Sample records for volcanic center eastern

  1. Volcanism in Eastern Africa (United States)

    Cauthen, Clay; Coombs, Cassandra R.


    In 1891, the Virunga Mountains of Eastern Zaire were first acknowledged as volcanoes, and since then, the Virunga Mountain chain has demonstrated its potentially violent volcanic nature. The Virunga Mountains lie across the Eastern African Rift in an E-W direction located north of Lake Kivu. Mt. Nyamuragira and Mt. Nyiragongo present the most hazard of the eight mountains making up Virunga volcanic field, with the most recent activity during the 1970-90's. In 1977, after almost eighty years of moderate activity and periods of quiescence, Mt. Nyamuragira became highly active with lava flows that extruded from fissures on flanks circumscribing the volcano. The flows destroyed vast areas of vegetation and Zairian National Park areas, but no casualties were reported. Mt. Nyiragongo exhibited the same type volcanic activity, in association with regional tectonics that effected Mt. Nyamuragira, with variations of lava lake levels, lava fountains, and lava flows that resided in Lake Kivu. Mt. Nyiragongo, recently named a Decade volcano, presents both a direct and an indirect hazard to the inhabitants and properties located near the volcano. The Virunga volcanoes pose four major threats: volcanic eruptions, lava flows, toxic gas emission (CH4 and CO2), and earthquakes. Thus, the volcanoes of the Eastern African volcanic field emanate harm to the surrounding area by the forecast of volcanic eruptions. During the JSC Summer Fellowship program, we will acquire and collate remote sensing, photographic (Space Shuttle images), topographic and field data. In addition, maps of the extent and morphology(ies) of the features will be constructed using digital image information. The database generated will serve to create a Geographic Information System for easy access of information of the Eastem African volcanic field. The analysis of volcanism in Eastern Africa will permit a comparison for those areas from which we have field data. Results from this summer's work will permit

  2. Signs of Recent Volcanism and Hydrothermal Activity Along the Eastern Segment of the Galapagos Spreading Center (United States)

    Raineault, N.; Smart, C.; Mayer, L. A.; Ballard, R. D.; Fisher, C. R.; Marsh, L.; Shank, T. M.


    Since the initial discovery of the Galápagos Spreading Center (GSC) vents in 1977, large-scale disturbances resulting from eruptive and tectonic activity have both destroyed and created vent habitats along the GSC. In 2015, the E/V Nautilus returned to the GSC with remotely operated vehicles (ROVs) to explore 17 kilometers of the rift valley from the Rosebud site in the west, to a previously unexplored temperature anomaly east of the Tempus Fugit vent site. In the years to over a decade since scientists last visited the Rosebud, Rose Garden, and Tempus Fugit sites, there were many changes. Most notably, the Rosebud site, where scientists found a nascent vent community and left site markers in 2002, was apparently covered with glassy basaltic sheet flows. In addition to visual exploration, oceanographic sensor measurements and direct sampling, we used the ROV Hercules imaging suite, comprised of stereo cameras and a structured light laser sensor to map an area of diffuse flow in the Tempus Fugit field (100 m x 150 m). The centimeter-level photographic and bathymetric maps created with this system, along with ROV HD video, samples, and environmental sensors, documented hydrothermal activity and changes in biological community structure (e.g., Riftia tubeworms observed in nascent stages of community development in 2011 were now, in 2015, in greater abundance (with tubes almost 4 m in length). The detection of active venting and associated faunal assemblages will provide insight into the temporal and spatial variability of venting activity at the Tempus Fugit site. On a visual survey of the Rift east of the Tempus Fugit site, extinct sulfide chimney structures were discovered and sampled. There were several chimneys and sulfide deposits in a span of over 8 km that ranged in height from over a half meter to 1.5 m tall. Diffuse flow hosting white and blue bacterial mats was observed near the chimneys complexes. The base of a large chimney structure, venting white fluids

  3. Geology and geochemistry of volcanic centers within the eastern half of the Sonoma volcanic field, northern San Francisco Bay region, California (United States)

    Sweetkind, Donald S.; Rytuba, James J.; Langenheim, V.E.; Fleck, Robert J.


    Volcanic rocks in the Sonoma volcanic field in the northern California Coast Ranges contain heterogeneous assemblages of a variety of compositionally diverse volcanic rocks. We have used field mapping, new and existing age determinations, and 343 new major and trace element analyses of whole-rock samples from lavas and tuff to define for the first time volcanic source areas for many parts of the Sonoma volcanic field. Geophysical data and models have helped to define the thickness of the volcanic pile and the location of caldera structures. Volcanic rocks of the Sonoma volcanic field show a broad range in eruptive style that is spatially variable and specific to an individual eruptive center. Major, minor, and trace-element geochemical data for intracaldera and outflow tuffs and their distal fall equivalents suggest caldera-related sources for the Pinole and Lawlor Tuffs in southern Napa Valley and for the tuff of Franz Valley in northern Napa Valley. Stratigraphic correlations based on similarity in eruptive sequence and style coupled with geochemical data allow an estimate of 30 km of right-lateral offset across the West Napa-Carneros fault zones since ~5 Ma.

  4. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc (United States)

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.


    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain


    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis


    Full Text Available Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic processes have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity from Strombolian to Plinian. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure perturbations, nuéss ardentes, pyroclastic flows, lahars, or cascading debris avalanches. Submarine volcanic caldera collapses can also generate locally destructive tsunami waves. Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be generated from aerial and submarine volcanic edifice mass edifice flank failures, which may be triggered by volcanic episodes, lava dome collapses, or simply by gravitational instabilities. The present report evaluates volcanic mechanisms, resulting flank failure processes and their potential for tsunami generation. More specifically, the report evaluates recent volcanic eruption mechanisms of the Soufriere Hills volcano on Montserrat, of Mt. Pel

  6. Contemporary State of the Elbrus Volcanic Center (The Northern Caucasus) (United States)

    Milyukov, Vadim; Rogozhin, Eugeny; Gorbatikov, Andrey; Mironov, Alexey; Myasnikov, Andrey; Stepanova, Marina


    The Elbrus volcanic center is located in southern Russia on the northern slope of the main ridge of the Greater Caucasus. Current classifications define Elbrus as a dormant volcano that could become active even after millennia of quiescence. In this study, we use two new geophysical methods to assess the contemporary state of the Elbrus volcano. The first method is based on an evaluation of parameters of resonant modes "reemitted" by the resonant structure (i.e., volcanic chamber) in response to the excitation of a seismic impact and recorded by a precise laser interferometer-strainmeter. The second method is based on low-frequency microseismic sounding and allows determination of the deep structure of complicated geological objects. Our study locates the magma chamber at depths of 1-8 km and extended magma source at depths of 15-40 km beneath the Elbrus eastern summit. An unknown magmatic structure, comparable to the Elbrus magmatic structure but currently much colder, was also identified 50 km from Mt. Elbrus. Based on our analysis, we assess the Elbrus volcano to be currently in a quasi-stable state of thermodynamic equilibrium.

  7. Anomalous Geologic Setting of the Spencer-High Point Volcanic Field, Eastern Snake River Plain, Idaho (United States)

    Iwahashi, G. S.; Hughes, S. S.


    The Spencer-High Point (SHP) volcanic field comprises an ~1700 sq km mafic volcanic rift zone located near Yellowstone in the eastern Snake River Plain (ESRP). SHP lava flows are both similar to and distinct from typical olivine tholeiite lavas of the ESRP. SHP has unique physical volcanic features characterized by numerous cinder cones and short lava flows; whereas, spatter ramparts, fissures and longer flows dominate in other ESRP regions. Topography and aerial photos indicate that vents are generally aligned northwest- southeast, which is sub-parallel to adjacent Basin and Range faults in much of the ESRP. Yet individual vents and other structural elements in SHP where Basin and Range, ESRP and thrust-faulted mountain belts all intersect, are elongated in a more east-west direction. Distinct structural control is manifested in an overall southward slope over the entire volcanic field. Short lava flows tend to flow north or south off of a central topographically higher zone of overlapping lava flows and smaller vents. Several smaller vents appear to be parasitic cones adjacent to larger eruptive centers. Contrary to these relations, preliminary geochemical data by Leeman (1982) and Kuntz et al. (1992) suggest SHP lavas are typical ESRP olivine tholeiite basalts, which notably have coarsely diktytaxitic texture. The central and eastern sections of the SHP field contain lavas with large (3-8cm), clear, euhedral plagioclase phenocrysts but without diktytaxitic texture. Lava flows in the central and eastern sections of SHP volcanic field are pahoehoe. These also contain crustal xenoliths implying a prolonged crustal history. Geochemical whole rock and microprobe analyses are currently being processed for petrogenetic history.

  8. Eastern forest environmental threat assessment center (United States)

    Southern Research Station. USDA Forest Service


    The Eastern Forest Environmental Threat Assessment Center (EFETAC) provides the latest research and expertise concerning threats to healthy forests – such as insects and disease, wildland loss, invasive species, wildland fire, and climate change – to assist forest landowners, managers and scientists throughout the East. Established in 2005, EFETAC is a joint effort of...

  9. New evidence of the Monchique - Madeira hot spot volcanism at the Coral Patch seamount, Central Eastern Atlantic Sea (United States)

    D'Oriano, F.; Angeletti, L.; Laurenzi, M. A.; Trua, T.; Capotondi, L.; Taviani, M.; Torelli, L.; Zitellini, N.


    Detailed swath bathymetry, high resolution seismic profiles and bottom sampling, collected during the SWIM 2005 and SWIM 2005 cruises, provide new data to constrain the emplacement mechanism of the Monchique-Madeira hotspot in the Central - Eastern Atlantic Sea. During last decades, although this volcanic province has been the object of several investigations, the location of hotspot track and the alignments of the volcanic centers, such as Ormonde, Ampere and Coral Patch seamounts, are still matter of debate. Several alkaline volcanic centers are recognized at Coral Patch and volcanic rocks obtained from the top of the seamount provides a radiometric (40Ar-39Ar) age of 31.4±1.98 Ma. Our data suggest that volcanism was emplaced on the top of a preexistent seamount and was strongly affected by the regional tectonic compressive regime, active on this sector of the Africa Eurasia plate boundary since Oligocene. The compression formed lithospheric scale structures acting as a reserved lane for the upwelling of mantle material during the transit of the hotspot. Lithified pelagic carbonates, infilling fissures in lava blocks and hosting planktic foraminifers, permit to date at the Chattian (24-28 Ma) the first documentation of Coral Patch acting as an offshore terrigenous-starved deep seamount. This situation protracts to recent times as shown by the occurrence of veneers of foraminifer-pteropod oozes and deep-sea mollusc-coral hash and pelagic limestones as the sole sediment types recovered from Coral Patch.

  10. Miocene to quaternary volcanism in eastern Kenya: Sequence and geochronology (United States)

    Brotzu, P.; Morbidelli, L.; Nicoletti, M.; Piccirillo, E. M.; Traversa, G.


    This paper presents the results of the first systematic geochronological study of widespread volcanic sequences in the region east of the Kenya Rift Valley between the Nyambeni Hills near the equator and the Hurri Hills-Dukana area close to the Ethiopian border. Volcanic activity in this area developed from Upper Miocene to Quaternary. Miocene activity (12-5 m.y.) was of fissure-type while the Plio-Quaternary volcanism was mainly of central type. This last volcanism occurred from early Pliocene (4.5 m.y.) to Recent (0.5 m.y.). The products of the two volcanic phases can be distinguished also from a compositional point of view. Previous stratigraphical interpretations are discussed on the basis of field and laboratory evidence.

  11. Thermal regimes of major volcanic centers: Magnetotelluric constraints

    Energy Technology Data Exchange (ETDEWEB)

    Hermance, J.F.


    The interpretation of geophysical/electromagnetic field data has been used to study dynamical processes in the crust beneath three of the major tectono-volcanic features in North America: the Long Valley/Mono Craters Volcanic Complex in eastern California, the Cascades Volcanic Belt in Oregon, and the Rio Grande Rift in the area of Socorro, New Mexico. Primary accomplishments have been in the area of creating and implementing a variety of 2-D generalized inverse computer codes, and the application of these codes to fields studies on the basin structures and he deep thermal regimes of the above areas. In order to more fully explore the space of allowable models (i.e. those inverse solutions that fit the data equally well), several distinctly different approaches to the 2-D inverse problem have been developed: (1) an overdetermined block inversion; (2) an overdetermined spline inverstion; (3) a generalized underdetermined total inverse which allows one to tradeoff certain attributes of their model, such as minimum structure (flat models), roughness (smooth models), or length (small models). Moreover, we are exploring various approaches for evaluating the resolution model parameters for the above algorithms. 33 refs.

  12. Understanding thermal energy and mass transport in major volcanic centers (United States)

    Hermance, John F.


    An understanding of the thermal regions of the earth's interior and their associated dynamic processes is of central importance, not only to basic science but to a number of national priorities including resource and the mitigation of volcanic and earthquake hazards. Major thermal anomalies over large regions of the continent are associated with intraplate rifts and transform faults (e.g., the Salton Trough and the Rio Grande Rift), distributed extensional tectonics (e.g., the Basin and Range Province), and plate margins (e.g., the Cascade Range). However, it is clear that of all classes of volcanic phenomena within the conterminous United States, the major intraplate silicic caldera complexes (e.g., Yellowstone, the Valles Caldera, the Long Valley/Mono Craters volcanic complex) appear to have, according to present estimates, the highest accessible geothermal resource base and the greatest destructive power during major eruptive phases. In addition, the exhumed fossil analogs of these systems are associated with extensive mineralization and economic ore deposits. What is lacking, however, is a predictive scientific theory describing the fundamental physio-chemical processes responsible for the development and longterm sustenance of these major volcanic centers in space and time.

  13. Platinum-group elements in the Eastern Deccan volcanic province ...

    Indian Academy of Sciences (India)

    In contrast, eastern province values dominated in the Pd-Au-Cu region at the 'Cu' end of the profiles. A strong dominance of Pd in the eastern Deccan was also of interest. A number of factors, for example, percentage partial melting of the source rock and the temperature and pressure of partial melting strongly influence the ...

  14. Valles Marineris tectonic and volcanic history inferred from dikes in eastern Coprates Chasma

    NARCIS (Netherlands)

    Brustel, C.; Flahaut, J.; Hauber, E.; Fueten, F.; Quantin, C.; Stesky, R.; Davies, G. R.


    Magmatic dikes have been proposed to have weakened and fractured the crust, allowing the formation of Valles Marineris. Hence, dikes were studied in the region of eastern Coprates Chasma in an area that includes a major transition between Hesperian-aged volcanic deposits in the western walls and

  15. The mechanisms underpinning Cenozoic intraplate volcanism in eastern Australia: Insights from seismic tomography and geodynamic modeling (United States)

    Rawlinson, N.; Davies, D. R.; Pilia, S.


    Cenozoic intraplate volcanism is widespread throughout much of eastern Australia and manifests as both age-progressive volcanic tracks and non-age-progressive lava fields. Various mechanisms have been invoked to explain the origin and distribution of the volcanism, but a broad consensus remains elusive. We use results from seismic tomography to demonstrate a clear link between lithospheric thickness and the occurrence, composition, and volume of volcanic outcrop. Furthermore, we find that non-age-progressive lava fields overlie significant cavities in the base of the lithosphere. Based on numerical simulations of mantle flow, we show that these cavities generate vigorous mantle upwellings, which likely promote decompression melting. However, due to the intermittent nature of the lava field volcanics over the last 50 Ma, it is probable that transient mechanisms also operate to induce or enhance melting. In the case of the Newer Volcanics Province, the passage of a nearby plume appears to be a likely candidate. Our results demonstrate why detailed 3-D variations in lithospheric thickness, plate motion, and transient sources of mantle heterogeneity need to be considered when studying the origin of non age-progressive volcanism in continental interiors.

  16. Geology of the Ugashik-Mount Peulik Volcanic Center, Alaska (United States)

    Miller, Thomas P.


    The Ugashik-Mount Peulik volcanic center, 550 km southwest of Anchorage on the Alaska Peninsula, consists of the late Quaternary 5-km-wide Ugashik caldera and the stratovolcano Mount Peulik built on the north flank of Ugashik. The center has been the site of explosive volcanism including a caldera-forming eruption and post-caldera dome-destructive activity. Mount Peulik has been formed entirely in Holocene time and erupted in 1814 and 1845. A large lava dome occupies the summit crater, which is breached to the west. A smaller dome is perched high on the southeast flank of the cone. Pyroclastic-flow deposits form aprons below both domes. One or more sector-collapse events occurred early in the formation of Mount Peulik volcano resulting in a large area of debris-avalanche deposits on the volcano's northwest flank. The Ugashik-Mount Peulik center is a calcalkaline suite of basalt, andesite, dacite, and rhyolite, ranging in SiO2 content from 51 to 72 percent. The Ugashik-Mount Peulik magmas appear to be co-genetic in a broad sense and their compositional variation has probably resulted from a combination of fractional crystallization and magma-mixing. The most likely scenario for a future eruption is that one or more of the summit domes on Mount Peulik are destroyed as new magma rises to the surface. Debris avalanches and pyroclastic flows may then move down the west and, less likely, east flanks of the volcano for distances of 10 km or more. A new lava dome or series of domes would be expected to form either during or within some few years after the explosive disruption of the previous dome. This cycle of dome disruption, pyroclastic flow generation, and new dome formation could be repeated several times in a single eruption. The volcano poses little direct threat to human population as the area is sparsely populated. The most serious hazard is the effect of airborne volcanic ash on aircraft since Mount Peulik sits astride heavily traveled air routes connecting the U

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

    Benson, Thomas R.; Mahood, Gail A.


    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

  18. Volcanic geology of Hadriaca Patera and the eastern Hellas region of Mars (United States)

    Crown, David A.; Greeley, Ronald


    A detailed examination of the geomorphology of Hadriaca Patera, a low-relief volcano in the southern highlands of Mars northeast of the Hellas basin, is presented, and the surrounding eastern Hellas region is considered in order to assess whether the volcanic geology of Hadriaca Patera is consistent with previous characterizations and highland paterae. The morphologic characteristics of the channels suggest erosion by groundwater sapping and surface runoff. The erosional morphology of the volcano, the lack of lava flow features, and the friable nature of the flank materials indicate that Hadriaca Patera consists predominantly of pyroclastic deposits. From the predominance of hydrovolcanic eruptions in the development of Hadriaca and Tyrrhena patera, it is inferred that the transition in volcanic eruption style can be attributed to a volatile depletion of the crust, whereas magmatic eruptions at the paterae would be indicative of temporal changes in Martian magmas.

  19. Volcanic geology of Hadriaca Patera and the eastern Hellas region of Mars (United States)

    Crown, D. A.; Greeley, R.


    A detailed examination of the geomorphology of Hadriaca Patera, a low-relief volcano in the southern highlands of Mars northeast of the Hellas basin, is presented, and the surrounding eastern Hellas region is considered in order to assess whether the volcanic geology of Hadriaca Patera is consistent with previous characterizations and highland paterae. The morphologic characteristics of the channels suggest erosion by groundwater sapping and surface runoff. The erosional morphology of the volcano, the lack of lava flow features, and the friable nature of the flank materials indicate that Hadriaca Patera consists predominantly of pyroclastic deposits. From the predominance of hydrovolcanic eruptions in the development of Hadriaca and Tyrrhena patera, it is inferred that the transition in volcanic eruption style can be attributed to a volatile depletion of the crust, whereas magmatic eruptions at the paterae would be indicative of temporal changes in Martian magmas.

  20. Correlations between silicic volcanic rocks of the St Mary's Islands (southwestern India) and eastern Madagascar

    DEFF Research Database (Denmark)

    Melluso, Leone; Sheth, Hetu C.; Mahoney, John J.


    The St Mary's, Islands (southwestern India) expose silicic volcanic and sub-volcanic rocks (rhyolites and granophyric dacites) emplaced contemporaneously with the Cretaceous igneous province of Madagascar, roughly 88-90 Ma ago. I he St Mary's Islands rocks have phenocrysts of plagioclase...... and isotopic Compositions very close to those of rhyolites exposed between Vatomandry Ilaka and Mananjary in eastern Madagascar, and are distinctly different from rhyolites front other sectors of the Madagascan province. We therefore postulate that the St Mary's and the Vatomandry-Ilaka Mananjary silicic rock...... outcrops were adjacent before the Late Cretaceous rifting that split Madagascar from India, If so, they provide a valuable tool to check and aid traditional Cretaceous India Madagascar reconstructions based on palaeomagnetism, matching Precambrian geological features, and geometric fitting of continental...

  1. Tectonics and volcanism of Eastern Aphrodite Terra: No subduction, no spreading (United States)

    Hansen, Vicki L.; Keep, Myra; Herrick, Robert R.; Phillips, Roger J.


    Eastern Aphrodite Terra is approximately equal in size to the western North American Cordillera, from Mexico to Alaska. Its size and unique landforms make it an important area for understanding the tectonics of Venus, yet models for its formation are diametrically opposed. This region is part of the Equatorial Highlands, which was proposed as a region of lithospheric thinning, isostatic uplift, and attendant volcanism. Eastern Aphrodite Terra is dominated by circular structures within which deformation and volcanism are intimately related. These structures are marked by radial and concentric fractures, and volcanic flows that emanate from a central vent, as well as from concentric fracture sets. Cross-cutting relations between flows and concentric fracture sets indicate that outer concentric fracture sets are younger than inner fracture sets. The circular structures are joined by regional northeast- to east-trending fractures that dominantly postdate formation of the circular structures. We propose that the circular structures 'grow' outward with time. Although these structures probably represent addition of crust to the lithosphere, they do not represent significant lithospheric spreading or convergence, and the region does not mark the boundary between two distinct tectonic plates. This region is not easily explained by analogy with either terrestrial midocean rifts or subduction zones. It is perhaps best explained by upwelling of magma diapirs that blister the surface, but do not cause significant lithospheric spreading. Further study of the structural and volcanic evolution of this region using Magellan altimetry and SAR data should lead to better understanding of the tectonic evolution of this region.

  2. Volcanism in the eastern Hellas region of Mars: The geology of Hadriaca and Tyrrhena Paterae (United States)

    Crown, David Arden

    Photogeologic analyses of Viking Orbiter images and analytical models based on terrestrial volcanic processes are used to determine the types, distribution, and mode(s) of formation of the materials composing two ancient Martian volcanoes. Hadriaca Patera and Tyrrhena Patera are large, low-relief features located in the southern highlands of Mars northeast of the Hellas basin. Layered, dissected deposits compose the extensive channeled flanks of these volcanoes. The erosional characteristics, lack of lava flow features, and friable nature of the materials indicate that the paterae consist predominantly of pyroclastic deposits. Morphologic similarities between Hadriaca and Tyrrhena Paterae suggest similar volcanic histories, with an early phyroclastic-dominated, shield-building phase followed by effusive eruptions at their summit calderas and on the southwest flank of Tyrrhena Patera. Geomorphic analyses and crater statistics constrain the evolution of the eastern Hellas region. Relative ages of the geologic units support morphologic evidence for interactions between volcanic, tectonic, and volatile-driven processes. Degradation by fluvial erosion was widespread and dominated the region surrounding Hadriaca Patera. Application of gravity-driven flow models demonstrates that the distribution of units at Hadriaca and Tyrrhena Paterae can be attributed to the emplacement of pyroclastic flows. Explosive eruptions driven by either magmatic volatiles or groundwater could provide sufficient energy. Large volumes of groundwater could accumulate rapidly at flow rates determined for Mars to drive hydrovolcanism. Analysis of cooling during transport indicates that welding of pyroclastic flows can occur at large distances from a source vent on Mars and could explain the layering observed within the paterae. The volcanic evolution of the highland paterae and subsequent dominance of the ridged plains of Hesperia Planum suggest a transition from explosive to effusive volcanism in

  3. Quaternary Basanitic Rocks within the Eastern Anatolian Volcanism (Turkey): Petrological and Geochemical Constrains (United States)

    Özdemir, Yavuz; Mercan, Çaǧrı; Oyan, Vural; Atakul-Özdemir, Ayşe


    The Eastern Anatolian Cenozoic continental intraplate volcanism was initiated in Middle Miocene as a result of the convergence between the Arabian and Anatolian plates. The origin of Eastern Anatolian volcanism has been the focus of many petrological studies that have aimed to resolve the relative contributions of asthenospheric mantle and/or lithospheric mantle with/without subduction component in the genesis of magmas that compositionally have many affinities to ocean island basalts (OIB) and volcanic arcs. Volcanism in the region characterized by mainly stratovolcanoes, basaltic lava plateaus and are dominantly spread at the northern parts of Bitlis Pötürge Massif (BPM). Our study focuses on a small scale Quaternary basaltic system that firstly observed within the BPM. The volcanic rocks of our study located 50 km to the south of Lake Van and are basanitic in composition. They exposed along K-G striking tensional fissures and crosscut the Upper unit of the Bitlis Massif. Initial products of the volcanism are scoria fall deposits. Thick basanitic lava flows overly the pyroclastics and formed columnar structures. The basanites are generally fine-grained with phenocrysts of olivine+clinopyroxene. The groundmass is typically of clinopyroxene, olivine and Ti magnetite and Cr spinel with interstitial nepheline. The olivine phenocrysts are typically euhedral to subhedral with Forsterite contents of Fo73-83. Clinopyroxenes are highly calcic and show modest variations in Wo47-52-En34-42-Fs10-15 and are weakly zoned with mg# 89-87 at cores to 86-84 at rims. Nephelines occur as minor minerals within the networks of other groundmass minerals. Ti rich and Fe-Cr spinels occur as inclusions in olivine and clinopyroxenes as well as within the groundmass. LILE and LREE enrichments over HFSE and HREE suggest similarities with magmas generated from enriched mantle sources. EC-AFC modeling of trace element and isotope compositions indicates that assimilation of crustal

  4. Formation stages and ore matter sources of the Devdoraki copper deposit, Kazbek volcanic center, the Greater Caucasus (United States)

    Lebedev, V. A.; Chugaev, A. V.; Vashakidze, G. T.; Parfenov, A. V.


    Comprehensive petrological-mineralogical, geochronological, and isotope-geochemical studies have been carried out at the Devdoraki copper deposit situated in the Kazbek neovolcanic center, the frontier territory between Georgia and Russia. The formation history of this deposit has been deciphered on the basis of K-Ar isotopic geochronological data, and the multistage evolution of ore-magmatic system has been established. The subeconomic disseminated and less abundant stringer pyrite mineralization formed at the first stage in the Early Cretaceous back to 130-120 Ma at the retrograde stage of regional metamorphism. The second productive stage was related to intense Quaternary volcanism of the Kazbek center. The late stringer base-metal mineralization formed about 400 ka ago in connection with the activity of minor volcanoes in the eastern part of deposit. In its western part adjoining the Kazbek volcanic cone, ore formation apparently continued over the entire period of recent magmatic activity from 400 to 100 ka ago. It is quite probable that this process is currently proceeding at deep levels of the Devdoraki deposit. Pb-Pb isotope-geochemical data show that Jurassic metasedimentary rocks that host sulfide mineralization could have been a main source of matter for early pyrite. At the second stage of base-metal mineralization formation, the source of ore matter was earlier metamorphic pyrite combined with hydrothermal solutions related to Quaternary endogenic activity within the Kazbek volcanic center. Gangue mineral matter (quartz, carbonates) was supplied simultaneously from the postmagmatic hydrothermal solution and host shale.

  5. Petrography, geochemistry and tectonic setting of Salmabad Tertiary volcanic rocks, southeast of Sarbisheh, eastern Iran

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    Masoumeh Goodarzi


    Full Text Available Introduction The area reviewed and studied in this paper is located 5 km southeast of Sarbisheh city at eastern border of the Lut block (Jung et al., 1983; Karimpour et al., 2011; Richards et al., 2012 in eastern Iran between 59° 47′ and 59° 53′ E longitude and 32°30′ and 32°34′ N latitude. The magmatic activity in the Lut block began in middle Jurassic (165-162 Ma and reached its peak in Tertiary (Jung et al., 1983. Volcanic and subvolcanic rocks of Tertiary age cover over half of Lut block with up to 2000 m thickness and formed due to subduction prior to the collision of the Arabian and Asian plates (Camp and Griffis, 1982; Tirrul et al., 1983; Berberianet et al., 1982. Most of magmatic activity in the Lut block formed in middle Eocene (Karimpour et al., 2011 The andesitic volcanics were erupted together with the dacites and rhyodacites during a time interval of some 50 Ma from early Cretaceous to early Neogene. It can be assumed that the intensity of the volcanic activity was varying significantly during this time span (Jung et al., 1983.Tertiary volcanic rocks (Eocene-Oligocene to Pliocene with intermediate composition associated with pyroclastic rocks cropped out in eastern parts of Salmabad village, southeast of Sarbisheh. The main purpose of this paper is better understand the tectono-magmatic setting of the Tertiary volcanic rocks in southeast of Sarbisheh, eastern Iran based on geochemical characteristics. Materials and methods Eleven samples were analyzed for major elements by inductively coupled plasma (ICP technologies and trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS, following a lithium metaborate/tetraborate fusion and nitric acid total digestion, at the SGS Laboratories, Toronto, Canada. Results In the Salmabad area, Tertiary volcanic rocks with mainly intermediate (andesitic composition are exposed associated with pyroclastic deposits such as tuff, breccia and agglomerate

  6. Eastern North America as an independent center of plant domestication. (United States)

    Smith, Bruce D


    The status of eastern North America as an independent center of plant domestication has recently been called into question by a number of genetic and archaeological studies, which suggest that the region may not have witnessed the independent domestication of local crop plants, but rather may have been on the receiving end of domesticated crop plants introduced from Mexico. Here, I provide a synthesis of the currently available archaeological and genetic evidence from both eastern North America and Mexico regarding the spatial and temporal context of initial domestication of the four plant species identified as potential eastern North American domesticates: marshelder (Iva annua), chenopod (Chenopodium berlandieri), squash (Cucurbita pepo), and sunflower (Helianthus annuus). Genetic and archaeological evidence provides strong support for the independent domestication of all four of these plant species in the eastern United States and reconfirms the region as one of the world's independent centers of domestication.

  7. Eastern North America as an independent center of plant domestication


    Smith, Bruce D.


    The status of eastern North America as an independent center of plant domestication has recently been called into question by a number of genetic and archaeological studies, which suggest that the region may not have witnessed the independent domestication of local crop plants, but rather may have been on the receiving end of domesticated crop plants introduced from Mexico. Here, I provide a synthesis of the currently available archaeological and genetic evidence from both eastern North Ameri...

  8. Major element, REE, and Pb, Nd and Sr isotopic geochemistry of Cenozoic volcanic rocks of eastern China: implications for their origin from suboceanic-type mantle reservoirs (United States)

    Basu, A.R.; Wang, Junwen; Huang, Wankang; Xie, Guanghong; Tatsumoto, M.


    Major- and rare-earth-element (REE) concentrations and UThPb, SmNd, and RbSr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China. These volcanic rocks, characteristically lacking the calc-alkaline suite of orogenic belts, were emplaced in a rift system which formed in response to the subduction of the western Pacific plate beneath the eastern Asiatic continental margin. The rocks sampled range from basanite and alkali olivine basalt, through olivine tholeiite and quartz tholeiite, to potassic basalts, alkali trachytes, pantellerite, and limburgite. These rock suites represent the volcanic centers of Datong, Hanobar, Kuandian, Changbaishan and Wudalianchi in northeastern China, and Mingxi in the Fujian Province of eastern China. The major-element and REE geochemistry is characteristic of each volcanic suite broadly evolving through cogenetic magmatic processes. Some of the outstanding features of the isotopic correlation arrays are as follows: (1) NdSr shows an anticorrelation within the field of ocean island basalts, extending from the MORB end-member to an enriched, time-averaged high Rb Sr and Nd Sr end-member (EM1), (2) SrPb also shows an anticorrelation, similar to that of Hawaiian and walvis Ridge basalts, (3) NdPb shows a positive correlation, and (4) the 207Pb 204Pb vs 206Pb 204Pb plot shows linear arrays parallel to the general trend (NHRL) for MORB on both sides of the geochron, although in the 208Pb 204Pb vs 206Pb 204Pb plot the linear array is significantly displaced above the NHRL in a pattern similar to that of the oceanic island basalts that show the Dupal signatures. In all isotope correlation patterns, the data arrays define two different mantle components-a MORB-like component and an enriched mantle component. The isotopic data presented here clearly demonstrate the existence of Dupal compositions in the sources of the continental volcanic rocks of eastern China. We suggest that the subcontinental mantle

  9. Petrologic evaluation of Pliocene basaltic volcanism in Eastern Anatolian region, Turkey: Evidence for mixing of melts derived from both shallow and deep mantle sources (United States)

    Oyan, Vural; Özdemir, Yavuz; Keskin, Mehmet; Güleç, Nilgün


    Collision-related Neogene volcanism in the Eastern Anatolia region (EAR) began after the continent-continent collision between the Arabia and the Eurasia plates, and spreads in a wide zone from the Erzurum-Kars Plateau in the northeast to the Karacadaǧ in the south. Volcanic activity in the EAR started 15 Ma ago (Middle Miocene) in the south of the region. Voluminous basaltic lavas from local eruption centers formed basaltic lava plateaus and volcanic cones as a result of high production level of volcanism during the Pliocene time interval. Our dating results (Ar-Ar and K-Ar) indicate that age of this Late Miocene-Pliocene magmatic activity range between 6 and 3.5 Ma. Volcanic products contain alkaline and subalkaline lavas, ranging in composition from basalts to andesites and trachyandesites. Our EC-AFC and AFC modeling, based on trace element and Sr, Nd, Pb isotopic compositions, suggests about 2-7 % crustal contamination in the evolved andesites and trachyandesites. MORB and primitive mantle normalized patterns of the lavas and isotopic compositions imply that alkaline and subalkaline basalts erupted in Pliocene time interval in the EAR could have been derived from a mantle source that had previously been enriched by a clear subduction component. A partial melting model was conducted to evaluate partial melting processes in the mantle source of the Pliocene basalts. Our melting model calculations suggest that basaltic melts in the EAR could have been produced by melting of mantle sources containing spinel, garnet and amphibole with melting degree in the range of 0.7-7%. The products of mixing of these derivative melts are the Pliocene basaltic lavas of the Eastern Anatolian Region.

  10. Mud Volcanism and Fluid Venting In The Eastern Mediterranean Sea: Observations From Sidescan Sonar and Submersible Surveys (United States)

    Zitter, T. A. C.; Huguen, C.; Woodside, J. M.; Mascle, J.; Scientific Party, Medineth/Medinaut

    Mud volcanoes in the eastern Mediterranean Sea have been identified by their distinctive acoustic signature as well as their morphology and sedimentology. They appear as circular regions of high backscatter believed to be caused principally by the clast content of the mud flows forming the mud volcano. Both the MEDINAUT and MEDINETH expeditions, conducted in 1998 and 1999 over two mud fields, the Olimpi field and the Anaximander Mountains area, in Eastern Mediterranean Sea, studied mud volcanism using a multidisciplinary approach in order to determine the relationships between the activity of the mud volcanoes (importance of degassing, associated fauna) and their geophysical signature. Mud volcanoes in Eastern Mediterranean Sea vary from conical and dome-shaped reliefs from 500m to 2km wide and 100 to 200m high to large "mud pie" types up to 6km wide. Sidescan sonar records give a very high resolution of the acoustic response, enabling to distinguish several mud flows, often flowing along tectonic lineations. A clear relationship between the occurrence of mud volcanism and cold seeps and both thrust and transcurrent faulting has been observed in both mud fields, although the tectonic settings vary from purely compressional to a more transpressional stress field. The faults are inferred to provide pathways for over- pressured fluids, and secondary faulting (transcurrent and extensional faults) may facilitate mud ascension. On the basis of sidescan sonar interpretation, other typical features have been inferred such as main feeder channels, eruptive cone centers, or brine pools. The in situ observations have been used to characterize the seafloor over numerous mud volcanoes and ground-truth the sonar data. They reveal an abundance of fluid seeps, mainly methane and methane-rich brines, as well as associated specific fauna such as tube worms, clams and chemosynthetic bacteria, and specific diagenetic phenomenon i.e. carbonate crusts. Video observations proved that

  11. Major-element geochemistry of the Silent Canyon-Black Mountain peralkaline volcanic centers, northwestern Nevada Test Site: applications to an assessment of renewed volcanism (United States)

    Crowe, Bruce M.; Sargent, Kenneth A.


    The Silent Canyon and Black Mountain volcanic centers are located in the northern part of the Nevada Test Site. The Silent Canyon volcanic center is a buried cauldron complex of Miocene age (13-15 m.y.). Black Mountain volcanic center is an elliptical-shaped cauldron complex of late Miocene age. The lavas and tuffs of the two centers comprise a subalkaline-peralkaline association. Rock types range from quartz normative subalkaline trachyte and rhyolite to peralkaline comendite. The Gold Flat Member of the Thirsty Canyon Tuff (Black Mountain) is a pantellerite. The major-element geochemistry of the Black Mountain-Silent Canyon volcanic centers differs in the total range and distribution of Si02, contents, the degree of peralkalinity (molecular Na2O+K2O>Al2O3) and in the values of total iron and alumina through the range of rock types. These differences indicate that the suites were unrelated and evolved from differing magma bodies. The Black Mountain volcanic cycle represents a renewed phase of volcanism following cessation of the Timber Mountain-Silent Canyon volcanic cycles. Consequently, there is a small but numerically incalculable probability of recurrence of Black Mountain-type volcanism within the Nevada Test Site region. This represents a potential risk with respect to deep geologic storage of high-level radioactive waste at the Nevada Test Site.

  12. Center for Volcanic and Tectonic Studies: 1992--1993 annual report

    Energy Technology Data Exchange (ETDEWEB)



    The annual report of the Center for Volcanic Studies (CVTS) contains a series of papers, reprints and a Master of Science thesis that review the progress made by the CVTS between October 1, 1992 and February 1, 1994. During this period CVTS staff focused on several topics that have direct relevance to volcanic hazards related to the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. These topics include: (1) polygenetic/polycyclic volcanism in Crater Flat, Nevada; (2) the role of the mantle during crustal extension; (3) the detailed geology of Crater Flat, Nevada; (4) Pliocene volcanoes in the Reveille Range, south-central Nevada; (5) estimating the probability of disruption of the proposed repository by volcanic eruptions. This topic is being studied by Dr. C.H. Ho at UNLV. The report contains copies of these individual papers as they were presented in various conference proceedings.

  13. Volcanic Centers in the East Africa Rift: Volcanic Processes with Seismic Stresses to Identify Potential Hydrothermal Vents (United States)

    Patlan, E.; Wamalwa, A. M.; Kaip, G.; Velasco, A. A.


    The Geothermal Development Company (GDC) in Kenya actively seeks to produce geothermal energy, which lies within the East African Rift System (EARS). The EARS, an active continental rift zone, appears to be a developing tectonic plate boundary and thus, has a number of active as well as dormant volcanoes throughout its extent. These volcanic centers can be used as potential sources for geothermal energy. The University of Texas at El Paso (UTEP) and the GDC deployed seismic sensors to monitor several volcanic centers: Menengai, Silali, and Paka, and Korosi. We identify microseismic, local events, and tilt like events using automatic detection algorithms and manual review to identify potential local earthquakes within our seismic network. We then perform the double-difference location method of local magnitude less than two to image the boundary of the magma chamber and the conduit feeding the volcanoes. In the process of locating local seismicity, we also identify long-period, explosion, and tremor signals that we interpret as magma passing through conduits of the magma chamber and/or fluid being transported as a function of magma movement or hydrothermal activity. We used waveform inversion and S-wave shear wave splitting to approximate the orientation of the local stresses from the vent or fissure-like conduit of the volcano. The microseismic events and long period events will help us interpret the activity of the volcanoes. Our goal is to investigate basement structures beneath the volcanoes and identify the extent of magmatic modifications of the crust. Overall, these seismic techniques will help us understand magma movement and volcanic processes in the region.

  14. Fluid flow and mud volcanism in the Eastern Mediterranean incipient collision zones (United States)

    Zitter, T. A. C.; Woodside, J. M.; Mascle, J.


    Fluid venting activity, either coupled with mud volcanism or along deep active faults or both, has been investigated in the Eastern Mediterranean Sea, mainly in two areas associated with the incipient collision process between Africa and Eurasia. Mud volcanoes are abundant on the crestal part of the Mediterranean Ridge accretionary prism, in association with thrusts, back-thrusts and transcurrent features. They are also found in the Anaximander Mountains/Florence Rise area, to the west of Cyprus, where a wrench system accommodates the pre-collisional deformation. Combined swath multibeam bathymetry and imagery, seismic profiling (ANAXIPROBE survey, 1995 and PRISMED II survey, 1998) and O.R.E.Tech sidescan sonar data (MEDINETH survey, 1999) indicate the genetic relationship between mud volcanoes and tectonics, particularly potential influence of strike-slip faulting. The in situ observations of mud volcanoes (MEDINAUT survey, 1998) have revealed common characteristics at cold seeps, such as carbonate crust constructions and specific chemosynthetic-based fauna. Ground-truth of the sonar data shows that the geophysical signature of mud volcanoes may be related to spatial and temporal evolution of mud volcanism activity, because the seafloor characteristics (surface of the mud flows, distribution and nature of the crusts) and the degree of colonization by benthic fauna vary with the intensity and age of the fluid seepage. Moreover, clay mineralogy studies on the mud matrix samples give insights into the depositional environment, age, and depth of the lithological unit from which the mud breccia is extruded. The shallow signature of the mud reservoir tends to indicate that the overpressured fluids originate from deeper strata than the solid phase of the expelled material.

  15. Induced thermoluminescence as a method for dating recent volcanism: Eastern Snake River Plain, Idaho, USA (United States)

    Sears, Derek W. G.; Sears, Hazel; Sehlke, Alexander; Hughes, Scott S.


    The induced thermoluminescence properties of 24 samples of basalts from volcanoes in the eastern Snake River Plain, Idaho, were measured as part of an investigation into the possibility of using this technique for dating purposes. The volcanic flows sampled ranged in age from 2200 years to 400,000 years. The thermoluminescence (TL) sensitivity values obtained, i.e., maximum induced TL normalized to that of the Dhajala meteorite (where Dhajala = 1000), ranged from 1.6 ± 0.3 to 226 ± 15 and showed a correlation between log TL and age with an r2 value of 0.47. Thus, TL sensitivity values correlate with age in the manner expected, although there is a high level of scatter. We discuss various mechanisms for the correlation and scatter, particularly (1) the role of primary (igneous processes) and secondary (solid state processes), (2) composition of the plagioclase feldspar, and (3) weathering. The induced TL signal from feldspars, the mineral responsible for the TL, is strongly dependent on their composition, and correcting for this improved the correlation (r2 = 0.7). Variations in primary feldspar are affecting the data, but we find no evidence that weathering of the samples is important. Further work is required to explore the remaining causes for the scatter and the TL-age trend. However, it is clear from the present study that induced TL has the potential for dating volcanism on the 2200 to 400,000 year time frame. This dating method, if successful, would be well-suited to spacecraft use since it requires low mass and low power instruments with a low data demand.

  16. Chemical evolution of a high-level magma system: the Black Mountain volcanic center, southern Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, T.A.; Noble, D.C.; Younker, L.W.


    A comprehensive study of stratigraphically controlled samples of both lavas and ash-flow tuffs from the Black Mountain volcanic center enables us to evaluate magmatic processes. The results of this study are used to: (1) determine how this high-level magma system developed; (2) compare this system with other similar systems; and (3) correlate ash-flow sheets using their chemical characteristics.

  17. The Geology of East Butte, a Rhyolitic Volcanic Dome on the Eastern Snake River Plain, Idaho (United States)

    Bretches, J. E.; King, J. S.


    East Butte is a prominent volcanic dome located on the eastern Snake River Plain. It is situated 51 km west of Idaho Fallls in the southeast corner of the Idaho National Engineering facility. East Butte rises 350 meters above the Quaternary basalt flows which encircle its 2.4 kilometer diameter base. Its maximum elevation is 2003 meters above sea level. East Butte is composed dominantly of rhyolite. Armstrong and others (1975) determined a K-Ar age of 0.6 +/- m.y. for a rhyolite sample from East Butte. Detailed geologic mapping revealed East Butte to be a single, large cumulo-dome composed dominantly of rhyolite. Major element geochemical analyses indicate that the rhyolite of East Butte is mildly peralkaline (molecular excess of Na2O and K2O over Al2O3 and compositionally homogeneous. Color variations in the East Butte rhyolite result from varying amounts of chemical and physical weathering and to the degree of devitrification that the glass in the groundmass of the rhyolite underwent.

  18. Integration of measurements and model simulations to characterize Eyjafjallajökull volcanic aerosols over south-eastern Italy

    Directory of Open Access Journals (Sweden)

    M. R. Perrone


    Full Text Available Volcanic aerosols resulting from the Eyjafjallajökull eruption were detected in south-eastern Italy from 20 to 22 April 2010, at a distance of approximately 4000 km from the volcano, and have been characterized by lidar, sun/sky photometer, and surface in-situ measurements. Volcanic particles added to the pre-existing aerosol load and measurement data allow quantifying the impact of volcanic particles on the aerosol vertical distribution, lidar ratios, the aerosol size distribution, and the ground-level particulate-matter concentrations. Lidar measurements reveal that backscatter coefficients by volcanic particles were about one order of magnitude smaller over south-eastern Italy than over Central Europe. Mean lidar ratios at 355 nm were equal to 64 ± 5 sr inside the volcanic aerosol layer and were characterized by smaller values (47 ± 2 sr in the underlying layer on 20 April, 19:30 UTC. Lidar ratios and their dependence with the height reduced in the following days, mainly because of the variability of the volcanic particle contributions. Size distributions from sun/sky photometer measurements reveal the presence of volcanic particles with radii r > 0.5 μm on 21 April and that the contribution of coarse volcanic particles increased from 20 to 22 April. The aerosol fine mode fraction from sun/sky photometer measurements varied between values of 0.85 and 0.94 on 20 April and decreased to values between 0.25 and 0.82 on 22 April. Surface measurements of particle size distributions were in good accordance with column averaged particle size distributions from sun/sky photometer measurements. PM1/PM2.5 mass concentration ratios of 0.69, 0.66, and 0.60 on 20, 21, and 22 April, respectively, support the increase of super-micron particles at ground. Measurements from the Regional Air Quality Agency show that PM10 mass concentrations on 20, 21, and 22 April 2010 were enhanced in the entire Apulia Region. More

  19. Field-trip guide to Columbia River flood basalts, associated rhyolites, and diverse post-plume volcanism in eastern Oregon (United States)

    Ferns, Mark L.; Streck, Martin J.; McClaughry, Jason D.


    The Miocene Columbia River Basalt Group (CRBG) is the youngest and best preserved continental flood basalt province on Earth, linked in space and time with a compositionally diverse succession of volcanic rocks that partially record the apparent emergence and passage of the Yellowstone plume head through eastern Oregon during the late Cenozoic. This compositionally diverse suite of volcanic rocks are considered part of the La Grande-Owyhee eruptive axis (LOEA), an approximately 300-kilometer-long (185 mile), north-northwest-trending, middle Miocene to Pliocene volcanic belt located along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the (1) flood basalt-dominated Columbia Plateau on the north, (2) bimodal basalt-rhyolite vent complexes of the Owyhee Plateau on the south, (3) bimodal basalt-rhyolite and time-transgressive rhyolitic volcanic fields of the Snake River Plain-Yellowstone Plateau, and (4) the High Lava Plains of central Oregon.This field-trip guide describes a 4-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the Columbia River Basalt Group and coeval and compositionally diverse volcanic rocks associated with the early “Yellowstone track” and High Lava Plains in eastern Oregon. Beginning in Portland, the Day 1 log traverses the Columbia River gorge eastward to Baker City, focusing on prominent outcrops that reveal a distal succession of laterally extensive, large-volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Basalt formations of the CRBG. These “great flows” are typical of the well-studied flood basalt-dominated Columbia Plateau, where interbedded silicic and calc-alkaline lavas are conspicuously absent. The latter part of Day 1 will highlight exposures of middle to late Miocene silicic ash-flow tuffs, rhyolite domes, and

  20. Shallow crustal structure of eastern-central Trans-Mexican Volcanic Belt. (United States)

    Campos-Enriquez, J. O.; Ramón, V. M.; Lermo-Samaniego, J.


    Central-eastern Trans-Mexican Volcanic Belt (TMVB) is featured by large basins (i.e., Toluca, Mexico, Puebla-Tlaxcala, Libres-Oriental). It has been supposed that major crustal faults limit these basins. Sierra de Las Cruces range separates the Toluca and Mexico basins. The Sierra Nevada range separates Mexico basin from the Puebla-Tlaxcala basin. Based in gravity and seismic data we inferred the Toluca basin is constituted by the Ixtlahuaca sub-basin, to the north, and the Toluca sub-basin to the south, which are separated by a relative structural high. The Toluca depression is more symmetric and bounded by sub-vertical faults. In particular its eastern master fault controlled the emplacement of Sierra de Las Cruces range. Easternmost Acambay graben constitutes the northern and deepest part of the Ixtlahuaca depression. The Toluca-Ixtlahuaca basin is inside the Taxco-San Miguel de Allende fault system, and limited to the west by the Guerrero terrane which continues beneath the TMVB up to the Acambay graben. Mexico basin basement occupies an intermediate position and featured by a relative structural high to the north-east, as established by previous studies. This relative structural high is limited to the west by the north-south Mixhuca trough, while to the south it is bounded by the east-west Copilco-Xochimilco-Chalco sub-basin. The Puebla-Tlaxcala basin basement is the shallowest of these 3 tectonic depressions. In general, features (i.e., depth) and relationship between these basins, from west to east, are controlled by the regional behavior of the Sierra Madre Oriental fold and thrust belt basement (i.e., Oaxaca Complex?). This study indicates that an active east-west regional fault system limits to the south the TMVB (from the Nevado de Toluca volcano through the Popocatepetl volcano and eastward along southern Puebla-Tlaxcala basin). The Tenango and La Pera fault systems constituting the western part of this regional fault system coincide with northern

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

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


    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. Effects of Magma Supply on Volcanic Morphology along the Hotspot-Influenced Galapagos Spreading Center (United States)

    White, S. M.; Meyer, J. D.; Haymon, R. M.; Anderson, P.; MacDonald, K. C.


    The relationship between lava morphology and spreading rate, with a predominance of pillows at slow- spreading ridges and sheets at fast-spreading ridges, is well known although not well understood. New EM300 and DSL-120A sonar data collected along the GSC from {94.5°}-{89.5°} W in 2006 reveals that increasing magma supply decreases the tendency for eruptions to focus to point-source volcanic vents, and ultimately produces fissure-fed sheet flow eruptions. The change in spreading rate is insignificant over this area, thus the additional magma supply provided by the Galapagos hotspot is the main variable. The high- resolution sonar data images volcanic vents clearly so that their morphology may be analyzed. Approaching the focus of hotspot influence on the GSC at {91.5°}W from {95°}W, volcanic vents become progressively lower in relief and more elongate. Volcanic vent morphology consists primarily of individual cones from {95°}-{92.5°}W presumably produced by eruptions that focus quickly to point-source vents, although the average size of the cones decreases toward the east, as magma supply increases. Where the ridge topography changes from an axial valley to axial rise, the volcanic morphology also becomes dominated by axial volcanic ridges rather than cones. Finally, along the ridge segment farthest east we find that the volcanic vents are simply expressed as fissures. Although the volcanic vent morphology progressively changes, it is only along this last, easternmost segment at {91.5°}W that we find a significant abundance of sheet lava flows based on extensive visual coverage with Medea. Elsewhere, the ridge is composed almost exclusively of pillow lava flows. These results suggest that magma supply, rather than other variables, is responsible for the relationship between lava morphology and spreading rate. Unlike true fast-spreading ridges, each ridge segment on the GSC from {93°}- {91°}W contains a single large volcanic cone centered at the segment

  3. Cancers in Eastern Libya: first results from Benghazi Medical Center. (United States)

    Bodalal, Zuhir; Azzuz, Raouf; Bendardaf, Riyad


    To study the pattern of cancer incidence and determine the incidence rates in Eastern Libya (for the first time in a decade). A hospital-based registry of cancer patients was formed using records from the primary oncology center in eastern Libya - focusing on those diagnosed in the year 2012. The most common malignancies in men were cancers of the colon (22.3%, n = 90), lung (20.3%, n = 82), prostate (16.1%, n = 65), pancreas (4.2%, n = 17) and liver (4.2%, n = 17). For women, they were found to be cancers of the breast (41.5%, n = 213), colon (16.4%, n = 84), uterus (8%, n = 41), ovary (5.5%, n = 28) and pancreas (3.1%, n = 16). Additionally age-standardized rates (ASR) were determined for Libya. The different cities and towns in eastern Libya were compared for any variation. The city of Beida in particular was found to have a remarkably high incidence of gastric cancer. The different findings were discussed and comparisons were made with past literature as well as the incidence rates for neighbouring countries. The incidence rates given for the eastern region showed differences from previously reported values (i.e., the rate of colon cancer was the highest in North Africa whereas other malignancies occurred less frequently). Potential explanations for the urban-rural difference as well as the difference in incidence rates were put forth. The significance of this study is that it establishes a baseline of cancer incidence which should be the backbone for any future national cancer plan in Libya. Proper surveillance programs need to be in place and healthcare policy should be adjusted to take into account the more prevalent and pressing cancers in society.

  4. Rifting, volcanism, and magma genesis at the northern end of the Danakil Depression: The Alid volcanic center of Eritrea (Invited) (United States)

    Lowenstern, J. B.; Clynne, M. A.; Duffield, W. A.; Smith, J. G.; Woldegiorgis, L.


    The Alid volcanic center, Eritrea, is a structural dome formed by subvolcanic intrusion of pyroxene-bearing rhyolite, subsequently erupted as pumice and lava, during the period 40,000 to 15,000 years ago. The northern Danakil Depression is thought to be the most recently developed part of the Afar, and represents an active continental rift subparallel to the Red Sea spreading center. The location of Alid may be controlled by the intersection of the structural grain of the NE trending Senafe-Alid lineament with the NW trending Danakil Depression. Our work began as a geothermal assessment (Duffield et al., 1997, USGS Open-file 97-291) that found evidence for 300 meters of vertical offset of early Pleistocene basalt flows over the past 1.1 million years. Structural uplift at Alid reveals Proterozoic metamorphic basement rocks overlain by Quaternary marine sediments including siltstone, and sandstones interbedded with pillow lavas and hyaloclastites. These units are overlain by subaerial amphibole-bearing rhyolites (dated at ~200 ka), basalts, and andesites that were deposited on a relatively flat surface and before significant growth of a large volcanic edifice. About 1 km of structural uplift of the marine sediments began 40 ka when pyroxene-bearing rhyolitic magma intruded close to the surface. Uplift was accompanied by contemporaneous eruptions of pumice falls and more common obsidian domes and lava flows over the next 20,000 years. Uplift apparently ceased after eruption of pyroclastic flows and vent-clogging lava about 15 ka. The pumice deposits contain cognate xenoliths of granophyric pyroxene-granite (Lowenstern et al., 1997, J. Petrol. 38:1707). Our geochronology of the uplift is consistent with the idea that growth of the Alid volcanic center played a role in isolating the southern Danakil Depression from the Red Sea, helping to initiate dessication of the rift and producing the young evaporites found today at Baddha and further south at Dallol. U

  5. FIERCE: FInding volcanic ERuptive CEnters by a grid-searching algorithm in R (United States)

    Carniel, Roberto; Guzmán, Silvina; Neri, Marco


    Most eruptions are fed by dikes whose spatial distribution can provide important insights into the positions of possible old eruptive centers that are no longer clearly identifiable in the field. Locating these centers can in turn have further applications, e.g., in hazard assessment. We propose a purely geometrical algorithm—implemented as an R open-source script—named FIERCE (FInding volcanic ERuptive CEnters) based on the number of intersections of dikes identified within a grid of rectangular cells overlain onto a given search region. The algorithm recognizes radial distributions, tangential distributions, or combinations of both. We applied FIERCE to both well-known and less-studied volcanic edifices, in different tectonic settings and having different evolution histories, ages, and compositions. At Summer Coon volcano, FIERCE demonstrated that a radial dike distribution clearly indicates the position of the central vent. On Etna, it confirmed the position of the most important ancient eruptive centers and allowed us to study effects of the structural alignments and topography. On Stromboli, FIERCE not only enabled confirmation of some published locations of older vents but also identified possible vent areas not previously suggested. It also highlighted the influence of the regional structural trend and the collapse scars. FIERCE demonstrated that the dikes at the Somma-Vesuvius were emplaced before formation of Mt. Somma's caldera and indicated a plausible location for the old volcanic crater of Mt. Somma which is compatible with previous studies. At the Vicuña Pampa Volcanic Complex, FIERCE highlights the position of two different vents of a highly degraded volcano.

  6. Magnetic anomalies on Io and their relationship to the spatial distribution of volcanic centers (United States)

    Knicely, Joshua; Everett, Mark E.; Sparks, David W.


    Forward modeling of planetary-scale magnetic anomalies due to induced crustal magnetization of Io is developed. The approach involves finite difference modeling of a temporally- and spatially-averaged steady state geotherm superimposed by the thermal evolution of an instantaneously emplaced volcanic pipe with and without an underlying magma chamber. A slight adjustment to previous studies results in a preferred steady state geotherm. The crustal magnetization is based on the calculated distribution of temperature, the strength of an idealized Jovian magnetic field, and a temperature-dependent susceptibility. Magnetite is assumed to be the dominant magnetic mineral. Synthetic satellite flyby data are generated along selected meridional swaths of Io's surface, based on observed locations of volcanic centers, hotspots, and accumulations of ejected volcanic material. This work produces a 1-D geotherm which remains at approximately the surface temperature to within a few kilometers of the thermal lithosphere/mantle boundary. This solution shows little dependence on porosity due to the depth at which rapid temperature change occurs. These conclusions hold for largely varying mantle temperatures. Silicate volcanic centers cool to the temperature of sulfur eruptions rapidly and become indistinguishable from sulfur volcanism within 10,000 years. The magnetic anomaly due to temperature variation is smaller than detectable for nominal conditions. The modeling herein requires a flyby altitude of ∼25 km and a pipe radius of ∼640 m for detection, or, for a more reasonable flyby altitude of 100 km, a pipe radius of ∼6000 m. If a crustal anomaly is detected by future satellite missions, it would suggest different conditions at Io than modeled here.

  7. Preliminary volcano hazard assessment for the Emmons Lake volcanic center, Alaska (United States)

    Waythomas, Christopher; Miller, Thomas P.; Mangan, Margaret T.


    The Emmons Lake volcanic center is a large stratovolcano complex on the Alaska Peninsula near Cold Bay, Alaska. The volcanic center includes several ice- and snow-clad volcanoes within a nested caldera structure that hosts Emmons Lake and truncates a shield-like ancestral Mount Emmons edifice. From northeast to southwest, the main stratovolcanoes of the center are: Pavlof Sister, Pavlof, Little Pavlof, Double Crater, Mount Hague, and Mount Emmons. Several small cinder cones and vents are located on the floor of the caldera and on the south flank of Pavlof Volcano. Pavlof Volcano, in the northeastern part of the center, is the most historically active volcano in Alaska (Miller and others, 1998) and eruptions of Pavlof pose the greatest hazards to the region. Historical eruptions of Pavlof Volcano have been small to moderate Strombolian eruptions that produced moderate amounts of near vent lapilli tephra fallout, and diffuse ash plumes that drifted several hundreds of kilometers from the vent. Cold Bay, King Cove, Nelson Lagoon, and Sand Point have reported ash fallout from Pavlof eruptions. Drifting clouds of volcanic ash produced by eruptions of Pavlof would be a major hazard to local aircraft and could interfere with trans-Pacific air travel if the ash plume achieved flight levels. During most historical eruptions of Pavlof, pyroclastic material erupted from the volcano has interacted with the snow and ice on the volcano producing volcanic mudflows or lahars. Lahars have inundated most of the drainages heading on the volcano and filled stream valleys with variable amounts of coarse sand, gravel, and boulders. The lahars are often hot and would alter or destroy stream habitat for many years following the eruption. Other stratocones and vents within the Emmons Lake volcanic center are not known to have erupted in the past 300 years. However, young appearing deposits and lava flows suggest there may have been small explosions and minor effusive eruptive activity

  8. Rheological responses to plate boundary deformation at the Eastern Volcanic Zone in Iceland (United States)

    Tariqul Islam, Md.; Sturkell, Erik


    Located on the mid-Atlantic ridge, Iceland allows for direct measurement of crustal deformation. Global Positioning System (GPS) data from the Eastern Volcanic Zone (EVZ), Iceland, and crustal deformation of the rift near its southern end at 64°N show a spreading rate of 13.8 ± 1.8 mm yr- 1. About 90% of the deformation occurs in an 80 to 90-km wide zone. To understand how the rheology of the lithosphere influences rifting, we applied a thermo-mechanical stretching model that includes thermal states in Iceland using temperature- and stress-dependent wet and dry olivine rheology. We attempt to reproduce the thermal structure of a rift by defining 700 °C from 5- to 15-km depth at the rift axis that leads to variation in rheological structure, and to estimate the layer (from surface to a depth of 700 °C) where the elastic deformation of the lithosphere is the greatest. At a fixed spreading rate, the deformation field is controlled by the sub-surface thermal state. The vertical subsidence rate at the ridge axis increases almost linearly as the half-velocity increases. The best fitted model suggests a thermal gradient of 54 °C km- 1 at depth below where 700 °C occurs at the ridge axis. The models have little sensitivity to the wet or dry olivine rheology. Estimated viscosity is 1 × 1019 Pa s at 20-km depth at the ridge axis and 1 × 1018 Pa s up to 100-km depth in the model. The spreading rate influences the tangential (non-linearity) shape of the deformation field, and a change in spreading rate affects the deformation field the most. After spreading velocity, the model's second most sensitive parameter is the location of the 700 °C at the rift axis. The thermomechanical model confirms that the rheological responses at the central part of the rift zone in the EVZ, Iceland caused of plate spreading is nonlinear, comparable with surface deformation observed by GPS measurement.

  9. Characteristics of zircons from volcanic ash-derived tonsteins in Late Permian coal fields of eastern Yunnan, China (United States)

    Zhou, Y.; Ren, Y.; Tang, D.; Bohor, B.


    Kaolinitic tonsteins of altered synsedimentary volcanic ash-fall origin are well developed in the Late Permian coal-bearing formations of eastern Yunnan Province. Because of their unique origin, wide lateral extent, relatively constant thickness and sharp contacts with enclosing strata, great importance has been attached to these isochronous petrographic markers. In order to compare tonsteins with co-existing, non-cineritic claystones and characterize the individuality of tonsteins from different horizons for coal bed correlation, a semi-quantitative method was developed that is based on statistical analyses of the concentration and morphology of zircons and their spatial distribution patterns. This zircon-based analytical method also serves as a means for reconstructing volcanic ash-fall dispersal patterns. The results demonstrate that zircons from claystones of two different origins (i.e., tonstein and non-cineritic claystone) differ greatly in their relative abundances, crystal morphologies and spatial distribution patterns. Tonsteins from the same area but from different horizons are characterized by their own unique statistical patterns in terms of zircon concentration values and morphologic parameters (crystal length, width and the ratio of these values), thus facilitating stratigraphic correlation. Zircons from the same tonstein horizon also show continuous variation in these statistical patterns as a function of areal distribution, making it possible to identify the main path and direction in which the volcanic source materials were transported by prevailing winds. ?? 1994.

  10. Mapping local singularities using magnetic data to investigate the volcanic rocks of the Qikou depression, Dagang oilfield, eastern China

    Directory of Open Access Journals (Sweden)

    G. Chen


    Full Text Available The spatial structural characteristics of geological anomaly, including singularity and self-similarity, can be analysed using fractal or multifractal modelling. Here we apply the multifractal methods to potential fields to demonstrate that singularities can characterise geological bodies, including rock density and magnetic susceptibility. In addition to enhancing weak gravity and magnetic anomalies with respect to either strong or weak background levels, the local singularity index (α ≈ 2 can be used to delineate the edges of geological bodies. Two models were established to evaluate the effectiveness of mapping singularities for extracting weak anomalies and delineating edges of buried geological bodies. The Qikou depression of the Dagang oilfield in eastern China has been chosen as a study area for demonstrating the extraction of weak anomalies of volcanic rocks, using the singularity mapping technique to analyse complex magnetic anomalies caused by complex geological background. The results have shown that the singularities of magnetic data mapped in the paper are associated with buried volcanic rocks, which have been verified by both drilling and seismic survey, and the S–N and E–W faults in the region. The targets delineated for deeply seated faults and volcanic rocks in the Qikou depression should be further investigated for the potential application in undiscovered oil and gas reservoirs exploration.

  11. The origin of volcanic rock fragments in Upper Pliocene Grad Member of the Mura Formation, North-Eastern Slovenia

    Directory of Open Access Journals (Sweden)

    Polona Kralj


    Full Text Available Fresh-water, coarse-grained and detritus-dominated Mura Formation in North Eastern Slovenia includes pyroclastic and volcaniclastic deposits originating from Upper Pliocene volcanic activity of basaltic geochemical character. Although localized in occurrence at the hamlet Grad, these pyroclastic and volcaniclastic sediments forma distinctive depositional unit, for which the term “Grad Member” is proposed and introduced in this paper.In the Grad area no lavas or cinder cones are preserved, and the origin of volcaniclastic fragments still uncertain. For this reason, chemical composition of basaltic rock fragments from the Grad Member volcaniclastics has been studied and compared with basaltic rocks from the neighboring locations at Klöch, Kindsberg, Dölling and Neuhaus. The Grad Member pyroclastic and volcaniclastic deposits seem to be fed from the same source which is different from the occurrences in Austria. That supports the idea about the existence of a local volcanic centre in the present Grad area. The old volcanic edificeswerepossiblydestroyed by the late-stage hydrovolcanic eruptions, and pyroclastic and volcaniclastic deposits subjected to constant reworking by fluvial currents in a dynamic sedimentary environment of alluvial fan and braided river systems.

  12. Petrology, Magnetic susceptibility, Tectonic setting and mineralization associated with Plutonic and Volcanic Rocks, Eastern Bajestan and Taherabad, Iran

    Directory of Open Access Journals (Sweden)

    Malihe Ghoorchi


    Full Text Available Study area is located in district of Bajestan and Ferdows cities, NE of Iran. Structurally, this area is part of Lut block. The oldest exposed rocks, to the north of intrusive rocks and in Eastern Bajestan, are meta-chert, slate, quartzite, thin-bedded crystalline limestone and meta-argillite. The sedimentary units are: Sardar Formation (Carboniferous, Jamal Formation (Permian, Sorkh Shale and Shotori Formations (Triassic, carbonateous rocks (Cretaceous and lithostratigraphically equivalent to Kerman conglomerate (Cretaceous-Paleocene are exposed in this area. Based on relative age, magmatism in eastern Bajestan and Taherabad started after Late Cretaceous and it has been active and repeated during Tertiary time. At least, three episodes of volcanic activities are recognized in this area. The first stage was mainly volcanic flow with mafic composition and minor intermediate. The second episode was mainly intermediate in composition. The third stage was changed to acid-intermediate in composition. Since the plutonic rocks intruded the volcanic rocks, therefore they may be Oligo-Miocene age. Bajestan intrusive rocks are granite-granodiorite-quartz monzonite. Taherabad intrusive rocks are diorite-quartz diorite- monzonite-latite. Bajestan intrusive rocks are reduced type (ilmenite series and Taherabad intrusive rocks are oxidized type (magnetite series.Based on geochemical analysis including trace elements, REE and isotopic data, Bajestan intrusive rocks formed in continental collision zone and the magma has crustal origin. Taherabad intrusive rocks were formed in subduction zone and magma originated from oceanic crust. Taherabad intrusive rock has exploration potential for Cu-Au and pb.

  13. Geologic Evolution of the Sierra de Nanchititla Silicic Volcanic Center, Southern Mexico (United States)

    Gonzalez, N.; Ferrari, L.; Lopez, M.; Cerca, M.; Orozco, M.


    The Sierra de Nanchititla Volcanic Center (SNVC) is located at the borders of the States of Mexico, Michoacán and Guerrero, in the northern sector of Sierra Madre del Sur magmatic province (SMS) of México. Previous studies in the areas of Taxco and Tilzapotla recognized an Early Tertiary brittle deformation along WNW-ESE to NW-SE trending strike slip fault systems at the north of the SMS (Alaniz-Alvarez et al., 2002, JVGR; Morán-Zenteno et al., 2005, JVGR). This fault systems apparently favored the emplacement of several silicic volcanic centers aligned in a WNW-ESE direction during the Eocene and earliest Oligocene. These volcanic centers include Huatla, Tilzapotla, Taxco, La Goleta and Sierra de Nanchititla. We carried out a detailed geologic study of the SNVC backed by Ar/Ar geochronology and trace element geochemistry. Our results indicate that the SNVC is part of the Eocene magmatic episode recorded in the SMS. The first volcanic rocks in the area are basaltic-andesitic lavas dated at ~42 Ma. However, the activity of the SNVC proper is concentrated between 37.8±0.2 and 35.6±0.5 Ma and was characterized by the emplacement of rhyolitic sub-volcanic bodies (cryptodomes), voluminous pyroclastic deposits and endogenous domes. The oldest magmatic event is the intrusion of WNW-ESE-trending mafic aphyric dikes dated 35.6±0.5 Ma that fed the Puerto El Salitre andesite. Magmatic activity continued with the emplacement of cryptodomes with sub-volcanic texture. The main phase of the SNVC took place in late Eocene with the emplacement of three units: (1) WNW-ESE-trending felsic pyroclastic dikes feeding the large Nanchititla Ignimbrite (35.6±0.5 Ma), (2) rhyolitic domes with vents aligned in a WNW-ESE direction (35.6±0.1 Ma), the and (3) a pyroclastic flow (Tequezquite Ignimbrite) likely vented from a dome. Geochemical data are consistent with a differentiation process, starting with primary mafic magmas and originating both basaltic- andesitic and andesitic rocks

  14. Jurassic Volcanism in the Eastern Pontides: Is it Rift Related or Subduction Related?




    The Jurassic volcanic rocks in the centre of the northern zone (south of Trabzon City) provide important constraints on the evolution of Pontides. The investigated volcanic rocks form a transitional series between tholeiitic and calc-alkaline, and is dominated by basalt, basaltic andesite and andesite. Geochemically, they are enriched in LILE and LREE contents and depleted in HFSE [(La/Yb)N= 2.2 - 8.5; (Nb/La)N= 0.1 - 0.77)] compared to mid-ocean ridge basalts and have radiogenic Nd isotope r...

  15. Geochemical/hydrochemical evaluation of the geothermal potential of the Lamongan volcanic field (Eastern Java, Indonesia)

    NARCIS (Netherlands)

    Deon, F.; Förster, H.J.; Brehme, M.; Wiegand, B.; Scheytt, T.; Moeck, I.; Jaya, M.S.; Putriatni, D.J.


    Magmatic settings involving active volcanism are potential locations for economic geothermal systems due to the occurrence of high temperature and steam pressures. Indonesia, located along active plate margins, hosts more than 100 volcanoes and, therefore, belongs to the regions with the greatest

  16. Age, petrogenesis, and tectonic setting of the Permian bimodal volcanic rocks in the eastern Jiamusi Massif, NE China (United States)

    Bi, Jun-Hui; Ge, Wen-Chun; Yang, Hao; Wang, Zhi-Hui; Dong, Yu; Liu, Xi-Wen; Ji, Zheng


    We present new in situ zircon U-Pb and Hf isotope, whole-rock geochemical, and Sr-Nd isotopic data for volcanic rocks from the Jiejinkou and Baoqing areas in the eastern Jiamusi Massif. These volcanic rocks are bimodal and consist of basalts, basaltic andesites, rhyolites, and rhyolitic tuffs that can be subdivided into mafic and silicic groups. Zircon U-Pb dating by LA-ICP-MS indicates that these volcanic rocks were erupted between the Early and Middle Permian (290-267 Ma). The mafic rocks in this area have positive εNd(t) (+0.07 to +6.43) values, and are enriched in light rare earth elements (LREEs) and depleted in heavy REE, Nb, and Ta. From these rocks, the meta-basalt of Jinlu and basaltic andesite of Taipinggou and Haojiatun were derived from parental magmas generated by the partial melting of depleted mantle wedge material that was metasomatized by subduction-related melts. These magmas then underwent variable degrees of fractional crystallization and assimilated insignificant amounts of crustal material. The meta-basalt of Liming likely originated from the metasomatized mantle-derived melts hybridized by the convective asthenosphere during the evolution of the magmas. In comparison, the silicic rocks have negative εNd(t) and variable zircon εHf(t) values, are enriched in the large-ion lithophile elements (LILEs) and LREE, and are depleted in high-field-strength elements (e.g., Nb, Ta, and Ti), yielding arc-like geochemical signatures. The geochemical and zircon εHf(t) characteristics of Jiangfeng and Longtouqiao rhyolites are indicative of formation from magmas generated by the partial melting of mafic lower crustal material, whereas the Liming meta-rhyolite was probably produced from a source involving some depleted mantle components. The bimodal volcanic rocks provide convincing evidence that the Early-Middle Permian volcanism in the Jiamusi Massif occurred in an extensional environment probably associated with slab break-off during the westward

  17. Tectonics and volcanism of Eastern Aphrodite Terra, Venus - No subduction, no spreading (United States)

    Hansen, Vicki L.; Phillips, Roger J.


    Eastern Aphrodite Terra, a deformed region with high topographic relief on Venus, has been interpreted as analogous to a terrestrial extensional or convergent plate boundary. However, analysis of geological and structural relations indicates that the tectonics of eastern Aphrodite Terra is dominated by blistering of the crust by magma diapirs. The findings imply that, within this region, vertical tectonism dominates over horizontal tectonism and, consequently, that this region is neither a divergent nor a convergent plate boundary.

  18. Internal Structure of the Tuxtla Volcanic Field, Eastern mexico, Derived from Gravity and Aeromagnetic data. (United States)

    Espindola, J. M.; Lopez Loera, H.; Zamora-Camacho, A.; Mena, M.


    The TVF is a basaltic volcanic field located in the western margin of the Gulf of Mexico in the Mexican State of Veracruz, about 230 km to the SSE of the easternmost tip of the Trans-Mexican Volcanic Belt, and about the same distance from El Chichon volcano, in the Chiapanecan Volcanic Arc, to the SE. It is separated from both volcanic chains also in composition as its rocks are predominantly alkaline. These characteristics prompt questions about its origin, more so since, one of the large volcanoes of the field, San Martin Tuxtla, erupted in 1793 CE. The TVF stands out from the lowlands of the Veracruz margins and is approximately surrounded by the 100 m contour line, while the surrounding areas along the Gulf of Mexico shoreline lie below this contour. Assuming that the rocks above this contour were deposited by the volcanic activity in the area, a good estimate of its volume is obtained by calculating the amount of material contained above this contour. We performed this calculation from the digital elevation model of the area received from restitutions carried out by Mexicós National Institute of Statistics, Geography, and Informatics (Spanish acronym: INEGI). We obtained a total amount of 1300 km3 for this volume. To understand more about the volcanism that has deposited this volume of products, we analyzed the gravimetric and aeromagnetic anomalies of the area and obtained a density model of the causative body. We got a body with a somewhat flattened top at 16 km below sea level from the inversion of the regional. Three separate slender bodies with tops 6 km deep were obtained from the inversion of the residual. The gravity and magnetic anomalies, as well as the inferred source bodies that produce those geophysical anomalies, lie between two large regional faults (Sontecomapan and Catemaco faults), which are proposed as flower structures associated with an inferred deep-seated fault termed the Veracruz Fault. We suggest that the process leading to the

  19. Global positioning system survey data for active seismic and volcanic areas of eastern Sicily, 1994 to 2013. (United States)

    Bonforte, Alessandro; Fagone, Sonia; Giardina, Carmelo; Genovese, Simone; Aiesi, Gianpiero; Calvagna, Francesco; Cantarero, Massimo; Consoli, Orazio; Consoli, Salvatore; Guglielmino, Francesco; Puglisi, Biagio; Puglisi, Giuseppe; Saraceno, Benedetto


    This work presents and describes a 20-year long database of GPS data collected by geodetic surveys over the seismically and volcanically active eastern Sicily, for a total of more than 6300 measurements. Raw data were initially collected from the various archives at the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania-Osservatorio Etneo and organized in a single repository. Here, quality and completeness checks were performed, while all necessary supplementary information were searched, collected, validated and organized together with the relevant data. Once all data and information collections were completed, raw binary data were converted into the universal ASCII RINEX format; all data are provided in this format with the necessary information for precise processing. In order to make the data archive readily consultable, we developed software allowing the user to easily search and obtain the needed data by simple alphanumeric and geographic queries.

  20. Impact of volcanism on the evolution of Lake Van I: evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past >400,000 years (United States)

    Sumita, Mari; Schmincke, Hans-Ulrich


    The historically active Nemrut Volcano (2,948 m asl) (Eastern Anatolia), rising close to the western shore of huge alkaline Lake Van, has been the source of intense Plinian eruptions for >530,000 years (drilled lake sediments). About 40 widespread, newly recognized trachytic and less common rhyolitic fallout tephras and ca. 12 interbedded ignimbrites, sourced in Nemrut Volcano, are documented in stratigraphic traverses throughout an area of >6,000 km2 mostly west of Lake Van. Phenocrysts in the moderately peralkaline trachytes and rarer large-volume comenditic rhyolites comprise anorthoclase, hedenbergite-augite, fayalite and, especially in trachytic units, augite, minor aenigmatite, apatite and quartz, and rare chevkinite and zircon. Dacitic to rhyolitic tephras from nearby calcalkalic Süphan Volcano (4,058 m asl), locally interbedded with Nemrut tephras, are characterized by disequilibrium phenocryst assemblages (biotite, augitic clinopyroxene and hypersthene, minor olivine, common crystal clots and/or, in some deposits, amphibole). The magma volume (DRE) of the largest Nemrut tephra sheet (AP-1) described in detail may exceed 30 km3. Extreme facies and systematic compositional changes are documented in the ca. 30 ka Nemrut Formation (NF) deposits formed from one large and complex eruption (thick rhyolitic fallout overlain by ignimbrite, welded agglutinate, overbank surge deposits, and final more mafic fallout deposits). Common evidence of magma mixing in Nemrut ignimbrites reflects eruption from compositionally zoned magma reservoirs. Several young Çekmece Formation trachytes overlying ca. 30 ka old NF deposits and the late trachytes of the NF deposits show compositional affinities to tephra from Süphan Volcano possibly due to temporary influx of Süphan magmas into the Nemrut system following the evacuation of >10 km3 magma (DRE) during the caldera-forming NF eruption. Axes of large fallout fans are dominantly SW-NE but W-E in the younger sheets resembling

  1. International collaboration between Volcanic Ash Advisory Centers: Geospatially enabled tools to ensure forecast harmonization across global air routes (United States)

    Osiensky, J. M.; Moore, D.; Kibler, J.; Bensimon, D.


    Volcanic plumes and drifting ash clouds pose a risk to flight operations somewhere across the globe every day. Airborne ash plumes pose a significant hazard to aircraft and timely and accurate forecasts greatly help mitigate the risk of an encounter. The world's nine (9) Volcanic Ash Advisory Centers (VAACs) provide products and services to address the volcanic ash hazard to aviation. These nine centers are operated by the meteorological authority within the state in which they are located. Each VAAC has its unique set of tools and procedures on how the data will be captured, displayed, analyzed and turned into a suite of products. The end products (e.g. Volcanic Ash Advisories (VAA) and Volcanic Ash Graphic (VAG)) are standardized through the International Civil Aviation Organization's International Airways Volcano Watch Operations Group (ICAO IAVWOPSG). Improvements in methods of collaboration between the VAACs are needed to allow for a seamless global harmonization of volcanic ash products. A geospatially enabled tool would allow for a common operating platform, data sharing, and situational awareness. The North American VAACs have been testing a capability to provide this environment to make forecast collaboration simple across the globe. This presentation highlights work that has been done to demonstrate this capability.

  2. Stratigraphy, petrology, and geochemistry of the Spurr Volcanic Complex, eastern Aleutian Arc, Alaska. [(Appendix for geothermal fluid chemistry)

    Energy Technology Data Exchange (ETDEWEB)

    Nye, C.J.


    The Spurr Volcanic Complex (SVC) is a calcalkaline, medium-K, sequence of andesites erupted over the last quarter of a million years by the easternmost currently active volcanic center in the Aleutian Arc. The ancestral Mt. Spurr was built mostly of andesites of uniform composition (58 to 60% SiO/sub 2/), although andesite production was episodically interrupted by the introduction of new batches of more mafic magma. Near the end of the Pleistocene the ancestral Mt. Spurr underwent Bezyianny-type avalanche caldera formation, resulting in the production of a volcanic debris avalanche with overlying ashflows. Immediately afterward, a large dome (the present Mt. Spurr) was emplaced in the caldera. Both the ashflows and dome are made of acid andesite more silicic than any analyzed lavas from the ancestral Mt. Spurr (60 to 63% SiO/sub 2/), yet contain olivine and amphibole xenocrysts derived from more mafic magma. The mafic magma (53 to 57% SiO/sub 2/) erupted during and after dome emplacement, forming proto-Crater Peak and Crater Peak. Hybrid pyroclastic flows and lavas were also produced. Proto-Crater Peak underwent glacial dissection prior to the formation of Crater Peak in approximately the same location. Appendices II through VIII contain a summary of mineral compositions; Appendix I contains geochemical data. Appendix IX by R.J. Motyka and C.J. Nye describes the chemistry of geothermal fluids. 78 refs., 16 figs., 3 tabs.

  3. The geochemistry of host arc volcanic rocks to the Co-O epithermal gold deposit, Eastern Mindanao, Philippines (United States)

    Sonntag, Iris; Kerrich, Robert; Hagemann, Steffen G.


    Mindanao is the second largest island of the Philippines and is located in the southern part of the archipelago. It comprises the suture zone between the Eurasian and the Philippine plate, which is displayed in the Philippine Mobile Belt. Eastern Mindanao is part of the Philippine Mobile Belt and outcropping rocks are mainly Eocene to Pliocene in age related to episodes of arc volcanism alternating with sedimentation. New high-precision elemental analysis of the Oligocene magma series, hosting the Co-O epithermal Au deposit, which represents an arc segment in the central part of Eastern Mindanao, revealed dominantly calc-alkaline rocks ranging in composition between basalt and dacites. Major element trends (MgO vs. TiO2 and Fe2O3) are comparable to other magmas in Central and Eastern Mindanao as well as other SW Pacific Islands such as Borneo. Rare earth and trace element distribution patterns display typical island arc signatures highlighted by the conjunction of LILE-enrichment with troughs at Nb, Ta, and Ti. Ratios of Zr/Nb in basalts vary between 17 and 39, signifying a depleted subarc mantle wedge comparable to the range of MORB, and other Indonesian island arc basalts. In basalts, Nb/Ta and Zr/Sm ratios are 12-37 and 14-27 respectively indicative of deep melts of rutile-eclogite subducted slab, as well as fluids, infiltrating the mantle wedge source of basalts. Moderate large ion lithophile element contents and low Th/La and Th/Ce ratios suggest no significant slab-derived components such as sediment or crustal fragments. The comparatively low Ce and Yb values in basalts, but also andesites and dacites, are consistent with a thin arc crust related to an intraoceanic convergent margin setting. This is further supported by Nb contents in basalts that range between 1 and 3 ppm and are within the range of modern oceanic convergent margin basalts. The range of HREE fractionation signifies that basaltic melts separated at deeper levels of the subarc wedge, possibly

  4. Stability of Hydrothermal Vent Communities on the Eastern Lau Spreading Center (United States)

    Fisher, C. R.; Du Preez, C.; Ferrini, V. L.; Beinart, R.; Seewald, J.; Hoer, D.; Girguis, P. R.


    With polymetalic sulfide deposit mining imminent in the Western Pacific, understanding the pace and patterns of natural change in the hydrothermal vent communities of the region is critical to the design of pre-mining surveys and post-exploitation monitoring that should accompany responsible resource extraction. The overarching goals of our April 2016 expedition to the Eastern Lau Spreading Center (ELSC) with the RV Falkor, were therefore to significantly increase our understanding of the natural patterns of change in the vent geology, chemistry, and biology along the ELSC, and the processes that govern these changes. During the expedition we were able to revisit 17 community study sites in four vent fields, which were established during the NSF Ridge 2000 program. In each vent field, we acquired high resolution multibeam and spatially explicit chemical data and imagery for photo mosaics of seven chimney, six diffuse flow, and four peripheral vent faunal communities to compare with similar data collected in 2005, 2006 and 2009. Advances in chemical sensor and imaging technology not only facilitate comparisons to the pre-existing data sets, but also provide new insights to the physiological ecology of the fauna and the factors contributing to their realized distribution. Notably, our preliminary analyses have found no evidence of significant volcanic or tectonic activity at any of the sites since 2005. The most surprising observation, however, was the remarkable stability in the community structure and faunal distribution at most of the chimney, diffuse flow, and peripheral community study sites at three of the major vent fields, which showed little evidence of change over the decade that they have been monitored. While the discovery of fauna with chemoautotrophic symbionts at the southern-most vent field visited, Mariner, suggests significant changes in the chemistry of the diffuse flow in this vent field since 2009, the apparent geological and ecological stability

  5. U-series disequilibria of trachyandesites from minor volcanic centers in the Central Andes (United States)

    Huang, Fang; Sørensen, Erik V.; Holm, Paul M.; Zhang, Zhao-Feng; Lundstrom, Craig C.


    Young trachyandesite lavas from minor volcanic centers in the Central Andes record the magma differentiation processes at the base of the lower continental crust. Here we report U-series disequilibrium data for the historical lavas from the Andagua Valley in Southern Peru to define the time-scale and processes of magmatism from melting in the mantle wedge to differentiation in the crust. The Andagua lavas show (230Th)/(238U), (231Pa)/(235U), and (226Ra)/(230Th) above unity except for one more evolved lava with 230Th depletion likely owing to fractional crystallization of accessory minerals. The 226Ra excess indicates that the time elapsed since magma emplacement and differentiation in the deep crust is within 8000 years. Based on the correlations of U-series disequilibria with SiO2 content and ratios of incompatible elements, we argue that the Andagua lavas were produced by mixing of fresh mantle-derived magma with felsic melt of earlier emplaced basalts in the deep crust. Because of the lack of sediment in the Chile-Peru trench, there is no direct link of recycled slabs with 230Th and 231Pa excesses in the Andagua lavas. Instead, 230Th and 231Pa excesses are better explained by in-growth melting in the upper mantle followed by magma differentiation in the crust. Such processes also produced the 226Ra excess and the positive correlations among (226Ra)/(230Th), Sr/Th, and Ba/Th in the Andagua lavas. The time-scale of mantle wedge melting should be close to the half-life of 231Pa (ca. 33 ka), while it takes less than a few thousand years for magma differentiation to form intermediate volcanic rocks at a convergent margin.

  6. Long-term in situ observations at the Athina mud volcano, Eastern Mediterranean: Taking the pulse of mud volcanism (United States)

    Menapace, Walter; Völker, David; Sahling, Heiko; Zoellner, Christian; dos Santos Ferreira, Christian; Bohrmann, Gerhard; Kopf, Achim


    Long-term monitoring on mud volcanoes is fundamental to unravel episodic processes and transient changes that might otherwise be missed by using snapshot observations during time-limited research expeditions. We deployed a pore- and seafloor-pressure observatory close to the main conduit of the Athina mud volcano, south of Turkey (Eastern Mediterranean Sea), for a period of 26 months between February 2014 and April 2016. The observatory recorded 32 pore pressure transients related to as many seismic events (out of 625 earthquakes with Mw ≥ 2.5 occurred over the monitoring period in a radius of 1000 km) and few pore pressure excursions related to mud volcanism. The data helped to define a threshold for earthquake-triggered changes in mud volcano pore pressure, thus delineating possible pore pressure-distance relationships for different magnitudes ranges. Peak ground accelerations, as representative for earthquakes ground motion at the observatory have been calculated with different ground motion prediction equations. Using a conservative approach, an empirical equation has been identified, which specify the lowermost PGA necessary to induce a change in pore pressure record at the Athina mud volcano. Moreover, internal variations of the mud volcano system recordable through the pore pressure signal have been described for the first time in such a submarine feature.

  7. Storage of Explosive versus Effusive Rhyolite Magma at the Yellowstone Volcanic Center (United States)

    Gardner, J. E.


    The Yellowstone volcanic center has erupted more than 900 km3 of rhyolitic magma in the last 600,000 years (1). Most of that magma extruded as large lava flows, with only a few known explosive eruptions. Why have explosive eruptions been so rare in the recent history of the Yellowstone volcanic system? To explore that question, we focus on the Tuff of Bluff Point (TBP), about 50 km3 of magma that explosively erupted 173 ka, forming the West Thumb caldera (1). Like most other recent eruptions of Yellowstone, TBP is high silica rhyolite, with phenocrysts of quartz, sanidine, and minor ferro-pyroxenes and Fe-Ti oxides. Fe-Ti oxide and pyroxene compositions indicate that the magma had equilibrated at an oxygen fugacity equal to the QFM buffer. Rehomogenized glass inclusions (n=7) in quartz contain 2.2-3.1 wt.% water and between 400-650 ppm CO2. Those volatile contents indicate storage pressures of 90-160 MPa. Ubiquitous pyrrhotite shows that the magma was sulfur saturated, and most likely volatile saturated. The co-existing fluid would be only 42-47% water. Cathodoluminescence (CL) images of quartz phenocrysts reveal mainly concentric growth zones, with occasional dissolution boundaries present. Ti contents in quartz generally decrease from core to rim, indicating cooling of the magma, although the relative temperature changes recorded are only 10-15°, with only minor changes across dissolution boundaries. To put our observations in perspective of the recent Yellowstone magma system, we have begun examining some of the recent rhyolitic lavas, including the Pitchstone Plateau (PP), a single homogeneous lava flow of 70 km3 that erupted 79 ka (1). CL images also reveal mainly concentric quartz growth, with few dissolution boundaries obvious. Ti contents in quartz also generally decrease from core to rim, but are uniformly lower than in those in TBP, suggesting that PP magma was colder than TBP magma. Glass inclusions (n=20) in PP are generally water poor and rarely

  8. Ore-bearing hydrothermal metasomatic processes in the Elbrus volcanic center, the northern Caucasus, Russia (United States)

    Gurbanov, A. G.; Bogatikov, O. A.; Dokuchaev, A. Ya.; Gazeev, V. M.; Abramov, S. S.; Groznova, E. O.; Shevchenko, A. V.


    Precaldera, caldera, and postcaldera cycles are recognized in the geological evolution of the Pleistocene-Holocene Elbrus volcanic center (EVC). During the caldera cycle, the magmatic activity was not intense, whereas hydrothermal metasomatic alteration of rocks was vigorous and extensive. The Kyukyurtli and Irik ore-magmatic systems have been revealed in the EVC, with the former being regarded as the more promising one. The ore mineralization in rocks of the caldera cycle comprises occurrences of magnetite, ilmenite, pyrite and pyrrhotite (including Ni-Co varieties), arsenopyrite, chalcopyrite, millerite, galena, and finely dispersed particles of native copper. Pyrite and pyrrhotite from volcanics of the caldera cycle and dacite of the Kyukyurtli extrusion are similar in composition and differ from these minerals of the postcaldera cycle, where pyrite and pyrrhotite are often enriched in Cu, Co, and Ni and millerite is noted as well. The composition of ore minerals indicates that the hydrothermal metasomatic alteration related to the evolution of the Kyukyurtli hydrothermal system was superimposed on rocks of the caldera cycle, whereas the late mineralization in rocks of the postcaldera cycle developed autonomously. The homogenization temperature of fluid inclusions in quartz and carbonate from crosscutting veinlets in the apical portion of the Kyukyurtli extrusion is 140-170°C and in quartz from geyserite, 120-150°C. The temperature of formation of the chalcopyrite-pyrite-pyrrhotite assemblage calculated using mineral geothermometers is 156 and 275°C in dacite from the middle and lower portions of the Malka lava flow and 190°C in dacite of the Kyukyurtli extrusion. The hydrothermal solutions that participated in metasomatic alteration of rocks pertaining to the Kyukyurtli ore-magmatic system (KOMS) and formed both secondary quartzite and geyserite were enriched in fluorine, as evidenced from the occurrence of F-bearing minerals-zharchikhite, ralstonite,

  9. High-Resolution Studies of Oceanic Spreading Center Volcanic and Hydrothermal Features and Processes - New Insights from Ridge 2000 Program Experiments (United States)

    Fornari, D. J.


    During the past 60 years of research on mid-ocean ridges (MORs) we have exponentially increased our understandings one of the planet's most fundamental features and the myriad processes associated with the transfer of energy from the mantle to the hydrosphere that is focused along accretionary plate boundaries. The past decade's research, implemented by a broad community of scientists in numerous disciplines has yielded a watershed of information that has helped to make both temporal and spatial connections between processes that store and deliver magma to the crust and seafloor, and the consequent hydrothermal and biological phenomena that derive from that energy transfer. Ridge 2000 Program research at each of the three Integrated Study Sites (ISSs) - East Pacific Rise 8-10N, Juan de Fuca - Endeavour Segment, and Eastern Lau Spreading Center - provided an opportunity to coordinate field experiments, laboratory studies and modeling that has lead to new concepts of oceanic spreading center processes. In particular, the latest generation of near-bottom seafloor mapping and sampling systems and a new array of deep submergence vehicles, which include remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs), as well more traditional human occupied vehicles (HOVs) like Alvin, have yielded important new views of MOR seafloor. These systems have allowed us to resolve the sub-meter topography of specific volcanic and hydrothermal features and relate them to distributions of hydrothermal communities, chemical variations among hydrothermal chimneys and their fluid effluent, and to axial structures that are surface manifestations of tectonic processes. In situ chemical, biological and microbial studies carried out during the past decade have increasingly shown how tightly linked chemical and biological processes are within MOR hydrothermal communities. Previous hypotheses concerning frequency of magmatism and volcanic eruptions that have related

  10. Rhyolite genesis at the Picabo Volcanic Center of the Snake River Plain: Progressive recycling of hydrothermally altered rhyolites revealed by high resolution analysis of individual zircons (United States)

    Drew, D.; Bindeman, I. N.; Watts, K. E.; Schmitt, A. K.; McCurry, M. O.


    calderas is obscured, the following observations indicate that the Picabo center represents a series of nested calderas with a mechanism of formation similar to the eastern centers, Heise and Yellowstone: 1) 10's of meters thick 10.4-6.6 Ma ignimbrite outflow sheets with great spatial extent; 2) abundance of post TAV low δ18O units with diverse δ18Ozircon, indicative of remelting of previously erupted rhyolites; 3) a δ18Omelt signature distinguishable from contemporaneous eruptions in adjacent volcanic centers. The development of caldera clusters and the critical transitions between major volcanic centers provides deeper insight into magma genesis through "crustal cannibalism" and rhyolite recycling, processes involved in rhyolite genesis at Picabo, Heise, Yellowstone, and likely other caldera complexes in the SRP and worldwide.

  11. Variation of Crustal Shear Velocity Structure Along the Eastern Lau Back-Arc Spreading Center Constrained By Seafloor Compliance (United States)

    Zha, Y.; Webb, S. C.; Dunn, R. A.


    Measurements of seafloor compliance, the deformation under long period (typically 30-300 s) ocean wave forcing, are primarily sensitive to crustal shear velocity structure. We analyze seafloor compliance from data collected from a subset of 50 broadband Ocean Bottom Seismographs (OBS) deployed at the Eastern Lau spreading center (ELSC) from 2009 to 2010. The ELSC is a 400-km-long back-arc spreading center lying closely to the Tonga subduction trench in the southwestern Pacific. Seafloor morphology, crustal seismic structure and lava composition data show rapid variations along the ridge as the ridge migrates away from the volcanic arc front to the north, indicating a decreasing influence of the subducting slab. We calculate seafloor compliance functions by taking the spectral transfer function between the vertical displacement and pressure signal recorded by the 4-component OBSs, which are equipped with differential pressure gauges (DPGs). In the ridge perpendicular direction, compliance amplitude vary by more than an order of magnitude from the ridge crest to older seafloor covered by sediment. Along the spreading ridge, compliance measured from on-axis sites increases southwards, indicative of a decrease in the upper crustal shear velocity possibly due to increasing porosity and a thickening extrusive layer [Jacobs et al., 2007; Dunn et al., 2013]. We apply a Markov Chain Monte Carlo method to invert the compliance functions for crustal shear velocities at various locations along the ELSC.

  12. Paleocene on-spreading-axis hotspot volcanism along the Ninetyeast Ridge: An interaction between the Kerguelen hotspot and the Wharton spreading center

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Gopala Rao, D.; SubbaRaju, L.V.; Chaubey, A.K.; Shcherbakov, V.S.; Pilipenko, A.I.; Murthy, I.V.R.

    Investigations of three plausible tectonic settings of the Kerguelen hotspot relative to the Wharton spreading center evoke the on-spreading-axis hotspot volcanism of Paleocene (60-54 Ma) age along the Ninetyeast Ridge. The hypothesis is consistent...

  13. Recycling, Remobilization, and Eruption of Crystals from the Lassen Volcanic Center (United States)

    Schrecengost, K.; Cooper, K. M.; Kent, A. J.; Huber, C.; Clynne, M. A.


    The Lassen Volcanic Center recently produced two relatively small dacitic eruptions (0.03 km3 -1.4 km3) with a complex mixing history. Preliminary data for the 1915 Lassen Peak (LP) and the 1103±13 ybp Chaos Crags (CC) eruptions indicate complex mixing between a remobilized crystal mush (hornblende, biotite, sodic plagioclase, quartz) and basalt or basaltic andesite. U-series bulk ages represent crystallization of plagioclase at an average age of either a single event or a mixture of different plagioclase populations that crystallized during distinct crystallization events separated in time. We present 238U-230Th disequilibria for the LP light dacite and black dacite along with three stages (upper pyroclastic flow deposit, Dome B, and Dome F) of the CC eruption. Initial 230Th/232Th activity ratios for the LP plagioclase are higher than the LP host liquid and modeled equilibrium zero-age plagioclase towards the CC host liquid composition. The LP plagioclase data are inconsistent with crystallization from the LP host liquid. Therefore, at least a portion of the plagioclase carried by the LP eruptive products are antecrystic originating from an older and/or isotopically distinct host liquid composition. Moreover, LP bulk plagioclase is consistent with crystallization from the CC host liquid, suggesting that both eruptions are sourced from a similar host reservoir (i.e., crystal mush). Hornblende and biotite from the LP eruption have isotopic ratios that are consistent with zero age crystallization from the LP liquid composition, suggesting that they are younger and originate from a different magma than the plagioclase, with mixing between the magmas prior to eruption. However, it is more likely that hornblende, biotite, and plagioclase with varying average crystal ages were remobilized and erupted from a common crystal mush reservoir during the LP and CC eruptions. These data are consistent with zircon 238U-230Th model ages [1] that emphasize the importance of local

  14. Stable carbon and oxygen isotope chronologies from Araucaria angustifolia trees as proxies for investigating the impacts of Andean volcanism on South-Eastern American climate (United States)

    Churakova (Sidorova), Olga; Saurer, Matthias; Evangelista da Silva, Heitor; Prestes, Alan; Corona, Christophe; Guillet, Sèbastien; Siegwolf, Rolf; Stoffel, Markus


    Stratospheric volcanic eruptions may lead to global cooling effects due to decreasing incoming solar radiation and perturbation of atmospheric circulation masses. Tree rings as indirect climate proxies, are able to capture information about temperature and precipitation changes from seasonal to annual scale. During past decades, studies of the impact of volcanic eruptions on tree-rings as well as stable isotopes in tree rings were focused mostly on the Northern Hemisphere. However, little attention has been paid to the Southern Hemisphere, particular to South America. Therefore, our goal is to quantify the impacts of Andean volcanism on Eastern South American climate in terms of temperature and hydrological changes over the past half millennium. To reconstruct past hydroclimatic and temperature changes after the 12 largest volcanic eruptions of the past 500 years we analyzed carbon and oxygen stable isotopes from cellulose chronologies from Araucaria angustifolia, indigenous climate sensitive conifer species from General Carneiro, State of Paraná, Brazil. The species distribution in southern Brazil is limited between the latitudes of 18° and 30° south, where species occurrence is often associated with Atlantic forest remnants, in mono dominant or mixed forest matrices. To date, a database of 20 tree-ring width chronologies is currently available and spans the last 634 years. We analyzed that material for precipitation and temperature anomalies, and model allocation of atmospheric circulation patterns after major volcanic eruptions. This will improve our understanding of driving factors of Southern Hemispheric climate over the past centuries. Acknowledgements: This work was supported by Brazilian-Swiss Joint Research Programme (BSJRP).

  15. Transition of the Slab Geometry at the Eastern End of the Trans-Mexican Volcanic Belt from Ambient Noise and Earthquake Surface Waves (United States)

    Castillo, J.; Clayton, R. W.; Spica, Z.; Perez-Campos, X.


    The Trans-Mexican Volcanic Belt (TMVB) is one of the largest continental volcanic arcs on the North America plate, spanning 1200 km in central Mexico. Its diversity in volcanic style and non-parallel orientation with the trench are explained by along-strike variations in the subduction parameters of the Rivera and Cocos plates. However, the abrupt termination of the TMVB on its eastern end with the Pico de Orizaba volcano is puzzling as the transition of the Cocos flat-slab geometry to normal subduction appears to be smooth through this region. There is evidence that a tear in the slab is developing, but it is unclear how this feature can support the unusually large topographic gradient. Here, we use 6-70 s surface waves from ambient-noise cross-correlations, correlations of coda of cross-correlations, and earthquake data, to image the shear wave velocity structure to a depth of 150 km. The structures observed in the proposed velocity model are in agreement with the major tectonic features of the region. Low velocities correlate well with the active volcanos of the TMVB and the Veracruz Basin whereas high velocities coincide with the southern end of the Sierra Madre Oriental mountain range. Large velocity contrasts for the upper crust also show strong correspondence with the tectonostratigraphic terrane boundaries. A strong negative velocity perturbation that transitions to positive at 30 km depth and continues with a NE-SW orientation beneath Los Tuxtlas volcanic field is imaged and suggested to be related to the anomalous south-west dipping structure that has been evidenced by previous receiver function studies.

  16. Response of Hydrothermal System to Stress Transients at Lassen Volcanic Center, California inferred from Seismic Interferometry with Ambient Noise (United States)

    Taira, T.; Brenguier, F.


    Time-lapse monitoring of seismic velocity at volcanic areas can provide unique insight into the property of hydrothermal and magmatic fluids and their temporal variability. We established a quasi real-time velocity monitoring system by using seismic interferometry with ambient noise to explore the temporal evolution of velocity in the Lassen Volcanic Center, northern California. Our monitoring system finds temporal variability of seismic velocity in response to stress changes imparted by an earthquake and by seasonal environmental changes. Dynamic stress changes from a magnitude 5.7 local earthquake induced a 0.1% velocity reduction at a depth of about 1 km. The seismic velocity susceptibility defined as ratio of seismic velocity change to dynamic stress change is estimated to be about 0.006 MPa-1, which suggests the Lassen hydrothermal system is marked by high-pressurized hydrothermal fluid. By combining geodetic measurements, our observation shows that the long-term seismic velocity fluctuation closely tracks snow-induced vertical deformation without time delay, which is most consistent with an hydrologic load model (either elastic or poroelastic response) in which surface loading drives hydrothermal fluid diffusion that leads to an increase of opening of cracks and subsequently reductions of seismic velocity. We infer that heated-hydrothermal fluid in a vapor-dominated zone at a depth of 2-4 km range is responsible for the long-term variation in seismic velocity.

  17. Sedimentological and paleontological features of sea floor sediments of Penta Palummo and Miseno volcanic highs, Gulf od Naples (South-eastern Tyrrhenian Sea)

    Energy Technology Data Exchange (ETDEWEB)

    Ferraro, L.; Molisso, F. [Consiglio Nazionale delle Ricerche, Naples (Italy). Ist. di Ricerca Geomare Sud


    A sedimentological and paleontological study has been carried out on surficial sediments of Penta Palummo and Miseno volcanic banks, in the Gulf of Naples (South-eastern Tyrrhenian Sea, Italy). The deposits consist of bioclastic sand (coralline algae, bryozoans, gastropods, bivalvs and echinoderms). The benthic foraminiferal assemblage is mainly characterized by epiphytic species. Bioclastics sand is autochtonous and derived from breakdown of algal buildups. [Italian] Uno studio sedimentologico e paleontologico e' stato condotto sui sedimenti superficiali dei banchi vulcanici di Penta Palummo e di Miseno (Golfo di Napoli, Mar Tirreno sudorientale). I depositi sono costituiti da sabbie bioclastiche (alghe coralline, briozoi, gasteropodi, bivalvi ed echonodermi). L'associazione a foraminiferi bentonici e' caratterizzata principalmente da specie epifite. Le sabbie bioclastiche sono autoctone e derivano dal disfacimento di biocostruzioni algali.

  18. First data on the environment and climate change within the Zhom-Bolok volcanic field (Eastern Sayan Mountains) in the Middle-Late Holocene (United States)

    Bezrukova, E. V.; Shchetnikov, A. A.; Kuzmin, M. I.; Sharova, O. G.; Kulagina, N. V.; Letunova, P. P.; Ivanov, E. V.; Kraynov, M. A.; Kerber, E. V.; Filinov, I. A.; Levina, O. V.


    This paper considers the results of comprehensive lithological, biostratigraphic, and geochemical investigation of sediments in Khara-Nur Lake (Eastern Sayan Mountains) situated in the area of the greatest Holocene eruptions in the Central Asia Region. The age of the basal sediment layer is estimated at 6881 ± 53 years. The local natural environment and climate have undergone great changes since that time. The Holocene volcanic events did not exert a catastrophic impact on the regional landscape, but they caused dramatic changes in the local vegetation. The well-defined correlation of the regional events with the well-known records of the natural environment in the Northern Hemisphere is indicative of the decisive influence of global atmospheric circulation on restructuring the landscape and climate system in the Zhom-Bolok Region in the Middle-Late Holocene.

  19. Radiocarbon dating versus volcanic event stratigraphy: Age modelling of Quaternary marine sequences in the coastal region of the Eastern Tyrrhenian Sea

    Energy Technology Data Exchange (ETDEWEB)

    Molisso, F., E-mail: flavia.molisso@iamc.cnr.i [Istituto per l' Ambiente Marino Costiero (IAMC) - CNR, Napoli, Calata P.ta di Massa, Porto di Napoli, 80133 Napoli (Italy); Insinga, D. [Istituto per l' Ambiente Marino Costiero (IAMC) - CNR, Napoli, Calata P.ta di Massa, Porto di Napoli, 80133 Napoli (Italy); Marzaioli, F. [Dipartimento di Scienze Ambientali, Seconda Universita di Napoli, Via Vivaldi, 43-81100 Caserta (Italy); CIRCE, INNOVA, Via Campi Flegrei 34, Pozzuoli 80078 (Italy); Sacchi, M. [Istituto per l' Ambiente Marino Costiero (IAMC) - CNR, Napoli, Calata P.ta di Massa, Porto di Napoli, 80133 Napoli (Italy); Lubritto, C. [Dipartimento di Scienze Ambientali, Seconda Universita di Napoli, Via Vivaldi, 43-81100 Caserta (Italy); CIRCE, INNOVA, Via Campi Flegrei 34, Pozzuoli 80078 (Italy)


    We present the results of an integrated stratigraphic study conducted on eight marine sediment cores collected in the Naples and Salerno Bays, Eastern Tyrrhenian Sea. The aim of the study is the understanding of the timing and the impacts on the sedimentary environment of explosive volcanic events that occurred over the coastal zone of the Campania region during the latest Quaternary. Accurate dating and correlation have been essential for the construction of reliable models of the sediment architecture and influx rates in this area, as well as for establishing the links between changes in sedimentation and palaeoenvironmental events. While in case of deep marine sequences distal ash layers usually offer a significant potential for accurate geochronology, in the case of shallow marine sequences (continental shelf to upper slope) radiocarbon dating revealed to be essential in order to refine correlation among clusters of marine tephra layers with the equivalent proximal pyroclastic deposit onland, particularly where depositional rates are high and the chemistry and age of tephra layers display little variability. The integrated use of AMS {sup 14}C dating on marine materials and the tephrostratigraphic approach based on reconstructions of historical volcanic events is fundamental in order to minimize the uncertainties that affect chronologic constraints derived from radiocarbon-based age models.

  20. New Data on mid-Miocene Rhyolite Volcanism in Eastern Oregon Extend Early, co-CRBG Rhyolite Flare up and Constrain Storage Sites of Grande Ronde Flood Basalts (United States)

    Streck, M. J.; Ferns, M. L.; McIntosh, W. C.


    The classical view of relating mid-Miocene rhyolites of the tri-state area of Oregon, Nevada, and Idaho to the flood basalts of the Columbia River Basalt was that a mantle plume impinging along the Oregon-Idaho border first causes eruption of the flood basalts but shortly thereafter causes generation of rhyolites at the McDermitt volcanic field from which then hot-spot track rhyolites developed progressively younging towards Yellowstone. More recent work reveals rhyolites as old as found at McDermitt (~16.5 Ma) to occur along a wide E-W tangent along the Oregon-Nevada-Idaho border. And now, our data extend such early rhyolites (>16 Ma) to several locations further north within and in the periphery of the Lake Owyhee Volcanic Field (LOVF) adding to the geographically orphaned old age of 16.7 Ma of the Silver City Rhyolite, Idaho. Hence, the rhyolite flare-up associated with flood basalt magmatism occurred within a circular area of ~400 km centered 100 km NNE of McDermitt. Consequently, no south-to-north progression exists in the onset of rhyolite volcanism; instead, rhyolites started up at the same time over this large area. Province-wide rhyolite volcanism was strongest between ~16.4 and 15.4 Ma coincident with eruptions of the most voluminous member of the CRBG - the Grande Ronde Basalt (GRB). Field evidence for such bimodal volcanism consists of intercalated local GRB units with the Dinner Creek Tuff and Littlefield Rhyolite in the Malheur River Gorge corridor. GRB eruption sites exist and were likely fed from reservoirs residing below or near rhyolitic chambers. Presently, we have petrological evidence for pinning down GRB storages sites to areas from where rhyolites of the Dinner Creek Tuff and lava flows of the Littlefield Rhyolite erupted. In summary, input of GRG and other CRBG magmas were driving co-CRBG rhyolite volcanism which in turn may have influenced whether flood basalt magmas erupted locally or travelled in dikes to more distally located areas.

  1. Geothermal Potential of the Cascade and Aleutian Arcs, with Ranking of Individual Volcanic Centers for their Potential to Host Electricity-Grade Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Shevenell, Lisa [ATLAS Geosciences, Inc., Reno, NV (United States); Coolbaugh, Mark [ATLAS Geosciences, Inc., Reno, NV (United States); Hinz, Nick [Univ. of Nevada, Reno, NV (United States); Stelling, Pete [Western Washington Univ., Bellingham, WA (United States); Melosh, Glenn [GEODE, Santa Rosa, CA (United States); Cumming, William [Cumming Geoscience, Santa Rosa, CA (United States)


    This project brings a global perspective to volcanic arc geothermal play fairway analysis by developing statistics for the occurrence of geothermal reservoirs and their geoscience context worldwide in order to rank U.S. prospects. The focus of the work was to develop play fairways for the Cascade and Aleutian arcs to rank the individual volcanic centers in these arcs by their potential to host electricity grade geothermal systems. The Fairway models were developed by describing key geologic factors expected to be indicative of productive geothermal systems in a global training set, which includes 74 volcanic centers world-wide with current power production. To our knowledge, this is the most robust geothermal benchmark training set for magmatic systems to date that will be made public.

  2. A geochemical approach for assessing the possible uses of the geothermal resource in the eastern sector of the Sabatini Volcanic District (Central Italy) (United States)

    Cinti, Daniele; Tassi, Franco; Procesi, Monia; Brusca, Lorenzo; Cabassi, Jacopo; Capecchiacci, Francesco; Delgado Huertas, Antonio; Galli, Gianfranco; Grassa, Fausto; Vaselli, Orlando; Voltattorni, Nunzia


    The Sabatini Volcanic District (SVD) hosts a hydrothermal reservoir heated by the post-magmatic activity that affected the peri-Tyrrhenian sector of central Italy, giving rise to a number of thermal and mineral discharges. In this study, a complete geochemical and isotopic dataset based on the composition of 215 water and 9 bubbling gases, collected from the eastern sector of this huge hydrothermal system, is reported. The main aims are to (i) investigate the fluid sources and the main chemical-physical processes controlling the fluid chemistry and (ii) construct a conceptual fluid circulation model to provide insights into the possible use(s) of the geothermal resource. The fluid discharges are fed by two main aquifers, characterized by: (1) a Ca-HCO3 to Ca(Na)-HCO3 composition, typical of a shallow hydrological circuit within volcanic and sedimentary formations, and (2) a Ca-HCO3(SO4) to Na(Ca)-HCO3(Cl) composition, produced by the interaction of CO2-rich fluids with Mesozoic and Triassic carbonate-evaporite rocks. A thick sequence of low-permeability volcanic products represents a physical barrier between the two fluid reservoirs. As commonly occurring in central-southern Italy, CO2 is mainly produced by thermo-metamorphic decarbonation within the carbonate-evaporite reservoir, with minor contribution of mantle CO2. A dominant crustal source is also indicated by the relatively low R/Ra values (0.07-1.04). Methane and light hydrocarbons are mostly thermogenic, whereas H2S derives from thermogenic reduction of the Triassic anhydrites. Slightly positive 15N/14N values suggest minor N2 contribution from deep sedimentary sources. On the whole, a comparison of these geochemical features with those of the thermal fluids from the western portion of SVD highlights an eastward increasing influence of the shallow aquifer on the deep-originated fluids, likely caused by the proximity of the Apennine range from where the meteoric water, recharging the hydrothermal system

  3. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NARCIS (Netherlands)

    Klaver, M.; Djuly, T.; de Graaf, S.; Sakes, A.; Wijbrans, J.R.; Davies, G.R.; Vroon, P.Z.


    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by

  4. Irradiation of ready-to-eat foods at USDA'S Eastern Regional Reasearch Center-2003 update (United States)

    Sommers, Christopher; Fan, Xuetong; Niemira, Brendan; Rajkowski, Kathleen


    Ionizing radiation is a safe and effective method for eliminating bacterial pathogens from food products and disinfestation of fruits and vegetables. Since 1980 research has been conducted at USDA's Eastern Regional Research Center pertaining to the elimination of food-borne pathogens from meat, poultry, fruit and vegetable products. Recent work has focused on elimination of pathogens such as Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes from ready-to-eat (RTE) food products including hot dogs, bologna, lettuce, cilantro, sprouts and seeds, and frozen vegetables. The ionizing radiation dose required to eliminate those pathogens from RTE foods has been found to be commodity, formulation and temperature dependent. The need to eliminate bacterial pathogens from RTE food products must always be balanced with the maintenance of product quality. In addition to determining the effective ionizing radiation doses required for pathogen elimination the effects of irradiation on product chemistry, nutritional value and organoleptic quality have also been determined. A review of the studies conducted at USDA's Eastern Regional Research Center in 2002 and 2003 is presented in this article.

  5. Volcanic successions in Marquesas eruptive centers: A departure from the Hawaiian model (United States)

    Guillou, Hervé; Maury, René C.; Guille, Gérard; Chauvel, Catherine; Rossi, Philippe; Pallares, Carlos; Legendre, Christelle; Blais, Sylvain; Liorzou, Céline; Deroussi, Sébastien


    The temporal evolution and geochemical evolution of Marquesas hotspot volcanoes have often been interpreted with reference to the Hawaiian model, where a tholeiitic shield-building stage is followed by an alkali basaltic post-shield stage, followed after a 0.4 to 2.5 Myr long quiescence period, by a rejuvenated basanitic/nephelinitic stage. Here we discuss geochemical data on 110 Marquesas lavas also dated using the unspiked 40K-40Ar method on separated groundmass (including 45 new ages measured on the southern islands of Hiva Oa, Motane, Tahuata and Fatu Hiva). Sample locations were positioned on detailed geological maps to determine their shield or post-shield position with respect to the caldera collapse event(s), without taking into account their geochemical features. A rather regular decrease of the ages towards SE, consistent with the Pacific plate motion, is observed from Eiao (5.52 Ma) to Fatu Hiva (1.11 Ma), and rejuvenated basanitic volcanism occurs only in Ua Huka (1.15-0.76 Ma). The occurrence of intermediate and evolved lavas is restricted to the post-caldera stage, with the exception of Eiao island. However, many other features of the Marquesas chain are rather atypical with respect to those of Hawaii. Although Marquesas shields are tholeiitic, several of them (Eiao, Tahuata) contain interbedded alkali basaltic and basanitic flows. Moreover, post-shield volcanoes are either alkali basalts (Ua Huka), tholeiites (Hiva Oa, Tahuata, Fatu Hiva) or both (Nuku Hiva). This feature is consistent with the temporal continuity of the two stages and the usually short length of the post-shield period (< 0.2 Myr). In a given island, the trace element and isotopic compositions of shield and post-shield lavas overlap, although both display large variations. The sources of alkali basalts and basanites are more enriched than those of the contemporaneous tholeiites. These specific features support the hypothesis of an extremely heterogeneous Marquesas plume. The

  6. Comparison of quality control for trauma management between Western and Eastern European trauma center

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    Gambale Giorgio


    Full Text Available Abstract Background Quality control of trauma care is essential to define the effectiveness of trauma center and trauma system. To identify the troublesome issues of the system is the first step for validation of the focused customized solutions. This is a comparative study of two level I trauma centers in Italy and Romania and it has been designed to give an overview of the entire trauma care program adopted in these two countries. This study was aimed to use the results as the basis for recommending and planning changes in the two trauma systems for a better trauma care. Methods We retrospectively reviewed a total of 182 major trauma patients treated in the two hospitals included in the study, between January and June 2002. Every case was analyzed according to the recommended minimal audit filters for trauma quality assurance by The American College of Surgeons Committee on Trauma (ACSCOT. Results Satisfactory yields have been reached in both centers for the management of head and abdominal trauma, airway management, Emergency Department length of stay and early diagnosis and treatment. The main significant differences between the two centers were in the patients' transfers, the leadership of trauma team and the patients' outcome. The main concerns have been in the surgical treatment of fractures, the outcome and the lacking of documentation. Conclusion The analyzed hospitals are classified as Level I trauma center and are within the group of the highest quality level centers in their own countries. Nevertheless, both of them experience major lacks and for few audit filters do not reach the mmum standard requirements of ACS Audit Filters. The differences between the western and the eastern European center were slight. The parameters not reaching the minimum requirements are probably occurring even more often in suburban settings.

  7. Diagnosis and treatment outcome of mycotic keratitis at a tertiary eye care center in eastern india

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    Rautaraya Bibhudutta


    Full Text Available Abstract Background Mycotic keratitis is an important cause of corneal blindness world over including India. Geographical location and climate are known to influence the profile of fungal diseases. While there are several reports on mycotic keratitis from southern India, comprehensive clinico-microbiological reports from eastern India are few. The reported prevalence of mycotic keratitis are 36.7%,36.3%,25.6%,7.3% in southern, western, north- eastern and northern India respectively. This study reports the epidemiological characteristics, microbiological diagnosis and treatment outcome of mycotic keratitis at a tertiary eye care center in eastern India. Methods A retrospective review of medical and microbiology records was done for all patients with laboratory proven fungal keratitis. Results Between July 2006 and December 2009, 997 patients were clinically diagnosed as microbial keratitis. While no organisms were found in 25.4% (253/997 corneal samples, 23.4% (233/997 were bacterial, 26.4% (264/997 were fungal (45 cases mixed with bacteria, 1.4% (14/997 were Acanthamoeba with or without bacteria and 23.4% (233/997 were microsporidial with or without bacteria. Two hundred fifteen of 264 (81.4%, 215/264 samples grew fungus in culture while 49 corneal scrapings were positive for fungal elements only in direct microscopy. Clinical diagnosis of fungal keratitis was made in 186 of 264 (70.5% cases. The microscopic detection of fungal elements was achieved by 10% potassium hydroxide with 0.1% calcoflour white stain in 94.8%(238/251 cases. Aspergillus species (27.9%, 60/215 and Fusarium species (23.2%, 50/215 were the major fungal isolates. Concomitant bacterial infection was seen in 45 (17.1%, 45/264 cases of mycotic keratitis. Clinical outcome of healed scar was achieved in 94 (35.6%, 94/264 cases. Fifty two patients (19.7%, 52/264 required therapeutic PK, 9 (3.4%, 9/264 went for evisceration, 18.9% (50/264 received glue application with bandage

  8. Geochemistry and geochronology of late Mesozoic volcanic rocks in the northern part of the Eastern Pontide Orogenic Belt (NE Turkey): Implications for the closure of the Neo-Tethys Ocean (United States)

    Özdamar, Şenel


    This paper presents 40Ar/39Ar and U-Pb age data, Sr-Nd isotopes, whole-rock and mineral compositions of Upper Cretaceous volcanic rocks from the Ordu area of the Eastern Pontide Orogenic Belt (EPOB) in northeastern Turkey. The volcanic rocks exhibit a wide compositional range: basalt, basaltic-andesites, andesites and a rhyodacite suite; they are characterized by subparallel light rare earth element (LREE)-enrichment, relatively flat heavy rare earth element (HREE) patterns with Eu anomalies and moderate fractionation [average (La/Yb)N = 8.55]. The geochemical results show that the volcanic rocks have calc-alkaline affinity consistent with arc volcanic rocks erupted in an active continental margin. Initial 87Sr/86Sr values vary between 0.70569 and 0.70606, while initial 143Nd/144Nd values lie between 0.51244 and 0.51249. Crustal contamination affected the mantle-originated primary magma, as indicated by increased 87Sr/86Sr and decreased 143Nd/144Nd ratios with increasing SiO2. New precise laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS) 206Pb-238U age analyses of zircon and 40Ar/39Ar age data of plagioclase from the volcanics enable a more precise reconstruction of the EBOP. The ages provide insight into the timing of arc formation in this region, constrain the volcanic activity between 86 My (Coniacian) and 75 My (Campanian) and constrain the timing of closure of the Neo-Tethys.

  9. Lahar hazard zones for eruption-generated lahars in the Lassen Volcanic Center, California (United States)

    Robinson, Joel E.; Clynne, Michael A.


    lahar generation, we assume that the maximum historical water equivalent, 3.90 m, covers the entire basin area inside the H/L cone. The product of planimetric area of each basin inside the H/L and the maximum historical water equivalent yields the maximum water volume available to generate a lahar. We then double the water volumes to approximate maximum lahar volumes. The maximum lahar volumes and an understanding of the statistical uncertainties inherent to the LAHARZ calculations guided our selection of six hypothetical volumes, 1, 3, 10, 30, 60, and 90x106 m3, to delineate concentric lahar inundation zones. The lahar inundation zones extend, in general, tens of kilometers away from Lassen Peak. The small, more-frequent lahar inundation zones (1 and 3x106 m3) are, on average, 10 km long. The exceptions are the zones in Warner Creek and Mill Creek, which extend much further. All but one of the small, more-frequent lahar inundation zones reach outside of the Lassen Volcanic National Park boundary, and the zone in Mill Creek extends well past the park boundary. All of the medium, moderately frequent lahar inundation zones (10 and 30x106 m3) extend past the park boundary and could potentially impact the communities of Viola and Old Station and State Highways 36 and 44, both north and west of Lassen Peak. The approximately 27-km-long on average, large, less-frequent lahar inundation zones (60 and 90x106 m3) represent worst-case lahar scenarios that are unlikely to occur. Flood hazards continue downstream from the toes of the lahars, potentially affecting communities in the Sacramento River Valley.

  10. Origin of Volcanic Seamounts Offshore California Related to Interaction of Abandoned Spreading Centers with the Continental Margin (United States)

    Davis, A. S.; Clague, D. A.; Paduan, J. B.; Cousens, B. L.; Huard, J.


    The numerous NE-SW trending volcanic seamounts at the continental margin offshore central to Southern California owe their existence to the complex tectonics that resulted when small spreading ridge segments intersected and partly subducted beneath the continental margin during the Miocene plate reorganization. A limited number of dredged samples had indicated multiple episodes of coeval, alkalic volcanism at geographically widely separated sites (Davis et al., 2002, GSA Bull. 114, 316-333). 450 new samples were collected from 8 seamounts from 37. 5°N to 32.3°N with MBARI's ROV Tiburon. Ar-Ar ages for 50 of these samples extend the ages of volcanism from 18 Ma to 2.8 Ma. The dominant whole rock compositions are differentiated alkalic basalt, hawaiite, and mugearite, but include minor benmoreite, trachyte, and rare tholeiitic basalt. This entire range of compositions is also present in glassy margins or in volcaniclastic breccias, except for the trachyte, which had no glassy margins. Trace element abundances and ratios (e.g. REE, Zr, Nb, Ta, Th, Ba, etc.) are typical for ocean island basalt, whether the seamount is located on the Pacific plate (e.g. Pioneer, Gumdrop, Guide, Davidson, San Juan, San Marcos) or on the continental slope (Rodriguez) or within the Southern Continental Borderland (Northeast Bank). Nine samples, predominantly from Rodriguez Seamount, show a calc-alkaline trend with lower Nb, Ta, and higher Th. These samples may be erratics (Paduan et al., 2007, Marine Geology, in press). Sr, Nd, and Pb isotopic compositions plot within the Pacific N-MORB field for the northern seamounts (Pioneer, Gumdrop, Guide) but suggest progressively more radiogenic sources southward. There is considerable scatter at each site, especially with regard to 87Sr/86Sr, despite severe acid-leaching of the samples. Isotopic and trace element compositions indicate sources that are heterogeneous at a small scale. Chondrite-normalized Ce/Yb suggest smaller degree of melting and

  11. Localized rejuvenation of a crystal mush recorded in zircon temporal and compositional variation at the Lassen Volcanic Center, northern California.

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    Erik W Klemetti

    Full Text Available Zircon ages and trace element compositions from recent silicic eruptions in the Lassen Volcanic Center (LVC allow for an evaluation of the timing and conditions of rejuvenation (reheating and mobilization of crystals within the LVC magmatic system. The LVC is the southernmost active Cascade volcano and, prior to the 1980 eruption of Mount St. Helens, was the site of the only eruption in the Cascade arc during the last century. The three most recent silicic eruptions from the LVC were very small to moderate-sized lava flows and domes of dacite (1915 and 27 ka eruptions of Lassen Peak and rhyodacite (1.1 ka eruption of Chaos Crags. These eruptions produced mixed and mingled lavas that contain a diverse crystal cargo, including zircon. 238U-230Th model ages from interior and surface analyses of zircon reveal ages from ∼17 ka to secular equilibrium (>350 ka, with most zircon crystallizing during a period between ∼60-200 ka. These data support a model for localized rejuvenation of crystal mush beneath the LVC. This crystal mush evidently is the remnant of magmatism that ended ∼190 ka. Most zircon are thought to have been captured from "cold storage" in the crystal mush (670-725°C, Hf >10,000 ppm, Eu/Eu* 0.25-0.4 locally remobilized by intrusion of mafic magma. A smaller population of zircon (>730°C, Hf 0.4 grew in, and are captured from, rejuvenation zones. These data suggest the dominant method to produce eruptible melt within the LVC is small-scale, local rejuvenation of the crystal mush accompanied by magma mixing and mingling. Based on zircon stability, the time required to heat, erupt and then cool to background conditions is relatively short, lasting a maximum of 10 s-1000 s years. Rejuvenation events in the LVC are ephemeral and permit eruption within an otherwise waning and cooling magmatic body.

  12. Profile of retinal vasculitis in a tertiary eye care center in Eastern India

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    Kumar Saurabh


    Full Text Available Aims: To provide a fact file on the etiology, clinical presentations and management of retinal vasculitis in Eastern India. Materials and Methods: Retrospective, record based analysis of retinal vasculitis cases in a tertiary care center in Eastern India from January 2007 to December 2009 . Results: One hundred and thirteen eyes of 70 patients of retinal vasculitis were included in this study. Sixty (85.7% patients were male (mean age 33± 11.1 years and 10 (14.3% were female (mean age 32.4 ± 13.6 years. Vasculitis was bilateral in 43 (61.4% and unilateral in 27 (38.6% patients. Commonest symptoms were dimness of vision (73; 64.6% and floaters (36; 31.9%. Vascular sheathing (82; 72.6% and vitritis (51; 45.1% were commonest signs. Mantoux test was positive in 21 (30% patients but tuberculosis was confirmed in only four (5.71% patients. Raised serum angiotensin-converting enzyme level and positive antinuclear antibody level were reported in four (5.71% patients each. Human leukocyte antigen B5 (HLA B5 marker was present in one (1.4% patient. However, none of the total 70 patients were found to have a conclusively proven systemic disease attributable as the cause of retinal vasculitis. Oral corticosteroid (60; 85.7% was the mainstay of treatment. Forty-eight (42.5% eyes maintained their initial visual acuity and 43 (38% gained one or more line at mean follow-up of 16.6± 6.3 months. Conclusion: Retinal vasculitis cases had similar clinical presentations and common treatment plan. There was no systemic disease association with vasculitis warranting a careful approach in prescribing investigations.

  13. Localized rejuvenation of a crystallizing pluton recorded in zircon from the Lassen Volcanic Center, southern Cascade Range, California (United States)

    Klemetti, E. W.; Clynne, M. A.; Ring, M.; Bertolett, E. M.


    The Lassen Volcanic Center (LVC) in northern California produced the only eruption in the Cascades other than Mount St. Helens over the past century with its activity in 1914-17. The LVC dates back to ~825 ka and has produced ~215 km3 of dominantly andesite to rhyodacite (with minor basaltic andesite and rhyolite) lava and tephra over that period with activity since 90 ka divided into the Twin Lakes (~90 to 0.01 ka) and Eagle Peak sequences (~66 to 1.1 ka). The Twin Lakes sequences has a higher proportion of basaltic input relative to the Eagle Peak sequence, however both sequence show extensive evidence of magma mixing and mingling. Examining the age spectra and composition of zircon from representative eruptions in the LVC can illuminate the petrologic conditions of the underlying magmatic system. We collected (via SHRIMP-RG) the first 238U-230Th model ages and trace-element compositions of zircon from one Twin Lakes sequence eruption (1915 dacite of Lassen Peak) and three Eagle Peak sequence eruptions (the rhyodacite of Chaos Crags, the 27 ka dacite of Lassen Peak and the 66 ka rhyodacite of Eagle Peak). Zircon age spectra from the rhyodacite of Chaos Crags and 1915 and 27 ka dacites of Lassen Peak (62 zircon analyses) are similar, with a range of 25 ka to secular equilibrium (~350 ka) with no crystals within error of their host eruption age. The dominant period of zircon crystallization falls between 190-90 ka. This is a period of volcanic quiescence in the LVC and this zircon bloom represents the crystallization of a proto-pluton following the end of the Bumpass Sequence (350-193 ka). Surface analyses of zircons from the analyzed eruptions range from 25 ka to 74 ka; none of which is within error of the eruption age of the host lava. This suggests that zircon crystallization effectively ended at ~25-30 ka. The host lavas, when erupted, were zircon undersaturated, so zircon preservation is likely due to inclusion in other phases. Overall, the zircon from these

  14. Geochronology and geochemistry of Permian bimodal volcanic rocks from central Inner Mongolia, China: Implications for the late Palaeozoic tectonic evolution of the south-eastern Central Asian Orogenic Belt (United States)

    Zhang, Zhicheng; Chen, Yan; Li, Ke; Li, Jianfeng; Yang, Jinfu; Qian, Xiaoyan


    Zircon U-Pb ages, geochemical data and Sr-Nd isotopic data are presented for volcanic rocks from the lower Permian Dashizhai Formation. These rocks are widely distributed in the south-eastern Central Asian Orogenic Belt in central Inner Mongolia, China. The volcanic rocks mainly consist of basaltic andesite and rhyolite, subordinate dacite and local andesite, and exhibit bimodal geochemical features. The results of zircon U-Pb dating indicate that the volcanic rocks formed during the early Permian (292-279 Ma). The mafic volcanic rocks belong to low-K tholeiitic to medium-K calc-alkaline series. These mafic volcanic rocks are also characterised by moderately enriched light rare earth element (LREE) patterns; high abundances of Th, U, Zr and Hf; negative Nb, Ta and Ti anomalies; initial 87Sr/86Sr ratios of 0.70514-0.70623; and positive εNd(t) values (+1.9 to +3.8). These features indicate that the mafic volcanic rocks were likely derived from the high-percentage partial melting of subduction-related metasomatised asthenospheric mantle. The felsic rocks show an A-type affinity, with enrichments in alkalis, Th, U and LREEs. The felsic rocks are depleted in Ba, Sr, Nb, Ta and Ti and exhibit moderately LREE-enriched patterns (LaN/YbN = 2.09-6.45) and strongly negative Eu anomalies (Eu/Eu∗ = 0.04-0.25). These features, along with the positive εNd(t) values (+2.6 to +7.7) and young TDM2 ages (TDM2 = 435-916 Ma), indicate that the felsic rocks were likely derived from a juvenile crustal source that mainly consisted of juvenile mid-ocean ridge basalt-related rocks. The volcanic association in this study and in previously published work widely distributed in central Inner Mongolia. The observations in this study suggest that the lower Permian volcanic rocks formed in an identical tectonic environment. The regional geological data indicate that the bimodal volcanic rocks from the lower Permian Dashizhai Formation in the study area formed in an extensional setting that was

  15. Radical operation for hilar cholangiocarcinoma in comparable Eastern and Western centers: Outcome analysis and prognostic factors. (United States)

    Kimura, Norihisa; Young, Alastair L; Toyoki, Yoshikazu; Wyatt, Judith I; Toogood, Giles J; Hidalgo, Ernest; Prasad, K Rajendra; Kudo, Daisuke; Ishido, Keinosuke; Hakamada, Kenichi; Lodge, J Peter A


    Extensive resection for hilar cholangiocarcinoma is the most effective treatment, but high morbidity and poor prognosis remain concerns. Previous data have shown marked differences in outcomes between comparable Eastern and Western centers. We compared the outcomes of the management for hilar cholangiocarcinoma at one Japanese and one British institution with comparable experience. Of 298 consecutive patients with hilar cholangiocarcinoma evaluated at Hirosaki University Hospital, Japan and St. James's University Hospital, Leeds, UK, 183 underwent radical resection. Clinicopathologic variables and postoperative outcomes were compared. Significant differences were not observed between the Hirosaki and Leeds cohorts in overall outcomes despite several differences in the patient characteristics. Although there was a difference in 90-day mortality (2.5% vs 13.6%, respectively), disease-specific 5-year survival rates were 32.8% and 31.9%, respectively (P = .767). Multivariate analysis identified trisectionectomy (odds ratio = 2.32; P = .010), combined pancreatoduodenectomy (odds ratio = 7.88; P = .010), and perioperative blood transfusion (odds ratio = 1.88; P = .045) were associated with postoperative major complications, while preoperative biliary drainage associated with postoperative major complications, while preoperative biliary drainage (risk ratio = 2.21; P = .018), perioperative blood transfusion (risk ratio = 1.58; P = .029), lymph node metastasis (risk ratio = 2.00; P = .002), moderate/poorly differentiated tumor (risk ratio = 1.72; P = .029), microvascular invasion (risk ratio = 1.63; P = .046), and R1 resection (risk ratio = 1.90; P = .005) were risk factors for poor survival. Disease-specific survival and prognostic factors were similar in both centers. Meticulous operative technique to avoid perioperative blood transfusion may improve long-term survival. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Edge, Center, and Spine: Exploring the Multi-Dimentionality of Contemporary Landscapes in Middle Eastern Cities

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    Ashraf M. Salama


    Full Text Available This paper offers an overview of landscape interventions in three Middle Eastern cities and a positional interpretation of the way in which different landscape typologies can contribute to their socio-spatial and environmental contexts. The paper identifies three levels of contribution of contemporary landscape – edge, center, and spine - corresponding to three landscape typologies: the edge typology is a linear coastal landscape that acts as an interface between the city and the sea; the central typology is a city park that reactivates or regenerates a fragment of the city and communities that surround it; and the spine is an ecological infrastructure – a wadi - that articulates and curates the natural and constructed flow of water creating productive landscapes and public spaces. In undertaking the discussion and analysis, a multi-layered general methodology was employed. First, to induct generalities on three projects identified a literature review and analysis of development and technical review reports is conducted in order to elucidate a considerable number of issues underlying each landscape typology while classifying them under three main sub-headings that include contextual background, evolutionary design and planning aspects, and key spatial design features. Second, to deduct particularities concerning the contribution of each typology, critical discussion, reflection, and reference to some empirical studies are carried out with the intention of unveiling the contribution of each typology to its context and to the city within which it exists.

  17. Lifestyle and Dietary Behaviors among Saudi Preschool Children Attending Primary Health Care Centers, Eastern Saudi Arabia

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    Magdy A. Darwish


    Full Text Available Objective. To study life styles and dietary behaviors among Saudi preschool children (1–5 years attending primary health care centers (PHCCs in Dammam and Qatif areas, eastern province, Saudi Arabia. Material and Methods. Cross-sectional study. Data were collected using structured, interviewer-filled questionnaire. Children and their mothers were encountered during their well-baby clinic visits. A total number of 300 preschool children and their mothers were interviewed during study period. Results. Unsatisfactory areas include smoking fathers (32%, smoking in front of children (11.3%, overweight and obesity among mothers (60.3%, noncompliance using seat belts for both parents (56.3% and children (68%, children watching television (T.V more than 2 hours (50%, adherence to exclusive breast feeding (only 20.7%, and late solid food introduction (65.3%. Frequent intake of unhealthy food items was 26%, 25%, and 24% for pizza, burger, and soft drinks. Unfortunately frequent intake of the following unhealthy food items was high: biscuits, deserts/chocolates, and chips which was 78%, 67%, and 72%, respectively. Conclusion. This study provides benchmark about the current situation. It provides health care workers and decision makers with important information that may help to improve health services.

  18. Volatiles in Olivine Hosted Melt Inclusions from Small Eruptive Centers of the Central Southern Volcanic Zone (CSVZ), Chile (United States)

    Wacaster, S.; Hickey-Vargas, R.; Wallace, P.


    This study is a geochemical analysis of basaltic scoria cones of the CSVZ, where bulk rock analyses have revealed two predominant lava types. We consider the relationship of cones to nearby stratovolcanos and the proximity of both to the Liquine-Ofqui Fault Zone to understand how primitive melts with wide ranging compositions are generated. We characterize melt inclusions to see if they show similar trends as bulk rocks and to evaluate degassing of melts during ascent and crystallization. We report new CO2, H2O, F, S, and Cl data collected by SIMS and FTIR. Type 1 and Type 2 lavas have been identified in prior studies. Type 1 rocks have significant 238U/232Th excesses and higher abundances of fluid mobile elements. Type 2 lavas and scorias have higher LREE/HREE ratios, lower abundances of fluid mobile elements, lower 87Sr/86Sr and U- series isotopes near secular equilibrium. Type 1, usually associated with composite volcanic centers, erupt at one cone in our field area, while Type 2 is found only at other individual cones aligned with the LOFZ. We characterize olivine-hosted melt inclusions with emphasis on volatile element analyses to test the hypotheses of flux melting beneath Type 1 centers versus a lesser extent of decompression melting beneath Type 2 centers. Melt inclusions show the following overall ranges of volatiles: CO2: below detection-1208 ppm; H2O(Total): 0.11-3.9 wt percent: F: 52-1442 ppm; S: 34-2884 ppm, and Cl: 177-1606 ppm. Inclusions from lavas are generally more degassed when compared to those from scoria for CO2 and H2O. Some Cl and F values are lower in inclusions from lavas, but not all. Sulfur is variably degassed in melt inclusions from both lavas and scoria. Melt inclusions from Type 2 Caburgua scoria show evidence for variable degassing and crystallization pressures. One subset of the inclusions were trapped at low pressures (P CO2 CO2 (1.5-4.0 wt % and 300-800 ppm and all under 1100 bars). Type I San Jorge melt inclusions also show

  19. Immigrant Workers Centers in Eastern Massachusetts, USA: Fostering Services, Support, Advocacy, and Community Organizing

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    Humberto Reynoso-Vallejo


    Full Text Available Immigrant Workers Centers (IWCs are community-based organizations that have been developed in the United States to promote and protect workers’ rights through support, services, advocacy, and organizing initiatives. The purpose of this research study was to examine how IWCs in the Eastern part of the state of Massachusetts are structured along twelve dimensions of organizational development and community organizing. Qualitative research methods were used to identify shared themes within the six IWCs and three immigrant support organizations, as well as their organizational responses to the current anti-immigrant environment. IWCs constituted a convenience sample which enabled the researchers to gather data utilizing a case study methodology. In-depth semi-structured interviews were conducted between the months of July and September of 2009 to answer the following research questions: 1What are the shared themes for the development of Immigrant Workers Centers?, and 2 How do Immigrant Workers Centers respond to current anti-immigrant sentiment, intolerant immigration policies, and increased exploitation in this troubled economy? Shared themes among the IWCs include prioritizing community organizing for workers’ rights and collective empowerment. Sub-modalities such as education, training and leadership development area common feature. While some individual support is provided, and in some cases, programming, it always is offered within a context that emphasizes the need for collective action to overcome injustice. Issues addressed include health/safety, sexual harassment, discrimination, and various problems associated with wages (underpayment, missed payments, collecting back wages, and lack of overtime pay. IWCs respond to antiimmigrant policies and practices by supporting larger efforts for immigration reformat the municipal, state, and federal levels. Coalitions of IWCS and their allies attempt to make state wide and federal policy changes

  20. Geodetic observations and modeling of magmatic inflation at the Three Sisters volcanic center, central Oregon Cascade Range, USA (United States)

    Dzurisin, Daniel; Lisowski, Michael; Wicks, Charles W.; Poland, Michael P.; Endo, Elliot T.


    Tumescence at the Three Sisters volcanic center began sometime between summer 1996 and summer 1998 and was discovered in April 2001 using interferometric synthetic aperture radar (InSAR). Swelling is centered about 5 km west of the summit of South Sister, a composite basaltic-andesite to rhyolite volcano that last erupted between 2200 and 2000 yr ago, and it affects an area ˜20 km in diameter within the Three Sisters Wilderness. Yearly InSAR observations show that the average maximum displacement rate was 3-5 cm/yr through summer 2001, and the velocity of a continuous GPS station within the deforming area was essentially constant from June 2001 to June 2004. The background level of seismic activity has been low, suggesting that temperatures in the source region are high enough or the strain rate has been low enough to favor plastic deformation over brittle failure. A swarm of about 300 small earthquakes ( Mmax = 1.9) in the northeast quadrant of the deforming area on March 23-26, 2004, was the first notable seismicity in the area for at least two decades. The U.S. Geological Survey (USGS) established tilt-leveling and EDM networks at South Sister in 1985-1986, resurveyed them in 2001, the latter with GPS, and extended them to cover more of the deforming area. The 2001 tilt-leveling results are consistent with the inference drawn from InSAR that the current deformation episode did not start before 1996, i.e., the amount of deformation during 1995-2001 from InSAR fully accounts for the net tilt at South Sister during 1985-2001 from tilt-leveling. Subsequent InSAR, GPS, and leveling observations constrain the source location, geometry, and inflation rate as a function of time. A best-fit source model derived from simultaneous inversion of all three datasets is a dipping sill located 6.5 ± 2.5 km below the surface with a volume increase of 5.0 × 10 6 ± 1.5 × 10 6 m 3/yr (95% confidence limits). The most likely cause of tumescence is a pulse of basaltic magma

  1. Sr, Nd, and Pb isotopes of ultramafic xenoliths in volcanic rocks of Eastern China: enriched components EMI and EMII in subcontinental lithosphere (United States)

    Tatsumoto, M.; Basu, A.R.; Wankang, H.; Junwen, W.; Guanghong, X.


    The UThPb, SmNd, and RbSr isotopic systematics of mafic and ultramafic xenolithic rocks and associated megacrystic inclusions of aluminous augite and garnet, that occur in three alkalic volcanic suites: Kuandian in eastern Liaoning Province, Hanluoba in Hebei Province, and Minxi in western Fujian Province, China are described. In various isotopic data plots, the inclusion data invariably fall outside the isotopic ranges displayed by the host volcanic rocks, testifying to the true xenolithic nature of the inclusions. The major element partitioning data on Ca, Mg, Fe, and Al among the coexisting silicate minerals of the xenoliths establish their growth at ambient mantle temperatures of 1000-1100??C and possible depths of 70-80 km in the subcontinental lithosphere. Although the partitioning of these elements reflects equilibrium between coexisting minerals, equilibria of the Pb, Nd, and Sr isotopic systems among the minerals were not preserved. The disequilibria are most notable with respect to the 206Pb 204Pb ratios of the minerals. On a NdSr isotopic diagram, the inclusion data plot in a wider area than that for oceanic basalts from a distinctly more depleted component than MORB with higher 143Nd 144Nd and a much broader range of 87Sr 86Sr values, paralleling the theoretical trajectory of a sea-water altered lithosphere in NdSr space. The garnets consistently show lower ?? and ?? values than the pyroxenes and pyroxenites, whereas a phlogopite shows the highest ?? and ?? values among all the minerals and rocks studied. In a plot of ??207 and ??208, the host basalts for all three areas show lower ??207 and higher ??208 values than do the xenoliths, indicating derivation of basalts from Th-rich (relative to U) sources and xenoliths from U-rich sources. The xenolith data trends toward the enriched mantle components, EMI and EMII-like, characterized by high 87Sr 86Sr and ??207 values but with slightly higher 143Nd 144Nd. The EMI trend is shown more distinctly by the host

  2. Integrated Archaeological and Geophysical Surveys in the Historical Center of Augusta (Eastern Sicily, Italy). (United States)

    Malfitana, Daniele; Leucci, Giovanni; Fragalà, Giovanni; Cacciaguerra, Giuseppe; De Giorgi, Lara


    Syracuse (Eastern Sicily, Italy) and its vast hinterland played a crucial role in the economy of ancient Sicily, largely because of the management, exploitation and trade of agricultural supply. Nevertheless, the socio-economic aspects of its territorial management and the relation between the countryside and coastal centres in the complex system of the Mediterranean markets have not yet been analysed in depth by scholars. Despite the historical, monumental and economic importance of the surrounding area of Syracuse in the Antiquity, the knowledge of the roman and medieval landscape and archaeological sites are still limited. The research undertaken by Istituto per i Beni Archeologici e Monumentali - CNR of Catania (Sicily, Italy) attempted to remedy this omission by outlining a preliminary picture of the rich historical and archaeological heritage of Syracuse and its surrounding territory, which will be analysed using a multidisciplinary approach. Augusta, a town near Syracuse (Sicily), was founded by emperor Frederick of Suavia between 1232 and 1239. In medieval period, the area of Giardini Pubblici was the downtown and untill the XVII Cent. AD it was occupied by two urban blocks of buildings. In 1670 they were demolished to allow free area firing line from the near castle. Integrated archaeological and geophysical investigations allowed a wide range knowledge of the roman and medieval landscapes, archaeological sites and monumental remains. Particularly the geophysical surveys undertaken in the historical center of Augusta, by means Ground-penetrating Radar (GPR), allowed a 3D reconstruction of archaeological structures in the subsoil until the depth of about 4m. The geophysical survey has identified the building of medieval and modern urban settlement of Augusta and has allowed to recreate the urban plan and its transformation.

  3. The West Elk Breccia: Evidence of a Massive Volcanic Debris Avalanche in the Eastern Gunnison River Valley, West-Central Colorado, USA (United States)

    Whalen, P. J.; Ettensohn, F. R.


    The West Elk Breccia of the Gunnison River Valley in west-central Colorado is an Oligocene diamictite ascribed to a lahar origin by previous workers. In contrast, our work suggests that one or more volcanic debris avalanches that transformed to debris flows are a more likely depositional mechanism in the eastern Gunnison River valley and tributaries. We examined deposits over an area of 250 km2 for sedimentological and stratigraphic evidence of depositional mechanisms and flow rheology. Large blocks, or megaclasts, of stratified volcaniclastic deposits, which retain original stratigraphy, can be found over 30 km from the likely source volcano in a tuffaceous stream-gravel conglomerate. The most proximal conglomerate probably represents the transition from debris avalanche to debris flow as the initial avalanche bulked up and dilated during entry into the local drainage basins of the ancient Gunnison River and its tributaries. Mono-lithologic breccia beds of proximal deposits, almost entirely surrounded by the tuffaceous conglomerate, may represent megaclasts that dip at angles greater than normal stream gradient (up to 50 degrees or more with no thickening or thinning of beds). Some beds in distal deposits (>20 km from the source) show graded bedding and inverse grading, indicative of deposition by lahars; others contain breadcrust bombs, typically the product of dome collapse and block-and-ash flows. Jigsaw fracturing of individual clasts and megaclasts are further evidence of debris avalanche emplacement. Conversely, beds in proximal locations, which represent the steepest slopes of the ancient volcano, show sub-horizontal bedding of andesite and basaltic andesite. The presence of megaclasts is difficult to determine greater than 30 km from the source, and exposures are sparse in the most distal deposits, about 40 km from the source. Field observations and comparisons with Quaternary events suggest that the West Elk Breccia probably represents a series of sector

  4. Petrological insights on the effusive-explosive transitions of the Nisyros-Yali Volcanic Center, South Aegean Sea (United States)

    Popa, Razvan-Gabriel; Bachmann, Olivier; Ellis, Ben; Degruyter, Wim; Kyriakopoulos, Konstantinos


    Volcanoes erupting silicic, volatile-rich magmas can exhibit both effusive and explosive eruptions, even during closely spaced eruptive episodes. Understanding the effusive-explosive transition is fundamental in order to assess the hazards involved. Magma properties strongly influence the processes during magma ascent that determine the eruptive style. Here, we investigate the link between changing conditions in the magma reservoir and the eruptive style. The Quaternary Nisyros-Yali volcanic center, from the South Aegean Sea, provides an excellent natural laboratory to study this process. Over the last 60-100 kyrs, it produced a series of dacitic to rhyolitic eruptions that emplaced alternating effusive and explosive deposits (with explosive eruptions likely shortly following effusive ones). For this study, nine fresh and well-preserved units (five effusive and four explosive) were sampled and analyzed for whole-rock, groundmass glass and mineral compositions, in order to draw insights into the magma chamber processes and thermodynamic conditions that preceded both types of eruptions. Silicic magmas in Nisyros-Yali record a complex, open-system evolution, dominated by fractionation in mushy reservoirs at mid to upper crustal depths, frequently recharged by warmer input from below. Storage temperatures recorded by the amphibole-plagioclase thermometer span a wide range, and they are always cooler than the pre-eruptive temperatures yielded by Fe-Ti oxide thermometry for the same unit, whether it is effusive or explosive. However, magmas feeding effusive eruptions typically reached cooler conditions (expressed by the presence of low-Al, low-Ti amphiboles) than in the explosive cases. The difference between the pre-eruptive and the lowest storing temperatures in the Nisyros series are in the order of 10-30°C for explosive units, while the difference is of about 40-110°C for the effusive units. The Yali series does not perfectly fit this pattern, where explosive units

  5. Geochemical and Sr-Nd isotopic characteristics of Upper Cretaceous (calc-alkaline) and Miocene (alkaline) volcanic rocks: Elazığ, Eastern Taurides, Turkey (United States)

    Kürüm, Sevcan; Tanyıldızı, Özge


    The massive volcanic suite of Upper Cretaceous Elazığ Magmatic Complex, and Miocene basic volcanic rocks of crop out to the southern vicinity of Elazığ. The petrographical studies indicated that the massive volcanic suite of Upper Cretaceous are of basalt, spilitic basalt, basaltic andesite, andesite, trachite, dacite/ryolithe and dolerite in composition, and the Miocene volcanic rocks are basalt in composition. According to the geochemical data, which are conformable with the petrographical ones, Upper Cretaceous volcanic rocks are of low and medium-K contaning types and calc-alkalin in general, and enriched with respect to LILE and HREE contents. They also contain low Ti, have negative Nb and Ta anomaly and low 143Nd/147Nd and high 87Sr/86Sr ratios. Geochemical and isotopic data for the massive volcanic suite point out that these volcanic rocks were originated from an upper mantle source (lithospheric) which undergone fractional crystallisation and crustal contamination and enriched by these processes and metasomatized within a subduction zone. Miocene volcanic rocks are of high-K alkaline type, alkali basalt/basanite in composition and products of intraplate volcanism. These rocks are richer in some major oxide contents such as Na2O, K2O, MgO and trace element contents such as Nb, Sr, Zr compared to the massive volcanic rocks of Upper Cretaceous, and they are also enriched with respect to their LILE and HREE contents. The remarkable decrease from LREE towards HREE in the REE/Chondrite-normalized variation diagram indicates a magmatic differentiation process. The MgO and Ni ratios of Miocene volcanic rocks are not conformable with those of primitive basalt composition. However, all the chemical and isotopic (low 87Sr/86Sr ratio and positive (+) εNd values) data indicate that the source magma of these volcanic rocks was derived from a depleted garnet free magma (astenospheric mantle) and was modified once again by the post collosional geodynamical events and

  6. Sediments of Lake Van - a high-resolution archive of changing climate, volcanic events and seismic activity in Eastern Anatolia for the last 500'000 yrs (United States)

    Stockhecke, M.; Anselmetti, F. S.; Sturm, M.; Paleovan Scientific Party


    Varved sedimentary records have shown their high potential to reconstruct abrupt and global climate change within the marine realm (e.g. Cariaco Basin, Santa Barbara Basin). Continental counterparts, consisting of long and varved lacustrine records can be found in the subsurface of some deep lakes, such as Lake Van. Lake Van is a 440 m deep closed soda lake situated in a climatically sensitive semiarid and tectonically active region in Eastern Anatolia, Turkey. The ICDP project Paleovan aims to reconstruct the climatic, tectonic and volcanic history of Lake Van. Driven by an international and interdisciplinary scientific team, two sites, Ahlat Ridge (AR) and Northern Basin (NB) were drilled in summer 2010 recovering sedimentary records of 220 and 140 m, respectively. A total of 800 m of sediment-cores were opened, described and photographed in spring 2011 at the IODP core repository in Bremen. Lithologies of up to five parallel cores (multiple coring) were correlated and a composite profile was defined giving priority to core quality and continuity. Preliminary Ar/Ar dates of the core catcher yielded a basal ages of ~500´000 years. Using this rough age model, geochemical measurements (every 20 cm) indicate that TOC is high in warmer periods (interglacials) and low in colder periods (glacials). These TOC fluctuations match marine isotope stages and extrapolated Holocene sedimentation rates. The 219 m long AR composite profile consists of ~80 % lacustrine sediments, ~10 % of volcaniclastic deposits and 10 % gaps interpreted to be coarse-grained volcaniclastic that are difficult to be recovered. The lacustrine mud, i.e., clayey silt composed of mainly clay minerals and carbonate. Based on major macroscopic sediment features eight major lacustrine sediment types (~900 layer) were differentiated and separated from the volcaniclastic deposits (300 layer). Impressive color transitions and a repetitive pattern of similar lithological successions occur throughout the

  7. Studies of crustal structure, seismic precursors to volcanic eruptions and earthquake hazard in the eastern provinces of the Democratic Republic of Congo

    CSIR Research Space (South Africa)

    Mavonga, T


    Full Text Available of an effort to monitor the volcanoes and quantitatively assess the earthquake hazard. This information can be used to regulate the settlement of displaced people and to 'build back better'. In order to investigate volcanic processes in the Virunga area, a...

  8. Irradiation of ready-to-eat foods at USDA'S Eastern Regional Reasearch Center - 2003 update

    Energy Technology Data Exchange (ETDEWEB)

    Sommers, Christopher; Fan Xuetong; Niemira, Brendan; Rajkowski, Kathleen


    Ionizing radiation is a safe and effective method for eliminating bacterial pathogens from food products and disinfestation of fruits and vegetables. Since 1980 research has been conducted at USDA's Eastern Regional Research Center pertaining to the elimination of food-borne pathogens from meat, poultry, fruit and vegetable products. Recent work has focused on elimination of pathogens such as Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes from ready-to-eat (RTE) food products including hot dogs, bologna, lettuce, cilantro, sprouts and seeds, and frozen vegetables. The ionizing radiation dose required to eliminate those pathogens from RTE foods has been found to be commodity, formulation and temperature dependent. The need to eliminate bacterial pathogens from RTE food products must always be balanced with the maintenance of product quality. In addition to determining the effective ionizing radiation doses required for pathogen elimination the effects of irradiation on product chemistry, nutritional value and organoleptic quality have also been determined. A review of the studies conducted at USDA's Eastern Regional Research Center in 2002 and 2003 is presented in this article.

  9. Establishment of the South-Eastern Norway Regional Health Authority Resource Center for Children with Prenatal Alcohol/Drug Exposure

    Directory of Open Access Journals (Sweden)

    Gro C. C. Løhaugen


    Full Text Available This paper presents a new initiative in the South-Eastern Health Region of Norway to establish a regional resource center focusing on services for children and adolescents aged 2–18 years with prenatal exposure to alcohol or other drugs. In Norway, the prevalence of fetal alcohol spectrum (FAS is not known but has been estimated to be between 1 and 2 children per 1000 births, while the prevalence of prenatal exposure to illicit drugs is unknown. The resource center is the first of its kind in Scandinavia and will have three main objectives: (1 provide hospital staff, community health and child welfare personnel, and special educators with information, educational courses, and seminars focused on the identification, diagnosis, and treatment of children with a history of prenatal alcohol/drug exposure; (2 provide specialized health services, such as diagnostic services and intervention planning, for children referred from hospitals in the South-Eastern Health Region of Norway; and (3 initiate multicenter studies focusing on the diagnostic process and evaluation of interventions.

  10. Center for Volcanic and Tectonic Studies, Department of Geoscience annual report, October 1, 1989--September 30, 1990

    Energy Technology Data Exchange (ETDEWEB)

    Smith, E.I. [Nevada Univ., Las Vegas, NV (United States). Center for Volcanic and Tectonic Studies


    This report summarizes our activities during the period October 1, 1989 to September 30, 1990. Our goal was to develop an understanding of late-Miocene and Pliocene volcanism in the Great Basin by studying Pliocene volcanoes in the vicinity of the proposed high-level nuclear waste repository at Yucca Mountain, Nevada. Field studies during this period concentrated on the Quaternary volcanoes in Crater Flat, Yucca Mountain, Fortification Hill, at Buckboard Mesa and Sleeping Butte, and in the Reveille Range. Also, a study was initiated on structurally disrupted basaltic rocks in the northern White Hills of Mohave County, Arizona. As well as progress reports of our work in Crater Flat, Fortification Hill and the Reveille Range, this paper also includes a summary of model that relates changing styles of Tertiary extension to changing magmatic compositions, and a summary of work being done in the White Hills, Arizona. In the Appendix, we include copies of published papers not previously incorporated in our monthly reports.

  11. Volcanic Gas (United States)

    ... often escape continuously into the atmosphere from the soil, volcanic vents , fumaroles , and hydrothermal systems. By far the ... after falling into a snow depression surrounding a volcanic fumarole and filled ... of CO 2 gas in soils can also damage or destroy vegetation, as is ...

  12. Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center (United States)

    Clague, D. A.; Paduan, J. B.; Duncan, R. A.; Huard, J. J.; Davis, A. S.; Castillo, P. R.; Lonsdale, P.; Devogelaere, A.


    Davidson Seamount, a volcano located about 80 km off the central California coast, has a volume of ˜320 km3 and consists of a series of parallel ridges serrated with steep cones. Davidson was sampled and its morphology observed during 27 ROV Tiburon dives. During those dives, 286 samples of lava, volcaniclastite, and erratics from the continental margin were collected, with additional samples from one ROV-collected push core and four gravity cores. We report glass compositions for 99 samples and 40Ar-39Ar incremental heating age data for 20 of the samples. The glass analyses are of hawaiite (62%), mugearite (13%), alkalic basalt (9%), and tephrite (8%), with minor transitional basalt (2%), benmoreite (2%), and trachyandesite (2%). The lithologies are irregularly distributed in space and time. The volcano erupted onto crust inferred to be 20 Ma from seafloor magnetic anomalies. Ages of the lavas range from 9.8 to 14.8 Ma. The oldest rocks are from the central ridge, and the youngest are from the flanks and southern end of the edifice. The compositions of the 18 reliably dated volcanic cones vary with age such that the oldest lavas are the most fractionated. The melts lost 65% to nearly 95% of their initial S because of bubble loss during vesiculation, and the shallowest samples have S contents similar to lava erupted subaerially in Hawaii. Despite this similarity in S contents, there is scant other evidence to suggest that Davidson was ever an island. The numerous small cones of disparate chemistry and the long eruptive period suggest episodic growth of the volcano over at least 5 Myr and perhaps as long as 10 Myr if it began to grow when the spreading ridge was abandoned.

  13. [Assessment of Cyto- and Genotoxicity of Underground Waters from the Far Eastern Center on Radioactive Waste Treatment Site]. (United States)

    Oudalova, A A; Pyatkova, S V; Geras'kin, S A; Kiselev, S M; Akhromeev, S V


    This study has been completed in the frames of activities on the environment assessment in the vicinity of the Far Eastern center (FEC) on radioactive waste treatment (a branch of Fokino, Sysoev Bay). Underground waters collected at the FEC technical site were surveyed both with instrumental techniques and bioassays. Concentrations of some chemicals (ranged to the third hazard category) in the samples collected are over the permitted limits. Activities of 137Cs and 90Sr in waters amount up to 3.8 and 16.2 Bq/l, correspondingly. The integral pollution index is over 1 in all the samples and could amount up to 165. The Allium-test application allows the detection of the sample points where underground waters have an enhanced mutagenic potential. Dependencies between biological effects and pollution levels are analyzed. The findings obtained could be used for the monitoring optimized and decision making on rehabilitation measures to decrease negative influence of the enterprise on the environment.

  14. 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) (United States)

    Creon, L.; Levresse, G.; Carrasco Nuñez, G.


    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 often affected by the formation of a bubble after trapping; this is a natural consequence of the PVTX properties of crystal-melt-volatile systems. Previous workers have recognized that bubble formation is an obstacle, which affects the interpretation of SMI trapping conditions based only on analysis of the glass phase. Indeed, they explained that bubbles can contain a significant percentage of the volatiles, particularly for those with low solubility in the melt (e.g. CO2). In this study, we propose to define the pre-eruptive PTX conditions of Los Humeros magma chamber using SMI from the various eruption events within 460 and 30 Ka. An innovative analytical coupling has been used in order to determine: (1) the volume of the SMI glass and bubble, using high resolution 3D X-ray microtomography; (2) the density and composition of the bubbles, using Raman spectroscopy; (3) the volatile element contents in glass, using NanoSIMS; and, (4) the major elements composition of the glass, using EPMA. The recalculated volatile concentrations of the total SMI (glass + bubble), illustrate clearly that the volatile content determinations using only the glass phase, underestimate drastically the total volatile content and therefore induce significant error on the determination of the pre-eruptive volcanic budget and on the constrain on the volcanic and thermal history. This study had moreover highlighted the complex evolution of Los Humeros composite magma chamber and, gave constrains for geothermal exploration purpose.

  15. Early Devonian back-arc extension in the eastern Central Asian Orogenic Belt: Evidence from a bimodal volcanic sequence from Xilinhot, central Inner Mongolia (North China) (United States)

    Liao, Wen; Xu, Bei; Wang, Yanyang; Zhao, Pan; Li, Qunsheng


    The Early Devonian bimodal volcanic sequence is firstly recognized in the Xilinhot area, central Inner Mongolia (North China). Zircon U-Pb dating of rhyolitic sample gives crystallization age of 407 ± 2 Ma, which is interpreted as the extrusive age of this bimodal volcanic sequence. Basaltic samples belong to tholeiite series whereas rhyolitic samples are peraluminous. Basaltic rocks show typical N-MORB-like REE and trace elemental patterns, with depletion of LREEs and negligible anomalies of Eu (δEu = 0.83-1.00). They have initial 87Sr/86Sr ratios ranging from 0.7077 to 0.7086, and positive εNd(t) values from +7.5to +9.0. By contrast, rhyolitic rocks show enrichment in LREEs and LILEs but depletion in HFSEs, with negative Eu anomalies (δEu = 0.58-0.68). They have negative εNd(t) values from -6.7 to -7.7 and TDM2 (Nd) values from 1695 to 1771 Ma. These elemental and isotopic data indicate that basaltic rocks were derived from a depleted mantle source with input of slab-derived fluids, whereas rhyolitic rocks might have been derived from remelting of Paleoproterozoic crustal materials. From our data and previous geological studies in this region, a back-arc setting was proposed for the Early Devonian bimodal volcanic rocks in the Xilinhot region. Subduction of the Paleo-Asian oceanic lithosphere caused opening of this back-arc basin and upwelling of mantle caused the formation of basalts and provided heat for remelting of crustal materials and formation of rhyolite.the

  16. Timing and Outcome of Referral to the First Stand-Alone Palliative Care Center in the Eastern Mediterranean Region, the Palliative Care Center of Kuwait. (United States)

    Al-Saleh, Khaled; Al-Awadi, Ahmad; Soliman, Najla A; Mostafa, Sobhy; Mostafa, Mohammad; Mostafa, Wafaa; Alsirafy, Samy A


    Compared to other regions of the world, palliative care (PC) in the Eastern Mediterranean region is at an earlier stage of development. The Palliative Care Center of Kuwait (PCC-K) was established a few years ago as the first stand-alone PC center in the region. This study was conducted to investigate the timing of referral to the PCC-K and its outcome. Retrospective review of referrals to the PCC-K during its first 3 years of action. Late referral was defined as referral during the last 30 days of life. During the 3-year period, 498 patients with cancer were referred to the PCC-K of whom 467 were eligible for analysis. Referral was considered late in 58% of patients. Nononcology facilities were more likely to refer patients late when compared to oncology facilities ( P = .033). The palliative performance scale (PPS) was ≤30 in 59% of late referrals and 21% in earlier referrals ( P < .001). Among 467 referred patients, 342 (73%) were eligible for transfer to the PCC-K, 102 (22%) were ineligible, and 23 (5%) died before assessment by the PCC-K consultation team. From the 342 eligible patients, the family caregivers refused the transfer of 64 (19%) patients to the PCC-K. Patients are frequently referred late to the PCC-K. Further research to identify barriers to PC and its early integration in Kuwait is required. The PPS may be useful in identifying late referrals.

  17. Atlantic salmon and eastern oyster breeding programs at the National Cold Water Marine Aquaculture Center (United States)

    The USDA-ARS National Cold Water Marine Aquaculture Center (NCWMAC) focuses on the coldwater marine aquaculture industry’s highest priority research needs including development of improved genetic stocks. Coldwater aquaculture production has potential for expansion, and both Atlantic salmon and Eas...

  18. Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1979-February 29, 1980

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, K.H.; Davies, J.N.; Sykes, L.R.


    The modern and historic seismicity of the eastern Aleutian arc was thoroughly researched and shows clear evidence that the Shumagin Islands region of the arc has been ruptured at least partly by previous large or great earthquakes; has recurrence times for large earthquakes between 50 and 115 years; has presently the properties of a seismic gap, i.e., was not ruptured by a large or great earthquake for at least 76 years; shows a donut configuration of modest seismicity including high-stress-drop events around the rim of the expected rupture zone of a future large earthquake. From this combined evidence it is concluded that the likelihood for a large or great earthquake to occur within the Shumagin Island gap is high (about 50% probability) within the next decade and very high (about 80% to 90% probability) within the next three decades. This study includes detailed determinations of stress, stress-drop, and other source parameters of moderate earthquakes in the Shumagin islands gap, and similar results for the St. Elias earthquake near the Yakataga gap in the eastern Gulf of Alaska. Volcano seismicity, crustal deformantion, and P-residuals continue to be monitored and analyzed in the eastern Aleutian arc segment. 36 figures, 3 tables.

  19. Review of Eastern coral snake (Micrurus fulvius fulvius) exposures managed by the Florida Poison Information Center Network: 1998-2010. (United States)

    Wood, A; Schauben, J; Thundiyil, J; Kunisaki, T; Sollee, D; Lewis-Younger, C; Bernstein, J; Weisman, R


    Envenomation by the Eastern coral snake is rare but may be associated with significant morbidity. While effective, acquisition of North American Coral Snake Antivenin (NACSAV) is difficult because production was discontinued for many years. The purpose of this study is to characterize coral snake exposures in Florida and determine the effects of varying treatment paradigms on patient outcomes. This study is an observational case series of cases received at Florida poison centers. Included cases were Eastern coral snake exposures occurring between January 1, 1998 and October 31, 2010. Excluded cases included those found to be unrelated or those not followed for at least 24 h post envenomation. Case comments were reviewed to obtain data. Comparisons were made between asymptomatic patients receiving empiric antivenom therapy (empiric group) and those asymptomatic patients who received antivenom upon developing signs of systemic envenomation (withhold group). Of the 553 cases identified, 387 were included in the final analysis. According to case comments, 56.3% of patients had no reported systemic symptoms. Most commonly, patients were reported to have pain (40.6%), paresthesias (28.4%), nausea (12.7%), and emesis (11.4%). NACSAV was administered to 252 patients (65%). Of those patients receiving NACSAV, 18.25% were reported to have had an adverse reaction. Patients in the withhold group (n = 106) had significantly fewer minor, moderate, and major outcomes than patients in the empiric group (n = 134, p < 0.01). While patients in the withhold group had favorable outcomes compared with those in the empiric group, this strategy cannot be applied to all patients presenting asymptomatic to healthcare facilities due to study limitations. Further studies are needed to determine what treatment strategy is most appropriate for asymptomatic patients presenting to healthcare facilities.

  20. Continuing inflation at Three Sisters volcanic center, central Oregon Cascade Range, USA, from GPS, leveling, and InSAR observations (United States)

    Dzurisin, Daniel; Lisowski, Michael; Wicks, Charles W.


    Uplift of a broad area centered ~6 km west of the summit of South Sister volcano started in September 1997 (onset estimated from model discussed in this paper) and was continuing when surveyed in August 2006. Surface displacements were measured whenever possible since August 1992 with satellite radar interferometry (InSAR), annually since August 2001 with GPS and leveling surveys, and with continuous GPS since May 2001. The average maximum displacement rate from InSAR decreased from 3-5 cm/yr during 1998-2001 to ~1.4 cm/yr during 2004-2006. The other datasets show a similar pattern, i.e., surface uplift and extension rates decreased over time but deformation continued through August 2006. Our best-fit model to the deformation data is a vertical, prolate, spheroidal point-pressure source located 4.9-5.4 km below the surface. The source inflation rate decreased exponentially during 2001-2006 with a 1/ e decay time of 5.3 ± 1.1 years. The net increase in source volume from September 1997 to August 2006 was 36.5-41.9 x 106 m3. A swarm of ~300 small ( M max = 1.9) earthquakes occurred beneath the deforming area in March 2004; no other unusual seismicity has been noted. Similar deformation episodes in the past probably would have gone unnoticed if, as we suspect, most are small intrusions that do not culminate in eruptions.

  1. Chronic myeloid leukemia in children and adolescents: A single center experience from Eastern India. (United States)

    Raut, Lalit; Bohara, Vinay V; Ray, Siddhartha S; Chakrabarti, Prantar; Chaudhuri, Utpal


    Chronic Myeloid Leukemia (CML) constitutes around 3% of leukemia in the children and adolescent age group. The aim of the study was to evaluate the characteristics at presentation and the treatment outcome of CML in the children and adolescent age group. Retrospective analysis was carried out at a single center in India. Thirteen patients (≤17 years) attending CML outdoor from April 2008 to August 2012 were included in the analysis. The mean and median of various parameters were calculated using a Microsoft excel sheet. SPSS 16.0 version software was used to calculate OS and PFS. CML-CP was the most common phase at presentation. Maximum patients belonged to the 14 - 17 year old age group. Disease was common in the male sex. Splenic discomfort and asthenia were the most common symptoms and splenomegaly was the most common sign. The treatment with Imatinib was effective and well-tolerated.

  2. Temporal and geochemical evolution of Miocene volcanism in the Andean back-arc between 36°S and 38°S and U-series analyses of young volcanic centers in the arc and back-arc, Argentina

    DEFF Research Database (Denmark)

    Dyhr, Charlotte Thorup

    of the subducting slab at ca. 20 Ma is inferred. The eruption of 24-20 Ma alkali olivine basalt up to 500 km east of the trench marks the beginning of a long-lasting magmatic episode with widespread volcanism north of the Cortaderas lineament following a regional magmatic hiatus lasting from 39 Ma to 26 Ma...... and showing evidence of a weak, but temporally increasing, arc component in the mantle source were erupted in a contractional regime. The increasing arc-influence in lavas erupted up to 500 km east of the trench indicates a shallowing of the subducting zone. A long period of volcanic quiescence followed......New 40Ar/39Ar, major and trace element, and Sr, Nd and Pb isotopic data for the c. 24-7 Ma volcanic rocks from the Andean back-arc (35°S – 38°S) in the Mendoza and Neuquén (Argentina) regions shed light on the Miocene evolution of the back-arc of the Southern Volcanic Zone. Incipient shallowing...

  3. Continuing Inflation at Three Sisters Volcanic Center, Central Oregon Cascade Range, USA, From GPS, InSAR, and Leveling Observations (United States)

    Lisowski, M.; Dzurisin, D.; Wicks, C. W.


    Uplift of a broad area centered ~5 km west of South Sister volcano in central Oregon started sometime after fall 1996, accelerated after fall 1998, and was continuing when last surveyed with GPS and leveling in fall 2006. Surface displacements were measured whenever possible since 1992 with satellite radar interferometry (InSAR), annually since 2001 with GPS and leveling campaigns, and with a continuous GPS station since 2001. The average maximum displacement rate from InSAR was 3 to 5 cm/yr during 1998--2001 and ~1.4 cm/yr during 2004--2006. The other three datasets show a similar pattern, i.e., surface dilation and uplift rates decreased over time but deformation continued through 2006. Our best-fit model is a spherical point pressure (Mogi) source located 6.0--6.5 km below the surface and 4.5--5 km west-southwest of the summit of South Sister volcano. Any marginal improvement gained by using a more complicated source shape is not constrained by the data. This same model fits the deformation data for 2001--2003 and 2003--2006 equally well, so there is no indication that the location or shape of the source has changed. However, the source inflation rate has decreased exponentially since 2001 with a 1/e decay time of about 4 years. The net increase in source volume from the beginning of the episode (~1997) through 2006 was 60 × 106 m3 ± 10 × 106 m3. The only unusual seismicity near the deforming area was a swarm of about 300 small earthquakes on March 23- -26, 2004 ---the first notable seismicity for at least two decades. Timing of the swarm generally coincides with slowing of surface deformation, but any link between the two, if one exists, is not understood. Similar episodes in the past probably would have gone unnoticed if, as we suspect, most were small intrusions that do not culminate in eruptions.

  4. A Field Trip Guide to the Petrology of Quaternary Volcanism on the Yellowstone Plateau (United States)

    Vazquez, Jorge A.; Stelten, Mark; Bindeman, Ilya N.; Cooper, Kari M


    The Yellowstone Plateau is one of the largest manifestations of silicic volcanism on Earth, and marks the youngest focus of magmatism associated with the Yellowstone Hot Spot. The earliest products of Yellowstone Hot Spot volcanism are from ~17 million years ago, but may be as old as ~32 Ma, and include contemporaneous eruption of voluminous mafic and silicic magmas, which are mostly located in the region of northwestern Nevada and southeastern Oregon. Since 17 Ma, the main locus of Yellowstone Hot Spot volcanism has migrated northeastward producing numerous silicic caldera complexes that generally remain active for ~2–4 million years, with the present-day focus being the Yellowstone Plateau. Northeastward migration of volcanism associated with the Yellowstone Hot Spot resulted in the formation of the Snake River Plain, a low relief physiographic feature extending ~750 kilometers from northern Nevada to eastern Idaho. Most of the silicic volcanic centers along the Snake River Plain have been inundated by younger basalt volcanism, but many of their ignimbrites and lava flows are exposed in the extended regions at the margins of the Snake River Plain. 

  5. A field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau (United States)

    Vazquez, Jorge A.; Stelten, Mark; Bindeman, Ilya N.; Cooper, Kari


    The Yellowstone Plateau is one of the largest manifestations of silicic volcanism on Earth, and marks the youngest focus of magmatism associated with the Yellowstone Hot Spot. The earliest products of Yellowstone Hot Spot volcanism are from ~17 million years ago, but may be as old as ~32 Ma, and include contemporaneous eruption of voluminous mafic and silicic magmas, which are mostly located in the region of northwestern Nevada and southeastern Oregon. Since 17 Ma, the main locus of Yellowstone Hot Spot volcanism has migrated northeastward producing numerous silicic caldera complexes that generally remain active for ~2–4 million years, with the present-day focus being the Yellowstone Plateau. Northeastward migration of volcanism associated with the Yellowstone Hot Spot resulted in the formation of the Snake River Plain, a low relief physiographic feature extending ~750 kilometers from northern Nevada to eastern Idaho. Most of the silicic volcanic centers along the Snake River Plain have been inundated by younger basalt volcanism, but many of their ignimbrites and lava flows are exposed in the extended regions at the margins of the Snake River Plain. 

  6. Comprehensive study of the seismotectonics of the Eastern Aleutian arc and associated volcanic systems. Annual progress report, April 1, 1985-March 31, 1986

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, K.H.; Taber, J.; Boyd, T.; McNutt, S.; Beavan, J.; Rosen, S.; Luckman, M.A.; Johnson, D.; Skinta, L.


    In the five-week period between October 9 and November 14, 1985, a sequence of 5 moderate-sized events with magnitudes m/sub b/ = 6.4, 5.0, 5.2, 5.0, and 5.6 occurred in the Shumagin Islands seismic network region of the Eastern Aleutian arc. In addition to this cluster of moderate-sized events the microseismicity rate in the Shumagin region has increased by 35 to 80% for at least a 6-months period beginning in April 1985. While we cannot be sure that these unusual seismicity patterns are part of a precursory activity to a large impending Shumagin earthquake, such a possibility must at least be considered. In addition to these observations of recent seismicity in the Eastern Aleutians, we have thoroughly reviewed the entire historic and instrumental seismicity, the tectonics and seismic hazards for most of the Alaska-Aleutian seismic zone, and have redetermined the probabilities for the occurrence of great earthquakes at this active plate boundary for the twenty year period 1985-2005. The aftershock sequence, amount of slip and magnitude Mwgreater than or equal to8.6) of the great 1957 earthquake in the central Aleutians, have been reanalyzed and its effect on the seismic potential for the Unalaska seismic gap is assessed. We find this questionable gap at present capable to sustain a Mwapprox. =8.6 event. 11 refs., 4 figs.

  7. Levodopa-Carbidopa Intestinal Gel Infusion Therapy in Advanced Parkinson's Disease: Single Middle Eastern Center Experience. (United States)

    Bohlega, Saeed; Abou Al-Shaar, Hussam; Alkhairallah, Thamer; Al-Ajlan, Fahad; Hasan, Nael; Alkahtani, Khalid


    Levodopa therapy in Parkinson's disease (PD) is often associated with disabling motor and non-motor complications in patients with advanced disease due to the variable absorption of levodopa because of an irregular or erratic emptying of the gastric content. Prospective single movement disorder center study using pre-set selection criteria, unified PD scale (UPDRS III), non-motor symptoms scale (NMSS), and PD questionnaire-8 (PDQ-8) to evaluate the efficacy, safety, and long-term treatment outcomes using levodopa-carbidopa intestinal gel (LCIG) infusion in patients with advanced PD, who were followed up every 6 months. Twenty patients were recruited over a period of 6 years. Disease duration prior to LCIG infusion ranged from 5 to 18 years (mean 11.4 ± 4.2). The mean follow-up time on LCIG therapy was 48.5 ± 23.2 months (range 11-83 months). Mean 'off' time, UPDRS III, NMSS, and PDQ-8 improvement were statistically significant. Two patients dropped out and 66.7% of patients required tube replacement. LCIG infusion monotherapy demonstrated significant improvement in reducing the 'off' time, reducing levodopa-induced dyskinesia, and improving non-motor symptoms and quality of life. This therapy is recommended for patients in whom motor fluctuations are inadequately treated with traditional oral PD therapy. © 2015 S. Karger AG, Basel.

  8. Hypofractionated radiotherapy for breast cancers--preliminary results from a tertiary care center in eastern India. (United States)

    Nandi, Moujhuri; Mahata, Anurupa; Mallick, Indranil; Achari, Rimpa; Chatterjee, Sanjoy


    The standard radiotherapy (RT) fractionation practiced in India and worldwide is 50 Gy in 25 fractions over 5 weeks to the chest wall or whole breast followed by tumour bed boost in case of breast conservation (BCS). A body of validated data exists regarding hypofractionation in breast cancer. We here report initial results for 135 patients treated at our center with the START-B type of fractionation. From May 2011 till July 2012, women with all stages of breast cancer (excluding metastatic), who had undergone BCS or mastectomy were planned for 40 Gy in 15 fractions over 3 weeks to chest wall/whole breast and supraclavicular fossa (where indicated) followed by tumour bed boost in BCS patients. Planning was done using Casebow's technique. The primary end point was to assess the acute toxicity and the cosmetic outcomes. Using cosmetic scales; patients were assessed during radiotherapy and at subsequent follow up visits with the radiation oncologist. Of the 135 patients, 62 had undergone BCS and 73 mastectomy. Median age of the population was 52 years. Some 80% were T1 and T2 tumours in BCS whereas most patients in mastectomy group were T3 and T4 tumours (60%). 45% were node negative in BCS group whilst it was 23% in the mastectomy group. Average NPI scores were 3.9 and 4.9, respectively. Most frequently reported histopathology report was infiltrating ductal carcinoma (87%), grade III being most common (58%), and 69% were ER positive tumours, and 30% were Her 2 Neu positive. Triple negative tumours accounted for 13% and their mean age was young (43 yrs.) The maximum acute skin toxicity at the end of treatment was Grade 1 in 94% of the mastectomy group patients and 71% in BCS patients. Grade 2 toxicity was 6% in mast group and 23% in BCS group. Grade 3 was 6% in BCS group, no grade 3 toxicity in mastectomy patients and there was no grade 4 skin toxicity in any case. Post RT at 1 month; 39% of BCS patients had persisting Grade I skin reaction which was only 2% in

  9. Comprehensive study of the seismotectonics of the eastern Aleutian ARC and associated volcanic systems. Annual progress report, March 1, 1981-February 28, 1982

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, K. H.; Hauksson, E.; Sykes, L. R.


    Assessment of the seismic potential for occurrence of great earthquakes in three seismic gaps (Shumagin Islands, Unalaska Island, and Yakataga-Kayak regions) has been completed. In the best-instrumented seismic gap in the Shumagin Islands region, the likelihood for a great earthquake within the next two decades is high. Analysis of earthquake data collected from a telemetered network operated in the Shumagin seismic gap shows near-quiescence in the shallow portion of the main thrust zone. Installation of digital recording equipment at the central station of the Shumagin network, combined with interactive computer analysis at Lamont-Doherty of either digitally recorded or digitized analog seismic data has provided new research possibilities for studying seismic source properties, wave propagation in a laterally heterogeneous velocity structure of the subduction zone, and for seismically screening the root-zone and volcanic pile of Pavlof volcano. High time-resolution data (0.01 sec), and wider frequency band-pass data (0.5 to 30 Hz) are now being collected. Seismic data for two eruptive sequences of Pavlof-volcano have been obtained.

  10. Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1983-February 29, 1984

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, K.H.; Hauksson, E.; McNutt, S.; Davison, R.; Beavan, J.; Rosen, S.; Luckman, M.A.; Johnson, D.; Skinta, L.


    Integration of seismic network data from the Shumagin Islands seismic gap with crustal deformation and volcanicity data indicate that the previously reported tilt anomaly in 1978 to 1980 was associated with an 80-cm amount of slip of the descending slab at depth between 20 and approx. = 80 km. The slip event was mostly aseismic although it caused increasing microearthquake activity. The shallow (< 30 km) main thrust zone remained locked but may have been further stressed so as to increase the likelihood for a future great earthquake. The basic conditional probability for the Shumagin Gap rupture in a great earthquake (M > approx. = 8) in the next decades has been determined to lie between 30 and 99%, probably the highest value for a potential great earthquake anywhere in the US. Composite focal mechanisms close to the location of the slip event are found to be highly variable since 1978 (both in space and time). An earthquake sequence in the Shumagins of February 14, 1983, included two moderately large shocks, M = 6.3 and 5.7, that provided significant strong-motion records. Three dimensional ray tracing has been applied to relocate hypocenters in the descending slab and thereby redefining the dipping slab geometry. We find the slab dips beneath 80 km at an almost constant dip of approx. = 45/sup 0/ to depths of approx. = 250 km without significant bend. 12 references.

  11. The community of deep-sea decapod crustaceans between 175 and 2600 m in submarine canyons of a volcanic oceanic island (central-eastern Atlantic) (United States)

    Pajuelo, José G.; Triay-Portella, Raül; Santana, José I.; González, José A.


    The community structure and faunal composition of deep-sea decapod crustaceans in submarine canyons on the slope off Gran Canaria Island (Canary Islands, central-eastern Atlantic) were investigated. Samples were collected during five research cruises (115 stations) at depths between 175 and 2554 m. A total of 26387 decapod specimens, belonging to 24 families and 38 species, were collected with traps. A cluster analysis of the stations showed four distinct assemblages: (i) in the transition area between shelf and slope (175-302 m); (ii) on the upper slope (361-789 m); (iii) on the middle slope (803-1973 m); and iv) on the lower slope (2011-2554 m). The deep-sea decapod fauna of the Canary Islands is dominated by shrimp of the family Pandalidae, which make up more than 23% of the species. Within the Pandalidae, species of the genus Plesionika stand out as those of greatest abundance on the island slope. The greatest diversity of species was located on the upper slope. The standardized mean abundance and mean biomass for the transition zone between the shelf and slope and for the upper slope were nearly 5 times greater in abundance and 4 times greater in biomass than those estimated for the middle slope, and nearly 53 and 29 times greater for the lower slope, indicating a lower abundance and biomass at the shallower part of the insular slope. The mean weight per individual showed an increasing pattern with depth and an inverse pattern with the bottom temperature and salinity. The existence of depth boundaries around the Canary Islands is known to be closely linked to oceanographic conditions, determined by the water masses present in this archipelago explaining the discontinuities observed at depths of 800 and 2000 m. The boundary observed inside the bathymetric region of the Eastern North Atlantic Central Water can be related with the transition zone between the shelf and the slope of the island.

  12. Compositional Differences between Felsic Volcanic rocks from the ...

    African Journals Online (AJOL)

    Pliocene felsic rift margin and Quaternary rift center volcanic rocks from the northern Main Ethiopian Rift (MER) exhibit contrasts in major and trace element contents and Sr-Nd isotopic ratios. Quaternary rift center felsic volcanic rocks are mainly peralkaline trachytes and rhyolites, whereas Pliocene felsic rift margin volcanic ...

  13. Beyond the center: Sciences in Central and Eastern Europe and their histories. An interview with professor Michael Jordan conducted by Jan Surman

    Directory of Open Access Journals (Sweden)

    Michael Gordin


    Full Text Available What is special about sciences in Central and Eastern Europe? What are the obstacles for writing histories of science done beyond metropoles? Is this science different than the science in the centers and what makes it so? How imperial are sciences made by representatives of dominant nations compared to non-dominant nations? These are some of the questions touched upon in the interview with Michael Gordin, a leading historian of science from Princeton University.

  14. Pilot Study of Reimbursement Practices in Private Healthcare Centers in the Eastern Province of Saudi Arabia: To What Extent Do They Meet International Best Practices?


    Bah, Sulaiman; Almutawa, Hanadi Hassan Ali; Alassaf, Nouf Fahad M.; Al Hareky, Mai Saad; Hashishi, Aqilah Salman M.; Alkhater, Zainab Jassem Hassan; Ajaimi, Jenan Ali M.


    This pilot study examines reimbursement practices in private healthcare centers in the Eastern Province of Saudi Arabia. The objective of the study was to assess the extent to which the private healthcare sector in Saudi Arabia follows international best practices in reimbursement, as identified in a literature review. The study examined reimbursement practices in a sample of six private healthcare facilities through the use of similar questionnaire guidelines with each facility. Similarities...

  15. Volcanic gas (United States)

    McGee, Kenneth A.; Gerlach, Terrance M.


    In Roman mythology, Vulcan, the god of fire, was said to have made tools and weapons for the other gods in his workshop at Olympus. Throughout history, volcanoes have frequently been identified with Vulcan and other mythological figures. Scientists now know that the “smoke" from volcanoes, once attributed by poets to be from Vulcan’s forge, is actually volcanic gas naturally released from both active and many inactive volcanoes. The molten rock, or magma, that lies beneath volcanoes and fuels eruptions, contains abundant gases that are released to the surface before, during, and after eruptions. These gases range from relatively benign low-temperature steam to thick hot clouds of choking sulfurous fume jetting from the earth. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other volcanic gases are hydrogen sulfide, hydrochloric acid, hydrogen, carbon monoxide, hydrofluoric acid, and other trace gases and volatile metals. The concentrations of these gas species can vary considerably from one volcano to the next.

  16. Genesis of the post-caldera eastern Upper Basin Member rhyolites, Yellowstone, WY: from volcanic stratigraphy, geochemistry, and radiogenic isotope modeling (United States)

    Pritchard, Chad J.; Larson, Peter B.


    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.

  17. Eastern Regional Research Center (United States)

    Federal Laboratory Consortium — More than 20,000 sq. ft. of space with utilities and equipment for researchat pilot and near commercial scales.Food and bio-based processing pilot plant (10,000 sq....

  18. Are the alteration halos of massive sulfide deposits syngenetic Evidence from U-Pb dating of hydrothermal rutile at the Kidd volcanic center, Abitibi subprovince, Canada

    Energy Technology Data Exchange (ETDEWEB)

    Schandl, E.S.; Davis, D.W.; Krogh, T.E. (Royal Ontario Museum, Toronto, Ontario (Canada))


    The Kidd volcanic complex is composed of felsic volcanic and subvolcanic rocks of Archean age. Metasomatic events affecting the lithology of the Kidd volcanic complex include silicification, extensive CO{sub 2} metasomatism (carbonate), K-metasomatism (sericite-fuchsite), and chlorite and minor carbonate alterations. Petrographic evidence, supported by stable isotope and fluid inclusion studies, suggests that silicification and early carbonate alteration were synvolcanic, and therefore related to ore deposition. During subsequent extensive K-metasomatism, sericite precipitated in the rhyolite, and fuschsite precipitated in the ultramafic rocks. Although chlorite postdates K-metasomatism, the micas and chlorite are both found in anastomosing microfissures, commonly occupying the same set of fractures. Hydrothermal rutile formed by the breakdown of magnetite-ilmenite during K-metasomatism and chlorite alteration gives an age of 2624 {plus minus} 62 Ma (95% confidence level). It is therefore approximately 100 m.y. younger than syngenetic massive sulfide mineralization (2712 {plus minus} 2 Ma). Sulfide stringers within sericite and chlorite veins suggest some remobilization of the ores during these later events. This alteration assemblage, is identical to that found associated with many lode-gold deposits in the Superior province. Recent dating of micas and rutile associated with gold deposits in the Abitibi subprovince gives comparable ages to the rutile in the Kidd volcanic complex, which must therefore record a widespread, late hydrothermal event affecting mineralized rocks.

  19. Volcanic Catastrophes (United States)

    Eichelberger, J. C.


    The big news from 20th century geophysics may not be plate tectonics but rather the surprise return of catastrophism, following its apparent 19th century defeat to uniformitarianism. Divine miracles and plagues had yielded to the logic of integrating observations of everyday change over time. Yet the brilliant interpretation of the Cretaceous-Tertiary Boundary iridium anomaly introduced an empirically based catastrophism. Undoubtedly, decades of contemplating our own nuclear self-destruction played a role in this. Concepts of nuclear winter, volcanic winter, and meteor impact winter are closely allied. And once the veil of threat of all-out nuclear exchange began to lift, we could begin to imagine slower routes to destruction as "global change". As a way to end our world, fire is a good one. Three-dimensional magma chambers do not have as severe a magnitude limitation as essentially two-dimensional faults. Thus, while we have experienced earthquakes that are as big as they get, we have not experienced volcanic eruptions nearly as great as those preserved in the geologic record. The range extends to events almost three orders of magnitude greater than any eruptions of the 20th century. Such a calamity now would at the very least bring society to a temporary halt globally, and cause death and destruction on a continental scale. At maximum, there is the possibility of hindering photosynthesis and threatening life more generally. It has even been speculated that the relative genetic homogeneity of humankind derives from an evolutionary "bottleneck" from near-extinction in a volcanic cataclysm. This is somewhat more palatable to contemplate than a return to a form of Original Sin, in which we arrived at homogeneity by a sort of "ethnic cleansing". Lacking a written record of truly great eruptions, our sense of human impact must necessarily be aided by archeological and anthropological investigations. For example, there is much to be learned about the influence of

  20. Distribution of mega fauna on sulfide edifices on the Eastern Lau Spreading Center and Valu Fa Ridge (United States)

    Sen, Arunima; Becker, Erin L.; Podowski, Elizabeth L.; Wickes, Leslie N.; Ma, Shufen; Mullaugh, Katherine M.; Hourdez, Stéphane; Luther, George W.; Fisher, Charles R.


    Hydrothermal vent sulfide edifices contain some of the most extreme thermal and chemical conditions in which animals are able to live. As a result, sulfide edifices in the East Pacific Rise, Juan de Fuca Ridge, and Mid Atlantic Ridge vent systems often contain distinct faunal assemblages. In this study, we used high-resolution imagery and in-situ physico-chemical measurements within the context of a Geographic Information System (GIS) to examine community structure and niche differentiation of dominant fauna on sulfide edifices in the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the Western Pacific Ocean. Our results show that ELSC and VFR sulfide edifices host two distinct types of communities. One type, that covers the majority of sulfide edifice faces, is overall very similar to nearby lava communities and biomass is dominated by the same chemoautotrophic symbiont-containing molluscs that dominate lava communities, namely the provannid gastropods Alviniconcha spp. and Ifremeria nautilei and the mytilid bivalve Bathymodiolus brevior. The spatial distribution of the dominant molluscs is often a variation of the pattern of concentric rings observed on lavas, with Alviniconcha spp. at the tops of edifices where exposure to vent flow is the highest, and I. nautilei and B. brevior below. Our physico-chemical measurements indicate that because of rapid dispersion of vent fluid, habitable area for symbiont-containing fauna is quite limited on sulfide edifices, and the realized niches of the mollusc groups are narrower on sulfide edifices than on lavas. We suggest that competition plays an important role in determining the realized distributions of the mollusc groups on edifices. The other habitat, present in small patches of presumably hot, new anhydrite, is avoided by the dominant symbiont-containing molluscs and inhabited by crabs, shrimp and polynoids that are likely more heat tolerant. The ratio of sulfide concentration to temperature anomaly of

  1. Are the alteration halos of massive sulfide deposits syngenetic? Evidence from U-Pb dating of hydrothermal rutile at the Kidd volcanic center, Abitibi subprovince, Canada (United States)

    Schandl, E. S.; Davis, D. W.; Krogh, T. E.


    The Kidd volcanic complex is composed of felsic volcanic and subvolcanic rocks of Archean age. The felsic rocks are intercalated with sedimentary rocks, and are in contact with komatiitic ultramafic rocks. Large diorite plutons were emplaced into the rhyolite, and the complex is overlain by younger basalts. Metasomatic events affecting the lithology of the Kidd volcanic complex include silicification, extensive CO2 metasomatism (carbonate), K-metasomatism (sericite-fuchsite), and chlorite and minor carbonate alterations. Petrographic evidence, supported by stable isotope and fluid inclusion studies, suggests that silicification and early carbonate alteration were synvolcanic, and therefore related to ore deposition. During subsequent extensive K-metasomatism, sericite precipitated in the rhyolite, and fuchsite precipitated in the ultramafic rocks. Although chlorite post-dates K-metasomatism, the micas and chlorite are both found in anastomosing microfissures, commonly occupying the same set of fractures. Hydrothermal rutile formed by the breakdown of magnetiteilmenite during K-metasomatism and chlorite alteration gives an age of 2624 ±62 Ma (95% confidence level) by Pb-Pb isotopic measurements. It is therefore approximately 100 m.y. younger than syngenetic massive sulfide mineralization (2717 ±2 Ma). Sulfide stringers within sericite and chlorite veins suggest some remobilization of the ores during these later events. This alteration assemblage, generally thought to be intimately associated with mineralization, is identical to that found associated with many lode-gold deposits in the Superior province. Recent dating of micas and rutile associated with gold deposits in the Abitibi subprovince gives comparable ages to the rutile in the Kidd volcanic complex, which must therefore record a widespread, late hydrothermal event affecting mineralized rocks.

  2. Tectonic Geomorphology and Volcano-Tectonic Interaction in the Eastern Boundary of the Southern Cascades (Hat Creek Graben), California, USA (United States)

    Paguican, E. M. R.; Bursik, M. I.


    The eastern boundary of the Southern Cascades (Hat Creek Graben), California, USA is an extensively faulted volcanic corridor with spectacular, high, steep scarps in a bedrock of late Tertiary and Quaternary volcanic and sedimentary deposits. The morphology of the graben is a result of the plate motions associated with multiple tectonic provinces, faulting, and recurring volcanic activity from more than 500 vents, over the past 7 my. The graben is at the boundary between two distinct geologic and geomorphic areas -- the Cascade Range on the west and the Modoc Plateau on the east -- between Mt. Shasta and Medicine Lake Highlands volcano, and Lassen Volcanic Center on the north and south, respectively. This study describes the geomorphological and tectonic features, their alignment and distribution, to understand the volcano-tectonic and geomorphology relationships in the Hat Creek Graben. We interpret topographic models generated from satellite images to create a database of volcanic centers and structures, and analyze the spatial distribution of the volcanic centers in the Hat Creek Graben. Poisson Nearest Neighbor analysis reveals a clustered distribution of volcanic centers, implying continuous or recurrent activity of magma sources as it propagates to the surface. Volcanic centers in the Hat Creek Graben have multiple preferred alignments, typical for extensional tectonic environments because of competing regional and local stress field influences and the presence of pre-existing, near-surface fractures. Most small stratovolcanoes ("lava cones") on the west are influenced by normal regional stress, and have crater amphitheater openings perpendicular to the maximum horizontal stress (σHmax), while those on the east, in a transcurrent regional stress regime, are at an acute angle. These results can be used as an indicator of the degree of impingement of the Walker Lane shear zone on the Cascades region.

  3. Food safety intervention research at the Eastern Regional Research Center: innovative sanitizers, natural antimicrobials and nonthermal processing technologies (United States)

    Foodborne pathogens such as Salmonella, Listeria monocytogenes and Escherichia coli O157:H7cause millions of illnesses every year. A variety of technologies have been advanced in recent years to expand on the suite of tools available to food processors. At the US Department of Agriculture’s Eastern ...

  4. H, O, Sr, Nd, and Pb isotope geochemistry of the Latir volcanic field and cogenetic intrusions, New Mexico, and relations between evolution of a continental magmatic center and modifications of the lithosphere (United States)

    Johnson, C.M.; Lipman, P.W.; Czamanske, G.K.


    Over 200 H, O, Sr, Nd, and Pb isotope analyses, in addition to geologic and petrologic constraints, document the magmatic evolution of the 28.5-19 Ma Latir volcanic field and associated intrusive rocks, which includes multiple stages of crustal assimilation, magma mixing, protracted crystallization, and open- and closed-system evolution in the upper crust. In contrast to data from younger volcanic centers in northern New Mexico, relatively low and restricted primary ??18O values (+6.4 to +7.4) rule out assimilation of supracrustal rocks enriched in 18O. Initial 87Sr/86Sr ratios (0.705 to 0.708), ??18O values (-2 to-7), and 206Pb/204Pb ratios (17.5 to 18.4) of metaluminous precaldera volcanic rocks and postcaldera plutonic rocks suggest that most Latir rocks were generated by fractional crystallization of substantial volumes of mantle-derived basaltic magma that had near-chondritic Nd isotope ratios, accompanied by assimilation of crustal material in two main stages: 1) assimilation of non-radiogenic lower crust, followed by 2) assimilation of middle and upper crust by inter-mediate-composition magmas that had been contaminated during the first stage. Magmatic evolution in the upper crust peaked with eruption of the peralkaline Amalia Tuff (???26 Ma), which evolved from metaluminous parental magmas. A third stage of late, roofward assimilation of Proterozoic rocks in the Amalia Tuff magma is indicated by trends in initial 87Sr/86Sr and 206Pb/204Pb ratios from 0.7057 to 0.7098 and 19.5 to 18.8, respectively, toward the top of the pre-eruptive magma chamber. Highly evolved postcaldera plutons are generally fine grained and are zoned in initial 87Sr/86Sr and 206Pb/204Pb ratios, varying from 0.705 to 0.709 and 17.8 to 18.6, respectively. In contrast, the coarser-grained Cabresto Lake (???25 Ma) and Rio Hondo (???21 Ma) plutons have relatively homogeneous initial 87Sr/86Sr and 206Pb/204Pb ratios of approximately 0.7053 and 17.94 and 17.55, respectively. ??18O values for

  5. Prevalence of Intestinal Parasites in Dogs from Two Centers of Animal Welfare from Medellín and eastern Antioquia (Colombia, 2014

    Directory of Open Access Journals (Sweden)

    Verónica Sierra-Cifuentes


    Full Text Available In Colombia, there are very few studies about intestinal parasitosis in dogs, and street dogs constitute a high-risk group for the acquisition of parasitic zoonotic diseases. Through a cross-sectional descriptive study carried out in 2014, the prevalence of intestinal parasitosis and its associated factors were determined in 68 dogs of both sexes from two animal welfare centers in Medellin and eastern Antioquia (Colombia. The parasitological diagnosis was made by direct examination with saline solution at 0.8% and iodine, and the Sheather flotation method. The overall prevalence of intestinal parasitosis was 72.1% (49, helminths 58.8% (40, protozoa 33.8% (23 and parasitism in 45.6% (31. 11 parasitic agents, of which the most prevalent were Uncinaria stenocephala with 39.7% (27, were identified; Ancylostoma caninum, with 20.6% (14; Trichuris vulpis, with 16.2% (11 and Toxocara spp., with 11.8% (8. These were statistically higher in eastern Antioquia (p value chi2 0.05. A high prevalence of intestinal parasitism in dogs from Medellin and eastern Antioquia was evidenced, as well as a great diversity in the prevalence of the subgroups studied. This information highlights the need to promote research in order to determine the magnitude and associated factors in specific populations as the foundation for targeting actions on veterinary health and public health, given the zoonotic potential of some parasitosis of dogs.

  6. Controls on volcanism at intraplate basaltic volcanic fields (United States)

    van den Hove, Jackson C.; Van Otterloo, Jozua; Betts, Peter G.; Ailleres, Laurent; Cas, Ray A. F.


    A broad range of controlling mechanisms is described for intraplate basaltic volcanic fields (IBVFs) in the literature. These correspond with those relating to shallow tectonic processes and to deep mantle plumes. Accurate measurement of the physical parameters of intraplate volcanism is fundamental to gain an understanding of the controlling factors that influence the scale and location of a specific IBVF. Detailed volume and geochronology data are required for this; however, these are not available for many IBVFs. In this study the primary controls on magma genesis and transportation are established for the Pliocene-Recent Newer Volcanics Province (NVP) of south-eastern Australia as a case-study for one of such IBVF. The NVP is a large and spatio-temporally complex IBVF that has been described as either being related to a deep mantle plume, or upper mantle and crustal processes. We use innovative high resolution aeromagnetic and 3D modelling analysis, constrained by well-log data, to calculate its dimensions, volume and long-term eruptive flux. Our estimates suggest volcanic deposits cover an area of 23,100 ± 530 km2 and have a preserved dense rock equivalent of erupted volcanics of least 680 km3, and may have been as large as 900 km3. The long-term mean eruptive flux of the NVP is estimated between 0.15 and 0.20 km3/ka, which is relatively high compared with other IBVFs. Our comparison with other IBVFs shows eruptive fluxes vary up to two orders of magnitude within individual fields. Most examples where a range of eruptive flux is available for an IBVF show a correlation between eruptive flux and the rate of local tectonic processes, suggesting tectonic control. Limited age dating of the NVP has been used to suggest there were pulses in its eruptive flux, which are not resolvable using current data. These changes in eruptive flux are not directly relatable to the rate of any interpreted tectonic driver such as edge-driven convection. However, the NVP and other

  7. Preliminary Results of Paleomagnetic Study on the Miocene - Quaternary Volcanic Rocks from the North of Lake Van, Turkey (United States)

    Kayın, Sercan; İşseven, Turgay


    Collision between the Arabian and the Eurasian plates initiated in Serravallian age (12-13 Ma). This collision caused a large plateau formation about 2 km elevation. Result of the collision, Eastern Anatolian Region still continious to evolve as a young mountain belt. East-West trending folds, thrust faults and strike-slip fault systems were developed due to the compressional tectonic regime in the region. After the formation of the plateau, volcanism took place occupying large areas. The thickness of this volcanic series reaches to 1 km. In order to determine tectonic evolution (rotational and latitudinal movements) of the North of the Lake Van, oriented paleomagnetic samples were collected from the volcanic rocks whose ages has already been determined from radiometric methods and ages range from Miocene to Quaternary times. The origin of the collected palaeomagnetic samples from different volcanic series were came from volcanic centers in this region such as the followings: Aladaǧ, Tendurek, Etrusk, Girekol Mounths and Pliocene plate basalts. Our preliminary results indicate that most of the clockwise and anticlockwise rotations and deformation occured during the Miocene- Pliocene times. However, in Pleistosene time there weren't any considerable rotations and deformations. The main reason of the deformations were related with the collision between the Arabian plate and the Eurasian plate and accomodated by regional faults and westards escape of Anatolia. Our results are in good agreement with previously done palaeomagnetic studies, seismological and GPS data in the region.

  8. Petrologic and petrographic variation of youthful eruptive products in the Tuxtla Volcanic Field, Veracruz, Mexico (United States)

    Parrish, C. B.; Kobs Nawotniak, S. E.; Fredrick, K. C.; Espindola, J.


    The Tuxtla Volcanic Field (TVF) is located near the Gulf of Mexico in the southern part of the state of Veracruz, Mexico. Volcanism in the region began around 7 Ma and has continued until recent times with the volcano San Martín Tuxtla’s latest eruptions in AD 1664 and 1793. The TVF rocks are mainly of alkaline composition and have been divided into two separate volcanic series, an older and younger. The TVF is a structural high located between the Veracruz Basin to the southwest and the Gulf of Mexico to the northeast, characterized by relatively thin crust with the depth to the Moho around 28 to 34 km. The TVF is unique because it is isolated from the nearest volcanic fields (the Mexican Volcanic Belt, Central American Volcanic Belt and the Eastern Alkaline Province) by at least 230km and because of the on-going debate over its magmatic origin. Many models have been proposed to explain the TVF’s alkaline nature in a unique location with most linking it either to the subduction of the Cocos plate to the west of Mexico and/or to extensional faulting in the region. The purpose of our study was to determine systematic changes in the youthful volcanic deposits across the TVF. Regional and local mapping was conducted and lava and scoria samples were collected from seven sites associated with two vent clusters in the TVF. Mapping of the easternmost cluster of deposits suggests chronological emplacement of the deposits through superposition and vent location and morphology. The petrography of lava and tephra deposits may further indicate magmatic origins and other factors influencing the development of the field, including chronology and possible mixing and/or differentiation. Previous published studies analyzed samples near the San Martin Tuxtla volcanic center. Their data is used as a comparative reference for these samples, most of which were collected from another, younger cluster east of Laguna Catemaco. From this study, a better understanding of past eruptive

  9. Epidemiological, Clinico-Pathological Profile and Management of Colorectal Carcinoma in a Tertiary Referral Center of Eastern India

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    Shyamal Kumar Halder


    Full Text Available Background: The colorectal carcinoma is a common cancer in males and in females and second most common cause of death in Europe and third commonest cause in the United States. Recent Indian study shows that there is a significant increase in incidence of colonic carcinoma but the incidence of rectal carcinoma remains steady. Aims and Objectives: This prospective study was undertaken to assess the clinico-pathological profile and management of colorectal malignancy in a tertiary referral institute of eastern India and to compare the above data with the data from the western world. Material and Methods: The patients admitted with the diagnosis of colorectal carcinoma in IPGME and R (SSKM, a tertiary hospital in eastern India, between January 2006 and December 2010, were included in this study. These patients were prospectively analyzed for age, sex, site of the lesion, clinical presentations, nature of the growth and types of surgery performed. Results: 192 patients were included in this study of which 78 patients were of younger age group (35 years. The mean age of this series was 44.1 years. The male to female ratio of younger and older group was 1.68:1 and 1.85:1 respectively. Reetal bleeding was the commenest symptom irrespective of age and sex. Pain in abdomen (39.7% and intestinal obstruction (21.8% were the predominant presenting features in the patients of younger group whereas weight loss was commonest presenting feature in the patients of older age group. Most common histological type, irrespective of age, was adenocarcinoma (93.8%. Overall, right sided colonic growth was more common in females while rectum was the commonest site of affection in males. The patients of younger age group presented in advanced stage like Duke’s C and Duke’s D. Conclusions: The younger patients are diagnosed with colorectal carcinoma. Cancer of right colon is more common than that of left. The younger patients present more often with abdominal pain and

  10. Large Volume 18O-depleted Rhyolitic Volcanism: the Bruneau-Jarbidge Volcanic Field, Idaho (United States)

    Boroughs, S.; Wolff, J.; Bonnichsen, B.; Godchaux, M. M.; Larson, P. B.


    The Bruneau-Jarbidge (BJ) volcanic field is located in southern Idaho at the intersection of the western and eastern arms of the Snake River Plain. The BJ region is an oval structural basin of about 6000 km2, and is likely a system of nested caldera and collapse structures similar to, though larger than, the Yellowstone Volcanic Plateau. BJ rocks are high-temperature rhyolite tuffs, high-temperature rhyolite lavas, and volumetrically minor basalts. Exposed volumes of individual rhyolite units range up to greater than 500 km3. We have analyzed feldspar and, where present, quartz from 30 rhyolite units emplaced throughout the history of the BJ center. All, including the Cougar Point Tuff, are 18O depleted (δ 18OFSP = -1.3 to 3.7‰ ), while petrographically, temporally, and chemically similar lavas erupted along the nearby Owyhee Front have "normal" rhyolite magmatic δ 18O values of 7 - 9‰ . There is no evidence for significant modification of δ 18O values by post-eruptive alteration. No correlation exists between δ 18O and age, magmatic temperature, major element composition or trace element abundances among depleted BJ rhyolites. The BJ and WSRP rhyolites possess the geochemical characteristics (depressed Al, Ca, Eu, and Sr contents, high Ga/Al and K/Na) expected of liquids derived from shallow melting of calc-alkaline granitoids with residual plagioclase and orthopyroxene (Patino-Douce, Geology v.25 p.743-746, 1997). The classic Yellowstone low δ 18O rhyolites are post-caldera collapse lavas, but at BJ, both lavas and caldera-forming ignimbrites are strongly 18O-depleted. The total volume of low δ 18O rhyolite may be as high as 10,000 km3, requiring massive involvement of meteoric-hydrothermally altered crust in rhyolite petrogenesis. Regional hydrothermal modification of the crust under the thermal influence of the Yellowstone hotspot apparently preceded voluminous rhyolite generation at Bruneau-Jarbidge.

  11. The Martian highland paterae: Evidence for explosive volcanism on Mars (United States)

    Crown, David A.; Greeley, Ronald


    The Martian surface exhibits numerous volcanic landforms displaying great diversity in size, age, and morphology. Most research regarding Martian volcanology has centered around effusive basaltic volcanism, including analyses of individual lava flows, extensive lava plains, and large shield volcanoes. These studies were hindered by a lack of definitive morphologic criteria for the remote identification of ash deposits. Knowledge of the abundances, ages, and geologic settings of explosive volcanic deposits on Mars is essential to a comprehensive understanding of the evolution of the Martian surface, with implications for the evolution of the lithosphere and atmosphere as well as the histories of specific volcanic centers and provinces.

  12. Silicate volcanism on Io (United States)

    Carr, M. H.


    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  13. Testing the performance of the local area network of the eastern Libyan control center under the high voltage network expansion

    Energy Technology Data Exchange (ETDEWEB)

    Al-Abaidi, O.S.; BenDardaf, A.B. [GECOL, Tripoli (Libyan Arab Jamahiriya)


    A local area network (LAN) for a 220 kV Libyan transmission system consisting of 20 substations and a modernized control centre was modelled. Data were collected from the power and substations and sent to the control centre. The LAN consisted of servers, clients, and interfacing tools. Problems facing the network included data collision, shut-downs, and slow-downs. It is also expected that the addition of future substations will continue to cause delays in data transmission. Scenarios modelled in the study included normal conditions, peak conditions, and unusually high levels of activity. Display response, alarms response, and request completion times were optimized. Required total load was defined by the following 3 different components: process loads, loads related to operator activities, and server loads. A simulation processing tool was installed to select variables from planned system data. Operator activity loads were generated automatically. Tools were also developed to measure LAN and server loading performance. Tests were conducted to measure central processing unit (CPU) and disk loading of the servers at specified intervals. It was concluded that the LAN configuration used by the control center will accommodate planned transmission expansion in the region. 3 refs., 4 figs.

  14. Minor and trace element geochemistry of volcanic rocks dredged from the Galapagos spreading center: role of crystal fractionation and mantle heterogeneity. (United States)

    Clague, D.A.; Frey, F.A.; Thompson, G.; Rindge, S.


    A wide range of rock types (abyssal tholeiite, Fe-Ti-rich basalt, andesite, and rhyodacite) were dredged from near 95oW and 85oW on the Galapagos spreading center. Computer modeling of major element compositions has shown that these rocks could be derived from common parental magmas by successive degrees of fractional crystallization. However, the P2O5/K2O ratio implies distinct mantle source compositions for the two areas. These source regions also have different rare earth element (REE) abundance patterns. The sequence of fractionated lavas differs for the two areas and indicates earlier fractionation of apatite and titanomagnetite in the lavas from 95oW. The mantle source regions for these two areas are interpreted to be depleted in incompatible (and volatile?) elements, although the source region beneath 95oW is less severely depleted in La and K. -Authors

  15. Defining the Risk of Zika and Chikungunya Virus Transmission in Human Population Centers of the Eastern United States.

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    Carrie A Manore


    Full Text Available The recent spread of mosquito-transmitted viruses and associated disease to the Americas motivates a new, data-driven evaluation of risk in temperate population centers. Temperate regions are generally expected to pose low risk for significant mosquito-borne disease; however, the spread of the Asian tiger mosquito (Aedes albopictus across densely populated urban areas has established a new landscape of risk. We use a model informed by field data to assess the conditions likely to facilitate local transmission of chikungunya and Zika viruses from an infected traveler to Ae. albopictus and then to other humans in USA cities with variable human densities and seasonality. Mosquito-borne disease occurs when specific combinations of conditions maximize virus-to-mosquito and mosquito-to-human contact rates. We develop a mathematical model that captures the epidemiology and is informed by current data on vector ecology from urban sites. The model demonstrates that under specific but realistic conditions, fifty-percent of introductions by infectious travelers to a high human, high mosquito density city could initiate local transmission and 10% of the introductions could result in 100 or more people infected. Despite the propensity for Ae. albopictus to bite non-human vertebrates, we also demonstrate that local virus transmission and human outbreaks may occur when vectors feed from humans even just 40% of the time. Inclusion of human behavioral changes and mitigations were not incorporated into the models and would likely reduce predicted infections. This work demonstrates how a conditional series of non-average events can result in local arbovirus transmission and outbreaks of human disease, even in temperate cities.

  16. Sharp Injury and Exposure to Blood and Body Fluids among Health Care Workers in Health Care Centers of Eastern Ethiopia

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    T Alemayehu


    Full Text Available Background: Health care workers are facing certain occupational hazards because of sharp injury and exposure to human blood and body fluids as a result of handling wastes. Though much attention is paid for the protection of these workers, the number of exposures and injuries do not show a sign of decline from time to time. Objective: To examine the occurrence of sharp injury and exposure to blood and body fluids in health care workers in health care centers in Ethiopia. Methods: In a case-control study, a randomly selected sample of 65 health facilities with 391 cases and 429 controls were studied. Data were collected through a self-administered questionnaire. Detailed analysis of exposure among the health care workers was done by logistic regression analysis with generalized estimating equations model to control correlation effects of responses within the cluster of health facilities. Results: The number of health care workers who got sharp injury was 217 (26.5%. 296 (36.1% had exposure to blood and body fluids. Working at Harari region (adjusted OR 0.44, 95% CI 0.26 to 0.75 and East Hararghea (adjusted OR 0.61, 95% CI 0.40 to 0.94, being male (adjusted OR 0.56, 95% CI 0.44 to 0.91, and a being nurse (adjusted OR 0.188, 95% CI 0.06 to 0.63 were independent risk factors of the exposure. Conclusion: Regardless of the anticipated low self-reporting for exposure status, the number of health care workers reported having sharp injury and exposure to blood and body fluids was high. Such high exposures indicate that health care workers are at high risk of acquiring blood-borne viral infections such as hepatitis B, hepatitis C, and HIV.

  17. Epidemiology and outcome analysis of hand burns: A 5-year retrospective review of 378 cases in a burn center in Eastern China. (United States)

    Wang, Kang-an; Sun, Yu; Wu, Guo-sheng; Wang, Yi-ru; Xia, Zhao-fan


    Hands are frequent sites of burn but few related studies were reported in China. The aim of this study was to examine the impacts of gender, age, seasons, place, etiology, total body surface area (TBSA), depth, infection and comorbidities on prognosis following injury in a cohort of hand burn inpatients. This is a retrospective study of total 378 inpatients admitted to the burn center of Changhai hospital from January 2009 to December 2013. The present research showed the male inpatients were predominant and most of the inpatients aged from 20 to 49. Flame (37.04%) and electricity (25.40%) were the major causes of hand burns. Hand burns happened more commonly in work place (60.85%). The study preliminarily pointed out that male, flame and depth were the most significant factors impacting surgery. The main factors relevant to amputation were identified including the electrical burns and other etiology of burns. In addition, depth of hand burns was proved to have a higher impact on length of hospital stay (LOS) than other factors. The results of this study not only provide the necessary information of hand burns in Eastern China but also give the suggestions for the prevention of hand burns. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.


    Kiselev, S M; Shandala, N K; Akhromeev, S V; Gimadova, T I; Seregin, V A; Titov, A V; Biryukova, N G


    Intensification ofactivities in the field of spent nuclear fuel (SNF) and radioactive waste (RW) management in the Far East region of Russia assumes an increase of the environmental load on the territories adjacent to the enterprise and settlements. To ensure radiation safety during works on SNF and radioactive waste management in the standard mode of operation and during the rehabilitation works in the contaminated territories, there is need for the optimization of the existing system of radiation-hygienic monitoring, aimed at the implementation of complex dynamic observation of parameters of radiation-hygienic situation and radiation amount of the population living in the vicinity of the Far Eastern Center for Radioactive Waste Management (FEC "DALRAO"). To solve this problem there is required a significant amount of total and enough structured information on the character of the formation of the radiation situation, the potential ways of the spread of man-made pollution to the surrounding area, determining the radiation load on the population living in the vicinity of the object. In this paper there are presented the results of field studies of the radiation situation at the plant FEC "DALRAO", which were obtained during the course of expedition trips in 2009-2012.

  19. Pilot Study of Reimbursement Practices in Private Healthcare Centers in the Eastern Province of Saudi Arabia: To What Extent Do They Meet International Best Practices? (United States)

    Bah, Sulaiman; Almutawa, Hanadi Hassan Ali; Alassaf, Nouf Fahad M; Al Hareky, Mai Saad; Hashishi, Aqilah Salman M; Alkhater, Zainab Jassem Hassan; Ajaimi, Jenan Ali M


    This pilot study examines reimbursement practices in private healthcare centers in the Eastern Province of Saudi Arabia. The objective of the study was to assess the extent to which the private healthcare sector in Saudi Arabia follows international best practices in reimbursement, as identified in a literature review. The study examined reimbursement practices in a sample of six private healthcare facilities through the use of similar questionnaire guidelines with each facility. Similarities among the facilities' practices included the use of contracts with insurance companies and the availability of a chargemaster. Differences included the types of reimbursement software used. Bundled payment systems were identified in four facilities but were not examined in all of the facilities studied. International best practices that were not present in any of the facilities in the study included electronic transfer protocols to link healthcare facilities, insurance companies, and banks; the use of reimbursement key performance indicators; the use of diagnosis-related groups; and the integration of disease coding into the reimbursement process. Major findings of this pilot study are that diverse types of reimbursement systems are in use in Saudi healthcare facilities and that these systems are preliminary and are largely unregulated. The authors suggest that regulation and standardization would therefore be easier at this stage than at later stages of the development of private healthcare systems in Saudi Arabia.

  20. Faulting, volcanism, and basin development along the western margin of the southern San Luis Basin segment of the Rio Grande rift, New Mexico and Colorado (United States)

    Turner, K. J.; Thompson, R. A.; Cosca, M. A.; Drenth, B.; Lee, J.; Budahn, J. R.


    The San Luis Basin segment of the northern Rio Grande rift, straddling the Colorado-New Mexico border, is an asymmetrical graben where the major basin-bounding fault is on the east side. In contrast, the west side is a basin-directed dip slope surface cut by north to northwest trending faults with predominantly down-to-southwest displacement. Around 26 Ma, initial rift-related faulting formed broad, shallow basins coincident with basaltic volcanism of the Hinsdale Formation. Later episodes of rifting produced deep and narrow sub-basins generally along the eastern boundary. Basin-fill deposits along the western margin are generally thin. However, in the northern Tusas Mountains, gravity data identifies a small, yet deep, sub-basin that may contain 750 m of basin-filling Los Pinos Formation based on thickness projections derived from mapping. The Los Pinos Formation is overlain by early rift-related Hinsdale Formation basalt flows indicating this sub-basin formed as part of early rifting; the sub-basin may be a southern extension of the Monte Vista graben to the north. The stratigraphic section along the western boundary includes Precambrian basement up to volcanic rocks of the Taos Plateau volcanic field (~5-2Ma). Dips on the early-rift Miocene to Oligocene Hinsdale Formation lavas (3-5 degrees) reflect the cumulative eastward tilting corresponding to continued basin subsidence. Shallower dips (1-2 degrees) on early Pliocene volcanic rocks suggest continued subsidence up to about 3 Ma, or younger. Down-to-southwest faults accommodating eastward tilting are mostly in areas west of Pliocene volcanic rocks; individual faults offset Hinsdale Formation and older rocks by up to 200 m. The few observed faults in the Pliocene volcanic rocks have minor offset. Numerous volcanic vents are in close proximity to the faults along the western boundary. Volcanoes are commonly low to medium relief shield volcanoes with basaltic andesite composition capped by late stage cinder cones

  1. Tropical Volcanic Soils From Flores Island, Indonesia

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    Full Text Available Soils that are developed intropical region with volcanic parent materials have many unique properties, and high potential for agricultural use.The purpose of this study is to characterize the soils developed on volcanic materials from Flores Island, Indonesia,and to examine if the soils meet the requirements for andic soil properties. Selected five soils profiles developed fromandesitic volcanic materials from Flores Island were studied to determine their properties. They were compared intheir physical, chemical and mineralogical characteristics according to their parent material, and climatic characteristicdifferent. The soils were developed under humid tropical climate with ustic to udic soil moisture regimes withdifferent annual rainfall. The soils developed from volcanic ash parent materials in Flores Island showed differentproperties compared to the soils derived from volcanic tuff, even though they were developed from the sameintermediary volcanic materials. The silica contents, clay mineralogy and sand fractions, were shown as the differences.The different in climatic conditions developed similar properties such as deep solum, dark color, medium texture, andvery friable soil consistency. The soils have high organic materials, slightly acid to acid, low to medium cationexchange capacity (CEC. The soils in western region have higher clay content and showing more developed than ofthe eastern region. All the profiles meet the requirements for andic soil properties, and classified as Andisols order.The composition of sand mineral was dominated by hornblende, augite, and hypersthenes with high weatherablemineral reserves, while the clay fraction was dominated by disordered kaolinite, and hydrated halloysite. The soilswere classified into subgroup as Thaptic Hapludands, Typic Hapludands, and Dystric Haplustands

  2. Volcanism Studies: Final Report for the Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce M. Crowe; Frank V. Perry; Greg A. Valentine; Lynn M. Bowker


    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is

  3. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.


    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean integrates volcanic radiative cooling and responds over a wide range of time scales. The associated processes, especially ocean heat uptake, play a key role in ongoing climate change. However, they are not well constrained by observations, and attempts to simulate them in current climate models used for climate predictions yield a range of uncertainty. Volcanic impacts on the ocean provide an independent means of assessing these processes. This study focuses on quantification of the seasonal to multidecadal time scale response of the ocean to explosive volcanism. It employs the coupled climate model CM2.1, developed recently at the National Oceanic and Atmospheric Administration\\'s Geophysical Fluid Dynamics Laboratory, to simulate the response to the 1991 Pinatubo and the 1815 Tambora eruptions, which were the largest in the 20th and 19th centuries, respectively. The simulated climate perturbations compare well with available observations for the Pinatubo period. The stronger Tambora forcing produces responses with higher signal-to-noise ratio. Volcanic cooling tends to strengthen the Atlantic meridional overturning circulation. Sea ice extent appears to be sensitive to volcanic forcing, especially during the warm season. Because of the extremely long relaxation time of ocean subsurface temperature and sea level, the perturbations caused by the Tambora eruption could have lasted well into the 20th century.

  4. Geomorphology of debris aprons in the eastern Hellas region of Mars (United States)

    Stewart, Keith H.; Crown, David A.


    Recent geologic mapping and geomorphic analyses have documented the geologic history of the eastern Hellas region of Mars in terms of the styles, timing, and evolution of volcanic activity associated with eruptive centers at Hadriaca and Tyrrhena Paterae. As a result of the geologic relationships between regional volcanic units and the Dao, Harmakhis, and Reull Valles outflow channel systems, constraints have been established for the timing and nature of erosional and depositional processes occurring in the region. The present study examines late-stage (Amazonian) degradation processes recorded in a series of debris aprons and debris flows located predominantly around massifs in the eroded southern highlands along the Reull and Harmakhis Valles outflow systems.

  5. Insights on the Biology of the Eastern Lau Spreading Center from Studies on the East Pacific Rise and Juan de Fuca Ridge (United States)

    Fisher, C. R.; Sen, A.; Becker, E.


    A primary goal of the Ridge 2000 program was to conduct comparable interdisciplinary studies at a few fundamentally different sites that would facilitate comparisons among sites and development of concepts with broad application across deep ocean ridge spreading centers. Although the Eastern Lau Spreading Center (ELSC) was the least known of the three Integrated Study Sites, we were able to make amazingly fast progress on understanding this system because we could draw on technology and experience developed during the RIDGE program to plan and conduct the work, and now interpret our findings in the context of the rich literature and Ridge 2000 studies on East Pacific Rise (EPR) , Juan de Fuca Ridge (JdFR), and Mid Atlantic Ridge communities. The ELSC communities not only house different species than those of the other regions, but unlike the often tubeworm dominated E. Pacific vents, they are structured by symbiont reliant species that are mobile; snails and mussels. Although there is some variation with lava type on the ELSC, the 4 species of large, symbiont-containing snails largely occupy the niches filled by tubeworms and mussels on the EPR, while the niche of the mussel in the W. Pacific vents is quite different from that of its EPR cousin. Although we have not observed any significant tectonic or magmatic events during our studies of the ELSC, 4 years of study considered in the context of what we have learned on the EPR and JdFR allow us to formulate and begin testing hypotheses about temporal change and succession in these very different and much less visited ecosystems. Furthermore, athough Paralvinella fijiensis are only found in limited areas on some chimneys and flanges, unlike the situation on the EPR and JdFR ,the ELSC chimney communities are largely composed of the same species as are found in diffuse flow on the lavas. The ELSC chimney communities are also remarkably stable, hosting some of the largest and apparently oldest individuals found on the

  6. Arc-rift transition volcanism in the Volcanic Hills, Jacumba and Coyote Mountains, San Diego and Imperial Counties, california (United States)

    Fisch, Gregory Zane

    Neogene volcanism associated with the subduction of the Farallon-Pacific spreading center and the transition from a subduction zone to a rift zone has been studied extensively in Baja, California, Mexico. One of the main goals of these studies was to find a geochemical correlation with slab windows that may have formed during that complicated transition. While workers have been able to find distinct geochemical signatures in samples from Baja California, none have shown statistically significant correlation with samples from southern California that are thought to be related to the same arc-rift transition events. All of the basaltic samples from this study of southern California rocks have prominent Nb depletions typical of island-arc subduction-related volcanism, in contrast to the chemistry of Baja California volcanics that have trace element patterns typical of synrift related volcanism. The work done by previous investigators has been additionally complicated due to each investigator's choice of important ratios or patterns, which bears little, if any, correlation with work done by others working in the same area. For example, Martin-Barajas et al. (1995) use K/Rb ratios in their study of the Puertocitos Volcanic Province, while Castillo (2008) argues that Sr/Y vs. Y is a better indicator of petrogenetic processes. Little petrologic work has been done on Neogene volcanic rocks in the Imperial Valley and eastern San Diego County region of Southern California. This thesis combines new research with that of previous workers and attempts to establish a better understanding of the processes involved with the transition volcanism. Prior work documents significant differences in the geochemistry between some of these areas, especially those in close proximity to each other (e.g. the Volcanic Hills and Coyote Mountains). These differences were thought to be largely the result different magmatic sources. The potential of finding two differing magma types in close

  7. An Alternative to Channel-Centered Views of the Landscape for Understanding Modern Streams in the Mid-Atlantic Piedmont Region, Eastern USA (United States)

    Merritts, D. J.; Walter, R. C.; Rahnis, M. A.; Oberholtzer, W.


    Stream channels generally are the focus of conceptual models of valley bottom geomorphology. The channel-centered model prevalent in the tectonically inactive eastern U. S. invokes meandering stream channels migrating laterally across valley floors, eroding one bank while depositing relatively coarse sediment in point bars on the other. According to this model, overbank deposition during flooding deposits a veneer of fine sediment over the gravel substrate. Erosion is considered normal, and the net volume of sediment is relatively constant with time. A dramatic change in conditions-land-clearing during European settlement--led to widespread aggradation on valley bottoms. This historic sedimentation was incorporated in the channel-centered view by assuming that meandering streams were overwhelmed by the increased sediment load and rapidly aggraded vertically. Later, elevated stream channels cut through these deposits because of decreased sediment supply and increased stormwater runoff accompanying urbanization. This view can be traced to early ideas of stream equilibrium in which incoming sediment supply and runoff determine stream-channel form. We propose a different conceptual model. Our trenching and field work along hundreds of km of stream length in the mid-Atlantic Piedmont reveal no point bars prior to European settlement. Instead, a polygenetic valley-bottom landscape underlies the drape of historic sediment. The planar surface of this veneer gives the appearance of a broad floodplain generated by long-term meandering and overbank deposition, but the "floodplain" is a recent aggradational surface from regional base-level rise due to thousands of early American dams that spanned valley bottoms. As modern streams incise into the historic fine-grained slackwater sediment, they expose organic-rich hydric soils along original valley bottom centers; talus, colluvium, bedrock, and saprolite with forest soils along valley margins; and weathered Pleistocene (and

  8. The pace of arc volcanism (United States)

    Palmer, M. R.; Fraass, A. J.; Hatfield, R. G.; McCanta, M. C.


    Being able to reconstruct the long-term history of activity at an island arc volcanic centre has important implications for a wide variety of geologic processes. On-land records are frequently incomplete and radiometric dating is complicated in many systems. Here, we describe the application of rapid and non-destructive measurements of sediment physical properties (colour reflectance, gamma ray attenuation and magnetic susceptibility) from marine sediments recovered from IODP site U1396 to produce a tephra index (TI). This approach is combined with palaeomagnetic and foram isotope stratigraphy to yield a 4.5 Myr record of volcanic activity in the northern Lesser Antilles. Pb isotope data on visible tephra layers and volcanological models suggest the tephra is predominantly derived from the nearby island of Montserrat. When examined over a range of time-averaged intervals, the TI record shows long term (order 106 year) cycles of relative quiescence and heightened activity. In accordance with the model of Hall & Kincaid (2001, Science, 292, 2472), this record suggests that the long-term pace of volcanic activity in the northern Lesser Antilles is established by diapirs rising from deep within the mantle wedge. The diapirs do not themselves act as the major source of melt, but rather they create a conduit network that facilitates the rapid rise of melt to the surface. Within the order 106 year cycles, there are shorter-term fluctuations (order 104 years) that may reflect cycles of edifice growth and destruction, and/or pulses of melt rising through conduit networks established by the rising diapirs. The U1396 TI record provides the most complete and non-aliased long-term record of activity at an island arc volcanic center yet determined. It thus provides the first field evidence that can be used to test models of the deep mantle processes that control the pace of arc volcanism. Importantly, the approach presented here is readily applicable to other arc and island

  9. Volcanic Rocks and Features (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanoes have contributed significantly to the formation of the surface of our planet. Volcanism produced the crust we live on and most of the air we breathe. The...

  10. Languages of volcanic landscapes (United States)

    Frederick J. Swanson


    As a young geologist in 1980, I felt a powerful attraction to volcanoes, and I thought I knew volcanoes rather well. I had studied volcanology. I had climbed volcanic peaks in the Cascades. And I had tried to be an attentive citizen of my volcanic region, the Pacific Northwest. But when I had a chance to go with other scientists to Mount St. Helens within days of its...

  11. Formation of Zn- and Fe-sulfides near hydrothermal vents at the Eastern Lau Spreading Center: implications for sulfide bioavailability to chemoautotrophs

    Directory of Open Access Journals (Sweden)

    Yucel Mustafa


    Full Text Available Abstract Background The speciation of dissolved sulfide in the water immediately surrounding deep-ocean hydrothermal vents is critical to chemoautotrophic organisms that are the primary producers of these ecosystems. The objective of this research was to identify the role of Zn and Fe for controlling the speciation of sulfide in the hydrothermal vent fields at the Eastern Lau Spreading Center (ELSC in the southern Pacific Ocean. Compared to other well-studied hydrothermal systems in the Pacific, the ELSC is notable for unique ridge characteristics and gradients over short distances along the north-south ridge axis. Results In June 2005, diffuse-flow ( 250°C vent fluids were collected from four field sites along the ELSC ridge axis. Total and filtered Zn and Fe concentrations were quantified in the vent fluid samples using voltammetric and spectrometric analyses. The results indicated north-to-south variability in vent fluid composition. In the high temperature vent fluids, the ratio of total Fe to total Zn varied from 39 at Kilo Moana, the most northern site, to less than 7 at the other three sites. The concentrations of total Zn, Fe, and acid-volatile sulfide indicated that oversaturation and precipitation of sphalerite (ZnS(s and pyrite (FeS2(s were possible during cooling of the vent fluids as they mixed with the surrounding seawater. In contrast, most samples were undersaturated with respect to mackinawite (FeS(s. The reactivity of Zn(II in the filtered samples was tested by adding Cu(II to the samples to induce metal-exchange reactions. In a portion of the samples, the concentration of labile Zn2+ increased after the addition of Cu(II, indicating the presence of strongly-bound Zn(II species such as ZnS clusters and nanoparticles. Conclusion Results of this study suggest that Zn is important to sulfide speciation at ELSC vent habitats, particularly at the southern sites where Zn concentrations increase relative to Fe. As the hydrothermal

  12. Volcanic hazards to airports (United States)

    Guffanti, M.; Mayberry, G.C.; Casadevall, T.J.; Wunderman, R.


    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies

  13. Eruptive dynamics and hazards associated with obsidian bearing ignimbrites of the Geghama Volcanic Highland, Central Armenia: a textural insight (United States)

    Matthews, Zoe; Manning, Christina J.


    The Geghama Volcanic highland in central Armenia is an ideal setting to study the young ( 750-25 ka [1]) volcanism that characterises the Lesser Caucasus region. The volcanism in the area is bimodal in composition: the eastern highlands are dominated by numerous monogenetic scoria cones, whilst the west shows more evolved volcanism centered on two obsidian bearing, polygenetic domes (Hatis and Gutanasar) [2]. Activity at Hatis and Gutanasar is thought to have spanned 550ka-200ka [3] and produced a range of products including obsidian flows, ignimbrites and basaltic scoria cones, consistent with long lived and complex magma storage systems. During a similar time period there is evidence for the presence of hominin groups in the surrounding region [3] and it is likely that at least some of the volcanic activity at Hatis and Gutanasar impacted on their distribution [4]. A better understanding of the eruptive behaviour of these volcanoes during this period could therefore shed light on the effect of volcanic activity on the dispersal of man through this period. Whilst large regional studies have striven to better understand the timing and source of volcanism in Armenia, there have been few detailed studies on single volcanoes. Obsidian is ubiquitous within the volcanic material of both Gutanasar and Hatis as lava flows, dome deposits and within ignimbrites. This study aims to better understand the eruptive history of Gutanasar, with specific focus upon the determination of the petrogenetic history of obsidian lenses observed within the ignimbrite deposits. Identification of these obsidians as the result of welding or in-situ melting will help constrain eruptive volumes and flow thickness, important for the reconstruction of palaeo-volcanic hazards. In order to interpret how this obsidian was deposited, macro textural analysis is combined with micro textural measurements of microlite crystals. Quantitative measurements of microlites in obsidian can provide significant

  14. Precambrian Lunar Volcanic Protolife

    Directory of Open Access Journals (Sweden)

    Jack Green


    Full Text Available Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated.

  15. Volcanic activity and climatic changes. (United States)

    Bryson, R A; Goodman, B M


    Radiocarbon dates of volcanic activity suggest variations that appear to be related to climatic changes. Historical eruption records also show variations on the scale of years to centuries. These records can be combined with simple climatic models to estimate the impact of various volcanic activity levels. From this analysis it appears that climatic prediction in the range of 2 years to many decades requires broad-scale volcanic activity prediction. Statistical analysis of the volcanic record suggests that some predictability is possible.

  16. National volcanic ash operations plan for aviation (United States)

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    International Civil Aviation Organization’s (ICAO) International Airways Volcano Watch. This plan defines agency responsibilities, provides a comprehensive description of an interagency standard for volcanic ash products and their formats, describes the agency backup procedures for operational products, and outlines the actions to be taken by each agency following an occurrence of a volcanic eruption that subsequently affects and impacts aviation services. Since our most recent International Conference on Volcanic Ash and Aviation Safety, volcanic ash-related product and service activities have grown considerably along with partnerships and alliances throughout the aviation community. In January 2005, the National Oceanic and Atmospheric Administration’s National Centers for Environment Prediction began running the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model in place of the Volcanic Ash Forecast Transport and Dispersion (VAFTAD) model, upgrading support to the volcanic ash advisory community. Today, improvements to the HYSPLIT model are ongoing based on recommendations by the OFCM-sponsored Joint Action Group for the Selection and Evaluation of Atmospheric Transport and Diffusion Models and the Joint Action Group for Atmospheric Transport and Diffusion Modeling (Research and Development Plan). Two international workshops on volcanic ash have already taken place, noticeable improvements and innovations in education, training, and outreach have been made, and federal and public education and training programs on volcanic ash-related products, services, and procedures iv continue to evolve. For example, in partnership with Embry-Riddle Aeronautical University and other academic institutions, volcanic ash hazard and mitigation training has been incorporated into aviation meteorology courses. As an essential next step, our volcanic ash-related efforts in the near term will be centered on the development of an interagency implementation plan to

  17. Influences of the Tonga Subduction Zone on seafloor massive sulfide deposits along the Eastern Lau Spreading Center and Valu Fa Ridge (United States)

    Evans, Guy N.; Tivey, Margaret K.; Seewald, Jeffrey S.; Wheat, C. Geoff


    This study investigates the morphology, mineralogy, and geochemistry of seafloor massive sulfide (SMS) deposits from six back-arc hydrothermal vent fields along the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the context of endmember vent fluid chemistry and proximity to the Tonga Subduction Zone. To complement deposit geochemistry, vent fluid analyses of Cu, Zn, Ba, Pb and H2,(aq) were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions. Results document southward increases in the abundance of mantle-incompatible elements in hydrothermal fluids (Ba and Pb) and SMS deposits (Ba, Pb, As, and Sb), which is also expressed in the abundance of barite (BaSO4) and galena (PbS) in SMS deposits. These increases correspond to a decrease in distance between the ELSC/VFR and the Tonga Subduction Zone that correlates with a change in crustal lithology from back-arc basin basalt in the north to mixed andesite, rhyolite, and dacite in the south. Barite influences deposit morphology, contributing to the formation of horizontal flanges and squat terraces. Results are also consistent with a regional-scale lowering of hydrothermal reaction zone temperatures from north to south (except at the southernmost Mariner vent field) that leads to lower-temperature, higher-pH vent fluids relative to mid-ocean ridges of similar spreading rates (Mottl et al., 2011). These fluids are Cu- and Zn-poor and the deposits formed from these fluids are Cu-poor but Zn-rich. In contrast, at the Mariner vent field, higher-temperature and lower pH vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles (Mottl et al., 2011). The Mariner fluids are Cu- and Zn-rich and vent from SMS deposits that are rich in Cu but poor in Zn with moderate amounts of Pb. Thermodynamic calculations indicate that the contrasting metal contents of vent fluids

  18. Modeling volcanic ash dispersal

    CERN Multimedia

    CERN. Geneva


    The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard...

  19. Multiple expressions of plume-ridge interaction at the Galapagos: Volcanic lineaments and ridge jumps (United States)

    Mittelstaedt, E. L.; Soule, S. A.; Harpp, K. S.; Fornari, D. J.


    Despite significant evidence for communication between an upwelling mantle plume beneath the Galápagos Archipelago (GA) and the nearby Galápagos Spreading Center (GSC), little is known about the dynamics of the interaction between the ridge and the hotspot. We use new bathymetry, sidescan sonar, magnetic, subbottom seismic, and gravity data from the FLAMINGO cruise (MV1007) to address the mechanism of plume-ridge interaction in the Northern Galápagos Volcanic Province (NGVP), a region centered on the 90° 50'W Galápagos transform fault (GTF). West of the GTF, the Nazca Plate is dominated by numerous seamounts aligned in 3 volcanic lineaments. Volumetrically, the lineaments are composed of ~1500 km3 of erupted lavas. Faulting patterns and seamount elongations suggest that the locations and orientations of the lineaments may be partly controlled by the lithospheric stress field. In contrast, east of the GTF on the Cocos Plate, there is little evidence of constructional volcanism (~69 km3). However, we observe several linear, nearly ridge-parallel, faulted features separating sediment-filled basins, and two large bathymetric highs with up to 1km of relief. Differences in seafloor west and east of the GTF are also observed in the Residual Mantle Bouguer Anomaly (RMBA). On the Nazca Plate, RMBA lows closely contour the volcanic lineaments with minima at the centers of the largest volcanoes along the Wolf-Darwin Lineament. On the Cocos Plate, the RMBA at a given distance from the ridge axis is generally more negative than at similar locations on the Nazca Plate. In addition, two RMBA lows are observed coincident with the observed bathymetric highs, both of which are slightly elongate in a direction sub-parallel to the Eastern GSC, possibly reflecting a period of increased magma flux along a former ridge axis. Magnetic anomalies reveal a complicated history of plate evolution including a series of ridge jumps since ~3 Ma that result in creation of the GTF. We invert

  20. Sustaining Volcanism of the Klyuchevskoy Group (United States)

    Nikulin, A.; Levin, V. L.; Carr, M. J.; Herzberg, C. T.; West, M. E.


    A primary control on the geographic position of volcanic arcs is the depth of fluid release from the subducting plate beneath the arc. Volcanoes of the Klyuchevskoy Group in Eastern Russia comprise the most active volcanic arc system in the world with the depth of the subducting Pacific plate beneath the arc estimated at 180-200km, greatly in excess of the global average. We attribute this deviation to a presence of a secondary melt generation source beneath this arc and present geophysical, geochemical and petrological evidence in support of this hypothesis. We present seismological constraints based on receiver function migration on the upper mantle structure beneath the Klyuchevskoy Group. We identify a sharply bounded low-velocity seismic feature at ~110 km depth separated from the subducting Pacific Plate. Analysis of open-access geochemical databases yields a previously unnoted bi-modal distribution of Zr/Nb concentrations in the Klyuchevskoy Group lavas. If the Zr/Nb ratio has some sensitivity for the depth to the slab, as it appears to in Central America, the observed bi-modal distribution of Zr/Nb values within lavas of the Klyuchevskoy Group may be associated with two sources, a deep source and a shallower source with higher Zr/Nb. Results of petrological modeling of melting conditions inferred from unfractionated basalt indicate melting pressures consistent with a source at a depth shallower than the estimated depth to the subducting plate. Inferred pressures of initial melting indicate a depth of about 70 to 90 km depth, roughly consistent with the position of the low -velocity seismic anomaly. We hypothesize that this upper mantle structure may serve as a second source of melts driving volcanism of the Klyuchevskoy Group. Presence of such source may explain both the extraordinary productivity of this volcanic arc and its unusual location.

  1. Impact of volcanism on the evolution of Lake Van (eastern Anatolia) III: Periodic (Nemrut) vs. episodic (Süphan) explosive eruptions and climate forcing reflected in a tephra gap between ca. 14 ka and ca. 30 ka (United States)

    Schmincke, Hans-Ulrich; Sumita, Mari


    Fifteen Lateglacial to Holocene rhyolitic, dominantly primary tephra layers piston-cored and drilled (ICDP Paleovan drilling project) in western Lake Van (eastern Anatolia, Turkey) were precisely correlated to either of the two adjacent and active large volcanoes Nemrut and Süphan based on shard textures, mineralogy and mineral and glass compositions. The young peralkaline (comenditic to pantelleritic) primary rhyolitic Nemrut tephras are characterized by anorthoclase, hedenbergitic to augitic clinopyroxene, fayalitic olivine, minor quartz, and rare accessory chevkinite and zircon. Phenocrysts in subalkaline primary rhyolitic Süphan tephras are chiefly oligoclase-labradorite, with minor K-rich sanidine in some, biotite, amphibole, hypersthene, rare augitic clinopyroxene, relatively common allanite and rare zircon. Two contrasting explosive eruptive modes are distinguished from each other: episodic (Süphan) and periodic (Nemrut). The Lateglacial Süphan tephra swarm covers a short time interval of ca. 338 years between ca. 13,078 vy BP and 12,740 vy BP, eruptions having occurred statistically every ca. 42 years with especially short intervals between V-11 (reworked) and V-14. Causes for the strongly episodic Süphan explosive behavior might include seismic triggering of a volcano-magma system unable to erupt explosively without the benefit of external triggering, as reflected in pervasive faulting preceding the Süphan tephra swarm. Seismic triggering may have caused the rise of more mafic ("trachyandesitic") parent magma, heating near-surface pockets of highly evolved magma - that might have formed silicic domes during this stage of volcano evolution - resulting in ascent and finally explosive fragmentation of magma essentially by external factors, probably significantly enhanced by magma-water/ice interaction. Explosive eruptions of the Nemrut volcano system, interpreted to be underlain by a large fractionating magma reservoir, follow a more periodic mode of (a

  2. The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: tectonically anomalous forearc volcanism in an urban setting (United States)

    Evarts, Russell C.; Conrey, Richard M.; Fleck, Robert J.; Hagstrum, Jonathan T.; O'Connor, Jim; Dorsey, Rebecca; Madin, Ian P.


    More than 80 small volcanoes are scattered throughout the Portland-Vancouver metropolitan area of northwestern Oregon and southwestern Washington. These volcanoes constitute the Boring Volcanic Field, which is centered in the Neogene Portland Basin and merges to the east with coeval volcanic centers of the High Cascade volcanic arc. Although the character of volcanic activity is typical of many monogenetic volcanic fields, its tectonic setting is not, being located in the forearc of the Cascadia subduction system well trenchward of the volcanic-arc axis. The history and petrology of this anomalous volcanic field have been elucidated by a comprehensive program of geologic mapping, geochemistry, 40Ar/39Ar geochronology, and paleomag-netic studies. Volcanism began at 2.6 Ma with eruption of low-K tholeiite and related lavas in the southern part of the Portland Basin. At 1.6 Ma, following a hiatus of ~0.8 m.y., similar lavas erupted a few kilometers to the north, after which volcanism became widely dispersed, compositionally variable, and more or less continuous, with an average recurrence interval of 15,000 yr. The youngest centers, 50–130 ka, are found in the northern part of the field. Boring centers are generally monogenetic and mafic but a few larger edifices, ranging from basalt to low-SiO2 andesite, were also constructed. Low-K to high-K calc-alkaline compositions similar to those of the nearby volcanic arc dominate the field, but many centers erupted magmas that exhibit little influence of fluids derived from the subducting slab. The timing and compositional characteristics of Boring volcanism suggest a genetic relationship with late Neogene intra-arc rifting.

  3. Backprojection of volcanic tremor (United States)

    Haney, Matthew M.


    Backprojection has become a powerful tool for imaging the rupture process of global earthquakes. We demonstrate the ability of backprojection to illuminate and track volcanic sources as well. We apply the method to the seismic network from Okmok Volcano, Alaska, at the time of an escalation in tremor during the 2008 eruption. Although we are able to focus the wavefield close to the location of the active cone, the network array response lacks sufficient resolution to reveal kilometer-scale changes in tremor location. By deconvolving the response in successive backprojection images, we enhance resolution and find that the tremor source moved toward an intracaldera lake prior to its escalation. The increased tremor therefore resulted from magma-water interaction, in agreement with the overall phreatomagmatic character of the eruption. Imaging of eruption tremor shows that time reversal methods, such as backprojection, can provide new insights into the temporal evolution of volcanic sources.

  4. Volcanic eruptions on Io (United States)

    Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Cook, A. F.; Hansen, C.


    Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

  5. Status of volcanism studies for the Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.; Perry, F.; Murrell, M.; Poths, J.; Valentine, G.A. [Los Alamos National Lab., NM (United States); Wells, S. [Univ. of California, Riverside, CA (United States); Bowker, L.; Finnegan, K. [Univ. of Nevada, Las Vegas, NV (United States); Geissman, J.; McFadden, L.


    Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. Geophysical data are described for the YMR and are used as an aid to understand the distribution of basaltic volcanic centers. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. The long time of activity and characteristic small volume of the Postcaldera basalt of the YMR result in one of the lowest eruptive rates in a volcanic field in the southwest United States. Chapter 5 summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Chapter 6 summarizes the history of volcanism studies (1979 through early 1994), including work for the Yucca Mountain Site Characterization Project and overview studies by the state of Nevada and the Nuclear Regulatory Commission. Chapter 7 summarizes probabilistic volcanic hazard assessment using a three-part conditional probability model. Chapter 8 describes remaining volcanism work judged to be needed to complete characterization studies for the YMR. Chapter 9 summarizes the conclusions of this volcanism status report.

  6. Holocene Volcanic Records in the Siple Dome Ice Cores (United States)

    Zielinski, G. A.; Dunbar, N. W.; Kurbatov, A. V.; Voisin, D. T.


    Using both the SO42- and Cl- time series and tephrochronological analyses, a highly detailed record of Holocene volcanism is being reconstructed from the Siple Dome A ice core. The volcanic glaciochemical record is being developed at a 2-4 year resolution for the last 10,000 years. Volcanic peaks were identified as those having a concentration of 2{σ } above the mean positive residual of the spline fit, as was done for the GISP2 volcanic record. We identified about 70 volcanic events for the mid-late Holocene. The largest sulfate signal (350 ppb) over the time period evaluated occurs at 2242 years ago. Large signals of volcanically enhanced sulfate in the ice core record also occur around 720 years ago (1280 C.E.;194-249 ppb)and 4710 years ago (378ppb). Ages for large equatorial or southern hemisphere volcanic eruptions are synchronous with identified sulfate peaks in the reconstructed volcanic record. However, the continuous scan for volcanic glass in these same samples yielded glass compositions more in-line with Antarctica volcanic zones (i.e., local eruptions). Nevertheless, our record provides important information on the atmospheric impact of volcanism in Antarctica geochemical cycles. The glass (i.e., tephra) found in various samples indicate that volcanoes within the McMurdo Volcanic Center (Victoria Land and the islands off its coast) including Mt. Melbourne, The Pleaides and Buckle Island appear to be the most active in Antarctica during the late Holocene. Rhyolitic shards of a composition not found in Antarctica also are present in some layers, although they are not overly abundant. The presence of dust with a Patagonian origin in East Antarctica ice cores as well as the nature of the Antarctica vortex indicate that material from this part of the southern hemisphere can reach various parts of Antarctica. Common circulation patterns around the Ross and Amundson Seas as well as the satellite trace of aerosols from the 1991 Cerro Hudson eruption, Argentina

  7. Mineral chemistry of lava flows from Linga area of the Eastern ...

    Indian Academy of Sciences (India)

    Several basaltic lava flows have been identified in the study area in and around Linga, in the Eastern Deccan Volcanic Province (EDVP) on the basis of distinctly developed structural zones defined by primary volcanic structures such as columnar joints and vesicles. These basaltic lava flows are spatially distributed in four ...

  8. California's Vulnerability to Volcanic Hazards: What's at Risk? (United States)

    Mangan, M.; Wood, N. J.; Dinitz, L.


    California is a leader in comprehensive planning for devastating earthquakes, landslides, floods, and tsunamis. Far less attention, however, has focused on the potentially devastating impact of volcanic eruptions, despite the fact that they occur in the State about as frequently as the largest earthquakes on the San Andreas Fault Zone. At least 10 eruptions have occurred in the past 1,000 years—most recently in northern California (Lassen Peak 1914 to 1917)—and future volcanic eruptions are inevitable. The likelihood of renewed volcanism in California is about one in a few hundred to one in a few thousand annually. Eight young volcanoes, ranked as Moderate to Very High Threat [1] are dispersed throughout the State. Partially molten rock (magma) resides beneath at least seven of these—Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, and Salton Buttes— causing earthquakes, toxic gas emissions, hydrothermal activity, and (or) ground deformation. Understanding the hazards and identifying what is at risk are the first steps in building community resilience to volcanic disasters. This study, prepared in collaboration with the State of California Governor's Office of Emergency Management and the California Geological Survey, provides a broad perspective on the State's exposure to volcano hazards by integrating mapped volcano hazard zones with geospatial data on at-risk populations, infrastructure, and resources. The study reveals that ~ 16 million acres fall within California's volcano hazard zones, along with ~ 190 thousand permanent and 22 million transitory populations. Additionally, far-field disruption to key water delivery systems, agriculture, utilities, and air traffic is likely. Further site- and sector-specific analyses will lead to improved hazard mitigation efforts and more effective disaster response and recovery. [1] "Volcanic Threat and Monitoring Capabilities

  9. 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)


    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).

  10. Prevention of Catastrophic Volcanic Eruptions


    Fujii, Yoshiaki; Kodama, Jun-ichi; Fukuda, Daisuke; Dassanayake, Abn


    Giant volcanic eruptions emit sulphate aerosols as well as volcanic ash. Needless to say that volcanic ash causes significant damage to the environment and human at large. However, the aerosols are even worse. They reach the Stratosphere and stay there for months to years reflecting insolation. As a result, air temperature at the Earth's surfaces drops. Even a slight temperature drop may cause severe food shortage. Yellowstone supervolcano, for example, can even make human in the Northern Hem...

  11. NOAA Coastal Services Center Coastal Inundation Digital Elevation Model: Philadelphia, Pennsylvania Weather Forecast Office (PHI WFO) and Wakefield, Virginia Weather Forecast Office (AKQ WFO) - Eastern Shore of Maryland (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data were created as part of the National Oceanic and Atmospheric Administration Coastal Services Center's efforts to create an online mapping viewer called...

  12. Volcanic Ash Nephelometer Probe Project (United States)

    National Aeronautics and Space Administration — Advanced dropsondes that could effectively be guided through atmospheric regions of interest such as volcanic plumes may enable unprecedented observations of...

  13. Structural significance of the south Tyrrhenian volcanism (United States)

    Gaudiosi, G.; Musacchio, G.; Ventura, G.; de Astis, G.


    The southern part of the Tyrrhenian Sea represents a transition from ocenic- (the Tyrrhenian Sea) to continental-domain (the Calabrian Arc) and is affected by active calkalkaline to potassic volcanism (the Eolian Islands). Active extensional tectonics, coupled with the general upwelling of northern Sicily and Calabria continental crust, coexists with active subduction of the Ionian Plate beneath the Calabrian Arc. This has been interpreted as the result of the detachment of the slab beneath the Calbrian Arc. Present-day tectonics is characterized by NE-SW normal faults and NNW- SSE dextral oblique-slip faults. The normal faults form the major peri- Tyrrhenian basins. Refraction and high resolution onshore-offshore wide-angle-reflection profiles, as well as potential field modeling, provide a 3D image of the Moho. Short wave-length undulations characterize the Moho beneath the Aeolian Arch. The major upraise is about 6 km, beneath the Aeolian active volcanic area, and affects all the crustal boundaries. Another sharp crustal thinning is observed beneath the gulf of Patti at the south-eastern edge of the Tyrrhenian basin. We suggest that the graben-like structure, occurring along the Salina-Lipari-Vulcano islands and oriented at high angles to the trench, is lithospheric and can be followed down to Moho depths. NNW-SSE dextral oblique-slip faults, like the Tindari Letojanni fault system, control the Salina-Lipari-Vulcano portion of the Aeolian volcanism and connect the oceanic crust of the Marsili Basin to the Malta Escarpment, through the Etna volcano. Across this lineament seismicity changes from mostly shallow to the west, to deep intra- slab to the east.

  14. The Satah Mountain and Baldface Mountain volcanic fields: Pleistocene hot spot volcanism in the Anahim Volcanic Belt, west-central British Columbia, Canada (United States)

    Kuehn, Christian; Guest, Bernard; Russell, James K.; Benowitz, Jeff A.


    The Satah Mountain and Baldface Mountain volcanic fields (SMVF, BMVF) comprise more than three dozen small volcanic centers and erosional remnants thereof. These fields are located in the Chilcotin Highland of west-central British Columbia, Canada, and are spatially associated with the Anahim Volcanic Belt (AVB), a linear feature of alkaline to peralkaline plutonic and volcanic centers of Miocene to Holocene ages. The AVB has been postulated to be the track of a hot spot passing beneath the westward moving Cordilleran lithosphere. We test the AVB hot spot model by applying whole-rock 40Ar/39Ar geochronology ( n = 24) and geochemistry. Whole-rock chemical compositions of volcanic rock samples ( n = 59) from these two fields suggest a strong geochemical affinity with the nearby Itcha Range shield volcano; however, SMVF and BMVF centers are mostly small in volume (<1 km3) and differ in composition from one another, even where they are in close spatial proximity. Trace element and REE patterns of mafic AVB lavas are similar to ocean island basalts (OIB), suggesting a mantle source for these lavas. The age ranges for the SMVF ( n = 11; ~2.21 to ~1.43 Ma) and BMVF ( n = 7; ~3.91 to ~0.91 Ma) are largely coeval with the Itcha Range. The distribution of volcanoes in these two volcanic fields is potentially consistent with the postulated AVB hot spot track. Eruption rates in the SMVF were high enough to build an elongated ridge that deviates from the E-W trend of the AVB by almost 90°. This deviation might reflect the mechanisms and processes facilitating magma generation and ascent through the lithosphere in this tectonically complex region and may also indicate interaction of the potential hot spot with (pre)existing fracture systems in vicinity of the Itcha Range.

  15. Volcan Reventador's Unusual Umbrella (United States)

    Chakraborty, P.; Gioia, G.; Kieffer, S. W.


    In the past two decades, field observations of the deposits of volcanoes have been supplemented by systemmatic, and sometimes, opportunistic photographic documentation. Two photographs of the umbrella of the December 3, 2002 eruption of Volcan Reventador, Ecuador, reveal a prominently scalloped umbrella that is unlike any umbrella previously documented on a volcanic column. The material in the umbrella was being swept off a descending pyroclastic flow, and was, therefore, a co-ignimbrite cloud. We propose that the scallops are the result of a turbulent Rayleigh-Taylor (RT) instability with no precedents in volcanology. We ascribe the rare loss of buoyancy that drives this instability to the fact that the Reventador column fed on a cool co-ignimbrite cloud. On the basis of the observed wavelength of the scallops, we estimate a value for the eddy viscosity of the umbrella of 4000 ~m2/s. This value is consistent with a previously obtained lower bound (200 ~m2/s, K. Wohletz, priv. comm., 2005). We do not know the fate of the material in the umbrella subsequent to the photos. The analysis suggests that the umbrella was negatively buoyant. Field work on the co-ignimbrite deposits might reveal whether or not the material reimpacted, and if so, where and whether or not this material was involved in the hazardous flows that affected the main oil pipeline across Ecuador.

  16. Platinum-group elements in the Eastern Deccan volcanic province ...

    Indian Academy of Sciences (India)

    The first two localities represent two lava piles of about 170 and 400 m thickness respectively. In Umaria, 16 flows have been demarcated based on petrography and field studies. The Shahdol samples are basal lava formations overlying Gondwana sediments (Carboniferous) and the Chirimiri samples are dykes. In this ...

  17. Magnetic signature of the Sicily Channel volcanism (United States)

    Lodolo, E.; Civile, D.; Zanolla, C.; Geletti, R.


    Widespread Late Miocene to Quaternary volcanic activity is know to have occurred in the Sicily Channel continuing up to historical time. New magnetic anomaly data acquired in the Pantelleria Graben, one of the three main tectonic depressions forming the WNW-trending Sicily Channel rift system, integrated with available profiles, are used to identify and map volcanic bodies in this sector of the northern African margin. Some of these manifestations, both outcropping at the sea-floor or buried beneath a variable thickness of Plio-Quaternary sedimentary cover, have been imaged by seismic reflection profiles. Three main positive magnetic anomalies have been found: to the S-E of the Pantelleria Island, the largest emerged caldera of the Sicily Channel, along the eastern margin of the Nameless Bank, and at the north-western termination of the Linosa Graben. Only the anomaly located off the south-eastern coast of the Pantelleria Island, associated with a large outcropping body gradually buried beneath a substantially undisturbed Upper Pliocene-Quaternary sediments, aligns with the trend of the tectonic depression. 2-D geophysical models produced along seismic transects perpendicularly crossing the Pantelleria Graben have allowed to derive its deep crustal structure, and detect the presence of buried magmatic bodies which generate the anomalies. Marginal faults seem to have played a major role in focussing magma emplacement in this sector of the Sicily Channel. The other anomalies represent off-axis volcanic episodes and generally do not show evident magmatic manifestations at the sea-floor. These magnetic maxima seem to follow a NNE-SSW-trending belt extending from Linosa Island to the Nameless Bank, where pre-existing crustal anisotropies may have conditioned magma emplacement both at deep and shallow crustal levels. In general, data analysis has shown that there is a structural control on magma emplacement, with the major magmatic features located in specific locations

  18. Subaqueous early eruptive phase of the late Aptian Rajmahal volcanism, India: Evidence from volcaniclastic rocks, bentonite, black shales, and oolite

    Directory of Open Access Journals (Sweden)

    Naresh C. Ghose


    Full Text Available The late Aptian (118–115 Ma continental flood basalts of the Rajmahal Volcanic Province (RVP are part of the Kerguelen Large Igneous Province, and constitute the uppermost part of the Gondwana Supergroup on the eastern Indian shield margin. The lower one-third of the Rajmahal volcanic succession contains thin layers of plant fossil-rich inter-trappean sedimentary rocks with pyroclasts, bentonite, grey and black shale/mudstone and oolite, whereas the upper two-thirds consist of sub-aerial fine-grained aphyric basalts with no inter-trappean material. At the eastern margin and the north-central sector of the RVP, the volcanics in the lower part include rhyolites and dacites overlain by enstatite-bearing basalts and enstatite-andesites. The pyroclastic rocks are largely felsic in composition, and comprise ignimbrite as well as coarse-grained tuff with lithic clasts, and tuff breccia with bombs, lapilli and ash that indicate explosive eruption of viscous rhyolitic magma. The rhyolites/dacites (>68 wt.% are separated from the andesites (<60 wt.% by a gap in silica content indicating their formation through upper crustal anatexis with only heat supplied by the basaltic magma. On the other hand, partially melted siltstone xenoliths in enstatite-bearing basalts suggest that the enstatite-andesites originated through mixing of the upper crust with basaltic magma, crystallizing orthopyroxene at a pressure-temperature of ∼3 kb/1150 °C. In contrast, the northwestern sector of the RVP is devoid of felsic-intermediate rocks, and the volcaniclastic rocks are predominantly mafic (basaltic in composition. Here, the presence of fine-grained tuffs, tuff breccia containing sideromelane shards and quenched texture, welded tuff breccia, peperite, shale/mudstone and oolite substantiates a subaqueous environment. Based on these observations, we conclude that the early phase of Rajmahal volcanism occurred under predominantly subaqueous conditions. The presence

  19. Active Volcanic Plumes on Io (United States)


    This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon (see inset at upper right), erupting over a caldera (volcanic depression) named Pillan Patera after a South American god of thunder, fire and volcanoes. The plume seen by Galileo is 140 kilometers (86 miles) high and was also detected by the Hubble Space Telescope. The Galileo spacecraft will pass almost directly over Pillan Patera in 1999 at a range of only 600 kilometers (373 miles).The second plume, seen near the terminator (boundary between day and night), is called Prometheus after the Greek fire god (see inset at lower right). The shadow of the 75-kilometer (45- mile) high airborne plume can be seen extending to the right of the eruption vent. The vent is near the center of the bright and dark rings. Plumes on Io have a blue color, so the plume shadow is reddish. The Prometheus plume can be seen in every Galileo image with the appropriate geometry, as well as every such Voyager image acquired in 1979. It is possible that this plume has been continuously active for more than 18 years. In contrast, a plume has never been seen at Pillan Patera prior to the recent Galileo and Hubble Space Telescope images.North is toward the top of the picture. The resolution is about 6 kilometers (3.7 miles) per picture element. This composite uses images taken with the green, violet and near infrared filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The images were obtained on June 28, 1997, at a range of more than 600,000 kilometers (372,000 miles).The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http

  20. Compositional Differences between Felsic Volcanic Rocks from the ...

    African Journals Online (AJOL)


    Plateau unit is in fault contact with the overlying Intoto unit (22.2-22 Ma) (Morton et al. 1979;. Chernet et al. 1998). ... (1986). The alkaline-sub-alkaline boundary is from Irvine and Baragar (1971). .... Volume 1 (1): 4 – 35, 2009. Compositional differences exist between the rift margin and rift center volcanic rocks (Table 1;. Fig.

  1. Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes Geoquímica de tefras de volcanes Cuaternarios de la Península Antártica

    Directory of Open Access Journals (Sweden)

    Stefan Kraus


    Full Text Available In the northern Antarctic Peninsula area, at least 12 Late Plelstocene-Holocene volcanic centers could be potential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoes using major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. The volcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguish between volcanic centers located on the eastern (Larsen Rift and those situated on the western side (Bransfield Rift of the Antarctic Peninsula. In addition, the Sr/Nb ratio (for samples with SiO2 En la parte norte de la Península Antártica existen, por lo menos, 12 centros volcánicos del Pleistoceno Tardío-Holoceno que podrían representar las fuentes de horizontes de tefra reconocidos en la región. Se reportan aquí análisis químicos de 10 de estos volcanes, que incluyen análisis de elementos mayores, trazas, tierras raras y composición isotópica de 95 muestras de tefra u otros productos eruptivos. Los volcanes tienen, en su mayoría, composición basáltica a basáltico-andesítica. Las razones Nb/Y resultan útiles para distinguir entre centros volcánicos ubicados al lado oriental (Larsen Rift de aquellos ubicados al lado occidental (Bransfield Rift de la Península Antártica. Adicionalmente, las razones Sr/Nb (para muestras con SiO2 <63 wt%, Sr/Y, Ba/La, Zr/Hf y Th/Nb sirven para caracterizar los productos generados por cada centro volcánico. Análisis de microsonda en vidrio muestran que las rocas estudiadas tienen bajos contenidos de K2O, y que vidrios de rocas provenientes de volcanes ubicados en el rift de Bransfield son ricos en SiO2, mientras que las de volcanes del rift de Larsen tienden hacía contenidos elevados de álcalis. Se propone un algoritmo para la identificación del volcán de origen de un horizonte de tefra cualquiera, basado en las distintivas

  2. Development of micro-scale joints in volcanic rocks under thermal ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging Solutions)

    mal stress induced joints under varying cooling conditions. 2. Micro-scale joints in the Rajmahal volcanics. To study the micro-scale joints in rock systems, fresh samples of olivine basalt were chosen from the Rajmahal Trap of eastern India. The rocks consist of phenocrysts of olivine, clino-pyroxene. (augite) and plagioclase ...

  3. Gish Bar Patera, Io: Geology and Volcanic Activity, 1996-2001 (United States)

    Perry, Jason; Radebaugh, Jani; Lopes, Rosaly; McEwen, Alfred; Keszthelyi, Laszlo


    Since the two Voyagers passed by Jupiter in 1979, it has been known that volcanic activity is ubiquitous on the surface of Io. With over 400 volcanic centers, Io is even more volcanically active than the earth with massive flood basalt-style eruptions and komatitite lavas a common occurrence. Additionally, some volcanoes appear to be giant lava lakes, with violent activity churning the crust of the lake for periods of 20 years or more. Finally, sulfur is believed to play a large role in Io's volcanism, be it as a primary lava or as a secondary product of large, high-temperature eruptions. By studying one volcano in particular, Gish Bar Patera, one can observe many of these characteristics in one volcanic center.

  4. Chromian spinel-rich black sands from eastern shoreline of ...

    Indian Academy of Sciences (India)

    Black sands rich in chromian spinel commonly occur in pockets along the eastern shoreline of Andaman Island where various types of peridotites and volcanics belonging to the Andaman ophiolite suite are exposed in close vicinity. The chemistry of these detrital chromian spinels has been extensively used here in ...

  5. Late Jurassic–Early Cretaceous intra-arc sedimentation and volcanism linked to plate motion change in northern Japan




    The Sorachi Group, composed of Upper Jurassic ophiolite and Lower Cretaceous island-arc volcano-sedimentary cover, provides a record of Late Jurassic–Early Cretaceous sedimentation and volcanism in an island-arc setting off the eastern margin of the Asian continent. Stratigraphic changes in the nature and volume of the Sorachi Group volcanic and volcaniclastic rocks reveal four tectonic stages. These stages resulted from changes in the subduction direction of the Pacific oceanic plate. Stage ...

  6. Age and petrogenetic constraints on the Lower Glassy Ignimbrite of the Mount Somers Volcanic Group, New Zealand

    DEFF Research Database (Denmark)

    van der Meer, Quinten; Waight, Tod Earle; Whitehouse, Martin


    The Mount Somers Volcanic Group (MSVG) forms a large (~18000 km2) calc-alkaline volcanic complex on New Zealand’s Eastern Province. U-Pb SIMS spot ages on zircon from the lower glassy ignimbrite in Rakaia Gorge reveal a bimodal distribution of 99.0 ± 0.5 and 96.3 ± 0.5 Ma (2σ). These ages...

  7. Volcanology: Volcanic bipolar disorder explained (United States)

    Jellinek, Mark


    Eruptions come in a range of magnitudes. Numerical simulations and laboratory experiments show that rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.

  8. Hygroscopic properties of volcanic ash

    National Research Council Canada - National Science Library

    T. L. Lathem; P. Kumar; A. Nenes; J. Dufek; I. N. Sokolik; M. Trail; A. Russell


      Volcanic ash is hygroscopic Water vapor adsorption is the main proceess controlling ash hygroscopicity The results can be parameterized in a simple correlation for use in models Limited observational...

  9. Monogenetic volcanic hazards and assessment (United States)

    Connor, C.; Connor, L. J.; Richardson, J. A.


    Many of the Earth's major cities are build on the products of monogenetic volcanic eruptions and within geologically active basaltic volcanic fields. These cities include Mexico City (Mexico), Auckland (New Zealand), Melbourne (Australia), and Portland (USA) to name a few. Volcanic hazards in these areas are complex, and involve the potential formation of new volcanic vents and associated hazards, such as lava flows, tephra fallout, and ballistic hazards. Hazard assessment is complicated by the low recurrence rate of volcanism in most volcanic fields. We have developed a two-stage process for probabilistic modeling monogenetic volcanic hazards. The first step is an estimation of the possible locations of future eruptive vents based on kernel density estimation and recurrence rate of volcanism using Monte Carlo simulation and accounting for uncertainties in age determinations. The second step is convolution of this spatial density / recurrence rate model with hazard codes for modeling lava inundation, tephra fallout, and ballistic impacts. A methodology is presented using this two-stage approach to estimate lava flow hazard in several monogenetic volcanic fields, including at a nuclear power plant site near the Shamiram Plateau, a Quaternary volcanic field in Armenia. The location of possible future vents is determined by estimating spatial density from a distribution of 18 mapped vents using a 2-D elliptical Gaussian kernel function. The SAMSE method, a modified asymptotic mean squared error approach, uses the distribution of known eruptive vents to optimally determine a smoothing bandwidth for the Gaussian kernel function. The result is a probability map of vent density. A large random sample (N=10000) of vent locations is drawn from this probability map. For each randomly sampled vent location, a lava flow inundation model is executed. Lava flow input parameters (volume and average thickness) are determined from distributions fit to field observations of the low

  10. Volcanic hazards and aviation safety (United States)

    Casadevall, Thomas J.; Thompson, Theodore B.; Ewert, John W.; ,


    An aeronautical chart was developed to determine the relative proximity of volcanoes or ash clouds to the airports and flight corridors that may be affected by volcanic debris. The map aims to inform and increase awareness about the close spatial relationship between volcanoes and aviation operations. It shows the locations of the active volcanoes together with selected aeronautical navigation aids and great-circle routes. The map mitigates the threat that volcanic hazards pose to aircraft and improves aviation safety.

  11. Los volcanes y los hombres


    García, Carmen


    Desde las entrañas de la tierra, los volcanes han creado la atmósfera, el agua de los océanos, y esculpido los relieves del planeta: son, pues, los zahoríes de la vida. Existen volcanes que los hombres explotan o cultivan, y otros sobre los cuales se han construido observatorios en los que se llevan a cabo avanzadas investigaciones científicas.


    Energy Technology Data Exchange (ETDEWEB)

    Perry, F. V.; Crowe, G. A.; Valentine, G. A.; Bowker, L. M.


    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the

  13. Volcanic and Tectonic Deformation of Unimak Island in the Aleutian Arc (United States)

    Mann, D.; Freymueller, J. T.


    Unimak Island is located in the central part of the Alaska-Aleutian Arc. It hosts several volcanoes and is part of a complex tectonic setting. It is one of the target areas for the proposed Plate Boundary Observatory. We present results from GPS surveys investigating volcanic and tectonic deformation on the island. Westdahl volcano, at the southwest end of the island, last erupted in 1991-1992. GPS surveys conducted between 1998 and 2001 show radial displacement and general uplift of the volcanic edifice, indicating inflation. The inflation source is modeled to be at 9 km depth beneath the summit, producing a subsurface volume change of approximately 0.04 km^{3}/year. This is in agreement with previous results from INSAR studies betwen 1993 and 1998, and shows that Westdahl has been inflating continuously for almost 10 years now. Neighbouring Fisher Caldera has not had recent significant eruptions, but it does have an active hydrothermal system. The GPS data show subsidence of the caldera floor up to 20 mm/year between 1999 and 2001, and horizontal shortening across the center. In the eastern part of Unimak Island, GPS data indicate that there is no strain accumulation across the arc. This is the same scenario as for the western Shumagin section of the arc extending to the northeast. The situation is different at the western end of Unimak. This area is part of the rupture zone of the 1957 M_{W}$9.1 earthquake, and strain accumulation currently causes surface deformation. Elastic dislocation modeling is used to constrain the interseismic coupling. The boundary between the uncoupled segment and the coupled segment is probably close to the western end of the island.

  14. Venus - False Color of Volcanic Plains (United States)


    This Magellan full-resolution mosaic of Venus, centered at 10 degrees north latitude, 301 degrees east longitude, shows an area replete with diverse volcanic features. The image, of an area 489 kilometers long by 311 kilometers wide (303 by 193 miles), is dominated by volcanic plains which appear mottled because of varying roughnesses of each solidified lava flow. The rougher the terrain the brighter it appears in the radar image. The small, bright bumps clustered in the left portion of the image are a grouping of small volcanoes called a shield field. Each shield volcano is approximately 2 to 5 kilometers (1.2 to 3.1 miles) in diameter and has very subdued relief. It is believed that the lava flows that make up each shield originates from a common source. To the right of the shield field is another type of volcano, called a scalloped dome. It is 25 kilometers (16 miles) in diameter and has a central pit. Some of the indistinct lobe-shaped pattern around the dome may either be lava flows or rocky debris which has fallen from the scalloped cliffs surrounding the domes. The small radial ridges characteristic of scalloped domes are remnants of catastrophic landslides. To the right of that feature is a large depression called a volcanic caldera. The caldera was formed when lava was expelled from an underground chamber, which when emptied, subsequently collapsed forming the depression. The feature furthermost to the east (right) is another scalloped dome, 35 kilometers (22 miles) in diameter. That feature is unusual in that lava came out through the southeastern margin, rafting a large portion of the dome for 20 kilometers (12 miles). The lava continues into the lower right portion of the area in the image. Its steep rounded boundaries suggest it was a very sticky, oozing lava. That same type of lava is what scientists propose formed the steep-sided domes such as the bright, round feature, slightly northeast of center. It is highly likely that the features are all part

  15. Volcanism on Mercury: Evidence from the first MESSENGER flyby for extrusive and explosive activity and the volcanic origin of plains (United States)

    Head, James W.; Murchie, Scott L.; Prockter, Louise M.; Solomon, Sean C.; Chapman, Clark R.; Strom, Robert G.; Watters, Thomas R.; Blewett, David T.; Gillis-Davis, Jeffrey J.; Fassett, Caleb I.; Dickson, James L.; Morgan, Gareth A.; Kerber, Laura


    The first MESSENGER flyby of Mercury obtained images of 21% of the surface not seen by Mariner 10, including the center and western half of the Caloris basin and regions near the terminator that show details of the nature of smooth and intercrater plains. These new data have helped to address and resolve a series of longstanding questions on the existence and nature of volcanism on Mercury and the distribution of volcanic materials. Data from the Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft have shown the following: (1) Numerous volcanic vents, in the form of irregularly shaped rimless depressions, are concentrated around the interior edge of the Caloris basin. (2) These vents appear to be sources for effusive volcanism that in one case built a shield in excess of 100 km in diameter and in some cases formed bright haloes around the vents that are interpreted to represent pyroclastic eruptions. (3) Lobate margins of plains units, seen previously in Mariner 10 data, are documented in MESSENGER images with more clarity and are often distinctive in morphology and color properties, supporting the interpretation that these features are the edges of lava flow units. (4) The interior of the Caloris basin is filled with plains units spectrally distinctive from the rim deposits, and comparison with the lunar Imbrium basin and superposed impact crater stratigraphy provide evidence that these units are volcanic in origin; detailed differences in the mineralogy of lava flow units, so prominent in Imbrium, are not seen in the Caloris interior. (5) Some of the smooth plains surrounding the exterior of the Caloris basin show distinct differences in color and morphological properties, supporting a volcanic origin. (6) Some smooth and intercrater plains units distant from the Caloris basin show evidence of flooding and embayment relations unrelated to Caloris ejecta emplacement; local and regional geological and color relationships support a volcanic origin for

  16. The Effect of Folic Acid Consumption (In Prenatal Care on Blood Pressure Change during Pregnancy in Urban and Rural Health Centers in Eastern Azerbaijan

    Directory of Open Access Journals (Sweden)

    Leila Rasoolpoor-Farzin


    Full Text Available Background and Objectives : Preeclampsia is one of the most threatening problems in pregnancy and potentially is followed by preterm birth, miscarriage, low birth weight and maternal mortality. Folic acid supplementation is commonly prescribed for women in child bearing age to reduce the prevalence of neural tube defects. However, its role in pre-eclampsia and hypertension is not proven and is debatable. The aim of this study was to evaluate the influence of folic acid on before pregnancy care on blood pressure in pregnancy. Material and Methods: This retrospective cohort study was conducted as census on all 1939 women referred to receive prenatal care between 2008 and 2013 in rural and urban healthcare centers in Sarab, Bostanabad and Khosroshahr. We compared blood pressure changes in two groups with folic acid consumption and another group, not consuming folic acid. Collected data were filled in the checklist and underwent statistical analysis of descriptive and analytical methods by SPSS 16. Results: The mean age of women in this study was 25.98±5.78 years. Ninety-two percent of mothers had regular consumption of folic acid during pregnancy. The peak period of high blood pressure was reported at weeks 37-35 with 8.2% in systolic blood pressure and diastolic blood pressure at week 37-35 and more than 37 weeks with 1.6%. Systolic and diastolic pressure in mothers taking folic acid was significantly lower (P Conclusion: Folic acid intake during pregnancy, as a part of prenatal care, significantly reduces the incidence of hypertension of pregnancy. During this period, folic acid intake can diminish pre-eclampsia and promote maternal and new born health.

  17. Spatio-temporal evolution of the Tuxtla Volcanic Field (United States)

    Kobs Nawotniak, S. E.; Espindola, J.; Godinez, L.


    Mapping of the Tuxtla Volcanic Field (TVF), located in Veracruz, Mexico, through the use of digital elevation models, aerial photography, and field confirmation has found 353 distinct cones, 4 large composite volcanoes, and 42 maars. Eruptive activity in the TVF began in the late Miocene, underwent a quiescent period approximately 2.6-0.8 Ma, and continues into historic times with the most recent eruption occurring at San Martín Tuxtla volcano in 1793. The covariance of the minimum cone separation in the TVF indicates that, despite the influence of clear vent alignments following regional faulting trends, the field as a whole is anticlustered. Dividing the cones by morphometric age shows that while the older cones have an anti-clustered distribution, the younger cones (Catemaco. These areas of concentrated volcanism roughly correspond to the locations of two gravity anomalies previously identified in the area. While the average height/width ratio is equal between the two clusters, the cones in the eastern group are significantly smaller than their counterparts in the western group. The maars of the TVF are mostly located within the younger volcanic series, west of Laguna Catemaco, and have an anticlustered distribution; many of the maars are evenly spaced along curved lines, where they are weakly grouped according to crater diameter. Results indicate volcanism TVF has undergone continued spatial restriction over time, concentrating in the western half of the TVF with the onset of the eruption of the younger volcanic series 0.8 Ma and further contracting along the principle fault system within the last 50 Ka.

  18. Detection and Classification of Volcanic Earthquakes/Tremors in Central Anatolian Volcanic Province (United States)

    Kahraman, Metin; Arda Özacar, A.; Bülent Tank, S.; Uslular, Göksu; Kuşcu, Gonca; Türkelli, Niyazi


    Central Anatolia has been characterized by active volcanism since 10 Ma which created the so called Central Anatolia Volcanic Province (CAVP) where a series of volcanoes are located along the NE-SW trend. The petrological investigations reveal that the magma source in the CAVP has both subduction and asthenospheric signature possibly due to tearing of ongoing northward subduction of African plate along Aegean and Cyprus arcs. Recently, a temporary seismic array was deployed within the scope of Continental Dynamics: Central Anatolian Tectonics (CD-CAT) project and provided a unique opportunity to study the deep seismic signature of the CAVP. Passive seismic imaging efforts and magnetotellurics (MT) observations revealed low velocity and high conductivity zones supporting the presence of localized partial melt bodies beneath the CAVP at varying depths, especially around Mt. Hasan which exhibits both geological and archeological evidences for its eruption around 7500 B.C. In Central Anatolia, local seismicity detected by the CD-CAT array coincides well with the active faults zones. However, active or potentially active volcanoes within CAVP are characterized by the lack of seismic activity. In this study, seismic data recorded by permanent stations of Regional Earthquake-Tsunami Monitoring Center were combined with temporary seismic data collected by the CD-CAT array to improve sampling density across the CAVP. Later, the continuous seismic waveforms of randomly selected time intervals were manually analyzed to identify initially undetected seismic sources which have signal characters matching to volcanic earthquakes/tremors. For candidate events, frequency spectrums are constructed to classify the sources according to their physical mechanisms. Preliminary results support the presence of both volcano-tectonic (VT) and low-period (LT) events within the CAVP. In the next stage, the spectral and polarization analyses techniques will be utilized to the entire seismic

  19. Correlating geochemistry, tectonics, and volcanic volume along the Central American volcanic front (United States)

    Bolge, Louise L.; Carr, Michael J.; Milidakis, Katherine I.; Lindsay, Fara N.; Feigenson, Mark D.


    The Central American volcanic front consists of several distinct volcanic lineaments or segments, separated by right steps and/or changes in strike. Each volcanic line is rotated slightly counterclockwise from the strike of the inclined seismic zone. Right stepping volcanic lines, oblique to the strike of the slab, create a sawtooth pattern in the depth to the slab. Zr/Nb is the first geochemical signature with consistent large offsets at the right steps in the volcanic front. Moreover, Zr/Nb mirrors the sawtooth variation in depth to the slab; within a segment it increases from SE to NW, and at the right steps, separating segments, it abruptly decreases. Unfortunately, there is no simple negative correlation between Zr/Nb and depth to the slab because Zr/Nb also has a regional variation, similar to previously documented regional variations in slab tracers in Central America (e.g., Ba/La, U/Th, and 87Sr/86Sr). Within a segment, Zr/Nb decreases with increasing depth to slab. This can be explained in two ways: a Nb retaining mineral, e.g., amphibole, in the subducting slab is breaking down gradually with increasing depth causing more Nb to be released and consequently a smaller Nb depletion in deeper melts; alternatively, all melts have the same initial Nb depletion which is then diluted by acquiring Nb from the surrounding mantle wedge as melts rise and react. Deeper melts have longer paths and therefore more reaction with the mantle wedge diluting the initial Nb depletion. Within each volcanic segment there is variation in eruptive volume. The largest volcanoes generally occur in the middle of the segments, and the smaller volcanoes tend to be located at the ends. Connecting the largest volcanoes in each segment suggests an axis of maximum productivity. This is likely the surface projection of the center of the melt aggregation zone. The largest volcanoes tap the entire melt zone. Those with shallow depths to the slab tap just the front part of the melt zone and

  20. Volcanism in slab tear faults is larger than in island-arcs and back-arcs. (United States)

    Cocchi, Luca; Passaro, Salvatore; Tontini, Fabio Caratori; Ventura, Guido


    Subduction-transform edge propagators are lithospheric tears bounding slabs and back-arc basins. The volcanism at these edges is enigmatic because it is lacking comprehensive geological and geophysical data. Here we present bathymetric, potential-field data, and direct observations of the seafloor on the 90 km long Palinuro volcanic chain overlapping the E-W striking tear of the roll-backing Ionian slab in Southern Tyrrhenian Sea. The volcanic chain includes arc-type central volcanoes and fissural, spreading-type centers emplaced along second-order shears. The volume of the volcanic chain is larger than that of the neighbor island-arc edifices and back-arc spreading center. Such large volume of magma is associated to an upwelling of the isotherms due to mantle melts upraising from the rear of the slab along the tear fault. The subduction-transform edge volcanism focuses localized spreading processes and its magnitude is underestimated. This volcanism characterizes the subduction settings associated to volcanic arcs and back-arc spreading centers.

  1. Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA (United States)

    Morgan, L.A.; McIntosh, W.C.


    The Snake River Plain (SRP) developed over the last 16 Ma as a bimodal volcanic province in response to the southwest movement of the North American plate over a fixed melting anomaly. Volcanism along the SRP is dominated by eruptions of explosive high-silica rhyolites and represents some of the largest eruptions known. Basaltic eruptions represent the final stages of volcanism, forming a thin cap above voluminous rhyolitic deposits. Volcanism progressed, generally from west to east, along the plain episodically in successive volcanic fields comprised of nested caldera complexes with major caldera-forming eruptions within a particular field separated by ca. 0.5-1 Ma, similar to, and in continuation with, the present-day Yellowstone Plateau volcanic field. Passage of the North American plate over the melting anomaly at a particular point in time and space was accompanied by uplift, regional tectonism, massive explosive eruptions, and caldera subsidence, and followed by basaltic volcanism and general subsidence. The Heise volcan ic field in the eastern SRP, Idaho, represents an adjacent and slightly older field immediately to the southwest of the Yellowstone Plateau volcanic field. Five large-volume (>0.5 km3) rhyolitic ignimbrites constitute a time-stratigraphic framework of late Miocene to early Pliocene volcanism for the study region. Field relations and high-precision 40Ar/39Ar age determinations establish that four of these regional ignimbrites were erupted from the Heise volcanic field and form the framework of the Heise Group. These are the Blacktail Creek Tuff (6.62 ?? 0.03 Ma), Walcott Tuff (6.27 ?? 0.04 Ma), Conant Creek Tuff (5.51 ?? 0.13 Ma), and Kilgore Tuff (4.45 ?? 0.05 Ma; all errors reported at ?? 2??). The fifth widespread ignimbrite in the regions is the Arbon Valley Tuff Member of the Starlight Formation (10.21 ?? 0.03 Ma), which erupted from a caldera source outside of the Heise volcanic field. These results establish the Conant Creek Tuff as a

  2. The impact of the characteristics of volcanic ash on forecasting. (United States)

    Beckett, Frances; Hort, Matthew; Millington, Sarah; Stevenson, John; Witham, Claire


    The eruption of Eyjafjallajökull during April - May 2010 and Grímsvötn in May 2011, Iceland, caused the widespread dispersion of volcanic ash across the NE Atlantic, and ultimately into UK and European airspace. This resulted in thousands of flights to and from affected countries across Europe to be cancelled. The Met Office, UK, is the home of the London VAAC, a Volcanic Ash Advisory Centre, and as such is responsible for providing reports and forecasts for the movement of volcanic ash clouds covering the UK, Iceland and the north-eastern part of the North Atlantic ocean. To forecast the dispersion of volcanic ash requires that the sedimentation of ash particles through the atmosphere is effectively modelled. The settling velocity of an ash particle is a function of its size, shape and density, plus the density and viscosity of the air through which it is falling. We consider the importance of characterising the physical properties of ash when modelling the long range dispersion of ash particles through the atmosphere. Using the Reynolds number dependent scheme employed by NAME, the Lagrangian particle model used operationally by the Met Office, we calculate the settling velocity and thus the maximum travel distance of an ash particle through an idealised atmosphere as a function of its size, shape and density. The results are compared to measured particle sizes from deposits across Europe following the eruption of Eyjafjallajökull in 2010. Further, the particle size distribution (PSD) of ash in a volcanic cloud with time is modelled using NAME: the particle density distribution and particle shape factor are varied and the modelled PSD compared to the PSD measured in the ash cloud during the eruption of Eyjafjallajökull in 2010 by the FAAM research aircraft. The influence of the weather on PSD is also considered by comparing model output using an idealised atmosphere to output using NWP driven meteorological fields. We discuss the sensitivity of forecasts of

  3. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  4. Quaternary volcanism, tectonics, and sedimentation in the Idaho National Engineering Laboratory area

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R.; Smith, R.P.


    In this article, we discuss the regional context and describe localities for a two-day field excursion in the vicinity of the Idaho National Engineering Laboratory (INEL). We address several geologic themes: (1) Late Cenozoic, bimodal volcanism of the Eastern Snake River Plain (ESRP), (2) the regional tectonics and structural geology of the Basin and Range province to the northwest of the ESRP, (3) fluvial, lacustrine, and aeolian sedimentation in the INEL area, and (4) the influence of Quaternary volcanism and tectonics on sedimentation near the INEL.

  5. Eastern Canada

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, R.G.; Roliff, W.A.; Sealey, R.; Palonen, P.A.


    Uncertainty of increased taxation of petroleum revenues proposed under the Canadian national energy program effected a minor slowdown of the rapid exploration in 1980. Total numbers of wells drilled in eastern Canada were: Ontario, 224; Quebec, 3; Nova Scotia, 1; and the Atlantic offshore, 13. Much of the Ontario drilling, 123 wells, was for development purposes. The success ratio on exploratory drilling in Ontario was 34.7, while all Quebec and Nova Scotia wells were dry. Production of oil and gas declined by 16.8% and 18.5% in New Brunswick. Oil production in Ontario increased by 1.2%. The increase in gas production of 14.3% to almost 443,535.5 x 10/sup 3/m/sup 3/ was due almost entirely to development of known fields underlying Lake Erie. The exploration of offshore eastern Canada continued at a stable rate, with 12 wells completed. Of these, 2 were in the Gulf of St. Lawrence, 3 on the Grand Banks, 6 on the Labrador Shelf, and 1 in Davis Strait. All wells were abandoned or suspended at year end, although discoveries of hydrocarbon were made in Davis Strait and the Grand Banks. The early exploration stage, combined with record water depths, prevented any of these wells from being put into production, although testing will be continued on the most promising shows. Seismic exploration increased to approximately 30,000 km in the Atlantic offshore areas. In addition, 1,420.94 km was shot in Lake Erie. Onshore seismic exploration accounted for 1,078.67 km in Ontario, 350 km in Nova Scotia and 242.76 km in Quebec. 3 figures, 8 tables.

  6. High-resolution aeromagnetic mapping of volcanic terrain, Yellowstone National Park (United States)

    Finn, Carol A.; Morgan, Lisa A.


    High-resolution aeromagnetic data acquired over Yellowstone National Park (YNP) show contrasting patterns reflecting differences in rock composition, types and degree of alteration, and crustal structures that mirror the variable geology of the Yellowstone Plateau. The older, Eocene, Absaroka Volcanic Supergroup, a series of mostly altered, andesitic volcanic and volcaniclastic rocks partially exposed in mountains on the eastern margin of YNP, produces high-amplitude, positive magnetic anomalies, strongly contrasting with the less magnetic, younger, latest Cenozoic, Yellowstone Plateau Group, primarily a series of fresh and variably altered rhyolitic rocks covering most of YNP. The Yellowstone caldera is the centerpiece of the Yellowstone Plateau; part of its boundary can be identified on the aeromagnetic map as a series of discontinuous, negative magnetic anomalies that reflect faults or zones along which extensive hydrothermal alteration is localized. The large-volume rhyolitic ignimbrite deposits of the 0.63-Ma Lava Creek Tuff and the 2.1-Ma Huckleberry Ridge Tuff, which are prominent lithologies peripheral to the Yellowstone caldera, produce insignificant magnetic signatures. A zone of moderate amplitude positive anomalies coincides with the mapped extent of several post-caldera rhyolitic lavas. Linear magnetic anomalies reflect the rectilinear fault systems characteristic of resurgent domes in the center of the caldera. Peripheral to the caldera, the high-resolution aeromagnetic map clearly delineates flow unit boundaries of pre- and post-caldera basalt flows, which occur stratigraphically below the post-caldera rhyolitic lavas and are not exposed extensively at the surface. All of the hot spring and geyser basins, such as Norris, Upper and Lower Geyser Basins, West Thumb, and Gibbon, are associated with negative magnetic anomalies, reflecting hydrothermal alteration that has destroyed the magnetic susceptibility of minerals in the volcanic rocks. Within

  7. Geology, geochronology, and paleogeography of the southern Sonoma volcanic field and adjacent areas, northern San Francisco Bay region, California (United States)

    Wagner, David L.; Saucedo, George J.; Clahan, Kevin B.; Fleck, Robert J.; Langenheim, Victoria E.; McLaughlin, Robert J.; Sarna-Wojcicki, Andrei M.; Allen, James R.; Deino, Alan L.


    Recent geologic mapping in the northern San Francisco Bay region (California, USA) supported by radiometric dating and tephrochronologic correlations, provides insights into the framework geology, stratigraphy, tectonic evolution, and geologic history of this part of the San Andreas transform plate boundary. There are 25 new and existing radiometric dates that define three temporally distinct volcanic packages along the north margin of San Pablo Bay, i.e., the Burdell Mountain Volcanics (11.1 Ma), the Tolay Volcanics (ca. 10–8 Ma), and the Sonoma Volcanics (ca. 8–2.5 Ma). The Burdell Mountain and the Tolay Volcanics are allochthonous, having been displaced from the Quien Sabe Volcanics and the Berkeley Hills Volcanics, respectively. Two samples from a core of the Tolay Volcanics taken from the Murphy #1 well in the Petaluma oilfield yielded ages of 8.99 ± 0.06 and 9.13 ± 0.06 Ma, demonstrating that volcanic rocks exposed along Tolay Creek near Sears Point previously thought to be a separate unit, the Donnell Ranch volcanics, are part of the Tolay Volcanics. Other new dates reported herein show that volcanic rocks in the Meacham Hill area and extending southwest to the Burdell Mountain fault are also part of the Tolay Volcanics. In the Sonoma volcanic field, strongly bimodal volcanic sequences are intercalated with sediments. In the Mayacmas Mountains a belt of eruptive centers youngs to the north. The youngest of these volcanic centers at Sugarloaf Ridge, which lithologically, chemically, and temporally matches the Napa Valley eruptive center, was apparently displaced 30 km to the northwest by movement along the Carneros and West Napa faults. The older parts of the Sonoma Volcanics have been displaced at least 28 km along the Rodgers Creek fault since ca. 7 Ma. The Petaluma Formation also youngs to the north along the Rodgers Creek–Hayward fault and the Bennett Valley fault. The Petaluma basin formed as part of the Contra Costa basin in the Late Miocene and

  8. Sismos y volcanes en Colombia


    Duque Escobar, Gonzalo


    Notas sobre las zonas de amenaza sísmica y principales fuentes sísmicas de Colombia, y los segmentos volcánicos de los Andes colombianos con los principales volcanes activos, de conformidad con los estudios del Ingeominas. Anexos a títulos con sus correspondientes enlaces, para ofrecer artículos relacionados con sismos y volcanes, en los que se consideran aspectos de interés para la gestión del riesgo sísmico y volcánico en Colombia

  9. Morphological Analysis of Apo Volcanic Complex in Southern Mindanao, Philippines: implications on volcano-tectonic evolution of different volcanic units (United States)

    Herrero, T. M. L.; van Wyk de Vries, B.; Lagmay, A. M. A.; Eco, R. C.


    The Apo Volcanic Complex (AVC) is one of the largest volcanic centers in the Philippines, located in the southern island of Mindanao. It is composed of four edifices and several smaller cones. The youngest volcanic unit, the Apo Dome, is the highest elevation in the Philippines. This unit is classified as potentially active, whereas other units, Talomo, Sibulan and Kitubod, are inactive. The study gives insight to the construction and deformation history of the volcanic units and imparts foresight to subsequent events that can affect populated areas. A morphological analysis integrating high-resolution digital terrain models and public domain satellite data and images was done to recognize and discriminate volcanic units and characterize volcano-tectonic features and processes. Morphological domains were defined based on surface textures, slope variation, degrees and controls of erosion, and lineament density and direction. This establishes the relative ages and extent of volcanic units as well as the volcano-tectonic evolution of the complex. Six edifice building events were recognized, two of which form the elevated base of Apo dome. The geodynamic setting of the region is imprinted in the volcanic units as five morphostructural lineaments. They reveal the changes in maximum regional stress through time such as the N-S extension found across the whole volcanic complex displaying the current stress regime. This has implications on the locality and propagation of geothermal activity, magma ascent, and edifice collapses. One main result of the compounded effects of inherited structures and current stress regime is the Sandawa Collapse Zone. This is a large valley formed by several collapses where NE-SW fractures propagate and the increasing lateral spreading by debuttressing continue to eat away the highest peak. The AVC is surrounded by the major metropolitan area of Davao City to the east and the cities of Kidapawan and Digos to the west and south, respectively

  10. Magnetotelluric Investigation of the South Aegean Volcanic Arc, Greece (United States)

    Kalisperi, Despina; Romano, Gerardo; Smirnov, Maxim; Kouli, Maria; Perrone, Angela; Makris, John P.; Vallianatos, Filippos


    The South Aegean Volcanic Arc (SAVA) is a chain of volcanic islands in the South Aegean resulting from the subduction of the African tectonic plate beneath the Eurasian plate. It extends from Methana, northwest, to the Island of Nisyros southeast (450 km total length). SAVA comprises a series of dormant and historically active volcanoes, with the most prominent to be Aegina, Methana, Milos, Santorini, Kolumbo, Kos and Nisyros. The aim of the ongoing research project "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)" is to contribute to the investigation of the geoelectric structure of Southern Aegean, and particularly to attempt to image the Hellenic Subduction Zone. In this context, onshore magnetotelluric (MT) measurements were recently carried out on the central and eastern part of SAVA (Milos, Santorini, Nisyros and Kos Islands). Data were collected using two MT systems running simultaneously plus a remote reference station installed in Omalos plateau (Western Crete). Robust MT data analysis of the broad-band MT soundings and the resulting model of the conductivity structure of the South Aegean Volcanic Arc is presented. The research is co-funded by the European Social Fund (ESF) and National Resources under the Operational Programme 'Education and Lifelong Learning (EdLL) within the context of the Action 'Supporting Postdoctoral Researchers' in the framework of the project title "MagnetoTellurics in studying Geodynamics of the hEllenic ARc (MT-GEAR)".

  11. Cryogenic Origin for Mars Analog Carbonates in the Bockfjord Volcanic Complex Svalbard (Norway) (United States)

    Amundsen, H. E. F.; Benning, L.; Blake, D. F.; Fogel, M.; Ming, D.; Skidmore, M.; Steele, A.


    The Sverrefjell and Sigurdfjell eruptive centers in the Bockfjord Volcanic Complex (BVC) on Svalbard (Norway) formed by subglacial eruptions ca. 1 Ma ago. These eruptive centers carry ubiquitous magnesian carbonate deposits including dolomitemagnesite globules similar to those in the Martian meteorite ALH84001. Carbonates in mantle xenoliths are dominated by ALH84001 type carbonate globules that formed during quenching of CO2-rich mantle fluids. Lava hosted carbonates include ALH84001 type carbonate globules occurring throughout lava vesicles and microfractures and massive carbonate deposits associated with vertical volcanic vents. Massive carbonates include < or equal 5 cm thick magnesite deposits protruding downwards into clear blue ice within volcanic vents and carbonate cemented lava breccias associated with volcanic vents. Carbonate cements comprise layered deposits of calcite, dolomite, huntite, magnesite and aragonite associated with ALH84001 type carbonate globules lining lava vesicles. Combined Mossbauer, XRD and VNIR data show that breccia carbonate cements at Sverrefjell are analog to Comanche carbonates at Gusev crater.

  12. A 12,000 year record of explosive volcanism in the Siple Dome Ice Core, West Antarctica (United States)

    Kurbatov, A. V.; Zielinski, G. A.; Dunbar, N. W.; Mayewski, P. A.; Meyerson, E. A.; Sneed, S. B.; Taylor, K. C.


    Air mass trajectories in the Southern Hemisphere provide a mechanism for transport to and deposition of volcanic products on the Antarctic ice sheet from local volcanoes and from tropical and subtropical volcanic centers. This study extends the detailed record of Antarctic, South American, and equatorial volcanism over the last 12,000 years using continuous glaciochemical series developed from the Siple Dome A (SDMA) ice core, West Antarctica. The largest volcanic sulfate spike (280 μg/L) occurs at 5881 B.C.E. Other large signals with unknown sources are observed around 325 B.C.E. (270 μg/L) and 2818 B.C.E. (191 μg/L). Ages of several large equatorial or Southern Hemisphere volcanic eruptions are synchronous with many sulfate peaks detected in the SDMA volcanic ice chemistry record. The microprobe "fingerprinting" of glass shards in the SDMA core points to the following Antarctic volcanic centers as sources of tephra found in the SDMA core: Balenny Island, Pleiades, Mount Berlin, Mount Takahe, and Mount Melbourne as well as Mount Hudson and possibly Mount Burney volcanoes of South America. Identified volcanic sources provide an insight into the poorly resolved transport history of volcanic products from source volcanoes to the West Antarctic ice sheet.

  13. The alkaline volcanic rocks of Craters of the Moon National Monument, Idaho and the Columbia Hills of Gusev Crater, Mars (United States)

    Neakrase, L. D.; Lim, D. S. S.; Haberle, C. W.; Hughes, S. S.; Kobs-Nawotniak, S. E.; Christensen, P. R.


    Idaho's Eastern Snake River Plain (ESRP) is host to extensive expressions of basaltic volcanism dominated by non evolved olivine tholeiites (NEOT) with localized occurrences of evolved lavas. Craters of the Moon National Monument (COTM) is a polygenetic lava field comprised of more than 60 lava flows emplaced during 8 eruptive periods spanning the last 15 kyrs. The most recent eruptive period (period A; 2500-2000 yr B.P.) produced flows with total alkali vs. silica classifications spanning basalt to trachyte. Coeval with the emplacement of the COTM period A volcanic pile was the emplacement of the Wapi and King's Bowl NEOT 70 km SSE of COTM along the Great Rift. Previous investigations have determined a genetic link between these two compositionally distinct volcanic centers where COTM compositions can be generated from NEOT melts through complex ascent paths and variable degrees of fractionation and assimilation of lower-middle crustal materials. The Mars Exploration Rover, Spirit, conducted a robotic investigation of Gusev crater from 2004-2010. Spirit was equipped with the Athena science payload enabling the determination of mineralogy (mini-Thermal Emission Spectrometer, Pancam multispectral camera, and Mössbauer spectrometer), bulk chemistry (Alpha Particle X-ray Spectrometer) and context (Pancam and Microscopic Imager). During sol 32 Spirit investigated an olivine basalt named Adirondack, the type specimen for a class of rock that composes much of the plains material within Gusev Crater and embays the Columbia Hills. Following the characterization of the plains material, Spirit departed the plains targeting the Columbia Hills and ascending at Husband Hill. During Spirit's ascent of Husband Hill three additional classes of volcanic rock were identified as distinct by their mini-TES spectra; Wishstone, Backstay and Irvine. These rocks are classified as tephrite, trachy-basalt and basalt, respectively, and are the first alkaline rocks observed on Mars. These

  14. 2014 volcanic activity in Alaska: Summary of events and response of the Alaska Volcano Observatory (United States)

    Cameron, Cheryl E.; Dixon, James P.; Neal, Christina A.; Waythomas, Christopher F.; Schaefer, Janet R.; McGimsey, Robert G.


    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2014. The most notable volcanic activity consisted of intermittent ash eruptions from long-active Cleveland and Shishaldin Volcanoes in the Aleutian Islands, and two eruptive episodes at Pavlof Volcano on the Alaska Peninsula. Semisopochnoi and Akutan volcanoes had seismic swarms, both likely the result of magmatic intrusion. The AVO also installed seismometers and infrasound instruments at Mount Cleveland during 2014.

  15. 2015 Volcanic activity in Alaska—Summary of events and response of the Alaska Volcano Observatory (United States)

    Dixon, James P.; Cameron, Cheryl E.; Iezzi, Alexandra M.; Wallace, Kristi


    The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 14 volcanic centers in Alaska during 2015. The most notable volcanic activity consisted of continuing intermittent ash eruptions from Cleveland and Shishaldin volcanoes in the Aleutian Islands. Two eruptive episodes, at Veniaminof and Pavlof, on the Alaska Peninsula ended in 2015. During 2015, AVO re-established the seismograph network at Aniakchak, installed six new broadband seismometers throughout the Aleutian Islands, and added a Multiple component Gas Analyzer System (MultiGAS) station on Augustine.

  16. Assessing the Altitude and Dispersion of Volcanic Plumes Using MISR Multi-angle Imaging from Space: Sixteen Years of Volcanic Activity in the Kamchatka Peninsula, Russia (United States)

    Flower, Verity J. B.; Kahn, Ralph A.


    Volcanic eruptions represent a significant source of atmospheric aerosols and can display local, regional and global effects, impacting earth systems and human populations. In order to assess the relative impacts of these events, accurate plume injection altitude measurements are needed. In this work, volcanic plumes generated from seven Kamchatka Peninsula volcanoes (Shiveluch, Kliuchevskoi, Bezymianny, Tolbachik, Kizimen, Karymsky and Zhupanovsky), were identified using over 16 years of Multi-angle Imaging SpectroRadimeter (MISR) measurements. Eighty-eight volcanic plumes were observed by MISR, capturing 3-25% of reported events at individual volcanoes. Retrievals were most successful where high intensity events persisted over a period of weeks to months. Compared with existing ground and airborne observations, and alternative satellite-based reports compiled by the Global Volcanism Program (GVP), MISR plume height retrievals showed general consistency; the comparison reports appear to be skewed towards the region of highest concentration observed in MISR-constrained vertical plume extent. The report observations display less discrepancy with MISR toward the end of the analysis period, with improvements in the suborbital data likely the result of the deployment of new instrumentation. Conversely, the general consistency of MISR plume heights with conventionally reported observations supports the use of MISR in the ongoing assessment of volcanic activity globally, especially where other types of volcanic plume observations are unavailable. Differences between the northern (Shiveluch, Kliuchevskoi, Bezymianny and Tolbachik) and southern (Kizimen, Karymsky and Zhupanovsky) volcanoes broadly correspond to the Central Kamchatka Depression (CKD) and Eastern Volcanic Front (EVF), respectively, geological sub-regions of Kamchatka distinguished by varying magma composition. For example, by comparison with reanalysis-model simulations of local meteorological conditions

  17. Field-trip guides to selected volcanoes and volcanic landscapes of the western United States (United States)



    The North American Cordillera is home to a greater diversity of volcanic provinces than any comparably sized region in the world. The interplay between changing plate-margin interactions, tectonic complexity, intra-crustal magma differentiation, and mantle melting have resulted in a wealth of volcanic landscapes.  Field trips in this guide book collection (published as USGS Scientific Investigations Report 2017–5022) visit many of these landscapes, including (1) active subduction-related arc volcanoes in the Cascade Range; (2) flood basalts of the Columbia Plateau; (3) bimodal volcanism of the Snake River Plain-Yellowstone volcanic system; (4) some of the world’s largest known ignimbrites from southern Utah, central Colorado, and northern Nevada; (5) extension-related volcanism in the Rio Grande Rift and Basin and Range Province; and (6) the eastern Sierra Nevada featuring Long Valley Caldera and the iconic Bishop Tuff.  Some of the field trips focus on volcanic eruptive and emplacement processes, calling attention to the fact that the western United States provides opportunities to examine a wide range of volcanological phenomena at many scales.The 2017 Scientific Assembly of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) in Portland, Oregon, was the impetus to update field guides for many of the volcanoes in the Cascades Arc, as well as publish new guides for numerous volcanic provinces and features of the North American Cordillera. This collection of guidebooks summarizes decades of advances in understanding of magmatic and tectonic processes of volcanic western North America. These field guides are intended for future generations of scientists and the general public as introductions to these fascinating areas; the hope is that the general public will be enticed toward further exploration and that scientists will pursue further field-based research.

  18. Potential volcanic impacts on future climate variability (United States)

    Bethke, Ingo; Outten, Stephen; Otterå, Odd Helge; Hawkins, Ed; Wagner, Sebastian; Sigl, Michael; Thorne, Peter


    Volcanic activity plays a strong role in modulating climate variability. Most model projections of the twenty-first century, however, under-sample future volcanic effects by not representing the range of plausible eruption scenarios. Here, we explore how sixty possible volcanic futures, consistent with ice-core records, impact climate variability projections of the Norwegian Earth System Model (NorESM) under RCP4.5 (ref. ). The inclusion of volcanic forcing enhances climate variability on annual-to-decadal timescales. Although decades with negative global temperature trends become ~50% more commonplace with volcanic activity, these are unlikely to be able to mitigate long-term anthropogenic warming. Volcanic activity also impacts probabilistic projections of global radiation, sea level, ocean circulation, and sea-ice variability, the local-scale effects of which are detectable when quantifying the time of emergence. These results highlight the importance and feasibility of representing volcanic uncertainty in future climate assessments.

  19. Source mechanisms of volcanic tsunamis. (United States)

    Paris, Raphaël


    Volcanic tsunamis are generated by a variety of mechanisms, including volcano-tectonic earthquakes, slope instabilities, pyroclastic flows, underwater explosions, shock waves and caldera collapse. In this review, we focus on the lessons that can be learnt from past events and address the influence of parameters such as volume flux of mass flows, explosion energy or duration of caldera collapse on tsunami generation. The diversity of waves in terms of amplitude, period, form, dispersion, etc. poses difficulties for integration and harmonization of sources to be used for numerical models and probabilistic tsunami hazard maps. In many cases, monitoring and warning of volcanic tsunamis remain challenging (further technical and scientific developments being necessary) and must be coupled with policies of population preparedness. © 2015 The Author(s).

  20. Evaluation of quantitative satellite-based retrievals of volcanic ash clouds (United States)

    Schneider, D. J.; Pavolonis, M. J.; Bojinski, S.; Siddans, R.; Thomas, G.


    Volcanic ash clouds are a serious hazard to aviation, and mitigation requires a robust system of volcano monitoring, eruption detection, characterization of cloud properties, forecast of cloud movement, and communication of warnings. Several research groups have developed quantitative satellite-based volcanic ash products and some of these are in operational use by Volcanic Ash Advisory Centers around the world to aid in characterizing cloud properties and forecasting regions of ash hazard. The algorithms applied to the satellite data utilize a variety of techniques, and thus produce results that differ. The World Meteorological Organization has recently sponsored an intercomparison study of satellite-based retrievals with four goals: 1) to establish a validation protocol for satellite-based volcanic ash products, 2) to quantify and understand differences in products, 3) to develop best practices, and 4) to standardize volcanic cloud geophysical parameters. Six volcanic eruption cases were considered in the intercomparison: Eyjafallajökull, Grimsvötn, Kelut, Kirishimayama, Puyehue-Cordón Caulle, and Sarychev Peak. Twenty-four algorithms were utilized, which retrieved parameters including: ash cloud top height, ash column mass loading, ash effective radius, and ash optical depth at visible and thermal-infrared wavelengths. Results were compared to space-based, airborne, and ground-based lidars; complementary satellite retrievals; and manual "expert evaluation" of ash extent. The intercomparison results will feed into the International Civil Aviation Organization "Roadmap for International Airways Volcano Watch", which integrates volcanic meteorological information into decision support systems for aircraft operations.

  1. 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.


    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.

  2. Detecting Volcanic Ash Plumes with GNSS Signals (United States)

    Rainville, N.; Larson, K. M.; Palo, S. E.; Mattia, M.; Rossi, M.; Coltelli, M.; Roesler, C.; Fee, D.


    Global Navigation Satellite Systems (GNSS) receivers are commonly placed near volcanic sites to measure ground deformation. In addition to the carrier phase data used to measure ground position, these receivers also record Signal to Noise ratio (SNR) data. Larson (2013) showed that attenuations in SNR data strongly correlate with ash emissions at a series of eruptions of Redoubt Volcano. This finding has been confirmed at eruptions for Tongariro, Mt Etna, Mt Shindake, and Sakurajima. In each of these detections, very expensive geodetic quality GNSS receivers were used. If low-cost GNSS instruments could be used instead, a networked array could be deployed and optimized for plume detection and tomography. The outputs of this sensor array could then be used by both local volcanic observatories and Volcano Ash Advisory Centers. Here we will describe progress in developing such an array. The sensors we are working with are intended for navigation use, and thus lack the supporting power and communications equipment necessary for a networked system. Reliably providing those features is major challenge for the overall sensor design. We have built prototypes of our Volcano Ash Plume Receiver (VAPR), with solar panels, lithium-ion batteries and onboard data storage for preliminary testing. We will present results of our field tests of both receivers and antennas. A second critical need for our array is a reliable detection algorithm. We have tested our algorithm on data from recent eruptions and have incorporated the noise characteristics of the low-cost GNSS receiver. We have also developed a simulation capability so that the receivers can be deployed to optimize vent crossing GNSS signals.

  3. Scientific Drilling in a Central Italian Volcanic District

    Directory of Open Access Journals (Sweden)

    Paola Montone


    Full Text Available The Colli Albani Volcanic District, located 15 km SE of Rome (Fig. 1, is part of the Roman Magmatic Province, a belt of potassic to ultra-potassic volcanic districts that developed along the Tyrrhenian Sea margin since Middle Pleistocene time (Conticelli and Peccerillo, 1992; Marra et al., 2004; Giordano et al., 2006 and references therein. Eruption centers are aligned along NW-SE oriented majorextensional structures guiding the dislocation of Meso-Cenozoic siliceous-carbonate sedimentary successions at the rear of the Apennine belt. Volcanic districts developed in structural sectors with most favorable conditions for magma uprise. In particular, the Colli Albani volcanism is located in a N-S shear zone where it intersects the extensional NW- and NE-trending fault systems. In the last decade, geochronological measurements allowed for reconstructions of the eruptive history and led to the classification as "dormant" volcano. The volcanic history may be roughly subdivided into three main phases marked by different eruptive mechanisms andmagma volumes. The early Tuscolano-Artemisio Phase (ca. 561–351 ky, the most explosive and voluminous one, is characterized by five large pyroclastic flow-forming eruptions. After a ~40-ky-long dormancy, a lesser energetic phase of activity took place (Faete Phase; ca. 308–250 ky, which started with peripheral effusive eruptions coupled with subordinate hydromagmatic activity. A new ~50-ky-long dormancypreceded the start of the late hydromagmatic phase (ca. 200–36 ky, which was dominated by pyroclastic-surge eruptions, with formation of several monogenetic or multiple maars and/or tuff rings.

  4. Volcanism and associated hazards: The Andean perspective (United States)

    Tilling, R.I.


    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (volcano risk in the Andean region. But much remains to be done.

  5. Disruptive event analysis: volcanism and igneous intrusion

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M.


    An evaluation is made of the disruptive effects of volcanic activity with respect to long term isolation of radioactive waste through deep geologic storage. Three major questions are considered. First, what is the range of disruption effects of a radioactive waste repository by volcanic activity. Second, is it possible, by selective siting of a repository, to reduce the risk of disruption by future volcanic activity. And third, can the probability of repository disruption by volcanic activity be quantified. The main variables involved in the evaluation of the consequences of repository disruption by volcanic activity are the geometry of the magma-repository intersection (partly controlled by depth of burial) and the nature of volcanism. Potential radionuclide dispersal by volcanic transport within the biosphere ranges in distance from several kilometers to global. Risk from the most catastrophic types of eruptions can be reduced by careful site selection to maximize lag time prior to the onset of activity. Certain areas or volcanic provinces within the western United States have been sites of significant volcanism and should be avoided as potential sites for a radioactive waste repository. Examples of projection of future sites of active volcanism are discussed for three areas of the western United States. Probability calculations require two types of data: a numerical rate or frequency of volcanic activity and a numerical evaluation of the areal extent of volcanic disruption for a designated region. The former is clearly beyond the current state of art in volcanology. The latter can be approximated with a reasonable degree of satisfaction. In this report, simplified probability calculations are attempted for areas of past volcanic activity.

  6. Mechanical interaction between volcanic systems in Libya (United States)

    Elshaafi, Abdelsalam; Gudmundsson, Agust


    The spatial distributions of monogenetic volcanoes, primarily volcanic craters, within the four principal volcanic provinces of Libya are examined and presented on a volcano-density map. Six main volcanic clusters have been identified, referred to as volcanic systems. Remarkably, the Al Haruj (AHVP) and Nuqay (NVP) volcanic provinces have double-peak volcano-density distributions, while the Gharyan (GVP) and As Sawda (SVP) volcanic provinces have single-peak volcano-density distributions. We interpret each volcano-density peak as corresponding to a separate volcanic system, so that there is a total of six systems in these four provinces. There was an overlap in volcanic activity in these provinces with at least three simultaneously active. We propose that each of the 6 volcanic systems was/is supplied with magma from a large sill-like reservoir - similar in lateral dimensions to the systems/clusters themselves. Numerical results show zones of high tensile and shear stresses between the reservoirs that coincide roughly with the main swarms of extension (dykes and volcanic fissures) and shear (faults) fractures in the areas. The most recent volcanic eruptions in Libya fall within the modelled high-stress concentration zones, primarily eruptions in the volcano Waw an Namus and the Holocene Al Mashaqaq lava flow. There are no known eruptions in Libya in historical time, but some or all the volcanic systems may have had one or more arrested historical dyke injections. In particular, part of the recurrent seismic events in the Hun Graben in the northwest Libya may be related to dyke propagation and arrest. If some of the inferred magma reservoirs are still fluid, as is likely, they pose earthquake and volcanic hazards to parts of Libya, particularly to the city of Gharyan and Zallah town, as well as to many oil-field operations.

  7. Assessing the altitude and dispersion of volcanic plumes using MISR multi-angle imaging from space: Sixteen years of volcanic activity in the Kamchatka Peninsula, Russia (United States)

    Flower, Verity J. B.; Kahn, Ralph A.


    Volcanic eruptions represent a significant source of atmospheric aerosols and can display local, regional and global effects, impacting earth systems and human populations. In order to assess the relative impacts of these events, accurate plume injection altitude measurements are needed. In this work, volcanic plumes generated from seven Kamchatka Peninsula volcanoes (Shiveluch, Kliuchevskoi, Bezymianny, Tolbachik, Kizimen, Karymsky and Zhupanovsky), were identified using over 16 years of Multi-angle Imaging SpectroRadiometer (MISR) measurements. Eighty-eight volcanic plumes were observed by MISR, capturing 3-25% of reported events at individual volcanoes. Retrievals were most successful where eruptive events persisted over a period of weeks to months. Compared with existing ground and airborne observations, and alternative satellite-based reports compiled by the Global Volcanism Program (GVP), MISR plume height retrievals show general consistency; the comparison reports appear to be skewed towards the region of highest concentration observed in MISR-constrained plume vertical extent. The report observations display less discrepancy with MISR toward the end of the analysis period (2013-2016), with improvements in the suborbital data likely the result of the deployment of new instrumentation. Conversely, the general consistency of MISR plume heights with conventionally reported observations supports the use of MISR in the ongoing assessment of volcanic activity globally, especially where ground-based observations are unavailable. Differences between the northern (Shiveluch, Kliuchevskoi, Bezymianny and Tolbachik) and southern (Kizimen, Karymsky and Zhupanovsky) volcanoes broadly corresponding to the Central Kamchatka Depression (CKD) and Eastern Volcanic Front (EVF) geological sub-regions of Kamchatka, respectively, are distinguished by varying magma composition. For example, by comparison with reanalysis-model simulations of local meteorological conditions, CKD

  8. Video Games in Volcanic Hazard Communications: Methods & Issues (United States)

    Mani, Lara; Cole, Paul; Stewart, Iain


    Educational outreach plays a vital role in improving the resilience of vulnerable populations at risk from natural disasters. Currently, that activity is undertaken in many guises including the distribution of leaflets and posters, maps, presentations, education sessions and through radio and TV broadcasts. Such tried-and-tested communication modes generally target traditional stakeholder groups, but it is becoming increasingly important to engage with the new generation of learners who, due to advancements in technology, obtain information in ways different to their predecessors. That new generation is defined by a technological way of life and it remains a challenge to keep them motivated. On the eastern Caribbean island of St. Vincent, the La Soufriere Volcano lies in quiescence since the last eruption in 1979. Since then, an entire generation - over 56% of the population (Worldbank, 2015) - has little or no direct experience of a volcanic eruption. The island experiences, more frequently, other hazards (hurricanes, flooding, earthquakes landsliding), such that disaster preparedness measures give less priority to volcanic threats, which are deemed to pose less of a risk. With no accurate predictions to warn of the next eruption, it is especially important to educate residents about the potential of future volcanic hazards on the island, and to motivate them to prepare to mitigate their risk. This research critically examines the application of video games in supporting and enhancing existing public education and outreach programmes for volcanic hazards. St. Vincent's Volcano is a computer game designed to improve awareness and knowledge of the eruptive phenomena from La Soufriere that could pose a threat to residents. Within an interactive and immersive environment, players become acquainted with a 3D model of St. Vincent together with an overlay of the established volcanic hazard map (Robertson, 2005). Players are able to view visualisations of two historical

  9. Petrogenesis and tectonic setting of the Roman Volcanic Province, Italy (United States)

    Beccaluva, L.; Di Girolamo, P.; Serri, G.


    The volcanism in the Roman Province of Italy can be modelled by the partial melting of heterogeneously enriched mantle sources. The heterogeneity was created by materials derived from a subducted slab which can still be traced geophysically beneath the central Apennines. New petrographical and chemical data are presented for the high-K calc-alkaline and the shoshonitic volcanics of the Campania region. Primary magmas are present only locally. The existence of spatial zonation in the volcanism of Campania is documented for the first time. The shoshonitic, leucite-basanitic and leucititic volcanics of the Phlegraean Fields-Procida-Ischia and the Somma-Vesuvius areas are, at similar degrees of evolution, about two times richer in Nb and Ba than those of northwestern Campania and the Latium part of the Roman Province. Accordingly, distinct north-western and south-eastern subprovinces can be defined. The evaluation of enrichment factors, that is the abundance ratio between the average contents of each element in the relatively primitive lavas of the low K- and the high K suites, shows that the mantle sources prior to K-metasomatism were different in the two sub-provinces of the Roman Province. In the north-western one, they resembled the sources of ocean-island tholeiites and moderately enriched MOR-basalts. In the south-east they were similar to those of ocean island alkaline lavas and enriched MORB's. Modelling based on K, P, Ce, Sr, Rb, Ba, Th, Sm, Eu, Gd, Y, Nb and {87 Sr}/{86 Sr} was carried out. It indicates that the range of mantle sources of the volcanics in northwestern Campania and Latium can be modelled by the addition of 3 to 20% of materials derived by partial melting of carbonaceous pelites to a Sr-enriched mantle wedge comparable to the Honolulu mantle source least enriched in Nb. The production of Sr-enriched mantle wedge requires either the action of fluids produced by dehydration of subducted oceanic crust, or a small amount of metasomatism caused by

  10. Assessing Mesoscale Volcanic Aviation Hazards using ASTER (United States)

    Pieri, D.; Gubbels, T.; Hufford, G.; Olsson, P.; Realmuto, V.


    The Advanced Spaceborne Thermal Emission and Reflection (ASTER) imager onboard the NASA Terra Spacecraft is a joint project of the Japanese Ministry for Economy, Trade, and Industry (METI) and NASA. ASTER has acquired over one million multi-spectral 60km by 60 km images of the earth over the last six years. It consists of three sub-instruments: (a) a four channel VNIR (0.52-0.86um) imager with a spatial resolution of 15m/pixel, including three nadir-viewing bands (1N, 2N, 3N) and one repeated rear-viewing band (3B) for stereo-photogrammetric terrain reconstruction (8-12m vertical resolution); (b) a SWIR (1.6-2.43um) imager with six bands at 30m/pixel; and (c) a TIR (8.125-11.65um) instrument with five bands at 90m/pixel. Returned data are processed in Japan at the Earth Remote Sensing Data Analysis Center (ERSDAC) and at the Land Processes Distributed Active Archive Center (LP DAAC), located at the USGS Center for Earth Resource Observation and Science (EROS) in Sioux Falls, South Dakota. Within the ASTER Project, the JPL Volcano Data Acquisition and Analyses System (VDAAS) houses over 60,000 ASTER volcano images of 1542 volcanoes worldwide and will be accessible for downloads by the general public and on-line image analyses by researchers in early 2007. VDAAS multi-spectral thermal infrared (TIR) de-correlation stretch products are optimized for volcanic ash detection and have a spatial resolution of 90m/pixel. Digital elevation models (DEM) stereo-photogrammetrically derived from ASTER Band 3B/3N data are also available within VDAAS at 15 and 30m/pixel horizontal resolution. Thus, ASTER visible, IR, and DEM data at 15-100m/pixel resolution within VDAAS can be combined to provide useful boundary conditions on local volcanic eruption plume location, composition, and altitude, as well as on topography of underlying terrain. During and after eruptions, low- altitude winds and ash transport can be affected by topography, and other orographic thermal and water vapor

  11. Volcanic caves of East Africa - an overview


    Jim W. Simons


    Numerous Tertiary to recent volcanoes are located in East Africa. Thus, much of the region is made up volcanic rock, which hosts the largest and greatest variety of East Africas caves. Exploration of volcanic caves has preoccupied members of Cave Exploration Group of East Africa (CEGEA) for the past 30 years. The various publications edited by CEGEA are in this respect a treasure troves of speleological information. In the present paper an overview on the most important volcanic caves and are...

  12. Evidence of a modern deep water magmatic hydrothermal system in the Canary Basin (eastern central Atlantic Ocean) (United States)

    Medialdea, T.; Somoza, L.; González, F. J.; Vázquez, J. T.; de Ignacio, C.; Sumino, H.; Sánchez-Guillamón, O.; Orihashi, Y.; León, R.; Palomino, D.


    New seismic profiles, bathymetric data, and sediment-rock sampling document for the first time the discovery of hydrothermal vent complexes and volcanic cones at 4800-5200 m depth related to recent volcanic and intrusive activity in an unexplored area of the Canary Basin (Eastern Atlantic Ocean, 500 km west of the Canary Islands). A complex of sill intrusions is imaged on seismic profiles showing saucer-shaped, parallel, or inclined geometries. Three main types of structures are related to these intrusions. Type I consists of cone-shaped depressions developed above inclined sills interpreted as hydrothermal vents. Type II is the most abundant and is represented by isolated or clustered hydrothermal domes bounded by faults rooted at the tips of saucer-shaped sills. Domes are interpreted as seabed expressions of reservoirs of CH4 and CO2-rich fluids formed by degassing and contact metamorphism of organic-rich sediments around sill intrusions. Type III are hydrothermal-volcanic complexes originated above stratified or branched inclined sills connected by a chimney to the seabed volcanic edifice. Parallel sills sourced from the magmatic chimney formed also domes surrounding the volcanic cones. Core and dredges revealed that these volcanoes, which must be among the deepest in the world, are constituted by OIB-type, basanites with an outer ring of blue-green hydrothermal Al-rich smectite muds. Magmatic activity is dated, based on lava samples, at 0.78 ± 0.05 and 1.61 ± 0.09 Ma (K/Ar methods) and on tephra layers within cores at 25-237 ky. The Subvent hydrothermal-volcanic complex constitutes the first modern system reported in deep water oceanic basins related to intraplate hotspot activity.Plain Language SummarySubmarine volcanism and associated hydrothermal systems are relevant processes for the evolution of the ocean basins, due their impact on the geochemistry of the oceans, their potential to form significant ore deposits, and their implications for global climate

  13. The San Franciscan volcanic field, Arizona (United States)

    Robinson, Henry Hollister


    LOCATION OF AREAThe San Franciscan volcanic field, which takes its name from San Francisco Mountain, the largest volcano of the group, covers about 3,000 square miles in the north-central part of Arizona, as shown by the shaded space on the index map forming figure 1. The center of the field lies about 50 miles south of the Grand Canyon of the Colorado and the southern boundary is in part coterminous with that of the San Francisco Plateau, which forms the southwestern division of the great Colorado Plateau.The region is easily reached, for the main line of the Atchison, Topeka, & Santa Fe Railway traverses it from east to west for more than 60 miles. Flagstaff, a town of 1,500 inhabitants 10 miles south of the summit of San Francisco Mountain, is on the railroad, amid a branch line runs from Williams, 34 miles farther west, to the Grand Canyon. All the more important points of interest in the field may be reached without difficulty by wagon, and outfits may be obtained at Flagstaff.OUTLINE OF THE REPORTThis report deals primarily with the volcanic phenomena of the region as determined in the field and laboratory. Chapter I contains a brief description of the geography of the field and Chapter II is devoted largely to the sedimentary formations and structure. The rest of the report Chapters III to VI—treats entirely of the various features of the volcanoes and igneous rocks, both individually and collectively. Detailed descriptions of the volcanoes and lava fields are given in Chapter III; the volcanic history of the region and its correlation with the general history of the surrounding country are presented in Chapter IV. These two chapters will presumably suffice for the general reader who may desire to become acquainted with the broader volcanic features of the region. Chapter V (Petrography) is devoted entirely to the detailed description of the individual igneous rocks of the region, as represented by a selected set of type specimens. In Chapter VI (Petrology

  14. Nephelometric Dropsonde for Volcanic Ash Project (United States)

    National Aeronautics and Space Administration — Advanced dropsondes that could effectively be guided through atmospheric regions of interest such as volcanic plumes could enable unprecedented observations of...

  15. Felsic Volcanics on the Moon (United States)

    Jolliff, B. L.; Lawrence, S. J.; Stopar, J.; Braden, S.; Hawke, B. R.; Robinson, M. S.; Glotch, T. D.; Greenhagen, B. T.; Seddio, S. M.


    Lunar Reconnaissance Orbiter (LRO) imaging and thermal data provide new morphologic and compositional evidence for features that appear to be expressions of nonmare silicic volcanism. Examples reflecting a range of sizes and volcanic styles include the Gruithuisen and Mairan Domes, and the Hansteen Alpha (H-A) and Compton-Belkovich (C-B) volcanic complexes. In this work we combine new observations with existing compositional remote sensing and Apollo sample data to assess possible origins. Images and digital topographic data at 100 m scale (Wide Angle Camera) and ~0.5 to 2 m (Narrow Angle Camera) reveal (1) slopes on volcanic constructs of ~12° to 27°, (2) potential endogenic summit depressions, (3) small domical features with dense boulder populations, and (4) irregular collapse features. Morphologies in plan view range from the circular to elliptical Gruithuisen γ and δ domes (~340 km2 each), to smaller cumulodomes such as Mairan T and C-B α (~30 km2, each), to the H-A (~375 km2) and C-B (~680 km2) volcanic complexes. Heights range from ~800-1800 m, and most domes are relatively flat-topped or have a central depression. Positions of the Christiansen Feature in LRO Diviner data reflect silicic compositions [1]. Clementine UVVIS-derived FeO varies from ~5 to 10 wt%. Lunar Prospector Th data indicate model values of 20-55 ppm [2,3], which are consistent with compositions ranging from KREEP basalt to lunar granite. The Apollo collection contains small rocks and breccia clasts of felsic/granitic lithologies. Apollo 12 samples include small, pristine and brecciated granitic rock fragments and a large, polymict breccia (12013) consisting of felsic material (quartz & K-feldspar-rich) and mafic phases (similar to KREEP basalt). Many of the evolved lunar rocks have geochemically complementary compositions. The lithologic associations and the lack of samples with intermediate composition suggest a form of magmatic differentiation that produced mafic and felsic

  16. Volcanic hazards and public response (United States)

    Peterson, Donald W.


    Although scientific understanding of volcanoes is advancing, eruptions continue to take a substantial toll of life and property. Some of these losses could be reduced by better advance preparation, more effective flow of information between scientists and public officials, and better understanding of volcanic behavior by all segments of the public. The greatest losses generally occur at volcanoes that erupt infrequently where people are not accustomed to dealing with them. Scientists sometimes tend to feel that the blame for poor decisions in emergency management lies chiefly with officials or journalists because of their failure to understand the threat. However, the underlying problem embraces a set of more complex issues comprising three pervasive factors. The first factor is the volcano: signals given by restless volcanoes are often ambiguous and difficult to interpret, especially at long-quiescent volcanoes. The second factor is people: people confront hazardous volcanoes in widely divergent ways, and many have difficulty in dealing with the uncertainties inherent in volcanic unrest. The third factor is the scientists: volcanologists correctly place their highest priority on monitoring and hazard assessment, but they sometimes fail to explain clearly their conclusions to responsible officials and the public, which may lead to inadequate public response. Of all groups in society, volcanologists have the clearest understanding of the hazards and vagaries of volcanic activity; they thereby assume an ethical obligation to convey effectively their knowledge to benefit all of society. If society resists, their obligation nevertheless remains. They must use the same ingenuity and creativity in dealing with information for the public that they use in solving scientific problems. When this falls short, even excellent scientific results may be nullified.

  17. Corrigendum: Small volcanic eruptions and the stratospheric sulfate aerosol burden (United States)

    Pyle, David M.


    In my original perspective piece (Pyle 2012), I mistakenly suggested that both Sawamura et al (2012) and Bourassa et al (2012) had attributed the lofting of the Nabro plume into the stratosphere to the strong Asian summer monsoon. In fact, while the ash clouds that accompanied the most explosive phases of the Nabro eruption were reported by the Toulouse VAAC to have reached 9-14 km on 13-14 June (Smithsonian Institution 2011), the Micro Pulse Lidar profile from Sede Boker, Israel, for the same date (14 June) shows a strong peak in the scattering ratio at around 17 km elevation. This was interpreted by Sawamura et al (2012) as being potentially due to ash and sulfate particles, and would suggest that the initial phase of the eruption injected material to this altitude. Sawamura et al (2012) also showed that the transport of the volcanic plume to Sede Boker was consistent with forward air-trajectory models, which for that time period showed a strong anticyclonic vortex due to the Asian summer monsoon, but they did not suggest that the monsoonal circulation was responsible for lofting of the plume. Bourassa et al (2012) identified a stratospheric enhancement of aerosol optical depth across eastern Asia beginning in early July 2011, which they attributed to the vertical transport of volcanic SO2 from the eruption plume into the lower stratosphere. Further work, using other techniques that can resolve altitude, is required to fully understand the time-history of the volcanic ash and gas plumes, and the sulfate aerosol that subsequently developed.

  18. Seismic signals at the Nirano Mud Volcanic Field, Italy (United States)

    Antunes, Verónica; Lupi, Matteo; Carrier, Aurore; Planès, Thomas; Obermann, Anne; Mazzini, Adriano; Ricci, Tullio; Sciarra, Alessandra; Moretti, Milena


    Mud volcanoes are geological phenomena that only recently are beginning to be investigated with passive seismic methods. To shed light on the seismic signals associated with mud volcanic activity we deployed a temporary network composed of 7 seismic stations around Nirano, Italy. We identified the different types of signals generated by this active system. During the three months survey period, the stations repeatedly recorded drumbeat signals beneath the structure. We have identified two types of drumbeat signals: one with durations of about 50 seconds and frequency range of 10-45 Hz; the second has a duration of about 4 seconds and frequency range of 5-45 Hz. These drumbeat signals were captured depending on the position of the seismic station and the distance from the mud vents. We also identified a third signal, present in almost every station in the network, with a duration of about 10 seconds and frequency range of 5-45 Hz. The amplitude of these signals varies across the stations suggesting that the most active part of the system is located in the north eastern-most area of the mud volcanic field where new mud vents recently appeared.

  19. Geology of mud volcanos in the Eastern Mediterranean from combined sidescan and submersible surveys

    NARCIS (Netherlands)

    Zitter, T.A.C.; Huguen, C.; Woodside, J.M.


    Submersible observations and seafloor mapping over areas of mud volcanism in the eastern Mediterranean Sea reveal an abundance of methane-rich fluid emissions, as well as specific seep-associated fauna (e.g. tubeworms, bivalves and chemosynthetic bacteria) and diagenetic deposits (i.e. carbonates

  20. Mud volcanoes and gas hydrates in the Anaximander mountains (Eastern Mediterranean Sea)

    NARCIS (Netherlands)

    Lykousis, V.; Alexandri, S.; Woodside, J.M.; de Lange, G.; Dahlmann, A.; Perissoratis, C.; Heeschen, K.; Ioakim, Chr.; Sakellariou, D.; Nomikou, P.; Rousakis, G.; Casas, D.; Ballas, D.; Ercilla, G.


    Detailed multibeam, sedimentological, and geophysical surveys provide ample new data to confirm that the Anaximander Mountains (Eastern Mediterranean) are an important area for active mud volcanism and gas hydrate formation. More than 3000 km of multibeam track length was acquired during two recent

  1. Volcanic eruptions; energy and size (United States)

    de la Cruz-Reyna, S.


    The Earth is a dynamic planet. Many different processes are continuously developing, creating a delicate balance between the energy stored and generated in its interior and the heat lost into space. The heat in continuously transferred through complex self-regulating convection mechanisms on a planetary scale. The distribution of terrestrial heat flow reveals some of the fine structure of the energy transport mechanisms in the outer layers of the Earth. Of these mechanisms in the outer layers of the Earth. Of these mechanisms, volcanism is indeed the most remarkable, for it allows energy to be transported in rapid bursts to the surface. In order to maintain the subtle balance of the terrestrial heat machine, one may expect that some law or principle restricts the ways in which these volcanic bursts affect the overall energy transfer of the Earth. For instance, we know that the geothermal flux of the planet amounts to 1028 erg/year. On the other hand, a single large event like the Lava Creek Tuff eruption that formed Yellowstone caldera over half a million years ago may release the same amount of energy in a very small area, over a short period of time. 

  2. Monogenetic volcanism in the Cordillera Central of Colombia: unknown volcanic fields associated with the northernmost Andes' volcanic chain related subduction (United States)

    Murcia, Hugo; Borrero, Carlos; Németh, Károly


    Monogenetic volcanic fields are commonly related to rifts and/or intraplate tectonic settings. However, although less common, they appear also associated with subduction zones, including both front and back-arc volcanoes. To nourish this uncommon tectonic location, it is shown here that monogenetic volcanic fields, in addition to polygenetic volcanoes, also appear at the northernmost part of the Andes Northern Volcanic Zone (NVZ) (2° S to 4°30´N). These fields are associated with the main axe of the Quaternary active volcanic structures; they are linked to the polygenetic Cerro Bravo - Cerro Machín Volcanic Chain ( 80 km long; CBCMVC) in Colombia, the chain that hosts the iconic Nevado del Ruiz volcano. To the present, three monogenetic volcanic fields, with a typical calc-alkaline signature, have been identified in both sides of this chain: 1) Villamaría - Termales Monogenetic Volcanic Field (VTMVF) located to the northwestern part (>5 km) of the CBCMVC. This field is made up of at least 14 volcanoes aligned with the Villamaría - Termales fault zone. The volcanism has been mainly effusive, represented by lava domes and some lava flows. The volcanoes are andesitic to dacitic in composition. It is inferred that the magmatic source is a magma chamber close to Nevado del Ruiz volcano. Based on stratigraphic relationships, it is assumed that the last eruption occurred 10 wt.%) in the whole CBCMVC. Its source is related to the same magmas that feed the volcanoes in the CBCMVC. Stratigraphic relationships show that the volcanoes are younger than the underlying alluvial and volcaniclastic Ibagué fan (<1 Ma). Overall, it is clear that monogenetic volcanic fields are not atypical in the area, although their relationship with the magmatism feeding the polygenetic arc of the Andes' volcanic chain related subduction, is still unknown.

  3. Plavica epithermal Au-Ag-Cu deposit in eastern Macedonia: Geology and 3D model of valuable component distribution in ore (United States)

    Serafimovski, T.; Volkov, A. V.; Serafimovski, D.; Tasev, G.; Ivanovski, I.; Murashov, K. Yu.


    The Plavica Au-Ag-Cu deposit is related to the large Neogene volcanic center, which complicates the paleocaldera in the central Kratovo-Zletovo ore district of eastern Macedonia. Based on the geology, ore mineralogy, wall-rock alteration, and fluid inclusions, the Plavica deposit has been referred to the epithermal high-sulfidation type. The general 3D model of orebody at this deposit is based on its general geological structure and complex distribution of metal contents. The framework of the 3D model, which has been constructed in the ArcGIS System, comprises 195 exploration boreholes 47295.8 m in total length. The 3D model allows to a better understanding of distribution of mineralization and supplements the geological data on the deposit.

  4. The role of magmatic loads and rift jumps in generating seaward dipping reflectors on volcanic rifted margins (United States)

    Buck, W. Roger


    The largest volcanic constructs on Earth are the seismically imaged seaward dipping reflector (SDR) units found offshore of many rifted continental margins, including most that border the Atlantic Ocean. Whether their formation requires large magnitude (i.e. 10 s of km) of normal fault slip or results from the deflection of the lithosphere by the weight of volcanic flows is controversial. Though there is evidence for faulting associated with some SDRs, this paper considers the range of structures that can be produced by magmatic and volcanic loading alone. To do this an idealized mechanical model for the construction of rift-related volcanic flow structures is developed. Dikes open as plates move away from the center of a model rift and volcanic flows fill the depression produced by the load caused by dike solidification. The thin elastic plate flexure approximation allows a closed form description of the shape of both the contacts between flows and between the flows and underlying dikes. The model depends on two independent parameters: the flexure parameter, α, and the maximum isostatically supported extrusive layer thickness, w0. For reasonable values of these parameters the model reproduces the observed down-dip thickening of flows and the range of reflector dip angles. A numerical scheme using the analytic results allows simulation of the effect of temporal changes in the locus of magmatic spreading as well as changes in the amount of volcanic infill. Either jumps in the location of the center of diking or periods with no volcanism result in separate units or "packages" of model SDRs, in which the flow-dike contact dips landward, consistent with observations previously attributed only to listric normal fault offset. When jumps in the spreading center are small (i.e. less than α) they result in thicker, narrower volcanic units on one side of a rift compared to those on the other side. This is similar to the asymmetric distributions of volcanic packages seen

  5. A multidisciplinary approach to quantify the permeability of the Whakaari/White Island volcanic hydrothermal system (Taupo Volcanic Zone, New Zealand) (United States)

    Heap, Michael J.; Kennedy, Ben M.; Farquharson, Jamie I.; Ashworth, James; Mayer, Klaus; Letham-Brake, Mark; Reuschlé, Thierry; Gilg, H. Albert; Scheu, Bettina; Lavallée, Yan; Siratovich, Paul; Cole, Jim; Jolly, Arthur D.; Baud, Patrick; Dingwell, Donald B.


    Our multidisciplinary study aims to better understand the permeability of active volcanic hydrothermal systems, a vital prerequisite for modelling and understanding their behaviour and evolution. Whakaari/White Island volcano (an active stratovolcano at the north-eastern end of the Taupo Volcanic Zone of New Zealand) hosts a highly reactive hydrothermal system and represents an ideal natural laboratory to undertake such a study. We first gained an appreciation of the different lithologies at Whakaari and (where possible) their lateral and vertical extent through reconnaissance by land, sea, and air. The main crater, filled with tephra deposits, is shielded by a volcanic amphitheatre comprising interbedded lavas, lava breccias, and tuffs. We deployed field techniques to measure the permeability and density/porosity of (1) > 100 hand-sized sample blocks and (2) layered unlithified deposits in eight purpose-dug trenches. Our field measurements were then groundtruthed using traditional laboratory techniques on almost 150 samples. Our measurements highlight that the porosity of the materials at Whakaari varies from ∼ 0.01 to ∼ 0.7 and permeability varies by eight orders of magnitude (from ∼ 10-19 to ∼ 10-11 m2). The wide range in physical and hydraulic properties is the result of the numerous lithologies and their varied microstructures and alteration intensities, as exposed by a combination of macroscopic and microscopic (scanning electron microscopy) observations, quantitative mineralogical studies (X-ray powder diffraction), and mercury porosimetry. An understanding of the spatial distribution of lithology and alteration style/intensity is therefore important to decipher fluid flow within the Whakaari volcanic hydrothermal system. We align our field observations and porosity/permeability measurements to construct a schematic cross section of Whakaari that highlights the salient findings of our study. Taken together, the alteration typical of a volcanic

  6. Soils of volcanic regions in Europe

    NARCIS (Netherlands)

    Arnalds, O.; Bartoli, F.; Buurman, P.; Oskarsson, H.; Stoops, G.; García-Rodeja, E.


    Soils of volcanic areas often exhibit unique properties differentiating them from other soils on Earth. This book gives comprehensive coverage of soils in volcanic regions within Europe, dealing with most aspects of modern day soil science. It covers a range of issues such as mineralogy, chemistry,

  7. Optical properties of volcanic ash: improving remote sensing observations. (United States)

    Whelley, Patrick; Colarco, Peter; Aquila, Valentina; Krotkov, Nickolay; Bleacher, Jake; Garry, Brent; Young, Kelsey; Rocha Lima, Adriana; Martins, Vanderlei; Carn, Simon


    Many times each year explosive volcanic eruptions loft ash into the atmosphere. Global travel and trade rely on aircraft vulnerable to encounters with airborne ash. Volcanic ash advisory centers (VAACs) rely on dispersion forecasts and satellite data to issue timely warnings. To improve ash forecasts model developers and satellite data providers need realistic information about volcanic ash microphysical and optical properties. In anticipation of future large eruptions we can study smaller events to improve our remote sensing and modeling skills so when the next Pinatubo 1991 or larger eruption occurs, ash can confidently be tracked in a quantitative way. At distances >100km from their sources, drifting ash plumes, often above meteorological clouds, are not easily detected from conventional remote sensing platforms, save deriving their quantitative characteristics, such as mass density. Quantitative interpretation of these observations depends on a priori knowledge of the spectral optical properties of the ash in UV (>0.3μm) and TIR wavelengths (>10μm). Incorrect assumptions about the optical properties result in large errors in inferred column mass loading and size distribution, which misguide operational ash forecasts. Similarly, simulating ash properties in global climate models also requires some knowledge of optical properties to improve aerosol speciation.

  8. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina

    primitive basalts and trachybasalts but also more evolved samples from the retroarc region and the larger volcanoes Payún Matrú and Payún Liso are presented. The samples cover a broad range of compositions from intraplate lavas similar to ocean island basalts to arc andesites. A common feature found...... are isotopically similar to the Andean Southern Volcanic Zone arc rocks and their mantle source possibly resembled the source of South Atlantic N-MORB prior to addition of fluids and melts from the subduction channel. However, it must have been more enriched than the estimates of depleted upper mantle from...... the lithosphere is thinnest and possibly in areas of elevated mantle temperatures. The pyroxenite melts formed at deeper levels react with the surrounding peridotite and thereby changes composition leading to eruption of melts which experienced variable degrees of melt-peridotite interaction. This can presumably...

  9. Volcanic unrest and hazard communication in Long Valley Volcanic Region, California (United States)

    Hill, David P.; Mangan, Margaret T.; McNutt, Stephen R.


    The onset of volcanic unrest in Long Valley Caldera, California, in 1980 and the subsequent fluctuations in unrest levels through May 2016 illustrate: (1) the evolving relations between scientists monitoring the unrest and studying the underlying tectonic/magmatic processes and their implications for geologic hazards, and (2) the challenges in communicating the significance of the hazards to the public and civil authorities in a mountain resort setting. Circumstances special to this case include (1) the sensitivity of an isolated resort area to media hype of potential high-impact volcanic and earthquake hazards and its impact on potential recreational visitors and the local economy, (2) a small permanent population (~8000), which facilitates face-to-face communication between scientists monitoring the hazard, civil authorities, and the public, and (3) the relatively frequent turnover of people in positions of civil authority, which requires a continuing education effort on the nature of caldera unrest and related hazards. Because of delays associated with communication protocols between the State and Federal governments during the onset of unrest, local civil authorities and the public first learned that the U.S. Geological Survey was about to release a notice of potential volcanic hazards associated with earthquake activity and 25-cm uplift of the resurgent dome in the center of the caldera through an article in the Los Angeles Times published in May 1982. The immediate reaction was outrage and denial. Gradual acceptance that the hazard was real required over a decade of frequent meetings between scientists and civil authorities together with public presentations underscored by frequently felt earthquakes and the onset of magmatic CO2 emissions in 1990 following a 11-month long earthquake swarm beneath Mammoth Mountain on the southwest rim of the caldera. Four fatalities, one on 24 May 1998 and three on 6 April 2006, underscored the hazard posed by the CO2

  10. Active Volcanism on Io as Seen by Galileo SSI (United States)

    McEwen, A.S.; Keszthelyi, L.; Geissler, P.; Simonelli, D.P.; Carr, M.H.; Johnson, T.V.; Klaasen, K.P.; Breneman, H.H.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Senske, D.A.; Belton, M.J.S.; Schubert, G.


    -150 km high, long-lived, associated with high-temperature hot spots) may result from silicate lava flows or shallow intrusions interacting with near-surface SO2. A major and surprising result is that ~30 of Io's volcanic vents glow in the dark at the short wavelengths of SSI. These are probably due to thermal emission from surfaces hotter than 700 K (with most hotter than 1000 K), well above the temperature of pure sulfur volcanism. Active silicate volcanism appears ubiquitous. There are also widespread diffuse glows seen in eclipse, related to the interaction of energetic particles with the atmosphere. These diffuse glows are closely associated with the most active volcanic vents, supporting suggestions that Io's atmopshere is dominated by volcanic outgassing. Globally, volcanic centers are rather evenly distributed. However, 14 of the 15 active plumes seen by Voyager and/or Galileo are within 30?? of the equator, and there are concentrations of glows seen in eclipse at both the sub- and antijovian points. These patterns might be related to asthenospheric tidal heating or tidal stresses. Io will continue to be observed during the Galileo Europa Mission, which will climax with two close flybys of Io in late 1999. ?? 1998 Academic Press.

  11. Geologic evolution of the Jemez Mountains and their potential for future volcanic activity

    Energy Technology Data Exchange (ETDEWEB)

    Burton, B.W.


    Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10/sup -9//km/sup 2//y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10/sup -7//y.

  12. Geomorphological Approach for Regional Zoning In The Merapi Volcanic Area

    Directory of Open Access Journals (Sweden)

    Langgeng Wahyu Santosa


    Full Text Available Geomorphologial approach can be used as the basic for identifying and analyzing the natural resources potentials, especially in volcanic landscape. Based on its geomorphology, Merapi volcanic landscape can be divided into 5 morphological units, i.e.: volcanic cone, volcanic slope, volcanic foot, volcanic foot plain, and fluvio-volcanic plain. Each of these morphological units has specific characteristic and natural resources potential. Based on the condition of geomorphology, the regional zoning can be compiled to support the land use planning and to maintain the conservation of environmental function in the Merapi Volcanic area.

  13. Volcanism and associated hazards: the Andean perspective (United States)

    Tilling, R. I.


    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

  14. Io Eclipse/Volcanic Eruption (United States)


    This image was acquired while Io was in eclipse (in Jupiter's shadow) during Galileo's eighth orbit, and reveals several dynamic processes. The most intense features are red, while glows of lesser intensity are yellow or green, and very faint glows appear blue in this color-coded image. The small red or yellow spots mark the sites of high-temperature magma erupting onto the surface in lava flows or lava lakes.This image reveals a field of bright spots near Io's sub-Jupiter point (right-hand side of image). The sub-Jupiter hemisphere always faces Jupiter just as the Moon's nearside always faces Earth. There are extended diffuse glows on the equatorial limbs or edges of the planet (right and left sides). The glow on the left is over the active volcanic plume Prometheus, but whereas Prometheus appears to be 75 kilometers (46.6 miles) high in reflected light, here the diffuse glow extends about 800 kilometers (497 miles) from Io's limb. This extended glow indicates that gas or small particles reach much greater heights than the dense inner plume. The diffuse glow on the right side reaches a height of 400 kilometers (249 miles), and includes a prominence with a plume-like shape. However, no volcanic plume has been seen at this location in reflected light. This type of observation is revealing the relationships between Io's volcanism, atmosphere and exosphere.Taken on May 6, 1997, north is toward the top. The image was taken with the clear filter of the solid state imaging (CCD) system on NASA's Galileo spacecraft at a range of 1.8 million kilometers (1.1 million miles).The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL Background information and educational

  15. The NASA Applied Sciences Program: Volcanic Ash Observations and Applications (United States)

    Murray, John J.; Fairlie, Duncan; Green, David; Haynes, John; Krotkov, Nickolai; Meyer, Franz; Pavolonis, Mike; Trepte, Charles; Vernier, Jean-Paul


    Since 2000, the NASA Applied Sciences Program has been actively transitioning observations and research to operations. Particular success has been achieved in developing applications for NASA Earth Observing Satellite (EOS) sensors, integrated observing systems, and operational models for volcanic ash detection, characterization, and transport. These include imager applications for sensors such as the MODerate resolution Imaging SpectroRadiometer (MODIS) on NASA Terra and Aqua satellites, and the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NASA/NOAA Suomi NPP satellite; sounder applications for sensors such as the Atmospheric Infrared Sounder (AIRS) on Aqua, and the Cross-track Infrared Sounder (CrIS) on Suomi NPP; UV applications for the Ozone Mapping Instrument (OMI) on the NASA Aura Satellite and the Ozone Mapping Profiler Suite (OMPS) on Suomi NPP including Direct readout capabilities from OMI and OMPS in Alaska (GINA) and Finland (FMI):; and lidar applications from the Caliop instrument coupled with the imaging IR sensor on the NASA/CNES CALIPSO satellite. Many of these applications are in the process of being transferred to the Washington and Alaska Volcanic Ash Advisory Centers (VAAC) where they support operational monitoring and advisory services. Some have also been accepted, transitioned and adapted for direct, onboard, automated product production in future U.S. operational satellite systems including GOES-R, and in automated volcanic cloud detection, characterization and alerting tools at the VAACs. While other observations and applications remain to be developed for the current constellation of NASA EOS sensors and integrated with observing and forecast systems, future requirements and capabilities for volcanic ash observations and applications are also being developed. Many of these are based on technologies currently being tested on NASA aircraft, Unmanned Aerial Systems (UAS) and balloons. All of these efforts and the potential advances

  16. Geochronology and geology of late Oligocene through Miocene volcanism and mineralization in the western San Juan Mountains, Colorado (United States)

    Bove, D.J.; Hon, Ken; Budding, K.E.; Slack, J.F.; Snee, L.W.; Yeoman, R.A.


    resurgent intrusions indicates that it is closely related to the early stages of bimodal high-silica rhyolite-alkali basalt volcanism that accompanied the onset of extensional tectonism in the region. Both 40Ar/39Ar ages and paleomagnetic data confirm that the entire caldera sequence formed in less than 330,000 years. Only weak quartz vein mineralization is present in the center of the caldera, and it appears to be related to leaching of metals from the intracaldera tuffs above the resurgent intrusion. Massive alunitization and weak Mo and Cu mineralization along the eastern ring fracture are associated with calc-alkaline lavas and stocks related to late stages of the caldera cycle. These calc-alkaline stocks also appear to be genetically and temporally linked to a radial pattern of barite-precious metal veins on the northeastern margin of the Lake City caldera.

  17. Petrography, mineral chemistry and geochemistry of post-ophiolitic volcanic rocks in the Ratouk area (south of Gazik, east of Iran

    Directory of Open Access Journals (Sweden)

    Zahra Vahedi Tabas


    Full Text Available Introduction Basaltic volcanoes are one of the volcanisms that have occurred in different parts of the world. The study of these lavas is important for petrologists, because they are seen in different tectonic settings and therefore diverse mechanisms affect their formation (Chen et al., 2007. Young volcanic rocks such as Quaternary basalts are one of latest products of magmatism in Iran that are related to deep fractures and active faults in Quaternary (Emami, 2000. The study area is located at 140km east of Birjand at Gazik 1:100000 geological map (Guillou et al., 1981 and have 60̊ 11' to 60̊ 15 '27" eastward longitude and 32̊ 33' 24" to 32̊ 39' 10" northward latitude. On the basis of structural subdivisions of Iran, this area is located in the northern part of the Sistan suture zone (Tirrul et al., 1983. Because of the importance of basaltic rocks in Sistan suture, this research is done with the aim of investigating the petrography and mineralogy of basaltic lavas, the nature of basaltic and intermediate magmatism and finally determination of tectonomagmatic regime. Materials and methods After field studies and sampling, 85 thin sections were prepared and carefully studied. Then ten samples with the lowest alteration were analyzed for major elements by inductively coupled plasma (ICP technologies and trace elements were analyzed using inductively coupled plasma mass spectrometry (ICP-MS, following a lithium metaborate/tetraborate fusion and nitric acid total digestion at the Acme laboratories, Vancouver, Canada. Electron probe micro analyses of clinopyroxene and olivine were done at the Iranian mineral processing research center (IMPRC by Cameca SX100 machine. X-ray diffraction analysis of minerals was done at the X-ray laboratory of the University of Birjand. Results In 60km south of GaziK at the east of the southern Khorasan province and the northern part of the Sistan suture zone, volcanic rocks with intermediate (Oligomiocene and

  18. Dome collapse eruption in Tatun Volcanic Group near metropolitan Taipei, Taiwan at ~6 kyrs (United States)

    Chen, C.; Lee, T.


    The Tatun Volcanic Group (TVG) is located in the north of metropolitan Taipei, Taiwan. Over 6 million inhabitants are living in Taipei City and suburban area. Another critical issue is an international airport and two nuclear power plants are lying at the foot of the TVG. If the TGV will be re-active, the serious hazard for human lives and economies in this area will definitely occur. Understanding the youngest eruption history of the TVG will be much important for prediction the future activity of eruption. The core was collected from the Dream Lake at the eastern slop of Cising Mt.. Total 21 samples from depth 190 cm to 231.5 cm have been tested. Comparison of chemical compositions of glass and minerals in the volcanic clasts with those of lava around TVG, they clearly showed that the volcanic clasts can be correlated with the eruption of the closest Cising Mt. According to the radiocarbon (C-14) age of core sample at the depth 225 cm, the age was extrapolated around 6150 yrs ca. C-14 B.P.. Moreover, the respiratory cristobalite in the volcanic clasts were firstly identified by the identical morphology, chemical composition and Laser Raman Spectrometry (LRS). The crystalline silica was produced by vapor-phase crystallization and devitrification in the andesite lava dome and volcanic ash generated by pyroclastic flows formed by lava dome collapse in Soufriere Hills volcano, Montserrat (Baxter et al.,1999). These new evidence demonstrated that there would probably have the lava dome collapse eruptions in the TVG in the last 6 kyrs. The result in this paper also sustained that the landslide caused by the weak phreatic eruption within the last 6000 yrs in the TVG (Belousov et al., 2010). It must further be noted that an efficient program of the volcanic hazard reduction should be practiced for the metropolitan Taipei and suburban area.

  19. Effect of Aseismic Ridge Subduction on Volcanism in the NE Lesser Antilles Arc (United States)

    Stinton, A. J.; Hatfield, R. G.; McCanta, M. C.


    The interaction of aseismic ridges or buoyant crust in subduction zones can affect the volcanism occurring on the overriding plate. Here we describe the affect of the subduction of an aseismic ridge on volcanism in the NE Lesser Antilles. The Lesser Antilles island arc is a result of westward subduction of the North American plate beneath the Caribbean plate and stretches 800 km from Saba in the north to Grenada in the south. From Guadeloupe northwards, the arc bifurcates into an eastern, inactive arc (known as the Limestone Caribees) and a western, active arc (Volcanic Caribees). It has been suggested that this bifurcation is the result of the subduction of buoyant crust in the form of at least two aseismic ridges, in the North American plate. In 2012, IODP Expedition 340 recovered 130 m of core from site U1396, located 55 km SW of Montserrat, Lesser Antilles. The core contains a detailed record of volcanism, in the form of more than 180 tephra layers, that stretches back nearly 4.5 Ma. This is the longest and most complete record of volcanism for the NE Lesser Antilles and provides insight into the evolution and development of the island arc in this region. A variety of techniques are being applied to the tephra layers from U1396 to determine their age, chemistry, components and origin. Here we present preliminary results from paeleomagnetic age determinations for each tephra layer to show how the subduction of aseismic ridges on the North American plate has affected the rate of volcanism and development of the island arc in the NE Lesser Antilles over the last 4.5 Ma.

  20. Structure of the Volcanic Vent Distribution of the Cascades Arc from a New Database of Holocene and Pleistocene Volcanism, with Focus on Pre-Caldera Monogenetic Volcanism at Mount Mazana, Oregon (United States)

    Loh, L.; Karlstrom, L.; Ramsey, D. W.; Wright, H. M.


    The spatial and temporal distribution of volcanoes in the Cascades Arc, USA,reflects modulation of time-varying mantle melt influx by crustal magmatic plumbing and tectonic forces. The relative contribution of spatio-temporal source variations versus crustal focusing in generating the observed distribution of vents is poorly constrained. To identify patterns in preserved eruptive products and validate models for crustal magma transport we have assembled the most complete database of Cascades volcanism to date. Our database contains >2900 volcanic vent locations from the Holocene and Pleistocene, and includes vent types, ages, and major element geochemistry of eruptive products from the Holocene and Pleistocene. Bulk geochemistry is obtained from USGS Professional Papers and the American Volcanic and Intrusive Rock Database (NAVDAT). We also include arc-wide heat flow data, modeled ambient noise crustal seismic tomography and crust thickness interpolated to each vent. We perform spectral clustering on vent locations to define volcanic centers for the Holocene and Pleistocene. Centers found through Spectral Clustering reproduce the major loci of volcanism in the Cascades, and show time-varying structure in the number, type and distribution eruptions. There is significant North-South variation in vent type and distribution that correlates with variations in heat flow, bulk silica content and average crustal shear velocity. Although precise eruption ages for the complete dataset are not yet available, Mount Mazama, OR, has a well-resolved time/composition/volume/location history of eruptions <400 ka that allow for further analysis. The spatial distribution of Mazamaeruptive units does not follow a Poisson distribution when well resolved in time, but rather clusters around an evolved center that exhibits progressively more evolved eruptive products in time. Monogenetic eruptions preceding the 7.8 ka Crater Lake eruption define a spatial and temporal pattern that is

  1. Modulation of ENSO evolution by strong tropical volcanic eruptions (United States)

    Wang, Tao; Guo, Dong; Gao, Yongqi; Wang, Huijun; Zheng, Fei; Zhu, Yali; Miao, Jiapeng; Hu, Yongyun


    The simulated responses of the El Niño-Southern Oscillation (ENSO) to volcanic forcings are controversial, and some mechanisms of these responses are not clear. We investigate the impacts of volcanic forcing on the ENSO using a long-term simulation covering 1400-1999 as simulated by the Bergen Climate Model (BCM) and a group of simulations performed with the Community Atmosphere Model version 4.0 (CAM4) and the BCM's ocean component Miami Isopycanic Coordinated Ocean Model (MICOM). The analysis of the long-term BCM simulation indicates that ENSO has a negative-positive-negative response to strong tropical volcanic eruptions (SVEs), which corresponds to the different stages of volcanic forcing. In the initial forcing stage, a brief and weak La Niña-like response is caused by the cooling along the west coast of the South American continent and associated enhancement of the trade winds. In the peak forcing stage, westerly wind anomalies are excited by both reduced east-west sea level pressure gradients and weakened and equatorward shifted tropical convergence zones. These westerly wind anomalies extend to the equatorial eastern Pacific, leading to an El Niño-like response. At the same time, easterly wind anomalies west of 120°E and strong cooling effects can promote a discharged thermocline state and excite an upwelling Kelvin wave in the western Pacific. In the declining forcing stage, forced by the recovered trade winds, the upwelling Kelvin wave propagates eastward and reaches the equatorial eastern Pacific. Through the Bjerknes feedback, a strong and temporally extended La Niña-like response forms. Additional CAM4 simulations suggest a more important role of the surface cooling over the Maritime Continent and surrounding ocean in shaping the westerly wind anomalies over the equatorial central-eastern Pacific and the easterly wind anomalies west of 120° E, which are key to causing the El Niño-like responses and subsequent La Niña-like responses

  2. Eastern Redcedar Seedling Assessment (United States)

    U.S. Environmental Protection Agency — Eastern redcedar tree seedling growth in response to various soil, nitrogen, and photosynthetic radiation characteristics. This dataset is associated with the...

  3. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey (United States)

    Keskin, Mehmet


    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  4. Impacts of a Pinatubo-size volcanic eruption on ENSO

    KAUST Repository

    Predybaylo, Evgeniya


    Observations and model simulations of the climate responses to strong explosive low-latitude volcanic eruptions suggest a significant increase in the likelihood of El Niño during the eruption and posteruption years, though model results have been inconclusive and have varied in magnitude and even sign. In this study, we test how this spread of responses depends on the initial phase of El Niño-Southern Oscillation (ENSO) in the eruption year and on the eruption\\'s seasonal timing. We employ the Geophysical Fluid Dynamics Laboratory CM2.1 global coupled general circulation model to investigate the impact of the Pinatubo 1991 eruption, assuming that in 1991 ENSO would otherwise be in central or eastern Pacific El Niño, La Niña, or neutral phases. We obtain statistically significant El Niño responses in a year after the eruption for all cases except La Niña, which shows no response in the eastern equatorial Pacific. The eruption has a weaker impact on eastern Pacific El Niños than on central Pacific El Niños. We find that the ocean dynamical thermostat and (to a lesser extent) wind changes due to land-ocean temperature gradients are the main feedbacks affecting El Niño development after the eruption. The El Niño responses to eruptions occurring in summer are more pronounced than for winter and spring eruptions. That the climate response depends on eruption season and initial ENSO phase may help to reconcile apparent inconsistencies among previous studies.

  5. Volcanic activity in the Acambay Graben: a < 25 Ka subplinian eruption from the Temascalcingo volcano and implications for volcanic hazard. (United States)

    Pedrazzi, Dario; Aguirre Díaz, Gerardo; Sunyé Puchol, Ivan; Bartolini, Stefania; Geyer, Adelina


    The Trans-Mexican Volcanic Belt (TMVB) contains a large number of stratovolcanoes, some well-known, as Popocatepetl, Iztaccihuatl, Nevado de Toluca, or Colima and many others of more modest dimensions that are not well known but constitute the majority in the TMVB. Such volcanoes are, for example, Tequila, San Juan, Sangangüey, Cerro Culiacán, Cerro Grande, El Zamorano, La Joya, Palo Huerfano, Jocotitlán, Altamirano and Temascalcingo, among many others. The Temascalcingo volcano (TV) is an andesitic-dacitic stratovolcano located in the Trans-Mexican Volcanic Belt (TMVB) at the eastern part of the Acambay Graben (northwest portion of Estado de México). The TV is composed mainly by dacitic, porphyritic lavas, block and ash deposits and subordinate pumice fall deposits and ignimbrites (Roldán-Quintana et al., 2011). The volcanic structure includes a summit caldera that has a rectangular shape, 2.5×3.5 km, with the largest side oriented E-W, parallel to major normal faults affecting the edifice. The San Mateo Pumice eruption is one of the greatest paroxysmal episodes of this volcano with pumice deposits mainly exposed at the scarp of the Acambay-Tixmadeje fault and at the northern and northeastern flanks of TV. It overlies a paleosol dated at 25 Ka. A NE-trending dispersion was obtained from field data covering an area of at least 80 km2. These deposits overlie older lava flows and mud flows and are discontinuously covered and eroded by younger reworked deposits of Temascalcingo volcano. This event represents a highly explosive phase that generated a relatively thick and widespread pumice fallout deposit that may occur again in future eruptions. A similar eruption today would have a significantly impact in the region, overall due to the fact that there has been no systematic assessment of the volcanic hazard in any of the studies that have been conducted so far in the area. So, this is a pending and urgent subject that must be tackled without delay. Financed by

  6. Volcanic caves of East Africa - an overview

    Directory of Open Access Journals (Sweden)

    Jim W. Simons


    Full Text Available Numerous Tertiary to recent volcanoes are located in East Africa. Thus, much of the region is made up volcanic rock, which hosts the largest and greatest variety of East Africas caves. Exploration of volcanic caves has preoccupied members of Cave Exploration Group of East Africa (CEGEA for the past 30 years. The various publications edited by CEGEA are in this respect a treasure troves of speleological information. In the present paper an overview on the most important volcanic caves and areas are shortly reported.

  7. Eastern Europe's Silicon Rush (United States)

    Woodard, Colin


    This article presents how the fast expansion of information technology industry in eastern Slovakia is putting a strain on its labor supply. Suddenly, computer-science graduates have become one of the former Eastern Bloc's greatest assets, attracting multinational technology companies hungry for skilled programmers, technicians, and engineers.…

  8. The Eastern Partnership

    DEFF Research Database (Denmark)

    Nielsen, Kristian L.; Vilson, Maili


    When the EU launched the Eastern Partnership (EaP) in 2009, it did so with much rhetoric about projecting its soft power into Eastern Europe. Yet today, the EU's soft power project seems to have stalled, with developments in the region being less than favourable. This article argues that the Ea...

  9. The velocity structure of a post-spreading volcanic seamount in the Southwest Sub-basin, South China Sea (United States)

    Zhang, Jie; Li, Jiabiao; Ruan, Aiguo; Yu, Zhiteng; Niu, Xiongwei


    Post-spreading magmatism is extremely strong in the South China Sea and it is common feature for the pacific area (e.g. Castillo et al., 2010). Such seamounts formed by the post-spreading magmatism may provide key insights into a unique mechanism of strong magmatism without mantle convection as well as the crustal emplacement (e.g. Baloga et al., 1995; Kipf et al., 2013). We conducted a seismic refraction survey over an axial seamount (Longnan Seamount) in the Southwest Sub-basin, South China Sea in 2010. Results show that the post-spreading axial seamount is mainly formed by an extrusive process. Low upper-crustal velocities observed under the seamount are attributed to volcaniclastic rocks and high-porosity basalts. Velocity models reveal the lack of a large root and a relative high-velocity layer 3 underlying the seamount. The origin of axial seamounts is supposed to be buoyant decompression melting mechanism (Castillo et al., 2010; Meng and Zhang, 2014). This research was granted by the Natural Science Foundation of China (91028006, 91228205), the Scientific Research Fund of the Second Institute of Oceanography, SOA (JG1602) and the National Programme on Global Change and Air-Sea Interaction, SOA (GASI-GEOGE-01). References Castillo, P. R., Clague, D. A., Davis, A. S., et al., 2010. Petrogenesis of Davidson Seamount lavas and its implications for fossil spreading center and intraplate magmatism in the eastern Pacific. Geochemistry, Geophysics, Geosystems, 11, Q02005, doi:10.1029/2009GC002992 Baloga, S., Spudis, P. D. and Guest, J. E., 1995. The dynamics of rapidly emplaced terrestrial lava flows and implications for planetary volcanism. J. Geophys. Res., 100 (B12), 24509-24519. Kipf, A, Hauff, F., Werner, R., et al., 2014. Seamounts off the West Antarctic margin: A case for non-hotspot driven intraplate volcanism. Gondwana Res., 25 (4), 1660-1679. Meng, L., Zhang, J., 2014. The magmatic activity mechanism of the fossil spreading center in the Southwest sub

  10. Petrographic features of Middle-Late Triassic volcanic rocks of the Transdanubian Range and their comparison to contemporaneous volcanic rocks of the Southern Alps (United States)

    Farics, Éva; Józsa, Sándor; Haas, János


    During the early stage of the Alpine plate tectonic cycle, the Transdanubian Range Unit was located close to the area of the Southern Alps; they were situated at the western margin of the Neotethys. Ocean began opening in the Middle Triassic. Our aim is to present and evaluate the petrographic characteristics of the Middle to Late Triassic volcanic rocks of the Transdanubian Range formed in an extensional regime of the ocean margin and compare them to coeval volcanic formations of the Southern Alps formed in similar geodynamic settings. Andesite (porphyric pilotaxitic texture, with plagioclase and hypersthene, subordinately augite and biotite phenocrysts) is the dominant volcanic rock type in the NE part of the Transdanubian Range (Eastern Bakony - Balatonfő and Buda Hills, which occur as dikes (Buda Hills) and lava flows (Szár Hill). Other volcanic rocks occur only as pebble populations in Eocene basal conglomerates in Buda Hills or Middle-Late Triassic volcanoclastites in the Eastern Bakony and Zsámbék basin. We defined the following rock types: amafitic andesite/microdiorite (consist of two populations of oriented plagioclase and only small abundant glassy groundmass); microdiorite (microophitic texture with large hypersthene, which has plagioclase inclusions in it); trachyte or latite (more primary K-feldspar and less plagioclase phenocrysts with microphenocrysts of augite and biotite); basalt (vesicular texture with pseudomorph after plagioclase, pyroxene and olivine phenocrysts); microdolerite (intergranular texture with pseudomorph after xenomorphic mafic minerals and plagioclase); aplite (microholocrystalline and micropoikilite texture with well-crystallized groundmass; quartz, K-feldspar and biotite crystals); rhyolite (dark and light flow banding and has poorly-developed micropoikilite texture with quartz, K-feldspar and biotite crystals); rhyolite tuff (ignimbrit texture with plagioclase, K-feldspar and biotite as well as lithic fragments - andesite

  11. Late Pleistocene-Holocene Volcanism of the Mexico Basin and Assessment of Volcanic Hazards in One of the World’s Largest Cities (United States)

    Layer, P. W.; Macías, J.; Arce, J.; García, F.


    The Mexico City metropolitan area is home to more than 22 million people living in sight of, or living on, several volcanoes that either are currently active or show evidence of Late Pleistocene-Holocene activity (e.g., pyroclastic flows, debris avalanches and lahars). The volcanic rocks are located in five main belts or ranges: Sierra Nevada, Sierra de las Cruces, Sierra Guadalupe, Sierra de Santa Catarina, and the Chichinautzin Volcanic Field which surround the Mexico Basin and belong to the Trans-Mexican Volcanic Belt, preserving approx. 14 Ma of geologic history. Much attention has been devoted to the youngest of the volcanoes such as Popocatépetl in the Sierra Nevada which resumed activity in 1994-present and Chichinautzin which includes the 1600 year bp Xitle volcano. Surprisingly, the pre-Holocene history is not well constrained in the Mexico City area, due of the lack of detailed mapping coupled with high precision geochronology. Our new 40Ar/39Ar and petrologic data and detailed mapping focus on the earliest history of these volcanic systems and their temporal, spatial and geochemical evolution. For example, data from Tlaloc and Telapón volcanoes in the Sierra Nevada show at least two significant periods of edifice building (1.0 to 1.5 Ma and 0 to 400 ka) with an apparent long period of quiescence that clearly suggests that volcanism in the region did not migrate from north to south but that it has a more complex evolution that continues to pose a serious threat to the population of Mexico City. In addition, a 450 ka age, based on dome and pumice dating, constrains the timing of a major sector collapse of Iztaccíhuatl volcano that produced a Mt. St. Helens - sized debris avalanche deposit towards the present metropolitan area of the City of Puebla. In the Sierra de las Cruces Range, volcanic centers do show a north-south age progression from ~5 Ma, cumulating with the Zempoala edifice collapse approximately 900 ka, producing lahars and block and ash

  12. Submarine Arc Volcanism in the Southern Mariana Arc: Results of Recent ROV studies (United States)

    Nichols, A. R.; Tamura, Y.; Stern, R. J.; Embley, R. W.; Hein, J. R.; Jordan, E.; Ribeiro, J. M.; Sica, N.; Kohut, E. J.; Whattam, S. A.; Hirahara, Y.; Senda, R.; Nunokawa, A.


    The submarine Diamante cross-arc volcanoes (~16°N) and the Sarigan-Zealandia Bank Multi-Volcano Complex (SZBMVC; ~16°45’N), north and south, respectively, of Anatahan Island in the southern Mariana Arc, were studied during several dives in June 2009 using the ROV Hyper-Dolphin, cruise NT09-08 (R/V Natsushima); neither has been studied in detail before. The data collected provide a new perspective on how the subduction factory operates to complement previous studies on other cross-arc volcanic chains in the Izu-Bonin-Mariana Arc. The Diamante complex consists of three major edifices, two cones (West and Central Diamante) and a more complex caldera-like edifice at the volcanic front (East Diamante). West and Central Diamante are basaltic volcanoes but East Diamante has a more complex history. Our studies indicate initial construction of a basaltic volcano. Magmatic evolution led to a violent caldera-forming and quieter dome-building events. Post-caldera quiescence allowed a carbonate platform to grow, now preserved on the eastern caldera wall. Felsic magma or hot rock provides a heat source for an active hydrothermal field associated with felsic domes in the caldera, which NOAA investigators discovered in 2004. A new type of hydrothermal deposit was discovered in the hydrothermal field, consisting of large sulfide-sulfate mounds topped by bulbous constructions of low-temperature Fe and Mn oxides. Vents on the mounds were observed to emit shimmering water. The SZBMVC consists of six closely spaced edifices whose loci are aligned along two parallel trends, one along the volcanic front (Zealandia Bank, Sarigan and South Sarigan), and one about 15 km west towards the rear-arc (Northwest Zealandia, West Zealandia and West Sarigan). Zealandia Bank dives revealed that, as with East Diamante, initial activity was basaltic and became more evolved with time. The western half of Zealandia Bank is dominated by felsic lavas centered on a small (~2 km diameter) caldera and

  13. Crustal thickness and composition beneath the High Lava Plains of Eastern Oregon from teleseismic receiver functions (United States)

    Eagar, K. C.; Fouch, M. J.; James, D. E.; Carlson, R. W.


    The nature of the crust beneath the High Lava Plains of eastern Oregon is fundamental for understanding the origins of widespread Cenozoic volcanism in the region. Eruptions of flood basalts in the southern Cascadian back arc peaked ~17-15 Ma, and were followed by distributed bimodal volcanism along two perpendicular migrating tracks; the Snake River Plain and the High Lava Plains. The orientations of eruptive centers have led to several competing hypotheses about their cause, including a deep mantle plume, slab retreat and asthenospheric inflow, lithospheric delamination, and lithospheric extension. The goal of this project is to constrain the nature, geometry, and depth of the Moho across the High Lava Plains, which will shed light on questions regarding crustal influence on melt generation and differentiation and the degree of magmatic underplating. In this study, we analyze teleseismic receiver functions from 118 stations of the High Lava Plains temporary broadband array, 34 nearby EarthScope/USArray stations, and 5 other regional broadband stations to determine bulk crustal features of thickness (H) and Vp/Vs ratio (κ). Applying the H-κ stacking method, we search for the best-fitting solution of timing predictions for direct and multiple P-to-S conversions from the Moho interface. Converting Vp/Vs to Poisson ratio, which is dependent primarily upon rock composition, allows for comparison with other direct geological observations. Preliminary results show that the crust of the High Lava Plains is relatively thin (~31 km) with a very sharp gradient to thicker crust (~42 km) at the western edge of the Owyhee Plateau in southwestern Idaho. This gradient is co-located with the western margin of Precambrian North America and is in the vicinity of the Jordan Craters volcanic center. The sharp topography of the Moho might have been a factor in melt migration beneath this area. West of the High Lava Plains, the crust thickens to ~40 km into the Cascade volcanic arc

  14. Volcanism and an Ancient Atmosphere on the Moon (United States)

    Taylor, G. J.


    One of the distinguishing features of the Moon is its flimsy atmosphere, which has a pressure 300 trillion times smaller than Earth's pressure at sea level. The density is so low that gas molecules rarely collide and readily escape into space. Micrometeorites hit the surface at their full cosmic velocities and the solar wind implants hydrogen, helium, carbon, and other elements into the dusty lunar surface. This airless body has been like this for billions of years. However, Debra Needham (NASA Marshall Space Flight Center) and David Kring (Center for Lunar Science and Exploration at the Lunar and Planetary Institute, Houston) show that the Moon probably had a significant atmosphere for about 70 million years during the peak production rate of the lunar maria 3.5 billion years ago. The maria (dark regions that decorate the lunar nearside) are composed of overlapping lava flows. Needham and Kring show that the lavas would have transported sufficient volatiles such as carbon monoxide, sulfur gases, and H2O to the surface to create an atmosphere. The volcanism would have released about 20 quadrillion kilograms of gases, creating an atmosphere with a pressure 50% higher than in the current Martian atmosphere. Calculations show that the loss rate to space from this atmosphere would have been 10 kilograms per second, implying that it would take about 70 million years to remove this volcanically produced atmosphere.

  15. Caldera volcanoes of the Taupo Volcanic Zone, New Zealand (United States)

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


    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

  16. Volcanic Hazards Assessment at the Island of Ischia, Within the Neapolitan Area (Italy) (United States)

    Orsi, G.; de Vita, S.; Marotta, E.; Sansivero, F.


    The island of Ischia is one of the three active volcanoes of the Neapolitan area. It hosts a permanent population of about 50,000 people, which increases up to 200,000 in summer time. The volcanic hazard of the island is extremely high also because of its explosive character. The intense population of both island and surrounding Neapolitan area, thriving farms and a complex trade-network with the near city of Naples, contribute to determine a high volcanic risk in the area. Volcanic hazards assessment, including possible eruption scenarios, is critically based on knowledge of the volcano past behavior and the definition of its present structural setting. Volcanism at Ischia began prior to 150 ka bp and continued until the 1302 A.D. last eruption. It is dominated by the Mt. Epomeo Green Tuff caldera-forming eruption (55 ka), followed by resurgence, which has caused a net uplift of the central part of the island of about 900 m over the past 33 ka. The most recent period of activity began at about 10 ka, with volcanism mainly concentrated around 5.5 ka and in the past 2.9 ka. During the past 5.5 ka, about 45 effusive and explosive eruptions took place, with almost all the vents located in the eastern portion of the island. The time-space vents distribution has been directly related to a simple-shearing block resurgence mechanism. Effusive eruptions emplaced lava domes and lava flows moving along the valleys of the north-eastern sector of the island. Explosive eruptions, both magmatic and phreatomagmatic, generated tuff cones, tuff rings and variably dispersed pyroclastic-fall and -current deposits in the eastern sector of the island. Areal distribution maps of these deposits do not permit to estimate the magnitude of the explosive eruptions, as a large amount of tephra was deposited into the sea. Maps of the frequency of deposition show the areas that more frequently have been covered by fallout deposits and invaded by pyroclastic currents. Three classes of frequency

  17. Volcanic Ash Advisory Database, 1983-2003 (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanic ash is a significant hazard to aviation and can also affect global climate patterns. To ensure safe navigation and monitor possible climatic impact, the...

  18. Palaeoclimate: Volcanism caused ancient global warming (United States)

    Meissner, Katrin J.; Bralower, Timothy J.


    A study confirms that volcanism set off one of Earth's fastest global-warming events. But the release of greenhouse gases was slow enough for negative feedbacks to mitigate impacts such as ocean acidification. See Letter p.573

  19. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    The occurrence of submarine silicic volcanics is rare at the mid-oceanic ridges, abyssal depths, seamounts and fracture zones. Hydrothermal processes are active in submarine silicic environments and are associated with host ores of Cu, Au, Ag, Pb...

  20. Tectonic geomorphology and volcano-tectonic interaction in the eastern boundary of the Southern Cascades (Hat Creek Graben region, California, USA

    Directory of Open Access Journals (Sweden)

    Engielle Mae Raot-raot Paguican


    Full Text Available The eastern boundary of the Southern Cascades (Hat Creek Graben region, California, USA, is an extensively faulted volcanic corridor between the Cascade Range and Modoc Plateau. The east-west extending region is in the transition zone between the convergence and subduction of the Gorda Plate underneath the North American Plate; north-south shortening within the Klamath Mountain region; and transcurrent movement in the Walker Lane. We describe the geomorphological and tectonic features, their alignment and distribution, in order to understand the tectonic geomorphology and volcano-tectonic relationships. One outcome of the work is a more refined morpho-structural description that will affect future hazard assessment in the area.A database of volcanic centers and structures was created from interpretations of topographic models generated from satellite images. Volcanic centers in the region were classified by morphological type into cones, sub-cones, shields and massifs. A second classification by height separated the bigger and smaller edifices and revealed an evolutionary trend. Poisson Nearest Neighbor analysis shows that bigger volcanoes are spatially dispersed while smaller ones are clustered. Using volcano centroid locations, about 90 lineaments consisting of at least three centers within 6km of one another were found, revealing that preferential north-northwest directed pathways control the transport of magma from the source to the surface, consistent with the strikes of the major fault systems. Most of the volcano crater openings are perpendicular to the maximum horizontal stress, expected for extensional environments with dominant normal regional faults. These results imply that the extension of the Hat Creek Graben region and impingement of the Walker Lane is accommodated mostly by extensional faults and partly by the intrusions that formed the volcanoes. Early in the history of a volcano or volcano cluster, melt produced at depth in the

  1. Volcanic rock properties control sector collapse events (United States)

    Hughes, Amy; Kendrick, Jackie; Lavallée, Yan; Hornby, Adrian; Di Toro, Giulio


    Volcanoes constructed by superimposed layers of varying volcanic materials are inherently unstable structures. The heterogeneity of weak and strong layers consisting of ash, tephra and lavas, each with varying coherencies, porosities, crystallinities, glass content and ultimately, strength, can promote volcanic flank and sector collapses. These volcanoes often exist in areas with complex regional tectonics adding to instability caused by heterogeneity, flank overburden, magma movement and emplacement in addition to hydrothermal alteration and anomalous geothermal gradients. Recent studies conducted on the faulting properties of volcanic rocks at variable slip rates show the rate-weakening dependence of the friction coefficients (up to 90% reduction)[1], caused by a wide range of factors such as the generation of gouge and frictional melt lubrication [2]. Experimental data from experiments conducted on volcanic products suggests that frictional melt occurs at slip rates similar to those of plug flow in volcanic conduits [1] and the bases of mass material movements such as debris avalanches from volcanic flanks [3]. In volcanic rock, the generation of frictional heat may prompt the remobilisation of interstitial glass below melting temperatures due to passing of the glass transition temperature at ˜650-750 ˚C [4]. In addition, the crushing of pores in high porosity samples can lead to increased comminution and strain localisation along slip surfaces. Here we present the results of friction tests on both high density, glass rich samples from Santaguito (Guatemala) and synthetic glass samples with varying porosities (0-25%) to better understand frictional properties underlying volcanic collapse events. 1. Kendrick, J.E., et al., Extreme frictional processes in the volcanic conduit of Mount St. Helens (USA) during the 2004-2008 eruption. J. Structural Geology, 2012. 2. Di Toro, G., et al., Fault lubrication during earthquakes. Nature, 2011. 471(7339): p. 494-498. 3

  2. Volcanism and associated hazards: the Andean perspective

    Directory of Open Access Journals (Sweden)

    R. I. Tilling


    Full Text Available Andean volcanism occurs within the Andean Volcanic Arc (AVA, which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions" recognized worldwide that have occurred from the Ordovician to the Pleistocene.

    The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru. The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km3 in 1985 of Nevado del Ruiz (Colombia killed about 25 000 people – the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent

  3. Using high-precision 40Ar/39Ar geochronology to understand volcanic hazards within the Rio Grande rift and along the Jemez lineament, New Mexico (United States)

    Zimmerer, M. J.; McIntosh, W. C.; Heizler, M. T.; Lafferty, J.


    High-precision Ar/Ar ages were generated for late Quaternary volcanic fields in the Rio Grande rift and along the Jemez Lineament, New Mexico, to assess the time-space patterns of volcanism and begin quantifying volcanic hazards for the region. The published chronology of most late Quaternary volcanic centers in the region is not sufficiently precise, accurate, or complete for a comprehensive volcanic hazard assessment. Ar/Ar ages generated as part of this study were determined using the high-sensitivity, multi-collector ARGUS VI mass spectrometer, which provides about an order of magnitude more precise isotopic measurements compared to older generation, single-detector mass spectrometers. Ar/Ar ages suggest an apparent increase in eruption frequency during the late Quaternary within the Raton-Clayton volcanic field, northeastern NM. Only four volcanoes erupted between 426±8 and 97±3 ka. Contrastingly, four volcanoes erupted between 55±2 and 32±5 ka. This last eruptive phase displays a west to east migration of volcanism, has repose periods of 0 to 17 ka, and an average recurrence rate of 1 eruption per 5750 ka. The Zuni-Bandera volcanic field, west-central NM, is composed of the ~100 late Quaternary basaltic vents. Preliminary results suggest that most of the Chain of Craters, the largest and oldest part of the Zuni-Bandera field, erupted between ~100 and 250 ka. Volcanism then migrated to the east, where published ages indicate at least seven eruptions between 50 and 3 ka. Both volcanic fields display a west to east migration of volcanism during the last ~500 ka, although the pattern is more pronounced in the Zuni-Bandera field. A reassessment of low-precision published ages for other late Quaternary volcanic fields in region indicates that most fields display a similar west to east migration of volcanism during the last ~500 ka. One possible mechanism to explain the observed patterns of volcanism is the westward migration of the North American plate relative

  4. Timing and composition of continental volcanism at Harrat Hutaymah, western Saudi Arabia (United States)

    Duncan, Robert A.; Kent, Adam J R; Thornber, Carl; Schliedler, Tyler D; Al-Amri, Abdullah M


    Harrat Hutaymah is an alkali basalt volcanic field in north-central Saudi Arabia, at the eastern margin of a large Neogene continental, intraplate magmatic province. Lava flow, tephra and spatter cone compositions in the field include alkali olivine basalts and basanites. These compositions contrast with the predominantly tholeiitic, fissure-fed basalts found along the eastern margin of the Red Sea. The Hutaymah lava flows were erupted through Proterozoic arc-associated plutonic and meta-sedimentary rocks of the Arabian shield, and commonly contain a range of sub-continental lithospheric xenoliths, although the lavas themselves show little indication of crustal contamination. Previous radiometric dating of this volcanic field (a single published K–Ar age; 1.8 Ma) is suspiciously old given the field measurement of normal magnetic polarity only (i.e. Brunhes interval, ≤ 780 Ka). We report new age determinations on 14 lava flows by the 40Ar–39Ar laser step heating method, all younger than ~ 850 Ka, to better constrain the time frame of volcanism, and major, trace and rare earth element compositions to describe the chemical variation of volcanic activity at Harrat Hutaymah. Crystal fractionation was dominated by olivine ± clinopyroxene at a range of upper mantle and crustal pressures. Rapid ascent and eruption of magma is indicated by the array of lower crustal and lithospheric xenoliths observed in lava flows and tephra. Modeling suggests 1–7% melting of an enriched asthenospheric mantle source occurred beneath Harrat Hutaymah under a relatively thick lithospheric cap (60–80 km).

  5. Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET

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    G. Pappalardo


    Full Text Available The eruption of the Icelandic volcano Eyjafjallajökull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET. Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D distribution of the Eyjafjallajökull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010. All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio are stored in the EARLINET database available at A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL. After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May, material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on

  6. Formation of the Yandangshan volcanic-plutonic complex (SE China) by melt extraction and crystal accumulation (United States)

    Yan, Li-Li; He, Zhen-Yu; Jahn, Bor-ming; Zhao, Zhi-Dan


    The association of volcanic and shallow plutonic rocks in caldera may provide important clues to the geochemical evolution of silicic magma systems. The Yandangshan caldera is a typical example of late Mesozoic volcanic-plutonic complex in SE China. It is composed of a series of rhyolitic extrusives and subvolcanic intrusions of porphyritic quartz syenites. In this work, we conducted petrological and geochemical studies, as well as zircon dating, on the coexisting volcanic and plutonic rocks from the Yandangshan caldera. The results of SHRIMP and LA-ICP-MS zircon U-Pb dating revealed that the crystallization of the rhyolitic extrusives and subvolcanic intrusions was contemporaneous within analytical errors and in a short period (104-98 Ma). Geochemically, the volcanic rocks are characterized by high Rb/Sr and Rb/Ba ratios and depletion in Ba, Sr, P, Eu and Ti, while the shallow plutons show high K, Ba, Al, Fe and low Rb/Sr and Rb/Ba ratios with insignificant negative Eu anomalies. The volcanic and plutonic rocks have a similar range of zircon Hf isotopic compositions (εHf(t) = - 10.0 to + 1.5) and TDM2 model ages of 2.10-1.23 Ga. They also have comparable whole-rock Sr and Nd isotopic compositions ((87Sr/86Sr)i = 0.7084-0.7090; εNd(t) = - 7.8 to - 6.5) and zircon oxygen isotopic compositions (δ18O mainly = 4.5 to 6.0‰). We argue that the volcanic-plutonic complex of the Yandangshan caldera was formed by reworking of Paleoproterozoic lower crusts in the eastern Cathaysia block, and that the complex could be linked by fractional crystallization and crystal accumulation in a shallow magma chamber. The volcanic rocks represent the highly fractionated end-member, whereas the subvolcanic intrusions of porphyritic quartz syenites could be the residual crystal mushes. This case study could have a general implication for the genetic relationship between volcanic and shallow plutonic rocks in calderas.

  7. Shape measurements of volcanic particles by CAMSIZER


    Lo Castro, Maria Deborah; Andronico, Daniele; Nunnari, Giuseppe; Spata, Alessandro; Torrisi, Alessio


    The shape of volcanic particles is an important parameter holding information related to physical and geochemical processes. The study of particle shape may help improving knowledge on the main eruptive processes (fragmentation, transport and sedimentation) during explosive activity. In general, volcanic ash is formed by different components, namely juvenile, lithic and crystal particles, each one characterized by peculiar morphology. Moreover, quantifying the shape of pyroclasts is needed by...

  8. About the Mechanism of Volcanic Eruptions

    CERN Document Server

    Nechayev, Andrei


    A new approach to the volcanic eruption theory is proposed. It is based on a simple physical mechanism of the imbalance in the system "magma-crust-fluid". This mechanism helps to explain from unified positions the different types of volcanic eruptions. A criterion of imbalance and magma eruption is derived. Stratovolcano and caldera formation is analyzed. High explosive eruptions of the silicic magma is discussed

  9. Medical effects of volcanic eruptions (United States)

    Baxter, Peter J.


    Excluding famine and tsunamis, most deaths in volcanic eruptions have been from pyroclastic flows and surges (nuées ardentes) and wet debris flows (lahars). Information on the causes of death and injury in eruptions is sparse but the available literature is summarised for the benefit of volcanologists and emergency planners. In nuées, thermal injury may be at least as important as asphyxia in causing immediate deaths. The high temperature of the gases and entrained particles readily causes severe burns to the skin and the air passages and the presence of both types of injury in an individual may combine to increase the delayed mortality risk from respiratory complications or from infection of burns. Trauma from missiles or body displacement is also common, but the role of asphyxiant or irritant gases, and steam, remains unclear. The ratio of dead: injured is much higher than in other natural disasters. At the periphery of a nuée being protected inside buildings which remain intact appears to greatly increase the chances of survival. In lahars, infected wounds and crush injury are the main delayed causes of death, and the scope for preventive measures, other than evacuation, is small. The evidence from Mount St. Helens, 1980, and other major eruptions indicates that, although mortality is high within the main zone of devastation and in the open, emergency planning should concentrate on the periphery of a nuée where preventive measures are feasible and could save many lives in densely populated areas.

  10. Late Ediacaran volcano-sedimentary successions of southern Sinai (Egypt): tracing the evolution from late- to post-collisional volcanism and its relation to A-type rocks (United States)

    Azer, Mokhles; Asimow, Paul; Obeid, Mohamed; Price, Jason; Wang, Max


    andesite and dacite have characteristics of low-silica adakitic rocks. The evolved rhyolites of the second phase have characteristics that are transitional to alkaline, A-type magmas but this is attributed to extensive fractionation and does not require a change in the tectonic regime. Although their eruption in a post-collisional setting, the Sahiya, Iqna Shar'a and Meknas volcanic suites all display geochemical fingerprints of subduction influence, interpreted to reflect remelting of previously formed arc material ca. 750-650 Ma in age. The formation of Late Ediacaran post-collisional lavas and tuffs in southern Sinai can be understood as a consequence of upwelling of hot asthenospheric material during thinning of the previously thickened lithosphere, leading to partial melting of mafic lower crust. The presence of inherited zircons indicates crustal contamination during evolution of the volcanic successions. Our results indicate that the studied volcanic successions correlate with the Dokhan volcanics of the northern Eastern Desert of Egypt. The earlier volcanic sequence also compares well with 625-600 Ma calc-alkaline plutonic rocks in the north Eastern Desert and Sinai, whereas the younger volcanic phase displays geochemical similarities with 610-585 Ma alkaline plutonic rocks in the north Eastern Desert and Sinai.

  11. Satellite Derived Volcanic Ash Product Inter-Comparison in Support to SCOPE-Nowcasting (United States)

    Siddans, Richard; Thomas, Gareth; Pavolonis, Mike; Bojinski, Stephan


    In support of aeronautical meteorological services, WMO organized a satellite-based volcanic ash retrieval algorithm inter-comparison activity, to improve the consistency of quantitative volcanic ash products from satellites, under the Sustained, Coordinated Processing of Environmental Satellite Data for Nowcasting (SCOPEe Nowcasting) initiative (http:/ nowcasting_en.php). The aims of the intercomparison were as follows: 1. Select cases (Sarychev Peak 2009, Eyjafyallajökull 2010, Grimsvötn 2011, Puyehue-Cordón Caulle 2011, Kirishimayama 2011, Kelut 2014), and quantify the differences between satellite-derived volcanic ash cloud properties derived from different techniques and sensors; 2. Establish a basic validation protocol for satellite-derived volcanic ash cloud properties; 3. Document the strengths and weaknesses of different remote sensing approaches as a function of satellite sensor; 4. Standardize the units and quality flags associated with volcanic cloud geophysical parameters; 5. Provide recommendations to Volcanic Ash Advisory Centers (VAACs) and other users on how to best to utilize quantitative satellite products in operations; 6. Create a "road map" for future volcanic ash related scientific developments and inter-comparison/validation activities that can also be applied to SO2 clouds and emergent volcanic clouds. Volcanic ash satellite remote sensing experts from operational and research organizations were encouraged to participate in the inter-comparison activity, to establish the plans for the inter-comparison and to submit data sets. RAL was contracted by EUMETSAT to perform a systematic inter-comparison of all submitted datasets and results were reported at the WMO International Volcanic Ash Inter-comparison Meeting to held on 29 June - 2 July 2015 in Madison, WI, USA (http:/ /cimss.ssec.wisc.edujmeetings/vol_ash14). 26 different data sets were submitted, from a range of passive imagers and spectrometers and

  12. 2-D tomography of volcanic CO2 from scanning hard-target differential absorption lidar: the case of Solfatara, Campi Flegrei (Italy) (United States)

    Queißer, Manuel; Granieri, Domenico; Burton, Mike


    Solfatara is part of the active volcanic zone of Campi Flegrei (Italy), a densely populated urban area where ground uplift and increasing ground temperature are observed, connected with rising rates of CO2 emission. A major pathway of CO2 release at Campi Flegrei is diffuse soil degassing, and therefore quantifying diffuse CO2 emission rates is of vital interest. Conventional in situ probing of soil gas emissions with accumulation chambers is accurate over a small footprint but requires significant time and effort to cover large areas. An alternative approach is differential absorption lidar, which allows for a fast and spatially integrated measurement. Here, a portable hard-target differential absorption lidar has been used to acquire horizontal 1-D profiles of column-integrated CO2 concentration at the Solfatara crater. To capture heterogenic features in the CO2 distribution, a 2-D tomographic map of the CO2 distribution has been inverted from the 1-D profiles. The scan was performed one-sided, which is unfavorable for the inverse problem. Nonetheless, the result is in agreement with independent measurements and furthermore confirms an area of anomalous CO2 degassing along the eastern edge as well as the center of the Solfatara crater. The method may have important implications for measurements of degassing features that can only be accessed from limited angles, such as airborne sensing of volcanic plumes. CO2 fluxes retrieved from the 2-D map are comparable, but modestly higher than emission rates from previous studies, perhaps reflecting an increase in CO2 flux or a more integrated measurement or both.

  13. Geology and metallogeny of the Ar Rayn terrane, eastern Arabian shield: Evolution of a Neoproterozoic continental-margin arc during assembly of Gondwana within the East African orogen (United States)

    Doebrich, J.L.; Al-Jehani, A. M.; Siddiqui, A.A.; Hayes, T.S.; Wooden, J.L.; Johnson, P.R.


    The Neoproterozoic Ar Rayn terrane is exposed along the eastern margin of the Arabian shield. The terrane is bounded on the west by the Ad Dawadimi terrane across the Al Amar fault zone (AAF), and is nonconformably overlain on the east by Phanerozoic sedimentary rocks. The terrane is composed of a magmatic arc complex and syn- to post-orogenic intrusions. The layered rocks of the arc, the Al Amar group (>689 Ma to ???625 Ma), consist of tholeiitic to calc-alkaline basaltic to rhyolitic volcanic and volcaniclastic rocks with subordinate tuffaceous sedimentary rocks and carbonates, and are divided into an eastern and western sequence. Plutonic rocks of the terrane form three distinct lithogeochemical groups: (1) low-Al trondhjemite-tonalite-granodiorite (TTG) of arc affinity (632-616 Ma) in the western part of the terrane, (2) high-Al TTG/adakite of arc affinity (689-617 Ma) in the central and eastern part of the terrane, and (3) syn- to post-orogenic alkali granite (607-583 Ma). West-dipping subduction along a trench east of the terrane is inferred from high-Al TTG/adakite emplaced east of low-Al TTG. The Ar Rayn terrane contains significant resources in epithermal Au-Ag-Zn-Cu-barite, enigmatic stratiform volcanic-hosted Khnaiguiyah-type Zn-Cu-Fe-Mn, and orogenic Au vein deposits, and the potential for significant resources in Fe-oxide Cu-Au (IOCG), and porphyry Cu deposits. Khnaiguiyah-type deposits formed before or during early deformation of the Al Amar group eastern sequence. Epithermal and porphyry deposits formed proximal to volcanic centers in Al Amar group western sequence. IOCG deposits are largely structurally controlled and hosted by group-1 intrusions and Al Amar group volcanic rocks in the western part of the terrane. Orogenic gold veins are largely associated with north-striking faults, particularly in and near the AAF, and are presumably related to amalgamation of the Ar Rayn and Ad Dawadimi terranes. Geologic, structural, and metallogenic

  14. Geologic and geophysical investigations of the Zuni-Bandera volcanic field, New Mexico (United States)

    Ander, M. E.; Heiken, G.; Eichelberger, J.; Laughlin, A. W.; Huestis, S.


    A positive, northeast-trending gravity anomaly, 90 km long and 30 km wide, extends southwest from the Zuni uplift, New Mexico. The Zuni-Bandera volcanic field, an alignment of 74 basaltic vents, is parallel to the eastern edge of the anomaly. Lavas display a bimodal distribution of tholeiitic and alkalic compositions, and were erupted over a period from 4 Myr to present. A residual gravity profile taken perpendicular to the major axis of the anomaly was analyzed using linear programming and ideal body theory to obtain bounds on the density contrast, depth, and minimum thickness of the gravity body.

  15. Multi-disciplinary approach in volcanic areas: case study of Kamchatka, Far East of Russia (United States)

    Kuznetsova, Elena


    Volcanic ash is associated with a considerable proportion of the Earth's land surface. At the same time, it is estimated that 15% of the land surface is affected by permafrost and glacial ice. As a consequences volcanic ash may play an important role in the aggradation and degradation of cold regions (Kellerer-Pirklbauer et al., 2007; Froese et al., 2008). An understanding of the influence of volcanic ash on these frozen areas allows for more accurate prediction of their stability in the future and provides a better knowledge of the factors affecting past climates, soils and soil stability. Vital to making accurate predictions is an understanding of the thermal properties of volcanic ash (Juen et al., 2013). For example, even for the same region of Kamchatka in eastern Russia volcanic ash may have not only different ages, different chemical composition of the glass, but also different weathering stages, mineralogical composition, and water saturation, furthermore, these ashes may be permanently frozen or unfrozen, all of which may affect their thermal properties (Kuznetsova & Motenko, 2014). These differences might be the reason why the critical thickness of tephra, at which the effect on ice and snow is rather insulating than ablative, for the volcanic material from different volcanoes may vary so much. The determined values of critical thickness deviate from 24 mm reported by Driedger (1980) for the glaciers at Mt. St. Helens, USA, and by (Manville et al., 2000) for tephra erupted in 1996 by Mt. Ruapehu, New Zealand, to Chile, reported by Kirkbride and Dugmore (2003) and by Brock et al. (2007). So far the reasons of disparity are not known. Ayris and Delmelle (2012) assumed that the particle size and porosity might be the reason. Taking into considerations that during ablation period tephra covering the glaciers is wet, thermal conductivity of this material should not be overlooked (Kuznetsova et al., 2012). Of particular importance in understanding the thermal

  16. Sensitivity of the regional climate in the Middle East and North Africa to volcanic perturbations (United States)

    Dogar, Muhammad Mubashar; Stenchikov, Georgiy; Osipov, Sergey; Wyman, Bruce; Zhao, Ming


    The Middle East and North Africa (MENA) regional climate appears to be extremely sensitive to volcanic eruptions. Winter cooling after the 1991 Pinatubo eruption far exceeded the mean hemispheric temperature anomaly, even causing snowfall in Israel. To better understand MENA climate variability, the climate responses to the El Chichón and Pinatubo volcanic eruptions are analyzed using observations, NOAA/National Centers for Environmental Prediction Climate Forecast System Reanalysis, and output from the Geophysical Fluid Dynamics Laboratory's High-Resolution Atmospheric Model. A multiple regression analysis both for the observations and the model output is performed on seasonal summer and winter composites to separate out the contributions from climate trends, El Niño-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Indian summer monsoon, and volcanic aerosols. Strong regional temperature and precipitation responses over the MENA region are found in both winter and summer. The model and the observations both show that a positive NAO amplifies the MENA volcanic winter cooling. In boreal summer, the patterns of changing temperature and precipitation suggest a weakening and southward shift of the Intertropical Convergence Zone, caused by volcanic surface cooling and weakening of the Indian and West African monsoons. The model captures the main features of the climate response; however, it underestimates the total cooling, especially in winter, and exhibits a different spatial pattern of the NAO climate response in MENA compared to the observations. The conducted analysis sheds light on the internal mechanisms of MENA climate variability and helps to selectively diagnose the model deficiencies.

  17. A method for multi-hazard mapping in poorly known volcanic areas: an example from Kanlaon (Philippines) (United States)

    Neri, M.; Le Cozannet, G.; Thierry, P.; Bignami, C.; Ruch, J.


    Hazard mapping in poorly known volcanic areas is complex since much evidence of volcanic and non-volcanic hazards is often hidden by vegetation and alteration. In this paper, we propose a semi-quantitative method based on hazard event tree and multi-hazard map constructions developed in the frame of the FP7 MIAVITA project. We applied this method to the Kanlaon volcano (Philippines), which is characterized by poor geologic and historical records. We combine updated geological (long-term) and historical (short-term) data, building an event tree for the main types of hazardous events at Kanlaon and their potential frequencies. We then propose an updated multi-hazard map for Kanlaon, which may serve as a working base map in the case of future unrest. The obtained results extend the information already contained in previous volcanic hazard maps of Kanlaon, highlighting (i) an extensive, potentially active ~5 km long summit area striking north-south, (ii) new morphological features on the eastern flank of the volcano, prone to receiving volcanic products expanding from the summit, and (iii) important riverbeds that may potentially accumulate devastating mudflows. This preliminary study constitutes a basis that may help local civil defence authorities in making more informed land use planning decisions and in anticipating future risk/hazards at Kanlaon. This multi-hazard mapping method may also be applied to other poorly known active volcanoes.

  18. Lower Pliensbachian caldera volcanism in high-obliquity rift systems in the western North Patagonian Massif, Argentina (United States)

    Benedini, Leonardo; Gregori, Daniel; Strazzere, Leonardo; Falco, Juan I.; Dristas, Jorge A.


    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.

  19. Anisotropy of Magnetic Susceptibility Studies in Lava Flows of the Eastern Anatolia Region, Turkey (United States)

    Ucar, Hakan; Cengiz Cinku, Mualla


    Eastern Anatolia comprises one of the high plateaus of the Alpine-Himalaya mountain belt with an average elevation of 2 km above the sea level. Available geochronologic data indicate that the volcanism started in the south of the region around the north of Lake Van and continued towards the norths in a age interval of 15.0 Ma to 0.4 Ma. The products are exposed as stratovolcanoes like Agri, Tendurek, Suphan and Girekol with the eruption of andesitic to rhyolitic lavas, ignimbrites and basaltic lava flows. In this study, anisotropy of magnetic susceptibility measurements were carried out on different lava flows (Tendurek, Girekol and Suphan) to determine the flow direction of lavas. It has been shown that the direction of maximum susceptibility is associated with magma flow direction in the vertical direction, while a horizontal flow direction is predicted for the volcano structure of Suphan. Anisotropy of magnetic measurements show a trend of lineation towards the center of the projection and shallow-dipping foliations which are largely scattered.

  20. Development of the Central-Afar volcanic margin, mantle upwelling and break-up processes (United States)

    Pik, Raphaël; Bellahsen, Nicolas; Leroy, Sylvie; Stab, Martin; Ayalew, Dereje; Yirgu, Gezahegn


    Whereas the present day mantle dynamics is now well imaged by geophysical investigations, the long-term expression of mantle dynamics below rifted lithosphere is not directly recorded at the surface of the earth. Such information must therefore be extracted from non-direct manifestations of mantle upwelling, which are principally (i) the uplift of the upperlying lithosphere and (ii) the melts produced when the solidus of mantle mineral assemblages is crossed. These first order and unique evidences should therefore represent corner stones output of any geodynamic models used to deduce the interplay between mantle dynamics and surface deformations. For magmatism produced during extension of lithosphere, the dynamics of mantle upwelling can be recognized in the volumes of magmas and also in their geochremistry, which allow tracking the various types of mantle sources and the various types of mantle melting regime (P, T and intensity of partial melting). Volcanism has been closely associated with extension in the East African rift system. It is yet (and logically) heterogeneously distributed along the western, eastern and northern volcanic provinces. We have concentrated the efforts of a multidisciplinary team these last years in the northern Ethiopian volcanic province where the most important volumes of volcanism have been emplaced since 30 Ma, from Continental Flood Basalts episode to active extension along the Central Afar magmatic segment. These structural and geochemical data point out new constraints on the interplay between the upwelling of the Afar mantle plume and the style and mechanisms of extension, and imply to update and revise our understanding of the development of this volcanic margin.

  1. On the Role of Climate Forcing by Volcanic Sulphate and Volcanic Ash

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    Baerbel Langmann


    Full Text Available There is overall agreement that volcanic sulphate aerosols in the stratosphere can reduce solar radiation reaching the earth’s surface for years, thereby reducing surface temperatures, affecting global circulation patterns and generally the global climate system. However, the response of the climate system after large volcanic eruptions is not fully understood and global climate models have difficulties to reproduce the observed variability of the earth system after large volcanic eruptions until now. For geological timescales, it has been suggested that, in addition to the stratospheric climate forcing by volcanic sulphate aerosols, volcanic ash affects climate by modifying the global carbon cycle through iron fertilising the surface ocean and stimulating phytoplankton growth. This process has recently also been observed after the eruption of the volcano Kasatochi on the Aleutian Islands in summer 2008. To trigger future research on the effect of volcanic ash on the climate system via ocean iron fertilisation, this review paper describes the formation processes and atmospheric life cycles of volcanic sulphate and volcanic ash, contrasts their impact on climate, and emphasises current limitations in our understanding.

  2. Life at cold seeps : a synthesis of biogeochemical and ecological data from Kazan mud volcano, eastern Mediterranean Sea

    NARCIS (Netherlands)

    Werne, JP; Haese, RR; Zitter, T; Aloisi, G; Bouloubassi, L; Heijs, S; Fiala-Medioni, A; Pancost, RD; Damste, JSS; de Lange, G; Forney, LJ; Gottschal, JC; Foucher, JP; Mascle, J; Woodside, J


    Recent field observations have identified the widespread occurrence of fluid seepage through the eastern Mediterranean Sea floor in association with mud volcanism or along deep faults. Gas hydrates and methane seeps are frequently found in cold seep areas and were anticipated targets of the

  3. Life at cold seeps: a synthesis of biogeochemical and ecological data from Kazan mud volcano, eastern Mediterranean Sea

    NARCIS (Netherlands)

    Sinninghe Damsté, J.S.; Werne, J.P.; Zitter, T.; Haese, R.R.; Aloisi, G.; Bouloubassi, I.; Heijs, S.; Fiala-Medioni, A.; Pancost, R.D.; Lange, G.J. de; Gottschal, J.; Foucher, J.-P.; Mascle, J.; Woodside, J.


    Recent field observations have identified the widespread occurrence of fluid seepage through the eastern Mediterranean Sea floor in association with mud volcanism or along deep faults. Gas hydrates and methane seeps are frequently found in cold seep areas and were anticipated targets of the

  4. Eastern Equine Encephalitis (United States)

    ... bite of an infected mosquito. Eastern equine encephalitis (EEE) is a rare illness in humans, and only ... EEEV have no apparent illness. Severe cases of EEE (involving encephalitis, an inflammation of the brain) begin ...

  5. Backscattering and geophysical features of volcanic ridges offshore Santa Rosalia, Baja California Sur, Gulf of California, Mexico (United States)

    Fabriol, Hubert; Delgado-Argote, Luis A.; Dañobeitia, Juan José; Córdoba, Diego; González, Antonio; García-Abdeslem, Juan; Bartolomé, Rafael; Martín-Atienza, Beatriz; Frias-Camacho, Víctor


    Volcanic ridges formed by series of volcanic edifices are identified in the central part of the Gulf of California, between Isla Tortuga and La Reforma Caldera-Santa Rosalı´a region. Isla Tortuga is part of the 40-km-long Tortuga Volcanic Ridge (TVR) that trends almost perpendicular to the spreading center of the Guaymas Basin. The Rosalı´a Volcanic Ridge (RVR), older than TVR, is characterized by volcanic structures oriented towards 310°, following a fracture zone extension and the peninsular slope. It is interpreted that most of the aligned submarine volcanic edifices are developed on continental crust while Isla Tortuga lies on oceanic-like crust of the Guaymas Basin. From a complete Bouguer anomaly map, it is observed that the alignments of gravity highs trending 310° and 290° support the volcanic and subvolcanic origin of the bathymetric highs. Volcanic curvilinear structures, lava flows and mounds were identified from backscattering images around Isla Tortuga and over a 400-m high (Vı´rgenes High), where the TVR and the RVR intersect. A refraction/wide-angle seismic profile crossing perpendicular to the Vı´rgenes High, together with gravity and magnetic data indicate the presence of shallow intrusive bodies presumably of basaltic or andesitic composition. It is inferred that most volcanic edifices along the ridges have similar internal structures. We suggest that the growth of different segments of the ridges have a volcano-tectonic origin. The older RVR lies along the extension of a fracture zone and it probably is associated with Pliocene NE-SW extension.

  6. Application of MODIS-ASTER (MASTER) simulator data to geological mapping of young volcanic regions in Baja California, Mexico (United States)

    Dmochowski, Jane Ellen

    Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful. The analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a "site calibration," which provides good results in the calculated weight percent SiO2 with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition. Analysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a "leaky" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera.

  7. Volcanic Supersites as cross-disciplinary laboratories (United States)

    Provenzale, Antonello; Beierkuhnlein, Carl; Giamberini, Mariasilvia; Pennisi, Maddalena; Puglisi, Giuseppe


    Volcanic Supersites, defined in the frame of the GEO-GSNL Initiative, are usually considered mainly for their geohazard and geological characteristics. However, volcanoes are extremely challenging areas from many other points of view, including environmental and climatic properties, ecosystems, hydrology, soil properties and biogeochemical cycling. Possibly, volcanoes are closer to early Earth conditions than most other types of environment. During FP7, EC effectively fostered the implementation of the European volcano Supersites (Mt. Etna, Campi Flegrei/Vesuvius and Iceland) through the MED-SUV and FUTUREVOLC projects. Currently, the large H2020 project ECOPOTENTIAL (2015-2019, 47 partners, contributes to GEO/GEOSS and to the GEO ECO Initiative, and it is devoted to making best use of remote sensing and in situ data to improve future ecosystem benefits, focusing on a network of Protected Areas of international relevance. In ECOPOTENTIAL, remote sensing and in situ data are collected, processed and used for a better understanding of the ecosystem dynamics, analysing and modelling the effects of global changes on ecosystem functions and services, over an array of different ecosystem types, including mountain, marine, coastal, arid and semi-arid ecosystems, and also areas of volcanic origin such as the Canary and La Reunion Islands. Here, we propose to extend the network of the ECOPOTENTIAL project to include active Volcanic Supersites, such as Mount Etna and other volcanic Protected Areas, and we discuss how they can be included in the framework of the ECOPOTENTIAL workflow. A coordinated and cross-disciplinary set of studies at these sites should include geological, biological, ecological, biogeochemical, climatic and biogeographical aspects, as well as their relationship with the antropogenic impact on the environment, and aim at the global analysis of the volcanic Earth Critical Zone - namely, the upper layer of the Earth

  8. Constraining volcanic inflation at Three Sisters Volcanic Field in Oregon, USA, through microgravity and deformation modeling (United States)

    Zurek, Jeffrey; William-Jones, Glyn; Johnson, Dan; Eggers, Al


    Microgravity data were collected between 2002 and 2009 at the Three Sisters Volcanic Complex, Oregon, to investigate the causes of an ongoing deformation event west of South Sister volcano. Three different conceptual models have been proposed as the causal mechanism for the deformation event: (1) hydraulic uplift due to continual injection of magma at depth, (2) pressurization of hydrothermal systems and (3) viscoelastic response to an initial pressurization at depth. The gravitational effect of continual magma injection was modeled to be 20 to 33 μGal at the center of the deformation field with volumes based on previous deformation studies. The gravity time series, however, did not detect a mass increase suggesting that a viscoelactic response of the crust is the most likely cause for the deformation from 2002 to 2009. The crust, deeper than 3 km, in the Three Sisters region was modeled as a Maxwell viscoelastic material and the results suggest a dynamic viscosity between 1018 to 5 × 1019 Pa s. This low crustal viscosity suggests that magma emplacement or stall depth is controlled by density and not the brittle ductile transition zone. Furthermore, these crustal properties and the observed geochemical composition gaps at Three Sisters can be best explained by different melt sources and limited magma mixing rather than fractional crystallization. More generally, low intrusion rates, low crustal viscosity, and multiple melt sources could also explain the whole rock compositional gaps observed at other arc volcanoes.

  9. Volcanic Alert System (VAS) developed during the (2011-2013) El Hierro (Canary Islands) volcanic process (United States)

    Ortiz, Ramon; Berrocoso, Manuel; Marrero, Jose Manuel; Fernandez-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Garcia, Alicia


    In volcanic areas with long repose periods (as El Hierro), recently installed monitoring networks offer no instrumental record of past eruptions nor experience in handling a volcanic crisis. Both conditions, uncertainty and inexperience, contribute to make the communication of hazard more difficult. In fact, in the initial phases of the unrest at El Hierro, the perception of volcanic risk was somewhat distorted, as even relatively low volcanic hazards caused a high political impact. The need of a Volcanic Alert System became then evident. In general, the Volcanic Alert System is comprised of the monitoring network, the software tools for the analysis of the observables, the management of the Volcanic Activity Level, and the assessment of the threat. The Volcanic Alert System presented here places special emphasis on phenomena associated to moderate eruptions, as well as on volcano-tectonic earthquakes and landslides, which in some cases, as in El Hierro, may be more destructive than an eruption itself. As part of the Volcanic Alert System, we introduce here the Volcanic Activity Level which continuously applies a routine analysis of monitoring data (particularly seismic and deformation data) to detect data trend changes or monitoring network failures. The data trend changes are quantified according to the Failure Forecast Method (FFM). When data changes and/or malfunctions are detected, by an automated watchdog, warnings are automatically issued to the Monitoring Scientific Team. Changes in the data patterns are then translated by the Monitoring Scientific Team into a simple Volcanic Activity Level, that is easy to use and understand by the scientists and technicians in charge for the technical management of the unrest. The main feature of the Volcanic Activity Level is its objectivity, as it does not depend on expert opinions, which are left to the Scientific Committee, and its capabilities for early detection of precursors. As a consequence of the El Hierro

  10. Georesistivity structure in the central part of North-Eastern Japan Arc; Tohoku chiho chubu chiiki no denki dendodo kozo

    Energy Technology Data Exchange (ETDEWEB)

    Fujinawa, Y. [National Research Institute for Disaster Prevention, Tsukuba (Japan); Kawakami, N. [GERD Geothermal Energy Research and Development Co. Ltd., Tokyo (Japan); Ueshima, M. [The University of Tokyo, Tokyo (Japan). Earthquake Research Institute; Honkura, Y. [Tokyo Institute of Technology, Tokyo (Japan)


    MT measurement of transects was made in the central part of North-Eastern Japan Arc to clarify tectonics of subduction zones. 1-D, 2-D and 3-D resistivity structures are observed in surface layers, and zones shallower and deeper than a Conrad surface, respectively. A main structure direction is S-N or NNE-SSW. Ishinomaki-Chokai tectonic line and low- resistivity zones due to Quaternary volcanos (Naruko, Onikobe) exist in a backbone range region. Resistivity is 100{Omega}{center_dot}m or less by Bostick Inversion except Mesozoic and Palaeozoic layers in the southern Kitakami mountainous region, resulting in a good agreement with previous results in a north transect. Resistivity is several {Omega}{center_dot}m and depth is several km around Shinjo basin and in surface layers of Kitakami River region. The backbone range region shows complex resistivity structures because of volcanic activity and wide-area hot water activity. High-resistivity layers correspond to stable Mesozoic and Palaeozoic land layers. Seismic velocity increases in the low-resistivity zone. Earthquake generally occurs at the boundary between resistivity structures. 68 refs., 9 figs., 2 tabs.

  11. Structure and topography of the Siqueiros transform fault system: Evidence for the development of intra-transform spreading centers (United States)

    Fornari, Daniel J.; Gallo, David G.; Edwards, Margo H.; Madsen, John A.; Perfit, Michael R.; Shor, Alexander N.


    The Siqueiros transform fault system, which offsets the East Pacific Rise between 8°20'N 8°30'N, has been mapped with the Sea MARC II sonar system and is found to consist of four intra-transform spreading centers and five strike-slip faults. The bathymetric and side-looking sonar data define the total width of the transform domain to be ≈20km. The transform domain includes prominent topographic features that are related to either seafloor spreading processes at the short spreading centers or shearing along the bounding faults. The spreading axes and the seafloor on the flanks of each small spreading center comprise morphological and structural features which suggest that the two western spreading centers are older than the eastern spreading centers. Structural data for the Clipperton, Orozco and Siqueiros transforms, indicate that the relative plate motion geometry of the Pacific-Cocos plate boundary has been stable for the past ≈1.5 Ma. Because the seafloor spreading fabric on the flanks of the western spreading centers is ≈500 000 years old and parallels the present EPR abyssal hill trend (350°) we conclude that a small change in plate motion was not the cause for intra-transform spreading center development in Siqueiros. We suggest that the impetus for the development of intra-transform spreading centers along the Siqueiros transform system was provided by the interaction of small melt anomalies in the mantle (SMAM) with deepseated, throughgoing lithospheric fractures within the shear zone. Initially, eruption sites may have been preferentially located along strike-slip faults and/or along cross-faults that eventually developed into pull-apart basins. Spreading centers C and D in the eastern portion of Siqueiros are in this initial pull-apart stage. Continued intrusion and volcanism along a short ridge within a pull-apart basin may lead to the formation of a stable, small intra-transform spreading center that creates a narrow swath of ridge

  12. Role of volcanism in climate and evolution

    Energy Technology Data Exchange (ETDEWEB)

    Axelrod, D.I.


    Several major episodes of Tertiary explosive volcanism coincided with sharply lowered temperature as inferred from oxygen-isotope composition of foraminiferal tests in deep-sea cores. At these times, fossil floras in the western interior recorded significant changes. Reductions in taxa that required warmth occurred early in the Paleogene. Later, taxa that demand ample summer rain were reduced during a progressive change reflecting growth of the subtropic high. Other ecosystem changes that appear to have responded to volcanically induced climatic modifications include tachytely in Equidae (12 to 10 m.y. B.P.), rapid evolution of grasses (7 to 5 m.y. B.P.), evolution of marine mammals, and plankton flucuations. Although Lake Cretaceous extinctions commenced as epeiric seas retreated, the pulses of sharply lowered temperature induced by explosive volcanism, together with widespread falls of volcanic ash, may have led to extinction of dinosaurs, ammonites, cycadeoids, and other Cretaceous taxa. earlier, as Pangaea was assembled, Permian extinctions resulted not only from the elimination of oceans, epeiric seas, and shorelines, and the spread of more-continental climates, bu also from the climatic effects of major pulses of global volcanism and Gondwana glaciation.

  13. Active Volcanic Eruptions on Io (United States)


    Six views of the volcanic plume named Prometheus, as seen against Io's disk and near the bright limb (edge) of the satellite by the SSI camera on the Galileo spacecraft during its second (G2) orbit of Jupiter. North is to the top of each frame. To the south-southeast of Prometheus is another bright spot that appears to be an active plume erupting from a feature named Culann Patera. Prometheus was active 17 years ago during both Voyager flybys, but no activity was detected by Voyager at Culann. Both of these plumes were seen to glow in the dark in an eclipse image acquired by the imaging camera during Galileo's first (G1) orbit, and hot spots at these locations were detected by Galileo's Near-Infrared Mapping Spectrometer.The plumes are thought to be driven by heating sulfur dioxide in Io's subsurface into an expanding fluid or 'geyser'. The long-lived nature of these eruptions requires that a substantial supply of sulfur dioxide must be available in Io's subsurface, similar to groundwater. Sulfur dioxide gas condenses into small particles of 'snow' in the expanding plume, and the small particles scatter light and appear bright at short wavelengths. The images shown here were acquired through the shortest-wavelength filter (violet) of the Galileo camera. Prometheus is about 300 km wide and 75 km high and Culann is about 150 km wide and less than 50 km high. The images were acquired on September 4, 1996 at a range of 2,000,000 km (20 km/pixel resolution). Prometheus is named after the Greek fire god and Culann is named after the Celtic smith god.The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL Background information and educational context for the images can

  14. Space-time distribution of ignimbrite volcanism in the southern SMO: From Eocene to Pliocene (United States)

    Nieto-Obregon, J.; Aguirre-Diaz, G. J.


    A distinct variation in the age of the ignimbrites of the Sierra Madre Occidental (SMO) is observed in the southern portion, which includes the area between Tepic, Nayarit (-105° W) and Aguascalientes, Ags (-102° W). Older, high-grade ignimbrites are Eocene and occur as scattered outcrops. These are in turn covered by a widespread and voluminous sequence of high-grade ignimbrites and silicic to intermediate lavas that ranges in age from Middle Oligocene to Middle Miocene. The peak of this ignimbrite volcanism was at about 21 Ma to 22 Ma, but there is evidence showing that it initiated since about 30 Ma and ended at about 17.5 Ma. This ignimbrite and lava sequence is in turn covered by another series of lavas, predominantly mafic to intermediate, in the southern part of the area. This latest volcanism represents the initiation of the Mexican Volcanic Belt. Ignimbrite volcanism apparently initiated at the NE part of the study area, and migrated to the SW with time, that is from the area Presa Calles to the valley of Bolaños. Isotopic ages reported on these rocks, cluster in various groups reflecting the time evolution of volcanism. Rocks older than 30 Ma tend to occur on the raised blocks of Sierra de El Laurel and Northern Sierra de Morones, in the eastern part of the area. The interval from 30 to 20 Ma comprises a discontinuous set of ages that are concentrated in the blocks of Southern Sierra de Morones, Tlaltenango, Bolaños and the area around Cinco Minas-San Pedro Analco-Hostotipaquillo. An apparent gap of ages occurs between 12 to 18 Ma, followed by a predominantly mafic volcanism scattered mainly to the south of the area, that represents the transition of SMO to MVB. Finally mafic volcanism of the MVB of 3 to 4 Ma is present in the south, in the area excavated on the vicinity of Rio Grande de Santiago. A similar migration pattern has been reported in general for the whole SMO by Aguirre-Diaz and Labarthe-Hernandez (2003), from NE Chihuahua to SW Nayarit

  15. Thermal and mass implications of magmatic evolution in the Lassen volcanic region, California, and minimum constraints on basalt influx to the lower crust (United States)

    Guffanti, M.; Clynne, M.A.; Muffler, L.J.P.


    We have analyzed the heat and mass demands of a petrologic model of basaltdriven magmatic evolution in which variously fractionated mafic magmas mix with silicic partial melts of the lower crust. We have formulated steady state heat budgets for two volcanically distinct areas in the Lassen region: the large, late Quaternary, intermediate to silicic Lassen volcanic center and the nearby, coeval, less evolved Caribou volcanic field. At Caribou volcanic field, heat provided by cooling and fractional crystallization of 52 km3 of basalt is more than sufficient to produce 10 km3 of rhyolitic melt by partial melting of lower crust. Net heat added by basalt intrusion at Caribou volcanic field is equivalent to an increase in lower crustal heat flow of ???7 mW m-2, indicating that the field is not a major crustal thermal anomaly. Addition of cumulates from fractionation is offset by removal of erupted partial melts. A minimum basalt influx of 0.3 km3 (km2 Ma)-1 is needed to supply Caribou volcanic field. Our methodology does not fully account for an influx of basalt that remains in the crust as derivative intrusives. On the basis of comparison to deep heat flow, the input of basalt could be ???3 to 7 times the amount we calculate. At Lassen volcanic center, at least 203 km3 of mantle-derived basalt is needed to produce 141 km3 of partial melt and drive the volcanic system. Partial melting mobilizes lower crustal material, augmenting the magmatic volume available for eruption at Lassen volcanic center; thus the erupted volume of 215 km3 exceeds the calculated basalt input of 203 km3. The minimum basalt input of 1.6 km3 (km2 Ma)-1 is >5 times the minimum influx to the Caribou volcanic field. Basalt influx high enough to sustain considerable partial melting, coupled with locally high extension rate, is a crucial factor in development of Lassen volcanic center; in contrast. Caribou volcanic field has failed to develop into a large silicic center primarily because basalt supply

  16. Insights into volcanic processes using seismic data techniques (United States)

    Patlan Almeida, Ezer

    The country of Kenya, lying within the East African Rift System (EARS), has been continuously studied for geothermal energy production. EARS, an active continental rift zone, has a number of active and inactive volcanoes throughout its extent that represent potential sources for geothermal energy. The University of Texas at El Paso and the Kenyan Geothermal Development Company (GDC) collaborated to monitor several volcanic centers by deploying 14 passive seismic instruments around Menengai caldera. The temporary seismic network is located close to Nakuru city and it is southeast from the main capital of Nairobi city. Using this local seismic network, we located 198 earthquake hypocenters, which help to identify the margin of the volcano and caldera and faults that could form conduits for fluid flow. In particular, we performed double-difference location and a b-value analysis to define the behavior of magma systems feeding the caldera. Focal mechanisms delineate a normal and low-angle thrust fault striking NE-SW of the caldera floor. We compare our seismicity to InSAR results from different timelines in order to better understand the volcanic process. We suggest that the seismicity is related to magma passing through conduits of the magma chamber and/or fluid being transported as a function of magma movement or hydrothermal activity.

  17. A new way to detect volcanic plumes (United States)

    Larson, Kristine M.


    of volcanic plumes, especially ash-laden ones, is important both for public health and aircraft safety. A variety of geophysical tools and satellite data are used to monitor volcanic eruptions and to predict the movement of ash. However, satellite-based methods are restricted by time of day and weather, while radars are often unavailable because of cost/portability. Here a method is proposed to detect volcanic plumes using GPS signal strength data. The strengths and limitations of the method are assessed using GPS data collected during the 2008 and 2009 eruptions of the Okmok and Mt. Redoubt volcanoes. Plume detections using this GPS technique are consistent with independently collected seismic and radar data.

  18. Ozone depletion following future volcanic eruptions (United States)

    Eric Klobas, J.; Wilmouth, David M.; Weisenstein, Debra K.; Anderson, James G.; Salawitch, Ross J.


    While explosive volcanic eruptions cause ozone loss in the current atmosphere due to an enhancement in the availability of reactive chlorine following the stratospheric injection of sulfur, future eruptions are expected to increase total column ozone as halogen loading approaches preindustrial levels. The timing of this shift in the impact of major volcanic eruptions on the thickness of the ozone layer is poorly known. Modeling four possible climate futures, we show that scenarios with the smallest increase in greenhouse gas concentrations lead to the greatest risk to ozone from heterogeneous chemical processing following future eruptions. We also show that the presence in the stratosphere of bromine from natural, very short-lived biogenic compounds is critically important for determining whether future eruptions will lead to ozone depletion. If volcanic eruptions inject hydrogen halides into the stratosphere, an effect not considered in current ozone assessments, potentially profound reductions in column ozone would result.

  19. Geochemical and oxygen isotope studies of high-silica rhyolitic ignimbrites from the Eastern and Central Snake River Plain and Yellowstone (United States)

    Shanks, W. P.; Morgan, L. A.; Bindeman, I.


    Volcanism along the track of the Yellowstone hot spot has progressed from SW to NE in successive volcanic fields comprised of nested caldera complexes. Most caldera-forming eruptions within a field are separated by 0.2 to 1 m.y., similar to the present-day Yellowstone Plateau volcanic field. Volcanic fields may be separated in time and space by as much as 2 m.y. and 50-150 km from center to center. A series of 4.5- to 12-Ma ignimbrites from the eastern and central Snake River Plain, related to large-volume caldera eruptions, have been analyzed for major, minor, and trace elements, and for δ18O to examine how individual ignimbrites and volcanic fields have varied with respect to chemistry in space and space. An additional 45 samples of Lava Creek Tuff (LCT), erupted from the Yellowstone Caldera at 0.640 Ma, were similarly analyzed for comparison. SRP-Yellowstone high-silica rhyolitic ignimbrites have a large range and systematic variation in incompatible elements such as Zr, Hf, Rb, Sr, Ce, and Sc. Zr-Hf systematics show trends toward lower Zr and Hf in progressively younger rocks, with LCT having the lowest values. Samples from City of Rocks, Road Canyon, and Basin are significantly off trend due to enrichment in Zr relative other SRP ignimbrites. Rhyolitic SRP ignimbrites have whole rock δ18O values ranging from 0.4-7.5, and averaging 3.8 per mil. Quartz separates from the SRP ignimbrites have δ18O values that range from 1.9-9.4 and average 4.7 per mil. Unaltered, normal granites and rhyolites have whole rock oxygen isotope values of about 6.5-7.0 per mil and quartz separates generally have isotopic values that are 1.5-2.0 per mil higher than whole rock values. Therefore, most of our data on quartz and whole rock samples from SRP ignimbrites have low δ18O values, due to either hydrothermal alteration by meteoric waters or low δ18O magmas. LCT samples have δ18O values from 0.3-7.4, averaging 5.8 per mil. Previous studies have shown that low δ18O magma occurs

  20. Spain as an emergency air traffic hub during volcanic air fall events? Evidence of past volcanic ash air fall over Europe during the late Pleistocene (United States)

    Hardiman, Mark; Lane, Christine; Blockley, Simon P. E.; Moreno, Ana; Valero-Garcés, Blas; Ortiz, José E.; Torres, Trino; Lowe, John J.; Menzies, Martin A.


    proved to be almost devoid of volcanic ash, which contrasts with results obtained from sites throughout central and northern Europe. This suggests that Spain has remained free of ashfall events throughout the late Pleistocene, or that any ash dispersal over Spain has been short-lived and/or infrequent. This appears to accord with the pattern of dispersal of Eyjafjallajökull ash clouds over April to May 2010. Most of the active period was characterised by low eruptive columns and the tropospheric dispersal of ash. Under these conditions, ash dispersal was multi-directional from eastern Europe to Greenland and beyond, but did not encroach on to the Iberian peninsula. In contrast, when the eruptive columns became more elevated and entrained in the jet stream, the dispersal directions were more uni-directional and passed over Iberia and North Africa. Thus the apparent lack of volcanic ash in Iberia (10 - 40ka) may have as much to do with eruptive column height and volcano location as with circulation patterns (tropospheric v. stratospheric). A more comprehensive assessment of geological records of non-visible ash layers in selected sites may hold the key to examining this matter more robustly.

  1. Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission (United States)

    Keszthelyi, L.; McEwen, A.S.; Phillips, C.B.; Milazzo, M.; Geissler, P.; Turtle, E.P.; Radebaugh, J.; Williams, D.A.; Simonelli, D.P.; Breneman, H.H.; Klaasen, K.P.; Levanas, G.; Denk, T.; Alexander, D.D.A.; Capraro, K.; Chang, S.-H.; Chen, A.C.; Clark, J.; Conner, D.L.; Culver, A.; Handley, T.H.; Jensen, D.N.; Knight, D.D.; LaVoie, S.K.; McAuley, M.; Mego, V.; Montoya, O.; Mortensen, H.B.; Noland, S.J.; Patel, R.R.; Pauro, T.M.; Stanley, C.L.; Steinwand, D.J.; Thaller, T.F.; Woncik, P.J.; Yagi, G.M.; Yoshimizu, J.R.; Alvarez, Del; Castillo, E.M.; Belton, M.J.S.; Beyer, R.; Branston, D.; Fishburn, M.B.; Mueller, B.; Ragan, R.; Samarasinha, N.; Anger, C.D.; Cunningham, C.; Little, B.; Arriola, S.; Carr, M.H.; Asphaug, E.; Moore, J.; Morrison, D.; Rages, K.; Banfield, D.; Bell, M.; Burns, J.A.; Carcich, B.; Clark, B.; Currier, N.; Dauber, I.; Gierasch, P.J.; Helfenstein, P.; Mann, M.; Othman, O.; Rossier, L.; Solomon, N.; Sullivan, R.; Thomas, P.C.; Veverka, J.; Becker, T.; Edwards, K.; Gaddis, L.; Kirk, R.; Lee, E.; Rosanova, T.; Sucharski, R.M.; Beebe, R.F.; Simon, A.; Bender, K.; Chuang, F.; Fagents, S.; Figueredo, P.; Greeley, R.; Homan, K.; Kadel, S.; Kerr, J.; Klemaszewski, J.; Lo, E.; Schwarz, W.; Williams, K.; Bierhaus, E.; Brooks, S.; Chapman, C.R.; Merline, B.; Keller, J.; Schenk, P.; Tamblyn, P.; Bouchez, A.; Dyundian, U.; Ingersoll, A.P.; Showman, A.; Spitale, J.; Stewart, S.; Vasavada, A.; Cunningham, W.F.; Johnson, T.V.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Meredith, M.K.; Orton, G.S.; Senske, D.A.; West, A.; Winther, D.; Collins, G.; Fripp, W.J.; Head, J. W.; Pappalardo, R.; Pratt, S.; Procter, L.; Spaun, N.; Colvin, T.; Davies, M.; DeJong, E.M.; Hall, J.; Suzuki, S.; Gorjian, Z.; Giese, B.; Koehler, U.; Neukum, G.; Oberst, J.; Roatsch, T.; Tost, W.; Schuster, P.; Wagner, R.; Dieter, N.; Durda, D.; Greenberg, R.J.; Hoppa, G.; Jaeger, W.; Plassman, J.; Tufts, R.; Fanale, F.P.; Gran,


    The Solid-State Imaging (SSI) instrument provided the first high- and medium-resolution views of Io as the Galileo spacecraft closed in on the volcanic body in late 1999 and early 2000. While each volcanic center has many unique features, the majority can be placed into one of two broad categories. The "Promethean" eruptions, typified by the volcanic center Prometheus, are characterized by long-lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years to decades. In contrast, "Pillanian" eruptions are characterized by large pyroclastic deposits and short-lived but high effusion rate eruptions from fissures feeding open-channel or open-sheet flows. Both types of eruptions commonly have ???100-km-tall, bright, SO2-rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas. Copyright 2001 by the American Geophysical Union.

  2. Volcanic air pollution hazards in Hawaii (United States)

    Elias, Tamar; Sutton, A. Jeff


    Noxious sulfur dioxide gas and other air pollutants emitted from Kīlauea Volcano on the Island of Hawai‘i react with oxygen, atmospheric moisture, and sunlight to produce volcanic smog (vog) and acid rain. Vog can negatively affect human health and agriculture, and acid rain can contaminate household water supplies by leaching metals from building and plumbing materials in rooftop rainwater-catchment systems. U.S. Geological Survey scientists, along with health professionals and local government officials are working together to better understand volcanic air pollution and to enhance public awareness of this hazard.

  3. Tellurium in active volcanic environments: Preliminary results (United States)

    Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco


    Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

  4. Volcanic Pipe of the Namuaiv Mountain

    Directory of Open Access Journals (Sweden)

    Vladimir K. Karzhavin


    Full Text Available This research was aimed at reconstructing thermodynamic conditions required for the studied mineral assemblages to be created and exist in nature. The results of the investigations confirm to the recent ideas about an important, even leading, role of temperature, pressure and dioxide carbon in diamond formation in volcanic pipers. The results of this theoretical research allows assuming that one of the reasons for the absence of diamonds in the Namuaiv Mountain volcanic pipe may lie in the increased content of water and oxidizing environmental conditions of their formation

  5. Assessing Volcanic Risk in Saudi Arabia (United States)

    Lindsay, Jan Marie; Rashad Moufti, Mohammed


    The Kingdom of Saudi Arabia has numerous large monogenetic volcanic fields, known locally as "harrats." The largest of these, Harrat Rahat (Figure 1), produced a basaltic fissure eruption in 1256 C.E. with lava flows traveling within 20 kilometers of the city Al-Madinah, which currently has a population of 1.5 million plus an additional 3 million pilgrims annually. With more than 950 visible vents and periodic seismic swarms, an understanding of the risk of future eruptions in this volcanic field is vital.

  6. Emplacement Scenarios for Volcanic Domes on Venus (United States)

    Glaze, Lori S.; Baloga, Steve M.; Stofan, Ellen R.


    One key to understanding the history of resurfacing on Venus is better constraints on the emplacement timescales for the range of volcanic features visible on the surface. A figure shows a Magellan radar image and topography for a putative lava dome on Venus. 175 such domes have been identified with diameters ranging from 19 - 94 km, and estimated thicknesses as great as 4 km. These domes are thought to be volcanic in origin and to have formed by the flow of viscous fluid (i.e., lava) on the surface.

  7. AVAL - The ASTER Volcanic Ash Library (United States)

    Williams, D.; Ramsey, M. S.


    Volcanic ash is a rich data source for understanding the causal mechanisms behind volcanic eruptions. Petrologic and morphometric information can provide direct information on the characteristics of the parent magma. Understanding how erupted ash interacts with the atmosphere can help quantify the effect that explosive volcanism has on the local to regional climate, whereas a measure of the particle size distribution enables more accurate modeling of plume propagation. Remote sensing is regularly employed to monitor volcanic plumes using a suite of high temporal/low spatial resolution sensors. These methods employ radiative transfer modeling with assumptions of the transmissive properties of infrared energy through the plume to determine ash density, particle size and sulfur dioxide content. However, such approaches are limited to the optically-transparent regions, and the low spatial resolution data are only useful for large-scale trends. In a new approach, we are treating the infrared-opaque regions of the plume in a similar way to a solid emitting surface. This allows high spatial resolution orbital thermal infrared data from the dense proximal plume to be modeled using a linear deconvolution approach coupled with a spectral library to extract the particle size and petrology. The newly created ASTER Volcanic Ash Library (AVAL) provides the end member spectral suite, and is comprised of laboratory emission measurements of volcanic ash taken from a variety of different volcanic settings, to obtain a wide range of petrologies. These samples have been further subdivided into particle size fractions to account for spectral changes due to diffraction effects. Once mapped to the ASTER sensor's spectral resolution, this library is applied to image data and the plume deconvolved to estimate composition and particle size. We have analyzed eruptions at the Soufrière Hills Volcano, Montserrat, Chaitén and Puyehue-Cordón Caulle, both Chile, and Eyjafjallajökull, Iceland

  8. Improving volcanic ash predictions with the HYSPLIT dispersion model by assimilating MODIS satellite retrievals (United States)

    Chai, Tianfeng; Crawford, Alice; Stunder, Barbara; Pavolonis, Michael J.; Draxler, Roland; Stein, Ariel


    Currently, the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) runs the HYSPLIT dispersion model with a unit mass release rate to predict the transport and dispersion of volcanic ash. The model predictions provide information for the Volcanic Ash Advisory Centers (VAAC) to issue advisories to meteorological watch offices, area control centers, flight information centers, and others. This research aims to provide quantitative forecasts of ash distributions generated by objectively and optimally estimating the volcanic ash source strengths, vertical distribution, and temporal variations using an observation-modeling inversion technique. In this top-down approach, a cost functional is defined to quantify the differences between the model predictions and the satellite measurements of column-integrated ash concentrations weighted by the model and observation uncertainties. Minimizing this cost functional by adjusting the sources provides the volcanic ash emission estimates. As an example, MODIS (Moderate Resolution Imaging Spectroradiometer) satellite retrievals of the 2008 Kasatochi volcanic ash clouds are used to test the HYSPLIT volcanic ash inverse system. Because the satellite retrievals include the ash cloud top height but not the bottom height, there are different model diagnostic choices for comparing the model results with the observed mass loadings. Three options are presented and tested. Although the emission estimates vary significantly with different options, the subsequent model predictions with the different release estimates all show decent skill when evaluated against the unassimilated satellite observations at later times. Among the three options, integrating over three model layers yields slightly better results than integrating from the surface up to the observed volcanic ash cloud top or using a single model layer. Inverse tests also show that including the ash-free region to constrain the model is not

  9. Assessing and optimizing the performance of infrasound networks to monitor volcanic eruptions (United States)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Assink, Jelle; Vergniolle, Sylvie


    We propose a numerical modeling technique based on a frequency-dependent attenuation relation to assess, quantify and optimize the performance of any arbitrary infrasound network to monitor explosive sources such as volcanic eruptions. Simulations are further enhanced by including realistic sources and propagation effects. We apply our approach to both hemispheres by considering the Euro-Mediterranean and the Eastern Australian regions. In these regions, we use quasi-permanent infrasound signals from Mt. Etna recorded in Tunisia and from Mt. Yasur recorded in New Caledonia. These well-instrumented volcanoes offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near- and far-field recordings demonstrate the potential of the proposed methodology to remotely monitor volcanoes. A good agreement is found between modeled and observed results, especially when incorporating representative 10 m s-1 wind perturbations in the atmospheric specifications according to previous campaign measurements. To optimize the network layout in order to ensure the best monitoring of the volcanoes, we proceed through a grid search to find optimum locations of an additional array. We show that adding one array at an appropriate location in both regions under study could significantly improve detections half of the year. The application of the proposed methodology can provide in near real-time a realistic confidence level of volcanic eruption detections, useful to mitigate the risk of aircrafts encountering volcanic ash.

  10. Investigation of Along-Arc Geochemical Variations in the Southern Volcanic Zone: Azufre-Planchon-Peteroa Volcanic Complex, Southern Chile (United States)

    Holbik, S. P.; Hickey-Vargas, R.; Tormey, D.


    The Andean Southern Volcanic Zone (SVZ) is a vast and complex continental arc that has been studied extensively to provide an understanding of arc-magma genesis, the origin and chemical evolution of the continental crust, and geochemical compositions of volcanic products. This study focuses on volcanic rocks from the Azufre-Planchon-Peteroa (APP 35°15'S) volcanic complex, within the Transitional SVZ (34.3-37.0 °S), where crustal thickness increases from approximately 30 km in the south (Central SVZ), to 55 km in the north (Northern SVZ). Planchon is the northernmost volcano in the SVZ to erupt basaltic products, while Peteroa is the currently active cone, erupting tephra of andesitic composition, most recently in September of 2011. New data for the APP are consistent with the hypothesis of Tormey et al. (1995) that the APP experienced variable depths of crystal fractionation, and that crustal assimilation at Planchon is restricted to the lower crustal depths, as reflected by limited variability in 87Sr/86Sr isotopes. New δ18O data (26.5‰) from an outcropping dolomitic limestone country rock in the vicinity of the Azufre volcano also confirms the upper crustal source of anomalously high (7.1 and 7.3‰) oxygen isotopic values for Azufre dacites. A trend of high La/Yb (6.5-9.1) and Yb depletion with increasing La/Yb for Planchon basalts is consistent with the role of garnet as a residual or crystallizing phase at lower crustal depths, however, the La/Yb range is small when compared to published data from nearby TSVZ centers such as Nevado de Longavi (La/Yb = 5.5 to 16.7) and San Pedro Pellado (La/Yb =7.2 to 13.6). Geochemical modeling of the Planchon data shows that both hornblende and garnet must be involved in the magmatic evolution, even though erupted basalts are free of major hydrous phases, in order to account for the more limited range of La/Yb. Interestingly, baseline values of La/Yb for basalt and basaltic andesites from throughout the TSVZ, including

  11. The identification and tracking of volcanic ash using the Meteosat Second Generation (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) (United States)

    Naeger, A. R.; Christopher, S. A.


    In this paper, we develop an algorithm based on combining spectral, spatial, and temporal thresholds from the geostationary Spinning Enhanced Visible and Infrared Imager (SEVIRI) daytime measurements to identify and track different aerosol types, primarily volcanic ash. Contemporary methods typically do not use temporal information to identify ash. We focus not only on the identification and tracking of volcanic ash during the Eyjafjallajökull volcanic eruption period beginning in 14 April and ending 17 May 2010 but also on a pixel-level classification method for separating various classes in the SEVIRI images. Three case studies on 13, 16, and 17 May are analyzed in extensive detail with other satellite data including from the Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), and Facility for Airborne Atmospheric Measurements (FAAM) BAe146 aircraft data to verify the aerosol spatial distribution maps generated by the SEVIRI algorithm. Our results indicate that the SEVIRI algorithm is able to track volcanic ash when the solar zenith angle is lower than about 65°. Furthermore, the BAe146 aircraft data show that the SEVIRI algorithm detects nearly all ash regions when AOD > 0.2. However, the algorithm has higher uncertainties when AOD is ash spatial distributions provided by this algorithm can be used as a critical input and validation for atmospheric dispersion models simulated by Volcanic Ash Advisory Centers (VAACs). Identifying volcanic ash is an important first step before quantitative retrievals of ash concentration can be made.

  12. The Hawaiian Volcano Observatory: a natural laboratory for studying basaltic volcanism: Chapter 1 in Characteristics of Hawaiian volcanoes (United States)

    Tilling, Robert I.; Kauahikaua, James P.; Brantley, Steven R.; Neal, Christina A.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.


    In the beginning of the 20th century, geologist Thomas A. Jaggar, Jr., argued that, to fully understand volcanic and associated hazards, the expeditionary mode of studying eruptions only after they occurred was inadequate. Instead, he fervently advocated the use of permanent observatories to record and measure volcanic phenomena—at and below the surface—before, during, and after eruptions to obtain the basic scientific information needed to protect people and property from volcanic hazards. With the crucial early help of American volcanologist Frank Alvord Perret and the Hawaiian business community, the Hawaiian Volcano Observatory (HVO) was established in 1912, and Jaggar’s vision became reality. From its inception, HVO’s mission has centered on several goals: (1) measuring and documenting the seismic, eruptive, and geodetic processes of active Hawaiian volcanoes (principally Kīlauea and Mauna Loa); (2) geological mapping and dating of deposits to reconstruct volcanic histories, understand island evolution, and determine eruptive frequencies and volcanic hazards; (3) systematically collecting eruptive products, including gases, for laboratory analysis; and (4) widely disseminating observatory-acquired data and analysis, reports, and hazard warnings to the global scientific community, emergency-management authorities, news media, and the public. The long-term focus on these goals by HVO scientists, in collaboration with investigators from many other organizations, continues to fulfill Jaggar’s career-long vision of reducing risks from volcanic and earthquake hazards across the globe.

  13. Huygens Crater: Insights into Noachian Volcanism, Stratigraphy, and Aqueous Processes (United States)

    Ackiss, S. E.; Wray, J. J.; Seelos, K. D.; Niles, P. B.


    Huygens crater is a well preserved peak ring structure on Mars centered at 13.5 deg S, 55.5 deg E in the Noachian highlands between Terras Tyrrhena and Sabaea near the NW rim of Hellas basin. With a diameter of approximately 470 km, it uplifted and exhumed pre-Noachian crustal materials from depths greater than 25 km, penetrating below the thick, ubiquitous layer of Hellas ejecta. In addition, Huygens served as a basin for subsequent aqueous activity, including erosion/deposition by fluvial valley networks and subsurface alteration that is now exposed by smaller impacts. Younger mafic-bearing plains that partially cover the basin floor and surrounding intercrater areas were likely emplaced by later volcanism.

  14. Eastern Pacific Ocean Conference (United States)

    The promotion of interaction among investigators of all oceanographic disciplines studying the eastern Pacific Ocean was the goal of the 1990 Eastern Pacific Ocean Conference (EPOC), held October 17-19 on the snow-covered slopes of Mt. Hood, Oreg. Thirty oceanographers representing all disciplines attended.Dick Barber, Duke University Marine Lab, Beaufort, N.C., chaired a session on the eastern equatorial Pacific Ocean, emphasizing issues related to biological activity. Steve Ramp of the Naval Postgraduate School in Montery, Calif., chaired a session on recent results from northern and central California experiments. On October 19, following an early morning earthquake, a business meeting and discussions regarding a collaboration in future experiments were held.

  15. Multiple episodes of hydrothermal activity and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic activity, volcanism and regional extension

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Jackson, M.C. [Univ. of Nevada, Reno, NV (United States)] [and others


    Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of hydrothermal alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of hydrothermal activity mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma).

  16. Quaternary volcanism in the Acambay graben, Mexican Volcanic Belt: Re-evaluation for potential volcanic danger in central Mexico (United States)

    Aguirre-Diaz, G. J.; Pedrazzi, D.; Lacan, P.; Roldan-Quintana, J.; Ortuňo, M.; Zuniga, R. R.; Laurence, A.


    The Mexican Volcanic Belt (MVB) is best known for the major active stratovolcanoes, such as Popocatépetl, Citlaltépetl and Colima. The most common stratovolcanoes in this province are modest-size cones with heights of 800 to 1000 m. Examples are Tequila, Sangangüey, Las Navajas, Culiacán, La Joya, El Zamorano, Temascalcingo and Altamirano; these last two were formed within the Acambay Graben in central MVB. The Acambay graben (20 x 70 km) is 100 km to the NW of Mexico City, with E-W trending seismically active normal faults; in particular the Acambay-Tixmadejé fault related to a mB =7 earthquake in 1912. Within the graben there are many volcanic structures, including calderas, domes, cinder cones and stratovolcanoes; Temascalcingo and Altamirano are the largest, with about 800 and 900 m heights, respectively. Temascalcingo is mostly composed of dacitic lavas and block and ash flow deposits. Includes a 3 x 2.5 km summit caldera and a magmatic sector collapse event with the associated debris avalanche deposit. 14C ages of 37-12 ka correspond to the volcano's latest phases that produced pyroclastic deposits. A major plinian eruption formed the San Mateo Pumice with an age of deposits, and pumice fallouts. Morphologically is better preserved than Temascalcingo, and it should be younger. 14C ages of 4.0-2.5 ka were performed in charcoal within pyroclastic flow deposits that apparently were erupted from Altamirano. An undated 3 m thick pumice fallout on the flanks of Altamirano volcano could be also Holocene. It represents a major explosive event. The relatively young ages found in volcanic deposits within the Acambay graben raise the volcanic danger level in this area, originally thought as an inactive volcanic zone. The two major volcanoes, Temascalcingo and Altamirano, should be considered as dormant volcanoes that could restart activity at any time. We thanks grant DGAPA-UNAM-PAPIIT IN-104615.





    This thesis is a palaeoenviromnental investigation into possible non-climatic effects on the environment from volcanic ash fall and toxic emissions outside the blast zone of a volcanic eruption. These effects are determined from palynological and geochemical changes following tephra fall at a range of sites across the North Island of New Zealand which were located at increasing distances from the main volcanic source, the Taupo Volcanic Zone. These sites collectively covered a wid...

  18. Volcanic Surface Deformation in Dominica From GPS Geodesy: Results From the 2007 NSF- REU Site (United States)

    Murphy, R.; James, S.; Styron, R. H.; Turner, H. L.; Ashlock, A.; Cavness, C.; Collier, X.; Fauria, K.; Feinstein, R.; Staisch, L.; Williams, B.; Mattioli, G. S.; Jansma, P. E.; Cothren, J.


    GPS measurements have been collected on the island of Dominica in the Lesser Antilles between 2001 and 2007, with five month-long campaigns completed in June of each year supported in part by a NSF REU Site award for the past two years. All GPS data were collected using dual-frequency, code-phase receivers and geodetic-quality antenna, primarily choke rings. Three consecutive 24 hr observation days were normally obtained for each site. Precise station positions were estimated with GIPSY-OASISII using an absolute point positioning strategy and final, precise orbits, clocks, earth orientation parameters, and x-files. All position estimates were updated to ITRF05 and a revised Caribbean Euler pole was used to place our observations in a CAR-fixed frame. Time series were created to determine the velocity of each station. Forward and inverse elastic half-space models with planar (i.e. dike) and Mogi (i.e. point) sources were investigated. Inverse modeling was completed using a downhill simplex method of function minimization. Selected site velocities were used to create appropriate models for specific regions of Dominica, which correspond to known centers of pre-historic volcanic or recent shallow, seismic activity. Because of the current distribution of GPS sites with robust velocity estimates, we limit our models to possible magmatic activity in the northern, proximal to the volcanic centers of Morne Diablotins and Morne aux Diables, and southern, proximal to volcanic centers of Soufriere and Morne Plat Pays, regions of the island. Surface deformation data from the northernmost sites may be fit with the development of a several km-long dike trending approximately northeast- southwest. Activity in the southern volcanic centers is best modeled by an expanding point source at approximately 1 km depth.

  19. Improving volcanic ash forecasts with ensemble-based data assimilation

    NARCIS (Netherlands)

    Fu, Guangliang


    The 2010 Eyjafjallajökull volcano eruption had serious consequences to civil aviation. This has initiated a lot of research on volcanic ash forecasting in recent years. For forecasting the volcanic ash transport after eruption onset, a volcanic ash transport and diffusion model (VATDM) needs to be

  20. Deccan volcanism, the KT mass extinction and dinosaurs

    Indian Academy of Sciences (India)


    Oct 29, 2009 ... Recent advances in Deccan volcanic studies indicate three volcanic phases with the phase-1 at 67.5 Ma followed by a 2 m.y. period of quiescence. Phase-2 marks the main Deccan volcanic eruptions in Chron 29r near the end of the Maastrichtian and accounts for ∼80% of the entire 3500 m thick Deccan ...

  1. Implications of volcanic erratics in Quaternary deposits of North Greenland

    DEFF Research Database (Denmark)

    Funder, Svend Visby; Larsen, Ole


    Erratic boulders, petrographically similar to the volcanics exposed around Kap Washington, are found on islands and along the coast much further to the east. Isotopic measurements on two such boulders show that these volcanic rocks are of the same age as the Kap Washington volcanics. The regional...

  2. Widespread Neogene and Quaternary Volcanism on Central Kerguelen Plateau, Southern Indian Ocean (United States)

    Duncan, R. A.; Falloon, T.; Quilty, P. G.; Coffin, M. F.


    We report new age determinations and compositions for rocks from 18 dredge hauls collected from eight submarine areas across Central Kerguelen Plateau (CKP). Sea knolls and volcanic fields with multiple small cones were targeted over a 125,000 km2 region that includes Heard and McDonald islands. Large early Miocene (16-22 Ma) sea knolls rise from the western margin of the CKP and are part of a NNW-SSE line of volcanic centers that lie between Îles Kerguelen and Heard and McDonald islands. A second group of large sea knolls is aligned E-W across the center of this region. We see evidence of much younger activity (5 Ma to present) in volcanic fields to the north of, and up to 300 km NE of Heard Island. Compositions include basanite, basalt, and trachybasalt, that are broadly similar to plateau lava flows from nearby Ocean Drilling Program (ODP) Site 1138, lower Miocene lavas at Îles Kerguelen, dredged rocks from the early Miocene sea knolls, and Big Ben lavas from Heard Island. Geochemical data indicate decreasing fractions of mantle source melting with time. The western line of sea knolls has been related to hotspot activity now underlying the Heard Island area. In view of the now recognized much larger area of young volcanic activity, we propose that a broad region of CKP became volcanically active in Neogene time due to incubation of plume material at the base of the relatively stationary overlying plateau. The presence of pre-existing crustal faults promotes access for melts from the Heard mantle plume to rise to the surface.

  3. The Elusive Evidence of Volcanic Lightning. (United States)

    Genareau, K; Gharghabi, P; Gafford, J; Mazzola, M


    Lightning strikes are known to morphologically alter and chemically reduce geologic formations and deposits, forming fulgurites. A similar process occurs as the result of volcanic lightning discharge, when airborne volcanic ash is transformed into lightning-induced volcanic spherules (LIVS). Here, we adapt the calculations used in previous studies of lightning-induced damage to infrastructure materials to determine the effects on pseudo-ash samples of simplified composition. Using laboratory high-current impulse experiments, this research shows that within the lightning discharge channel there is an ideal melting zone that represents roughly 10% or less of the total channel radius at which temperatures are sufficient to melt the ash, regardless of peak current. The melted ash is simultaneously expelled from the channel by the heated, expanding air, permitting particles to cool during atmospheric transport before coming to rest in ash fall deposits. The limited size of this ideal melting zone explains the low number of LIVS typically observed in volcanic ash despite the frequent occurrence of lightning during explosive eruptions.

  4. Amazonian volcanism inside Valles Marineris on Mars

    Czech Academy of Sciences Publication Activity Database

    Brož, Petr; Hauber, E.; Wray, J. J.; Michael, G.


    Roč. 473, September (2017), s. 122-130 ISSN 0012-821X Institutional support: RVO:67985530 Keywords : Mars * Valles Marineris * volcanism * scoria cone * hydrothermal activity Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 4.409, year: 2016

  5. Geochemistry and petrogenesis of anorogenic basic volcanic ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    anorogenic setting for the basic rocks of Kundal area is suggested, which is in conformity with the similar setting for Malani Igneous Suite. 1. Introduction. The Malani magmatism is characterized by sub- volcanic setting, volcano-plutonic ring structures, anorogenic (A-type), high heat producing magma- tism and controlled by ...

  6. Assessing quality in volcanic ash soils (United States)

    Terry L. Craigg; Steven W. Howes


    Forest managers must understand how changes in soil quality resulting from project implementation affect long-term productivity and watershed health. Volcanic ash soils have unique properties that affect their quality and function; and which may warrant soil quality standards and assessment techniques that are different from other soils. We discuss the concept of soil...

  7. Halogen Chemistry in Volcanic Plumes (Invited) (United States)

    Roberts, Tjarda


    Volcanoes release vast amounts of gases and particles in the atmosphere. Volcanic halogens (HF, HCl, HBr, HI) are co-emitted alongside SO2, and observations show rapid formation of BrO and OClO in the plume as it disperses into the troposphere. The development of 1D and Box models (e.g. PlumeChem) that simulate volcanic plume halogen chemistry aims to characterise how volcanic reactive halogens form and quantify their atmospheric impacts. Following recent advances, these models can broadly reproduce the observed downwind BrO/SO2 ratios using "bromine-explosion" chemistry schemes, provided they use a "high-temperature initialisation" to inject radicals (OH, Cl, Br and possibly NOx) which "kick-start" the low-temperature chemistry cycles that convert HBr into reactive bromine (initially as Br2). The modelled rise in BrO/SO2 and subsequent plateau/decline as the plume disperses downwind reflects cycling between reactive bromine, particularly Br-BrO, and BrO-HOBr-BrONO2. BrCl is produced when aerosol becomes HBr-depleted. Recent model simulations suggest this mechanism for reactive chlorine formation can broadly account for OClO/SO2 reported at Mt Etna. Predicted impacts of volcanic reactive halogen chemistry include the formation of HNO3 from NOx and depletion of ozone. This concurs with HNO3 widely reported in volcanic plumes (although the source of NOx remains under question), as well as observations of ozone depletion reported in plumes from several volcanoes (Mt Redoubt, Mt Etna, Eyjafjallajokull). The plume chemistry can transform mercury into more easily deposited and potentially toxic forms, for which observations are limited. Recent incorporation of volcanic halogen chemistry in a 3D regional model of degassing from Ambrym (Vanuatu) also predicts how halogen chemistry causes depletion of OH to lengthen the SO2 lifetime, and highlights the potential for halogen transport from the troposphere to the stratosphere. However, the model parameter-space is vast and

  8. Stability of volcanic conduits during explosive eruptions (United States)

    Aravena, Álvaro; de'Michieli Vitturi, Mattia; Cioni, Raffaello; Neri, Augusto


    Geological evidences of volcanic conduit widening are common in most pyroclastic deposits (e.g. presence of lithic fragments from different depths), suggesting a continuous modification of the conduit geometry during volcanic eruptions. However, the controlling factors of the mechanisms driving conduit enlargement (e.g. erosion, local collapse) are still partially unclear, as well as the influence of conduit geometry on the eruptive dynamics. Although numerical models have been systematically employed to study volcanic conduits, their mechanical stability and the eruptive dynamics related to non-cylindrical conduits have been poorly addressed. We present here a 1D steady-state model which includes the main processes experimented by ascending magmas (i.e. crystallization, rheological changes, fragmentation, drag forces, outgassing and degassing), and the application of two mechanical stability criteria (Mohr-Coulomb and Mogi-Coulomb), in order to study the collapse conditions of volcanic conduits during a representative explosive rhyolitic eruption. It emerges that mechanical stability of volcanic conduits is mainly controlled by its radial dimension, and a minimum radius for reaching stable conditions can be computed, as a function of water content and inlet overpressure. Additionally, for a set of input parameters thought typical of explosive rhyolitic volcanism, we estimated a minimum magma flux for developing a mechanically stable conduit ( 7 • 107 - 3 • 108 kg/s). Results are consistent with the unsteady character usually observed in sub-Plinian eruptions, opposite to mainly stationary Plinian eruptions, commonly characterized by higher magma discharge rates. We suggest that cylindrical conduits represent a mechanically stable configuration only for large radii. Because the instability conditions are not uniform along the conduit, the widening processes probably lead to conduit geometries with depth-varying width. Consequently, as our model is able to

  9. Wet melting along the Tonga Volcanic Arc (United States)

    Cooper, L. B.; Plank, T.; Arculus, R. J.; Hauri, E. H.; Hall, P.


    Melting in the mantle at convergent margins is driven by water from the subducting slab. Previous work has found a strong role for water-fluxed melting from correlations between the concentration of water in the mantle source, (H2O)o, and the extent of melting beneath backarcs, Fba. Here we explore how wet melting beneath the Lau Backarc Basin relates to that beneath the Tonga Arc, Farc, by providing the first systematic study of water contents in Tonga arc magmas. We have measured volatiles and major and trace elements in melt inclusions, glasses, and whole rocks obtained from recently sampled submarine and subaerial Tonga arc volcanoes. The compositions are varied and range mostly between andesite and basalt/boninite, and least-degassed water contents range from 2 to 5 wt%. We estimate (H2O)o and Farc independently by combining pressure (P) and temperature (T) estimates from an olivine-orthopyroxene-melt thermobarometer with a wet melting productivity model. When P, T, and (H2O)o are known, Farc is uniquely constrained. Results for the volcanoes in the Tonga Arc are bimodal with respect to T: volcanoes located near active backarc spreading centers reflect cooler melting (~1275°C) than those located far from active spreading centers (~1365°C). The cooler primary T’s may result from removal of the heat of fusion during prior melting beneath the Lau backarc, Fba. In the northern portion of the arc, the warmest primary T’s may be due to proximity to the Samoan mantle plume. Farc varies non-systematically along-strike, indicating that Fba is the primary driver of along-arc variability in primary melt compositions. Farc can also be used to calculate the TiO2 concentration of the arc mantle source, (TiO2)o (a proxy for source depletion), which varies monotonically along the Tonga Arc. Arc volcanoes adjacent to the Southern Lau Rifts and Valu Fa Ridge melt mantle with a fertile N-MORB TiO2, while those adjacent to the northern extent of the Eastern Lau Spreading

  10. Methodology for the study of the Mexican Volcanic Belt; Metodologia para el estudio del Cinturon Volcanico Mexicano

    Energy Technology Data Exchange (ETDEWEB)

    Pal Verma, Surendra [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)


    The Mexican Volcanic Belt (MVB) is an structure 20 to 150 kilometers wide an {approx}1000 km long, oriented approximately east-west, from nearby Puerto Vallarta up until Veracruz; it contains a great number ({approx}7000) of volcanic apparatus or volcanic centers (Verma, 1987a, and the cited references in this paper). Fig. 1 represents the location of some of its main volcanic centers. The MVB forms part of the ring of fire that extends all along the circumpacific region (see Fig. 2) named this way because it refers to a very high volcanoes population (many of them active volcanoes), to its seismic activity and to the large geothermal manifestations. [Espanol] El Cinturon Volcanico Mexicano (CVM) es una estructura de 20 a 150 kilometros de ancho, {approx}1,000 km de largo, orientada aproximadamente este-oeste desde cerca de Puerto Vallarta hasta Veracruz; contiene gran numero ({approx}7,000) de aparatos o centros volcanicos (Verma, 1987a, y las referencias citadas en este trabajo). La figura 1 presenta la localizacion de algunos de sus principales centros volcanicos. El CVM forma parte del llamado anillo del fuego, que se extiende a todo lo largo de la region circumpacifica (vease la Fig. 2), denominada asi porque se trata de una poblacion muy alta de volcanes (mucho de ellos activos), de la actividad sismica y de grandes manifestaciones geotermicas.

  11. International Database of Volcanic Ash Impacts (United States)

    Wallace, K.; Cameron, C.; Wilson, T. M.; Jenkins, S.; Brown, S.; Leonard, G.; Deligne, N.; Stewart, C.


    Volcanic ash creates extensive impacts to people and property, yet we lack a global ash impacts catalog to organize, distribute, and archive this important information. Critical impact information is often stored in ephemeral news articles or other isolated resources, which cannot be queried or located easily. A global ash impacts database would improve 1) warning messages, 2) public and lifeline emergency preparation, and 3) eruption response and recovery. Ashfall can have varying consequences, such as disabling critical lifeline infrastructure (e.g. electrical generation and transmission, water supplies, telecommunications, aircraft and airports) or merely creating limited and expensive inconvenience to local communities. Impacts to the aviation sector can be a far-reaching global issue. The international volcanic ash impacts community formed a committee to develop a database to catalog the impacts of volcanic ash. We identify three user populations for this database: 1) research teams, who would use the database to assist in systematic collection, recording, and storage of ash impact data, and to prioritize impact assessment trips and lab experiments 2) volcanic risk assessment scientists who rely on impact data for assessments (especially vulnerability/fragility assessments); a complete dataset would have utility for global, regional, national and local scale risk assessments, and 3) citizen science volcanic hazard reporting. Publication of an international ash impacts database will encourage standardization and development of best practices for collecting and reporting impact information. Data entered will be highly categorized, searchable, and open source. Systematic cataloging of impact data will allow users to query the data and extract valuable information to aid in the development of improved emergency preparedness, response and recovery measures.

  12. Cooling Rates of Lunar Volcanic Glass Beads (United States)

    Hui, Hejiu; Hess, Kai-Uwe; Zhang, Youxue; Peslier, Anne; Lange, Rebecca; Dingwell, Donald; Neal, Clive


    It is widely accepted that the Apollo 15 green and Apollo 17 orange glass beads are of volcanic origin. The diffusion profiles of volatiles in these glass beads are believed to be due to degassing during eruption (Saal et al., 2008). The degree of degassing depends on the initial temperature and cooling rate. Therefore, the estimations of volatiles in parental magmas of lunar pyroclastic deposits depend on melt cooling rates. Furthermore, lunar glass beads may have cooled in volcanic environments on the moon. Therefore, the cooling rates may be used to assess the atmospheric condition in an early moon, when volcanic activities were common. The cooling rates of glasses can be inferred from direct heat capacity measurements on the glasses themselves (Wilding et al., 1995, 1996a,b). This method does not require knowledge of glass cooling environments and has been applied to calculate the cooling rates of natural silicate glasses formed in different terrestrial environments. We have carried out heat capacity measurements on hand-picked lunar glass beads using a Netzsch DSC 404C Pegasus differential scanning calorimeter at University of Munich. Our preliminary results suggest that the cooling rate of Apollo 17 orange glass beads may be 12 K/min, based on the correlation between temperature of the heat capacity curve peak in the glass transition range and glass cooling rate. The results imply that the parental magmas of lunar pyroclastic deposits may have contained more water initially than the early estimations (Saal et al., 2008), which used higher cooling rates, 60-180 K/min in the modeling. Furthermore, lunar volcanic glass beads could have been cooled in a hot gaseous medium released from volcanic eruptions, not during free flight. Therefore, our results may shed light on atmospheric condition in an early moon.

  13. Petrography, Geochemistry and Petrogenesis of Volcanic Rocks, NW Ghonabad, Iran

    Directory of Open Access Journals (Sweden)

    Sedigheh Zirjanizadeh


    Full Text Available Introduction The study area is located in NW Gonabad, Razavi Khorasan Province, northern Lut block and eastern Iran north of the Lut Block. Magmatism in NW Gonabad produced plutonic and volcanic rock associations with varying geochemical compositions. These rocks are related to the Cenozoic magmatic rocks in Iran and belong to the Lut Block volcanic–plutonic belt. In this study, petrogenesis of volcanic units in northwest Gonabad was investigated. The volcanic rocks are andesites/trachyandesites, rhyolites, dacites/ rhyodacites and pyroclastics.These rocks show porphyritic, trachytic and embayed textures in phenocrysts with plagioclase, sanidine and quartz (most notably in dacite and rhyolite, hornblende and rare biotite. The most important alteration zones are propylitic, silicification and argillic.Four kaolinite- bearing clay deposits have been located in areas affectedby hydrothermal alteration of Eocene rhyolite, dacite and rhyodacite. Analytical techniques Five samples were analyzed for major elements by wavelength dispersive X-ray fluorescence (XRF and six samples were analyzed for trace elements using inductively coupled plasma-mass spectrometry (ICP-MS in the Acme Laboratories, Vancouver (Canada.Sr and Nd isotopic compositions were determined for four whole-rock samples at the Laboratório de GeologiaIsotópica da Universidade de Aveiro, Portugal. Results Petrography. The rocks in this area are consist of trachyte, andesite/ trachyandesite, dacite/ rhyodacite, principally as ignimbrites and soft tuff. The textures of phenocrysts are mainly porphyritic, glomerophyric, trachytic and embayed textures in plagioclase, hornblende and biotite. The groundmasses consist of plagioclase and fine-grainedcrystals of hornblende. Plagioclase phenocrysts and microlitesare by far the most abundant textures in andesite - trachyandesites (>25% and in size from 0.01 to 0.1mm. Euhedral to subhedral hornblende phenocrysts areabundant (3-5%and 0.1 to 0

  14. Intercontinental and intracontinental biogeography of the eastern Asian - Eastern North American disjunct Panax (the ginseng genus, Araliaceae), emphasizing its diversification processes in eastern Asia. (United States)

    Zuo, Yun-Juan; Wen, Jun; Zhou, Shi-Liang


    The intercontinental biogeography between eastern Asia and eastern North America has attracted much attention from evolutionary biologists. Further insights into understanding the evolution of the intercontinental disjunctions have been hampered by the lack of studies on the intracontinental biogeography in eastern Asia, a region with complex geology, geography, climates and habitats. Herein we studied the biogeographic history of the eastern Asian-eastern North American disjunct genus Panax with special emphasis on the investigation of its uneven diversification in Asia. This study reconstructs the diversification history of Panax and also emphasizes a large clade of Panax taxa, which has a wide distribution in eastern Asia, but was unresolved in previous studies. We examined the noncoding plastid DNA fragments of trnH-psbA, rps16, and psbM-trnD, the mitochondrial b/c intron of NAD1, and the nuclear ribosomal internal transcribed spacer (ITS) region of 356 samples from 47 populations. The results revealed the subtropical Northern Hemisphere origin (Asia or Asia and North America) of Panax in the Paleocene. Intercontinental disjunctions between eastern Asia and eastern North America formed twice in Panax, once estimated in early Eocene for the split of P. trifolius and another in mid-Miocene for the divergence of P. quinquefolius. Intercontinental diversifications in Panax showed temporal correlation with the increase of global temperature. The evolutionary radiation of the P. bipinnatifidus species complex occurred around the boundary of Oligocene and Miocene. Strong genetic structure among populations of the species complex was detected and the populations may be isolated by distance. The backbone network and the Bayesian clustering analysis revealed a major evolutionary radiation centered in the Hengduan Mountains of western China. Our results suggested that the evolutionary radiation of Panax was promoted by geographic barriers, including mountain ranges

  15. Eastern Frequency Response Study

    Energy Technology Data Exchange (ETDEWEB)

    Miller, N.W.; Shao, M.; Pajic, S.; D' Aquila, R.


    This study was specifically designed to investigate the frequency response of the Eastern Interconnection that results from large loss-of-generation events of the type targeted by the North American Electric Reliability Corp. Standard BAL-003 Frequency Response and Frequency Bias Setting (NERC 2012a), under possible future system conditions with high levels of wind generation.

  16. Geologic and geophysical investigations of the Zuni-Bandera volcanic field, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Ander, M.E.; Heiken, G.; Eichelberger, J.; Laughlin, A.W.; Huestis, S.


    A positive, northeast-trending gravity anomaly, 90 km long and 30 km wide, extends southwest from the Zuni uplift, New Mexico. The Zuni-Bandera volcanic field, an alignment of 74 basaltic vents, is parallel to the eastern edge of the anomaly. Lavas display a bimodal distribution of tholeiitic and alkalic compositions, and were erupted over a period from 4 Myr to present. A residual gravity profile taken perpendicular to the major axis of the anomaly was analyzed using linear programming and ideal body theory to obtain bounds on the density contrast, depth, and minimum thickness of the gravity body. Two-dimensionality was assumed. The limiting case where the anomalous body reaches the surface gives 0.1 g/cm/sup 3/ as the greatest lower bound on the maximum density contrast. If 0.4 g/cm/sup 3/ is taken as the geologically reasonable upper limit on the maximum density contrast, the least upper bound on the depth of burial is 3.5 km and minimum thickness is 2 km. A shallow mafic intrusion, emplaced sometime before Laramide deformation, is proposed to account for the positive gravity anomaly. Analysis of a magnetotelluric survey suggests that the intrusion is not due to recent basaltic magma associated with the Zuni-Bandera volcanic field. This large basement structure has controlled the development of the volcanic field; vent orientations have changed somewhat through time, but the trend of the volcanic chain followed the edge of the basement structure. It has also exhibited some control on deformation of the sedimentary section.

  17. Comparing Volcanic Terrains on Venus and Earth: How Prevalent are Pyroclastic Deposits on Venus? (United States)

    Carter, Lynn M.; Campbell, B. A.; Glaze, L. S.


    In the last several years, astronomers have discovered several exoplanets with masses less than 10 times that of the Earth [1]. Despite the likely abundance of Earth-sized planets, little is known about the pathways through which these planets evolve to become habitable or uninhabitable. Venus and Earth have similar planetary radii and solar orbital distance, and therefore offer a chance to study in detail the divergent evolution of two objects that now have radically different climates. Understanding the extent, duration, and types of volcanism present on Venus is an important step towards understanding how volatiles released from the interior of Venus have influenced the development of the atmosphere. Placing constraints on the extent of explosive volcanism on Venus can provide boundary conditions for timing, volumes, and altitudes for atmospheric injection of volatiles. In addition, atmospheric properties such as near-surface temperature and density affect how interior heat and volatiles are released. Radar image data for Venus can be used to determine the physical properties of volcanic deposits, and in particular, they can be used to search for evidence of pyroclastic deposits that may result from explosive outgassing of volatiles. For explosive volcanism to occur with the current high atmospheric pressure, magma volatile contents must be higher than is typical on Earth (at least 2-4% by weight) [2,3]. In, addition, pyroclastic flows should be more prevalent on Venus than convective plumes and material may not travel as far from the vent source as it would on Earth [3]. Areas of high radar backscatter with wispy margins that occur near concentric fractures on Sapho Patera [4] and several coronae in Eastern Eistla Regio [5] have been attributed to collapse of eruption columns and runout of rough materials.

  18. The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism (United States)

    Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.


    The awesome power and intricate inner workings of volcanoes have made them a popular subject with scientists and the general public alike. About 1500 known volcanoes have been active on Earth during the Holocene, approximately 50 of which erupt per year. With so much activity occurring around the world, often in remote locations, it can be difficult to find up-to-date information about current volcanism from a reliable source. To satisfy the desire for timely volcano-related information the Smithsonian Institution and US Geological Survey combined their strengths to create the Weekly Volcanic Activity Report. The Smithsonian's Global Volcanism Program (GVP) has developed a network of correspondents while reporting worldwide volcanism for over 30 years in their monthly Bulletin of the Global Volcanism Network. The US Geological Survey's Volcano Hazards Program studies and monitors volcanoes in the United States and responds (upon invitation) to selected volcanic crises in other countries. The Weekly Volcanic Activity Report is one of the most popular sites on both organization's websites. The core of the Weekly Volcanic Activity Report is the brief summaries of current volcanic activity around the world. In addition to discussing various types of volcanism, the summaries also describe precursory activity (e.g. volcanic seismicity, deformation, and gas emissions), secondary activity (e.g. debris flows, mass wasting, and rockfalls), volcanic ash hazards to aviation, and preventative measures. The summaries are supplemented by links to definitions of technical terms found in the USGS photoglossary of volcano terms, links to information sources, and background information about reported volcanoes. The site also includes maps that highlight the location of reported volcanoes, an archive of weekly reports sorted by volcano and date, and links to commonly used acronyms. Since the Weekly Volcanic Activity Report's inception in November 2000, activity has been reported at

  19. Geochemical Evidence of Island-Arc Origin for Sumatra Island; A New Perspective based on Volcanic Rocks in Lampung Province, Indonesia

    Directory of Open Access Journals (Sweden)

    Iskandar Zulkarnain


    Full Text Available DOI: 10.17014/ijog.v6i4.128Since decades, Sumatra Island is considered as the Eurasia continental margin where the Indian Ocean plate has been subducted oblique beneath the continental plate of Sumatra. But, the occurrences of volcanic rocks in almost all areas of Lampung Province in the southernmost of Sumatra Island, as the presence of the Quaternary Tanggamus Volcano in the western part of the province together with the Quaternary Rajabasa Volcano in the eastern area cannot be justified using the consideration. Spider diagrams of trace and rare earth elements of volcanic rocks from the western and eastern areas of the province reveal that the rocks come from three different tectonic settings, namely island-arc, active continental margin (ACM, and intra continental plate. All basalt and one dacite of western volcanic rocks show a character of island-arc origin, while the eastern volcanic rocks are reflecting characters of ACM and intra continental plate. Plot of the rocks in the diagram of Ta/Yb versus Ce/P and in Ta/Yb versus Th/Yb confirmed the tectonic environments and specifically classify the intra continental plate into Within Plate Volcanic Zone (WPVZ. The island-arc group is characterized by Ta/Yb ratio of less than 2.0 and Ce/P less than 1.8. The ACM group is recognized having Ta/Yb ratio between 2 and 4 with Ce/P more 1.8, while the WPVZ group is defined as a group having Ta/Yb more than 6 and Ce/P more than 1.0. The result indicates that the western part of Sumatra is an island-arc fragment and the eastern part belongs to the Eurasia continental margin. The concentration of volcanics having ACM character from areas around the Sumatra Fault System to the east indicates that the collision zone between the Sumatra island-arc fragments with the Eurasia continental margin is probably located along the SFS. More statistical data is still needed from other Sumatra volcanics to confirm this conclusion.


    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R.


    The Eyjafjallajokull volcanic eruption in Iceland in April 2010 disrupted transportation in Europe which ultimately affected travel plans for many on a global basis. The Volcanic Ash Advisory Centre (VAAC) is responsible for providing guidance to the aviation industry of the transport of volcanic ash clouds. There are nine such centers located globally, and the London branch (headed by the United Kingdom Meteorological Office, or UKMet) was responsible for modeling the Iceland volcano. The guidance provided by the VAAC created some controversy due to the burdensome travel restrictions and uncertainty involved in the prediction of ash transport. The Iceland volcanic eruption provides a useful exercise of the European ENSEMBLE program, coordinated by the Joint Research Centre (JRC) in Ispra, Italy. ENSEMBLE, a decision support system for emergency response, uses transport model results from a variety of countries in an effort to better understand the uncertainty involved with a given accident scenario. Model results in the form of airborne concentration and surface deposition are required from each member of the ensemble in a prescribed format that may then be uploaded to a website for manipulation. The Savannah River National Laboratory (SRNL) is the lone regular United States participant throughout the 10-year existence of ENSEMBLE. For the Iceland volcano, four separate source term estimates have been provided to ENSEMBLE participants. This paper focuses only on one of those source terms. The SRNL results in relation to other modeling agency results along with useful information obtained using an ensemble of transport results will be discussed.

  1. Using Spatial Density to Characterize Volcanic Fields on Mars (United States)

    Richardson, J. A.; Bleacher, J. E.; Connor, C. B.; Connor, L. J.


    We introduce a new tool to planetary geology for quantifying the spatial arrangement of vent fields and volcanic provinces using non parametric kernel density estimation. Unlike parametricmethods where spatial density, and thus the spatial arrangement of volcanic vents, is simplified to fit a standard statistical distribution, non parametric methods offer more objective and data driven techniques to characterize volcanic vent fields. This method is applied to Syria Planum volcanic vent catalog data as well as catalog data for a vent field south of Pavonis Mons. The spatial densities are compared to terrestrial volcanic fields.

  2. Aeromagnetic anomalies reveal hidden tectonic and volcanic structures in the central sector of the Aeolian Islands, southern Tyrrhenian Sea, Italy (United States)

    de Ritis, Riccardo; Ventura, Guido; Chiappini, Massimo


    Salina Island (Italy) in the central Aeolian chain is the northernmost volcanic structure of an elongated ridge on a regional shear zone with NNW-SSE strike-slip faults and second-order N-S and NE-SW faults. Modeling of high-resolution, low-altitude aeromagnetic data collected in 2003 and 2005 using volcanological data constraints reveals the inner structure of the Salina volcanoes and surrounding marine regions. Regional negative anomalies overlie E-W elongated sedimentary basins related to the early Pliocene-Pleistocene opening of the southern Tyrrhenian Sea. These negative anomalies flank positively magnetized crust of Salina and seamounts off its eastern coast where the shorter-wavelength anomalies map late Pleistocene-Holocene volcanic conduits, dikes, and faults. The magnetic and volcanological data indicate that the early (circa 168-100 ka) basaltic to andesitic Salina volcanism developed along N-S and NE-SW tectonic faults, whereas the more recent andesitic lavas and rhyolitic pyroclastics (circa 100-13 ka) were emitted by vents related to the main NW-SE faults. The tectonic structures also controlled the location of the seamounts around the island and the geometry of the volcano-tectonic collapses. Salina volcanism was emplaced on a NNW-SSE tear fault of the presently developing roll-back slab in the southern Tyrrhenian Sea.

  3. Insight of the fusion behavior of volcanic ash: Implications for Volcanic ash Hazards to Aircraft Safety (United States)

    Song, Wenjia; Hess, Kai-Uwe; Küppers, Ulrich; Scheu, Bettina; Cimarelli, Corrado; Lavallée, Yan; Sohyun, Park; Gattermann, Ulf; Müller, Dirk; Dingwell, Donald Bruce


    The interaction of volcanic ash with jet turbines during via ingestion of ash into engines operating at supra-volcanic temperatures is widely recognized as a potentially fatal hazard for jet aircraft. In the past 12 years, more than 60 modern jet airplanes, mostly jumbo jets, have been damaged by drifting clouds of volcanic ash that have contaminated air routes and airport facilities. Seven of these encounters are known to have caused in flight loss of engine power to jumbo jets carrying a total of more than 2000 passengers. The fusibility of volcanic ash is believed to impact strongly its deposition in the hotter parts of jet engines. Despite this, explicit investigation of ash sintering using standardized techniques is in its infancy. Volcanic ash may vary widely in its physical state and chemical composition between and even within explosive volcanic eruptions. Thus a comparative study of the fusibility of ash which involves a standard recognized techniques would be highly desirable. In this work, nine samples of fine ash, deposited from co-pyroclastic offrom nine different volcanoes which cover a broad range of chemical composition, were investigated. Eight of them were collected from 2001-2009 eruptions. Because of the currently elevated level of eruptive activity and its potential hazards to aircraft safety and the remaining one sample was collected from a 12,121 ± 114 yr B.P. eruption. We used the method of accessing the behavior of deposit-forming impurities in high temperature boiler plants on the basis of observations of the change in shape and size of a cylindrical coal ash to study the fusion phenomena as well as determine the volcanic ash melting behavior by defining four characteristic temperatures (shrinkage temperature, deformation temperature, hemispherical temperature, and flow temperature) by means of heating microscope instrument and different thermal analysis methods. Here, we find that there are similar sticking ability and flow behavior of

  4. 2.9 GA Magmatism in Eastern Hebei, North China Craton (United States)

    Liu, P.; Guo, J.


    We report the results of a comprehensive isotopic investigation of zircons from metamorphosed volcanic rocks from Caochang village in Zunhua complex, Eastern Hebei. A detailed investigation of internal structures of zircons, combined with SIMS U-Pb and oxygen isotope analyses and ICP-MS Hf zircon analyses as well as whole-rock geochemical study revealed the previously unknown 2.9Ga magmatic event and 2.87Ga metamorphic event in Eastern Hebei. The Mesoarchean rocks include high silica rhyolites, high silica sodic rhyolites, dacites and basalts. They together constitute an ancient bimodal volcanic rock series, which may be the largest outcrop of Mesoarchean supracrustal rocks in North China craton. Low δ18O compositions and inherited cores of zircons, low Cr, Ni composition and negative Eu anomaly in whole rock geochemical characteristic, as well as the relevant study of experimental petrology indicate a genesis of shallow crustal recycling with deep hydrothermal circulation. Their lower ɛNd(t) and ɛHf(t) (close to CHUR) indicate rapid reworking of altered juvenile crust. Thus these rhyolites may be formed by remelting of young hydrothermally altered basaltic crust or altered felsic wallrocks. All the geochemical evidence and the existence of Archean potassic rhyolites as well as the bimodal volcanic rock series imply a continent rift zone setting. The existence of Mesoarchean rocks and widespread ancient inherited and detrital zircons (>2.6 Ga) imply a possible ancient continent in Eastern Hebei, not only in Caozhuang nearby but also in Zunhua-Qinglong area. They provide valuable information about the Mesoarchean magmatic evolution. Meanwhile, they may imply the mesoarchean era (especially the 2.9 Ga) represent another major magmatic event of equal importance with 2.6-2.5 Ga period, at least in the eastern block. The magmatic and metamorphic history in Eastern Hebei are far more complex than previously thought.

  5. Role of crustal and slab components in the Northern Volcanic Zone of the Andes (Ecuador) constrained by Sr-Nd-O isotopes


    Hidalgo, S.; Gerbe, M. C.; Martin, H.; Samaniego, Pablo; Bourdon, E.


    A combined approach based on trace elements, radiogenic (Sr-Nd) and stable (O) isotopes allows us to discuss the role of crustal assimilation and mantle metasomatism in Quaternary Ecuadorian magmatism. Magmas emplaced in the Eastern Cordillera have high Sr isotopic ratios and relatively high delta O-18 values, which reflect crustal assimilation (6-13 vol.%) of igneous and metamorphic Palaeozoic and Mesozoic rocks during ascent and storage in the continental crust. However, in the Volcanic Fro...

  6. Ancient Mudflows in the Tuxtla Volcanic Field, Veracruz, Mexico (United States)

    Espindola, J.; Zamora-Camacho, A.; Godinez, M.


    The Tuxtla Volcanic Field (TVF) is a basaltic volcanic enclave in eastern Mexico at the margin of the Gulf of Mexico. Due to the high rates of precipitation floods and mudflows are common. Resulting from a systematic study of geologic hazard in the TVF we found several mudflow deposits that impacted pre-Columbian settlements. Sections of the deposits were observed in detail and sampled for granulometric studies. The deposits contained materials suitable for dating: ceramic shards and some of them charcoal fragments. Shards from the interior of the deposit were collected and placed in black bags to prevent the action of light and to be analyzed by thermoluminiscense (TL), the charcoal samples were dated using standard radiocarbon methods (C-14). The sites were dubbed La Mojarra (18°37.711', 95°18.860'), Revolución (18° 35.848', 95°11.412'), Pisatal (18°36.618', 95°10.634'), and Toro Prieto (18°38.229, 95°12.037'). These places were named after the nearby villages the first two, lake Pisatal the third and Toro Prieto creek the fourth. All the deposits occur close to the margins of riverbeds or lakes. Samples of these sites yielded ages of 1176±100 (TL), 1385±70 (C-14), 1157±105 (TL), 2050+245-235 (C-14), respectively. These locations have undergone recurrent floods in the last decades, showing that these phenomena impact the same areas over centuries. The dates mentioned are important because, no vestiges of human settlements had been reported in the area, which in the past was covered by a dense forest. The settlements must have been very small and depended of such cities as nearby Matacapan an important city with strong ties to Teotihuacán in central Mexico. The ages agree with the findings of archeologic studies in Matacapan, which indicate that the population became increasingly ruralized since the late classic period (≈ 600-800 AD).

  7. [Effects of volcanic eruptions on human health in Iceland. Review]. (United States)

    Gudmundsson, Gunnar; Larsen, Guðrun


    Volcanic eruptions are common in Iceland and have caused health problems ever since the settlement of Iceland. Here we describe volcanic activity and the effects of volcanic gases and ash on human health in Iceland. Volcanic gases expelled during eruptions can be highly toxic for humans if their concentrations are high, irritating the mucus membranes of the eyes and upper respiratory tract at lower concentrations. They can also be very irritating to the skin. Volcanic ash is also irritating for the mucus membranes of the eyes and upper respiratory tract. The smalles particles of volcanic ash can reach the alveoli of the lungs. Described are four examples of volcanic eruptions that have affected the health of Icelanders. The eruption of Laki volcanic fissure in 1783-1784 is the volcanic eruption that has caused the highest mortality and had the greatest effects on the well-being of Icelanders. Despite multiple volcanic eruptions during the last decades in Iceland mortality has been low and effects on human health have been limited, although studies on longterm effects are lacking. Studies on the effects of the Eyjafjallajökul eruption in 2010 on human health showed increased physical and mental symptoms, especially in those having respiratory disorders. The Directorate of Health in Iceland and other services have responded promptly to recurrent volcanic eruptions over the last few years and given detailed instructions on how to minimize the effects on the public health. Key words: volcanic eruptions, Iceland, volcanic ash, volcanic gases, health effects, mortality. Correspondence: Gunnar Guðmundsson,

  8. Indentifying dikes in the eastern Hellas rim region, Mars (United States)

    Korteniemi, J.; Raitala, J.; Kostama, V.-P.; Aittola, M.; Hyvärinen, M.


    Abstract The Hadriaca Patera (HP) volcano [e.g. 1-9] on Mars is situated on the north-easten rim of the giant Hellas impact basin, and on the western edge of the vast volcanic plains of Hesperia Planum [10, 11]. The eastern Hellas rim region harbours also other, possibly separate centers of volcanism that have only recently been proposed [12, 13]. The area is additionally characterized by a multitude of fluvial features, extending from small, partly dendritic channel networks (e.g 14-16, references therein) to vast, several km deep and hundreds of km long outflow valleys (e.g. 14, 16-19, references therein). The origins of the latter type have been theorized to be in volcanism and creation of sills and dikes beneath or near the channel heads [7, 19]. The Hesperia-Hellas region also shows evidence of even more significant volatile erosion prior to the formation of the outflow channels, also induced by endogenic activity [20]. We study a roughly 1200-km wide region around the HP volcano in search of real-life dike-indicative formations [for details and more discussion, see 21]. The origin and distribution of the dikes in the east Hellas region is of importance when discussing the regional geology, and especially when attempting to synthesize a chronology and causal relationships between regional events such as outflow channel formation. The dike patterns and sizes are related to the whereabouts and characteristics of their feeding magma bodies. Thus, the dike distribution around HP gives a hint about the heat flux in the region. This reflects on the possible formation scenarios of e.g. the outflow channels near HP as well as the formation of the several floor-fractured craters in the NE Hellas region. We have identified and documented a large number of straight/curvilinear ridges, fractures and grabens on the volcano itself, on its flanks, and on the whole eastern Hellas rim region. The best candidates for actual dike manifestations include e.g. transitions from

  9. Eastern Luzon Arc Affinity of Benham Rise Tephras from Major Element Chemistry of MD06-3047 Glasses (United States)

    Mandanas, A. A.; Tejada, M. G.; Catane, S.; Teves, J.; Arpa, M. B.; Mirabueno, M. T.; Bringas, C. L.; Lit, C. C.; Solidum, R. U.


    Piston coring on the Benham Rise in the western Philippine Sea during the Marco Polo 2 cruise of R/V Marion Dufresne in 2006 provided a rare opportunity to study tephra deposits offshore the Eastern Luzon volcanic arc. Four tephra layers were analyzed from the upper 7 m of core MD06-3047 (~450 km from the arc, 2510 mbsl): A 6 cm-thick black ash overlies three, 2 cm-thick light grey to grey tephras. Sediment samples within 1 cm below each of the grey tephra yielded AMS 14C ages in excess of ~40,000 ybp. Electron microprobe analysis on tephra glass revealed that the black ash has andesitic-dacitic compositions (57-66 wt% SiO2), whereas the three grey ashes cluster to rhyolitic compositions (73-78 wt% SiO2). Furthermore, the rhyolitic tephras also exhibit geochemical distinctions from each other, forming unique fields in variation diagrams with K2O or MgO abscissae. Average major element concentrations of the tephras, except K2O, increase towards the bottom of the core section. Tight linear trends on FeOtotal, MgO and CaO plots, and the abundance of pumiceous shards and bubble wall fragments, imply primary magmatic sources for the glasses. Depositional distances reaching 600 km from volcanic provenances have been reported for andesitic to rhyolitic tephras from Pinatubo volcano and the Japan arc. A comparable distance from the core site would cover several active arcs in the Philippines. The EPMA data points to affinity only with volcanic centers from the Bicol segment of the Eastern Luzon arc (or Bicol arc), based on review of new and literature data. The andesitic glasses bear a strong geochemical resemblance to historical Mayon volcanics, deviating moderately in average Al2O3 and FeOtotal levels. However, correlation of the andesitic tephra with Mayon may be problematic, as the oldest age for this volcano is only 20 cal. ka [1]. The age (~35-41 cal.ka) [2,3] and compositional similarities of the rhyolitic tephras with the calderagenic eruption products of Irosin

  10. The 1978 Yellowstone-Eastern Snake River Plain Seismic Profiling Experiment: Crustal structure of the Yellowstone Region and experiment design (United States)

    Smith, R. B.; Schilly, M. M.; Braile, L. W.; Ansorge, J.; Lehman, J. L.; Baker, M. R.; Prodehl, C.; Healy, J. H.; Mueller, S.; Greensfelder, R. W.


    , and (6) a total crustal thickness of ˜43 km. The upper crustal layer, 5.5 to 6.0 km/s, is thought to be the thermally altered equivalent of the continental crystalline basement that is normally 15 to 20 km thick in the surrounding thermally undisturbed Archean crust. An interpretation from these results suggests that mafic melts from the mantle have penetrated the lower crust without significant variations in the velocity structure but produce the main source of heat that drives the volcanic and hydrothermal systems of Yellowstone. The high apparent attenuation and large lateral velocity variations in the upper crust are consistent with a model in which partial fractionation, partial melting, and metamorphism differentiate the original upper crust to produce silicic melts that were extruded as rhyolites and ash flow tuffs across the Yellowstone Plateau. This seismic model is consistent with the evidence for a systematic northeastward propogation of silicic volcanic centers along the eastern Snake River Plain to their present location beneath the Yellowstone hydrothermal system. While these findings do not bear directly on the origin and source of the heat, i.e., mantle lumes, lithospheric fractures, mantle radiogenetic heat, basal lithospheric shearing, etc., they provide a constraint on the configuration and lateral extent of crustal layers that reflect thermal and compositional boundaries.

  11. Page 1 Paleocene On-spreading-axis hotspot volcanism along the ...

    Indian Academy of Sciences (India)

    centers of the eastern Indian Ocean and seismic structure and radiometric dates of the Ninetyeast Ridge. Furthermore, it is supported by the occurrence of oceanic andesites at Deep Sea Drilling Project (DSDP). Site 214, isotopically heterogeneous basalts at Ocean Drilling Program (ODP) Site 757 of approximately.

  12. Mapping natural radioactivity of soils in the eastern Canary Islands. (United States)

    Arnedo, M A; Rubiano, J G; Alonso, H; Tejera, A; González, A; González, J; Gil, J M; Rodríguez, R; Martel, P; Bolivar, J P


    The Canary Islands archipielago (Spain) comprises seven main volcanic islands and several islets that form a chain extending for around 500 km across the eastern Atlantic, between latitudes 27°N and 30°N, with its eastern edge only 100 km from the NW African coast. The administrative province of Las Palmas comprises the three eastern Canary Islands (Lanzarote, Fuerteventura and Gran Canaria). An extensive study of terrestrial gamma dose rates in surface soils has been carried out to cover the entire territory of the province (4093 km2). The average outdoor gamma dose rate in air at 1 m above ground is 73 nGyh-1 at Gran Canaria, 32 nGyh-1 at Fuerteventura, and 25 nGyh-1 at Lanzarote. To complete the radiological characterization of this volcanic area, 350 soil samples at 0-5 cm depth were collected to cover all the geologic typologies of the islands. These samples were measured using high resolution gamma spectrometry to determine the activity concentrations of 226Ra, 232Th and 40K. The average values obtained were 25.2 Bq/kg, 28.9 Bq/kg, and 384.4 Bq/kg, respectively. Maps of terrestrial gamma activity, effective dose, and activity concentrations of 226Ra, 232Th and 40K for the region have been developed through the use of geostatistical interpolation techniques. These maps are in accord with the geology of the islands. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Volcanic ash impacts on critical infrastructure (United States)

    Wilson, Thomas M.; Stewart, Carol; Sword-Daniels, Victoria; Leonard, Graham S.; Johnston, David M.; Cole, Jim W.; Wardman, Johnny; Wilson, Grant; Barnard, Scott T.


    Volcanic eruptions can produce a wide range of hazards. Although phenomena such as pyroclastic flows and surges, sector collapses, lahars and ballistic blocks are the most destructive and dangerous, volcanic ash is by far the most widely distributed eruption product. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation and primary production can lead to significant societal impacts. Even relatively small eruptions can cause widespread disruption, damage and economic loss. Volcanic eruptions are, in general, infrequent and somewhat exotic occurrences, and consequently in many parts of the world, the management of critical infrastructure during volcanic crises can be improved with greater knowledge of the likely impacts. This article presents an overview of volcanic ash impacts on critical infrastructure, other than aviation and fuel supply, illustrated by findings from impact assessment reconnaissance trips carried out to a wide range of locations worldwide by our international research group and local collaborators. ‘Critical infrastructure’ includes those assets, frequently taken for granted, which are essential for the functioning of a society and economy. Electricity networks are very vulnerable to disruption from volcanic ash falls. This is particularly the case when fine ash is erupted because it has a greater tendency to adhere to line and substation insulators, where it can cause flashover (unintended electrical discharge) which can in turn cause widespread and disruptive outages. Weather conditions are a major determinant of flashover risk. Dry ash is not conductive, and heavy rain will wash ash from insulators, but light rain/mist will mobilise readily-soluble salts on the surface of the ash grains and lower the ash layer’s resistivity. Wet ash is also heavier than dry ash, increasing the risk of line breakage or tower/pole collapse. Particular issues for water

  14. Volcanic disasters and incidents: A new database (United States)

    Witham, C. S.


    A new database on human mortality and morbidity, and civil evacuations arising from volcanic activity is presented. The aim is to quantify the human impacts of volcanic phenomena during the 20th Century. Data include numbers of deaths, injuries, evacuees and people made homeless, and the nature of the associated volcanic phenomena. The database has been compiled from a wide range of sources, and discrepancies between these are indicated where they arise. The quality of the data varies according to the source and the impacts reported. Data for homelessness are particularly poor and effects from ashfall and injuries appear to be under-reported. Of the 491 events included in the database, ˜53% resulted in deaths, although the total death toll of 91,724 is dominated by the disasters at Mt Pelée and Nevado del Ruiz. Pyroclastic density currents account for the largest proportion of deaths, and lahars for the most injuries incurred. The Philippines, Indonesia, and Southeast Asia, as a region, were the worst affected, and middle-income countries experienced greater human impacts than low or high-income countries. Compilation of the database has highlighted a number of problems with the completeness and accuracy of the existing CRED EM-DAT disaster database that includes volcanic events. This database is used by a range of organisations involved with risk management. The new database is intended as a resource for future analysis and will be made available via the Internet. It is hoped that it will be maintained and expanded.

  15. The Zuni-Bandera Volcanic Field, NM: An Analog for Exploring Planetary Volcanic Terrains (United States)

    Bleacher, J. E.; Garry, W. B.; Zimbelman, J. R.; Crumpler, L. S.; Aubele, J. C.


    The Zuni-Bandera volcanic field, near Grants, New Mexico, is comprised of volcanic deposits from several basaltic eruptions during the last million years. This vent field exhibits a diverse group of coalesced lava flows and displays well-preserved volcanic features including a’a and pahoehoe flows, collapsed lava tubes, cinder cones and low shields. The McCartys flow is a 48-km long inflated basalt flow and is the youngest in the field at around 3000 years old. Over the last three years we have used the Zuni-Bandera volcanic field, and the McCartys flow in particular, as a terrestrial analog for exploring planetary volcanic fields, and understanding the role of lava sheet inflation in flow field development. We have conducted three different styles of analog tests, 1) basic field science focused on understanding lava sheet inflation, 2) mission operations tests related to EVA design and real-time modification of traverse plans, and 3) science enabling technology tests. The Zuni-Bandera field is an ideal location for each style of analog test because it provides easy access to a diverse set of volcanic features with variable quality of preservation. However, many limitations must also be considered in order to maximize lessons learned. The McCartys flow displays well-preserved inflation plateaus that rise up to 15 m above the surrounding field. The preservation state enables textures and morphologies indicative of this process to be characterized. However, the pristine nature of the flow does not compare well with the much older and heavily modified inflated flows of Mars and the Moon. Older flows west of McCartys add value to this aspect of analog work because of their degraded surfaces, development of soil horizons, loose float, and limited exposure of outcrops, similar to what might be observed on the Moon or Mars. EVA design tests and science enabling technology tests at the Zuni-Bandera field provide the opportunity to document and interpret the relationships

  16. Volcanic alert system (VAS) developed during the 2011-2014 El Hierro (Canary Islands) volcanic process (United States)

    García, Alicia; Berrocoso, Manuel; Marrero, José M.; Fernández-Ros, Alberto; Prates, Gonçalo; De la Cruz-Reyna, Servando; Ortiz, Ramón


    The 2011 volcanic unrest at El Hierro Island illustrated the need for a Volcanic Alert System (VAS) specifically designed for the management of volcanic crises developing after long repose periods. The VAS comprises the monitoring network, the software tools for analysis of the monitoring parameters, the Volcanic Activity Level (VAL) management, and the assessment of hazard. The VAS presented here focuses on phenomena related to moderate eruptions, and on potentially destructive volcano-tectonic earthquakes and landslides. We introduce a set of new data analysis tools, aimed to detect data trend changes, as well as spurious signals related to instrumental failure. When data-trend changes and/or malfunctions are detected, a watchdog is triggered, issuing a watch-out warning (WOW) to the Monitoring Scientific Team (MST). The changes in data patterns are then translated by the MST into a VAL that is easy to use and understand by scientists, technicians, and decision-makers. Although the VAS was designed specifically for the unrest episodes at El Hierro, the methodologies may prove useful at other volcanic systems.

  17. UNAVCO Conference explores advances in volcanic geodesy (United States)

    Stein, Seth; Hamburger, Michael; Meertens, Charles; Dixon, Timothy; Owen, Susan

    Volcanic eruptions are among Earth's most spectacular surface phenomena. However, attempts to understand their basic physics face the challenge that the key processes occur at great depth and are difficult to observe. Thus volcanologists have been interested for years in using ground deformation measurements to study active volcanoes and predict their behavior during extended volcanic crises, such as the dramatic six weeks in 1980 between the initial and major eruptions of Mt. Saint Helens.The advent of new technologies in recent years—in particular the Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (INSAR)—has shown potential for significant advances in volcano studies. Progress in this direction was explored at a conference organized by the University Navstar Consortium (UNAVCO) on September 15-17, 1999, with financial support from the National Science Foundation (NSF), NASA, and the U.S. Geological Survey (USGS). The meeting aimed to assess the status of various geodetic technologies and their potential to address crucial scientific and social needs in volcanic science and monitoring, as well as to develop recommendations on ways to spur further progress in these areas.

  18. Amazonian volcanism inside Valles Marineris on Mars (United States)

    Brož, Petr; Hauber, Ernst; Wray, James J.; Michael, Gregory


    The giant trough system of Valles Marineris is one of the most spectacular landforms on Mars, yet its origin is still unclear. Although often referred to as a rift, it also shows some characteristics that are indicative of collapse processes. For decades, one of the major open questions was whether volcanism was active inside the Valles Marineris. Here we present evidence for a volcanic field on the floor of the deepest trough of Valles Marineris, Coprates Chasma. More than 130 individual edifices resemble scoria and tuff cones, and are associated with units that are interpreted as lava flows. Crater counts indicate that the volcanic field was emplaced sometime between ∼0.4 Ga and ∼0.2 Ga. The spatial distribution of the cones displays a control by trough-parallel subsurface structures, suggesting magma ascent in feeder dikes along trough-bounding normal faults. Spectral data reveal an opaline-silica-rich unit associated with at least one of the cones, indicative of hydrothermal processes. Our results point to magma-water interaction, an environment of astrobiological interest, perhaps associated with late-stage activity in the evolution of Valles Marineris, and suggest that the floor of Coprates Chasma is promising target for the in situ exploration of Mars.

  19. Geothermal and volcanism in west Java (United States)

    Setiawan, I.; Indarto, S.; Sudarsono; Fauzi I, A.; Yuliyanti, A.; Lintjewas, L.; Alkausar, A.; Jakah


    Indonesian active volcanoes extend from Sumatra, Jawa, Bali, Lombok, Flores, North Sulawesi, and Halmahera. The volcanic arc hosts 276 volcanoes with 29 GWe of geothermal resources. Considering a wide distribution of geothermal potency, geothermal research is very important to be carried out especially to tackle high energy demand in Indonesia as an alternative energy sources aside from fossil fuel. Geothermal potency associated with volcanoes-hosted in West Java can be found in the West Java segment of Sunda Arc that is parallel with the subduction. The subduction of Indo-Australian oceanic plate beneath the Eurasian continental plate results in various volcanic products in a wide range of geochemical and mineralogical characteristics. The geochemical and mineralogical characteristics of volcanic and magmatic rocks associated with geothermal systems are ill-defined. Comprehensive study of geochemical signatures, mineralogical properties, and isotopes analysis might lead to the understanding of how large geothermal fields are found in West Java compared to ones in Central and East Java. The result can also provoke some valuable impacts on Java tectonic evolution and can suggest the key information for geothermal exploration enhancement.

  20. Venus volcanism: Initial analysis from Magellan data (United States)

    Head, J.W.; Campbell, D.B.; Elachi, C.; Guest, J.E.; Mckenzie, D.P.; Saunders, R.S.; Schaber, G.G.; Schubert, G.


    Magellan images confirm that volcanism is widespread and has been fundamentally important in the formation and evolution of the crust of Venus. High-resolution imaging data reveal evidence for intrusion (dike formation and cryptodomes) and extrusion (a wide range of lava flows). Also observed are thousands of small shield volcanoes, larger edifices up to several hundred kilometers in diameter, massive outpourings of lavas, and local pyroclastic deposits. Although most features are consistent with basaltic compositions, a number of large pancake-like domes are morphologically similar to rhyolite-dacite domes on Earth. Flows and sinuous channels with lengths of many hundreds of kilometers suggest that extremely high effusion rates or very fluid magmas (perhaps komatiites) may be present. Volcanism is evident in various tectonic settings (coronae, linear extensional and compressional zones, mountain belts, upland rises, highland plateaus, and tesserae). Volcanic resurfacing rates appear to be low (less than 2 km3/yr) but the significance of dike formation and intrusions, and the mode of crustal formation and loss remain to be established.

  1. Probability of large explosive volcanic eruptions in the Cascades (United States)

    Nathenson, M.; Clynne, M. A.


    Estimating the probability of large explosive eruptions in the Cascades is problematic because they occur relatively infrequently. Although some volcanic centers have been more likely to have large eruptions than others, the calculation of the probability of large eruptions for individual volcanic centers is inappropriate. A center that has had a large eruption in the past will not necessarily have a large eruption in the future, and the occurrence for individual volcanic centers is too infrequent to have much confidence in a probability estimate. The sources of some large eruptions are ambiguous (e.g. Shevlin Park Tuff, Oregon) or unknown (Dibekulewe ash), but because the effects of large eruptions are quite widespread, the precise location of the source is less important in terms of hazards. Thus, we focus on the calculation of probability of large eruptions for the Cascade arc as a whole. To estimate the probability, we have chosen a time period for documenting eruptions of 1.15 Ma (the age of the eruption of Kulshan caldera) as a balance between the likelihood of there being good information but with a long enough time period to get a reasonable number of occurrences. We have compiled data from the literature on eruptions larger than 5 km3 in erupted volume to exclude the relatively frequent eruptions ~1-2 km3. The largest eruptions are clearly or likely to have been associated with caldera formation. For erupted volumes greater than 5 km3, 19 events have occurred in the last 1.15 Ma. A plot of event number versus age shows a high rate of occurrence since 13.5 ka and a much lower rate before then. Most of the events since 13.5 ka are 5-10 km3. Events 10 km3 and larger have occurred at a reasonably constant rate since 630 ka. The difference between the two data sets is probably the poor preservation of deposits for events between 5 and 10 km3 that occurred prior to the ending of the glaciation at about 15 ka. Before 630 ka, the only eruption > 10 km3 is Kulshan

  2. Hierarchical probabilistic regionalization of volcanism for Sengan region in Japan using multivariate statistical techniques and geostatistical interpolation techniques

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jinyong [Univ. of Arizona, Tucson, AZ (United States); Balasingham, P [Univ. of Arizona, Tucson, AZ (United States); McKenna, Sean Andrew [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kulatilake, Pinnaduwa H.S.W. [Univ. of Arizona, Tucson, AZ (United States)


    pH value, presence of volcanic rocks and presence of hydrothermal alteration. Data available for each of these important geologic variables were used to perform directional variogram modeling and kriging to estimate values for each variable at 23949 centers of the chosen 1 km cell grid system that represents the Sengan region. These values formed complete geologic variable vectors at each of the 23,949 one km cell centers.

  3. Lunar farside volcanism in and around the South Pole-Aitken basin (United States)

    Pasckert, Jan Hendrik; Hiesinger, Harald; van der Bogert, Carolyn H.


    We identified and mapped 129 mare basalt deposits in and around the South Pole-Aitken (SPA) basin, and determined absolute model ages (AMAs) for 101 of these units by performing crater size-frequency distribution (CSFD) measurements. The derived AMAs range from 2.2 Ga to 3.7 Ga, with the youngest deposits within Antoniadi crater and the oldest deposits at Jules Verne crater. Our investigations indicate a major peak in volcanic activity between 3.6 Ga and 3.2 Ga, which is a similar time range as the major volcanic activity on the nearside, and the rest of the farside. However, a second peak in volcanic activity (2.2-2.5 Ga), as observed for the nearside and parts of the farside, is not observed for the mare deposits within the SPA basin. Combining all AMAs derived for farside mare basalts reveals that volcanic activity was more abundant and lasted longer on the nearside than on the farside. We propose that the stripping of insulating crust by the large SPA-forming impact event, in combination with lower amounts of heat producing elements like Th, might be responsible for the reduced volcanic activity in the SPA basin. In addition, we estimated the thicknesses and volumes of the investigated mare deposits. With thicknesses between ∼31 m and ∼273 m and volumes of ∼1 km³ to ∼2630 km³, the mare basalt deposits in and around the SPA basin show a wide range of dimensions, similar to other mare basalts of the near- and farsides. A trend between the AMAs and the estimated volumes was not observed, but the mare deposits within the large northern craters (e.g., Apollo, Ingenii, or Leibnitz) seem to be generally larger and more voluminous than the mare basalt deposits at the center of the SPA basin.

  4. International Collaboration on Building Local Technical Capacities for Monitoring Volcanic Activity at Pacaya Volcano, Guatemala. (United States)

    Escobar-Wolf, R. P.; Chigna, G.; Morales, H.; Waite, G. P.; Oommen, T.; Lechner, H. N.


    Pacaya volcano is a frequently active and potentially dangerous volcano situated in the Guatemalan volcanic arc. It is also a National Park and a major touristic attraction, constituting an important economic resource for local municipality and the nearby communities. Recent eruptions have caused fatalities and extensive damage to nearby communities, highlighting the need for risk management and loss reduction from the volcanic activity. Volcanic monitoring at Pacaya is done by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), instrumentally through one short period seismic station, and visually by the Parque Nacional Volcan de Pacaya y Laguna de Calderas (PNVPLC) personnel. We carry out a project to increase the local technical capacities for monitoring volcanic activity at Pacaya. Funding for the project comes from the Society of Exploration Geophysicists through the Geoscientists Without Borders program. Three seismic and continuous GPS stations will be installed at locations within 5 km from the main vent at Pacaya, and one webcam will aid in the visual monitoring tasks. Local educational and outreach components of the project include technical workshops on data monitoring use, and short thesis projects with the San Carlos University in Guatemala. A small permanent exhibit at the PNVPLC museum or visitor center, focusing on the volcano's history, hazards and resources, will also be established as part of the project. The strategy to involve a diverse group of local collaborators in Guatemala aims to increase the chances for long term sustainability of the project, and relies not only on transferring technology but also the "know-how" to make that technology useful. Although not a primary research project, it builds on a relationship of years of joint research projects at Pacaya between the participants, and could be a model of how to increase the broader impacts of such long term collaboration partnerships.

  5. A 150-ka-long record for the volcano-tectonic deformation of Central Anatolian Volcanic Province (United States)

    Karabacak, Volkan; Tonguç Uysal, I.; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin


    The Anatolian Block represents one of the most outstanding examples of intra-plate deformation related to continental collision. Deformation related to the convergence of the Afro-Arabian continent toward north gives rise to widespread and intense arc volcanism in the Central Anatolia. All the usual studies on dating the volcano-tectonic deformation of the region are performed entirely on volcanic events of the geological record resulted in eruptions. However, without volcanic eruption, magma migration and related fluid pressurization also generate crustal deformation. In the current study has been funded by the Scientific and Technological Research Council of Turkey with the project no. 115Y497, we focused on fracture systems and their carbonate veins around the Ihlara Valley (Cappadocia) surrounded by well-known volcanic centers with latest activities of the southern Central Anatolian Volcanic Province. We dated 37 samples using the Uranium-series technique and analyzed their isotope systematics from fissure veins, which are thought to be controlled by the young volcanism in the region. Our detailed fracture analyses in the field show that there is a regional dilatation as a result of a NW-SE striking extension which is consistent with the results of recent GPS studies. The Uranium-series results indicate that fracture development and associated carbonate vein deposition occurred in the last 150 ka. Carbon and oxygen isotope systematics have almost remained unchanged in the studied time interval. Although veins in the region were precipitated from fluids primarily of meteoric origin, fluids originating from water-rock interaction also contribute for the deposition of carbonate veins. The age distribution indicates that the crustal deformation intensified during 7 different period at about 4.7, 34, 44, 52, 83, 91, 149 ka BP. Four of these periods (4.7, 34, 91, 149 ka BP) correspond to the volcanic activities suggested in the previous studies. The three crustal

  6. Global volcanic emissions: budgets, plume chemistry and impacts (United States)

    Mather, T. A.


    Over the past few decades our understanding of global volcanic degassing budgets, plume chemistry and the impacts of volcanic emissions on our atmosphere and environment has been revolutionized. Global volcanic emissions budgets are needed if we are to make effective use of regional and global atmospheric models in order to understand the consequences of volcanic degassing on global environmental evolution. Traditionally volcanic SO2 budgets have been the best constrained but recent efforts have seen improvements in the quantification of the budgets of other environmentally important chemical species such as CO2, the halogens (including Br and I) and trace metals (including measurements relevant to trace metal atmospheric lifetimes and bioavailability). Recent measurements of reactive trace gas species in volcanic plumes have offered intriguing hints at the chemistry occurring in the hot environment at volcanic vents and during electrical discharges in ash-rich volcanic plumes. These reactive trace species have important consequences for gas plume chemistry and impacts, for example, in terms of the global fixed nitrogen budget, volcanically induced ozone destruction and particle fluxes to the atmosphere. Volcanically initiated atmospheric chemistry was likely to have been particularly important before biological (and latterly anthropogenic) processes started to dominate many geochemical cycles, with important consequences in terms of the evolution of the nitrogen cycle and the role of particles in modulating the Earth's climate. There are still many challenges and open questions to be addressed in this fascinating area of science.

  7. Historical Eastern North Pacific Tropical Cyclone Tracks, 1949-2004 - Direct Download (United States)

    U.S. Geological Survey, Department of the Interior — This Historical Eastern North Pacific Tropical Cyclone Tracks file contains the six-hourly (0000, 0600, 1200, 1800 UTC) center locations and intensities for all...

  8. Analysis of concentration patterns in volcanic rocks: Insights into dynamics of highly explosive volcanic eruptions (United States)

    Perugini, D.; Petrelli, M.; Poli, G.


    In this contribution we present new data resulting from the analysis of concentration patterns of mixed juvenile fragments ejected by a highly explosive volcanic eruption that occurred on Salina Island (Aeolian Islands, Italy) and our aim is to identify the fluid-dynamic regime characterizing the magma mixing process. Concentration patterns are studied by calculating the power spectrum of concentration variability along transects crossing the magma mixing structures. Results indicate that the slope of power spectrum has an average value of about -5/3, according to Kolmogorov law of turbulence, and suggest that the magma mixing process, in the studied conditions, can be approximated by considering the passive scalar mixing hypothesis in homogeneous isotropic turbulent flow. These results represent a first step towards a better understanding of magma mixing processes associated to highly explosive volcanic eruptions and this first step is taken by studying concentration patterns in volcanic rocks by coupling petrological and non-linear dynamics methods.

  9. Short-lived and discontinuous intraplate volcanism in the South Pacific: Hot spots or extensional volcanism? (United States)

    Koppers, Anthony A. P.; Staudigel, Hubert; Pringle, Malcolm S.; Wijbrans, Jan R.


    South Pacific intraplate volcanoes have been active since the Early Cretaceous. Their HIMU-EMI-EMII mantle sources can be traced back into the West Pacific Seamount Province (WPSP) using plate tectonic reconstructions, implying that these distinctive components are enduring features within the Earth's mantle for, at least, the last 120 Myr. These correlations are eminent on the scale of the WPSP and the South Pacific Thermal and Isotopic Anomaly (SOPITA), but the evolution of single hot spots emerges notably more complicated. Hot spots in the WPSP and SOPITA mantle regions typically display intermittent volcanic activity, longevities shorter than 40 Myr, superposition of hot spot volcanism, and motion relative to other hot spots. In this review, we use 40Ar/39Ar seamount ages and Sr-Nd-Pb isotopic signatures to map out Cretaceous volcanism in the WPSP and to characterize its evolution with respect to the currently active hot spots in the SOPITA region. Our plate tectonic reconstructions indicate cessation of volcanism during the Cretaceous for the Typhoon and Japanese hot spots; whereas the currently active Samoan, Society, Pitcairn and Marquesas hot spots lack long-lived counterparts in the WPSP. These hot spots may have become active during the last 20 Myr only. The other WPSP seamount trails can be only "indirectly" reconciled with hot spots in the SOPITA region. Complex age distributions in the Magellan, Anewetak, Ralik and Ratak seamount trails would necessitate the superposition of multiple volcanic trails generated by the Macdonald, Rurutu and Rarotonga hot spots during the Cretaceous; whereas HIMU-type seamounts in the Southern Wake seamount trail would require 350-500 km of hot spot motion over the last 100 Myr following its origination along the Mangaia-Rurutu "hotline" in the Cook-Austral Islands. These observations, however, violate all assumptions of the classical Wilson-Morgan hot spot hypothesis, indicating that long-lived, deep and fixed mantle

  10. Structural setting and tectonic control of mud volcanous from the central Mediterranean Ridge (Eastern Mediterranean)

    NARCIS (Netherlands)

    Huguen, C.; Mascle, J.; Chaumillon, E.; Kopf, A.; Woodside, J.M.; Zitter, T.A.C.


    Based on a recent marine geophysical data set, including swath bathymetry, acoustic imagery and six-channel seismics, recorded over a large area of the Mediterranean Ridge (MR) in early 1998 during the Prismed 2 survey, this paper presents a study of the various relationships observed between

  11. Geochemistry of coastal sands of Eastern Mediterranean: The case of Nisyros volcanic materials

    DEFF Research Database (Denmark)

    Tzifas, I.T.; Misaelides, P.; Godelitsas, A.


    of the island, which areespecially enriched in Large-Ion Lithophile Elements (LILE) and depleted in High Field Strength Elements (HFSE), such as Nb and Ta. On the other hand, the caldera material is enriched in volatile components,sulfur, chalcophile elements (Se, Bi, Hg, As, Pb) and Ba. Micro-XRF analyses...

  12. Multiple expressions of plume-ridge interaction in the Galápagos: Volcanic lineaments and ridge jumps (United States)

    Mittelstaedt, E.; Soule, S.; Harpp, K.; Fornari, D.; McKee, C.; Tivey, M.; Geist, D.; Kurz, M. D.; Sinton, C.; Mello, C.


    Anomalous volcanism and tectonics between near-ridge mantle plumes and mid-ocean ridges provide important insights into the mechanics of plume-lithosphere interaction. We present new observations and analysis of multibeam, side scan sonar, sub-bottom chirp, and total magnetic field data collected during the R/V Melville FLAMINGO cruise (MV1007; May-June, 2010) to the Northern Galápagos Volcanic Province (NGVP), the region between the Galápagos Archipelago and the Galápagos Spreading Center (GSC) on the Nazca Plate, and to the region east of the Galápagos Transform Fault (GTF) on the Cocos Plate. The NGVP exhibits pervasive off-axis volcanism related to the nearby Galápagos hot spot, which has dominated the tectonic evolution of the region. Observations indicate that ˜94% of the excess volcanism in our survey area occurs on the Nazca Plate in three volcanic lineaments. Identified faults in the NGVP are consistent with normal ridge spreading except for those within a ˜60 km wide swath of transform-oblique faults centered on the GTF. These transform-oblique faults are sub-parallel to the elongation direction of larger lineament volcanoes, suggesting that lineament formation is influenced by the lithospheric stress field. We evaluate current models for lineament formation using existing and new observations as well as numerical models of mantle upwelling and melting. The data support a model where the lithospheric stress field controls the location of volcanism along the lineaments while several processes likely supply melt to these eruptions. Synthetic magnetic models and an inversion for crustal magnetization are used to determine the tectonic history of the study area. Results are consistent with creation of the GTF by two southward ridge jumps, part of a series of jumps that have maintained a plume-ridge separation distance of 145 km to 215 km since ˜5 Ma.

  13. Geothermal Fields on the Volcanic Axis of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Mercado, S.; Gonzalez, A.


    At present in Mexico, geothermal energy is receiving a great impulse due to the excellent results obtained in the Cerro Prieto geothermal field, in which a geothermoelectric plant is operated. This plant has four units of 37.5 MW each, with a total capacity of 150 MW, and under program 470 MW more by 1984. The Government Institution, Comisi6n Federal de Electricidad, is in charge of the exploration and exploitation of geothermal fields as well as construction and operation of power plants in Mexico. By this time CFE has an extensive program of exploration in the central part of Mexico, in the Eje Neovolcdnico. In this area, several fields with hydrothermal alteration are under exploration, like the Michoac6n geothermal area, where Los Azufres geothermal field is being developed. Seventeen wells have been drilled and twelve of them presented excellent results, including two dry steam wells. In other areas, such as Arar6, Cuitzeo, San Agustln del Maiz,Ixtldn de Los Hervores and Los Negritos, geological, geophysical and geochemical explorations have been accomplished, including shallow well drilling with good results. Another main geothermal area is in the State of Jalisco with an extension of 5,000 m2, where La Primavera geothermal field shows a lot of volcanic domes and has an intensive hydrothermal activity. Deep wells have been drilled, one of them with a bottom temperature of 29OOC. Other fields in this area, like San Narcos, Hervores de La Vega, La Soledad, Villa Corona, etc., have a good geothermal potential. A new geothermal area has been explored recently in the eastern part of the country named Los Humeros, Puebla. In this area studies are being made and there are plans for well drilling exploration by the beginning of 1981. Like this one, there are many other areas in the country in which 300 hydrothermal alteration zones are been classified and 100 of them are considered economically exploitable.

  14. Diffuse and bi-directional reflectance spectrometry to study European volcanic soils

    Directory of Open Access Journals (Sweden)

    Roberto Salzano


    Full Text Available Diffuse and bi-directional reflectance spectroscopy were applied in this research in order to characterize chemical and mineralogical properties in volcanic soils. The study was conducted on 77 volcanic soil profiles from several European countries. Diffuse reflectance spectroscopy was used in conjunction with parameterization using the second derivative of the Kubelka-Munk function and colour calculation. From derivative curves, one band of interest was characterized and identified around 450 nm. Using correlation analysis, significant relationships were observed between amplitude of this band and Fed (r = 0.6. In addition, the data showed that soil organic matter content, Ald and Fep were moderately correlated with reflectance values centered at 546, 579 and 2048 nm.

  15. Database for the Quaternary and Pliocene Yellowstone Plateau volcanic field of Wyoming, Idaho, and Montana (Database for Professional Paper 729-G) (United States)

    Koch, Richard D.; Ramsey, David W.; Christiansen, Robert L.


    The superlative hot springs, geysers, and fumarole fields of Yellowstone National Park are vivid reminders of a recent volcanic past. Volcanism on an immense scale largely shaped the unique landscape of central and western Yellowstone Park, and intimately related tectonism and seismicity continue even now. Furthermore, the volcanism that gave rise to Yellowstone's hydrothermal displays was only part of a long history of late Cenozoic eruptions in southern and eastern Idaho, northwestern Wyoming, and southwestern Montana. The late Cenozoic volcanism of Yellowstone National Park, although long believed to have occurred in late Tertiary time, is now known to have been of latest Pliocene and Pleistocene age. The eruptions formed a complex plateau of voluminous rhyolitic ash-flow tuffs and lavas, but basaltic lavas too have erupted intermittently around the margins of the rhyolite plateau. Volcanism almost certainly will recur in the Yellowstone National Park region. This digital release contains all the information used to produce the geologic maps published as plates in U.S. Geological Survey Professional Paper 729-G (Christiansen, 2001). The main component of this digital release is a geologic map database prepared using geographic information systems (GIS) applications. This release also contains files to view or print the geologic maps and main report text from Professional Paper 729-G.

  16. On the Trail of Missing Heat: Forward Gravity Modeling of the San Francisco Volcanic Field, Northern Arizona (United States)

    Fry, B. N.; Morgan, P.


    The San Francisco volcanic field is a Quaternary field in northern Arizona, the age and size of which suggests there is a high possibility for an associated exploitable high temperature geothermal resource. Sunset Crater, the youngest dated feature in the field, erupted less than 1000 years ago. The youngest felsic volcanism in the area, located near Strawberry Crater, has been dated at about 51,000 years b.p. Felsic magmas are viscous, and therefore felsic magmatism is generally associated with upper crustal plutons, whereas mafic magmas commonly form surface flows. Heat from felsic magmatism tends to remain near subsurface ponds of the magma. Felsic magmatic systems can sustain substantial geothermal heat for tens to hundreds of thousands of years after emplacement. Knowledge of the quantity and distribution of felsic magmatism is therefore paramount to understanding the geothermal potential of the field. Surface heat flow in the study area ranges from ˜20 to ˜50 mW/m2, anomalously low for the region. Hydrological characteristics of the San Francisco volcanic field are thought to mask increased surface heat flow from the magmatic system. The deep water table (>300m) and a 2-level hydraulic system prevent characteristic surface manifestations of hydrothermal potential, such as hot springs and elevated surface heat flow. Lack of these thermal features at the surface precludes analysis of the resource based solely on surficial mapping and measurements. Forward modeling of the gravity field of a 50 km x 45 km area covering the eastern San Francisco volcanic field has been completed. Results suggest that a large felsic body ( ˜-0.15 g/cc contrast) trends northeastward under the Sugarloaf Mountain-O'Leary Peak-Strawberry Crater magmatic trend. This trend parallels a regional basement fabric, likely of early- to middle-Proterozoic origin. These results are being correlated with new surface geologic mapping and radiometric dating of young felsic volcanic rocks to

  17. Volcanic ash plume identification using polarization lidar: Augustine eruption, Alaska (United States)

    Sassen, Kenneth; Zhu, Jiang; Webley, Peter W.; Dean, K.; Cobb, Patrick


    During mid January to early February 2006, a series of explosive eruptions occurred at the Augustine volcanic island off the southern coast of Alaska. By early February a plume of volcanic ash was transported northward into the interior of Alaska. Satellite imagery and Puff volcanic ash transport model predictions confirm that the aerosol plume passed over a polarization lidar (0.694 mm wavelength) site at the Arctic Facility for Atmospheric Remote Sensing at the University of Alaska Fairbanks. For the first time, lidar linear depolarization ratios of 0.10 – 0.15 were measured in a fresh tropospheric volcanic plume, demonstrating that the nonspherical glass and mineral particles typical of volcanic eruptions generate strong laser depolarization. Thus, polarization lidars can identify the volcanic ash plumes that pose a threat to jet air traffic from the ground, aircraft, or potentially from Earth orbit.

  18. Supervolcanoes Within an Ancient Volcanic Province in Arabia Terra, Mars (United States)

    Michalski, Joseph. R.; Bleacher, Jacob E.


    Several irregularly shaped craters located within Arabia Terra, Mars represent a new type of highland volcanic construct and together constitute a previously unrecognized martian igneous province. Similar to terrestrial supervolcanoes, these low-relief paterae display a range of geomorphic features related to structural collapse, effusive volcanism, and explosive eruptions. Extruded lavas contributed to the formation of enigmatic highland ridged plains in Arabia Terra. Outgassed sulfur and erupted fine-grained pyroclastics from these calderas likely fed the formation of altered, layered sedimentary rocks and fretted terrain found throughout the equatorial region. Discovery of a new type of volcanic construct in the Arabia volcanic province fundamentally changes the picture of ancient volcanism and climate evolution on Mars. Other eroded topographic basins in the ancient Martian highlands that have been dismissed as degraded impact craters should be reconsidered as possible volcanic constructs formed in an early phase of widespread, disseminated magmatism on Mars.

  19. The Maars of the Tuxtla Volcanic Field: the Example of 'laguna Pizatal' (United States)

    Espindola, J.; Zamora-Camacho, A.; Hernandez-Cardona, A.; Alvarez del Castillo, E.; Godinez, M.


    Los Tuxtlas Volcanic Field (TVF), also known as Los Tuxtlas massif, is a structure of volcanic rocks rising conspicuously in the south-central part of the coastal plains of eastern Mexico. The TVF seems related to the upper cretaceous magmatism of the NW part of the Gulf's margin (e.g. San Carlos and Sierra de Tamaulipas alkaline complexes) rather than to the nearby Mexican Volcanic Belt. The volcanism in this field began in late Miocene and has continued in historical times, The TVF is composed of 4 large volcanoes (San Martin Tuxtla, San Martin Pajapan, Santa Marta, Cerro El Vigia), at least 365 volcanic cones and 43 maars. In this poster we present the distribution of the maars, their size and depths. These maars span from a few hundred km to almost 1 km in average diameter, and a few meters to several tens of meters in depth; most of them filled with lakes. As an example on the nature of these structures we present our results of the ongoing study of 'Laguna Pizatal or Pisatal' (18° 33'N, 95° 16.4'W, 428 masl) located some 3 km from the village of Reforma, on the western side of San Martin Tuxtla volcano. Laguna Pisatal is a maar some 500 meters in radius and a depth about 40 meters from the surrounding ground level. It is covered by a lake 200 m2 in extent fed by a spring discharging on its western side. We examined a succession of 15 layers on the margins of the maar, these layers are blast deposits of different sizes interbedded by surge deposits. Most of the contacts between layers are irregular; which suggests scouring during deposition of the upper beds. This in turn suggests that the layers were deposited in a rapid series of explosions, which mixed juvenile material with fragments of the preexisting bedrock. We were unable to find the extent of these deposits since the surrounding areas are nowadays sugar cane plantations and the lake has overspilled in several occassions.

  20. Late Cretaceous intraplate silicic volcanism in the Lake Chad region: incipient continental rift volcanism vs. Cameroon Line volcanism (United States)

    Shellnutt, G.; Lee, T. Y.; Torng, P. K.; Yang, C. C.


    The crustal evolution of west-central Africa during the Cretaceous was directly related to plate motion associated with the opening of the central Atlantic Ocean. Late Cretaceous (~66 Ma) to recent magmatism related to the Cameroon Line stretches from Northern Cameroon (i.e. Golda Zuelva) to the Gulf of Guinea (i.e. Pagalu) and is considered to be due to mantle-crust interaction. The volcanic rocks at Hadjer el Khamis, west-central Chad, are considered to be amongst the oldest volcanic rocks of the Cameroon Line but their relationship is uncertain because they erupted during a period of a regional extension associated with the opening of the Late Cretaceous (~75 Ma) Termit basin. The silicic volcanic rocks can be divided into a peraluminous group and a peralkaline group with both rock types having similar chemical characteristics as within-plate granitoids. In situ U/Pb zircon dating yielded a mean 206Pb/238U age of 74.4 ± 1.3 Ma and indicates the rocks erupted ~10 million years before the next oldest eruption attributed to the Cameroon Line. The Sr isotopes (i.e. ISr = 0.7050 to 0.7143) show a wide range but the Nd isotopes (i.e. 143Nd/144Ndi = 0.51268 to 0.51271) are more uniform and indicate that the rocks were derived from a moderately depleted mantle source. Major and trace elemental modeling show that the silicic rocks likely formed by shallow fractionation of a mafic parental magma where the peraluminous rocks experienced crustal contamination and the peralkaline rocks did not. The silicic rocks are more isotopically similar to Late Cretaceous basalts in the Doba and Bongor basins (i.e. ISr = 0.7040 to 0.7060; 143Nd/144Ndi = 0.51267 to 0.51277) of southern Chad than to rocks of the Cameroon Line (i.e. ISr = 0.7026 to 0.7038; 143Nd/144Ndi = 0.51270 to 0.51300). Given the age and isotopic compositions, it is likely that the silicic volcanic rocks of the Lake Chad area are related to Late Cretaceous extensional tectonics rather than to Cameroon Line magmatism.

  1. Transform Tectonics and Non-Volcanic Oceanic Islands


    Palmiotto, Camilla


    Oceanic islands can be divided, according to their origin, in volcanic and tectonic. Volcanic islands are due to excess volcanism. Tectonic islands are mainly formed due to vertical tectonic motions of blocks of oceanic lithosphere along transverse ridges flanking transform faults at slow and ultraslow mid-ocean ridges. Vertical tectonic motions are due to a reorganization of the geometry of the transform plate boundary, with the transition from a transcurrent tectonics to a transtensive and/...

  2. Role of volcanic forcing on future global carbon cycle


    J. F. Tjiputra; O. H. Otterå


    Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller but more frequent eruptions, such as Pinatubo, would hav...

  3. Volatile Transport by Volcanic Plumes on Earth, Venus and Mars (United States)

    Glaze, Lori S.; Self, Stephen; Baloga, Steve; Stofan, Ellen R.


    Explosive volcanic eruptions can produce sustained, buoyant columns of ash and gas in the atmosphere (Fig. 1). Large flood basalt eruptions may also include significant explosive phases that generate eruption columns. Such eruptions can transport volcanic volatiles to great heights in the atmosphere. Volcanic eruption columns can also redistribute chemical species within the atmosphere by entraining ambient atmosphere at low altitudes and releasing those species at much higher altitudes.

  4. Los volcanes del Sistema Volcánico Transversal

    Directory of Open Access Journals (Sweden)

    Esperanza Yarza de la Torre


    Full Text Available Si hizo la selección de textos referentes a algunos de los volcanes que integran el Sistema Volcánico Transversal. Publicado en: Yarza de De la Torre, E. (1992, "Los volcanes del Sistema Volcánico Transversal", Volcanes de México, 4a ed. corregida y aumentada, Instituto de Geografía, UNAM, México, pp. 82-83, 89-136.

  5. Los volcanes del Sistema Volcánico Transversal


    Esperanza Yarza de la Torre


    Si hizo la selección de textos referentes a algunos de los volcanes que integran el Sistema Volcánico Transversal. Publicado en: Yarza de De la Torre, E. (1992), "Los volcanes del Sistema Volcánico Transversal", Volcanes de México, 4a ed. corregida y aumentada, Instituto de Geografía, UNAM, México, pp. 82-83, 89-136.

  6. Strategy Formation in Eastern Jutland

    DEFF Research Database (Denmark)

    Olesen, Kristian


      In Eastern Jutland a strategy formation process has been initiated with the aim of developing a strategic spatial plan for the city region.  An organisation has been set up to deal with the first phase of the process, which is to carry out three functional analyses and prepare a common vision...... for Eastern Jutland.  This process relies on the municipalities in Eastern Jutland reaching consensus on a common vision for the city region.   The key issue in spatial planning in Eastern Jutland is a conflict between preserving the high quality of landscape and maintaining the divide between the countryside...

  7. Eastern equine encephalitis. (United States)

    Berlin, Daniel; Gilani, Ahmed I; Grewal, Amrit K; Fowkes, Mary


    We describe a patient who died from a fulminant presentation of encephalitis. After an exhaustive search, we found no treatable cause. Postmortem PCR analysis of brain tissue led to a diagnosis of eastern equine encephalitis. We have identified several clinical pearls that may assist others in making the diagnosis earlier in the disease course. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  8. MODIS volcanic ash retrievals vs FALL3D transport model: a quantitative comparison (United States)

    Corradini, S.; Merucci, L.; Folch, A.


    Satellite retrievals and transport models represents the key tools to monitor the volcanic clouds evolution. Because of the harming effects of fine ash particles on aircrafts, the real-time tracking and forecasting of volcanic clouds is key for aviation safety. Together with the security reasons also the economical consequences of a disruption of airports must be taken into account. The airport closures due to the recent Icelandic Eyjafjöll eruption caused millions of passengers to be stranded not only in Europe, but across the world. IATA (the International Air Transport Association) estimates that the worldwide airline industry has lost a total of about 2.5 billion of Euro during the disruption. Both security and economical issues require reliable and robust ash cloud retrievals and trajectory forecasting. The intercomparison between remote sensing and modeling is required to assure precise and reliable volcanic ash products. In this work we perform a quantitative comparison between Moderate Resolution Imaging Spectroradiometer (MODIS) retrievals of volcanic ash cloud mass and Aerosol Optical Depth (AOD) with the FALL3D ash dispersal model. MODIS, aboard the NASA-Terra and NASA-Aqua polar satellites, is a multispectral instrument with 36 spectral bands operating in the VIS-TIR spectral range and spatial resolution varying between 250 and 1000 m at nadir. The MODIS channels centered around 11 and 12 micron have been used for the ash retrievals through the Brightness Temperature Difference algorithm and MODTRAN simulations. FALL3D is a 3-D time-dependent Eulerian model for the transport and deposition of volcanic particles that outputs, among other variables, cloud column mass and AOD. Three MODIS images collected the October 28, 29 and 30 on Mt. Etna volcano during the 2002 eruption have been considered as test cases. The results show a general good agreement between the retrieved and the modeled volcanic clouds in the first 300 km from the vents. Even if the

  9. Melting Behavior of Volcanic Ash relevant to Aviation Ash Hazard (United States)

    Song, W.; Hess, K.; Lavallee, Y.; Cimarelli, C.; Dingwell, D. B.


    Volcanic ash is one of the major hazards caused by volcanic eruptions. In particular, the threat to aviation from airborne volcanic ash has been widely recognized and documented. In the past 12 years, more than 60 modern jet airplanes, mostly jumbo jets, have been damaged by drifting clouds of volcanic ash that have contaminated air routes and airport facilities. Seven of these encounters are known to have caused in-flight loss of engine power to jumbo jets carrying a total of more than 2000 passengers. The primary cause of engine thrust loss is that the glass in volcanic ash particles is generated at temperatures far lower than the temperatures in the combustion chamber of a jet engine ( i.e. > 1600 oC) and when the molten volcanic ash particles leave this hottest section of the engine, the resolidified molten volcanic ash particles will be accumulated on the turbine nozzle guide vanes, which reduced the effective flow of air through the engine ultimately causing failure. Thus, it is essential to investigate the melting process and subsequent deposition behavior of volcanic ash under gas turbine conditions. Although few research studies that investigated the deposition behavior of volcanic ash at the high temperature are to be found in public domain, to the best our knowledge, no work addresses the formation of molten volcanic ash. In this work, volcanic ash produced by Santiaguito volcano in Guatemala in November 8, 2012 was selected for study because of their recent activity and potential hazard to aircraft safety. We used the method of accessing the behavior of deposit-forming impurities in high temperature boiler plants on the basis of observations of the change in shape and size of a cylindrical coal ash to study the sintering and fusion phenomena as well as determine the volcanic ash melting behavior by using characteristic temperatures by means of hot stage microscope (HSM), different thermal analysis (DTA) and Thermal Gravimetric Analysis (TGA) to

  10. Effect of volcanic tuff on the characteristics of cement mortar

    Directory of Open Access Journals (Sweden)

    Jehad Al-Zou'by


    Full Text Available This paper examines how Jordanian volcanic tuff aggregates affect the characteristics of cement mortar. Five mortar mixes were prepared by replacing normal aggregate (standard sand with volcanic tuff aggregate in ratios of 0, 25, 50, 75, and 100% (M1 to M5, respectively. Compressive strength, flexural strength, and unit weight were tested at mortar ages of 3, 7, 28, and 56 days. The results revealed improved compressive and flexural strength, which were maximal for the M3 sample. Unit weight decreased as the ratio of volcanic tuff increased. Based on these results, adding Jordanian volcanic tuff in the appropriate ratio will improve these mortar characteristics.

  11. The volcanic and tectonic history of Enceladus (United States)

    Kargel, J.S.; Pozio, S.


    Enceladus has a protracted history of impact cratering, cryo-volcanism, and extensional, compressional, and probable strike-slip faulting. It is unique in having some of the outer Solar System's least and most heavily cratered surfaces. Enceladus' cratering record, tectonic features, and relief elements have been analyzed more comprehensively than done previously. Like few other icy satellites, Enceladus seems to have experienced major lateral lithospheric motions; it may be the only icy satellite with global features indicating probable lithospheric convergence and folding. Ridged plains, 500 km across, consist of a central labyrinthine ridge complex atop a broad dome surrounded by smooth plains and peripheral sinuous ridge belts. The ridged plains have few if any signs of extension, almost no craters, and an average age of just 107 to 108 years. Ridge belts have local relief ranging from 500 to 2000 m and tend to occur near the bottoms of broad regional troughs between swells. Our reanalysis of Peter Thomas' (Dermott, S. F., and P. C. Thomas, 1994, The determination of the mass and mean density of Enceladus from its observed shape, Icarus, 109, 241-257) limb profiles indicates that high peaks, probably ridge belts, also occur in unmapped areas. Sinuous ridges appear foldlike and are similar to terrestrial fold belts such as the Appalachians. If they are indeed folds, it may require that the ridged plains are mechanically (perhaps volcanically) layered. Regional topography suggests that folding may have occurred along zones of convective downwelling. The cratered plains, in contrast to the ridged plains, are heavily cratered and exhibit extensional structures but no obvious signs of compression. Cratered plains contain a possible strike-slip fault (Isbanir Fossa), along which two pairs of fractures seem to have 15 km of right-lateral offset. The oldest cratered plains might date from shortly after the formation of the saturnian system or the impact disruption and

  12. Geodynamical evolution of Central Andes at 24°S as inferred by magma composition along the Calama-Olacapato-El Toro transversal volcanic belt (United States)

    Matteini, M.; Mazzuoli, R.; Omarini, R.; Cas, R.; Maas, R.


    crustal signatures. At the same time, the eastern sector of the Puna plateau experienced westward underthrusting of the Brazilian shield and upper crustal brittle deformation. Partial melts from underthrust upper crustal wedges mixed with lower crustal magmas to produce lavas at Aguas Calientes and Quevar. During Pliocene to Quaternary, delamination of the lithosphere and lowermost crust promoted a widespread monogenetic ocean island basalt-type and shoshonitic volcanism.

  13. Volcanic hazard assessment at Deception Island (United States)

    Bartolini, S.; Sobradelo, R.; Geyer, A.; Martí, J.


    Deception Island is the most active volcano of the South Shetland Islands (Antarctica) with more than twenty eruptions recognised over the past two centuries. The island was formed on the expansion axis of the Central Bransfield Strait and its evolution consists of constructive and destructive phases. A first a shield phase was followed by the construction of a central edifice and formation of the caldera with a final monogenetic volcanism along the caldera rim. The post-caldera magma composition varies from andesitic-basaltic to dacitic. The activity is characterised by monogenetic eruptions of low volume and short duration. The eruptions show a variable degree of explosivity, strombolian or phreatomagmatic, with a VEI 2 to 4, which have generated a wide variety of pyroclastic deposits and lavas. It is remarkable how many phases of phreatic explosive eruptions are associated to the emission of large ballistic blocks. Tephra record preserved in the glacier ice of Livingston Island or in marine sediments show the explosive power of the phreatomagmatic phases and the wide dispersal of its finest products in a great variety of directions of the prevailing winds. Also it is important to highlight the presence of different lahar deposits associated with some of these eruptions. In this contribution we present the guidelines to conduct a short-term and long-term volcanic hazard assessment at Deception Island. We apply probabilistic methods to estimate the susceptibility, statistical techniques to determine the eruption recurrence and eruptive scenario, and reproduce the effects of historical eruptions too. Volcanic hazard maps and scenarios are obtained using a Voris-based model tool (Felpeto et al., 2007) in a free Geographical Information System (GIS), a Quantum GIS.

  14. Hubble Captures Volcanic Eruption Plume From Io (United States)


    The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through the plume and is

  15. Volcanism/tectonics working group summary

    Energy Technology Data Exchange (ETDEWEB)

    Kovach, L.A. [Nuclear Regulatory Commission, Washington, DC (United States); Young, S.R. [Center for Nuclear Waste Regulatory Analyses, San Antonio, TX (United States)


    This article is a summary of the proceedings of a group discussion which took place at the Workshop on the Role of Natural Analogs in Geologic Disposal of High-Level Nuclear Waste in San Antonio, Texas on July 22-25, 1991. The working group concentrated on the subject of the impacts of earthquakes, fault rupture, and volcanic eruption on the underground repository disposal of high-level radioactive wastes. The tectonics and seismic history of the Yucca Mountain site in Nevada is discussed and geologic analogs to that site are described.

  16. Automatic classification of seismo-volcanic signatures (United States)

    Malfante, Marielle; Dalla Mura, Mauro; Mars, Jérôme; Macedo, Orlando; Inza, Adolfo; Métaxian, Jean-Philippe


    The prediction of volcanic eruptions and the evaluation of their associated risks is still a timely and open issue. For this purpose, several types of signals are recorded in the proximity of volcanoes and then analysed by experts. Typically, seismic signals that are considered as precursor or indicator of an active volcanic phase are detected and manually classified. In this work, we propose an architecture for automatic classification of seismo-volcanic waves. The system we propose is based on supervised machine learning. Specifically, a prediction model is built from a large dataset of labelled examples by the means of a learning algorithm (Support Vector Machine or Random Forest). Four main steps are involved: (i) preprocess the signals, (ii) from each signal, extract features that are useful for the classes discrimination, (iii) use an automatic learning algorithm to train a prediction model and (iv) classify (i.e., assign a semantic label) newly recorded and unlabelled examples. Our main contribution lies in the definition of the feature space used to represent the signals (i.e., in the choice of the features to extract from the data). Feature vectors describe the data in a space of lower dimension with respect to the original one. Ideally, signals are separable in the feature space depending on their classes. For this work, we consider a large set of features (79) gathered from an extensive state of the art in both acoustic and seismic fields. An analysis of this feature set shows that for the application of interest, 11 features are sufficient to discriminate the data. The architecture is tested on 4725 seismic events recorded between June 2006 and September 2011 at Ubinas, the most active volcano of Peru. Six main classes of signals are considered: volcanic tremors (TR), long period (LP), volcano-tectonic (VT), explosion (EXP), hybrids (HIB) and tornillo (TOR). Our model reaches above 90% of accuracy, thereby validating the proposed architecture and the

  17. Laboratory simulations of volcanic ash charging and conditions for volcanic lightning on Venus (United States)

    Airey, Martin; Warriner-Bacon, Elliot; Aplin, Karen


    Lightning may be important in the emergence of life on Earth and elsewhere, as significant chemical reactions occur in the superheated region around the lightning channel. This, combined with the availability of phosphates in volcanic clouds, suggests that volcanic lightning could have been the catalyst for the formation of biological compounds on the early Earth [1]. In addition to meteorological lightning, volcanic activity also generates electrical discharges within charged ash plumes, which can be a significant contributor to atmospheric electricity on geologically active planets. The physical properties of other planetary atmospheres, such as that of Venus, have an effect on the processes that lead to the generation of volcanic lightning. Volcanism is known to have occurred on Venus in the past, and recent observations made by ESA's Venus Express satellite have provided evidence for currently active volcanism [2-4], and lightning discharges [e.g. 5]. Venusian lightning could potentially be volcanic in origin, since no meteorological mechanisms are known to separate charge effectively in its clouds [6]. The hunt for further evidence for lightning at Venus is ongoing, for example by means of the Lightning and Airglow Camera (LAC) [7] on Akatsuki, the current JAXA mission at Venus. Our laboratory experiments simulate ash generation and measure electrical charging of the ash under typical atmospheric conditions on Earth and Venus. The study uses a 1 litre chamber, which, when pressurised and heated, can simulate the high-pressure, high-temperature, carbon dioxide-dominated atmosphere of Venus at 10 km altitude ( 5 MPa, 650 K). A key finding of previous work [8] is that ash plume-forming eruptions are more likely to occur at higher altitudes such as these on Venus. The chamber contains temperature/pressure monitoring and logging equipment, a rock collision apparatus (based on [9]) to generate the charged rock fragments, and charge measurement electrodes connected

  18. Hadriaca Patera: Insights into its volcanic history from Mars Express High Resolution Stereo Camera (United States)

    Williams, David A.; Greeley, Ronald; Zuschneid, Wilhelm; Werner, Stephanie C.; Neukum, Gerhard; Crown, David A.; Gregg, Tracy K. P.; Gwinner, Klaus; Raitala, Jouko


    High Resolution Stereo Camera (HRSC) images of Hadriaca Patera, Mars, in combination with Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Infrared Imaging System (THEMIS) data sets, reveal morphologic details about this volcano and enable determination of a chronology of the major geologic events through new cratering age assessments. New topographic measurements of the Hadriaca edifice were also made from a HRSC-based high-resolution (125 m) digital terrain model (DTM) and compared to the MOLA DTM. We find evidence for a complex formation and erosional history at Hadriaca Patera, in which volcanic, fluvial, and aeolian processes were all involved. Crater counts and associated model ages suggest that Hadriaca Patera formed from early shield-building volcanic (likely explosive pyroclastic) eruptions at ~3.7-3.9 Ga, with caldera formation no later than ~3.5 Ga. A variety of geologic activity occurred in the caldera and on the northern flank and plains at ~3.3-3.5 Ga, likely including pyroclastic flows (that partially filled a large crater NW of the caldera, and plains to the NE) and differential erosion/deposition by aeolian and/or fluvial activity. There were some resurfacing event(s) in the caldera and on the eastern flank at ~2.4-2.6 Ga, in which the eastern flank's morphology is indicative of fluvial erosion. The most recent dateable geologic activity on Hadriaca Patera includes caldera resurfacing by some process (most likely differential aeolian erosion/deposition) in the Amazonian Period, as recent as ~1.5 Ga. This is coincident with the resurfacing of the heavily channeled south flank by fluvial erosion. Unlike the Tharsis shields, major geologic activity ended at Hadriaca Patera over a billion years ago.

  19. The response of the North Pacific Decadal Variability to strong tropical volcanic eruptions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tao [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Otteraa, Odd Helge [Uni Bjerknes Centre, Uni Research, Bergen (Norway); Bjerknes Center for Climate Research, Bergen (Norway); Gao, Yongqi [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Bjerknes Center for Climate Research, Bergen (Norway); Nansen Environmental and Remote Sensing Center, Bergen (Norway); Wang, Huijun [Chinese Academy of Sciences, Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Beijing (China); Chinese Academy of Sciences, Climate Change Research Center, Institute of Atmospheric Physics, Beijing (China)


    In this study, the effects of volcanic forcing on North Pacific climate variability, on interannual to decadal time scales, are examined using climate model simulations covering the last 600 years. The model used is the Bergen Climate Model, a fully coupled atmosphere-ocean general circulation model. It is found that natural external forcings, such as tropical strong volcanic eruptions (SVEs) and variations in total solar irradiance, play an important role in regulating North Pacific Decadal Variability (NPDV). In response to tropical SVEs the lower stratospheric pole-to-equator temperature gradient is enhanced. The North polar vortex is strengthened, which forces a significant positive Arctic Oscillation. At the same time, dipole zonal wind anomalies associated with strong polar vortex propagate downward from the lower stratosphere. Through positive feedbacks in the troposphere, the surface westerly winds across the central North Pacific are significantly weakened, and positive sea level pressure anomalies are formed in the North Pacific. This anomalous surface circulation results in changes in the net heat fluxes and the oceanic advection across the North Pacific. As a result of this, warm water converges in the subtropical western North Pacific, where the surface waters in addition are heated by significantly reduced latent and sensible heat fluxes from the ocean. In the eastern and high-latitude North Pacific the ocean loses more heat, and large-scale decreases in sea surface temperatures are found. The overall response of this chain of events is that the North Pacific enters a negative phase of the Pacific decadal oscillation (PDO), and this negative phase of the PDO is maintained for several years. It is thus concluded that the volcanic forcing plays a key role in the phasing of the PDO. The model results furthermore highlight the important role of troposphere-stratosphere coupling, tropical-extratropical teleconnections and extratropical ocean

  20. New insights on the petrology of submarine volcanics from the Western Pontine Archipelago (Tyrrhenian Sea, Italy) (United States)

    Conte, A. M.; Perinelli, C.; Bianchini, G.; Natali, C.; Martorelli, E.; Chiocci, F. L.


    The Pontine Islands form a volcanic archipelago in the Tyrrhenian Sea. It consists of two edifices, the islands of Ponza, Palmarola and Zannone and the islands of Ventotene and Santo Stefano, respectively. The Archipelago developed during two main volcanic cycles in the Plio-Pleistocene: 1) the Pliocene episode erupted subalkaline, silica-rich volcanic units, which constitute the dominant products in the western edifice (Ponza and Zannone Islands); 2) the Pleistocene episode erupted more alkaline products, represented by evolved rocks (trachytes to peralkaline rhyolites) in the islands of Ponza and Palmarola and by basic to intermediate rocks in the eastern edifice (Ventotene and Santo Stefano Islands). In this paper we present new geochemical and petrological data from submarine rock samples collected in two oceanographic cruises and a scuba diving survey. The main result is the recovery of relatively undifferentiated lithotypes that provide further insights on the magmatic spectrum existing in the Pontine Archipelago, allowing modelling of the whole suite of rocks by fractional crystallization processes. New major and trace element data and thermodynamic constrains (by the software PELE) indicate the existence of three distinct evolutionary trends corresponding to a HK calcalkaline series in the Pliocene, followed by a transitional and then by a shoshonite series in the Pleistocene. In particular, the transitional series, so far overlooked in the literature, is required in order to explain the genesis of several peralkaline felsic rocks recognized in the Archipelago. On the whole, the new geochemical data i) confirm the orogenic signature of the suites, ii) allow to rule out an anatectic origin for both subalkaline and peralkaline rhyolites and iii) indicate highly heterogeneous mantle sources, due to crustal components variously recycled in the mantle via subduction.

  1. Evaluation of Risk from Volcanic Ashfalls at the Los Tuxtlas Region, Veracruz, Mexico (United States)

    Espindola, J. M.; Godinez, M. L.; Zamora-Camacho, A.


    The Los Tuxtlas region is an area in the eastern Mexican State of Veracruz, located over the Tuxtla volcanic field and surroundings. This field is composed of 353 distinct cones, 4 large composite volcanoes, and 42 maars. Eruptive activity in the TVF began in the late Miocene, underwent a quiescent period approximately 2.6-0.8 Ma, and continues into historic times with the most recent eruptions occurring at San Martín Tuxtla volcano in 1640 and 1793. Due to the historical occurrence of these eruptions, the volcano is considered hazardous. Although no casualties were derived from those eruptions, the population in the area has grown at a fast pace and a similar eruption occurring today would cause enormous social problems. According to INEGI, the country's organism in charge of demographic studies, there are some 200,000 people settled 20 km around the volcano. Furthermore, since the volcanic field is basaltic, the magma's transfer time from depth to surface is short, and volcanic eruptions such as that of 1793 occur without much warning time. These aspects point out to the need for an estimation of the effects of a similar eruption in our days. Espindola et al. (2010; JVGR, 197, 188-208) estimated the isopachs of the ash deposited during that eruption of 1793; we used these isopachs to the 1 cm contour to evaluate some of those effects. The 1 cm isopach spans an area of 541 km2 of which 385 km2 is grazing lands and plantations, more than 149 km2 are covered by dense vegetation and 5 km2 are occupied by settlements of various sizes. There are about 34 km of paved roads that are also the main communication access to the southern State of Veracruz. These figures are a basis for the estimation of the cost of the assistance to the region in case of an eruption and the elaboration of plan of contingency in case of eruption.

  2. Surface deformation of active volcanic areas retrieved with the SBAS-DInSAR technique: an overview

    Directory of Open Access Journals (Sweden)

    G. Zeni


    Full Text Available This paper presents a comprehensive overview of the surface deformation retrieval capability of the Differential Synthetic Aperture Radar Interferometry (DInSAR algorithm, referred to as Small BAseline Subset (SBAS technique, in the context of active volcanic areas. In particular, after a brief description of the algorithm some experiments relevant to three selected case-study areas are presented. First, we concentrate on the application of the SBAS algorithm to a single-orbit scenario, thus considering a set of SAR data composed by images acquired on descending orbits by the European Remote Sensing (ERS radar sensors and relevant to the Long Valley caldera (eastern California area. Subsequently, we address the capability of the SBAS technique in a multipleorbit context by referring to Mt. Etna volcano (southern Italy test site, with respect to which two different ERS data set, composed by images acquired both on ascending and descending orbits, are available. Finally, we take advantage of the capability of the algorithm to work in a multi-platform scenario by jointly exploiting two different sets of SAR images collected by the ERS and the Environment Satellite (ENVISAT radar sensors in the Campi Flegrei caldera (southern Italy area. The presented results demonstrate the effectiveness of the algorithm to investigate the deformation field in active volcanic areas and the potential of the DInSAR methodologies within routine surveillance scenario.

  3. The lithospheric shear-wave velocity structure of Saudi Arabia: Young volcanism in an old shield

    KAUST Repository

    Tang, Zheng


    We investigate the lithospheric shear-wave velocity structure of Saudi Arabia by conducting H-κ stacking analysis and jointly inverting teleseismic P-receiver functions and fundamental-mode Rayleigh wave group velocities at 56 broadband stations deployed by the Saudi Geological Survey (SGS). The study region, the Arabian plate, is traditionally divided into the western Arabian shield and the eastern Arabian platform: The Arabian shield itself is a complicated mélange of crustal material, composed of several Proterozoic terrains separated by ophiolite-bearing suture zones and dotted by outcropping Cenozoic volcanic rocks (locally known as harrats). The Arabian platform is primarily covered by 8 to 10 km of Paleozoic, Mesozoic and Cenozoic sedimentary rocks. Our results reveal high Vp/Vs ratios in the region of Harrat Lunayyir, which are interpreted as solidified magma intrusions from old magmatic episodes in the shield. Our results also indicate slow velocities and large upper mantle lid temperatures below the southern and northern tips of the Arabian shield, when compared with the values obtained for the central shield. We argue that our inferred patterns of lid velocity and temperature are due to heating by thermal conduction from the Afar plume (and, possibly, the Jordan plume), and that volcanism in western Arabia may result from small-scale adiabatic ascent of magma diapirs.

  4. Analysis of GOSAT XCO2 in explosive volcanic plumes (United States)

    Popp, Christoph; Andrews, Benjamin J.; Carn, Simon A.; Chance, Kelly; Cottrell, Elizabeth; Schwandner, Florian M.


    In this study, we analyze columnar averaged dry air mole fraction of CO2 (XCO2) in volcanic gas plumes after major eruptions using space-borne near-infrared measurements from the Japanese Greenhouse gas Observing SATellite (GOSAT). Volcanic emissions are assumed to dominate the flux from the deep Earth to the surface but those global emissions as well as the partitioning between eruptive and non-eruptive emissions are to date highly uncertain. Satellite measurements are an indispensable complement to ground-based measurements of volcanic CO2 emissions because they are performed globally and regularly and they therefore have the potential to significantly broaden our knowledge of volcanic CO2 releases. However, the remote sensing of volcanic CO2 is challenging for various reasons, including the increasingly high atmospheric background, relatively coarse spatial resolution and/or sampling, and scattering effects of aerosols and clouds. We mined existing standard product level 2 GOSAT XCO2 data sets for a volcanic CO2 signal in the gas plumes of the largest volcanic eruptions since GOSAT's launch in 2009. These eruptions include the Volcanic Explosivity Index (VEI) 4 events of Sarychev Peak (Kuril Islands, Russia) in June 2009, Nabro (Ethiopia) in June 2011, and Puyehue-Cordon Caulle (Chile) in June 2011. GOSAT background and plume soundings are distinguished using corresponding Ozone Monitoring Instrument (OMI) SO2 retrievals taking advantage of the usually low atmospheric SO2 background abundance. A volcanic CO2 signal in the GOSAT products can subsequently be found by comparing GOSAT XCO2 for the plume and background soundings. Possible XCO2 enhancements in the volcanic plumes are converted to an estimated CO2 release of the investigated eruptions. Based on this analysis, the current capabilities and added value of GOSAT TANSO-FTS to detect and quantify CO2 emissions from explosive volcanism are outlined.

  5. Crustal structure beneath Eastern Greenland

    DEFF Research Database (Denmark)

    Reiche, Sönke; Thybo, H.; Kaip, G.


    The conjugate Atlantic passive margins of western Norway and eastern Greenland are characterized by the presence of coast-parallel mountain ranges with peak elevations of more than 3.5 km close to Scoresby Sund in Eastern Greenland. Knowledge about crustal thickness and composition below these mo...

  6. Forest industries of eastern Washington. (United States)

    Brian R. Wall; Donald R. Gedney; Robert B. Forster


    A sawmill, built in 1872, marked the beginning of the forest industry in eastern Washington -- almost half a century after the emergence of the lumber industry in western Washington. Since then, this industry has increased in importance to eastern Washington's economy, now furnishing about one-fifth of the total manufacturing employment and wages paid—in...

  7. Eastern Sources of Invitational Education. (United States)

    Ryback, David


    Presents historical perspective suggesting that invitational theory shares many beliefs with ancient Eastern philosophies. Submits that teachers and other educators who embrace the invitational perspective may benefit from an understanding of Eastern principles. Briefly describes Buddhism, Confucianism, Taoism, Zen Buddhism, and their relevance to…

  8. Nano-volcanic Eruption of Silver. (United States)

    Lin, Shih-Kang; Nagao, Shijo; Yokoi, Emi; Oh, Chulmin; Zhang, Hao; Liu, Yu-Chen; Lin, Shih-Guei; Suganuma, Katsuaki


    Silver (Ag) is one of the seven metals of antiquity and an important engineering material in the electronic, medical, and chemical industries because of its unique noble and catalytic properties. Ag thin films are extensively used in modern electronics primarily because of their oxidation-resistance. Here we report a novel phenomenon of Ag nano-volcanic eruption that is caused by interactions between Ag and oxygen (O). It involves grain boundary liquation, the ejection of transient Ag-O fluids through grain boundaries, and the decomposition of Ag-O fluids into O2 gas and suspended Ag and Ag2O clusters. Subsequent coating with re-deposited Ag-O and the de-alloying of O yield a conformal amorphous Ag coating. Patterned Ag hillock arrays and direct Ag-to-Ag bonding can be formed by the homogenous crystallization of amorphous coatings. The Ag "nano-volcanic eruption" mechanism is elaborated, shedding light on a new mechanism of hillock formation and new applications of amorphous Ag coatings.

  9. Mantle updrafts and mechanisms of oceanic volcanism (United States)

    Anderson, Don L.; Natland, James H.


    Convection in an isolated planet is characterized by narrow downwellings and broad updrafts-consequences of Archimedes' principle, the cooling required by the second law of thermodynamics, and the effect of compression on material properties. A mature cooling planet with a conductive low-viscosity core develops a thick insulating surface boundary layer with a thermal maximum, a subadiabatic interior, and a cooling highly conductive but thin boundary layer above the core. Parts of the surface layer sink into the interior, displacing older, colder material, which is entrained by spreading ridges. Magma characteristics of intraplate volcanoes are derived from within the upper boundary layer. Upper mantle features revealed by seismic tomography and that are apparently related to surface volcanoes are intrinsically broad and are not due to unresolved narrow jets. Their morphology, aspect ratio, inferred ascent rate, and temperature show that they are passively responding to downward fluxes, as appropriate for a cooling planet that is losing more heat through its surface than is being provided from its core or from radioactive heating. Response to doward flux is the inverse of the heat-pipe/mantle-plume mode of planetary cooling. Shear-driven melt extraction from the surface boundary layer explains volcanic provinces such as Yellowstone, Hawaii, and Samoa. Passive upwellings from deeper in the upper mantle feed ridges and near-ridge hotspots, and others interact with the sheared and metasomatized surface layer. Normal plate tectonic processes are responsible both for plate boundary and intraplate swells and volcanism.

  10. Forecasting volcanic explosions based on seismic quiescence (United States)

    Roman, D.; La Femina, P.; Rodgers, M.; Geirsson, H.; Tenorio, V.


    Volcanic eruptions are generally forecast based on strong increases in monitoring parameters such as seismicity or gas emissions above a relatively low background level. Because of this, forecasting individual explosions during an ongoing eruption, or at persistently restless volcanoes, is difficult as seismicity, gas emissions, and other indicators of unrest are already in a heightened state. Therefore, identification of short-term precursors to individual explosions at volcanoes already in heightened states of unrest, and an understanding of explosion trigger mechanisms, is important for the reduction of volcanic risk worldwide. Seis