanzadas. Los aceros estudiados se han fabricado en hornos de inducción de alta frecuencia al vacío y laminados en caliente.

  12. Monitoring the hydrothermal system in Long Valley caldera, California

    Science.gov (United States)

    Farrar, C.D.; Sorey, M.L.

    1985-01-01

    An ongoing program to monitor the hydrothermal system in Long Valley for changes caused by volcanic or tectonic processes has produced considerable data on the water chemistry and discharge of springs and fluid temperatures and pressures in wells. Chemical and isotopic data collected under this program have greatly expanded the knowledge of chemical variability both in space and time. Although no chemical or isotopic changes in hot spring waters can be attributed directly to volcanic or tectonic processes, changes in hot spring chemistry that have been recorded probably relate to interactions between and variations in the quantity of liquid and gas discharged. Stable carbon isotope data are consistent with a carbon source either perform the mantle or from metamorphosed carbonate rocks. Continuous and periodic measurements of hot spring discharge at several sites show significant co seismic and a seismic changes since 1980.

  13. Peeking Beneath the Caldera: Communicating Subsurface Knowledge of Newberry Volcano

    Science.gov (United States)

    Mark-Moser, M.; Rose, K.; Schultz, J.; Cameron, E.

    2016-12-01

    "Imaging the Subsurface: Enhanced Geothermal Systems and Exploring Beneath Newberry Volcano" is an interactive website that presents a three-dimensional subsurface model of Newberry Volcano developed at National Energy Technology Laboratory (NETL). Created using the Story Maps application by ArcGIS Online, this format's dynamic capabilities provide the user the opportunity for multimedia engagement with the datasets and information used to build the subsurface model. This website allows for an interactive experience that the user dictates, including interactive maps, instructive videos and video capture of the subsurface model, and linked information throughout the text. This Story Map offers a general background on the technology of enhanced geothermal systems and the geologic and development history of Newberry Volcano before presenting NETL's modeling efforts that support the installation of enhanced geothermal systems. The model is driven by multiple geologic and geophysical datasets to compare and contrast results which allow for the targeting of potential EGS sites and the reduction of subsurface uncertainty. This Story Map aims to communicate to a broad audience, and provides a platform to effectively introduce the model to researchers and stakeholders.

  14. Age and impacts of the caldera-forming Aniakchak II eruption in western Alaska

    NARCIS (Netherlands)

    Blackford, J. J.; Payne, R. J.; Heggen, M. P.; Caballero, A. de la Riva; van der Plicht, J.

    The mid-Holocene eruption of Aniakchak volcano (Aniakchak II) in southwest Alaska was among the largest eruptions globally in the last 10,000 years (VEI-6). Despite evidence for possible impacts on global climate, the precise age of the eruption is not well-constrained and little is known about

  15. Some water mites (Acari, Hydrachnidia from Caldera de Taburiente National Park (La Palma, Canary Islands

    Directory of Open Access Journals (Sweden)

    Valdecasas, A. G.

    2002-12-01

    Full Text Available Protzia cf. lata, Lebertia fimbriata Thor, 1899; Limnesia martianezi Lundblad, 1962; Atractides gomerae Lundblad, 1962 are mentioned for the first time for the island of La Palma: Feltria menzeli Walter, 1922 and Aturus atlantica Lundblad, 1942 for the first time in the Canary islands. It is the first record of the genus Feltria Koenike, 1892 in Macaronesia.

    Protzia cf. lata, Lebertia fimbriata Thor, 1899; Limnesia martianezi Lundblad, 1962; Atractides gomerae Lundblad, 1962 han sido encontradas por primera vez en la isla de La Palma: Feltria menzeli Walter, 1922 y Aturus atlantica Lundblad, 1942 son nueva cita para las islas Canarias y es la primera vez que se registra el género Feltria Koenike, 1892 en Macaronesia.

  16. Genuine modern analogues of Precambrian stromatolites from caldera lakes of Niuafo'ou Island, Tonga.

    Science.gov (United States)

    Kazmierczak, Józef; Kempe, Stephan

    2006-03-01

    Calcareous or dolomitic, often secondarily silicified, laminated microbial structures known as stromatolites are important keys to reconstruct the chemical and biotic evolution of the early ocean. Most authors assume that cyanobacteria-associated microbialitic structures described from Shark Bay, Western Australia, and Exuma Sound, Bahamas, represent modern marine analogues for Precambrian stromatolites. Although they resemble the Precambrian forms macroscopically, their microstructure and mineralogical composition differ from those characterizing their purported ancient counterparts. Most Precambrian stromatolites are composed of presumably in situ precipitated carbonates, while their assumed modern marine analogues are predominantly products of accretion of grains trapped and bound by microbial, predominantly cyanobacterial, benthic mats and biofilms and only occasionally by their physicochemical activity. It has therefore been suggested that the carbonate chemistry of early Precambrian seawater differed significantly from modern seawater, and that some present-day quasi-marine or non-marine environments supporting growth of calcareous microbialites reflect the hydrochemical conditions controlling the calcification potential of Precambrian microbes better than modern seawater. Here we report the discovery of a non-marine environment sustaining growth of calcareous cyanobacterial microbialites showing macroscopic and microscopic features resembling closely those described from many Precambrian stromatolites.

  17. Giant caldera in the Arctic Ocean: Evidence of the catastrophic eruptive event

    National Research Council Canada - National Science Library

    Alexey Piskarev; Daria Elkina

    2017-01-01

    ... (Yellowstone and Toba). Time of the eruption is estimated as ~1.1 Ma. Thin layers of the volcanic material related to the eruption had been identified in sedimentary cores located about 1000 km away from the Gakkel Ridge...

  18. Magma storage and evolution of the Central Plateau Member Rhyolites, Yellowstone caldera, USA

    Science.gov (United States)

    Befus, K. S.

    2015-12-01

    We use volatile and trace element contents from quartz-hosted melt inclusions to place constraints on the pre-eruptive storage and evolution of 6 lavas and 3 tuffs from the Central Plateau Member Rhyolites, Yellowstone. Overall, inclusions contain 1.0-2.5% H2O and 50-600 ppm CO2. Individual units have more restricted volatile contents, and define regions in H2O and CO2 space with internal variability of ±0.5 wt.% and ±100 ppm, respectively. Water contents in both lavas and pyroclastic units are similar, but CO2 contents vary and can be used to separate the units as CO2-rich and CO2-poor. CO2-rich units contain 300 to 600 ppm CO2 (Tuff of Bluff Point, Pitchstone Plateau, Trischmann Knob, Buffalo Lake, Summit Lake). CO2-poor units contain 50 to 200 ppm CO2 (Solfatara Plateau, West Yellowstone, Tuff of Cold Mountain Creek, unnamed tuff on Douglas Knob). Volatile contents do not correlate with eruption age, volume, or style. Inclusions from individual units contain incompatible trace-element concentrations that range from primitive to evolved. Incompatible elements within each unit increase systematically from primitive inclusions (units differ by <20%), to more evolved inclusions, and finally to highly evolved matrix. The inclusions preserve a systematic evolution produced by crystal fractionation, which we estimate to range from 38±8 wt.% to 54±11 wt.%. Inclusions from the Tuffs of Bluff Point and Cold Mountain Creek display similar evolution, except that matrix glass in those tuffs is less evolved than the inclusions. We infer the magmas were volatile-saturated at depth because H2O and CO2 do not correlate positively with incompatible elements. If true, then the CO2-rich magmas were stored at 90 to 150 MPa and contained a fluid that was 60-75 mol.% CO2, whereas CO2-poor magmas were stored at 50 to 70 MPa and contained a more H2O-rich fluid (XCO2 = 40-60%). The variations in pressure/depth suggest the magmas were at least temporarily stored as separate batches that followed similar evolutionary paths in the shallow crust.

  19. Ascent Rates of Rhyolitic Magma During the Opening Stages of Explosive Caldera-Forming Eruptions

    Science.gov (United States)

    Myers, M.; Wallace, P. J.; Wilson, C. J. N.; Watkins, J. M.; Liu, Y.; Morgan, D. J.

    2016-12-01

    We investigate the timescales of rhyolitic magma ascent for three supereruptions that show contrasting eruptive behavior at eruption onset: (1) the Bishop Tuff, CA where early fallout graded directly into climactic eruption, (2) the Oruanui eruption, Taupo NZ, which experienced a significant time break between the initial fallout and subsequent activity and (3) the Huckleberry Ridge, Yellowstone where initial activity was episodic, with eruptive pauses totaling days to weeks. During ascent, decompression causes volatile exsolution from the host melt, creating H2O and CO2 gradients in reentrants (REs; unsealed inclusions) that can be modeled to estimate ascent timescales1,2,3. Using a code1 refined to include an error minimization function, we present modeled ascent rates for REs from Huckleberry Ridge (n=10), Bishop (n=14), and Oruanui (n=4), measured using FTIR (20 μm resolution, 4-15 points per RE). Best-fit profiles for the Bishop REs give ascent rates of 0.6-30 m/s, which overlap with those of the Huckleberry (0.3-5.5 m/s), but extend to higher values. Although ascent rate and initial eruptive behavior are somewhat decoupled, there is an increase in the number of faster ascent rates and greater starting depths with higher stratigraphic height in the Huckleberry Ridge and Bishop fall deposits. Preliminary work on Oruanui REs indicates rates of 0.15-2.0 m/s, which overlie the lower end of the Bishop and Huckleberry REs, in agreement with previous data1. Overall, there is significant overlap between the three datasets (average 4±7 m/s). Our calculated ascent rates fall towards the lower end of ascent rates that have been estimated (5-40 m/s4) using theoretical and numerical modeling of conduit flow for Plinian rhyolitic eruptions below the fragmentation depth. 1 Liu Y et al. 2007: J Geophys Res 112, B06204; 2 Humphreys MCS et al. 2008: Earth Planet Sci Lett 270, 25; 3 Lloyd et al., 2014: J Volcanol Geotherm Res 283, 1; 4Rutherford MJ 2008: Rev Mineral Geochem 69, 241.

  20. Boiling Water at Hot Creek - The Dangerous and Dynamic Thermal Springs in California's Long Valley Caldera

    Science.gov (United States)

    Farrar, Christopher D.; Evans, William C.; Venezky, Dina Y.; Hurwitz, Shaul; Oliver, Lynn K.

    2007-01-01

    The beautiful blue pools and impressive boiling fountains along Hot Creek in east-central California have provided enjoyment to generations of visitors, but they have also been the cause of injury or death to some who disregarded warnings and fences. The springs and geysers in the stream bed and along its banks change location, temperature, and flow rates frequently and unpredictably. The hot springs and geysers of Hot Creek are visible signs of dynamic geologic processes in this volcanic region, where underground heat drives thermal spring activity.

  1. Potassium metasomatism of volcanic and sedimentary rocks in rift basins, calderas and detachment terranes

    Science.gov (United States)

    Chapin, C. E.; Lindley, J. I.

    The chemical, mineralogical, and oxygen-isotopic changes accompanying K-metasomatism are described. The similarities with diagenetic reactions in both deep marine and alkaline, saline-lake environments are noted. The common occurrence of K-metasomatism in upper-plate rocks of detachment terranes indicates that the early stage of severe regional extension causes crustal downwarping and, in arid to semi-arid regions, development of closed hydrographic basins.

  2. Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz.

    Science.gov (United States)

    Budd, David A; Troll, Valentin R; Deegan, Frances M; Jolis, Ester M; Smith, Victoria C; Whitehouse, Martin J; Harris, Chris; Freda, Carmela; Hilton, David R; Halldórsson, Sæmundur A; Bindeman, Ilya N

    2017-01-25

    Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ(18)O values. Overall, Toba quartz crystals exhibit comparatively high δ(18)O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ(18)O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core-rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ(18)O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ(18)O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

  3. Obtención de un modelo de densidad de la Caldera del Teide

    OpenAIRE

    Camacho, Antonio G.; Vieira, Ricardo; Araña, Vicente

    1988-01-01

    Comunicación presentada en la sesión científica de la Real Academia de Ciencias Exactas, Físicas y Naturales, celebrada el día 4 de mayo de 1988. Publicada a su vez en la revista de la "Real Academia de Ciencias Exactas, Físicas y Naturales de Madrid".

  4. Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

    Science.gov (United States)

    Budd, David A.; Troll, Valentin R.; Deegan, Frances M.; Jolis, Ester M.; Smith, Victoria C.; Whitehouse, Martin J.; Harris, Chris; Freda, Carmela; Hilton, David R.; Halldórsson, Sæmundur A.; Bindeman, Ilya N.

    2017-01-01

    Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core-rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

  5. Constraints on tree seedling establishment in montane grasslands of the Valles Caldera, New Mexico

    Science.gov (United States)

    Jonathan D. Coop; Thomas J. Givnish

    2008-01-01

    Montane and subalpine grasslands are prominent, but poorly understood, features of the Rocky Mountains. These communities frequently occur below reversed tree lines on valley floors, where nightly cold air accumulation is spatially coupled with fine soil texture. We used field experiments to assess the roles of minimum temperature, soil texture, grass competition, and...

  6. Numerical models of caldera-scale volcanic eruptions on Earth, Venus, and Mars

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, S.W. [Univ. of British Columbia, British Columbia (Canada)

    1995-09-08

    Volcanic eruptions of gassy magmas on Earth, Venus, and Mars produce plumes with markedly different fluid dynamics regimes. In large part the differences are caused by the differing atmospheric pressures and ratios of volcanic vent pressure to atmospheric pressure. For each of these planets, numerical simulations of an eruption of magma containing 4 weight percent gas were run on a workstation. On Venus the simulated eruption of a pressure-balanced plume formed a dense fountain over the vent and continuous pyroclastic flows. On Earth and Mars, simulated pressure-balanced plumes produced ash columns, ash falls, and possible small pyroclastic flows. An overpressured plume, illustrated for Mars, exhibited a complex supersonic velocity structure and internal shocks. 31 refs., 7 figs., 2 tabs.

  7. Multibeam collection for DRFT04RR: Multibeam data collected aboard Roger Revelle from 2001-08-23 to 2001-09-25, Puerto Caldera, Costa Rica to Puerto Caldera, Costa Rica

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  8. Multibeam collection for MGL1106: Multibeam data collected aboard Marcus G. Langseth from 2011-04-09 to 2011-05-12, departing from Puerto Caldera, Costa Rica and returning to Puerto Caldera, Costa Rica

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  9. Multibeam collection for DRFT03RR: Multibeam data collected aboard Roger Revelle from 2001-07-29 to 2001-08-17, departing from Puerto Caldera, Costa Rica and returning to Puerto Caldera, Costa Rica

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  10. Multibeam collection for VANC02MV: Multibeam data collected aboard Melville from 2002-09-07 to 2002-10-09, Puerto Caldera, Costa Rica to Puerto Caldera, Costa Rica

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  11. Temporal evolution of a post-caldera, mildly peralkaline magmatic system: Furnas volcano, São Miguel, Azores

    Science.gov (United States)

    Jeffery, A. J.; Gertisser, R.; O'Driscoll, B.; Pacheco, J. M.; Whitley, S.; Pimentel, A.; Self, S.

    2016-05-01

    Furnas is one of three active central volcanoes on São Miguel Island, Azores, and is considered to be one of the most hazardous in the archipelago. In this study, the pre-eruptive magma plumbing system of the 10 young (peralkalinity, which contribute to low pre-eruptive melt viscosities and efficient crystal settling. Compositional zoning patterns between individual eruptions cannot be accounted for by periodic tapping of a single magma batch undergoing fractional crystallisation. Instead, up to four individual cycles are recognised, in which a zoned cap of eruptible trachytic magma, formed at the top of the reservoir, was erupted in one or more eruptions and was re-established via intermittent replenishment and subsequent fractional crystallisation.

  12. On the application of Hidden Markov Model and Bayesian Belief Network to seismic noise at Las Canadas Caldera, Tenerife, Spain

    Energy Technology Data Exchange (ETDEWEB)

    Quintero Oliveros, Anggi [Dipartimento di Georisorse e Territorio, Universita di Udine (Italy); Departamento de Ciencias de La Tierra, Universidad Simon Bolivar, Caracas (Venezuela); Carniel, Roberto [Dipartimento di Georisorse e Territorio, Universita di Udine (Italy)], E-mail: roberto.carniel@uniud.it; Tarraga, Marta [Departamento de Volcanologia, Museo Nacional de Ciencias Naturales, CSIC, Madrid (Spain); Aspinall, Willy [Aspinall and Associates, 5 Woodside Close, Beaconsfield, Bucks (United Kingdom)

    2008-08-15

    The Teide-Pico Viejo volcanic complex situated in Tenerife Island (Canary Islands, Spain) has recently shown signs of unrest, long after its last eruptive episode at Chinyero in 1909, and the last explosive episode which happened at Montana Blanca, 2000 years ago. In this paper we study the seismicity of the Teide-Pico Viejo complex recorded between May and December 2004, in order to show the applicability of tools such as Hidden Markov Models and Bayesian Belief Networks which can be used to build a structure for evaluating the probability of given eruptive or volcano-related scenarios. The results support the existence of a bidirectional relationship between volcano-tectonic events and the background seismic noise - in particular its frequency content. This in turn suggests that the two phenomena can be related to one unique process influencing their generation.

  13. Constraints on the upper crustal magma reservoir beneath Yellowstone Caldera inferred from lake-seiche induced strain observations

    Science.gov (United States)

    Luttrell, Karen; Mencin, David; Francis, Oliver; Hurwitz, Shaul

    2013-01-01

    Seiche waves in Yellowstone Lake with a ~78-minute period and heights 11 Pa s. These strain observations and models provide independent evidence for the presence of partially molten material in the upper crust, consistent with seismic tomography studies that inferred 10%–30% melt fraction in the upper crust.

  14. The types of unrest occurring at Campi Flegrei caldera (Southern Italy) since 1982 and the role of magma

    Science.gov (United States)

    Moretti, Roberto; De Natale, Giuseppe; Sarno, Federica; Schiavone, Roberto; Troise, Claudia

    2017-04-01

    The thermodynamic response of a multiphase (at least biphasic) and multicomponent system that has enough degrees of freedom to respond to variations of external constraints consists in re-equilibrating phase proportions and compositions of dissolved components. For volcanic systems in unrest, such as CampiFlegrei, this puts first-order thermal constraints that typically the procedures of geophysical inversion of geodetic and gravimetric data cannot identify.In this study, based on a thermodyamically internally consistent approach to the geochemical data recorded in the last 35 years, we show that: 1) The fumarole-feeding portions of the Solfatara geothermal field have fluid pressures below the lithostatic gradients. Shallow steam condensation occurs certainly in the surroundingsof fumarole emissions, and was attained in few circumstances during the 1982-84 unrest. 2) Inert gases help evaluating the geochemical signature of the deep upcoming gas, not compatible with a magma migrating to shallow depths in recent times. Any magma emplaced at shallow depth should have a volatile content and a size incompatible with geophysical measurements and models on shallow magma emplacement.After exhaustion of the shallow magma emplaced in1982-84, the system is fed by a deep magmatic gas. 3) Gas indicators and the observed increase in magmatic fraction (Y) after year 2000 require a raise in the temperature of the formed hydrothermal vapour and the likely involvement of a supercritical fluid phase. This determines the opening of awindow for magmatic gases at surface, which is however hardly compatible with a magma raising to shallow depths. 4) The unrest style can be related to the P-T-H conditions of the deep hydrothermal vapour. These determine if the pore-filling fluid is a biphasic liquid+vapour. like in 1982-84, when pore overpressures developed under nearly undrained conditions. 5) The nature of the 1982-84 unrest was magmatic, due to the emplacement of a shallow (3-4 km deep) magma. This interfered with the "normal" degassing dynamics of deep (8 km) and regional origin. On the contrary, the post-2005 unrest is unlikely magmatic and likely hydrothermal, following the crystallizing history of the magma emplaced in 1982-84. 6) The pictured scenarios confirm in all cases, and independently of the type of unrest, the strong role played by the CO2-rich gas release of deep provenance. This is in line with the recent discovery of huge doming, due to gas overpressures, in the offshore portion of the CFc, i.e., the nearby Pozzuoli harbour (Passaro et al., 2016).

  15. Substitució d'una caldera de gas natural per una altra de biomassa per la producció de vapor industrial

    OpenAIRE

    Bessal, Fatene

    2017-01-01

    The current energy models, both nationally and internationally, is going through an important transition due to an imminent need to preserve our planet in terms of sustainability, since high levels of consumption and contaminant emissions frame these current model as unsustainable. This energy transition establishes the maximization of the use of renewable energy sources to obtain 100% renewable long-term models with the objective of achieving an independent economy of fossil fuels with the i...

  16. A new record of Chironomus (Chironomus) acidophilus Keyl (Diptera, Chironomidae) from the Uzon volcanic caldera (Kronotsky Reserve, Kamchatka Peninsula, Russia), its karyotype, ecology and biology.

    Science.gov (United States)

    Orel, Oksana V; Lobkova, Ludmila E; Zhirov, Sergey V; Petrova, Ninel A

    2015-07-03

    Morphology, cytology, ecology and biology of Holarctic Chironomus (Chironomus) acidophilus Keyl, 1960 (Diptera, Chironomidae) was examined from material collected in the geothermal Vosmerka Lake (pH=2.0-2.5). An illustrated redescription of C. acidophilus is given on the basis of adult males reared from field-collected pupae, and of simultaneously collected larvae. Additional larvae belonging to the pseudothummi-complex were identified as C. acidophilus on the basis of their karyotype. The karyotype of C. acidophilus (2n=8) and detailed mapping of the 4 chromosome arms A, E, D and F are provided. The population of C. acidophilus from Kamchatka was found to be karyologically monomorphic. Information on distribution and ecology of C. acidophilus from Vosmerka Lake (total mineralization 1583.5 mg/l) is also given. Chironomus acidophilus is the only species of aquatic insects recorded in this lake. Lack of competition and a richness of food resources contribute to the high abundance (35161 ind./m2) and biomass (11.342 g/m2) of the larvae of C. acidophilus in Vosmerka Lake.

  17. Multibeam collection for VANC03MV: Multibeam data collected aboard Melville from 2002-10-12 to 2002-10-30, Puerto Caldera, Costa Rica to Arica, Chile

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set is part of a larger set of data called the Multibeam Bathymetry Database (MBBDB) where other similar data can be found at...

  18. Livestock and elk grazing effects on stream morphology, brown trout population dynamics, movement, and growth rate, Valles Caldera National Preserve, New Mexico

    Science.gov (United States)

    Michael C. Anderson

    2009-01-01

    Ungulate grazing in riparian areas has been shown to detrimentally impact stream morphology and fish populations. Goals of this research were to assess changes in stream morphology and responses of a brown trout (Salmo trutta) population to exclusion of cattle (Bos taurus) and elk (Cervus elaphus) from riparian...

  19. The integration of solar power plants for domestic water services in buildings; Integracion de calderas y calentadores individuales en las instalaciones de ACS con energia solar

    Energy Technology Data Exchange (ETDEWEB)

    Martin, J. V.; Garcia, R.; Lopez de Subijana, R.; Casado, J. M.

    2004-07-01

    The integration of solar power plants for domestic water services in buildings with individual heating and domestic water facilities has some problems which must be solved by the manufacturers of boilers and individual heaters; the most important is the water temperature in the entrance to the individual equipment because of solar heating. Therefore, we must care about materials in boilers and heaters, and temperature control systems of domestic water production. We analyse the technical conditions which appear in these equipment in the usual schemes: Centralized accumulation, distributed accumulation, serial heating, etc., and propose some elements which can be integrated in these facilities to obtain a better operation. (Author)

  20. New approach on volatile contents determination in silicate melt inclusions: A coupling X-ray microtomography and geochemical approach in Los Humeros caldera complex (Eastern Mexican Volcanic Belt)

    Science.gov (United States)

    Creon, L.; Levresse, G.; Carrasco Nuñez, G.

    2016-12-01

    Volatile contents and magma degassing behavior are known to affect the style, frequency, and intensity of near-surface magmatic processes. For this reason, much effort have been devoted to characterize the volatile evolution of shallow magmatic systems to better constrain volcanic history. Silicate melt inclusions (SMI) represent samples of melt that were isolated from the bulk magma at depth, thus preserving the PTX conditions of the pre-eruptive material. SMI are ofte