Catastrophic precipitation-triggered lahar at Casita volcano, Nicaragua: Occurrence, bulking and transformation

Science.gov (United States)

Scott, K.M.; Vallance, J.W.; Kerle, N.; Macias, J.L.; Strauch, W.; Devoli, G.

2005-01-01

A catastrophic lahar began on 30 October 1998, as hurricane precipitation triggered a small flank collapse of Casita volcano, a complex and probably dormant stratovolcano. The initial rockslide-debris avalanche evolved on the flank to yield a watery debris flood with a sediment concentration less than 60 per cent by volume at the base of the volcano. Within 2-5 km, however, the watery flow entrained (bulked) enough sediment to transform entirely to a debris flow. The debris flow, 6 km downstream and 1??2 km wide and 3 to 6 m deep, killed 2500 people, nearly the entire populations of the communities of El Porvenir and Rolando Rodriguez. These 'new towns' were developed in a prehistoric lahar pathway: at least three flows of similar size since 8330 14C years BP are documented by stratigraphy in the same 30-degree sector. Travel time between perception of the flow and destruction of the towns was only 2??5-3??0 minutes. The evolution of the flow wave occurred with hydraulic continuity and without pause or any extraordinary addition of water. The precipitation trigger of the Casita lahar emphasizes the nee d, in volcano hazard assessments, for including the potential for non-eruption-related collapse lahars with the more predictable potential of their syneruption analogues. The flow behaviour emphasizes that volcano collapses can yield not only volcanic debris avalanches with restricted runouts, but also mobile lahars that enlarge by bulking as they flow. Volumes and hence inundation areas of collapse-runout lahars can increase greatly beyond their sources: the volume of the Casita lahar bulked to at least 2??6 times the contributing volume of the flank collapse and 4??2 times that of the debris flood. At least 78 per cent of the debris flow matrix (sediment < -1??0??; 2 mm) was entrained during flow. Copyright c 2004 John Wiley & Sons, Ltd.

ANALYSIS OF EFFECTIVE RAINFALL INTENSITY AND WORKING RAINFALL FOR BASIC WARNING CRITERIA DEVELOPMENT ON LAHAR FLOW EVENT

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Fitriyadi Fitriyadi

2015-05-01

The research results showed that the number of reviewed serial rain with total value ≥ 80 mm is 9.28% of the whole serial rain, and 12.5% of them caused lahar flow in Gendol River. Debris flow occurrence probability on total rainfall amount of ≥ 80 mm that may occur on Gendol River amounted to 1.89%. This value represents less possibility of debris flow in Gendol River, this is due to the rain conditions in the Gendol Watershed different from the situation in Japan as well as the limitations of the available data. It is recommended for further research on the limitation of total rainfall in accordance with the conditions in Gendol Watershed by considering other parameters becoming the lahar flow controller factor. Further, it is necessary to perform the analysis using rain catchment method by averaging rainfall values on each of serial rain.

Hierarchy of facies of pyroclastic flow deposits generated by Laacher See type eruptions

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Freundt, A.; Schmincke, H.-U.

1985-04-01

The upper Quaternary pyroclastic flow deposits of Laacher See volcano show compositional and structural facies variations on four different scales: (1) eruptive units of pyroclastic flows, composed of many flow units; (2) depositional cycles of as many as five flow units; flow units containing (3) regional intraflow-unit facies; and (4) local intraflow-unit subfacies. These facies can be explained by successively overlapping processes beginning in the magma column and ending with final deposition. The pyroclastic flow deposits thus reflect major aspects of the eruptive history of Laacher See volcano: (a) drastic changes in eruptive mechanism due to increasing access of water to the magma chamber and (b) change in chemical composition and crystal and gas content as evacuation of a compositionally zoned magma column progressed. The four scales of facies result from four successive sets of processes: (1) differentiation in the magma column and external factors governing the mechanism of eruption; (2) temporal variations of factors inducing eruption column collapse; (3) physical conditions in the eruption column and the way in which its collapse proceeds; and (4) interplay of flow-inherent and morphology-induced transport mechanics.

Lahars at Cotopaxi and Tungurahua Volcanoes, Ecuador: Highlights from stratigraphy and observational records and related downstream hazards: Chapter 6

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Mothes, Patricia A; Vallance, James W.

2015-01-01

Lahars are volcanic debris flows that are dubbed primary when triggered by eruptive activity or secondary when triggered by other factors such as heavy rainfall after eruptive activity has waned. Variation in time and space of the proportion of sediment to water within a lahar dictates lahar flow phase and the resultant sedimentary character of deposits. Characteristics of source material and of debris eroded and incorporated during flow downstream may strongly affect the grain-size composition of flowing lahars and their deposits. Lahars borne on the flanks of two steep-sided stratocones in Ecuador exemplify two important lahar types. Glacier-clad Cotopaxi volcano has been a producer of primary lahars that flow great distances downstream. Such primary lahars include those of both clast-rich and matrix-rich composition—some of which have flowed as far as 325 km to the Pacific Ocean. Cotopaxi's last important eruption in 1877 generated formidable syneruptive lahars comparable in size to those that buried Armero, Colombia, following the 1985 eruption of Nevado del Ruiz volcano. In contrast, ash-producing eruptive activity during the past 15 years at Tungurahua volcano has generated a continual supply of fresh volcaniclastic debris that is regularly remobilized by precipitation. Between 2000 and 2011, 886 rain-generated lahars were registered at Tungurahua. These two volcanoes pose dramatically different hazards to nearby populations. At Tungurahua, the frequency and small sizes of lahars have resulted in effective mitigation measures. At Cotopaxi 137 years have passed since the last important lahar-producing eruption, and there is now a high-risk situation for more than 100,000 people living in downstream valleys.

Seismic signals of snow-slurry lahars in motion: 25 September 2007, Mt Ruapehu, New Zealand

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Cole, S. E.; Cronin, S. J.; Sherburn, S.; Manville, V.

2009-05-01

Detection of ground shaking forms the basis of many lahar-warning systems. Seismic records of two lahar types at Ruapehu, New Zealand, in 2007 are used to examine their nature and internal dynamics. Upstream detection of a flow depends upon flow type and coupling with the ground. 3-D characteristics of seismic signals can be used to distinguish the dominant rheology and gross physical composition. Water-rich hyperconcentrated flows are turbulent; common inter-particle and particle-substrate collisions engender higher energy in cross-channel vibrations relative to channel-parallel. Plug-like snow-slurry lahars show greater energy in channel-parallel signals, due to lateral deposition insulating channel margins, and low turbulence. Direct comparison of flow size must account for flow rheology; a water-rich lahar will generate signals of greater amplitude than a similar-sized snow-slurry flow.

The enormous Chillos Valley Lahar: An ash-flow-generated debris flow from Cotopaxi Volcano, Ecuador

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Mothes, P.A.; Hall, M.L.; Janda, R.J.

1998-01-01

The Chillos Valley Lahar (CVL), the largest Holocene debris flow in area and volume as yet recognized in the northern Andes, formed on Cotopaxi volcano's north and northeast slopes and descended river systems that took it 326 km north-northwest to the Pacific Ocean and 130+ km east into the Amazon basin. In the Chillos Valley, 40 km downstream from the volcano, depths of 80-160 m and valley cross sections up to 337000m2 are observed, implying peak flow discharges of 2.6-6.0 million m3/s. The overall volume of the CVL is estimated to be ???3.8 km3. The CVL was generated approximately 4500 years BP by a rhyolitic ash flow that followed a small sector collapse on the north and northeast sides of Cotopaxi, which melted part of the volcano's icecap and transformed rapidly into the debris flow. The ash flow and resulting CVL have identical components, except for foreign fragments picked up along the flow path. Juvenile materials, including vitric ash, crystals, and pumice, comprise 80-90% of the lahar's deposit, whereas rhyolitic, dacitic, and andesitic lithics make up the remainder. The sand-size fraction and the 2- to 10-mm fraction together dominate the deposit, constituting ???63 and ???15 wt.% of the matrix, respectively, whereas the silt-size fraction averages less than ???10 wt.% and the clay-size fraction less than 0.5 wt.%. Along the 326-km runout, these particle-size fractions vary little, as does the sorting coefficient (average = 2.6). There is no tendency toward grading or improved sorting. Limited bulking is recognized. The CVL was an enormous non-cohesive debris flow, notable for its ash-flow origin and immense volume and peak discharge which gave it characteristics and a behavior akin to large cohesive mudflows. Significantly, then, ash-flow-generated debris flows can also achieve large volumes and cover great areas; thus, they can conceivably affect large populated regions far from their source. Especially dangerous, therefore, are snowclad volcanoes

Giant Subaqueous Pyroclastic-Flow Deposits Revealed: Sedimentological Revision of the Holocene Outcrops of Izu-Oshima Island, Japan

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Hemmi, R.; Yoshida, S.; Nemoto, Y.; Kotake, N.

2010-12-01

The early-to-middle Holocene outcrops of Izu-Oshima island, 100 km SSW of Tokyo, comprise sand- to gravel-size pyroclasts, and exhibit undulating layered structures, with each wavelet typically measuring 5-10 m high. These outcrops were traditionally interpreted as exemplary subaerial "ash-fall" deposits in volcanology textbooks (e.g. Schmincke 2006). Our detailed sedimentological analyses, however, have revealed that it is of pyroclastic density-current origin, the majority of which formed in shallow-marine settings. The present study focuses on the outcrops along the western coast of the Island, where the three-dimensional architecture of the outcrops is superbly exposed, and the existing archaeological framework provides a reliable chronostratigraphic control. The outcrops contain abundant compound bedforms, where small bedforms (dunes/antidunes) occur within the larger bedforms. The compound bedforms exhibit four-fold hierarchy (ranks 1 to 4), and bedforms for each scale display dominantly upstream-accreting geometry. The largest scale (Rank 1) of these bedforms show wavy parallel-bedding geometry (each wavelet typically measuring 5-10 m high and 50-100 m wide). We interpreted the large-scale architecture as sediment waves (gigantic antidunes) similar to the one reported from the shallow-marine deposits associated with AD 79 Mt. Vesuvius eruptions (Milia et al. 2008). Moreover, we have identified crustacean burrows and other trace fossils indicative of a nearshore shallow-marine environment. The pervasive occurrence of these fossils throughout the outcrops and abundant water-escape structures also suggests their subaqueous origin. On the other hand, evidence of subaerial deposition (e.g., paleosols and rootlets) or subaerial reworking (e.g., lahar) is absent, except for some spots on several regional unconformities that divide 10’s-m-thick sediment-wave deposits. On some of these unconformities, ribbon- to fan-shaped lava and/or ancient human-dwelling sites

Analysis of the Pyroclastic Flow Deposits of Mount Sinabung and Merapi Using Landsat Imagery and the Artificial Neural Networks Approach

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Prima Riza Kadavi

2017-09-01

Full Text Available Volcanic eruptions cause pyroclastic flows, which can destroy plantations and settlements. We used image data from Landsat 7 Bands 7, 4 and 2 and Landsat 8 Bands 7, 5 and 3 to observe and analyze the distribution of pyroclastic flow deposits for two volcanos, Mount Sinabung and Merapi, over a period of 10 years (2001–2017. The satellite data are used in conjunction with an artificial neural network method to produce maps of pyroclastic precipitation for Landsat 7 and 8, then we calculated the pyroclastic precipitation area using an artificial neural network method after dividing the images into four classes based on color. Red, green, blue and yellow were used to indicate pyroclastic deposits, vegetation and forest, water and cloud, and farmland, respectively. The area affected by a volcanic eruption was deduced from the neural network processing, including calculating the area of pyroclastic deposits. The main differences between the pyroclastic flow deposits of Mount Sinabung and Mount Merapi are: the sediment deposits of the pyroclastic flows of Mount Sinabung tend to widen, whereas those of Merapi elongated; the direction of pyroclastic flow differed; and the area affected by an eruption was greater for Mount Merapi than Mount Sinabung because the VEI (Volcanic Explosivity Index during the last 10 years of Mount Merapi was larger than Mount Sinabung.

Geomorphological evolution of a fluvial channel after primary lahar deposition: Huiloac Gorge, Popocatépetl volcano (Mexico)

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Tanarro, L. M.; Andrés, N.; Zamorano, J. J.; Palacios, D.; Renschler, C. S.

2010-10-01

Popocatépetl volcano (19°02' N, 98°62' W, 5424 m) began its most recent period of volcanic activity in December 1994. The interaction of volcanic and glacier activity triggered the formation of lahars through the Huiloac Gorge, located on the northern flank of the volcano, causing significant morphological changes in the channel. The most powerful lahars occurred in April 1995, July 1997 and January 2001, and were followed by secondary lahars that formed during the post-eruptive period. This study interprets the geomorphological evolution of the Huiloac Gorge after the January 2001 lahar. Variations in channel morphology at a 520 m-long research site located mid-way down the gorge were recorded over a 4 year period from February 2002 to March 2005, and depicted in five geomorphological maps (scale 1:200) for 14 February and 15 October 2002, 27 September 2003, 9 February 2004, and 16 March 2006. A GIS was used to calculate the surface area for the landforms identified for each map and detected changes and erosion-deposition processes of the landforms using the overlay function for different dates. Findings reveal that secondary lahars and others types of flows, like sediment-laden or muddy streamflows caused by precipitation, rapidly modified the gorge channel following the January 2001 non-eruptive lahar, a period associated with volcanic inactivity and the disappearance of the glacier once located at the headwall of the gorge. Field observations also confirmed that secondary flows altered the dynamics and geomorphological development of the channel. These flows incised and destroyed the formations generated by the primary lahars (1997 and 2001), causing a widening of the channel that continues today. After February 2004, a rain-triggered lahar and other flows infilled the channel with materials transported by these flows. The deposits on the lateral edges of the channel form terraces. A recent lull in lahar activity contrasts with the increasing instability of

Slow-moving and far-travelled dense pyroclastic flows during the Peach Spring super-eruption

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Roche, Olivier; Buesch, David C.; Valentine, Greg A.

2016-01-01

Explosive volcanic super-eruptions of several hundred cubic kilometres or more generate long run-out pyroclastic density currents the dynamics of which are poorly understood and controversial. Deposits of one such event in the southwestern USA, the 18.8 Ma Peach Spring Tuff, were formed by pyroclastic flows that travelled >170 km from the eruptive centre and entrained blocks up to ~70–90 cm diameter from the substrates along the flow paths. Here we combine these data with new experimental results to show that the flow’s base had high-particle concentration and relatively modest speeds of ~5–20 m s−1, fed by an eruption discharging magma at rates up to ~107–108 m3 s−1 for a minimum of 2.5–10 h. We conclude that sustained high-eruption discharge and long-lived high-pore pressure in dense granular dispersion can be more important than large initial velocity and turbulent transport with dilute suspension in promoting long pyroclastic flow distance.

Community Exposure to Lahar Hazards from Mount Rainier, Washington

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Wood, Nathan J.; Soulard, Christopher E.

2009-01-01

Geologic evidence of past events and inundation modeling of potential events suggest that lahars associated with Mount Rainier, Washington, are significant threats to downstream development. To mitigate potential impacts of future lahars and educate at-risk populations, officials need to understand how communities are vulnerable to these fast-moving debris flows and which individuals and communities may need assistance in preparing for and responding to an event. To support local risk-reduction planning for future Mount Rainier lahars, this study documents the variations among communities in King, Lewis, Pierce, and Thurston Counties in the amount and types of developed land, human populations, economic assets, and critical facilities in a lahar-hazard zone. The lahar-hazard zone in this study is based on the behavior of the Electron Mudflow, a lahar that traveled along the Puyallup River approximately 500 years ago and was due to a slope failure on the west flank of Mount Rainier. This lahar-hazard zone contains 78,049 residents, of which 11 percent are more than 65 years in age, 21 percent do not live in cities or unincorporated towns, and 39 percent of the households are renter occupied. The lahar-hazard zone contains 59,678 employees (4 percent of the four-county labor force) at 3,890 businesses that generate $16 billion in annual sales (4 and 7 percent, respectively, of totals in the four-county area) and tax parcels with a combined total value of $8.8 billion (2 percent of the study-area total). Employees in the lahar-hazard zone are primarily in businesses related to manufacturing, retail trade, transportation and warehousing, wholesale trade, and construction. Key road and rail corridors for the region are in the lahar-hazard zone, which could result in significant indirect economic losses for businesses that rely on these networks, such as the Port of Tacoma. Although occupancy values are not known for each site, the lahar-hazard zone contains numerous

Reducing risk from lahar hazards: concepts, case studies, and roles for scientists

Science.gov (United States)

Pierson, Thomas C.; Wood, Nathan J.; Driedger, Carolyn L.

2014-01-01

Lahars are rapid flows of mud-rock slurries that can occur without warning and catastrophically impact areas more than 100 km downstream of source volcanoes. Strategies to mitigate the potential for damage or loss from lahars fall into four basic categories: (1) avoidance of lahar hazards through land-use planning; (2) modification of lahar hazards through engineered protection structures; (3) lahar warning systems to enable evacuations; and (4) effective response to and recovery from lahars when they do occur. Successful application of any of these strategies requires an accurate understanding and assessment of the hazard, an understanding of the applicability and limitations of the strategy, and thorough planning. The human and institutional components leading to successful application can be even more important: engagement of all stakeholders in hazard education and risk-reduction planning; good communication of hazard and risk information among scientists, emergency managers, elected officials, and the at-risk public during crisis and non-crisis periods; sustained response training; and adequate funding for risk-reduction efforts. This paper reviews a number of methods for lahar-hazard risk reduction, examines the limitations and tradeoffs, and provides real-world examples of their application in the U.S. Pacific Northwest and in other volcanic regions of the world. An overriding theme is that lahar-hazard risk reduction cannot be effectively accomplished without the active, impartial involvement of volcano scientists, who are willing to assume educational, interpretive, and advisory roles to work in partnership with elected officials, emergency managers, and vulnerable communities.

The 15 September 1991 pyroclastic flows at Unzen Volcano (Japan): a flow model for associated ash-cloud surges

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Fujii, Toshitsugu; Nakada, Setsuya

1999-04-01

Large-scale collapse of a dacite dome in the late afternoon of 15 September 1991 generated a series of pyroclastic-flow events at Unzen Volcano. Pyroclastic flows with a volume of 1×10 6 m 3 (as DRE) descended the northeastern slope of the volcano, changing their courses to the southeast due to topographic control. After they exited a narrow gorge, an ash-cloud surge rushed straight ahead, detaching the main body of the flow that turned and followed the topographic lows to the east. The surge swept the Kita-Kamikoba area, which had been devastated by the previous pyroclastic-flow events, and transported a car as far as 120 m. Following detachment, the surge lost its force after it moved several hundred meters, but maintained a high temperature. The deposits consist of a bottom layer of better-sorted ash (unit 1), a thick layer of block and ash (unit 2), and a thin top layer of fall-out ash (unit 3). Unit 2 overlies unit 1 with an erosional contact. The upper part of unit 2 grades into better-sorted ash. At distal block-and-ash flow deposits, the bottom part of unit 2 also consists of better-sorted ash, and the contact with the unit 1 deposits becomes ambiguous. Video footage of cascading pyroclastic flows during the 1991-1995 eruption, traveling over surfaces without any topographic barriers, revealed that lobes of ash cloud protruded intermittently from the moving head and sides, and that these lobes surged ahead on the ground surface. This fact, together with the inspection by helicopter shortly after the events, suggests that the protruded lobes consisted of better-sorted ash, and resulted in the deposits of unit 1. The highest ash-cloud plume at the Oshigadani valley exit, and the thickest deposition of fall-out ash over Kita-Kamikoba and Ohnokoba, indicate that abundant ash was also produced when the flow passed through a narrow gorge. In the model presented here, the ash clouds from the pyroclastic flows were composed of a basal turbulent current of high

Synthesizing large-scale pyroclastic flows: Experimental design, scaling, and first results from PELE

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Lube, G.; Breard, E. C. P.; Cronin, S. J.; Jones, J.

2015-03-01

Pyroclastic flow eruption large-scale experiment (PELE) is a large-scale facility for experimental studies of pyroclastic density currents (PDCs). It is used to generate high-energy currents involving 500-6500 m3 natural volcanic material and air that achieve velocities of 7-30 m s-1, flow thicknesses of 2-4.5 m, and runouts of >35 m. The experimental PDCs are synthesized by a controlled "eruption column collapse" of ash-lapilli suspensions onto an instrumented channel. The first set of experiments are documented here and used to elucidate the main flow regimes that influence PDC dynamic structure. Four phases are identified: (1) mixture acceleration during eruption column collapse, (2) column-slope impact, (3) PDC generation, and (4) ash cloud diffusion. The currents produced are fully turbulent flows and scale well to natural PDCs including small to large scales of turbulent transport. PELE is capable of generating short, pulsed, and sustained currents over periods of several tens of seconds, and dilute surge-like PDCs through to highly concentrated pyroclastic flow-like currents. The surge-like variants develop a basal <0.05 m thick regime of saltating/rolling particles and shifting sand waves, capped by a 2.5-4.5 m thick, turbulent suspension that grades upward to lower particle concentrations. Resulting deposits include stratified dunes, wavy and planar laminated beds, and thin ash cloud fall layers. Concentrated currents segregate into a dense basal underflow of <0.6 m thickness that remains aerated. This is capped by an upper ash cloud surge (1.5-3 m thick) with 100 to 10-4 vol % particles. Their deposits include stratified, massive, normally and reversely graded beds, lobate fronts, and laterally extensive veneer facies beyond channel margins.

Frozen Martian lahars? Evaluation of morphology, degradation and geologic development in the Utopia-Elysium transition zone

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Pedersen, G. B. M.

2013-09-01

Regional coverage of high-resolution data from the CTX camera has permitted new, detailed morphologic analysis of the enigmatic Utopia-Elysium flows which dominate the transition zone between Elysium volcanic province and Utopia Planitia. Based on topographic and morphologic analysis of the Galaxias region, this study supports the lahar hypothesis put forth by previous works and suggests that the center and the margins of the outflow deposits have very diverse morphologies that can be explained by varying degrees of water drainage and freezing. Regular channel and flood plain deposits are found in the central part of the outflow deposits, whereas the marginal deposits are interpreted to contain significant amount of ice because of their distinct morphological properties (smooth, lobate flow-fronts with upward convex snouts, unusual crater morphologies, raised rim fractures and localized flow fronts indicating rheomorphism). Thus, this study suggest that, unlike terrestrial lahars, lahar emplacement under Martian conditions only drain in the central parts, whereas the water in the margins of the outflow deposit (∼75% of the total outflow deposit in the Galaxias region) freezes up resulting in a double-layered deposit consisting of ice-rich core with an ice-poor surface layer. It is here furthermore suggested that continued intrusive volcanic activity was highly affected by the presence of the ice-rich lahar deposits, generating ground-ice-volcano interactions resulting in a secondary suite of morphologies. These morphologies include seventeen ridges that are interpreted to be möberg ridges (due to their NW-SE orientation, distinct ridge-crests and association with fractures and linear ridges) and depressions with nested faults interpreted to be similar to terrestrial ice-cauldrons, which form by enhanced subglacial geothermal activity including subglacial volcanic eruptions. These sub-lahar intrusions caused significant volatile loss in the ice-rich core of the

Utilizing NASA Earth Observations to Model Volcanic Hazard Risk Levels in Areas Surrounding the Copahue Volcano in the Andes Mountains

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Keith, A. M.; Weigel, A. M.; Rivas, J.

2014-12-01

Copahue is a stratovolcano located along the rim of the Caviahue Caldera near the Chile-Argentina border in the Andes Mountain Range. There are several small towns located in proximity of the volcano with the two largest being Banos Copahue and Caviahue. During its eruptive history, it has produced numerous lava flows, pyroclastic flows, ash deposits, and lahars. This isolated region has steep topography and little vegetation, rendering it poorly monitored. The need to model volcanic hazard risk has been reinforced by recent volcanic activity that intermittently released several ash plumes from December 2012 through May 2013. Exposure to volcanic ash is currently the main threat for the surrounding populations as the volcano becomes more active. The goal of this project was to study Copahue and determine areas that have the highest potential of being affected in the event of an eruption. Remote sensing techniques were used to examine and identify volcanic activity and areas vulnerable to experiencing volcanic hazards including volcanic ash, SO2 gas, lava flow, pyroclastic density currents and lahars. Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Landsat 8 Operational Land Imager (OLI), EO-1 Advanced Land Imager (ALI), Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topography Mission (SRTM), ISS ISERV Pathfinder, and Aura Ozone Monitoring Instrument (OMI) products were used to analyze volcanic hazards. These datasets were used to create a historic lava flow map of the Copahue volcano by identifying historic lava flows, tephra, and lahars both visually and spectrally. Additionally, a volcanic risk and hazard map for the surrounding area was created by modeling the possible extent of ash fallout, lahars, lava flow, and pyroclastic density currents (PDC) for future eruptions. These model results were then used to identify areas that should be prioritized for disaster relief and evacuation orders.

Lahar flow simulation using Laharz_py program: Application for the Mt. Halla volcano, Jeju, Korea

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Chang, C.; Yun, S. H.; Yi, W.

2017-12-01

Lahar, one of catastrophic events, has the potential to cause the loss of life and damage to infrastructure over inhabited areas. This study using Laharz_py, was performed schematic prediction on the impact area of lahar hazards at the Mt. Halla volcano, Jeju island. In order to comprehensively address the impact of lahar for the Mt. Halla, two distinct parameters, H/L ratio and lahar volume, were selected to influence variable for Laharz_py simulation. It was carried out on the basis of numerical simulation by estimating a possible lahar volumes of 30,000, 50,000, 70,000, 100,000, 300,000, 500,000 m3 according to H/L ratios (0.20, 0.22 and 0.25) was applied. Based on the numerical simulations, the area of the proximal hazard zone boundary is gradually decreased with increasing H/L ratio. The number of streams which affected by lahar, tended to decrease with increasing H/L ratio. In the case of H/L ratio 0.20, three streams (Gwangryeong stream, Dogeun stream, Han stream) in the Jeju-si area and six streams (Gungsan stream, Hogeun stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. In the case of H/L ratio 0.22, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and five streams (Gungsan stream, Seohong stream, Donghong stream, Bomok stream, Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. And in the case of H/L ratio 0.25, two streams (Gwangryeong stream and Han stream) in the Jeju-si area and one stream (Yeong stream-Hyodon stream) in the Seogwipo-si area are affected. The results of this study will be used as basic data to create a risk map for the direct damage that can be caused due to volcanic hazards arising from Mt. Halla. This research was supported by a grant [MPSS-NH-2015-81] through the Disaster and Safety Management Institute funded by Ministry of Public Safety and Security of Korean government.

Correlation and stratigraphic eruption age of the pyroclastic flow deposits and wide spread volcanic ashes intercalated in the Pliocene-Pleistocene strata, central Japan

International Nuclear Information System (INIS)

Nagahashi, Yoshitaka; Satoguchi, Yasufumi; Yoshikawa, Shusaku

2000-01-01

Three pyroclastic flow deposits in the Takayama and Omine area, central Honshu, are correlated to the distal widespread volcanic ashes intercalated in the Plio-Pleistocene boundary strata in central Japan. The correlation is based on these stratigraphic relationships, facies, magnetostratigraphy, petrographic properties such as mineral assemblage, refractive index and chemical composition of the volcanic glasses and orthopyroxene. As the result of these correlation, the eruption age of the proximal pyroclastic flow deposits have become clear. And precise correlation between proximal eruption units and distal depositional units is now possible. Ho-Kd 39 Tephra erupted at about 1.76 Ma, forming a co-ignimbrite ash, which deposited in the Kanto sedimentary basin. Eb-Fukuda Tephra erupted at about 1.75 Ma, and distal volcaniclastic deposit sedimented in the Kinki, Niigata and Kanto sedimentary basins. The eruptional and depositional phase are divided into the stage 1, stage 2 (early), stage 2 (late) and stage 3. Stage 1 is phreato-plinian type eruption phase, forming distal ash fall deposit. Stage 2 (early) is plinian pumice fall, intra-plinian pyroclastic flow and plinian pumice fall eruption phase, forming distal ash fall. Stage 2 (late) is final eruptional phase of the biggest pyroclastic flow of the Eb-Fukuda Tephra, forming a co-ignimbrite ash fall. Stage 3 is resedimented stage after the end of the explosive eruption. It is notable that resedimented volcaniclastic deposit reached Osaka sedimentary basin 300 km away from the eruption center. Om-SK110 Tephra erupted at about 1.65 Ma, divided into the stage 1, stage 2 and stage 3. Stage 1 is eruption phase of the plinian pumice fall and first pyroclastic flow. Stage 2 is pauses in eruption activity. Stage 3 is second pyroclastic flow phase, it is inferred that the pyroclastic flow of the stage 3 directly entered the Niigata sedimentary basin and simultaneously formed a co-ignimbrite ash. (author)

Pyroclastic Flow Deposits and InSAR: Analysis of Long-Term Subsidence at Augustine Volcano, Alaska

Directory of Open Access Journals (Sweden)

David B. McAlpin

2016-12-01

Full Text Available Deformation of pyroclastic flow deposits begins almost immediately after emplacement, and continues thereafter for months or years. This study analyzes the extent, volume, thickness, and variability in pyroclastic flow deposits (PFDs on Augustine Volcano from measuring their deformation rates with interferometric synthetic aperture radar (InSAR. To conduct this analysis, we obtained 48 SAR images of Augustine Volcano acquired between 1992 and 2010, spanning its most recent eruption in 2006. The data were processed using d-InSAR time-series analysis to measure the thickness of the Augustine PFDs, as well as their surface deformation behavior. Because much of the 2006 PFDs overlie those from the previous eruption in 1986, geophysical models were derived to decompose deformation contributions from the 1986 deposits underlying the measured 2006 deposits. To accomplish this, we introduce an inversion approach to estimate geophysical parameters for both 1986 and 2006 PFDs. Our analyses estimate the expanded volume of pyroclastic flow material deposited during the 2006 eruption to be 3.3 × 107 m3 ± 0.11 × 107 m3, and that PFDs in the northeastern part of Augustine Island reached a maximum thickness of ~31 m with a mean of ~5 m. Similarly, we estimate the expanded volume of PFDs from the 1986 eruption at 4.6 × 107 m3 ± 0.62 × 107 m3, with a maximum thickness of ~31 m, and a mean of ~7 m.

Pyroclastic flows generated by gravitational instability of the 1996-97 lava dome of Soufriere Hills Volcano, Montserrat

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Cole, P.D.; Calder, E.S.; Druitt, T.H.; Hoblitt, R.; Robertson, R.; Sparks, R.S.J.; Young, S.R.

1998-01-01

Numerous pyroclastic flows were produced during 1996-97 by collapse of the growing andesitic lava dome at Soufriere Hills Volcano, Montserrat. Measured deposit volumes from these flows range from 0.2 to 9 ?? 106 m3. Flows range from discrete, single pulse events to sustained large scale dome collapse events. Flows entered the sea on the eastern and southern coasts, depositing large fans of material at the coast. Small runout distance (Soufriere Hills Volcano, Montserrat. Measured deposit volumes from these flows range from 0.2 to 9??106 m3. Flows range from discrete, single pulse events to sustained large scale dome collapse events. Flows entered the sea on the eastern and southern coasts, depositing large fans of material at the coast. Small runout distance (<1 km) flows had average flow front velocities in the order of 3-10 m/s while flow fronts of the larger runout distance flows (up to 6.5 km) advanced in the order of 15-30 m/s. Many flows were locally highly erosive. Field relations show that development of the fine grained ash cloud surge component was enhanced during the larger sustained events. Periods of elevated dome pyroclastic flow productivity and sustained collapse events are linked to pulses of high magma extrusion rates.

Arenal-type pyroclastic flows: A probabilistic event tree risk analysis

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Meloy, Anthony F.

2006-09-01

A quantitative hazard-specific scenario-modelling risk analysis is performed at Arenal volcano, Costa Rica for the newly recognised Arenal-type pyroclastic flow (ATPF) phenomenon using an event tree framework. These flows are generated by the sudden depressurisation and fragmentation of an active basaltic andesite lava pool as a result of a partial collapse of the crater wall. The deposits of this type of flow include angular blocks and juvenile clasts, which are rarely found in other types of pyroclastic flow. An event tree analysis (ETA) is a useful tool and framework in which to analyse and graphically present the probabilities of the occurrence of many possible events in a complex system. Four event trees are created in the analysis, three of which are extended to investigate the varying individual risk faced by three generic representatives of the surrounding community: a resident, a worker, and a tourist. The raw numerical risk estimates determined by the ETA are converted into a set of linguistic expressions (i.e. VERY HIGH, HIGH, MODERATE etc.) using an established risk classification scale. Three individually tailored semi-quantitative risk maps are then created from a set of risk conversion tables to show how the risk varies for each individual in different areas around the volcano. In some cases, by relocating from the north to the south, the level of risk can be reduced by up to three classes. While the individual risk maps may be broadly applicable, and therefore of interest to the general community, the risk maps and associated probability values generated in the ETA are intended to be used by trained professionals and government agencies to evaluate the risk and effectively manage the long-term development of infrastructure and habitation. With the addition of fresh monitoring data, the combination of both long- and short-term event trees would provide a comprehensive and consistent method of risk analysis (both during and pre-crisis), and as such

A new high-performance 3D multiphase flow code to simulate volcanic blasts and pyroclastic density currents: example from the Boxing Day event, Montserrat

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Ongaro, T. E.; Clarke, A.; Neri, A.; Voight, B.; Widiwijayanti, C.

2005-12-01

For the first time the dynamics of directed blasts from explosive lava-dome decompression have been investigated by means of transient, multiphase flow simulations in 2D and 3D. Multiphase flow models developed for the analysis of pyroclastic dispersal from explosive eruptions have been so far limited to 2D axisymmetric or Cartesian formulations which cannot properly account for important 3D features of the volcanic system such as complex morphology and fluid turbulence. Here we use a new parallel multiphase flow code, named PDAC (Pyroclastic Dispersal Analysis Code) (Esposti Ongaro et al., 2005), able to simulate the transient and 3D thermofluid-dynamics of pyroclastic dispersal produced by collapsing columns and volcanic blasts. The code solves the equations of the multiparticle flow model of Neri et al. (2003) on 3D domains extending up to several kilometres in 3D and includes a new description of the boundary conditions over topography which is automatically acquired from a DEM. The initial conditions are represented by a compact volume of gas and pyroclasts, with clasts of different sizes and densities, at high temperature and pressure. Different dome porosities and pressurization models were tested in 2D to assess the sensitivity of the results to the distribution of initial gas pressure, and to the total mass and energy stored in the dome, prior to 3D modeling. The simulations have used topographies appropriate for the 1997 Boxing Day directed blast on Montserrat, which eradicated the village of St. Patricks. Some simulations tested the runout of pyroclastic density currents over the ocean surface, corresponding to observations of over-water surges to several km distances at both locations. The PDAC code was used to perform 3D simulations of the explosive event on the actual volcano topography. The results highlight the strong topographic control on the propagation of the dense pyroclastic flows, the triggering of thermal instabilities, and the elutriation

Chronology, morphology and stratigraphy of pumiceous pyroclastic-flow (ignimbrite) deposits from the eruption of Mount St. Helens on 18 May 1983

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Criswell, C. W.; Elston, W. E.

1984-01-01

Between 1217 and 1620 hours (PDT), on May 18, 1980, the magmatic eruption column of Mount St. Helens formed an ash fountain and pyroclastic flows dominated the eruption process over tephra ejection. Eurption-rate pulsations generally increased to a maximum at 1600 to 1700 hrs. After 1620 hrs, the eruption assumed an open-vent discharge with strong, vertical ejection of tephra. Relative eruption rates (relative mass flux rates) of the pyroclastic flows were determined by correlating sequential photographs and SLAR images, obtained during the eruption, with stratigraphy and surface morphology of the deposits.

Two coarse pyroclastic flow deposits, northern Mono-Inyo Craters, CA

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Dennen, R. L.; Bursik, M. I.; Stokes, P. J.; Lagamba, M.; Fontanella, N.; Hintz, A. R.; Jayko, A. S.

2010-12-01

The ~1350 A.D., rhyolitic North Mono eruption, Mono-Inyo Craters, CA, included the extrusion and destruction of Panum Dome and associated clastic deposits. Overlying the tephras of the North Mono sequence, the Panum deposits include a block-and-ash flow (BAF) deposit, covering ~3.5 km2. Blocks within the deposit are typically lithic rhyolite and banded gray micro-vesicular glass, showing white, almost powdery marks ranging from circular to linear in shape. These marks are interpreted as friction marks resulting from collisions between clasts. The deposit also contains bread-crusted obsidians with pressed-in clasts as well as reticulite with a bread-crusted surface texture. Near the centerline of the deposit is a ridge-topping train of jigsaw fractured blocks, often with reddish-orange alteration. One house sized jigsaw block sits upstream of a long, thinning pile of reddish orange debris; this “flow shadow” indicates that the block remained relatively stationary while the block and ash flow continued to propagate around it. The bread-crusted reticulite is most common at proximal localities. It is proposed that the dome destruction included a debris avalanche emplacing the train of jigsaw fractured blocks and creating a topographic high, the block-and-ash flow (the farthest reaching deposit from this event) which flowed around the debris avalanche deposits, and a final “lateral expansion” of a magma foam, creating the reticulite seen concentrated at proximal locations. Another coarse pyroclastic flow (here termed the “lower blast deposit”) underlies the North Mono tephra. It is more obsidian rich and finer grained than the Panum BAF. The lower blast deposit may have originated from Pumice Pit vent, which is now capped with an older dome ~0.5 km southeast of Panum. The lower blast deposit extends farther from the Panum vent than does the Panum BAF deposit, and apparently was mistaken for the Panum BAF deposit by previous workers. Hence the run

Lahar hazards at Agua volcano, Guatemala

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Schilling, S.P.; Vallance, J.W.; Matías, O.; Howell, M.M.

2001-01-01

At 3760 m, Agua volcano towers more than 3500 m above the Pacific coastal plain to the south and 2000 m above the Guatemalan highlands to the north. The volcano is within 5 to 10 kilometers (km) of Antigua, Guatemala and several other large towns situated on its northern apron. These towns have a combined population of nearly 100,000. It is within about 20 km of Escuintla (population, ca. 100,000) to the south. Though the volcano has not been active in historical time, or about the last 500 years, it has the potential to produce debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas.

Using InSAR for Characterizing Pyroclastic Flow Deposits at Augustine Volcano Across Two Eruptive Cycles

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McAlpin, D. B.; Meyer, F. J.; Lu, Z.; Beget, J. E.

2014-12-01

Augustine Island is a small, 8x11 km island in South Central Alaska's lower Cook Inlet. It is approximately 280 km southwest of Anchorage, and occupied entirely by its namesake Augustine Volcano. At Augustine Volcano, SAR data suitable for interferometry is available from 1992 to 2005, from March 2006 to April 2007, and from July 2007 to October 2010. Its last two eruptive episodes, in 1986 and 2006, resulted in substantial pyroclastic flow deposits (PFDs) on the Volcano's north flank. Earlier InSAR analyses of the area, from 1992-1999, identified local subsidence, but no volcano-wide deformation indicative of magma-chamber evacuation. In contrast to previous studies, we use InSAR data to determine a range of geophysical parameters for PFDs emplaced during the Augustine's two most recent eruption cycles. Based on InSAR measurements between 1992 and 2010, we reconstruct the deformation behavior of PFDs emplaced during Augustine's last two eruption cycles. Using a combination of InSAR measurements and modeling, we determine the thickness and long-term deformation of overlaying pyroclastic flow deposits emplaced in 1986 and 2006. Consistent with previous observations of pyroclastic flows, we found that the PFDs on Augustine Island rapidly subsided after emplacement due to an initial compaction of the material. We determined the length of this initial settling period and measured the compaction rate. Subsequent to this initial rapid subsidence, we found that PFD deformation slowed to a more persistent, linear, long-term rate, related to cooling of the deposits. We established that the deposits' contraction rate is linearly related to their thickness and measured the contraction rate. Finally, a study of long term coherence properties of the Augustine PFDs showed remarkable stability of the surface over long time periods. This information provides clues on the structural properties and composition of the emplaced material.

Assessing lahars from ice-capped volcanoes using ASTER satellite data, the SRTM DTM and two different flow models: case study on Iztaccíhuatl (Central Mexico

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D. Schneider

2008-06-01

Full Text Available Lahars frequently affect the slopes of ice-capped volcanoes. They can be triggered by volcano-ice interactions during eruptions but also by processes such as intense precipitation or by outbursts of glacial water bodies not directly related to eruptive activity. We use remote sensing, GIS and lahar models in combination with ground observations for an initial lahar hazard assessment on Iztaccíhuatl volcano (5230 m a.s.l., considering also possible future developments of the glaciers on the volcano. Observations of the glacial extent are important for estimations of future hazard scenarios, especially in a rapidly changing tropical glacial environment. In this study, analysis of the glaciers on Iztaccíhuatl shows a dramatic retreat during the last 150 years: the glaciated area in 2007 corresponds to only 4% of the one in 1850 AD and the glaciers are expected to survive no later than the year 2020. Most of the glacial retreat is considered to be related to climate change but in-situ observations suggest also that geo- and hydrothermal heat flow at the summit-crater area can not be ruled out, as emphasized by fumarolic activity documented in a former study. However, development of crater lakes and englacial water reservoirs are supposed to be a more realistic scenario for lahar generation than sudden ice melting by rigorous volcano-ice interaction. Model calculations show that possible outburst floods have to be larger than ~5×10⁵ m³ or to achieve an H/L ratio (Height/runout Length of 0.2 and lower in order to reach the populated lower flanks. This threshold volume equals 2.4% melted ice of Iztaccíhuatl's total ice volume in 2007, assuming 40% water and 60% volumetric debris content of a potential lahar. The model sensitivity analysis reveals important effects of the generic type of the Digital Terrain Model (DTM used on the results. As a consequence, the predicted affected areas can vary significantly. For such

Hydrological sensitivity of volcanically disturbed watersheds—a lesson reinforced at Pinatubo

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Major, J. J.; Janda, R. J.

2016-12-01

The climactic June 1991 eruption of Mount Pinatubo devastated many surrounding catchments with thick pyroclastic fall and flow deposits, and subsequent hydrogeomorphic responses were dramatic and persisted for years. But in the 24 hours preceding the climactic eruption there was less devastating eruptive activity that had more subtle, yet significant, impact on catchment hydrology. Stratigraphic relations show damaging lahars swept all major channels east of the volcano, starting late on June 14 and continuing through (and in some instances after) midday on June 15, before the climactic phase of the eruption began and before Typhoon Yunya struck the region. These early lahars were preceded by relatively small explosions and pyroclastic surges that emplaced fine-grained ash in the upper catchments, locally damaged or destroyed vegetation, reduced hillside infiltration capacity, and smoothed surface roughness. Thus the lahars, likely triggered by typical afternoon monsoon storms perhaps enhanced by local thermal influences of fresh volcanic deposits, did not result from extraordinary tropical rainfall or exceptional volcaniclastic deposition. Instead, direct rainfall-runoff volume increased substantially as a consequence of vegetation damage and moderate deposition of fine ash. Rapid runoff from hillsides to channels initiated hillside and bank erosion as well as channel scour, producing debris flows and hyperconcentrated flows. Timing of some lahars varied across catchments as well as downstream within catchments with respect to climactic pumice fall, demonstrating complex interplay among volcanic processes, variations in catchment disturbance, and rainfall timing and intensity. Occurrence of these early lahars supports the hypothesis that eruptions that deposit fine ash in volcanic catchments can instigate major hydrogeomorphic responses even when volcanic disturbances are modest—an effect that can be masked by later eruption impacts.

Nested Architecture of Pyroclastic Bedforms Generated by a Single Flow Event: Outcrop Examples from the Izu Volcanic Islands, Japan

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Nemoto, Y.; Yoshida, S.

2009-12-01

We claim that compound bedforms, where small bedforms (e.g., dunes and antidunes) occur within and around the larger bedforms, are common in pyroclastic-flow deposits, using Quaternary-Holocene outcrop examples from the modern Izu volcanic island chain some 100-150 km SSW of Tokyo. The nested occurrence of bedforms have been well documented for siliciclastic deposits, as exemplified by compound dunes where small dunes (c. cm- dm thick) occur between the avalanche surfaces within larger dunes, indicating that these dunes of different sizes were produced simultaneously. However, compound dunes have rarely been reported from pyroclastic deposits. In contrast, we have discovered that compound dunes are common in pyroclastic flow deposits in the late Pleistocene & Holocene outcrops in Niijima and Oshima of the Izu volcanic island chain. Moreover, these outcrops contain abundant compound antidunes, which have been reported from neither siliciclastic or pyroclastic deposits. This is probably because flume studies, where most of published antidune studies are based, focus on small (c. cm-dm high) antidunes. In Niijima Island, we examined pyroclastic-flow deposits shed from Mt. Miyatsuka (14 ka) and Mt. Mukai (886 A.D.). Both groups of deposits contain abundant antidune stratifications, which commonly form nested structures in a two- or three-fold hierarchy, with subordinate crossbeddings originated from dune migrations. Each class of antidunes is characterized by multiple scour surfaces and vertical aggradations around mounds of lag deposits above erosion surfaces, and typically has both upstream and downstream accretion components with different proportions. The late Pleistocene pyroclastic outcrops of the nearby Oshima Island exhibit similar patterns. The geometry of the accretion surfaces vary significantly in the outcrops of both Niijima and Oshima. Whereas the antidunes dominated by upstream accretion are characterized by (1) gently inclined accretion surface and (2

Generation of pyroclastic density currents from pyroclastic fountaining or transient explosions: insights from large scale experiments

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Sulpizio, Roberto; Dellino, Pierfrancesco; Mele, Daniela; La Volpe, Luigi [CIRISIVU, c/o Dipartimento Geomineralogico, via Orabona 4, 70125, Bari (Italy)], E-mail: r.sulpizio@geomin.uniba.it

2008-10-01

Pyroclastic density currents (PDCs) are among the most amazing, complex and dangerous volcanic phenomena. They are moving mixtures of particles and gas that flow across the ground, and originate in different ways and from various sources, during explosive eruptions or gravity-driven collapse of domes. We present results from experimental work to investigate the generation of large-scale, multiphase, gravity-driven currents. The experiments described here are particularly devoted to understanding the inception and development of PDCs under impulsive injection conditions by means of the fast application of a finite stress to a finite mass of pyroclastic particles via expansion of compressed gas. We find that, in summary, PDC generation from collapse of pressure-adjusted or overpressurised pyroclastic jets critically depends on behaviour of injection into the atmosphere, which controls the collapsing mechanisms and then the physical parameters of the initiating current.

Geology of proximal, small-volume trachyte-trachyandesite pyroclastic flows and associated surge deposits, Roccamonfina volcano, Italy

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Giannetti, Bernardino

1998-01-01

This paper describes the 232 ka B.P. MTTT trachyte-trachyandesite pyroclastic succession of Roccamonfina volcano. This small-volume, proximal sequence crops out along Mulino di Sotto, Paratone, and Pisciariello ravines in the southwest sector of the central caldera, and covers a minimum extent of 3.5 km 2 area. It is made up of seven pyroclastic flows and pyroclastic surge units consisting of trachytic ash matrix containing juvenile trachyandesitic scoria and dense lava fragments, pumice clasts of uncertain trachyandesite, and a foreign trachyandesitic lithic facies. Two stratigraphic markers allow correlation of the units. No paleosoils and Plinian fallout have been observed at the base and within the succession. Some lateral grading of scoria and lithic clasts suggests that MTTT derived from three distinct source vents. The sequence consists of a basal ash flow passing laterally to laminated surge deposits (Unit A). This is overlain by a reversely graded scoria and pumice lapilli flow (Unit B) which is in turn overlain by a thinly cross-stratified scoria lapilli surge (Unit C). Unit C is capped by a prominent ash-and-scoria flow (Unit D). A ground layer (Marker MK1) divides Unit D from a massive ignimbrite which grades upcurrent to sand-wave surge deposits (Unit E). Another ground layer (Marker MK2) separates Unit E from Unit F. This unit consists of a basal ignimbrite passing laterally to bedded surge deposits with convolute structures (subunit Fl), and grading upcurrent to a subhorizontally plane-laminated ash cloud (subunit F2) containing near the top a layer of millimetric lithic clasts embedded in fine ash. The succession is closed by the pyroclastic flow Unit G. Surge Unit C can be interpreted in terms of vertical gradients in turbulence, particle concentration, and velocity during flowage, whereas the bedded surge parts present in the massive deposits of Units A and E-F1 can be related to abrupt changes of velocity down the steep slopes of ravines. Reverse

Volcanic-glacial interactions: GIS applications to the assessment of lahar hazards (case study of Kamchatka

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Ya. D. Muraviev

2014-01-01

Full Text Available On the Kamchatka peninsula, lahars or volcanogenic mudflows arise as a result of intensive snow melting caused by incandescent material ejected by volcanoes onto the surface. Such flows carrying volcanic ash and cinders together with lava fragments and blocks move with a speed up to 70 km/h that can result in significant destructions and even human victims. Formation of such water flows is possible during the whole year.Large-scale GIS «Hazards of lahars (volcanogenic mudflows» has been developed for some volcano group as well as for individual volcanoes on the peninsula in framework of the GIS «Volcanic hazard of the Kuril-Kamchatka island arc». Main components of this database are the following: physic-geographical information on region of active volcanism and adjacent areas, on human settlements; data on the mudflow activity; data on distribution of the snow and ice reserves. This database is aimed at mapping of surrounding territories and estimating a hazard of lahars.For illustration the paper presents a map of the lahar hazards, results of calculations of the distances of ejects and maximal area of ejected material spreading in dependence on a character and power of an eruption. In future we plan to perform operational calculations of maximal possible volumes of such flows and areas of their spreading. The calculations will be made on the basis of the GIS «Volcanic hazard of the Kuril-Kamchatka island arc».A volume of hard material carried by lahars onto slopes and down to foot of the Kluchevskaya volcanic massif is estimated on the basis of data on the snow and ice reserves on volcano slopes. On the average for many years, the snow accumulation in zones of the mudflow formations their volume often reaches 15–17 millions of cubic meters. Depending on the snowfall activity in different years this value may vary within 50% relative to the norm. Further on, calculations of maximal possible volume of such flows will be performed in a

Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

OpenAIRE

Thouret , Jean-Claude; Enjolras , G.; Martelli , K.; Santoni , O.; Luque , A.; Nagata , M.; Arguedas , A.; Macedo , L.

2013-01-01

Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows), and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash fl...

Modeled inundation limits of potential lahars from Mount Adams in the White Salmon River Valley, Washington

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Griswold, Julia P.; Pierson, Thomas C.; Bard, Joseph A.

2018-05-09

Lahars large enough to reach populated areas are a hazard at Mount Adams, a massive volcano in the southern Cascade Range of Washington State (fig. 1). It is considered to be still active and has the potential to erupt again. By definition, lahars are gravity-driven flows of water-saturated mixtures of mud and rock (plus or minus ice, wood, and other debris), which originate from volcanoes and have a variety of potential triggering mechanisms (Vallance, 2000; Vallance and Iverson, 2015). Flowing mixtures can range in fluid consistency from something like a milkshake to something more like wet concrete, and they behave like flash floods, in that they can appear suddenly in river channels with little warning and commonly have boulder- or log-choked flow fronts. Lahars are hazardous because they can flow rapidly in confined valleys (commonly 20–35 miles per hour [mph] or 9–16 meters per second [m/s]), can travel more than 100 miles (mi) (161 kilometers [km]) from a source volcano, and can move with incredible destructive force, carrying multi-ton boulders and logs that can act as battering rams (Pierson, 1998). The biggest threats from lahars to downstream communities are present during eruptive activity, and impacts to communities can be dire. For example, a very large eruption-triggered lahar in Colombia in 1985 surprised and killed more than 20,000 people in a large town located about 45 mi (72 km) downstream and out of sight of the volcano that produced it (Pierson and others, 1990).Mount Adams, one of the largest volcanoes in the Cascade Range, is a composite stratocone composed primarily of andesite lava flows. It has been the most continuously active volcano within the 480-mi2 Mount Adams volcanic field—a region covering parts of Klickitat, Skamania, Yakima, andLewis Counties and part of the Yakama Nation Reservation in Washington State (Hildreth and Fierstein,1995, 1997). About 500,000 years in age, Mount Adams reached its present size by about 15

The Utilization of Remotely Sensed Data to Analyze the Estimated Volume of Pyroclastic Deposits and Morphological Changes Caused by the 2010-2015 Eruption of Sinabung Volcano, North Sumatra, Indonesia

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Yulianto, Fajar; Suwarsono; Sofan, Parwati

2016-08-01

In this research, remotely sensed data has been used to estimate the volume of pyroclastic deposits and analyze morphological changes that have resulted from the eruption of Sinabung volcano. Topographic information was obtained from these data and used for rapid mapping to assist in the emergency response. Topographic information and change analyses (pre- and syn- eruption) were conducted using digital elevation models (DEMs) for the period 2010-2015. Advanced spaceborne thermal emission and reflection radiometer (ASTER) global digital elevation model (GDEM) data from 2009 were used to generate the initial DEMs for the condition prior to the eruption of 2010. Satellite pour l'observation de la terre 6 (SPOT 6) stereo images acquired on 21 June 2015 and were used to make a DEM for that time. The results show that the estimated total volume of lava and pyroclastic deposits, produced during the period 2010 to mid-2015 is approximately 2.8 × 108 m3. This estimated volume of pyroclastic deposits can be used to predict the magnitude of future secondary lahar hazards, which are also related to the capacity of rivers in the area. Morphological changes are illustrated using cross-sectional analysis of the deposits, which are currently deposited to the east, southeast and south of the volcano. Such analyses can also help in forecasting the direction of the future flow hazards. The remote sensing and analysis methods used at Sinabung can also be applied at other volcanoes and to assess the threats of other types of hazards such as landslides and land subsidence.

Hydrological control of large hurricane-induced lahars: evidence from rainfall-runoff modeling, seismic and video monitoring

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Capra, Lucia; Coviello, Velio; Borselli, Lorenzo; Márquez-Ramírez, Víctor-Hugo; Arámbula-Mendoza, Raul

2018-03-01

The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h -1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5-6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s -1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green-Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses

Objective rapid delineation of areas at risk from block-and-ash pyroclastic flows and surges

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Widiwijayanti, C.; Voight, B.; Hidayat, D.; Schilling, S.P.

2009-01-01

Assessments of pyroclastic flow (PF) hazards are commonly based on mapping of PF and surge deposits and estimations of inundation limits, and/or computer models of varying degrees of sophistication. In volcanic crises a PF hazard map may be sorely needed, but limited time, exposures, or safety aspects may preclude fieldwork, and insufficient time or baseline data may be available for reliable dynamic simulations. We have developed a statistically constrained simulation model for block-and-ash type PFs to estimate potential areas of inundation by adapting methodology from Iverson et al. (Geol Soc America Bull 110:972-984, (1998) for lahars. The predictive equations for block-and-ash PFs are calibrated with data from several volcanoes and given by A = (0.05 to 0.1) V2/3, B = (35 to 40) V2/3, where A is cross-sectional area of inundation, B is planimetric area and V is deposit volume. The proportionality coefficients were obtained from regression analyses and comparison of simulations to mapped deposits. The method embeds the predictive equations in a GIS program coupled with DEM topography, using the LAHARZ program of Schilling (1998). Although the method is objective and reproducible, any PF hazard zone so computed should be considered as an approximate guide only, due to uncertainties on the coefficients applicable to individual PFs, the authenticity of DEM details, and the volume of future collapses. The statistical uncertainty of the predictive equations, which imply a factor of two or more in predicting A or B for a specified V, is superposed on the uncertainty of forecasting V for the next PF to descend a particular valley. Multiple inundation zones, produced by simulations using a selected range of volumes, partly accommodate these uncertainties. The resulting maps show graphically that PF inundation potentials are highest nearest volcano sources and along valley thalwegs, and diminish with distance from source and lateral distance from thalweg. The model does

Lahar hazards at Mombacho Volcano, Nicaragua

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Vallance, J.W.; Schilling, S.P.; Devoli, G.

2001-01-01

Mombacho volcano, at 1,350 meters, is situated on the shores of Lake Nicaragua and about 12 kilometers south of Granada, a city of about 90,000 inhabitants. Many more people live a few kilometers southeast of Granada in 'las Isletas de Granada and the nearby 'Peninsula de Aseses. These areas are formed of deposits of a large debris avalanche (a fast moving avalanche of rock and debris) from Mombacho. Several smaller towns with population, in the range of 5,000 to 12,000 inhabitants are to the northwest and the southwest of Mombacho volcano. Though the volcano has apparently not been active in historical time, or about the last 500 years, it has the potential to produce landslides and debris flows (watery flows of mud, rock, and debris -- also known as lahars when they occur on a volcano) that could inundate these nearby populated areas. -- Vallance, et.al., 2001

PYROCLASTIC FLOW MODELING TO RECONSTRUCT A VOLCANIC EDIFICE IN PAIPA (BOYACÁ-COLOMBIA.

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Rodríguez Óscar

2004-06-01

Full Text Available Pyroclastic deposits produced by the domes collapse (resurgence of a caldera collapse, at the west of the Honda Grande creek (Paipa, Boyacá-Colombia were related by INGEOMINAS. These deposits fill the valleys of Olitas, Calderitas and a creek at the south of the Alto de los Volcanes reaching distances near to 3 km from the focus between the Alto de los Volcanes and El Mirador Hill.The flows were modeled using 3D Software (Sheridan and Kover, 1996. A volcanic simulation was done obtaining the height and morphology of the volcanic edifice before the collapse during the last eruptive event.

Suitability of simple rheological laws for the numerical simulation of dense pyroclastic flows and long-runout volcanic avalanches

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Kelfoun, Karim

2011-08-01

The rheology of volcanic rock avalanches and dense pyroclastic flows is complex, and it is difficult at present to constrain the physics of their processes. The problem lies in defining the most suitable parameters for simulating the behavior of these natural flows. Existing models are often based on the Coulomb rheology, sometimes with a velocity-dependent stress (e.g., Voellmy), but other laws have also been used. Here I explore the characteristics of flows, and their deposits, obtained on simplified topographies by varying source conditions and rheology. The Coulomb rheology, irrespective of whether there is a velocity-dependent stress, forms cone-shaped deposits that do not resemble those of natural long-runout events. A purely viscous or a purely turbulent flow can achieve realistic velocities and thicknesses but cannot form a deposit on slopes. The plastic rheology, with (e.g., Bingham) or without a velocity-dependent stress, is more suitable for the simulation of dense pyroclastic flows and long-runout volcanic avalanches. With this rheology, numerical flows form by pulses, which are often observed during natural flow emplacement. The flows exhibit realistic velocities and deposits of realistic thicknesses. The plastic rheology is also able to generate the frontal lobes and lateral levées which are commonly observed in the field. With the plastic rheology, levée formation occurs at the flow front due to a divergence of the driving stresses at the edges. Once formed, the levées then channel the remaining flow mass. The results should help future modelers of volcanic flows with their choice of which mechanical law corresponds best to the event they are studying.

Pyroclastic sulphur eruption at Poas Volcano, Costa Rica

Energy Technology Data Exchange (ETDEWEB)

Francis, P.W.; Thorpe, R.S.; Brown, G.C.; Glasscock, J.

1980-01-01

The recent Voyager missions to Jupiter have highlighted the role of sulphur in volcanic processes on io. Although fumarolic sulphur and SO/sub 2/ gas are almost universal in terrestrial active volcanoes, and rare instances of sulphur lava flows have been reported, sulphur in a pyroclastic form has only been described from Poas Volcano, Costa Rica. Here we amplify the original descriptions by Bennett and Raccichini and describe a recent eruption of pyroclastic sulphur scoria and ejected blocks that are characterised by miniature sulphur stalactites and stalagmites.

Assessment of motion-induced fluidization of dense pyroclastic gravity currents

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P. Salatino

2005-06-01

Full Text Available The paper addresses some fundamental aspects of the dynamics of dense granular flows down inclines relevant to pyroclastic density currents. A simple mechanistic framework is presented to analyze the dynamics of the frontal zone, with a focus on the establishment of conditions that promote air entrainment at the head of the current and motion-induced self-fluidization of the flow. The one-dimensional momentum balance on the current along the incline is considered under the hypothesis of strongly turbulent flow and pseudo-homogeneous behaviour of the two-phase gas-solid flow. Departures from one-dimensional flow in the frontal region are also analyzed and provide the key to the assessment of air cross-flow and fluidization of the solids in the head of the current. The conditions for the establishment of steady motion of pyroclastic flows down an incline, in either the fluidized or «dry» granular states, are examined.

Tephrostratigraphy of the A.D. 79 pyroclastic deposits in perivolcanic areas of Mt. Vesuvio (Italy)

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Lirer, Lucio; Munno, Rosalba; Petrosino, Paola; Vinci, Anna

1993-11-01

Correlations between pyroclastic deposits in perivolcanic areas are often complicated by lateral and vertical textural variations linked to very localized depositional effects. In this regard, a detailed sampling of A.D. 79 eruption products has been performed in the main archaeological sites of the perivolcanic area, with the aim of carrying out a grain-size, compositional and geochemical investigation so as to identify the marker layers from different stratigraphic successions and thus reconstruct the eruptive sequence. In order to process the large number of data available, a statistical approach was considered the most suitable. Statistical processing highlighted 14 marker layers among the fall, stratified surge and pyroclastic flow deposits. Furthermore statistical analysis made it possible to correlate pyroclastic flow and surge deposits interbedded with fall, interpreted as a lateral facies variation. Finally, the passage from magmatic to hydromagmatic activity is marked by the deposition of pyroclastic flow, surge and accretionary lapilli-bearing deposits. No transitional phase from magmatic to hydromagmatic activity has been recognized.

New tools to investigate textures of pyroclastic deposits

Energy Technology Data Exchange (ETDEWEB)

Sarocchi, Damiano [Instituto de GeologIa / Fac. IngenierIa UASLP, Dr. M. Nava No 5, Zona Universitaria 78240, San Luis PotosI (Mexico); Borselli, Lorenzo [Istituto di Ricerca per la Protezione Idrogeologica, Consiglio Nazionale delle Ricerche, Via Madonna del Piano 10, 50019, Sesto Fiorentino (Italy); MacIas, Jose Luis [Departamento de VulcanologIa, Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, Coyoacan 04510, D.F. (Mexico)

2008-10-01

A pyroclastic flow deposit keeps a fingerprint of the physical processes that occurred in the flow during transport and settling. Part of this information is recorded in the texture of the deposit offering an instantaneous view of the flow prior to freezing. In this work we introduce some texture's analysis techniques, based on image analysis, that we have developed or tuned during the last years.

EVALUATION OF DISASTER MITIGATION SYSTEM AGAINST LAHAR FLOW OF PUTIH RIVER, MT. MERAPI AREA

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T. Maksal Saputra

2013-05-01

Result of the evaluation shows that the existing early warning system does not produce sufficient time for the sand miners to save themselves. The proposed solution is to divide sand mine area in Putih River into 3 zones, each zone has different procedure of the early warning and evacuation. This is arranged to avoid casualties to the sand miners. Keywords: Lahar flood, sand miners, early warning.

Field-trip guide to Mount St. Helens, Washington - An overview of the eruptive history and petrology, tephra deposits, 1980 pyroclastic density current deposits, and the crater

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Pallister, John S.; Clynne, Michael A.; Wright, Heather M.; Van Eaton, Alexa R.; Vallance, James W.; Sherrod, David R.; Kokelaar, B. Peter

2017-08-02

This field trip will provide an introduction to several fascinating features of Mount St. Helens. The trip begins with a rigorous hike of about 15 km from the Johnston Ridge Observatory (9 km north-northeast of the crater vent), across the 1980 Pumice Plain, to Windy Ridge (3.6 km northeast of the crater vent) to examine features that document the dynamics and progressive emplacement of pyroclastic flows. The next day, we examine classic tephra outcrops of the past 3,900 years and observe changes in thickness and character of these deposits as we traverse their respective lobes. We examine clasts in the deposits and discuss how the petrology and geochemistry of Mount St. Helens deposits reveal the evolution of the magmatic system through time. We also investigate the stratigraphy of the 1980 blast deposit and review the chronology of this iconic eruption as we travel through the remains of the blown-down forest. The third day is another rigorous hike, about 13 km round trip, climbing from the base of Windy Ridge (elevation 1,240 m) to the front of the Crater Glacier (elevation 1,700 m). En route we examine basaltic andesite and basalt lava flows emplaced between 1,800 and 1,700 years before present, a heterolithologic flow deposit produced as the 1980 blast and debris avalanche interacted, debris-avalanche hummocks that are stranded on the north flank and in the crater mouth, and shattered dacite lava domes that were emplaced between 3,900 and 2,600 years before present. These domes underlie the northern part of the volcano. In addition, within the crater we traverse well-preserved pyroclastic-flow deposits that were emplaced on the crater floor during the summer of 1980, and a beautiful natural section through the 1980 deposits in the upper canyon of the Loowit River.Before plunging into the field-trip log, we provide an overview of Mount St. Helens geology, geochemistry, petrology, and volcanology as background. The volcano has been referred to as a �

Simulating Lahars Using A Rotating Drum

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Neather, Adam; Lube, Gert; Jones, Jim; Cronin, Shane

2014-05-01

A large (0.5 m in diameter, 0.15 m wide) rotating drum is used to investigate the erosion and deposition mechanics of lahars. To systematically simulate the conditions occurring in natural mass flows our experimental setup differs from the common rotating drum employed in industrial/engineering studies. Natural materials with their typical friction properties are used, as opposed to the frequently employed spherical glass beads; the drum is completely water-proof, so solid/air and solid/liquid mixtures can be investigated; the drum velocity and acceleration can be precisely controlled using a software interface to a micro-controller, allowing for the study of steady, unsteady and intermediate flow regimes. The drum has a toughened glass door, allowing high-resolution, high-speed video recording of the material inside. Vector maps of the velocities involved in the flows are obtained using particle image velocimetry (PIV). The changes in velocity direction and/or magnitude are used to locate the primary internal boundaries between layers of opposite flow direction, as well as secondary interfaces between shear layers. A range of variables can be measured: thickness and number of layers; the curvature of the free surface; frequency of avalanching; position of the centre of mass of the material; and the velocity profiles of the flowing material. Experiments to date have focussed on dry materials, and have had a fill factor of approximately 0.3. Combining these measured variables allows us to derive additional data of interest, such as mass and momentum flux. It is these fluxes that we propose will allow insight into the erosion/deposition mechanics of a lahar. A number of conclusions can be drawn to date. A primary interface separates flowing and passive region (this interface has been identified in previous studies). As well as the primary interface, the flowing layer separates into individual shear layers, with individual erosion/deposition and flow histories. This

Variations in community exposure to lahar hazards from multiple volcanoes in Washington State (USA)

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Diefenbach, Angela K.; Wood, Nathan J.; Ewert, John W.

2015-01-01

Understanding how communities are vulnerable to lahar hazards provides critical input for effective design and implementation of volcano hazard preparedness and mitigation strategies. Past vulnerability assessments have focused largely on hazards posed by a single volcano, even though communities and officials in many parts of the world must plan for and contend with hazards associated with multiple volcanoes. To better understand community vulnerability in regions with multiple volcanic threats, we characterize and compare variations in community exposure to lahar hazards associated with five active volcanoes in Washington State, USA—Mount Baker, Glacier Peak, Mount Rainier, Mount Adams and Mount St. Helens—each having the potential to generate catastrophic lahars that could strike communities tens of kilometers downstream. We use geospatial datasets that represent various population indicators (e.g., land cover, residents, employees, tourists) along with mapped lahar-hazard boundaries at each volcano to determine the distributions of populations within communities that occupy lahar-prone areas. We estimate that Washington lahar-hazard zones collectively contain 191,555 residents, 108,719 employees, 433 public venues that attract visitors, and 354 dependent-care facilities that house individuals that will need assistance to evacuate. We find that population exposure varies considerably across the State both in type (e.g., residential, tourist, employee) and distribution of people (e.g., urban to rural). We develop composite lahar-exposure indices to identify communities most at-risk and communities throughout the State who share common issues of vulnerability to lahar-hazards. We find that although lahars are a regional hazard that will impact communities in different ways there are commonalities in community exposure across multiple volcanoes. Results will aid emergency managers, local officials, and the public in educating at-risk populations and developing

Investigating the use of Pyroclastics for Palaeointensity Determinations

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Paterson, G. A.; Muxworthy, A. R.; Roberts, A. P.; Mac Niocaill, C.

2008-12-01

Palaeointensity experiments are time consuming and prone to failure, making it difficult to obtain good data. This limits the global palaeointensity database, which has inadequate spatial and temporal resolution. Developing reliable yet efficient experimental techniques is important for improving data quality, as is expanding the range of materials to investigate. By characterizing and understanding the behaviour of different materials, such as lithic clasts found within pyroclastic flows, we can assess their potential usefulness as palaeomagnetic recorders. Pre-existing lithic fragments are reheated as they are incorporated into pyroclastic density currents (PDCs) and their subsequent deposits. This partially resets their magnetization to record the ambient field at the time of eruption. The explosive nature of volcanic eruptions associated with PDCs frequently results in a wide range of lithic fragments in such deposits and the high temperatures involved (up to ~1200°C) can allow acquisition of an entirely new magnetization. We have studied the pyroclastic deposits of four historic volcanoes: Láscar in the Chilean Andes, Colima in Mexico, Mount St. Helens, USA, and Vesuvius, Italy. At Láscar, the emplacement temperature of the deposits exceeds the Curie temperature of the magnetic minerals, which maximizes the potential temperature range for obtaining palaeointensity determinations. Triple heating palaeointensity experiments, with strict selection criteria, yield a mean palaeointensity of 24.3±2.1 μT (N=22), which is in good agreement with the expected value of 24 μT. This indicates that the method has promise. The use of multiple lithologies in a single palaeointensity determination also provides confidence that the result is not biased by alteration within one of the lithologies. Pyroclastics, however, still suffer from the problems associated with palaeointensity experiments on lava flows. Samples collected from Mount St. Helens show a high degree of

Sedimentology and geomorphology of the deposits from the August 2006 pyroclastic density currents at Tungurahua volcano, Ecuador.

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Douillet, Guilhem Amin; Tsang-Hin-Sun, Ève; Kueppers, Ulrich; Letort, Jean; Pacheco, Daniel Alejandro; Goldstein, Fabian; Von Aulock, Felix; Lavallée, Yan; Hanson, Jonathan Bruce; Bustillos, Jorge; Robin, Claude; Ramón, Patricio; Hall, Minard; Dingwell, Donald B

The deposits of the pyroclastic density currents from the August 2006 eruption of Tungurahua show three facies associations depending on the topographic setting: the massive, proximal cross-stratified, and distal cross-stratified facies. (1) The massive facies is confined to valleys on the slopes of the volcano. It contains clasts of >1 m diameter to fine ash material, is massive, and interpreted as deposited from dense pyroclastic flows. Its surface can exhibit lobes and levees covered with disk-shaped and vesicular large clasts. These fragile large clasts must have rafted at the surface of the flows all along the path in order to be preserved, and thus imply a sharp density boundary near the surface of these flows. (2) The proximal cross-stratified facies is exposed on valley overbanks on the upper part of the volcano and contains both massive coarse-grained layers and cross-stratified ash and lapilli bedsets. It is interpreted as deposited from (a) dense pyroclastic flows that overflowed the gentle ridges of valleys of the upper part of the volcano and (b) dilute pyroclastic density currents created from the dense flows by the entrainment of air on the steep upper flanks. (3) The distal cross-stratified facies outcrops as spatially limited, isolated, and wedge-shaped bodies of cross-stratified ash deposits located downstream of cliffs on valleys overbanks. It contains numerous aggrading dune bedforms, whose crest orientations reveal parental flow directions. A downstream decrease in the size of the dune bedforms, together with a downstream fining trend in the grain size distribution are observed on a 100-m scale. This facies is interpreted to have been deposited from dilute pyroclastic density currents with basal tractional boundary layers. We suggest that the parental flows were produced from the dense flows by entrainment of air at cliffs, and that these diluted currents might rapidly deposit through "pneumatic jumps". Three modes are present in the grain

Volcano Trial Case on GEP: Systematically processing EO data

OpenAIRE

Baumann, Andreas Bruno Graziano

2017-01-01

Volcanoes can be found all over the world; on land and below water surface. Even nowadays not all volcanoes are known. About 600 erupted in geologically recent times and about 50-70 volcanoes are currently active. Volcanoes can cause earthquakes; throw out blasts and tephras; release (toxic) gases; lava can flow relatively slow down the slopes; mass movements like debris avalanches, and landslides can cause tsunamis; and fast and hot pyroclastic surge, flows, and lahars can travel fast down ...

Long-term contraction of pyroclastic flow deposits at Augustine Volcano using InSAR

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McAlpin, D. B.; Meyer, F. J.; Lu, Z.; Beget, J. E.

2013-12-01

Augustine Island is a small, 8x11 km island in South Central Alaska's lower Cook Inlet. It is approximately 280 km southwest of Anchorage, and occupied entirely by its namesake Augustine Volcano. The volcano's nearly symmetrical central cone reaches an altitude of 1260 m, and the surrounding island is composed almost entirely of volcanic deposits. It is the youngest and most frequently active volcano in the lower Cook Inlet, with at least seven known eruptions since the beginning of written records in 1812. Its two most recent eruptions occurred during March-August 1986, and January-March 2006 The 1986 and 2006 Augustine eruptions produced significant pyroclastic flow deposits (PFDs) on the island, both which have been well mapped by previous studies. Subsidence of material deposited by these pyroclastic flows has been measured by InSAR data, and can be attributed to at least four processes: (1) initial, granular settling; (2) thermal contraction; (3) loading of 1986 PFDs from overlying 2006 deposits; and (4) continuing subsidence of 1986 PFDs buried beneath 2006 flows. For this paper, SAR data for PFDs from Augustine Volcano were obtained from 1992 through 2005, from 2006-2007, and from 2007-2011. These time frames provided InSAR data for long-term periods after both 1986 and 2006 eruptions. From time-series analysis of these datasets, deformation rates of 1986 PFDs and 2006 PFDs were determined, and corrections applied where newer deposits were emplaced over old deposits. The combination of data sets analyzed in this study enabled, for the first time, an analysis of long and short term subsidence rates of volcanic deposits emplaced by the two eruptive episodes. The generated deformation time series provides insight into the significance and duration of the initial settling period and allows us to study the thermal regime and heat loss of the PFDs. To extract quantitative information about thermal properties and composition of the PFDs, we measured the thickness

Characteristics of the summit lakes of Ambae volcano and their potential for generating lahars

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P. Bani

2009-08-01

Full Text Available Volcanic eruptions through crater lakes often generate lahars, causing loss of life and property. On Ambae volcano, recent eruptive activities have rather tended to reduce the water volume in the crater lake (Lake Voui, in turn, reducing the chances for outburst floods. Lake Voui occupies a central position in the summit caldera and is well enclosed by the caldera relief. Eruptions with significantly higher magnitude than that of 1995 and 2005 are required for an outburst. A more probable scenario for lahar events is the overflow from Lake Manaro Lakua bounded on the eastern side by the caldera wall. Morphology and bathymetry analysis have been used to identify the weakest point of the caldera rim from which water from Lake Manaro Lakua may overflow to initiate lahars. The 1916 disaster described on south-east Ambae was possibly triggered by such an outburst from Lake Manaro Lakua. Taking into account the current level of Lake Manaro Lakua well below a critical overflow point, and the apparently low potential of Lake Voui eruptions to trigger lahars, the Ambae summit lakes may not be directly responsible for numerous lahar deposits identified around the Island.

The grain-size distribution of pyroclasts: Primary fragmentation, conduit sorting or abrasion?

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Kueppers, U.; Schauroth, J.; Taddeucci, J.

2013-12-01

Explosive volcanic eruptions expel a mixture of pyroclasts and lithics. Pyroclasts, fragments of the juvenile magma, record the state of the magma at fragmentation in terms of porosity and crystallinity. The grain size distribution of pyroclasts is generally considered to be a direct consequence of the conditions at magma fragmentation that is mainly driven by gas overpressure in bubbles, high shear rates, contact with external water or a combination of these factors. Stress exerted by any of these processes will lead to brittle fragmentation by overcoming the magma's relaxation timescale. As a consequence, most pyroclasts exhibit angular shapes. Upon magma fragmentation, the gas pyroclast mixture is accelerated upwards and eventually ejected from the vent. The total grain size distribution deposited is a function of fragmentation conditions and transport related sorting. Porous pyroclasts are very susceptible to abrasion by particle-particle or particle-conduit wall interaction. Accordingly, pyroclastic fall deposits with angular clasts should proof a low particle abrasion upon contact to other surfaces. In an attempt to constrain the degree of particle interaction during conduit flow, monomodal batches of washed pyroclasts have been accelerated upwards by rapid decompression and subsequently investigated for their grain size distribution. In our set-up, we used a vertical cylindrical tube without surface roughness as conduit. We varied grain size (0.125-0.25; 0.5-1; 1-2 mm), porosity (0; 10; 30 %), gas-particle ratio (10 and 40%), conduit length (10 and 28 cm) and conduit diameter (2.5 and 6 cm). All ejected particles were collected after settling at the base of a 3.3 m high tank and sieved at one sieve size below starting size (half-Φ). Grain size reduction showed a positive correlation with starting grain size, porosity and overpressure at the vent. Although milling in a volcanic conduit may take place, porous pyroclasts are very likely to be a primary product

Paleomagnetic intensity of Aso pyroclastic flows: Additional results with LTD-DHT Shaw method, Thellier method with pTRM-tail check

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Maruuchi, T.; Shibuya, H.

2009-12-01

For the sake to calibrate the absolute value of the ’relative paleointensity variation curve’ drawn from sediment cores, Takai et al. (2002) proposed to use pyroclastic flows co-bearing with wide spread tephras. The pyroclastic flows prepare volcanic rocks with TRM, which let us determine absolute paleointensity, and the tephras prepare the correlation with sediment stratigraphy. While 4 out of 6 pyroclastic flows are consistent with Sint-800 paleointensity variation curve, two flows, Aso-2 and Aso-4, show weaker and stronger than Sint-800 beyond the error, respectively. We revisited the paleointensity study of Aso pyroclastic flows, adding LTD- DHT Shaw method, the pTRM-tail check in Thellier experiment, and LTD-DHT Shaw method by using volcanic glasses. We prepared 11 specimens from 3 sites of Aso-1 welded tuff for LTD-DHT Shaw method experiments, and obtained 6 paleointensities satisfied a set of strict criteria. They yield an average paleointensity of 21.3±5.8uT, which is smaller than 31.0±3.4uT provided by Takai et al. (2002). For Aso-2 welded tuff, 11 samples from 3 sites were submitted to Thellier experiments, and 6 passed a set of pretty stringent criteria including pTRM-tail check, which is not performed by Takai et al. (2002). They give an average paleointensity of 20.2±1.5uT, which is virtually identical to 20.2±1.0uT (27 samples) given by Takai et al. (2002). Although the success rate was not good in LTD-DHT Shaw method, 2 out of 12 specimens passed the criteria, and gave 25.8±3.4uT, which is consistent with Takai et al. (2002). In addition, we obtained a reliable paleointensity from a volcanic glass in LTD-DHT Shaw method, it gives a paleointensity of 23.6 uT. It is also consitent with Takai et al. (2002). For Aso-3 welded tuff, we performed only LTD-DHT Shaw method for one specimen from one site yet. It gives a paleointensity of 43.0uT, which is higher than 31.8±3.6uT given by Takai et al. (2002). Eight sites were set for Aso-4 welded tuff

The anatomy of a pyroclastic density current: the 10 July 2015 event at Volcán de Colima (Mexico)

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Capra, L.; Sulpizio, R.; Márquez-Ramirez, V. H.; Coviello, V.; Doronzo, D. M.; Arambula-Mendoza, R.; Cruz, S.

2018-04-01

Pyroclastic density currents (PDCs) represent one of the most dangerous phenomena occurring in explosive volcanic eruptions, and any advance in the physical understanding of their transport and sedimentation processes can contribute to improving their hazard assessment. The 10-11 July 2015 eruption at Volcán de Colima provided a unique opportunity to better understand the internal behaviour of PDCs based on seismic monitoring data. On 10 July 2015, the summit dome collapsed, producing concentrated PDCs that filled the main channel of the Montegrande ravine. A lahar monitoring station installed 6 km from the volcano summit recorded a PDC before being completely destroyed. Real-time data acquisition from a camcorder and a geophone that were part of the station, along with field observations and grain-size data of the pyroclastic deposits, are used here to interpret the internal flow structure and time-variant transport dynamics of low-volume, valley-confined concentrated PDCs. The PDC that reached the monitoring station moved at a velocity of 7 m/s and filled a 12-m-deep channel. The outcrops show massive, block-and-ash flow deposits with trains of coarse clasts in the middle and towards the top of the depositional units. The seismic record gathered with the geophone was analysed for the time window when the flow travelled past the sensor. The geophone record was also compared with the recordings of a broadband seismic station located nearby. Two main frequency ranges were recognised which could be correlated with the basal frictional forces exerted by the flow on the channel bed (10-20 Hz) and a collisional regime (20-40 Hz) interpreted to be associated with a clast segregation process (i.e. kinematic squeezing). This latter regime promoted the upward migration of large blocks, which subsequently deviated towards the margin of the flow where they interacted with the sidewall of the main channel. The energy calculated for both seismic components shows that the

Spectral Unmixing Modeling of the Aristarchus Pyroclastic Deposit: Assessing the Eruptive History of Glass-Rich Regional Lunar Pyroclastic Deposits

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Jawin, E. R.; Head, J. W., III; Cannon, K.

2017-12-01

The Aristarchus pyroclastic deposit in central Oceanus Procellarum is understood to have formed in a gas-rich explosive volcanic eruption, and has been observed to contain abundant volcanic glass. However, the interpreted color (and therefore composition) of the glass has been debated. In addition, previous analyses of the pyroclastic deposit have been performed using lower resolution data than are currently available. In this work, a nonlinear spectral unmixing model was applied to Moon Mineralogy Mapper (M3) data of the Aristarchus plateau to investigate the detailed mineralogic and crystalline nature of the Aristarchus pyroclastic deposit by using spectra of laboratory endmembers including a suite of volcanic glasses returned from the Apollo 15 and 17 missions (green, orange, black beads), as well as synthetic lunar glasses (orange, green, red, yellow). Preliminary results of the M3 unmixing model suggest that spectra of the pyroclastic deposit can be modeled by a mixture composed predominantly of a featureless endmember approximating space weathering and a smaller component of glass. The modeled spectra were most accurate with a synthetic orange glass endmember, relative to the other glasses analyzed in this work. The results confirm that there is a detectable component of glass in the Aristarchus pyroclastic deposit which may be similar to the high-Ti orange glass seen in other regional pyroclastic deposits, with only minimal contributions of other crystalline minerals. The presence of volcanic glass in the pyroclastic deposit, with the low abundance of crystalline material, would support the model that the Aristarchus pyroclastic deposit formed in a long-duration, hawaiian-style fire fountain eruption. No significant detection of devitrified black beads in the spectral modeling results (as was observed at the Apollo 17 landing site in the Taurus-Littrow pyroclastic deposit), suggests the optical density of the eruptive plume remained low throughout the

Plant community establishment on the volcanic deposits following the 2006 nuées ardentes (pyroclastic flows of Mount Merapi: diversity and floristic variation

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SUTOMO

2011-04-01

Full Text Available Sutomo, Hobbs R, Cramer V (2011 Plant community establishment on the volcanic deposits following the 2006 nuées ardentes (pyroclastic flows of Mount Merapi: diversity and floristic variation. Biodiversitas 12: 86-91. Species establishment and composition changes in a substrate with little or no biological legacy is known as primary succession, and volcanoes, erosion, landslides, floodplains and glaciers are some type of disturbances that can create this kind of environment. Mount Merapi with its Merapi-type nuées ardentes or pyroclastic flows provides excellent opportunities to study primary succession. Using chronosequence approach, plant establishment and succession was studied, and thus five areas that were affected by nuées ardentes deposits between 1994 and 2006 were chosen as study sites. Results showed that there was a rapid colonization by vascular plants in primary succession as the sites aged. Imperata cylindrica, Eupatorium riparium, Anaphalis javanica, Athyrium macrocarpum, Brachiaria paspaloides, Dichantium caricosum, Selaginella doederleinii, Eleusine indica, Cyperus flavidus, Calliandra callothyrsus and Acacia decurrens were the species mainly responsible in explaining the differences between sites. Furthermore, the species richness and diversity reach their peak 14 years after disturbance.

Alteration, slope-classified alteration, and potential lahar inundation maps of volcanoes for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Volcano Archive

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Mars, John C.; Hubbard, Bernard E.; Pieri, David; Linick, Justin

2015-01-01

This study identifies areas prone to lahars from hydrothermally altered volcanic edifices on a global scale, using visible and near infrared (VNIR) and short wavelength infrared (SWIR) reflectance data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and digital elevation data from the ASTER Global Digital Elevation Model (GDEM) dataset. This is the first study to create a global database of hydrothermally altered volcanoes showing quantitatively compiled alteration maps and potentially affected drainages, as well as drainage-specific maps illustrating modeled lahars and their potential inundation zones. We (1) identified and prioritized 720 volcanoes based on population density surrounding the volcanoes using the Smithsonian Institution Global Volcanism Program database (GVP) and LandScan™ digital population dataset; (2) validated ASTER hydrothermal alteration mapping techniques using Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) and ASTER data for Mount Shasta, California, and Pico de Orizaba (Citlaltépetl), Mexico; (3) mapped and slope-classified hydrothermal alteration using ASTER VNIR-SWIR reflectance data on 100 of the most densely populated volcanoes; (4) delineated drainages using ASTER GDEM data that show potential flow paths of possible lahars for the 100 mapped volcanoes; (5) produced potential alteration-related lahar inundation maps using the LAHARZ GIS code for Iztaccíhuatl, Mexico, and Mount Hood and Mount Shasta in the United States that illustrate areas likely to be affected based on DEM-derived volume estimates of hydrothermally altered rocks and the ~2x uncertainty factor inherent within a statistically-based lahar model; and (6) saved all image and vector data for 3D and 2D display in Google Earth™, ArcGIS® and other graphics display programs. In addition, these data are available from the ASTER Volcano Archive (AVA) for distribution (available at http://ava.jpl.nasa.gov/recent_alteration_zones.php).

Pyroclastic Deposits in the Floor-fractured Crater Alphonsus

Science.gov (United States)

Allen, Carlton C.; Donaldson-Hanna, Kerri L.; Pieters, Carle M.; Moriarty, Daniel P.; Greenhagen, Benjamin T.; Bennett, Kristen A.; Kramer, Georgiana Y.; Paige, David A.

2013-01-01

Alphonsus, the 118 km diameter floor-fractured crater, is located immediately east of Mare Nubium. Eleven pyroclastic deposits have been identified on the crater's floor. Early telescopic spectra suggest that the floor of Alphonsus is noritic, and that the pyroclastic deposits contain mixtures of floor material and a juvenile component including basaltic glass. Head and Wilson contend that Nubium lavas intruded the breccia zone beneath Alphonsus, forming dikes and fractures on the crater floor. In this model, the magma ascended to the level of the mare but cooled underground, and a portion broke thru to the surface in vulcanian (explosive) eruptions. Alternatively, the erupted material could be from a source unrelated to the mare, in the style of regional pyroclastic deposits. High-resolution images and spectroscopy from the Moon Mineralogy Mapper (M3), Diviner Lunar Radiometer, and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (NAC) provide data to test these formation models. Spectra from M3 confirm that the crater floor is primarily composed of noritic material, and that the Nubium lavas are basaltic. Spectra from the three largest pyroclastic deposits in Alphonsus are consistent with a minor low- Ca pyroxene component in a glass-rich matrix. The centers of the 2 micron absorption bands have wavelengths too short to be of the same origin as the Nubium basalts. Diviner Christiansen feature (CF) values were used to estimate FeO abundances for the crater floor, Nubium soil, and pyroclastic deposits. The estimated abundance for the crater floor (7.5 +/- 1.4 wt.%) is within the range of FeO values for Apollo norite samples. However, the estimated FeO abundance for Nubium soil (13.4 +/- 1.4 wt.%) is lower than those measured in most mare samples. The difference may reflect contamination of the mare soil by highland ejecta. The Diviner-derived FeO abundance for the western pyroclastic deposit is 13.8 +/- 3.3 wt.%. This is lower than the values for mare soil

Permeability and microstructural changes due to weathering of pyroclastic rocks in Cappadocia, central Turkey

Science.gov (United States)

Sato, M.; Takahashi, M.; Anma, R.; Shiomi, K.

2014-12-01

Studies of permeability changes of rocks during weathering are important to understand the processes of geomorphological development and how they are influenced by cyclic climatic conditions. Especially volcanic tuffs and pyroclastic flow deposits are easily affected by water absorption and freezing-thawing cycle (Erguler. 2009, Çelik and Ergül 2014). Peculiar erosional landscapes of Cappadocia, central Turkey, with numerous underground cities and carved churches, that made this area a world heritage site, are consists of volcanic tuffs and pyroclastic flow deposits. Understanding permeability changes of such rocks under different conditions are thus important not only to understand fundamental processes of weathering, but also to protect the landscapes of the world heritage sites and archaeological remains. In this study, we aim to evaluate internal void structures and bulk permeability of intact and weathered pyroclastic rocks from Cappadocia using X-ray CT, mercury intrusion porosimetry data and permeability measurement method of flow pump test. Samples of pyroclastic deposits that comprise the landscapes of Rose Valley and Ihlara Valley, were collected from the corresponding strata outside of the preservation areas. Porosity and pore-size distribution for the same samples measured by mercury intrusion porosimetry, indicate that the intact samples have lower porosity than weathered samples and pore sizes were dominantly 1-10μm in calculated radii, whereas weathered samples have more micropores (smaller than 1 μm). X-ray CT images were acquired to observe internal structure of samples. Micro-fractures, probably caused by repeated expansion and contraction due to temperature changes, were observed around clast grains. The higher micropore ratio in weathered samples could be attributed to the development of the micro-farctures. We will discuss fundamental processes of weathering and geomorphological development models using these data.

Characterization of pyroclastic deposits and pre-eruptive soils following the 2008 eruption of Kasatochi Island Volcano, Alaska

Science.gov (United States)

Wang, B.; Michaelson, G.; Ping, C.-L.; Plumlee, G.; Hageman, P.

2010-01-01

The 78 August 2008 eruption of Kasatochi Island volcano blanketed the island in newly generated pyroclastic deposits and deposited ash into the ocean and onto nearby islands. Concentrations of water soluble Fe, Cu, and Zn determined from a 1:20 deionized water leachate of the ash were sufficient to provide short-term fertilization of the surface ocean. The 2008 pyroclastic deposits were thicker in concavities at bases of steeper slopes and thinner on steep slopes and ridge crests. By summer 2009, secondary erosion had exposed the pre-eruption soils along gulley walls and in gully bottoms on the southern and eastern slopes, respectively. Topographic and microtopographic position altered the depositional patterns of the pyroclastic flows and resulted in pre-eruption soils being buried by as little as 1 m of ash. The different erosion patterns gave rise to three surfaces on which future ecosystems will likely develop: largely pre-eruptive soils; fresh pyroclastic deposits influenced by shallowly buried, pre-eruptive soil; and thick (>1 m) pyroclastic deposits. As expected, the chemical composition differed between the pyroclastic deposits and the pre-eruptive soils. Pre-eruptive soils hold stocks of C and N important for establishing biota that are lacking in the fresh pyroclastic deposits. The pyroclastic deposits are a source for P and K but have negligible nutrient holding capacity, making these elements vulnerable to leaching loss. Consequently, the pre-eruption soils may also represent an important long-term P and K source. ?? 2010 Regents of the University of Colorado.

Groundwater drainage from fissures as a source for lahars

Science.gov (United States)

Johnson, P. J.; Valentine, G. A.; Stauffer, P. H.; Lowry, C. S.; Sonder, I.; Pulgarín, B. A.; Santacoloma, C. C.; Agudelo, A.

2018-04-01

One mechanism for generating lahars at volcanoes experiencing unrest is the disruption of internal aquifers. These disruptions can trigger releases of large quantities of groundwater. An example of such aquifer disruption occurred at Nevado del Huila Volcano, Colombia, during February and April 2007 when large fractures formed across the summit area of the volcano and lahars were emitted from them. Previous work interpreted that lahar volumes could not be accounted for by melted glacial snow or precipitation, and by elimination suggested that the primary water source was groundwater. Conceptual models have been developed for perched, confined aquifers that have been heated and pressurized by magma intrusions, followed by sudden pressure release and water emission during fracture formation. We consider an alternative end member wherein water release from large fissures at volcanoes is driven by simple gravity drainage. We apply numerical modeling to quantify water discharge from the porous medium surrounding a fissure with a low-elevation free exit. If a long fracture with high vertical extent (on the order of hundreds of meters) intersects a highly connected saturated porous medium, large volumes (on order 103 m3/m of crack length) of water may be released within tens of minutes. The drainage rates from the model may be adequate to account for the Nevado del Huila events if the medium surrounding the crack contains a large volume of water and has high horizontal permeability. This simple but poorly understood mechanism can present a hazard on its own or compound other processes releasing water from volcanoes.

Database for geologic maps of pyroclastic-flow and related deposits of the 1980 eruptions of Mount St. Helens, Washington

Science.gov (United States)

Furze, Andrew J.; Bard, Joseph A.; Robinson, Joel; Ramsey, David W.; Kuntz, Mel A.; Rowley, Peter D.; MacLeod, Norman S.

2017-10-31

This publication releases digital versions of the geologic maps in U.S. Geological Survey Miscellaneous Investigations Map 1950 (USGS I-1950), “Geologic maps of pyroclastic-flow and related deposits of the 1980 eruptions of Mount St. Helens, Washington” (Kuntz, Rowley, and MacLeod, 1990) (https://pubs.er.usgs.gov/publication/i1950). The 1980 Mount St. Helens eruptions on May 18, May 25, June 12, July 22, August 7, and October 16–18 produced pyroclastic-flow and related deposits. The distribution and morphology of these deposits, as determined from extensive field studies and examination of vertical aerial photographs, are shown on four maps in I-1950 (maps A–D) on two map sheets. Map A shows the May 18, May 25, and June 12 deposits; map B shows the July 22 deposits; map C shows the August 7 deposits; and map D shows the October 16–18 deposits. No digital geospatial versions of the geologic data were made available at the time of publication of the original maps. This data release consists of attributed vector features, data tables, and the cropped and georeferenced scans from which the features were digitized, in order to enable visualization and analysis of these data in GIS software. This data release enables users to digitally re-create the maps and description of map units of USGS I-1950; map sheet 1 includes text sections (Introduction, Physiography of Mount St. Helens at the time of the 1980 eruptions, Processes of the 1980 eruptions, Deposits of the 1980 eruptions, Limitations of the maps, Preparation of the maps, and References cited) and associated tables and figures that are not included in this data release.

Ignimbrites of Armenia - Paleomagnetic constraints on flow direction and stratigraphy of pyroclastic activity of Mount Aragats

Science.gov (United States)

Kirscher, Uwe; Meliksetian, Khachatur; Gevorgyan, Hripsime; Navasardyan, Gevorg; Bachtadse, Valerian

2017-04-01

The Aragats volcano is one of the largest stratovolcanoes within the Turkish-Armenian-Iranian orogenic plateau. It is located close to the Armenian capital Yerevan, and only 30 km from the only nuclear power plant within the country. Additional to numerous lava flows, Mount Aragats is thought to be the source of at least two large pyroclastic eruptions leading to a huge number of ignimbrite outcrops, which are located surrounding Mount Aragats with an evaluated eruption radius of 50 km. The age of several ignimbrite outcrops has recently been determined to be 0.65 Ma (Meliksetian et al., 2014). The different ignimbrite flows are characterized by huge diversity of colors, degree of welding and textures. Due to that reason some disagreement exist on how these outcrops can be linked and how the eruption process actually happened in terms of different eruption phases and mixing mechanism of magmas during the eruption. To add constraints to this debate we carried out an intensive paleomagnetic investigation on most of the ignimbrite outcrops (32 sites) in terms of directional and anisotropy measurements. Paleomagnetic directional measurements yield basically two polarities: (1) a well grouped normal polarity is present in the majority of the studied sites including 3 sites which have supposedly originated from a different vent located on Turkish territory in the west; (2) a reversed polarity of the remaining sites with a somewhat increased scatter. Based on secular variation arguments and considering the high quality of the data we suggest that at least all young outcrops represent a single eruption phase in the area at 0.65 Ma, which is in agreement with an occurrence during the Brunhes geomagnetic chron. Additional to that, at least one earlier phase of pyroclastic activity took place prior to the Brunhes-Matuyama boundary (0.781 Ma). Anisotropy of magnetic susceptibility (AMS) suggests initial radial flow directions, which shortly after the eruption become

Ilmenite-rich pyroclastic deposits - An ideal lunar resource

Science.gov (United States)

Hawke, B. R.; Clark, B.; Coombs, C. R.

1990-01-01

With a view of investigating possible economic benefits that a permanent lunar settlement might provide to the near-earth space infrastructures, consideration was given to the ilmenite-rich pyroclastic deposits as sources of oxygen (for use as a propellant) and He-3 (for nuclear fusion fuel). This paper demonstrates that ilmenite-rich pyroclastic deposits would be excellent sources of a wide variety of valuable elements besides O and He-3, including Fe, Ti, H2, N, C, S, Cu, Zn, Cd, Bi, and Pb. It is shown that several ilmenite-rich pyroclastic deposits of regional extent exist on the lunar surface. The suitability of regional pyroclastic deposits for lunar mining operations, construction activities, and the establishment of permanent lunar settlements is examined.

The volcaniclastic sequence of Aranzazu: Record of the impact of volcanism on Neogene fluvial system in the middle part of the Central Cordillera, Colombia

International Nuclear Information System (INIS)

Borrero Pena, Carlos Alberto; Rosero Cespedes, Juan Sebastian; Valencia M, Julian David; Pardo Trujillo, Andres

2008-01-01

The volcaniclastic sequence of Aranzazu (VSA, late Pliocene - early Pleistocene?) was sourced from the northernmost sector of the Machin - Cerro Bravo volcanic complex. The volcaniclastic accumulations filled the pre-existing fault-bend depressions in the surroundings of Aranzazu town (Caldas department, Colombia). A new classification of volcaniclastic deposits is proposed, in which the lahars are defined as volcaniclastic resedimented deposits, and differentiated from the primary volcaniclastic and epiclastic deposits. The updating the sedimentology and rheology of the deposits related with the laharic events is aimed. The VSA stratigraphy is based on the lithofacies identification and the definition of the architectural elements for syn- and inter-eruptive periods. The VSA lower member corresponds to the successive aggradation of syneruptive lahars (SV and SB elements) resulted from re-sedimentation of pumice-rich pyroclastic deposits and transported as debris and hyperconcentrated stream/flood flows. The VSA middle and upper members defined by coal contents were formed during the dominion of inter-eruptive (FF element) over the syn-eruptive (SV and SB elements) periods. They were formed during the reestablishment of the fluvial condition after the syn-eruptive laharic activity. Once the fluvial deposition was strengthened, the necessary conditions for the peat formation were propitious and the coal-bearing bed sets were developed.

High and highly variable cooling rates during pyroclastic eruptions on Axial Seamount, Juan de Fuca Ridge

Science.gov (United States)

Helo, Christoph; Clague, David A.; Dingwell, Donald B.; Stix, John

2013-03-01

We present a calorimetric analysis of pyroclastic glasses and glassy sheet lava flow crusts collected on Axial Seamount, Juan de Fuca Ridge, NE Pacific Ocean, at a water depth of about 1400 m. The pyroclastic glasses, subdivided into thin limu o Pele fragments and angular, blocky clasts, were retrieved from various stratigraphic horizons of volcaniclastic deposits on the upper flanks of the volcanic edifice. Each analysed pyroclastic sample consists of a single type of fragment from one individual horizon. The heat capacity (cp) was measured via differential scanning calorimetry (DSC) and analysed using relaxation geospeedometry to obtain the natural cooling rate across the glass transition. The limu o Pele samples (1 mm grain size fraction) and angular fragments (0.5 mm grain size fraction) exhibit cooling rates of 104.3 to 106.0 K s- 1 and 103.9 to 105.1 K s- 1, respectively. A coarser grain size fraction, 2 mm for limu o Pele and 1 mm for the angular clasts yields cooling rates at the order of 103.7 K s- 1. The range of cooling rates determined for the different pyroclastic deposits presumably relates to the size or intensity of the individual eruptions. The outer glassy crusts of the sheet lava flows were naturally quenched at rates between 63 K s- 1 and 103 K s- 1. By comparing our results with published data on the very slow quenching of lava flow crusts, we suggest that (1) fragmentation and cooling appear to be coupled dynamically and (2) ductile deformation upon the onset of cooling is restricted due to the rapid increase in viscosity. Lastly, we suggest that thermally buoyant plumes that may arise from rapid heat transfer efficiently separate clasts based on their capability to rise within the plume and as they subsequently settle from it.

First Volcanological-Probabilistic Pyroclastic Density Current and Fallout Hazard Map for Campi Flegrei and Somma Vesuvius Volcanoes.

Science.gov (United States)

Mastrolorenzo, G.; Pappalardo, L.; Troise, C.; Panizza, A.; de Natale, G.

2005-05-01

Integrated volcanological-probabilistic approaches has been used in order to simulate pyroclastic density currents and fallout and produce hazard maps for Campi Flegrei and Somma Vesuvius areas. On the basis of the analyses of all types of pyroclastic flows, surges, secondary pyroclastic density currents and fallout events occurred in the volcanological history of the two volcanic areas and the evaluation of probability for each type of events, matrixs of input parameters for a numerical simulation have been performed. The multi-dimensional input matrixs include the main controlling parameters of the pyroclasts transport and deposition dispersion, as well as the set of possible eruptive vents used in the simulation program. Probabilistic hazard maps provide of each points of campanian area, the yearly probability to be interested by a given event with a given intensity and resulting demage. Probability of a few events in one thousand years are typical of most areas around the volcanoes whitin a range of ca 10 km, including Neaples. Results provide constrains for the emergency plans in Neapolitan area.

Comparative lahar hazard mapping at Volcan Citlaltépetl, Mexico using SRTM, ASTER and DTED-1 digital topographic data

Science.gov (United States)

Hubbard, Bernard E.; Sheridan, Michael F.; Carrasco-Nunez, Gerardo; Diaz-Castellon, Rodolfo; Rodriguez, Sergio R.

2007-01-01

In this study, we evaluated and compared the utility of spaceborne SRTM and ASTER DEMs with baseline DTED-1 “bald-earth” topography for mapping lahar inundation hazards from volcan Citlaltépetl, Mexico, a volcano which has had a history of producing debris flows of various extents. In particular, we tested the utility of these topographic datasets for resolving ancient valley-filling deposits exposed around the flanks of the volcano, for determining their magnitude using paleohydrologic methods and for forecasting their inundation limits in the future. We also use the three datasets as inputs to a GIS stream inundation flow model, LAHARZ, and compare the results.

The Osceola Mudflow from Mount Rainier: Sedimentology and hazard implications of a huge clay-rich debris flow

Science.gov (United States)

Vallance, J.W.; Scott, K.M.

1997-01-01

The 3.8 km3 Osceola Mudflow began as a water-saturated avalanche during phreatomagmatic eruptions at the summit of Mount Rainier about 5600 years ago. It filled valleys of the White River system north and northeast of Mount Rainier to depths of more than 100 m, flowed northward and westward more than 120 km, covered more than 200 km2 of the Puget Sound lowland, and extended into Puget Sound. The lahar had a velocity of ???19 m/s and peak discharge of ???2.5 ?? 106 m3/s, 40 to 50 km downstream, and was hydraulically dammed behind a constriction. It was coeval with the Paradise lahar, which flowed down the south side of Mount Rainier, and was probably related to it genetically. Osceola Mudflow deposits comprise three facies. The axial facies forms normally graded deposits 1.5 to 25 m thick in lowlands and valley bottoms and thinner ungraded deposits in lowlands; the valley-side facies forms ungraded deposits 0.3 to 2 m thick that drape valley slopes; and the hummocky facies, interpreted before as a separate (Greenwater) lahar, forms 2-10-m-thick deposits dotted with numerous hummocks up to 20 m high and 60 m in plan. Deposits show progressive downstream improvement in sorting, increase in sand and gravel, and decrease in clay. These downstream progressions are caused by incorporation (bulking) of better sorted gravel and sand. Normally graded axial deposits show similar trends from top to bottom because of bulking. The coarse-grained basal deposits in valley bottoms are similar to deposits near inundation limits. Normal grading in deposits is best explained by incremental aggradation of a flow wave, coarser grained at its front than at its tail. The Osceola Mudflow transformed completely from debris avalanche to clay-rich (cohesive) lahar within 2 km of its source because of the presence within the preavalanche mass of large volumes of pore water and abundant weak hydrothermally altered rock. A survey of cohesive lahars suggests that the amount of hydrothermally

Magmas in motion: Degassing in volcanic conduits and fabrics of pyroclastic density current

Science.gov (United States)

Burgisser, Alain

Volcanoes are caused by the transport of magma batches from the Earth's crust to the surface. These magmas in motion undergo drastic changes of rheologic properties during their journey to the surface and this work explores how these changes affect volcanic eruptions. The first part of this study is devoted to the dynamic aspects of degassing and permeability in magmas with high pressure, high temperature experiments on natural volcanic rocks. Degassing is measured by the influence of decompression rate on the growth of the bubbles present in the magma while permeability is deduced from the temporal evolution of these bubbles. The parameterization of our results in a numerical model of volcanic conduit flow show that previous models based on equilibrium degassing overestimate the acceleration and the decompression rate of the magma. Assessing permeability effects derived form our results show that the transition between explosive and effusive eruptions is a strong function of the magma initial ascent rate. The second part of this work is a unification of two end-members of pyroclastic currents (highly concentrated pyroclastic flows and dilute, turbulent pyroclastic surges) using theoretical scaling arguments based on multiphase physics. Starting from the dynamics of the particle interactions with a fundamental eddy, we consider the full spectrum of eddies generated within a turbulent current. We demonstrate that the presence of particles with various sizes induces a density stratification of the current, leading to its segregation into a basal concentrated part overlain by a dilute cloud. To verify our predictions on the interactions of such a segregated pyroclastic current with its surroundings (hills and sea), we studied the products of the 2050 BP caldera-forming eruption of Okmok Volcano (Alaska). This field study allowed us to reconstruct the eruptive sequence and to validate the main aspects of our theoretical model, such as the superposition of a dense and

Boiling-over dense pyroclastic density currents during the formation of the 100 km3 Huichapan ignimbrite in Central Mexico: Stratigraphic and lithofacies analysis

Science.gov (United States)

Pacheco-Hoyos, Jaime G.; Aguirre-Díaz, Gerardo J.; Dávila-Harris, Pablo

2018-01-01

A lithofacies analysis of the Huichapan ignimbrite has been undertaken to evaluate its depositional history from large pyroclastic density currents. The Huichapan ignimbrite is a massive ignimbrite sheet with a maximum runout of at least 55 km and thickness variations between 6 and 80 m. The lower portion of the Huichapan ignimbrite consists of a large plateau [ 100 km3; 69 km3 as dense-rock equivalent (DRE)] of massive ignimbrites with welding variations from densely welded to partly welded, devitrification, and high-temperature vapor-phase alteration. The lower part grades laterally to moderately welded and non-devitrified ignimbrites. These variations are interpreted as the sedimentation of density-stratified pyroclastic density currents erupted as boiling-over pulses from the Huichapan-Donguinyó caldera complex at a continuous rate, supporting deposition by quasi-steady progressive aggradation of sustained and hot currents. To the north of the caldera, the lower portion of the ignimbrite consists of a small plateau (< 10 km3) in which the densely welded and devitrified lithofacies are absent. Our interpretation is that the pyroclastic density currents flowed late to the north of the caldera and formed a smaller ignimbrite plateau with respect to the western one. This northern ignimbrite plateau cooled faster than the western ignimbrite plateau. Deposition-induced topographic modifications suggest that topographic obstacles, such as remnants of older volcanoes, may have promoted the deviation of the density currents to the north. The upper portion of the ignimbrite is composed of extensive, massive, coarse clast-rich, non-devitrified, and non-welded ignimbrites with abundant fines-poor pipes. This upper part was deposited from largely sustained and rapidly aggrading high-concentration currents in a near end-member, fluid escape-dominated flow boundary zone. The absence of welding in the upper portion may record pyroclastic density currents cooling during the

Compositional analyses of small lunar pyroclastic deposits using Clementine multispectral data

Science.gov (United States)

Gaddis, L.R.; Hawke, B.R.; Robinson, M.S.; Coombs, C.

2000-01-01

Clementine ultraviolet-visible (UVVIS) data are used to examine the compositions of 18 pyroclastic deposits (15 small, three large) at 13 sites on the Moon. Compositional variations among pyroclastic deposits largely result from differing amounts of new basaltic (or juvenile) material and reworked local material entrained in their ejecta upon eruption. Characterization of pyroclastic deposit compositions allows us to understand the mechanisms of lunar explosive volcanism. Evidence for compositional differences between small pyroclastic deposits at a single site is observed at Atlas crater. At all sites, compositional variation among the small pyroclastic deposits is consistent with earlier classification based on Earth-based spectra: three compositional groups can be observed, and the trend of increasing mafic absorption band strength from Group 1 to Group 2 to Group 3 is noted. As redefined here, Group 1 deposits include those of Alphonsus West, Alphonsus Southeast, Alphonsus Northeast 2, Atlas South, Crüger, Franklin, Grimaldi, Lavoisier, Oppenheimer, Orientale, and Riccioli. Group 1 deposits resemble lunar highlands, with weak mafic bands and relatively high UV/VIS ratios. Group 2 deposits include those of Alphonsus Northeast 1, Atlas North, Eastern Frigoris East and West, and Aristarchus Plateau; Group 2 deposits are similar to mature lunar maria, with moderate mafic band depths and intermediate UV/VIS ratios. The single Group 3 deposit, J. Herschel, has a relatively strong mafic band and a low UV/VIS ratio, and olivine is a likely juvenile component. Two of the deposits in these groups, Orientale and Aristarchus, are large pyroclastic deposits. The third large pyroclastic deposit, Apollo 17/Taurus Littrow, has a very weak mafic band and a high UV/VIS ratio and it does not belong to any of the compositional groups for small pyroclastic deposits. The observed compositional variations indicate that highland and mare materials are also present in many large and

Does exposure to lahars risk affect people's risk-preferences and other attitudes? Field data from incentivized experiments and surveys in Arequipa - Peru

Science.gov (United States)

Heitz, C.; Bchir, M. A.; Willinger, M.

2012-04-01

Many individuals are exposed to risks which are either difficult to insure or hard to mitigate, such as tsunamis, floods, volcanic eruption,... Little is known about how exposure to such risks shapes individuals' risk-preferences. Are they more (less) risk-averse than people who are unexposed to such hazard risk? We provide empirical evidence about this question for the case of individuals exposed to lahars risk. Lahars are sediments laden flows from volcanic origin. We compare the risk-attitude of people exposed - versus non-exposed ones - to lahars risk. The originality of our approach is that we combine standard survey data to behavioural data collected by means of incentivized experiments. We collected data in various locations of the city of Arequipa (Peru), a densely populated area down the volcano El Misti. Participants in our experiment were identified as (non-)exposed to lahars risk based on risk zoning. Our survey questionnaire allows us to compare assessed exposure and the perceived exposure. We elicit risk-preference, time-preference, and trusting behaviour (a measure of social capital) for each respondent in addition to standard survey data. Our field experiment involved a total of 209 respondents from exposed and non-exposed areas. While respondents endow legitimacy in risk reduction (more than 74%) to a national authority (Defensa Civil) in charge of the management of risk in the city, more than 64% of them consider that they are not sufficiently informed about the behaviours to adopt in case of a disaster. Respondents are therefore poorly motivated to adopt initiatives of self-protection (23%) and express instead high expectations with respect to authorities' actions for decreasing their vulnerability (73%). The experimental data show that participants who live in exposed areas are not significantly more risk-averse than those living in non-exposed ones. Furthermore, there is no significant difference in time-preference between exposed and non

Bedform reconstruction using Terrestrial Laser Scanning at Hunt's Hole, New Mexico: implications for sediment transport in pyroclastic surge deposits and criteria for their identification on Mars

Science.gov (United States)

Edgar, L.; Grotzinger, J. P.; Ewing, R. C.; Southard, J. B.; Lamb, M. P.

2011-12-01

Pyroclastic surges are dilute flows of gas and rock fragments, typically generated by the interaction of magma and water. Due to their hazardous nature, very little is known about sediment transport during these eruptions. However, the cross-stratified deposits that they leave behind provide an important record of flow conditions, if properly interpreted. In the absence of geologic context (and volcanic indicators such as bombs and lapilli), it may be difficult to distinguish bedforms in pyroclastic surge deposits from those in eolian or fluvial deposits. There has been some debate about the identification of pyroclastic surge deposits on Mars, suggesting a need to establish better criteria for recognizing these deposits in remote sensing applications. The goals of this study are to use physical characteristics to better understand bedform kinematics and gain insight into the flow dynamics of pyroclastic surges, and to establish criteria to distinguish pyroclastic surges from other depositional environments on Mars. Two examples of pyroclastic surge deposits are exposed in Hunt's Hole (HH) and Kilbourne Hole in southern NM. These volcanic craters expose up to 13 m of stratigraphy, dominated by dm-to-m-scale bedforms. The geomorphic pattern around the rim of HH provides 3D exposures at the scale of the bedforms, which enables observations of bedform geometries. We identify several facies, and measure bedform characteristics in the cross-stratified facies. Bedforms range in height from 25-80 cm, and wavelength from 190-460 cm. Stoss slope angles range from 4-11°, and lee slope from 2-18°. Geometries indicate possible bedform merging, as smaller bedforms overtake others to build larger features. Bedform interactions have been described in modern eolian systems, typically in plan-view, but these surge deposits may provide an opportunity to observe them in outcrop in cross-section. We propose that bedforms in pyroclastic surges can be identified by a unique style of

Hazard Map of the Poás Volcano

Directory of Open Access Journals (Sweden)

Gustavo Barrantes Castillo

2015-07-01

Full Text Available The Poás volcano presents a series of hazards to the lives and activities of the communities in its surroundings; these hazards include ash fall, volcanic gases, ballistic projection, pyroclastic flows, lahars and lava flows. In the study described in this article, risks were zoned and integrated to form combined hazard maps for later use in territorial planning processes. With respect to methodology, the study was based on a heuristic approximation, which was supported with cartographic, geomorphological, and historical impact criteria to achieve a suitable product in terms of scale and ease of interpretation. These maps present greater detail and integration than other works and cartographies of volcanic hazards in Costa Rica.

Formation of obsidian pyroclasts by sintering of ash particles in the volcanic conduit

Science.gov (United States)

Gardner, James E.; Llewellin, Edward W.; Watkins, James M.; Befus, Kenneth S.

2017-02-01

The ranges in intensity and style of volcanic eruptions, from highly explosive Plinian eruptions to quiescent lava extrusions, depend on the style and efficiency of gas loss from ascending magma. Obsidian pyroclasts - small, glassy pieces of quenched magma found in some volcanic tephra beds - may preserve valuable information about magma degassing in their vesicle textures and volatile contents. Accurate interpretation of their textures and volatiles, however, requires understanding the mechanism of formation of the pyroclasts. Obsidian pyroclasts from the ca. 1325-1350 C.E. North Mono eruption of Mono Craters (CA, USA) were analyzed and found to have H2O and CO2 contents indicating that they were formed at pressures in the approximate range of 3-40 MPa. Many also contain domains with differing vesicle textures, separated by boundaries containing xenocrystic material, indicating that they are composed of smaller fragments that have sutured together. More than half of the pyroclasts analyzed contained small (∼10 μm), highly distorted vesicles, with multi-cuspate morphology, interpreted as the remnants of interstitial gas trapped amongst sintered fragments of melt/glass. Rounded vesicles are also common and are interpreted to result from surface tension-driven relaxation of the distorted vesicles. Calculated timescales of sintering and relaxation are consistent with timescales for pyroclast formation indicated by H2O re-equilibration within the heterogeneous pyroclasts. This sintering model for the origin of obsidian pyroclasts is further supported by the observation that spherical vesicles are found mainly in H2O-rich pyroclasts, and distorted vesicles mainly in H2O-poor pyroclasts. We conclude that obsidian pyroclasts generated during the North Mono eruption were formed by cycles of fragmentation, sintering/suturing, and relaxation, over a very wide range of depths within the conduit; we find no evidence to support pumice (foam) collapse as the formation

Dynamic Statistical Models for Pyroclastic Density Current Generation at Soufrière Hills Volcano

Science.gov (United States)

Wolpert, Robert L.; Spiller, Elaine T.; Calder, Eliza S.

2018-05-01

To mitigate volcanic hazards from pyroclastic density currents, volcanologists generate hazard maps that provide long-term forecasts of areas of potential impact. Several recent efforts in the field develop new statistical methods for application of flow models to generate fully probabilistic hazard maps that both account for, and quantify, uncertainty. However a limitation to the use of most statistical hazard models, and a key source of uncertainty within them, is the time-averaged nature of the datasets by which the volcanic activity is statistically characterized. Where the level, or directionality, of volcanic activity frequently changes, e.g. during protracted eruptive episodes, or at volcanoes that are classified as persistently active, it is not appropriate to make short term forecasts based on longer time-averaged metrics of the activity. Thus, here we build, fit and explore dynamic statistical models for the generation of pyroclastic density current from Soufrière Hills Volcano (SHV) on Montserrat including their respective collapse direction and flow volumes based on 1996-2008 flow datasets. The development of this approach allows for short-term behavioral changes to be taken into account in probabilistic volcanic hazard assessments. We show that collapses from the SHV lava dome follow a clear pattern, and that a series of smaller flows in a given direction often culminate in a larger collapse and thereafter directionality of the flows change. Such models enable short term forecasting (weeks to months) that can reflect evolving conditions such as dome and crater morphology changes and non-stationary eruptive behavior such as extrusion rate variations. For example, the probability of inundation of the Belham Valley in the first 180 days of a forecast period is about twice as high for lava domes facing Northwest toward that valley as it is for domes pointing East toward the Tar River Valley. As rich multi-parametric volcano monitoring dataset become

Characterizing the Morphology, Distribution, and Formation Geometry of Mercury's Pyroclastic Vents

Science.gov (United States)

Jozwiak, L. M.; Head, J. W.; Wilson, L.

2018-05-01

We present a final catalog of pyroclastic vents on Mercury, identifying 104 candidate pyroclastic vents. We then assess the vent distribution, morphologic variation, and probable formation geometries.

Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

Science.gov (United States)

Thouret, J.-C.; Enjolras, G.; Martelli, K.; Santoni, O.; Luque, J. A.; Nagata, M.; Arguedas, A.; Macedo, L.

2013-02-01

Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows), and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season) ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials. In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water) in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access to vital resources. Our

Rapid mapping using low-cost structure-from-motion photogrammetry expedites the lahar modeling process

Science.gov (United States)

Ratner, Jacqueline; Pyle, David; Mather, Tamsin

2014-05-01

Structure-from-motion (SfM) is a branch of photogrammetry that triangulates points in digital photos to produce a 3D model. When applied to topographical modeling, SfM presents a powerful tool for rapid terrain mapping. At little to no cost and on a timescale of hours, a metric-resolution digital terrain model (DTM) can be produced; the resultant DTM can be used for many types of hazard scenario modeling and is here applied to lahars and floods. This study demonstrates the robustness of the SfM method through two case studies. First, an SfM DTM of Boscastle, UK, is compared against LiDAR and SRTM DTMs in a flood simulation model. Resolution is found to be more robust than for satellite based DTMs, and though less precise than the most detailed LiDAR survey, still perfectly adequate for the purposes of modeling flows. Next, the same method is applied to a region of Ecuador lacking the regionally comprehensive LiDAR survey available in the UK. Compared against the only other topographical data available, (SRTM, ASTER, 1956 topographical map), the SfM DTM is shown to have a higher resolution and is a preferable alternative for modeling lahars. The advantages of this study for emergency management are to provide a cheap and rapid metric-resolution alternative to low resolution or costly topography data sets. In regions such as Ecuador where scientific resources are scarce, SfM assists in providing a thorough, but otherwise unattainable, understanding of potential disaster scenarios that is accessible to local authorities to be used in the disaster prevention and mitigation processes.

Pyroclastic Eruption Boosts Organic Carbon Fluxes Into Patagonian Fjords

Science.gov (United States)

Mohr, Christian H.; Korup, Oliver; Ulloa, Héctor; Iroumé, Andrés.

2017-11-01

Fjords and old-growth forests store large amounts of organic carbon. Yet the role of episodic disturbances, particularly volcanic eruptions, in mobilizing organic carbon in fjord landscapes covered by temperate rainforests remains poorly quantified. To this end, we estimated how much wood and soils were flushed to nearby fjords following the 2008 eruption of Chaitén volcano in south-central Chile, where pyroclastic sediments covered >12 km2 of pristine temperate rainforest. Field-based surveys of forest biomass, soil organic content, and dead wood transport reveal that the reworking of pyroclastic sediments delivered 66,500 + 14,600/-14,500 tC of large wood to two rivers entering the nearby Patagonian fjords in less than a decade. A similar volume of wood remains in dead tree stands and buried beneath pyroclastic deposits ( 79,900 + 21,100/-16,900 tC) or stored in active river channels (5,900-10,600 tC). We estimate that bank erosion mobilized 132,300+21,700/-30,600 tC of floodplain forest soil. Eroded and reworked forest soils have been accreting on coastal river deltas at >5 mm yr-1 since the eruption. While much of the large wood is transported out of the fjord by long-shore drift, the finer fraction from eroded forest soils is likely to be buried in the fjords. We conclude that the organic carbon fluxes boosted by rivers adjusting to high pyroclastic sediment loads may remain elevated for up to a decade and that Patagonian temperate rainforests disturbed by excessive loads of pyroclastic debris can be episodic short-lived carbon sources.

Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

Directory of Open Access Journals (Sweden)

J.-C. Thouret

2013-02-01

Full Text Available Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows, and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials.

In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access

Stratigraphy and AMS radiocarbon dates of cored sediments (IrBH-2) from the Irosin caldera, the Philippines

International Nuclear Information System (INIS)

Mirabueno, Ma. Hannah T.; Laguerta, Eduardo P.; Delos Reyes, Perla J.; Bariso, Ericson B.; Torii, Masayuki; Fujiki, Toshiyuki; Okuno, Mitsuru; Nakamura, Toshio; Danhara, Tohru; Saito-Kokubu, Yoko; Kobayashi, Tetsuo

2014-01-01

Core drilling at Site IrBH-2 within the Irosin caldera in Sorsogon Province, southern Luzon reached a depth of 50 m. Systematic logging and documentation were carried out to describe and interpret the sediments. The accelerator mass spectrometer (AMS) radiocarbon dates obtained from plant fragments at 7.02-10.40-m depth were 1000 to 1800 BP. Lahars and fluvial deposits were the predominant deposits in the core sequence. The upper 12 m consisted mostly of andesitic fluvial and minor lahar deposits. These deposits may be correlated with the reworking of eruptive products from resurgent andesitic volcanism. One pyroclastic flow and 12 fallout deposits, including five possible fallout deposits, were intercalated with reworked sediments at depths of 12-50 m. The refractive index of representative samples indicated that post-caldera eruptions involved mainly andesite to dacite, with minor rhyolite magmas. The rhyolite fallout in the core had similar petrographic characteristics to the 41 cal kBP Irosin ignimbrite, suggesting that the fallout and the ignimbrite were sourced from the same magma. (author)

Chronology and pyroclastic stratigraphy of the May 18, 1980, eruption of Mount St. Helens, Washington

Science.gov (United States)

Criswell, C. William

1987-01-01

The eruption of Mount St. Helens on May 18, 1980 can be subdivided into six phases: the paroxysmal phase I, the early Plinian phase II, the early ash flow phase III, the climactic phase IV, the late ash flow phase V, and phase VI, the activity of which consisted of a low-energy ash plume. These phases are correlated with stratigraphic subunits of ash-fall tephra and pyroclastic flow deposits. Sustained vertical discharge of phase II produced evolved dacite with high S/Cl ratios. Ash flow activity of phase III is attributed to decreases in gas content, indicated by reduced S/Cl ratios and increased clast density of the less evolved gray pumice. Climactic events are attributed to vent clearing and exhaustion of the evolved dacite.

Pleistocene cohesive debris flows at Nevado de Toluca Volcano, central Mexico

Science.gov (United States)

Capra, L.; Macías, J. L.

2000-10-01

During the Pleistocene, intense hydrothermal alteration promoted a flank failure of the southern portion of Nevado de Toluca volcano. This event produced a debris avalanche that transformed into a cohesive debris flow (Pilcaya deposit) owing to water saturation and weakness of the altered pre-avalanche rocks. The Pilcaya debris flow traveled along a narrow tectonic depression up to a distance of 40 km and then spread over a flat plain reaching up to 55 km from the volcano summit. This transition zone corresponds with a sudden break in slope from 5 to 0.5° that caused a rapid reduction in velocity and thickening of the flow that consequently reduced its competence to transport large particles. The resulting deposit thickens from 15 to 40 m, and contains boulders up to 15 m in diameter that form hummocky morphology close to the transitional zone. Sometime after the emplacement of the Pilcaya debris flow, heavy rains and superficial drainage contributed to remobilize the upper portions of the deposit causing two secondary lahars. These debris flows called El Mogote, traveled up to 75 km from the volcano. The edifice collapse generated lahars with a total volume of 2.8 km3 that devastated an approximate area of 250 km2. The area versus volume plot for both deposits shows that the magnitude of the event is comparable to other cohesive debris flows such as the Teteltzingo lahar (Pico de Orizaba, Mexico) and the Osceola mudflow (Mount Rainier, Wa). The Pilcaya debris flow represents additional evidence of debris flow transformed from a flank failure, a potentially devastating phenomenon that could threaten distant areas from the volcano previously considered without risk.

Topography and Volcanology of the Huangtsuishan Volcano Subgroup, Northern Taiwan

Directory of Open Access Journals (Sweden)

Yu-Ming Lai

2010-01-01

Full Text Available Combining the shaded relief topography model and the slope map from the Digital Terrain Model (DTM images, toporaphical map, field occurrences and petrography, the volcanic sequences of the Huangtsuishan Volcano Subgroup (HVS can be constructed. Two types of volcanic centers can be identified in this area. One is the Tachienhou volcanic dome, which may be located in the center of an older caldera. The other is the Huangtsui composite volcano, which is composed of interbedding lava flows and pyroclastic deposits with a volcanic crater named the Huangtsui pond at the summit. Eight lava plateaus radiated from Mts. Huangtsui and Tachienhou to the north and the east can be distinguished based on the DTM images. The volcanic deposits are comprised of four lithofacies, the lava flows, pyroclastic breccias, tuffs and lahars on the base of field occurrences. At least thirteen layers of lava flow, named the H1 to H13 can be recognized in the HVS and can be reconstructed and categorized into four stages. An old and large volcano erupted lava flows to form the products of stages one and two, then collapsed to form a caldera with a dome for the third stage. The latest stage of lava flow was poured out from the Huangtsui volcano, which formed a crater at the summit.

Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records

Science.gov (United States)

Portner, Ryan A.; Clague, David A.; Helo, Christoph; Dreyer, Brian M.; Paduan, Jennifer B.

2015-08-01

A comprehensive understanding of explosive basaltic eruption processes in the deep-sea relies upon detailed analysis and comparison of the variety of volcaniclastic lithologies on the seafloor, which has been challenged by insufficient sample recovery. A dedicated ROV-based sampling approach using long push cores offers an unparalleled opportunity to fully characterize the diversity of unconsolidated volcaniclastic lithofacies on a recently active seamount. Lithofacies from Axial Seamount record two styles of pyroclastic eruptions, strombolian and phreatomagmatic, at 1.5 km water depth. Strombolian eruptions are represented by abundant fluidal and highly vesicular (up to 50%) vitriclasts within limu o Pele lapilli tuff and tuffaceous mud lithofacies. Lapilli-ash grain size, normal grading, good sorting, rip-up clasts and homogeneous glass geochemistry characterize individual limu o Pele lapilli tuff beds, and imply proximal deposition from a turbidity flow associated with a single eruption (i.e. event bed). Limu o Pele lapilli tuff beds are interbedded with poorly sorted, chemically heterogeneous and bioturbated tuffaceous mud units that preserve reworking and biologic habitation of more distal pyroclastic fallout and dilute turbidity flows. The phreatomagmatic eruption style is preserved by hydrothermal mineral-bearing muddy tuff that exhibits characteristics distinct from lapilli ash and tuffaceous mud lithofacies. Hydrothermal muddy tuff lithofacies are well-sorted and fine-grained with notable components of non-fluidal basaltic ash (∼45%), fluidal ash (∼30%) and accessory lithics (∼25%). Heterogeneous geochemistry of ash shards implies that juvenile components are minimal. The abundance, mineralogy and texture of lithic components (Fe-Mg clays, pyrite, epidote, actinolite, altered glass, basalt/diabase, hydrothermal breccia and agglutinate), and very fine-grain size of basaltic ash, are consistent with phreatomagmatic eruption deposits. A lack of

Volcanic hazard map for Telica, Cerro Negro and El Hoyo volcanoes, Nicaragua

Science.gov (United States)

Asahina, T.; Navarro, M.; Strauch, W.

2007-05-01

A volcano hazard study was conducted for Telica, Cerro Negro and El Hoyo volcanoes, Nicaragua, based on geological and volcanological field investigations, air photo analyses, and numerical eruption simulation. These volcanoes are among the most active volcanoes of the country. This study was realized 2004-2006 through technical cooperation of Japan International Cooperation Agency (JICA) with INETER, upon the request of the Government of Nicaragua. The resulting volcanic hazard map on 1:50,000 scale displays the hazards of lava flow, pyroclastic flows, lahars, tephra fall, volcanic bombs for an area of 1,300 square kilometers. The map and corresponding GIS coverage was handed out to Central, Departmental and Municipal authorities for their use and is included in a National GIS on Georisks developed and maintained by INETER.

Nové poznatky o vulkanickém stylu děčínského souvrství, získané dokumentací příležitostných odkryvů při stavbě dálnice D8 u Radejčína

Czech Academy of Sciences Publication Activity Database

Rapprich, V.; Cajz, Vladimír; Kycl, P.; Suchý, J.; Radoň, M.

2010-01-01

Roč. 2009, - (2010), s. 39-42 ISSN 0514-8057 Institutional research plan: CEZ:AV0Z30130516 Keywords : volcanology * eruptiove style * pyroclastic deposit * lahar * Děčín Formation * České středohoří Volcanic Complex Subject RIV: DB - Geology ; Mineralogy http://www.geology.cz/zpravy/obsah/2009/2009-11.pdf

Earth Girl Volcano: An Interactive Casual Game about Complex Volcanic Hazards

Science.gov (United States)

Kerlow, I.

2017-12-01

Earth Girl Volcano is an interactive casual strategy game for disaster preparedness. The project is designed for mainstream audiences, particularly for children, as an engaging and fun way to learn about volcano hazards, monitoring, and mitigation strategies. The game is deceptively simple but it provides a toolbox to address practically all volcanic hazards ranging from gas and ash fall to pyroclastic flows, lava and lahars. This presentation shows the basic dynamic to explore the area, assess the risk, choose the best-suited tools and execute a mitigation strategy within the available budget. This game is a real-time simulation of a crowd evacuation that allows players to intervene before and during the disaster.

Spectro-Morphologic Analysis of Pyroclastic Deposits on Mercury

Science.gov (United States)

Doressoundiram, A.; Besse, S.; Hersérant, W.

2014-12-01

Observations of the MESSENGER spacecraft in orbit around Mercury have shown that volcanism is a very important process that has shaped the surface of the planet. Kerber et al. [2011,2014] have identified 200 pyroclastic deposits candidates based on color ratio and morphology images. Goudge et al. [2014] used the visible portion of the MASCS spectrometer to do further analysis on the spectral nature of the deposits. The authors have shown that the deposits have specific UV properties probably caused by Oxygen-Metal charges transfer, and a correlation between the slope of the UV-downturn and the age of the surrounding terrains. In this study, we use the full range of the MASCS spectrometer (300-1400nm) to characterize the spectral properties of the pyroclastic deposits. Moreover, additional observations have been obtained since the last publications, and this allows specific studies of previously non-imaged deposits. This study shows that the visible slope of the deposits is changing as a function of distance from the vent, as seen on the Moon for pyroclastic deposits and their mafic absorption bands [Besse et al, 2013]. This is consistent with a decrease of thickness of the deposits that are mixed with background material. Surprisingly, the UV-downturn parameter proposed by Goudge et al. [2014] does not change as the distance to the vent increase. Eventually, the near infrared portion does not appear to have absorption bands in the range 900nm-1200nm, consistent with the very low iron abundance of the surface of Mercury. This could also be due to the lower signal to noise ratio of the near infrared portion of the MASCS instrument, and further analysis are needed to confirm these results. The use of visible images from the MDIS camera has revealed that some of the pyroclastic deposits candidates are certainly correlated with hollows.

A "simulation chain" to define a Multidisciplinary Decision Support System for landslide risk management in pyroclastic soils

Science.gov (United States)

Damiano, E.; Mercogliano, P.; Netti, N.; Olivares, L.

2012-04-01

This paper proposes a Multidisciplinary Decision Support System (MDSS) as an approach to manage rainfall-induced shallow landslides of the flow type (flowslides) in pyroclastic deposits. We stress the need to combine information from the fields of meteorology, geology, hydrology, geotechnics and economics to support the agencies engaged in land monitoring and management. The MDSS consists of a "simulation chain" to link rainfall to effects in terms of infiltration, slope stability and vulnerability. This "simulation chain" was developed at the Euro-Mediterranean Centre for Climate Change (CMCC) (meteorological aspects), at the Geotechnical Laboratory of the Second University of Naples (hydrological and geotechnical aspects) and at the Department of Economics of the University of Naples "Federico II" (economic aspects). The results obtained from the application of this simulation chain in the Cervinara area during eleven years of research allowed in-depth analysis of the mechanisms underlying a flowslide in pyroclastic soil.

Characterization of previously unidentified lunar pyroclastic deposits using Lunar Reconnaissance Orbiter Camera (LROC) data

Science.gov (United States)

Gustafson, J. Olaf; Bell, James F.; Gaddis, Lisa R.R.; Hawke, B. Ray Ray; Giguere, Thomas A.

2012-01-01

We used a Lunar Reconnaissance Orbiter Camera (LROC) global monochrome Wide-angle Camera (WAC) mosaic to conduct a survey of the Moon to search for previously unidentified pyroclastic deposits. Promising locations were examined in detail using LROC multispectral WAC mosaics, high-resolution LROC Narrow Angle Camera (NAC) images, and Clementine multispectral (ultraviolet-visible or UVVIS) data. Out of 47 potential deposits chosen for closer examination, 12 were selected as probable newly identified pyroclastic deposits. Potential pyroclastic deposits were generally found in settings similar to previously identified deposits, including areas within or near mare deposits adjacent to highlands, within floor-fractured craters, and along fissures in mare deposits. However, a significant new finding is the discovery of localized pyroclastic deposits within floor-fractured craters Anderson E and F on the lunar farside, isolated from other known similar deposits. Our search confirms that most major regional and localized low-albedo pyroclastic deposits have been identified on the Moon down to ~100 m/pix resolution, and that additional newly identified deposits are likely to be either isolated small deposits or additional portions of discontinuous, patchy deposits.

A "simulation chain" to define a Multidisciplinary Decision Support System for landslide risk management in pyroclastic soils

Directory of Open Access Journals (Sweden)

E. Damiano

2012-04-01

Full Text Available This paper proposes a Multidisciplinary Decision Support System (MDSS as an approach to manage rainfall-induced shallow landslides of the flow type (flowslides in pyroclastic deposits. We stress the need to combine information from the fields of meteorology, geology, hydrology, geotechnics and economics to support the agencies engaged in land monitoring and management. The MDSS consists of a "simulation chain" to link rainfall to effects in terms of infiltration, slope stability and vulnerability. This "simulation chain" was developed at the Euro-Mediterranean Centre for Climate Change (CMCC (meteorological aspects, at the Geotechnical Laboratory of the Second University of Naples (hydrological and geotechnical aspects and at the Department of Economics of the University of Naples "Federico II" (economic aspects. The results obtained from the application of this simulation chain in the Cervinara area during eleven years of research allowed in-depth analysis of the mechanisms underlying a flowslide in pyroclastic soil.

Petrogenesis and depositional history of felsic pyroclastic rocks from the Melka Wakena archaeological site-complex in South central Ethiopia

Science.gov (United States)

Resom, Angesom; Asrat, Asfawossen; Gossa, Tegenu; Hovers, Erella

2018-06-01

The Melka Wakena archaeological site-complex is located at the eastern rift margin of the central sector of the Main Ethiopian Rift (MER), in south central Ethiopia. This wide, gently sloping rift shoulder, locally called the "Gadeb plain" is underlain by a succession of primary pyroclastic deposits and intercalated fluvial sediments as well as reworked volcaniclastic rocks, the top part of which is exposed by the Wabe River in the Melka Wakena area. Recent archaeological survey and excavations at this site revealed important paleoanthropological records. An integrated stratigraphic, petrological, and major and trace element geochemical study has been conducted to constrain the petrogenesis of the primary pyroclastic deposits and the depositional history of the sequence. The results revealed that the Melka Wakena pyroclastic deposits are a suite of mildly alkaline, rhyolitic pantellerites (ash falls, pumiceous ash falls and ignimbrites) and slightly dacitic ash flows. These rocks were deposited by episodic volcanic eruptions during early to middle Pleistocene from large calderas along the Wonji Fault Belt (WFB) in the central sector of the MER and from large silicic volcanic centers at the eastern rift shoulder. The rhyolitic ash falls, pumiceous ash falls and ignimbrites have been generated by fractional crystallization of a differentiating basaltic magma while the petrogenesis of the slightly dacitic ash flows involved some crustal contamination and assimilation during fractionation. Contemporaneous fluvial activities in the geomorphologically active Gadeb plain deposited overbank sedimentary sequences (archaeology bearing conglomerates and sands) along meandering river courses while a dense network of channels and streams have subsequently down-cut through the older volcanic and sedimentary sequences, redepositing the reworked volcaniclastic sediments further downstream.

Sustained Water Quality Impacts in Marine Environments Due to Mechanical Milling of Volcanic Deposits

Science.gov (United States)

Genareau, K. D.; Cronin, S. J.; Stewart, C.; Back, E.

2015-12-01

Explosive volcanic eruptions are known to be a significant geohazard, but post- or inter-eruptive processes (such as lahars, landslides, and debris avalanches) can be equally damaging to local and regional areas by remobilizing deposits. Numerous studies have found that soluble salts bound to ash grain surfaces may be quickly released into exposed waters, often lowering pH and adding trace metals with both beneficial and deleterious effects on marine flora and fauna (e.g., Fe influx initiating blooms of marine phytoplankton). Most of the cation content of pyroclastic deposits is released slowly into the environment through weathering and alteration processes. However, other pathways exist through the physical comminution of pyroclasts in fluvial and marine settings. In this case, mechanical fracturing of pyroclasts during progressive stages of disaggregation will lead to exposure of reactive particle surfaces. This study evaluates the potential, ongoing effects on water quality by experimental, mechanical milling of pyroclasts and the evaluation of released metals into exposed waters using the pyroclastic density current deposits of both the 2010 eruption of Merapi and the 2014 eruption of Kelud (Java, Indonesia), which have a bulk basaltic andesite/andesite composition (60-65 wt% SiO2). The electrical conductivity (EC) of water samples positively correlates with Ca and Sr concentrations in the case of bulk ash, whole, and crushed lapilli, but correlates with Na for the milled samples. Compared to other stages of pyroclast disaggregation, milled lapilli have the greatest effect on the concentration of alkali elements and produce a significant increase in Ca, Na, K, and Si. Mechanical milling of pyroclasts grinds down minerals and glass, resulting in an increased EC, pH, and Na concentration of exposed waters. Similar experiments are currently being conducted using basalt (50 wt% SiO2) and rhyolite (70 wt% SiO2) deposits, and these results will be presented

Three-Dimensional Grain Shape-Fabric from Unconsolidated Pyroclastic Density Current Deposits: Implications for Extracting Flow Direction and Insights on Rheology

Science.gov (United States)

Hawkins, T. T.; Brand, B. D.; Sarrochi, D.; Pollock, N.

2016-12-01

One of the greatest challenges volcanologists face is the ability to extrapolate information about eruption dynamics and emplacement conditions from deposits. Pyroclastic density current (PDC) deposits are particularly challenging given the wide range of initial current conditions, (e.g., granular, fluidized, concentrated, dilute), and rapid flow transformations due to interaction with evolving topography. Analysis of particle shape-fabric can be used to determine flow direction, and may help to understand the rheological characteristics of the flows. However, extracting shape-fabric information from outcrop (2D) apparent fabric is limited, especially when outcrop exposure is incomplete or lacks context. To better understand and quantify the complex flow dynamics reflected in PDC deposits, we study the complete shape-fabric data in 3D using oriented samples. In the field, the prospective sample is carved from the unconsolidated deposit in blocks, the dimensions of which depend on the average clast size in the sample. The sample is saturated in situ with a water-based sodium silicate solution, then wrapped in plaster-soaked gauze to form a protective cast. The orientation of the sample is recorded on the block faces. The samples dry for five days and are then extracted in intact blocks. In the lab, the sample is vacuum impregnated with sodium silicate and cured in an oven. The fully lithified sample is first cut along the plan view to identify orientations of the long axes of the grains (flow direction), and then cut in the two plains perpendicular to grain elongation. 3D fabric analysis is performed using high resolution images of the cut-faces using computer assisted image analysis software devoted to shape-fabric analysis. Here we present the results of samples taken from the 18 May 1980 PDC deposit facies, including massive, diffuse-stratified and cross-stratified lapilli tuff. We show a relationship between the strength of iso-orientation of the elongated

Lahar—River of volcanic mud and debris

Science.gov (United States)

Major, Jon J.; Pierson, Thomas C.; Vallance, James W.

2018-05-09

Lahar, an Indonesian word for volcanic mudflow, is a mixture of water, mud, and volcanic rock flowing swiftly along a channel draining a volcano. Lahars can form during or after eruptions, or even during periods of inactivity. They are among the greatest threats volcanoes pose to people and property. Lahars can occur with little to no warning, and may travel great distances at high speeds, destroying or burying everything in their paths.Lahars form in many ways. They commonly occur when eruptions melt snow and ice on snow-clad volcanoes; when rains fall on steep slopes covered with fresh volcanic ash; when crater lakes, volcano glaciers or lakes dammed by volcanic debris suddenly release water; and when volcanic landslides evolve into flowing debris. Lahars are especially likely to occur at erupting or recently active volcanoes.Because lahars are so hazardous, U.S. Geological Survey scientists pay them close attention. They study lahar deposits and limits of inundation, model flow behavior, develop lahar-hazard maps, and work with community leaders and governmental authorities to help them understand and minimize the risks of devastating lahars.

Stratigraphic And Lithofacies Study Of Distal Rain-Triggered Lahars: The Case Of West Coast Of Ecuador

Science.gov (United States)

Mulas, M.; Chunga, K.; Peña Carpio, E.; Falquez Torres, D. A.; Alcivar, R., Sr.; Lopez Coronel, M. C.

2015-12-01

The central zone of the coast of Ecuador at the north of Manabí Province, on the area comprised between Salango and Jama communities, is characterized by the presence of whitish to grey, centimeters to meters thick, consolidated to loose distal ash deposits. Recent archeological studies on Valdivia (3500 BC) and Manteña (800-1500 AC - Harris et al. 2004) civilizations remains link this deposits with the intense eruptive phases that afflicted Ecuador 700-900 years ago (Usselman, 2006). Stratigraphic evidences and bibliographic datations of paleosols (Estrada, 1962; Mothes and Hall, 2008), allowed to estimate that these deposits are linked with the 800 BP eruption of Quilotoa and the following eruptions of Cotopaxi. According to the Smith and Lowe classification (1991), the deposits outcropping on the coast (located at a distance greater than 160 km from the volcanic vents), varied from whitish to grey, loose to weakly consolidated, massive to weakly stratified, centimeters to meters thick, coarse to fine ash matrix layers (diluite streamflow facies) to massive, large angular to sub-rounded siltitic blocks-rich and coarse to medium ash matrix deposits (debris flow facies). These types of lithofacies are associated to a rain-triggered lahar (De Belizal et al., 2013). The presence in some stratigraphic sections of sharp contacts, laminated layers of very fine ash, and also cm-thick sand and silt layers between the ash beds of the same deposits permit to understand that the different pulses were generated in short periods and after a long period. Structures like water pipes imply that the lahar went into the sea (Schneider, 2004), and allow the reconstruction of the paleotopographic condition during the emplacement of these deposits. This study focuses on the characterization of these types of deposits, permit to understand the kind of risk that may affect the towns located on the coast of Ecuador after VEI 4 to 6 eruptions on short time and within years.

Effects of volcanic deposit disaggregation on exposed water composition

Science.gov (United States)

Back, W. E.; Genareau, K. D.

2016-12-01

Explosive volcanic eruptions produce a variety of hazards. Pyroclastic material can be introduced to water through ash fallout, pyroclastic flows entering water bodies, and/or lahars. Remobilization of tephras can occur soon after eruption or centuries later, introducing additional pyroclastic material into the environment. Introduction of pyroclastic material may alter the dissolved element concentration and pH of exposed waters, potentially impacting drinking water supplies, agriculture, and ecology. This study focuses on the long-term impacts of volcanic deposits on water composition due to the mechanical breakup of volcanic deposits over time. Preliminary work has shown that mechanical milling of volcanic deposits will cause significant increases in dissolved element concentrations, conductivity, and pH of aqueous solutions. Pyroclastic material from seven eruptions sites was collected, mechanically milled to produce grain sizes Soufriere Hills, Ruapehu), mafic (Lathrop Wells) and ultramafic (mantle xenoliths) volcanic deposits. Lathrop Wells has an average bulk concentration of 49.15 wt.% SiO2, 6.11 wt. % MgO, and 8.39 wt. % CaO and produces leachate concentrations of 85.69 mg/kg for Ca and 37.22 mg/kg for Mg. Taupo and Valles Caldera samples have a bulk concentration of 72.9 wt.% SiO2, 0.59 wt. % MgO, and 1.48 wt. % CaO, and produces leachate concentrations of 4.08 mg/kg for Ca and 1.56 mg/kg for Mg. Similar testing will be conducted on the intermediate and ultramafic samples to test the hypothesis that bulk magma composition and mineralogy will directly relate to the increased dissolved element concentration of exposed waters. The measured effects on aqueous solutions will aid in evaluation of impacts to marine and freshwater systems exposed to volcanic deposits.

Analysis on the Capacity Building Efforts for Mitigating Volcanic Risks during 2010 Eruption of Mount Merapi, Central Java, Indonesia

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SARI BAHAGIARTI KUSUMAYUDHA

2012-12-01

Full Text Available Mount Merapi is one of the most active volcanoes on the World erupted again during October to November 2010. Its climax activities happened on 5th November at 00.10 pm, with different type of eruption from Mount Merapi of last 50 years. Ordinary, Mount Merapi activity starts from lava dome development, followed by dome collapse to create pyroclastic flow. This specific character of eruption is called Merapi type. The pyroclastic flows at that time killed 341 people and buried many villages on the southeastern slope, while the secondary hazard of lahar destroyed many other human settlements and infrastructures on the western slope of the volcano. Actually, capacity building program in the areas of around Mount Merapi has been established since more than 15 years ago. In most villages, there are community associations that well trained on volcanic hazard mitigation and early warning system. The association name is Association of Mountains Belt of Merapi. Map of Mount Merapi hazards was also already set by the Center of Volcanology and Geologic Disaster Mitigation. Unfortunately, human are not able to order the nature. The character of Mount Merapi eruption in the year 2010 was inconsistent. There was much higher gas pressure, much longer distant of pyroclastic flow, and much greater volume of volcanic material poured from the crater. This made people and stake holders very astonished in handling the evacuation. However, a socio-cultural factor in this respect is that the local people and agriculturists view Mount Merapi as a God which gives them fertile soil and water for agriculture and are reluctant to move away even under an impending threat of a volcanic hazard. This mind-set of people is a challenge in capacity building as the people prefer in-situ protective measures rather than moving away.

PYFLOW_2.0: a computer program for calculating flow properties and impact parameters of past dilute pyroclastic density currents based on field data

Science.gov (United States)

Dioguardi, Fabio; Mele, Daniela

2018-03-01

This paper presents PYFLOW_2.0, a hazard tool for the calculation of the impact parameters of dilute pyroclastic density currents (DPDCs). DPDCs represent the dilute turbulent type of gravity flows that occur during explosive volcanic eruptions; their hazard is the result of their mobility and the capability to laterally impact buildings and infrastructures and to transport variable amounts of volcanic ash along the path. Starting from data coming from the analysis of deposits formed by DPDCs, PYFLOW_2.0 calculates the flow properties (e.g., velocity, bulk density, thickness) and impact parameters (dynamic pressure, deposition time) at the location of the sampled outcrop. Given the inherent uncertainties related to sampling, laboratory analyses, and modeling assumptions, the program provides ranges of variations and probability density functions of the impact parameters rather than single specific values; from these functions, the user can interrogate the program to obtain the value of the computed impact parameter at any specified exceedance probability. In this paper, the sedimentological models implemented in PYFLOW_2.0 are presented, program functionalities are briefly introduced, and two application examples are discussed so as to show the capabilities of the software in quantifying the impact of the analyzed DPDCs in terms of dynamic pressure, volcanic ash concentration, and residence time in the atmosphere. The software and user's manual are made available as a downloadable electronic supplement.

Estimating the Wet-Rock P-Wave Velocity from the Dry-Rock P-Wave Velocity for Pyroclastic Rocks

Science.gov (United States)

Kahraman, Sair; Fener, Mustafa; Kilic, Cumhur Ozcan

2017-07-01

Seismic methods are widely used for the geotechnical investigations in volcanic areas or for the determination of the engineering properties of pyroclastic rocks in laboratory. Therefore, developing a relation between the wet- and dry-rock P-wave velocities will be helpful for engineers when evaluating the formation characteristics of pyroclastic rocks. To investigate the predictability of the wet-rock P-wave velocity from the dry-rock P-wave velocity for pyroclastic rocks P-wave velocity measurements were conducted on 27 different pyroclastic rocks. In addition, dry-rock S-wave velocity measurements were conducted. The test results were modeled using Gassmann's and Wood's theories and it was seen that estimates for saturated P-wave velocity from the theories fit well measured data. For samples having values of less and greater than 20%, practical equations were derived for reliably estimating wet-rock P-wave velocity as function of dry-rock P-wave velocity.

Investigation on the water retention curve of loose pyroclastic ashes of Campania (Italy) and its potential implications on slope stability

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Comegna, Luca; Damiano, Emilia; Greco, Roberto; Olivares, Lucio; Piccolo, Marco; Picarelli, Luciano

2017-04-01

Loose pyroclastic soils in Campania cover a large amount of steep slopes in the area surrounding the volcanic complex of Somma-Vesuvius. The stability of such slopes is assured by the contribution of suction to soil shear strength, which decreases during rainy periods till the possible attainment of a failure condition. The resulting landslide may evolve in form of a fast flow, if at the onset of instability the soil is nearly saturated and undrained conditions establish, so that soil liquefaction arises. The attainment of instability near saturation is not uncommon, as it requires the slope to have an inclination close to the friction angle of the soil constituting the deposit. The pyroclastic ashes of Campania are typically silty sands with friction angle between 36° and 38°, and small or even null cohesion. Many of the flow-like landslides, occurred during the last decades, were indeed triggered along slopes with inclination around 40°, which are quite common in Campania. As a suction of few kPa may be enough to guarantee the stability of a slope, knowledge of the water retention curve of the soil constituting the deposit is mandatory to correctly predict soil conditions at failure. Several studies report that the pyroclastic ashes of Campania exhibit a quite complex water retention behavior, showing a bimodal porosity distribution and, in some cases, a marked hysteresis domain, possibly enhanced by air entrapment during the infiltration of steep wetting fronts. In this study, a series of vertical infiltration and evaporation cycles have been carried out over two reconstituted specimens, both 20cm high, of pyroclastic ashes collected at the slope of Cervinara. TDR probes and minitensiometers were buried at various depths to provide coupled measurements of soil water content and suction. In order to highlight the possible hysteretic effects due to air entrapment, different hydraulic boundary conditions were established at the base of the two specimens: in one

Sedimentology, Behavior, and Hazards of Debris Flows at Mount Rainier, Washington

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Scott, K.M.; Vallance, J.W.; Pringle, P.T.

1995-01-01

middle segments of flow waves that begin and end as flood surges. Proximally, through the bulking of poorly sorted volcaniclastic debris on the flanks of the volcano, flow waves expand rapidly in volume by transforming from water surges through hyperconcentrated stream flow (20 to 60 percent sediment by volume) to debris flow. Distally, the transformations occur more slowly in reverse order - from debris flow, to hyperconcentrated flow, and finally to normal streamflow with less than 20 percent sediment by volume. During runout of the largest noncohesive flows, hyperconcentrated flow has continued for as much as 40 to 70 kilometers. Lahars (volcanic debris flows and their deposits) have occurred frequently at Mount Rainier over the past several thousand years, and generally they have not clustered within discrete eruptive periods as at Mount St. Helens. An exception is a period of large noncohesive flows during and after construction of the modern summit cone. Deposits from lahar-runout flows, the hyperconcentrated distal phases of lahars, document the frequency and extent of noncohesive lahars. These deposits also record the following transformations of debris flows: (1) the direct, progressive dilution of debris flow to hyperconcentrated flow, (2) deposition of successively finer grained lobes of debris until only the hyperconcentrated tail of the flow remains to continue downstream, and (3) dewatering of coarse debris flow deposits to yield fine-grained debris flow or hyperconcentrated flow. Three planning or design case histories represent different lengths of postglacial time. Case I is representative of large, infrequent (500 to 1,000 years on average) cohesive debris flows. These flows need to be considered in long-term planning in valleys around the volcano. Case II generalizes the noncohesive debris flows of intermediate size and recurrence (100 to 500 years). This case is appropriate for consideration in some structural design. Case III flows are

Experimental Determination of Bed Conditions in Concentrated Pyroclastic Density Currents

Science.gov (United States)

Winner, A.; Ferrier, K.; Dufek, J.

2016-12-01

Pyroclastic density currents (PDCs) are ground-hugging mixtures of hot gas and rock that can reach temperatures > 800 oC and speeds of 200 m/s. These flows are capable of eroding and entraining the underlying bed material into the flow, which can strongly influence flow momentum, runout distance, and hazards associated with PDCs. However, the mechanism of erosion remains poorly constrained, with proposed mechanisms including under-pressure following the head of the fluidized current, force chain enhanced stresses at the bed, and discrete particle impacts and friction. The interactions between PDCs and the bed have been difficult to observe in the field, as their infrequent occurrence, opacity, and hostile environment make real-time measurement difficult. This study is aimed at obtaining a better understanding of the interactions between PDCs and the bed through a quantitative analysis of bed forces. Our experimental apparatus consists of a rotating cylindrical flume of radius 22 cm, within which gas-rich granular material flows along the interior of the cylinder as it rotates. By using a rotating cylinder, we are able to simulate long-duration flows, allowing us to observe impact forces at the bed over timescales comparable to the flow duration of natural PDCs. To measure the distribution and evolution of forces imparted by the flow on the bed, we constructed a cylindrical insert with a non-erodible bed in which we embedded force sensor arrays parallel and perpendicular to the direction of flow. To measure the forces felt by the particles in the flow, we added "smart particles" 25 to 50 mm in diameter to the flow. Each smart particle contains a three-axis accelerometer and a micro SD card enclosed in a spherical plastic casing, and possesses a density similar to that of the pumice in the experimental flow. Each smart particle also contains a three-axis magnetometer which permits its location to be tracked by means of a unique applied magnetic field. Ultimately

Effects of slope on the formation of dunes in dilute, turbulent pyroclastic currents: May 18th, 1980 Mt. St. Helens eruption

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Bendana, Sylvana; Brand, Brittany D.; Self, Stephen

2014-05-01

The flanks of Mt St Helens volcano (MSH) are draped with thin, cross-stratified and stratified pyroclastic density current (PDC) deposits. These are known as the proximal bedded deposits produced during the May 18th, 1980 eruption of MSH. While the concentrated portions of the afternoon PDCs followed deep topographic drainages down the steep flanks of the volcano, the dilute overriding cloud partially decoupled to develop fully dilute, turbulent PDCs on the flanks of the volcano (Beeson, D.L. 1988. Proximal Flank Facies of the May 18, 1980 Ignimbrite: Mt. St. Helens, Washington.). The deposits along the flank thus vary greatly from those found in the pumice plain, which are generally thick, massive, poorly-sorted, block-rich deposits associated with the more concentrated portions of the flow (Brand et al, accepted. Dynamics of pyroclastic density currents: Conditions that promote substrate erosion and self-channelization - Mount St Helens, Washington (USA). JVGR). We explore the influence of topography on the formation of these dilute currents and influence of slope on the currents transport and depositional mechanisms. The deposits on steeper slopes (>15°) are fines depleted relative to the proximal bedded deposits on shallower slopes (<15°). Bedform amplitude and wavelength increase with increasing slope, as does the occurrence of regressive dunes. Increasing slope causes an increase in flow velocity and thus an increase in flow turbulence. The fines depleted deposits suggest that fine ash elutriation is more efficient in flows with stronger turbulence. The longer wavelength and amplitudes suggest that bedform morphology is directly related to flow velocity, an important finding since the controls on bedform wavelength and amplitude in density stratified flows remains poorly constrained. The occurrence of regressive dunes, often interpreted as high flow-regime bedforms, on steeper slopes relative to progressive dunes on shallower slopes further attests to the

Pyroclastic rocks: another manifestation of ultramafic volcanism on Gorgona Island, Colombia

Science.gov (United States)

Echeverría, Lina M.; Aitken, Bruce G.

1986-04-01

Tertiary ultramafic volcanism on Gorgona Island, Colombia, is manifested not only by komatiite flows, but also by a more voluminous sequence of tuff breccias, which is cut by comagmatic picrite dikes. The ultramafic pyroclastic rocks are chaotic to stratified mixtures of angular to subrounded glassy picritic blocks and a fine grained volcaniclastic matrix that consists primarily of plastically-deformed, glassy globules. The entire deposit is interpreted to have formed by an explosive submarine eruption of phenocryst-laden picritic magma. MgO contents of tuff breccias and picrite dikes range from 21 to 27 wt%. Relative to nearby komatiite flows, these rocks are MgO-rich, and FeO-, TiO2- and Ni-poor. HREE concentrations are very low (flows. Nevertheless Pb isotopic data as well as whole rock geochemistry preclude such a connection, either due to olivine fractionation/accumulation or to different degrees of partial melting. These ultramafic rock types crystallized from magmas which most likely were extracted from distinct mantle source regions.

Técnicas de información geográfica aplicadas al estudio del origen de los lahares y su experimentación en estratovolcanes tropicales

OpenAIRE

Andrés de Pablo, Nuria

2011-01-01

El objetivo de esta investigación se centra en el seguimiento de los factores que controlan el inicio de los lahares, mediante el empleo de técnicas de información geográfica asequibles, y en la aplicación práctica de los métodos elegidos a casos concretos. Los objetivos específicos se proponen en función de las características de cada uno de los procesos que intervienen en la generación de los lahares, que, a su vez, están condicionados por las áreas de experimentación elegidas. Entre la var...

Lahar inundated, modified, and preserved 1.88 Ma early hominin (OH24 and OH56) Olduvai DK site.

Science.gov (United States)

Stanistreet, I G; Stollhofen, H; Njau, J K; Farrugia, P; Pante, M C; Masao, F T; Albert, R M; Bamford, M K

2018-03-01

Archaeological excavations at the DK site in the eastern Olduvai Basin, Tanzania, age-bracketed between ∼1.88 Ma (Bed I Basalt) and ∼1.85 Ma (Tuff IB), record the oldest lahar inundation, modification, and preservation of a hominin "occupation" site yet identified. Our landscape approach reconstructs environments and processes at high resolution to explain the distribution and final preservation of archaeological materials at the DK site, where an early hominin (likely Homo habilis) assemblage of stone tools and bones, found close to hominin specimens OH24 and OH56, developed on an uneven heterogeneous surface that was rapidly inundated by a lahar and buried to a depth of 0.4-1.2 m (originally ∼1.0-2.4 m pre-compaction). The incoming intermediate to high viscosity mudflow selectively modified the original accumulation of "occupation debris," so that it is no longer confined to the original surface. A dispersive debris "halo" was identified within the lahar deposit: debris is densest immediately above the site, but tails off until not present >150 m laterally. Voorhies indices and metrics derived from limb bones are used to define this dispersive halo spatially and might indicate a possible second assemblage to the east that is now eroded away. Based upon our new data and prior descriptions, two possibilities for the OH24 skull are suggested: it was either entrained by the mudflow from the DK surface and floated due to lower density toward its top, or it was deposited upon the solid top surface after its consolidation. Matrix adhering to material found in association with the parietals indicates that OH56 at least was relocated by the mudflow. Copyright © 2017 Elsevier Ltd. All rights reserved.

Obsidian Pyroclasts: Where Do They Come From and What Can They Tell Us?

Science.gov (United States)

Watkins, J. M.; Gardner, J. E.; Befus, K.

2016-12-01

Models for how volcanic gases behave during volcanic eruptions are constructed from measurements of volatiles (δD, H2O and CO2) in melt that has been quenched to glass. Volatile measurements on obsidian pyroclasts from Mono Craters, California, have been central to the development of open- versus closed-system and equilibrium versus non-equilibrium degassing models, and these models have been applied to the interpretation of volatile data from volcanic centers worldwide. Even for the well-studied Mono Craters system, however, there are several different degassing models that are compatible with existing data, and the origin of the vesicle-poor obsidian pyroclasts (upon which the degassing models have been built) remains ambiguous. To better establish the link between the volatiles in the pyroclasts and volcanic eruption processes, we combine textural analysis with area maps of CO2 and H2O. We show that obsidian pyroclasts are heterogeneous with respect to dissolved CO2 and H2O, and that many clasts have multiple textural and chemical domains that are sutured together. The observations suggest that clasts are assembled from non-equilibrated juvenile melt and ash during repeated melt fracturing and healing, ash sintering, and shearing along conduit margins. Melt fracturing promotes gas extraction from magma, whereas healing promotes gas resorption and glass densification. Some of the clasts have bands or patches of elevated CO2 associated with cuspate vesicles, which are evidence for CO2-rich vapor fluxing through the magmatic system. Collectively, the data support a model of open-system, non-equilibrium degassing with intermittent regassing caused by increases in pressure and exposure to different vapor compositions.

Volcanic Processes and Geology of Augustine Volcano, Alaska

Science.gov (United States)

Waitt, Richard B.; Beget, James E.

2009-01-01

recently in A.D. 1883. The decapitated summit after the 1883 eruption, replaced by andesite domes of six eruptions since, shows a general process: collapse of steep summit domes, then the summit regrown by later dome eruptions. The island's stratigraphy is based on six or seven coarse-pumice tephra 'marker beds'. In upward succession they are layers G (2,100 yr B.P.), I (1,700 yr B.P.), H (1,400 yr B.P.), C (1,200-1,000 yr B.P.), M (750 yr B.P.), and B (390 yr B.P.). A coarse, hummocky debris-avalanche deposit older than about 2,100 yr B.P. - or perhaps a stack of three of them - lies along the east coast, the oldest exposed such bouldery diamicts on Augustine Island. Two large debris avalanches swept east and southeast into the sea between about 2,100 and 1,800 yr B.P. A large debris avalanche shed east and east-northeast into the sea between 1,700 and 14,00 yr B.P. Between about 1,400 and 1,100 yr B.P. debris avalanches swept into the sea on the volcano's south, southwest, and north-northwest. Pumiceous pyroclastic fans spread to the southeast and southwest, lithic pyroclastic flows and lahars (?) to the south and southeast. Pyroclastic flows, pyroclastic surges, and lahars swept down the west and south flanks between about 1,000 and 750 yr B.P. A debris avalanche swept into the sea on the west, and a small one on the south-southeast, between about 750 and 400 yr B.P. Large lithic pyroclastic flows shed to the southeast; smaller ones descended existing swales on the southwest and south. Between about 400 yr B.P. and historical time (late 1770s), three debris avalanches swept into the sea on the west-northwest, north-northwest, and north flanks. One of them (West Island) was large and fast: most of it rode to sea far beyond a former sea cliff, and its surface includes geomorphic evidence of having initiating a tsunami. Augustine's only conspicuous lava flow erupted on the north flank. During this prehistoric period numerous domes grew at th

Flow-permeability feedbacks and the development of segregation pipes in volcanic materials

Science.gov (United States)

Rust, Alison

2014-05-01

Flow and transformation in volcanic porous media is important for the segregation of melts and aqueous fluids from magmas as well as elutriation of fine ash from pyroclastic flows and vents. The general topic will be discussed in the framework of understanding sets of vertical pipes found in two very different types of volcanic deposits: 1) vesicular (bubbly) cylinders in basalt lava flows and 2) gas escape pipes in pyroclastic flow deposits. In both cases the cylinders can be explained by a flow-permeability feedback where perturbations in porosity and thus permeability cause locally higher flow speeds that in turn locally increase the permeability. For vesicular cylinders in lava flows, the porous medium is a framework of crystals within the magma. Above a critical crystallinity, which depends on the shape and size distribution of the crystals, the crystals form a touching framework. As the water-saturated magma continues to cool, it crystallizes anhydrous minerals, resulting in the exsolution of water vapour bubbles that can drive flow of bubbly melt through the crystal network. It is common to find sets of vertical cylinders of bubby melt in solidified lava flows, with compositions that match the residual melt from 35-50% crystallization of the host basalt. These cylinders resemble chimneys in experiments of crystallising ammonium chloride solution that are explained by reactive flow with porous medium convection. The Rayleigh number for the magmatic case is too low for convection but the growth of steam bubbles as the magma crystallizes induces pore fluid flow up through the permeable crystal pile even if there is no convective instability. This bubble-growth-driven upward flow is reactive and can lead to channelization because of a feedback between velocity and permeability. For the gas escape pipes in pyroclastic flows, the porous medium is a very poorly sorted granular material composed of fragments of solid magma with a huge range of grain sizes from ash

Volcanic Hazards Associated with the NE Sector of Tacaná Volcano, Guatemala.

Science.gov (United States)

Hughes, S. R.; Saucedo, R.; Macias, J.; Arce, J.; Garcia-Palomo, A.; Mora, J.; Scolamacchia, T.

2003-12-01

Tacaná volcano, with a height of 4,030 m above sea level, straddles the southern Mexico/Guatemala border. Last active in 1986, when there was a small phreatic event with a duration of a few days, this volcano presents an impending hazard to over 250,000 people. The NE sector of the volcano reveals the violent volcanic history of Tacaná that may be indicative of a serious potential risk to the area. Its earliest pyroclastic history appears to consist of fall, flow, and surge deposits, together with lavas, that have formed megablocks within a series of old debris avalanche deposits. This sector collapse event is overlain by a sequence of pumice fall and ash flow deposits, of which the youngest, less-altered pumice fall deposit shows a minimum thickness of > 4 m, with a dispersal axis trending toward the NE. A second debris avalanche deposit, separated from the above deposits by a paleosoil, is dominated by megablocks of lava and scoriaceous dome material. The current topography around the northeastern flank of the volcano is determined by a third, and most recent debris avalanche deposit, a thick (> 20 m) sequence of six block and ash flows dated at around 16,000 years BP, each separated by 1-10 cm thick ash cloud surge deposit, together with secondary lahar deposits. These are followed by a at least 4 lava flows that extend 2 km down the flank of the volcano. It appears that the most recent pyroclastic event at Tacaná is also recorded in this sector of the volcano: above the block and ash flows occurs a > 1 m thick ash flow unit that can be seen at least 5 km from the vent. Lastly, the Santa Maria Ash fall deposit, produced in 1902, has capped most of the deposits at Tacaná.

Preparing for Volcanic Hazards: An Examination of Lahar Knowledge, Risk Perception, and Preparedness around Mount Baker and Glacier Peak, WA

Science.gov (United States)

Corwin, K.; Brand, B. D.

2015-12-01

As the number of people living at risk from volcanic hazards in the U.S. Pacific Northwest continues to rise, so does the need for improved hazard science, mitigation, and response planning. The effectiveness of these efforts relies not only on scientists and policymakers, but on individuals and their risk perception and preparedness levels. This study examines the individual knowledge, perception, and preparedness of over 500 survey respondents living or working within the lahar zones of Mount Baker and Glacier Peak volcanoes. We (1) explore the common disconnect between accurate risk perception and adequate preparedness; (2) determine how participation in hazard response planning influences knowledge, risk perception, and preparedness; and (3) assess the effectiveness of current lahar hazard maps for public risk communication. Results indicate that a disconnect exists between perception and preparedness for the majority of respondents. While 82% of respondents accurately anticipate that future volcanic hazards will impact the Skagit Valley, this knowledge fails to motivate increased preparedness. A majority of respondents also feel "very responsible" for their own protection and provision of resources during a hazardous event (83%) and believe they have the knowledge and skills necessary to respond effectively to such an event (56%); however, many of these individuals still do not adequately prepare. When asked what barriers prevent them from preparing, respondents primarily cite a lack of knowledge about relevant local hazards. Results show that participation in response-related activities—a commonly recommended solution to this disconnect—minimally influences preparedness. Additionally, although local hazard maps successfully communicate the primary hazard—97% of respondents recognize the lahar hazard—many individuals incorrectly interpret other important facets of the maps. Those who participate in response-related activities fail to understand these

Delineation of a Re-establishing Drainage Network Using SPOT and Landsat Images

Science.gov (United States)

Bailey, J. E.; Self, S.; Mouginis-Mark, P. J.

2008-12-01

The 1991 eruption of Mt. Pinatubo, The Philippines, provided a unique opportunity to study the effects on the landscape of a large eruption in part because it took place after the advent of regular satellite-based observations. The eruption formed one large (>100km2) ignimbrite sheet, with over 70% of the total deposit deposited in three primary drainage basins to the west of the volcano. High-resolution (20 m/pixel) satellite images, showing the western drainage basins and surrounding region both before and after the eruption were used to observe the re-establishment and evolution of drainage networks on the newly emplaced ignimbrite sheet. Changes in the drainage networks were delineated from a time series of SPOT (Satellite Pour l'Observation de la Terre) and Landsat multi-spectral satellite images. The analysis of which was supplemented by ground- based observations. The satellite images showed that the blue prints for the new drainage systems were established early (within days of the eruption) and at a large-scale followed the pre-eruption pattern. However, the images also illustrated the ephemeral nature of many channels due to the influence of secondary pyroclastic flows, lahar- dammed lake breakouts, stream piracy and shifts due to erosion. Characteristics of the defined drainage networks were used to infer the relative influence on the lahar hazard within each drainage basin.

The relative effectiveness of empirical and physical models for simulating the dense undercurrent of pyroclastic flows under different emplacement conditions

Science.gov (United States)

Ogburn, Sarah E.; Calder, Eliza S

2017-01-01

High concentration pyroclastic density currents (PDCs) are hot avalanches of volcanic rock and gas and are among the most destructive volcanic hazards due to their speed and mobility. Mitigating the risk associated with these flows depends upon accurate forecasting of possible impacted areas, often using empirical or physical models. TITAN2D, VolcFlow, LAHARZ, and ΔH/L or energy cone models each employ different rheologies or empirical relationships and therefore differ in appropriateness of application for different types of mass flows and topographic environments. This work seeks to test different statistically- and physically-based models against a range of PDCs of different volumes, emplaced under different conditions, over different topography in order to test the relative effectiveness, operational aspects, and ultimately, the utility of each model for use in hazard assessments. The purpose of this work is not to rank models, but rather to understand the extent to which the different modeling approaches can replicate reality in certain conditions, and to explore the dynamics of PDCs themselves. In this work, these models are used to recreate the inundation areas of the dense-basal undercurrent of all 13 mapped, land-confined, Soufrière Hills Volcano dome-collapse PDCs emplaced from 1996 to 2010 to test the relative effectiveness of different computational models. Best-fit model results and their input parameters are compared with results using observation- and deposit-derived input parameters. Additional comparison is made between best-fit model results and those using empirically-derived input parameters from the FlowDat global database, which represent “forward” modeling simulations as would be completed for hazard assessment purposes. Results indicate that TITAN2D is able to reproduce inundated areas well using flux sources, although velocities are often unrealistically high. VolcFlow is also able to replicate flow runout well, but does not capture

Towards the definition of AMS facies in the deposits of pyroclastic density currents

Science.gov (United States)

Ort, M.H.; Newkirk, T.T.; Vilas, J.F.; Vazquez, J.A.; Ort, M.H.; Porreca, Massimiliano; Geissman, J.W.

2014-01-01

Anisotropy of magnetic susceptibility (AMS) provides a statistically robust technique to characterize the fabrics of deposits of pyroclastic density currents (PDCs). AMS fabrics in two types of pyroclastic deposits (small-volume phreatomagmatic currents in the Hopi Buttes volcanic field, Arizona, USA, and large-volume caldera-forming currents, Caviahue Caldera, Neuquén, Argentina) show similar patterns. Near the vent and in areas of high topographical roughness, AMS depositional fabrics are poorly grouped, with weak lineations and foliations. In a densely welded proximal ignimbrite, this fabric is overprinted by a foliation formed as the rock compacted and deformed. Medial deposits have moderate–strong AMS lineations and foliations. The most distal deposits have strong foliations but weak lineations. Based on these facies and existing models for pyroclastic density currents, deposition in the medial areas occurs from the strongly sheared, high-particle-concentration base of a density-stratified current. In proximal areas and where topography mixes this denser base upwards into the current, deposition occurs rapidly from a current with little uniformity to the shear, in which particles fall and collide in a chaotic fashion. Distal deposits are emplaced by a slowing or stalled current so that the dominant particle motion is vertical, leading to weak lineation and strong foliation.

Pyroclastic Density Current Hazards in the Auckland Volcanic Field, New Zealand

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Brand, B. D.; Gravley, D.; Clarke, A. B.; Bloomberg, S. H.

2012-12-01

The most dangerous phenomena associated with phreatomagmatic eruptions are dilute pyroclastic density currents (PDCs). These are turbulent, ground-hugging sediment gravity currents that travel radially away from the explosive center at up to 100 m/s. The Auckland Volcanic Field (AVF), New Zealand, consists of approximately 50 eruptive centers, at least 39 of which have had explosive phreatomagmatic behaviour. A primary concern for future AVF eruptions is the impact of dilute PDCs in and around the Auckland area. We combine field observations from the Maungataketake tuff ring, which has one of the best exposures of dilute PDC deposits in the AVF, with a quantitative model for flow of and sedimentation from a radially-spreading, steady-state, depth-averaged dilute PDC (modified from Bursik and Woods, 1996 Bull Volcanol 58:175-193). The model allows us to explore the depositional mechanisms, macroscale current dynamics, and potential impact on societal infrastructure of dilute PDCs from a future AVF eruption. The lower portion of the Maungataketake tuff ring pyroclastic deposits contains trunks, limbs and fragments of Podocarp trees (strength of the wood, we calculate that dynamic pressures (Pdyn) of 10-75 kPa are necessary to topple trees of this size and composition. Thus the two main criteria for model success based on the field evidence include (a) Pdyn must be >10 kPa nearer than 0.9 km to the vent, and 35 kPa can be expected within 3 km from source, ensuring complete destruction of the area; Pdyn > 15 kPa up to 5 km from source, resulting in heavy structural damage to most buildings and near destruction of weaker buildings; and Pdyn <10 kPa at ~6 km from source, resulting in severe damage to weaker structures at least up to this distance. This exercise illustrates our ability to combine field measurements with numerical techniques to explore controlling parameters of dilute PDC dynamics. These tools can be used to understand and estimate the damage potential and

Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

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Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, E.; Muller, S. K.; Kueppers, U.; Dingwell, D. B.

2015-05-01

Soft-sediment deformation structures can provide valuable information about the conditions of parent flows, the sediment state and the surrounding environment. Here, examples of soft-sediment deformation in deposits of dilute pyroclastic density currents are documented and possible syn-eruptive triggers suggested. Outcrops from six different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Soufriere Hills (Montserrat), Tungurahua (Ecuador), Ubehebe craters (USA), Laacher See (Germany), and Tower Hill and Purrumbete lakes (both Australia). The variety of features can be classified in four groups: (1) tubular features such as pipes; (2) isolated, laterally oriented deformation such as overturned or oversteepened laminations and vortex-shaped laminae; (3) folds-and-faults structures involving thick (>30 cm) units; (4) dominantly vertical inter-penetration of two layers such as potatoids, dishes, or diapiric flame-like structures. The occurrence of degassing pipes together with basal intrusions suggest fluidization during flow stages, and can facilitate the development of other soft-sediment deformation structures. Variations from injection dikes to suction-driven, local uplifts at the base of outcrops indicate the role of dynamic pore pressure. Isolated, centimeter-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. Vertical inter-penetration and those folds-and-faults features related to slumps are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. The passage of shock waves emanating from the vent may also produce trains of isolated, fine-grained overturned beds that disturb the surface bedding

Geophysical evidence for widespread reversely magnetised pyroclastics in the western Taupo Volcanic Zone (New Zealand)

International Nuclear Information System (INIS)

Soengkono, S.; Hochstein, M.P.; Smith, I.E.M.; Itaya, T.

1992-01-01

Low-altitude aeromagnetic data show that negative residual anomalies are widespread over the western Taupo Volcanic Zone, New Zealand. Paleomagnetic study of eight rhyolitic ignimbrite units and two lava flows which are exposed in this area, together with new K-Ar dates of four of the ignimbrite units, indicate that the two lava units and seven of the ignimbrite units were erupted during the Matuyama geomagnetic epoch (>0.73 Ma B.P.) and suggest that rhyolitic volcanism in the western Taupo Volcanic Zone began as early as 1.6 Ma B.P. These results provide the basis for an interpretation of our aeromagnetic data which confirms the hypothesis that the magnetic anomalies observed in the western Taupo Volcanic Zone are caused by widespread, thick, reversely magnetised pyroclastic and lava flows. Magnetic modelling also allows thickness estimates of the younger, normally magnetised cover rocks which reach a maximum thickness of the order of 0.5 km in the Mangakino area. The magnetic structure of these volcanic rocks defines approximately the lateral extent of the Mangakino Volcanic Centre. (author). 41 refs., 2 figs., 3 tabs

Thorium abundances on the aristarchus plateau: Insights into the composition of the aristarchus pyroclastic glass deposits

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Hagerty, Justin J.; Lawrence, D.J.; Hawke, B.R.; Gaddis, Lisa R.

2009-01-01

Thorium (Th) data from the Lunar Prospector gamma ray spectrometer (LP-GRS) are used to constrain the composition of lunar pyroclastic glass deposits on top of the Aristarchus plateau. Our goal is to use forward modeling of LP-GRS Th data to measure the Th abundances on the plateau and then to determine if the elevated Th abundances on the plateau are associated with the pyroclastic deposits or with thorium-rich ejecta from Aristarchus crater. We use a variety of remote sensing data to show that there is a large, homogenous portion of the pyroclastics on the plateau that has seen little or no contamination from the Th-rich ejecta of Aristarchus crater. Our results show that the uncontaminated pyroclastic glasses on Aristarchus plateau have an average Th content of 6.7 ppm and ???7 wt % TiO2. These Th and Ti values are consistent with Th-rich, intermediate-Ti yellow glasses from the lunar sample suite. On the basis of this information, we use petrologic equations and interelement correlations for the Moon to estimate the composition of the source region from which the Aristarchus glasses were derived. We find that the source region for the Aristarchus glasses contained high abundances of heat-producing elements, which most likely served as a thermal driver for the prolonged volcanic activity in this region of the Moon. Copyright 2009 by the American Geophysical Union.

The Ottaviano eruption of Somma-Vesuvio (8000 y B.P.): a magmatic alternating fall and flow-forming eruption

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Rolandi, G.; Maraffi, S.; Petrosino, P.; Lirer, L.

1993-11-01

The Ottaviano eruption occurred in the late neolithic (8000 y B.P.). 2.40 km 3 of phonolitic pyroclastic material (0.61 km 3 DRE) were emplaced as pyroclastic flow, surge and fall deposits. The eruption began with a fall phase, with a model column height of 14 km, producing a pumice fall deposit (LA). This phase ended with short-lived weak explosive activity, giving rise to a fine-grained deposit (L1), passing to pumice fall deposits as the result of an increasing column height and mass discharge rate. The subsequent two fall phases (producing LB and LC deposits), had model column heights of 20 and 22 km with eruption rates of 2.5 × 10 7 and 2.81 × 10 7 kg/s, respectively. These phases ended with the deposition of ash layers (L2 and L3), related to a decreasing, pulsing explosive activity. The values of dynamic parameters calculated for the eruption classify it as a sub-plinian event. Each fall phase was characterized by variations in the eruptive intensity, and several pyroclastic flows were emplaced (F1 to F3). Alternating pumice and ash fall beds record the waning of the eruption. Finally, owing to the collapse of a eruptive column of low gas content, the last pyroclastic flow (F4) was emplaced.

Eruptive origins of a lacustrine pyroclastic succession: insights from the middle Huka Falls Formation, Taupo Volcanic Zone, New Zealand

International Nuclear Information System (INIS)

Cattell, H.J.; Cole, J.W.; Oze, C.; Allen, S.R.

2014-01-01

Current and ancestral lakes within the central Taupo Volcanic Zone (TVZ) provide depocentres for pyroclastic deposits, providing a reliable record of eruption history. These lakes can also be the source of explosive eruptions that directly feed pyroclast-rich density currents. The lithofacies characteristics of pyroclastic deposits allow discrimination between eruption-fed and resedimented facies. The most frequently recognised styles of subaqueous eruptions in the TVZ are shallow-water phreatomagmatic and phreatoplinian eruptions that form subaerial eruption columns. However, deeper source conditions (>150 m water depth) could generate subaqueous explosive eruptions that feed water-supported pyroclast-rich density currents, similar to neptunian eruptions. Such deep-water eruptions have not previously been recognised in the TVZ. Here we study a subsurface deposit, the middle Huka Falls Formation (MHFF), in the Wairakei-Tauhara geothermal fields (Wairakei-Tauhara), TVZ, which we interpret to be the product of a relatively deep-water pyroclastic eruption (150-250 m). The largely subsurface Huka Falls Formation records past sedimentary and volcaniclastic deposition in ancient Lake Huka. Deposits examined from eight drill cores reveal a lithic-rich lower unit, a middle volumetrically dominant pumice lapilli-tuff and an upper thinly bedded suspension-settled tuff unit. A coarse lithic lapilli-tuff within the lower unit is locally thick and coarse near well THM12, suggesting proximity to a source located beneath Lake Huka. This research provides an understanding of the origin of the MHFF deposit and offers insights for evaluating and interpreting the diversity of subaqueous volcanic lake deposits elsewhere. (author)

Probabilistic-numerical assessment of pyroclastic current hazard at Campi Flegrei and Naples city: Multi-VEI scenarios as a tool for "full-scale" risk management.

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Mastrolorenzo, Giuseppe; Palladino, Danilo M; Pappalardo, Lucia; Rossano, Sergio

2017-01-01

The Campi Flegrei volcanic field (Italy) poses very high risk to the highly urbanized Neapolitan area. Eruptive history was dominated by explosive activity producing pyroclastic currents (hereon PCs; acronym for Pyroclastic Currents) ranging in scale from localized base surges to regional flows. Here we apply probabilistic numerical simulation approaches to produce PC hazard maps, based on a comprehensive spectrum of flow properties and vent locations. These maps are incorporated in a Geographic Information System (GIS) and provide all probable Volcanic Explosivity Index (VEI) scenarios from different source vents in the caldera, relevant for risk management planning. For each VEI scenario, we report the conditional probability for PCs (i.e., the probability for a given area to be affected by the passage of PCs in case of a PC-forming explosive event) and related dynamic pressure. Model results indicate that PCs from VEIextreme event) would affect a large part of the Campanian Plain to the north and the city of Naples to the east. Thus, in case of renewal of eruptive activity at Campi Flegrei, up to 3 million people will be potentially exposed to volcanic hazard, pointing out the urgency of an emergency plan. Considering the present level of uncertainty in forecasting the future eruption type, size and location (essentially based on statistical analysis of previous activity), we suggest that appropriate planning measures should face at least the VEI 5 reference scenario (at least 2 occurrences documented in the last 10 ka).

Sr isotope geochemistry of voluminous acidic pyroclastics erupted at 1-3 Ma in Northeast Japan

International Nuclear Information System (INIS)

Shirahase, Teruo; Tamanyu, Shiro; Togashi, Shigeko

1989-01-01

Sr isotope ratios are analyzed for voluminous acidic pyroclastics erupted at 1 - 3 Ma in five areas on the volcanic front of Northeast Japan. The initial values of 87 Sr/ 86 Sr ratios range from 0.7040 to 0.7055. There is no significant difference in ratios between 1 - 3 Ma acidic pyroclastics and 0 - 1 Ma andesitic volcanics in each area in spite of differences in age and in mean SiO 2 content. On the other hand, the ratios in both of 1 - 3 Ma and 0 - 1 Ma volcanics vary along arc in the same manner. The changes of Sr and Rb contents in each area are consistent with systematic changes by fractional crystallization. The low 87 Sr/ 86 Sr ratios and chemistry suggest that 1 - 3 Ma acidic pyroclastics of Northeast Japan formed by a high degree of fractional crystallization from basic magma which is common in genesis with young andesitic volcanism. The mechanisms of the formation of the basic magma and the character of mantle source in each area have not changed for the past 3 Ma. Degrees of fractional crystallization changed with changes of the tectonic condition of shallow magma chamber from a weak horizontal compression stress field to a strong one. (author)

Characterization of juvenile pyroclasts from the Kos Plateau Tuff (Aegean Arc): insights into the eruptive dynamics of a large rhyolitic eruption

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Bouvet de Maisonneuve, Caroline; Bachmann, Olivier; Burgisser, Alain

2009-08-01

Silicic pumices formed during explosive volcanic eruptions are faithful recorders of the state of the magma in the conduit, close to or at the fragmentation level. We have characterized four types of pumices from the non-welded rhyolitic Kos Plateau Tuff, which erupted 161,000 years ago in the East Aegean Arc, Greece. The dominant type of pumice (>90 vol.%) shows highly elongated tubular vesicles. These tube pumices occur throughout the eruption. Less common pumice types include: (1) “frothy” pumice (highly porous with large, sub-rounded vesicles), which form 5-10 vol.% of the coarsest pyroclastic flow deposits, (2) dominantly “microvesicular” and systematically crystal-poor pumices, which are found in early erupted, fine-grained pyroclastic flow units, and are characterized by many small (<50 μm in diameter) vesicles and few mm-sized, irregular voids, (3) grey or banded pumices, indicating the interaction between the rhyolite and a more mafic magma, which are found throughout the eruption sequence and display highly irregular bubble shapes. Except for the grey-banded pumices, all three other types are compositionally identical and were generated synchronously as they are found in the same pyroclastic units. They, therefore, record different conditions in the volcanic conduit leading to variable bubble nucleation, growth and coalescence. A total of 74 pumice samples have been characterized using thin section observation, SEM imagery, porosimetry, and permeametry. We show that the four pumice types have distinct total and connected porosity, tortuosity and permeability. Grey-banded pumices show large variations in petrophysical characteristics as a response to mingling of two different magmas. The microvesicular, crystal-poor, pumices have a bimodal bubble size distribution, interpreted as reflecting an early heterogeneous bubble nucleation event followed by homogeneous bubble nucleation close to fragmentation. Finally, the significant differences in

Constraining recent Shiveluch volcano eruptions (Kamchatka, Russia by means of dendrochronology

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O. Solomina

2008-10-01

Full Text Available Shiveluch (N 56°38´, E 161°19´; elevation: active dome ~2500 m, summit of Old Shiveluch 3283 m is one of the most active volcanoes in Kamchatka. The eruptions of Shiveluch commonly result in major environmental damage caused by debris avalanches, hot pyroclastic flows, tephra falls and lahars. Constraining these events in time and space is important for the understanding and prediction of these natural hazards. The last major eruption of Shiveluch occurred in 2005; earlier ones, dated by instrumental, historical, ¹⁴C and tephrochronological methods, occurred in the last millennium around AD 1030, 1430, 1650, 1739, 1790–1810, 1854, 1879–1883, 1897–1898, 1905, 1927–1929, 1944–1950, and 1964. A lava dome has been growing in the 1964 crater since 1980, occasionally producing tephra falls and pyroclastic flows. Several Shiveluch eruptions (~AD 1050, 1650, 1854, 1964 may have been climatically effective and are probably recorded in the Greenland ice cores.

Previously, most dates for eruptions before AD 1854 were obtained by tephrochronology and constrained by radiocarbon dating with an accuracy of several decades or centuries. In this paper we report tree-ring dates for a recent pyroclastic flow in Baidarnaia valley. Though the wood buried in these deposits is carbonized, fragile and poorly preserved, we were able to measure ring-width using standard tree-ring equipment or photographs and to cross-date these samples against the regional Kamchatka larch ring-width chronology. The dates of the outer rings indicate the date of the eruptions. In the Baidarnaia valley the eruption occurred shortly after AD 1756, but not later than AD 1758. This date coincides with the decrease of ring-width in trees growing near Shiveluch volcano in 1758–1763 in comparison with the control "non-volcanic" chronology. The pyroclastic flow in Kamenskaia valley, although similar in appearance to the one in Baidarnaia valley, definitively

Joint M3 and Diviner Analysis of the Mineralogy, Glass Composition, and Country Rock Content of Pyroclastic Deposits in Oppenheimer Crater

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Bennett, Kristen A.; Horgan, Briony H. N.; Greenhagen, Benjamin T.; Allen, Carlton C.; Paige, David A.; Bell, James F., III

2013-01-01

Here we present our analysis of the near- and mid-infrared spectral properties of pyroclastic deposits within the floor fractured Oppenheimer Crater that are hypothesized to be Vulcanian in origin. These are the first results of our global study of lunar pyroclastic deposits aimed at constraining the range of eruption processes on the Moon. In the near-infrared, we have employed a new method of spectral analysis developed in Horgan et al. (2013) of the 1 ?m iron absorption band in Chandrayaan-1 Moon Mineralogy Mapper (M3) spectra. By analyzing both the position and shape of the 1 ?m band we can detect and map the distribution of minerals, glasses, and mixtures of these phases in pyroclastic deposits. We are also using mid-infrared spectra from the Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment to develop 200 m/pixel Christiansen Feature (CF) maps, which correlate with silica abundance. One of the benefits of using CF maps for analysis of pyroclastic deposits is that they can be used to detect silicic country rock that may have been emplaced by Vulcanian-style eruptions, and are sensitive to iron abundance in glasses, neither of which is possible in the near-infrared. M3 analysis reveals that the primary spectral endmembers are low-calcium pyroxene and iron-bearing glass, with only minor high-calcium pyroxene, and no detectable olivine. The large deposit in the south shows higher and more extensive glass concentrations than the surrounding deposits. We interpret the M3 spectra of the pyroclastic deposits as indicating a mixture of low-calcium pyroxene country rock and juvenile glass, and no significant olivine. Analysis of Diviner CF maps of the Oppenheimer crater floor indicates an average CF value of 8.16, consistent with a mixture of primarily plagioclase and some pyroxene. The average CF values of the pyroclastic deposits range from 8.31 in the SW to 8.24 in the SE. Since CF values within the deposits are as high as 8.49, the lower average CF

Criteria for the Identification of Pyroclastic Surge Deposits on Mars: Insight from Hunt's Hole, New Mexico

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Edgar, L. A.; Grotzinger, J. P.; Southard, J. B.; Ewing, R. C.; Lamb, M. P.

2012-03-01

We combine field observations, Terrestrial Laser Scanning (TLS), and hydrodynamic considerations to understand pyroclastic surge deposits at Hunt’s Hole, New Mexico, and provide criteria for their identification on Mars.

The use of geographical information systems for disaster risk reduction strategies: a case study of Volcan de Colima, Mexico

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Landeg, O.

Contemporary disaster risk management requires the analysis of vulnerability and hazard exposure, which is imperative at Volcan de Colima (VdC), Mexico, due to the predicted, large-magnitude eruption forecast to occur before 2025. The methods used to gauge social vulnerability included the development and application of proxies to census records, the undertaking of a building vulnerability survey and the spatial mapping of civil and emergency infrastructure. Hazard exposure was assessed using primary modelling of laharic events and the digitalisation of secondary data sources detailing the modelled extent of pyroclastic flows and tephra deposition associated with a large-magnitude (VEI 5) eruption at VdC. The undertaking and analysis of a risk perception survey of the population enabled an understanding of the cognitive behaviour of residents towards the volcanic risk. In comparison to the published hazard map, the GIS analysis highlighted an underestimation of lahar hazard on the western flank of VdC and the regional tephra hazard. Vulnerability analysis identified three communities where social deprivation is relatively high, and those with significant elderly and transient populations near the volcano. Furthermore, recognition of the possibility of an eruption in the near future was found to be low across the study region. These results also contributed to the analysis of emergency management procedures and the preparedness of the regional authorities. This multidisciplinary research programme demonstrates the success of applying a GIS platform to varied integrative spatial and temporal analysis. Furthermore, ascertaining the impact of future activity at VdC upon its surrounding populations permits the evaluation of emergency preparedness and disaster risk reduction strategies.

Occurrence of inter-eruption debris flow and hyperconcentrated flood-flow deposits on Vesuvio volcano, Italy

Science.gov (United States)

Lirer, L.; Vinci, A.; Alberico, I.; Gifuni, T.; Bellucci, F.; Petrosino, P.; Tinterri, R.

2001-02-01

In the period between AD 79 and AD 472 eruptions, inter-eruption debris flow and hyperconcentrated-flood-flow deposits were deposited in the Somma-Vesuvio areas. These deposits, forming cliffs at the Torre Bassano and Torre Annunziata, were generated by highly erosive floods, whose erosive capacity was enhanced by acceleration due to the steepness of the volcano slopes. In this type of deposits were distinguished five depositional facies (from A to E) outcropping well at Torre Bassano where they are stacked in three fining-upward (FU) sequences, probably representing three forestepping — backstepping episodes in the emplacement area of gravity flows. These five facies from coarse to fine are interpreted to represent the downcurrent evolution of particular composite sediment gravity flows characterized by horizontal segregation of the main grain-size population. The blocking of these highly concentrated composite parent flows would first produce the deposition of the coarse front part to form facies A and then the overriding of this deposit by the bipartite flow, which constitutes the body of the flow. This flow is composed of a highly concentrated basal inertia carpet responsible for the deposition of facies B, C and D and an upper hyperconcentrated flood flow that forms facies E, through traction plus fallout processes, respectively. Finally, the occurrence of "lahar" type events at Somma-Vesuvio region even at present times is discussed.

Volcanic Risk Perception and Preparedness in Communities within the Mount Baker and Glacier Peak Lahar Hazard Zones

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Corwin, K.; Brand, B. D.

2014-12-01

A community's ability to effectively respond to and recover from natural hazards depends on both the physical characteristics of the hazard and the community's inherent resilience. Resilience is shaped by a number of factors including the residents' perception of and preparedness for a natural hazard as well as the level of institutional preparedness. This study examines perception of and preparedness for lahar hazards from Mount Baker and Glacier Peak in Washington's Skagit Valley. Through an online survey, this study isolates the influence of specific variables (e.g., knowledge, past experience, scientific background, trust in various information sources, occupation, self-efficacy, sense of community) on risk perception and explores reasons behind the frequent disconnect between perception and preparedness. We anticipate that individuals with more extensive education in the sciences, especially geology or earth science, foster greater trust in scientists and a more accurate knowledge, understanding, and perception of the volcanic hazards in their community. Additionally, little research exists examining the extent to which first responders and leaders in response-related institutions prepare on a personal level. Since these individuals work toward community preparedness professionally, we hypothesize that they will be more prepared at home than members of the general public. Finally, the Skagit Valley has a significant history of flooding. We expect that the need to respond to and recover from frequent flooding creates a community with an inherently higher level of preparedness for other hazards such as lahars. The results of this study will contribute to the understanding of what controls risk perception and the interplay between perception and preparedness. At a broader level, this study provides local and state-level emergency managers information to evaluate and improve response capabilities and communication with the public and key institutions in order to

Runout distance and dynamic pressure of pyroclastic density currents: Evidence from 18 May 1980 blast surge of Mount St. Helens

Science.gov (United States)

Gardner, J. E.; Andrews, B. J.

2016-12-01

Pyroclastic density currents (flows and surges) are one of the most deadly hazards associated with volcanic eruptions. Understanding what controls how far such currents will travel, and how their dynamic pressure evolves, could help mitigate their hazards. The distance a ground hugging, pyroclastic density current travels is partly limited by when it reverses buoyancy and lifts off into the atmosphere. The 1980 blast surge of Mount St. Helens offers an example of a current seen to lift off. Before lofting, it had traveled up to 20 km and leveled more than 600 km3 of thick forest (the blowdown zone). The outer edge of the devastated area - where burned trees that were left standing (the singe zone) - is where the surge is thought to have lifted off. We recently examined deposits in the outer parts of the blowdown and in the singe zone at 32 sites. The important finding is that the laterally moving surge travelled into the singe zone, and hence the change in tree damage does not mark the run out distance of the ground hugging surge. Eyewitness accounts and impacts on trees and vehicles reveal that the surge consisted of a fast, dilute "overcurrent" and a slower "undercurrent", where most of the mass (and heat) was retained. Reasonable estimates for flow density and velocity show that dynamic pressure of the surge (i.e., its ability to topple trees) peaked near the base of the overcurrent. We propose that when the overcurrent began to lift off, the height of peak dynamic pressure rose above the trees and stopped toppling them. The slower undercurrent continued forward, burning trees but it lacked the dynamic pressure needed to topple them. Grain-size variations argue that it slowed from 30 m/s when it entered the singe zone to 3 m/s at the far end. Buoyancy reversal and liftoff are thus not preserved in the deposits where the surge lofted upwards.

The geology of Mount Taftan stratovolcano, southeast of Iran

International Nuclear Information System (INIS)

Biabangard, H.; Moradian, A.

2008-01-01

Mount Taftan is a double-peaked stratovolcano, located in southeast of Iran. This volcano constructed a number of calderas among which one of the most important is Anjerk. The magmas erupted from this multi-caldera complex range from andesi-basalt to dacite, but are dominated by andesite and dacite. Two terminal cones, Narkuh and Matherkuh, culminate at 4100 m and 3950 m, respectively. There are three evolutionary stages in the history of the volcanic complex (stage 1: Palaevolcanism, 6.95±0.72Ma, stage 2: Mesovolcanism, 6.01±0.15Ma and stage 3: Neo volcanism, 0.71± 0.03Ma). The eruptive products consist of lava flows, iguimbrites and pyroclastic rocks. The later include tuffs, nuees ardents, breccias and sometimes reworked as lahars. Textural and mineralogical data suggest that both magma mixing and fractional crystallization were involved in the generation of the andesites and dacites. The magmas erupted from this volcano show a calc-alkaline trend. The corresponding lavas are calk-alkaline with a potasic tendency.

Synthetic aperture radar (SAR-based mapping of volcanic flows: Manam Island, Papua New Guinea

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J. K. Weissel

2004-01-01

Full Text Available We present new radar-based techniques for efficient identification of surface changes generated by lava and pyroclastic flows, and apply these to the 1996 eruption of Manam Volcano, Papua New Guinea. Polarimetric L- and P-band airborne synthetic aperture radar (SAR data, along with a C-band DEM, were acquired over the volcano on 17 November 1996 during a major eruption sequence. The L-band data are analyzed for dominant scattering mechanisms on a per pixel basis using radar target decomposition techniques. A classification method is presented, and when applied to the L-band polarimetry, it readily distinguishes bare surfaces from forest cover over Manam volcano. In particular, the classification scheme identifies a post-1992 lava flow in NE Valley of Manam Island as a mainly bare surface and the underlying 1992 flow units as mainly vegetated surfaces. The Smithsonian's Global Volcanism Network reports allow us to speculate whether the bare surface is a flow dating from October or November in the early part of the late-1996 eruption sequence. This work shows that fully polarimetric SAR is sensitive to scattering mechanism changes caused by volcanic resurfacing processes such as lava and pyroclastic flows. By extension, this technique should also prove useful in mapping debris flows, ash deposits and volcanic landslides associated with major eruptions.

Investigating pyroclast ejection dynamics using shock-tube experiments: temperature, grain size and vent geometry effects.

Science.gov (United States)

Cigala, V.; Kueppers, U.; Dingwell, D. B.

2015-12-01

Explosive volcanic eruptions eject large quantities of gas and particles into the atmosphere. The portion directly above the vent commonly shows characteristics of underexpanded jets. Understanding the factors that influence the initial pyroclast ejection dynamics is necessary in order to better assess the resulting near- and far-field hazards. Field observations are often insufficient for the characterization of volcanic explosions due to lack of safe access to such environments. Fortunately, their dynamics can be simulated in the laboratory where experiments are performed under controlled conditions. We ejected loose natural particles from a shock-tube while controlling temperature (25˚ and 500˚C), overpressure (15MPa), starting grain size distribution (1-2 mm, 0.5-1 mm and 0.125-0.250 mm), sample-to-vent distance and vent geometry. For each explosion we quantified the velocity of individual particles, the jet spreading angle and the production of fines. Further, we varied the setup to allow for different sample-to-gas ratios and deployed four different vent geometries: 1) cylindrical, 2) funnel with a flaring of 30˚, 3) funnel with a flaring of 15˚ and 4) nozzle. The results showed maximum particle velocities up to 296 m/s, gas spreading angles varying from 21˚ to 37˚ and particle spreading angles from 3˚ to 40˚. Moreover we observed dynamically evolving ejection characteristics and variations in the production of fines during the course of individual experiments. Our experiments mechanistically mimic the process of pyroclast ejection. Thus the capability for constraining the effects of input parameters (fragmentation conditions) and conduit/vent geometry on ballistic pyroclastic plumes has been clearly established. These data obtained in the presence of well-documented conduit and vent conditions, should greatly enhance our ability to numerically model explosive ejecta in nature.

Geology, tectonics, and the 2002-2003 eruption of the Semeru volcano, Indonesia: Interpreted from high-spatial resolution satellite imagery

Science.gov (United States)

Solikhin, Akhmad; Thouret, Jean-Claude; Gupta, Avijit; Harris, Andy J. L.; Liew, Soo Chin

2012-02-01

have also compared two 10 m-pixel images acquired before and after the event to describe the extent and impact of an estimated volume of 5.45 × 10 6 m 3 of block-and-ash flow deposits. An ash-rich pyroclastic surge escaped from one of the valley-confined block-and ash flows at 5 to 8 km distance from the crater and swept across the forest and tilled land on the SW side of the Bang River Valley. Downvalley, the temperature of the pyroclastic surge decreased and a mud-rich deposit coated the banks of the Bang River Valley. Thus, hazard mitigation at Semeru should combine: (1) continuous monitoring of the eruptive activity through an early-warning system, and (2) continuous remote sensing of the morphological changes in the drainage system due to the impact of frequent pyroclastic density currents and lahars.

Clast comminution during pyroclastic density current transport: Mt St Helens

Science.gov (United States)

Dawson, B.; Brand, B. D.; Dufek, J.

2011-12-01

Volcanic clasts within pyroclastic density currents (PDCs) tend to be more rounded than those in fall deposits. This rounding reflects degrees of comminution during transport, which produces an increase in fine-grained ash with distance from source (Manga, M., Patel, A., Dufek., J. 2011. Bull Volcanol 73: 321-333). The amount of ash produced due to comminution can potentially affect runout distance, deposit sorting, the volume of ash lofted into the upper atmosphere, and increase internal pore pressure (e.g., Wohletz, K., Sheridan, M. F., Brown, W.K. 1989. J Geophy Res, 94, 15703-15721). For example, increased pore pressure has been shown to produce longer runout distances than non-comminuted PDC flows (e.g., Dufek, J., and M. Manga, 2008. J. Geophy Res, 113). We build on the work of Manga et al., (2011) by completing a pumice abrasion study for two well-exposed flow units from the May 18th, 1980 eruption of Mt St Helens (MSH). To quantify differences in comminution from source, sampling and the image analysis technique developed in Manga et al., 2010 was completed at distances proximal, medial, and distal from source. Within the units observed, data was taken from the base, middle, and pumice lobes within the outcrops. Our study is unique in that in addition to quantifying the degree of pumice rounding with distance from source, we also determine the possible range of ash sizes produced during comminution by analyzing bubble wall thickness of the pumice through petrographic and SEM analysis. The proportion of this ash size is then measured relative to the grain size of larger ash with distance from source. This allows us to correlate ash production with degree of rounding with distance from source, and determine the fraction of the fine ash produced due to comminution versus vent-fragmentation mechanisms. In addition we test the error in 2D analysis by completing a 3D image analysis of selected pumice samples using a Camsizer. We find that the roundness of PDC

Plastic Models Designed to Produce Large Height-to-Length Ratio Steady-State Planar and Axisymmetric (Radial) Viscous Liquid Laminar Flow Gravity Currents

Science.gov (United States)

Blanck, Harvey F.

2012-01-01

Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…

Monitoring and behavior of unsaturated volcanic pyroclastic in the Metropolitan Area of San Salvador, El Salvador.

Science.gov (United States)

Chávez, José Alexander; Landaverde, José; Landaverde, Reynaldo López; Tejnecký, Václav

2016-01-01

Field monitoring and laboratory results are presented for an unsaturated volcanic pyroclastic. The pyroclastic belongs to the latest plinian eruption of the Ilopango Caldera in the Metropolitan Area of San Salvador, and is constantly affected by intense erosion, collapse, slab failure, sand/silt/debris flowslide and debris avalanche during the rainy season or earthquakes. Being the flowslides more common but with smaller volume. During the research, preliminary results of rain threshold were obtained of flowslides, this was recorded with the TMS3 (a moisture sensor device using time domain transmission) installed in some slopes. TMS3 has been used before in biology, ecology and soil sciences, and for the first time was used for engineering geology in this research. This device uses electromagnetic waves to obtain moisture content of the soil and a calibration curve is necessary. With the behavior observed during this project is possible to conclude that not only climatic factors as rain quantity, temperature and evaporation are important into landslide susceptibility but also information of suction-moisture content, seepage, topography, weathering, ground deformation, vibrations, cracks, vegetation/roots and the presence of crust covering the surface are necessary to research in each site. Results of the field monitoring indicates that the presence of biological soil crusts a complex mosaic of soil, green algae, lichens, mosses, micro-fungi, cyanobacteria and other bacteria covering the slopes surface can protect somehow the steep slopes reducing the runoff process and mass wasting processes. The results obtained during the assessment will help explaining the mass wasting problems occurring in some pyroclastic soils and its possible use in mitigation works and early warning system.

Sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone terrane, western Dharwar Craton: Implications on pyroclastic volcanism and sedimentation in an active continental margin

Science.gov (United States)

Manikyamba, C.; Saha, Abhishek; Ganguly, Sohini; Santosh, M.; Lingadevaru, M.; Rajanikanta Singh, M.; Subba Rao, D. V.

2014-12-01

We report sediment-infill volcanic breccia from the Neoarchean Shimoga greenstone belt of western Dharwar Craton which is associated with rhyolites, chlorite schists and pyroclastic rocks. The pyroclastic rocks of Yalavadahalli area of Shimoga greenstone belt host volcanogenic Pb-Cu-Zn mineralization. The sediment-infill volcanic breccia is clast-supported and comprises angular to sub-angular felsic volcanic clasts embedded in a dolomitic matrix that infilled the spaces in between the framework of volcanic clasts. The volcanic clasts are essentially composed of alkali feldspar and quartz with accessory biotite and opaques. These clasts have geochemical characteristics consistent with that of the associated potassic rhyolites from Daginkatte Formation. The rare earth elements (REE) and high field strength element (HFSE) compositions of the sediment-infill volcanic breccia and associated mafic and felsic volcanic rocks suggest an active continental margin setting for their generation. Origin, transport and deposition of these rhyolitic clasts and their aggregation with infiltrated carbonate sediments may be attributed to pyroclastic volcanism, short distance transportation of felsic volcanic clasts and their deposition in a shallow marine shelf in an active continental margin tectonic setting where the rhyolitic clasts were cemented by carbonate material. This unique rock type, marked by close association of pyroclastic volcanic rocks and shallow marine shelf sediments, suggest shorter distance between the ridge and shelf in the Neoarchean plate tectonic scenario.

Volcanic glass signatures in spectroscopic survey of newly proposed lunar pyroclastic deposits

Science.gov (United States)

Besse, S.; Sunshine, J.M.; Gaddis, L.R.

2014-01-01

Moon Mineralogy Mapper spectroscopic observations are used to assess the mineralogy of five sites that have recently been proposed to include lunar dark mantle deposits (DMDs). Volcanic glasses have, for the first time, clearly been identified at the location of three of the proposed pyroclastic deposits. This is the first time that volcanic glasses have been identified at such a small scale on the lunar surface from remote sensing observations. Deposits at Birt E, Schluter, and Walther A appear to be glassy DMDs. Deposits at Birt E and Schluter show (1) morphological evidence suggesting a likely vent and (2) mineralogical evidence indicative of the presence of volcanic glasses. The Walther A deposits, although they show no morphological evidence of vents, have the spectroscopic characteristics diagnostic of volcanic glasses. The deposits of the Freundlich-Sharonov basin are separated in two areas: (1) the Buys-Ballot deposits lack mineralogical and morphological evidence and thus are found to be associated with mare volcanism not with DMDs and (2) the Anderson crater deposits, which do not exhibit glassy DMD signatures, but they appear to be associated with possible vent structures and so may be classifiable as DMDs. Finally, dark deposits near the crater Kopff are found to be associated with likely mare volcanism and not associated with DMDs. The spectral identification of volcanic glass seen in many of the potential DMDs is a strong indicator of their pyroclastic origin.

Near-surface flow of volcanic gases on Io

International Nuclear Information System (INIS)

Lee, S.W.; Thomas, P.C.

1980-01-01

Significant near-surface flow of gas several hundred kilometers from Pele (Plume 1) on Io is indicated by a series of bright, elongate albedo markings. Particles produced at small, local vents are apparently carried as much as 70 km farther 'downwind' from Pele. The gas densities and velocities necessary to suspend 0.1 to 10 micron particles at such a distance imply mass flow rates of 10 to the 7th - 10 to the 9th g/sec. Such flow rates are consistent with other estimates of mass transport by the plume. The large flow rates so far from the source allow an estimate of the rate of resurfacing of Io by lava flows and pyroclastics that is independent of estimates based on meteorite flux or on the amount of solids carried within the plumes themselves

Historical tephra-stratigraphy of the Cosiguina Volcano (Western Nicaragua)

International Nuclear Information System (INIS)

Hradecky, Petr; Rapprich, Vladislav

2008-01-01

New detailed geological field studies and 14 C dating of the Cosiguina Volcano (westernmost Nicaragua) have allowed to reconstruct a geological map of the volcano and to establish a recent stratigraphy, including three historical eruptions. Five major sequences are represented. I: pyroclastic flows around 1500 AD, II: pyroclastic flows, scoria and pumice flows and surges, III: pyroclastic deposits related to a littoral crater, IV: pyroclastic flows related to 1709 AD eruption, and finally, V: pyroclastic deposits corresponding to the cataclysmic 1835 AD phreatic, phreatomagmatic and subplinian eruption, which seems to be relatively small-scale in comparison with the preceding historical eruptions. The pulsating geochemical character of the pyroclastic rocks in the last five centuries has been documented. The beginning of every eruption is marked by increasing contents of silica and Zr. Based on that, regardless of present-day volcanic repose, the entire Cosiguina Peninsula should be considered as a very hazardous volcanic area. (author)

From Chaitén to the Chilean volcano monitoring network Jorge Munoz, Hugo Moreno, Servicio Nacional de Geología y Minería, Chile, jmunoz@sernageomin.cl

Science.gov (United States)

Muñoz, J.; Moreno, H.

2010-12-01

Chaitén volcano in southern Andes started a plinian to subplinian rhyolitic eruption on May 2008 following a long period of quiescence. A new dome complex grew up at high rates during 2008-2009 inside a 2 kilometers caldera like structure. Pyroclastic, laharic, block and ash flows and ash falls deposits have been affecting the surrounding populations, ground, vegetation, ocean and rivers, such as the laharic flows burying the currently evacuated Chaitén city. The geological, volcanologic and seismic knowledge produced during the eruption and the determination of evolutionary sceneries were properly transferred and consequently taken in account during complex decisions of authorities in charge of the emergency. As a result, no fatalities or major people injuries were produced during this rhyolitic eruption. Mainly as the consequence of the eruption of the Chaitén volcano but also due to the valuable technical advice during the crisis management, evacuation, hazards evolution, volcanic alerts and selection of sites for relocation of the Chaitén city provided by geologist and volcanologist from SERNAGEOMIN, the funding for the National Volcano Monitoring Network (RNVV) was approved during 2008 and it was integrated as a Bicentenary initiative. During the lapse of 5 year, RNVV need to create professional capacity and working teams, improve the current volcano observatory at Temuco and conform three new observatories at Coihaique, Talca and Antofagasta cities to implement volcano monitoring networks at the 43 hazardous volcanoes along the Chilean Andes. Monitoring net is currently conformed by seismic stations in 10 volcanoes or volcanic groups (San Pedro-San Pablo in Central Volcanic Andes and Llaima, Villlarrica, Mocho-Choshuenco, Carrán-Los Venados, Cordón Caulle, Osorno, Calbuco, Chaitén and Melimoyu in the southern volcanic Andes), in addition to gas measure and video camera stations in Llaima, Villarrica and Chaitén volcanoes. In addition, the geologic and

Determination of Trace and Volatile Element Abundance Systematics of Lunar Pyroclastic Glasses 74220 and 15426 Using LA-ICP-MS

Science.gov (United States)

McIntosh, E. Carrie; Porrachia, Magali; McCubbin, Francis M.; Day, James M. D.

2017-01-01

Since their recognition as pyroclastic glasses generated by volcanic fire fountaining on the Moon, 74220 and 15426 have garnered significant scientific interest. Early studies recognized that the glasses were particularly enriched in volatile elements on their surfaces. More recently, detailed analyses of the interiors of the glasses, as well as of melt inclusions within olivine grains associated with the 74220 glass beads, have determined high H2O, F, Cl and S contents. Such elevated volatile contents seem at odds with evidence from moderately volatile elements (MVE), such as Zn and K, for a volatile- depleted Moon. In this study, we present initial results from an analytical campaign to study trace element abundances within the pyroclastic glass beads. We report trace element data determined by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for 15426 and 74220.

40Ar/39Ar stratigraphy of pyroclastic units from the Cañadas Volcanic Edifice (Tenerife, Canary Islands) and their bearing on the structural evolution

OpenAIRE

Huertas Coronel, María José; Arnaud, N.; Ancochea Soto, Eumenio; Cantagrel, Jean Marie; Fúster Casas, José María

2002-01-01

Many felsic pyroclastic units of various types are exposed in different sectors of Tenerife. New 40Ar/39Ar determinations allow them to be placed more precisely in the general volcano-stratigraphic succession. According to geographic distribution, stratigraphic position and isotopic ages, four main pyroclastic phases may be identified. The first, San Juan de la Rambla phase (2.1 Ma), is only known in the north of Tenerife in the Tigaiga massif. The second, Adeje phase (1.8–1.5 Ma), is most co...

Probabilistic-numerical assessment of pyroclastic current hazard at Campi Flegrei and Naples city: Multi-VEI scenarios as a tool for "full-scale" risk management.

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Giuseppe Mastrolorenzo

Full Text Available The Campi Flegrei volcanic field (Italy poses very high risk to the highly urbanized Neapolitan area. Eruptive history was dominated by explosive activity producing pyroclastic currents (hereon PCs; acronym for Pyroclastic Currents ranging in scale from localized base surges to regional flows. Here we apply probabilistic numerical simulation approaches to produce PC hazard maps, based on a comprehensive spectrum of flow properties and vent locations. These maps are incorporated in a Geographic Information System (GIS and provide all probable Volcanic Explosivity Index (VEI scenarios from different source vents in the caldera, relevant for risk management planning. For each VEI scenario, we report the conditional probability for PCs (i.e., the probability for a given area to be affected by the passage of PCs in case of a PC-forming explosive event and related dynamic pressure. Model results indicate that PCs from VEI<4 events would be confined within the Campi Flegrei caldera, PC propagation being impeded by the northern and eastern caldera walls. Conversely, PCs from VEI 4-5 events could invade a wide area beyond the northern caldera rim, as well as part of the Naples metropolitan area to the east. A major controlling factor of PC dispersal is represented by the location of the vent area. PCs from the potentially largest eruption scenarios (analogous to the ~15 ka, VEI 6 Neapolitan Yellow Tuff or even the ~39 ka, VEI 7 Campanian Ignimbrite extreme event would affect a large part of the Campanian Plain to the north and the city of Naples to the east. Thus, in case of renewal of eruptive activity at Campi Flegrei, up to 3 million people will be potentially exposed to volcanic hazard, pointing out the urgency of an emergency plan. Considering the present level of uncertainty in forecasting the future eruption type, size and location (essentially based on statistical analysis of previous activity, we suggest that appropriate planning measures should

Conceptual Development of a National Volcanic Hazard Model for New Zealand

Science.gov (United States)

Stirling, Mark; Bebbington, Mark; Brenna, Marco; Cronin, Shane; Christophersen, Annemarie; Deligne, Natalia; Hurst, Tony; Jolly, Art; Jolly, Gill; Kennedy, Ben; Kereszturi, Gabor; Lindsay, Jan; Neall, Vince; Procter, Jonathan; Rhoades, David; Scott, Brad; Shane, Phil; Smith, Ian; Smith, Richard; Wang, Ting; White, James D. L.; Wilson, Colin J. N.; Wilson, Tom

2017-06-01

We provide a synthesis of a workshop held in February 2016 to define the goals, challenges and next steps for developing a national probabilistic volcanic hazard model for New Zealand. The workshop involved volcanologists, statisticians, and hazards scientists from GNS Science, Massey University, University of Otago, Victoria University of Wellington, University of Auckland, and University of Canterbury. We also outline key activities that will develop the model components, define procedures for periodic update of the model, and effectively articulate the model to end-users and stakeholders. The development of a National Volcanic Hazard Model is a formidable task that will require long-term stability in terms of team effort, collaboration and resources. Development of the model in stages or editions that are modular will make the process a manageable one that progressively incorporates additional volcanic hazards over time, and additional functionalities (e.g. short-term forecasting). The first edition is likely to be limited to updating and incorporating existing ashfall hazard models, with the other hazards associated with lahar, pyroclastic density currents, lava flow, ballistics, debris avalanche, and gases/aerosols being considered in subsequent updates.

Conceptual Development of a National Volcanic Hazard Model for New Zealand

Directory of Open Access Journals (Sweden)

Mark Stirling

2017-06-01

Full Text Available We provide a synthesis of a workshop held in February 2016 to define the goals, challenges and next steps for developing a national probabilistic volcanic hazard model for New Zealand. The workshop involved volcanologists, statisticians, and hazards scientists from GNS Science, Massey University, University of Otago, Victoria University of Wellington, University of Auckland, and University of Canterbury. We also outline key activities that will develop the model components, define procedures for periodic update of the model, and effectively articulate the model to end-users and stakeholders. The development of a National Volcanic Hazard Model is a formidable task that will require long-term stability in terms of team effort, collaboration, and resources. Development of the model in stages or editions that are modular will make the process a manageable one that progressively incorporates additional volcanic hazards over time, and additional functionalities (e.g., short-term forecasting. The first edition is likely to be limited to updating and incorporating existing ashfall hazard models, with the other hazards associated with lahar, pyroclastic density currents, lava flow, ballistics, debris avalanche, and gases/aerosols being considered in subsequent updates.

Lime treatment of an Italian pyroclastic soil: a multi-scale analysis for the correlation of mechanical and chemo-mineralogical effects.

Science.gov (United States)

Guidobaldi, Giulia; Cambi, Costanza; Cecconi, Manuela; Comodi, Paola; Zucchini, Azzurra

2017-04-01

In recent years, the ever-growing need to minimize costs and environmental impact in the construction of major civil infrastructure has led to the development of a large amount of methods based on the reuse of local materials. In particular, one of the most diffused methods is represented by lime treatment, widely applied in earthwork field to achieve mechanical improvement of otherwise unsuitable fine grained soils. However, unlike fine grained soils, many other types of world-wide common natural soils still represent a geotechnical obstacle. Among these, pyroclastic soils are a typology widely spread in Central and Southern Italy that finds marginal applications in earthworks practice due to the intrinsic complexities in terms of nature, heterogeneity, microstructural features and unsaturated hydro-mechanical behaviour. The need to overcome the described limitations motivates the focus of this work on the geotechnical characterization of pyroclastic deposits along with the increasing attention on the volume-scale and micro-scale features characterization and correlation. The main goal of the present study is to highlight the effects of lime treatment on a zeolite rich pyroclastic soil, focusing on the relationship between macro and micro modifications induced by lime addition. Within this research, an extensive experimental work was developed on a zeolitic pyroclastic soil coming from Orvieto cliff (Vulsini volcanic district, Central Italy). The overall investigation was organized in three phases: the first phase was devoted to the thorough chemo-physical and mineralogical characterization of the raw soil; subsequently, conventional direct shear tests were performed on reconstituted specimens of both raw and lime treated soil (2% and 5% Ca(OH)2) at increasing curing times and stress levels; finally, a wide chemo-mineralogical investigation was carried out on the lime treated samples to gain a more complete knowledge of the reactions responsible for the mechanical

The 2011-2012 eruption of Cordón Caulle volcano (Southern Andes): Evolution, crisis management and current hazards

Science.gov (United States)

Silva Parejas, C.; Lara, L. E.; Bertin, D.; Amigo, A.; Orozco, G.

2012-04-01

A new kind of integrated approach was for first time achieved during the eruptive crisis of Cordón Caulle volcano (Southern Andes, 40.59°S, 72.12°W) in Chile. The monitoring network of SERNAGEOMIN around the volcano detected the increasing precursory seismicity, alerting the imminence of an eruption about 5 hours before its onset, on June 4, 2011. In addition, SERNAGEOMIN generated daily forecasts of tephra dispersal and fall (ASHFALL advection-diffusion model), and prepared simulations of areas affected by the possible occurrence of lahars and pyroclastic flows. Models were improved with observed effects on the field and satellite imagery, resulting in a good correlation. The information was timely supplied to the authorities as well as recommendations in order to better precise the vulnerable areas. Eruption has initially occurred from a couple of overlapped cones located along the eastern fault scarp of the Pleistocene-Holocene extensional graben of Cordón Caulle. Eruptive products have virtually the same bulk composition as those of the historical 1921 and 1960 eruptions, corresponding to phenocryst-poor rhyodacites (67-70 % SiO2). During the first eruptive stage, a ca. 15-km strong Plinian column lasting 27 hours emitted 0.2-0.4 km3 of magma (DRE). Thick tephra deposits have been accumulated in Chile and Argentina, whereas fine particles and aerosols dispersion disrupted air navigation across the Southern Hemisphere. The second ongoing eruptive stage, which started in mid-June, has been characterized by lava emission already covering a total area comparable to the 1960 lava flows with a total estimated volume Argentina until the end of the year. Main current hazards at Cordón Caulle volcano are fine tephra fallout, secondary lahars, minor explosions and lava flow front collapse. Even if this case can be considered successful from the point of view of eruption forecast and hazard assessment, a new protocol of volcanic alerts has been recently signed

Petrology of a sequence of pyroclastic rocks from the Taurus-Littrow (Apollo 17 landing site)

International Nuclear Information System (INIS)

Heiken, G.; McKay, D.S.

1978-01-01

We have studied 13 samples from core 740012 using petrographic methods and electron probe microanalysis. The samples represent most of the major units described in the core by Nagle (1978). Below 5.5 cm, the samples consist entirely of whole and broken orange glass droplets and the partly to completely crystallized black equivalents. We believe these droplets are pyroclastic ejecta from a lunar volcano. The crystalline droplets contain olivine and ilmenite as major phases. Minor phases include pyroxene, Cr-spinels, and metallic Fe. Four different properties of these droplets suggest that a wide range of cooling rates are represented. These properties are the grain shapes, the degree of crystallization, the olivine shapes or textures, and the olivine compositions. Many droplets contain vesicles indicating that a gas phase was involved in the eruption. Above 5.5 cm the core sequence has undergone in situ reworking by micrometeorites and contains ''exotic'' fragments including basalt and agglutinates. We conclude that the sequence below 5.5 cm represents 3.5 b.y. old volcanic pyroclastic ejecta which was deposited in a relativley short time period, was buried, and was subsequently brought to the lunar surface by the Shorty Crater impact where it was subjected to minor in situ reworking

Hazard map for volcanic ballistic impacts at El Chichón volcano (Mexico)

Science.gov (United States)

Alatorre-Ibarguengoitia, Miguel; Ramos-Hernández, Silvia; Jiménez-Aguilar, Julio

2014-05-01

The 1982 eruption of El Chichón Volcano in southeastern Mexico had a strong social and environmental impact. The eruption resulted in the worst volcanic disaster in the recorded history of Mexico, causing about 2,000 casualties, displacing thousands, and producing severe economic losses. Even when some villages were relocated after the 1982 eruption, many people still live and work in the vicinities of the volcano and may be affected in the case of a new eruption. The hazard map of El Chichón volcano (Macías et al., 2008) comprises pyroclastic flows, pyroclastic surges, lahars and ash fall but not ballistic projectiles, which represent an important threat to people, infrastructure and vegetation in the case of an eruption. In fact, the fatalities reported in the first stage of the 1982 eruption were caused by roof collapse induced by ashfall and lithic ballistic projectiles. In this study, a general methodology to delimit the hazard zones for volcanic ballistic projectiles during volcanic eruptions is applied to El Chichón volcano. Different scenarios are defined based on the past activity of the volcano and parameterized by considering the maximum kinetic energy associated with ballistic projectiles ejected during previous eruptions. A ballistic model is used to reconstruct the "launching" kinetic energy of the projectiles observed in the field. The maximum ranges expected for the ballistics in the different explosive scenarios defined for El Chichón volcano are presented in a ballistic hazard map which complements the published hazard map. These maps assist the responsible authorities to plan the definition and mitigation of restricted areas during volcanic crises.

Juvenile pumice and pyroclastic obsidian reveal the eruptive conditions necessary for the stability of Plinian eruption of rhyolitic magma

Science.gov (United States)

Giachetti, T.; Shea, T.; Gonnermann, H. M.; McCann, K. A.; Hoxsie, E. C.

2016-12-01

Significant explosive activity generally precedes or coexists with the large effusion of rhyolitic lava (e.g., Mono Craters; Medicine Lake Volcano; Newberry; Chaitén; Cordón Caulle). Such explosive-to-effusive transitions and, ultimately, cessation of activity are commonly explained by the overall waning magma chamber pressure accompanying magma withdrawal, albeit modulated by magma outgassing. The tephra deposits of such explosive-to-effusive eruptions record the character of the transition - abrupt or gradual - as well as potential changes in eruptive conditions, such as magma composition, volatiles content, mass discharge rate, conduit size, magma outgassing. Results will be presented from a detailed study of both the gas-rich (pumice) and gas-poor (obsidian) juvenile pyroclasts produced during the Plinian phase of the 1060 CE Glass Mountain eruption of Medicine Lake Volcano, California. In the proximal deposits, a multitude of pumice-rich sections separated by layers rich in dense clasts suggests a pulsatory behavior of the explosive phase. Density measurements on 2,600 pumices show that the intermediate, most voluminous deposits have a near constant median porosity of 65%. However, rapid increase in porosity to 75-80% is observed at both the bottom and the top of the fallout deposits, suggestive of rapid variations in magma degassing. In contrast, a water content of pyroclastic obsidians of approximately 0.6 wt% does remain constant throughout the eruption, suggesting that the pyroclastic obsidians degassed up to a constant pressure of a few megapascals. Numerical modeling of eruptive magma ascent and degassing is used to provide constraints on eruption conditions.

Pyroclastic density currents at Etna volcano, Italy: The 11 February 2014 case study

Science.gov (United States)

Andronico, Daniele; Di Roberto, Alessio; De Beni, Emanuela; Behncke, Boris; Bertagnini, Antonella; Del Carlo, Paola; Pompilio, Massimo

2018-05-01

On 11 February 2014, a considerable volume (0.82 to 1.29 × 106 m3) of unstable and hot rocks detached from the lower-eastern flank of the New Southeast Crater (NSEC) at Mt. Etna, producing a pyroclastic density current (PDC). This event was by far the most extensive ever recorded at Mt. Etna since 1999 and has attracted the attention of the scientific community and civil protection to this type of volcanic phenomena, usually occurring without any clear volcanological precursor and especially toward the mechanisms which led to the crater collapse, the PDC flow dynamics and the related volcanic hazard. We present here the results of the investigation carried out on the 11 February 2014 collapse and PDC events; data were obtained through a multidisciplinary approach which includes the analysis of photograph, images from visible and thermal surveillance cameras, and the detailed stratigraphic, textural and petrographic investigations of the PDC deposits. Results suggest that the collapse and consequent PDC was the result of a progressive thermal and mechanical weakening of the cone by repeated surges of magma passing through it during the eruptive activity prior to the 11 February 2014 events, as well as pervasive heating and corrosion by volcanic gas. The collapse of the lower portion of the NSEC was followed by the formation of a relatively hot (up to 750 °C) dense flow which travelled about 2.3 km from the source, stopping shortly after the break of the slope and emplacing the main body of the deposit which ranges between 0.39 and 0.92 × 106 m3. This flow was accompanied a relatively hot cloud of fine ash that dispersed over a wider area. The results presented may contribute to the understanding of this very complex type of volcanic phenomena at Mt. Etna and in similar volcanic settings of the world. In addition, results will lay the basis for the modeling of crater collapse and relative PDC events and consequently for the planning of hazard assessment strategies

Le volcan Cayambe (Equateur: son activité au cours des 5000 dernières années et les menaces qui en résultent

Directory of Open Access Journals (Sweden)

1996-01-01

ACTIVITY DURING THE LAST 5,000 YEARS AND POTENTIAL HAZARDS. The study of recent products emitted by dacite domes located on the upper flanks of Cayambe volcano, situated 60 km to the NE of Quito, yields four pyroclastic units of block and ash flows, surges and associated lahars. The youngest unit was erupted about 360 years BP. Moreover, the identification of numerous airfall deposits (ash and lapilli in a peat bog reveals that at least 23 volcanic events have occured since 4,000 years ago, forming 3 main cycles of activity, each 700 to 1,000 years in duration. The last cycle, to which are correlated the four pyroclastic flow units, has probably not ended, as suggested by a small eruption in 1785-1786. These results shed a new light on the potential hazards presented by this large ice-capped volcano.

Geology and petrology of the Woods Mountains Volcanic Center, southeastern California: Implications for the genesis of peralkaline rhyolite ash flow tuffs

Science.gov (United States)

McCurry, Michael

1988-12-01

The Woods Mountains Volcanic Center is a middle Miocene silicic caldera complex located at the transition from the northern to the southern Basin and Range provinces of the western United States. It consists of a trachyte-trachydacite-rhyolite-peralkaline rhyolite association of lava flows, domes, plugs, pyroclastic rocks, and epiclastic breccia. Volcanism began at about 16.4 Ma, near the end of a local resurgence of felsic to intermediate magmatism and associated crustal extension. Numerous metaluminous high-K trachyte, trachydacite, and rhyolite lava flows, domes, and pyroclastic deposits accumulated from vents scattered over an area of 200 km2 forming a broad volcanic field with an initial volume of about 10 km3. At 15.8 Ma, about 80 km3 of metaluminous to mildly peralkaline high-K rhyolite ash flows were erupted from vents in the western part of fhe field in three closely spaced pulses, resulting in the formation of a trap door caldera 10 km in diameter. The ash flows formed the Wild Horse Mesa Tuff, a compositionally zoned ash flow sheet that originally covered an area of about 600 km2 to a maximum thickness of at least 320 m. High-K trachyte pumice lapilli, some of which are intimately banded with rhyolite, were produced late in the two later eruptions, Intracaldera volcanism from widely distributed vents rapidly filled the caldera with about 10 km3 of high-K, mildly peralkaline, high-silica rhyolite lava flows and pyroclastic deposits. These are interlayered with breccia derived from the caldera scarp. They are intruded by numerous compositionally similar plugs, some of which structurally uplifted and fractured the center of the caldera. The center evolved above a high-K trachyte magma chamber about 10 km in diameter that had developed and differentiated within the upper crust at about 15.8 Ma. Petrological, geochemical, and geophysical data are consistent with the idea that a cap of peralkaline rhyolite magma formed within the trachyte chamber as a result

Titan2D simulations of dome-collapse pyroclastic flows for crisis assessments on Montserrat

Science.gov (United States)

Widiwijayanti, C.; Voight, B.; Hidayat, D.; Patra, A.; Pitman, E.

2010-12-01

The Soufriere Hills Volcano (SHV), Montserrat, has experienced numerous episodes of lava dome collapses since 1995. Collapse volumes range from small rockfalls to major dome collapses (as much as ~200 M m3). Problems arise in hazards mitigation, particularly in zoning for populated areas. Determining the likely extent of flowage deposits in various scenarios is important for hazards zonation, provision of advice by scientists, and decision making by public officials. Towards resolution of this issue we have tested the TITAN2D code, calibrated parameters for an SHV database, and using updated topography have provided flowage maps for various scenarios and volume classes from SHV, for use in hazards assessments. TITAN2D is a map plane (depth averaged) simulator of granular flow and yields mass distributions over a DEM. Two Coulomb frictional parameters (basal and internal frictions) and initial source conditions (volume, source location, and source geometry) of single or multiple pulses in a dome-collapse type event control behavior of the flow. Flow kinematics are captured, so that the dynamics of flow can be examined spatially from frame to frame, or as a movie. Our hazard maps include not only the final deposit, but also areas inundated by moving debris prior to deposition. Simulations from TITAN2D were important for analysis of crises in the period 2007-2010. They showed that any very large mass released on the north slope would be strongly partitioned by local topography, and thus it was doubtful that flows of very large size (>20 M m3) could be generated in the Belham River drainage. This partitioning effect limited runout toward populated areas. These effects were interpreted to greatly reduce the down-valley risk of ash-cloud surges.

Lateral blasts at Mount St. Helens and hazard zonation

Science.gov (United States)

Crandell, D.R.; Hoblitt, R.P.

1986-01-01

Lateral blasts at andesitic and dacitic volcanoes can produce a variety of direct hazards, including ballistic projectiles which can be thrown to distances of at least 10 km and pyroclastic density flows which can travel at high speed to distances of more than 30 km. Indirect effect that may accompany such explosions include wind-borne ash, pyroclastic flows formed by the remobilization of rock debris thrown onto sloping ground, and lahars. Two lateral blasts occurred at a lava dome on the north flank of Mount St. Helens about 1200 years ago; the more energetic of these threw rock debris northeastward across a sector of about 30?? to a distance of at least 10 km. The ballistic debris fell onto an area estimated to be 50 km2, and wind-transported ash and lapilli derived from the lateral-blast cloud fell on an additional lobate area of at least 200 km2. In contrast, the vastly larger lateral blast of May 18, 1980, created a devastating pyroclastic density flow that covered a sector of as much as 180??, reached a maximum distance of 28 km, and within a few minutes directly affected an area of about 550 km2. The May 18 lateral blast resulted from the sudden, landslide-induced depressurization of a dacite cryptodome and the hydrothermal system that surrounded it within the volcano. We propose that lateral-blast hazard assessments for lava domes include an adjoining hazard zone with a radius of at least 10 km. Although a lateral blast can occur on any side of a dome, the sector directly affected by any one blast probably will be less than 180??. Nevertheless, a circular hazard zone centered on the dome is suggested because of the difficulty of predicting the direction of a lateral blast. For the purpose of long-term land-use planning, a hazard assessment for lateral blasts caused by explosions of magma bodies or pressurized hydrothermal systems within a symmetrical volcano could designate a circular potential hazard area with a radius of 35 km centered on the volcano

The Active Lava Flows of Kilauea Volcano, Hawaii

Indian Academy of Sciences (India)

'lahar' is from Indonesia, a country with some of the most active and destructive volcanoes .... tourist-dependent businesses such as airlines, rental car compa- nies, and hotels. ... excellent viewing conditions and photo opportunities. The heat.

Social and environmental impact of volcaniclastic flows related to 472 AD eruption at Vesuvius from stratigraphic and geoarcheological data

Science.gov (United States)

Di Vito, Mauro A.; de Vita, Sandro; Rucco, Ilaria; Bini, Monica; Zanchetta, Giovanni; Aurino, Paola; Cesarano, Mario; Ebanista, Carlo; Rosi, Mauro; Ricciardi, Giovanni

2017-04-01

There is a growing number of evidences in the surrounding plain of Somma-Vesuvius volcano which indicate that along with primary volcanic processes (i.e. fallout, pyroclastic density currents) the syn-eruptive and post-eruptive volcaniclastic remobilization has severely impacted the ancient civilizations, which flourished in the area. This represents an important starting point for understanding the future hazard related to a potential (and not remote) renewal of volcanic activity of the Campaniana volcanoes. We present geoarcheological and stratigraphic data obtained from the analysis of more than 160 sections in the Campanian plain showing the widespread impact of volcaniclastic debris flows and floods originated from the rapid remobilization of the products of the AD 472 eruption of Somma-Vesuvius, both on the environment and on the human landscape. This eruption was one of the two sub-Plinian historical events of Somma Vesuvius. This event largely impacted the northern and eastern territory surrounding the volcano with deposition of a complex sequence of pyroclastic-fallout and -current deposits. These sequences were variably affected by syn- and post-eruptive mobilization both along the Somma-Vesuvius slopes and the Apennine valleys with the emplacement of thick mud- and debris-flows which strongly modified the preexisting paleogeography of the Plain with irretrievable damages to the agricultural and urban landscape. The multidisciplinary approach to the study of the sequences permitted to reconstruct the palaeoenvironment before the eruption and the timing of the emplacement of both pyroclastic and volcanoclastic deposits. The preexisting landscape was characterized by intense human occupation, although showing strong evidences of degradation and abandonment due to the progressive decline of the Roman Empire. The impact of volcaniclastic flows continued for decades after the eruption as highlighted in the studied sequences by stratigraphic and archaeologic

A revised Lithostratigraphic Framework for the Southern Yucca Mountain Area, Nye County, Nevada

International Nuclear Information System (INIS)

R.W. Spengler; F.M. Byers; R.P. Dickerson

2006-01-01

An informal, revised lithostratigraphic framework for the southern Yucca Mountain area, Nevada has been developed to accommodate new information derived from subsurface investigations of the Nye County Early Warning Drilling Program. Lithologies penetrated by recently drilled boreholes at locations between Stagecoach Road and Highway 95 in southern Nye County include Quaternary and Pliocene alluvium and alluvial breccia, Miocene pyroclastic flow deposits and intercalated lacustrine siltstone and claystone sequences, early Miocene to Oligocene pre-volcanic sedimentary rocks, and Paleozoic strata. Of the 37 boreholes currently drilled, 21 boreholes have sufficient depth, spatial distribution, or traceable pyroclastic flow, pyroclastic fall, and reworked tuff deposits to aid in the lateral correlation of lithostrata. Medial and distal parts of regional pyroclastic flow deposits of Miocene age can be correlated with the Timber Mountain, Paintbrush, Crater Flat, and Tram Ridge Groups. Rocks intercalated between these regional pyroclastic flow deposits are substantially thicker than in the central part of Yucca Mountain, particularly near the downthrown side of major faults and along the southern extent of exposures at Yucca Mountain

Paleoseismic and Paleogeographic Reconstruction of the Central Coastal of Ecuador: Insights from Quaternary Geological Data for the Jaramijó bay area

Science.gov (United States)

Chunga, K.; Maurizio, M.; Garces, D.; Quiñonez, M. F.; Peña, G. E.

2015-12-01

Late Holocene sequences of loose to weakly consolidated sand and clay sediments intercalated with volcanic-ash layers (particles transported by fall-out), are outcrops on a sea cliff in the Jaramijó bay area (situated 7 km away in the East direction from Manta city, Manabí, at the middle section of Ecuador's Pacific coastline). The main geomorphologic feature in the site is the wave-cut beach platform permanently exposed at the lowest tides and an 18 m-high coastal cliff retreat with an estimated rate of ca. 2.5 meter/year (Chunga, 2014). One of the most remarkable geoarchaeological evidences found in this outcrop, it is the remains of two large bones (ie., radius and radial) of the human forearm of ca. 800 years ago (with archaeological vestiges of the Manteña culture) covered by a 8 to 25 cm-thick volcanic ash layer, stratigraphically at the top, an erosive contact with chaotic deposition of medium to fine-grained sand which indicates a potential tsunami deposit. Moreover, several volcanic ash and lahar layers are well distinguished on the sea cliff, which are associated with pyroclastic products transported as lahars from the Quilotoa and Cotopaxi, Pululahua volcanic structures (northern Andes in Ecuador) situated at a distance between of 150-190 kilometers (Mothes and Hall, 2008; Usselman, 2006). It is not excluded that previous pre-Columbian cultures also have been displaced in the last 2,000 years by disastrous geological events such as subduction earthquakes, local tsunami and volcanic lahar-ash deposits. All of these stratigraphic and palaeoseismologic features will allow us to understand the catastrophic geological events that abruptly shaped the landscape, furthermore, to investigate the changes of moderate to high Late Holocene progradation rates of the Jaramijó bay coastline.

An Integrative Approach for Defining Plinian and Sub-Plinian Eruptive Scenarios at Andesitic Volcanoes: Event-Lithostratigraphy, Eruptive Parameters and Pyroclast Textural Variations of the Largest Late-Holocene Eruptions of Mt. Taranaki, New Zealand.

Science.gov (United States)

Torres-Orozco, R.; Cronin, S. J.; Damaschke, M.; Kosik, S.; Pardo, N.

2016-12-01

Three eruptive scenarios were determined based on the event-lithostratigraphic reconstruction of the largest late-Holocene eruptions of the andesitic Mt. Taranaki, New Zealand: a) sustained dome-effusion followed by sudden stepwise collapse and unroofing of gas-rich magma; b) repeated plug and burst events generated by transient open-/closed-vent conditions; and c) open-vent conditions of more mafic magmas erupting from a satellite vent. Pyroclastic density currents (PDCs) are the most frequent outcome in every scenario. They can be produced in any/every eruption phase by formation and either repetitive-partial or total gravity-driven collapse of lava domes in the summit crater (block-and-ash flows), frequently followed by sudden magma decompression and violent, highly unsteady to quasi-steady lateral expansion (blast-like PDCs); by collapse or single-pulse fall-back of unsteady eruption columns (pyroclastic flow- and surge-type currents); or during highly unsteady and explosive hydromagmatic phases (wet surges). Fall deposits are produced during the climatic phase of each eruptive scenario by the emplacement of (i) high, sustained and steady, (ii) sustained and height-oscillating, (iii) quasi-steady and pulsating, or (iv) unsteady and totally collapsing eruption columns. Volumes, column heights and mass- and volume-eruption rates indicate that these scenarios correspond to VEI 4-5 plinian and sub-plinian multi-phase and style-shifting episodes, similar or larger than the most recent 1655 AD activity, and comparable to plinian eruptions of e.g. Apoyeque, Colima, Merapi and Tarawera volcanoes. Whole-rock chemistry, textural reconstructions and density-porosity determinations suggest that the different eruptive scenarios are mainly driven by variations in the density structure of magma in the upper conduit. Assuming a simple single conduit model, the style transitions can be explained by differing proportions of alternating gas-poor/degassed and gas-rich magma.

Flow-type landslides magnitude evaluation: the case study of the Campania Region (Southern Italy)

Science.gov (United States)

Santo, Antonio; De Falco, Melania; Di Crescenzo, Giuseppe

2015-04-01

In the last years studies concerning the triggering and the run-out susceptibility for different kind of landslides have become more and more precise. In the most of the cases the methodological approach involve the production of detailed thematic maps (at least 1:5000 scale) which represent a very useful tool for territorial planning, especially in urbanized areas. More recently these researches were accompanied by the growth of other studies dealing with landslide magnitude evaluation (especially in terms of volume and velocity estimate). In this paper the results of a flow-type landslides magnitude evaluation are presented. The study area is located in Southern Italy and is very wide (1,500 square kilometres) including all the Campania region. In this context flow type landslides represent the most frequent instabilities as shown by the large number of victims and the huge economic damage caused in the last few centuries. These shallow landslides involve thin cohesionless, unsaturated pyroclastic soils found over steep slopes around Somma-Vesuvio and Phlegrean district, affecting a wide area where over 100 towns are located. Since the potential volume of flow-type landslides is a measure of event magnitude we propose to estimate the potential volume at the scale of slope or basin for about 90 municipalities affecting 850 hierarchized drainage basins and 900 regular slopes. An empirical approach recently proposed in literature (De Falco et al., 2012), allows to estimate the volume of the pyroclastic cover that can be displaced along the slope. The method derives from the interpretation of numerous geological and geomorphological data gathered from a vast amount of case histories on landslides in volcanic and carbonatic contexts and it is based on determining the thickness of the pyroclastic cover and the width of the detachment and erosion-transport zone. Thickness can be evaluated with a good degree of approximation since, in these landslides, the failure

A closer look at the pyroclastic density current deposits of the May 18, 1980 eruption of Mt St Helens

Science.gov (United States)

Mackaman-Lofland, C. A.; Brand, B. D.; Dufek, J.

2010-12-01

Pyroclastic Density Currents (PDCs) are the most dangerous hazard associated with explosive volcanic eruptions. Due to the danger associated with observing these ground-hugging currents of searing hot gas, ash, and rock in real time, their processes are poorly understood. In order to understand flow dynamics, including what controls how far PDCs travel and how they interact with topography, it is necessary to study their deposits. The May 18th, 1980 eruption of Mt. St. Helens produced multiple PDCs, burying the area north of the volcano under 10s of meters of PDC deposits. Because the eruption is one of the best observed on record, individual flow units can be correlated to changes in eruptive intensity throughout the day (e.g., Criswell, 1987). Deep drainage erosion over the past 30 years has exposed the three-dimensional structure of the PDC deposits, making this intensive study possible. Up to six flow units have been identified along the large western drainage of the pumice plain. Each flow unit has intricate vertical and lateral facies changes and complex cross-cutting relationships away from source. The most proximal PDC deposits associated with the afternoon flows on May 18 are exposed 4 km from source in tributaries of the large drainage on the western side of the pumice plain. Hummocks from the debris avalanche are also exposed above and within these proximal drainages. It is apparent that the PDCs were often erosional, entraining large blocks from the hummocks and depositing them in close proximity downstream. The currents were also depositional, as thick sequences of PDC deposits are found in areas between hummocks, which thin to veneers above them. This indicates that the currents were interacting with complex topography early in their propagation, and is reflected by spatially variable bed conditions including rapid changes in bedding and granulometry characteristics within individual flow units. For example, within 20 lateral meters of a given flow

Topographic controls on pyroclastic density current dynamics: Insight from 18 May 1980 deposits at Mount St. Helens, Washington (USA)

Science.gov (United States)

Brand, Brittany D.; Bendaña, Sylvana; Self, Stephen; Pollock, Nicholas

2016-07-01

Our ability to interpret the deposits of pyroclastic density currents (PDCs) is critical for understanding the transport and depositional processes that control PDC dynamics. This paper focuses on the influence of slope on flow dynamics and criticality as recorded in PDC deposits from the 18 May 1980 eruption of Mt. St. Helens (USA). PDC deposits are found along the steep flanks (10°-30°) and across the pumice plain ( 5°) up to 8 km north of the volcano. Granulometry, componentry and descriptions of depositional characteristics (e.g., bedform morphology) are recorded with distance from source. The pumice plain deposits are primarily thick (3-12 m), massive and poorly-sorted, and represent deposition from a series of concentrated PDCs. By contrast, the steep flank deposits are stratified to cross-stratified, suggesting deposition from PDCs where turbulence strongly influenced transport and depositional processes. We propose that acceleration of the concentrated PDCs along the steep flanks resulted in thinning of the concentrated, basal region of the current(s). Enhanced entrainment of ambient air, and autofluidization from upward fluxes of air from substrate interstices and plunging breakers across rugged, irregular topography further inflated the currents to the point that the overriding turbulent region strongly influenced transport and depositional mechanisms. Acceleration in combination with partial confinement in slot canyons and high surface roughness would also increase basal shear stress, further promoting shear and traction transport in the basal region of the current. Conditions along the steep flank resulted in supercritical flow, as recorded by regressive bedforms, which gradually transitioned to subcritical flow downstream as the concentrated basal region thickness increased as a function of decreasing slope and flow energy. We also find that (1) PDCs were erosive into the underlying granular substrate along high slopes (> 25°) where currents were

Update of the volcanic risk map of Colima volcano, Mexico

Science.gov (United States)

Suarez-Plascencia, C.; Nuñez Cornu, F. J.; Marquez-Azua, B.

2010-12-01

The Colima volcano, located in western Mexico (19° 30.696 N, 103° 37.026 W) began its current eruptive process in February 10, 1999. This event was the basis for the development of two volcanic hazard maps: one for ballistics (rock fall) lahars, and another one for ash fall. During the period of 2003 to 2008 this volcano has had an intense effusive-explosive activity, similar to the one that took place during the period of 1890 through 1900. Intense pre-Plinian eruption in January 20, 1913, generated little economic losses in the lower parts of the volcano thanks to the low population density and low socio-economic activities at the time The current volcanic activity has triggered ballistic projections, pyroclastic and ash flows, and lahars, all have exceeded the maps limits established in 1999. Vulnerable elements within these areas have gradually changed due to the expansion of the agricultural frontier on the east and southeast sides of the Colima volcano. On the slopes of the northwest side, new blue agave Tequilana weber and avocado orchard crops have emerged along with important production of greenhouse tomato, alfalfa and fruit (citrus) crops that will eventually be processed and dried for exportation to the United States and Europe. Also, in addition to the above, large expanses of corn and sugar cane have been planted on the slopes of the volcano since the nineteenth century. The increased agricultural activity has had a direct impact in the reduction of the available forest land area. Coinciding with this increased activity, the 0.8% growth population during the period of 2000 - 2005, - due to the construction of the Guadalajara-Colima highway-, also increased this impact. The growth in vulnerability changed the level of risk with respect to the one identified in the year 1999 (Suarez, 2000), thus motivating us to perform an update to the risk map at 1:25,000 using vector models of the INEGI, SPOT images of different dates, and fieldwork done in order

Volcanism and associated hazards: the Andean perspective

Science.gov (United States)

Tilling, R. I.

2009-12-01

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 (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 hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant

Mud Flow - Slow and Fast

Science.gov (United States)

Mei, C. C.; Liu, K.-F.; Yuhi, M.

Heavy and persistent rainfalls in mountainous areas can loosen the hillslope and induce mud flows which can move stones, boulders and even trees, with destructive power on their path. In China where 70% of the land surface is covered by mountains, debris flows due to landslides or rainfalls affect over 18.6% of the nation. Over 10,000 debris flow ravines have been identified; hundreds of lives are lost every year [1]. While accurate assessment is still pending, mud flows caused by Hurr icane Mitch in 1998 have incurred devastating floods in Central America. In Honduras alone more than 6000 people perished. Half of the nation's infrastructures were damaged. Mud flows can also be the result of volcanic eruption. Near the volcano, lava and pyroclastic flows dominate. Further downstream solid particles become smaller and can mix with river or lake water, rainfall, melting snow or ice, or eroded soil, resulting in hyperconcentrated mud mixed with rocks. The muddy debris can travel at high speeds over tens of miles down the hill slopes and devastate entire communities. In 1985 the catastrophic eruption of Nevado del Ruiz in Colombia resulted in mud flows which took the life of 23,000 inhabitants in the town of Amero [2]. During the eruption of Mt. Pinatubo in Phillipnes in 1991, one cubic mile of volcanic ash and rock fragments fell on the mountain slopes. Seasonal rain in the following months washed down much of the loose deposits, causing damage to 100,000 villages. These catastrophes have been vividly recorded in the film documentary by Lyons [3].

Hydraulics of subaqueous ash flows as deduced from their deposits

Science.gov (United States)

Doronzo, Domenico M.; Dellino, Pierfrancesco

2012-09-01

Subaqueous ash flows are gravity currents consisting of a mixture of sea water and ash particles. Also called volcaniclastic turbidity currents (VTCs), they can be generated because of remobilization of pyroclastic fall deposits, which are emplaced into the sea around a volcanic island, as well as far away, during an explosive eruption. The VTC upper part is the turbulent transport system for the flow, whereas the viscous basal one is the depositional system. Typical sequences of VTC deposits are characterized by cross-laminations, planar and convolute laminations, and massive beds, which reflect the stratified nature of the flow. Here, the analysis of some VTC hydraulic parameters is presented in order to depict flow behavior and sedimentation during deposition. A reverse engineering approach is proposed, which consists of calculating hydraulic parameters by starting from deposit features. The calculated values show that a VTC is homogeneously-turbulent for most of the thickness, but is viscous at its base. First, cross-laminations are directly acquired over the rough pre-existing seafloor, then planar or convolute laminations aggrade over the newly formed substrate. Finally, fine-grained suspended particles gently settle and cap the flow deposit.

Hydrological modelling of a slope covered with shallow pyroclastic deposits from field monitoring data

Directory of Open Access Journals (Sweden)

R. Greco

2013-10-01

Full Text Available A one-dimensional hydrological model of a slope covered with pyroclastic materials is proposed. The soil cover is constituted by layers of loose volcanic ashes and pumices, with a total thickness between 1.8 m and 2.5 m, lying upon a fractured limestone bedrock. The mean inclination of the slope is around 40°, slightly larger than the friction angle of the ashes. Thus, the equilibrium of the slope, significantly affected by the cohesive contribution exerted by soil suction in unsaturated conditions, may be altered by rainfall infiltration. The model assumes a single homogeneous soil layer occupying the entire depth of the cover, and takes into account seasonally variable canopy interception of precipitation and root water uptake by vegetation, mainly constituted by deciduous chestnut woods with a dense underbrush growing during late spring and summer. The bottom boundary condition links water potential at the soil–bedrock interface with the fluctuations of the water table of the aquifer located in the fractured limestone, which is conceptually modelled as a linear reservoir. Most of the model parameters have been assigned according to literature indications or from experimental data. Soil suction and water content data measured between 1 January 2011 and 20 July 2011 at a monitoring station installed along the slope allowed the remaining parameters to be identified. The calibrated model, which reproduced very closely the data of the calibration set, has been applied to the simulation of the hydrological response of the slope to the hourly precipitation record of 1999, when a large flow-like landslide was triggered close to the monitored location. The simulation results show that the lowest soil suction ever attained occurred just at the time the landslide was triggered, indicating that the model is capable of predicting slope failure conditions.

The Summer 1997 Eruption at Pillan Patera on Io: Implications for Ultrabasic Lava Flow Emplacement

Science.gov (United States)

Williams, David A.; Davies, Ashley G.; Keszthelyi, Laszlo P.; Greeley, Ronald

2001-01-01

Galileo data and numerical modeling were used to investigate the summer 1977 eruption at Pillan Patera on Io. This event, now defined as "Pillanian" eruption style, included a high-temperature (greater than 1600 C), possible ultrabasic , 140-km-high plume eruption that deposited dark, orthopyroxene-rich pyroclastic material over greater than 125,000 sq km, followed by emplacement of dark flow-like material over greater than 3100 sq km to the north of the caldera. We estimate that the high-temperature, energetic episode of this eruption had a duration of 52 - 167 days between May and September 1997, with peak eruption temperatures around June 28, 1997. Galileo 20 m/pixel images of part of the Pillan flow field show a wide-spread, rough, pitted surface that is unlike any flow surface we have seen before. We suggest that this surface may have resulted from: 1. A fractured lava crust formed during rapid, low-viscosity lava surging, perhaps including turbulent flow emplacement. 2. Disruption of the lava flow by explosive interaction with a volatile-rich substrate. or 3. A combination of 1 and 2 with or without accumulation of pyroclastic material on the surface. Well-developed flow lobes are observed, suggesting that this is a relatively distant part of the flow field.Shadow measurements at flow margins indicate a thickness of-8 - 10 m. We have modeled the emplacement of putative ultrabasic flow from the summer 1997 Pillan eruption using constraints from new Galileo data. Results suggest that either laminar sheet flows or turbulent channelized flows could have traveled 50 - 150 km on a flat, unobstructed surface, which is consistent with the estimated length of the Pillan flow field (approx. 60 km). Our modeling suggests low thermal erosion rates (less than 4.1 m/d), and that the formation of deep (greater than 20 m) erosion channels was unlikely, especially distal to the source. We calculate a volumetric flow rate of approx. 2 - 7 x 10(exp 3)cu m/s, which is greater

Hazard maps of Colima volcano, Mexico

Science.gov (United States)

Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Escudero Ayala, C. R.

2011-12-01

(rockfall) and pyroclastic flows, b) Hazard map of lahars and debris flow, and c) Hazard map of ash-fall. The cartographic and database information obtained will be the basis for updating the Operational Plan of the Colima Volcano by the State Civil & Fire Protection Unit of Jalisco, Mexico, and the urban development plans of surrounding municipalities, in order to reduce their vulnerability to the hazards of the volcanic activity.

Local to global: a collaborative approach to volcanic risk assessment

Science.gov (United States)

Calder, Eliza; Loughlin, Sue; Barsotti, Sara; Bonadonna, Costanza; Jenkins, Susanna

2017-04-01

Volcanic risk assessments at all scales present challenges related to the multitude of volcanic hazards, data gaps (hazards and vulnerability in particular), model representation and resources. Volcanic hazards include lahars, pyroclastic density currents, lava flows, tephra fall, ballistics, gas dispersal and also earthquakes, debris avalanches, tsunamis and more ... they can occur in different combinations and interact in different ways throughout the unrest, eruption and post-eruption period. Volcanoes and volcanic hazards also interact with other natural hazards (e.g. intense rainfall). Currently many hazards assessments consider the hazards from a single volcano but at national to regional scales the potential impacts of multiple volcanoes over time become important. The hazards that have the greatest tendency to affect large areas up to global scale are those transported in the atmosphere: volcanic particles and gases. Volcanic ash dispersal has the greatest potential to directly or indirectly affect the largest number of people worldwide, it is currently the only volcanic hazard for which a global assessment exists. The quantitative framework used (primarily at a regional scale) considers the hazard at a given location from any volcano. Flow hazards such as lahars and floods can have devastating impacts tens of kilometres from a source volcano and lahars can be devastating decades after an eruption has ended. Quantitative assessment of impacts is increasingly undertaken after eruptions to identify thresholds for damage and reduced functionality. Some hazards such as lava flows could be considered binary (totally destructive) but others (e.g. ash fall) have varying degrees of impact. Such assessments are needed to enhance available impact and vulnerability data. Currently, most studies focus on physical vulnerability but there is a growing emphasis on social vulnerability showing that it is highly variable and dynamic with pre-eruption socio

Human survival in volcanic eruptions: Thermal injuries in pyroclastic surges, their causes, prognosis and emergency management.

Science.gov (United States)

Baxter, Peter J; Jenkins, Susanna; Seswandhana, Rosadi; Komorowski, Jean-Christophe; Dunn, Ken; Purser, David; Voight, Barry; Shelley, Ian

2017-08-01

This study of burns patients from two eruptions of Merapi volcano, Java, in 1994 and 2010, is the first detailed analysis to be reported of thermal injuries in a large series of hospitalised victims of pyroclastic surges, one of the most devastating phenomena in explosive eruptions. Emergency planners in volcanic crises in populated areas have to integrate the health sector into disaster management and be aware of the nature of the surge impacts and the types of burns victims to be expected in a worst scenario, potentially in numbers and in severity that would overwhelm normal treatment facilities. In our series, 106 patients from the two eruptions were treated in the same major hospital in Yogyakarta and a third of these survived. Seventy-eight per cent were admitted with over 40% TBSA (total body surface area) burns and around 80% of patients were suspected of having at least some degree of inhalation injury as well. Thirty five patients suffered over 80% TBSA burns and only one of these survived. Crucially, 45% of patients were in the 40-79% TBSA range, with most suspected of suffering from inhalation injury, for whom survival was most dependent on the hospital treatment they received. After reviewing the evidence from recent major eruptions and outlining the thermal hazards of surges, we relate the type and severity of the injuries of these patients to the temperatures and dynamics of the pyroclastic surges, as derived from the environmental impacts and associated eruption processes evaluated in our field surveys and interviews conducted by our multi-disciplinary team. Effective warnings, adequate evacuation measures, and political will are all essential in volcanic crises in populated areas to prevent future catastrophes on this scale. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

Comparing Pyroclastic Density Current (PDC) deposits at Colima (Mexico) and Tungurahua (Ecuador) volcanoes

Science.gov (United States)

Goldstein, Fabian; Varley, Nick; Bustillos, Jorge; Kueppers, Ulrich; Lavallee, Yan; Dingwell, Donald B.

2010-05-01

Sudden transitions from effusive to explosive eruptive behaviour have been observed at several volcanoes. As a result of explosive activity, pyroclastic density currents represent a major threat to life and infrastructure, mostly due to their unpredictability, mass, and velocity. Difficulties in direct observation force us to deduce crucial information from their deposits. Here, we present data from field work performed in 2009 on primary deposits from recent explosive episodes at Volcán de Colima (Mexico) and Tungurahua (Ecuador). Volcán de Colima, located 40km away from the Capital city Colima with 300,000 inhabitants, has been active since 1999. Activity has been primarily characterized by the slow effusion of lava dome with the daily occurrence of episodic gas (and sometimes ash) explosion events. During a period of peak activity in 2005, explosive eruptions repeatedly destroyed the dome and column collapse resulted in several PDCs that travelled down the W, S, and SE flanks. Tungurahua looms over the 20,000 inhabitants of the city of Baños, located 5km away, and is considered one of the most active volcanoes in Ecuador. The most recent eruptive cycle began in 1999 and climaxed in July and August of 2006 with the eruptions of several PDCs that traveled down the western flanks, controlled by the hydrological network. During two field campaigns, we collected an extensive data set of porosity and grain size distribution on PDCs at both volcanoes. The deposits have been mapped in detail and the porosity distribution of clasts across the surface of the deposits has been measured at more than 30 sites (> 3.000 samples). Our porosity distribution data (mean porosity values range between 17 and 24%) suggests an influence of run out distance and lateral position. Preliminary results of grain size analysis of ash and lapilli (structures such as dunes, grain size distribution, and the observed damage to vegetation help depict the progression of the flow and its

Reconstruction of Ancestral Hydrothermal Systems on Mount Rainier Using Hydrothermally Altered Rocks in Holocene Debris Flows and Tephras

Science.gov (United States)

John, D. A.; Breit, G. N.; Sisson, T. W.; Vallance, J. W.; Rye, R. O.

2005-12-01

Mount Rainier is the result of episodic stages of edifice growth during periods of high eruptive activity and edifice destruction during periods of relative magmatic quiescence over the past 500 kyr. Edifice destruction occurred both by slow erosion and by catastrophic collapses, some of which were strongly influenced by hydrothermal alteration. Several large-volume Holocene debris-flow deposits contain abundant clasts of hydrothermally altered rocks, most notably the 4-km3 clay-rich Osceola Mudflow which formed by collapse of the northeast side and upper 1000+ m of the edifice about 5600 ya and flowed >120 km downstream into Puget Sound. Mineral assemblages and stable isotope data of hydrothermal alteration products in Holocene debris-flow deposits indicate formation in distinct hydrothermal environments, including magmatic-hydrothermal, steam-heated (including a large fumarolic component), magmatic steam (including a possible fumarolic component), and supergene. The Osceola Mudflow and phreatic components of coeval tephras contain the highest-temperature and inferred most deeply formed alteration minerals; assemblages include magmatic-hydrothermal quartz-alunite, quartz-topaz, quartz-pyrophyllite and quartz-illite (all +pyrite), in addition to steam-heated opal-alunite-kaolinite and abundant smectite-pyrite. In contrast, the Paradise lahar, which formed by a collapse of the surficial upper south side of the edifice, contains only steam-heated assemblages including those formed largely above the water table from condensation of fumarolic vapor (opal-alunite-jarosite). Younger debris-flow deposits on the west side of the volcano (Round Pass lahar and Electron Mudflow) contain only smectite-pyrite alteration, whereas an early 20th century rock avalanche on Tahoma Glacier also contains magmatic-hydrothermal alteration that is exposed in the avalanche headwall of Sunset Amphitheater. Mineralogy and isotopic composition of the alteration phases, geologic and

The impacts of pyroclastic surges on buildings at the eruption of the Soufrière Hills volcano, Montserrat

Science.gov (United States)

Baxter, Peter J.; Boyle, Robin; Cole, Paul; Neri, Augusto; Spence, Robin; Zuccaro, Giulio

2005-04-01

We investigated the impacts on buildings of three pyroclastic surges that struck three separate villages on 25 June, 21 September and 26 December, 1997, during the course of the andesitic dome building eruption of the Soufrière Hills Volcano, Montserrat, which began on 18 July, 1995. A detailed analysis of the building damage of the 26 December event was used to compare the findings on the flow and behaviour of dilute pyroclastic density currents (PDCs) with the classical reports of PDCs from historical eruptions of similar size. The main characteristics of the PDC, as inferred from the building damage, were the lateral loading and directionality of the current; the impacts corresponded to the dynamic pressure of the PDC, with a relatively slow rate of rise and without the peak overpressure or a shock front associated with explosive blast; and the entrainment of missiles and ground materials which greatly added to the destructiveness of the PDC. The high temperature of the ash, causing the rapid ignition of furniture and other combustibles, was a major cause of damage even where the dynamic pressure was low at the periphery of the current. The vulnerability of buildings lay in the openings, mainly windows, which allowed the current to enter the building envelope, and in the flammable contents, as well as the lack of resistance to the intense heat and dynamic pressure of some types of vernacular building construction, such as wooden chattel houses, rubble masonry walls and galvanised steel-sheet roofs. Marked variability in the level of damage due to dynamic pressure (in a range 1-5 kPa, or more) was evident throughout most of the impact area, except for the zone of total loss, and this was attributable to the effects of topography and sheltering, and projectiles, and probably localised variations in current velocity and density. A marked velocity gradient existed from the outer part to the central axis of the PDC, where buildings and vegetation were razed to the

Ice Thickness, Melting Rates and Styles of Activity in Ice-Volcano Interaction

Science.gov (United States)

Gudmundsson, M. T.

2005-12-01

In most cases when eruptions occur within glaciers they lead to rapid ice melting, jokulhlaups and/or lahars. Many parameters influence the style of activity and its impact on the environment. These include ice thickness (size of glacier), bedrock geometry, magma flow rate and magma composition. The eruptions that have been observed can roughly be divided into: (1) eruptions under several hundred meters thick ice on a relatively flat bedrock, (2) eruptions on flat or sloping bed through relatively thin ice, and (3) volcanism where effects are limitied to confinement of lava flows or melting of ice by pyroclastic flows or surges. This last category (ice-contact volcanism) need not cause much ice melting. Many of the deposits formed by Pleistocene volcanism in Iceland, British Columbia and Antarctica belong to the first category. An important difference between this type of activity and submarine activity (where pressure is hydrostatic) is that pressure at vents may in many cases be much lower than glaciostatic due to partial support of ice cover over vents by the surrounding glacier. Reduced pressure favours explosive activity. Thus the effusive/explosive transition may occur several hundred metres underneath the ice surface. Explosive fragmentation of magma leads to much higher rates of heat transfer than does effusive eruption of pillow lavas, and hence much higher melting rates. This effect of reduced pressure at vents will be less pronounced in a large ice sheet than in a smaller glacier or ice cap, since the hydraulic gradient that drives water away from an eruption site will be lower in the large glacier. This may have implications for form and type of eruption deposits and their relationship with ice thickness and glacier size.

Merging field mapping and modeling to interpret the lithofacies variations from unsteady ash-rich pyroclastic density currents on uneven topography

Science.gov (United States)

Doronzo, Domenico; Dellino, Pierfrancesco; Sulpizio, Roberto; Lucchi, Federico

2017-04-01

In order to obtain significant volcanological results from computer simulations of explosive eruptions, one either needs a systematic statistical approach to test a wide range of initial and boundary conditions, or needs using a well-constrained field case study. Here we followed the second approach, using data obtained from field mapping of the Grotta dei Palizzi 2 pyroclastic deposits (Vulcano Island, Italy) as input for numerical modeling. This case study deals with impulsive phreatomagmatic explosions that generated ash-rich pyroclastic density currents, interacting with the high topographic obstacle of the La Fossa Caldera rim. We demonstrate that by merging field data with 3D numerical simulation it is possible to highlight the details of the dynamical current-terrain interaction, and to interpret the lithofacies variations of the associated deposits as a function of topography-induced sedimentation rate. Results suggest that a value of the sedimentation rate lower than 5 kg/m2s at the bed load can still be sheared by the overlying current, producing tractional structures in the deposit. Instead, a sedimentation rate in excess of that threshold can preclude the formation of tractional structures, producing thick massive deposits. We think that the approach used in this study could be applied to other case studies to confirm or refine such threshold value of the sedimentation rate, which is to be considered as an upper value as for the limitations of the numerical model.

Fluid flow in disrupted porous media: Volcanological and radiological waste applications

Energy Technology Data Exchange (ETDEWEB)

Johnson, Peter Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-10-04

This presentation provides Technical defense supporting documents, with the following slides: (1) Introduction (2) Long boundary drainage as a source for lahars (submitted for review) (3) Development and implementation of a porosity-dependent capillary suction function in FEHM (4) Modeling in support of field testing high-level radioactive waste in salt (5) Conclusions.

Quantitative physical models of volcanic phenomena for hazards assessment of critical infrastructures

Science.gov (United States)

Costa, Antonio

2016-04-01

Volcanic hazards may have destructive effects on economy, transport, and natural environments at both local and regional scale. Hazardous phenomena include pyroclastic density currents, tephra fall, gas emissions, lava flows, debris flows and avalanches, and lahars. Volcanic hazards assessment is based on available information to characterize potential volcanic sources in the region of interest and to determine whether specific volcanic phenomena might reach a given site. Volcanic hazards assessment is focussed on estimating the distances that volcanic phenomena could travel from potential sources and their intensity at the considered site. Epistemic and aleatory uncertainties strongly affect the resulting hazards assessment. Within the context of critical infrastructures, volcanic eruptions are rare natural events that can create severe hazards. In addition to being rare events, evidence of many past volcanic eruptions is poorly preserved in the geologic record. The models used for describing the impact of volcanic phenomena generally represent a range of model complexities, from simplified physics based conceptual models to highly coupled thermo fluid dynamical approaches. Modelling approaches represent a hierarchy of complexity, which reflects increasing requirements for well characterized data in order to produce a broader range of output information. In selecting models for the hazard analysis related to a specific phenomenon, questions that need to be answered by the models must be carefully considered. Independently of the model, the final hazards assessment strongly depends on input derived from detailed volcanological investigations, such as mapping and stratigraphic correlations. For each phenomenon, an overview of currently available approaches for the evaluation of future hazards will be presented with the aim to provide a foundation for future work in developing an international consensus on volcanic hazards assessment methods.

Parametric analysis of lava dome-collapse events and pyroclastic deposits at Shiveluch volcano, Kamchatka, using visible and infrared satellite data

Science.gov (United States)

Krippner, Janine B.; Belousov, Alexander B.; Belousova, Marina G.; Ramsey, Michael S.

2018-04-01

For the years 2001 to 2013 of the ongoing eruption of Shiveluch volcano, a combination of different satellite remote sensing data are used to investigate the dome-collapse events and the resulting pyroclastic deposits. Shiveluch volcano in Kamchatka, Russia, is one of the world's most active dome-building volcanoes, which has produced some of the largest known historical block-and-ash flows (BAFs). Globally, quantitative data for deposits resulting from such large and long-lived dome-forming eruptions, especially like those at Shiveluch, are scarce. We use Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) thermal infrared (TIR), shortwave infrared (SWIR), and visible-near infrared (VNIR) data to analyze the dome-collapse scars and BAF deposits that were formed during eruptions and collapse events in 2001, 2004, 2005, 2007, 2009, 2010, and two events in 2013. These events produced flows with runout distances of as far as 19 km from the dome, and with aerial extents of as much as 22.3 km2. Over the 12 years of this period of investigation, there is no trend in deposit area or runout distances of the flows through time. However, two potentially predictive features are apparent in our data set: 1) the largest dome-collapse events occurred when the dome exceeded a relative height (from dome base to top) of 500 m; 2) collapses were preceded by thermal anomalies in six of the cases in which ASTER data were available, although the areal extent of these precursory thermal areas did not generally match the size of the collapse events as indicated by scar area (volumes are available for three collapse events). Linking the deposit distribution to the area, location, and temperature profiles of the dome-collapse scars provides a basis for determining similar future hazards at Shiveluch and at other dome-forming volcanoes. Because of these factors, we suggest that volcanic hazard analysis and mitigation at volcanoes with similar BAF emplacement behavior may

Quartzites beneath pyroclastic flows – mineralogical aspects

Czech Academy of Sciences Publication Activity Database

Malý, Karel; Cajz, Vladimír

2005-01-01

Roč. 37, č. 3 (2005), s. 370-371 ISSN 0369-2086 R&D Projects: GA AV ČR(CZ) IAA3013302 Institutional research plan: CEZ:AV0Z30130516 Keywords : quartzite * ignimbrite * mineralogy Subject RIV: DB - Geology ; Mineralogy

Geographic Information Systems and geomorphological mapping applied to landslide inventory and susceptibility mapping in El Estado river, Pico de Orizaba, Mexico

Directory of Open Access Journals (Sweden)

José Fernando Aceves Quesada

2016-11-01

-off switching of layers in the GIS system, a base map is created to assist in the digitizing of landslides and the modeling of susceptibility. A landslide inventory is created from aerial photographs, field investigations, and all the above GIS thematic layers. El Estado river watershed on the southwestern flank of Pico de Orizaba volcano has been selected as study area. The watershed is located in the southwestern slope of Citlaltepetl or Pico de Orizaba volcano. Geological (the stream channel of El Estado river erodes Tertiary and Quaternary lavas, disjointed volcanoclastic materials such as pyroclastic flows, fall deposits, lahars deposits, and alluvium and geomorphological factors (steep slopes, energy relief, and vertical erosion in combination with high seasonal rainfall (annual rainfall averages 1000-1100 mm/yr at > 4000 m a.s.l. and 927 mm/yr at <1500 m a.s.l., and the high degree of weathering, make the study area susceptible to landslides. To assess landslide susceptibility, a landslide inventory map and geomorphometric cartography (altimetry, slope and geomorphography were reviewed, and field work was conducted. In the study area, more than one hundred landslides were mapped. Shallow landslides (including debris slides and debris flows are the predominant type. Shallow landslides predominate on hills capped with ash and pyroclastic deposits. The second major landslide process includes rock falls (which occur where the stream erodes lava flows and lahars and deep-seated landslides (which occur in ash and pyroclastic deposits where lava flows act as a slip plane. In parallel, the spatial geodatabase of landslides was constructed from standardized GIS datasets. Pertinent attributes are recorded on a geo-dataset. These include 1 mass wasting process, 2 level of certainty of the observation, 3 photo identification date, 4 landslide size, 5 landslide activity, 6 landslide parts (head, evacuation zone, deposit, 7 slope shape, 8 field slope gradient, 9 map gradient measured

Eruptive history, current activity and risk estimation using geospatial information in the Colima volcano, Mexico

Science.gov (United States)

Suarez-Plascencia, C.; Camarena-Garcia, M.; Nunez-Cornu, F. J.; Flores-Peña, S.

2013-12-01

avocado orchards and fruits like blueberries, raspberries, and blackberries within the radius of 15 km from the crater. The population dynamics in the Colima volcano area had a population of 552,954 inhabitants in 2010, and a growth at an annual rate of 1.6 percent of the total population. 60 percent of the populations live in 105 towns with a population less than 250 inhabitants. Also, the region showed an increase in vulnerability for the development of economic activities, supported by the highway, railway, natural gas pipelines and electrical infrastructure that connect to the Port of Manzanillo to Guadalajara city. With the use of geospatial information quantify the vulnerability, together with the hazard maps and exposure, enabled us to build the following volcanic risk maps: a) Exclusion areas and moderate hazard for explosive events (ballistic) and pyroclastic flows, b) Hazard map of lahars and debris flow, and c) Hazard map of ash-fall. The geospatial database, a GIS mapping and current volcano monitoring, are the basis of the Operational Plan Colima Volcano. Civil Protection by the state of Jalisco and the updating of urban development plans of municipalities converge on the volcano. These instruments of land planning will help reduce volcanic risk in the region.

Using video games for volcanic hazard education and communication: an assessment of the method and preliminary results

Science.gov (United States)

Mani, Lara; Cole, Paul D.; Stewart, Iain

2016-07-01

This paper presents the findings from a study aimed at understanding whether video games (or serious games) can be effective in enhancing volcanic hazard education and communication. Using the eastern Caribbean island of St. Vincent, we have developed a video game - St. Vincent's Volcano - for use in existing volcano education and outreach sessions. Its twin aims are to improve residents' knowledge of potential future eruptive hazards (ash fall, pyroclastic flows and lahars) and to integrate traditional methods of education in a more interactive manner. Here, we discuss the process of game development including concept design through to the final implementation on St. Vincent. Preliminary results obtained from the final implementation (through pre- and post-test knowledge quizzes) for both student and adult participants provide indications that a video game of this style may be effective in improving a learner's knowledge. Both groups of participants demonstrated a post-test increase in their knowledge quiz score of 9.3 % for adults and 8.3 % for students and, when plotted as learning gains (Hake, 1998), show similar overall improvements (0.11 for adults and 0.09 for students). These preliminary findings may provide a sound foundation for the increased integration of emerging technologies within traditional education sessions. This paper also shares some of the challenges and lessons learnt throughout the development and testing processes and provides recommendations for researchers looking to pursue a similar study.

Geomorphic consequences of volcanic eruptions in Alaska: A review

Science.gov (United States)

Waythomas, Christopher F.

2015-01-01

Eruptions of Alaska volcanoes have significant and sometimes profound geomorphic consequences on surrounding landscapes and ecosystems. The effects of eruptions on the landscape can range from complete burial of surface vegetation and preexisting topography to subtle, short-term perturbations of geomorphic and ecological systems. In some cases, an eruption will allow for new landscapes to form in response to the accumulation and erosion of recently deposited volcaniclastic material. In other cases, the geomorphic response to a major eruptive event may set in motion a series of landscape changes that could take centuries to millennia to be realized. The effects of volcanic eruptions on the landscape and how these effects influence surface processes has not been a specific focus of most studies concerned with the physical volcanology of Alaska volcanoes. Thus, what is needed is a review of eruptive activity in Alaska in the context of how this activity influences the geomorphology of affected areas. To illustrate the relationship between geomorphology and volcanic activity in Alaska, several eruptions and their geomorphic impacts will be reviewed. These eruptions include the 1912 Novarupta–Katmai eruption, the 1989–1990 and 2009 eruptions of Redoubt volcano, the 2008 eruption of Kasatochi volcano, and the recent historical eruptions of Pavlof volcano. The geomorphic consequences of eruptive activity associated with these eruptions are described, and where possible, information about surface processes, rates of landscape change, and the temporal and spatial scale of impacts are discussed.A common feature of volcanoes in Alaska is their extensive cover of glacier ice, seasonal snow, or both. As a result, the generation of meltwater and a variety of sediment–water mass flows, including debris-flow lahars, hyperconcentrated-flow lahars, and sediment-laden water floods, are typical outcomes of most types of eruptive activity. Occasionally, such flows can be quite

Merging field mapping and numerical simulation to interpret the lithofacies variations from unsteady pyroclastic density currents on uneven terrain: The case of La Fossa di Vulcano (Aeolian Islands, Italy)

Science.gov (United States)

Doronzo, Domenico M.; Dellino, Pierfrancesco; Sulpizio, Roberto; Lucchi, Federico

2017-01-01

In order to obtain results from computer simulations of explosive volcanic eruptions, one either needs a statistical approach to test a wide range of initial and boundary conditions, or needs using a well-constrained field case study via stratigraphy. Here we followed the second approach, using data obtained from field mapping of the Grotta dei Palizzi 2 pyroclastic deposits (Vulcano Island, Italy) as input for numerical modeling. This case study deals with impulsive phreatomagmatic explosions of La Fossa Cone that generated ash-rich pyroclastic density currents, interacting with the topographic high of the La Fossa Caldera rim. One of the simplifications in dealing with well-sorted ash (one particle size in the model) is to highlight the topographic effects on the same pyroclastic material in an unsteady current. We demonstrate that by merging field data with 3D numerical simulation results it is possible to see key details of the dynamical current-terrain interaction, and to interpret the lithofacies variations of the associated deposits as a function of topography-induced sedimentation (settling) rate. Results suggest that a value of the sedimentation rate lower than 5 kg/m2 s at the bed load can still be sheared by the overlying current, producing tractional structures (laminae) in the deposits. Instead, a sedimentation rate higher than that threshold can preclude the formation of tractional structures, producing thicker massive deposits. We think that the approach used in this study could be applied to other case studies (both for active and ancient volcanoes) to confirm or refine such threshold value of the sedimentation rate, which is to be considered as an upper value as for the limitations of the numerical model.

Field-trip guide for exploring pyroclastic density current deposits from the May 18, 1980, eruption of Mount St. Helens, Washington

Science.gov (United States)

Brand, Brittany D.; Pollock, Nicholas; Sarocchi, Damiano; Dufek, Josef; Clynne, Michael A.

2017-07-05

Pyroclastic density currents (PDCs) are one of the most dangerous phenomena associated with explosive volcanism. To help constrain damage potential, a combination of field studies, laboratory experiments, and numerical modeling are used to establish conditions that influence PDC dynamics and depositional processes, including runout distance. The objective of this field trip is to explore field relations that may constrain PDCs at the time of emplacement.The PDC deposits from the May 18, 1980, eruption of Mount St. Helens are well exposed along the steep flanks (10–30° slopes) and across the pumice plain (5–12° slopes) as far as 8 km north of the volcano. The pumice plain deposits represent deposition from a series of concentrated PDCs and are primarily thick (3–12 m), massive, and poorly sorted. In contrast, the steep east-flank deposits are stratified to cross-stratified, suggesting deposition from PDCs where turbulence strongly influenced transport and depositional processes.The PDCs that descended the west flank were largely nondepositional; they maintained a higher flow energy and carrying capacity than PDCs funneled through the main breach, as evidenced by the higher concentration of large blocks in their deposits. The PDC from the west flank collided with PDCs funneled through the breach at various points along the pumice plain. Evidence for flow collision will be explored and debated throughout the field trip.Evidence for substrate erosion and entrainment is found (1) along the steep eastern flank of the volcano, which has a higher degree of rough, irregular topography relative to the west flanks where PDCs were likely nonerosive, (2) where PDCs encountered debris-avalanche hummocks across the pumice plain, and (3) where PDCs eroded and entrained material deposited by PDCs produced during earlier phases of the eruption. Two features interpreted as large-scale (tens of meters wide) levees and a large (~200 m wide) channel scour-and-fill feature

Validation and Analysis of SRTM and VCL Data Over Tropical Volcanoes

Science.gov (United States)

Mouginis-Mark, Peter J.

2004-01-01

The focus of our investigation was on the application of digital topographic data in conducting first-order volcanological and structural studies of tropical volcanoes, focusing on the Java, the Philippines and the Galapagos Islands. Kilauea volcano, Hawaii, served as our test site for SRTM data validation. Volcanoes in humid tropical environments are frequently cloud covered, typically densely vegetated and erode rapidly, so that it was expected that new insights into the styles of eruption of these volcanoes could be obtained from analysis of topographic data. For instance, in certain parts of the world, such as Indonesia, even the regional structural context of volcanic centers is poorly known, and the distribution of volcanic products (e.g., lava flows, pyroclastic flows, and lahars) are not well mapped. SRTM and Vegetation Canopy Lidar (VCL) data were expected to provide new information on these volcanoes. Due to the cancellation of the VCL mission, we did not conduct any lidar studies during the duration of this project. Digital elevation models (DEMs) such as those collected by SRTM provide quantitative information about the time-integrated typical activity on a volcano and allow an assessment of the spatial and temporal contributions of various constructional and destructional processes to each volcano's present morphology. For basaltic volcanoes, P_c?w!m-d and Garbed (2000) have shown that gradual slopes (less than 5 deg.) occur where lava and tephra pond within calderas or in the saddles between adjacent volcanoes, as well as where lava deltas coalesce to form coastal plains. Vent concentration zones (axes of rift zones) have slopes ranging from 10 deg. to 12 deg. Differential vertical growth rates between vent concentration zones and adjacent mostly-lava flanks produce steep constructional slopes up to 40". The steepest slopes (locally approaching 90 deg.) are produced by fluvial erosion, caldera collapse, faulting, and catastrophic avalanches, all of

DEBRIS FLOW DISASTER MITIGATION THROUGH COMMUNITY-BASED INTEGRATED SEDIMENT MANAGEMENT (BEST PRACTICE IN MT. MERAPI AREA, INDONESIA

Directory of Open Access Journals (Sweden)

Kazuhiko Otani

2015-02-01

Full Text Available Mt. Merapi is one of many active volcanoes in Indonesia which erupts frequently. The small eruption occurred nearly every year, whereas the big ones occurred at approximately once every five years. The eruption often produces impacts at both positive and negative view points, such as production of sediment as construction material and damage on infrastructures due to debris flow occurrences respectively. The eruption produces two types of disasters, i.e. primary disaster (such as ash fall, pyroclastic flow, and lava flow, and secondary disaster such as debris flow. This paper presents the long term effort on the development of community participation in the sand mining management as one of strategic disaster mitigation activities. The raising awareness of the community on the necessity of conducting proper sand mining management and its effect on reducing the risk due to debris flow disaster has shown the effectives of the approach being introduced. The local government acceptance on the presence of the community participation in the whole system of sediment management may involve further collaboration between the local government authority and community society in the future.

A review of laboratory and numerical modelling in volcanology

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J. L. Kavanagh

2018-04-01

Full Text Available Modelling has been used in the study of volcanic systems for more than 100 years, building upon the approach first applied by Sir James Hall in 1815. Informed by observations of volcanological phenomena in nature, including eye-witness accounts of eruptions, geophysical or geodetic monitoring of active volcanoes, and geological analysis of ancient deposits, laboratory and numerical models have been used to describe and quantify volcanic and magmatic processes that span orders of magnitudes of time and space. We review the use of laboratory and numerical modelling in volcanological research, focussing on sub-surface and eruptive processes including the accretion and evolution of magma chambers, the propagation of sheet intrusions, the development of volcanic flows (lava flows, pyroclastic density currents, and lahars, volcanic plume formation, and ash dispersal. When first introduced into volcanology, laboratory experiments and numerical simulations marked a transition in approach from broadly qualitative to increasingly quantitative research. These methods are now widely used in volcanology to describe the physical and chemical behaviours that govern volcanic and magmatic systems. Creating simplified models of highly dynamical systems enables volcanologists to simulate and potentially predict the nature and impact of future eruptions. These tools have provided significant insights into many aspects of the volcanic plumbing system and eruptive processes. The largest scientific advances in volcanology have come from a multidisciplinary approach, applying developments in diverse fields such as engineering and computer science to study magmatic and volcanic phenomena. A global effort in the integration of laboratory and numerical volcano modelling is now required to tackle key problems in volcanology and points towards the importance of benchmarking exercises and the need for protocols to be developed so that models are routinely tested against real

A review of laboratory and numerical modelling in volcanology

Science.gov (United States)

Kavanagh, Janine L.; Engwell, Samantha L.; Martin, Simon A.

2018-04-01

Modelling has been used in the study of volcanic systems for more than 100 years, building upon the approach first applied by Sir James Hall in 1815. Informed by observations of volcanological phenomena in nature, including eye-witness accounts of eruptions, geophysical or geodetic monitoring of active volcanoes, and geological analysis of ancient deposits, laboratory and numerical models have been used to describe and quantify volcanic and magmatic processes that span orders of magnitudes of time and space. We review the use of laboratory and numerical modelling in volcanological research, focussing on sub-surface and eruptive processes including the accretion and evolution of magma chambers, the propagation of sheet intrusions, the development of volcanic flows (lava flows, pyroclastic density currents, and lahars), volcanic plume formation, and ash dispersal. When first introduced into volcanology, laboratory experiments and numerical simulations marked a transition in approach from broadly qualitative to increasingly quantitative research. These methods are now widely used in volcanology to describe the physical and chemical behaviours that govern volcanic and magmatic systems. Creating simplified models of highly dynamical systems enables volcanologists to simulate and potentially predict the nature and impact of future eruptions. These tools have provided significant insights into many aspects of the volcanic plumbing system and eruptive processes. The largest scientific advances in volcanology have come from a multidisciplinary approach, applying developments in diverse fields such as engineering and computer science to study magmatic and volcanic phenomena. A global effort in the integration of laboratory and numerical volcano modelling is now required to tackle key problems in volcanology and points towards the importance of benchmarking exercises and the need for protocols to be developed so that models are routinely tested against real world data.

Pyritic ash-flow tuff, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Castor, S.B.; Tingley, J.V.; Bonham, H.F. Jr.

1994-01-01

The Yucca Mountain site is underlain by a 1,500-m-thick Miocene volcanic sequence that comprises part of the southwestern Nevada volcanic field. Rocks of this sequence, which consists mainly of ash-flow tuff sheets with minor flows and bedded tuff, host precious metal mineralization in several areas as near as 10 km from the site. In two such areas, the Bullfrog and Bare Mountain mining districts, production and reserves total over 60 t gold and 150 t silver. Evidence of similar precious metal mineralization at the Yucca Mountain site may lead to mining or exploratory drilling in the future, compromising the security of the repository. The authors believe that most of the pyrite encountered by drilling at Yucca Mountain was introduced as pyroclastic ejecta, rather than by in situ hydrothermal activity. Pyritic ejecta in ash-flow tuff are not reported in the literature, but there is no reason to believe that the Yucca Mountain occurrence is unique. The pyritic ejecta are considered by us to be part of a preexisting hydrothermal system that was partially or wholly destroyed during eruption of the tuff units. Because it was introduced as ejecta in tuff units that occur at depths of about 1,000 m, such pyrite does not constitute evidence of shallow mineralization at the proposed repository site; however, the pyrite may be evidence for mineralization deep beneath Yucca Mountain or as much as tens of kilometers from it

Deterministic estimation of hydrological thresholds for shallow landslide initiation and slope stability models: case study from the Somma-Vesuvius area of southern Italy

Science.gov (United States)

Baum, Rex L.; Godt, Jonathan W.; De Vita, P.; Napolitano, E.

2012-01-01

Rainfall-induced debris flows involving ash-fall pyroclastic deposits that cover steep mountain slopes surrounding the Somma-Vesuvius volcano are natural events and a source of risk for urban settlements located at footslopes in the area. This paper describes experimental methods and modelling results of shallow landslides that occurred on 5–6 May 1998 in selected areas of the Sarno Mountain Range. Stratigraphical surveys carried out in initiation areas show that ash-fall pyroclastic deposits are discontinuously distributed along slopes, with total thicknesses that vary from a maximum value on slopes inclined less than 30° to near zero thickness on slopes inclined greater than 50°. This distribution of cover thickness influences the stratigraphical setting and leads to downward thinning and the pinching out of pyroclastic horizons. Three engineering geological settings were identified, in which most of the initial landslides that triggered debris flows occurred in May 1998 can be classified as (1) knickpoints, characterised by a downward progressive thinning of the pyroclastic mantle; (2) rocky scarps that abruptly interrupt the pyroclastic mantle; and (3) road cuts in the pyroclastic mantle that occur in a critical range of slope angle. Detailed topographic and stratigraphical surveys coupled with field and laboratory tests were conducted to define geometric, hydraulic and mechanical features of pyroclastic soil horizons in the source areas and to carry out hydrological numerical modelling of hillslopes under different rainfall conditions. The slope stability for three representative cases was calculated considering the real sliding surface of the initial landslides and the pore pressures during the infiltration process. The hydrological modelling of hillslopes demonstrated localised increase of pore pressure, up to saturation, where pyroclastic horizons with higher hydraulic conductivity pinch out and the thickness of pyroclastic mantle reduces or is

Natural radioactivity in volcanic ash from Mt. Pinatubo eruption

International Nuclear Information System (INIS)

Duran, E.B.; De Vera, C.M.; Garcia, T.Y.; Dela Cruz, F.M.; Esguerra, L.V.; Castaneda, S.S.

1992-01-01

Last June 15, 1991, a major pyroclastic eruption occurred from Mt. Pinatubo volcano located in Zambales, Central Luzon. The radiological impact of this eruption was assessed based on the concentrations of the principal naturally occurring radionuclides observed in volcanic ash. The volcanic ash samples were collected from locations which are within 50-km radius of Mt. Pinatubo at various times after the eruption. The mean activity concentrations in Bq/kg wet weight of the natural radionuclides in volcanic ash were as follows: 12.6 for 238 U, 14.0 for 232 Th and 330 for 40 K. These values are significantly higher than the mean activity concentrations of these radionuclides observed in topsoil in the same provinces before the eruption. This suggests that with the deposition of large quantities of volcanic ash and lahar in Central Luzon and concomitant topographic changes, the distribution and quantities of radionuclides which gave rise to terrestrial radiation may have also changed. Outdoor radon concentrations measured three days and later after the eruption were within normal background values. (auth.). 4 refs.; 5 tabs.; 1 fig

The relationship between carbonate facies, volcanic rocks and plant remains in a late Palaeozoic lacustrine system (San Ignacio Fm, Frontal Cordillera, San Juan province, Argentina)

Science.gov (United States)

Busquets, P.; Méndez-Bedia, I.; Gallastegui, G.; Colombo, F.; Cardó, R.; Limarino, O.; Heredia, N.; Césari, S. N.

2013-07-01

The San Ignacio Fm, a late Palaeozoic foreland basin succession that crops out in the Frontal Cordillera (Argentinean Andes), contains lacustrine microbial carbonates and volcanic rocks. Modification by extensive pedogenic processes contributed to the massive aspect of the calcareous beds. Most of the volcanic deposits in the San Ignacio Fm consist of pyroclastic rocks and resedimented volcaniclastic deposits. Less frequent lava flows produced during effusive eruptions led to the generation of tabular layers of fine-grained, greenish or grey andesites, trachytes and dacites. Pyroclastic flow deposits correspond mainly to welded ignimbrites made up of former glassy pyroclasts devitrified to microcrystalline groundmass, scarce crystals of euhedral plagioclase, quartz and K-feldspar, opaque minerals, aggregates of fine-grained phyllosilicates and fiammes defining a bedding-parallel foliation generated by welding or diagenetic compaction. Widespread silicified and silica-permineralized plant remains and carbonate mud clasts are found, usually embedded within the ignimbrites. The carbonate sequences are underlain and overlain by volcanic rocks. The carbonate sequence bottoms are mostly gradational, while their tops are usually sharp. The lower part of the carbonate sequences is made up of mud which appear progressively, filling interstices in the top of the underlying volcanic rocks. They gradually become more abundant until they form the whole of the rock fabric. Carbonate on volcanic sandstones and pyroclastic deposits occur, with the nucleation of micritic carbonate and associated production of pyrite. Cyanobacteria, which formed the locus of mineral precipitation, were related with this nucleation. The growth of some of the algal mounds was halted by the progressive accumulation of volcanic ash particles, but in most cases the upper boundary is sharp and suddenly truncated by pyroclastic flows or volcanic avalanches. These pyroclastic flows partially destroyed the

A study of the stability analysis of pyroclastic covers based on electrical resistivity measurements

International Nuclear Information System (INIS)

Di Maio, R; Piegari, E

2012-01-01

Usually, the degree of stability of a slope is quantified by the factor of safety whose values depend on physical and mechanical soil properties analysed on samples of much reduced sizes or referring to very small soil volumes around porous probes. To overcome the limit of point-sampled information, we propose a semi-empirical approach based on the use of geophysical methods and the employment of a geophysical factor of safety recently introduced by the authors in terms of local resistivities and slope angles. In this paper, we show an application of our proposal on a test area of about 2000 m 2 on Sarno Mountains (Campania Region, Southern Italy), where shallow landslides involving pyroclastic soils periodically occur triggered by critical rainfall events. Starting from two resistivity tomography surveys performed on the test area in autumn and spring, we obtained maps of the geophysical factor of safety at different depths for the two seasons. We also estimated the values of the factor of safety by using the infinite-slope model in the dry and saturated scenarios. A comparison between the values of the geophysical and geotechnical factors of safety shows advantages and disadvantages of our approach. (paper)

Lithostratigraphy of the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Moyer, T.C.; Geslin, J.K.

1995-01-01

Lithostratigraphic relations within the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) were reconstructed from analysis of core samples and observation of outcrop exposures. The Calico Hills Formation is composed of five nonwelded pyroclastic units (each formed of one or more pyroclastic-flow deposits) that overlie an interval of bedded tuff and a basal volcaniclastic sandstone unit. The Prow Pass Tuff is divided into four pyroclastic units and an underlying interval of bedded tuff. The pyroclastic units of the Prow Pass Tuff are distinguished by the sizes and amounts of their pumice and lithic clasts and their degree of welding. Pyroclastic units of the Prow Pass Tuff are distinguished from those of the Calico Hills Formation by their phenocryst assemblage, chemical composition, and ubiquitous siltstone lithic clasts. Downhole resistivity tends to mirror the content of authigenic minerals, primarily zeolites, in both for-mations and may be useful for recognizing the vitric-zeolite boundary in the study area. Maps of zeolite distribution illustrate that the bedded tuff and basal sandstone units of the Calico Hills Formation are altered over a wider area than the pyroclastic units of both the Calico Hills Formation and the upper Prow Pass Tuff

Lithostratigraphy of the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) at Yucca Mountain, Nevada

Energy Technology Data Exchange (ETDEWEB)

Moyer, T.C.; Geslin, J.K. [Science Applications International Corp., Las Vegas, NV (United States)

1995-07-01

Lithostratigraphic relations within the Calico Hills Formation and Prow Pass Tuff (Crater Flat Group) were reconstructed from analysis of core samples and observation of outcrop exposures. The Calico Hills Formation is composed of five nonwelded pyroclastic units (each formed of one or more pyroclastic-flow deposits) that overlie an interval of bedded tuff and a basal volcaniclastic sandstone unit. The Prow Pass Tuff is divided into four pyroclastic units and an underlying interval of bedded tuff. The pyroclastic units of the Prow Pass Tuff are distinguished by the sizes and amounts of their pumice and lithic clasts and their degree of welding. Pyroclastic units of the Prow Pass Tuff are distinguished from those of the Calico Hills Formation by their phenocryst assemblage, chemical composition, and ubiquitous siltstone lithic clasts. Downhole resistivity tends to mirror the content of authigenic minerals, primarily zeolites, in both for-mations and may be useful for recognizing the vitric-zeolite boundary in the study area. Maps of zeolite distribution illustrate that the bedded tuff and basal sandstone units of the Calico Hills Formation are altered over a wider area than the pyroclastic units of both the Calico Hills Formation and the upper Prow Pass Tuff.

Stratigraphy of the Bandelier Tuff in the Pajarito Plateau. Applications to waste management

International Nuclear Information System (INIS)

Crowe, B.M.; Linn, G.W.; Heiken, G.; Bevier, M.L.

1978-04-01

The Bandelier Tuff within the Pajarito Plateau consists of a lower sequence of air-fall and ash-flow deposits (Otowi Member) disconformably overlain by an upper sequence of air-fall and ash-flow deposits (Tshirege Member). The ash-flow sequence of the Tshirege Member consists of three cooling units throughout much of the Pajarito Plateau. The lower cooling unit is formed by three to as many as six pyroclastic flow units; the middle and upper cooling units each consist of at least three pyroclastic flow units. The contact between the lower and middle cooling unit coincides with a pyroclastic flow unit contact. This horizon is a prominent stratigraphic marker within distal sections of the Tshirege Member. Major and trace element analyses of unaltered and altered samples of the Bandelier Tuff were determined by neutron activation and delayed neutron activation and delayed neutron activation techniques. Petrographic, granulometric and morphologic characteristics of the Bandelier Tuff were determined to provide background information on the suitability of the Tuff as a medium for radioactive waste disposal. The hydrologic characteristics of the Bandelier Tuff are controlled primarily by secondary features of the Tuff (cooling zones). These features vary with emplacement temperature and transport distance of the Tuff. Primary depositional features provide second order control on transport pathways in distal sections of the Tuff

Proximal stratigraphy and event sequence of the c. 5600 cal. yr BP Whakatane rhyolite eruption episode from Haroharo volcano, Okataina Volcanic Centre, New Zealand

International Nuclear Information System (INIS)

Kobayashi, T.; Nairn, I.; Smith, V.; Shane, P.

2005-01-01

The c. 5600 cal. yr BP Whakatane eruption episode consisted of a sequence of intracaldera rhyolite eruptions from at least five vents spread over 11 km of the Haroharo linear vent zone within Okataina Volcanic Centre. Initial vent-opening eruptions from the Haroharo vent produced coarse lithic clast 'blast beds' and pyroclastic density currents surges). These were immediately followed by eruption of very mobile pumiceous pyroclastic surges from the Makatiti vent 6 km to the southwest. Major plinian eruptions from the Makatiti vent then dispersed Whakatane Tephra pumice fall deposits (bulk volume c. 6 km 3 ) across the northeastern North Island while smaller explosive eruptions produced pyroclastic flows and falls from the Haroharo-Rotokohu vents and at the Pararoa vent on the caldera rim 11 km northeast from Makatiti. The pyroclastic eruptions at all vents were followed by the extrusion of lava flows and domes; extruded lava volumes ranged from 0.03 km 3 for the Pararoa dome to 7.5 km 3 for the Makatiti-Tapahoro lava flows and domes. Minor variations in whole rock and glass chemistry show that the three main vent areas each tapped a slightly different high-silica rhyolite magma. About 10 km 3 of M-type magma was erupted from the Makatiti-Tapahoro vents; c. 1.3 km 3 of H-type magma from the Haroharo-Rotokohu vents, and 0.04 km 3 of P-type magma from the Pararoa vent. There are no significant weathering or erosional breaks within the Whakatane eruptive sequence, which suggests that all Whakatane eruptions occurred within a short time interval. However, extrusion of the Haroharo dome within the Makatiti pyroclastic eruption sequence suggests a duration of c. 2 yr for the main pyroclastic eruption phase. Emplacement of the following voluminous (7.5 km 3 ) lavas from the Makatiti-Tapahoro vents would have occurred over >10 yr at the c. 10-20 m 3 /s inferred extrusion rates. (author). 19 refs., 16 figs., 7 tabs

Directed blasts and blast-generated pyroclastic density currents: a comparison of the Bezymianny 1956, Mount St Helens 1980, and Soufrière Hills, Montserrat 1997 eruptions and deposits

Science.gov (United States)

Belousov, Alexander; Voight, Barry; Belousova, Marina

2007-01-01

We compare eruptive dynamics, effects and deposits of the Bezymianny 1956 (BZ), Mount St Helens 1980 (MSH), and Soufrière Hills volcano, Montserrat 1997 (SHV) eruptions, the key events of which included powerful directed blasts. Each blast subsequently generated a high-energy stratified pyroclastic density current (PDC) with a high speed at onset. The blasts were triggered by rapid unloading of an extruding or intruding shallow magma body (lava dome and/or cryptodome) of andesitic or dacitic composition. The unloading was caused by sector failures of the volcanic edifices, with respective volumes for BZ, MSH, and SHV c. 0.5, 2.5, and 0.05 km3 . The blasts devastated approximately elliptical areas, axial directions of which coincided with the directions of sector failures. We separate the transient directed blast phenomenon into three main parts, the burst phase, the collapse phase, and the PDC phase. In the burst phase the pressurized mixture is driven by initial kinetic energy and expands rapidly into the atmosphere, with much of the expansion having an initially lateral component. The erupted material fails to mix with sufficient air to form a buoyant column, but in the collapse phase, falls beyond the source as an inclined fountain, and thereafter generates a PDC moving parallel to the ground surface. It is possible for the burst phase to comprise an overpressured jet, which requires injection of momentum from an orifice; however some exploding sources may have different geometry and a jet is not necessarily formed. A major unresolved question is whether the preponderance of strong damage observed in the volcanic blasts should be attributed to shock waves within an overpressured jet, or alternatively to dynamic pressures and shocks within the energetic collapse and PDC phases. Internal shock structures related to unsteady flow and compressibility effects can occur in each phase. We withhold judgment about published shock models as a primary explanation for the

Rockfall-induced impact force causing a debris flow on a volcanoclastic soil slope: a case study in southern Italy

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P. Budetta

2010-09-01

Full Text Available On 10 January 2003, a rockfall of approximately 10 m³ affected a cliff some 25 m high located along the northern slopes of Mt. St. Angelo (Nocera Inferiore, province of Salerno in the southern Italian region of Campania. The impact of boulders on the lower sector of the slope, along which detrital-pyroclastic soils outcrop, triggered a small channelled debris flow of about 500 m³. Fortunately, no damage nor victims resulted from the landslide. Several marks of the impacts were observed at the cliff toe and outside the collapsed area, and the volumes of some fallen boulders were subsequently measured. By means of in-situ surveys, it was possible to reconstruct the cliff's geo-structural layout in detail. A rockfall back-analysis was subsequently performed along seven critical profiles of the entire slope (surface area of about 4000 m². The results of this numerical modelling using the lumped-mass method were then used to map the kinetic iso-energy curves. In the triggering area of the debris flow, for a falling boulder of 1 m³, the mean kinetic energy was estimated at 120 kJ, this value being equivalent to an impact force, on an inclined surface, of some 800 kN. After landing, due to the locally high slope gradient (about 45°, and low angle of trajectory at impact (about 23°, some boulders slid down the slope as far as the endpoints. The maximum depth of penetration into the ground by a sliding block was estimated at about 16 cm. Very likely, owing to the high impact force of boulders on the saturated soil slope outcropping at the cliff base, the debris flow was triggered under undrained loading conditions. Initial failure was characterized by a translational slide involving a limited, almost elliptical area where the pyroclastic cover shows greater thickness in comparison with the surrounding areas.

Rockfall-induced impact force causing a debris flow on a volcanoclastic soil slope: a case study in southern Italy

Science.gov (United States)

Budetta, P.

2010-09-01

On 10 January 2003, a rockfall of approximately 10 m3 affected a cliff some 25 m high located along the northern slopes of Mt. St. Angelo (Nocera Inferiore, province of Salerno) in the southern Italian region of Campania. The impact of boulders on the lower sector of the slope, along which detrital-pyroclastic soils outcrop, triggered a small channelled debris flow of about 500 m3. Fortunately, no damage nor victims resulted from the landslide. Several marks of the impacts were observed at the cliff toe and outside the collapsed area, and the volumes of some fallen boulders were subsequently measured. By means of in-situ surveys, it was possible to reconstruct the cliff's geo-structural layout in detail. A rockfall back-analysis was subsequently performed along seven critical profiles of the entire slope (surface area of about 4000 m2). The results of this numerical modelling using the lumped-mass method were then used to map the kinetic iso-energy curves. In the triggering area of the debris flow, for a falling boulder of 1 m3, the mean kinetic energy was estimated at 120 kJ, this value being equivalent to an impact force, on an inclined surface, of some 800 kN. After landing, due to the locally high slope gradient (about 45°), and low angle of trajectory at impact (about 23°), some boulders slid down the slope as far as the endpoints. The maximum depth of penetration into the ground by a sliding block was estimated at about 16 cm. Very likely, owing to the high impact force of boulders on the saturated soil slope outcropping at the cliff base, the debris flow was triggered under undrained loading conditions. Initial failure was characterized by a translational slide involving a limited, almost elliptical area where the pyroclastic cover shows greater thickness in comparison with the surrounding areas.

Pigeonholing pyroclasts: Insights from the 19 March 2008 explosive eruption of Kīlauea volcano

Science.gov (United States)

Houghton, Bruce F.; Swanson, D.A.; Carey, R.J.; Rausch, J.; Sutton, A.J.

2011-01-01

We think, conventionally, of volcanic explosive eruptions as being triggered in one of two ways: by release and expansion of volatiles dissolved in the ejected magma (magmatic explosions) or by transfer of heat from magma into an external source of water (phreatic or phreatomagmatic explosions). We document here an event where neither magma nor an external water source was involved in explosive activity at K??lauea. Instead, the eruption was powered by the expansion of decoupled magmatic volatiles released from deeper magma, which was not ejected by the eruption, and the trigger was a collapse of near-surface wall rocks that then momentarily blocked that volatile flux. Mapping of the advected fall deposit a day after this eruption has highlighted the difficulty of constraining deposit edges from unobserved or prehistoric eruptions of all magnitudes. Our results suggest that the dispersal area of advected fall deposits could be miscalculated by up to 30% of the total, raising issues for accurate hazard zoning and assessment. Eruptions of this type challenge existing classification schemes for pyroclastic deposits and explosive eruptions and, in the past, have probably been interpreted as phreatic explosions, where the eruptive mechanism has been assumed to involve flashing of groundwater to steam. ?? 2011 Geological Society of America.

Evolution of volcaniclastic apron during initiation of Cascade volcanism in southern Oregon

Energy Technology Data Exchange (ETDEWEB)

Bestland, E.A.

1986-05-01

The Oligocene Colestin Formation consists of volcaniclastic apron sequence that records the initiation of Cascade volcanism in the western Cascade Range of southern Oregon. The formation in the type area is largely confined to an east-west-trending graben approximately 8 km wide. This graben and other smaller grabens within it developed to the west of and perpendicular to the axis of the Oligocene Cascade arc. The apron, which fills and locally overflows the graben, consists of coalesced lobes of volcaniclastic and pyroclastic deposits and lesser amounts of lava flows. Abrupt lateral facies changes on a scale of tens to hundreds of meters were produced by the lobe style of deposition and contemporaneous basin faulting. Interstratified with the discontinuous apron sediments are marker units that consist of pyroclastic flows, paleosols, and lava-flow sequences. In the upper half of the formation, the apron can be subdivided into informal members (lobes and sequences of lobes), which can be mapped according to their composition and stratigraphic position. Each member formed during a distinct interval of volcanism. An epiclastic lobe in the upper part of the formation, containing debris-flow and hyperconcentrated flood-flow deposits, represents a period of effusive or mildly explosive andesitic and basaltic volcanism. This epiclastic lobe pinches out to the south under a member that consists of tuffaceous sandstones and interbedded welded and nonwelded pyroclastic flows. The pulselike style of apron growth was produced by the episodic shifting of volcanism along the arc.

The initial giant umbrella cloud of the May 18th, 1980, explosive eruption of Mount St. Helens

Science.gov (United States)

Sparks, R.S.J.; Moore, J.G.; Rice, C.J.

1986-01-01

The initial eruption column of May 18th, 1980 reached nearly 30 km altitude and released 1017 joules of thermal energy into the atmosphere in only a few minutes. Ascent of the cloud resulted in forced intrusion of a giant umbrella-shaped cloud between altitudes of 10 and 20 km at radial horizontal velocities initially in excess of 50 m/s. The mushroom cloud expanded 15 km upwind, forming a stagnation point where the radial expansion velocity and wind velocity were equal. The cloud was initiated when the pyroclastic blast flow became buoyant. The flow reduced its density as it moved away from the volcano by decompression, by sedimentation, and by mixing with and heating the surrounding air. Observations indicate that much of the flow, covering an area of 600 km2, became buoyant within 1.5 minutes and abruptly ascended to form the giant cloud. Calculations are presented for the amount of air that must have been entrained into the flow to make it buoyant. Assuming an initial temperature of 450??C and a magmatic origin for the explosion, these calculations indicate that the flow became buoyant when its temperature was approximately 150??C and the flow consisted of a mixture of 3.25 ?? 1011 kg of pyroclasts and 5.0 ?? 1011 kg of air. If sedimentation is considered, these figures reduce to 1.1 ?? 1011 kg of pyroclasts and 1.0 ?? 1011 kg of air. ?? 1986.

Formation of a spatter-rich pyroclastic density current deposit in a Neogene sequence of trachytic-mafic igneous rocks at Mason Spur, Erebus volcanic province, Antarctica

Science.gov (United States)

Martin, A. P.; Smellie, J. L.; Cooper, A. F.; Townsend, D. B.

2018-01-01

Erosion has revealed a remarkable section through the heart of a volcanic island, Mason Spur, in the southwestern Ross Sea, Antarctica, including an unusually well-exposed section of caldera fill. The near-continuous exposure, 10 km laterally and > 1 km vertically, cuts through Cenozoic alkalic volcanic rocks of the Erebus volcanic province (McMurdo Volcanic Group) and permits the study of an ancient volcanic succession that is rarely available due to subsequent burial or erosion. The caldera filling sequence includes an unusual trachytic spatter-rich lapilli tuff (ignimbrite) facies that is particularly striking because of the presence of abundant black fluidal, dense juvenile spatter clasts of trachytic obsidian up to 2 m long supported in a pale cream-coloured pumiceous lapilli tuff matrix. Field mapping indicates that the deposit is an ignimbrite and, together with petrological considerations, it is suggested that mixing of dense spatter and pumiceous lapilli tuff in the investigated deposit occurred during emplacement, not necessarily in the same vent, with the mixed fragmental material emplaced as a pyroclastic density current. Liquid water was not initially present but a steam phase was probably generated during transport and may represent water ingested during passage of the current as it passed over either wet ground, stream, shallow lake or (possibly) snow. Well-exposed caldera interiors are uncommon and that at Mason Spur is helping understand eruption dynamics associated with a complex large island volcano. The results of our study should help to elucidate interpretations of other, less well exposed, pyroclastic density current deposits elsewhere in Antarctica and globally.

Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification

Science.gov (United States)

Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

2017-01-01

Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The ~7,700 calendar year B.P. climactic eruption of Mount Mazama, USA vented ~50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Mazama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ±1 m lateral and ±4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow- parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of pit craters caused by phreatic explosions, fractures and cracks caused by extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented

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

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Andrea Bevilacqua

2017-09-01

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

Experimental study on the rheological behaviour of debris flow

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A. Scotto di Santolo

2010-12-01

Full Text Available A model able to describe all the processes involved in a debris flow can be very complex owing to the sudden changing of the material that turns from solid into liquid state. The two phases of the phenomenon are analysed separately referring to soil mechanics procedures with regard to the trigger phase, and to an equivalent fluid for the post-failure phase. The present paper is devoted to show the experimental results carried out to evaluate the behaviour assumed by a pyroclastic-derived soil during the flow. A traditional fluid tool has been utilized: a standard rotational rheometer equipped with two different geometries. The soils tested belong to deposits that cover the slopes of the Campania region, Italy, often affected by debris flows. The influence of solid concentration C_v and grain size distribution was tested: the soils were destructurated, sieved and mixed with water starting from the in situ porosity. All material mixtures showed a non-Newtonian fluid behaviour with a yield stress τ_y that increases with a solid volumetric concentration and decreases for an increase of sand fraction. The experimental data were fitted with standard model for fluids. A simple relation between C_v and τ_y was obtained. The yield stress seems to be a key parameter for describing and predicting the post-failure behaviour of debris flows. These results suggest that in the field a small change in solid fraction, due to rainfall, will cause a slight decrease of the static yield stress, readily inducing a rapid flow which will stop only when the dynamic yield stress is reached, namely on a much smoother slope. This can explain the in situ observed post-failure behaviour of debris flows, which are able to flow over very long distances even on smooth slopes.

Theory for Deducing Volcanic Activity From Size Distributions in Plinian Pyroclastic Fall Deposits

Science.gov (United States)

Iriyama, Yu; Toramaru, Atsushi; Yamamoto, Tetsuo

2018-03-01

Stratigraphic variation in the grain size distribution (GSD) of plinian pyroclastic fall deposits reflects volcanic activity. To extract information on volcanic activity from the analyses of deposits, we propose a one-dimensional theory that provides a formula connecting the sediment GSD to the source GSD. As the simplest case, we develop a constant-source model (CS model), in which the source GSD and the source height are constant during the duration of release of particles. We assume power laws of particle radii for the terminal fall velocity and the source GSD. The CS model can describe an overall (i.e., entire vertically variable) feature of the GSD structure of the sediment. It is shown that the GSD structure is characterized by three parameters, that is, the duration of supply of particles to the source scaled by the fall time of the largest particle, ts/tM, and the power indices of the terminal fall velocity p and of the source GSD q. We apply the CS model to samples of the Worzel D ash layer and compare the sediment GSD structure calculated by using the CS model to the observed structure. The results show that the CS model reproduces the overall structure of the observed GSD. We estimate the duration of the eruption and the q value of the source GSD. Furthermore, a careful comparison of the observed and calculated GSDs reveals new interpretation of the original sediment GSD structure of the Worzel D ash layer.

Analysis of the 2006 block-and-ash flow deposits of Merapi Volcano, Java, Indonesia, using high-spatial resolution IKONOS images and complementary ground based observations

Science.gov (United States)

Thouret, Jean-Claude; Gupta, Avijit; Liew, Soo Chin; Lube, Gert; Cronin, Shane J.; Surono, Dr

2010-05-01

On 16 June 2006 an overpass of IKONOS coincided with the emplacement of an active block-and-ash flow fed by a lava dome collapse event at Merapi Volcano (Java, Indonesia). This was the first satellite image recorded for a moving pyroclastic flow. The very high-spatial resolution data displayed the extent and impact of the pyroclastic deposits emplaced during and prior to, the day of image acquisition. This allowed a number of features associated with high-hazard block-and-ash flows emplaced in narrow, deep gorges to be mapped, interpreted and understood. The block-and-ash flow and surge deposits recognized in the Ikonos images include: (1) several channel-confined flow lobes and tongues in the box-shaped valley; (2) thin ash-cloud surge deposit and knocked-down trees in constricted areas on both slopes of the gorge; (3) fan-like over bank deposits on the Gendol-Tlogo interfluves from which flows were re-routed in the Tlogo secondary valley; (4) massive over bank lobes on the right bank from which flows devastated the village of Kaliadem 0.5 km from the main channel, a small part of this flow being re-channeled in the Opak secondary valley. The high-resolution IKONOS images also helped us to identify geomorphic obstacles that enabled flows to ramp and spill out from the sinuous channel, a process called flow avulsion. Importantly, the avulsion redirected flows to unexpected areas away from the main channel. In the case of Merapi we see that the presence of valley fill by previous deposits, bends and man-made dams influence the otherwise valley-guided course of the flows. Sadly, Sabo dams (built to ameliorate the effect of high sediment load streams) can actually cause block-and-ash flows to jump out of their containing channel and advance into sensitive areas. Very-high-spatial resolution satellite images are very useful for mapping and interpreting the distribution of freshly erupted volcanic deposits. IKONOS-type images with 1-m resolution provide opportunities to

physical volcanology of pyroclastic tephra deposit at batoke mt.

African Journals Online (AJOL)

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2013-04-16

Apr 16, 2013 ... In the deposit three facies types; which are the lava flow, the lapilli and ash ... flow flanked by the tephra pile, the lack of accidental clasts, and the ..... Origin of the Lethal gas ... eruption behaviour and petrochemistry of lava.

Bulbous head formation in bidisperse shallow granular flows over inclined planes

Science.gov (United States)

Denissen, I.; Thornton, A.; Weinhart, T.; Luding, S.

2017-12-01

Predicting the behaviour of hazardous natural granular flows (e.g. debris-flows and pyroclastic flows) is vital for an accurate assessment of the risks posed by such events. In these situations, an inversely graded vertical particle-size distribution develops, with larger particles on top of smaller particles. As the surface velocity of such flows is larger than the mean velocity, the larger material is then transported to the flow front. This creates a downstream size-segregation structure, resulting in a flow front composed purely of large particles, that are generally more frictional in geophysical flows. Thus, this segregation process reduces the mobility of the flow front, resulting in the formation of, a so-called, bulbous head. One of the main challenges of simulating these hazardous natural granular flows is the enormous number of particles they contain, which makes discrete particle simulations too computationally expensive to be practically useful. Continuum methods are able to simulate the bulk flow- and segregation behaviour of such flows, but have to make averaging approximations that reduce the huge number of degrees of freedom to a few continuum fields. Small-scale periodic discrete particle simulations can be used to determine the material parameters needed for the continuum model. In this presentation, we use a depth-averaged model to predict the flow profile for particulate chute flows, based on flow height, depth-averaged velocity and particle-size distribution [1], and show that the bulbous head structure naturally emerges from this model. The long-time behaviour of this solution of the depth-averaged continuum model converges to a novel travelling wave solution [2]. Furthermore, we validate this framework against computationally expensive 3D particle simulations, where we see surprisingly good agreement between both approaches, considering the approximations made in the continuum model. We conclude by showing that the travelling distance and

Post-depositional fracturing and subsidence of pumice flow deposits: Lascar Volcano, Chile.

Science.gov (United States)

Whelley, Patrick L; Jay, J; Calder, E S; Pritchard, M E; Cassidy, N J; Alcaraz, S; Pavez, A

Unconsolidated pyroclastic flow deposits of the 1993 eruption of Lascar Volcano, Chile, have, with time, become increasingly dissected by a network of deeply penetrating fractures. The fracture network comprises orthogonal sets of decimeter-wide linear voids that form a pseudo-polygonal grid visible on the deposit surface. In this work, we combine shallow surface geophysical imaging tools with remote sensing observations and direct field measurements of the deposit to investigate these fractures and their underlying causal mechanisms. Based on ground penetrating radar images, the fractures are observed to have propagated to depths of up to 10 m. In addition, orbiting radar interferometry shows that deposit subsidence of up to 1 cm/year -1 occurred between 1993 and 1996 with continued subsidence occurring at a slower rate thereafter. In situ measurements show that 1 m below the surface, the 1993 deposits remain 5°C to 15°C hotter, 18 years after emplacement, than adjacent deposits. Based on the observed subsidence as well as estimated cooling rates, the fractures are inferred to be the combined result of deaeration, thermal contraction, and sedimentary compaction in the months to years following deposition. Significant environmental factors, including regional earthquakes in 1995 and 2007, accelerated settling at punctuated moments in time. The spatially variable fracture pattern relates to surface slope and lithofacies variations as well as substrate lithology. Similar fractures have been reported in other ignimbrites but are generally exposed only in cross section and are often attributed to formation by external forces. Here we suggest that such interpretations should be invoked with caution, and deformation including post-emplacement subsidence and fracturing of loosely packed ash-rich deposits in the months to years post-emplacement is a process inherent in the settling of pyroclastic material.

Field-based description of rhyolite lava flows of the Calico Hills Formation, Nevada National Security Site, Nevada

Science.gov (United States)

Sweetkind, Donald S.; Bova, Shiera C.

2015-01-01

Contaminants introduced into the subsurface of Pahute Mesa, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas at Pahute Mesa and into the accessible environment is greatest by groundwater transport through fractured volcanic rocks. The 12.9 Ma (mega-annums, million years) Calico Hills Formation, which consists of a mixture of rhyolite lava flows and intercalated nonwelded and bedded tuff and pyroclastic flow deposits, occurs in two areas of the Nevada National Security Site. One area is north of the Rainier Mesa caldera, buried beneath Pahute Mesa, and serves as a heterogeneous volcanic-rock aquifer but is only available to study through drilling and is not described in this report. A second accumulation of the formation is south of the Rainier Mesa caldera and is exposed in outcrop along the western boundary of the Nevada National Security Site at the Calico Hills near Yucca Mountain. These outcrops expose in three dimensions an interlayered sequence of tuff and lava flows similar to those intercepted in the subsurface beneath Pahute Mesa. Field description and geologic mapping of these exposures described lithostratigraphic variations within lava flows and assisted in, or at least corroborated, conceptualization of the rhyolite lava-bearing parts of the formation.

Synergistic Use of Satellite Volcano Detection and Science: A Fifteen Year Perspective of ASTER on Terra

Science.gov (United States)

Ramsey, M. S.

2014-12-01

The success of Terra-based observations using the ASTER instrument of active volcanic processes early in the mission gave rise to a funded NASA program designed to both increase the number of ASTER observations following an eruption and validate the satellite data. The urgent request protocol (URP) system for ASTER grew out of this initial study and has now operated in conjunction with and the support of the Alaska Volcano Observatory, the University of Alaska Fairbanks, the University of Hawaii, the USGS Land Processes DAAC, and the ASTER science team. The University of Pittsburgh oversees this rapid response/sensor-web system, which until 2011 had focused solely on the active volcanoes in the North Pacific region. Since that time, it has been expanded to operate globally with AVHRR and MODIS and now ASTER VNIR/TIR data are being acquired at numerous erupting volcanoes around the world. This program relies on the increased temporal resolution of AVHRR/MODIS midwave infrared data to trigger the next available ASTER observation, which results in ASTER data as frequently as every 2-5 days. For many targets, the URP has increased the observational frequency over active eruptions by as much 50%. The data have been used for operational response to new eruptions, longer-term scientific studies such as capturing detailed changes in lava domes/flows, pyroclastic flows and lahars. These data have also been used to infer the emplacement of new lava lobes, detect endogenous dome growth, and interpret hazardous dome collapse events. The emitted TIR radiance from lava surfaces has also been used effectively to model composition, texture and degassing. Now, this long-term archive of volcanic image data is being mined to provide statistics on the expectations of future high-repeat TIR data such as that proposed for the NASA HyspIRI mission. In summary, this operational/scientific program utilizing the unique properties of ASTER and the Terra mission has shown the potential for

Evidence for a welded tuff in the Rhyolite of Calico Hills

International Nuclear Information System (INIS)

Dickerson, R.P.; Hunter, W.C.

1994-01-01

A welded pyroclastic deposit has been identified in the Rhyolite of Calico Hills near Yucca Mountain, Nevada, where only lava flows and nonwelded pyroclastic deposits were previously described. Field data from Fortymile Wash show that nonwelded, bedded tuff grades upward into partially welded massive ruff, and thence into densely welded vitrophyre. Petrographic data show a progressive decrease in inter- and intragranular porosity and amount of vapor-phase minerals, with increasing welding. Pumice fragments are first deformed, then develop diffuse boundaries which become increasingly obscure with progressive welding. The most densely welded rock is a perlitic vitrophyre. The origin of this welded tuff is not clear, as it could represent an ignimbrite or a tuff fused beneath a thick lava flow

The Disruption of Tephra Fall Deposits by Basaltic Lava Flows

Science.gov (United States)

Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

2010-12-01

Complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents of the Roza Member in the Columbia River Basalt Province, (CRBP), USA, illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter tephra fall deposits. Thin pahoehoe lobes and sheet lobes occur intercalated with tephra deposits and provide evidence for synchronous effusive and explosive activity. Tephra that accumulated on the tops of inflating pahoehoe flows became disrupted by tumuli, which dissected the overlying sheet into a series of mounds. During inflation of subjacent tumuli tephra percolated down into the clefts and rubble at the top of the lava, and in some cases came into contact with lava hot enough to thermally alter it. Lava breakouts from the tumuli intruded up through the overlying tephra deposit and fed pahoehoe flows that spread across the surface of the aggrading tephra fall deposit. Non-welded scoria fall deposits were compacted and welded to a depth of ~50 cm underneath thick sheet lobes. These processes, deduced from the field relationships, have resulted in considerable stratigraphic complexity in proximal regions. We also demonstrate that, when the advance of lava and the fallout of tephra are synchronous, the contacts of some tephra sheets can be diachronous across their extent. The net effect is to reduce the usefulness of pyroclastic deposits in reconstructing eruption dynamics.

Volcanic stratigraphy and geochemistry of the Soufrière Volcanic Centre, Saint Lucia with implications for volcanic hazards

Science.gov (United States)

Lindsay, Jan M.; Trumbull, Robert B.; Schmitt, Axel K.; Stockli, Daniel F.; Shane, Phil A.; Howe, Tracy M.

2013-05-01

The Soufrière Volcanic Complex (SVC), Saint Lucia, represents one of the largest silicic centres in the Lesser Antilles arc. It comprises extensive pumiceous pyroclastic flow deposits, lava flows as well as Peléan-style domes and dome collapse block-and-ash-flow deposits. These deposits occur within and around the Qualibou Depression, a ~ 10-km diameter wide sector collapse structure. To date, vent locations for SVC pyroclastic deposits and their relationship to the sector collapse have been unclear because of limited stratigraphic correlation and few radiometric ages. In this study we reconstruct the geologic history of the SVC in light of new and recently published (U-Th)/He, U-Th and U-Pb zircon chronostratigraphic data, aided by mineralogical and geochemical correlation. Compositionally, SVC deposits are monotonous medium-K, calc-alkaline rocks with 61.6 to 67.7 wt.% SiO2 and display similar trace element abundances. Combined U-Th and (U-Th)/He zircon dating together with 14C ages and mineral fingerprinting reveals significant explosive eruptions at 640, 515, 265, 104, 60 and 40 ka (producing deposits previously grouped together as the "Choiseul" unit) and at 20 ka (Belfond unit). The mineralogically and geochemically distinct Belfond unit is a large, valley-filling pumiceous pyroclastic flow deposit distributed to the north, northeast, south and southeast of the Qualibou Depression that was probably deposited during a single plinian eruption. The unit previously referred to as ‘Choiseul tuff' is much less well defined. The typical Choiseul unit comprises a series of yellowish-white, crystal-poor, non-welded pumiceous pyroclastic deposits cropping out to the north and southeast of the Qualibou depression; however its age is poorly constrained. A number of other units previously mapped as Choiseul can be distinguished based on age, and in some cases mineral and whole rock chemistry. Pyroclastic deposits at Micoud (640 ± 19 ka), Bellevue (264 ± 8 ka), Anse

Stratigraphy, sedimentology and inferred flow dynamics from the July 2015 block-and-ash flow deposits at Volcán de Colima, Mexico

Science.gov (United States)

Macorps, Elodie; Charbonnier, Sylvain J.; Varley, Nick R.; Capra, Lucia; Atlas, Zachary; Cabré, Josep

2018-01-01

overspill and lateral spreading of the upper and marginal regions of the main flow body, generating highly mobile overbank flows that travel outside of the main valley. Volume- and distance-dependent critical channel capacities for the generation of overbank flows are used to better estimate the inundation area of these hazardous unconfined pyroclastic flows. These results highlight the importance of including and correctly assessing the hazards posed by large volume and long runout BAFs associated with frequent, small VEI, sustained dome-collapse eruptions.

Deposits from the 12 July Dome Collapse and Explosive Activity at Soufriere Hills Volcano, 12-15 July 2003

Science.gov (United States)

Edmonds, M.; Herd, R.; Strutt, M.; Mann, C.

2003-12-01

A large dome collapse took place on 12-13 July 2003 at Soufriere Hills Volcano. This event was the largest in magnitude during the 1995-2003 eruption and involved over 120 million m3 andesite dome and talus material. The collapse took place over 18 hours and culminated in an explosive phase that continued intermittently until 15 July 2003. Prior to the collapse, the total volume of the dome was 230 million m3 and was made up of remnants of lava erupted 1997-2001, talus material and fresh andesite dome lava erupted during the last two years. Talus made up around 50% of the total dome volume. This paper describes and interprets the pyroclastic flow and airfall deposits from this event, using other monitoring data and empirical evidence to reconstruct the dome collapse. The airfall and pyroclastic flow deposits were studied in detail over the weeks following the collapse. Airfall deposits were studied at 45 locations around the island and 75 samples were collected for analysis. The surge deposit stretched over 10 km2 on land and 35 pits were dug at intervals through it. The sections were described and sampled, yielding a further 60 samples for grain size analysis. Further sampling was carried out on the block and ash deposits in the Tar River Valley and on the Tar River Fan. Pumices from the post-collapse explosion sequence were collected and their densities measured and mass coverage estimated. Deposit maps for airfall, lithics and pumices were constructed for all of the individual events and a map to show the distribution of the main surge unit was generated. The collapse was monitored in real-time using the MVO seismic network and observations from the field. The sequence of events was as follows. From 09:00 to 18:00, low-energy pyroclastic flows took place, confined to the Tar River Valley, which reached the sea at the mouth of Tar River. These flows gradually increased in energy throughout the day but were not associated with energetic, large surges. By 18:00 the

Evolution of Rajabasa Volcano in Kalianda Area and Its Vicinity, South Lampung Regency

Directory of Open Access Journals (Sweden)

Sutikno Bronto

2014-06-01

Full Text Available DOI: 10.17014/ijog.v7i1.132Rajabasa Volcano (± 1281 m and Lampung Tuff, located in the South Lampung Regency, is the main point in order to understand the evolution of Quaternary volcanism in the area. A remote sensing analysis and field geologic work are the methods of the study. The volcanism began with the construction period of the Pre-Rajabasa composite cone which was followed by the destruction period of the cone to form the Pre-Rajabasa Caldera having ca. 25 km in diameter. The present Rajabasa Volcano, along with cones of flank eruptions and monogenesis, has appeared in the Pre-Rajabasa Caldera depression. Those volcanic activities are considered as the second construction period. During the first and the second construction periods, basaltic to andesitic lava flows, pyroclastic breccias, and tuffs were erupted. The Rajabasa eruption points moved in WNW - ESE direction, which were possibly controlled by a subsurface weak zone. The Pre-Rajabasa Caldera erupted voluminous Lampung Tuffs having rhyolite in composition, and they are considered as a combination of pyroclastic falls, flows, and surges, or pyroclastic density currents.

Pyroclast textural variation as an indicator of eruption column steadiness in andesitic Plinian eruptions at Mt. Ruapehu

Science.gov (United States)

Pardo, Natalia; Cronin, Shane J.; Wright, Heather M.N.; Schipper, C. Ian; Smith, Ian; Stewart, Bob

2014-01-01

Between 27 and 11 cal. ka BP, a transition is observed in Plinian eruptions at Mt. Ruapehu, indicating evolution from non-collapsing (steady and oscillatory) eruption columns to partially collapsing columns (both wet and dry). To determine the causes of these variations over this eruptive interval, we examined lapilli fall deposits from four eruptions representing the climactic phases of each column type. All eruptions involve andesite to basaltic andesite magmas containing plagioclase, clinopyroxene, orthopyroxene and magnetite phenocrysts. Differences occur in the dominant pumice texture, the degree of bulk chemistry and textural variability, the average microcrystallinity and the composition of groundmass glass. In order to investigate the role of ascent and degassing processes on column stability, vesicle textures were quantified by gas volume pycnometry (porosity), X-ray synchrotron and computed microtomography (μ-CT) imagery from representative clasts from each eruption. These data were linked to groundmass crystallinity and glass geochemistry. Pumice textures were classified into six types (foamy, sheared, fibrous, microvesicular, microsheared and dense) according to the vesicle content, size and shape and microlite content. Bulk porosities vary from 19 to 95 % among all textural types. Melt-referenced vesicle number density ranges between 1.8 × 102 and 8.9 × 102 mm−3, except in fibrous textures, where it spans from 0.3 × 102 to 53 × 102 mm−3. Vesicle-free magnetite number density varies within an order of magnitude from 0.4 × 102 to 4.5 × 102 mm−3 in samples with dacitic groundmass glass and between 0.0 and 2.3 × 102 mm−3 in samples with rhyolitic groundmass. The data indicate that columns that collapsed to produce pyroclastic flows contained pumice with the greatest variation in bulk composition (which overlaps with but extends to slightly more silicic compositions than other eruptive products); textures

Caracterización morfoscópica de los materiales piroclásticos sálicos del sur de Tenerife (Islas Canarias

Directory of Open Access Journals (Sweden)

Alonso, J. J.

1987-12-01

Full Text Available In this work, several morphological aspects of volcanic ash grains from southern Tenerife are studied by S.E.M. Important variations in vesiculation, fracture and wheathering of pyroclasts are observed. It's possible to characterize diferent types of deposits (pyroclastic falIs, pyroclastic flow, surges, etc. in function of the pumice fragments surface.En este trabajo se estudian mediante M.E.B. (Microscopio Electrónico de Barrido diversos aspectos morfológicos de granos de cenizas volcánicas del sur de Tenerife. Son observadas importantes variaciones en la vesiculación, fracturación y alteraciones de los piroclastos. Es posible caracterizar distintos tipos de depósitos (piroclastos de caída, coladas piroclásticas, surges, etc. en función de las características superficiales de los fragmentos pumíticos.

Dynamics of an unusual cone-building trachyte eruption at Pu`u Wa`awa`a, Hualālai volcano, Hawai`i

Science.gov (United States)

Shea, Thomas; Leonhardi, Tanis; Giachetti, Thomas; Lindoo, Amanda; Larsen, Jessica; Sinton, John; Parsons, Elliott

2017-04-01

The Pu`u Wa`awa`a pyroclastic cone and Pu`u Anahulu lava flow are two prominent monogenetic eruptive features assumed to result from a single eruption during the trachyte-dominated early post-shield stage of Hualālai volcano (Hawaíi). Púu Wa`awa`a is composed of complex repetitions of crudely cross-stratified units rich in dark dense clasts, which reversely grade into coarser pumice-rich units. Pyroclasts from the cone are extremely diverse texturally, ranging from glassy obsidian to vesicular scoria or pumice, in addition to fully crystalline end-members. The >100-m thick Pu`u Anahulu flow is, in contrast, entirely holocrystalline. Using field observations coupled with whole rock analyses, this study aimed to test whether the Pu`u Wa`awa`a tephra and Pu`u Anahulu lava flows originated from the same eruption, as had been previously assumed. Crystal and vesicle textures are characterized along with the volatile contents of interstitial glasses to determine the origin of textural variability within Pu`u Wáawáa trachytes (e.g., magma mixing vs. degassing origin). We find that (1) the two eruptions likely originated from distinct vents and magma reservoirs, despite their proximity and similar age, (2) the textural diversity of pyroclasts forming Pu`u Wa`awa`a can be fully explained by variable magma degassing and outgassing within the conduit, (3) the Pu`u Wa`awa`a cone was constructed during explosions transitional in style between violent Strombolian and Vulcanian, involving the formation of a large cone and with repeated disruption of conduit plugs, but without production of large pyroclastic density currents (PDCs), and (4) the contrasting eruption styles of Hawaiian trachytes (flow-, cone-, and PDC-forming) are probably related to differences in the outgassing capacity of the magmas prior to reaching the surface and not in intrinsic compositional or temperature properties. These results further highlight that trachytes are "kinetically faster" magmas compared

Polygenic eruptions on Alba Patera, Mars

International Nuclear Information System (INIS)

Mouginis-Mark, P.J.; Wilson, L.; Zimbelman, J.R.

1988-01-01

A new model for the evolution of the martian volcano Alba Patera is constructed. Numerous digitate channel networks on the flanks of the volcano are interpreted to be carved by sapping due to the release of nonjuvenile water from unconsolidated flank deposits. The particle size of these deposits is estimated to be 3-10 microns, which, together with theoretical modelling of the disperison of explosively derived volcanic materials, leads to the conclusion that the flank deposits on Alba Patera are low-relief pyroclastic flows. The recognition of numerous late-stage summit and subterminal lava flows thus makes Alba Patera a unique martian volcano that is transitional between the older pyroclastic-dominated highland paterae and the more recent effusive central-vent volcanoes such as the Tharsis Montes. 61 refs

Using rocks to reveal the inner workings of magma chambers below volcanoes in Alaska’s National Parks

Science.gov (United States)

Coombs, Michelle L.; Bacon, Charles R.

2012-01-01

Alaska is one of the most vigorously volcanic regions on the planet, and Alaska’s national parks are home to many of the state’s most active volcanoes. These pose both local and more distant hazards in the form of lava and pyroclastic flows, lahars (mudflows), ash clouds, and ash fall. Alaska’s volcanoes lie along the arc of the Aleutian-Alaskan subduction zone, caused as the oceanic Pacific plate moves northward and dips below the North American plate. These volcanoes form as water-rich fluid from the down-going Pacific plate is released, lowering the melting temperature of rock in the overlying mantle and enabling it to partially melt. The melted rock (magma) migrates upward, collecting at the base of the approximately 25 mile (40 km) thick crust, occasionally ascending into the shallow crust, and sometimes erupting at the earth’s surface.During volcanic unrest, scientists use geophysical signals to remotely visualize volcanic processes, such as movement of magma in the upper crust. In addition, erupted volcanic rocks, which are quenched samples of magmas, can tell us about subsurface magma characteris-tics, history, and the processes that drive eruptions. The chemical compositions of and the minerals present in the erupted magmas can reveal conditions under which these magmas were stored in crustal “chambers”. Studies of the products of recent eruptions of Novarupta (1912), Aniakchak (1931), Trident (1953-74), and Redoubt (2009) volcanoes reveal the depths and temperatures of magma storage, and tell of complex interactions between magmas of different compositions. One goal of volcanology is to determine the processes that drive or trigger eruptions. Information recorded in the rocks tells us about these processes. Here, we demonstrate how geologists gain these insights through case studies from four recent eruptions of volcanoes in Alaska national parks.

25 years of ecological change at Mount St. Helens.

Science.gov (United States)

V.H. Dale; C.M. Crisafulli; F.J. Swanson

2005-01-01

18 May 2005 marks the 25th anniversary of the massive eruption of Mount St. Helens. This eruption involved diverse geological processes (1) that disturbed forests, meadows, lakes, an drivers (2) (see the figure). A huge landslide and searing flows of hot gases and pumic framents (pyroclastic flows) inundated 60 km2 of land, obliterating...

K-Ar Geochronology and isotopic composition of the late oligocene- early miocene Ancud volcanic complex, Chiloe

International Nuclear Information System (INIS)

Munoz B, Jorge; Duhart O, Paul; Farmer, G. Lang; Stern, Charles R

2001-01-01

The Ancud Volcanic Complex (Gally and Sanchez , 1960) forms a portion of the Mid-Tertiary Coastal Magmatic Belt which outcrops in the area of northern Chiloe island. Main exposures occur at Ancud, Punta Polocue, Punihuil, Pumillahue, Tetas de Teguaco and Bahia Cocotue. The Ancud Volcanic Complex consists of basaltic to basaltic andesites lava flows and volcanic necks and rhyolitic pyroclastic flows and vitric domes. Previous studies indicate a Late Oligocene-Early Miocene age (Garcia et al., 1988; Stern and Vergara, 1992; Munoz et al., 2000). The Ancud Volcanic Complex covers and intrudes Palaeozoic-Triassic metamorphic rocks and is partially covered by an early to middle Miocene marine sedimentary sequence known as Lacui Formation (Valenzuela, 1982) and by Pleistocene glacial deposits (Heusser, 1990). At Punihuil locality, lava flows are interbedded with the lower part of the marine sedimentary sequence, which includes significant amounts of redeposited pyroclastic components. Locally, the presence of hyaloclastic breccias suggests interaction of magma with marine water (au)

Rheology of the 2006 eruption at Tungurahua volcano, Ecuador

Science.gov (United States)

Hanson, J. B.; Lavallée, Y.; Hess, K.-U.; von Aulock, F. W.; Dingwell, D. B.

2009-04-01

During August 16th to 18th 2006, the eruptive crisis at Tungurahua volcano (Ecuador) culminated in VEI 2 eruption with tens of pyroclastic flows and the extrusion of a lava flow. The nearly simultaneous occurrence of a lava flow and a pyroclastic flow from a single vent deserves attention. Generally, the rheology is a chief determinant of eruption style. Specifically, magmas are ductile (effusive) at low strain rates whereas they are brittle (explosive) at high strain rates. Although this distinction has been extensively described for single-phase magmas, there remain many questions as to the rheological implications of crystals and bubbles present in magmas. Here we present preliminary characterizations of the complex rheology of the magma involved in the 2006 eruption at Tungurahua volcano. The magma present in this eruption was andesitic with an interstitial melt composition averaging ~58 wt.% SiO2. The bombs present in the pyroclastic deposit show an open porosity ranging from 15 to 35 vol.% and a crystallinity generally greater than ~30 vol.% and occasionally up to 60 vol.% in samples affected by microlite growth. Petrographic analyses revealed magma batches with different crystallization histories. In high-porosity samples containing microlites, a recrystallization rim around clinopyroxene and resorption of the plagioclase were observed. In contrast, the dense samples show pristine, euhedral crystals and a near absence of microlites. The heterogeneous petrographic structures suggest the possibilities of mingling in the conduit or of magma batches with different decompression rates. Dilatometric analyses suggest glass transition temperatures (Tg) of ~974 °C for the dense material (porosity~15 vol.%) and as high as ~1060 °C for the high-porosity bombs (porosity~35 vol.%). Successive series of heating and cooling of the glass reveal an increase of Tg by as much as 60 °C indicative of significant water left in the melt. Preliminary analyses of images obtained

A combined field and numerical approach to understanding dilute pyroclastic density current dynamics and hazard potential: Auckland Volcanic Field, New Zealand

Science.gov (United States)

Brand, Brittany D.; Gravley, Darren M.; Clarke, Amanda B.; Lindsay, Jan M.; Bloomberg, Simon H.; Agustin-Flores, Javier; Németh, Károly

2014-04-01

The most dangerous and deadly hazards associated with phreatomagmatic eruptions in the Auckland Volcanic Field (AVF; Auckland, New Zealand) are those related to volcanic base surges - dilute, ground-hugging, particle laden currents with dynamic pressures capable of severe to complete structural damage. We use the well-exposed base surge deposits of the Maungataketake tuff ring (Manukau coast, Auckland), to reconstruct flow dynamics and destructive potential of base surges produced during the eruption. The initial base surge(s) snapped trees up to 0.5 m in diameter near their base as far as 0.7-0.9 km from the vent. Beyond this distance the trees were encapsulated and buried by the surge in growth position. Using the tree diameter and yield strength of the wood we calculate that dynamic pressures (Pdyn) in excess of 12-35 kPa are necessary to cause the observed damage. Next we develop a quantitative model for flow of and sedimentation from a radially-spreading, dilute pyroclastic density currents (PDCs) to determine the damage potential of the base surges produced during the early phases of the eruption and explore the implications of this potential on future eruptions in the region. We find that initial conditions with velocities on the order of 65 m s- 1, bulk density of 38 kg m- 3 and initial, near-vent current thicknesses of 60 m reproduce the field-based Pdyn estimates and runout distances. A sensitivity analysis revealed that lower initial bulk densities result in shorter run-out distances, more rapid deceleration of the current and lower dynamic pressures. Initial velocity does not have a strong influence on run-out distance, although higher initial velocity and slope slightly decrease runout distance due to higher rates of atmospheric entrainment. Using this model we determine that for base surges with runout distances of up to 4 km, complete destruction can be expected within 0.5 km from the vent, moderate destruction can be expected up to 2 km, but much

New geochemical, geochronological and structural constraints on the Ediacaran evolution of the south Sirwa, Agadir-Melloul and Iguerda inliers, Anti-Atlas, Morocco

Science.gov (United States)

Blein, O.; Baudin, T.; Soulaimani, A.; Cocherie, A.; Chèvremont, P.; Admou, H.; Ouanaimi, H.; Hafid, A.; Razin, P.; Bouabdelli, M.; Roger, J.

2014-10-01

Paleoproterozoic metamorphic and igneous rocks, Tonian (?)-lower Cryogenian passive margin sedimentary rocks, Neoproterozoic dolerites, and Upper Ediacaran volcaniclastic, volcanic and pyroclastic rocks are exposed in the Agadir Melloul, Iguerda and the southern edge of the Sirwa inliers. A recent field mapping program of the Ediacaran Ouarzazate Group in these areas allow to distinguish three principal volcanic sequences. The first sequence (Adrar-n-Takoucht Formation) outcrops mainly south of the Sirwa inlier, and is composed of felsic pyroclastic deposits and local basaltic lavas with ages ranging between 572 and 570 Ma. The second sequence (Anammar and Tadoughast formations) occurs primarily in the Agadir Melloul-Jbel Iguiguil inlier. The Anammar Formation contains essentially volcano-detrital sediments, with fine airfall pyroclastic deposits. The Tadoughast Formation is composed of felsic pyroclastic deposits and rhyolitic domes with ages ranging between 567 and 564 Ma. The third sequence (Fajjoud Formation) contains felsic pyroclastic deposits, with an age of 556 Ma, associated with porphyritic basalts. The magmatism of the Ouarzazate Group was not continuous between 572 and 556 Ma, but related to distinct pyroclastic pulses. Geochemical data indicate that the pyroclastic rocks of the Ouarzazate Group have a highly potassic calc-alkaline to shoshonitic affinity. However, the basaltic facies associated with the Adrar-n-Takoucht Formation demonstrate a calc-alkaline affinity whereas those associated with the Fajjoud Formation have a tholeiitic affinity. Rhyolitic domes were derived from hyperaluminous leucogranites. In sum, the typology of zircons defines three poles: (i) subalkaline granites; (ii) calc-alkaline monzogranites and granodiorites frequently associated with basic rocks; and (iii) aluminous leucogranites. In addition, the volcaniclastic deposits of the Ouarzazate Group are submitted to a syn-sedimentary tectonic. The Adrar-n-Takoucht Formation is

Disruption of tephra fall deposits caused by lava flows during basaltic eruptions

Science.gov (United States)

Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

2015-10-01

Observations in the USA, Iceland and Tenerife, Canary Islands reveal how processes occurring during basaltic eruptions can result in complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity arises through synchronous and alternating effusive and explosive activity that results in intercalated lavas and tephra deposits. Tephra deposits can become disrupted into mounds and ridges by lateral and vertical displacement caused by movement (including inflation) of underlying pāhoehoe lavas and clastogenic lavas. Mounds of tephra can be rafted away over distances of 100 s to 1,000 s m from proximal pyroclastic constructs on top of lava flows. Draping of irregular topography by fall deposits and subsequent partial burial of topographic depressions by later lavas can result in apparent complexity of tephra layers. These processes, deduced from field relationships, have resulted in considerable stratigraphic complexity in the studied proximal regions where fallout was synchronous or alternated with inflation of subjacent lava sheets. These mechanisms may lead to diachronous contact relationships between fall deposits and lava flows. Such complexities may remain cryptic due to textural and geochemical quasi-homogeneity within sequences of interbedded basaltic fall deposits and lavas. The net effect of these processes may be to reduce the usefulness of data collected from proximal fall deposits for reconstructing basaltic eruption dynamics.

Non-equilibrium processes in ash-laden volcanic plumes: new insights from 3D multiphase flow simulations

Science.gov (United States)

Esposti Ongaro, Tomaso; Cerminara, Matteo

2016-10-01

In the framework of the IAVCEI (International Association of Volcanology and Chemistry of the Earth Interior) initiative on volcanic plume models intercomparison, we discuss three-dimensional numerical simulations performed with the multiphase flow model PDAC (Pyroclastic Dispersal Analysis Code). The model describes the dynamics of volcanic and atmospheric gases (in absence of wind) and two pyroclastic phases by adopting a non-equilibrium Eulerian-Eulerian formulation. Accordingly, gas and particulate phases are treated as interpenetrating fluids, interacting with each other through momentum (drag) and heat exchange. Numerical results describe the time-wise and spatial evolution of weak (mass eruption rate: 1.5 × 106 kg/s) and strong (mass eruption rate: 1.5 × 109 kg/s) plumes. The two tested cases display a remarkably different phenomenology, associated with the different roles of atmospheric stratification, compressibility and mechanism of buoyancy reversal, reflecting in a different structure of the plume, of the turbulent eddies and of the atmospheric circulation. This also brings about different rates of turbulent mixing and atmospheric air entrainment. The adopted multiphase flow model allows to quantify temperature and velocity differences between the gas and particles, including settling, preferential concentration by turbulence and thermal non-equilibrium, as a function of their Stokes number, i.e., the ratio between their kinetic equilibrium time and the characteristic large-eddy turnover time of the turbulent plume. As a result, the spatial and temporal distribution of coarse ash in the atmosphere significantly differs from that of the fine ash, leading to a modification of the plume shape. Finally, three-dimensional numerical results have been averaged in time and across horizontal slices in order to obtain a one-dimensional picture of the plume in a stationary regime. For the weak plume, the results are consistent with one-dimensional models, at

October 2005 Debris Flows at Panabaj, Guatemala:Hazard Assessment

Science.gov (United States)

Sheridan, M. F.; Connor, C.; Connor, L.; Stinton, A.; Galacia, O. R.; Barrios, G.

2007-05-01

In October, 2005, tropical storm Stan caused heavy precipitation throughout much of Guatemala. In the community of Panabaj, Santiago Atitlán, a landslide of pyroclastic material originating high on the slopes of Tolimán volcano buried much of the community, leaving approximately 400 people dead. Current estimates by the Coordinadora Nacional para la Reducción de Desastres (CONRED) suggest that at least 2,600 people from the community of Panabaj, Santiago Atitlán have been displaced by the debris flows. Because the temporary housing for people displaced by the debris flows is located in an area that is geologically and morphologically similar to the area inundated by flows in October, 2005, this area may be potentially inundated by debris flows as well. In addition to the thousands of people living in temporary shelters, many hundreds of people are currently reoccupying land adjacent to or on the October, 2005 debris flows. Thus a large fraction of the surviving Panabaj community appears to remain at risk from future debris flows. We used differential GPS (Global Positioning System) to outline the boundaries of the debris flows, to estimate variation in flow thicknesses, and to determine their volumes. Mass movement on Tolimán volcano resulted in the generation of a moderate size debris flow (360,000 m3 of sediment plus water) that descended the volcano rapidly, bifurcated into two stream valleys high on the flanks of the volcano, and continued to descend both channels until these flows reached the alluvial fan near the shores of Lago de Atitlán. After bifurcating into two flows high on the flanks of the volcano, about 65% of the flow (by volume) descended the western channel, forming the Western flow. Approximately one kilometer above the alluvial fan, this channel descends steep topography, with a slope of 11.5°. This average slope gradually decreases down the channel, reaching only 5.3° just above the alluvial fan. In contrast, average slopes on the

Performance characteristics of tunnel boring machine in basalt and pyroclastic rocks of Deccan traps – A case study

Directory of Open Access Journals (Sweden)

Prasnna Jain

2014-02-01

Full Text Available A 12.24 km long tunnel between Maroshi and Ruparel College is being excavated by tunnel boring machine (TBM to improve the water supply system of Greater Mumbai, India. In this paper, attempt has been made to establish the relationship between various litho-units of Deccan traps, stability of tunnel and TBM performances during the construction of 5.83 km long tunnel between Maroshi and Vakola. The Maroshi–Vakola tunnel passes under the Mumbai Airport and crosses both runways with an overburden cover of around 70 m. The tunneling work was carried out without disturbance to the ground. The rock types encountered during excavation are fine compacted basalt, porphyritic basalt, amygdaloidal basalt, pyroclastic rocks with layers of red boles and intertrappean beds consisting of various types of shales. Relations between rock mass properties, physico-mechanical properties, TBM specifications and the corresponding TBM performance were established. A number of support systems installed in the tunnel during excavation were also discussed. The aim of this paper is to establish, with appropriate accuracy, the nature of subsurface rock mass condition and to study how it will react to or behave during underground excavation by TBM. The experiences gained from this project will increase the ability to cope with unexpected ground conditions during tunneling using TBM.

Long-term volcanic hazard assessment on El Hierro (Canary Islands)

Science.gov (United States)

Becerril, L.; Bartolini, S.; Sobradelo, R.; Martí, J.; Morales, J. M.; Galindo, I.

2014-07-01

Long-term hazard assessment, one of the bastions of risk-mitigation programs, is required for land-use planning and for developing emergency plans. To ensure quality and representative results, long-term volcanic hazard assessment requires several sequential steps to be completed, which include the compilation of geological and volcanological information, the characterisation of past eruptions, spatial and temporal probabilistic studies, and the simulation of different eruptive scenarios. Despite being a densely populated active volcanic region that receives millions of visitors per year, no systematic hazard assessment has ever been conducted on the Canary Islands. In this paper we focus our attention on El Hierro, the youngest of the Canary Islands and the most recently affected by an eruption. We analyse the past eruptive activity to determine the spatial and temporal probability, and likely style of a future eruption on the island, i.e. the where, when and how. By studying the past eruptive behaviour of the island and assuming that future eruptive patterns will be similar, we aim to identify the most likely volcanic scenarios and corresponding hazards, which include lava flows, pyroclastic fallout and pyroclastic density currents (PDCs). Finally, we estimate their probability of occurrence. The end result, through the combination of the most probable scenarios (lava flows, pyroclastic density currents and ashfall), is the first qualitative integrated volcanic hazard map of the island.

Post-eruptive sediment transport and surface processes on unvegetated volcanic hillslopes - A case study of Black Tank scoria cone, Cima Volcanic Field, California

Science.gov (United States)

Kereszturi, Gábor; Németh, Károly

2016-08-01

Conical volcanic edifices that are made up from lapilli to block/bomb pyroclastic successions, such as scoria cones, are widespread in terrestrial and extraterrestrial settings. Eruptive processes responsible for establishing the final facies architecture of a scoria cone are not well linked to numerical simulations of their post-eruptive sediment transport. Using sedimentological, geomorphic and 2D fragment morphology data from a 15-ky-old scoria cone from the Cima Volcanic Field, California, this study provides field evidence of the various post-eruptive sediment transport and degradation processes of scoria cones located in arid to semi-arid environments. This study has revealed that pyroclast morphologies vary downslope due to syn-eruptive granular flows, along with post-eruptive modification by rolling, bouncing and sliding of individual particles down a slope, and overland flow processes. The variability of sediment transport rates on hillslopes are not directly controlled by local slope angle variability and the flank length but rather by grain size, and morphological characteristics of particles, such as shape irregularity of pyroclast fragments and block/lapilli ratio. Due to the abundance of hillslopes degrading in unvegetated regions, such as those found in the Southwestern USA, granulometric influences should be accounted for in the formulation of sediment transport laws for geomorphic modification of volcanic terrains over long geologic time.

A new U-Pb zircon age and a volcanogenic model for the early Permian Chemnitz Fossil Forest

Science.gov (United States)

Luthardt, Ludwig; Hofmann, Mandy; Linnemann, Ulf; Gerdes, Axel; Marko, Linda; Rößler, Ronny

2018-04-01

The Chemnitz Fossil Forest depicts one of the most completely preserved forest ecosystems in late Paleozoic Northern Hemisphere of tropical Pangaea. Fossil biota was preserved as a T0 taphocoenosis resulting from the instantaneous entombment by volcanic ashes of the Zeisigwald Tuff. The eruption depicts one of the late magmatic events of post-variscan rhyolitic volcanism in Central Europe. This study represents a multi-method evaluation of the pyroclastic ejecta encompassing sedimentological and (isotope) geochemical approaches to shed light on magmatic and volcanic processes, and their role in preserving the fossil assemblage. The Zeisigwald Tuff pyroclastics (ZTP) reveal a radiometric age of 291 ± 2 Ma, pointing to a late Sakmarian/early Artinskian (early Permian) stratigraphic position for the Chemnitz Fossil Forest. The initial eruption was of phreatomagmatic style producing deposits of cool, wet ashes, which deposited from pyroclastic fall out and density currents. Culmination of the eruption is reflected by massive hot and dry ignimbrites. Whole-rock geochemistry and zircon grain analysis show that pyroclastic deposits originated from a felsic, highly specialised magma, which underwent advanced fractionation, and is probably related to post-Carboniferous magmatism in the Western Erzgebirge. The ascending magma recycled old cadomic crust of the Saxo-thuringian zone, likely induced by a mantle-derived heat flow during a phase of post-variscan crustal delamination. Geochemical trends within the succession of the basal pyroclastic horizons reflect inverse zonation of the magma chamber and provide evidence for the continuous eruption and thus a simultaneous burial of the diverse ecosystem.

Stratigraphy and eruption age of the volcanic rocks in the west of Miyanoharu area, Kumamoto Prefecture

International Nuclear Information System (INIS)

Kamata, Hiroki

1985-01-01

The detailed stratigraphic survey, K-Ar age determinations and NRM measurements of the volcanic rocks in the west of Miyanoharu area revealed the volcanic history as follows: Hornblende andesite lava with plagioclase megacryst (Yoshinomoto lava) erupted during 2.8 - 2.5 Ma (Gauss normal epoch), accompanied by small amount of pyroclastic materials. After this eruption, Kamitarumizu hypersthene-augite andesite lava (1.7 - 1.3 Ma; reversed), Yabakei pyroclastic flow (0.99 Ma; Jaramillo normal event), Yamakogawa biotite rhyolite lava (0.9 Ma; reversed) and Daikanbo hypersthene-augite andesite lava (0.8 Ma; normal) erupted successively prior to the Aso-1 pyroclastic flow (0.3 - 0.4 Ma). Both the K-Ar ages and NRM data are consistent with the stratigraphic sequence (Fig. 2), which suggests that the activity of andesite and rhyolite is intercalated with each other during Pleistocene in the studied area. The compiled radiometric age data in the central-north Kyushu show that the age of volcanic activity that has previously been inferred as middle Miocene is of Pliocene, and its distribution is limited within the quadrilateral (60 km x 40 km) where the pre-Tertiary basement rocks are absent. The distribution of volcanic rocks is historically zonated such that the rocks of older age up to 5 Ma develop toward the outer rim of the quadrilateral, which coincides with the 0 mgal contour bordering the large low Bouguer anomaly. These facts suggest that the volcanic activity is remarkably relevant to the subsidence of this area, where the volcano-tectonic depression has been formed after 5 Ma to the present, and filled with lavas and pyroclastic materials with scarce sedimentary rocks in the tension stress field during Plio-Pleistocene age. (Kubozono, M.)

Felsic tuff from Rutland Island – A pyroclastic flow deposit in ...

Indian Academy of Sciences (India)

: • white massive tuff with ill-defined bedding contacts (facies-A) and. • dominantly green tuff exhibiting well-developed turbidite sequence with up-section change from a massive unit to plane laminated units to ripple drift lamination (facies-B).

Applying genetic algorithms for calibrating a hexagonal cellular automata model for the simulation of debris flows characterised by strong inertial effects

Science.gov (United States)

Iovine, G.; D'Ambrosio, D.; Di Gregorio, S.

2005-03-01

In modelling complex a-centric phenomena which evolve through local interactions within a discrete time-space, cellular automata (CA) represent a valid alternative to standard solution methods based on differential equations. Flow-type phenomena (such as lava flows, pyroclastic flows, earth flows, and debris flows) can be viewed as a-centric dynamical systems, and they can therefore be properly investigated in CA terms. SCIDDICA S 4a is the last release of a two-dimensional hexagonal CA model for simulating debris flows characterised by strong inertial effects. S 4a has been obtained by progressively enriching an initial simplified model, originally derived for simulating very simple cases of slow-moving flow-type landslides. Using an empirical strategy, in S 4a, the inertial character of the flowing mass is translated into CA terms by means of local rules. In particular, in the transition function of the model, the distribution of landslide debris among the cells is obtained through a double cycle of computation. In the first phase, the inertial character of the landslide debris is taken into account by considering indicators of momentum. In the second phase, any remaining debris in the central cell is distributed among the adjacent cells, according to the principle of maximum possible equilibrium. The complexities of the model and of the phenomena to be simulated suggested the need for an automated technique of evaluation for the determination of the best set of global parameters. Accordingly, the model is calibrated using a genetic algorithm and by considering the May 1998 Curti-Sarno (Southern Italy) debris flow. The boundaries of the area affected by the debris flow are simulated well with the model. Errors computed by comparing the simulations with the mapped areal extent of the actual landslide are smaller than those previously obtained without genetic algorithms. As the experiments have been realised in a sequential computing environment, they could be

Early neogene history of the central American arc from Bocas del Toro, western Panama

Science.gov (United States)

Coates, Anthony G.; Aubry, Marie-Pierre; Berggren, William A.; Collins, Laurel S.; Kunk, Michael J.

2003-01-01

A newly discovered sequence of lower to middle Miocene rocks from the eastern Bocas del Toro archipelago, western Panama, reveals the timing and environment of the earliest stages in the rise of the Isthmus of Panama in this region. Two new formations, the Punta Alegre Formation (lower Miocene, Aquitanian to Burdigalian) and the Valiente Formation (middle Miocene, Langhian to Serravallian), are here named and formally described. The Punta Alegre Formation contains a diagnostic microfauna of benthic and planktic foraminifera and calcareous nannofossils that indicate deposition in a 2000-m-deep pre-isthmian neotropical ocean from as old as 21.5–18.3 Ma. Its lithology varies from silty mudstone to muddy foraminiferal ooze with rare thin microturbidite layers near the top. The Valiente Formation, which ranges in age from 16.4 to ca. 12.0 Ma, lies with slight angular unconformity on the Punta Alegre Formation and consists of five lithofacies: (1) columnar basalt and flow breccia, (2) pyroclastic deposits, (3) coarse-grained volcaniclastic deposits, (4) coral-reef limestone with diverse large coral colonies, and (5) marine debris-flow deposits and microturbidites. These lithofacies are interpreted to indicate that after ca. 16 Ma a volcanic arc developed in the region of Bocas del Toro and that by ca. 12 Ma an extensively emergent archipelago of volcanic islands had formed. 39Ar/40Ar dating of basalt flows associated with the fossiliferous sedimentary rocks in the upper part of the Valiente Formation strongly confirms the ages derived from planktic foraminifera and nannofossils. Paleobathymetric analysis of the two new formations in the Valiente Peninsula and Popa Island, in the Bocas del Toro archipelago, shows a general shallowing from lower- through upper-bathyal to upper-neritic and emergent laharic and fluviatile deposits from ca. 19 to 12 Ma. The overlying nonconformable Bocas del Toro Group contains a lower transgressive sequence ranging from basal nearshore

Conditions and timescales for welding block-and-ash flow deposits

Science.gov (United States)

Heap, M. J.; Kolzenburg, S.; Russell, J. K.; Campbell, M. E.; Welles, J.; Farquharson, J. I.; Ryan, A.

2014-12-01

Welding of pyroclastic deposits to reform a coherent rock mass is a common phenomenon, especially for pumiceous pyroclastic density current deposits (i.e., ignimbrites). However, and despite the pervasive abundance of block-and-ash flow (BAF) deposits in the geological and modern record, instances of strongly welded BAF deposits are few. Here, we present a series of high-temperature (800-900 °C) compaction experiments designed to map the conditions (deposit thickness/stress and temperature/viscosity) and timescales that permit or inhibit the welding of BAF deposits. Our experiments were performed on unconsolidated aggregates (containing an ash and lapilli component) derived from crushed and sieved lava blocks (containing 25% crystals) taken from the well-documented welded BAF deposit at Mount Meager volcano (British Columbia, Canada). The experiments demonstrate that welding efficiency increases with increasing time and temperature. Progressive welding is expressed by increasing axial strain, porosity loss, and bulk density. The rate of change of each of these physical properties reduces as welding progresses. Microstructural analysis of the experimental products shows that the loss of interclast porosity during welding results from the progressive sintering and amalgamation of vitric fragments, and that the pore shape changes from sub-equant pores to stretched lenses sandwiched between vitric and crystal fragments. The coincidence between the microstructure and rock physical properties of the natural and experimental samples highlight that we have successfully reproduced welded BAF in the laboratory. Furthermore, our permeability measurements highlight a hysteresis in the return journey of the "there-and-back-again" volcanic permeability cycle (expressed by an increase in permeability due to vesiculation and fragmentation followed by a decrease due to welding). This hysteresis cannot be described by a single porosity-permeability power law relationship and

Late Ordovician (post-Sardic) rifting branches in the North Gondwanan Montagne Noire and Mouthoumet massifs of southern France

DEFF Research Database (Denmark)

Javier Álvaro, J.; Colmenar Lallena, Jorge; Monceret, Eric

2016-01-01

, and the subsequent Middle-Ordovician stratigraphic gap is related to the Sardic phase. Upper Ordovician sedimentation started in the rifting branches of Cabrières and Mouthoumet with deposition of basaltic lava flows and lahar deposits (Roque de Bandies and Villerouge formations) of continental tholeiite signature...... (CT), indicative of continental fracturing.The infill of both rifting branches followed with the onset of (1) Katian (Ka1-Ka2) conglomerates and sandstones (Glauzy and Gascagne formations), which have yielded a new brachiopod assemblage representative of the Svobodaina havliceki Community; (2) Katian...

14C ages and activity for the past 50 ka at Volcán Galeras, Colombia

Science.gov (United States)

Banks, N.G.; Calvache, V.M.L.; Williams, S.N.

1997-01-01

Volcán Galeras is the southernmost Colombian volcano with well-recorded historic activity. The volcano is part of a large and complex volcanic center upon which 400,000 people live. Historic activity has centered on a small-volume cone inside the youngest of several large amphitheaters that breach the west flank of the volcano, away from the city of Pasto (population 300,000). Lava flows (SiO2 between 54.6 and 64.7 wt.%) have dominated activity for more than 1 Ma, but explosive events have also occurred. Joint studies by volcanologists from Colombia, Ecuador, Peru, Bolivia, Argentina, and the United States produced 24 new14C ages and more than 100 stratigraphic sections to interpret the past 50 ka of activity at Galeras, including sector collapse events. The youngest collapse event truncated 12.8 ka lava flows and may have occurred as recently as 8 to 10 ka. Tephra-fall material rapidly thins and becomes finer away from the vent area. The only widespread marker in the < 10 ka section is a biotite-bearing tephra deposited between 4.1 and 4.5 ka from a source south of Galeras. It separates cryoturbated from largely undisturbed layers on Galeras, and thus dates a stratigraphic horizon which is useful in the interpretation of other volcanoes and geotectonics in the equatorial Andes. Pyroclastic flows during the past 50 ka have been small to moderate in volume, but they have left numerous thin deposits on the north and east flanks where lava flows have been impeded by crater and amphitheater walls. Many of the pyroclastic-flow deposits are lithic rich, with fines and clasts so strongly altered by hydrothermal action before eruption that they, as well as the sector collapse deposits, resemble waste dumps of leached cappings from disseminated sulfide deposits more than volcanogenic deposits. This evidence of a long-lived hydrothermal system indicates susceptibility to mass failure and explosive events higher than expected for a volcano built largely by lava flows and

Thermal interactions of the AD79 Vesuvius pyroclastic density currents and their deposits at Villa dei Papiri (Herculaneum archaeological site, Italy)

Science.gov (United States)

Giordano, G.; Zanella, E.; Trolese, M.; Baffioni, C.; Vona, A.; Caricchi, C.; De Benedetti, A. A.; Corrado, S.; Romano, C.; Sulpizio, R.; Geshi, N.

2018-05-01

Pyroclastic density currents (PDCs) can have devastating impacts on urban settlements, due to their dynamic pressure and high temperatures. Our degree of understanding of the interplay between these hot currents and the affected infrastructures is thus fundamental not only to implement our strategies for risk reduction, but also to better understand PDC dynamics. We studied the temperature of emplacement of PDC deposits that destroyed and buried the Villa dei Papiri, an aristocratic Roman edifice located just outside the Herculaneum city, during the AD79 plinian eruption of Mt Vesuvius (Italy) by using the thermal remanent magnetization of embedded lithic clasts. The PDC deposits around and inside the Villa show substantial internal thermal disequilibrium. In areas affected by convective mixing with surface water or with collapsed walls, temperatures average at around 270 °C (min 190 °C, max 300 °C). Where the deposits show no evidence of mixing with external material, the temperature is much higher, averaging at 350 °C (min 300 °C; max 440 °C). Numerical simulations and comparison with temperatures retrieved at the very same sites from the reflectance of charcoal fragments indicate that such thermal disequilibrium can be maintained inside the PDC deposit for time-scales well over 24 hours, i.e. the acquisition time of deposit temperatures for common proxies. We reconstructed in detail the history of the progressive destruction and burial of Villa dei Papiri and infer that the rather homogeneous highest deposit temperatures (average 350 °C) were carried by the ash-sized fraction in thermal equilibrium with the fluid phase of the incoming PDCs. These temperatures can be lowered on short time- (less than hours) and length-scales (meters to tens of meters) only where convective mixing with external materials or fluids occurs. By contrast, where the Villa walls remained standing the thermal exchange was only conductive and very slow, i.e. negligible at 50 cm

Late Pleistocene and Holocene activity of the Atacazo-Ninahuilca Volcanic Complex (Ecuador)

NARCIS (Netherlands)

Hidalgo, Silvana; Monzier, Michel; Almeida, Eduardo; Chazot, Gilles; Eissen, Jean-Philippe; van der Plicht, Johannes; Hall, Minard L.

2008-01-01

The Atacazo-Ninahuilca Volcanic Complex (ANVC) is located in the Western Cordillera of Ecuador, 10 km southwest of Quito. At least six periods of Pleistocene to Holocene activity (N1 to N6) have been preserved in the geologic record as tephra fallouts and pyroclastic flow deposits. New field data,

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

Felsic tuff from Rutland Island – A pyroclastic flow deposit in Miocene-sediments of Andaman-Java subduction complex · Tapan Pal Biswajit Ghosh Anindya Bhattacharya S K Bhaduri · More Details Abstract Fulltext PDF. The bedded felsic tuff exposed in Rutland Island, Andaman, consists of two facies: white massive tuff ...

The 2014 eruptions of Pavlof Volcano, Alaska

Science.gov (United States)

Waythomas, Christopher F.; Haney, Matthew M.; Wallace, Kristi; Cameron, Cheryl E.; Schneider, David J.

2017-12-22

Pavlof Volcano is one of the most frequently active volcanoes in the Aleutian Island arc, having erupted more than 40 times since observations were first recorded in the early 1800s . The volcano is located on the Alaska Peninsula (lat 55.4173° N, long 161.8937° W), near Izembek National Wildlife Refuge. The towns and villages closest to the volcano are Cold Bay, Nelson Lagoon, Sand Point, and King Cove, which are all within 90 kilometers (km) of the volcano (fig. 1). Pavlof is a symmetrically shaped stratocone that is 2,518 meters (m) high, and has about 2,300 m of relief. The volcano supports a cover of glacial ice and perennial snow roughly 2 to 4 cubic kilometers (km3) in volume, which is mantled by variable amounts of tephra fall, rockfall debris, and pyroclastic-flow deposits produced during historical eruptions. Typical Pavlof eruptions are characterized by moderate amounts of ash emission, lava fountaining, spatter-fed lava flows, explosions, and the accumulation of unstable mounds of spatter on the upper flanks of the volcano. The accumulation and subsequent collapse of spatter piles on the upper flanks of the volcano creates hot granular avalanches, which erode and melt snow and ice, and thereby generate watery debris-flow and hyperconcentrated-flow lahars. Seismic instruments were first installed on Pavlof Volcano in the early 1970s, and since then eruptive episodes have been better characterized and specific processes have been documented with greater certainty. The application of remote sensing techniques, including the use of infrasound data, has also aided the study of more recent eruptions. Although Pavlof Volcano is located in a remote part of Alaska, it is visible from Cold Bay, Sand Point, and Nelson Lagoon, making distal observations of eruptive activity possible, weather permitting. A busy air-travel corridor that is utilized by a numerous transcontinental and regional air carriers passes near Pavlof Volcano. The frequency of air travel

Update of map the volcanic hazard in the Ceboruco volcano, Nayarit, Mexico

Science.gov (United States)

Suarez-Plascencia, C.; Camarena-Garcia, M. A.; Nunez-Cornu, F. J.

2012-12-01

(Hibiscus sabdariffa). Recently it has established tomato and green pepper crops in greenhouses. The regional commercial activities are concentrated in the localities of Ixtlán, Jala and Ahuacatlán. The updated hazard maps are: a) Hazard map of pyroclastic flows, b) Hazard map of lahars and debris flow, and c) Hazard map of ash-fall. The cartographic and database information obtained will be the basis for updating the Operational Plan of the Ceboruco Volcano by the State Civil & Fire Protection Unit of Nayarit, Mexico, and the urban development plans of surrounding municipalities, in order to reduce their vulnerability to the hazards of the volcanic activity.

Magma viscosity estimation based on analysis of erupted products. Potential assessment for large-scale pyroclastic eruptions

International Nuclear Information System (INIS)

Takeuchi, Shingo

2010-01-01

After the formulation of guidelines for volcanic hazards in site evaluation for nuclear installations (e.g. JEAG4625-2009), it is required to establish appropriate methods to assess potential of large-scale pyroclastic eruptions at long-dormant volcanoes, which is one of the most hazardous volcanic phenomena on the safety of the installations. In considering the volcanic dormancy, magma eruptability is an important concept. The magma eruptability is dominantly controlled by magma viscosity, which can be estimated from petrological analysis of erupted materials. Therefore, viscosity estimation of magmas erupted in past eruptions should provide important information to assess future activities at hazardous volcanoes. In order to show the importance of magma viscosity in the concept of magma eruptability, this report overviews dike propagation processes from a magma chamber and nature of magma viscosity. Magma viscosity at pre-eruptive conditions of magma chambers were compiled based on previous petrological studies on past eruptions in Japan. There are only 16 examples of eruptions at 9 volcanoes satisfying data requirement for magma viscosity estimation. Estimated magma viscosities range from 10 2 to 10 7 Pa·s for basaltic to rhyolitic magmas. Most of examples fall below dike propagation limit of magma viscosity (ca. 10 6 Pa·s) estimated based on a dike propagation model. Highly viscous magmas (ca. 10 7 Pa·s) than the dike propagation limit are considered to lose eruptability which is the ability to form dikes and initiate eruptions. However, in some cases, small precursory eruptions of less viscous magmas commonly occurred just before climactic eruptions of the highly viscous magmas, suggesting that the precursory dike propagation by the less viscous magmas induced the following eruptions of highly viscous magmas (ca. 10 7 Pa·s). (author)

Geologic setting of diverse volcanic materials in northern Elysium Planitia, Mars

International Nuclear Information System (INIS)

Mouginis-Mark, P.J.

1990-01-01

Geologic mapping of high-resolution (30-50 m/pixel) Viking Orbiter images of northern Elysium Planitia has identified seven sites where current problems in martian volcanology, chronology, and stratigraphy can be resolved. These sites, which are discussed in the context of a potential Mars rover/sample return mission, would permit the following investigations: (1) the dating of Lower Amazonian lava flows from Elysium Mons (thereby providing absolute calibration for global crater size/frequency relative chronologies), (2) the petrologic investigation of long run-out lava flows, (3) the geologic interpretation of materials that may either be lava flows or lahar deposits, (4) the analysis of materials believed to be ash deposits produced by explosive eruptions of Hecates Tholus, and (5) the investigation of the stratigraphy of fractured terrain along the boundary between northern Elysium Planitia and southern Utopia Planitia. 63 refs

Posteruption arthropod succession on the Mount St. Helens volcano: the ground-dwelling beetle fauna (Coleoptera).

Science.gov (United States)

R.R. Parmenter; C.M. Crisafulli; N. Korbe; G. Parsons; M. Edgar; J.A. MacMahon

2005-01-01

The 1980 eruptions of Mount St. Helens created a complex mosaic of disturbance types over a 600 km2 area. From 1980 through 2000 we monitored beetle species relative abundance and faunal composition of assemblages at undisturbed reference sites and in areas subjected to tephra-fall, blowdown, and pyroclastic flow volcanic disturbance. We...

Nature and Intensity of the 22-23 April 2015 Eruptions of Volcán Calbuco, Chile, from Satellite, Lightning, and Field Observations

Science.gov (United States)

Van Eaton, A. R.; Amigo, A.; Bertin, D.; Mastin, L. G.; Giacosa, R.; Behnke, S. A.

2015-12-01

On 22 April 2015, Calbuco Volcano in southern Chile erupted for the first time in 43 years. The two primary phases of eruption, separated by a few hours, produced pyroclastic density currents, lahars, and spectacular vertical eruption columns that rose into the stratosphere. Clear weather conditions allowed the populated areas of Puerto Montt and Puerto Varas full view of the lightning-rich eruption, which was rapidly shared through social media. A wealth of remote-sensing data was also publically available in near real-time. We used this information to assess the eruption behavior by combining satellite-based umbrella growth rates, and the location and frequency of volcanic lightning. Umbrella expansion rates from GOES-13 satellite retrievals correspond to eruption rates of about 4x106 kg s-1 for the first eruptive phase and 6x106 kg s-1 for the second phase, following the approach of Pouget et al. (2013, JVGR, 258, 100-112). The location and timing of lightning flashes were obtained from the World Wide Lightning Location Network (WWLLN) Global Volcanic Lightning Monitor, which is updated approximately every minute (Ewert et al., 2010, Fall AGU Abstract AE31A-04). Interestingly, the onset of detected flashes was delayed by ~30 min after the start of each eruptive phase. Lighting provided a useful proxy for the waxing or waning intensity of the eruption, and helped identify the end of significant ash emissions. Using the 1-D volcanic plume model Plumeria, we have also simulated the vertical distribution of ash and ice in the plumes to examine potential causes of the extraordinary amount of volcanic lightning (1,094 flashes detected). Our analysis provides information on eruption timing, duration, and mass flow rate, which are necessary for ash dispersal modeling within hours of eruption. Results are also consistent with the field-based measurements of total erupted volume. We suggest that the combination of satellite-detected umbrella expansion rates with lightning

VOLCANIC TSUNAMI GENERATING SOURCE MECHANISMS IN THE EASTERN CARIBBEAN REGION

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George Pararas-Carayannis

2004-01-01

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

Volcanic Ash Hazards and Risk in Argentina: Scientific and Social Collaborative Approaches.

Science.gov (United States)

Rovere, E. I., II; Violante, R. A.; Vazquez Herrera, M. D.; Martinez Fernandez, M. D. L. P.

2015-12-01

Due to the absence of alerts or volcanic impacts during 60 years (from 1932, Quizapu-Descabezado Grande -one of the major eruptions of the XX Century- until 1991 Hudson eruption) there was mild remembrance of volcanic hazards in the collective memory of the Argentina citizens. Since then and until April 2015, the social perception changed according to different factors: age, location, education, culture, vulnerability. This variability produces a maze of challenges that go beyond the scientific knowledge. Volcanic health hazards began to be understood in 2008 after the eruption of Chaiten volcano. The particle size of ashfall (concern on epidemiological monitoring. In 2011 the volcanic complex Puyehue - Cordon Caulle eruption produced ashfall through plumes that reached densely populated cities like San Carlos de Bariloche and Buenos Aires. Farther away in South Africa and New Zealand ash plumes forced airlines to cancel local and international flights for several weeks. The fear of another eruption did not wait long when Calbuco volcano started activity in April 2015, it came at a time when Villarrica volcano was also in an eruptive phase, and the SERNAGEOMIN Chile, through the Observatory OVDAS of the Southern Andes, faced multiple natural disasters at the same time, 3 volcanoes in activity, lahars, pyroclastic flows and floods in the North. In Argentina, critical infrastructure, farming, livestock and primary supplies were affected mainly in the western region. Copahue volcano, is increasing unstability on seismic and geochemistry data since 2012. Caviahue resort village, distant only 8 Km. from the active vent happens to be a high vulnerable location. In 2014 GEVAS (Geology, Volcanoes, Environment and Health) Network ARGENTINA Civil Association started collaborative activities with SEGEMAR and in 2015 with the IAPG (Geoethics, Argentina), intending to promote Best Practices in volcanic and geological hazards. Geoscientists and the volcano vulnerable population

Stratigraphy, sedimentology and eruptive mechanism of the El Golfo phreatomagmatic edifice (Lanzarote, Canary Islands)

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Pedrazzi, D.; Marti, J.; Geyer, A.

2012-04-01

The El Golfo tuff cone is an example of phreatomagmatic edifice, developed in the western coast of Lanzarote (Canary Islands). El Golfo, together with other edifices of the same age, is aligned along a fracture oriented NEE-SWW coinciding with the main lineation of the historic volcanism in this part of the island. In this contribution we present a detailed stratigraphic study of the succession of deposits and we interpret them in terms of depositional processes and eruptive dynamics. The eruptive sequence is exclusively represented by a succession of pyroclastic deposits, and we infer it according to variations in flow regime and the magma-water interaction. Several pyroclastic units were identified according to facies variations based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms following the facies model proposed by Chough and Sohn (1990). The growth of the El Golfo tuff cone involved several stages based on variations in depositional processes. The edifice was constructed very rapidly around the vent controlling the amount of water that got access to the eruption conduit. Although the invariable phreatomagmatic character of most of the pyroclastic sequence, it is possible to deduce variations in the explosive energy, with a general increment upwards, according to the increase in the degree of fragmentation of pyroclasts, The absence of hyaloclastites, the nature of the palagonite alteration and the observed sedimentary structures, demonstrate the subaereal character of most of the deposits

Interpretasi Vulkanostratigrafi Daerah Mamuju Berdasarkan Analisis Citra Landsat-8

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Frederikus Dian Indrastomo

2015-11-01

Full Text Available Mamuju and its surrounding area are constructed mainly by volcanic rocks. Volcanoclastic sedimentary rocks and limestones are laid above the volcanic rocks. Volcanic activities create some unique morphologies such as craters, lava domes, and pyroclastic flow paths as their volcanic products. These products are identified from their circular features characters on Landsat-8 imagery. After geometric and atmospheric corrections had been done, a visual interpretation on Landsat-8 imagery was conducted to identify structure, geomorphology, and geological condition of the area. Regional geological structures show trend to southeast – northwest direction which is affects the formation of Adang volcano. Geomorphology of the area are classified into 16 geomorphology units based on their genetic aspects, i.e Sumare fault block ridge, Mamuju cuesta ridge, Adang eruption crater, Labuhan Ranau eruption crater, Sumare eruption crater, Ampalas volcanic cone, Adang lava dome, Labuhan Ranau intrusion hill, Adang pyroclastic flow ridge, Sumare pyroclastic flow ridge, Adang volcanic remnant hills, Malunda volcanic remnant hills, Talaya volcanic remnant hills, Tapalang karst hills, Mamuju alluvium plains, and Karampuang reef terrace plains. Based on the Landsat-8 imagery interpretation result and field confirmation, the geology of Mamuju area is divided into volcanic rocks and sedimentary rocks. There are two groups of volcanic rocks; Talaya complex and Mamuju complex. The Talaya complex consists of Mambi, Malunda, and Kalukku volcanic rocks with andesitic composition, while Mamuju complex consist of Botteng, Ahu, Tapalang, Adang, Ampalas, Sumare, danLabuhanRanau volcanic rocks with andesite to leucitic basalt composition. The volcanostratigraphy of Mamuju area was constructed based on its structure, geomorphology and lithology distribution analysis. Volcanostratigraphy of Mamuju area is classified into Khuluk Talaya and Khuluk Mamuju. The Khuluk Talaya consists

Volcano stratigraphy interpretation of Mamuju area based on Landsat-8 imagery analysis

International Nuclear Information System (INIS)

Frederikus Dian Indrastomo; I Gde Sukadana; Dhatu Kamajati; Asep Saepuloh; Agus Handoyo Harsolumakso

2015-01-01

Mamuju and its surrounding area are constructed mainly by volcanic rocks. Volcanoclastic sedimentary rocks and limestones are laid above the volcanic rocks. Volcanic activities create some unique morphologies such as craters, lava domes, and pyroclastic flow paths as their volcanic products. These products are identified from their circular features characters on Landsat-8 imagery. Geometric and atmospheric corrections had been done, a visual interpretation on Landsat-8 imagery was conducted to identify structure, geomorphology, and geological condition of the area. Regional geological structures show trend to southeast – northwest direction which is affects the formation of Adang volcano. Geomorphology of the area are classified into 16 geomorphology units based on their genetic aspects, i.e Sumare fault block ridge, Mamuju cuesta ridge, Adang eruption crater, Labuhan Ranau eruption crater, Sumare eruption crater, Ampalas volcanic cone, Adang lava dome, Labuhan Ranau intrusion hill, Adang pyroclastic flow ridge, Sumare pyroclastic flow ridge, Adang volcanic remnant hills, Malunda volcanic remnant hills, Talaya volcanic remnant hills, Tapalang karst hills, Mamuju alluvium plains, and Karampuang reef terrace plains. Based on the Landsat-8 imagery interpretation result and field confirmation, the geology of Mamuju area is divided into volcanic rocks and sedimentary rocks. There are two groups of volcanic rocks; Talaya complex and Mamuju complex. The Talaya complex consists of Mambi, Malunda, and Kalukku volcanic rocks with andesitic composition, while Mamuju complex consist of Botteng, Ahu, Tapalang, Adang, Ampalas, Sumare, and Labuhan Ranau volcanic rocks with andesite to leucitic basalt composition. The volcano stratigraphy of Mamuju area was constructed based on its structure, geomorphology and lithology distribution analysis. Volcano stratigraphy of Mamuju area is classified into Khuluk Talaya and Khuluk Mamuju. The Khuluk Talaya consists of Gumuk Mambi, Gumuk

Effects of volcanic and hydrologic processes on forest vegetation: Chaitén Volcano, Chile

Science.gov (United States)

Frederick J. Swanson; Julia A. Jones; Charles M. Crisafulli; Antonio. Lara

2013-01-01

The 2008-2009 eruption of Chaiten Volcano (Chile) involved a variety of volcanic and associated hydrologic processes that damaged nearby forests. These processes included coarse (gravel) and fine (silt to sand) tephra fall, a laterally directed blast, fluvial deposition of remobilized tephra, a variety of low-temperature mass-movement processes, and a pyroclastic flow...

La phase explosive précédant l'extrusion des dômes volcaniques : exemple du dôme rhyodacitique de Dikkartin Dag, Erciyes, Anatolie centrale, TurquieInitial explosive phases during extrusion of volcanic lava domes: example from rhyodacitic dome of Dikkartin Dag, Erciyes stratovolcano, Central Anatolia, Turkey

Science.gov (United States)

Sen, Erdal; Aydar, Erkan; Gourgaud, Alain; Kurkcuoglu, Biltan

2002-01-01

The Erciyes stratovolcano, in Central Anatolia, exhibits rhyodacitic domes on its flanks that emplaced after important eruptive pyroclastic events. The changes in eruption dynamics are well defined. Measurements of density and porosity of pumices have been carried out. Initial gas content of erupted magma decreased during the first Plinian phase (units 1 to 3) and then the gas content progressively increased in U4 and in pumiceous ash flow. The latter two deposits contain bread crust bombs that become very abundant in following phreatomagmatic products. The Last Plinian phase, rich in vitreous fragments, where porosity is minimum while density is maximal, preceded the dome extrusion. Although mineralogical and chemical compositions, further thermodynamical conditions of erupted magmas did not change during the eruptive sequence, the eruption mode changed. These changes in eruption mode are the results of the degassing of magma and the meteoric water contribution to the eruption. The transition observed is as follows: Plinian, pyroclastic flow, phreatomagmatism, Plinian and extrusion. To cite this article: E. Sen et al., C. R. Geoscience 334 (2002) 27-33

Kulanaokuaiki Tephra (ca, A.D. 400-1000): Newly recognized evidence for highly explosive eruptions at Kilauea Volcano, Hawai'i

Science.gov (United States)

Fiske, R.S.; Rose, T.R.; Swanson, D.A.; Champion, D.E.; McGeehin, J.P.

2009-01-01

K??lauea may be one of the world's most intensively monitored volcanoes, but its eruptive history over the past several thousand years remains rather poorly known. Our study has revealed the vestiges of thin basaltic tephra deposits, overlooked by previous workers, that originally blanketed wide, near-summit areas and extended more than 17 km to the south coast of Hawai'i. These deposits, correlative with parts of tephra units at the summit and at sites farther north and northwest, show that K??lauea, commonly regarded as a gentle volcano, was the site of energetic pyroclastic eruptions and indicate the volcano is significantly more hazardous than previously realized. Seventeen new calibrated accelerator mass spectrometry (AMS) radiocarbon ages suggest these deposits, here named the Kulanaokuaiki Tephra, were emplaced ca. A.D. 400-1000, a time of no previously known pyroclastic activity at the volcano. Tephra correlations are based chiefly on a marker unit that contains unusually high values of TiO2 and K2O and on paleomagnetic signatures of associated lava flows, which show that the Kulanaokuaiki deposits are the time-stratigraphic equivalent of the upper part of a newly exhumed section of the Uw??kahuna Ash in the volcano's northwest caldera wall. This section, thought to have been permanently buried by rockfalls in 1983, is thicker and more complete than the previously accepted type Uw??kahuna at the base of the caldera wall. Collectively, these findings justify the elevation of the Uw??kahuna Ash to formation status; the newly recognized Kulanaokuaiki Tephra to the south, the chief focus of this study, is defined as a member of the Uw??kahuna Ash. The Kulanaokuaiki Tephra is the product of energetic pyroclastic falls; no surge- or pyroclastic-flow deposits were identified with certainty, despite recent interpretations that Uw??kahuna surges extended 10-20 km from K??lauea's summit. ?? 2009 Geological Society of America.

Ruiz Volcano: Preliminary report

Science.gov (United States)

Ruiz Volcano, Colombia (4.88°N, 75.32°W). All times are local (= GMT -5 hours).An explosive eruption on November 13, 1985, melted ice and snow in the summit area, generating lahars that flowed tens of kilometers down flank river valleys, killing more than 20,000 people. This is history's fourth largest single-eruption death toll, behind only Tambora in 1815 (92,000), Krakatau in 1883 (36,000), and Mount Pelée in May 1902 (28,000). The following briefly summarizes the very preliminary and inevitably conflicting information that had been received by press time.

Characterization of volcanic deposits and geoarchaeological studies from the 1815 eruption of Tambora volcano

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Igan Supriatman Sutawidjaja

2014-06-01

Full Text Available http://dx.doi.org/10.17014/ijog.vol1no1.20066aThe eruption of Tambora volcano on the island of Sumbawa in 1815 is generally considered as the largest and the most violent volcanic event in recorded history. The cataclysmic eruption occurred on 11 April 1815 was initiated by Plinian eruption type on 5 April and killed more than 90,000 people on Sumbawa and nearby Lombok. The type plinian eruptions occurred twice and ejected gray pumice and ash, to form stratified deposits as thick as 40-150 cm on the slopes and mostly distributed over the district west of the volcano. Following this, at about 7 pm, on 11 April the first pyroclastic surge was generated and progressively became greater extending to almost whole direction, mainly to the north, west, and south districts from the eruption center. The deadliest volcanic eruption buried ancient villages by pyroclastic surge and flow deposits in almost intact state, thus preserving important archaeological evidence for the period. High preservation in relatively stable conditions and known date of the eruptions provide approximate dating for the archaeological remains. Archaeological excavations on the site uncovered a variety of remains were relieved by ground penetrating radar (GPR to map structural remains of the ancient villages under the pyroclastic surge and flow deposits. These traverses showed that GPR could define structures as deep as 10 m (velocity 0.090 m/ns and could accurately map the thickness of the stratified volcanic deposits in the Tambora village area.    

Explosive Volcanic Eruptions from Linear Vents on Earth, Venus and Mars: Comparisons with Circular Vent Eruptions

Science.gov (United States)

Glaze, Lori S.; Baloga, Stephen M.; Wimert, Jesse

2010-01-01

Conditions required to support buoyant convective plumes are investigated for explosive volcanic eruptions from circular and linear vents on Earth, Venus, and Mars. Vent geometry (linear versus circular) plays a significant role in the ability of an explosive eruption to sustain a buoyant plume. On Earth, linear and circular vent eruptions are both capable of driving buoyant plumes to equivalent maximum rise heights, however, linear vent plumes are more sensitive to vent size. For analogous mass eruption rates, linear vent plumes surpass circular vent plumes in entrainment efficiency approximately when L(sub o) > 3r(sub o) owing to the larger entrainment area relative to the control volume. Relative to circular vents, linear vents on Venus favor column collapse and the formation of pyroclastic flows because the range of conditions required to establish and sustain buoyancy is narrow. When buoyancy can be sustained, however, maximum plume heights exceed those from circular vents. For current atmospheric conditions on Mars, linear vent eruptions are capable of injecting volcanic material slightly higher than analogous circular vent eruptions. However, both geometries are more likely to produce pyroclastic fountains, as opposed to convective plumes, owing to the low density atmosphere. Due to the atmospheric density profile and water content on Earth, explosive eruptions enjoy favorable conditions for producing sustained buoyant columns, while pyroclastic flows would be relatively more prevalent on Venus and Mars. These results have implications for the injection and dispersal of particulates into the planetary atmosphere and the ability to interpret the geologic record of planetary volcanism.

Hierarchical Bayesian modelling of mobility metrics for hazard model input calibration

Science.gov (United States)

Calder, Eliza; Ogburn, Sarah; Spiller, Elaine; Rutarindwa, Regis; Berger, Jim

2015-04-01

In this work we present a method to constrain flow mobility input parameters for pyroclastic flow models using hierarchical Bayes modeling of standard mobility metrics such as H/L and flow volume etc. The advantage of hierarchical modeling is that it can leverage the information in global dataset for a particular mobility metric in order to reduce the uncertainty in modeling of an individual volcano, especially important where individual volcanoes have only sparse datasets. We use compiled pyroclastic flow runout data from Colima, Merapi, Soufriere Hills, Unzen and Semeru volcanoes, presented in an open-source database FlowDat (https://vhub.org/groups/massflowdatabase). While the exact relationship between flow volume and friction varies somewhat between volcanoes, dome collapse flows originating from the same volcano exhibit similar mobility relationships. Instead of fitting separate regression models for each volcano dataset, we use a variation of the hierarchical linear model (Kass and Steffey, 1989). The model presents a hierarchical structure with two levels; all dome collapse flows and dome collapse flows at specific volcanoes. The hierarchical model allows us to assume that the flows at specific volcanoes share a common distribution of regression slopes, then solves for that distribution. We present comparisons of the 95% confidence intervals on the individual regression lines for the data set from each volcano as well as those obtained from the hierarchical model. The results clearly demonstrate the advantage of considering global datasets using this technique. The technique developed is demonstrated here for mobility metrics, but can be applied to many other global datasets of volcanic parameters. In particular, such methods can provide a means to better contain parameters for volcanoes for which we only have sparse data, a ubiquitous problem in volcanology.

Managing the effects of accelerated glacial melting on volcanic collapse and debris flows: Planchon-Peteroa Volcano, Southern Andes

Science.gov (United States)

Tormey, Daniel

2010-11-01

Glaciated mountains are among the most sensitive environments to climatic changes, and recent work has shown that large-scale glacial melting, including at the end of the Pleistocene, caused a significant increase in the incidence of large volcanic sector collapse and debris flows on then-active volcanoes. With current accelerated rates of glacial melting, glaciated active volcanoes are at an increasing risk of sector collapse, debris flow and landslide. These catastrophic events are Earth's most damaging erosion phenomenon, causing extensive property damage and loss of life. This paper illustrates these effects in well-studied settings, focusing on the end-Pleistocene to Holocene glaciovolcanic growth and destruction of the cone of the active volcano Planchon-Peteroa in the Andean Southern Volcanic Zone at latitude 35° 15' S, along the border between Chile and Argentina. The development of the volcano over the last 14,000 years illustrates how glacial melting and magmatic activity can trigger landslides and sector collapses. Planchon had a large sector collapse that produced a highly mobile and erosive debris avalanche 11,000 years BP, and other slope instabilities during the end-Pleistocene/early Holocene deglaciation. The summit amphitheater left after the sector collapse was subject to alternating periods of glaciation and melting-induced lake formation. Breaching of the moraine dams then formed lahars and landslides originating at the western edge of the summit amphitheater, and the deposits are preserved along the western flank of the volcano. Deep incision of moraine deposits further down the western slope of the volcano indicates that the lahars and landslides were water-rich and had high erosive power. As illustrated by Planchon-Peteroa, the interplay among glacial growth and melting, magmatic activity, and slope stability is complex, but must be accounted for in volcanic hazard assessment. Planchon-Peteroa currently has the southernmost temperate zone

Strongly coupled dispersed two-phase flows; Ecoulements diphasiques disperses fortement couples

Energy Technology Data Exchange (ETDEWEB)

Zun, I.; Lance, M.; Ekiel-Jezewska, M.L.; Petrosyan, A.; Lecoq, N.; Anthore, R.; Bostel, F.; Feuillebois, F.; Nott, P.; Zenit, R.; Hunt, M.L.; Brennen, C.E.; Campbell, C.S.; Tong, P.; Lei, X.; Ackerson, B.J.; Asmolov, E.S.; Abade, G.; da Cunha, F.R.; Lhuillier, D.; Cartellier, A.; Ruzicka, M.C.; Drahos, J.; Thomas, N.H.; Talini, L.; Leblond, J.; Leshansky, A.M.; Lavrenteva, O.M.; Nir, A.; Teshukov, V.; Risso, F.; Ellinsen, K.; Crispel, S.; Dahlkild, A.; Vynnycky, M.; Davila, J.; Matas, J.P.; Guazelli, L.; Morris, J.; Ooms, G.; Poelma, C.; van Wijngaarden, L.; de Vries, A.; Elghobashi, S.; Huilier, D.; Peirano, E.; Minier, J.P.; Gavrilyuk, S.; Saurel, R.; Kashinsky, O.; Randin, V.; Colin, C.; Larue de Tournemine, A.; Roig, V.; Suzanne, C.; Bounhoure, C.; Brunet, Y.; Tanaka, A.T.; Noma, K.; Tsuji, Y.; Pascal-Ribot, S.; Le Gall, F.; Aliseda, A.; Hainaux, F.; Lasheras, J.; Didwania, A.; Costa, A.; Vallerin, W.; Mudde, R.F.; Van Den Akker, H.E.A.; Jaumouillie, P.; Larrarte, F.; Burgisser, A.; Bergantz, G.; Necker, F.; Hartel, C.; Kleiser, L.; Meiburg, E.; Michallet, H.; Mory, M.; Hutter, M.; Markov, A.A.; Dumoulin, F.X.; Suard, S.; Borghi, R.; Hong, M.; Hopfinger, E.; Laforgia, A.; Lawrence, C.J.; Hewitt, G.F.; Osiptsov, A.N.; Tsirkunov, Yu. M.; Volkov, A.N.

2003-07-01

-phase flow, current distribution and mass transfer along a vertical gas evolving electrode; a two-way coupled model for dilute multiphase flows. Topic 3: turbulence modulation by particles, droplets or bubbles in dense systems: influence of particles on the transition to turbulence in pipe flow; comparison between a point particle model and a finite-diameter-model for the particle turbulence interaction in a suspension; the effect on turbulence by bubbles rising through it under buoyancy; the physical mechanisms of modifying the structure of turbulent homogeneous shear flows by dispersed particles; influence of hydrodynamic interactions between particles on the turbulent flow in a suspension; review of relationships between Lagrangian and Eulerian scales; a two-point PDF for modelling turbulent dispersed two-phase flows and derivation of a two field model; mathematical and numerical modeling of two-phase compressible flows with micro-inertia. Topic 4: collective effects in dispersed two-phase flows clustering and phase distribution: hydrodynamic structure of downward bubbly flow; influence of gravity on the dynamics of a turbulent bubbly pipe flow; experimental study of two-phase flows; particle clusters formed in dispersed gas-solid flows: simulations and experiments; experimental study of the turbulence in bubbly flows at high void fraction; first step in the study of the correlation between air/water flow fluctuations and random buffering forces; clustering and settling velocity of micro-droplets in a grid turbulence. Topic 5: large scale instabilities and gravity driven dispersed flows: new 'non-isothermal' linear instability modes in fluidized beds and bubbly flows; large scale instability in a confined buoyant shear layer; convective instability in uniform dispersed layers; structures in gravity driven bubbly flows; effects of concentration profiles on velocity profiles in sewer; pyroclastic density currents viewed as mammoth scale two-phase flows; mixing and

Stratigraphy, age and correlation of middle Pleistocene silicic tephras in the Auckland region, New Zealand : a prolific distal record of Taupo Volcanic Zone volcanism

International Nuclear Information System (INIS)

Alloway, B.V.; Westgate, J.; Pillans, B.; Pearce, N.; Newnham, R.; Byrami, M.; Aarburg, S.

2004-01-01

Coastal sections in the Auckland region reveal highly carbonaceous and/or highly weathered clay-dominated cover-bed successions with numerous discrete distal volcanic ash (tephra) layers, fluvially reworked siliciclastic (tephric) deposits, and two widely distributed pyroclastic density current (PDC) deposits generated from explosive silicic volcanism within the Taupo Volcanic Zone (TVZ). The younger of the two PDC deposits (informally named Waiuku tephra) is glass-isothermal plateau fission-track (ITPFT) dated at 1.00 ± 0.03 Ma and occurs in a normal polarity interval interpreted as the Jaramillo Subchron. Waiuku tephra is correlated with Unit E sourced from the Mangakino Volcanic Centre of the TVZ. Waiuku tephra can be subdivided into two distinctive units enabling unequivocal field correlation: a lower stratified unit (dominantly pyroclastic surge with fall component) and an upper massive to weakly stratified unit (pyroclastic flow). At many sites in south Auckland, Waiuku tephra retains basal 'surge-like' beds (<1.4 m thickness). This provides clear evidence for primary emplacement and is an exceptional feature considering the c. 200 km this PDC has travelled from its TVZ source area. However, at many other Auckland sites, Waiuku tephra displays transitional sedimentary characteristics indicating lateral transformation from hot, gas-supported flow/surge into water-supported mass flow and hyperconcentrated flow (HCF) deposits. The older PDC deposit is dated at 1.21 ± 0.09 Ma, is enveloped by tephras that are ITPFT-dated at 1.14 ± 0.06 Ma (above) and 1.21 ± 0.06 Ma (below), respectively, and occurs below a short normal polarity interval (Cobb Mountain Subchron) at c. 1.19 Ma. This PDC deposit, correlated with Ongatiti Ignimbrite sourced from the Mangakino Volcanic Centre of TVZ, has laterally transformed from a gas-supported, fine-grained pyroclastic flow deposit at Oruarangi, Port Waikato, into a water-supported volcaniclastic mass flow deposit farther north

Cost Effective, Ultra Sensitive Groundwater Monitoring for Site Remediation and Management

Science.gov (United States)

2015-05-01

evaporites, sandstone, gravel, conglomerate, and andesitic basalt . Closed basin; playa, alluvial fan, fluvial 600 to 10,000+ Unconfined, leaky...confined Lower unit Breccia, conglomerate, sandstone, siltstone, and local basaltic to rhyolitic flows and pyroclastic rocks. Alluvial fan, fluvial...with large volumes of groundwater. Three of the cartridges additionally protected by glass fiber filters (Acrodisc AP-4523; Pall GmbH, Dreieich, GE

Impact of the AD 79 explosive eruption on Pompeii, II. Causes of death of the inhabitants inferred by stratigraphic analysis and areal distribution of the human casualties

Science.gov (United States)

Luongo, Giuseppe; Perrotta, Annamaria; Scarpati, Claudio; De Carolis, Ernesto; Patricelli, Giovanni; Ciarallo, Annamaria

2003-08-01

Detailed descriptions of the effects of explosive eruptions on urban settlements available to volcanologists are relatively rare. Apart from disease and starvation, the largest number of human deaths caused by explosive eruptions in the twentieth century are due to pyroclastic flows. The relationship between the number of victims related to a specific hazard and the presence of urban settlements in the area covered by the eruption has been shown. However, pyroclastic falls are also extremely dangerous under certain conditions. These conclusions are based on archaeological and volcanological studies carried out on the victims of the well-known AD 79 eruption of Vesuvius that destroyed and buried the Roman city of Pompeii. The stratigraphic level in the pyroclastic deposit and the location of all the casualties found are described and discussed. The total number of victims recovered during the archaeological excavations amounts to 1150. Of these, 1044 well recognisable bodies plus an additional group of 100 individuals were identified based on the analysis of several groups of scattered bones. Of the former, 394 were found in the lower pumice lapilli fall deposit and 650 in the upper stratified ash and pumice lapilli pyroclastic density currents (PDCs) deposits. In addition, a tentative evaluation suggests that 464 corpses may still be buried in the unexcavated part of the city. According to the reconstruction presented in this paper, during the first phase of the eruption (August 24, AD 79) a huge quantity of pumice lapilli fell on Pompeii burying the city under 3 m of pyroclastic material. During this eruptive phase, most of the inhabitants managed to leave the city. However, 38% of the known victims were killed during this phase mainly as a consequence of roofs and walls collapsing under the increasing weight of the pumice lapilli deposit. During the second phase of the eruption (August 25, AD 79) 49% of the total victims were on the roadways and 51% inside

Full-wave Ambient Noise Tomography of Mt Rainier volcano, USA

Science.gov (United States)

Flinders, Ashton; Shen, Yang

2015-04-01

Mount Rainier towers over the landscape of western Washington (USA), ranking with Fuji-yama in Japan, Mt Pinatubo in the Philippines, and Mt Vesuvius in Italy, as one of the great stratovolcanoes of the world. Notwithstanding its picturesque stature, Mt Rainier is potentially the most devastating stratovolcano in North America, with more than 3.5 million people living beneath is shadow in the Seattle-Tacoma area. The primary hazard posed by the volcano is in the form of highly destructive debris flows (lahars). These lahars form when water and/or melted ice erode away and entrain preexisting volcanic sediment. At Mt Rainier these flows are often initiated by sector collapse of the volcano's hydrothermally rotten flanks and compounded by Mt Rainier's extensive snow and glacial ice coverage. It is therefore imperative to ascertain the extent of the volcano's summit hydrothermal alteration, and determine areas prone to collapse. Despite being one of the sixteen volcanoes globally designated by the International Association of Volcanology and Chemistry of the Earth's Interior as warranting detailed and focused study, Mt Rainier remains enigmatic both in terms of the shallow internal structure and the degree of summit hydrothermal alteration. We image this shallow internal structure and areas of possible summit alteration using ambient noise tomography. Our full waveform forward modeling includes high-resolution topography allowing us to accuratly account for the effects of topography on the propagation of short-period Rayleigh waves. Empirical Green's functions were extracted from 80 stations within 200 km of Mt Rainier, and compared with synthetic greens functions over multiple frequency bands from 2-28 seconds.

RESEARCH: Effects of Recent Volcanic Eruptions on Aquatic Habitat in the Drift River, Alaska, USA: Implications at Other Cook Inlet Region Volcanoes.

Science.gov (United States)

DORAVA; MILNER

1999-02-01

/ Numerous drainages supporting productive salmon habitat are surrounded by active volcanoes on the west side of Cook Inlet in south-central Alaska. Eruptions have caused massive quantities of flowing water and sediment to enter the river channels emanating from glaciers and snowfields on these volcanoes. Extensive damage to riparian and aquatic habitat has commonly resulted, and benthic macroinvertebrate and salmonid communities can be affected. Because of the economic importance of Alaska's fisheries, detrimental effects on salmonid habitat can have significant economic implications. The Drift River drains glaciers on the northern and eastern flanks of Redoubt Volcano. During and following eruptions in 1989-1990, severe physical disturbances to the habitat features of the river adversely affected the fishery. Frequent eruptions at other Cook Inlet region volcanoes exemplify the potential effects of volcanic activity on Alaska's important commercial, sport, and subsistence fisheries. Few studies have documented the recovery of aquatic habitat following volcanic eruptions. The eruptions of Redoubt Volcano in 1989-1990 offered an opportunity to examine the recovery of the macroinvertebrate community. Macroinvertebrate community composition and structure in the Drift River were similar in both undisturbed and recently disturbed sites. Additionally, macroinvertebrate samples from sites in nearby undisturbed streams were highly similar to those from some Drift River sites. This similarity and the agreement between the Drift River macroinvertebrate community composition and that predicted by a qualitative model of typical macroinvertebrate communities in glacier-fed rivers indicate that the Drift River macroinvertebrate community is recovering five years after the disturbances associated with the most recent eruptions of Redoubt Volcano. KEY WORDS: Aquatic habitat; Volcanoes; Lahars; Lahar-runout flows; Macroinvertebrates; Community structure; Community composition

Low probability natural phenomena and crustal movement on high level radioactive waste geological disposal

International Nuclear Information System (INIS)

Kusunose, Kinichiro; Sato, Takashi; Cho, Akio; Togashi, Shigeko; Matsumoto, Akikazu; Kanai, Yutaka; Okumura, Koji; Shimokawa, Koichi; Mizuno, Kiyohide

1998-01-01

On subtheme ''development of long-term estimate method of crystal movement'', a control method has been developed under the conditions of 500 MPa confining pressure at 300degC. The method was tested under the conditions of 100 MPa confining pressure at room temperature and the rock fracture experiment was succeeded. On subtheme ''estimation method on the effect of volcanic activity'', in order to evaluate the effects of tephra fall on environment, pollen analysis of sample on outcrop in Sakaida and the topographic and geological survey of river terrace along Nyu-river in Yamagata prefecture were carried out. These results showed number of pollen was decreased immediately after AT tephra fall originated in Kyushu, so that effect of ash on forest was proved. However, the effect of AT tephra fall on ecological system was not so large as changing forest compositing species. On establishment of accurate geologic time measurement of pyroclastic materials, uranium and thorium were chemically separated from various kinds of mineral concentrated materials separated from pyroclastic materials. Iso chron of them was obtained by alpha count. Moreover, a direct geologic time measurement method for distal tephra was developed by pottasium-argon method. It makes possible direct measurement of geological time of young pyroclastic flow sediment. (S.Y.)

Summit crater lake observations, and the location, chemistry, and pH of water samples near Mount Chiginagak volcano, Alaska: 2004-2012

Science.gov (United States)

Schaefer, Janet R.; Scott, William E.; Evans, William C.; Wang, Bronwen; McGimsey, Robert G.

2013-01-01

Mount Chiginagak is a hydrothermally active volcano on the Alaska Peninsula, approximately 170 km south–southwest of King Salmon, Alaska (fig. 1). This small stratovolcano, approximately 8 km in diameter, has erupted through Tertiary to Permian sedimentary and igneous rocks (Detterman and others, 1987). The highest peak is at an elevation of 2,135 m, and the upper ~1,000 m of the volcano are covered with snow and ice. Holocene activity consists of debris avalanches, lahars, and lava flows. Pleistocene pyroclastic flows and block-and-ash flows, interlayered with andesitic lava flows, dominate the edifice rocks on the northern and western flanks. Historical reports of activity are limited and generally describe “steaming” and “smoking” (Coats, 1950; Powers, 1958). Proximal tephra collected during recent fieldwork suggests there may have been limited Holocene explosive activity that resulted in localized ash fall. A cluster of fumaroles on the north flank, at an elevation of ~1,750 m, commonly referred to as the “north flank fumarole” have been emitting gas throughout historical time (location shown in fig. 2). The only other thermal feature at the volcano is the Mother Goose hot springs located at the base of the edifice on the northwestern flank in upper Volcano Creek, at an elevation of ~160 m (fig. 2, near sites H1, H3, and H4). Sometime between November 2004 and May 2005, a ~400-m-wide, 100-m-deep lake developed in the snow- and ice-filled summit crater of the volcano (Schaefer and others, 2008). In early May 2005, an estimated 3 million cubic meters (3×106 m3) of sulfurous, clay-rich debris and acidic water exited the crater through tunnels at the base of a glacier that breaches the south crater rim. More than 27 km downstream, these acidic flood waters reached approximately 1.3 m above normal water levels and inundated a fertile, salmon-spawning drainage, acidifying the entire water column of Mother Goose Lake from its surface waters to its

Magma fracturing and degassing associated with obsidian formation: The explosive–effusive transition

Science.gov (United States)

Cabrera, Agustin; Weinberg, Roberto; Wright, Heather M.

2015-01-01

This paper explores the role of melt fracturing in degassing rhyolitic volcanic systems. The Monte Pilato-Rocche Rosse eruptions in Italy evolved from explosive to effusive in style, and H2O content in quenched glasses changed over time from relatively H2O-rich (~ 0.90 wt.%) to H2O-poor dense obsidian (~ 0.10–0.20 wt.%). In addition, healed fractures have been recorded in all different eruptive materials, from the glass of early-erupted tube pumice and rinds of breadcrusted obsidian pyroclasts, to the glass of late-erupted dense obsidian pyroclasts, and throughout the final effusive Rocche Rosse lava flow. These rocks show multiple fault sets, some with crenulated fault planes indicating resumption of viscous flow after faulting, complex obsidian breccias with evidence for post-brecciation folding and stretching, and centimetre- to metre-thick tuffisite preserved in pyroclasts and lava, representing collapsed foam due to fracturing of vesicle walls. These microstructural observations indicate that multiple fracturing and healing events occurred during both explosive and effusive eruptions. H2O content in glass decreases by as much as 0.14 wt.% towards healed fractures/faults and decreases in stretched obsidian breccias towards regions of intense brecciation. A drop in pressure and/or increase in temperature along fractures caused diffusive H2O migration through melt towards fracture surfaces. Repetitive and pervasive fracturing and healing thereby create conditions for diffusive H2O loss into fractures and subsequent escape through permeable paths. This type of progressive magma degassing provides a potential mechanism to explain the formation of dense obsidian and the evolution from explosive to effusive eruption style.

Advances in volcano monitoring and risk reduction in Latin America

Science.gov (United States)

McCausland, W. A.; White, R. A.; Lockhart, A. B.; Marso, J. N.; Assitance Program, V. D.; Volcano Observatories, L. A.

2014-12-01

We describe results of cooperative work that advanced volcanic monitoring and risk reduction. The USGS-USAID Volcano Disaster Assistance Program (VDAP) was initiated in 1986 after disastrous lahars during the 1985 eruption of Nevado del Ruiz dramatizedthe need to advance international capabilities in volcanic monitoring, eruption forecasting and hazard communication. For the past 28 years, VDAP has worked with our partners to improve observatories, strengthen monitoring networks, and train observatory personnel. We highlight a few of the many accomplishments by Latin American volcano observatories. Advances in monitoring, assessment and communication, and lessons learned from the lahars of the 1985 Nevado del Ruiz eruption and the 1994 Paez earthquake enabled the Servicio Geológico Colombiano to issue timely, life-saving warnings for 3 large syn-eruptive lahars at Nevado del Huila in 2007 and 2008. In Chile, the 2008 eruption of Chaitén prompted SERNAGEOMIN to complete a national volcanic vulnerability assessment that led to a major increase in volcano monitoring. Throughout Latin America improved seismic networks now telemeter data to observatories where the decades-long background rates and types of seismicity have been characterized at over 50 volcanoes. Standardization of the Earthworm data acquisition system has enabled data sharing across international boundaries, of paramount importance during both regional tectonic earthquakes and during volcanic crises when vulnerabilities cross international borders. Sharing of seismic forecasting methods led to the formation of the international organization of Latin American Volcano Seismologists (LAVAS). LAVAS courses and other VDAP training sessions have led to international sharing of methods to forecast eruptions through recognition of precursors and to reduce vulnerabilities from all volcano hazards (flows, falls, surges, gas) through hazard assessment, mapping and modeling. Satellite remote sensing data

Geochemical constraints on the petrogenesis of the pyroclastic rocks in Abakaliki basin (Lower Benue Rift), Southeastern Nigeria

Science.gov (United States)

Chukwu, Anthony; Obiora, Smart C.

2018-05-01

The pyroclastic rocks in the Cretaceous Abakaliki basin occur mostly as oval-shaped bodies, consisting of lithic/lava and vitric fragments. They are commonly characterized by parallel and cross laminations, as well contain xenoliths of shale, mudstone and siltstones from the older Asu River Group of Albian age. The rocks are basic to ultrabasic in composition, comprising altered alkali basalts, altered tuffs, minor lapillistones and agglomerates. The mineral compositions are characterized mainly by laths of calcic plagioclase, pyroxene (altered), altered olivines and opaques. Calcite, zeolite and quartz represent the secondary mineral constituents. Geochemically, two groups of volcaniclastic rocks, are distinguished: alkaline and tholeiitic rocks, both represented by fresh and altered rock samples. The older alkali basalts occur within the core of the Abakaliki anticlinorium while the younger tholeiites occur towards the periphery. Though most of the rocks are moderate to highly altered [Loss on ignition (LOI, 3.43-22.07 wt. %)], the use of immobile trace element such as Nb, Zr, Y, Hf, Ti, Ta and REEs reflect asthenospheric mantle source compositions. The rocks are enriched in incompatible elements and REEs (∑REE = 87.98-281.0 ppm for alkaline and 69.45-287.99 ppm for tholeiites). The ratios of La/Ybn are higher in the alkaline rocks ranging from 7.69 to 31.55 compared to the tholeiitic rocks which range from 4.4 to 16.89 and indicating the presence of garnet-bearing lherzolite in the source mantle. The spidergrams and REEs patterns along with Zr/Nb, Ba/Nb, Rb/Nb ratios suggest that the rocks were generated by a mantle plume from partial melting of mixed enriched mantle sources (HIMU, EMI and EMII) similar to the rocks of the south Atlantic Ocean such as St. Helena (alkaline rocks) and Ascension rocks (tholeiitic rocks). The rocks were formed in a within-plate setting of the intra-continental rift type similar to other igneous rocks in the Benue Rift and are not

Final Environmental Assessment (EA) Addressing the Repair of Runway 05/23 at Fairchild Air Force Base, Washington

Science.gov (United States)

2009-11-01

farmland is defined as land that has the best combination of physical and chemical characteristics for producing food, feed, forage, fiber , and...flows. Layers of basalt could be as much as 500 feet thick with gravel, silt, or pyroclastic deposits interbedded. During the Pleistocene (from...unconformably atop the bedrock and is composed of weakly lithified sedimentary deposits from a Miocene-aged shallow lake. The Columbia River Basalts

Evaluation on the Implementation of Early Warning System for Debris Flow in Merapi Area (Case Study at Boyong River

Directory of Open Access Journals (Sweden)

Ali Cahyadi Achmad

2015-09-01

Full Text Available One of disasters caused by volcanic activity of Mount Merapi is secondary disaster. The disaster usually occurs after eruption and this volcanic activity produces volcanic and pyroclastic material deposit around the top of the mountain as a result of previous eruption. This material might collapse downward in the form of debris flow as it is affected by natural event such as high intensity rainfall. Therefore, a research is needed to analyze whether existing forecasting and early warning system are capable to provide information for the people living in hazardous area before the debris flood occur. This research was carried out using field survey, observation and interview method. Data analysis used qualitative descriptive method by making description of actual condition of the researched location general condition and qualitative analysis of telemetry system installed on Mount Merapi. The qualitative analysis of telemetry system covers network, hardware, software, power supply, security system, operation and maintenance, also human resources. Research analysis used primary and secondary data. Research results revealed that mean rainfall intensity above of 60 mm/hour might trigger debris flood. Early warning should be given at the rainfall intensity level of 50-55 mm/hour, and debris flood time travel from the upstream to the observed location in Pulowatu Village is 45 minute. Based on the analysis of the present forecasting and early warning system, it is known that some of the equipment is not well functioned, so that debris flow cannot be predicted and detected. This is caused by the lack of human resource quality of the officers in operating and maintaining the equipment. Concerning that matter, it is necessary to conduct some improvement to achieve better forecasting and early warning system in order to give information regarding occurrence of debris flow.

The Upper Toluca Pumice (10.5 kyr): Product of the last major Plinian eruption of Nevado de Toluca volcano, Central Mexico

Science.gov (United States)

Arce, J. L.; Macias, J. L.

2001-12-01

The last Plinian eruption at Nevado de Toluca volcano occurred 10.5 kyr ago producing the Upper Toluca Pumice (UTP). The UTP consists of four widespread fallout layers, interbedded with pyroclastic flow and surge deposits. The UTP event occurred under open vent conditions starting with hydromagmatic explosions that emplaced a hot pyroclastic flow (F0) on the east and northern flanks of the volcano. This explosion decompressed the magmatic system allowing almost immediately the formation of a 21 km high Plinian column that was dispersed by predominant winds 5o to the NE (PC0), which waned after some time. The eruption recommenced with the establishment of three Plinian columns that were dispersed in a NE-E direction, reaching heights of 39, 42, and 28 km, and deposited fall layers (PC1, PC2, and PC3) respectively. These Plinian columns were interrupted several times by phreatomagmatic and collapse events that emplaced pyroclastic flows (F1, F2, and F3) and surges (S1, and S2), mainly on the eastern and northern flanks of the volcano. The juvenile components of the UTP sequence are white, gray and banded pumice and gray juvenile lithic clasts both of dacitic composition (63-66wt% SiO2), and minor accidental lithics. The fallout deposits (PC1 and PC2) covered a minimum area of 2000 km2 with a total volume of 14 km3 (ca. 6 km3 D.R.E.); a mass eruption rate ranging from 3\\times107 to 5\\times108 kg/s and a total mass of 1.2\\times1013 kg. The UTP emplaced 1.5 m of gravel-sized pumice in the modern City of Toluca region and ca. 20 cm of fine sand in the Mexico City region. A future event of this magnitude might represent a major catastrophe to the 30 million people living in these cities and their surroundings.

Volcaniclastic dykes tell on fracturing, explosive eruption and lateral collapse at Stromboli volcano (Italy)

Science.gov (United States)

Vezzoli, Luigina; Corazzato, Claudia

2016-05-01

In the upper part of the Stromboli volcano, in the Le Croci and Bastimento areas, two dyke-like bodies of volcanic breccia up to two-metre thick crosscut and intrude the products of Vancori and Neostromboli volcanoes. We describe the lithofacies association of these unusual volcaniclastic dykes, interpret the setting of dyke-forming fractures and the emplacement mechanism of internal deposits, and discuss their probable relationships with the explosive eruption and major lateral collapse events that occurred at the end of the Neostromboli period. The dyke volcaniclastic deposits contain juvenile magmatic fragments (pyroclasts) suggesting a primary volcanic origin. Their petrographic characteristics are coincident with the Neostromboli products. The architecture of the infilling deposits comprises symmetrically-nested volcaniclastic units, separated by sub-vertical boundaries, which are parallel to the dyke margins. The volcanic units are composed of distinctive lithofacies. The more external facies is composed of fine and coarse ash showing sub-vertical laminations, parallel to the contact wall. The central facies comprises stratified, lithic-rich breccia and lapilli-tuff, whose stratification is sub-horizontal and convolute, discordant to the dyke margins. Only at Le Croci dyke, the final unit shows a massive tuff-breccia facies. The volcaniclastic dykes experienced a polyphasic geological evolution comprising three stages. The first phase consisted in fracturing, explosive intrusion related to magma rising and upward injection of magmatic fluids and pyroclasts. The second phase recorded the dilation of fractures and their role as pyroclastic conduits in an explosive eruption possibly coeval with the lateral collapse of the Neostromboli lava cone. Finally, in the third phase, the immediately post-eruption mass-flow remobilization of pyroclastic deposits took place on the volcano slopes.

Eruptive history of Mount Katmai, Alaska

Science.gov (United States)

Hildreth, Edward; Fierstein, Judith

2012-01-01

Mount Katmai has long been recognized for its caldera collapse during the great pyroclastic eruption of 1912 (which vented 10 km away at Novarupta in the Valley of Ten Thousand Smokes), but little has previously been reported about the geology of the remote ice-clad stratovolcano itself. Over several seasons, we reconnoitered all parts of the edifice and sampled most of the lava flows exposed on its flanks and caldera rim. The precipitous inner walls of the 1912 caldera remain too unstable for systematic sampling; so we provide instead a photographic and interpretive record of the wall sequences exposed. In contrast to the several andesite-dacite stratovolcanoes nearby, products of Mount Katmai range from basalt to rhyolite. Before collapse in 1912, there were two overlapping cones with separate vent complexes and craters; their products are here divided into eight sequences of lava flows, agglutinates, and phreatomagmatic ejecta. Latest Pleistocene and Holocene eruptive units include rhyodacite and rhyolite lava flows along the south rim; a major 22.8-ka rhyolitic plinian fall and ignimbrite deposit; a dacite-andesite zoned scoria fall; a thick sheet of dacite agglutinate that filled a paleocrater and draped the west side of the edifice; unglaciated leveed dacite lava flows on the southeast slope; and the Horseshoe Island dacite dome that extruded on the caldera floor after collapse. Pre-collapse volume of the glaciated Katmai edifice was ∼30 km3, and eruptive volume is estimated to have been 57±13 km3. The latter figure includes ∼40±6 km3 for the edifice, 5±2 km3 for off-edifice dacite pyroclastic deposits, and 12±5 km3 for the 22.8-ka rhyolitic pyroclastic deposits. To these can be added 13.5 km3 of magma that erupted at Novarupta in 1912, all or much of which is inferred to have been withdrawn from beneath Mount Katmai. The oldest part of the edifice exposed is a basaltic cone, which gave a 40Ar/39Ar plateau age of 89 ± 25 ka.

3_D modeling using TLS and GPR techniques to characterize above and below-ground wood distribution in pyroclastic deposits along the Blanco River (Chilean Patagonia)

Science.gov (United States)

Valdebenito, Galo; Tonon, Alessia; Iroume, Andrés; Alvarado, David; Fuentes, Carlos; Picco, Lorenzo; Lenzi, Mario

2016-04-01

To date, the study of in-stream wood in rivers has been focused mainly on quantifying wood pieces deposited above the ground. However, in some particular river systems, the presence of buried dead wood can also represent an important component of wood recruitment and budgeting dynamics. This is the case of the Blanco River (Southern Chile) severely affected by the eruption of Chaitén Volcano occurred between 2008 and 2009. The high pyroclastic sediment deposition and transport affected the channel and the adjacent forest, burying wood logs and standing trees. The aim of this contribution is to assess the presence and distribution of wood in two study areas (483 m2 and 1989 m2, respectively) located along the lower streambank of the Blanco River, and covered by thick pyroclastic deposition up to 5 m. The study areas were surveyed using two different devices, a Terrestrial Laser Scanner (TLS) and a Ground Penetrating Radar (GPR). The first was used to scan the above surface achieving a high point cloud density (≈ 2000 points m-2) which allowed us to identify and measure the wood volume. The second, was used to characterize the internal morphology of the volcanic deposits and to detect the presence and spatial distribution of buried wood up to a depth of 4 m. Preliminary results have demonstrated differences in the numerousness and volume of above wood between the two study areas. In the first one, there were 43 wood elements, 33 standing trees and 10 logs, with a total volume of 2.96 m3 (109.47 m3 km-1), whereas the second one was characterized by the presence of just 7 standing trees and 11 wood pieces, for a total amount of 0.77 m3 (7.73 m3 km-1). The dimensions of the wood elements vary greatly according to the typology, standing trees show the higher median values in diameter and length (0.15 m and 2.91 m, respectively), whereas the wood logs were smaller (0.06 m and 1.12 m, respectively). The low dimensions of deposited wood can be probably connected to their

Digital data for preliminary geologic map of the Mount Hood 30- by 60-minute quadrangle, northern Cascade Range, Oregon

Science.gov (United States)

Lina Ma,; Sherrod, David R.; Scott, William E.

2014-01-01

The Mount Hood 30- by 60-minute quadrangle covers the axis and east flank of the Cascade Range in northern Oregon. Its namesake, Mount Hood volcano, dominates the view in the northwest quarter of the quadrangle, but the entire area is underlain by Oligocene and younger volcanic and volcaniclastic rocks of the Cascade Range. Since the time of the Columbia River Basalt Group about 15 million years (m.y.) ago, the locus and composition of Cascade Range volcanism have shifted sporadically across the map area. Andesitic eruptions were predominant in the western part from about 14 to 10 m.y. ago (Salmon and Sandy Rivers area), producing the Rhododendron Formation and overlying lava flows. From about 8 to 6.5 m.y. ago, lithic pyroclastic debris of the Dalles Formation was shed by chiefly andesitic volcanoes in the north-central part of the map area (Hood River valley escarpment). Andesitic to dacitic volcanism was again predominant about 5 to 3 m.y. ago, with known eruptive centers located from Lookout Mountain westward to Lolo Pass, probably including the area now occupied by Mount Hood. A major episode of mafic volcanism-basalt and basaltic andesite-began about 3-4 m.y. ago and lasted until about 2 m.y. ago. Volcanism since about 2 m.y. ago has been concentrated along the axis of the High Cascades. North and south of Mount Hood these youngest rocks are predominantly basaltic andesite lava flows; whereas at Mount Hood itself, andesite is predominant, forming pyroclastic and debris-flow deposits and lava flows.

Volcanic mercury in Pinus canariensis

Science.gov (United States)

Rodríguez Martín, José Antonio; Nanos, Nikos; Miranda, José Carlos; Carbonell, Gregoria; Gil, Luis

2013-08-01

Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg-1) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg-1). Thus, mercury emissions originating from the eruption remained only as a mark—in pyroclastic wounds—and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg-1) and bark (6.0 μg kg-1) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

Volcanic mercury in Pinus canariensis.

Science.gov (United States)

Rodríguez Martín, José Antonio; Nanos, Nikos; Miranda, José Carlos; Carbonell, Gregoria; Gil, Luis

2013-08-01

Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg(-1)) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg(-1)). Thus, mercury emissions originating from the eruption remained only as a mark-in pyroclastic wounds-and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg(-1)) and bark (6.0 μg kg(-1)) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species.

From hot rocks to glowing avalanches: Numerical modelling of gravity-induced pyroclastic density currents and hazard maps at the Stromboli volcano (Italy)

Science.gov (United States)

Salvatici, Teresa; Di Roberto, Alessio; Di Traglia, Federico; Bisson, Marina; Morelli, Stefano; Fidolini, Francesco; Bertagnini, Antonella; Pompilio, Massimo; Hungr, Oldrich; Casagli, Nicola

2016-11-01

Gravity-induced pyroclastic density currents (PDCs) can be produced by the collapse of volcanic crater rims or due to the gravitational instability of materials deposited in proximal areas during explosive activity. These types of PDCs, which are also known as ;glowing avalanches;, have been directly observed, and their deposits have been widely identified on the flanks of several volcanoes that are fed by mafic to intermediate magmas. In this research, the suitability of landslide numerical models for simulating gravity-induced PDCs to provide hazard assessments was tested. This work also presents the results of a back-analysis of three events that occurred in 1906, 1930 and 1944 at the Stromboli volcano by applying a depth-averaged 3D numerical code named DAN-3D. The model assumes a frictional internal rheology and a variable basal rheology (i.e., frictional, Voellmy and plastic). The numerical modelling was able to reproduce the gravity-induced PDCs' extension and deposit thicknesses to an order of magnitude of that reported in the literature. The best results when compared with field data were obtained using a Voellmy model with a frictional coefficient of f = 0.19 and a turbulence parameter ξ = 1000 m s- 1. The results highlight the suitability of this numerical code, which is generally used for landslides, to reproduce the destructive potential of these events in volcanic environments and to obtain information on hazards connected with explosive-related, mass-wasting phenomena in Stromboli Island and at volcanic systems characterized by similar phenomena.

A contribution to the hazards assessment at Copahue volcano (Argentina-Chile) by facies analysis of a recent pyroclastic density current deposit

Science.gov (United States)

Balbis, C.; Petrinovic, I. A.; Guzmán, S.

2016-11-01

We recognised and interpreted a recent pyroclastic density current (PDC) deposit at the Copahue volcano (Southern Andes), through a field survey and a sedimentological study. The relationships between the behaviour of the PDCs, the morphology of the Río Agrio valley and the eruptive dynamics were interpreted. We identified two lithofacies in the deposit that indicate variations in the eruptive dynamics: i) the opening of the conduit and the formation of a highly explosive eruption that formed a diluted PDC through the immediate collapse of the eruptive column; ii) a continued eruption which followed immediately and records the widening of the conduit, producing a dense PDC. The eruption occurred in 2000 CE, was phreatomagmatic (VEI ≤ 2), with a vesiculation level above 4000 m depth and fragmentation driven by the interaction of magma with an hydrothermal system at ca. 1500 m depth. As deduced from the comparison between the accessory lithics of this deposit and those of the 2012 CE eruption, the depth of onset of vesiculation and fragmentation level in this volcano is constant in depth. In order to reproduce the distribution pattern of this PDC's deposit and to simulate potential PDC's forming-processes, we made several computational modelling from "denser" to "more diluted" conditions. The latter fairly reproduces the distribution of the studied deposit and represents perhaps one of the most dangerous possible scenarios of the Copahue volcanic activity. PDCs occurrence has been considered in the last volcanic hazards map as a low probability process; evidences found in this contribution suggest instead to include them as more probable and thus very important for the hazards assessment of the Copahue volcano.

Sr, Nd and Pb isotope and geochemical data from the Quaternary Nevado de Toluca volcano, a source of recent adakitic magmatism, and the Tenango Volcanic Field, Mexico

Science.gov (United States)

Martínez-Serrano, Raymundo G.; Schaaf, Peter; Solís-Pichardo, Gabriela; Hernández-Bernal, Ma. del Sol; Hernández-Treviño, Teodoro; Julio Morales-Contreras, Juan; Macías, José Luis

2004-11-01

Volcanic activity at Nevado de Toluca (NT) volcano began 2.6 Ma ago with the emission of andesitic lavas, but over the past 40 ka, eruptions have produced mainly lava flows and pyroclastic deposits of predominantly orthopyroxene-hornblende dacitic composition. In the nearby Tenango Volcanic Field (TVF) pyroclastic products and lava flows ranging in composition from basaltic andesite to andesite were erupted at most of 40 monogenetic volcanic centers and were coeval with the last stages of NT. All volcanic rocks in the study area are characterized by a calc-alkaline affinity that is consistent with a subduction setting. Relatively high concentrations of Sr (>460 ppm) coupled with low Y (45 km) that underlies the volcanoes of the study area, the geochemical and isotopic patterns of these rocks indicate low interaction with this crust. NT volcano was constructed at the intersection of three fault systems, and it seems that the Plio-Quaternary E-W system played an important role in the ascent and storage of magmas during the recent volcanic activity in the two regions. Chemical and textural features of orthopyroxene, amphibole and Fe-Ti oxides from NT suggest that crystallization of magmas occurred at polybaric conditions, confirming the rapid upwelling of magmas.

Pulmonary epithelial response in the rat lung to instilled Montserrat respirable dusts and their major mineral components.

Science.gov (United States)

Housley, D G; Bérubé, K A; Jones, T P; Anderson, S; Pooley, F D; Richards, R J

2002-07-01

The Soufriere Hills, a stratovolcano on Montserrat, started erupting in July 1995, producing volcanic ash, both from dome collapse pyroclastic flows and phreatic explosions. The eruptions/ash resuspension result in high concentrations of suspended particulate matter in the atmosphere, which includes cristobalite, a mineral implicated in respiratory disorders. To conduct toxicological studies on characterised samples of ash, together with major components of the dust mixture (anorthite, cristobalite), and a bioreactive mineral control (DQ12 quartz). Rats were challenged with a single mass (1 mg) dose of particles via intratracheal instillation and groups sacrificed at one, three, and nine weeks. Acute bioreactivity of the particles was assessed by increases in lung permeability and inflammation, changes in epithelial cell markers, and increase in the size of bronchothoracic lymph nodes. Data indicated that respirable ash derived from pyroclastic flows (20.1% cristobalite) or phreatic explosion (8.6% cristobalite) had minimal bioreactivity in the lung. Anorthite showed low bioreactivity, in contrast to pure cristobalite, which showed progressive increases in lung damage. Results suggests that either the percentage mass of cristobalite particles present in Montserrat ash was not sufficient as a catalyst in the lung environment, or its surface reactivity was masked by the non-reactive volcanic glass components during the process of ash formation.

Geochemistry of obsidian from Krasnoe Lake on the Chukchi Peninsula (Northeastern Siberia)

Science.gov (United States)

Popov, V. K.; Grebennikov, A. V.; Kuzmin, Ya. V.; Glascock, M. D.; Nozdrachev, E. A.; Budnitsky, S. Yu.; Vorobey, I. E.

2017-09-01

This report considers features of the geochemical composition of obsidian from beach sediments of Krasnoe Lake along the lower course of the Anadyr River, as well as from lava-pyroclastic rocks constituting the lake coastal outcrops and the surrounding branches of Rarytkin Ridge. The two geochemical types of obsidian, for the first time distinguished and researched, correspond in their chemical composition to lavas and ignimbrite-like tuffs of rhyolites from the Rarytkin area. The distinguished types represent the final stage of acidic volcanism in the West Kamchatkan-Koryak volcanic belt. It was assumed that the accumulation of obsidian in coastal pebble beds was caused by the erosion of extrusive domes and pyroclastic flows. The geochemical studies of obsidian artifacts from archeological sites of the regions of the Sea of Okhotsk, the Kolyma River, and the Chukchi Peninsula along with the correlation of geological and archeological samples show that Krasnoe Lake was an important source of "archeological" obsidian in Northeastern Siberia.

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

Science.gov (United States)

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

2016-01-01

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0–2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production. PMID:27824353

九州北部の山地河川に堆積する倒・流木と土砂

OpenAIRE

宮縁, 育夫; 清水, 晃; 小川, 泰浩; ミヤブチ, ヤスオ; シミズ, アキラ; オガワ, ヤスヒロ; Miyabuchi, Yasuo; Shimizu, Akira; Ogawa, Yasuhiro

1999-01-01

Distribution of woody debris and sediment was examined in a mountain stream, northern Kyushu, southwestern Japan. A densely-welded pyroclastic flow deposit dominates the study basin, and forms steep sideslopes and a flat valley floor. The watershed was disturbed by a powerful typhoon in 1991, which leveled many trees on the hillslopes. Subsequent storm-triggered shallow slope failures deposited timber along streambeds. Channel morphology (gradient, channel width and sinuosity), location and v...

Inner structure of La Fossa di Vulcano (Vulcano Island, southern Tyrrhenian Sea, Italy) revealed by high-resolution electric resistivity tomography coupled with self-potential, temperature, and CO2 diffuse degassing measurements

OpenAIRE

Revil , A.; Finizola , Anthony; Piscitelli , A.; Rizzo , E.; Ricci , T.; Crespy , A.; Angeletti , B.; Balasco , M.; Barde-Cabusson , Stéphanie; Bennati , L.; Boleve , A.; Byrdina , S.; Carzaniga , N.; Di Gangi , F.; Morin , Julie

2008-01-01

International audience; La Fossa cone is an active stratovolcano located on Vulcano Island in the Aeolian Archipelago (southern Italy). Its activity is characterized by explosive phreatic and phreatomagmatic eruptions producing wet and dry pyroclastic surges, pumice fall deposits, and highly viscous lava flows. Nine 2-D electrical resistivity tomograms (ERTs; electrode spacing 20 m, with a depth of investigation >200 m) were obtained to image the edifice. In addition, we also measured the sel...

Effects of volcanic and hydrologic processes on forest vegetation: Chaitén Volcano, Chile

OpenAIRE

Swanson,Frederick J; Jones,Julia A; Crisafulli,Charles M; Lara,Antonio

2013-01-01

The 2008-2009 eruption of Chaitén Volcano (Chile) involved a variety of volcanic and associated hydro-logic processes that damaged nearby forests. These processes included coarse (gravel) and fine (silt to sand) tephra fall, a laterally directed blast, fluvial deposition of remobilized tephra, a variety of low-temperature mass-movement processes, and a pyroclastic flow. Each of these geophysical processes constitutes a type of ecosystem disturbance which involves a distinctive suite of distur...

Surface-discharging hydrothermal systems at Yucca Mountain: Examining the evidence

International Nuclear Information System (INIS)

Levy, S.S.

1992-01-01

This paper discusses exposures of altered rock that have been thought to form by recent discharge of water from depth. They were examined to address a concern that hydrothermal processes could compromise the isolation capability of a potential high-level nuclear waste repository at Yucca Mountain. Suspected hot-spring and hydrothermal-vent deposits are more likely the products of infiltration of meteoric water into newly deposited and still-hot pyroclastic flows >12 Myr ago

Geomorphology and stratigraphy of Alba Patera, Mars

Science.gov (United States)

Schneeberger, Dale M.; Pieri, David C.

1991-01-01

Geomorphic and stratigraphic analysis of Alba Patera suggests a volcanic construct built by lavas with rheologic properties similar to basalts. A series of evolving eruptive styles is suggested by changes in morphology and inferred progressive reductions in flow volume with higher stratigraphic position. Alba Patera's volcanic history has been summarized into four main phases. The first is characterized by extensive flood like flows presumably erupted from fissures associated with the initial intrusion of magma into the region. The second phase is associated with the emplacement of pyroclastic rock, a more speculative interpretation. The third phase produced the voluminous tabular, crested, and undifferentiated flows, probably from a more centralized vent source. The fourth and last phase is marked the effusion of levee like flows and the collapse of the summit calderas and final graben formation.

Stratigraphy of the Grande Savane Ignimbrite Sequence, Dominica, Lesser Antilles

Science.gov (United States)

Schneider, S.; Smith, A. L.; Deuerling, K.; Killingsworth, N.; Daly, G.

2007-12-01

The island of Dominica, located in the central part of the Lesser Antilles island arc has eight potentially active volcanoes. One of these, Morne Diablotins, is a composite stratovolcano with several superimposed stratigraphic sequences ranging in age from Pliocene (4-2 Ma) to "Younger" Pleistocene (22,000 and >40,000 years B.P. The ignimbrite sequences form four flow fans that reached both the east and west coasts of the island. One of these flow fans, the Grande Savane, on the west coast of the island, also extends off-shore for a distance of at least 14 km as a distinctive submarine fan. Stratigraphical studies of the on- shore deposits that make up this fan indicate an older sequence of block and ash flow deposits, within which occurs a distinctive vulcanian fall deposit. These are overlain, with no evidence of an intervening paleosol, by a sequence of ignimbrites containing welded horizons (ranging in thickness from around 4 m to 16m). The lack of fall deposits beneath the ignimbrites suggest they may have been formed by instantaneous continuous collapse of the eruption column. This whole succession is overlain by a series of planar and dune bedded pumiceous surge deposits with interbedded pumiceous lapilli fall and ash fall deposits, that extend laterally outside of the main area of ignimbrite deposition. Beds within this upper sequence often contain accretionary lapilli and gas cavities suggesting magma-water interaction. The youngest deposits from Morne Diablotins appear to be valley- fill deposits of both ignimbrite and block and ash flow. A comparison of the of the Grande Savane pyroclastic sequence with the Pointe Ronde (west coast) and Londonderry (east coast) pyroclastic flow fans will provide information on the eruptive history of this major Plinian episode.

Using the New Two-Phase-Titan to Evaluate Potential Lahar Hazard at Villa la Angostura, Argentina

Science.gov (United States)

Sheridan, M. F.; Cordoba, G. A.; Viramonte, J. G.; Folch, A.; Villarosa, G.; Delgado, H.

2013-05-01

The 2011 eruption of Puyehue Volcano, located in the Cordon del Caulle volcanic complex, Chile, produced an ash plume that mainly affected downwind areas in Argentina. This plume forced air transport in the region to be closed for several weeks. Tephra fall deposits from this eruption affected many locations and pumice deposits on lakes killed most of the fish. As the ash emission occurred during the southern hemisphere winter (June), ash horizons were inter layered with layers of snow. This situation posed a potential threat for human settlements located downslope of the mountains. This was the case at Villa la Angostura, Neuquen province, Argentina, which sits on a series of fluvial deposits that originate in three major basins: Piedritas, Colorado, and Florencia. The Institute of Geological Survey of Argentina (SEGEMAR) estimated that the total accumulated deposit in each basin contains a ratio of approximately 30% ash and 70% snow. The CyTED-Ceniza Iberoamerican network worked together with Argentinean, Colombian and USA institutions in this hazard assessment. We used the program Two-Phase-Titan to model two scenarios in each of the basins. This computer code was developed at SUNY University at Buffalo supported by NSF Grant EAR 711497. Two-Phase-Titan is a new depth-averaged model for two phase flows that uses balance equations for multiphase mixtures. We evaluate the stresses using a Coulomb law for the solid phase and the typical hydraulic shallow water approach for the fluid phase. The linkage for compositions in the range between the pure end-member phases is accommodated by the inclusion of a phenomenological-based drag coefficient. The model is capable of simulating the whole range of particle volumetric fractions, from pure fluid flows to pure solid avalanches. The initial conditions, volume and solid concentration, required by Two-Phase-Titan were imposed using the SEGEMAR estimation of total deposited volume, assuming that the maximum volume that can

Morphology and Composition of Localized Lunar Dark Mantle Deposits With LROC Data

Science.gov (United States)

Gustafson, O.; Bell, J. F.; Gaddis, L. R.; Hawke, B. R.; Robinson, M. S.; LROC Science Team

2010-12-01

Clementine color (ultraviolet, visible or UVVIS) and Lunar Reconnaissance Orbiter (LRO) Wide Angle (WAC) and Narrow Angle (NAC) camera data provide the means to investigate localized lunar dark-mantle deposits (DMDs) of potential pyroclastic origin. Our goals are to (1) examine the morphology and physical characteristics of these deposits with LROC WAC and NAC data; (2) extend methods used in earlier studies of lunar DMDs with Clementine spectral reflectance (CSR) data; (3) use LRO WAC multispectral data to complement and extend the CSR data for compositional analyses; and (4) apply these results to identify the likely mode of emplacement and study the diversity of compositions among these deposits. Pyroclastic deposits have been recognized all across the Moon, identified by their low albedo, smooth texture, and mantling relationship to underlying features. Gaddis et al. (2003) presented a compositional analysis of 75 potential lunar pyroclastic deposits (LPDs) based on CSR measurements. New LRO camera (LROC) data permit more extensive analyses of such deposits than previously possible. Our study began with six sites on the southeastern limb of the Moon that contain nine of the cataloged 75 potential pyroclastic deposits: Humboldt (4 deposits), Petavius, Barnard, Abel B, Abel C, and Titius. Our analysis found that some of the DMDs exhibit qualities characteristic of fluid emplacement, such as flat surfaces, sharp margins, embaying relationships, and flow textures. We conclude that the localized DMDs are a complex class of features, many of which may have formed by a combination of effusive and pyroclastic emplacement mechanisms. We have extended this analysis to include additional localized DMDs from the catalog of 75 potential pyroclastic deposits. We have examined high resolution (up to 0.5 m/p) NAC images as they become available to assess the mode of emplacement of the deposits, locate potential volcanic vents, and assess physical characteristics of the DMDs

Stratigraphic reconstruction of two debris avalanche deposits at Colima Volcano (Mexico): Insights into pre-failure conditions and climate influence

Science.gov (United States)

Roverato, M.; Capra, L.; Sulpizio, R.; Norini, G.

2011-10-01

Throughout its history, Colima Volcano has experienced numerous partial edifice collapses with associated emplacement of debris avalanche deposits of contrasting volume, morphology and texture. A detailed stratigraphic study in the south-eastern sector of the volcano allowed the recognition of two debris avalanche deposits, named San Marcos (> 28,000 cal yr BP, V = ~ 1.3 km 3) and Tonila (15,000-16,000 cal yr BP, V = ~ 1 km 3 ). This work sheds light on the pre-failure conditions of the volcano based primarily on a detailed textural study of debris avalanche deposits and their associated pyroclastic and volcaniclastic successions. Furthermore, we show how the climate at the time of the Tonila collapse influenced the failure mechanisms. The > 28,000 cal yr BP San Marcos collapse was promoted by edifice steep flanks and ongoing tectonic and volcanotectonic deformation, and was followed by a magmatic eruption that emplaced pyroclastic flow deposits. In contrast, the Tonila failure occurred just after the Last Glacial Maximum (22,000-18,000 cal BP) and, in addition to the typical debris avalanche textural characteristics (angular to sub-angular clasts, coarse matrix, jigsaw fit) it shows a hybrid facies characterized by debris avalanche blocks embedded in a finer, homogenous and partially cemented matrix, a texture more characteristic of debris flow deposits. The Tonila debris avalanche is directly overlain by a 7-m thick hydromagmatic pyroclastic succession. Massive debris flow deposits, often more than 10 m thick and containing large amounts of tree trunk logs, represent the top unit in the succession. Fluvial deposits also occur throughout all successions; these represent periods of highly localized stream reworking. All these lines of evidence point to the presence of water in the edifice prior to the Tonila failure, suggesting it may have been a weakening factor. The Tonila failure appears to represent an anomalous event related to the particular climatic

Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 2: Predicted emplacement processes and observations)

Science.gov (United States)

Head, James W.; Wilson, Lionel

2017-02-01

, inhibiting dike emplacement and surface eruptions. In contrast to small dike volumes and low propagation velocities in terrestrial environments, lunar dike propagation velocities are typically sufficiently high that shallow sill formation is not favored; local low-density breccia zones beneath impact crater floors, however, may cause lateral magma migration to form laccoliths (e.g., Vitello Crater) and sills (e.g., Humboldt Crater) in floor-fractured craters. Dikes emplaced into the shallow crust may stall and produce crater chains due to active and passive gas venting (e.g., Mendeleev Crater Chain) or, if sufficiently shallow, may create a near-surface stress field that forms linear and arcuate graben, often with pyroclastic and small-scale effusive eruptions (e.g., Rima Parry V). Effusive eruptions are modulated by effusion rates, eruption durations, cooling and supply limitations to flow length, and pre-existing topography. Relatively low effusion rate, cooling-limited flows lead to small shield volcanoes (e.g., Tobias Mayer, Milicius); higher effusion rate, cooling-limited flows lead to compound flow fields (e.g., most mare basins) and even higher effusion rate, long-duration flows lead to thermal erosion of the vent, effusion rate enhancement, and thermal erosion of the substrate to produce sinuous rilles (e.g., Rimae Prinz). Extremely high effusion rate flows on slopes lead to volume-limited flow with lengths of many hundreds of kilometers (e.g., the young Imbrium basin flows). Explosive, pyroclastic eruptions are common on the Moon. The low pressure environment in propagating dike crack-tips can cause gas formation at great depths and throughout dike ascent; at shallow crustal depths both the smelting reaction and the recently documented abundant magmatic volatiles in mare basalt magmas contribute to significant shallow degassing and pyroclastic activity associated with the dike as it erupts at the surface. Dikes penetrating to the surface produce a wide range of

Geology of the Ugashik-Mount Peulik Volcanic Center, Alaska

Science.gov (United States)

Miller, Thomas P.

2004-01-01

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

In vitro toxicology of respirable Montserrat volcanic ash.

Science.gov (United States)

Wilson, M R; Stone, V; Cullen, R T; Searl, A; Maynard, R L; Donaldson, K

2000-11-01

In July 1995 the Soufriere Hills volcano on the island of Montserrat began to erupt. Preliminary reports showed that the ash contained a substantial respirable component and a large percentage of the toxic silica polymorph, cristobalite. In this study the cytotoxicity of three respirable Montserrat volcanic ash (MVA) samples was investigated: M1 from a single explosive event, M2 accumulated ash predominantly derived from pyroclastic flows, and M3 from a single pyroclastic flow. These were compared with the relatively inert dust TiO(2) and the known toxic quartz dust, DQ12. Surface area of the particles was measured with the Brunauer, Emmet, and Teller (BET) adsorption method and cristobalite content of MVA was determined by x ray diffraction (XRD). After exposure to particles, the metabolic competence of the epithelial cell line A549 was assessed to determine cytotoxic effects. The ability of the particles to induce sheep blood erythrocyte haemolysis was used to assess surface reactivity. Treatment with either MVA, quartz, or titanium dioxide decreased A549 epithelial cell metabolic competence as measured by ability to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). On addition of mannitol, the cytotoxic effect was significantly less with M1, quartz, and TiO(2). All MVA samples induced a dose dependent increase in haemolysis, which, although less than the haemolysis induced by quartz, was significantly greater than that induced by TiO(2). Addition of mannitol and superoxide dismutase (SOD) significantly reduced the haemolytic activity only of M1, but not M2 or M3, the samples derived from predominantly pyroclastic flow events. Neither the cristobalite content nor the surface area of the MVA samples correlated with observed in vitro reactivity. A role for reactive oxygen species could only be shown in the cytotoxicity of M1, which was the only sample derived from a purely explosive event. These results suggest that in general the

El Edificio Antiguo de la isla de San Vicente (Cabo Verde): características del sector occidental

OpenAIRE

Huertas, María José; Hernán, Francisco; Ancochea, Eumenio; Brändle, José Luis

2006-01-01

A more than 1000m thick pile of basaltic lava flows and pyroclasts dipping seawards rises on the western sector of San Vicente. Several systems of dikes cut across the succession that is composed of two different sequences. The lower sequence (Lazareto Formation), about 400 m thick, is formed mainly by pahoe-hoe, frequently ankaramitic, basalt lavas and some breccias intercalated. This sequence is exposed in small hills and low rounded ridges of gentle slopes. The upper sequence (...

Martian volcanism: A review

International Nuclear Information System (INIS)

Carr, M.H.

1987-01-01

Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

Science.gov (United States)

Husain, Taha Murtuza

Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995

Energy Technology Data Exchange (ETDEWEB)

Luckey, R.R.; Tucci, P.; Faunt, C.C.; Ervin, E.M. [and others

1996-12-31

Yucca Mountain, which is being studied extensively because it is a potential site for a high-level radioactive-waste repository, consists of a thick sequence of volcanic rocks of Tertiary age that are underlain, at least to the southeast, by carbonate rocks of Paleozoic age. Stratigraphic units important to the hydrology of the area include the alluvium, pyroclastic rocks of Miocene age (the Timber Mountain Group; the Paintbrush Group; the Calico Hills Formation; the Crater Flat Group; the Lithic Ridge Tuff; and older tuffs, flows, and lavas beneath the Lithic Ridge Tuff), and sedimentary rocks of Paleozoic age. The saturated zone generally occurs in the Calico Hills Formation and stratigraphically lower units. The saturated zone is divided into three aquifers and two confining units. The flow system at Yucca Mountain is part of the Alkali Flat-Furnace Creek subbasin of the Death Valley groundwater basin. Variations in the gradients of the potentiometric surface provided the basis for subdividing the Yucca Mountain area into zones of: (1) large hydraulic gradient where potentiometric levels change at least 300 meters in a few kilometers; (2) moderate hydraulic gradient where potentiometric levels change about 45 meters in a few kilometers; and (3) small hydraulic gradient where potentiometric levels change only about 2 meters in several kilometers. Vertical hydraulic gradients were measured in only a few boreholes around Yucca Mountain; most boreholes had little change in potentiometric levels with depth. Limited hydraulic testing of boreholes in the Yucca Mountain area indicated that the range in transmissivity was more than 2 to 3 orders of magnitude in a particular hydrogeologic unit, and that the average values for the individual hydrogeologic units generally differed by about 1 order of magnitude. The upper volcanic aquifer seems to be the most permeable hydrogeologic unit, but this conclusion was based on exceedingly limited data.

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995

International Nuclear Information System (INIS)

Luckey, R.R.; Tucci, P.; Faunt, C.C.; Ervin, E.M.

1996-01-01

Yucca Mountain, which is being studied extensively because it is a potential site for a high-level radioactive-waste repository, consists of a thick sequence of volcanic rocks of Tertiary age that are underlain, at least to the southeast, by carbonate rocks of Paleozoic age. Stratigraphic units important to the hydrology of the area include the alluvium, pyroclastic rocks of Miocene age (the Timber Mountain Group; the Paintbrush Group; the Calico Hills Formation; the Crater Flat Group; the Lithic Ridge Tuff; and older tuffs, flows, and lavas beneath the Lithic Ridge Tuff), and sedimentary rocks of Paleozoic age. The saturated zone generally occurs in the Calico Hills Formation and stratigraphically lower units. The saturated zone is divided into three aquifers and two confining units. The flow system at Yucca Mountain is part of the Alkali Flat-Furnace Creek subbasin of the Death Valley groundwater basin. Variations in the gradients of the potentiometric surface provided the basis for subdividing the Yucca Mountain area into zones of: (1) large hydraulic gradient where potentiometric levels change at least 300 meters in a few kilometers; (2) moderate hydraulic gradient where potentiometric levels change about 45 meters in a few kilometers; and (3) small hydraulic gradient where potentiometric levels change only about 2 meters in several kilometers. Vertical hydraulic gradients were measured in only a few boreholes around Yucca Mountain; most boreholes had little change in potentiometric levels with depth. Limited hydraulic testing of boreholes in the Yucca Mountain area indicated that the range in transmissivity was more than 2 to 3 orders of magnitude in a particular hydrogeologic unit, and that the average values for the individual hydrogeologic units generally differed by about 1 order of magnitude. The upper volcanic aquifer seems to be the most permeable hydrogeologic unit, but this conclusion was based on exceedingly limited data

Storage conditions of the mafic and silicic magmas at Cotopaxi, Ecuador

Science.gov (United States)

Martel, Caroline; Andújar, Joan; Mothes, Patricia; Scaillet, Bruno; Pichavant, Michel; Molina, Indira

2018-04-01

The 2015 reactivation of the Cotopaxi volcano urges us to understand the complex eruptive dynamics of Cotopaxi for better management of a potential major crisis in the near future. Cotopaxi has commonly transitioned from andesitic eruptions of strombolian style (lava flows and scoria ballistics) or nuées ardentes (pyroclastic flows and ash falls) to highly explosive rhyolitic ignimbrites (pumiceous pyroclastic flows), which entail drastically different risks. To better interpret geophysical and geochemical signals, Cotopaxi magma storage conditions were determined via existing phase-equilibrium experiments that used starting materials chemically close to the Cotopaxi andesites and rhyolites. The results suggest that Cotopaxi's most mafic andesites (last erupted products) can be stored over a large range of depth from 7 km to ≥16 km below the summit (pressure from 200 to ≥400 MPa), 1000 °C, NNO +2, and contain 4.5-6.0±0.7 wt% H2O dissolved in the melt in equilibrium with 30-40% phenocrysts of plagioclase, two pyroxenes, and Fe-Ti oxides. These mafic andesites sometimes evolve towards more silicic andesites by cooling to 950 °C. Rhyolitic magmas are stored at 200-300 MPa (i.e. 7-11 km below the summit), 750 °C, NNO +2, and contain 6-8 wt% H2O dissolved in a nearly aphyric melt (<5% phenocrysts of plagioclase, biotite, and Fe-Ti oxides). Although the andesites produce the rhyolitic magmas by fractional crystallization, the Cotopaxi eruptive history suggests reactivation of either reservoirs at distinct times, likely reflecting flux or time fluctuations during deep magma recharge.

After the disaster: the hydrogeomorphic, ecological, and biological responses to the 1980 eruption of Mount St. Helens, Washington

Science.gov (United States)

Major, Jon J.; Crisafulli, Charlie; Bishop, John

2009-01-01

The 1980 eruption of Mount St. Helens caused instantaneous landscape disturbance on a grand scale. On 18 May 1980, an ensemble of volcanic processes, including a debris avalanche, a directed pyroclastic density current, voluminous lahars, and widespread tephra fall, abruptly altered landscape hydrology and geomorphology, and created distinctive disturbance zones having varying impacts on regional biota. Response to the geological and ecological disturbances has been varied and complex. In general, eruption-induced alterations in landscape hydrology and geomorphology led to enhanced stormflow discharge and sediment transport. Although the hydrological response to landscape perturbation has diminished, enhanced sediment transport persists in some basins. In the nearly 30 years since the eruption, 350 million (metric) tons of suspended sediment has been delivered from the Toutle River watershed to the Cowlitz River (roughly 40 times the average annual preeruption suspended-sediment discharge of the Columbia River). Such prodigious sediment loading has wreaked considerable socioeconomic havoc, causing significant channel aggradation and loss of flood conveyance capacity. Significant and ongoing engineering efforts have been required to mitigate these problems. The overall biological evolution of the eruption-impacted landscape can be viewed in terms of a framework of survivor legacies. Despite appearances to the contrary, a surprising number of species survived the eruption, even in the most heavily devastated areas. With time, survivor “hotspots” have coalesced into larger patches, and have served as stepping stones for immigrant colonization. The importance of biological legacies will diminish with time, but the intertwined trajectories of geophysical and biological successions will influence the geological and biological responses to the 1980 eruption for decades to come.

Towards a Proactive Risk Mitigation Strategy at La Fossa Volcano, Vulcano Island

Science.gov (United States)

Biass, S.; Gregg, C. E.; Frischknecht, C.; Falcone, J. L.; Lestuzzi, P.; di Traglia, F.; Rosi, M.; Bonadonna, C.

2014-12-01

A comprehensive risk assessment framework was built to develop proactive risk reduction measures for Vulcano Island, Italy. This framework includes identification of eruption scenarios; probabilistic hazard assessment, quantification of hazard impacts on the built environment, accessibility assessment on the island and risk perception study. Vulcano, a 21 km2 island with two primary communities host to 900 permanent residents and up to 10,000 visitors during summer, shows a strong dependency on the mainland for basic needs (water, energy) and relies on a ~2 month tourism season for its economy. The recent stratigraphy reveals a dominance of vulcanian and subplinian eruptions, producing a range of hazards acting at different time scales. We developed new methods to probabilistically quantify the hazard related to ballistics, lahars and tephra for all eruption styles. We also elaborated field- and GIS- based methods to assess the physical vulnerability of the built environment and created dynamic models of accessibility. Results outline the difference of hazard between short and long-lasting eruptions. A subplinian eruption has a 50% probability of impacting ~30% of the buildings within days after the eruption, but the year-long damage resulting from a long-lasting vulcanian eruption is similar if tephra is not removed from rooftops. Similarly, a subplinian eruption results in a volume of 7x105 m3 of material potentially remobilized into lahars soon after the eruption. Similar volumes are expected for a vulcanian activity over years, increasing the hazard of small lahars. Preferential lahar paths affect critical infrastructures lacking redundancy, such as the road network, communications systems, the island's only gas station, and access to the island's two evacuation ports. Such results from hazard, physical and systemic vulnerability help establish proactive volcanic risk mitigation strategies and may be applicable in other island settings.

Sediment transport in headwaters of a volcanic catchment—Kamchatka Peninsula case study

Science.gov (United States)

Chalov, Sergey R.; Tsyplenkov, Anatolii S.; Pietron, Jan; Chalova, Aleksandra S.; Shkolnyi, Danila I.; Jarsjö, Jerker; Maerker, Michael

2017-09-01

Due to specific environmental conditions, headwater catchments located on volcanic slopes and valleys are characterized by distinctive hydrology and sediment transport patterns. However, lack of sufficient monitoring causes that the governing processes and patterns in these areas are rarely well understood. In this study, spatiotemporal water discharge and sediment transport from upstream sources was investigated in one of the numerous headwater catchments located in the lahar valleys of the Kamchatka Peninsula Sukhaya Elizovskaya River near Avachinskii and Koryakskii volcanoes. Three different subcatchments and corresponding channel types (wandering rivers within lahar valleys, mountain rivers within volcanic slopes and rivers within submountain terrains) were identified in the studied area. Our measurements from different periods of observations between years 2012-2014 showed that the studied catchment was characterized by extreme diurnal fluctuation of water discharges and sediment loads that were influenced by snowmelt patterns and high infiltration rates of the easily erodible lahar deposits. The highest recorded sediment loads were up to 9•104 mg/L which was related to an increase of two orders of magnitude within a one day of observations. Additionally, to get a quantitative estimate of the spatial distribution of the eroded material in the volcanic substrates we applied an empirical soil erosion and sediment yield model-modified universal soil loss equation (MUSLE). The modeling results showed that even if the applications of the universal erosion model to different non-agricultural areas (e.g., volcanic catchments) can lead to irrelevant results, the MUSLE model delivered might be acceptable for non-lahar areas of the studied volcanic catchment. Overall the results of our study increase our understanding of the hydrology and associated sediment transport for prediction of risk management within headwater volcanic catchments.

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

Directory of Open Access Journals (Sweden)

Heryadi Rachmat

2016-06-01

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

Geology of Tok Island, Korea: eruptive and depositional processes of a shoaling to emergent island volcano

Science.gov (United States)

Sohn, Y. K.

1995-02-01

Detailed mapping of Tok Island, located in the middle of the East Sea (Sea of Japan), along with lithofacies analysis and K-Ar age determinations reveal that the island is of early to late Pliocene age and comprises eight rock units: Trachyte I, Unit P-I, Unit P-II, Trachyandesite (2.7±0.1 Ma), Unit P-III, Trachyte II (2.7±0.1 Ma), Trachyte III (2.5±0.1 Ma) and dikes in ascending stratigraphic order. Trachyte I is a mixture of coherent trachytic lavas and breccias that are interpreted to be subaqueous lavas and related hyaloclastites. Unit P-I comprises massive and inversely graded basaltic breccias which resulted from subaerial gain flows and subaqueous debris flows. A basalt clast from the unit, derived from below Trachyte I, has an age of 4.6±0.4 Ma. Unit P-II is composed of graded and stratified lapilli tuffs with the characteristics of proximal pyroclastic surge deposits. The Trachyandesite is a massive subaerial lava ponded in a volcano-tectonic depression, probably a summit crater. A pyroclastic sequence containing flattened scoria clasts (Unit P-III) and a small volume subaerial lava (Trachyte II) occur above the Trachyandesite, suggesting resumption of pyroclastic activity and lava effusion. Afterwards, shallow intrusion of magma occurred, producing Trachyte III and trachyte dikes. The eight rock units provide an example of the changing eruptive and depositional processes and resultant succession of lithofacies as a seamount builds up above sea level to form an island volcano: Trachyte I represents a wholly subaqueous and effusive stage; Units P-I and P-II represent Surtseyan and Taalian eruptive phases during an explosive transitional (subaqueous to emergent) stage; and the other rock units represent later subaerial effusive and explosive stages. Reconstruction of volcano morphology suggests that the island is a remnant of the south-western crater rim of a volcano the vent of which lies several hundred meters to the north-east.

An overview of the 2009 eruption of Redoubt Volcano, Alaska

Science.gov (United States)

Bull, Katharine F.; Buurman, Helena

2013-06-01

In March 2009, Redoubt Volcano, Alaska erupted for the first time since 1990. Explosions ejected plumes that disrupted international and domestic airspace, sent lahars more than 35 km down the Drift River to the coast, and resulted in tephra fall on communities over 100 km away. Geodetic data suggest that magma began to ascend slowly from deep in the crust and reached mid- to shallow-crustal levels as early as May, 2008. Heat flux at the volcano during the precursory phase melted ~ 4% of the Drift glacier atop Redoubt's summit. Petrologic data indicate the deeply sourced magma, low-silica andesite, temporarily arrested at 9-11 km and/or at 4-6 km depth, where it encountered and mixed with segregated stored high-silica andesite bodies. The two magma compositions mixed to form intermediate-silica andesite, and all three magma types erupted during the earliest 2009 events. Only intermediate- and high-silica andesites were produced throughout the explosive and effusive phases of the eruption. The explosive phase began with a phreatic explosion followed by a seismic swarm, which signaled the start of lava effusion on March 22, shortly prior to the first magmatic explosion early on March 23, 2009 (UTC). More than 19 explosions (or “Events”) were produced over 13 days from a single vent immediately south of the 1989-90 lava domes. During that period multiple small pyroclastic density currents flowed primarily to the north and into glacial ravines, three major lahars flooded the Drift River Terminal over 35 km down-river on the coast, tephra fall deposited on all aspects of the edifice and on several communities north and east of the volcano, and at least two, and possibly three lava domes were emplaced. Lightning accompanied almost all the explosions. A shift in the eruptive character took place following Event 9 on March 27 in terms of infrasound signal onsets, the character of repeating earthquakes, and the nature of tephra ejecta. More than nine additional

Volcanic impediments in the progressive development of pre-Columbian civilizations in the Ecuadorian Andes

Science.gov (United States)

Hall, Minard L.; Mothes, Patricia A.

2008-10-01

Archaeological investigations in Ecuador have proposed that there appear to be hiatus or anomalous jumps in the progressive development of pre-Columbian indigenous cultures, based upon the fact that their ceramics and tools demonstrate abrupt advances in their sophistication at several horizons in the soil profile. Because some of these horizons are clearly associated with volcanic ash layers, archaeologists have sought a causal relation with volcanism, that is, the eruptive events or their products severely interfered with the early inhabitants, resulting in their abandonment of certain areas. Geological studies of the young volcanoes in the Ecuadorian Andes carried out during the past two decades now allow us to make a more thorough evaluation of the role of volcanism during the Holocene. This contribution briefly describes the principal Holocene volcanic events and the distribution of the corresponding eruptive products found along the InterAndean Valley, from southern Colombia to central Ecuador. Only those events that were sufficiently large that they could have had a detrimental effect on the valley's early residents are discussed. Dacitic and rhyolitic ash flows, as well as numerous debris flows (lahars) have occurred frequently and their deposits cover many valleys and floodplains, where early inhabitants probably settled. The enormous Chillos Valley lahar, associated with the 4500 yBP eruption of Cotopaxi volcano, buried soils containing ceramics of the early Formative Period. However, the greatest impact upon mankind was probably not these short-lived violent events, but rather the burying of settlements and agricultural fields by ash fallout, the effect of which may have lasted hundreds of years. Ash fall layers are observed in pre-Columbian cultural horizons in the soil profile, occurring in the InterAndean Valley, the lower flanks of the Andes, and along Ecuador's Pacific coast, the oldest corresponding to the 5800 yBP eruption of Cotopaxi. This brief

Field-trip guide to subaqueous volcaniclastic facies in the Ancestral Cascades arc in southern Washington State—The Ohanapecosh Formation and Wildcat Creek beds

Science.gov (United States)

Jutzeler, Martin; McPhie, Jocelyn

2017-06-27

Partly situated in the idyllic Mount Rainier National Park, this field trip visits exceptional examples of Oligocene subaqueous volcaniclastic successions in continental basins adjacent to the Ancestral Cascades arc. The >800-m-thick Ohanapecosh Formation (32–26 Ma) and the >300-m-thick Wildcat Creek (27 Ma) beds record similar sedimentation processes from various volcanic sources. Both show evidence of below-wave-base deposition, and voluminous accumulation of volcaniclastic facies from subaqueous density currents and suspension settling. Eruption-fed facies include deposits from pyroclastic flows that crossed the shoreline, from tephra fallout over water, and from probable Surtseyan eruptions, whereas re-sedimented facies comprise subaqueous density currents and debris flow deposits.

Flow patterns in vertical two-phase flow

International Nuclear Information System (INIS)

McQuillan, K.W.; Whalley, P.B.

1985-01-01

This paper is concerned with the flow patterns which occur in upwards gas-liquid two-phase flow in vertical tubes. The basic flow patterns are described and the use of flow patter maps is discussed. The transition between plug flow and churn flow is modelled under the assumption that flooding of the falling liquid film limits the stability of plug flow. The resulting equation is combined with other flow pattern transition equations to produce theoretical flow pattern maps, which are then tested against experimental flow pattern data. Encouraging agreement is obtained

Geology and Conceptual Model of the Domuyo Geothermal Area, Patagonia, Argentina

Science.gov (United States)

Fragoso, A. S.; Ferrari, L.; Norini, G.

2017-12-01

Cerro Domuyo is the highest mountain in Patagonia and its western slope is characterized by thermal springs with boiling fluids as well as silicic domes and pyroclastic deposits that suggest the existence of a geothermal reservoir. Early studies proposed that the thermal springs were fault-controlled and the reservoir was located in a graben bounded by E-W normal faults. A recent geochemical study estimated a temperature of 220ºC for the fluid reservoir and a thermal energy release of 1.1 GW, one of the world largest advective heat flux from a continental volcanic center. We carried out a geologic survey and U-Pb and U-Th geochronologic study to elaborate an updated conceptual model for the Domuyo geothermal area. Our study indicates that the Domuyo Volcanic Complex (DVC) is a dome complex overlying an older, Middle Miocene to Pliocene volcanic sequence widely exposed to the southwest and to the north, which in turn covers: 1) the Jurassice-Early Creteacoeus Neuquen marine sedimentary succession, 2) silicic ignimbrites dated at 186.7 Ma and, 3) the Paleozoic metamorphic basement intruded by 288 Ma granite bodies. These pre-Cenozoic successions are involved in dominantly N-S trending folds and thrust faults later displaced by E-W striking normal faults with a right lateral component of motion that underlie the DVC. The volcanic cycle forming the DVC is distinctly bimodal with the emplacement of massive silicic domes but also less voluminous olivine basalts on its southern slope. The central dome underwent a major collapse that produced 0.35 km3 of ash and block flow and associated pyroclastic flows that filled the valley to the southwest up to 30 km from the source. This was followed by a voluminous effusive activity that formed silicic domes dated between 254-322 Ky, which is inferred to overlain a partially molten silicic magma chamber. Integrating the geologic model with magnetotelluric and gravity surveys we developed a conceptual model of the geothermal system

Decompression Induced Crystallization of Basaltic Andesite Magma: Constraints on the Eruption of Arenal Volcano, Costa Rica.

Science.gov (United States)

Szramek, L. A.; Gardner, J. E.; Larsen, J. F.

2004-12-01

Arenal Volcano is a small stratovolcano located 90 km NW of San Jose, Costa Rica. In 1968 current activity began with a Plinian phase, and has continued to erupt lava flows and pyroclastic flows intermittently since. Samples from the Plinian, pyroclastic flow, strombolian, and effusive phases have been studied texturally. Little variation in crystallinity occurs amongst the different phases. Number density of crystals, both 2D and 3D are 50-70 mm-2 and 30,000-50,000 mm-3 in the Plinian sample, compared to the lesser values in other eruptive types. Characteristic crystal size also increases as explosivity decreases. Two samples, both lava flows collected while warm, overlap with the Plinian sample. This suggests that the variations seen may be a result of cooling history. Plagioclase differs between the Plinian sample, in which they are only tabular in shape, and the other eruptive types, which contain both tabular and equant crystals. To link decompression paths of the Arenal magma to possible pre-eruptive conditions, we have carried out hydrothermal experiments. The experiments were preformed in TZM pressure vessels buffered at a fugacity of Ni-NiO and water saturation. Phase equilibria results in conjunction with mineral compositions and temperature estimates by previous workers from active lava flows and two-pyroxene geothermometry, constrain the likely pre-eruptive conditions for the Arenal magma to 950-1040° C with a water pressure of 50-80 MPa. Samples that started from conditions that bracket our estimated pre-eruptive conditions were decompressed in steps of 5-30 MPa and held for various times at each step until 20 MPa was reached, approximating average decompression rates of 0.25, 0.025, 0.0013 MPa/s. Comparison of textures found in the natural samples to the experimentally produced textures suggest that the Plinian eruption likely was fed by magma ascending at 0.05-1 m/s, whereas the less explosive phases were fed by magma ascending at 0.05 m/s or less.

Fluid dynamics of the 1997 Boxing Day volcanic blast on Montserrat, West Indies

Science.gov (United States)

Esposti Ongaro, T.; Clarke, A. B.; Neri, A.; Voight, B.; Widiwijayanti, C.

2008-03-01

Directed volcanic blasts are powerful explosions with a significant laterally directed component, which can generate devastating, high-energy pyroclastic density currents (PDCs). Such blasts are an important class of eruptive phenomena, but quantified understanding of their dynamics and effects is still incomplete. Here we use 2-D and 3-D multiparticle thermofluid dynamic flow codes to examine a powerful volcanic blast that occurred on Montserrat in December 1997. On the basis of the simulations, we divide the blast into three phases: an initial burst phase that lasts roughly 5 s and involves rapid expansion of the gas-pyroclast mixture, a gravitational collapse phase that occurs when the erupted material fails to mix with sufficient air to form a buoyant column and thus collapses asymmetrically, and a PDC phase that is dominated by motion parallel to the ground surface and is influenced by topography. We vary key input parameters such as total gas energy and total solid mass to understand their influence on simulations, and we compare the simulations with independent field observations of damage and deposits, demonstrating that the models generally capture important large-scale features of the natural phenomenon. We also examine the 2-D and 3-D model results to estimate the flow Mach number and conclude that the range of damage sustained at villages on Montserrat can be reasonably explained by the spatial and temporal distribution of the dynamic pressure associated with subsonic PDCs.

Digital photogrammetry and GIS-based analysis of the bio-geomorphological evolution of Sakurajima Volcano, diachronic analysis from 1947 to 2006

Science.gov (United States)

Gomez, Christopher

2014-06-01

The Sakurajima Volcano is one of the most active volcanoes in the world with regular activity dominated by vulcanian eruptions since 1955. Located in Kagoshima Prefecture - Kyushu Island, Japan - the Sakurajima Volcano is a stratovolcano with two main vents at the summit, the Kitadake and the Minamidake, and a third smaller central vent, the Nakadake. The two firsts peak at 1117 and 1060 m dominate the slopes mainly composed of lava-flow deposits, secondary volcaniclastic material and recent ejectas from the Vulcanian eruptions. Although the volcano has been very closely monitored by Japanese Universities (mostly Kyoto University and Kagoshima University) and governmental agencies, there has been very little geomorphological investigation of the structure of the volcano. Using the digital photogammetric method SfM-MVS (Structure from Motion and Multiple-view Stereophotogrammetry) applied to historical aerial photographs, the present contribution aims to provide an analysis of the volcanic structure and the recent bio-geomorphological evolution for the period 1947-2006. First, the results have proved that SfM-MVS is a method that can be successfully applied to aerial photographs for diachronic reconstruction of geomorphological landscape evolution. This method is especially important in active volcanic areas, as the geomorphology can change very rapidly within the historical period. Secondly, the results have shown that during the last ~ 60 years, the summit area of the Sakurajima has greatly evolved: the morpholology of the Minamidake crater has changed due to its regular explosive activity; the upper slopes have been covered in ejecta, modifying their elevation and their smoothness. The lower slopes have seen the apparition of lahar deposition areas, while valleys, upslope, have widened due to the lahar activity and the upward progression of the deposits. The 3D derived from SfM-MVS has also shown how the lahar deposits are using the topographic low, created on

Petrography and geochemistry of the volcanic rocks of the Rodeio Velho Member, Ordovician of the Camaqua basin (RS-Brazil): preliminary results

International Nuclear Information System (INIS)

Almeida, Delia del Pilar M. de; Lopes, Ricardo da C.; Gomes, Cristiane H.; Lima, Larissa de.

2000-01-01

A geochemical study based in REE, minor elements and petrographic analyses from the volcanic rocks pertaining to the Rodeio Velho Member, comprising lava flows and epizonal intrusive bodies, both corresponding to andesites, subalkaline and alkaline basalts and trachyandesites; and stratified pyroclastic deposits, showed that fractional crystallization of deep source magma is the fundamental mechanism controlling the relationships among these rocks. This igneous event occurred in an alkaline intraplate environment, associated to a widespread extension tectonics, probably corresponding to a final stage of the Pan African - Brasiliano Orogeny during the Middle Ordovician. (author)

VOLCWORKS: A suite for optimization of hazards mapping

Science.gov (United States)

Delgado Granados, H.; Ramírez Guzmán, R.; Villareal Benítez, J. L.; García Sánchez, T.

2012-04-01

Making hazards maps is a process linking basic science, applied science and engineering for the benefit of the society. The methodologies for hazards maps' construction have evolved enormously together with the tools that allow the forecasting of the behavior of the materials produced by different eruptive processes. However, in spite of the development of tools and evolution of methodologies, the utility of hazards maps has not changed: prevention and mitigation of volcanic disasters. Integration of different tools for simulation of different processes for a single volcano is a challenge to be solved using software tools including processing, simulation and visualization techniques, and data structures in order to build up a suit that helps in the construction process starting from the integration of the geological data, simulations and simplification of the output to design a hazards/scenario map. Scientific visualization is a powerful tool to explore and gain insight into complex data from instruments and simulations. The workflow from data collection, quality control and preparation for simulations, to achieve visual and appropriate presentation is a process that is usually disconnected, using in most of the cases different applications for each of the needed processes, because it requires many tools that are not built for the solution of a specific problem, or were developed by research groups to solve particular tasks, but disconnected. In volcanology, due to its complexity, groups typically examine only one aspect of the phenomenon: ash dispersal, laharic flows, pyroclastic flows, lava flows, and ballistic projectile ejection, among others. However, when studying the hazards associated to the activity of a volcano, it is important to analyze all the processes comprehensively, especially for communication of results to the end users: decision makers and planners. In order to solve this problem and connect different parts of a workflow we are developing the

3-D high-speed imaging of volcanic bomb trajectory in basaltic explosive eruptions

Science.gov (United States)

Gaudin, D.; Taddeucci, J; Houghton, Bruce F.; Orr, Tim R.; Andronico, D.; Del Bello, E.; Kueppers, U.; Ricci, T.; Scarlato, P.

2016-01-01

Imaging, in general, and high speed imaging in particular are important emerging tools for the study of explosive volcanic eruptions. However, traditional 2-D video observations cannot measure volcanic ejecta motion toward and away from the camera, strongly hindering our capability to fully determine crucial hazard-related parameters such as explosion directionality and pyroclasts' absolute velocity. In this paper, we use up to three synchronized high-speed cameras to reconstruct pyroclasts trajectories in three dimensions. Classical stereographic techniques are adapted to overcome the difficult observation conditions of active volcanic vents, including the large number of overlapping pyroclasts which may change shape in flight, variable lighting and clouding conditions, and lack of direct access to the target. In particular, we use a laser rangefinder to measure the geometry of the filming setup and manually track pyroclasts on the videos. This method reduces uncertainties to 10° in azimuth and dip angle of the pyroclasts, and down to 20% in the absolute velocity estimation. We demonstrate the potential of this approach by three examples: the development of an explosion at Stromboli, a bubble burst at Halema'uma'u lava lake, and an in-flight collision between two bombs at Stromboli.

Source mechanisms of volcanic tsunamis.

Science.gov (United States)

Paris, Raphaël

2015-10-28

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).

Magnetic Fabrics and Source Implications of Chisulryoung Ignimbrites, South Korea

Directory of Open Access Journals (Sweden)

Hoabin Hong

2016-08-01

Full Text Available The anisotropy of magnetic susceptibility (AMS of late Cretaceous ash-flow tuffs in Chisulryoung Volcanic Formation, southeastern Korea was studied to define the primary pyroclastic flow azimuth. AMS data revealed a dominant oblate fabric with a tight clustering of k3 (minimum axis of magnetic susceptibility and shallow dispersal of k1 (maximum axis of magnetic susceptibility and k2 (intermediate axis of magnetic susceptibility. Dominance of oblate fabrics indicates clast imbrications imposed by compaction and welding. Flow azimuth inferred from AMS data indicates the nearby intrusive welded tuff (IWT as the source of calderas for ignimbrites. Such an inference is supported by geologic investigations, in which the IWT displays eutaxitic textures nearly parallel to its subvertical contacts. The results are compatible with a unique prolate fabric and an anomalously high inclination observed for the IWT, possibly produced by rheomorphic flows as the welded tuff is squeezed along the rough-surfaced dyke walls due to agglutination.

Flow chemistry vs. flow analysis.

Science.gov (United States)

Trojanowicz, Marek

2016-01-01

The flow mode of conducting chemical syntheses facilitates chemical processes through the use of on-line analytical monitoring of occurring reactions, the application of solid-supported reagents to minimize downstream processing and computerized control systems to perform multi-step sequences. They are exactly the same attributes as those of flow analysis, which has solid place in modern analytical chemistry in several last decades. The following review paper, based on 131 references to original papers as well as pre-selected reviews, presents basic aspects, selected instrumental achievements and developmental directions of a rapidly growing field of continuous flow chemical synthesis. Interestingly, many of them might be potentially employed in the development of new methods in flow analysis too. In this paper, examples of application of flow analytical measurements for on-line monitoring of flow syntheses have been indicated and perspectives for a wider application of real-time analytical measurements have been discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

A new approach to investigate an eruptive paroxysmal sequence using camera and strainmeter networks: Lessons from the 3-5 December 2015 activity at Etna volcano

Science.gov (United States)

Bonaccorso, A.; Calvari, S.

2017-10-01

Explosive sequences are quite common at basaltic and andesitic volcanoes worldwide. Studies aimed at short-term forecasting are usually based on seismic and ground deformation measurements, which can be used to constrain the source region and quantify the magma volume involved in the eruptive process. However, during single episodes of explosive sequences, integration of camera remote sensing and geophysical data are scant in literature, and the total volume of pyroclastic products is not determined. In this study, we calculate eruption parameters for four powerful lava fountains occurring at the main and oldest Mt. Etna summit crater, Voragine, between 3 and 5 December 2015. These episodes produced impressive eruptive columns and plume clouds, causing lapilli and ash fallout to more than 100 km away. We analyse these paroxysmal events by integrating the images recorded by a network of monitoring cameras and the signals from three high-precision borehole strainmeters. From the camera images we calculated the total erupted volume of fluids (gas plus pyroclastics), inferring amounts from 1.9 ×109 m3 (first event) to 0.86 ×109 m3 (third event). Strain changes recorded during the first and most powerful event were used to constrain the depth of the source. The ratios of strain changes recorded at two stations during the four lava fountains were used to constrain the pyroclastic fraction for each eruptive event. The results revealed that the explosive sequence was characterized by a decreasing trend of erupted pyroclastics with time, going from 41% (first event) to 13% (fourth event) of the total erupted pyroclastic volume. Moreover, the volume ratio fluid/pyroclastic decreased markedly in the fourth and last event. To the best of our knowledge, this is the first time ever that erupted volumes of both fluid and pyroclastics have been estimated for an explosive sequence from a monitoring system using permanent cameras and high precision strainmeters. During future

Using Crossflow for Flow Measurements and Flow Analysis

Energy Technology Data Exchange (ETDEWEB)

Gurevich, A.; Chudnovsky, L.; Lopeza, A. [Advanced Measurement and Analysis Group Inc., Ontario (Canada); Park, M. H. [Sungjin Nuclear Engineering Co., Ltd., Gyeongju (Korea, Republic of)

2016-10-15

Ultrasonic Cross Correlation Flow Measurements are based on a flow measurement method that is based on measuring the transport time of turbulent structures. The cross correlation flow meter CROSSFLOW is designed and manufactured by Advanced Measurement and Analysis Group Inc. (AMAG), and is used around the world for various flow measurements. Particularly, CROSSFLOW has been used for boiler feedwater flow measurements, including Measurement Uncertainty Recovery (MUR) reactor power uprate in 14 nuclear reactors in the United States and in Europe. More than 100 CROSSFLOW transducers are currently installed in CANDU reactors around the world, including Wolsung NPP in Korea, for flow verification in ShutDown System (SDS) channels. Other CROSSFLOW applications include reactor coolant gross flow measurements, reactor channel flow measurements in all channels in CANDU reactors, boiler blowdown flow measurement, and service water flow measurement. Cross correlation flow measurement is a robust ultrasonic flow measurement tool used in nuclear power plants around the world for various applications. Mathematical modeling of the CROSSFLOW agrees well with laboratory test results and can be used as a tool in determining the effect of flow conditions on CROSSFLOW output and on designing and optimizing laboratory testing, in order to ensure traceability of field flow measurements to laboratory testing within desirable uncertainty.

Flow analysis of HANARO flow simulated test facility

International Nuclear Information System (INIS)

Park, Yong-Chul; Cho, Yeong-Garp; Wu, Jong-Sub; Jun, Byung-Jin

2002-01-01

The HANARO, a multi-purpose research reactor of 30 MWth open-tank-in-pool type, has been under normal operation since its initial critical in February, 1995. Many experiments should be safely performed to activate the utilization of the NANARO. A flow simulated test facility is being developed for the endurance test of reactivity control units for extended life times and the verification of structural integrity of those experimental facilities prior to loading in the HANARO. This test facility is composed of three major parts; a half-core structure assembly, flow circulation system and support system. The half-core structure assembly is composed of plenum, grid plate, core channel with flow tubes, chimney and dummy pool. The flow channels are to be filled with flow orifices to simulate core channels. This test facility must simulate similar flow characteristics to the HANARO. This paper, therefore, describes an analytical analysis to study the flow behavior of the test facility. The computational flow analysis has been performed for the verification of flow structure and similarity of this test facility assuming that flow rates and pressure differences of the core channel are constant. The shapes of flow orifices were determined by the trial and error method based on the design requirements of core channel. The computer analysis program with standard k - ε turbulence model was applied to three-dimensional analysis. The results of flow simulation showed a similar flow characteristic with that of the HANARO and satisfied the design requirements of this test facility. The shape of flow orifices used in this numerical simulation can be adapted for manufacturing requirements. The flow rate and the pressure difference through core channel proved by this simulation can be used as the design requirements of the flow system. The analysis results will be verified with the results of the flow test after construction of the flow system. (author)

Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission

Science.gov (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,

2001-01-01

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.

Volcanic hazard zonation of the Nevado de Toluca volcano, México

Science.gov (United States)

Capra, L.; Norini, G.; Groppelli, G.; Macías, J. L.; Arce, J. L.

2008-10-01

The Nevado de Toluca is a quiescent volcano located 20 km southwest of the City of Toluca and 70 km west of Mexico City. It has been quiescent since its last eruptive activity, dated at ˜ 3.3 ka BP. During the Pleistocene and Holocene, it experienced several eruptive phases, including five dome collapses with the emplacement of block-and-ash flows and four Plinian eruptions, including the 10.5 ka BP Plinian eruption that deposited more than 10 cm of sand-sized pumice in the area occupied today by Mexico City. A detailed geological map coupled with computer simulations (FLOW3D, TITAN2D, LAHARZ and HAZMAP softwares) were used to produce the volcanic hazard assessment. Based on the final hazard zonation the northern and eastern sectors of Nevado de Toluca would be affected by a greater number of phenomena in case of reappraisal activity. Block-and-ash flows will affect deep ravines up to a distance of 15 km and associated ash clouds could blanket the Toluca basin, whereas ash falls from Plinian events will have catastrophic effects for populated areas within a radius of 70 km, including the Mexico City Metropolitan area, inhabited by more than 20 million people. Independently of the activity of the volcano, lahars occur every year, affecting small villages settled down flow from main ravines.

Turbine flow meter response in two-phase flows

International Nuclear Information System (INIS)

Shim, W.J.; Dougherty, T.J.; Cheh, H.Y.

1996-01-01

The purpose of this paper is to suggest a simple method of calibrating turbine flow meters to measure the flow rates of each phase in a two-phase flow. The response of two 50.8 mm (2 inch) turbine flow meters to air-water, two-phase mixtures flowing vertically in a 57 mm I.D. (2.25 inch) polycarbonate tube has been investigated for both upflow and downflow. The flow meters were connected in series with an intervening valve to provide an adjustable pressure difference between them. Void fractions were measured by two gamma densitometers, one upstream of the flow meters and the other downstream. The output signal of the turbine flow meters was found to depend only on the actual volumetric flow rate of the gas, F G , and liquid, F L , at the location of the flow meter

Use of Space and the Need for Planning in the Disaster-Prone Area of Code River, Yogyakarta, Indonesia

Directory of Open Access Journals (Sweden)

Rini Rachmawati

2017-01-01

  Abstrak Tepi Sungai Code merupakan daerah rawan terhadap banjir lahar yang disebabkan oleh erupsi Gunungapi Merapi. Penelitian ini menfokuskan pada daerah terdampak di Danurejan, Kota Yogyakarta, Indonesia. Tujuan dari penelitian ini adalah 1 untuk mengidentifikasi dan menganalisa fungsi ruang setelah bencana, dan 2 untuk menganalisa tindakan perencanaan ruang yang dibutuhkan setelah bencana. Data dikumpulkan dari data sekunder dan primer. Data primer diperoleh melalui observasi, interview mendalam, dan diskusi kelompok terfokus. Hasil menunjukkan bahwa pemanfaatan ruang dalam antisipasi dari bencana banjir lahar masih terbatas  untuk pembangunan peninggian tanggul. Temuan penelitian menyarankan perlunya perhatian terhadap pemanfaatan ruang untuk kelompok yang rentan. Selain itu juga perlunya partisipasi publik dalam pemanfaatan ruang, penyiapan design ekowisata dan kegiatan bernilai ekonomi. Selan itu juga perlu adanya integrasi analisis risiko dan distribusi spasial dari risiko yang  dituangkan dalam  rencana rinci tata ruang.

Mio Pliocene volcaniclastic deposits in the Famatina Ranges, southern Central Andes: A case of volcanic controls on sedimentation in broken foreland basins

Science.gov (United States)

Martina, Federico; Dávila, Federico M.; Astini, Ricardo A.

2006-04-01

A well-constrained record of Miocene-Pliocene explosive volcanism is preserved within the broken foreland of Western Argentina along the Famatina Ranges. This paper focuses on the volcaniclastic record known as the Río Blanco member of the El Durazno Formation. Three facies can be recognized in the study area: (1) massive tuffs; (2) volcaniclastic conglomerates and (3) pumiceous sandstones. These facies are interpreted as primary pyroclastic flow deposits (ignimbrites) and reworked volcanogenic deposits within interacting volcanic-fluvial depositional systems. Alternation between ignimbrites and volcanogenic sandstones and conglomerates suggest a recurrent pattern of sedimentation related to recurrent volcanic activity. Considering the facies mosaic and relative thicknesses of facies, short periods of syn-eruption sedimentation (volcaniclastic deposits) seem to have been separated by longer inter-eruption periods, where normal stream-flow processes were dominant. The volcaniclastic component decreases up-section, suggesting a gradual reduction in volcanic activity. The mean sedimentation rate of the Río Blanco member is higher (0.44 mm/year) than those obtained for the underlying and overlying units. This increase cannot be fully explained by foreland basement deformation and tectonic loading. Hence, we propose subsidence associated with volcanic activity as the causal mechanism. Volcanism would have triggered additional accommodation space through coeval pyroclastic deposition, modification of the stream equilibrium profile, flexural loading of volcanoes, and thermal processes. These mechanisms may have favored the preservation of volcaniclastic beds in the high-gradient foreland system of Famatina during the Mio-Pliocene. Thus, the Río Blanco member records the response of fluvial systems to large, volcanism-induced sediment loads.

Naples between two fires: eruptive scenarios for the next eruptions by an integrated volcanological-probabilistic approach.

Science.gov (United States)

Mastrolorenzo, G.; Pappalardo, L.; de Natale, G.; Troise, C.; Rossano, S.; Panizza, A.

2009-04-01

Probabilistic approaches based on available volcanological data from real eruptions of Campi Flegrei and Somma-Vesuvius, are assembled in a comprehensive assessment of volcanic hazards at the Neapolitan area. This allows to compare the volcanic hazards related to the different types of events, which can be used for evaluating the conditional probability of flows and falls hazard in case of a volcanic crisis. Hazard maps are presented, based on a rather complete set of numerical simulations, produced using field and laboratory data as input parameters relative to a large range (VEI 1 to 5) of fallout and pyroclastic-flow events and their relative occurrence. The results allow us to quantitatively evaluate and compare the hazard related to pyroclastic fallout and density currents (PDCs) at the Neapolitan volcanoes and their surroundings, including the city of Naples. Due to its position between the two volcanic areas, the city of Naples is particularly exposed to volcanic risk from VEI>2 eruptions, as recorded in the local volcanic succession. Because dominant wind directions, the area of Naples is particularly prone to fallout hazard from Campi Flegrei caldera eruptions in the VEI range 2-5. The hazard from PDCs decreases roughly radially with distance from the eruptive vents and is strongly controlled by the topographic heights. Campi Flegrei eruptions are particularly hazardous for Naples, although the Camaldoli and Posillipo hills produce an effective barrier to propagation to the very central part of Naples. PDCs from Vesuvius eruptions with VEI>4 can cover the city of Naples, whereas even VEI>3 eruptions have a moderate fallout hazard there.

Seismic monitoring of effusive-explosive activity and large lava dome collapses during 2013-2015 at Volcán de Colima, Mexico

Science.gov (United States)

Arámbula-Mendoza, Raúl; Reyes-Dávila, Gabriel; Vargas-Bracamontes Dulce, M.; González-Amezcua, Miguel; Navarro-Ochoa, Carlos; Martínez-Fierros, Alejandro; Ramírez-Vázquez, Ariel

2018-02-01

Volcán de Colima, the most active volcano in Mexico, started a new eruptive cycle in January 2013. Since this date, the volcano has presented effusive and explosive activity. The beginning of the cycle was marked by a moderate Vulcanian explosion which had hyperbolical behavior in its precursory seismicity, possibly related to a shallow rupture process. Then, during the whole eruptive stage, the effusive activity was accompanied by low to moderate explosions. The explosions had energies mainly of 106 joules and were located between 0 and 1600 m below the crater, whereas the locations of tremor sources were found to be deeper, reaching up to 3800 m beneath the crater. Very-long-period signals (VLPs) have been observed with Vulcanian explosions that produce pyroclastic flows. A few number of volcano-tectonic events (VTs) were recognized during the studied period (2013-2015), indicating that the volcano is an open system. This was particularly evidenced in July 2015, when a new batch of magma rose rapidly without large precursors, only an accelerated increase in the number of rockfalls and associated RSEM. This event generated two large lava dome collapses with several pulses of material and pyroclastic flows that travelled up to 10.3 km from the summit. The seismic monitoring of Volcán de Colima is currently the only tool in real-time employed to assess the state of the volcanic activity. It is thus necessary to integrate new seismic methods as well as other geophysical monitoring techniques able to detect precursory signals of an impending hazardous event.

Complex explosive volcanic activity on the Moon within Oppenheimer crater, Icarus

Science.gov (United States)

Bennett, Kristen A; Horgan, Briony H N; Gaddis, Lisa R.; Greenhagen, Benjamin T; Allen, Carlton C.; Hayne, Paul O; Bell, James F III; Paige, David A.

2016-01-01

Oppenheimer Crater is a floor-fractured crater located within the South Pole-Aitken basin on the Moon, and exhibits more than a dozen localized pyroclastic deposits associated with the fractures. Localized pyroclastic volcanism on the Moon is thought to form as a result of intermittently explosive Vulcanian eruptions under low effusion rates, in contrast to the higher-effusion rate, Hawaiian-style fire fountaining inferred to form larger regional deposits. We use Lunar Reconnaissance Orbiter Camera images and Diviner Radiometer mid-infrared data, Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra, and Clementine orbiter Ultraviolet/Visible camera images to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. Mineralogically, we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor, juvenile clinopyroxene, and juvenile iron-rich glass, and that the mineralogy of the pyroclastics varies both across the Oppenheimer deposits as a whole and within individual deposits. We observe similar variability in the inferred iron content of pyroclastic glasses, and note in particular that the northwest deposit, associated with Oppenheimer U crater, contains the most iron-rich volcanic glass thus far identified on the Moon, which could be a useful future resource. We propose that this variability in mineralogy indicates variability in eruption style, and that it cannot be explained by a simple Vulcanian eruption. A Vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit; however, large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material. Thus, we propose that at least the most recent portion of these deposits must have erupted via a Strombolian or more continuous fire

Felsic maar-diatreme volcanoes: a review

Science.gov (United States)

Ross, Pierre-Simon; Carrasco Núñez, Gerardo; Hayman, Patrick

2017-02-01

Felsic maar-diatreme volcanoes host major ore deposits but have been largely ignored in the volcanology literature, especially for the diatreme portion of the system. Here, we use two Mexican tuff rings as analogs for the maar ejecta ring, new observations from one diatreme, and the economic geology literature on four other mineralized felsic maar-diatremes to produce an integrated picture of this type of volcano. The ejecta rings are up to 50 m+ thick and extend laterally up to ˜1.5 km from the crater edge. In two Mexican examples, the lower part of the ejecta ring is dominated by pyroclastic surge deposits with abundant lithic clasts (up to 80% at Hoya de Estrada). These deposits display low-angle cross-bedding, dune bedforms, undulating beds, channels, bomb sags, and accretionary lapilli and are interpreted as phreatomagmatic. Rhyolitic juvenile clasts at Tepexitl have only 0-25% vesicles in this portion of the ring. The upper parts of the ejecta ring sequences in the Mexican examples have a different character: lithic clasts can be less abundant, the grain size is typically coarser, and the juvenile clasts can be different in character (with some more vesicular fragments). Fragmentation was probably shallower at this stage. The post-eruptive maar crater infill is known at Wau and consists of reworked pyroclastic deposits as well as lacustrine and other sediments. Underneath are bedded upper diatreme deposits, interpreted as pyroclastic surge and fall deposits. The upper diatreme and post-eruptive crater deposits have dips larger than 30° at Wau, with approximately centroclinal attitudes. At still lower structural levels, the diatreme pyroclastic infill is largely unbedded; Montana Tunnels and Kelian are good examples of this. At Cerro de Pasco, the pyroclastic infill seems bedded despite about 500 m of post-eruptive erosion relative to the pre-eruptive surface. The contact between the country rocks and the diatreme is sometimes characterized by country rock

Evidence of syn tectonic tephrites with nepheline in the Sidi Said Maachou Cambrian basin (coastal Meseta, Morocco); geo dynamic implications; Mise en evidence de tephrites a nepheline syntectoniques dans le bassin cambrien de Sidi Said Maachou (Meseta cotiere, Maroc); signification geodynamique

Energy Technology Data Exchange (ETDEWEB)

Remmal, T.; Mohsine, A.; El Hatimi, N.

2009-07-01

Based on a combined structural, petrographic, and geochemical analysis, a new interpretation of the basic magmatism of Sidi Said Maachou (coastal Meseta) in two stages of emplacement is proposed. The first stage is characterized by transitional pyroclastic flows that have accompanied the opening of the West-Mesetian basin, during the Cambrian; the second stage is made of dykes of basalts, dolerites, and tephrites bearing nepheline. The emplacement of this undersaturated alkaline magma is associated to a sinistral sub meridian shear zone which has been activated at the end of the Caledonian orogenesis, by a mantellic advection. (Author) 32 refs.

A critical evaluation of the evidence for multiple Late Pleistocene eruptions of Laacher See Volcano

DEFF Research Database (Denmark)

Zernack, Anke Verena; Hoggard, Christian Steven; Sauer, Florian Rudolf

The c. 12,900 BP Plinian eruption of Laacher See Volcano is one of the largest known volcanic events of the Late Pleistocene in the Northern Hemisphere. It buried proximal areas under tens of meters of pyroclastic flow, surge and fallout deposits and deposited a widespread tephra layer across much...... of dispersal of the products from varying eruptive stages and some sites even report two distinct Laacher See Tephra layers that have been interpreted as evidence of a precursor eruption. In order to assess the potential for multiple Late Pleistocene eruptions of Laacher See Volcano, we have compiled...

High-temperature, large-volume, lavalike ash-flow tuffs without calderas in southwestern Idaho

Science.gov (United States)

Ekren, E.B.; McIntyre, David H.; Bennett, Earl H.

1984-01-01

Rhyolitic rocks were erupted from vents in and adjacent to the Owyhee Mountains and Owyhee Plateau of southwestern Idaho from 16 m.y. ago to about 10 m.y. ago. They were deposited on a highly irregular surface developed on a variety of basement rocks that include granitic rocks of Cretaceous age, quartz latite and rhyodacite tuffs and lava flows of Eocene age, andesitic and basaltic lava flows of Oligocene age, and latitic and basaltic lava flows of early Miocene age. The rhyolitic rocks are principally welded tuffs that, regardless of their source, have one feature in common-namely internal characteristics indicating en-masse, viscous lavalike flowage. The flowage features commonly include considerable thicknesses of flow breccia at the bases of various cooling units. On the basis of the tabular nature of the rhyolitic deposits, their broad areal extents, and the local preservation of pyroclastic textures at the bases, tops, and distal ends of some of the deposits, we have concluded that the rocks were emplaced as ash flows at extremely high temperatures and that they coalesced to liquids before final emplacement and cooling. Temperatures of l090?C and higher are indicated by iron-titanium oxide compositions. Rhyolites that are about 16 m.y. old are preserved mostly in the downdropped eastern and western flanks of the Silver City Range and they are inferred to have been erupted from the Silver City Range. They rarely contain more than about 2 percent phenocrysts that consist of quartz and subequal amounts of plagioclase and alkali feldspar; commonly, they contain biotite, and they are the only rhyolitic rocks in the area to do so. The several rhyolitic units that are 14 m.y. to about 10 m.y. old contain only pyroxene-principally ferriferous and intermediate pigeonites-as mafic constituents. The rhyolites of the Silver City Range comprise many cooling units, none of which can be traced for great distances. Rocks erupted from the Owyhee Plateau include two sequences

Full waveform ambient noise tomography of Mount Rainer

Science.gov (United States)

Flinders, A. F.; Shen, Y.

2014-12-01

Mount Rainier towers over the landscape of western Washington, ranking with Fuji-yama in Japan, Mt. Pinatubo in the Philippines, and Mt. Vesuvius in Italy, as one of the great stratovolcanoes of the world. Notwithstanding it's picturesque stature, Mt. Rainier is potentially the most devastating stratovolcano in North America, with more than 3.5 million people living beneath its shadow in the Seattle-Tacoma area. The primary hazard posed by the volcano is in the form of highly destructive volcanic debris flows (lahars). These lahars form when water and/or melted ice erode away and entrain preexisting volcanic sediment. At Mt. Rainier these flows are often initiated by sector collapse of the volcano's hydrothermally rotten flanks and compounded from Mt. Rainier's extensive snow and glacial ice coverage. It is therefore imperative to ascertain the extent of summit hydrothermal alteration within the volcano, and determine areas prone to collapse. Despite being one of the sixteen volcanoes globally designated by the International Association of Volcanology and Chemistry of the Earth's Interior as warranting detailed and focused study, Mt. Rainier remains enigmatic both in terms of shallow internal structure and the degree of summit hydrothermal alteration. We image this shallow internal structure and areas of possible summit alteration using ambient noise tomography. Our full waveform forward modeling includes high-resolution topography, allowing us to accurately account for the effects of topography on the propagation of short-period Rayleigh waves. Empirical Green's functions were extracted from 80 stations within 200 km of Mount Rainier and compared with synthetic greens functions over multiple frequency bands from 2-28 seconds. The preliminary model shows a broad (60 km wide) low shear-wave velocity anomaly in the mid-crust beneath the volcano. The mid-crust low-velocity body extends to the surface beneath the volcano summit in a narrow near-vertical conduit, the

Investigations on flow reversal in stratified horizontal flow

International Nuclear Information System (INIS)

Staebler, T.; Meyer, L.; Schulenberg, T.; Laurien, E.

2005-01-01

The phenomena of flow reversal in stratified flows are investigated in a horizontal channel with application to the Emergency Core Cooling System (ECCS) in Pressurized Water Reactors (PWR). In case of a Loss-of-Coolant-Accident (LOCA), coolant can be injected through a secondary pipe within the feeding line of the primary circuit, the so called hot leg, counter-currently to the steam flow. It is essential that the coolant reaches the reactor core to prevent overheating. Due to high temperatures in such accident scenarios, steam is generated in the core, which escapes from the reactor vessel through the hot leg. In case of sufficiently high steam flow rates, only a reduced amount of coolant or even no coolant will be delivered to the reactor core. The WENKA test facility at the Institute for Nuclear and Energy Technologies (IKET) at Forschungszentrum Karlsruhe is capable to investigate the fluid dynamics of two-phase flows in such scenarios. Water and air flow counter-currently in a horizontal channel made of clear acrylic glass to allow full optical access. Flow rates of water and air can be varied independently within a wide range. Once flow reversal sets in, a strong hysteresis effect must be taken into account. This was quantified during the present investigations. Local experimental data are needed to expand appropriate models on flow reversal in horizontal two-phase flow and to include them into numerical codes. Investigations are carried out by means of Particle Image Velocimetry (PIV) to obtain local flow velocities without disturbing the flow. Due to the wavy character of the flow, strong reflections at the interfacial area must be taken into account. Using fluorescent particles and an optical filter allows eliminating the reflections and recording only the signals of the particles. The challenges in conducting local investigations in stratified wavy flows by applying optical measurement techniques are discussed. Results are presented and discussed allowing

Flow regimes

International Nuclear Information System (INIS)

Kh'yuitt, G.

1980-01-01

An introduction into the problem of two-phase flows is presented. Flow regimes arizing in two-phase flows are described, and classification of these regimes is given. Structures of vertical and horizontal two-phase flows and a method of their identification using regime maps are considered. The limits of this method application are discussed. The flooding phenomena and phenomena of direction change (flow reversal) of the flow and interrelation of these phenomena as well as transitions from slug regime to churn one and from churn one to annular one in vertical flows are described. Problems of phase transitions and equilibrium are discussed. Flow regimes in tubes where evaporating liquid is running, are described [ru

Opal-A in Glassy Pumice, Acid Alteration, and the 1817 Phreatomagmatic Eruption at Kawah Ijen (Java), Indonesia

Science.gov (United States)

Lowenstern, Jacob B.; van Hinsberg, Vincent; Berlo, Kim; Liesegang, Moritz; Iacovino, Kayla; Bindeman, Ilya N.; Wright, Heather M.

2018-02-01

At Kawah Ijen (Indonesia), vigorous SO2 and HCl degassing sustains a hyperacid lake (pH 0) and intensely alters the subsurface, producing widespread residual silica and advanced argillic alteration products. In 1817, a VEI 2 phreatomagmatic eruption evacuated the lake, depositing a widespread layer of muddy ash fall, and sending lahars down river drainages. We discovered multiple types of opaline silica in juvenile low-silica dacite pumice and in particles within co-erupted laharic sediments. Most spectacular are opal-replaced phenocrysts of plagioclase and pyroxene adjacent to pristine matrix glass and melt inclusions. Opal-bearing pumice has been found at numerous sites, including where post-eruption infiltration of acid water is unlikely. Through detailed analyses of an initial sampling of 1817 eruption products, we find evidence for multiple origins of opaline materials in pumice and laharic sediments. Evidently, magma encountered acid-altered materials in the subsurface and triggered phreatomagmatic eruptions. Syn-eruptive incorporation of opal-alunite clasts, layered opal, and fragment-filled vesicles of opal and glass, all suggest magma-rock interactions in concert with vesiculation, followed by cooling within minutes. Our experiments at magmatic temperature confirm that the opaline materials would show noticeable degradation in time periods longer than a few tens of minutes. Some glassy laharic sedimentary grains are more andesitic than the main pumice type and may represent older volcanic materials that were altered beneath the lake bottom and were forcefully ejected during the 1817 eruption. A post-eruptive origin remains likely for most of the opal-replaced phenocrysts in pumice. Experiments at 25°C and 100°C reveal that when fresh pumice is bathed in Kawah Ijen hyperacid fluid for six weeks, plagioclase is replaced without altering either matrix glass or melt inclusions. Moreover, lack of evidence for high-temperature annealing of the opal suggests

Opal-A in glassy pumice, acid alteration, and the 1817 phreatomagmatic eruption at Kawah Ijen (Java), Indonesia

Science.gov (United States)

Lowenstern, Jacob B.; van Hinsberg, Vincent; Berlo, Kim; Liesegang, Moritz; Iacovino, Kayla D.; Bindeman, Ilya N.; Wright, Heather M.

2018-01-01

At Kawah Ijen (Indonesia), vigorous SO2 and HCl degassing sustains a hyperacid lake (pH ~0) and intensely alters the subsurface, producing widespread residual silica and advanced argillic alteration products. In 1817, a VEI 2 phreatomagmatic eruption evacuated the lake, depositing a widespread layer of muddy ash fall, and sending lahars down river drainages. We discovered multiple types of opaline silica in juvenile low-silica dacite pumice and in particles within co-erupted laharic sediments. Most spectacular are opal-replaced phenocrysts of plagioclase and pyroxene adjacent to pristine matrix glass and melt inclusions. Opal-bearing pumice has been found at numerous sites, including where post-eruption infiltration of acid water is unlikely. Through detailed analyses of an initial sampling of 1817 eruption products, we find evidence for multiple origins of opaline materials in pumice and laharic sediments. Evidently, magma encountered acid-altered materials in the subsurface and triggered phreatomagmatic eruptions. Syn-eruptive incorporation of opal-alunite clasts, layered opal, and fragment-filled vesicles of opal and glass, all suggest magma-rock interactions in concert with vesiculation, followed by cooling within minutes. Our experiments at magmatic temperature confirm that the opaline materials would show noticeable degradation in time periods longer than a few tens of minutes. Some glassy laharic sedimentary grains are more andesitic than the main pumice type and may represent older volcanic materials that were altered beneath the lake bottom and were forcefully ejected during the 1817 eruption. A post-eruptive origin remains likely for most of the opal-replaced phenocrysts in pumice. Experiments at 25°C and 100°C reveal that when fresh pumice is bathed in Kawah Ijen hyperacid fluid for 6 weeks, plagioclase is replaced without altering either matrix glass or melt inclusions. Moreover, lack of evidence for high-temperature annealing of the opal suggests

Visualization study of flow in axial flow inducer.

Science.gov (United States)

Lakshminarayana, B.

1972-01-01

A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory.

Volcano Modelling and Simulation gateway (VMSg): A new web-based framework for collaborative research in physical modelling and simulation of volcanic phenomena

Science.gov (United States)

Esposti Ongaro, T.; Barsotti, S.; de'Michieli Vitturi, M.; Favalli, M.; Longo, A.; Nannipieri, L.; Neri, A.; Papale, P.; Saccorotti, G.

2009-12-01

Physical and numerical modelling is becoming of increasing importance in volcanology and volcanic hazard assessment. However, new interdisciplinary problems arise when dealing with complex mathematical formulations, numerical algorithms and their implementations on modern computer architectures. Therefore new frameworks are needed for sharing knowledge, software codes, and datasets among scientists. Here we present the Volcano Modelling and Simulation gateway (VMSg, accessible at http://vmsg.pi.ingv.it), a new electronic infrastructure for promoting knowledge growth and transfer in the field of volcanological modelling and numerical simulation. The new web portal, developed in the framework of former and ongoing national and European projects, is based on a dynamic Content Manager System (CMS) and was developed to host and present numerical models of the main volcanic processes and relationships including magma properties, magma chamber dynamics, conduit flow, plume dynamics, pyroclastic flows, lava flows, etc. Model applications, numerical code documentation, simulation datasets as well as model validation and calibration test-cases are also part of the gateway material.

Rotating flow

CERN Document Server

Childs, Peter R N

2010-01-01

Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics titles offer the essential background but generally include very sparse coverage of rotating flows-which is where this book comes in. Beginning with an accessible introduction to rotating flow, recognized expert Peter Childs takes you through fundamental equations, vorticity and vortices, rotating disc flow, flow around rotating cylinders and flow in rotating cavities, with an introduction to atmospheric and oceanic circul...

Continuum Mechanical and Computational Aspects of Material Behavior

Energy Technology Data Exchange (ETDEWEB)

Fried, Eliot [McGill Univ., Montreal, QC (Canada)

2015-02-11

Fluid flows are typically classified as laminar or turbulent. While the glassy, regular flow of water from a slightly opened tap is laminar, the sinuous, irregular flow of water from a fully opened tap is turbulent. In a laminar flow, the velocity and other relevant fields are deterministic functions of position and time. Photos taken at different times, no matter how far removed, of steady laminar flow from a tap will be identical. In a turbulent flow, the velocity and other relevant fields manifest complex spatial and temporal fluctuations. A video of steady turbulent flow from a tap will exhibit a constantly changing pattern and many length and time scales. In nature and technology, laminar flows are more the exception than the rule. Fluvial, oceanic, pyroclastic, atmospheric, and interstellar flows are generally turbulent, as are the flows of blood through the left ventricle and air in the lungs. Flows around land, sea, and air vehicles and through pipelines, heating, cooling, and ventilation systems are generally turbulent, as are most flows involved in industrial processing, combustion, chemical reactions, and crystal growth. Over the past year, a significant portion of our research activity has focused on numerical studies of Navier-Stokes-αβ model and extensions thereof. Our results regarding these and other approaches to turbulence modeling are described below.

Refrigeration. Two-Phase Flow. Flow Regimes and Pressure Drop

DEFF Research Database (Denmark)

Knudsen, Hans-Jørgen Høgaard

2002-01-01

The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature.......The note gives the basic definitions used in two-phase flow. Flow regimes and flow regimes map are introduced. The different contributions to the pressure drop are stated together with an imperical correlation from the litterature....

Flow visualization

CERN Document Server

Merzkirch, Wolfgang

1974-01-01

Flow Visualization describes the most widely used methods for visualizing flows. Flow visualization evaluates certain properties of a flow field directly accessible to visual perception. Organized into five chapters, this book first presents the methods that create a visible flow pattern that could be investigated by visual inspection, such as simple dye and density-sensitive visualization methods. It then deals with the application of electron beams and streaming birefringence. Optical methods for compressible flows, hydraulic analogy, and high-speed photography are discussed in other cha

On intermittent flow characteristics of gas–liquid two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Thaker, Jignesh; Banerjee, Jyotirmay, E-mail: jbaner@gmail.com

2016-12-15

Highlights: • Unified correlations for intermittent flow characteristics are developed. • Influence of inflow conditions on intermittent flow characteristics is analysed. • Developed correlations can be used for effective design of piping components. - Abstract: Flow visualisation experiments are reported for intermittent regime of gas–liquid two-phase flow. Intermittent flow characteristics, which include plug/slug frequency, liquid plug/slug velocity, liquid plug/slug length, and plug/slug bubble length are determined by image processing of flow patterns captured at a rate of 1600 frames per second (FPS). Flow characteristics are established as a function of inlet superficial velocity of both the phases (in terms of Re{sub SL} and Re{sub SG}). The experimental results are first validated with the existing correlations for slug flow available in literature. It is observed that the correlations proposed in literature for slug flow do not accurately predict the flow characteristics in the plug flow regime. The differences are clearly highlighted in this paper. Based on the measured database for both plug and slug flow regime, modified correlations for the intermittent flow regime are proposed. The correlations reported in the present paper, which also include plug flow characteristics will aid immensely to the effective design and optimization of operating conditions for safer operation of two-phase flow piping systems.

Long-term volcanic hazard forecasts based on Somma-Vesuvio past eruptive activity

Science.gov (United States)

Lirer, Lucio; Petrosino, Paola; Alberico, Ines; Postiglione, Immacolata

2001-02-01

Distributions of pyroclastic deposits from the main explosive events at Somma-Vesuvio during the 8,000-year B.P.-A.D. 1906 time-span have been analysed to provide maps of volcanic hazard for long-term eruption forecasting. In order to define hazard ratings, the spatial distributions and loads (kg/m2) exerted by the fall deposits on the roofs of buildings have been considered. A load higher than 300 kg/m2 is defined as destructive. The relationship load/frequency (the latter defined as the number of times that an area has been impacted by the deposition of fall deposits) is considered to be a suitable parameter for differentiating among areas according to hazard rating. Using past fall deposit distributions as the basis for future eruptive scenarios, the total area that could be affected by the products of a future Vesuvio explosive eruption is 1,500 km2. The perivolcanic area (274 km2) has the greatest hazard rating because it could be buried by pyroclastic flow deposits thicker than 0.5 m and up to several tens of metres in thickness. Currently, the perivolcanic area also has the highest risk because of the high exposed value, mainly arising from the high population density.

Transformation of Commercial Flows into Physical Flows of Electricity – Flow Based Method

Directory of Open Access Journals (Sweden)

M. Adamec

2009-01-01

Full Text Available We are witnesses of large – scale electricity transport between European countries under the umbrella of the UCTE organization. This is due to the inabilyof generators to satisfy the growing consumption in some regions. In this content, we distinguish between two types of flow. The first type is physical flow, which causes costs in the transmission grid, whilst the second type is commercial flow, which provides revenues for the market participants. The old methods for allocating transfer capacity fail to take this duality into account. The old methods that allocate transmission border capacity to “virtual” commercial flows which, in fact, will not flow over this border, do not lead to optimal allocation. Some flows are uselessly rejected and conversely, some accepted flows can cause congestion on another border. The Flow Based Allocation method (FBA is a method which aims to solve this problem.Another goal of FBA is to ensure sustainable development of expansion of transmission capacity. Transmission capacity is important, because it represents a way to establish better transmission system stability, and it provides a distribution channel for electricity to customers abroad. For optimal development, it is necessary to ensure the right division of revenue allocation among the market participants.This paper contains a brief description of the FBA method. Problems of revenue maximization and optimal revenue distribution are mentioned. 

Airfoil flow instabilities induced by background flow oscillations

Energy Technology Data Exchange (ETDEWEB)

Selerowicz, W.C.; Szumowski, A.P. [Technical Univ. Warsaw (Poland)

2002-04-01

The effect of background flow oscillations on transonic airfoil (NACA 0012) flow was investigated experimentally. The oscillations were generated by means of a rotating plate placed downstream of the airfoil. Owing to oscillating chocking of the flow caused by the plate, the airfoil flow periodically accelerated and decelerated. This led to strong variations in the surface pressure and the airfoil loading. The results are presented for two angles of attack, {alpha}=4 and {alpha}=8.5 , which correspond to the attached and separated steady airfoil flows, respectively. (orig.)

Electromagnetic application device for flow rate/flow speed control

International Nuclear Information System (INIS)

Yoshioka, Senji.

1994-01-01

Electric current and magnetic field are at first generated in a direction perpendicular to a flow channel of a fluid, and forces generated by electromagnetic interaction of the current and the magnetic field are combined and exerted on the fluid, to control the flow rate and the flow speed thereby decreasing flowing pressure loss. In addition, an electric current generation means and a magnetic field generation means integrated together are disposed to a structural component constituting the flow channel, and they are combined to attain the aimed effect. The current generating means forms a potential difference by supplying electric power to a pair of electrodes as a cathode and an anode by using structures disposed along the channel, to generate an electric field or electric current in a direction perpendicular to the flow channel. The magnetic field generating means forms a counter current (reciprocal current) by using structures disposed along the flow channel, to generate synthesized or emphasized magnetic field. The fluid can be applied with a force in the direction of the flowing direction by the electromagnetic interaction of the electric current and the magnetic field, thereby capable of propelling the fluid. Accordingly, the flowrate/flowing speed can be controlled inside of the flow channel and flowing pressure loss can be decreased. (N.H.)

Categorizing vitric lithofacies on seamounts: implications for recognizing deep-marine pyroclastic deposits

Science.gov (United States)

Portner, R. A.; Clague, D. A.

2011-12-01

Glassy fragmental deposits commonly found capping seamounts have been variably interpreted as the products of quench-fragmentation (hyaloclastite), suppressed steam expansion, and/or explosive fire-fountains (pyroclastite). To better understand these vitriclastic deposits we use a multidisciplinary approach that outlines six lithofacies based on textures, sedimentary structures, geochemical diversity, and associations with seamount landforms. All seamounts studied yield MORB compositions and formed on or near mid-ocean ridge axes of the northeast Pacific Ocean. Consolidated deposits were sampled from the Taney (~29 Ma), President Jackson (~3 Ma), and Vance (~2 Ma) seamounts using ROV manipulator arms and dredge hauls. Unconsolidated deposits from the currently active Axial Seamount of the Juan de Fuca Ridge were sampled using ROV push core and vacuum techniques. Lithofacies occur with talus breccias and pillow basalt on steeply dipping outer flanks and caldera walls, and with pillow and sheet flows on subhorizontal rims and nested caldera floors of the seamounts. Vitric lithofacies within or near steeply dipping regions have very angular textures, coarse grain-sizes and abundant crystalline basalt fragments. Jig-saw fit texture is common in units with monomict geochemistry and closely associated with adjacent pillow basalt, suggesting in-situ fragmentation akin to pillow breccia. Similar units bearing polymodal geochemistry are generally associated with talus breccias along caldera walls and basal slopes, and are interpreted as fault-scarp derived debrites. Laterally these lithofacies abruptly grade into bottom-current reworked lithofacies on flat caldera floors. Reworked lithofacies have >40% muddy matrix with abundant angular mineral fragments, biogenic grains and minor devitrified glass shards. They typically exhibit well-defined planar lamination and locally show sinusoidal ripple forms. Horizontal burrows including Planolites are common. Locally this

Evaluation of flow hood measurements for residential register flows; TOPICAL

International Nuclear Information System (INIS)

Walker, I.S.; Wray, C.P.; Dickerhoff, D.J.; Sherman, M.H.

2001-01-01

Flow measurement at residential registers using flow hoods is becoming more common. These measurements are used to determine if the HVAC system is providing adequate comfort, appropriate flow over heat exchangers and in estimates of system energy losses. These HVAC system performance metrics are determined by using register measurements to find out if individual rooms are getting the correct airflow, and in estimates of total air handler flow and duct air leakage. The work discussed in this paper shows that commercially available flow hoods are poor at measuring flows in residential systems. There is also evidence in this and other studies that flow hoods can have significant errors even when used on the non-residential systems they were originally developed for. The measurement uncertainties arise from poor calibrations and the sensitivity of exiting flow hoods to non-uniformity of flows entering the device. The errors are usually large-on the order of 20% of measured flow, which is unacceptably high for most applications. Active flow hoods that have flow measurement devices that are insensitive to the entering airflow pattern were found to be clearly superior to commercially available flow hoods. In addition, it is clear that current calibration procedures for flow hoods may not take into account any field application problems and a new flow hood measurement standard should be developed to address this issue

Experimental Flow Characterization of a Flow Diverting Device

Science.gov (United States)

Sparrow, Eph; Chow, Ricky; Campbell, Gary; Divani, Afshin; Sheng, Jian

2012-11-01

Flow diverters, such as the Pipeline Embolization Device, are a new class of endovascular devices for the treatment of intracranial aneurysms. While clinical studies have demonstrated safety and efficacy, their impact on intra-aneurysmal flow is not confirmed experimentally. As such, optimization of the flow diversion behavior is not currently possible. A quasi-3D PIV technique was developed and applied in various glass models at Re = 275 and 550 to determine the changes to flow characteristics due to the deployment of a flow diverter across the aneurysm neck. Outcomes such as mean velocity, wall shear stress, and others metrics will be presented. Glass models with varying radii of curvature and aneurysm locations will be examined. Experiments were performed in a fully index-matched flow facility using ~10 μm diameter polystyrene particles doped with Rhodium 6G dye. The particles were illuminated with a 532nm laser sheet and observed with a CCD camera and a 592nm +/-43 nm bandpass filter. A quasi 3D flow field was reconstructed from multiple orthogonal planes (spaced 0.4mm apart) encompassing the entire glass model. Wall stresses were evaluated from the near-wall flow viscous stresses.

Flow shapes and higher harmonics in anisotropic transverse collective flow

Energy Technology Data Exchange (ETDEWEB)

Argintaru, Danut; Baban, Valerica [Constanta Maritime University, Faculty of Navigation and Naval Transport, Constanta (Romania); Besliu, Calin; Jipa, Alexandru; Grossu, Valeriu [University of Bucharest, Faculty of Physics, Bucharest (Romania); Esanu, Tiberiu; Cherciu, Madalin [Institute of Space Sciences Bucharest-Magurele, Bucharest (Romania)

2017-01-15

In this paper we show that by using a jet-finder algorithm (the Anti-k{sub T} one) on UrQMD/C simulated (Au+Au at 4, 10 and 15A GeV) collisions, we can identify different flow shape structures (single flow stream events, two flow streams events, three flow streams events, etc.) and order the bulk of events in equivalence flow shape classes. Considering these flow streams as the main directions of anisotropic transverse flow, we show that the Fourier coefficients v{sub n} of anisotropic flow are better emphasized when we analyze the different event flow shape classes than when the events are mixed. Also, if we do not know the real orientation of the reaction plane, we can use as reference the Flow stream 1 - the main particle flow stream - orientation (Ψ{sub Flowstream} {sub 1}) to highlight the initial shape of the participant nuclear matter in a central to peripheral collision, and the orientation of the participant plane of order n. (orig.)

Flow Rate Measurement in Multiphase Flow Rig: Radiotracer and Conventional

International Nuclear Information System (INIS)

Nazrul Hizam Yusoff; Noraishah Othman; Nurliyana Abdullah; Amirul Syafiq Mohd Yunos; Rasif Mohd Zain; Roslan Yahya

2015-01-01

Applications of radiotracer technology are prevalent throughout oil refineries worldwide, and this industry is one of the main users and beneficiaries of the technology. Radioactive tracers have been used to a great extent in many applications i.e. flow rate measurement, RTD, plant integrity evaluation and enhancing oil production in oil fields. Chemical and petrochemical plants are generally continuously operating and technically complex where the radiotracer techniques are very competitive and largely applied for troubleshooting inspection and process analysis. Flow rate measurement is a typical application of radiotracers. For flow measurements, tracer data are important, rather than the RTD models. Research is going on in refining the existing methods for single phase flow measurement, and in developing new methods for multiphase flow without sampling. The tracer techniques for single phase flow measurements are recognized as ISO standards. This paper presents technical aspect of laboratory experiments, which have been carried out using Molybdenum-99 - Mo99 (radiotracer) to study and determine the flow rate of liquid in multiphase flow rig. The multiphase flow rig consists of 58.7 m long and 20 cm diameter pipeline that can accommodate about 0.296 m 3 of liquid. Tap water was used as liquid flow in pipeline and conventional flow meters were also installed at the flow rig. The flow rate results; radiotracer and conventional flow meter were compared. The total count method was applied for radiotracer technique and showed the comparable results with conventional flow meter. (author)

NEOGENE STRATIGRAPHY OF THE İZMİR -OUTER- BAY ISLANDS

Directory of Open Access Journals (Sweden)

Fikret GÖKTAŞ

2016-12-01

Full Text Available The volcaniclastics, derived from calcalkaline acidic-intermediate volcanism in the region during late Early Miocene, and lacustrine deposits of Middle Miocene and alkaline volcanics are exposed on Uzun Ada , Hekim Adası, Çiçek Adası and Karantina Adası  in the Outer Gulf of Izmir.Kocadağ volcaniclastics derived from Kocadağ volcanism, by extruding mainly calcalkaline andesitic-dacitic products during Late Early Miocene, represents the exposed oldest rock unit. The volcaniclastic succession extending in the north of Uzun Ada is composed of pyroclastics in ignimbrite and blocky ash flow facieses, and epiclastics in volcanic mass flow (lahar facies. Foça tuff, represented by rhyolitic ignimbrites, originated from an area around Foça and moving to an area around Uzun Ada, emplaced onto the Kocadağ volcaniclastics in two main explosive stages. The Değirmentepe Member alluvial deposits composed of coarse volcanic detritus were deposited during a inactive period between the explosion stages.  A K/Ar age of 16.0 Ma was obtained from a rhyolite dome, which shows lateral relationship with the correlant ignimbrites in Foça Peninsula, and so it is considered that Foça tuff emplaced onto the region at the end of late Early Miocene.Lacustrine-dominated Middle Miocene succession, which overlies the Foça tuff unconformably, differentiated as the Urla group. Urla group consists of alluvial Beşiktepe Formation, the Pırnallı island  volcaniclastics, which is composed of sublacustrine volcanic density-flow deposits and felsic ignimbrites, Hekim Adası basalt comprising basic volcanics and lacustrine Urla limestone, respectively from bottom to top. Beşiktepe Formation only exposed on Uzun Ada, overlies the Foça tuff with an unconformity indicating a basin margin deposition during the Middle Miocene. Pırnallı island volcaniclastic succession, which its lower boundary does not expose within the area on Hekim Adası and Çiçek Adaları, is

Online traffic flow model applying dynamic flow-density relation

International Nuclear Information System (INIS)

Kim, Y.

2002-01-01

This dissertation describes a new approach of the online traffic flow modelling based on the hydrodynamic traffic flow model and an online process to adapt the flow-density relation dynamically. The new modelling approach was tested based on the real traffic situations in various homogeneous motorway sections and a motorway section with ramps and gave encouraging simulation results. This work is composed of two parts: first the analysis of traffic flow characteristics and second the development of a new online traffic flow model applying these characteristics. For homogeneous motorway sections traffic flow is classified into six different traffic states with different characteristics. Delimitation criteria were developed to separate these states. The hysteresis phenomena were analysed during the transitions between these traffic states. The traffic states and the transitions are represented on a states diagram with the flow axis and the density axis. For motorway sections with ramps the complicated traffic flow is simplified and classified into three traffic states depending on the propagation of congestion. The traffic states are represented on a phase diagram with the upstream demand axis and the interaction strength axis which was defined in this research. The states diagram and the phase diagram provide a basis for the development of the dynamic flow-density relation. The first-order hydrodynamic traffic flow model was programmed according to the cell-transmission scheme extended by the modification of flow dependent sending/receiving functions, the classification of cells and the determination strategy for the flow-density relation in the cells. The unreasonable results of macroscopic traffic flow models, which may occur in the first and last cells in certain conditions are alleviated by applying buffer cells between the traffic data and the model. The sending/receiving functions of the cells are determined dynamically based on the classification of the

Gaseous slip flow analysis of a micromachined flow sensor for ultra small flow applications

OpenAIRE

Jang, Jaesung; Wereley, Steven

2007-01-01

The velocity slip of a fluid at a wall is one of the most typical phenomena in microscale gas flows. This paper presents a flow analysis considering the velocity slip in a capacitive micro gas flow sensor based on pressure difference measurements along a microchannel. The tangential momentum accommodation coefficient (TMAC) measurements of a particular channel wall in planar microchannels will be presented while the previous micro gas flow studies have been based on the same TMACs on both wal...

Investigation of the mixture flow rates of oil-water two-phase flow using the turbine flow meter

International Nuclear Information System (INIS)

Li Donghui; Feng Feifei; Wu Yingxiang; Xu Jingyu

2009-01-01

In this work, the mixture flow rate of oil-water flows was studied using the turbine flow-meter. The research emphasis focuses on the effect of oil viscosity and input fluids flow rates on the precision of the meter. Experiments were conducted to measure the in-situ mixture flow rate in a horizontal pipe with 0.05m diameter using seven different viscosities of white oil and tap water as liquid phases. Results showed that both oil viscosity and input oil fraction exert a remarkable effect on measured results, especially when the viscosity of oil phase remained in the area of high value. In addition, for metering mixture flow rate using turbine flow-meter, the results are not sensitive to two-phase flow pattern according to the experimental data.

Radiotracer techniques for measuring fluid flow and calibrating flow meters

International Nuclear Information System (INIS)

Cooper, E.L.

1987-08-01

Radiotracer techniques can be used to measure accurately both gas and liquid flow rates under operating conditions in a wide range of flow systems. They are ideally suited for calibrating flow meters as well as for measuring unmetered flows in industrial plants. Applications of these techniques range from measuring the flows of fuels and process fluids for energy and mass balance studies to measuring the flows of liquid and airborne effluents for pollution control. This report describes the various radiotracer techniques which can be used to measure fluid flows. The range of application and inherent accuracy of each technique is discussed

Volcanically-Triggered Rainfall and the Effect on Volcanological Hazards at Soufriere Hills, Montserrat

Science.gov (United States)

Poulidis, Alexandros-Panagiotis; Renfrew, Ian; Matthews, Adrian

2014-05-01

Atmospheric flow simulations over and around the Soufriere Hills volcano in the island of Montserrat in the Caribbean are studied, through a series of numerical model experiments, in order to link interactions between the volcano and the atmosphere. A heated surface is added on the top of the mountain, in order to simulate the dome of an active volcano that is not undergoing an eruption. A series of simulations with different atmospheric conditions and control parameters for the volcano will be presented. Simulations are made using the Weather Research and Forecasting (WRF) model, with a high resolution digital elevation map of Montserrat. Simulations with an idealised topography have also been examined, in order for the results to have general applicability to similar-sized volcanoes located in the Tropics. The model was initialised with soundings from representative days of qualitatively different atmospheric conditions from the rainy season. The heated volcanic dome changes the orographic flow response significantly, depending upon the atmospheric conditions and the magnitude of the dome surface temperature anomaly. The flow regime and qualitative characteristic features, such orographic clouds and rainfall patterns, can all change significantly. For example, the orographic rainfall over the volcano can be significantly enhanced with increased dome temperatures. The implications of these changes on the eruptive behaviour of the volcano and resulting secondary volcanic hazards, such as lahars, will be discussed.

Gaseous slip flow analysis of a micromachined flow sensor for ultra small flow applications

Science.gov (United States)

Jang, Jaesung; Wereley, Steven T.

2007-02-01

The velocity slip of a fluid at a wall is one of the most typical phenomena in microscale gas flows. This paper presents a flow analysis considering the velocity slip in a capacitive micro gas flow sensor based on pressure difference measurements along a microchannel. The tangential momentum accommodation coefficient (TMAC) measurements of a particular channel wall in planar microchannels will be presented while the previous micro gas flow studies have been based on the same TMACs on both walls. The sensors consist of a pair of capacitive pressure sensors, inlet/outlet and a microchannel. The main microchannel is 128.0 µm wide, 4.64 µm deep and 5680 µm long, and operated under nearly atmospheric conditions where the outlet Knudsen number is 0.0137. The sensor was fabricated using silicon wet etching, ultrasonic drilling, deep reactive ion etching (DRIE) and anodic bonding. The capacitance change of the sensor and the mass flow rate of nitrogen were measured as the inlet-to-outlet pressure ratio was varied from 1.00 to 1.24. The measured maximum mass flow rate was 3.86 × 10-10 kg s-1 (0.019 sccm) at the highest pressure ratio tested. As the pressure difference increased, both the capacitance of the differential pressure sensor and the flow rate through the main microchannel increased. The laminar friction constant f sdot Re, an important consideration in sensor design, varied from the incompressible no-slip case and the mass sensitivity and resolution of this sensor were discussed. Using the current slip flow formulae, a microchannel with much smaller mass flow rates can be designed at the same pressure ratios.

Flow lab.: flow visualization and simulation

International Nuclear Information System (INIS)

Park, Chung Kyun; Cho, Won Jin; Hahn, Pil Soo

2005-01-01

The experimental setups for flow visualization and processes identification in laboratory scale (so called Flow Lab.) has developed to get ideas and answer fundamental questions of flow and migration in geologic media. The setup was made of a granite block of 50x50cm scale and a transparent acrylate plate. The tracers used in this experiments were tritiated water, anions, and sorbing cations as well as an organic dye, eosine, to visualize migration paths. The migration plumes were taken with a digital camera as a function of time and stored as digital images. A migration model was also developed to describe and identify the transport processes. Computer simulation was carried out not only for the hydraulic behavior such as distributions of pressure and flow vectors in the fracture but also for the migration plume and the elution curves

Numerical simulation of internal flow in mixed-flow waterjet propulsion

International Nuclear Information System (INIS)

Wu, T T; Pan, Z Y; Zhang, D Q; Jia, Y Y

2012-01-01

In order to reveal the internal flow characteristic of a mixed-flow waterjet propulsion, a mixed-flow waterjet propulsion under different conditions was simulated based on multi-reference frame(MRF), the standard k − ε turbulent model and SIMPLEC algorithm. The relationship between pump performance instability and internal flow was obtained. The numerical results showed that characteristic instability occurred at 0.65-0.67Q BEP , the reason is that the backflow on the vaned diffuser hub-side blocks the downstream flow from the impeller. Therefore, the flow separates on the pressure surface of the impeller outlet and a strong vortex is generated, then the characteristic instability appeared due to the instability of internal flow. Backflow was found in diffuser passage at 0.65 Q BEP and 0.85 Q BEP , as flow rate decreases, the backflow region and velocity increases. Pressure fluctuation at diffuser inlet and diffuser passages was severe at at 0.65 Q BEP . According to the numerical simulation, the mixed-flow waterjet propulsion has characteristic instability at partial flow rate condition.

The activity of the Colima volcano and morphological changes in the summit between 2004 and 2013

Science.gov (United States)

Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Camarena Garcia, M. A.

2013-05-01

Colima Volcano, located in the West of the Volcanic Mexican Belt (19° 30.696 N, 103° 37.026 W), has shown a new cycle of explosive activity beginning May 30 1999, and reaching its maximum in March-April of 2005 and January 2013. In the 2005 the explosive activity increased gradually, having the largest event on May 23, when a new dome was created. Hours later this dome was destroyed by a strong explosion, forming an ash column 5.6 km high with subsequent pyroclastic flows that reached a distance of 4.2 km flowing along the ravines of the South sector. On May 30 the most intense explosion in 1999 occurred, when the plume reached heights in excess of 4.4 km above the crater, and pyroclastic flows were created. On the same year in July two explosive events occurred of characteristics similar to those in May. These constant explosions caused continuous morphological changes in the summit, the most significant being the collapse of the North and South walls of the crater, in the first week of June of 2005, and the creation of a new crater in July. In 2006 the most significant explosive activity took place during April, May and July, when the eruptive columns reached heights of more than 1500 meters above the crater, occasionally forming small pyroclastic flows. In May of 2007 morphological changes were observed in the summit. Among them a crater explosion on the East side, a dome was formed on the West side, with 20 m in high and 50 m in diameter. Since the end of 2008 to December of 2012 the volcano remained calm, with a dome diameter of 220 m and height of 60 m, in January 2013 three explosions occurred, destroying the dome and throwing a volume of 1.5 million cubic meters. The eruptive column reached a height of 3000 above the crater. It reported light ashfall to the NE to 100 km away from the volcano. The explosive events continue to date, but they have diminished in size and intensity. This activity was similar to the one observed in 1902-1903 and reported by

El Chichón's "surprise" eruption in 1982: lessons for reducing volcano risk

Science.gov (United States)

Tilling, R.I.

2009-01-01

During one week (28 March–4 April 1982), three powerful explosive eruptions (VEI 5) of El Chichón Volcano caused the worst volcanic disaster in Mexico's recorded history. Pyroclastic flows and surges obliterated nine villages, killing about 2,000 people, and ashfalls downwind posed socio–economic hardships for many thousands of inhabitants of the States of Chiapas and Tabasco. The unexpected and vigorous eruption of 28 caused a hasty, confused evacuation of most villagers in the area. Activity was greatly diminished the next five days, and then the most powerful and lethal eruptions occurred 3–4 April—tragically, after many evacuees were allowed by authorities to return home.

Cristobalite in volcanic ash of the soufriere hills volcano, montserrat, british west indies

Science.gov (United States)

Baxter; Bonadonna; Dupree; Hards; Kohn; Murphy; Nichols; Nicholson; Norton; Searl; Sparks; Vickers

1999-02-19

Crystalline silica (mostly cristobalite) was produced by vapor-phase crystallization and devitrification in the andesite lava dome of the Soufriere Hills volcano, Montserrat. The sub-10-micrometer fraction of ash generated by pyroclastic flows formed by lava dome collapse contains 10 to 24 weight percent crystalline silica, an enrichment of 2 to 5 relative to the magma caused by selective crushing of the groundmass. The sub-10-micrometer fraction of ash generated by explosive eruptions has much lower contents (3 to 6 percent) of crystalline silica. High levels of cristobalite in respirable ash raise concerns about adverse health effects of long-term human exposure to ash from lava dome eruptions.

Seismic observations of Redoubt Volcano, Alaska - 1989-2010 and a conceptual model of the Redoubt magmatic system

Science.gov (United States)

Power, John A.; Stihler, Scott D.; Chouet, Bernard A.; Haney, Matthew M.; Ketner, D.M.

2013-01-01

Seismic activity at Redoubt Volcano, Alaska, has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano's summit. Major eruptions occurred in 1989-1990 and 2009 and were characterized by large volcanic explosions, episodes of lava dome growth and failure, pyroclastic flows, and lahars. Seismic features of the 1989-1990 eruption were 1) weak precursory tremor and a short, 23-hour-long, intense swarm of repetitive shallow long-period (LP) events centered 1.4 km below the crater floor, 2) shallow volcano-tectonic (VT) and hybrid earthquakes that separated early episodes of dome growth, 3) 13 additional swarms of LP events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity, and 4) a persistent cluster of VT earthquakes at 6 to 9 km depth. In contrast the 2009 eruption was preceded by a pronounced increase in deep-LP (DLP) events at lower crustal depths (25 to 38 km) that began in mid-December 2008, two months of discontinuous shallow volcanic tremor that started on January 23, 2009, a strong phreatic explosion on March 15, and a 58-hour-long swarm of repetitive shallow LP events. The 2009 eruption consisted of at least 23 major explosions between March 23 and April 5, again accompanied by shallow VT earthquakes, several episodes of shallow repetitive LP events and dome growth continuing until mid July. Increased VT earthquakes at 4 to 9 km depth began slowly in early April, possibly defining a mid-crustal magma source zone. Magmatic processes associated with the 2009 eruption seismically activated the same portions of the Redoubt magmatic system as the 1989-1990 eruption, although the time scales and intensity vary considerably among the two eruptions. The occurrence of precursory DLP events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths. Based on the evolution of seismicity during the 1989-1990 and

Video Games in Volcanic Hazard Communications: Methods & Issues

Science.gov (United States)

Mani, Lara; Cole, Paul; Stewart, Iain

2016-04-01

eruptions (1902 &1979), which are reproduced based on historical data and personal accounts of the eruptions. Through a series of interactive scenes, each of the principal hazardous phenomena associated with La Soufriere - pyroclastic flows & surges, ash fall and lahars - are visualised and explained. The game concludes with a quiz in which players are required to answer questions are based on information provided throughout the game. The St. Vincent's Volcano game was trialled in St. Vincent during a volcano awareness education week in April 2015. The presentation will share reflections on how this type of interactive tool can be tested and implemented, and explore the issues and challenges with using video games in a dynamic environment.

Flow visualisation study of spiral flow in the aorta-renal bifurcation.

Science.gov (United States)

Fulker, David; Javadzadegan, Ashkan; Li, Zuming; Barber, Tracie

2017-10-01

The aim of this study was to analyse the flow dynamics in an idealised model of the aorta-renal bifurcation using flow visualisation, with a particular focus on the effect of aorta-to-renal flow ratio and flow spirality. The recirculation length was longest when there was low flow in the renal artery and smaller in the presence of spiral flow. The results also indicate that patients without spiral flow or who have low flow in the renal artery due to the presence of stenosis may be susceptible to heightened development of atherosclerotic lesions.

A flow meter for ultrasonically measuring the flow velocity of fluids

DEFF Research Database (Denmark)

2015-01-01

The invention regards a flow meter for ultrasonically measuring the flow velocity of fluids comprising a duct having a flow channel with an internal cross section comprising variation configured to generate at least one acoustic resonance within the flow channel for a specific ultrasonic frequency......, and at least two transducers for generating and sensing ultrasonic pulses, configured to transmit ultrasonic pulses at least at said specific ultrasonic frequency into the flow channel such that the ultrasonic pulses propagate through a fluid flowing in the flow channel, wherein the flow meter is configured...

The 2008 Puipui eruption and morphology of the Northeast Lau Spreading Center between Maka and Tafu (Invited)

Science.gov (United States)

Clague, D. A.; Caress, D. W.; Rubin, K. H.; Paduan, J. B.

2010-12-01

An event plume was discovered in the water column between Maka and Tafu volcanoes on the Northeast Lau Spreading Center in Nov. 2008. A Rapid Response cruise in May 2009 found that eruptive activity had ceased after observations on two Jason II ROV dives and one MBARI Mapping AUV survey that mapped most of the axis and flanks at 1.5-m resolution. Jason II located a recent lava flow, which was named Puipui. The small ridge of mounds aligned along two overlapping fissures extend for 1.8 km. The pillow ridge cuts obliquely across the ridge axis. The dive observations show mainly pillow lavas near the NE end and sheet flows near the SE end. A central 340 m portion observed by Jason II as predominantly ponded lobate flows was not mapped by the AUV. The Puipui and prior eruptions produced abundant vesicular angular glass fragments, Pele’s hair, and less abundant limu o Pele pyroclasts that thinly blanket the axial plateau and cascade down the steep flanks, mixing debris from many eruptions. Electron probe analyses of 91 fragments show that 15 Puipui pyroclasts are compositionally variable (normalized 6.5-7.2% MgO, ~49.6% SiO2) and distinct from prior eruptions in the area that have lower TiO2, K2O, Na2O, and K2O; and 52.3-53.7% SiO2. Pyroclasts of all compositions are highly degassed (<0.025% S) prior to eruption. The NE-trending segment, anchored by Maka volcano at the SE end, includes the Puipui flow. The morphology changes dramatically over short distances. The 1 km SW end is characterized by multiple extensional faults that parallel the ridge axis. The AUV survey ends on a sheet flow with drained ponds. To the NE, Maka is a 1.2 km diameter central volcano rising 300 m above the adjacent ridge to a summit at 1515 m. The ridge axis deepens steadily to 2140 m at the NE survey end and 1900 m to the SW. Rift zones on Maka parallel the ridge axis and are constructed of overlapping lava deltas. The NW and SE flanks are smooth like those at actively erupting West Mata

Ferrofluid-in-oil two-phase flow patterns in a flow-focusing microchannel

Science.gov (United States)

Sheu, T. S.; Chen, Y. T.; Lih, F. L.; Miao, J. M.

This study investigates the two-phase flow formation process of water-based Fe3O4 ferrofluid (dispersed phase) in a silicon oil (continuous phase) flow in the microfluidic flow-focusing microchannel under various operational conditions. With transparent PDMS chip and optical microscope, four main two-phase flow patterns as droplet flow, slug flow, ring flow and churn flow are observed. The droplet shape, size, and formation mechanism were also investigated under different Ca numbers and intended to find out the empirical relations. The paper marks an original flow pattern map of the ferrofluid-in-oil flows in the microfluidic flow-focusing microchannels. The flow pattern transiting from droplet flow to slug flow appears for an operational conditions of QR < 1 and Lf / W < 1. The power law index that related Lf / W to QR was 0.36 in present device.

Dubois Quadrangle, Idaho and Montana

International Nuclear Information System (INIS)

Wodzicki, A.; Krason, J.

1981-06-01

Within the Dubois Quadrangle (Idaho and Montana), environments favorable for uranium deposits, based on National Uranium Resource Evaluation criteria, occur in the McGowan Creek Formation and within some Tertiary sedimentary basins. The Mississippian McGowan Creek Formation consists of uraniferous, black, siliceous mudstone and chert with minor porous sedimentary channels. In the southern Beaverhead Mountains it has been fractured by a bedding-plane fault, and uranium has been further concentrated by circulating groundwater in the porous channels and brecciated zones, both of which contain about 200 ppM uranium. The northern parts of the Pahsimeroi River, Lemhi River, Medicine Lodge Creek, Horse Prairie, and Sage Creek Basins are considered favorable for sandstone-type uranium deposits. Evidence present includes suitable source rocks such as rhyolitic flow breccia, laharic deposits, or strongly welded tuffs; permeable sediments, including most sandstones and conglomerates, providing they do not contain devitrified glass; suitable reductants such as lignite, pyrite, or low-Eh geothermal water; and uranium occurrences

Augmentation of forced flow boiling heat transfer by introducing air flow into subcooled water flow

International Nuclear Information System (INIS)

Koizumi, Y.; Ohtake, H.; Yuasa, T.; Matsushita, N.

2001-01-01

The effect of air injection into a subcooled water flow on boiling heat transfer and a critical heat flux (CHF) was examined experimentally. Experiments were conducted in the range of subcooling of 50 K, a superficial velocity of water and air Ul = 0.17 ∼ 3.4 and Ug = 0 ∼ 15 m/s, respectively. A test heat transfer surface was a 5 mm wide, 40 mm long and 0.5 mm thick stainless steel sheet embedded on the bottom wall of a 10 mm high and 20 mm wide rectangular flow channel. Nine times enhancement of the heat transfer coefficient in the non-boiling region was attained at the most by introducing an air flow into a water single-phase flow. The heat transfer improvement was prominent when the water flow rate was low and the air introduction was large. The present results of the non-boiling heat transfer were well correlated with the Lockhart-Martinelli parameter X tt ; h TP /h L0 = 5.0(1/ X tt ) 0.5 . The air introduction has some effect on the augmentation of heat transfer in the boiling region, however, the two-phase flow effect was little and the boiling was dominant in the fully developed boiling region. The CHF was improved a little by the air introduction in the high water flow region. However, that was rather greatly reduced in the low flow region. Even so, the general trend by the air introduction was that qCHF increased as the air introduction was increased. The heat transfer augmentation in the non-boiling region was attained by less power increase than that in the case that only the water flow rate was increased. From the aspect of the power consumption and the heat transfer enhancement, the small air introduction in the low water flow rate region seemed more profitable, although the air introduction in the high water flow rate region and also the large air introduction were still effective in the augmentation of the heat transfer in the non-boiling region. (author)

Notes on Chameleons IV. A New Chameleon, from the Miocene of Fort Ternan, Kenya (Chamaeleonidae, Reptilia)

NARCIS (Netherlands)

Hillenius, D.

1978-01-01

A new, fossil chameleon is described, † Chamaeleo intermedius, found on the surface at Fort Ternan, Kenya. Most probably it eroded from a layer of fossilized lahar, close to 14 million years old. † Chamaeleo intermedius possesses characters which still occur in recent chameleons, in fact it combines

Mechanics of occurrence of critical flow in compressible two-phase flow

International Nuclear Information System (INIS)

Katto, Yoshiro; Sudo, Yukio

1976-01-01

Fundamental framework of mechanics for the occurrence of critical flow is investigated, following the principle that the critical flow appears as a limit in a continuous change of state of flow along a nozzle (or a pipe) and should be derived only from simultaneous mechanical equations concerned with the flow. Mathematical procedures with which the critical flow: (i) the single phase flow of an arbitrary fluid, unrestricted by the equation of state of ideal gas, where the number of simultaneous equations is equal to the number of independent variables, and (ii) the one-component, separated two-phase flow under saturated condition, where the number of equations exceeds that of variables. In each case, interesting mechanism of leading to the occurrence of a limiting state of flow at a definite cross-section in a nozzle (incl. a pipe) is clarified, and a definite state of flow at the critical cross-section is also determined. Then, the analysis is extended to the critical flow which should appear in the completely isolated and the homogeneously dispersed, two-component, two-phase flow (composed of a compressible and an incompressible substance). It is found that the analyses of these special flow patterns provide several supplementary information to the mechanics of critical flow. (auth.)

Performance of a vanadium redox flow battery with and without flow fields

International Nuclear Information System (INIS)

Xu, Q.; Zhao, T.S.; Zhang, C.

2014-01-01

Highlights: • The performances of a VRFB with/without flow fields are compared. • The respective maximum power efficiency occurs at different flow rates. • The battery with flow fields Exhibits 5% higher energy efficiency. - Abstract: A flow field is an indispensable component for fuel cells to macroscopically distribute reactants onto electrodes. However, it is still unknown whether flow fields are also required in all-vanadium redox flow batteries (VRFBs). In this work, the performance of a VRFB with flow fields is analyzed and compared with the performance of a VRFB without flow fields. It is demonstrated that the battery with flow fields has a higher discharge voltage at higher flow rates, but exhibits a larger pressure drop. The maximum power-based efficiency occurs at different flow rates for the both batteries with and without flow fields. It is found that the battery with flow fields Exhibits 5% higher energy efficiency than the battery without flow fields, when operating at the flow rates corresponding to each battery's maximum power-based efficiency. Therefore, the inclusion of flow fields in VRFBs can be an effective approach for improving system efficiency

Review of Constructed Subsurface Flow vs. Surface Flow Wetlands

International Nuclear Information System (INIS)

HALVERSON, NANCY

2004-01-01

The purpose of this document is to use existing documentation to review the effectiveness of subsurface flow and surface flow constructed wetlands in treating wastewater and to demonstrate the viability of treating effluent from Savannah River Site outfalls H-02 and H-04 with a subsurface flow constructed wetland to lower copper, lead and zinc concentrations to within National Pollutant Discharge Elimination System (NPDES) Permit limits. Constructed treatment wetlands are engineered systems that have been designed and constructed to use the natural functions of wetlands for wastewater treatment. Constructed wetlands have significantly lower total lifetime costs and often lower capital costs than conventional treatment systems. The two main types of constructed wetlands are surface flow and subsurface flow. In surface flow constructed wetlands, water flows above ground. Subsurface flow constructed wetlands are designed to keep the water level below the top of the rock or gravel media, thus minimizing human and ecological exposure. Subsurface flow wetlands demonstrate higher rates of contaminant removal per unit of land than surface flow (free water surface) wetlands, therefore subsurface flow wetlands can be smaller while achieving the same level of contaminant removal. Wetlands remove metals using a variety of processes including filtration of solids, sorption onto organic matter, oxidation and hydrolysis, formation of carbonates, formation of insoluble sulfides, binding to iron and manganese oxides, reduction to immobile forms by bacterial activity, and uptake by plants and bacteria. Metal removal rates in both subsurface flow and surface flow wetlands can be high, but can vary greatly depending upon the influent concentrations and the mass loading rate. Removal rates of greater than 90 per cent for copper, lead and zinc have been demonstrated in operating surface flow and subsurface flow wetlands. The constituents that exceed NPDES limits at outfalls H-02 a nd H

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

2006-12-01

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.

Modelling information flow along the human connectome using maximum flow.

Science.gov (United States)

Lyoo, Youngwook; Kim, Jieun E; Yoon, Sujung

2018-01-01

The human connectome is a complex network that transmits information between interlinked brain regions. Using graph theory, previously well-known network measures of integration between brain regions have been constructed under the key assumption that information flows strictly along the shortest paths possible between two nodes. However, it is now apparent that information does flow through non-shortest paths in many real-world networks such as cellular networks, social networks, and the internet. In the current hypothesis, we present a novel framework using the maximum flow to quantify information flow along all possible paths within the brain, so as to implement an analogy to network traffic. We hypothesize that the connection strengths of brain networks represent a limit on the amount of information that can flow through the connections per unit of time. This allows us to compute the maximum amount of information flow between two brain regions along all possible paths. Using this novel framework of maximum flow, previous network topological measures are expanded to account for information flow through non-shortest paths. The most important advantage of the current approach using maximum flow is that it can integrate the weighted connectivity data in a way that better reflects the real information flow of the brain network. The current framework and its concept regarding maximum flow provides insight on how network structure shapes information flow in contrast to graph theory, and suggests future applications such as investigating structural and functional connectomes at a neuronal level. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultrasonic flow meter

NARCIS (Netherlands)

Lötters, Joost Conrad; Snijders, G.J.; Volker, A.W.F.

2014-01-01

The invention relates to an ultrasonic flow meter comprising a flow tube for the fluid whose flow rate is to be determined. The flow meter comprises a transmitting element for emitting ultrasonic waves, which is provided on the outer jacket of the flow tube. A receiving element, which is provided on

Critical flow rate in a single phase flow. Blocking concept

International Nuclear Information System (INIS)

Giot, Michel

1978-01-01

After referring to the phenomena accompanying the appearance of a critical flow rate in a nozzle and presenting equations governing single phase flows, the critical condition is defined. Several particular cases are then examined; the horizontal and vertical isentropic flow, Fanno's flow and Raleigh's and the isothermal flow. The entropy deviation is calculated on either side of a normal impact. To conclude, the link existing between the concepts of critical flow and the propagation rate of small perturbations is demonstrated. To do so, the method of perturbations, that of Prandtl and that of characteristic directions are applied in turn [fr

Flow regime classification in air-magnetic fluid two-phase flow.

Science.gov (United States)

Kuwahara, T; De Vuyst, F; Yamaguchi, H

2008-05-21

A new experimental/numerical technique of classification of flow regimes (flow patterns) in air-magnetic fluid two-phase flow is proposed in the present paper. The proposed technique utilizes the electromagnetic induction to obtain time-series signals of the electromotive force, allowing us to make a non-contact measurement. Firstly, an experiment is carried out to obtain the time-series signals in a vertical upward air-magnetic fluid two-phase flow. The signals obtained are first treated using two kinds of wavelet transforms. The data sets treated are then used as input vectors for an artificial neural network (ANN) with supervised training. In the present study, flow regimes are classified into bubbly, slug, churn and annular flows, which are generally the main flow regimes. To validate the flow regimes, a visualization experiment is also performed with a glycerin solution that has roughly the same physical properties, i.e., kinetic viscosity and surface tension, as a magnetic fluid used in the present study. The flow regimes from the visualization are used as targets in an ANN and also used in the estimation of the accuracy of the present method. As a result, ANNs using radial basis functions are shown to be the most appropriate for the present classification of flow regimes, leading to small classification errors.

The Tala Tuff, La Primavera caldera Mexico. Pre-eruptive conditions and magma processes before eruption

Science.gov (United States)

Sosa-Ceballos, G.

2015-12-01

La Primavera caldera, Jalisco Mexico, is a Pleistocenic volcanic structure formed by dome complexes and multiple pyroclastic flows and fall deposits. It is located at the intersection of the Chapala, Colima, and Tepic grabens in western Mexico. The first volcanic activity associated to La Primavera started ~0.1 Ma with the emission of pre-caldera lavas. The caldera collapse occurred 95 ka and is associated to the eruption of ~20 km3of pumice flows known as the Tala tuff (Mahood 1980). The border of the caldera was replaced by a series of domes dated in 75-30 ky, which partially filled the inner depression of the caldera with pyroclastic flows and falls. For more than a decade the Federal Commission of Electricity in Mexico (CFE) has prospected and evaluated the geothermal potential of the Cerritos Colorados project at La Primavera caldera. In order to better understand the plumbing system that tapped the Tala tuff and to investigate its relation with the potential geothermal field at La Primavera we performed a series of hydrothermal experiments and studied melt inclusions hosted in quartz phenocrysts by Fourier Infra red stectroscopy (FTIR). Although some post caldera products at La Primavera contain fayalite and quartz (suggesting QFM conditions) the Tala tuff does not contain fayalite and we ran experiments under NNO conditions. The absence of titanomagnetite does not allowed us to calculate pre-eruptive temperature. However, the stability of quartz and plagioclase, which are natural phases, suggest that temperature should be less than 750 °C at a pressure of 200 MPa. The analyses of H2O and CO2 dissolved in melt inclusions yielded concentrations of 2-5 wt.% and 50-100 ppm respectively. This data confirm that the pre-eruptive pressure of the Tala tuff is ~200 MPa and in addition to major elements compositions suggest that the Tala tuff is either, compositionally zoned or mixed with other magma just prior to eruption.

Flooding and flow reversal of two-phase annular flow

International Nuclear Information System (INIS)

Asahi, Y.

1978-01-01

The flooding and flow reversal conditions of two-phase annular flow are mathematically defined in terms of a characteristic function representing a force balance. Sufficiently below the flooding point in counter-current flow, the interface is smooth and the characteristic equation reduces to the Nusselt relationship. Just below flooding point and above the flow reversal point in cocurrent flow, the interface is 'wavy', so that the interfacial shear effect plays an important role. The theoretical analysis is compared with experimental results by others. It is suggested that the various length effects which have been experimentally observed may be accounted for by the spatial variation of the droplet entrainment. (Auth.)

Flow area optimization in point to area or area to point flows

International Nuclear Information System (INIS)

Ghodoossi, Lotfollah; Egrican, Niluefer

2003-01-01

This paper deals with the constructal theory of generation of shape and structure in flow systems connecting one point to a finite size area. The flow direction may be either from the point to the area or the area to the point. The formulation of the problem remains the same if the flow direction is reversed. Two models are used in optimization of the point to area or area to point flow problem: cost minimization and revenue maximization. The cost minimization model enables one to predict the shape of the optimized flow areas, but the geometric sizes of the flow areas are not predictable. That is, as an example, if the area of flow is a rectangle with a fixed area size, optimization of the point to area or area to point flow problem by using the cost minimization model will only predict the height/length ratio of the rectangle not the height and length itself. By using the revenue maximization model in optimization of the flow problems, all optimized geometric aspects of the interested flow areas will be derived as well. The aim of this paper is to optimize the point to area or area to point flow problems in various elemental flow area shapes and various structures of the flow system (various combinations of elemental flow areas) by using the revenue maximization model. The elemental flow area shapes used in this paper are either rectangular or triangular. The forms of the flow area structure, made up of an assembly of optimized elemental flow areas to obtain bigger flow areas, are rectangle-in-rectangle, rectangle-in-triangle, triangle-in-triangle and triangle-in-rectangle. The global maximum revenue, revenue collected per unit flow area and the shape and sizes of each flow area structure have been derived in optimized conditions. The results for each flow area structure have been compared with the results of the other structures to determine the structure that provides better performance. The conclusion is that the rectangle-in-triangle flow area structure

Phreatomagmatic eruptive and depositional processes during the 1949 eruption on La Palma (Canary Islands)

Science.gov (United States)

White, James D. L.; Schmincke, Hans-Ulrich

1999-12-01

In 1949, a 5-week-long magmatic and phreatomagmatic eruption took place along the active volcanic ridge of La Palma (Canary Islands). Two vents, Duraznero and Hoyo Negro, produced significant pyroclastic deposits. The eruption began from Duraznero vent, which produced a series of deposits with an upward decrease in accidental fragments and increase in fluidal ash and spatter, together inferred to indicate decreasing phreatomagmatic interaction. Hoyo Negro erupted over a 2-week period, producing a variety of pyroclastic density currents and ballistic blocks and bombs. Hoyo Negro erupted within and modified an older crater having high walls on the northern to southeastern edges. Southwestern to western margins of the crater lay 50 to 100 m lower. Strongly contrasting deposits in the different sectors (N-SE vs. SW-W) were formed as a result of interaction between topography, weak eruptive columns and stratified pyroclastic density currents. Tephra ring deposits are thicker and coarser-grained than upper rim deposits formed along the higher edges of the crater, and beyond the crater margin, valley-confined deposits are thicker than more thinly bedded mantling deposits on higher topography. These differences indicate that the impact zone for the bulk of the collapsing, tephra-laden column lay within the crater and that the high crater walls inhibited escape of pyroclastic density currents to the north and east. The impact zone lay outside the low SW-W rims, however, thus allowing stratified pyroclastic density currents to move freely away from the crater in those directions, depositing thin sections (<30 cm) of well-bedded ash (mantling deposits) on ridges and thicker sections (1-3 m) of structureless ash beds in valleys and small basins. Such segregation of dense pyroclastic currents from more dilute ones at the crater wall is likely to be common for small eruptions from pre-existing craters and is an important factor to be taken into account in volcanic hazards

Experimental study on flow pattern and heat transfer of inverted annular flow

International Nuclear Information System (INIS)

Takenaka, Nobuyuki; Akagawa, Koji; Fujii, Terushige; Nishida, Koji

1990-01-01

Experimental results are presented on flow pattern and heat transfer in the regions from inverted annular flow to dispersed flow in a vertical tube using freon R-113 as a working fluid at atmospheric pressure to discuss the correspondence between them. Axial distributions of heat transfer coefficient are measured and flow patterns are observed. The heat transfer characteristics are divided into three regions and a heat transfer characteristics map is proposed. The flow pattern changes from inverted annular flow (IAF) to dispersed flow (DF) through inverted slug flow (ISF) for lower inlet velocities and through agitated inverted annular flow (AIAF) for higher inlet velocities. A flow pattern map is obtained which corresponds well with the heat transfer characteristic map. (orig.)

Flow regimes

International Nuclear Information System (INIS)

Liles, D.R.

1982-01-01

Internal boundaries in multiphase flow greatly complicate fluid-dynamic and heat-transfer descriptions. Different flow regimes or topological configurations can have radically dissimilar interfacial and wall mass, momentum, and energy exchanges. To model the flow dynamics properly requires estimates of these rates. In this paper the common flow regimes for gas-liquid systems are defined and the techniques used to estimate the extent of a particular regime are described. Also, the current computer-code procedures are delineated and introduce a potentially better method is introduced

Simulation of gas compressible flow by free surface water flow

International Nuclear Information System (INIS)

Altafini, C.R.; Silva Ferreira, R.T. da

1981-01-01

The analogy between the water flow with a free surface and the compressible fluid flow, commonly called hydraulic analogy, is analyzed and its limitations are identified. The water table is the equipment used for this simulation, which allows the quatitative analysis of subsonic and supersonic flow with a low cost apparatus. The hydraulic analogy is applied to subsonic flow around circular cylinders and supersonic flow around cones. The results are compared with available theoretical and experimental data and a good agreement is achieved. (Author) [pt

Screening criteria of volcanic hazards aspect in the NPP site evaluation

International Nuclear Information System (INIS)

Nur Siwhan

2013-01-01

Studies have been conducted on the completeness of regulation in Indonesia particularly on volcanic hazards aspects in the evaluation of nuclear power plant site. Volcanic hazard aspect needed to identify potential external hazards that may endanger the safety of the operation of nuclear power plants. There are four stages for evaluating volcanic hazards, which are initial assessment, characterization sources of volcanic activity in the future, screening volcanic hazards and assessment of capable volcanic hazards. This paper discuss the third stage of the general evaluation which is the screening procedure of volcanic hazards. BAPETEN Chairman Regulation No. 2 Year of 2008 has only one screening criteria for missile volcanic phenomena, so it required screening criteria for other hazard phenomena that are pyroclastic flow density; lava flows; avalanche debris materials; lava; opening hole new eruptions, volcano missile; tsunamis; ground deformation; and hydrothermal system and ground water anomaly. (author)

Experimental study on flow pattern transitions for inclined two-phase flow

Energy Technology Data Exchange (ETDEWEB)

Kwak, Nam Yee; Lee, Jae Young [Handong Univ., Pohang (Korea, Republic of); Kim, Man Woong [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

2007-07-01

In this paper, experimental data on flow pattern transition of inclination angles from 0-90 are presented. A test section is constructed 2 mm long and I.D 1inch using transparent material. The test section is supported by aluminum frame that can be placed with any arbitrary inclined angles. The air-water two-phase flow is observed at room temperature and atmospheric condition using both high speed camera and void impedance meter. The signal is sampled with sampling rate 1kHz and is analyzed under fully-developed condition. Based on experimental data, flow pattern maps are made for various inclination angles. As increasing the inclination angels from 0 to 90, the flow pattern transitions on the plane jg-jf are changed, such as stratified flow to plug flow or slug flow or plug flow to bubbly flow. The transition lines between pattern regimes are moved or sometimes disappeared due to its inclined angle.

Advanced porous electrodes with flow channels for vanadium redox flow battery

Science.gov (United States)

Bhattarai, Arjun; Wai, Nyunt; Schweiss, Ruediger; Whitehead, Adam; Lim, Tuti M.; Hng, Huey Hoon

2017-02-01

Improving the overall energy efficiency by reducing pumping power and improving flow distribution of electrolyte, is a major challenge for developers of flow batteries. The use of suitable channels can improve flow distribution through the electrodes and reduce flow resistance, hence reducing the energy consumption of the pumps. Although several studies of vanadium redox flow battery have proposed the use of bipolar plates with flow channels, similar to fuel cell designs, this paper presents the use of flow channels in the porous electrode as an alternative approach. Four types of electrodes with channels: rectangular open channel, interdigitated open cut channel, interdigitated circular poked channel and cross poked circular channels, are studied and compared with a conventional electrode without channels. Our study shows that interdigitated open channels can improve the overall energy efficiency up to 2.7% due to improvement in flow distribution and pump power reduction while interdigitated poked channel can improve up to 2.5% due to improvement in flow distribution.

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

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Rosana Peporine Lopes

Full Text Available The Fernando de Noronha Archipelago presents, on its main island, a centrally-located stratigraphic unit, the Remédios Formation (age around 8 - 12 Ma constituted by basal pyroclastic rocks intruded by dikes, plugs and domes of varied igneous rocks, capped by flows and pyroclastics of mafic to ultramafic rocks of the Quixaba Formation (age around 1 - 3 Ma, which is limited from the underlying unit by an extensive irregular erosion surface. A predominant sodic Remédios series (basanites, tephrites, tephriphonolites, essexite, phonolites can be separated from a moderately potassic Remédios sequence (alkali basalts, trachyandesites, trachytes, both alkaline series showing mostly continuous geochemical trends in variation diagrams for major as well as trace elements, indicating evolution by crystal fractionation (mainly, separation of mafic minerals, including apatites and titanites. There are textural and mineralogical evidences pointing to hybrid origin of some intermediate rocks (e.g., resorbed pyroxene phenocrysts in basaltic trachyandesites, and in some lamprophyres. The primitive Quixaba rocks are mostly melanephelinites and basanites, primitive undersaturated sodic types. Geology (erosion surface, stratigraphy (two distinct units separated by a large time interval, petrography (varied Remédios Formation, more uniform Quixaba unit and geochemistry indicate that the islands represent the activity of a protracted volcanic episode, fueled by intermittent melting of an enriched mantle, not related to asthenospheric plume activity.

Dynamics of lava flow - Thickness growth characteristics of steady two-dimensional flow

Science.gov (United States)

Park, S.; Iversen, J. D.

1984-01-01

The thickness growth characteristics of flowing lava are investigated using a heat balance model and a two-dimensional model for flow of a Bingham plastic fluid down an inclined plane. It is found that yield strength plays a crucial role in the thickening of a lava flow of given flow rate. To illustrate this point, downstream thickness profiles and yield strength distributions were calculated for flows with mass flow rates of 10,000 and 100,000 kg/m-sec. Higher flow rates led to slow cooling rates which resulted in slow rate of increase of yield strength and thus greater flow lengths.

The study on flow characteristics of butterfly valve using flow visualization

International Nuclear Information System (INIS)

Yang, S. M.; Hong, S. D.; Song, D. S.; Park, J. K.; Park, J. I.; Shin, S. K.; Kim, H. J.

2005-01-01

Flow visualization of butterfly valve is tested for four types(15 deg., 30 .deg., 45 .deg., and 90 .deg.) of valve opening angle. The inner flow characteristics of valve are studied. The flow variation was measured using a high speed camera which takes 500 frames per second with 1024 x 1024 pixels. These captured images were used for calculation to analyze two dimensional flow velocity of the valve. The smaller opening angle, the more increasing the differential pressure of a butterfly valve. Therefore, we know that the complex flow is occurred by increasing the differential pressure. And it is found that the flowing backward is more increased according to the increase of the opening angle of a butterfly valve. However, its flow pattern is similar to a simple pipe flow when the opening angle is 90 .deg.

Hazard assessment of long-range tephra dispersal for a Plinian eruptive scenario at Popocatépetl volcano (Mexico). Inplications on civil aviation

Science.gov (United States)

Bonasia, R.; Scaini, C.; Capra, L.; Nathenson, M.; Siebe, C.; Arana-Salinas, L.; Folch, A.

2013-12-01

Popocatépetl is one of the most active volcanoes in Mexico threatening a densely populated area that includes Mexico City with more than 20 million inhabitants. The destructive potential of this volcano is demonstrated by its Late Pleistocene-Holocene eruptive activity, which has been characterized by recurrent Plinian eruptions of large magnitude. The current volcanic hazards map, reconstructed after the crisis occurred in 1994, considers the potential occurrence of different volcanic phenomena, including pyroclastic density currents and lahars. However, no quantitative assessment of the tephra dispersal hazard, especially related to atmospheric dispersal, has been performed. Given the high number of important airports in the surroundings of Popocatépetl volcano and considering the potential threat posed to civil aviation in Mexico and adjacent regions in case of a Plinian eruption, a hazard assessment for tephra dispersal is strongly required. In this work we present the first probabilistic tephra dispersal hazard assessment for Popocatépetl volcano. We compute probabilistic hazard maps for critical thresholds of airborne ash concentrations at different flight levels. Tephra dispersal modelling is performed using the FALL3D numerical model. Probabilistic hazard maps are built for a Plinian eruptive scenario defined on the basis of geological field data for the 'Ochre Pumice' Plinian eruption (4965 14C yrBP). FALL3D model input eruptive parameters are constrained through an inversion method carried out with the semi-analytical HAZMAP model and are varied sampling them on the base of a Probability Density Function. We analyze the influence of seasonal variations on ash dispersal and estimate the average persistence of critical ash concentrations at relevant locations and airports. This study assesses the impact that a Plinian eruption similar to the Ochre Pumice eruption would have on the main airports of Mexico and adjacent areas. The hazard maps presented here

Cloud-processed 4D CMR flow imaging for pulmonary flow quantification

Energy Technology Data Exchange (ETDEWEB)

Chelu, Raluca G., E-mail: ralucachelu@hotmail.com [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Wanambiro, Kevin W. [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Radiology, Aga Khan University Hospital, Nairobi (Kenya); Hsiao, Albert [Department of Radiology, University of California, San Diego, CA (United States); Swart, Laurens E. [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Voogd, Teun [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Hoven, Allard T. van den; Kranenburg, Matthijs van [Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Coenen, Adriaan [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Boccalini, Sara [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Radiology, University Hospital, Genoa (Italy); Wielopolski, Piotr A. [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Vogel, Mika W. [MR Applications and Workflow – Europe, GE Healthcare B.V. Hoevelaken (Netherlands); Krestin, Gabriel P. [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Vasanawala, Shreyas S. [Department of Radiology, Stanford University, Stanford, CA (United States); Budde, Ricardo P.J. [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Roos-Hesselink, Jolien W. [Department of Cardiology, Erasmus MC, Rotterdam (Netherlands); Nieman, Koen [Department of Radiology, Erasmus MC, Rotterdam (Netherlands); Department of Cardiology, Erasmus MC, Rotterdam (Netherlands)

2016-10-15

Highlights: • With 4D flow, any plane of interest can be interactively chosen for quantitative measurements. • Anatomical and flow data are obtained during an approximately 10-min free-breathing scan. • 4D CMR flow measurements correlated well with the 2D PC ones. • Eddy current correction is important for good results with 4D flow. - Abstract: Objectives: In this study, we evaluated a cloud-based platform for cardiac magnetic resonance (CMR) four-dimensional (4D) flow imaging, with fully integrated correction for eddy currents, Maxwell phase effects, and gradient field non-linearity, to quantify forward flow, regurgitation, and peak systolic velocity over the pulmonary artery. Methods: We prospectively recruited 52 adult patients during one-year period from July 2014. The 4D flow and planar (2D) phase-contrast (PC) were acquired during same scanning session, but 4D flow was scanned after injection of a gadolinium-based contrast agent. Eddy-currents were semi-automatically corrected using the web-based software. Flow over pulmonary valve was measured and the 4D flow values were compared against the 2D PC ones. Results: The mean forward flow was 92 (±30) ml/cycle measured with 4D flow and 86 (±29) ml/cycle measured with 2D PC, with a correlation of 0.82 and a mean difference of −6 ml/cycle (−41–29). For the regurgitant fraction the correlation was 0.85 with a mean difference of −0.95% (−17–15). Mean peak systolic velocity measured with 4D flow was 92 (±49) cm/s and 108 (±56) cm/s with 2D PC, having a correlation of 0.93 and a mean difference of 16 cm/s (−24–55). Conclusion: 4D flow imaging post-processed with an integrated cloud-based application accurately quantifies pulmonary flow. However, it may underestimate the peak systolic velocity.

Cloud-processed 4D CMR flow imaging for pulmonary flow quantification

International Nuclear Information System (INIS)

Chelu, Raluca G.; Wanambiro, Kevin W.; Hsiao, Albert; Swart, Laurens E.; Voogd, Teun; Hoven, Allard T. van den; Kranenburg, Matthijs van; Coenen, Adriaan; Boccalini, Sara; Wielopolski, Piotr A.; Vogel, Mika W.; Krestin, Gabriel P.; Vasanawala, Shreyas S.; Budde, Ricardo P.J.; Roos-Hesselink, Jolien W.; Nieman, Koen

2016-01-01

Highlights: • With 4D flow, any plane of interest can be interactively chosen for quantitative measurements. • Anatomical and flow data are obtained during an approximately 10-min free-breathing scan. • 4D CMR flow measurements correlated well with the 2D PC ones. • Eddy current correction is important for good results with 4D flow. - Abstract: Objectives: In this study, we evaluated a cloud-based platform for cardiac magnetic resonance (CMR) four-dimensional (4D) flow imaging, with fully integrated correction for eddy currents, Maxwell phase effects, and gradient field non-linearity, to quantify forward flow, regurgitation, and peak systolic velocity over the pulmonary artery. Methods: We prospectively recruited 52 adult patients during one-year period from July 2014. The 4D flow and planar (2D) phase-contrast (PC) were acquired during same scanning session, but 4D flow was scanned after injection of a gadolinium-based contrast agent. Eddy-currents were semi-automatically corrected using the web-based software. Flow over pulmonary valve was measured and the 4D flow values were compared against the 2D PC ones. Results: The mean forward flow was 92 (±30) ml/cycle measured with 4D flow and 86 (±29) ml/cycle measured with 2D PC, with a correlation of 0.82 and a mean difference of −6 ml/cycle (−41–29). For the regurgitant fraction the correlation was 0.85 with a mean difference of −0.95% (−17–15). Mean peak systolic velocity measured with 4D flow was 92 (±49) cm/s and 108 (±56) cm/s with 2D PC, having a correlation of 0.93 and a mean difference of 16 cm/s (−24–55). Conclusion: 4D flow imaging post-processed with an integrated cloud-based application accurately quantifies pulmonary flow. However, it may underestimate the peak systolic velocity.

Boolean logic analysis for flow regime recognition of gas–liquid horizontal flow

International Nuclear Information System (INIS)

Ramskill, Nicholas P; Wang, Mi

2011-01-01

In order to develop a flowmeter for the accurate measurement of multiphase flows, it is of the utmost importance to correctly identify the flow regime present to enable the selection of the optimal method for metering. In this study, the horizontal flow of air and water in a pipeline was studied under a multitude of conditions using electrical resistance tomography but the flow regimes that are presented in this paper have been limited to plug and bubble air–water flows. This study proposes a novel method for recognition of the prevalent flow regime using only a fraction of the data, thus rendering the analysis more efficient. By considering the average conductivity of five zones along the central axis of the tomogram, key features can be identified, thus enabling the recognition of the prevalent flow regime. Boolean logic and frequency spectrum analysis has been applied for flow regime recognition. Visualization of the flow using the reconstructed images provides a qualitative comparison between different flow regimes. Application of the Boolean logic scheme enables a quantitative comparison of the flow patterns, thus reducing the subjectivity in the identification of the prevalent flow regime

How is flow experienced and by whom? Testing flow among occupations.

Science.gov (United States)

Llorens, Susana; Salanova, Marisa; Rodríguez, Alma M

2013-04-01

The aims of this paper are to test (1) the factorial structure of the frequency of flow experience at work; (2) the flow analysis model in work settings by differentiating the frequency of flow and the frequency of its prerequisites; and (3) whether there are significant differences in the frequency of flow experience depending on the occupation. A retrospective study among 957 employees (474 tile workers and 483 secondary school teachers) using multigroup confirmatory factorial analyses and multiple analyses of variance suggested that on the basis of the flow analysis model in work settings, (1) the frequency of flow experience has a two-factor structure (enjoyment and absorption); (2) the frequency of flow experience at work is produced when both challenge and skills are high and balanced; and (3) secondary school teachers experience flow more frequently than tile workers. Copyright © 2012 John Wiley & Sons, Ltd.

Internal Flow of a High Specific-Speed Diagonal-Flow Fan (Rotor Outlet Flow Fields with Rotating Stall

Directory of Open Access Journals (Sweden)

Norimasa Shiomi

2003-01-01

Full Text Available We carried out investigations for the purpose of clarifying the rotor outlet flow fields with rotating stall cell in a diagonal-flow fan. The test fan was a high–specific-speed (ns=1620 type of diagonal-flow fan that had 6 rotor blades and 11 stator blades. It has been shown that the number of the stall cell is 1, and its propagating speed is approximately 80% of its rotor speed, although little has been known about the behavior of the stall cell because a flow field with a rotating stall cell is essentially unsteady. In order to capture the behavior of the stall cell at the rotor outlet flow fields, hot-wire surveys were performed using a single-slant hotwire probe. The data obtained by these surveys were processed by means of a double phase-locked averaging technique, which enabled us to capture the flow field with the rotating stall cell in the reference coordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the three-dimensional velocity components at the rotor outlet flow fields were obtained. The behavior of the stall cell was shown for each velocity component, and the flow patterns on the meridional planes were illustrated.