Monitoring eruption activity using temporal stress changes at Mount Ontake volcano.

PubMed

Terakawa, Toshiko; Kato, Aitaro; Yamanaka, Yoshiko; Maeda, Yuta; Horikawa, Shinichiro; Matsuhiro, Kenjiro; Okuda, Takashi

2016-02-19

Volcanic activity is often accompanied by many small earthquakes. Earthquake focal mechanisms represent the fault orientation and slip direction, which are influenced by the stress field. Focal mechanisms of volcano-tectonic earthquakes provide information on the state of volcanoes via stresses. Here we demonstrate that quantitative evaluation of temporal stress changes beneath Mt. Ontake, Japan, using the misfit angles of focal mechanism solutions to the regional stress field, is effective for eruption monitoring. The moving average of misfit angles indicates that during the precursory period the local stress field beneath Mt. Ontake was deviated from the regional stress field, presumably by stress perturbations caused by the inflation of magmatic/hydrothermal fluids, which was removed immediately after the expulsion of volcanic ejecta. The deviation of the local stress field can be an indicator of increases in volcanic activity. The proposed method may contribute to the mitigation of volcanic hazards.

Monitoring eruption activity using temporal stress changes at Mount Ontake volcano

PubMed Central

Terakawa, Toshiko; Kato, Aitaro; Yamanaka, Yoshiko; Maeda, Yuta; Horikawa, Shinichiro; Matsuhiro, Kenjiro; Okuda, Takashi

2016-01-01

Volcanic activity is often accompanied by many small earthquakes. Earthquake focal mechanisms represent the fault orientation and slip direction, which are influenced by the stress field. Focal mechanisms of volcano-tectonic earthquakes provide information on the state of volcanoes via stresses. Here we demonstrate that quantitative evaluation of temporal stress changes beneath Mt. Ontake, Japan, using the misfit angles of focal mechanism solutions to the regional stress field, is effective for eruption monitoring. The moving average of misfit angles indicates that during the precursory period the local stress field beneath Mt. Ontake was deviated from the regional stress field, presumably by stress perturbations caused by the inflation of magmatic/hydrothermal fluids, which was removed immediately after the expulsion of volcanic ejecta. The deviation of the local stress field can be an indicator of increases in volcanic activity. The proposed method may contribute to the mitigation of volcanic hazards. PMID:26892716

Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

NASA Astrophysics Data System (ADS)

Ruch, J.; Vezzoli, L.; De Rosa, R.; Di Lorenzo, R.; Acocella, V.

2016-02-01

The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

A multidisciplinary study in the geodynamic active western Eger rift (Central Europe): The Quaternary volcanic complex Mytina and the recent CO2-degassing zone Hartousov

NASA Astrophysics Data System (ADS)

Flechsig, C.; Heinicke, J.; Kaempf, H. W.; Nickschick, T.; Mrlina, J.

2013-12-01

The Eger rift (Central Europe) belongs to the European Cenozoic rift system and represents an approximately 50 km wide and 300 km long ENE-WSW striking continental rift that formed during the Upper Cretaceous-Tertiary transition. This rift zone is one of the most active seismic regions in Central Europe. Especially, the western part of the Eger rift area is dominated by ongoing hidden magmatic processes in the intra-continental lithospheric mantle. Besides of known quaternary volcanoes, these processes take place in absence of any presently active volcanism at the surface. However, they are expressed by a series of phenomena distributed over a relatively large area, like occurrence of repeated earthquake swarms, surface exhalation of mantle-derived and CO2-enriched fluids at mofettes and mineral springs, and enhanced heat flow. At present this is the only known intra-continental region where such deep-seated, active lithospheric processes currently occur. The aim of the project is to investigate the tectonic/geologic near surface structure and the degassing processes of the mofette field of Hartousov, where soil gas measurements (concentration and flux rate) in an area of appr. 3x2 km traced a permeable NS extended segment of a fault zone and revealed highly permeable Diffuse Degassing Structures (DDS). The second target is volcanic environment of the Quaternary volcanic complex Mytina maar and the cinder cone Zelezna hurka/Eisenbühl. The investigations are intended to clarify: a) the spatio-temporal reconstruction of the maar complex, and the palaeo volcanic scenario (geological model, tectonic settings, distribution of pyroclastica, b) the geological structure and the tectonic control of the recent degassing zone, and c) the comperative interpretation of both regions in the consideration of potential future volcanic risk assessment in sub-regions of the western Eger Rift. To investigate both regions the following methods are used: geoelectrics, geomagnetics, shallow seismics, gravity and CO2-soil gas measurements, petrographic/petrophysical and remote sensing data. The results will be serve as for better understanding of geologic, volcanic and tectonic settings of the two regions as well as for the preparation of the ICDP drilling project 'Drilling the Eger rift' with a multidisciplinary approach consisting of geophysical, geochemical and other disciplines to understand the role of crustal fluid activity for swarm earthquake generation.

Early signs of geodynamic activity before the 2011-2012 El Hierro eruption

NASA Astrophysics Data System (ADS)

López, Carmen; García-Cañada, Laura; Martí, Joan; Domínguez Cerdeña, Itahiza

2017-02-01

The potential relation between mantle plume dynamics, regional tectonics and eruptive activity in the Canary Islands has not been studied yet through the analysis of long-time series of geophysical observational data. The existence of highly reliable seismic and geodetic data has enabled us to study from 1996 to 2014 the geodynamic evolution of the North Atlantic Azores-Gibraltar region (including the NW African margin) and its relationship with recent volcanic activity in El Hierro (Canary Islands). We compiled a new and unified regional seismic catalog and used long time-series of digital 3D surface displacements recorded by permanent GPS stations in the region. A joint regional- and local-scale analysis based on these data enabled us to identify signs of anomalous tectonic activity from 2003 onwards, whose intensity increased in 2007 and finally accelerated three months before the onset of the volcanic eruption on El Hierro in October 2011. Activity included the occurrence of regional extension and an uplift process affecting the southern Iberian Peninsula, NW Africa, and the Canary Islands. We interpret these observations as early signs of the geodynamic activity, which led to El Hierro eruption and the subsequent episodes of magma intrusion. Results point to the significant contribution of the mantle plume dynamics (i.e. external forces) in this renewed volcanic activity in the Canary Islands and emphasize the role of mantle dynamics in controlling regional tectonics.

Early signs of geodynamic activity before the 2011-2012 El Hierro eruption

NASA Astrophysics Data System (ADS)

López, Carmen; García-Cañada, Laura; Martí, Joan; Domínguez Cerdeña, Itahiza

2017-04-01

The potential relation between mantle plume dynamics, regional tectonics and eruptive activity in the Canary Islands has not been studied yet through the analysis of long-time series of geophysical observational data. The existence of highly reliable seismic and GNSS data has enabled us to study from 1996 to 2014 the geodynamic evolution of the North Atlantic Azores-Gibraltar region and its relationship with recent volcanic activity in El Hierro (Canary Islands, Spain). We compiled a new and unified regional seismic catalog and used long time-series of surface displacements recorded by permanent GNSS stations in the region. A regional- and local-scale analysis based on these data enabled us to identify signs of anomalous tectonic activity from 2003 onwards, whose intensity increased in 2007 and finally accelerated three months before the onset of the volcanic eruption on El Hierro in October 2011. This activity includes a regional extension and an uplift process that affects the southern Iberian Peninsula, NW Africa, and the Canary Islands. We interpret these observations as early signs of the geodynamic activity, which led to El Hierro eruption and the subsequent episodes of magma intrusion. Results point to the significant contribution of the mantle plume dynamics (i.e. external forces) in this renewed volcanic activity in the Canary Islands and emphasize the role of mantle dynamics in controlling regional tectonics.

Study of the structure changes caused by volcanic activity in Mexico applying the lineament analysis to the Aster (Terra) satellite data.

NASA Astrophysics Data System (ADS)

Arellano-Baeza, A. A.; Garcia, R. V.; Trejo-Soto, M.; Molina-Sauceda, E.

Mexico is one of the most volcanically active regions in North America Volcanic activity in central Mexico is associated with the subduction of the Cocos and Rivera plates beneath the North American plate Periods of enhanced microseismic activity associated with the volcanic activity of the Colima and Popocapetl volcanoes are compared to some periods of low microseismic activity We detected changes in the number and orientation of lineaments associated with the microseismic activity due to lineament analysis of a temporal sequence of high resolution satellite images of both volcanoes 15 m resolution multispectral images provided by the ASTER VNIR instrument were used The Lineament Extraction and Stripes Statistic Analysis LESSA software package was employed for the lineament extraction

Ambient Noise Surface Wave Tomography of the volcanic systems of eastern Iceland

NASA Astrophysics Data System (ADS)

Green, R. G.; Priestley, K. F.; White, R. S.

2015-12-01

The Vatnajökull region of central-east Iceland lies above the head of the Iceland mantle plume where the crust is thickest due to enhanced melt supply. As a result the region contains a high density of volcanic rift systems, with six large subglacial central volcanoes. Due to the ice cover, the geological structure of the area and the location of past eruptions are poorly known. Imaging of the crustal velocity heterogeneities beneath the ice sheet aims to reveal much in terms of the structure of these volcanic plumbing systems. Mapping of significant velocity changes through time may also be indicative of movement of melt around the central volcanoes; one of which (Bárðarbunga) experienced a major rifting event in August 2014 (Sigmundsson et al. Nature 2015, Green et al. Nature Geosci. 2015). We present results from tomographic imaging of the volcanic systems in the region, using continuous data from a local broadband seismic network in central-east Iceland which provides excellent ray path coverage of the volcanic systems. This is supplemented by data from the HOTSPOT and ICEMELT experiments and the permanent monitoring stations of the Icelandic Meteorological Office. We process the continuous data following Benson et al. 2007 and automatic frequency-time analysis (FTAN) routines are used to extract more than 9000 dispersion measurements. We then generate Rayleigh wave group velocity maps which we present here. We find low velocity regions beneath the Vatnajökull icecap which are bounded by the surface expression of the volcanic rift systems. The lower velocities also extend north-west to the volcanic system under the Hofsjökull ice cap, and northwards towards Askja and the volcanic systems of the northern volcanic zone. We also produce locations and focal mechanisms of earthquakes caused by magmatic and hydrothermal activity to correlate structure with the activity of the volcanic systems.

Widespread Neogene and Quaternary Volcanism on Central Kerguelen Plateau, Southern Indian Ocean

NASA Astrophysics Data System (ADS)

Duncan, R. A.; Falloon, T.; Quilty, P. G.; Coffin, M. F.

2016-12-01

We report new age determinations and compositions for rocks from 18 dredge hauls collected from eight submarine areas across Central Kerguelen Plateau (CKP). Sea knolls and volcanic fields with multiple small cones were targeted over a 125,000 km2 region that includes Heard and McDonald islands. Large early Miocene (16-22 Ma) sea knolls rise from the western margin of the CKP and are part of a NNW-SSE line of volcanic centers that lie between Îles Kerguelen and Heard and McDonald islands. A second group of large sea knolls is aligned E-W across the center of this region. We see evidence of much younger activity (5 Ma to present) in volcanic fields to the north of, and up to 300 km NE of Heard Island. Compositions include basanite, basalt, and trachybasalt, that are broadly similar to plateau lava flows from nearby Ocean Drilling Program (ODP) Site 1138, lower Miocene lavas at Îles Kerguelen, dredged rocks from the early Miocene sea knolls, and Big Ben lavas from Heard Island. Geochemical data indicate decreasing fractions of mantle source melting with time. The western line of sea knolls has been related to hotspot activity now underlying the Heard Island area. In view of the now recognized much larger area of young volcanic activity, we propose that a broad region of CKP became volcanically active in Neogene time due to incubation of plume material at the base of the relatively stationary overlying plateau. The presence of pre-existing crustal faults promotes access for melts from the Heard mantle plume to rise to the surface.

The Quaternary and Pliocene Yellowstone Plateau volcanic field of Wyoming, Idaho, and Montana

USGS Publications Warehouse

Christiansen, Robert L.

2001-01-01

This region of Yellowstone National Park has been the active focus of one of the Earth's largest magmatic systems for more than 2 million years. The resulting volcanism has been characterized by the eruption of voluminous rhyolites and subordinate basalts but virtually no lavas of intermediate composition. The magmatic system at depth remains active and drives the massive hydrothermal circulation for which the park is widely known. Studies of the volcanic field using geologic mapping and petrology have defined three major cycles of rhyolitic volcanism, each climaxed by the eruption of a rhyolitic ash-flow sheet having a volume of hundreds of thousands of cubic kilometers. The field also has been analyzed in terms of its magmatic and tectonic evolution, including its regional relation to the Snake River plain and to basin-range tectonic extension.

Noachian Faulting: What Do Faults Tell Us About the Tectonic History of Tharsis?

NASA Technical Reports Server (NTRS)

Anderson, R. C.; Dohm, J. M.

2001-01-01

The western hemisphere of Mars is dominated by the formation of Tharsis, which is an enormous high-standing region (roughly 25% of the surface area of the planet) capped by volcanics, including the solar system's largest shield volcanoes. Tharsis is surrounded by an enormous radiating system of grabens and a circumferential system of wrinkle ridges that extends over the entire western hemisphere of Mars. This region is perhaps the largest and most long lived tectonic and volcanic province of any of the terrestrial planets with a well-preserved history of magmatic-driven activity that began in the Noachian and has lasted throughout Martian geologic time. Tharsis and the surrounding regions comprise numerous components, including volcanic constructs of varying sizes and extensive lava flow fields, large igneous plateaus, fault and ridge systems of varying extent and relative age of formation, gigantic outflow channel systems, vast system of canyons, and local and regional centers of tectonic activity. Many of these centers are interpreted to be the result of magmatic-related activity, including uplift, faulting, dike emplacement, volcanism, and local hydrothermal activity. Below we present a summary of our work for Tharsis focusing primarily on the earliest stage of development, the Noachian period. Here we hone in on the early centers and how they relate to the early development of the Tharsis Magmatic Complex (TMC).

New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

NASA Astrophysics Data System (ADS)

Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.

2009-04-01

The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional earthquakes. It can be interpreted as the magmatic response to a change of the distribution of tectonic stress in the edifice before the earthquake. In the light of this hypothesis, we surmise that the magmatic system behaved similar to a dilatometer and promise news lines to forecasting the volcano activity. References M. Tárraga, R. Carniel, R. Ortiz, J. M. Marrero, and A. García, 2006. On the predictability of volcano.tectonic events by low frequency seismic noise analysis at Teide-Pico Viejo volcanic complex, Canary Islands. Nat. Hazards Earth Syst. Sci., 6, 365-376. Ortiz, R., H. Moreno, A. García, G. Fuentealba, M. Astiz, P. Peña, N. Sánchez, M. Tárraga, 2003. Villarrica volcano (Chile): characteristics of the volcanic tremor and forecasting of small explosions by means of a material failure method. J. Volcanol. Geotherm. Res. 128: 247-259. B. Voight, 1988. A method for prediction of volcanic eruptions. Nature 332, 10:125-130.

Steam explosions, earthquakes, and volcanic eruptions -- what's in Yellowstone's future?

USGS Publications Warehouse

Lowenstern, Jacob B.; Christiansen, Robert L.; Smith, Robert B.; Morgan, Lisa A.; Heasler, Henry

2005-01-01

Yellowstone, one of the world?s largest active volcanic systems, has produced several giant volcanic eruptions in the past few million years, as well as many smaller eruptions and steam explosions. Although no eruptions of lava or volcanic ash have occurred for many thousands of years, future eruptions are likely. In the next few hundred years, hazards will most probably be limited to ongoing geyser and hot-spring activity, occasional steam explosions, and moderate to large earthquakes. To better understand Yellowstone?s volcano and earthquake hazards and to help protect the public, the U.S. Geological Survey, the University of Utah, and Yellowstone National Park formed the Yellowstone Volcano Observatory, which continuously monitors activity in the region.

Active and Recent Volcanism and Hydrogeothermal Activity on Mars

NASA Astrophysics Data System (ADS)

Edgett, Kenneth S.; Cantor, B. A.; Harrison, T. N.; Kennedy, M. R.; Lipkaman, L. J.; Malin, M. C.; Posiolova, L. V.; Shean, D. E.

2010-10-01

There are no active volcanoes or geysers on Mars today, nor in the very recent past. Since 1997, we have sought evidence from targeted narrow angle camera images and daily, global wide angle images for active or very recent (decades to < 10 Ma) volcanism or hydrogeothermal events on Mars. Despite > 11 years of daily global imaging and coverage of > 60% of Mars at ≤ 6 m/pixel (with the remaining < 40% largely outside of volcanic regions), we have found no such evidence, although one lava field in Aeolis (5°N, 220°W) stands out as possibly the site of the most recent volcanism. Authors of impact crater size-frequency studies suggest some volcanic landforms on Mars are as young as tens to hundreds of Ma. This interpreted youth has implications for understanding the internal geophysical state of Mars and has encouraged those seeking sources for trace gases (methane) in the atmosphere and those seeking "warm havens for life” (Jakosky 1996, New Scientist 150, 38-42). We targeted thousands of Mars Global Surveyor (MGS) MOC and Mars Reconnaissance Orbiter (MRO) CTX (and HiRISE) images to examine volcanic regions; we also studied every MGS MOC and MRO MARCI wide angle image. For evidence of active volcanism, we sought eruption plumes, new vents, new tephra deposits, and new volcanogenic flows not observed in earlier images. For recent volcanism, we sought volcanogenic flows with zero or few superposed impact craters and minimal regolith development or superposed eolian sediment. Targets included all volcanic landforms identified in research papers as "recent” as well as areas speculated to have exhibited eruptive plumes. An independent search for endogenic heat sources, a key Mars Odyssey THEMIS objective, has also not produced a positive result (Christensen et al. 2005, P24A-01, Eos, Trans. Am. Geophys. Union 86/52).

"Mediterranean volcanoes vs. chain volcanoes in the Carpathians"

NASA Astrophysics Data System (ADS)

Chivarean, Radu

2017-04-01

Volcanoes have always represent an attractive subject for students. Europe has a small number of volcanoes and Romania has none active ones. The curricula is poor in the study of volcanoes. We want to make a parallel between the Mediterranean active volcanoes and the old extinct ones in the Oriental Carpathians. We made an comparison of the two regions in what concerns their genesis, space and time distribution, the specific relief and the impact in the landscape, consequences of their activities, etc… The most of the Mediterranean volcanoes are in Italy, in the peninsula in Napoli's area - Vezuviu, Campi Flegrei, Puzzoli, volcanic islands in Tirenian Sea - Ischia, Aeolian Islands, Sicily - Etna and Pantelleria Island. Santorini is located in Aegean Sea - Greece. Between Sicily and Tunisia there are 13 underwater volcanoes. The island called Vulcano, it has an active volcano, and it is the origin of the word. Every volcano in the world is named after this island, just north of Sicily. Vulcano is the southernmost of the 7 main Aeolian Islands, all volcanic in origin, which together form a small island arc. The cause of the volcanoes appears to be a combination of an old subduction event and tectonic fault lines. They can be considered as the origin of the science of volcanology. The volcanism of the Carpathian region is part of the extensive volcanic activity in the Mediterranean and surrounding regions. The Carpathian Neogene/Quaternary volcanic arc is naturally subdivided into six geographically distinct segments: Oas, Gutai, Tibles, Calimani, Gurghiu and Harghita. It is located roughly between the Carpathian thrust-and-fold arc to the east and the Transylvanian Basin to the west. It formed as a result of the convergence between two plate fragments, the Transylvanian micro-plate and the Eurasian plate. Volcanic edifices are typical medium-sized andesitic composite volcanoes, some of them attaining the caldera stage, complicated by submittal or peripheral domes or dome complexes. Dacitic volcanoes are smaller in size and consist of lava dome complexes, in places with associated pyroclastic cones and volcanic aprons. The volcanic history of Carpathian volcanic chain lasts since ca. 15 Ma, with the youngest occurring in the southern chain-terminus; the last eruption of Ciomadu volcano (Harghita) was ca. 10000 years ago. Using the knowledge acquired during the compulsory curriculum and complementary activities we we consider that the outdoor education is the best way to establish a relationship between the theory and the landscape reality in the field. As a follow up to our theoretical approach for the Earth's crust we organized two study trips in our region. During the first one the students could walk in a real crater, see scoria deposits and admire the basalt columns from Racos. In the second activity they could climb the Ciomadu volcano and go down to observe the crater lake St. Anna, the single volcanic lake in central Europe.

Volcanism and associated hazards: the Andean perspective

NASA Astrophysics Data System (ADS)

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 (<0.05 km3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

Volcanism and associated hazards: The Andean perspective

USGS Publications Warehouse

Tilling, R.I.

2009-01-01

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 (<0.05 km 3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and Peru has spurred significant improvements in reducing volcano risk in the Andean region. But much remains to be done.

Preliminary volcanic hazards evaluation for Los Alamos National Laboratory Facilities and Operations : current state of knowledge and proposed path forward

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keating, Gordon N.; Schultz-Fellenz, Emily S.; Miller, Elizabeth D.

2010-09-01

The integration of available information on the volcanic history of the region surrounding Los Alamos National Laboratory indicates that the Laboratory is at risk from volcanic hazards. Volcanism in the vicinity of the Laboratory is unlikely within the lifetime of the facility (ca. 50–100 years) but cannot be ruled out. This evaluation provides a preliminary estimate of recurrence rates for volcanic activity. If further assessment of the hazard is deemed beneficial to reduce risk uncertainty, the next step would be to convene a formal probabilistic volcanic hazards assessment.

Global scale concentrations of volcanic activity on Venus: A summary of three 23rd Lunar and Planetary Science Conference abstracts. 1: Venus volcanism: Global distribution and classification from Magellan data. 2: A major global-scale concentration of volcanic activity in the Beta-Atla-Themis region of Venus. 3: Two global concentrations of volcanism on Venus: Geologic associations and implications for global pattern of upwelling and downwelling

NASA Technical Reports Server (NTRS)

Crumpler, L. S.; Aubele, Jayne C.; Head, James W.; Guest, J.; Saunders, R. S.

1992-01-01

As part of the analysis of data from the Magellan Mission, we have compiled a global survey of the location, dimensions, and subsidiary notes of all identified volcanic features on Venus. More than 90 percent of the surface area was examined and the final catalog comprehensively identifies 1548 individual volcanic features larger than approximately 20 km in diameter. Volcanic features included are large volcanoes, intermediate volcanoes, fields of small shield volcanoes, calderas, large lava channels, and lava floods as well as unusual features first noted on Venus such as coronae, arachnoids, and novae.

Evidence of recent deep magmatic activity at Cerro Bravo-Cerro Machín volcanic complex, central Colombia. Implications for future volcanic activity at Nevado del Ruiz, Cerro Machín and other volcanoes

NASA Astrophysics Data System (ADS)

Londono, John Makario

2016-09-01

In the last nine years (2007-2015), the Cerro Bravo-Cerro Machín volcanic complex (CBCMVC), located in central Colombia, has experienced many changes in volcanic activity. In particular at Nevado del Ruiz volcano (NRV), Cerro Machin volcano (CMV) and Cerro Bravo (CBV) volcano. The recent activity of NRV, as well as increasing seismic activity at other volcanic centers of the CBCMVC, were preceded by notable changes in various geophysical and geochemical parameters, that suggests renewed magmatic activity is occurring at the volcanic complex. The onset of this activity started with seismicity located west of the volcanic complex, followed by seismicity at CBV and CMV. Later in 2010, strong seismicity was observed at NRV, with two small eruptions in 2012. After that, seismicity has been observed intermittently at other volcanic centers such as Santa Isabel, Cerro España, Paramillo de Santa Rosa, Quindío and Tolima volcanoes, which persists until today. Local deformation was observed from 2007 at NRV, followed by possible regional deformation at various volcanic centers between 2011 and 2013. In 2008, an increase in CO2 and Radon in soil was observed at CBV, followed by a change in helium isotopes at CMV between 2009 and 2011. Moreover, SO2 showed an increase from 2010 at NRV, with values remaining high until the present. These observations suggest that renewed magmatic activity is currently occurring at CBCMVC. NRV shows changes in its activity that may be related to this new magmatic activity. NRV is currently exhibiting the most activity of any volcano in the CBCMVC, which may be due to it being the only open volcanic system at this time. This suggests that over the coming years, there is a high probability of new unrest or an increase in volcanic activity of other volcanoes of the CBCMVC.

Epithermal gold-siver deposits in the western United States: time-space products of evolving plutonic, volcanic and tectonic environments

USGS Publications Warehouse

Berger, Byron R.; Bonham, Harold F.

1990-01-01

The western United States has been the locus of considerable subaerial volcanic and plutonic igneous activity since the mid-Mesozoic. After the destruction of the Jurassic-Cretaceous magmatic arc-trench system, subduction was re-established in the Late Mesozoic with low-angle underthrusting of the oceanic plate beneath western North America. This resulted in crustal shortening during the Late Cretaceous to Early Tertiary and removal of the mantle lithosphere west of the Rocky Mountains. Commencing in the Eocene, flat subduction ceased, the volcanic arc began to re-establish itself along the continental margin, and the hingeline along the steepening subducting plate migrated from east to west. The crust east of the migrating hingeline was exposed to hot asthenosphere, and widespread tectonics and volcanic activity resulted. Hydrothermal activity accompanied the volcanism resulting in numerous epithermal gold-silver deposits. The temporal and spatial distributions of epithermal deposits in the region are therefore systematic and can be subdivided into discrete time intervals which are related to widespread changes in magmatic activity. Time intervals selected for discussion are Pre-Cenozoic, 66-55 Ma, 54-43 Ma, 42-34 Ma, 33-24 Ma, 23-17 Ma, and <17 Ma. Many of these intervals contain both sedimentary-rock and two varieties of volcanic-rock hosted deposits (adularia-sericite and alunite-kaolinite ± pyrophyllite). Continental rifting is important to the formation of deposits, and, within any given region, it is at the initiation of deep rifting that alunite-kaolinite ± pyrophyllite type epithermal deposits are formed. Adularia-sericite type deposits are most common, being related to all compositions and styles of volcanic activity. Therefore, the volcano-tectonic context of the western United States provides a unified framework in which to understand and explore for epithermal type deposits.

Planetary Volcanism

NASA Technical Reports Server (NTRS)

Antonenko, I.; Head, J. W.; Pieters, C. W.

1998-01-01

The final report consists of 10 journal articles concerning Planetary Volcanism. The articles discuss the following topics: (1) lunar stratigraphy; (2) cryptomare thickness measurements; (3) spherical harmonic spectra; (4) late stage activity of volcanoes on Venus; (5) stresses and calderas on Mars; (6) magma reservoir failure; (7) lunar mare basalt volcanism; (8) impact and volcanic glasses in the 79001/2 Core; (9) geology of the lunar regional dark mantle deposits; and (10) factors controlling the depths and sizes of magma reservoirs in Martian volcanoes.

Mainshock-Aftershocks Clustering Detection in Volcanic Regions

NASA Astrophysics Data System (ADS)

Garza Giron, R.; Brodsky, E. E.; Prejean, S. G.

2017-12-01

Crustal earthquakes tend to break their general Poissonean process behavior by gathering into two main kinds of seismic bursts: swarms and mainshock-aftershocks sequences. The former is commonly related to volcanic or geothermal processes whereas the latter is a characteristic feature of tectonically driven seismicity. We explore the mainshock-aftershock clustering behavior of different active volcanic regions in Japan and its comparison to non-volcanic regions. We find that aftershock production in volcanoes shows mainshock-aftershocks clustering similar to what is observed in non-volcanic areas. The ratio of volanic areas that cluster in mainshock-aftershocks sequences vs the areas that do not is comparable to the ratio of non-volcanic regions that show clustering vs the ones that do not. Furthermore, the level of production of aftershocks for most volcanic areas where clustering is present seems to be of the same order of magnitude, or slightly higher, as the median of the non-volcanic regions. An interesting example of highly aftershock-productive volcanoes emerges from the 2000 Miyakejima dike intrusion. A big seismic cluster started to build up rapidly in the south-west flank of Miyakejima to later propagate to the north-west towards the Kozushima and Niijima volcanoes. In Miyakejima the seismicity showed a swarm-like signature with a constant earthquake rate, whereas Kozushima and Niijima both had expressions of highly productive mainshock-aftershocks sequences. These findings are surprising given the alternative mechanisms available in volcanic systems for releasing deviatoric strain. We speculate that aftershock behavior might hold a relationship with the rheological properties of the rocks of each system and with the capacity of a system to accumulate or release the internal pressures caused by magmatic or hydrothermal systems.

Volcanic Eruptions in Kamchatka

NASA Image and Video Library

2007-04-30

One of the most volcanically active regions of the world is the Kamchatka Peninsula in eastern Siberia, Russia. It is not uncommon for several volcanoes to be erupting at the same time. NASA Terra satellite acquired this image on April 26, 2007

A model for tropical-extratropical transport of volcanic ash in the lower stratosphere

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1993-01-01

Large nonspherical volcanic ash particles up to 30 micrometer in size were collected between 17-19 km altitude over the Northern Hemisphere at high latitudes between October 1988 and April 1990. These particles may be derived from minor Plinian eruptions in the tropics rather than from localized volcanic activity close to the collection region. Ash particles were injected into the lower equatorial stratosphere where they entered a regime of efficient transport just above the tropopause from the tropical region towards the northern extratropical region. Transport is enhanced by stable autorotation that generates a sufficient lift force to loft nonspherical ash with a rough surface during transport, and by the gradually decreasing altitude of the tropopause from the tropics to the polar regions.

Kasei Vallis of Mars: Dating the Interplay of Tectonics and Geomorphology

NASA Technical Reports Server (NTRS)

Wise, D. U.

1985-01-01

Crater density age dates on more than 250 small geomorphic surfaces in the Kasei Region of Mars show clusterings indicative of times of peak geomorphic and tectonic activity. Kasei Vallis is part of a 300 km wide channel system breaching a N-S trending ancient basement high (+50,000 crater age) separating the Chryse Basin from the Tharsis Volcanic Province of Mars. The basement high was covered by a least 3 groups of probable volcanic deposits. Major regional fracturing took place at age 4,000 to 5,000 and was immediately followed by deposition of regional volcanics of the Fesenkov Plains (age 3,000 to 4,200). Younger clusterings of dates in the 900 to 1,500 and 500 to 700 range represent only minor modification of the basic tectonic geomorphic landform. The data suggest that Kasei gap is a structurally controlled breach of a buried ridge by a rather brief episode of fluvial activity.

Regional Triggering of Volcanic Activity Following Large Magnitude Earthquakes

NASA Astrophysics Data System (ADS)

Hill-Butler, Charley; Blackett, Matthew; Wright, Robert

2015-04-01

There are numerous reports of a spatial and temporal link between volcanic activity and high magnitude seismic events. In fact, since 1950, all large magnitude earthquakes have been followed by volcanic eruptions in the following year - 1952 Kamchatka M9.2, 1960 Chile M9.5, 1964 Alaska M9.2, 2004 & 2005 Sumatra-Andaman M9.3 & M8.7 and 2011 Japan M9.0. While at a global scale, 56% of all large earthquakes (M≥8.0) in the 21st century were followed by increases in thermal activity. The most significant change in volcanic activity occurred between December 2004 and April 2005 following the M9.1 December 2004 earthquake after which new eruptions were detected at 10 volcanoes and global volcanic flux doubled over 52 days (Hill-Butler et al. 2014). The ability to determine a volcano's activity or 'response', however, has resulted in a number of disparities with <50% of all volcanoes being monitored by ground-based instruments. The advent of satellite remote sensing for volcanology has, therefore, provided researchers with an opportunity to quantify the timing, magnitude and character of volcanic events. Using data acquired from the MODVOLC algorithm, this research examines a globally comparable database of satellite-derived radiant flux alongside USGS NEIC data to identify changes in volcanic activity following an earthquake, February 2000 - December 2012. Using an estimate of background temperature obtained from the MODIS Land Surface Temperature (LST) product (Wright et al. 2014), thermal radiance was converted to radiant flux following the method of Kaufman et al. (1998). The resulting heat flux inventory was then compared to all seismic events (M≥6.0) within 1000 km of each volcano to evaluate if changes in volcanic heat flux correlate with regional earthquakes. This presentation will first identify relationships at the temporal and spatial scale, more complex relationships obtained by machine learning algorithms will then be examined to establish favourable conditions for response and gauge the effect of each variable on the relationship between earthquakes and volcanic activity. Finally, a volcanic forecast model will be assessed to evaluate the use of earthquakes as a precursory indicator to volcanic activity. If proven, the relationship between earthquakes and volcanic activity has the potential to aid our understanding of the conditions that influence triggering following an earthquake and provide vital clues for volcanic activity prediction and the identification of precursors. Hill-Butler, C.; Blackett, M.; Wright, R. and Trodd, N. (2014) Global Heat Flux Response to Large Earthquakes in the 21st Century. Geology in preparation. Kaufman, Y. J.; Justice, C.; Flynn, L.; Kendall, J.; Prins, E.; Ward, D. E.; Menzel, P. and Setzer, A. (1998) Monitoring Global Fires from EOS-MODIS. Journal of Geophysical Research 103, 32,215-32,238 Wright, R.; Blackett, M. and Hill-Butler, C. (2014) Some observations regarding the thermal flux from Earth's erupting volcanoes for the period 2000 to 2014. Geophysical Research Letters in review.

Episodic Cenozoic volcanism and tectonism in the Andes of Peru

USGS Publications Warehouse

Noble, D.C.; McKee, E.H.; Farrar, E.; Petersen, U.

1974-01-01

Radiometric and geologic information indicate a complex history of Cenozoic volcanism and tectonism in the central Andes. K-Ar ages on silicic pyroclastic rocks demonstrate major volcanic activity in central and southern Peru, northern Chile, and adjacent areas during the Early and Middle Miocene, and provide additional evidence for volcanism during the Late Eocene. A provisional outline of tectonic and volcanic events in the Peruvian Andes during the Cenozoic includes: one or more pulses of igneous activity and intense deformation during the Paleocene and Eocene; a period of quiescence, lasting most of Oligocene time; reinception of tectonism and volcanism at the beginning of the Miocene; and a major pulse of deformation in the Middle Miocene accompanied and followed through the Pliocene by intense volcanism and plutonism. Reinception of igneous activity and tectonism at about the Oligocene-Miocene boundary, a feature recognized in other circum-Pacific regions, may reflect an increase in the rate of rotation of the Pacific plate relative to fixed or quasifixed mantle coordinates. Middle Miocene tectonism and latest Tertiary volcanism correlates with and probably is genetically related to the beginning of very rapid spreading at the East Pacific Rise. ?? 1974.

Geologic map of the Lassen region, Cascade Range, USA

USGS Publications Warehouse

Clynne, Michael; Muffler, L.J.

1990-01-01

A preliminary geologic map at 1:50,000 of the Lassen region encompasses 1400 km2. The map displays many small, monogenetic volcanoes of basalt to andesite as well as three major late Pliocene and Quaternary volcanic centers that have erupted products ranging from basaltic andesite to rhyolite. The youngest of these volcanic centers is the Lassen volcanic center, active from 600,000 years B.P. to the present. A major caldera formed at 400,000 years B.P. and has subsequently been filled with silicic lavas. The Lassen geothermal system, which consists of a central vapor-dominated reservoir at a temperature of 235??C underlain by a reservoir of hot water, is centered at Bumpass Hell within Lassen Volcanic National Park.

Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

USGS Publications Warehouse

Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

2011-01-01

Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

Volcanic Ashes Intercalated with Cultural Vestiges at Archaeological Sites from the Piedmont to the Amazon, Ecuador

NASA Astrophysics Data System (ADS)

Valverde, Viviana; Mothes, Patricia; Andrade, Daniel

2014-05-01

A mineralogical analysis was done on 70 volcanic ashes; 9 corresponding to proximal samples of seven volcanoes: Cotopaxi (4500 yBP), Guagua Pichincha (3300 yBP, 1000 yBP and 1660 yAD), Cuicocha (3100 yBP), Pululahua (2400 yBP), Ninahuilca (2350 yBP and 4600 yBP) and 61 to distal ashes collected at eight archaeological sites in the Coastal, Sierra and Amazon regions of Ecuador. Cultural vestiges are from Pre-ceramic, Formative, Regional Development and Integration periods, with the exception of a site denominated Hacienda Malqui, which also has Inca vestiges. The sampling process was done in collaboration with various archaeologists in 2011-2013. The volcanic ashes were washed, dried and divided in order to obtain a representative fraction and their later analysis with binocular microscope. The microscope analysis allowed determination of the characteristics of each component of volcanic ash. These main elements are: pumice fragments, minerals, volcanic glass, lithics and exogenous material (non volcanic). The petrographic analysis of distal volcanic ash layers at each archaeological site was correlated by their components and characteristics with proximal volcanic ashes of source volcanoes. Some correlations permitted obtaining a relative age for the layers of distal volcanic ash in the archaeological sites. The petrographic analysis showed a correlation between the archaeological sites of Las Mercedes - Los Naranjos, Rumipamba and El Condado (located west of Quito) with the eruptive activity of Guagua Pichincha volcano (3300 yBP, 1000 yBP and 1660 yAD) and Pululahua volcano (2400 yBP). Also, a correlation with eruptive activity of Ninahuilca (2350 yBP), Cotopaxi (4500 yBP) and Quilotoa (800 yBP) volcanoes at Hda. Malqui (60 km west of Latacunga) was provided by mineralogy of the respective ashes expulsed by these volcanoes. The ash layers at Cuyuja (50 km east of Quito) are mostly superficial; they are associated with Quilotoa's 800 yBP plinian. Finally at the Huapula and Pablo VI sites (in the western Amazon region of Ecuador), the reworked ashes are predominantly of Sangay volcano (in permanent eruptive activity since 1628). Finally, the work shared between archaeologists and volcanologists allowed us to discover more deposits of volcanic ashes at archaeological sites. These layers sometimes have more than 30 cm thickness in distal regions, such as the thick ash layer left by Pululahua's 2400 yBP eruption, a fact which helps us to comprehend the impact of volcanoes on past cultures.

Time-space mapping of Easter Chain volcanism

NASA Astrophysics Data System (ADS)

O'Connor, John M.; Stoffers, Peter; McWilliams, Michael O.

1995-12-01

New 40Ar/ 39Ar and published K sbnd Ar ages show that the locus of volcanism along the Easter Volcanic Chain (EVC) has shifted systematically from the Nazca Ridge, at about 26 m.y., to the recently active Sala y Gomez Island/Easter Island region. This indicates a plume rather than a hotline (i.e., mantle roll) origin for the EVC. The time-space distribution of ages, combined with published ages for the Galapagos and Juan Fernandez volcanic chains, is used to reconstruct Nazca plate velocities over the past 26 m.y. A plume now located in the region of Sala y Gomez Island is most compatible with these data. West of the plume, the EVC records neither Nazca nor Pacific plate motions. This section of the EVC may be related to westward channeling of plume material to the Pacific-Nazca spreading boundary region.

Analysis of radar images of the active volcanic zone at Krafla, Iceland: The effects of look azimuth biasing

NASA Technical Reports Server (NTRS)

Garvin, J. B.; Williams, R. S., Jr.

1989-01-01

The geomorphic expression of Mid-Ocean-Ridge (MOR) volcanism in a subaerial setting occurs uniquely on Earth in Iceland, and the most recent MOR eruptive activity has been concentrated in the Northeastern Volcanic Zone in an area known as Krafla. Within the Krafla region are many of the key morphologic elements of MOR-related basaltic volcanism, as well as volcanic explosion craters, subglacial lava shields, tectonic fissure swarms known as gjar, and basaltic-andesite flows with well developed ogives (pressure-ridges). The objective was to quantify the degree to which the basic volcanic and structural features can be mapped from directional SAR imagery as a function of the look azimuth. To accomplish this, the current expression of volcanic and tectonic constructs was independently mapped within the Krafla region on the E, W, and N-looking SAR images, as well as from SPOT Panchromatic imagery acquired in 1987. The initial observations of the E, W, and N images indicates that fresh a'a lava surfaces are extremely radar bright (rough at 3 cm to meter scales) independent of look direction; this suggests that these flows do not have strong flow direction related structures at meter and cm scales, which is consistent with typical Icelandic a'a lava surfaces in general. The basic impression from a preliminary analysis of the effects of look azimuth biasing on interpretation of the geology of an active MOR volcanic zone is that up to 30 percent of the diagnostic features can be missed at any given look direction, but that having two orthogonal look direction images is probably sufficient to prevent gross misinterpretation.

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

NASA Technical Reports Server (NTRS)

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

2017-01-01

Volcanic eruptions represent a significant source of atmospheric aerosols and can display local, regional and global effects, impacting earth systems and human populations. In order to assess the relative impacts of these events, accurate plume injection altitude measurements are needed. In this work, volcanic plumes generated from seven Kamchatka Peninsula volcanoes (Shiveluch, Kliuchevskoi, Bezymianny, Tolbachik, Kizimen, Karymsky and Zhupanovsky), were identified using over 16 years of Multi-angle Imaging SpectroRadimeter (MISR) measurements. Eighty-eight volcanic plumes were observed by MISR, capturing 3-25% of reported events at individual volcanoes. Retrievals were most successful where high intensity events persisted over a period of weeks to months. Compared with existing ground and airborne observations, and alternative satellite-based reports compiled by the Global Volcanism Program (GVP), MISR plume height retrievals showed general consistency; the comparison reports appear to be skewed towards the region of highest concentration observed in MISR-constrained vertical plume extent. The report observations display less discrepancy with MISR toward the end of the analysis period, with improvements in the suborbital data likely the result of the deployment of new instrumentation. Conversely, the general consistency of MISR plume heights with conventionally reported observations supports the use of MISR in the ongoing assessment of volcanic activity globally, especially where other types of volcanic plume observations are unavailable. Differences between the northern (Shiveluch, Kliuchevskoi, Bezymianny and Tolbachik) and southern (Kizimen, Karymsky and Zhupanovsky) volcanoes broadly correspond to the Central Kamchatka Depression (CKD) and Eastern Volcanic Front (EVF), respectively, geological sub-regions of Kamchatka distinguished by varying magma composition. For example, by comparison with reanalysis-model simulations of local meteorological conditions, CKD plumes generally were less constrained by mid-tropospheric (< 6 km) layers of vertical stability above the boundary layer, suggesting that these eruptions were more energetic than those in the EVF

A field trip guide to the petrology of Quaternary volcanism on the Yellowstone Plateau

USGS Publications Warehouse

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

2017-12-19

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

A volcanic wind-stress origin of the Atlantic Multidecadal Oscillation

NASA Astrophysics Data System (ADS)

Birkel, S. D.; Mayewski, P. A.; Maasch, K. A.; Auger, J.; Lyon, B.

2016-12-01

The Atlantic Multidecadal Oscillation (AMO) is a mode of sea-surface temperature (SST) variability in the North Atlantic that has significant impact on global climate. Most previous studies ascribe the origin of the AMO to oceanic mechanisms, and suggest only a limited role for the atmosphere. Here, we suggest that the AMO is manifested from basin-wide changes in surface wind stress that arise in response to episodic volcanic activity. Our interpretation is based on historical SST, reanalysis, and stratospheric aerosol optical thickness data, wherein it is evident that cool (warm) intervals of the AMO coincide with emergence of strong (weak) winds and high (low) volcanic activity. We find that SST excursions ultimately develop from atmospheric forcing as volcanic events project onto the North Atlantic Oscillation (NAO). A volcanic signature is particularly evident beneath the westerlies in the subpolar region south of Greenland, where several large SST excursions occur coincident with identifiable major eruptions. High latitude surface waters cool when NAO+ circulation, which includes a deepened Icelandic Low, draws cold flow out of the Labrador Sea and into the subpolar region. Important feedbacks that cause SST anomalies to spread across the basin include cloud cover, wind-driven upwelling, and entrainment of Saharan dust into the tropical easterlies. Finally, we speculate that cooling in the North Atlantic observed since 2011 could be linked to renewed volcanic activity over Iceland, namely from the eruptions of Grímsvötn (2011) and Bárðarbunga (2014). An important question remains how North Atlantic SST variability will evolve as atmospheric circulation becomes increasingly modified by human activity.

A 150-ka-long record for the volcano-tectonic deformation of Central Anatolian Volcanic Province

NASA Astrophysics Data System (ADS)

Karabacak, Volkan; Tonguç Uysal, I.; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin

2017-04-01

The Anatolian Block represents one of the most outstanding examples of intra-plate deformation related to continental collision. Deformation related to the convergence of the Afro-Arabian continent toward north gives rise to widespread and intense arc volcanism in the Central Anatolia. All the usual studies on dating the volcano-tectonic deformation of the region are performed entirely on volcanic events of the geological record resulted in eruptions. However, without volcanic eruption, magma migration and related fluid pressurization also generate crustal deformation. In the current study has been funded by the Scientific and Technological Research Council of Turkey with the project no. 115Y497, we focused on fracture systems and their carbonate veins around the Ihlara Valley (Cappadocia) surrounded by well-known volcanic centers with latest activities of the southern Central Anatolian Volcanic Province. We dated 37 samples using the Uranium-series technique and analyzed their isotope systematics from fissure veins, which are thought to be controlled by the young volcanism in the region. Our detailed fracture analyses in the field show that there is a regional dilatation as a result of a NW-SE striking extension which is consistent with the results of recent GPS studies. The Uranium-series results indicate that fracture development and associated carbonate vein deposition occurred in the last 150 ka. Carbon and oxygen isotope systematics have almost remained unchanged in the studied time interval. Although veins in the region were precipitated from fluids primarily of meteoric origin, fluids originating from water-rock interaction also contribute for the deposition of carbonate veins. The age distribution indicates that the crustal deformation intensified during 7 different period at about 4.7, 34, 44, 52, 83, 91, 149 ka BP. Four of these periods (4.7, 34, 91, 149 ka BP) correspond to the volcanic activities suggested in the previous studies. The three crustal deformation periods occurred at 44, 52, and 83 ka BP were dated in addition to the known. They are interpreted to have possibly occurred without any eruption in the late Pleistocene and were controlled by magma movements and/or associated fluid pressure. Such crustal deformation controlled by volcanism is dated for the first time in the literature with a sampling other than extrusive material. The obtained age data revealed that crustal deformation linked to the young volcanism in the Central Anatolian Volcanic Province was repeated in short-term strain cycles of 8-10 ka and that the duration of activity lasted approximately 1100 ± 1000 years in each period, possibly triggered fracture development without any eruption in some periods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hochstein, M.P.; Sudarman, Sayogi

There are at least 30 high temperatures systems (with inferred reservoir temperatures > 200 C) along the active Sumatra Arc that transfer heat from crustal intrusions to the surface. These systems, together with eleven active volcanoes, five degassing volcanoes and one caldera volcano (Lake Toba), are controlled by the Sumatra Fault Zone, an active mega shear zone that follows the median axis of the arc. At least half of the active and degassing volcanoes are associated with volcanic geothermal reservoirs containing magmatic gases and acid fluids. Large, low temperature resources exist in the Tertiary sedimentary basins of east Sumatra (back-arcmore » region), where anomalously higher thermal gradients (up to 8 C/100 m) have been measured. Volcanic activity was not continuous during the Cenozoic; subduction and arc volcanism probably decreased after the Eocene as a result of a clockwise rotation of Sumatra. In the Late Miocene, subduction started again, and andesitic volcanism reached a new peak of intensity in the Pliocene and has been continuous ever since. Rhyolitic volcanism, which has produced voluminous ignimbrite flows, began later (Pliocene/Pleistocene). All known rhyolitic centers associated with ignimbrite flows appear to lie along the Sumatra Fault Zone.« less

Magma beneath Yellowstone National Park

USGS Publications Warehouse

Eaton, G.P.; Christiansen, R.L.; Iyer, H.M.; Pitt, A.M.; Mabey, D.R.; Blank, H.R.; Zietz, I.; Gettings, M.E.

1975-01-01

The Yellowstone plateau volcanic field is less than 2 million years old, lies in a region of intense tectonic and hydrothermal activity, and probably has the potential for further volcanic activity. The youngest of three volcanic cycles in the field climaxed 600,000 years ago with a voluminous ashflow eruption and the collapse of two contiguous cauldron blocks. Doming 150,000 years ago, followed by voluminous rhyolitic extrusions as recently as 70,000 years ago, and high convective heat flow at present indicate that the latest phase of volcanism may represent a new magmatic insurgence. These observations, coupled with (i) localized postglacial arcuate faulting beyond the northeast margin of the Yellowstone caldera, (ii) a major gravity low with steep bounding gradients and an amplitude regionally atypical for the elevation of the plateau, (iii) an aeromagnetic low reflecting extensive hydrothermal alteration and possibly indicating the presence of shallow material above its Curie temperature, (iv) only minor shallow seismicity within the caldera (in contrast to a high level of activity in some areas immediately outside), (v) attenuation and change of character of seismic waves crossing the caldera area, and (vi) a strong azimuthal pattern of teleseismic P-wave delays, strongly suggest that a body composed at least partly of magma underlies the region of the rhyolite plateau, including the Tertiary volcanics immediately to its northeast. The Yellowstone field represents the active end of a system of similar volcanic foci that has migrated progressively northeastward for 15 million years along the trace of the eastern Snake River Plain (8). Regional aeromagnetic patterns suggest that this course was guided by the structure of the Precambrian basement. If, as suggested by several investigators (24), the Yellowstone magma body marks a contemporary deep mantle plume, this plume, in its motion relative to the North American plate, would appear to be "navigating" along a fundamental structure in the relatively shallow and brittle lithosphere overhead. The concept that a northeastward-propagating major crustal fracture controls the migration path of the major foci of volcanisim is at least equally favored by existing data, as Smith et al. (19) noted.

A global tectonic activity map with orbital photographic supplement

NASA Technical Reports Server (NTRS)

Lowman, P. D., Jr.

1981-01-01

A three part map showing equatorial and polar regions was compiled showing tectonic and volcanic activity of the past one million years, including the present. Features shown include actively spreading ridges, spreading rates, major active faults, subduction zones, well defined plates, and volcanic areas active within the past one million years. Activity within this period was inferred from seismicity (instrumental and historic), physiography, and published literature. The tectonic activity map was used for planning global geodetic programs of satellite laser ranging and very long base line interferometry and for geologic education.

Volcanology and mineral deposits

USGS Publications Warehouse

Lipman, P.W.

1990-01-01

In contrast, old volcanic regions, which host many of the world's major hydrothermal-vein, porphyry, and massive-sulfide ore deposits, have been studied mainly by economic geologists, regional stratigraphers, and structural geologists who have limited familiarity with the complexities of volcanic processes. Such "dead" volcanoes, ranging in age from a few million million years (tertiary) to a few billion years (Precambrian), are commonly incompletely and discontinuously preserved due to rapid erosion of originally high-standing volcanic edifices. They can be difficult to date reliably, especially in terms of the time scales of individual volcanic events, and are variably hydrothermally altered-impeding high-resolution petrologic and geochemical studies. Many volcanologists, geochemists, and geophysicists who work on active volcanoes accordingly have been reluctant to become involved in studies of such less tractable rocks. 

Study of Regional Volcanic Impact on the Middle East and North Africa using high-resolution global and regional models

NASA Astrophysics Data System (ADS)

Osipov, Sergey; Dogar, Mohammad; Stenchikov, Georgiy

2016-04-01

High-latitude winter warming after strong equatorial volcanic eruptions caused by circulation changes associated with the anomalously positive phase of Arctic Oscillation is a subject of active research during recent decade. But severe winter cooling in the Middle East observed after the Mt. Pinatubo eruption of 1991, although recognized, was not thoroughly investigated. These severe regional climate perturbations in the Middle East cannot be explained by solely radiative volcanic cooling, which suggests that a contribution of forced circulation changes could be important and significant. To better understand the mechanisms of the Middle East climate response and evaluate the contributions of dynamic and radiative effects we conducted a comparative study using Geophysical Fluid Dynamics Laboratory global High Resolution Atmospheric Model (HiRAM) with the effectively "regional-model-resolution" of 25-km and the regional Weather Research and Forecasting (WRF) model focusing on the eruption of Mount Pinatubo on June 15, 1991 followed by a pronounced positive phase of the Arctic Oscillation. The WRF model has been configured over the Middle East and North Africa (MENA) region. The WRF code has been modified to interactively account for the radiative effect of volcanic aerosols. Both HiRAM and WRF capture the main features of the MENA climate response and show that in winter the dynamic effects in the Middle East prevail the direct radiative cooling from volcanic aerosols.

An investigation of the distribution of eruptive products on the shield volcanoes of the western Galapagos Islands using remotely sensed data

NASA Technical Reports Server (NTRS)

Munro, Duncan C.; Rowland, Scott K.; Mouginis-Mark, Peter J.; Wilson, Lionel; Oviedo-Perez, Victor-Hugo

1991-01-01

Recent volcanic activity in the Galapagos Islands is concentrated on the two westernmost islands, Isla Isabela and Isla Fernandina. Difficult access has thus far prevented comprehensive geological field studies, so we examine the potential of remotely sensed data as a means of studying volcanic processes in the region. Volcan Wolf is used as an example of the analysis of SPOT HRV-1 data undertaken for each volcano. Landsat TM data are analyzed in an attempt to construct a relative age sequence for the recent eruptive activity on Isla Fernandina. No systematic variation in the surface reflectance of lava flows as a function of age could be detected with these data. Thus it was not possible to complete a study of the temporal distribution of volcanic activity.

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

NASA Astrophysics Data System (ADS)

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

2004-12-01

Observed regional mega-rings define a zone ˜80-100 km in diameter centered on Timber Mountain (TM). The mega-rings encompass known smaller rhyolitic nested Miocene calderas ( ˜11-15 my, < 10 km circular to elliptical small "rings") and later stage basaltic features (< 11 my, small flows, cones, dikes) in the Southwest Nevada Volcanic Field. Miocene rhyolitic calderas cluster within the central area and on the outer margin of the interpreted larger mega-ring complex. The mega-ring interpretation is consistent with observations of regional physiography, tomographic images, seismicity patterns, and structural relationships. Mega-rings consist of arcuate faulted blocks with deformation (some remain active structures) patterns showing a genetic relationship to the TM volcanic system; they appear to be spatially associated and temporally correlated with Miocene volcanism and two geophysically identified crustal/upper mantle features. A 50+ km diameter pipe-like high velocity anomaly extends from crustal depth to over 200 km beneath TM (evidence for 400km depth to NE). The pipe is located between two ˜100 km sub-parallel N/S linear trends of small-magnitude earthquake activity, one extending through the central NV Test Site, and a second located near Beatty, NV. Neither the kinematics nor relational mechanism of 100km seismically active N/S linear zones, pipe, and mega-rings are understood. Interpreted mega-rings are: 1) Similar in size to larger terrestrial volcanic complexes (e.g., Yellowstone, Indonesia's Toba system); 2) Located in the region of structural transition from the Mohave block to the south, N/S Basin and Range features to the north, Walker Lane to the NW, and the Las Vegas Valley shear zone to the SE; 3) Associated with the two seismically active zones (similar to other caldera fault-bounded sags), the mantle high velocity feature, and possibly a regional bouguer gravity anomaly; 4) Nearly coincident with area hydrologic basins and sub-basins; 5) Similar to features described from terrestrial and planetary caldera-collapse studies, and as modeled in laboratory scaled investigations (ice melt, balloon/sand). Post Mid-Miocene basalts commonly occur within or adjacent to the older rhyolitic caldera moats; other basaltic material occurs marginal to both the outer rings of the interpreted mega-ring system and high velocity pipe. The YM repository may be situated in an isolated structural setting within the mega-ring system; basaltic materials are absent in the block for over 11my for geologic reasons. The mega-ring model may better explain YM area structures (Highway 95 fault), tectonism, and volcanism. Coincident physiographic, geologic, and geophysical features associated with the mega-rings feature, and temporal characteristics of regional seismicity and volcanism suggest the need to critically re-assess regional scale and YM tectonic, seismotectonic, and volcanic models.

Do Periodic Plate Reorganisations Control Late-stage Volcanism across a Broad Galápagos Hotspot?

NASA Astrophysics Data System (ADS)

O'Connor, J. M.; Hoernle, K.; Wijbrans, J. R.; Werner, R.; Hauff, S. F.; Stoffers, P.

2010-12-01

Much of the Galápagos Volcanic Province (GVP), consisting of the Cocos, Carnegie, Coiba and Malpelo aseismic ridges and related seamount provinces, remains poorly understood due to a lack of direct age and geochemical data. In recent years reconnaissance dredge/grab sampling of these submerged regions of the GVP provides some new insights that can be re-evaluated in the context of the three new cruises to the region in 2010. The distribution of 40Ar/39Ar basement ages [1-3] suggest that volcanism migrated time-progressively across GVP in broad regions of long-lived, possible concurrent, hotspot volcanism. Development of the GVP via such broad zones of overlapping volcanism leads to multiple phases of volcanism post-dating the onset of hotspot volcanism, similar to rejuvenescent volcanism that occurs million years after the main shield-building phase of mid-plate oceanic volcano, most notably along the Hawaiian-Emperor Seamount Chain. Evidence for rejuvenescent volcanism across the GVP provides an opportunity to evaluate this poorly understood process in a very different physical setting compared to the Hawaiian-Emperor Chain (mid-plate versus on/near spreading axis). Widespread episodes of coeval GVP volcanism show that the Galápagos hotspot influences broad regions of the lithosphere implying relative motion between the Cocos and Nazca plates and a broad Galápagos hotspot. The complex spreading history of the Cocos-Nazca spreading centre likely controlled the relative distribution of GVP volcanism between the Cocos and Nazca plates while creating lithosphere of variable age/thickness across the region [3]. But recent age and geochemical studies of other hotspot systems show that lithosphere influenced in the past by hotspot activity is more likely to generate late-stage volcanism in response to changing patterns of stress in the lithosphere. Late stage volcanism across a broad Galápagos hotspot might therefore reflect periodic reorganisations of the Galápagos spreading centre. [1] Werner, D.R. et al., 1999. A drowned 14-m.y.-old Galápagos Archipelago off the coast of Costa Rica: implications for tectonic and evolutionary models. Geology 27. [2] Werner, D.R. et al., 2003. Geodynamic evolution of the Galápagos hot spot system (Central East Pacific) over the past 20 m.y. Constraints from morphology, geochemistry, and magnetic anomalies. Geochem. Geophys. Geosyst. 4, 1108. [3] O’Connor et al., 2007. Migration of widespread long-lived volcanism across the Galápagos Volcanic Province: Evidence for a broad hotspot melting anomaly? Earth Planet. Sci. Letts. 263.

Evolution of Pleistocene to Holocene eruptions in the Lesser Caucasus Mts:Insights from geology, petrology, geochemistry and geochronology

NASA Astrophysics Data System (ADS)

Savov, Ivan; Meliksetian, Khachatur; Connor, Charles; Karakhanian, Arkadi; Sugden, Patrick; Navasardyan, Gevorg; Halama, Ralf; Ishizuka, Osamu; Connor, Laura; Karapetian, Sergei

2016-04-01

Both effusive and highly explosive (VEI>5) and often voluminous caldera volcanism has developed atop the collision zone between the Arabian and the Eurasian plates. Currently what is exposed on the Anatolian-Armenian-Iranian active orogenic plateau is post-Mesozoic felsic to intermediate collision-related plutons, and mostly collision or post-collision related Quaternary volcanic structures. We have studied in detail the volcanism, tectonics and geophysics on the territory of E.Turkey and Armenia, where several large stratovolcanoes (Ararat, Lesser Ararat, Aragats, Tsghuk, Ishkhanasar) are surrounded by distinct monogenetic volcanic fields (distributed volcanism). These large in volume stratovolcanoes and the associated low volume monogenetic cones range from normal calk-alkaline to high-K shoshonitic in affinity, with their products ranging from basanites to high K trachytes and rhyolites. Several volcanic provinces, namely Kechut/Javakheti, Aragats, Gegham, Vardenis and Syunik are recognized in Armenia and each of them has > 100 mapped volcanoes. These have distinct geochemical (mineral chemistry, trace element and Sr-Nd-B isotope systematics) and petrological (melt eruption temperatures and volatile contents) fingerprints that may or may not vary over time. Age determinations and volcano-stratigraphy sections for each of the case studies we aim to present shows that the volcanism includes a continuous record from Pleistocene to Holocene, or even historical eruptions. The excellent volcano exposures and the now complete high resolution database (GIS), geological mapping, and new and improved K-Ar and Ar-Ar geochronology, uniquely allows us to evaluate the driving forces behind the volcanism in this continent-continent collision setting that is uniquely associated with long lasting eruption episodes. We shall compare the now well studied historical/Holocene eruptions with those pre-dating them, with the aim to identify possible geochemical or petrological precursors, on both local and regional scales. Our presentation will include several case studies, new ages, high resolution maps of many volcanoes and their association with young active faulting and often large earthquakes. We will present one particular high resolution case study (on Aragats volcanic complex) where we attempted to quantify the volcanic hazards. This is important as this region hosts the active Metsamor nuclear power plant and the capital city of Yerevan (population > 1.4 million), where people live in area with very low (10^6), yet existing risk for a renewed volcanic activity.

Regional stratigraphy, sedimentology, and tectonic significance of Oligocene-Miocene sedimentary and volcanic rocks, northern Baja California, Mexico

NASA Astrophysics Data System (ADS)

Dorsey, Rebecca J.; Burns, Beverly

1994-01-01

Upper Oligocene (?) to middle Miocene sedimentary and volcanic rocks in northern Baja California were deposited along the western margin of North America during subduction of the Guadalupe plate and southward migration of the Rivera Triple Junction. Regional mapping and compilation of stratigraphic data reveal a sequence of three regionally traceable stratigraphic units. (1) Oligocene (?) to lower Miocene Mesa Formation: basal quartz-rich fluvial sandstone, grus, conglomerate, and accessory facies, whose detrital compositions reflect the composition of local pre-Tertiary basement rock. (2) Lower to middle Miocene Comondú Formation: laterally variable sequence of volcaniclastic conglomerate, breccia, sandstone, tuff and minor volcanic flow units. (3) Widespread mesa-capping rhyolite tuff, typically welded and crystal-rich, probably upper Miocene in age. The Mesa Formation overlies a highly irregular and deeply dissected erosional surface developed on pre-Tertiary basement rock. The shift from pre-Mesa erosion to widespread (though localized) deposition and valley-filling records the final phase of late Cretaceous to middle Tertiary regional subsidence and eastward transgression that resulted from slow cooling and thermal contraction of Cretaceous arc crust during a temporal gap in magmatic activity along the western Cordilleran margin. Nonmarine sediments of the Mesa Formation were deposited in small, steep-walled paleovalleys and basins that gradually filled and evolved to form through-going, low-energy ephemeral stream systems. The gradational upward transition from the Mesa to Comondú Formation records the early to middle Miocene onset of subduction-related arc magmatism in eastern Baja California and related westward progradation of alluvial volcaniclastic aprons shed from high-standing eruptive volcanic centers. Pre-existing streams were choked with the new influx of volcanic detritus, causing the onset of rapid sediment deposition by stream flows and dilute to viscous sediment gravity flows. Deposits of the Comondú Formation thin and fine systematically westward, from proximal volcanic conglomerate and breccia with thin basalt and andesite flows in the east, to distal volcaniclastic fluvial sandstone in the west. These proximal—distal relationships help to define the location and paleogeography of active arc-flanking volcaniclastic alluvial aprons of the Miocene magmatic arc in northern Baja California. A substantial late Miocene drop in regional base level (relative sea level) is best attributed to regional uplift caused by the renewal of magmatic and thermal activity in northern Baja California, which has continued to the present day.

Regional geochemistry Bandung Quadrangle West Java: for environmental and resources studies

NASA Astrophysics Data System (ADS)

Sendjaja, Purnama; Baharuddin

2017-06-01

Geochemical mapping based on the stream sediment method has been carried out in the whole of Java Region by the Centre for Geological Survey. The Regional Geochemistry Bandung Quadrangle as part of West Java Region has been mapped in 1:100.000 scale map, base on the Geological Map of Bandung Quadrangle. About 82 stream sediment samples collected and sieved in the 80 mesh sieve fraction during the field work session at 2011. This fraction was prepared and analysed for 30 elements by X-ray fluorescence spectrometry at the Centre for Geological Survey Laboratory. There are some elements indicating significant anomaly in this region, and it is important to determine the present abundance and spatial distribution of the elements for presuming result from natural product or derived from human activities. The volcanic products (Tangkuban Perahu Volcano, Volcanic Rock Complex and Quarternary Volcanic-Alluvial Deposit) are clearly identified on the distribution of As, Ba, Cl, Cu, Zr and La elements. However Mn, Zn, V and Sr are related to precipitation in the Tertiary Sediments, while the influence of human activities are showing from a geochemical map of Cl, Cr, Cu, Pb and Zn that show scattered anomalies localized close to the cities, farming and industries.

A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans.

PubMed

Hutchison, William; Fusillo, Raffaella; Pyle, David M; Mather, Tamsin A; Blundy, Jon D; Biggs, Juliet; Yirgu, Gezahegn; Cohen, Benjamin E; Brooker, Richard A; Barfod, Dan N; Calvert, Andrew T

2016-10-18

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth, however, current understanding of the magnitude and timing of large explosive eruptions in this region is poor. Detailed records of volcanism are essential for interpreting the palaeoenvironments occupied by our hominin ancestors; and also for evaluating the volcanic hazards posed to the 10 million people currently living within this active rift zone. Here we use new geochronological evidence to suggest that a 200 km-long segment of rift experienced a major pulse of explosive volcanic activity between 320 and 170 ka. During this period, at least four distinct volcanic centres underwent large-volume (>10 km 3 ) caldera-forming eruptions, and eruptive fluxes were elevated five times above the average eruption rate for the past 700 ka. We propose that such pulses of episodic silicic volcanism would have drastically remodelled landscapes and ecosystems occupied by early hominin populations.

A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans

PubMed Central

Hutchison, William; Fusillo, Raffaella; Pyle, David M.; Mather, Tamsin A.; Blundy, Jon D.; Biggs, Juliet; Yirgu, Gezahegn; Cohen, Benjamin E.; Brooker, Richard A.; Barfod, Dan N.; Calvert, Andrew T.

2016-01-01

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth, however, current understanding of the magnitude and timing of large explosive eruptions in this region is poor. Detailed records of volcanism are essential for interpreting the palaeoenvironments occupied by our hominin ancestors; and also for evaluating the volcanic hazards posed to the 10 million people currently living within this active rift zone. Here we use new geochronological evidence to suggest that a 200 km-long segment of rift experienced a major pulse of explosive volcanic activity between 320 and 170 ka. During this period, at least four distinct volcanic centres underwent large-volume (>10 km3) caldera-forming eruptions, and eruptive fluxes were elevated five times above the average eruption rate for the past 700 ka. We propose that such pulses of episodic silicic volcanism would have drastically remodelled landscapes and ecosystems occupied by early hominin populations. PMID:27754479

A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-10

USGS Publications Warehouse

Patrick, Matthew R.; Smellie, John L.

2015-01-01

Of the more than twenty historically active volcanoes in Antarctica and the sub-Antarctic region only two, to our knowledge, host any ground-based monitoring instruments. Moreover, because of their remoteness, most of the volcanoes are seldom visited, thus relegating the monitoring of volcanism in this region almost entirely to satellites. In this study, high temporal resolution satellite data from the Hawaii Institute of Geophysics and Planetology's MODVOLC system using MODIS (Moderate Resolution Imaging Spectroradiometer) are complemented with high spatial resolution data (ASTER, or Advanced Spaceborne Thermal Emission and Reflection Radiometer, and similar sensors) to document volcanic activity throughout the region during the period 2000–10. Five volcanoes were observed in eruption (Mount Erebus, Mount Belinda, Mount Michael, Heard Island and McDonald Island), which were predominantly low-level and effusive in nature. Mount Belinda produced tephra, building a cinder cone in addition to an extensive lava field. Five volcanoes exhibited detectable thermal, and presumed fumarolic, activity (Deception, Zavodovski, Candlemas, Bristol, and Bellingshausen islands). A minor eruption reported at Marion Island was not detected in our survey due to its small size. This study also discovered a new active vent on Mount Michael, tracked dramatic vent enlargement on Heard Island, and provides an improved picture of the morphology of some of the volcanoes.

Volcanic deformation in the Andes

NASA Astrophysics Data System (ADS)

Riddick, S.; Fournier, T.; Pritchard, M.

2009-05-01

We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

Volcanoes and human history

NASA Astrophysics Data System (ADS)

Cashman, K. V.; Giordano, G.

2008-10-01

The study of volcanic hazards leads inevitably to questions of how past cultures have lived in volcanically active regions of the world. Here we summarize linkages between volcanological, archaeological and anthropological studies of historic and prehistoric volcanic eruptions, with the goal of evaluating the impact of past eruptions on human populations to better prepare for future events. We use examples from papers collected in this volume to illustrate ways in which volcanological studies aid archaeological investigations by providing basic stratigraphic markers and information about the nature and timing of specific volcanic events. We then turn to archaeological perspectives, which provide physical evidence of the direct impacts of volcanic eruptions, such as site abandonment and human migration, as well as indirect impacts on local cultures as reflected in human artifacts. Finally we review anthropological studies of societal responses to past and recent volcanic eruptions. We pay particular attention to both the psychological impact of catastrophic events and records of these impacts encoded within oral traditions. Taken together these studies record drastic short-term eruption impacts but adaptation to volcanic activity over the longer term, largely through strategies of adaptive land use.

Introduction - The impacts of the 2008 eruption of Kasatochi Volcano on terrestrial and marine ecosystems in the Aleutian Islands, Alaska

USGS Publications Warehouse

DeGange, Anthony R.; Byrd, G. Vernon; Walker, Lawrence R.; Waythomas, C.F.

2010-01-01

The Aleutian Islands are situated on the northern edge of the so-called “Pacific Ring of Fire,” a 40,000-km-long horseshoe-shaped assemblage of continental landmasses and islands bordering the Pacific Ocean basin that contains many of the world's active and dormant volcanoes. Schaefer et al. (2009) listed 27 historically active volcanoes in the Aleutian Islands, of which nine have had at least one major eruptive event since 1990. Volcanic eruptions are often significant natural disturbances, and ecosystem responses to volcanic eruptions may vary markedly with eruption style (effusive versus explosive), frequency, and magnitude of the eruption as well as isolation of the disturbed sites from potential colonizing organisms (del Moral and Grishin, 1999). Despite the relatively high frequency of volcanic activity in the Aleutians, the response of island ecosystems to volcanic disturbances is largely unstudied because of the region's isolation. The only ecological studies in the region that address the effects of volcanic activity were done on Bogoslof Island, a remote, highly active volcanic island in the eastern Aleutians, which grew from a submarine eruption in 1796 (Merriam, 1910; Byrd et al., 1980; Byrd and Williams, 1994). Nevertheless, in the 214 years of Bogoslof's existence, the island has been visited only intermittently.Kasatochi Island is a small (2.9 km by 2.6 km, 314 m high) volcano in the central Aleutian Islands of Alaska (52.17°N latitude, 175.51°W longitude; Fig. 1) that erupted violently on 7-8 August 2008 after a brief, but intense period of precursory seismic activity (Scott et al., 2010 [this issue]; Waythomas et al., in review). The island is part of the Aleutian arc volcanic front, and is an isolated singular island. Although the immediate offshore areas are relatively shallow (20–50 m water depth), the island is about 10 km south of the 2000 m isobath, north of which, ocean depths increase markedly. Kasatochi is located between the deepwater basin of the Bering Sea to the north and shallower areas of intense upwelling in Atka and Fenimore Passes in the North Pacific Ocean to the south. This area apparently produces high marine productivity based on concentrations of feeding marine birds and mammals (see Drew et al., 2010 [this issue]). Kasatochi is about 85 km northeast of Adak, the nearest community and a regional transportation hub, and about 19 km northwest of the western end of Atka Island. The nearest historically active volcanoes are Great Sitkin volcano, about 35 km to the west, and Korovin volcano on Atka Island, about 94 km to the east. Koniuji Island, another small volcanic island, is located about 25 km east of Kasatochi (Fig. 1).

Stratigraphy, geochemistry and tectonic significance of the Oligocene magmatic rocks of western Oaxaca, southern Mexico

USGS Publications Warehouse

Martiny, B.; Martinez-Serrano, R. G.; Moran-Zenteno, D. J.; MacIas-Romo, C.; Ayuso, R.A.

2000-01-01

In Western Oaxaca, Tertiary magmatic activity is represented by extensive plutons along the continental margin and volcanic sequences in the inland region. K-Ar age determinations reported previously and in the present work indicate that these rocks correspond to a relatively broad arc in this region that was active mainly during the Oligocene (~ 35 to ~ 25 Ma). In the northern sector of western Oaxaca (Huajuapan-Monte Verde-Yanhuitlan), the volcanic suite comprises principally basaltic andesite to andesitic lavas, overlying minor silicic to intermediate volcaniclastic rocks (epiclastic deposits, ash fall tuffs, ignimbrites) that were deposited in the lacustrine-fluvial environment. The southern sector of the volcanic zone includes the Tlaxiaco-Laguna de Guadalupe region and consists of intermediate to silicic pyroclastic and epiclastic deposits, with silicic ash fall tuffs and ignimbrites. In both sectors, numerous andesitic to dacitic hypabyssal intrusions (stocks and dikes) were emplaced at different levels of the sequence. The granitoids of the coastal plutonic belt are generally more differentiated than the volcanic rocks that predominate in the northern sector and vary in composition from granite to granodiorite. The studied rocks show large-ion lithophile element (LILE) enrichment (K, Rb, Ba, Th) relative to high-field-strength (HFS) elements (Nb, Ti, Zr) that is characteristic of subduction-related magmatic rocks. On chondrite-normalized rare earth element diagrams, these samples display light rare earth element enrichment (LREE) and a flat pattern for the heavy rare earth elements (HREE). In spite of the contrasting degree of differentiation between the coastal plutons and inland volcanic rocks, there is a relatively small variation in the isotopic composition of these two suites. Initial 87Sr/86Sr ratios obtained and reported previously for Tertiary plutonic rocks of western Oaxaca range from 0.7042 to 0.7054 and ??Nd values, from -3.0 to +2.4, and for the volcanic rocks, from 0.7042 to 0.7046 and 0 +2.6. The range of these isotope ratios and those reported for the basement rocks in this region suggest a relatively low degree of old crustal involvement for most of the studied rocks. The Pb isotopic compositions of the Tertiary magmatic rocks also show a narrow range [(206Pb/204Pb) = 18.67-18.75; (207Pb/204Pb) = 15.59-15.62; (208Pb/204Pb) = 38.44-38.59], suggesting a similar source region for the volcanic and plutonic rocks. Trace elements and isotopic compositions suggest a mantle source in the subcontinental lithosphere that has been enriched by a subduction component. General tectonic features in this region indicate a more active rate of transtensional deformation for the inland volcanic region than along the coastal margin during the main events of Oligocene magmatism. The lower degree of differentiation of the inland volcanic sequences, particularly the upper unit of the northern sector, compared to the plutons of the coastal margin, suggests that the differentiation of the Tertiary magmas in southern Mexico was controlled to a great extent by the characteristics of the different strain domains. (C) 2000 Elsevier Science B.V. All rights reserved.

NW-SE Pliocene-Quaternary extension in the Apan-Acoculco region, eastern Trans-Mexican Volcanic Belt

NASA Astrophysics Data System (ADS)

García-Palomo, Armando; Macías, José Luis; Jiménez, Adrián; Tolson, Gustavo; Mena, Manuel; Sánchez-Núñez, Juan Manuel; Arce, José Luis; Layer, Paul W.; Santoyo, Miguel Ángel; Lermo-Samaniego, Javier

2018-01-01

The Apan-Acoculco area is located in the eastern portion of the Mexico basin and the Trans-Mexican Volcanic Belt. The area is transected by right-stepping variably dipping NE-SW normal faults. The Apan-Tlaloc Fault System is a major discontinuity that divides the region into two contrasting areas with different structural and volcanic styles. a) The western area is characterized by a horst-graben geometry with widespread Quaternary monogenetic volcanism and scattered outcrops of Miocene and Pliocene rocks. b) The eastern area is dominated by tilted horsts with a domino-like geometry with widespread Miocene and Pliocene rocks, scattered Quaternary monogenetic volcanoes and the Acoculco Caldera. Gravity data suggest that this structural geometry continues into the Mesozoic limestones. Normal faulting was active since the Pliocene with three stages of extension. One of them, an intense dilatational event began during late Pliocene and continues nowadays, contemporaneously with the emplacement of the Apan-Tezontepec Volcanic Field and the Acoculco caldera. Statistical analysis of cone elongation, cone instability, and the kinematic analysis of faults attest for a NW50°SE ± 7° extensional regime in the Apan-Acoculco area. The activity in some portions of the Apan-Tlaloc Fault System continues today as indicated by earthquake swarms recorded in 1992 and 1996, that disrupted late Holocene paleosols, and Holocene volcanism.

Etnean and Hyblean volcanism shifted away from the Malta Escarpment by crustal stresses

NASA Astrophysics Data System (ADS)

Neri, Marco; Rivalta, Eleonora; Maccaferri, Francesco; Acocella, Valerio; Cirrincione, Rosolino

2018-03-01

A fraction of the volcanic activity occurs intraplate, challenging our models of melting and magma transfer to the Earth's surface. A prominent example is Mt. Etna, eastern Sicily, offset from the asthenospheric tear below the Malta Escarpment proposed as its melt source. The nearby Hyblean volcanism, to the south, and the overall northward migration of the eastern Sicilian volcanism are also unexplained. Here we simulate crustal magma pathways beneath eastern Sicily, accounting for regional stresses and decompression due to the increase in the depth of the Malta Escarpment. We find non-vertical magma pathways, with the competition of tectonic and loading stresses controlling the trajectories' curvature and its change in time, causing the observed migration of volcanism. This suggests that the Hyblean and Etnean volcanism have been fed laterally from a melt pooling region below the Malta Escarpment. The case of eastern Sicily shows how the reconstruction of the evolution of magmatic provinces may require not only an assessment of the paleostresses, but also of the contribution of surface loads and their variations; at times, the latter may even prevail. Accounting for these competing stresses may help shed light on the distribution and wandering of intraplate volcanism

Earth observations taken during STS-77 mission

NASA Image and Video Library

1996-05-28

STS077-715-037 (19-29 May 1996) --- According to NASA scientists, Ruapehu, on New Zealand?s North Island, is one of the most active volcanoes in the South Pacific. Prior to the flight, crew members scheduled this site as one of their photographic targets. The volcano endured a significant eruption in late September, 1995. This view is the first image of the crater region since that eruption. Since then, numerous landslides and secondary explosions in the summit area has produced changes. In this view, recent mudflows extend from the summit region and down the mountain flank which is in the shadow. Ruapehu is also one of New Zealand?s high points - the mountain supports a glacier and permanent ice fields, and volcanic activity necessarily involves mixing hot volcanic products with snow and ice. Recent activity has produced destructive lahars (mudslides which are slurries of volcanic material with ice and water) downslope. A hazard warning to skiers is still in effect.

Late Holocene volcanic activity and environmental change in Highland Guatemala

NASA Astrophysics Data System (ADS)

Lohse, Jon C.; Hamilton, W. Derek; Brenner, Mark; Curtis, Jason; Inomata, Takeshi; Morgan, Molly; Cardona, Karla; Aoyama, Kazuo; Yonenobu, Hitoshi

2018-07-01

We present a record of late Holocene volcanic eruptions with elemental data for a sequence of sampled tephras from Lake Amatitlan in Highland Guatemala. Our tephrochronology is anchored by a Bayesian P_Sequence age-depth model based on multiple AMS radiocarbon dates. We compare our record against a previously published study from the same area to understand the record of volcanism and environmental changes. This work has implications for understanding the effects of climate and other environmental changes that may be related to the emission of volcanic aerosols at local, regional and global scales.

Volcanic CO2 Abundance of Kilauea Plume Retrieved by Meand of AVIRIS Data

NASA Technical Reports Server (NTRS)

Spinetti, C.; Carrere, V.; Buongiorno, M. F.; Pieri, D.

2004-01-01

Absorbing the electromagnetic radiation in several regions of the solar spectrum, CO2 plays an important role in the Earth radiation budget since it produces the greenhouse effect. Many natural processes in the Earth s system add and remove carbon dioxide. Overall, measurements of atmospheric carbon dioxide at different sites around the world show an increased carbon dioxide concentration in the atmosphere. At Mauna Loa Observatory (Hawaii) the measured carbon dioxide increased from 315 to 365 ppm, in the period 1958 2000 [Keeling et al., 2001]. While at the large scale, the relationship between CO2 increase and global warming is established [IPCC, 1996], at the local scale, many studies are still needed to understand regional and local sources of carbon dioxide, such as volcanoes. The volcanic areas are particularly rich in carbon dioxide; this is due to magma degassing in the summit craters region of active volcanoes, and to the presence of fractures and active faults [Giammanco et al., 1998]. Several studies estimate a global flux of volcanic CO2 (34+/-24)10(exp 6) tons/day from effusive volcanic emissions, such as the tropospheric volcanic plume (Table 1) [McClelland et al., 1989]. Plumes are a turbulent mixture of gases, solid particles and liquid droplets, emitted continuously at high temperature from summit craters, fumarolic fields or during eruptive episodes. Inside the plume, water vapour represents 70 90% of the volcanic gases. The main gaseous components are CO2, SO2, HCl, H2, H2S, HF, CO, N2 and CH4. Other plume components are volcanic ash, aqueous and acid droplets and solid sulphur-derived particles [Sparks et al., 1997]. Volcanic gases and aerosols are evidences of volcanic activity [Spinetti et al., 2003] and they have important climatic and environmental effects [Fiocco et al., 1994]. For example, Etna volcano is one of the world s major volcanic gas sources [Allard et al., 1991]. New studies on volcanic gaseous emissions have pointed out that a variation of the gas ratio CO2/SO2 is related to eruptive episodes [Caltabiano et al., 1994]. However, measurements and monitoring of volcanic carbon dioxide are difficult and often hazardous, due to the high background presence of atmospheric CO2 and the inaccessibility of volcanic sites. Hyperspectral remote sensing is a suitable technique to overcome the difficulties of ground measurement. It permits a rapid, comprehensive view of volcanic plumes and their evolution over time, detection of all gases with absorption molecular lines within the sensor s multispectral range and, in general, measurement of all the volatile components evolving from craters. The molecular and particle plume components scatter and absorb incident solar radiation. The integral of the radiation difference composes the signal measured by the remote spectrometer. The inversion technique consists of retrieving the plume component concentrations, hence decomposing the signal into the different contributions. The accuracy of remote sensing techniques depends primarily on the sensor capability and sensitivity.

Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

NASA Astrophysics Data System (ADS)

Lexa, Jaroslav; Seghedi, Ioan; Németh, Karoly; Szakács, Alexandru; Koneĉny, Vlastimil; Pécskay, Zoltan; Fülöp, Alexandrina; Kovacs, Marinel

2010-09-01

Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with rollback, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calclkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions, diatreme, lava lake) for various types of K- and Na-alkalic and ultra-potassic magmatism. Finally, we provide a summary of the eruptive history and distribution of volcanic forms in the CPR using several sub-region schemes.

Distribution of recent volcanism and the morphology of seamounts and ridges in the GLIMPSE study area: Implications for the lithospheric cracking hypothesis for the origin of intraplate, non-hot spot volcanic chains

USGS Publications Warehouse

Forsyth, D.W.; Harmon, N.; Scheirer, D.S.; Duncan, R.A.

2006-01-01

Lithospheric cracking by remotely applied stresses or thermoelastic stresses has been suggested to be the mechanism responsible for the formation of intraplate volcanic ridges in the Pacific that clearly do not form above fixed hot spots. As part of the Gravity Lineations Intraplate Melting Petrology and Seismic Expedition (GLIMPSE) project designed to investigate the origin of these features, we have mapped two volcanic chains that are actively forming to the west of the East Pacific Rise using multibeam echo sounding and side-scan sonar. Side-scan sonar reveals the distribution of rough seafloor corresponding to recent, unsedimented lava flows. In the Hotu Matua volcanic complex, recent flows and volcanic edifices are distributed over a region 450 km long and up to 65 km wide, with an apparent, irregular age progression from older flows in the west to younger in the east. The 550-km-long Southern Cross Seamount/Sojourn Ridge/Brown Ridge chain appears to have been recently active only at its eastern end near the East Pacific Rise. A third region of recent flows is found 120 km north of Southern Cross Seamount in seafloor approximately 9 Myr old. No indication of lithospheric extension in the form of faulting or graben formation paralleling the trend of the volcanic chains is found in the vicinity of recent flows or anywhere else in the study area. Thermoelastic cracking could be a factor in the formation of a few small, very narrow volcanic ridges, but most of the volcanic activity is broadly distributed in wide swaths with no indication of formation along narrow cracks. The Sojourn and Brown chains appear to begin as distributed zones of small seamounts that later develop into segmented ridges, perhaps under the influence of membrane stresses from self-loading. We suggest that the linear volcanic chains are created by moving melting anomalies in the asthenosphere and that lithospheric cracking plays at most a secondary role. Copyright 2006 by the American Geophysical Union.

40Ar/39Ar laser fusion and K-Ar ages from Lathrop Wells, Nevada, and Cima, California. The age of the latest volcanic activity in the Yucca Mountain area

USGS Publications Warehouse

Turrin, Brent D.; Champion, Duane E.; ,

1991-01-01

K-Ar and 40Ar/39Ar ages from the Lathrop Wells volcanic center, Nevada, and from the Cima volcanic field, California, indicate that the recently reported 20-ka age estimate for the Lathrop Wells volcanic center is incorrect. Instead an age of 119??11 to 141??10 ka is indicated for the Lathrop Wells volcanic center. This age corrected is concordant with the ages determined by two independent isotopic geochronometric techniques and with the stratigraphy of surficial deposits in the Yucca Mountain region. In addition, paleomagnetic data and radiometric age data indicate only two volcanic events at the Lathrop Wells volcanic center that are probably closely linked in time, not as many as five as recently reported.

Mauna Iki and the Kaju Desert: Kilauea Volcano, Hawaii

NASA Technical Reports Server (NTRS)

Cruikshank, D. P.

1974-01-01

The Ka'u Desert lies southwest of Kilauea Volcano. The region contains some of the most interesting and best preserved volcanic features found in the islands. The structural setting and synopsis of recent volcanic activity on the Ka'u Desert are discussed here, and a field guide to Mauna Iki is provided.

Tectonics and volcanism in central Mexico - A Landsat Thematic Mapper perspective

NASA Technical Reports Server (NTRS)

Johnson, C. A.; Harrison, C. G. A.

1989-01-01

Digitally enhanced Landsat Thematic Mapper (TM) images were used to map neotectonic deformation in central Mexico. This region has been studied for decades using a variety of geological and geophysical techniques, but synoptic mapping of neotectonic activity and major fault zones there, and an evaluation of their regional relationship to the character and location of volcanism were not previously possible until the application of synoptic, high resolution satellite imagery. Interpretation of the TM images shows that the tectonic deformation is closely linked in time and space to the dominantly calc-alkaline volcanics of the Mexican Volcanic Belt (MVB). The eruptive style and distribution of the volcanics is clearly related to the deformation resulting from relative motions of three large crustal blocks south of the MVB. Therefore, zones of weakness within the crust of central Mexico, which may be inherited from earlier episodes of deformation, are a principal factor controlling the oblique orientation of the MVB relative to the Acapulco Trench.

Io - Full Disk Centered on Media Regio

NASA Technical Reports Server (NTRS)

1996-01-01

The mottled face of Jupiter's volcanically active moon Io [pronounced 'EYE-oh' or 'EE-OH'], viewed by the camera onboard NASA's Galileo spacecraft, shows dramatic changes since it was seen 17 years ago by the exploratory NASA spacecraft Voyagers 1 and 2. This Galileo image, taken on June 25, 1996 at a range of 2.24 million kilometers (1.4 million miles), is centered on the Media Regio area and shows details of the volcanic regions and colored deposits that characterize Io. North is at the top of the picture and the Sun illuminates the surface from the east (right). The smallest features that can be discerned here are approximately 23 kilometers (14 miles) in size, a resolution comparable to the best Voyager images of this face of Io. Io's surface is covered with volcanic deposits that are thought to contain ordinary silicate rock, along with various sulfur-rich compounds that give the satellite its distinctive color. In the brighter areas the surface is coated with frosts of sulfur dioxide. Dark areas are regions of current or recent volcanic activity. Planetary scientists say many changes are evident in the surface markings since this region of Io was imaged 17 years ago by the Voyager spacecraft. The bright regions near the eastern limb of the moon are much more prominent in the Galileo images than they were previously. Surface details have also changed dramatically in the vicinity of the eruptive volcano Masubi (the large, predominantly white feature seen near the 6 o'clock position in this view). Masubi was discovered as an active volcano during the Voyager encounters of Io in 1979.

Constraint on the magma sources in Luzon Island Philippines by using P and S wave local seismic tomography

NASA Astrophysics Data System (ADS)

Nghia, N. C.; Huang, B. S.; Chen, P. F.

2017-12-01

The subduction of South China Sea beneath the Luzon Island has caused a complex setting of seismicity and magmatism because of the proposed ridge subduction and slab tearing. To constrain the validity of slab tearing induced by ridge subduction and their effect, we performed a P and S wave seismic tomography travel time inversion using LOTOS code. The dataset has been retrieved from International Seismological Centre from 1960 to 2008. A 1D velocity inverted by using VELEST with a Vp/Vs ratio of 1.74 is used as the starting input velocity for tomographic inversion. Total of 20905 P readings and 8126 S readings from 2355 earthquakes events were used to invert for velocity structure beneath Luzon Island. The horizontal tomographic results show low-velocity, high Vp/Vs regions at the shallow depth less than 50 km which are interpreted as the magmatic chambers of the volcanic system in Luzon. At the suspected region of slab tearing at 16oN to 18oN, two sources of magma have been indentified: slab window magma at shallow depth (< 50 km) and magma induced by mantle wedge partial melting from higher depth. This slab melting may have changed the composition of magmatic to become more silicic with high viscosity, which explains the volcanic gap in this region. At the region of 14oN to 15oN, large magma chambers under active volcanos are identified which explain the active volcanism in this region. Contrast to the region of slab tearing, in this region, the magma chambers are fed by only magma from partial melting of mantle wedge from the depth higher than 100 km. These observations are consistent with previous work on the slab tearing of South China Sea and the activities of volcanism in the Luzon Island.

Analysis of Distribution of Volcanoes around the Korean Peninsula and the Potential Effects on Korea

NASA Astrophysics Data System (ADS)

Choi, Eun-kyeong; Kim, Sung-wook

2017-04-01

Since the scale and disaster characteristics of volcanic eruptions are determined by their geological features, it is important not only to grasp the current states of the volcanoes in neighboring countries around the Korean Peninsula, but also to analyze the tectonic settings, tectonic regions, geological features, volcanic types, and eruption histories of these volcanoes. Volcanic data were based on the volcano information registered with the Global Volcanism Program at the Smithsonian Institute. We created a database of 289 volcanoes around Korea, Japan, China, Taiwan, and the Kamchatka area in Russia, and then identified a high-risk group of 29 volcanoes that are highly likely to affect the region, based on conditions such as volcanic activity, types of rock at risk of eruption, distance from Seoul, and volcanoes having Plinian eruption history with volcanic explosivity index (VEI) of 4 or more. We selected 29 hazardous volcanoes, including Baekdusan, Ulleungdo, and 27 Japanese volcanoes that can cause widespread ashfall on the Korean peninsula by potentially explosive eruptions. In addition, we identified ten volcanoes that should be given the highest priority, through an analysis of data available in literature, such as volcanic ash dispersion results from previous Japanese eruptions, the definition of a large-scale volcano used by Japan's Cabinet Office, and examination of cumulative magma layer volumes from Japan's quaternary volcanoes. We expect that predicting the extent of the spread of ash caused by this hazardous activity and analyzing its impact on the Korean peninsula will be help to predict volcanic ash damage as well as provide direction for hazard mitigation research. Acknowledgements 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.

Assessment of geothermal energy potential by geophysical methods: Nevşehir Region, Central Anatolia

NASA Astrophysics Data System (ADS)

Kıyak, Alper; Karavul, Can; Gülen, Levent; Pekşen, Ertan; Kılıç, A. Rıza

2015-03-01

In this study, geothermal potential of the Nevşehir region (Central Anatolia) was assessed by using vertical electrical sounding (VES), self-potential (SP), magnetotelluric (MT), gravity and gravity 3D Euler deconvolution structure analysis methods. Extensive volcanic activity occurred in this region from Upper Miocene to Holocene time. Due to the young volcanic activity Nevşehir region can be viewed as a potential geothermal area. We collected data from 54 VES points along 5 profiles, from 28 MT measurement points along 2 profiles (at frequency range between 320 and 0.0001 Hz), and from 4 SP profiles (total 19 km long). The obtained results based on different geophysical methods are consistent with each other. Joint interpretation of all geological and geophysical data suggests that this region has geothermal potential and an exploration well validated this assessment beyond doubt.

Snow cover correlation between Mt. Villarrica and Mt. Lliama in Chile

NASA Astrophysics Data System (ADS)

Kim, Jeong-Cheol; Park, Sung-Hwan; Jung, Hyung-Sup

2014-11-01

The Southern Volcanic Zone (SVZ) of Chile consists of many volcanoes, and all of the volcanoes are covered with snow at the top of mountain. Monitoring snow cover variations in these regions can give us a key parameter in order to understand the mechanisms of volcanic activity. In this study, we investigate on the volcanic activity and snow cover interaction from snow cover area mapping, snow-line extraction. The study areas cover Mt. Villarrica and Mt. Llaima, Chile. Both of them are most active volcanos in SVZ. Sixty Landsat TM and Landsat ETM+ images are used for observing snow cover variations of Mt. Villarrica and Mt. Llaima, spanning the 25 years from September 1986 to February 2011. Results show that snow cover area between volcanic activity and non-activity are largely changed from 42.84 km2 to 13.41 km2, temporarily decreased 79% at the Mt. Villarrica and from 28.98 km2 to 3.82 km2, temporarily decreased 87% at the Mt. Villarrica. The snow line elevation of snow cover retreated by approximately 260 m from 1,606m to 1,871 m at the Mt. Villarrica, approximately 266m from 1,741m to 2,007m at the Mt. Llaima. The results show that there are definitely correlations between snow cover and volcanic activity.

Analysis of Focal Mechanism and Microseismicity around the Lusi Mud Eruption Site, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

2016-04-01

The 29th of May 2006 numerous eruption sites started in northeast Java, Indonesia following to a M6.3 earthquake striking the island.Within a few weeks an area or nearly 2 km2 was covered by boiling mud and rock fragments and a prominent central crater (named Lusi) has been erupting for the last 9.5 years. The M.6.3 seismic event also triggered the activation of the Watukosek strike slip fault system that originates from the Arjuno-Welirang volcanic complex and extends to the northeast of Java hosting Lusi and other mud volcanoes. Since 2006 this fault system has been reactivated in numerous instances mostly following to regional seismic and volcanic activity. However the mechanism controlling this activity have never been investigated and remain poorly understood. In order to investigate the relationship existing between seismicity, volcanism, faulting and Lusi activity, we have deployed a network of 31 seismometers in the framework of the ERC-Lusi Lab project. This network covers a large region that monitors the Lusi activity, the Watukosek fault system and the neighboring Arjuno-Welirang volcanic complex. In particular, to understand the consistent pattern of the source mechanism, relative to the general tectonic stress in the study area, a detailed analysis has been carried out by performing the moment tensor inversion for the near field data collected from the network stations. Furthermore these data have been combined with the near field data from the regional network of the Meteorological, Climatological and Geophysical Agency of Indonesia that covers the whole country on a broader scale. Keywords: Lusi, microseismic event, focal mechanism

A satellite geodetic survey of large-scale deformation of volcanic centres in the central Andes.

PubMed

Pritchard, Matthew E; Simons, Mark

2002-07-11

Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Stratovolcanoes tend to exhibit a complex relationship between deformation and eruptive behaviour. The characteristically long time spans between such eruptions requires a long time series of observations to determine whether deformation without an eruption is common at a given edifice. Such studies, however, are logistically difficult to carry out in most volcanic arcs, as these tend to be remote regions with large numbers of volcanoes (hundreds to even thousands). Here we present a satellite-based interferometric synthetic aperture radar (InSAR) survey of the remote central Andes volcanic arc, a region formed by subduction of the Nazca oceanic plate beneath continental South America. Spanning the years 1992 to 2000, our survey reveals the background level of activity of about 900 volcanoes, 50 of which have been classified as potentially active. We find four centres of broad (tens of kilometres wide), roughly axisymmetric surface deformation. None of these centres are at volcanoes currently classified as potentially active, although two lie within about 10 km of volcanoes with known activity. Source depths inferred from the patterns of deformation lie between 5 and 17 km. In contrast to the four new sources found, we do not observe any deformation associated with recent eruptions of Lascar, Chile.

Lithospheric and Asthenospheric Contributions to Post-Collisional Volcanism in the Lesser Caucasus Mts (Armenia)

NASA Astrophysics Data System (ADS)

Sugden, P.; Savov, I. P.; Wilson, M.; Meliksetian, K.; Navasardyan, G.

2017-12-01

Continental collision zones remain the most enigmatic tectonic setting for volcanic activity on earth. The Lesser Caucasus Mts are host to widespread and unique intraplate volcanism, associated with the active Arabia-Eurasia continental collision. Volcanic products range from alkali basalts to rhyolites (including extensive ignimbrites), and occur as basaltic lava flow fields, large composite and shield volcanoes, and regions of distributed (mostly monogenetic) volcanism. Geomorphology, archaeology, and historical accounts suggest volcanic activity has extended in to the Holocene-historical period. The high quality of the exposures and the diversity of unaltered rock types makes Armenia an ideal natural laboratory for studying the sources of magmatism in an active continental collision zone. For the first time, we will present the mineral chemistry (ol, px, amph), whole rock major and trace element, and Sr-Nd isotope compositions of volcanic rocks from southernmost Armenia- namely the Gegham, Vardenis and Syunik volcanic highlands. We compare our dataset with the composition of post-collisional volcanic rocks elsewhere in the Arabia-Eurasia collision zone. Samples from S. Armenia are more mafic, more alkaline and more K2O rich. All volcanic rocks show negative HFSE anomalies and LILE and LREE enrichments reminiscent of continental volcanic arc settings. However, volcanic rocks in Southern Armenia are further enriched in some of the most incompatible trace elements, most notably LREE, Sr and P, and have higher La/Yb, Th/Yb, Ta/Yb, and more variable Th/Nb. Volcanic rocks from Eastern Anatolia and N. Armenia have Sr-Nd isotope compositions similar to those of the Mesozoic volcanic arc (87Sr/86Sr 0.7034-0.7045; 143Nd/144Nd 0.5128-0.5129), whereas samples from S. Armenia deviate towards more enriched compositions resembling a typical EM-I type reservoir (87Sr/86Sr 0.7041- 0.7047; 143Nd/144Nd 0.5127-0.5128). We argue that these distinctive geochemical characteristics result from the addition of an enriched lithospheric component to a ubiquitous subduction-modified baseline asthenospheric mantle. This EM-I like component may be characteristic for not only intraplate hotspot volcanoes but also to collisional and arc settings.

Palaeotectonic implications of increased late Eocene-early Oligocene volcanism from South Pacific DSDP sites

USGS Publications Warehouse

Kennett, J.P.; Von Der Borch, C.; Baker, P.A.; Barton, C.E.; Boersma, A.; Cauler, J.P.; Dudley, W.C.; Gardner, J.V.; Jenkins, D.G.; Lohman, W.H.; Martini, E.; Merrill, R.B.; Morin, R.; Nelson, Campbell S.; Robert, C.; Srinivasan, M.S.; Stein, R.; Takeuchi, A.; Murphy, M.G.

1985-01-01

Late Eocene-early Oligocene (42-35 Myr) sediments cored at two DSDP sites in the south-west Pacific contain evidence of a pronounced increase in local volcanic activity, particularly in close association with the Eocene-Oligocene boundary. This pulse of volcanism is coeval with that in New Zealand and resulted from the development of an Indo- Australian / Pacific Plate boundary through the region during the late Eocene. The late Eocene / earliest Oligocene was marked by widespread volcanism and tectonism throughout the Pacific and elsewhere, and by one of the most important episodes of Cenozoic climatic cooling. ?? 1985 Nature Publishing Group.

Resuspended volcanic ash from Katmai, Alaska

NASA Image and Video Library

2017-12-08

The Valley of Ten Thousand Smokes, located in Katmai National Park, forms a unique and ashen landscape. Encircled by volcanoes – both active and inactive – it has served as a perfect collection area for huge amounts of volcanic ash. According to the Alaska Historical Society (AHS), 2012 marked the centennial anniversary of the volcanic eruption that formed the valley, and led to the establishment, in 1918, of Katmai National Park. A massive eruption rocked the region on June 6, 1912 as the then-unknown volcano, Novarupta, became suddenly and violently active. According to the AHS, it erupted with “such force that mountains collapsed, ash darkened summer skies, earthquakes rocked population centers and were recorded as far away as Washington, D.C.” Glowing hot ash was reported to have smothered an area covering 40 square miles, and up to 700 feet deep. While the active volcanoes surrounding the valley - Novarupta, Mt. Mageik, Trident Volcano, Mt. Griggs, Mt. Martin and Mt. Katmai - have remained relatively quiescent, their ashen legacy continues to affect the landscape – and air traffic - even a century after it was laid down. The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image on September 29, 2014. Volcanic ash from the Katmai region has been lifted aloft by strong winds, and is blowing to the southeast, over Shelikof Strait, Kodiak Island, and the Gulf of Alaska. Although such clouds are not from active volcanoes, the remobilized volcanic ash still provides a potential hazard to aircraft flying through the region. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Crustal rifting and magmatic underplating in the Izu-Ogasawara (Bonin) intra-oceanic arc detected by active source seismic studies

NASA Astrophysics Data System (ADS)

Takahashi, N.; Kodaira, S.; Yamashita, M.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.; Kaneda, Y.

2009-12-01

Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic experiments using a multichannel reflection system and ocean bottom seismographs (OBSs) in the Izu-Ogasawara (Bonin)-Mariana (IBM) arc region since 2002 to understand growth process of continental crust. The source was an airgun array with a total capacity of 12,000 cubic inches and the OBSs as the receiver were deployed with an interval of 5 km for all seismic refraction experiments. As the results, we obtained crustal structures across the whole IBM arc with an interval of 50 km and detected the structural characteristics showing the crustal growth process. The IBM arc is one of typical oceanic island arc, which crustal growth started from subduction of an oceanic crust beneath the other oceanic crust. The arc crust has developed through repeatedly magmatic accretion from subduction slab and backarc opening. The volcanism has activated in Eocene, Oligocene, Miocene and Quaternary (e.g., Taylor, 1992), however, these detailed locations of past volcanic arc has been remained as one of unknown issues. In addition, a role of crustal rifting for the crustal growth has also been still unknown issue yet. Our seismic structures show three rows of past volcanic arc crusts except current arc. A rear arc and a forearc side have one and two, respectively. The first one, which was already reported by Kodaira et al. (2008), distributes in northern side from 27 N of the rear arc region. The second one, which develops in the forearc region next to the recent volcanic front, distributes in whole of the Izu-Ogasawara arc having crustal variation along arc direction. Ones of them sometimes have thicker crust than that beneath current volcanic front and no clear topographic high. Last one in the forearc connects to the Ogasawara Ridge. However, thickest crust is not always located beneath these volcanic arcs. The initial rifting region like the northern end of the Mariana Trough and the Sumisu Rift has thicker crust than that beneath recent volcanic front, although crustal thinning with high velocity lower crust was detected beneath advanced rifted region. This suggests that the magmatic underplating play a role to make open the crust. The magmatic underplating accompanied with the initial rifting is one of important issues to discuss the crustal evolution.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krier, D. J.; Perry, F. V.

Location, timing, volume, and eruptive style of post-Miocene volcanoes have defined the volcanic hazard significant to a proposed high-level radioactive waste (HLW) and spent nuclear fuel (SNF) repository at Yucca Mountain, Nevada, as a low-probability, high-consequence event. Examination of eruptive centers in the region that may be analogueues to possible future volcanic activity at Yucca Mountain have aided in defining and evaluating the consequence scenarios for intrusion into and eruption above a repository. The probability of a future event intersecting a repository at Yucca Mountain has a mean value of 1.7 x 10{sup -8} per year. This probability comes frommore » the Probabilistic Volcanic Hazard Assessment (PVHA) completed in 1996 and updated to reflect change in repository layout. Since that time, magnetic anomalies representing potential buried volcanic centers have been identified fiom magnetic surveys; however these potential buried centers only slightly increase the probability of an event intersecting the repository. The proposed repository will be located in its central portion of Yucca Mountain at approximately 300m depth. The process for assessing performance of a repository at Yucca Mountain has identified two scenarios for igneous activity that, although having a very low probability of occurrence, could have a significant consequence should an igneous event occur. Either a dike swarm intersecting repository drifts containing waste packages, or a volcanic eruption through the repository could result in release of radioactive material to the accessible environment. Ongoing investigations are assessing the mechanisms and significance of the consequence scenarios. Lathrop Wells Cone ({approx}80,000 yrs), a key analogue for estimating potential future volcanic activity, is the youngest surface expression of apparent waning basaltic volcanism in the region. Cone internal structure, lavas, and ash-fall tephra have been examined to estimate eruptive volume, eruption type, and subsurface disturbance accompanying conduit growth and eruption. The Lathrop Wells volcanic complex has a total volume estimate of approximately 0.1 km{sup 3}. The eruptive products indicate a sequence of initial magmatic fissure fountaining, early Strombolian activity, and a brief hydrovolcanic phase, and violent Strombolian phase(s). Lava flows adjacent to the Lathrop Wells Cone probably were emplaced during the mid-eruptive sequence. Ongoing investigations continue to address the potential hazards of a volcanic event at Yucca Mountain.« less

Geologic map of the Cochetopa Park and North Pass Calderas, northeastern San Juan Mountains, Colorado

USGS Publications Warehouse

Lipman, Peter W.

2012-01-01

The San Juan Mountains in southwestern Colorado have long been known as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 22 major ignimbrite sheets (each 150-5,000 km3) and associated caldera structures active at 33-23 Ma. Recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Platoro complex), western calderas (Uncompahgre-Silverton-Lake City), and the central cluster (La Garita-Creede calderas). Far less studied has been the northeastern San Juan region, which occupies a transition between earlier volcanism in central Colorado and large-volume younger ignimbrite-caldera foci farther south and west. The present map is based on new field coverage of volcanic rocks in seventeen 7.5' quadrangles in northeastern parts of the volcanic field, high-resolution age determinations for 120 new sites, and petrologic studies involving several hundred new chemical analyses. This mapping and the accompanying lab results (1) document volcanic evolution of the previously unrecognized North Pass caldera and the morphologically beautifully preserved but enigmatic Cochetopa basin, including unique features not previously described from ignimbrite calderas elsewhere; (2) provide evidence for a more rapid recurrence of large ignimbrite eruptions than previously known elsewhere; (3) quantify the regional time-space-volume progression from the earlier Sawatch magmatic trend southward into the San Juan region; and (4) permit more rigorous comparison between the broad mid-Tertiary magmatic belt in the western U.S. Cordillera and the type continental-margin arc volcanism in the central Andes.

Geologic field-trip guide to the volcanic and hydrothermal landscape of the Yellowstone Plateau

USGS Publications Warehouse

Morgan Morzel, Lisa Ann; Shanks, W. C. Pat; Lowenstern, Jacob B.; Farrell, Jamie M.; Robinson, Joel E.

2017-11-20

Yellowstone National Park, a nearly 9,000 km2 (~3,468 mi2) area, was preserved in 1872 as the world’s first national park for its unique, extraordinary, and magnificent natural features. Rimmed by a crescent of older mountainous terrain, Yellowstone National Park has at its core the Quaternary Yellowstone Plateau, an undulating landscape shaped by forces of late Cenozoic explosive and effusive volcanism, on-going tectonism, glaciation, and hydrothermal activity. The Yellowstone Caldera is the centerpiece of the Yellowstone Plateau. The Yellowstone Plateau lies at the most northeastern front of the 17-Ma Yellowstone hot spot track, one of the few places on Earth where time-transgressive processes on continental crust can be observed in the volcanic and tectonic (faulting and uplift) record at the rate and direction predicted by plate motion. Over six days, this field trip presents an intensive overview into volcanism, tectonism, and hydrothermal activity on the Yellowstone Plateau (fig. 1). Field stops are linked directly to conceptual models related to monitoring of the various volcanic, geochemical, hydrothermal, and tectonic aspects of the greater Yellowstone system. Recent interest in young and possible future volcanism at Yellowstone as well as new discoveries and synthesis of previous studies, (for example, tomographic, deformation, gas, aeromagnetic, bathymetric, and seismic surveys), provide a framework in which to discuss volcanic, hydrothermal, and seismic activity in this dynamic region.

Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM)

NASA Astrophysics Data System (ADS)

Mills, Michael J.; Schmidt, Anja; Easter, Richard; Solomon, Susan; Kinnison, Douglas E.; Ghan, Steven J.; Neely, Ryan R.; Marsh, Daniel R.; Conley, Andrew; Bardeen, Charles G.; Gettelman, Andrew

2016-03-01

Accurate representation of global stratospheric aerosols from volcanic and nonvolcanic sulfur emissions is key to understanding the cooling effects and ozone losses that may be linked to volcanic activity. Attribution of climate variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the rate of global average temperature increases. We have compiled a database of volcanic SO2 emissions and plume altitudes for eruptions from 1990 to 2014 and developed a new prognostic capability for simulating stratospheric sulfate aerosols in the Community Earth System Model. We used these combined with other nonvolcanic emissions of sulfur sources to reconstruct global aerosol properties from 1990 to 2014. Our calculations show remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD) and with in situ measurements of stratospheric aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD calculations represent a clear improvement over available satellite-based analyses, which generally ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at middle and high latitudes. Our SAD calculations greatly improve on that provided for the Chemistry-Climate Model Initiative, which misses about 60% of the SAD measured in situ on average during both volcanically active and volcanically quiescent periods.

Geological and Petrological Characteristics of Oligocene Magmatic Rocks in The Biga Peninsula, NW Turkey

NASA Astrophysics Data System (ADS)

Erenoglu, Oya

2016-04-01

Oligocene magmatic activity in the Biga Peninsula (NW-Anatolia) produced widespread volcano-plutonic complexes. The study region, where in north of the Evciler village in the middle of Biga Peninsula includes these igneous assemblages. In this study, the petrographic and geochemical characteristics of igneous rocks in the region were investigated as well as the geological locations. The magmatic rocks are classified as 6 different units using their lithostratigraphical properties. The volcanism in the region starts with basaltic andesite lava including basalt dykes in the Lower Oligocene. In the Upper Oligocene, the evolved magma by crustal contamination produced commonly dacitic and andesitic lavas. The volcanism continued with andesitic lavas which had significant alterations in the region during this period. Evciler pluton including granite and granodiorite composition with shallow intrusive, was located with the related volcanism at the same time. The volcanic products, i.e. andesitic and trachydacitic lavas, was completed in the interval between Upper Oligocene and Lower Miocene. The post-collisional Oligocene sequence is associated with calc-alkaline composition and it has middle, high-K. Trace and rare earth elements (REE) diagrams show the enrichment in both large-ion lithophile elements (LILE) and light rare earth elements (LREE) with respect to the high field strength elements (HFSE), and a significant increment in heavy rare earth element consumption (HREE). The features of major, trace and rare earth elements of plutonic and volcanic rocks and the compositional variations of Oligocene volcanic group indicate increasing amounts of partial melting, crustal contamination and/or assimilation. The Oligocene post-collisional volcanism in Biga Peninsula points out the lithospheric mantle source enriched by subduction which controlled by slab break-off and lithospheric delamination. Acknowledgement. This study was supported by Canakkale Onsekiz Mart University Scientific Research Project Coordination Unit (Project no: FBA-2015-566) Keywords: Biga Peninsula, oligocene, post-collisional volcanism, petrology

The spatial and temporal `cost' of volcanic eruptions: assessing economic impact, business inoperability, and spatial distribution of risk in the Auckland region, New Zealand

NASA Astrophysics Data System (ADS)

McDonald, Garry W.; Smith, Nicola J.; Kim, Joon-hwan; Cronin, Shane J.; Proctor, Jon N.

2017-07-01

Volcanic risk assessment has historically concentrated on quantifying the frequency, magnitude, and potential diversity of physical processes of eruptions and their consequent impacts on life and property. A realistic socio-economic assessment of volcanic impact must however take into account dynamic properties of businesses and extend beyond only measuring direct infrastructure/property loss. The inoperability input-output model, heralded as one of the 10 most important accomplishments in risk analysis over the last 30 years (Kujawaski Syst Eng. 9:281-295, 2006), has become prominent over the last decade in the economic impact assessment of business disruptions. We develop a dynamic inoperability input-output model to assess the economic impacts of a hypothetical volcanic event occurring at each of 7270 unique spatial locations throughout the Auckland Volcanic Field, New Zealand. This field of at least 53 volcanoes underlies the country's largest urban area, the Auckland region, which is home to 1.4 million people and responsible for 35.3% (NZ201481.2 billion) of the nation's GDP (Statistics New Zealand 2015). We apply volcanic event characteristics for a small-medium-scale volcanic eruption scenario and assess the economic impacts of an `average' eruption in the Auckland region. Economic losses are quantified both with, and without, business mitigation and intervention responses in place. We combine this information with a recent spatial hazard probability map (Bebbington and Cronin Bull Volcanol. 73(1):55-72, 2011) to produce novel spatial economic activity `at risk' maps. Our approach demonstrates how business inoperability losses sit alongside potential life and property damage assessment in enhancing our understanding of volcanic risk mitigation.

SHARAD Investigation of the Interaction Between Volcanism and Deep Water Release in Elysium Planitia, Mars

NASA Astrophysics Data System (ADS)

Morgan, G. A.; Campbell, B. A.; Carter, L. M.; Plaut, J. J.

2011-12-01

Situated between the equator and 12°N and extending from 130° to 180°E, Elysium Planitia is considered to be the youngest volcanic plain on Mars. Recent crater counts on individual lava units argue for multiple phases of activity over the last 230 Myrs, with the most recent volcanic features dating to just ~2 Ma. The region also contains the youngest outflow channels on the planet. Multiple channel systems which are present across the region are interpreted to have been carved by the release of deep ground water (>1 km) from the broadly east-west trending Cerberus Fossae graben system. Elysium Planitia is therefore a region of high scientific interest, as it represents an ideal site to investigate the interaction of lava and water both below and on the surface of Mars. Extensive geologic mapping of Elysium Planitia has provided detailed information concerning the stratigraphy of the major volcanic units in addition to the classification of other landforms attributed to volcanic (e.g. small shields), fluvial (e.g. outflow channels) and aeolian (e.g. yardangs) activity. Orbital sounding radar provides a means to take this work to the next level through the mapping of buried surfaces associated with a contrast in dielectric permittivity and thus can be used to investigate the 3-D structure of the subsurface. Previous studies using the SHARAD radar sounder onboard the Mars Reconnaissance Orbiter have identified multiple subsurface reflectors below the plains of Elysium Planitia. We will present our investigation of SHARAD data covering the eastern portion of this region of Mars - an area that includes the upstream reaches of Marte Vallis and the eastern extent of Cerberus Fossae. Our subsurface mapping shows remarkable correlations with published geologic maps produced using visible orbital datasets. These similarities allow us to use SHARAD data to make estimates of the average permittivity values and imply density measurements of the volcanic units. We will present these estimates and compare them to values derived over other young volcanic regions on Mars. Sounding radar provides the only type of orbital instrument to derive bulk estimates of geochemical properties of martian volcanic materials. Additionally we have identified the original fluvial eroded bed of Marte Vallis, prior to burial by younger lava flows. Through the mapping of the associated fluvial features we are able to tie the origin of Marte Vallis to Cerberus Fossae and provide further support for the recent (Late Amazonian) deep subsurface release of water on the surface of Mars. Our work will provide valuable constraints on the influence of recent volcanism on martian subsurface reservoirs of water.

The Surface of Venus

NASA Astrophysics Data System (ADS)

Ivanov, M. A.; Head, J. W.

2018-03-01

This chapter reviews the conditions under which the basic landforms of Venus formed, interprets their nature, and analyzes their local, regional, and global age relationships. The strong greenhouse effect on Venus causes hyper-dry, almost stagnant near-surface environments. These conditions preclude water-driven, and suppress wind-related, geological processes; thus, the common Earth-like water-generated geological record of sedimentary materials does not currently form on Venus. Three geological processes are important on the planet: volcanism, tectonics, and impact cratering. The small number of impact craters on Venus ( 1,000) indicates that their contribution to resurfacing is minor. Volcanism and tectonics are the principal geological processes operating on Venus during its observable geologic history. Landforms of the volcanic and tectonic nature have specific morphologies, which indicate different modes of formation, and their relationships permit one to establish their relative ages. Analysis of these relationships at the global scale reveals that three distinct regimes of resurfacing comprise the observable geologic history of Venus: (1) the global tectonic regime, (2) the global volcanic regime, and (3) the network rifting-volcanism regime. During the earlier global tectonic regime, tectonic resurfacing dominated. Tectonic deformation at this time caused formation of strongly tectonized terrains such as tessera, and deformational belts. Exposures of these units comprise 20% of the surface of Venus. The apparent beginning of the global tectonic regime is related to the formation of tessera, which is among the oldest units on Venus. The age relationships among the tessera structures indicate that this terrain is the result of crustal shortening. During the global volcanic regime, volcanism overwhelmed tectonic activity and caused formation of vast volcanic plains that compose 60% of the surface of Venus. The plains show a clear stratigraphic sequence from older shield plains to younger regional plains. The distinctly different morphologies of the plains indicate different volcanic formation styles ranging from eruption through broadly distributed local sources of shield plains to the volcanic flooding of regional plains. The density of impact craters on units of the tectonic and volcanic regimes suggests that these regimes characterized about the first one-third of the visible geologic history of Venus. During this time, 80%–85% of the surface of the planet was renovated. The network rifting-volcanism regime characterized the last two-thirds of the visible geologic history of Venus. The major components of the regime include broadly synchronous lobate plains and rift zones. Although the network rifting-volcanism regime characterized 2/3 of the visible geologic history of Venus, only 15%–20% of the surface was resurfaced during this time. This means that the level of endogenous activity during this time has dropped by about an order of magnitude compared with the earlier regimes.

Young Volcanism on 20 Million Year Old Seafloor: The DISCOL Area, Nazca Plate.

NASA Astrophysics Data System (ADS)

Devey, C. W.; Boetius, A.; Kwasnitschka, T.; Augustin, N.; Yeo, I. A.; Greinert, J.

2016-12-01

Volcanism in the ocean basins is traditionally assumed to occur only at the plate margins (mid-ocean ridges, subduction zones, possibly also transform boundaries) and areas of intraplate hotspot activity related to thermal plumes in the mantle. As a result, abyssal areas away from hotspots are seldom explored systematically for signs of volcanism and are generally regarded as volcanically "dead". Here we present serendipitous results from the Peru Basin, a site of Mn-nodule accumulation which was targetted in 1989 for a large-scale disturbance experiment (the DISCOL experiment) to simulate the effects of seabed nodule mining. The area is truly intraplate - it is 700 km from the south American subduction zone or the Galapagos Islands and 2000 km from the East Pacific Rise. A return trip to DISCOL in 2015 to assess the extent of environmental recovery also included a remotely-operated underwater vehicle (ROV) dive on a small (300m high) seamount adjacent to the Mn-nodule field. ROV video records show the seamount is generally heavily sedimented but has a small (100x150m) pillow mound and an area of indurated calcareous sediments apparently cut by basaltic dykes near its summit. The summit is also cut by N-S and E-W-trending faults, some with up to 20m of throw, whose scarps expose thick sedimentary sequences. The virtual absence of sediment covering the pillows or dyke outcrops suggest that they are very recent - the thick sediment pile exposed on the fault scarps suggests that they were erupted on top of an old seamount. Regionally, acoustic data (bathymetry and backscatter from the ship-mounted multibeam system) shows several other seamounts in the region which may have experienced recent volcanic activity, although no sign of a linear volcanic chain is seen. Taken together, these observations suggest that, even at age 20Ma, the Nazca Plate is volcanically active.

Neogene Tiporco Volcanic Complex, San Luis, Argentina: An explosive event in a regional transpressive - local transtensive setting in the pampean flat slab

NASA Astrophysics Data System (ADS)

Ibañes, Oscar Damián; Sruoga, Patricia; Japas, María Silvia; Urbina, y. Nilda Esther

2017-07-01

The Neogene Tiporco Volcanic Complex (TVC) is located in the Sierras Pampeanas of San Luis, Argentina, at the southeast of the Pampean flat-slab segment. Based on the comprehensive study of lithofacies and structures, the reconstruction of the volcanic architecture has been carried out. The TVC has been modeled in three subsequent stages: 1) initial updoming, 2) ignimbritic eruptive activity and 3) lava dome emplacement. Interplay of magma injection and transtensional tectonic deformation has been invoked to reproduce TVC evolution.

A Holocene Lake Record from Laguna Del Maule (LdM) in the Chilean Andes: Climatic and Volcanic Controls on Lake Depositional Dynamics

NASA Astrophysics Data System (ADS)

Valero-Garces, B. L.; Frugone Alvarez, M.; Barreiro-Lostres, F.; Carrevedo, M. L.; Latorre Hidalgo, C.; Giralt, S.; Maldonado, A.; Bernárdez, P.; Prego, R.; Moreno-Caballud, A.

2014-12-01

Central Chile is a tectonically active, drought-prone region sensitive to latitudinal variations in large-scale cold fronts associated with fluctuations of the Pacific subtropical high. Holocene high-resolution records of climate and volcanic events could help inform more on the frequency of extensive droughts as well as volcanic and seismic hazards. LdM is a high altitude, volcanic lake located in the Transition Southern Volcanic Zone (~36°S, 2200 m.a.s.l). The LdM volcanic field is a very seismically and volcanically active zone in the Andes, with several caldera-forming eruptions over the last 1.5 Ma, and intense postglacial activity. In 2013, we recovered over 40 m of sediment cores at four sites of LdM and collected > 20 km of seismic lines. The cores were imaged, their physical and geochemical properties analysed with a Geotek MSCL and XRF scanner respectively, and sampled for TOC, TIC, TS, TN, BioSi, and bulk mineralogy. The chronology was constructed with a Bayesian age-depth model including 210Pb-137Cs, the Quizapú volcanic ash (1932 AD) and 17 AMS 14C dates. The 4.8 m long composite sequence spans the Late glacial and Holocene.Sediments are massive to banded, quartz and plagioclase-rich silts with variable diatom (BioSi, 15- 30 %) and organic matter content (TOC, 1-5 %). Four main units have been defined based on sedimentological and geochemical composition. The transition from Unit 4 to 3 is ascribed to the onset of the Holocene; Unit 2 spans the mid Holocene, and Unit 1 the last 4 ka. Higher (lower) TOC, Br/Ti and Fe/Mn ratios in units 1 and 3 (2 and 4) suggest higher (lower) organic productivity in the lake and dominant oxic (anoxic) conditions at the bottom of the lake. Up to 17 ash and lapilli layers mark volcanic events, mostly grouped in units 1 and 3. Periods of higher lake productivity (units 1 and 3) are synchronous to higher frequency of volcanic events. Some climate transitions (LIA, 4ka, 8ka and 11ka) are evident in the LdM sequence underlining their paleohydrological regional significance.

Fault reactivation due to the M7.6 Nicoya earthquake at the Turrialba-Irazú volcanic complex, Costa Rica: Effects of dynamic stress triggering

NASA Astrophysics Data System (ADS)

Lupi, M.; Fuchs, Florian; Pacheco, Javier F.

2014-06-01

The M7.6 Nicoya earthquake struck at the interface between the Cocos plate and the Caribbean plate on 5 September 2012 inducing a ground acceleration of 0.5 m s-2 at the Irazú-Turrialba volcanic complex. We use data from six seismic stations deployed around and atop the Irazú-Turrialba volcanic complex to show the increase of local seismic activity after the M7.6 Nicoya earthquake. The response consists in more than 300 locatable earthquakes occurring in swarm sequences along a fault system that intersects the Irazú-Turrialba volcanic complex. In addition, we point out that major aftershocks are followed by increases of seismic activity in the same region. The weak static stress variation imposed by the main slip of the Nicoya earthquake at the Irazú-Turrialba volcanic complex suggests a dynamic triggering mechanism. We expand this concept suggesting that this behavior may be similar to the one observed in the Chilean and Japanese volcanic arcs during the M8.8 2010 Maule, Chile, and M9.0 2011 Tohoku, Japan, earthquakes. Finally, we highlight that the combined action of dynamic stress and short-lived coseismic relaxation may trigger seismic activity in geological systems in near-critical conditions.

ALVIN investigation of an active propagating rift system, Galapagos 95.5° W

USGS Publications Warehouse

Hey, R.N.; Sinton, J.M.; Kleinrock, M.C.; Yonover, R.N.; MacDonald, K.C.; Miller, S.P.; Searle, R.C.; Christie, D.M.; Atwater, T.M.; Sleep, Norman H.; Johnson, H. Paul; Neal, C.A.

1992-01-01

ALVIN investigations have defined the fine-scale structural and volcanic patterns produced by active rift and spreading center propagation and failure near 95.5° W on the Galapagos spreading center. Behind the initial lithospheric rifting, which is propagating nearly due west at about 50 km m.y.−1, a triangular block of preexisting lithosphere is being stretched and fractured, with some recent volcanism along curving fissures. A well-organized seafloor spreading center, an extensively faulted and fissured volcanic ridge, develops ~ 10 km (~ 200,000 years) behind the tectonic rift tip. Regional variations in the chemical compositions of the youngest lavas collected during this program contrast with those encompassing the entire 3 m.y. of propagation history for this region. A maximum in degree of magmatic differentiation occurs about 9 km behind the propagating rift tip, in a region of diffuse rifting. The propagating spreading center shows a gentle gradient in magmatic differentiation culminating at the SW-curving spreading center tip. Except for the doomed rift, which is in a constructional phase, tectonic activity also dominates over volcanic activity along the failing spreading system. In contrast to the propagating rift, failing rift lavas show a highly restricted range of compositions consistent with derivation from a declining upwelling zone accompanying rift failure. The lithosphere transferred from the Cocos to the Nazca plate by this propagator is extensively faulted and characterized by ubiquitous talus in one of the most tectonically disrupted areas of seafloor known. The pseudofault scarps, where the preexisting lithosphere was rifted apart, appear to include both normal and propagator lavas and are thus more lithologically complex than previously thought. Biological communities, probably vestimentiferan tubeworms, occur near the top of the outer pseudofault scarp, although no hydrothermal venting was observed.

Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations. Volume II

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowe, B.M.; Wohletz, K.H.; Vaniman, D.T.

1986-01-01

Volcanic hazard investigations during FY 1984 focused on five topics: the emplacement mechanism of shallow basalt intrusions, geochemical trends through time for volcanic fields of the Death Valley-Pancake Range volcanic zone, the possibility of bimodal basalt-rhyolite volcanism, the age and process of enrichment for incompatible elements in young basalts of the Nevada Test Site (NTS) region, and the possibility of hydrovolcanic activity. The stress regime of Yucca Mountain may favor formation of shallow basalt intrusions. However, combined field and drill-hole studies suggest shallow basalt intrusions are rare in the geologic record of the southern Great Basin. The geochemical patterns ofmore » basaltic volcanism through time in the NTS region provide no evidence for evolution toward a large-volume volcanic field or increases in future rates of volcanism. Existing data are consistent with a declining volcanic system comparable to the late stages of the southern Death Valley volcanic field. The hazards of bimodal volcanism in this area are judged to be low. The source of a 6-Myr pumice discovered in alluvial deposits of Crater Flat has not been found. Geochemical studies show that the enrichment of trace elements in the younger rift basalts must be related to an enrichment of their mantle source rocks. This geochemical enrichment event, which may have been metasomatic alteration, predates the basalts of the silicic episode and is, therefore, not a young event. Studies of crater dimensions of hydrovolcanic landforms indicate that the worst case scenario (exhumation of a repository at Yucca Mountain by hydrovolcanic explosions) is unlikely. Theoretical models of melt-water vapor explosions, particularly the thermal detonation model, suggest hydrovolcanic explosion are possible at Yucca Mountain. 80 refs., 21 figs., 5 tabs.« less

Imaging the transition from Aleutian subduction to Yakutat collision in central Alaska, with local earthquakes and active source data

USGS Publications Warehouse

Eberhart-Phillips, D.; Christensen, D.H.; Brocher, T.M.; Hansen, R.; Ruppert, N.A.; Haeussler, Peter J.; Abers, G.A.

2006-01-01

In southern and central Alaska the subduction and active volcanism of the Aleutian subduction zone give way to a broad plate boundary zone with mountain building and strike-slip faulting, where the Yakutat terrane joins the subducting Pacific plate. The interplay of these tectonic elements can be best understood by considering the entire region in three dimensions. We image three-dimensional seismic velocity using abundant local earthquakes, supplemented by active source data. Crustal low-velocity correlates with basins. The Denali fault zone is a dominant feature with a change in crustal thickness across the fault. A relatively high-velocity subducted slab and a low-velocity mantle wedge are observed, and high Vp/Vs beneath the active volcanic systems, which indicates focusing of partial melt. North of Cook Inlet, the subducted Yakutat slab is characterized by a thick low-velocity, high-Vp/Vs, crust. High-velocity material above the Yakutat slab may represent a residual older slab, which inhibits vertical flow of Yakutat subduction fluids. Alternate lateral flow allows Yakutat subduction fluids to contribute to Cook Inlet volcanism and the Wrangell volcanic field. The apparent northeast edge of the subducted Yakutat slab is southwest of the Wrangell volcanics, which have adakitic composition consistent with melting of this Yakutat slab edge. In the mantle, the Yakutat slab is subducting with the Pacific plate, while at shallower depths the Yakutat slab overthrusts the shallow Pacific plate along the Transition fault. This region of crustal doubling within the shallow slab is associated with extremely strong plate coupling and the primary asperity of the Mw 9.2 great 1964 earthquake. Copyright 2006 by the American Geophysical Union.

Impact of Magmatism on the Geodynamic Evolution of Southern Georgia on the Example of the Lesser Caucasus Artvin-Bolnisi Block.

NASA Astrophysics Data System (ADS)

Sadradze, Nino; Adamia, Shota; Zakariadze, Guram; Beridze, Tamara; Khutsishvili, Sophio

2017-04-01

The Georgian region occupies the central part of the collisional zone between the Eurasian and Africa-Arabian continents and is actually a collage of lithospheric fragments of the Tethyan Ocean and its northern and southern continental margins. Magmatic evolution is an important event in the formation and development of the geological structure of Southern Georgia, where several reliably dated volcanogenic and volcanogenic-sedimentary formations are established. The region represents a modern analogue of continental collision zone, where subduction-related volcanic activity lasted from Paleozoic to the end of Paleogene. After the period of dormancy in the Early-Middle Miocene starting from the Late Miocene and as far as the end of the Pleistocene, primarily subaerial volcanic eruptions followed by formation of volcanic highlands and plateaus occurred in the reigon. The Upper Miocene to Holocene volcanic rocks are related to the transverse Van-Transcaucasian uplift and belong to post-collisional calc- alkaline basalt-andesite-dacite-rhyolite series. A system of island arc and intra-arc rift basins (Artvin-Bolnisi and Achara-Trialeti) have been interpreted as characteristic of the pre-collisional stage of the region development, while syn- post-collisional geodynamic events have been attributed to intracontinental stage. Outcrops of the postcollisional magmatic rocks are exposed along the boundaries of the major tectonic units of the region. The Artvin-Bolnisi unit forms the northwestern part of the Lesser Caucasus and represents an island arc domain of so called the Somkheto-Karabakh Island Arc or Baiburt-Garabagh-Kapan belt. It was formed mainly during the Jurassic-Eocene time interval on the southern margin of the Eurasian plate by nort-dipping subduction of the Neotethys Ocean and subsequent collision to the Anatolia-Iranian continental plate. The Artvin-Bolnisi unit, including the Bolnisi district, was developing as a relatively uplifted island arc-type unit with suprasubduction extrusive and intrusive events. Volcanogenic complexes are characterized by variable lateral and vertical regional stratigraphic relationships and are subdivided into several formations, dominated by volcanic rocks: basalts, andesites, dacites, and rhyolites of calc-alkaline-subalkaline series. Volcanic rocks are of shallow-marine to subaerial type. The peculiarities of magmatic activity and geodynamic development of the region stipulated synchronous formation of significant base and precious metals deposits of the Bolnisi ore district.

Modeling of Small Martian Volcanoes: A Changing View of Volcanic Shield and Cone Fields

NASA Astrophysics Data System (ADS)

Sakimoto, S. E.; Bradley, B. A.; Garvin, J. B.

2001-05-01

The small volcanic features on Mars (channels, flows, shields, and cratered cones) are key to understanding eruption styles, rates, and volumes because they are ubiquitous and simple enough to attempt modeling. Several of these small features have been suggested to be geologically recent [1,2,3]. This study measures and models small (3-50 km) volcanic edifices. Recent Mars Global Surveyor data reveal that these small features are more common that we had previously thought from the lower resolution Viking mission data (e.g., [3,4]). Furthermore, there are clear geometric differences in the Mars Orbiter Laser Altimeter (MOLA) data between regions suggesting local and regional eruption styles may vary with latitude. While a few of the pre-MGS construction models predict the martian mid-latitude volcanic shield shapes fairly well, the small explosive volcanic edifice shapes were not well predicted by existing models (see[5]), and there are a host of types-mostly polar-that are not well described by prior modeling. We compare small edifice construction model results for a percolation style model of effusive and mixed effusive and explosive edifices to prior model results for several martian volcanic regions. While mid-latitude edifices match well to predicted cross-section shapes, steeper flank slopes (See [6]; Glaze and Sakimoto, this volume) for the polar edifices suggest that the magma supply rate or the edifice permeability may be higher in the polar regions for some edifices types. However, polar edifice flank slopes do not commonly reach the greater than 10 degree flanks expected from prior explosive edifice models. Additionally, we do not observe shallow flank slope shields in the polar regions. This suggests that simple shield building may be significantly influenced or modified by volatile involvement near the martian poles, while a range of poorly understood explosive activity may be active in both regions. [1] Keszthelyi et al. JGR 105, 15027-15049, 2000. [2] Hartmann and Berman, JGR, 105, 15011-15025, 2000. [3] Garvin, et al., Icarus, 145, 648-652, 2000. [4] Sakimoto, et al., LPSC XXXII, CDROM, abstract #1808, 2001. [5] Glaze and Baloga LPSC XXXII, CDROM, abstract #1209, 2001. [6] Wong, et al., LPSC XXXII, CDROM, abstract #1563, 2001.

Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand.

PubMed

Hamling, Ian J; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

2016-06-01

Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system.

Eruptive dynamics and hazards associated with obsidian bearing ignimbrites of the Geghama Volcanic Highland, Central Armenia: a textural insight

NASA Astrophysics Data System (ADS)

Matthews, Zoe; Manning, Christina J.

2017-04-01

The Geghama Volcanic highland in central Armenia is an ideal setting to study the young ( 750-25 ka [1]) volcanism that characterises the Lesser Caucasus region. The volcanism in the area is bimodal in composition: the eastern highlands are dominated by numerous monogenetic scoria cones, whilst the west shows more evolved volcanism centered on two obsidian bearing, polygenetic domes (Hatis and Gutanasar) [2]. Activity at Hatis and Gutanasar is thought to have spanned 550ka-200ka [3] and produced a range of products including obsidian flows, ignimbrites and basaltic scoria cones, consistent with long lived and complex magma storage systems. During a similar time period there is evidence for the presence of hominin groups in the surrounding region [3] and it is likely that at least some of the volcanic activity at Hatis and Gutanasar impacted on their distribution [4]. A better understanding of the eruptive behaviour of these volcanoes during this period could therefore shed light on the effect of volcanic activity on the dispersal of man through this period. Whilst large regional studies have striven to better understand the timing and source of volcanism in Armenia, there have been few detailed studies on single volcanoes. Obsidian is ubiquitous within the volcanic material of both Gutanasar and Hatis as lava flows, dome deposits and within ignimbrites. This study aims to better understand the eruptive history of Gutanasar, with specific focus upon the determination of the petrogenetic history of obsidian lenses observed within the ignimbrite deposits. Identification of these obsidians as the result of welding or in-situ melting will help constrain eruptive volumes and flow thickness, important for the reconstruction of palaeo-volcanic hazards. In order to interpret how this obsidian was deposited, macro textural analysis is combined with micro textural measurements of microlite crystals. Quantitative measurements of microlites in obsidian can provide significant insight into the eruptive dynamics and emplacement history [5]. In particular, microlite number density, volume and alignment represent the summation of degassing, conduit flow and emplacement [6]. As such, there is great significance in the quantification of these parameters for the determination of eruption dynamics. Analysis of these obsidians will establish patterns of textural heterogeneity as a signature for the distinction of volcanic glasses formed by different mechanisms and allow for identification of patterns in microlite number density, volume, alignment and plunge that characterise differing modes of emplacement. Together, these measurements will aid interpretation and improve understanding of this volcanic system, with applicability to the determination of the impact of these volcanic episodes on the distribution of early man in Armenia as well as assessment of the potential for future events. [1] Lebedev et al (2013) JVS, 7, 204-229 [2] Arutyunyan et al (2007) Dokl Earth Sci, 416, 1042-1046 [3] Alder et al (2014) Science, 345, 1609-1613 [4] Hutchison et al (2016) Nat. Commun, 7 [5] Manga (1998) JVGR, 86, 107-115 [6] Befus et al (2015) Bull. Volcanol, 77, 88

Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians

USGS Publications Warehouse

Ratcliffe, N.M.; Aleinikoff, J.N.; Burton, W.C.; Karabinos, P.

1991-01-01

A newly recognized suite of trondhjemite-tonalite and dacitic gneiss forms a 10 km wide belt of rocks within the Mount Holly Complex in the central part of the Green Mountain massif. Field relationships and chemistry indicate that these gneisses are calc-alkaline, volcanic, and hypabyssal plutonic rocks older than the Middle Proterozoic regional deformation that affected the Mount Holly Complex. U-Pb zircon dates indicate ages as great as 1.35 Ga for crystallization of the volcanic protoliths and for intrusion of crossing trondhjemite. Tonalitic plutonism continued until 1.31 Ga. The Mount Holly intrusives and volcanics may have formed during 1.35-1.31 Ga ensialic volcanic-arc activity, contemporaneous with ensimatic arc activity during the early part of the Elzevirian phase of the Grenville orogeny. -from Authors

Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: earthquake locations and source parameters

USGS Publications Warehouse

Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.

2011-01-01

An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.

Long-lived volcanism within Argyre basin, Mars

NASA Astrophysics Data System (ADS)

Williams, Jean-Pierre; Dohm, James M.; Soare, Richard J.; Flahaut, Jessica; Lopes, Rosaly M. C.; Pathare, Asmin V.; Fairén, Alberto G.; Schulze-Makuch, Dirk; Buczkowski, Debra L.

2017-09-01

The Argyre basin, one of the largest impact structures on Mars with a diameter >1200 km, formed in the Early Noachian ∼3.93 Ga. The basin has collected volatiles and other material through time, and experienced partial infilling with water evident from stratigraphic sequences, crater statistics, topography, and geomorphology. Although volcanism has not been previously associated with the Argyre basin, our study of the northwest portion of the basin floor has revealed landforms suggesting volcanic and tectonic activity occurred including Argyre Mons, a ∼50 km wide volcanic-structure formed ∼3 Ga. Giant polygons with a similar surface age are also identified on terrain adjacent to the base of Argyre Mons, indicating the structure may have formed in a water-rich environment. In addition to Argyre Mons, cones, vents, mounds, dikes, and cavi or hollows, many of which are associated with extensional tectonics, are observed in the region. Multiple features appear to disrupt icy (and largely uncratered) terrain indicating a relatively young, Late Amazonian, formation age for at least some of the volcanic and tectonic features. The discovery of Argyre Mons, along with additional endogenic modification of the basin floor, suggests that the region has experienced episodes of volcanism over a protracted period of time. This has implications for habitability as the basin floor has been a region of elevated heat flow coupled with liquid water, water ice, and accumulation of sediments of diverse provenance with ranging geochemistry, along with magma-water interactions.

Regional Observation of Seismic Activity in Baekdu Mountain

NASA Astrophysics Data System (ADS)

Kim, Geunyoung; Che, Il-Young; Shin, Jin-Soo; Chi, Heon-Cheol

2015-04-01

Seismic unrest in Baekdu Mountain area between North Korea and Northeast China region has called attention to geological research community in Northeast Asia due to her historical and cultural importance. Seismic bulletin shows level of seismic activity in the area is higher than that of Jilin Province of Northeast China. Local volcanic observation shows a symptom of magmatic unrest in period between 2002 and 2006. Regional seismic data have been used to analyze seismic activity of the area. The seismic activity could be differentiated from other seismic phenomena in the region by the analysis.

The Lanzarote Geodynamic Laboratory: new capabilities for monitoring of volcanic activity at Canary Islands

NASA Astrophysics Data System (ADS)

Arnoso, J.; Vélez, E. J.; Soler, V.; Montesinos, F. G.; Benavent, M.

2012-04-01

The volcanic island of Lanzarote is located at the northeastern end of the Canary Islands. Together with Fuerteventura Island, Lanzarote constitutes the emergent part of the East Canary Ridge, which presents a NNE-SSW volcanic alignment. Last eruptive events took place in 1824 and during the period 1730-1736, which is the largest to occur in the archipelago and throw out about 1.3 km3 of volcanic materials. The Lanzarote Geodynamic Laboratory (LGL) was created in 1986 with the idea of making Lanzarote as a natural laboratory to carry out studies in order to acquire more knowledge about its origin, present status and evolution (Vieira et al., 1991; 2006). The LGL has a multidisciplinary scientific purpose and, among others, various objectives are devoted to investigate mass distribution in the Earth system and surface displacements associated to volcanic and/or seismic activity in the island. The influence of LGL is extended throughout the whole geographical area of Lanzarote, including small islands located at the north. The laboratory has 3 observing modules distributed along the island according to its infrastructure and scientific objectives, where more than 70 sensors are recording continuously gravity variations, ground deformations, sea level, seismic activity, meteorological parameters, etc. All these observations are supplemented by periodic measurement of geodetic and geophysical networks that allow us to make studies at local, insular and regional scales. The application of geodetic and geophysical techniques to identify geodynamic signals related to volcanic processes is then a permanent research activity of the laboratory. Nowadays, this fact becomes more interesting due to the ongoing volcanic eruption that is taking place in other island of the Canary Archipelago, El Hierro, since past July 2011. That is, the multidisciplinary research carry on up to now at the LGL allow us to apply multiparameter observations of different kinds of volcanic manifestations at the surface level, and to compare geodynamic processes associated with an active area of the Earth's crust. In turn, the results obtained can provide new inputs for studying precursor of volcanic activity and also contribute to volcanic hazard mitigation. The LGL aims to be a permanent status of renewal, using new technologies for data recording and real time transmission, as well as for testing new sensors, scientific equipment and observational techniques related to monitoring and observation of volcanic activity. All these capabilities are necessary when high-resolution ground based observations must provide us the basis for studying the sources of volcanic deformation. The laboratory is thus open to support and to enhance the collaboration among scientists, as well as national and international institutions involved in research at active volcanic areas.

Assessing volcanic hazard at the most populated caldera in the world: Campi Flegrei, Southern Italy

NASA Astrophysics Data System (ADS)

Somma, R.; de Natale, G.; Troise, C.; Kilburn, C.; Moretti, R.

2017-12-01

Naples and its hinterland in Southern Italy are one of the most urbanized areas in the world under threat from volcanic activity. The region lies within range of three active volcanic centers: Vesuvius, Campi Flegrei, and Ischia. The Campi Flegrei caldera, in particular, has been in unrest for six decades. The unrest followed four centuries of quiescence and has heightened concern about an increased potential for eruption. Innovative geochemical and geophysical analysis, combined with scientific drilling, are being used to investigate Campi Flegrei. Results highlight key directions for better understanding the mechanisms of caldera formation and the respective roles of magma intrusion and hydrothermal activity in determining the volcano's behavior. They also provide a framework for evaluating and mitigating the risk from this caldera and other large ones worldwide.

Evidence of volcanic ash at a K-T boundary section: Ocean drilling program hole 690 C, Maud Rise, Weddell Sea off East Antarctica

NASA Technical Reports Server (NTRS)

Wise, S. W.; Hamilton, N.; Pospichal, J.; Barker, P. F.; Kennett, James P.; Oconnell, S.; Bryant, W. R.; Burckle, L. H.; Egeberg, P. K.; Futterer, D. K.

1988-01-01

Rare vitric volcanogenic ash but more abundant clay minerals considered volcanogenic in origin are associated with an expanded and essentially complete K-T boundary sequence from Ocean Drilling Project (ODP) Hole 690 C on Maud Rise in the Weddell Sea off East Antarctica. Results at this writing are preliminary and are still based to some extent on shipboard descriptions. Further shore-based studies are in progress. It would appear, however, that the presence of volcanic ash and altered ash in the Danian section beginning at the biostratigraphically and paleomagnetically determined K-T boundary on Maud Rise can be cited as evidence of significant volcanic activity within the South Atlantic-Indian Ocean sector of the Southern Ocean coincident with the time of biotic crises at the end of the Maestrichtian. This is a postulated time of tectonic and volcanic activity within this Southern Hemisphere region, including possible initiation of the Reunion hot spot and a peak in explosive volcanism on Walvis Ridge (1) among other events. A causal relationship with the biotic crisis is possible and volcanism should be given serious consideration as a testable working hypothesis to explain these extinctions.

E-W strike slip shearing of Kinwat granitoid at South East Deccan Volcanic Province, Kinwat, Maharashtra, India

NASA Astrophysics Data System (ADS)

Kaplay, R. D.; Kumar, T. Vijay; Mukherjee, Soumyajit; Wesanekar, P. R.; Babar, Md; Chavan, Sumeet

2017-07-01

We study the margin of South East Deccan Volcanic Province around Kinwat lineament, Maharashtra, India, which is NW extension of the Kaddam Fault. Structural field studies document ˜ E-W strike-slip mostly brittle faults from the basement granite. We designate this as `Western boundary East Dharwar Craton Strike-slip Zone' (WBEDCSZ). At local level, the deformation regime from Kinwat, Kaddam Fault, micro-seismically active Nanded and seismically active Killari corroborate with the nearby lineaments. Morphometric analyses suggest that the region is moderately tectonically active. The region of intense strike-slip deformation lies between seismically active fault along Tapi in NW and Bhadrachalam in the SE part of the Kaddam Fault/lineament. The WBEDCSZ with the surface evidences of faulting, presence of a major lineaments and intersection of faults could be a zone of intraplate earthquake.

Russian eruption warning systems for aviation

USGS Publications Warehouse

Neal, C.; Girina, O.; Senyukov, S.; Rybin, A.; Osiensky, J.; Izbekov, P.; Ferguson, G.

2009-01-01

More than 65 potentially active volcanoes on the Kamchatka Peninsula and the Kurile Islands pose a substantial threat to aircraft on the Northern Pacific (NOPAC), Russian Trans-East (RTE), and Pacific Organized Track System (PACOTS) air routes. The Kamchatka Volcanic Eruption Response Team (KVERT) monitors and reports on volcanic hazards to aviation for Kamchatka and the north Kuriles. KVERT scientists utilize real-time seismic data, daily satellite views of the region, real-time video, and pilot and field reports of activity to track and alert the aviation industry of hazardous activity. Most Kurile Island volcanoes are monitored by the Sakhalin Volcanic Eruption Response Team (SVERT) based in Yuzhno-Sakhalinsk. SVERT uses daily moderate resolution imaging spectroradiometer (MODIS) satellite images to look for volcanic activity along this 1,250-km chain of islands. Neither operation is staffed 24 h per day. In addition, the vast majority of Russian volcanoes are not monitored seismically in real-time. Other challenges include multiple time-zones and language differences that hamper communication among volcanologists and meteorologists in the US, Japan, and Russia who share the responsibility to issue official warnings. Rapid, consistent verification of explosive eruptions and determination of cloud heights remain significant technical challenges. Despite these difficulties, in more than a decade of frequent eruptive activity in Kamchatka and the northern Kuriles, no damaging encounters with volcanic ash from Russian eruptions have been recorded. ?? Springer Science+Business Media B.V. 2009.

Tephrostratigraphy of the late Quaternary record from Lake Chalco, central México

NASA Astrophysics Data System (ADS)

Ortega-Guerrero, Beatriz; Caballero García, Lizeth; Linares-López, Carlos

2018-01-01

Lacustrine sequences in active volcanic settings preserve the record of fall-out products (tephras) from explosive volcanic activity from both proximal and distal sources. Sediments of Lake Chalco, located in the western part of the Trans Mexican Volcanic Belt, offer the opportunity to develop a detailed tephrostratigraphy of proximal and distal sources, and to provide stratigraphic marker horizons for the correlation of paleoclimate records. Here, we present major oxide glass and pumice data from 18 tephra layers interbedded in the lacustrine sediments of Chalco, from 11.5 to 31.3 cal ka BP. Tephra glass compositions range from basaltic trachyandesitic to rhyolitic. Two tephras were successfully correlated with the Tutti Frutti Plinian Eruption of Popocatépetl volcano; and two tephra layers from the Nevado de Toluca Plinian activity: the Upper Toluca Pumice and the Lower Toluca Pumice. Although the source of most of the tephras analyzed is unknown, their geochemical characterization, coupled with a robust chronology, contributes to establish a detailed tephrostratigraphy for the region. This tephra record also contributes to improving the estimated frequency of explosive volcanic activity for future hazards in the Basin of México and surrounding areas, where more than 29 million people live. Our findings estimate a recurrence interval of volcanic activity of ca. 1100 years in the interval between ca. 32 and 11.5 cal ka BP, shorter than previously estimated.

3D upper crustal seismic structure across Santorini volcanic field: Constraints on magmatic and tectonic interactions

NASA Astrophysics Data System (ADS)

Heath, B.; Hooft, E. E. E.; Toomey, D. R.; Papazachos, C. V.; Walls, K.; Paulatto, M.; Morgan, J. V.; Nomikou, P.; Warner, M.

2017-12-01

To investigate magmatic-tectonic interactions at an arc volcano, we collected a dense, active-source, seismic dataset across the Santorini Volcano, Greece, with 90 ocean bottom seismometers, 65 land seismometers, and 14,300 marine sound sources. We use over 140,000 travel-time picks to obtain a P-wave tomography model of the upper crustal structure of the Santorini volcano and surrounding tectonically extended region. Regionally, the shallow (<2 km) velocity structure is dominated by low- and high-velocity anomalies of several sediment-filled grabens and horsts of Attico-Cycladic metamorphic basement, which correlate well with Bouguer gravity anomalies and preliminary shallow attenuation results (using waveform amplitudes and t* values). We find regional Pliocene and younger faults bounding basement grabens and horsts to be predominately oriented in a NE-SW direction with Santorini itself located in a graben bounded by faults striking in this direction. In contrast, volcanic vents and dikes expressed at the surface seem to strike about 20° clockwise relative to these regional faults. In the northern caldera of Santorini, a 4-km wide region of anomalously low velocities and high attenuation directly overlies an inferred source of 2011-2012 inflation (4-4.5 km depth), however it is located at shallower depths ( 1-2km). The imaged low-velocity anomaly may correspond to hydrothermal activity (due to increased porosity and alteration) and/or brecciation from a prior episode of caldera collapse. It is bounded by anomalously fast velocities (at 1-2 km depth) that parallel the regional fault orientation and are correspondingly rotated 20° to surface dikes. At 4-5 km depth beneath the northern caldera basin, low-velocity anomalies and attenuated seismic arrivals provide preliminary evidence for a magma body; the low-velocity anomaly is elongated in the same direction as regional volcanic vents. The difference in strike of volcanic and tectonic features indicates oblique extension and potential time-variation in the minimum stress direction.

Observations and modelling of inflation in the Lazufre volcanic region, South America

NASA Astrophysics Data System (ADS)

Pearse, J.; Lundgren, P.

2010-12-01

The Central Volcanic Zone (CVZ) is an active volcanic arc in the central Andes, extending through Peru, southwestern Bolivia, Chile, and northwestern Argentina [De Silva, 1989; De Silva and Francis, 1991]. The CVZ includes a number of collapsed calderas, remnants of catastrophic eruptions, which are now thought to be inactive. However, recent Interferometric Synthetic Aperture Radar (InSAR) observations [Pritchard and Simons, 2004] show surface deformation occurring at some of these large ancient volcanic regions, indicating that magma chambers are slowly inflating beneath the surface. The mechanisms responsible for the initiation and growth of large midcrustal magma chambers remains poorly understood, and InSAR provides an opportunity for us to observe volcanic systems in remote regions that are otherwise difficult to monitor and observe. The Lastarria-Cordon del Azufre ("Lazufre" [Pritchard and Simons, 2002]) volcanic area is one such complex showing recent deformation, with average surface uplift rates of approximately 2.5 cm/year [Froger et al., 2007; Ruch et al, 2008]. We have processed InSAR data from ERS-1/2 and Envisat in the Lazufre volcanic area, including both ascending and descending satellite tracks. Time series analysis of the data shows steady uplift beginning in about 2000, continuing into 2010. We use boundary-element elastic models to invert for the depth and shape of the magmatic source responsible for the surface deformation. Given data from both ascending and descending tracks, we are able to resolve the ambiguity between the source depth and size, and constrain the geometry of the inflating magma source. Finite element modelling allows us to understand the effect of viscoelasticity on the development of the magma chamber.

Magmatic evolution of the Easter microplate-Crough Seamount region (South East Pacific)

USGS Publications Warehouse

Hekinian, R.; Stoffers, P.; Akermand, D.; Binard, N.; Francheteau, Jean; Devey, C.; Garbe-Schonberg, D.

1995-01-01

The Easter microplate-Crough Seamount region located between 25?? S-116?? W and 25?? S-122?? W consists of a chain of seamounts forming isolated volcanoes and elongated (100-200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065??), to the present day general spreading direction (N 100??) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26??30??? S-115?? W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges ( 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)N = 1-2.5}, {(La/Sm)N = 0.4-1.2} and {(Zr/Y)N = 0.7-2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation (??? 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25?? S-118?? W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (< 800 m depth) was formed by earlier (7-10 Ma) hotspot magmatic activity which also created Easter Island. ?? 1995 Kluwer Academic Publishers.

Trace elements deposition in the Tierra del Fuego region (south Patagonia) by using lichen transplants after the Puyehue-Cordón Caulle (north Patagonia) volcanic eruption in 2011.

PubMed

Conti, Marcelo Enrique; Jasan, Raquel; Finoia, Maria Grazia; Iavicoli, Ivo; Plá, Rita

2016-04-01

Lichen Usnea barbata transplants were tested as a biomonitor of atmospheric deposition in an apparently pristine environment that is Tierra del Fuego region (Patagonia, Argentina). The present survey is connected with the volcanic eruption that started in north Patagonia on June 4, 2011 from the Puyehue-Cordón Caulle volcano, Chile (north Patagonia, at 1700 km of distance of our sampling sites). Lichens were collected in September 2011 (one month of exposure) and September 2012 (1 year of exposure) in 27 sites covering the northern region of the province where trees are not present. The atmospheric deposition of 27 elements by using Neutron Activation Analysis (NAA) was determined in the collected samples. The first aim of the study was to evaluate the influence of the volcanic eruption on the regional atmospheric deposition comparing our results with baseline data we determined in U. barbata in 2006 in the same sites. The second aim was to test possible patterns of bioaccumulation between the two sampling campaigns after the volcanic eruption. With respect to 2006 baseline levels, we found significant higher levels for As, Ba, Co, Cr, Cs, Na, Sb and U in lichens collected after 1 month of exposure (first sampling campaign--2011). Between the two sampling campaigns (2011-2012) after the eruption, lichens reflected the natural contamination by volcanic ashes with significantly higher median levels of Br, Cr, Fe, K, Na, Sc, and Se. Results confirmed the very good aptitude of U. barbata to reflect the levels of elements in the environment at global scale and to reflect the volcanic emissions at distant places. Volcanic eruptions cause the emission in the atmosphere of elevated levels of particulate matter. In this regard, our findings demonstrate the importance to evaluate the metal composition of the particles to avoid possible health effects.

The active submarine NW termination of the South Aegean Active Volcanic Arc: The Submarine Pausanias Volcanic Field

NASA Astrophysics Data System (ADS)

Foutrakis, Panagiotis M.; Anastasakis, George

2018-05-01

Methana peninsula shows the longest recorded volcanic history at the western end of the South Aegean Active Volcanic Arc, including volcanic products from the Upper Pliocene to recent times. The volcanic rocks comprise widespread dacite domes and andesite lava flows from several small volcanic centers and are only imprecisely dated. In this paper, the integrated analysis of swath bathymetry, side scan sonar data, and high resolution seismic reflection profiles correlated with core samples, has allowed detailed mapping, characterization and precise chronological identification of the Pausanias submarine volcanic field activity offshore northern Methana. Six volcanic cones or domes are recognized, typically 1-3 km in diameter, some elongated NE-SW and some with a small central crater. On their flanks, the acoustically reflective volcanic rocks pass laterally into incoherent transparent seismic facies interpreted as volcaniclastic deposits, possibly including hyaloclastites, that interfinger with the regional basin sediments. A sea-bottom hummocky field, is interpreted as volcanic avalanche and appears to be the submarine continuation of the volcaniclastic apron of northern Methana peninsula. A robust chronostratigraphic framework has been established, based on the recognition of shoreline progradational units and their connection with Quaternary eustatic sea level cycles. Relative dating of the different phases of submarine volcanic activity during the Upper Quaternary has been achieved by correlating the imaged volcaniclastic flows, interlayered within the chronostratigraphically dated sediments. Dating by stratigraphic position, relative to 2D imaged eustatic sea level clinoform wedges appears to be more precise than radiometric methods on land. Three main submarine Volcanic Events (VE) are recognized: VE3 at 450 ka, a less precisely dated interval at 200-130 ka (VE2), and VE1 at 14 ka. Based on chronostratigraphic constraints, subsidence rates of 0.16 (±0.008) m/ka in-between Marine Isotopic Stages 6 and 12 and 0.19 (±0.009) m/ka in-between Marine Isotopic Stages 12 and 16 were estimated for the marine basin north of Methana. The morphological similarity to the onshore volcanoes of Methana Peninsula implies that magmatic constructive processes were dominant, regardless of whether in air or in water. The Upper Quaternary submarine volcanic rocks of Methana differ from those known from stratovolcanoes elsewhere in the Mediterranean, (e.g. Kos-Nisyros, Stromboli) and in other volcanic arcs (e.g., Montserrat, St Vincent), in the submarine development of domes or small cones, the paucity of volcano flank failure deposits and the lack of explosive events. Pausanias volcanic products date the onset of NE-SW faulting as well as the following tectonic phase of E-W striking faults, possibly related to basin inversion, caused by a major rifting phase that also affected most of the South Aegean Arc and the adjacent Gulfs of Corinth and Argolikos.

New Insights on Mt. Etna's Crust and Relationship with the Regional Tectonic Framework from Joint Active and Passive P-Wave Seismic Tomography

NASA Astrophysics Data System (ADS)

Díaz-Moreno, A.; Barberi, G.; Cocina, O.; Koulakov, I.; Scarfì, L.; Zuccarello, L.; Prudencio, J.; García-Yeguas, A.; Álvarez, I.; García, L.; Ibáñez, J. M.

2018-01-01

In the Central Mediterranean region, the production of chemically diverse volcanic products (e.g., those from Mt. Etna and the Aeolian Islands archipelago) testifies to the complexity of the tectonic and geodynamic setting. Despite the large number of studies that have focused on this area, the relationships among volcanism, tectonics, magma ascent, and geodynamic processes remain poorly understood. We present a tomographic inversion of P-wave velocity using active and passive sources. Seismic signals were recorded using both temporary on-land and ocean bottom seismometers and data from a permanent local seismic network consisting of 267 seismic stations. Active seismic signals were generated using air gun shots mounted on the Spanish Oceanographic Vessel `Sarmiento de Gamboa'. Passive seismic sources were obtained from 452 local earthquakes recorded over a 4-month period. In total, 184,797 active P-phase and 11,802 passive P-phase first arrivals were inverted to provide three different velocity models. Our results include the first crustal seismic active tomography for the northern Sicily area, including the Peloritan-southern Calabria region and both the Mt. Etna and Aeolian volcanic environments. The tomographic images provide a detailed and complete regional seismotectonic framework and highlight a spatially heterogeneous tectonic regime, which is consistent with and extends the findings of previous models. One of our most significant results was a tomographic map extending to 14 km depth showing a discontinuity striking roughly NW-SE, extending from the Gulf of Patti to the Ionian Sea, south-east of Capo Taormina, corresponding to the Aeolian-Tindari-Letojanni fault system, a regional deformation belt. Moreover, for the first time, we observed a high-velocity anomaly located in the south-eastern sector of the Mt. Etna region, offshore of the Timpe area, which is compatible with the plumbing system of an ancient shield volcano located offshore of Mt. Etna.

40Ar-39Ar Age Constraints on Volcanism and Tectonism in the Terror Rift of the Ross Sea, Antarctica

USGS Publications Warehouse

2007-01-01

Volcanic sills and dikes inferred from seismic reflection profiles and geophysical studies of the Ross Sea are thought to be related to the rift basins in the region, and their emplacement to be coeval with extension. However, lack of precise geochronology in the Terror Rift of the Ross Sea region has left these inferred relationships poorly constrained and has hindered neotectonic studies, because of the large temporal gaps between seismic reflectors of known ages. New 40Ar/39Ar geochronology presented here for submarine volcanic rocks provides better age constraints for neotectonic interpretations within the Terror Rift. Several samples from seamounts yielded young ages between 156 ± 21 and 122 ± 26 Ka. These ages support interpretations that extension within the Terror Rift was active at least through the Pleistocene. Three evenly spaced samples from the lowermost 100 m of Franklin Island range in age from 3.28 ± 0.04 to 3.73 ± 0.05 Ma. These age determinations demonstrate that construction of a small volcanic edifice such as Franklin Island took at least several hundred thousand years, and therefore that much larger ones in the Erebus Volcanic Province are likely to have taken considerably longer than previously inferred. This warrants caution in applying a limited number of age determinations to define the absolute ages of events in the Ross Sea region

Potential Future Igneous Activity at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Cline, M.; Perry, F. V.; Valentine, G. A.; Smistad, E.

2005-12-01

Location, timing, and volumes of post-Miocene volcanic activity, along with expert judgement, provide the basis for assessing the probability of future volcanism intersecting a proposed repository for nuclear waste at Yucca Mountain, Nevada. Analog studies of eruptive centers in the region that may represent the style and extent of possible future igneous activity at Yucca Mountain have aided in defining the consequence scenarios for intrusion into and eruption through a proposed repository. Modeling of magmatic processes related to magma/proposed repository interactions has been used to assess the potential consequences of a future igneous event through a proposed repository at Yucca Mountain. Results of work to date indicate future igneous activity in the Yucca Mountain region has a very low probability of intersecting the proposed repository. Probability of a future event intersecting a proposed repository at Yucca Mountain is approximately 1.7 X 10-8 per year. Since completion of the Probabilistic Volcanic Hazard Assessment (PVHA) in 1996, anomalies representing potential buried volcanic centers have been identified from aeromagnetic surveys. A re-assessment of the hazard is currently underway to evaluate the probability of intersection in light of new information and to estimate the probability of one or more volcanic conduits located in the proposed repository along a dike that intersects the proposed repository. U.S. Nuclear Regulatory Commission regulations for siting and licensing a proposed repository require that the consequences of a disruptive event (igneous event) with annual probability greater than 1 X 10-8 be evaluated. Two consequence scenarios are considered; 1) igneous intrusion-groundwater transport case and 2) volcanic eruptive case. These scenarios equate to a dike or dike swarm intersecting repository drifts containing waste packages, formation of a conduit leading to a volcanic eruption through the repository that carries the contents of the waste packages into the atmosphere, deposition of a tephra sheet, and redistribution of the contaminated ash. In both cases radioactive material is released to the accessible environment either through groundwater transport or through the atmospheric dispersal and deposition. Six Quaternary volcanic centers exist within 20 km of Yucca Mountain. Lathrop Wells cone (LWC), the youngest (approximately 75,000 yrs), is a well-preserved cinder cone with associated flows and tephra sheet that provides an excellent analogue for consequence studies related to future volcanism. Cone, lavas, hydrovolcanic ash, and ash-fall tephra have been examined to estimate eruptive volume and eruption type. LWC ejecta volumes suggest basaltic volcanism may be waning in the Yucca Mountain region.. The eruptive products indicate a sequence of initial fissure fountaining, early Strombolian ash and lapilli deposition forming the scoria cone, a brief hydrovolcanic pulse (possibly limited to the NW sector), and a violent Strombolian phase. Mathematical models have been developed to represent magmatic processes and their consequences on proposed repository performance. These models address dike propagation, magma interaction and flow into drifts, eruption through the proposed repository, and post intrusion/eruption effects. These models continue to be refined to reduce the uncertainty associated with the consequences from a possible future igneous event.

Comparison of diffuse CO2 degassing at Miravalles and Rincón de la Vieja volcanoes (Guanacaste Province, Costa Rica)

NASA Astrophysics Data System (ADS)

Liegler, A.; Bakkar Hindeleh, H.; Deering, C. D.; Fentress, S. E.

2015-12-01

Volcanic gas emissions are a key component for monitoring volcanic activity, magmatic input of volatiles to the atmosphere and the assessment of geothermal potential in volcanic regions. Diffuse soil degassing has been shown to represent a major part of volcanic gas emissions. However, this type of gas emission has not yet been quantified in the Guanacaste province of Costa Rica; a region of the country with several large, active or dormant volcanoes. We conducted the first study of diffuse CO2 degassing at Rincón de la Vieja and Miravalles volcanoes, both located in Guanacaste. Diffuse degassing was measured using the accumulation chamber method to quantify CO2 flux in regions where hydrothermal surface features indicate anomalous activity. The total diffuse carbon dioxide flux estimated at Miravalles in two areas, together roughly 2 km2 in size, was 135 t/day and in several areas at Rincón de la Vieja a minimum of 4 t/day. Comparatively low flux values and a very local concentration (few m2) of CO2 flux were observed at the active Rincón de la Vieja volcano, compared to the dormant Miravalles volcano, where significant soil flux was found over extended areas, not only around vents. Our assessment of the origin of these differences leads to two possibilities depending on if the surface features on the two volcanoes are fed by a common hydrothermal system or two separate ones. In the former case, the different intensity of diffuse CO2 flux could indicate a different degassing behavior and stronger concentration of gas emissions at the active vent areas at Rincon de la Vieja. In the latter case, where the hydrothermal systems are not linked, the amount of CO2 degassed through the flanks of the volcanoes could indicate that different physical and chemical conditions are governing the degassing of the two systems.

Eruption probabilities for the Lassen Volcanic Center and regional volcanism, northern California, and probabilities for large explosive eruptions in the Cascade Range

USGS Publications Warehouse

Nathenson, Manuel; Clynne, Michael A.; Muffler, L.J. Patrick

2012-01-01

Chronologies for eruptive activity of the Lassen Volcanic Center and for eruptions from the regional mafic vents in the surrounding area of the Lassen segment of the Cascade Range are here used to estimate probabilities of future eruptions. For the regional mafic volcanism, the ages of many vents are known only within broad ranges, and two models are developed that should bracket the actual eruptive ages. These chronologies are used with exponential, Weibull, and mixed-exponential probability distributions to match the data for time intervals between eruptions. For the Lassen Volcanic Center, the probability of an eruption in the next year is 1.4x10-4 for the exponential distribution and 2.3x10-4 for the mixed exponential distribution. For the regional mafic vents, the exponential distribution gives a probability of an eruption in the next year of 6.5x10-4, but the mixed exponential distribution indicates that the current probability, 12,000 years after the last event, could be significantly lower. For the exponential distribution, the highest probability is for an eruption from a regional mafic vent. Data on areas and volumes of lava flows and domes of the Lassen Volcanic Center and of eruptions from the regional mafic vents provide constraints on the probable sizes of future eruptions. Probabilities of lava-flow coverage are similar for the Lassen Volcanic Center and for regional mafic vents, whereas the probable eruptive volumes for the mafic vents are generally smaller. Data have been compiled for large explosive eruptions (>≈ 5 km3 in deposit volume) in the Cascade Range during the past 1.2 m.y. in order to estimate probabilities of eruption. For erupted volumes >≈5 km3, the rate of occurrence since 13.6 ka is much higher than for the entire period, and we use these data to calculate the annual probability of a large eruption at 4.6x10-4. For erupted volumes ≥10 km3, the rate of occurrence has been reasonably constant from 630 ka to the present, giving more confidence in the estimate, and we use those data to calculate the annual probability of a large eruption in the next year at 1.4x10-5.

Asia-Pacific Region Global Earthquake and Volcanic Eruption Risk Management (G-EVER) project and a next-generation real-time volcano hazard assessment system

NASA Astrophysics Data System (ADS)

Takarada, S.

2012-12-01

The first Workshop of Asia-Pacific Region Global Earthquake and Volcanic Eruption Risk Management (G-EVER1) was held in Tsukuba, Ibaraki Prefecture, Japan from February 23 to 24, 2012. The workshop focused on the formulation of strategies to reduce the risks of disasters worldwide caused by the occurrence of earthquakes, tsunamis, and volcanic eruptions. More than 150 participants attended the workshop. During the workshop, the G-EVER1 accord was approved by the participants. The Accord consists of 10 recommendations like enhancing collaboration, sharing of resources, and making information about the risks of earthquakes and volcanic eruptions freely available and understandable. The G-EVER Hub website (http://g-ever.org) was established to promote the exchange of information and knowledge among the Asia-Pacific countries. Several G-EVER Working Groups and Task Forces were proposed. One of the working groups was tasked to make the next-generation real-time volcano hazard assessment system. The next-generation volcano hazard assessment system is useful for volcanic eruption prediction, risk assessment, and evacuation at various eruption stages. The assessment system is planned to be developed based on volcanic eruption scenario datasets, volcanic eruption database, and numerical simulations. Defining volcanic eruption scenarios based on precursor phenomena leading up to major eruptions of active volcanoes is quite important for the future prediction of volcanic eruptions. Compiling volcanic eruption scenarios after a major eruption is also important. A high quality volcanic eruption database, which contains compilations of eruption dates, volumes, and styles, is important for the next-generation volcano hazard assessment system. The volcanic eruption database is developed based on past eruption results, which only represent a subset of possible future scenarios. Hence, different distributions from the previous deposits are mainly observed due to the differences in vent position, volume, eruption rate, wind directions and topography. Therefore, numerical simulations with controlled parameters are needed for more precise volcanic eruption predictions. The use of the next-generation system should enable the visualization of past volcanic eruptions datasets such as distributions, eruption volumes and eruption rates, on maps and diagrams using timeline and GIS technology. Similar volcanic eruptions scenarios should be easily searchable from the eruption database. Using the volcano hazard assessment system, prediction of the time and area that would be affected by volcanic eruptions at any locations near the volcano should be possible, using numerical simulations. The system should estimate volcanic hazard risks by overlaying the distributions of volcanic deposits on major roads, houses and evacuation areas using a GIS enabled systems. Probabilistic volcanic hazards maps in active volcano sites should be made based on numerous numerical simulations. The next-generation real-time hazard assessment system would be implemented with user-friendly interface, making the risk assessment system easily usable and accessible online.

Morphological Analysis of Apo Volcanic Complex in Southern Mindanao, Philippines: implications on volcano-tectonic evolution of different volcanic units

NASA Astrophysics Data System (ADS)

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

2015-12-01

The Apo Volcanic Complex (AVC) is one of the largest volcanic centers in the Philippines, located in the southern island of Mindanao. It is composed of four edifices and several smaller cones. The youngest volcanic unit, the Apo Dome, is the highest elevation in the Philippines. This unit is classified as potentially active, whereas other units, Talomo, Sibulan and Kitubod, are inactive. The study gives insight to the construction and deformation history of the volcanic units and imparts foresight to subsequent events that can affect populated areas. A morphological analysis integrating high-resolution digital terrain models and public domain satellite data and images was done to recognize and discriminate volcanic units and characterize volcano-tectonic features and processes. Morphological domains were defined based on surface textures, slope variation, degrees and controls of erosion, and lineament density and direction. This establishes the relative ages and extent of volcanic units as well as the volcano-tectonic evolution of the complex. Six edifice building events were recognized, two of which form the elevated base of Apo dome. The geodynamic setting of the region is imprinted in the volcanic units as five morphostructural lineaments. They reveal the changes in maximum regional stress through time such as the N-S extension found across the whole volcanic complex displaying the current stress regime. This has implications on the locality and propagation of geothermal activity, magma ascent, and edifice collapses. One main result of the compounded effects of inherited structures and current stress regime is the Sandawa Collapse Zone. This is a large valley formed by several collapses where NE-SW fractures propagate and the increasing lateral spreading by debuttressing continue to eat away the highest peak. The AVC is surrounded by the major metropolitan area of Davao City to the east and the cities of Kidapawan and Digos to the west and south, respectively. In addition, within 3 km of Apo Dome is a geothermal power plant. With the obvious socio-economic significance of the area, it is imperative to understand these deformations that allow structures to propagate, resulting to instability of the edifice and possibly volcanic unrest, and ultimately for the assessment of hazards and risks to the immediate sectors.

Tectonic events, continental intraplate volcanism, and mantle plume activity in northern Arabia: Constraints from geochemistry and Ar-Ar dating of Syrian lavas

NASA Astrophysics Data System (ADS)

Krienitz, M.-S.; Haase, K. M.; Mezger, K.; van den Bogaard, P.; Thiemann, V.; Shaikh-Mashail, M. A.

2009-04-01

New 40Ar/39Ar ages combined with chemical and Sr, Nd, and Pb isotope data for volcanic rocks from Syria along with published data of Syrian and Arabian lavas constrain the spatiotemporal evolution of volcanism, melting regime, and magmatic sources contributing to the volcanic activity in northern Arabia. Several volcanic phases occurred in different parts of Syria in the last 20 Ma that partly correlate with different tectonic events like displacements along the Dead Sea Fault system or slab break-off beneath the Bitlis suture zone, although the large volume of magmas and their composition suggest that hot mantle material caused volcanism. Low Ce/Pb (<20), Nb/Th (<10), and Sr, Nd, and Pb isotope variations of Syrian lavas indicate the role of crustal contamination in magma genesis, and contamination of magmas with up to 30% of continental crustal material can explain their 87Sr/86Sr. Fractionation-corrected major element compositions and REE ratios of uncontaminated lavas suggest a pressure-controlled melting regime in western Arabia that varies from shallow and high-degree melt formation in the south to increasingly deeper regions and lower extents of the beginning melting process northward. Temperature estimates of calculated primary, crustally uncontaminated Arabian lavas indicate their formation at elevated mantle temperatures (Texcess ˜ 100-200°C) being characteristic for their generation in a plume mantle region. The Sr, Nd, and Pb isotope systematic of crustally uncontaminated Syrian lavas reveal a sublithospheric and a mantle plume source involvement in their formation, whereas a (hydrous) lithospheric origin of lavas can be excluded on the basis of negative correlations between Ba/La and K/La. The characteristically high 206Pb/204Pb (˜19.5) of the mantle plume source can be explained by material entrainment associated with the Afar mantle plume. The Syrian volcanic rocks are generally younger than lavas from the southern Afro-Arabian region, indicating a northward progression of the commencing volcanism since the arrival of the Afar mantle plume beneath Ethiopia/Djibouti some 30 Ma ago. The distribution of crustally uncontaminated high 206Pb/204Pb lavas in Arabia indicates a spatial influence of the Afar plume of ˜2600 km in northward direction with an estimated flow velocity of plume material on the order of 22 cm/a.

Monitoring unrest in a large silicic caldera, the long Valley-inyo craters volcanic complex in east-central California

NASA Astrophysics Data System (ADS)

Hill, D. P.

1984-06-01

Recent patterns of geologic unrest in long Valley caldera in east-central California emphasize that this large, silicic volcanic system and the adjacent, geologically youthful Inyo-Mono Craters volcanic chain are still active and capable of producing locally hazardous volcanic eruptions. A series of four magnitude -6 earthquakes in May 1980 called attention to this current episode of unrest, and subsequent activity has included numerous earthquake swarms in the south moat of the caldera accompanied by inflation of the resurgent dome by more than 50 cm over the last five years. The seismicity associated with this unrest is currently monitored by a network of 31 telemetered seismic stations with an automatic processing system that yelds hypocentral locations and earthquake magnitudes in near-real time. Deformation of the ground is monitored by a) a series of overlapping trilateration networks that provide coverage ranging from annual measurements of regional deformation to daily measurements of deformation local to the active, southern section of the caldera, b) a regional network of level lines surveyed annually, c) a regional network of precise gravity stations occupied annually, d) local, L-shaped level figures surveyed every few months, and e) a network of fourteen borehole tiltmeter clusters (two instruments in each cluster) and a borehole dilatometer, the telemetered signals from which provide continuous data on deformation rates. Additional telemetered data provide continuous information on fluctuations in the local magnetic field, hydrogen gas emission rates at three sites, and water level and temperatures in three wells. Continuous data on disharge rates and temperatures from hot springs and fumaroles are collected by several on-site recorders within the caldera, and samples for liquid and gas chemistry are collected several times per year from selected hot springs and fumaroles.

Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: Earthquake locations and source parameters

USGS Publications Warehouse

Ruppert, N.A.; Prejean, S.; Hansen, R.A.

2011-01-01

An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field. Copyright ?? 2011 by the American Geophysical Union.

Volcanic Surface Deformation in Dominica From GPS Geodesy: Results From the 2007 NSF- REU Site

NASA Astrophysics Data System (ADS)

Murphy, R.; James, S.; Styron, R. H.; Turner, H. L.; Ashlock, A.; Cavness, C.; Collier, X.; Fauria, K.; Feinstein, R.; Staisch, L.; Williams, B.; Mattioli, G. S.; Jansma, P. E.; Cothren, J.

2007-12-01

GPS measurements have been collected on the island of Dominica in the Lesser Antilles between 2001 and 2007, with five month-long campaigns completed in June of each year supported in part by a NSF REU Site award for the past two years. All GPS data were collected using dual-frequency, code-phase receivers and geodetic-quality antenna, primarily choke rings. Three consecutive 24 hr observation days were normally obtained for each site. Precise station positions were estimated with GIPSY-OASISII using an absolute point positioning strategy and final, precise orbits, clocks, earth orientation parameters, and x-files. All position estimates were updated to ITRF05 and a revised Caribbean Euler pole was used to place our observations in a CAR-fixed frame. Time series were created to determine the velocity of each station. Forward and inverse elastic half-space models with planar (i.e. dike) and Mogi (i.e. point) sources were investigated. Inverse modeling was completed using a downhill simplex method of function minimization. Selected site velocities were used to create appropriate models for specific regions of Dominica, which correspond to known centers of pre-historic volcanic or recent shallow, seismic activity. Because of the current distribution of GPS sites with robust velocity estimates, we limit our models to possible magmatic activity in the northern, proximal to the volcanic centers of Morne Diablotins and Morne aux Diables, and southern, proximal to volcanic centers of Soufriere and Morne Plat Pays, regions of the island. Surface deformation data from the northernmost sites may be fit with the development of a several km-long dike trending approximately northeast- southwest. Activity in the southern volcanic centers is best modeled by an expanding point source at approximately 1 km depth.

Crustal structure, evolution, and volcanic unrest of the Alban Hills, Central Italy

USGS Publications Warehouse

Chiarabba, C.; Amato, A.; Delaney, P.T.

1997-01-01

The Alban Hills, a Quaternary volcanic center lying west of the central Apennines, 15-25 km southeast of Rome, last erupted 19ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka. Earthquakes of moderate intensity have been generated there at least since the Roman age. Modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features, the phreatomagmatic craters on the west side of the volcano. Results from seismic tomography allow identification of a low-velocity region, perhaps still hot or partially molten, more than 6 km beneath the youngest craters and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct. Thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters. The volume of magma accumulation and the amount of maximum uplift was probably at least 40 ?? 106 m3 and 40 cm, respectively. Comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift. The magma chamber beneath the western Alban Hills is probably responsible for much of the past 200 ka of eruptive activity, is still receiving intermittent batches of magma, and is, therefore, continuing to generate modest levels of volcanic unrest. Bending of overburden is the most likely cause of the persistent earthquakes, which generally have hypocenters above the 6-km-deep top of the magma reservoir. In this view, the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity.

Iron mineralization at the Songhu deposit, Chinese Western Tianshan: a type locality with regional metallogenic implications

NASA Astrophysics Data System (ADS)

Wang, Chun-Long; Wang, Yi-Tian; Dong, Lian-Hui; Qin, Ke-Zhang; Evans, Noreen J.; Zhang, Bing; Ren, Yi

2018-01-01

Hosted by volcaniclastics of the Carboniferous Dahalajunshan Formation, the Songhu iron deposit is located in the central segment of the Awulale metallogenic belt, Chinese Western Tianshan. Mineralization and alteration are structurally controlled by orogen-parallel NWW-striking faults. Integrating with mineralogical and stable isotopic analyses based on paragenetic relationships, two types of iron mineralization have been identified. The deuteric mineralization (Type I) represented by brecciated, banded, and disseminated-vein ores juxtaposed with potassic-calcic alteration in the inner zone, which was formed from a magmatic fluid generated during the late stages of regional volcanism. In contrast, the volcanic-hydrothermal mineralization (Type II) is characterized by hydrothermal features occurring in massive and agglomerated ores with abundant sulfides, and was generated from the magmatic fluid with seawater contamination. Two volcaniclastic samples from the hanging and footwall of the main orebody yield zircon U-Pb ages of 327.8 ± 3.1 and 332.0 ± 2.0 Ma, respectively, which indicate Middle Carboniferous volcanism. Timing for iron mineralization can be broadly placed in the same epoch. By reviewing geological, mineralogical, and geochemical features of the primary iron deposits in the Awulale metallogenic belt, we propose that the two types of iron mineralization in the Songhu iron deposit are representative regionally. A summary of available geochronological data reveals Middle-Late Carboniferous polycyclic ore-related volcanism, and nearly contemporaneous iron mineralization along the belt. Furthermore, petro-geochemistry of volcanic-volcaniclastic host rocks indicates that partial melting of a metasomatized mantle wedge under a continental arc setting could have triggered the continuous volcanic activities and associated metallogenesis.

Global volcanic aerosol properties derived from emissions, 1990-2015, using CESM1(WACCM)

NASA Astrophysics Data System (ADS)

Mills, Michael; Schmidt, Anja; Easter, Richard; Solomon, Susan; Kinnison, Douglas; Ghan, Steven; Neely, Ryan; Marsh, Daniel; Conley, Andrew; Bardeen, Charles; Gettelman, Andrew

2016-04-01

Accurate representation of global stratospheric aerosols from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-losses that may be linked to volcanic activity. Attribution of climate variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the rate of global average temperature increases. We have compiled a database of volcanic SO2 emissions and plume altitudes for eruptions from 1990 to 2015, and developed a new prognostic capability for simulating stratospheric sulfate aerosols in the Community Earth System Model (CESM). We combined these with other non-volcanic emissions of sulfur sources to reconstruct global aerosol properties from 1990 to 2015. Our calculations show remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of stratospheric aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD calculations represent a clear improvement over available satellite-based analyses, which generally ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD calculations greatly improve on that provided for the Chemistry-Climate Model Initiative, which misses about 60% of the SAD measured in situ on average during both volcanically active and volcanically quiescent periods. The stark differences in SAOD and SAD compared to other data sets will have significant effects on calculations of the radiative forcing of climate and global stratospheric chemistry over the period 2005-2015. In light of these results, the impact of volcanic aerosols in reducing the rate of global average temperature increases since the year 2000 should be revisited. We have made our calculated aerosol properties from January 1990 to November 2015 available for public download.

Tectonic context of moderate to large historical earthquakes in the Lesser Antilles and mechanical coupling with volcanoes

NASA Astrophysics Data System (ADS)

Feuillet, Nathalie; Beauducel, FrançOis; Tapponnier, Paul

2011-10-01

The oblique convergence between North American and Caribbean plates is accommodated in a bookshelf faulting manner by active, oblique-normal faults in the northern part of the Lesser Antilles arc. In the last 20 years, two M > 6 earthquakes occurred along a large, arc parallel, en echelon fault system, the 16 March 1985 in Redonda and 21 November 2004 in Les Saintes. A better understanding of active faulting in this region permit us to review the location and magnitude of historical earthquakes by using a regional seismic attenuation law. Several others moderate earthquakes may have occurred along the en echelon fault system implying a strong seismic hazard along the arc. These faults control the effusion of volcanic products and some earthquakes seem to be correlated in time with volcanic unrest. Shallow earthquakes on intraplate faults induced normal stress and pressure changes around neighboring volcano and may have triggered volcanic activity. The Redonda earthquake could have initiated the 1995 eruption of Montserrat's Soufrière Hills by compressing its plumbing system. Conversely, pressure changes under the volcano increased Coulomb stress changes and brought some faults closer to failure, promoting seismicity. We also discuss the magnitude of the largest 11 January 1839 and 8 February 1843 megathrust interplate earthquakes. We calculate that they have increased the stress on some overriding intraplate faults and the extensional strain beneath several volcanoes. This may explain an increase of volcanic and seismic activity in the second half of the 19th century culminating with the devastating, 1902 Mount Pelée eruption.

Modelling ground deformation patterns associated with volcanic processes at the Okataina Volcanic Centre

NASA Astrophysics Data System (ADS)

Holden, L.; Cas, R.; Fournier, N.; Ailleres, L.

2017-09-01

The Okataina Volcanic Centre (OVC) is one of two large active rhyolite centres in the modern Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. It is located in a complex section of the Taupo rift, a tectonically active section of the TVZ. The most recent volcanic unrest at the OVC includes the 1315 CE Kaharoa and 1886 Tarawera eruptions. Current monitoring activity at the OVC includes the use of continuous GPS receivers (cGPS), lake levelling and seismographs. The ground deformation patterns preceding volcanic activity the OVC are poorly constrained and restricted to predictions from basic modelling and comparison to other volcanoes worldwide. A better understanding of the deformation patterns preceding renewed volcanic activity is essential to determine if observed deformation is related to volcanic, tectonic or hydrothermal processes. Such an understanding also means that the ability of the present day cGPS network to detect these deformation patterns can also be assessed. The research presented here uses the finite element (FE) modelling technique to investigate ground deformation patterns associated with magma accumulation and diking processes at the OVC in greater detail. A number of FE models are produced and tested using Pylith software and incorporate characteristics of the 1315 CE Kaharoa and 1886 Tarawera eruptions, summarised from the existing body of research literature. The influence of a simple ring fault structure at the OVC on the modelled deformation is evaluated. The ability of the present-day continuous GPS (cGPS) GeoNet monitoring network to detect or observe the modelled deformation is also considered. The results show the modelled horizontal and vertical displacement fields have a number of key features, which include prominent lobe based regions extending northwest and southeast of the OVC. The results also show that the ring fault structure increases the magnitude of the displacements inside the caldera, in particular in the vicinity of the southern margin. As a result, some of the cGPS stations in the vicinity of the OVC are more important for measuring deformation related to volcanic processes than others. The results have important implications for how any future observed deformation at the OVC is observed and interpreted.

Short-lived eruptive episodes during the construction of a Na-alkalic basaltic field (Perşani Mountains, SE Transylvania, Romania)

NASA Astrophysics Data System (ADS)

Seghedi, Ioan; Popa, Răzvan-Gabriel; Panaiotu, Cristian G.; Szakács, Alexandru; Pécskay, Zoltán

2016-10-01

The Perşani Mts. basaltic field covers >176 km2 (~22 × 8 km) and is one of the youngest and biggest monogenetic volcanic fields in Southeastern Europe. It consists of 21 monogenetic volcanic centers, most of which were built on a basement of Miocene rhyolitic tuffs and Mesozoic sedimentary rocks. 40Ar/39Ar dating shows that the eruptions took place in five episodes: 1220, 1142, 1060, 800, and 683 ka. An additional undated episode at 1060-800 ka has been identified using volcanological observations. Initial phreatomagmatic activity was commonly followed by explosive Strombolian/Hawaiian phases that deposited agglutinated spatter around the vents along with massive-to-bedded unconsolidated scoria and lapilli. Some volcanoes lack evidence for magmatic explosive activity, while others lack evidence for the initial phreatomagmatic phase. During most eruptions, the final activity was the effusion of lava flows that in some cases deformed (or partially destroyed) the volcanic edifices. The erupted volumes varied greatly from one episode to other, without showing any pattern: the highest volumes are recorded in deposits from the third pulse (1060 ka). The volcanoes are located close to faults and always on their footwall blocks, and it is inferred that the regional tectonic stress regime controlled both the timing and spacing of volcanic activity in the volcanic field.

Infrasound's capability to detect and characterise volcanic events, from local to regional scale.

NASA Astrophysics Data System (ADS)

Taisne, Benoit; Perttu, Anna

2017-04-01

Local infrasound and seismic networks have been successfully used for identification and quantification of explosions at single volcanoes. However the February, 2014 eruption of Kelud volcano, Indonesia, destroyed most of the local monitoring network. The use of remote seismic and infrasound sensors proved to be essential in the reconstruction of the eruptive sequence. The first recorded explosive event, with relatively weak seismic and infrasonic signature, was followed by a 2 hour sustained signal detected as far away as 11,000 km by infrasound sensors and up to 2,300 km away by seismometers. The volcanic intensity derived from these observations places the 2014 Kelud eruption between the intensity of the 1980 Mount St. Helens and the 1991 Pinatubo eruptions. The use of remote seismic stations and infrasound arrays in deriving valuable information about the onset, evolution, and intensity of volcanic eruptions is clear from the Kelud example. After this eruption the Singapore Infrasound Array became operational. This array, along with the other regional infrasound arrays which are part of the International Monitoring System, have recorded events from fireballs and regional volcanoes. The detection capability of this network for any specific volcanic event is not only dependent on the amplitude of the source, but also the propagation effects, noise level at each station, and characteristics of the regional persistent noise sources (like the microbarum). Combining the spatial and seasonal characteristics of this noise, within the same frequency band as significant eruptive events, with the probability of such events to occur, gives us a comprehensive understanding of detection capability for any of the 750 active or potentially active volcanoes in Southeast Asia.

Automated Identification of Volcanic Plumes using the Ozone Monitoring Instrument (OMI)

NASA Astrophysics Data System (ADS)

Flower, V. J. B.; Oommen, T.; Carn, S. A.

2015-12-01

Volcanic eruptions are a global phenomenon which are increasingly impacting human populations due to factors such as the extension of population centres into areas of higher risk, expansion of agricultural sectors to accommodate increased production or the increasing impact of volcanic plumes on air travel. In areas where extensive monitoring is present these impacts can be moderated by ground based monitoring and alert systems, however many volcanoes have little or no monitoring capabilities. In many of these regions volcanic alerts are generated by local communities with limited resources or formal communication systems, however additional eruption alerts can result from chance encounters with passing aircraft. In contrast satellite based remote sensing instruments possess the capability to provide near global daily monitoring, facilitating automated volcanic eruption detection. One such system generates eruption alerts through the detection of thermal anomalies, known as MODVOLC, and is currently operational utilising moderate resolution MODIS satellite data. Within this work we outline a method to distinguish SO2 eruptions from background levels recorded by the Ozone Monitoring Instrument (OMI) through the identification and classification of volcanic activity over a 5 year period. The incorporation of this data into a logistic regression model facilitated the classification of volcanic events with an overall accuracy of 80% whilst consistently identifying plumes with a mass of 400 tons or higher. The implementation of the developed model could facilitate the near real time identification of new and ongoing volcanic activity on a global scale.

Transtensional deformation and structural control of contiguous but independent magmatic systems: Mono-Inyo Craters, Mammoth Mountain, and Long Valley Caldera, California

USGS Publications Warehouse

Riley, P.; Tikoff, B.; Hildreth, Wes

2012-01-01

The Long Valley region of eastern California (United States) is the site of abundant late Tertiary–present magmatism, including three geochemically distinct stages of magmatism since ca. 3 Ma: Mammoth Mountain, the Mono-Inyo volcanic chain, and Long Valley Caldera. We propose two tectonic models, one explaining the Mammoth Mountain–Mono-Inyo magmatism and the other explaining the presence of Long Valley Caldera. First, the ongoing Mammoth Mountain–Mono-Inyo volcanic chain magmatism is explained by a ridge-transform-ridge system, with the Mono-Inyo volcanic chain acting as one ridge segment and the South Moat fault acting as a transform fault. Implicit in this first model is that this region of eastern California is beginning to act as an incipient plate boundary. Second, the older Long Valley Caldera system is hypothesized to occur in a region of enhanced extension resulting from regional fault block rotation, specifically involving activation of the sinistral faults of the Mina deflection. The tectonic models are consistent with observed spatial and temporal differences in the geochemistry of the regional magmas, and the westward progression of magmatism since ca. 12 Ma.

Global volcanic aerosol properties derived from emissions, 1990-2014, using CESM1(WACCM): VOLCANIC AEROSOLS DERIVED FROM EMISSIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mills, Michael J.; Schmidt, Anja; Easter, Richard

Accurate representation of global stratospheric aerosol properties from volcanic and non-volcanic sulfur emissions is key to understanding the cooling effects and ozone-loss enhancements of recent volcanic activity. Attribution of climate and ozone variability to volcanic activity is of particular interest in relation to the post-2000 slowing in the apparent rate of global average temperature increases, and variable recovery of the Antarctic ozone hole. We have developed a climatology of global aerosol properties from 1990 to 2014 calculated based on volcanic and non-volcanic emissions of sulfur sources. We have complied a database of volcanic SO2 emissions and plume altitudes for eruptionsmore » between 1990 and 2014, and a new prognostic capability for simulating stratospheric sulfate aerosols in version 5 of the Whole Atmosphere Community Climate Model, a component of the Community Earth System Model. Our climatology shows remarkable agreement with ground-based lidar observations of stratospheric aerosol optical depth (SAOD), and with in situ measurements of aerosol surface area density (SAD). These properties are key parameters in calculating the radiative and chemical effects of stratospheric aerosols. Our SAOD climatology represents a significant improvement over satellite-based analyses, which ignore aerosol extinction below 15 km, a region that can contain the vast majority of stratospheric aerosol extinction at mid- and high-latitudes. Our SAD climatology significantly improves on that provided for the Chemistry-Climate Model Initiative, which misses 60% of the SAD measured in situ. Our climatology of aerosol properties is publicly available on the Earth System Grid.« less

The geologic history of Margaritifer basin, Mars

USGS Publications Warehouse

Salvatore, M. R.; Kraft, M. D.; Edwards, Christopher; Christensen, P.R.

2016-01-01

In this study, we investigate the fluvial, sedimentary, and volcanic history of Margaritifer basin and the Uzboi-Ladon-Morava (ULM) outflow channel system. This network of valleys and basins spans more than 8000 km in length, linking the fluvially dissected southern highlands and Argyre Basin with the northern lowlands via Ares Vallis. Compositionally, thermophysically, and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in Margaritifer basin. Our analyses show that fluvial activity was separated in time by significant episodes of geologic activity, including the widespread volcanic resurfacing of Margaritifer basin and the formation of chaos terrain. The most recent fluvial activity within Margaritifer basin appears to terminate at a region of chaos terrain, suggesting possible communication between surface and subsurface water reservoirs. We conclude with a discussion of the implications of these observations on our current knowledge of Martian hydrologic evolution in this important region.

The geologic history of Margaritifer basin, Mars

NASA Astrophysics Data System (ADS)

Salvatore, M. R.; Kraft, M. D.; Edwards, C. S.; Christensen, P. R.

2016-03-01

In this study, we investigate the fluvial, sedimentary, and volcanic history of Margaritifer basin and the Uzboi-Ladon-Morava outflow channel system. This network of valleys and basins spans more than 8000 km in length, linking the fluvially dissected southern highlands and Argyre basin with the northern lowlands via Ares Vallis. Compositionally, thermophysically, and morphologically distinct geologic units are identified and are used to place critical relative stratigraphic constraints on the timing of geologic processes in Margaritifer basin. Our analyses show that fluvial activity was separated in time by significant episodes of geologic activity, including the widespread volcanic resurfacing of Margaritifer basin and the formation of chaos terrain. The most recent fluvial activity within Margaritifer basin appears to terminate at a region of chaos terrain, suggesting possible communication between surface and subsurface water reservoirs. We conclude with a discussion of the implications of these observations on our current knowledge of Martian hydrologic evolution in this important region.

Miocene volcanism in the Oaş-Gutâi Volcanic Zone, Eastern Carpathians, Romania: Relationship to geodynamic processes in the Transcarpathian Basin

NASA Astrophysics Data System (ADS)

Kovacs, Marinel; Seghedi, Ioan; Yamamoto, Masatsugu; Fülöp, Alexandrina; Pécskay, Zoltán; Jurje, Maria

2017-12-01

We present the first comprehensive study of Miocene volcanic rocks of the Oaş-Gutâi Volcanic Zone (OGVZ), Romania, which are exposed in the eastern Transcarpathian Basin (TB), within the Eastern Alpine-Western Carpathian-Northern Pannonian (ALCAPA) block. Collision between the ALCAPA block and Europe at 18-16 Ma produced the Carpathian fold-and-thrust belt. This was followed by clockwise rotation and an extensional regime forming core complexes of the separated TB fragment. Based on petrographic and geochemical data, including Srsbnd Nd isotopic compositions and Ksbnd Ar ages, we distinguish three types of volcanic activity in the OGVZ: (1) early Miocene felsic volcanism that produced caldera-related ignimbrites in the Gutâi Mountains (15.4-14.8 Ma); (2) widespread middle-late Miocene intermediate/andesitic volcanism (13.4-7.0 Ma); and (3) minor late Miocene andesitic/rhyolitic volcanism comprising the Oraşu Nou rhyolitic volcano and several andesitic-dacitic domes in the Oaş Mountains (11.3-9.5 Ma). We show that magma evolution in the OGVZ was controlled by assimilation-fractional crystallization and magma-mixing processes within an interconnected multi-level crustal magmatic reservoir. The evolution of volcanic activity within the OGVZ was controlled by the geodynamics of the Transcarpathian Basin. The early felsic and late intermediate Miocene magmas were emplaced in a post-collisional setting and were derived from a mantle source region that was modified by subduction components (dominantly sediment melts) and lower crust. The style of volcanism within the eastern TB system exhibits spatial variations, with andesitic composite volcanoes (Gutâi Mountains) observed at the margins, and isolated andesitic-rhyolitic monogenetic volcanoes (Oaş Mountains) in the center of the basin.

The forearc crustal evolution of Izu-Bonin (Ogasawara) region obtained by seismic reflection and refraction surveys

NASA Astrophysics Data System (ADS)

Yamashita, M.; Kodaira, S.; Takahashi, N.; Tatsumi, Y.; Kaneda, Y.

2009-12-01

The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. By previous seismic survey and deep sea drilling, convex basements are distributed along North-South direction in present forearc region. The convex basements are reported to be formed during Oligocene and Eocene (Taylor, 1992). In IBM forearc region, the middle crust with 6 km/s is recognized by seismic survey using OBSs. In IBM region, four IODP drilling sites are proposed in order to understand comprehensive growth process of arc and continental crust evolution. Two of them are located in forearc region. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection survey using 7,800/12,000 cu.in. air gun and 5-6 km streamer with 444/204 ch hydrophones in the IBM region since 2004. We investigate the crustal structure beneath the Izu-Bonin forearc region for contribution of IBM drilling site along five long survey lines, which are across from present volcanic front to forearc basin. Seismic refraction survey is also conducted across forearc region using 84 OBSs every 1 km interval. Shallow crustal structure can be classified four units including basement which compared between previous drilling results and obtained seismic profiles. In IBM forearc region, thick sedimentary basin distribute from east side of volcanic front. Two convex basement peaks are indicated in across profile of forearc region. These peaks are estimated the top of paleoarc (Oligocene and Eocene) by previous ODP drilling. The half graben structure with major displacement is identified from west side of present volcanic front to the top of Oligocene arc. On the other hand, there is no displacement of sediments between the Oligocene arc and Eocene arc. This result shows the same origin of basement between the present volcanic front and Oligocene arc. There is long time difference of tectonic activity of sediments between the west and east side of Oligocene paleoarc. We would present the crustal condition before rifting between present volcanic front and Oligocene paleoarc by comparison of reflection and velocity structure.

Potentially active volcanoes of Peru - Observations using Landsat Thematic Mapper and Space Shuttle imagery

NASA Technical Reports Server (NTRS)

De Silva, S. L.; Francis, P. W.

1990-01-01

A synoptic study of the volcanoes of southern Peru (14-17 deg S), the northernmost part of the Central Volcanic Zone (CVZ 14-28 deg S) of the Andes, was conducted on the basis of Landsat TM images and color photography. The volcanoes were classified and their relative ages determined using subtle glacial-morphological features. Eight of them were postulated as potentially active. These are located in a narrow volcanic zone which probably reflects a steep dip of the Nazca plate through the zone of magma generation. The break in the trend of the volcanic arc possibly reflects the complexity of the crustal stress field above a major segment boundary in the subducting plate. There are also fields of mafic monogenetic centers in this region. In comparison with the southern part of the CVZ, the general paucity of older volcanic edifices north of 17 deg S suggested a more recent onset of volcanism, a possible result of the oblique subduction of the Nazca ridge and the consequent northward migration of its intersection with the Peru-Chile trench. This, together with the lack of any large silicic caldera systems and youthful dacite domes, suggested that there are real differences in the volcanic evolution of the two parts of the CVZ.

New records of late Holocene tephras from Lake Futalaufquen (42.8°S), northern Patagonia

NASA Astrophysics Data System (ADS)

Daga, Romina; Ribeiro Guevara, Sergio; Arribére, María

2016-03-01

In regions with limited knowledge of the historical volcanic record, like remote areas in the Andean Southern Volcanic Zone, the definition of reliable age-depth models for lake sequences represents a valuable tool for tephra layers dating. In Lake Futalaufquen (42.8°S), Northern Patagonia, a short sedimentary sequence was extracted after the AD 2008 Chaitén eruption with the purpose to analyze the records of volcanic eruptions at these poorly studied latitudes. The sequence was dated by 210Pb, 137Cs, and 14C techniques. Five tephras were identified for the last 1600 years, restricted to the last 5 centuries. Sedimentology, morphology, and geochemical properties allowed the characterization of the tephras and their correlation with tephras recently identified proximal to the sources, mainly from Chaitén and Huequi volcanoes, and Michinmahuida accessory cones, representing the first distal records reported of these tephras. Furthermore, tephras modeled ages obtained by the sequence age-depth model shrink the ages for the volcanic events, like a potential cycle of activity from Michinmauida accessory cones during AD 1530 ± 55, one eruption from Huequi volcano at AD 1695 ± 50, and a possible recent eruption from Chaitén at AD 1775 ± 40. Additionally, the work contributes to improve the regional volcanic records knowledge, basic for volcanic hazard assessment.

Mapping of the Culann-Tohil region of Io from Galileo imaging data

USGS Publications Warehouse

Williams, D.A.; Schenk, P.M.; Moore, Johnnie N.; Keszthelyi, L.P.; Turtle, E.P.; Jaeger, W.L.; Radebaugh, J.; Milazzo, M.P.; Lopes, R.M.C.; Greeley, R.

2004-01-01

We have used Galileo spacecraft data to produce a geomorphologic map of the Culann-Tohil region of Io's antijovian hemisphere. This region includes a newly discovered shield volcano, Tsu??i Goab Tholus and a neighboring bright flow field, Tsu??i Goab Fluctus, the active Culann Patera and the enigmatic Tohil Mons-Radegast Patera-Tohil Patera complex. Analysis of Voyager global color and Galileo Solid-State Imaging (SSI) high-resolution, regional (50-330 m/pixel), and global color (1.4 km/pixel) images, along with available Galileo Near-Infrared Mapping Spectrometer (NIMS) data, suggests that 16 distinct geologic units can be defined and characterized in this region, including 5 types of diffuse deposits. Tsu??i Goab Fluctus is the center of a low-temperature hotspot detected by NIMS late during the Galileo mission, and could represent the best case for active effusive sulfur volcanism detected by Galileo. The Culann volcanic center has produced a range of explosive and effusive deposits, including an outer yellowish ring of enhanced sulfur dioxide (SO2), an inner red ring of SO2 with short-chain sulfur (S3-S4) contaminants, and two irregular green diffuse deposits (one in Tohil Patera) apparently produced by the interaction of dark, silicate lava flows with sulfurous contaminants ballistically-emplaced from Culann's eruption plume(s). Fresh and red-mantled dark lava flows west of the Culann vent can be contrasted with unusual red-brown flows east of the vent. These red-brown flows have a distinct color that is suggestive of a compositional difference, although whether this is due to surface alteration or distinct lava compositions cannot be determined. The main massif of Tohil Mons is covered with ridges and grooves, defining a unit of tectonically disrupted crustal materials. Tohil Mons also contains a younger unit of mottled crustal materials that were displaced by mass wasting processes. Neighboring Radegast Patera contains a NIMS hotspot and a young lava lake of dark silicate flows, whereas the southwest portion of Tohil Patera contains white flow-like units, perhaps consisting of 'ponds' of effusively emplaced SO2. From 0?? -15?? S the hummocky bright plains unit away from volcanic centers contains scarps, grooves, pits, graben, and channel-like features, some of which have been modified by erosion. Although the most active volcanic centers appear to be found in structural lows (as indicated by mapping of scarps), DEMs derived from stereo images show that, with the exception of Tohil Mons, there is less than 1 km of relief in the Culann-Tohil region. There is no discernable correlation between centers of active volcanism and topography. ?? 2003 Elsevier Inc. All rights reserved.

A regime shift in the Sun-Climate connection with the end of the Medieval Climate Anomaly.

PubMed

Smirnov, D A; Breitenbach, S F M; Feulner, G; Lechleitner, F A; Prufer, K M; Baldini, J U L; Marwan, N; Kurths, J

2017-09-11

Understanding the influence of changes in solar activity on Earth's climate and distinguishing it from other forcings, such as volcanic activity, remains a major challenge for palaeoclimatology. This problem is best approached by investigating how these variables influenced past climate conditions as recorded in high precision paleoclimate archives. In particular, determining if the climate system response to these forcings changes through time is critical. Here we use the Wiener-Granger causality approach along with well-established cross-correlation analysis to investigate the causal relationship between solar activity, volcanic forcing, and climate as reflected in well-established Intertropical Convergence Zone (ITCZ) rainfall proxy records from Yok Balum Cave, southern Belize. Our analysis reveals a consistent influence of volcanic activity on regional Central American climate over the last two millennia. However, the coupling between solar variability and local climate varied with time, with a regime shift around 1000-1300 CE after which the solar-climate coupling weakened considerably.

The onset of the volcanism in the Ciomadul Volcanic Dome Complex (Eastern Carpathians): Eruption chronology and magma type variation

NASA Astrophysics Data System (ADS)

Molnár, Kata; Harangi, Szabolcs; Lukács, Réka; Dunkl, István; Schmitt, Axel K.; Kiss, Balázs; Garamhegyi, Tamás; Seghedi, Ioan

2018-04-01

Combined zircon U-Th-Pb and (U-Th)/He dating was applied to refine the eruption chronology of the last 2 Myr for the andesitic and dacitic Pilişca volcano and Ciomadul Volcanic Dome Complex (CVDC), the youngest volcanic area of the Carpathian-Pannonian region, located in the southernmost Harghita, eastern-central Europe. The proposed eruption ages, which are supported also by the youngest zircon crystallization ages, are much younger than the previously determined K/Ar ages. By dating every known eruption center in the CVDC, repose times between eruptive events were also accurately determined. Eruption of the andesite at Murgul Mare (1865 ± 87 ka) and dacite of the Pilişca volcanic complex (1640 ± 37 ka) terminated an earlier pulse of volcanic activity within the southernmost Harghita region, west of the Olt valley. This was followed by the onset of the volcanism in the CVDC, which occurred after several 100s kyr of eruptive quiescence. At ca. 1 Ma a significant change in the composition of erupted magma occurred from medium-K calc-alkaline compositions to high-K dacitic (Baba-Laposa dome at 942 ± 65 ka) and shoshonitic magmas (Malnaş and Bixad domes; 964 ± 46 ka and 907 ± 66 ka, respectively). Noteworthy, eruptions of magmas with distinct chemical compositions occurred within a restricted area, a few km from one another. These oldest lava domes of the CVDC form a NNE-SSW striking tectonic lineament along the Olt valley. Following a brief (ca. 100 kyr) hiatus, extrusion of high-K andesitic magma continued at Dealul Mare (842 ± 53 ka). After another ca. 200 kyr period of quiescence two high-K dacitic lava domes extruded (Puturosul: 642 ± 44 ka and Balvanyos: 583 ± 30 ka). The Turnul Apor lava extrusion occurred after a ca. 200 kyr repose time (at 344 ± 33 ka), whereas formation of the Haramul Mic lava dome (154 ± 16 ka) represents the onset of the development of the prominent Ciomadul volcano. The accurate determination of eruption dates shows that the volcanic eruptions were often separated by prolonged (ca. 100 to 200 kyr) quiescence periods. Demonstration of recurrence of volcanism even after such long dormancy has to be considered in assessing volcanic hazards, particularly in seemingly inactive volcanic areas, where no Holocene eruptions occurred. The term of 'volcanoes with Potentially Active Magma Storage' illustrates the potential of volcanic rejuvenation for such long-dormant volcanoes with the existence of melt-bearing crustal magma body.

Investigation of forestry resources and other remote sensing data. 1: LANDSAT. 2: Remote sensing of volcanic emissions

NASA Technical Reports Server (NTRS)

Birnie, R. W.; Stoiber, R. E. (Principal Investigator)

1983-01-01

Computer classification of LANDSAT data was used for forest type mapping in New England. The ability to classify areas of hardwood, softwood, and mixed tree types was assessed along with determining clearcut regions and gypsy moth defoliation. Applications of the information to forest management and locating potential deer yards were investigated. The principal activities concerned with remote sensing of volcanic emissions centered around the development of remote sensors for SO2 and HCl gas, and their use at appropriate volcanic sites. Two major areas were investigated (Masaya, Nicaragua, and St. Helens, Washington) along with several minor ones.

Reinterpretation of Mesozoic and Cenozoic tectonic events, Mountain Pass area, northeastern San Bernardino County, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nance, M.A.

1993-04-01

Detailed mapping, stratigraphic structural analysis in the Mountain Pass area has resulted in a reinterpretation of Mesozoic and Cenozoic tectonic events in the area. Mesozoic events are characterized by north vergent folds and thrust faults followed by east vergent thrusting. Folding created two synclines and an anticline which were than cut at different stratigraphic levels by subsequent thrust faults. Thrusting created composite tectono-stratigraphic sections containing autochthonous, para-autothonous, and allochthonous sections. Normal faults cutting these composite sections including North, Kokoweef, White Line, and Piute fault must be post-thrusting, not pre-thrusting as in previous interpretations. Detailed study of these faults results inmore » differentiation of at least three orders of faults and suggest they represent Cenozoic extension correlated with regional extensional events between 11 and 19 my. Mesozoic stratigraphy reflects regional orogenic uplift, magmatic activity, and thrusting. Inclusion of Kaibab clasts in the Chinle, Kaibab and Chinle clasts in the Aztec, and Chinle, Aztec, and previously deposited Delfonte Volcanics clasts in the younger members of the Delfonte Volcanics suggest regional uplift prior to the thrusting of Cambrian Bonanza King over Delfonte Volcanics by the Mescal Thrust fault. The absence of clasts younger than Kaibab argues against pre-thrusting activity for the Kokoweef fault.« less

Deep low-frequency earthquake activities during the failed magmatic eruptions of Mts. Iwate and Fuji, Japan

NASA Astrophysics Data System (ADS)

Nakamichi, H.; Hamaguchi, H.; Ukawa, M.; Tanaka, S.; Ueki, S.; Nishimura, T.

2008-12-01

I review deep low-frequency earthquake (DLF) activities during the failed magmatic eruptions of Mts. Iwate and Fuji, Japan. Volcanic unrests at Mts. Iwate and Fuji were observed in 1998-1999 and 2000-2001, respectively. Several hundred DLFs occurred during the unrest at Mt. Iwate; the number of DLFs in a normal year is less than or equal to 10. The DLF activity at Mt. Fuji increased sharply during the period from September 2000 to May 2001. The frequency of DLFs at Mt. Fuji during the DLF swarm was 20 times higher than that during normal activity. The DLFs of Mts. Iwate and Fuji show non-DC source mechanisms and suggest fluid motion at the focal regions. The DLF hypocenters of Mt. Fuji defined an ellipsoid with a diameter of 5 km; their focal depths are 11-16 km. The ellipsoid was centered 3 km northeast of the summit, and its major axis was directed in the northwest-southeast direction. The center of the ellipsoid gradually migrated upward, and 2-3 km in the northwest direction during 1998-2001. The migration of the DLFs reflects the volcanic fluid migration associated with a northwest-southeast-oriented dike beneath Mt. Fuji. The DLFs of Mt. Iwate were located at intermediate depths (5-12 km) beneath the summit and at deep depths (31-37 km) in the regions located 10 km south and 10 km northeast of the summit. In April 1998, the frequency of DLFs increased five days before an increase in the occurrence of shallow volcanic earthquakes at Mt. Iwate. Hypocenter migration of the DLFs at intermediate depths was observed from April 1998 to September 1998. New fumarole activity in the western region of Mt. Iwate commenced in 1999. These observations indicate that DLFs at Mts. Fuji and Iwate have common features in their activities and source mechanisms. But, shallow volcanic activities at these two volcanoes were much different: strong shallow seismic activity and volcano inflations as well as a new formation of fumarolic area were observed at Mt. Iwate, while such shallow activities were not detected at Mt. Fuji. Although it is still unknown what mechanisms control their magma supply systems, we may say that activation of DLF beneath active volcanoes does not always accompany magma intrusions in the shallow volcano edifice.

Volcanism in Eastern Africa

NASA Technical Reports Server (NTRS)

Cauthen, Clay; Coombs, Cassandra R.

1996-01-01

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

USGS GNSS Applications to Volcano Disaster Response and Hazard Mitigation

NASA Astrophysics Data System (ADS)

Lisowski, M.; McCaffrey, R.

2015-12-01

Volcanic unrest is often identified by increased rates of seismicity, deformation, or the release of volcanic gases. Deformation results when ascending magma accumulates in crustal reservoirs, creates new pathways to the surface, or drains from magma reservoirs to feed an eruption. This volcanic deformation is overprinted by deformation from tectonic processes. GNSS monitoring of volcanoes captures transient volcanic deformation and steady and transient tectonic deformation, and we use the TDEFNODE software to unravel these effects. We apply the technique on portions of the Cascades Volcanic arc in central Oregon and in southern Washington that include a deforming volcano. In central Oregon, the regional TDEFNODE model consists of several blocks that rotate and deform internally and a decaying inflationary volcanic pressure source to reproduce the crustal bulge centered ~5 km west of South Sister. We jointly invert 47 interferograms that cover the interval from 1992 to 2010, as well as 2001 to 2015 continuous GNSS (cGNSS) and survey-mode (sGNSS) time series from stations in and around the Three Sisters, Newberry, and Crater Lake areas. A single, smoothly-decaying ~5 km deep spherical or prolate spheroid volcanic pressure source activated around 1998 provides the best fit to the combined geodetic data. In southern Washington, GNSS displacement time-series track decaying deflation of a ~8 km deep magma reservoir that fed the 2004 to 2008 eruption of Mount St. Helens. That deformation reversed when it began to recharge after the eruption ended. Offsets from slow slip events on the Cascadia subduction zone punctuate the GNSS displacement time series, and we remove them by estimating source parameters for these events. This regional TDEFNODE model extends from Mount Rainier south to Mount Hood, and additional volcanic sources could be added if these volcanoes start deforming. Other TDEFNODE regional models are planned for northern Washington (Mount Baker and Glacier Peak), northern California (Mount Shasta, Medicine Lake, Lassen Peak), and Long Valley. These models take advantage of the data from dense GNSS networks, they provide source parameters for volcanic and tectonic transients, and can be used to discriminate possible short- and long-term volcano- tectonic interactions.

AVAL - The ASTER Volcanic Ash Library

NASA Astrophysics Data System (ADS)

Williams, D.; Ramsey, M. S.

2016-12-01

Volcanic ash is a rich data source for understanding the causal mechanisms behind volcanic eruptions. Petrologic and morphometric information can provide direct information on the characteristics of the parent magma. Understanding how erupted ash interacts with the atmosphere can help quantify the effect that explosive volcanism has on the local to regional climate, whereas a measure of the particle size distribution enables more accurate modeling of plume propagation. Remote sensing is regularly employed to monitor volcanic plumes using a suite of high temporal/low spatial resolution sensors. These methods employ radiative transfer modeling with assumptions of the transmissive properties of infrared energy through the plume to determine ash density, particle size and sulfur dioxide content. However, such approaches are limited to the optically-transparent regions, and the low spatial resolution data are only useful for large-scale trends. In a new approach, we are treating the infrared-opaque regions of the plume in a similar way to a solid emitting surface. This allows high spatial resolution orbital thermal infrared data from the dense proximal plume to be modeled using a linear deconvolution approach coupled with a spectral library to extract the particle size and petrology. The newly created ASTER Volcanic Ash Library (AVAL) provides the end member spectral suite, and is comprised of laboratory emission measurements of volcanic ash taken from a variety of different volcanic settings, to obtain a wide range of petrologies. These samples have been further subdivided into particle size fractions to account for spectral changes due to diffraction effects. Once mapped to the ASTER sensor's spectral resolution, this library is applied to image data and the plume deconvolved to estimate composition and particle size. We have analyzed eruptions at the Soufrière Hills Volcano, Montserrat, Chaitén and Puyehue-Cordón Caulle, both Chile, and Eyjafjallajökull, Iceland. These results provide particle size distributions within actively-erupting volcanic plumes for the first time in high resolution, and the petrologic information is being studied to understand the underlying eruptive processes observed.

Lithospheric-folding-based understanding on the origin of the back-arc basaltic magmatism beneath Jeju volcanic island, Korea

NASA Astrophysics Data System (ADS)

Yun, S.; Shin, Y.; CHOI, K.; Koh, J.; Nakamura, E.; Na, S.

2012-12-01

Jeju Island is an intraplate volcanic island located at the eastern margin on the East Asia behind the Ryukyu Trench, the collisional/subduction boundary between the Eurasian plate and Philippine Sea plate. It is a symmetrical shield volcano, having numerous monogenetic cinder cones, over 365, on the Mt. Halla volcanic edifice. The basement rock mainly consists of Precambrian gneiss, Mesozoic granite and volcanic rocks. Unconsolidated sedimentary rock is found between basement rock and surface lava. The lava plateau is composed of voluminous basaltic lava flows, which extend to the coast region with a gentle slope. Based on the evidence obtained from volcanic stratigraphy, paleontology, and geochronology, the age of the Jeju basalts ranges from the early Pleistocene to Holocene(Historic). The alkaline and tholeiitic basalts exhibits OIB composition from intraplate volcanism which is not associated with plate subduction, while the basement xenolith contained in the volcanic rock indicates that there were volcanic activities associated with the Mesozoic plate subduction. The Geochemical characteristics have been explained with the plume model, lithospheric mantle origin, and melting of shallow asthenosphere by the rapid change of stress regimes between the collision of the India-Eurasia plates and subduction of the Pacific plate, while there has not been any geophysical investigation to disclose it. Compression near collisional plate boundaries causes lithospheric folding which results in the decrease of pressure beneath the ridge of the fold while the pressure increases beneath trough. The decompression beneath lithosphere is likely to accelerate basaltic magmatism along and below the ridge. We investigate the subsurface structure beneath Jeju volcanic island, South Korea and its vicinity and propose an alternative hypothesis that the basaltic magma beneath the island could be caused by episodic lithospheric folding. Unlike the prevailing hypothesis of the intraplate basaltic magmatism that requires extending lithosphere, ours can explain how the basaltic magma could be generated at the back-arc regions without the extension. A schematic diagram illustrating the magma formation beneath Arc and Back-arc regions due to the lithospheric folding: Basaltic magma could be generated at upper mantle beneath ridge of the lithospheric fold by decompression and pre-existing high temperature.

CO2 fluxes from diffuse degassing in Italy

NASA Astrophysics Data System (ADS)

Cardellini, C.; Chiodini, G.; Frondini, F.; Caliro, S.

2016-12-01

Central and southern Italy are affected by an intense process of CO2 Earth degassing from both active volcanoes, and tectonically active areas. Regional scale studies, based on C mass balance of groundwater of regional aquifers in not volcanically active areas, highlighted the presence of two large CO2 degassing structures that, for magnitude and the geochemical-isotopic features, were related to a regional process of mantle degassing. Quantitative estimates provided a CO2 flux of 9 Mt/y for the region (62000 km2). Besides the magnitude of the process, a strong link between the deep CO2 degassing and the seismicity of the region and a strict correlation between migration of deep CO2-rich fluids and the heat flux have been highlighted. In addition, the region is also characterised by the presence of many cold gas emissions where deeply derived CO2 is released by vents and soil diffuse degassing areas. Both direct CO2 expulsion at the surface and C-rich groundwater are different manifestations of the same process, in fact, the deeply produced gas can be dissolved by groundwater or emitted directly to the atmosphere depending on the gas flux rate, and the geological-structural and hydrogeological settings. Quantitative estimations of the CO2 fluxes are available only for a limited number ( 30) of the about 270 catalogued gas manifestations allowing an estimations of a CO2 flux of 1.4 Mt/y. Summing the two estimates the non-volcanic CO2 flux from the region results globally relevant, being from 2 to 10% of the estimated present-day global CO2 discharge from subaerial volcanoes. Large amounts of CO2 is also discharged by soil diffuse degassing in volcanic-hydrothermal systems. Specific surveys at Solfatara of Pozzuoli (Campi Flegrei Caldera) pointed out the relevance of this process. CO2 diffuse degassing at Solfatara, measured since 1998 shows a persistent CO2 flux of 1300 t/d (± 390 t/d), a flux comparable to an erupting volcano. The quantification of diffuse CO2 degassing in Italy points out the relevance of non-volcanic CO2 degassing and of soil degassing from volcanoes, suggesting that the actual underestimation of the global CO2 degassing, may arise also from the lack of specific and systematic studies of the numerous "degassing areas" of the world, that would contribute to better constrain the global CO2 budget.

Temporal and Spatial Analysis of Monogenetic Volcanic Fields

NASA Astrophysics Data System (ADS)

Kiyosugi, Koji

Achieving an understanding of the nature of monogenetic volcanic fields depends on identification of the spatial and temporal patterns of volcanism in these fields, and their relationships to structures mapped in the shallow crust and inferred in the deep crust and mantle through interpretation of geochemical, radiometric and geophysical data. We investigate the spatial and temporal distributions of volcanism in the Abu Monogenetic Volcano Group, Southwest Japan. E-W elongated volcano distribution, which is identified by a nonparametric kernel method, is found to be consistent with the spatial extent of P-wave velocity anomalies in the lower crust and upper mantle, supporting the idea that the spatial density map of volcanic vents reflects the geometry of a mantle diapir. Estimated basalt supply to the lower crust is constant. This observation and the spatial distribution of volcanic vents suggest stability of magma productivity and essentially constant two-dimensional size of the source mantle diapir. We mapped conduits, dike segments, and sills in the San Rafael sub-volcanic field, Utah, where the shallowest part of a Pliocene magmatic system is exceptionally well exposed. The distribution of conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. The comparison of San Rafael conduit distribution and the distributions of volcanoes in several recently active volcanic fields supports the use of statistical models, such as nonparametric kernel methods, in probabilistic hazard assessment for distributed volcanism. We developed a new recurrence rate calculation method that uses a Monte Carlo procedure to better reflect and understand the impact of uncertainties of radiometric age determinations on uncertainty of recurrence rate estimates for volcanic activity in the Abu, Yucca Mountain Region, and Izu-Tobu volcanic fields. Results suggest that the recurrence rates of volcanic fields can change by more than one order of magnitude on time scales of several hundred thousand to several million years. This suggests that magma generation rate beneath volcanic fields may change over these time scales. Also, recurrence rate varies more than one order of magnitude between these volcanic fields, consistent with the idea that distributed volcanism may be influenced by both the rate of magma generation and the potential for dike interaction during ascent.

Volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory 1993

USGS Publications Warehouse

Neal, Christina A.; McGimsey, Robert G.; Doukas, Michael P.

1996-01-01

During 1993, the Alaska Volcano Observatory (AVO) responded to episodes of eruptive activity or false alarms at nine volcanic centers in the state of Alaska. Additionally, as part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also responded to eruptions on the Kamchatka Peninsula, details of which are summarized in Miller and Kurianov (1993). In 1993, AVO maintained seismic instrumentation networks on four volcanoes of the Cook Inlet region--Spurr, Redoubt, Iliamna, and Augustine--and two stations at Dutton Volcano near King Cove on the Alaska Peninsula. Other routine elements of AVO's volcano monitoring program in Alaska include periodic airborne measurement of volcanic SO2 and CO2 at Cook Inlet volcanoes (Doukas, 1995) and maintenance of a lightning detection system in Cook Inlet (Paskievitch and others, 1995).

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

NASA Astrophysics Data System (ADS)

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.

The Role of Crustal Tectonics in Volcano Dynamics (ROCTEVODY) along the Southern Andes: seismological study with emphasis on Villarrica Volcano

NASA Astrophysics Data System (ADS)

Mora-Stock, Cindy; Tassara, Andrés

2016-04-01

The Southern Andean margin is intrinsically related to the Liquiñe-Ofqui Fault Zone (LOFZ), a 1000 km-long dextral strike-slip arc-parallel fault on which most of the volcanic centers of the Southern Volcanic Zone (SCVZ) of the Andes are emplaced. At large spatial (102 - 103 km) and temporal (105 - 107 yr) scales, regional tectonics linked to partitioning of the oblique convergence controls the distribution of magma reservoirs, eruption rates and style, as well as the magma evolution. At small scales in space (< 102 km) and time (10-1 - 102 yr), stress transfer mechanisms between magma reservoirs and seismically-active faults are though to transiently change the regional stress field, thus leading to eruptions and fault (re)activation. However, the mechanisms by which the interaction between (megathrust and crustal) earthquakes and volcanic eruptions actually occur, in terms of generating the relationships and characteristics verified at the long term, are still poorly understood. Since 2007, the Southern Andean margin has presented an increase of its tectonic and eruptive activity with several volcanic crisis and eruptions taking place in association with significant seismicity clusters and earthquakes both in the megathrust and the LOFZ. This increased activity offers a unique opportunity to improve our understanding of the physical relation between contemporary tectono-volcanic processes and the long-term construction of the LOFZ-SVZ system. Taking advantage of this opportunity by means of an integrated analysis of geodetic and seismological data through finite element numerical modeling at the scale of the entire margin and for selected cases is the main goal of project Active Tectonics and Volcanism at the Southern Andes (ACT&VO-SA, see Tassara et al. this meeting). Into the framework of the ACT&VO-SA project, the complementary ROCTEVODY-Villarrica project concentrates on the role that inherited crustal structures have in the volcano dynamics. The focus is on Villarrica volcano, which is emplaced at the intersection of the main NNE-branch of the LOFZ and the NW-SE inherited Mocha-Villarrica Fault (MVF). The extensional characteristics of previous eruptions at Villarrica contrasts with the dextral strike-slip motion of LOFZ and the compressive regime dominated by the subduction. Then, this projects aims to understand how the NW-SE inherited structures interacts with their intra-arc counterpart to allow the emplacement of volcanic edifices under the present day compressive stress regime. This goal will be achieved through the analysis of a seismic database for Villarrica volcano that combines data from a dense local network and the network of the Chilean volcanic observatory. These data will allow us to identify long period events and tremor signals from which we plan to perform a wave field characterization to extract information about fluid flow and seismic source, together with a precise location of tectonic crustal events. We will present preliminary results and a conceptual model to explain the role of the different structures at interplay in the region and their relation with volcano dynamics.

Multiple edifice-collapse events in the Eastern Mexican Volcanic Belt: The role of sloping substrate and implications for hazard assessment

USGS Publications Warehouse

Carrasco-Nunez, Gerardo; Diaz-Castellon, Rodolfo; Siebert, L.; Hubbard, B.; Sheridan, M.F.; Rodriguez, Sergio R.

2006-01-01

The Citlalte??petl-Cofre de Perote volcanic chain forms an important physiographic barrier that separates the Central Altiplano (2500??masl) from the Gulf Coastal Plain (GCP) (1300??masl). The abrupt eastward drop in relief between these provinces gives rise to unstable conditions and consequent gravitational collapse of large volcanic edifices built at the edge of the Altiplano. Eastward sloping substrate, caused by the irregular configuration of the basement rocks, is the dominant factor that controls the direction of collapsing sectors in all major volcanoes in the region to be preferentially towards the GCP. These collapses produced voluminous debris avalanches and lahars that inundated the well-developed drainages and clastic aprons that characterize the Coastal Plain. Large catastrophic collapses from Citlalte??petl, Las Cumbres, and Cofre de Perote volcanoes are well documented in the geologic record. Some of the avalanches and transformed flows have exceptionally long runouts and reach the Gulf of Mexico traveling more than 120??km from their source. So far, no direct evidence has been found for magmatic activity associated with the initiation of these catastrophic flank-collapses. Apparently, instability of the volcanic edifices has been strongly favored by very intense hydrothermal alteration, abrupt topographic change, and intense fracturing. In addition to the eastward slope of the substrate, the reactivation of pre-volcanic basement structures during the Late Tertiary, and the E-W to ENE-SSW oriented regional stress regimes may have played an important role in the preferential movement direction of the avalanches and flows. In addition to magmatic-hydrothermal processes, high amounts of rainfall in the area is another factor that enhances alteration and eventually weakens the rocks. It is very likely that seismic activity may be the principal triggering mechanism that caused the flank collapse of large volcanic edifices in the Eastern Mexican Volcanic Belt. However, critical pore water pressure from extraordinary amounts of rainfall associated with hurricanes or other meteorological perturbation cannot be ruled out, particularly for smaller volume collapses. There are examples in the area of small seismogenic debris flows that have occurred in historical times, showing that these processes are not uncommon. Assessing the stability conditions of major volcanic edifices that have experienced catastrophic sector collapses is crucial for forecasting future events. This is particularly true for the Eastern Mexican Volcanic Belt, where in many cases no magmatic activity was associated with the collapse. Therefore, edifice failure could occur again without any precursory warning. ?? 2006 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lagunova, I.A.

A characteristic feature of the products of mud-volcano activity in the Kerch-Taman region is their high boron content. Distribution of boron in waters of mud volcanoes is characterized by restriction of anomalously high concentrations of boron to mud volcanoes actively operating at the present time in general, and to the most active period of operation of the individual volcano; there is a direct correlation between boron and the hydrocarbonate ion (r/sub B//HCO/sub 3// = 0.5), and between boron and carbon dioxide from the mud-volcano gases (r/sub B//CO/sub 2// = 0.4). The correlation is lacking between boron and mineralization, and betweenmore » boron and chlorine, the correlation is close to inverse. A spatial connection between areas of development of mud volcanism and belts of boron mineralization has been established. Anomalously high boron concentrations in the products of mud volcanism in the Kerch-Taman region are part of the overall increased boron capacity of the Crimea and the Caucasus, which has been controlled by recent magmatic activity.« less

Background heatflow on hotspot planets - Io and Venus

NASA Technical Reports Server (NTRS)

Stevenson, David J.; Mcnamara, Sean C.

1988-01-01

It is suggested that there is no simple relationship between lithospheric thickness and heatflow on planets where volcanism dominates the heatflow. This applies locally and globally, even away from regions of volcanic activity. This indicates that there is no basis for the assumption that the Io heatflow is as low as (or lower than) the hotspot component alone would suggest. A model is presented to describe the heatflow on hotspot planets. The model is applied to Io and Venus.

The role of mantle CO2 in volcanism

USGS Publications Warehouse

Barnes, I.; Evans, William C.; White, L.D.

1988-01-01

Carbon dioxide is the propellant gas in volcanic eruptions and is also found in mantle xenoliths. It is speculated that CO2 occurs as a free gas phase in the mantle because there is no reason to expect CO2 to be so universally associated with volcanic rocks unless the CO2 comes from the same source as the volcanic rocks and their xenoliths. If correct, the presence of a free gas in the mantle would lead to physical instability, with excess gas pressure providing the cause of both buoyancy of volcanic melts and seismicity in volcanic regions. Convection in the mantle and episodic volcanic eruptions are likely necessary consequences. This suggestion has considerable implications for those responsible for providing warnings of impending disasters resulting from volcanic eruptions and earthquakes in volcanic regions. ?? 1988.

The Volcanism Ontology (VO): a model of the volcanic system

NASA Astrophysics Data System (ADS)

Myer, J.; Babaie, H. A.

2017-12-01

We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

Sulfur dioxide OMI retrievals combined with seismic network data reveals magma migration at active volcanoes in North Kivu region

NASA Astrophysics Data System (ADS)

Theys, Nicolas; Barrière, Julien; Oth, Adrien; Brenot, Hugues; Van Roozendael, Michel; Kervyn, François

2017-04-01

The Kivu region is a densely populated area hosting two very active volcanoes, Nyiragongo and Nyamulagira, which require continuous surveillance using the widest means of observation as possible. This study presents a 12-year dataset of satellite observations of SO2 over North Kivu from the OMI instrument. Short- and long-term changes in volcanic SO2 emissions are investigated and satellite data oversampling is used to discriminate the volcanic sources for the full OMI mission. As the same SO2 retrieval algorithm will be applied operationally to the forthcoming TROPOMI instrument (onboard the ESA Sentinel-5 Precursor platform), the observational time series will expand in the future, with enhanced quality. For the years 2014-2016, the satellite SO2 dataset is combined with seismic observations from a 11-stations network that operated continuously during that period. The variations of seismic activity and SO2 degassing display a high-level of consistency and we present a multidisciplinary tracking approach by combining the two types of observational data. This methodology allows for a robust discrimination of magma migration into and out of the shallow plumbing system, improving our ability to interpret signs of volcanic unrest on a daily time scale.

Petrologic considerations for hot dry rock geothermal site selection in the Clear Lake Region, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stimac, J.; Goff, F.; Hearn, B.C. Jr.

1992-01-01

The Clear Lake area is well known for anomalous heat flow, thermal springs, hydrothermal mineral deposits, and Quaternary volcanism. These factors, along with the apparent lack of a large reservoir of geothermal fluid north of Collayomi fault make the Clear Lake area an attractive target for hot dry rock (HDR) geothermal development. Petrologic considerations provide some constraints on site selection for HDR development. Spatial and temporal trends in volcanism in the Coast Ranges indicate that magmatism has migrated to the north with time, paralleling passage of the Mendocino triple junction and propagation of the San Andreas fault. Volcanism in themore » region may have resulted from upwelling of hot asthenosphere along the southern margin of the subducted segment of the Gorda plate. Spatial and temporal trends of volcanism within the Clear Lake volcanic field are similar to larger-scale trends of Neogene volcanism in the Cost Ranges. Volcanism (especially for silicic compositions) shows a general migration to the north over the {approximately}2 Ma history of the field, with the youngest two silicic centers located at Mt. Konocti and Borax Lake. The Mt. Konocti system (active from {approximately} 0.6 to 0.3 Ma) was large and long-lived, whereas the Borax Lake system is much smaller but younger (0.09 Ma). Remnants of silicic magma bodies under Mt. Konocti may be in the latter stages of cooling, whereas a magma body centered under Borax Lake may be in the early stages of development. The existence of an upper crustal silicic magma body of under Borax Lake has yet to be demonstrated by passive geophysics, however, subsurface temperatures in the area as high (> 200{degrees}C at 2000 m) as those beneath the Mt. Konocti area. Based on petrologic considerations alone, the Mt. Konocti-Borax Lake area appears to be the most logical choice for HDR geothermal development in the region.« less

Regional fracture patterns around volcanoes: Possible evidence for volcanic spreading on Venus

NASA Astrophysics Data System (ADS)

López, I.; Lillo, J.; Hansen, V. L.

2008-06-01

Magellan data show that the surface of Venus is dominated by volcanic landforms including large flow fields and a wide range of volcanic edifices that occur in different magmatic and tectonic environments. This study presents the results from a comprehensive survey of volcano-rift interaction in the BAT region and its surroundings. We carried out structural mapping of examples where interaction between volcanoes and regional fractures results in a deflection of the fractures around the volcanic features and discuss the nature of the local volcano-related stress fields that might be responsible for the observed variations of the regional fracture systems. We propose that the deflection of the regional fractures around these venusian volcanoes might be related to volcanic spreading, a process recognized as of great importance in the tectonic evolution of volcanoes on Earth and Mars, but not previously described on Venus.

Crustal Deformation in the Eastern Snake River Plain and Yellowstone Plateau Observed by SAR Interferometry

NASA Astrophysics Data System (ADS)

Aly, M. H.; Hughes, S. S.; Rodgers, D. W.; Glenn, N. F.; Thackray, G. D.

2007-12-01

The Snake River Plain-Yellowstone tectono-volcanic province was created when North America migrated over a fixed hotspot in the mantle. Synthetic Aperture Radar Interferometry (InSAR) has been applied in this study to address the recent tectono-volcanic activity in the Eastern Snake River Plain (ESRP) and the southwestern part of Yellowstone Plateau. InSAR results show that crustal deformation across the tectono-volcanic province is episodic. An episode of uplift (about 1 cm/yr) along the ESRP axial volcanic zone, directly southwest of Island Park, has been detected from a time-series of independent differential interferograms created for the 1993-2000 period. Episodes of subsidence (1 cm/yr) during 1997-2000 and uplift (3 cm/yr) during 2004-2006 have been also detected in the active Yellowstone caldera, just northeast of Island Park. The detected interferometric signals indicate that deformation across the axial volcanic zone near Island Park is inversely linked to deformation in the active Yellowstone caldera. One explanation is that the inverse motions reflect a flexure response of the ESRP crust to magma chamber activity beneath the active caldera, although other interpretations are possible. The time-series of differential interferograms shows that no regional deformation has occurred across the central part of ESRP during the periods of observations, but local surface displacements of 1-3 cm magnitude have been detected in the adjacent Basin-Range province. Differential surface movements of varying rates have been also detected along Centennial, Madison, and Hebgen faults between 1993 and 2006.

Geologic Mapping of the Juno Chasma Quadrangle, Venus: Establishing the Relation Between Rifting and Volcanism

NASA Technical Reports Server (NTRS)

Senske, D. A.

2008-01-01

To understand the spatial and temporal relations between tectonic and volcanic processes on Venus, the Juno Chasma region is mapped. Geologic units are used to establish regional stratigraphic relations and the timing between rifting and volcanism.

Geochemistry, geochronology, and Sr-Nd isotopic compositions of Permian volcanic rocks in the northern margin of the North China Block: implications for the tectonic setting of the southeastern Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

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

2018-02-01

The southeastern part of the Central Asian Orogenic Belt (CAOB), which records the collision of the North China Block (NCB) with the South Mongolian microcontinent, is a key area for reconstructing the tectonic history of the CAOB. Controversy persists regarding the timing of the final structural amalgamation of the region; therefore, it remains unclear whether the Late Paleozoic thick volcanic successions were generated in a subduction or post-orogenic environment. Redefining the age of the formation and analyzing the geochemical compositions of these volcanic rocks can provide clues regarding the regional tectonic evolution during the Late Paleozoic and place constraints on the closure time of the Paleo-Asian Ocean. In this study, we present geochemical, geochronologic, and Sr-Nd isotopic data for 29 volcanic rock samples from the Elitu Formation in Xianghuangqi, central Inner Mongolia. The Elitu volcanic rocks have latest early-to-middle Permian ages between 272 and 268 Ma. Most of the mafic-intermediate and felsic rocks show K-normal and high-K calc-alkaline characteristics. Melting is considered to be due to large scale upwelling of the metasomatic lithospheric mantle and different degrees of melting of the thickened lower crust. The northern margin of the NCB, which represents the southeastern boundary of the CAOB, records transtensional and, subsequently, extensional tectonics associated with late Carboniferous to middle Permian volcanic activity.

Climatic Impacts of a Volcanic Double Event: 536/540 CE

NASA Astrophysics Data System (ADS)

Toohey, M.; Krüger, K.; Sigl, M.; Stordal, F.; Svensen, H.

2015-12-01

Volcanic activity in and around the year 536 CE led to the coldest decade of the Common Era, and has been speculatively linked to large-scale societal crises around the world. Using a coupled aerosol-climate model, with eruption parameters constrained by recently re-dated ice core records and historical observations of the aerosol cloud, we reconstruct the radiative forcing resulting from a sequence of two major volcanic eruptions in 536 and 540 CE. Comparing with a reconstruction of volcanic forcing over the past 1200 years, we estimate that the decadal-scale Northern Hemisphere (NH) extra-tropical radiative forcing from this volcanic "double event" was larger than that of any known period. Earth system model simulations including the volcanic forcing are used to explore the temperature and precipitation anomalies associated with the eruptions, and compared to available proxy records, including maximum latewood density (MXD) temperature reconstructions. Special attention is placed on the decadal persistence of the cooling signal in tree rings, and whether the climate model simulations reproduce such long-term climate anomalies. Finally, the climate model results will be used to explore the probability of socioeconomic crisis resulting directly from the volcanic radiative forcing in different regions of the world.

Radiocarbon ages of lacustrine deposits in volcanic sequences of the Lomas Coloradas area, Socorro Island, Mexico

NASA Technical Reports Server (NTRS)

Farmer, J. D.; Farmer, M. C.; Berger, R.

1993-01-01

Extensive eruptions of alkalic basalt from low-elevation fissures and vents on the southern flank of the dormant volcano, Cerro Evermann, accompanied the most recent phase of volcanic activity on Socorro Island, and created the Lomas Coloradas, a broad, gently sloping terrain comprising the southern part of the island. We obtained 14C ages of 4690 +/- 270 BP (5000-5700 cal BP) and 5040 +/- 460 BP (5300-6300 cal BP) from lacustrine deposits that occur within volcanic sequences of the lower Lomas Coloradas. Apparently, the sediments accumulated within a topographic depression between two scoria cones shortly after they formed. The lacrustine environment was destroyed when the cones were breached by headward erosion of adjacent stream drainages. This was followed by the eruption of a thin basaltic flow from fissures near the base of the northernmost cone. The flow moved downslope for a short distance and into the drainages that presently bound the study area on the east and west. The flow postdates development of the present drainage system and may be very recent. Our 14C data, along with historical accounts of volcanic activity over the last century, including submarine eruptions that occurred a few km west of Socorro in early 1993, underscore the high risk for explosive volcanism in this region and the need for a detailed volcanic hazards plan and seismic monitoring.

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

USGS Publications Warehouse

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

2008-01-01

The northeastern San Juan Mountains, the least studied portion of this well-known segment of the Southern Rocky Mountains Volcanic Field are the site of several newly identified and reinterpreted ignimbrite calderas. These calderas document some unique eruptive features not described before from large volcanic systems elsewhere, as based on recent mapping, petrologic data, and a large array of newly determined high-precision, laser-fusion 40Ar/39Ar ages (140 samples). Tightly grouped sanidine ages document exceptionally brief durations of 50-100 k.y. or less for individual Oligocene caldera cycles; biotite ages are more variable and commonly as much as several hundred k.y. older than sanidine from the same volcanic unit. A previously unknown ignimbrite caldera at North Pass, along the Continental Divide in the Cochetopa Hills, was the source of the newly distinguished 32.25-Ma Saguache Creek Tuff (???400-500 km3). This regionally, distinctive crystal-poor alkalic rhyolite helps fill an apparent gap in the southwestward migration from older explosive activity, from calderas along the N-S Sawatch locus in central Colorado (youngest, Bonanza Tuff at 33.2 Ma), to the culmination of Tertiary volcanism in the San Juan region, where large-volume ignimbrite eruptions started at ca. 29.5 Ma and peaked with the enormous Fish Canyon Tuff (5000 km3) at 28.0 Ma. The entire North Pass cycle, including caldera-forming Saguache Creek Tuff, thick caldera-filling lavas, and a smaller volume late tuff sheet, is tightly bracketed at 32.25-32.17 Ma. No large ignimbrites were erupted in the interval 32-29 Ma, but a previously unmapped cluster of dacite-rhyolite lava flows and small tuffs, areally associated with a newly recognized intermediate-composition intrusion 5 ?? 10 km across (largest subvolcanic intrusion in San Juan region) centered 15 km north of the North Pass caldera, marks a near-caldera-size silicic system active at 29.8 Ma. In contrast to the completely filled North Pass caldera that has little surviving topographic expression, no voluminous tuffs vented directly from the adjacent Cochetopa Park caldera, which is morphologically beautifully preserved. Instead, Cochetopa Park subsided passively as the >500 km3 Nelson Mountain Tuff vented at 26.9 Ma from an "underfit" caldera (youngest of the San Luis complex) 30 km to the SW. Three separate regional ignimbrites were erupted sequentially from San Luis calderas within an interval of less than 50-100 k.y., a more rapid recurrence rate for large explosive eruptions than previously documented elsewhere. In eruptive processes, volcanic compositions, areal extent, duration of activity, and magmatic production rates and volumes, the Southern Rocky Mountains Volcanic Field represents present-day erosional remnants of a composite volcanic field, comparable to younger ignimbrite terranes of the Central Andes. ?? 2008 Geological Society of America.

The quality of our Nation's waters: groundwater quality in the Columbia Plateau and Snake River Plain basin-fill and basaltic-rock aquifers and the Hawaiian volcanic-rock aquifers, Washington, Idaho, and Hawaii, 1993-2005

USGS Publications Warehouse

Rupert, Michael G.; Hunt, Charles D.; Skinner, Kenneth D.; Frans, Lonna M.; Mahler, Barbara J.

2015-01-01

The Columbia Plateau, Snake River Plain, and Hawaii are large volcanic areas in the western United States and mid-Pacific ocean that contain extensive regional aquifers of a hard, gray, volcanic rock called basalt. Residents of the Columbia Plateau, the Snake River Plain, and the island of Oahu depend on groundwater as their primary source of drinking water. Although the depth to the water table can be several hundred feet, the groundwater is highly vulnerable to contamination because the permeable sediments and rocks allow contaminants to move readily down to the water table. Intense agricultural and urban activities occur above the drinking-water supply and are increasing in some areas. Contaminants, such as nitrate, pesticides, and volatile organic compounds, associated with agricultural and urban activities, have adversely affected groundwater quality.

San Miguel Volcanic Seismic and Structure in Central America: Insight into the Physical Processes of Volcanoes

NASA Astrophysics Data System (ADS)

Patlan, E.; Velasco, A.; Konter, J. G.

2010-12-01

The San Miguel volcano lies near the city of San Miguel, El Salvador (13.43N and - 88.26W). San Miguel volcano, an active stratovolcano, presents a significant natural hazard for the city of San Miguel. In general, the internal state and activity of volcanoes remains an important component to understanding volcanic hazard. The main technology for addressing volcanic hazards and processes is through the analysis of data collected from the deployment of seismic sensors that record ground motion. Six UTEP seismic stations were deployed around San Miguel volcano from 2007-2008 to define the magma chamber and assess the seismic and volcanic hazard. We utilize these data to develop images of the earth structure beneath the volcano, studying the volcanic processes by identifying different sources, and investigating the role of earthquakes and faults in controlling the volcanic processes. We initially locate events using automated routines and focus on analyzing local events. We then relocate each seismic event by hand-picking P-wave arrivals, and later refine these picks using waveform cross correlation. Using a double difference earthquake location algorithm (HypoDD), we identify a set of earthquakes that vertically align beneath the edifice of the volcano, suggesting that we have identified a magma conduit feeding the volcano. We also apply a double-difference earthquake tomography approach (tomoDD) to investigate the volcano’s plumbing system. Our preliminary results show the extent of the magma chamber that also aligns with some horizontal seismicity. Overall, this volcano is very active and presents a significant hazard to the region.

[Activities of Dept. of Geological Sciences, Colorado University

NASA Technical Reports Server (NTRS)

Bilham, Roger

1997-01-01

Using remotely sensed data and GPS observations we completed a study of neotectonic processes responsible for landscape changes in an area of active extensional deformation and volcanism. The findings from this study describe the extensional processes operating in the region of the Afar triple junction and the northern Ethiopian rift.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nugraha, Andri Dian, E-mail: andridn104@gmail.com; Widiyantoro, Sri; Shiddiqi, Hasbi Ash

Indonesian archipelago region is located in active tectonic setting and high seismicity zone. During the last decade, Indonesian was experienced with destructive major earthquakes causing damage and victims. The information of precise earthquake location parameters are very important in partular for earthquake early warning to the society and for advance seismic studies. In this study, we attempted to improve hypocenter location compiled by BMKG for time periods of April, 2009 up to June, 2014 for about 22,000 earthquake events around Indonesian region. For the firts time, we applied teleseismic double-difference relocation algorithm (teletomoDD) to improve hypocenter region in Indonesia regionmore » combining regional and teleseismic stations. Hypocenter relocation was performed utilizing local, regional, and teleseismic P-wave arrival time data. Our relocation result show that travel-time RMS errors were greatly reduced compared to the BMKG catalog. Seismicity at shallower depth (less than 50 km) shows significantly improvement especially in depth, and refined shallow geological structures, e.g. trench and major strike slip faults. Clustered seismicity is also detected beneath volcanic region, and probably related volcano activities and also major faults nearby. In the Sunda arc region, seismicity at shallower depth centered at two major distributions parallel to the trench strike direction, i.e. around fore-arc and in mainland that related to major fault, e.g. the Sumatran fault, and volcanic fronts. Below Central Java region, relocated hypocenter result showed double seismic zone pattern. A seismic gap is detected around the Sunda-Banda transition zone where transition between oceanic subduction to continental crust collision of Australian plate occurs. In Eastern Indonesia region, shallow earthquakes are observed related to major strike slip faults, e.g. Sorong and Palu-Koro fault, volcanism, and shallow part of subduction and collision zones. We also compare our result in the Sunda Arc region with slab1.0 model and our relocated seismicity shows good agreement with the previous slab geometry. Horizontal position shift of relocated events are mostly perpendicular to the trench directions.« less

Photochemistry of a Volcanically Driven Atmosphere on Io: Sulfur and Oxygen Species from a Pele-Type Eruption

NASA Astrophysics Data System (ADS)

Moses, Julianne I.; Zolotov, Mikhail Yu.; Fegley, Bruce

2002-03-01

To determine how active volcanism might affect the standard picture of sulfur dioxide photochemistry on Io, we have developed a one-dimensional atmospheric model in which a variety of sulfur-, oxygen-, sodium-, potassium-, and chlorine-bearing volatiles are volcanically outgassed at Io's surface and then evolve due to photolysis, chemical kinetics, and diffusion. Thermochemical equilibrium calculations in combination with recent observations of gases in the Pele plume are used to help constrain the composition and physical properties of the exsolved volcanic vapors. Both thermochemical equilibrium calculations (Zolotov and Fegley 1999, Icarus141, 40-52) and the Pele plume observations of Spencer et al. (2000; Science288, 1208-1210) suggest that S 2 may be a common gas emitted in volcanic eruptions on Io. If so, our photochemical models indicate that the composition of Io's atmosphere could differ significantly from the case of an atmosphere in equilibrium with SO 2 frost. The major differences as they relate to oxygen and sulfur species are an increased abundance of S, S 2, S 3, S 4, SO, and S 2O and a decreased abundance of O and O 2 in the Pele-type volcanic models as compared with frost sublimation models. The high observed SO/SO 2 ratio on Io might reflect the importance of a contribution from volcanic SO rather than indicate low eddy diffusion coefficients in Io's atmosphere or low SO "sticking" probabilities at Io's surface; in that case, the SO/SO 2 ratio could be temporally and/or spatially variable as volcanic activity fluctuates. Many of the interesting volcanic species (e.g., S 2, S 3, S 4, and S 2O) are short lived and will be rapidly destroyed once the volcanic plumes shut off; condensation of these species near the source vent is also likely. The diffuse red deposits associated with active volcanic centers on Io may be caused by S 4 radicals that are created and temporarily preserved when sulfur vapor (predominantly S 2) condenses around the volcanic vent. Condensation of SO across the surface and, in particular, in the polar regions might also affect the surface spectral properties. We predict that the S/O ratio in the torus and neutral clouds might be correlated with volcanic activity—during periods when volcanic outgassing of S 2 (or other molecular sulfur vapors) is prevalent, we would expect the escape of sulfur to be enhanced relative to that of oxygen, and the S/O ratio in the torus and neutral clouds could be correspondingly increased.

Preliminary volcano-hazard assessment for Mount Spurr Volcano, Alaska

USGS Publications Warehouse

Waythomas, Christopher F.; Nye, Christopher J.

2001-01-01

Mount Spurr volcano is an ice- and snow-covered stratovolcano complex located in the north-central Cook Inlet region about 100 kilometers west of Anchorage, Alaska. Mount Spurr volcano consists of a breached stratovolcano, a lava dome at the summit of Mount Spurr, and Crater Peak vent, a small stratocone on the south flank of Mount Spurr volcano. Historical eruptions of Crater Peak occurred in 1953 and 1992. These eruptions were relatively small but explosive, and they dispersed volcanic ash over areas of interior, south-central, and southeastern Alaska. Individual ash clouds produced by the 1992 eruption drifted east, north, and south. Within a few days of the eruption, the south-moving ash cloud was detected over the North Atlantic. Pyroclastic flows that descended the south flank of Crater Peak during both historical eruptions initiated volcanic-debris flows or lahars that formed temporary debris dams across the Chakachatna River, the principal drainage south of Crater Peak. Prehistoric eruptions of Crater Peak and Mount Spurr generated clouds of volcanic ash, pyroclastic flows, and lahars that extended to the volcano flanks and beyond. A flank collapse on the southeast side of Mount Spurr generated a large debris avalanche that flowed about 20 kilometers beyond the volcano into the Chakachatna River valley. The debris-avalanche deposit probably formed a large, temporary debris dam across the Chakachatna River. The distribution and thickness of volcanic-ash deposits from Mount Spurr volcano in the Cook Inlet region indicate that volcanic-ash clouds from most prehistoric eruptions were as voluminous as those produced by the 1953 and 1992 eruptions. Clouds of volcanic ash emitted from the active vent, Crater Peak, would be a major hazard to all aircraft using Ted Stevens Anchorage International Airport and other local airports and, depending on wind direction, could drift a considerable distance beyond the volcano. Ash fall from future eruptions could disrupt many types of economic and social activities, including oil and gas operations and shipping activities in the Cook Inlet area. Eruptions of Crater Peak could involve significant amounts of ice and snow that would lead to the formation of large lahars, formation of volcanic debris dams, and downstream flooding. The greatest hazards in order of importance are described below and shown on plate 1.

Ambient noise tomography reveals upper crustal structure of Icelandic rifts

NASA Astrophysics Data System (ADS)

Green, Robert G.; Priestley, Keith F.; White, Robert S.

2017-05-01

The structure of oceanic spreading centres and subsurface melt distribution within newly formed crust is largely understood from marine seismic experiments. In Iceland, however, sub-aerial rift elevation allows both accurate surface mapping and the installation of large broadband seismic arrays. We present a study using ambient noise Rayleigh wave tomography to image the volcanic spreading centres across Iceland. Our high resolution model images a continuous band of low seismic velocities, parallelling all three segments of the branched rift in Iceland. The upper 10 km contains strong velocity variations, with shear wave velocities 0.5 km s-1 faster in the older non-volcanically active regions compared to the active rifts. Slow velocities correlate very closely with geological surface mapping, with contours of the anomalies parallelling the edges of the neo-volcanic zones. The low-velocity band extends to the full 50 km width of the neo-volcanic zones, demonstrating a significant contrast with the narrow (8 km wide) magmatic zone seen at fast spreading ridges, where the rate of melt supply is similarly high. Within the seismically slow rift band, the lowest velocity cores of the anomalies occur above the centre of the mantle plume under the Vatnajökull icecap, and in the Eastern Volcanic Zone under the central volcano Katla. This suggests localisation of melt accumulation at these specific volcanic centres, demonstrating variability in melt supply into the shallow crust along the rift axis. Shear velocity inversions with depth show that the strongest velocity contrasts are found in the upper 8 km, and show a slight depression in the shear velocity through the mid crust (10-20 km) in the rifts. Our model also shows less intensity to the slow rift anomaly in the Western Volcanic Zone, supporting the notion that rift activity here is decreasing as the ridge jumps to the Eastern Volcanic Zone.

Monitoring unrest in a large silicic caldera, the long Valley-inyo craters volcanic complex in east-central California

USGS Publications Warehouse

Hill, D.P.

1984-01-01

Recent patterns of geologic unrest in long Valley caldera in east-central California emphasize that this large, silicic volcanic system and the adjacent, geologically youthful Inyo-Mono Craters volcanic chain are still active and capable of producing locally hazardous volcanic eruptions. A series of four magnitude -6 earthquakes in May 1980 called attention to this current episode of unrest, and subsequent activity has included numerous earthquake swarms in the south moat of the caldera accompanied by inflation of the resurgent dome by more than 50 cm over the last five years. The seismicity associated with this unrest is currently monitored by a network of 31 telemetered seismic stations with an automatic processing system that yelds hypocentral locations and earthquake magnitudes in near-real time. Deformation of the ground is monitored by a) a series of overlapping trilateration networks that provide coverage ranging from annual measurements of regional deformation to daily measurements of deformation local to the active, southern section of the caldera, b) a regional network of level lines surveyed annually, c) a regional network of precise gravity stations occupied annually, d) local, L-shaped level figures surveyed every few months, and e) a network of fourteen borehole tiltmeter clusters (two instruments in each cluster) and a borehole dilatometer, the telemetered signals from which provide continuous data on deformation rates. Additional telemetered data provide continuous information on fluctuations in the local magnetic field, hydrogen gas emission rates at three sites, and water level and temperatures in three wells. Continuous data on disharge rates and temperatures from hot springs and fumaroles are collected by several on-site recorders within the caldera, and samples for liquid and gas chemistry are collected several times per year from selected hot springs and fumaroles. ?? 1984 Intern. Association of Volcanology and Chemistry of the Earth's Interior.

Formation of magmatic brine lenses via focussed fluid-flow beneath volcanoes

NASA Astrophysics Data System (ADS)

Afanasyev, Andrey; Blundy, Jon; Melnik, Oleg; Sparks, Steve

2018-03-01

Many active or dormant volcanoes show regions of high electrical conductivity at depths of a few kilometres beneath the edifice. We explore the possibility that these regions represent lenses of high-salinity brine separated from a single-phase magmatic fluid containing H2O and NaCl. Since chloride-bearing fluids are highly conductive and have an exceptional capacity to transport metals, these regions can be an indication of an active hydrothermal ore-formation beneath volcanoes. To investigate this possibility we have performed hydrodynamic simulations of magma degassing into permeable rock. In our models the magma source is located at 7 km depth and the fluid salinity approximates that expected for fluids released from typical arc magmas. Our model differs from previous models of a similar process because it is (a) axisymmetric and (b) includes a static high-permeability pathway that links the magma source to the surface. This pathway simulates the presence of a volcanic conduit and/or plexus of feeder dykes that are typical of most volcanic systems. The presence of the conduit leads to a number of important hydrodynamic consequences, not observed in previous models. Importantly, we show that an annular brine lens capped by crystallised halite is likely to form above an actively degassing sub-volcanic magma body and can persist for more than 250 kyr after degassing ceases. Parametric analysis shows that brine lenses are more prevalent when the fluid is released at temperatures above the wet granite solidus, when magmatic fluid salinity is high, and when the high-permeability pathway is narrow. The calculated depth, form and electrical conductivity of our modelled system shares many features with published magnetotelluric images of volcano subsurfaces. The formation and persistence of sub-volcanic brine lenses has implications for geothermal systems and hydrothermal ore formation, although these features are not explored in the presented model.

Secular Variation and Paleomagnetic Studies of Southern Patagonian Plateau Lavas, 46S to 52S, Argentina

NASA Astrophysics Data System (ADS)

Brown, L.; Gorring, M.; Mason, D.; Condit, C.; Lillydahl-Schroeder, H.

2007-12-01

Regional studies of paleosecular variation of the Earth's magnetic field can provide us with information beyond that available from one location. Southern Patagonia, Argentina (46S to 52S latitude and 68W to 72W longitude) is a place where numerous Plio-Pleistocene lava flows are available for such a study. Volcanic activity in this area is related to back arc volcanism due to slab window activity as the South Chile Ridge is subducted beneath western South America, producing Neogene volcanic centers capping Mesozoic basement extending far to the east of the active plate boundary. Published studies on young lavas from both the northern (Meseta del Lago Buenos Aires, Brown et al, 2004) and southern (Pali Aike Volcanic Field, Mejia et al, 2004) portions provide stable paleomagnetic data on nearly 70 lava flows. Paleosecular variation values for the two studies differ, with 17.1 degrees obtained from the Pali Aike field and 20.0 degrees from the Lago Buenos Aires field. Recent fieldwork in the plateau lavas between these two locations has provided some 80 new sites allowing us to better investigate secular variation and the time-averaged field over this entire region during the past 5 myr. Rock magnetic studies on selected new samples (isothermal remanent magnetization and hysteresis measurements) as well as optical observations indicate low titanium magnetite as the primary carrier of remanence. Hysteresis properties range from 0.1 to 0.4 for Mr/Ms and 1.4 to 3.0 for Hcr/Hc indicating psuedo-single domain behavior. Mean destructive fields for AF demagnetization average 40 to 60 mT. Thirty-three new sites, mostly from Gran Meseta Central (48°S), yield a mean direction of inclination -61.8, declination of 356.6 with an alpha-95 of 5.7 degrees. These directions, with additional sites recently collected from Meseta de la Muerte south to Rio Santa Cruz, will allow us to further investigate paleosecular variation over this wide region.

U-Th age evidence from carbonate veins for episodic crustal deformation of Central Anatolian Volcanic Province

NASA Astrophysics Data System (ADS)

Karabacak, Volkan; Uysal, I. Tonguç; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin

2017-12-01

Central Anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back-arc extension generating non-uniformly distributed stress fields. In this study, we provide direct field evidence of various stress directions and investigate carbonate-filled fracture systems in the Central Anatolian Volcanic Province using U/Th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress. Field data reveal two independent fracture systems in the region. Successive fracture development has been controlled by two different volcanic eruption centers (Hasandağ Composite Volcano and Acıgöl Caldera). Trace element, and stable (C and O) and radiogenic (Sr) isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems. The U/Th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka. The NNE-trending first fracture system was formed as a result of strain cycles in a period from 149 ± 2.5, through 91 ± 1.5 to 83 ± 2.5 ka BP. Subsequent deformation events represented by the ENE-trending second fracture zone have been triggered during the period of 53 ± 3.5, 44 ± 0.6 and 34 ± 1 ka BP before the first fracture zone resumed the activity at about 4.7 ± 0.15 ka BP. Although further studies are needed to evaluate statistical significance of age correlations, the periods of carbonate precipitation inferred from U-Th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events.

Pissible Habitats in the Venusian Environment? How Can the Venus Payload Contribute?

NASA Astrophysics Data System (ADS)

Muller, C. L.; Schulze-Makuch, D.

2005-12-01

The Venusian conditions are unique in the solar system. Venus has a dense CO2 atmosphere, is volcanically active, and has plenty of energy sources such as light, UV radiation, volcanic activity, and chemical energy from atmospheric disequilibria conditions. Its surface conditions are sufficiently hot for sterilization and volcanism injects highly toxic gases which in the absence of unbound water can accumulate in the atmosphere. The Venusian surface is constantly regenerated by volcanism and any possible fossil record from early Venus history in which oceans existed on its surface is almost certainly destroyed. Its upper atmosphere lays bare to solar radiation with only carbon dioxide to act as a confirmed EUV filter. Any possibility of life was considered irrational before extremophile bacteria were discovered in dark undersea hot sulphur rich volcanic vents on Earth. However, some regions of the Venusian clouds might show conditions similar to the earth surface and could be a habitat of thermophilic microbial life similar to the one observed on Earth. A synergy between different instruments of the VENUS-Express payload, the SPICAV spectrometer and the VMC camera in a first step, and the spectrometers VIRTIS and PFS in a second step, will probe the actual environmental conditions of the cloud region. The SPICAV spectrometer, in particular, has three channels including, two infrared AOTF channels and could give access to organic signatures in both the UV and infrared. Given these observations we will be able to analyze whether the environmental conditions of the cloud layer would make it a possible habitat for extant microbial life. The instruments will shed answers to the availability of nutrients, water, types of energy sources, atmospheric dynamics, and organic chemistry.

Alaska volcanoes guidebook for teachers

USGS Publications Warehouse

Adleman, Jennifer N.

2011-01-01

Alaska’s volcanoes, like its abundant glaciers, charismatic wildlife, and wild expanses inspire and ignite scientific curiosity and generate an ever-growing source of questions for students in Alaska and throughout the world. Alaska is home to more than 140 volcanoes, which have been active over the last 2 million years. About 90 of these volcanoes have been active within the last 10,000 years and more than 50 of these have been active since about 1700. The volcanoes in Alaska make up well over three-quarters of volcanoes in the United States that have erupted in the last 200 years. In fact, Alaska’s volcanoes erupt so frequently that it is almost guaranteed that an Alaskan will experience a volcanic eruption in his or her lifetime, and it is likely they will experience more than one. It is hard to imagine a better place for students to explore active volcanism and to understand volcanic hazards, phenomena, and global impacts. Previously developed teachers’ guidebooks with an emphasis on the volcanoes in Hawaii Volcanoes National Park (Mattox, 1994) and Mount Rainier National Park in the Cascade Range (Driedger and others, 2005) provide place-based resources and activities for use in other volcanic regions in the United States. Along the lines of this tradition, this guidebook serves to provide locally relevant and useful resources and activities for the exploration of numerous and truly unique volcanic landscapes in Alaska. This guidebook provides supplemental teaching materials to be used by Alaskan students who will be inspired to become educated and prepared for inevitable future volcanic activity in Alaska. The lessons and activities in this guidebook are meant to supplement and enhance existing science content already being taught in grade levels 6–12. Correlations with Alaska State Science Standards and Grade Level Expectations adopted by the Alaska State Department of Education and Early Development (2006) for grades six through eleven are listed at the beginning of each activity. A complete explanation, including the format of the Alaska State Science Standards and Grade Level Expectations, is available at the beginning of each grade link at http://www.eed.state.ak.us/tls/assessment/GLEHome.html.

Track of the Yellowstone hotspot: young and ongoing geologic processes from the Snake River Plain to the Yellowstone Plateau and Tetons

USGS Publications Warehouse

Morgan, Lisa A.; Pierce, Kenneth L.; Shanks, Pat; Raynolds, Robert G.H.

2008-01-01

This field trip highlights various stages in the evolution of the Snake River Plain–Yellowstone Plateau bimodal volcanic province, and associated faulting and uplift, also known as the track of the Yellowstone hotspot. The 16 Ma Yellowstone hotspot track is one of the few places on Earth where time-transgressive processes on continental crust can be observed in the volcanic and tectonic (faulting and uplift) record at the rate and direction predicted by plate motion. Recent interest in young and possible renewed volcanism at Yellowstone along with new discoveries and synthesis of previous studies, i.e., tomographic, deformation, bathymetric, and seismic surveys, provide a framework of evidence of plate motion over a mantle plume. This 3-day trip is organized to present an overview into volcanism and tectonism in this dynamically active region. Field trip stops will include the young basaltic Craters of the Moon, exposures of 12–4 Ma rhyolites and edges of their associated collapsed calderas on the Snake River Plain, and exposures of faults which show an age progression similar to the volcanic fields. An essential stop is Yellowstone National Park, where the last major caldera-forming event occurred 640,000 years ago and now is host to the world's largest concentration of hydrothermal features (>10,000 hot springs and geysers). This trip presents a quick, intensive overview into volcanism and tectonism in this dynamically active region. Field stops are directly linked to conceptual models related to hotspot passage through this volcano-tectonic province. Features that may reflect a tilted thermal mantle plume suggested in recent tomographic studies will be examined. The drive home will pass through Grand Teton National Park, where the Teton Range is currently rising in response to the passage of the North American plate over the Yellowstone hotspot.

Tectonics of ridge-transform intersections at the Kane fracture zone

NASA Astrophysics Data System (ADS)

Karson, J. A.; Dick, H. J. B.

1983-03-01

The Kane Transform offsets spreading-center segments of the Mid-Atlantic Ridge by about 150 km at 24° N latitude. In terms of its first-order morphological, geological, and geophysical characteristics it appears to be typical of long-offset (>100 km), slow-slipping (2 cm yr-1) ridge-ridge transform faults. High-resolution geological observations were made from deep-towed ANGUS photographs and the manned submersible ALVIN at the ridge-transform intersections and indicate similar relationships in these two regions. These data indicate that over a distance of about 20 km as the spreading axes approach the fracture zone, the two flanks of each ridge axis behave in very different ways. Along the flanks that intersect the active transform zone the rift valley floor deepens and the surface expression of volcanism becomes increasingly narrow and eventually absent at the intersection where only a sediment-covered ‘nodal basin’ exists. The adjacent median valley walls have structural trends that are oblique to both the ridge and the transform and have as much as 4 km of relief. These are tectonically active regions that have only a thin (<200 m), highly fractured, and discontinuous carapace of volcanic rocks overlying a variably deformed and metamorphosed assemblage of gabbroic rocks. Overprinting relationships reveal a complex history of crustal extension and rapid vertical uplift. In contrast, the opposing flanks of the ridge axes, that intersect the non-transform zones appear to be similar in many respects to those examined elsewhere along slow-spreading ridges. In general, a near-axial horst and graben terrain floored by relatively young volcanics passes laterally into median valley walls with a simple block-faulted character where only volcanic rocks have been found. Along strike toward the fracture zone, the youngest volcanics form linear constructional volcanic ridges that transect the entire width of the fracture zone valley. These volcanics are continuous with the older-looking, slightly faulted volcanic terrain that floors the non-transform fracture zone valleys. These observations document the asymmetric nature of seafloor spreading near ridge-transform intersections. An important implication is that the crust and lithosphere across different portions of the fracture zone will have different geological characteristics. Across the active transform zone two lithosphere plate edges formed at ridge-transform corners are faulted against one another. In the non-transform zones a relatively younger section of lithosphere that formed at a ridge-non-transform corner is welded to an older, deformed section that initially formed at a ridge-transform corner.

Short-term volcano-tectonic earthquake forecasts based on a moving mean recurrence time algorithm: the El Hierro seismo-volcanic crisis experience

NASA Astrophysics Data System (ADS)

García, Alicia; De la Cruz-Reyna, Servando; Marrero, José M.; Ortiz, Ramón

2016-05-01

Under certain conditions, volcano-tectonic (VT) earthquakes may pose significant hazards to people living in or near active volcanic regions, especially on volcanic islands; however, hazard arising from VT activity caused by localized volcanic sources is rarely addressed in the literature. The evolution of VT earthquakes resulting from a magmatic intrusion shows some orderly behaviour that may allow the occurrence and magnitude of major events to be forecast. Thus governmental decision makers can be supplied with warnings of the increased probability of larger-magnitude earthquakes on the short-term timescale. We present here a methodology for forecasting the occurrence of large-magnitude VT events during volcanic crises; it is based on a mean recurrence time (MRT) algorithm that translates the Gutenberg-Richter distribution parameter fluctuations into time windows of increased probability of a major VT earthquake. The MRT forecasting algorithm was developed after observing a repetitive pattern in the seismic swarm episodes occurring between July and November 2011 at El Hierro (Canary Islands). From then on, this methodology has been applied to the consecutive seismic crises registered at El Hierro, achieving a high success rate in the real-time forecasting, within 10-day time windows, of volcano-tectonic earthquakes.

Constraints of texture and composition of clinopyroxene phenocrysts of Holocene volcanic rocks on a magmatic plumbing system beneath Tengchong, SW China

NASA Astrophysics Data System (ADS)

Hu, Jun-Hao; Song, Xie-Yan; He, Hai-Long; Zheng, Wen-Qin; Yu, Song-Yue; Chen, Lie-Meng; Lai, Chun-Kit

2018-04-01

Understanding processes of magma replenishment in a magma plumbing system is essential to predict eruption potential of a dormant volcano. In this study, we present new petrologic and thermobarometric data for youngest lava flows from the Holocene Heikongshan volcano in the Tengchong area, SW China. Clinopyroxene phenocrysts from the trachytic lava flows display various textural/compositional zoning styles (i.e., normal, reverse and oscillatory). Such zoning patterns are indicative of an open magmatic plumbing system with multiphase magma replenishment and mixing, which were likely a key drive of the volcanic eruptions. Thermobarometric calculations of these zoned clinopyroxene phenocrysts yield crystallization pressures of 3.8-7.1 kbar (peak at 4.5-7.0 kbar), corresponding to a magma chamber at depths of 14-21 km. The calculated depths are consistent with the large low-resistivity body at 12-30 km beneath the Heikongshan volcano, implying that the magmatic plumbing system may still be active. Recent earthquakes in the Tengchong area suggest that the regional strike-slip faulting are still active, and may trigger future volcanic eruptions if the magma chamber(s) beneath the Tengchong volcanic field is disturbed, in spite of the volcanic quiescence since 1609 CE.

A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d’Arc Cave (Ardèche, France)?

PubMed Central

Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean–François; Geneste, Jean-Michel

2016-01-01

Among the paintings and engravings found in the Chauvet-Pont d’Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d’Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey. PMID:26745626

A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d'Arc Cave (Ardèche, France)?

PubMed

Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean-François; Geneste, Jean-Michel

2016-01-01

Among the paintings and engravings found in the Chauvet-Pont d'Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d'Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey.

Hot Spots on Io: Initial Results From Galileo's Near Infrared Mapping Spectrometer

NASA Technical Reports Server (NTRS)

Lopes-Gautier, Rosaly; Davies, A. G.; Carlson, R.; Smythe, W.; Kamp, L.; Soderblom, L.; Leader, F. E.; Mehlman, R.

1997-01-01

The Near-Infrared Mapping Spectrometer on Galileo has monitored the volcanic activity on Io since June 28, 1996. This paper presents preliminary analysis of NIMS thermal data for the first four orbits of the Galileo mission. NIMS has detected 18 new hot spots and 12 others which were previously known to be active. The distribution of the hot spots on Io's surface may not be random, as hot spots surround the two bright, SO2-rich regions of Bosphorus Regio and Colchis Regio. Most hot spots scan to be persistently active from orbit to orbit and 10 of those detected were active in 1979 during the Voyager encounters. We report the distribution of hot spot temperatures and find that they are consistent with silicate volcanism.

Local to global: a collaborative approach to volcanic risk assessment

NASA Astrophysics Data System (ADS)

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-economic conditions tending to influence longer term well-being and recovery. The volcanological community includes almost 100 Volcano Observatories worldwide, the official institutions responsible for monitoring volcanoes. They may be dedicated institutions, or operate from national institutions (geological surveys, universities, met agencies). They have a key role in early warning, forecasting and long term hazard assessment (often in the form of volcanic hazards maps). The complexity of volcanic systems means that once unrest begins there are multiple potential eruptive outcomes and short term forecasts can change rapidly. This local knowledge of individual volcanoes underpins hazard and risk assessments developed at national, regional and global scales. Combining this local expertise with the knowledge of the international research community (including interdisciplinary perspectives) creates a powerful partnership. A collaborative approach is therefore needed to develop effective volcanic risk assessments at regional to global scale. The World Organisation of Volcano Observatories is a Commission of IAVCEI, alongside other Commissions such as 'Hazard and Risk' (with an active working group on volcanic hazards maps) and the 'Cities and Volcanoes' Commission. The Global Volcano Model network is a collaborative initiative developing hazards and risk information at national to global scales, underpinned by local expertise. Partners include IAVCEI, Smithsonian Institution, International Volcanic Health Hazard Network, VHub and other initiatives and institutions.

Differentiation of volcanic ash-fall and water-borne detrital layers in the Eocene Senakin coal bed, Tanjung Formation, Indonesia

USGS Publications Warehouse

Ruppert, L.F.; Moore, T.A.

1993-01-01

The Sangsang deposit of the Eocene Senakin coal bed, Tanjung Formation, southeastern Kalimantan, Indonesia, contains 11 layers, which are thin ( 70%). These layers are characterized by their pelitic macroscopic texture. Examination of eight of the layers by scanning-electron microscopy, energy-dispersive X-ray, and X-ray diffraction analyses show that they are composed primarily of fairly well-crystallized kaolinite, much of which is vermicular. Accessory minerals include abundant Ti oxide, rare-earth element-rich Ca and A1 phosphates, quartz that luminescences in the blue color range, and euhedral to subhedral pyroxene, hornblende, zircon, and sanidine. Although this mineral suite is suggestive of volcanic ash-fall material, only the four pelitic layers in the middle of the bed are thought to be solely derived from volcanic ash-falls on the basis of diagnostic minerals, replaced glass shards, and lithostratigraphic relationships observed in core and outcrop. The three uppermost pelitic layers contain octahedral chromites, some quartz grains that luminesce in teh orange color range, and some quartz grains that contain two-phase fluid inclusions. These layers are interpreted to be derived from a combination of volcanic ash-fall material and hydrologic transport of volcaniclastic sediment. In contrast, the lowermost pelitic layer, which contains large, rounded FeMg-rich chromites, is thought to have been dominantly deposited by water. The source of the volcanic ash-fall material may have been middle Tertiary volcanism related to plate tectonic activity between Kalimantan and Sulawesi. The volcanic ash was deposited in sufficient amounts to be preserved as layers within the coal only in the northern portions of the Senakin region: the southern coal beds in the region do not contain pelitic layers. ?? 1993.

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

NASA Astrophysics Data System (ADS)

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 (<10 μ) and the silica composition were the main factors of 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 are aware about the governmental commitment to assume a strategic planning for mitigation, facing a volcanic emergency. Recently, university undergraduate students from Chile and Argentina are networking to acquire the skills needed for a better preparedness to the next volcanic eruption.

The Pearlette family ash beds in the Great Plains: Finding their identities and their roots in the Yellowstone country

USGS Publications Warehouse

Wilcox, R.E.; Naeser, C.W.

1992-01-01

For many years the numerous deposits of so-called 'Pearlette volcanic ash' in the Great Plains region of the United States were considered to be the remnants of the same volcanic event, and were used as a time-stratigraphic marker of probable Middle Pleistocene age. Although a few early workers had suggested that more than one air-fall event might be represented among the Pearlette occurrences, it was not until the latter half of the present century, after identification of volcanic ash beds by detailed chemical and mineralogical methods had been developed, that it could be established that the 'Pearlette family' of volcanic ashes included three ash beds of subtly differing characteristics. Development of isotopic methods of age determination has established that the ages of the three are significantly different (2.09, 1.29, and 0.60 Ma). The area of distribution of the Pearlette family ash beds was found to include not only the Great Plains, but also to extend across the Rocky Mountain and the Basin and Range provinces to the Pacific Ocean. The search for the sources of these three similar appearing ash beds, facilitated greatly by information gained from concurrent mapping projects underway in areas of major Late Cenozoic volcanic activity in western United States, ultimately led to the sites of the caldera-forming eruptions in the Yellowstone National Park region. ?? 1992.

Mare volcanism in the Taurus-Littrow region

NASA Technical Reports Server (NTRS)

Delano, J. W.

1992-01-01

The products of mare volcanism at Taurus-Littrow occur in the form of crystalline basalts and volcanic glass beads. Both categories of samples define a compositionally diverse, but petrogenetically unrelated, suite of magmas derived by partial melting of a heterogenous, differentiated mantle beneath the region of the Apollo 17 landing site. This is a brief review of what is known and what is not known about mare volcanism at this location on the Moon.

Galileo SSI Observations of Volcanic Activity at Tvashtar Catena, Io

NASA Technical Reports Server (NTRS)

Milazzo, M. P.; Keszthely, L. P.; Radebaugh, J.; Davies, A. G.; Turtle, E. P.; Geissler, P.; Klaasen, K. P.; McEwen, A. S.

2005-01-01

Introduction: We report on the analysis of the Galileo SSI's observations of the volcanic activity at Tvashtar Catena, Io as discussed by Milazzo et al. Galileo's Solid State Imager (SSI) observed Tvashtar Catena (63 deg N, 120 deg W) four times between November 1999 and October 2001, providing a unique look at the distinctive high latitude volcanism on Io. The November 1999 observation spatially resolved, for the first time, an active extraterrestrial fissure eruption. The brightness temperature of the lavas at the November 1999 fissure eruption was 1300 K. The second observation (orbit I27, February 2000) showed a large (approx. 500 sq km) region with many, small spots of hot, active lava. The third observation was taken in conjunction with a Cassini observation in December 2000 and showed a Pele-like plume deposition ring, while the Cassini images revealed a 400 km high Pele-type plume above the Catena. The final Galileo SSI observation of Tvashtar was acquired in October 2001, and all obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. We have concentrated on analyzing the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of "simple" advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping (in time and space) eruptions.

Venus - Limited extension and volcanism along zones of lithospheric weakness

NASA Technical Reports Server (NTRS)

Schaber, G. G.

1982-01-01

Three global-scale zones of possible tectonic origin are described as occurring along broad, low rises within the Equatorial Highlands on Venus (lat 50 deg N to 50 deg S, long 60 deg to 310 deg). The two longest of these tectonic zones, the Aphrodite-Beta and Themis-Atla zones, extend for 21,000 and 14,000 km, respectively. Several lines of evidence indicate that Beta and Atla Regiones, located at the only two intersections of the three major tectonic zones, are dynamically supported volcanic terranes associated with currently active volcanism. Rift valleys south of Aphrodite Terra and between Beta and Phoebe Regiones are characterized by 75- to 100-km widths, raised rims, and extensions of only a few tens of kilometers, about the same magnitudes as in continental rifts on the earth. Horizontal extension on Venus was probably restricted by an early choking-off of plate motion by high crustal and upper-mantle temperatures, and the subsequent loss of water and an asthenosphere.

Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting

NASA Astrophysics Data System (ADS)

Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo

2016-04-01

Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian volcano-sedimentary basins. Our approach permits to better identify different processes operating on volcanic edifices and to constrain the depositional environment and thus geodynamic setting of Precambrian continental volcanic belts. Acknowledgments: We acknowledge CAPES/CNPq project n° 402564/2012-0 (Programa Ciências sem Fronteiras), CNPq/CT-Mineral (Proc. 550.342/2011-7) and INCT-Geociam (573733/2008-2) - CNPq/MCT/FAPESPA/PETROBRAS.

77 FR 11022 - Approval and Promulgation of Implementation Plans; State of Alaska; Regional Haze State...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-24

.... Congress amended the visibility provisions in the CAA in 1990 to focus attention on the problem of regional... address the problem of visibility impairment in Class I areas, States need to develop strategies in... vegetation) and geogenic sources (gas/oil seeps, wind erosion, and geothermal and volcanic activity) were not...

Distribution of Recent Volcanism and Morphology of Volcanic Features in the GLIMPSE Study Area west of the East Pacific Rise

NASA Astrophysics Data System (ADS)

Scheirer, D.; Forsyth, D.; Harmon, N.; Duncan, R.

2003-12-01

The existence of seamounts and volcanic ridges west of the East Pacific Rise (EPR), perhaps associated with cross-grain gravity lineations, was initially revealed by detailed satellite altimetry. Multibeam bathymetry and sidescan reflectivity measurements made on board the R/V Melville in 2001 and 2002 as part of the GLIMPSE Experiment, plus additional data gathered on other cruises including those of the MELT Experiment, have allowed us to map the distribution of recent, off-axis volcanic activity west of the EPR and south of the Garrett Fracture Zone and to more precisely define the form of the volcanic features. The Southern Cross Seamount, Sojourn Ridge and Brown Ridge combine to form a linear feature nearly 500 km long, oriented perpendicular to the EPR about 80 km south of the Garrett FZ. Both the Sojourn and Brown ridges comprise several en echelon segments, each about 30 km long, linked together to form continuous topographic highs standing 2000 m or more above the surrounding seafloor. Side-scan data reveal reflective patches along the Brown Ridge at the eastern end of this feature that appear to be recent lava flows. Dredging of fresh basalts dated by Ar/Ar methods at about 0.3 Ma confirm this interpretation. The Southern Cross Seamount, at the western end of the chain, is the largest individual feature, standing more than 3.5 km above the surrounding seafloor and shoaling to depths less than 200 m below sealevel. The Hotu-Matua volcanic complex also extends for several hundred km, but is much more varied in its morphology. The western end has some very small, very linear ridges, flanked on the south by an extensive region of resurfaced, hummocky seafloor. This area is more reflective and presumably younger than the surrounding seafloor, but less reflective than the areas interpreted as recent flows. Roughly midway along this complex are the Hotu and Matua seamounts. Surrounding Matua is an extensive region of highly reflective, recent lava flows, some of which seem to have been dammed against pre-existing, small seamounts. Age dates in this area are highly variable, ranging from <0.6 to about 6 Ma, also suggesting a mixture of pre-existing and resurfaced seafloor. Reflective flows are scattered over a roughly linear region extending another 150 km to the east of Matua, sometimes associated with very small seamounts and sometimes appearing just to fill topographic lows. We find no evidence in the detailed bathymetry or sidescan in this region for any pre-existing tectonic features or cracks extending along the line of volcanic activity.

Increase in earthquake swarm activity in the southern Red Sea, Afar and Gulf of Aden

NASA Astrophysics Data System (ADS)

Ruch, Joël; Keir, Derek; Ogubazghi, Ghebrebrhan; di Giacomo, Domenico; Ladron Viltres, Renier; Jónsson, Sigurjón

2017-04-01

Rifting events periodically occur at divergent plate boundaries, consisting of magmatic intrusions, seismic swarms, surface faulting and in some cases volcanic eruptions. While earthquake swarms also occur at other types of plate boundaries, the swarms that have been observed in inland rift zones (e.g., in Afar and Iceland) and in a few offshore cases show an unambiguous relation with magmatic intrusions. These swarms typically last for a few days to a few weeks, lack a clear mainshock-aftershock decay pattern. Here we present a new study on earthquake swarms in the southern Red Sea, Afar and Gulf of Aden. We provide the first earthquake swarm catalogue for the region, which we compiled by integrating reexamined global and local earthquake catalogues with historical observations from 1960 to 2016. We find that in several cases in all the three areas, swarms have been re-occurring at the same locations every few decades (e.g., in the Bada area in Eritrea and Port Sudan region in the southern Red Sea in 1967 and 1993, and in the western Gulf of Aden in 1979, 1997 and 2010-2012). This suggests the existence of active spreading centers that are more active than previously thought. The swarms show different families of earthquake magnitudes, with clusters of Mw4 and Mw5 events (southern Red Sea and Aden) and occasional larger than Mw6 events, primarily in the southern Afar region (the Serdo and Dobi areas). Of the three areas, Gulf of Aden shows the highest swarm activity, followed by the Afar area and the southern Red Sea. Despite seeing the least amount of activity and lower magnitudes, the southern Red Sea has experienced multiple earthquake swarms and three volcanic eruptions (two of which resulted in new volcanic islands) during the past 10 years. We show that the three areas have been subject to an almost simultaneous increase of earthquake swarm activity during the last 10 years. This period (2005-2014) was much more active compared to the preceding decades (1960-2005) and might indicate an increase of magma supply in the region.

Deception Island, Antarctica, harbors a diverse assemblage of wood decay fungi.

PubMed

Held, Benjamin W; Blanchette, Robert A

2017-02-01

Very little is known about fungal diversity in Antarctica as compared to other biomes and how these important organisms function in this unusual ecosystem. Perhaps one of the most unusual ecosystems is that of Deception Island; an active volcanic island part of the South Shetland Islands of the Antarctic Peninsula. Here we describe the fungal diversity associated with historic wood from structures on the island, which reveals a diverse fungal assemblage of known wood decay fungi as well as the discovery of undescribed species. The major group of wood decay fungi identified were species of Cadophora and as shown in previous studies in other geographic regions of Antarctica, they caused a soft-rot type of decay in the introduced woods. Additionally, unlike other areas of Antarctica that have been studied, filamentous basidiomycetes (Hypochniciellum spp. and Pholiota spp.) were also identified that have different modes of degradation including brown and white rot. Matches of fungal sequences to known species in temperate regions likely introduced on building materials indicates human influences and volcanic activity have greatly impacted fungal diversity. Lahars (mudslides from volcanic activity) have partially buried many of the structures and the buried environment as well as the moist, warm soils provided conditions conducive for fungal growth that are not found in other regions of Antarctica. The diverse assemblage of decay fungi and different forms of wood decomposition add to the difficulty of conserving wooden structures at these important polar heritage sites. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Volcanic Centers in the East Africa Rift: Volcanic Processes with Seismic Stresses to Identify Potential Hydrothermal Vents

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Earth Observation taken by the Expedition 33 crew

NASA Image and Video Library

2012-11-09

ISS033-E-019822 (9 Nov. 2012) --- An eruption plume from the Karymsky volcano on the Kamchatka Peninsula in the Russian Federation is visible in this image photographed by an Expedition 33 crew member on the International Space Station. The Karymsky stratovolcano stands 1,536 meters above sea level, with most eruptions and occasional lava flows originating from the summit. Karymsky is the most active of Kamchatka’s eastern volcanoes, with almost constant (on a geologic time scale) volcanism occurring since at least the late 18th century when the historical record for the region begins. In light of the high levels of volcanic activity on the Kamchatka Peninsula, the Kamchatka Volcanic Eruption Response Team (KVERT) monitors the activity levels of several volcanoes and issues updates including aviation alerts and webcams. KVERT reported moderate seismic activity at Karymsky during 2-9 Nov. 2012; such activity can indicate movement of magma beneath or within a volcanic structure and can indicate that an eruption is imminent. The Tokyo Volcanic Ash Advisory Center (VAAC) subsequently reported an explosive eruption at Karymsky on Nov. 9, 2012 at 22:15 GMT. This photograph of the resulting ash plume was taken approximately one hour and 35 minutes after the eruption began. The plume extends from the summit of Karymsky (bottom center) to the southeast, with brown ash deposits darkening the snow cover below the plume. The Akademia Nauk caldera – now filled with water to form the present-day Karymsky Lake - is located to the south of Karymsky volcano. Calderas are formed by explosive eruption and emptying of a volcano’s magma chamber – leading to collapse of the structure to form a large crater-like depression. Akademia Nauk last erupted in 1996.

Volcanic eruptions, hazardous ash clouds and visualization tools for accessing real-time infrared remote sensing data

NASA Astrophysics Data System (ADS)

Webley, P.; Dehn, J.; Dean, K. G.; Macfarlane, S.

2010-12-01

Volcanic eruptions are a global hazard, affecting local infrastructure, impacting airports and hindering the aviation community, as seen in Europe during Spring 2010 from the Eyjafjallajokull eruption in Iceland. Here, we show how remote sensing data is used through web-based interfaces for monitoring volcanic activity, both ground based thermal signals and airborne ash clouds. These ‘web tools’, http://avo.images.alaska.edu/, provide timely availability of polar orbiting and geostationary data from US National Aeronautics and Space Administration, National Oceanic and Atmosphere Administration and Japanese Meteorological Agency satellites for the North Pacific (NOPAC) region. This data is used operationally by the Alaska Volcano Observatory (AVO) for monitoring volcanic activity, especially at remote volcanoes and generates ‘alarms’ of any detected volcanic activity and ash clouds. The webtools allow the remote sensing team of AVO to easily perform their twice daily monitoring shifts. The web tools also assist the National Weather Service, Alaska and Kamchatkan Volcanic Emergency Response Team, Russia in their operational duties. Users are able to detect ash clouds, measure the distance from the source, area and signal strength. Within the web tools, there are 40 x 40 km datasets centered on each volcano and a searchable database of all acquired data from 1993 until present with the ability to produce time series data per volcano. Additionally, a data center illustrates the acquired data across the NOPAC within the last 48 hours, http://avo.images.alaska.edu/tools/datacenter/. We will illustrate new visualization tools allowing users to display the satellite imagery within Google Earth/Maps, and ArcGIS Explorer both as static maps and time-animated imagery. We will show these tools in real-time as well as examples of past large volcanic eruptions. In the future, we will develop the tools to produce real-time ash retrievals, run volcanic ash dispersion models from detected ash clouds and develop the browser interfaces to display other remote sensing datasets, such as volcanic sulfur dioxide detection.

Computable general equilibrium modelling of economic impacts from volcanic event scenarios at regional and national scale, Mt. Taranaki, New Zealand

NASA Astrophysics Data System (ADS)

McDonald, G. W.; Cronin, S. J.; Kim, J.-H.; Smith, N. J.; Murray, C. A.; Procter, J. N.

2017-12-01

The economic impacts of volcanism extend well beyond the direct costs of loss of life and asset damage. This paper presents one of the first attempts to assess the economic consequences of disruption associated with volcanic impacts at a range of temporal and spatial scales using multi-regional and dynamic computable general equilibrium (CGE) modelling. Based on the last decade of volcanic research findings at Mt. Taranaki, three volcanic event scenarios (Tahurangi, Inglewood and Opua) differentiated by critical physical thresholds were generated. In turn, the corresponding disruption economic impacts were calculated for each scenario. Under the Tahurangi scenario (annual probability of 0.01-0.02), a small-scale explosive (Volcanic Explosivity Index (VEI) 2-3) and dome forming eruption, the economic impacts were negligible with complete economic recovery experienced within a year. The larger Inglewood sub-Plinian to Plinian eruption scenario event (VEI > 4, annualised probability of 0.003) produced significant impacts on the Taranaki region economy of 207 million (representing 4.0% of regional gross domestic product (GDP) 1 year after the event, 2007 New Zealand dollars), that will take around 5 years to recover. The Opua scenario, the largest magnitude volcanic hazard modelled, is a major flank collapse and debris avalanche event with an annual probability of 0.00018. The associated economic impacts of this scenario were 397 million (representing 7.7% of regional GDP 1 year after the event) with the Taranaki region economy suffering permanent structural changes. Our dynamic analysis illustrates that different economic impacts play out at different stages in a volcanic crisis. We also discuss the key strengths and weaknesses of our modelling along with potential extensions.

Detailed Ar-Ar Geochronology of Volcanism at Minna Bluff, Antarctica: Two-Phased Growth and Influence on Ross Ice Shelf

NASA Astrophysics Data System (ADS)

Ross, J. I.; McIntosh, W. C.; Wilch, T. I.

2012-12-01

Minna Bluff has been a significant topographic barrier to the flow of the Ross Ice Shelf since the mid-Miocene. Detailed Ar-Ar analyses of kaersutite and sanidine phenocrysts, and groundmass concentrates from volcanic units indicate an overall west to east progression of volcanic activity. Eruptions of basaltic to intermediate lavas, domes, and scoria cones started at ~12 Ma in at what is now the eastern most point of Minna Bluff, "Minna Hook." Activity was centered in this area for ~4 Ma, constructing a pre-Minna Bluff island. Multiple glacial unconformities found at Minna Hook suggest repeated interaction with large warm-based, erosive ice sheets. Activity migrated westward from Minna Bluff Island at 7-8 Ma closing the gap created by the island and the mainland. Significant edifice construction continued until 4-5 Ma with sporadic and parasitic scoria cone eruptions, possibly associated with Mt. Discovery activity, continuing until 2 Ma. The orientations of Minna Bluff's two major axes are strongly controlled by regional tectonic features. Minna Bluff's E-W axis, McIntosh Cliffs, is sub-parallel to the Radial Lineament and the N-S axis, Minna Hook, appears as extension of faulting bounding the Terror Rift. The constructional evolution of the 70km long volcanic complex has an important role in interpreting the climate signals recovered by the ANDRILL Project. Minna Bluff influenced the material delivered to the AND-1B drill site (ANDRILL MIS 2006-2007) in three critical ways: 1) Minna Bluff diverted upstream material, 2) provided a pinning and stabilizing point for the Ross Ice Shelf, possible controlling the calving line prior to the emergence of Ross Island, and 3) was a significant source of fresh volcanic material throughout much of the period recovered by ANDRILL MIS. For example, a kaersutite-bearing clast recovered from 822.78 mbsf in AND-1B yielded an age of 8.53±0.51 Ma, and was likely derived from Minna Bluff. The results from this study can be incorporated into detailed glacier and ice-sheet models of the McMurdo Sound region, a critical area in the Ross Ice Sheet and global climate system.

Transient Volcano Deformation Event Detection over Variable Spatial Scales in Alaska

NASA Astrophysics Data System (ADS)

Li, J. D.; Rude, C. M.; Gowanlock, M.; Herring, T.; Pankratius, V.

2016-12-01

Transient deformation events driven by volcanic activity can be monitored using increasingly dense networks of continuous Global Positioning System (GPS) ground stations. The wide spatial extent of GPS networks, the large number of GPS stations, and the spatially and temporally varying scale of deformation events result in the mixing of signals from multiple sources. Typical analysis then necessitates manual identification of times and regions of volcanic activity for further study and the careful tuning of algorithmic parameters to extract possible transient events. Here we present a computer-aided discovery system that facilitates the discovery of potential transient deformation events at volcanoes by providing a framework for selecting varying spatial regions of interest and for tuning the analysis parameters. This site specification step in the framework reduces the spatial mixing of signals from different volcanic sources before applying filters to remove interfering signals originating from other geophysical processes. We analyze GPS data recorded by the Plate Boundary Observatory network and volcanic activity logs from the Alaska Volcano Observatory to search for and characterize transient inflation events in Alaska. We find 3 transient inflation events between 2008 and 2015 at the Akutan, Westdahl, and Shishaldin volcanoes in the Aleutian Islands. The inflation event detected in the first half of 2008 at Akutan is validated other studies, while the inflation events observed in early 2011 at Westdahl and in early 2013 at Shishaldin are previously unreported. Our analysis framework also incorporates modelling of the transient inflation events and enables a comparison of different magma chamber inversion models. Here, we also estimate the magma sources that best describe the deformation observed by the GPS stations at Akutan, Westdahl, and Shishaldin. We acknowledge support from NASA AIST-NNX15AG84G (PI: V. Pankratius).

Vegetation component of geothermal EIS studies: Introduced plants, ecosystem stability, and geothermal development

NASA Astrophysics Data System (ADS)

1994-10-01

This paper contributes new information about the impacts from introduced plant invasions on the native Hawaiian vegetation as consequences of land disturbance and geothermal development activities. In this regard, most geothermal development is expected to act as another recurring source of physical disturbance which favors the spread and maintenance of introduced organisms throughout the region. Where geothermal exploration and development activities extend beyond existing agricultural and residential development, they will become the initial or sole source of disturbance to the naturalized vegetation of the area. Kilauea has a unique ecosystem adapted to the dynamics of a volcanically active landscape. The characteristics of this ecosystem need to be realized in order to understand the major threats to the ecosystem and to evaluate the effects of and mitigation for geothermal development in Puna. The native Puna vegetation is well adapted to disturbances associated with volcanic eruption, but it is ill-adapted to compete with alien plant species in secondary disturbances produced by human activities. Introduced plant and animal species have become a major threat to the continued presence of the native biota in the Puna region.

Fore- and Back-Arc Structures Along the Hikurangi-Kermadec Subduction Zone

NASA Astrophysics Data System (ADS)

Scherwath, M.; Kopp, H.; Flueh, E. R.; Henrys, S. A.; Sutherland, R.

2009-04-01

The Hikurangi-Kermadec subduction zone northeast of New Zealand represents an ideal target to study lateral variations of subduction zone processes. The incoming Pacific plate changes from being a large igneous province, called the Hikurangi Plateau, in the south to normal oceanic plate north of the Rapuhia Scarp. The overriding Australian plate is continental in the south, forming the North Island of New Zealand, and changes to an island arc in the north. Further lateral variability exists in changes in volcanic and hydro-thermal activity, transitions from accretion to subduction erosion, backarc spreading and rifting, and is accompanied by northward increasing seismicity. As part of the MANGO project (Marine Geoscientific Investigations on the Input and Output of the Kermadec Subduction Zone), four marine geophysical transects of largely seismic reflection and refraction data provide constraints on the upper lithospheric structures across the Hikurangi-Kermadec Trench between 29-38 degrees South. On MANGO profile 1 in the south, the initially shallow subduction of the incoming plateau coincides with crustal underplating beneath the East Cape ridge. To the west lies the 100 km wide and over 10 km deep Raukumara Basin. Seismic velocities of the upper arc mantle are around 8 km/s and are considered normal. In contrast, on MANGO profile 4, about 1000 km to the north around the volcanically active Raoul Island, the incoming oceanic crust appears to bend considerably steeper and thus causes a 50 km narrower forearc with a smaller forearc basin. Furthermore, the upper mantle velocities in both plates are relatively low (7.4-7.7 km/s), likely indicating strong bending related deformation of the incoming plate and thermal activity within the arc possibly due to spreading. Here, arc volcanism is relatively active, with many large volcanoes directly on the ridge. The central two transects MANGO 2 and 3, though without data coverage of the structure of the incoming plate, are more similar to MANGO 4. The arc regions appear to be strongly affected by the activity of the arc. The arc crust of the northern MANGO 3 becomes significantly thinner in the backarc region due to extension, and much reduced volcanism behind the ridge. The structures on MANGO 2, on the other hand, cover strong and densely spaced thermal activity from the adjacent arc volcanism, possibly linked to a recent, fluid-rich passage of the Hikurangi Plateau.

Tectonic Evolution of Bell Regio, Venus: Regional Stress, Lithospheric Flexure, and Edifice Stresses

NASA Astrophysics Data System (ADS)

Rogers, P. G.; Zuber, M. T.

1996-03-01

Analyses of the tectonic features associated with large volcanoes provide important insight into the relationship between volcanic and tectonic processes and the stress state of a planet's crust over time, and provide constraints on the local and regional geologic evolution. This investigation focuses on the tectonism and volcanism of Bell Regio, a major highland uplift n Venus. The stress environments and resulting tectonic features associated with the major volcanic edifices in this region are examined using Magellan ynthetic aperture radar (SAR) images and altimeter measurements of topography. The major volcanoes of Bell Regio, Tepev Mons and the "Eastern Volcanic Center" (EVC), exhibit tectonic characteristics that are unique relative to other volcanic edifices on Venus. The most prominent distinctions are the lack of large rift zones within the overall highland uplift and the presence of radial tectonic and concentric fractures associated with the major edifices. This study examines the regional stress field in Bell Regio through analysis of structural features believed to be a consequence of lithospheric flexure due to volcanic loading and tectonic features that likely resulted from edifice stresses associated with magma chamber inflation.

Remote Sensing and Geologic Studies of Mare Australe: The North Australe Region

NASA Technical Reports Server (NTRS)

Lawrence, S. J.; Stopar, J. D.; Ostrach, L. R.; van der Bogert, C. H.; Hiesinger, H.; Jolliff, B. L.; Giguere, T. A.; Sato, H.; Robinson, M. S.

2017-01-01

A key goal of the Lunar Reconnaissance Orbiter (LRO) mission is to investigate volcanic processes at different temporal and physical scales, with one emphasis being the characterization of ancient (meaning, greater than 3.9 Ga) volcanic units. One such ancient volcanic terrain is Mare Australe, a loosely-circular collection of mare basalts centered at approximately 38.9 deg S, 93 deg E (Fig. 1). Mare Australe is a complex, extensive, and poorly understood volcanic region.

Geometry of miocene extensional deformation, lower Colorado River Region, Southeastern California and Southwestern Arizona: Evidence for the presence of a regional low-angle normal fault

NASA Technical Reports Server (NTRS)

Tosdal, R. M.; Sherrod, D. R.

1985-01-01

The geometry of Miocene extensional deformation, which changes along a 120 km-long, northeast-trending transect from the southestern Chocolate Mountains, southeastern California, to the Trigo and southern Dome Rock Mountains, southwestern Arizona is discussed. Based upon regional differences in the structural response to extension and estimated extensional strain, the transet can be divided into three northwesterly-trending structural domains. From southwest to northeast, these domains are: (1) southestern Chocolate-southernmost Trigo Mountains; (2) central to northern Trigo Mountains; and (3) Trigo Peaks-southern Dome Rock Mountains. All structures formed during the deformation are brittle in style; fault rocks are composed of gouge, cohesive gouge, and local microbreccia. In each structural domain, exposed lithologic units are composed of Mesozoic crystalline rocks unconformably overlain by Oligocene to Early Miocene volcanic and minor interbedded sedimentary rocks. Breccia, conglomerate, and sandstone deposited synchronously with regional extension locally overlie the volcanic rocks. Extensional deformation largely postdated the main phase of volcanic activity, but rare rhyolitic tuff and flows interbedded with the syndeformational clastic rocks suggest that deformation began during the waning stages of valcanism. K-Ar isotopic ages indicate that deformation occurred in Miocene time, between about 22 and m.y. ago.

Gravity in extensional regimes: A case study in the Central Volcanic Region, New Zealand

NASA Astrophysics Data System (ADS)

Greve, A.; Stern, T. A.

2017-12-01

Using the interpretation of a large crustal seismic experiment conducted in 2009 as boundary model, we produced a sequence of new 2D gravity models for the central North Island in New Zealand. The Bouguer gravity field in the region ranges from -100 to 60 mGal and is dominated by the long wavelength signals of the subduction of the Pacific beneath the Australian plate along the Hikurangi margin and the transition from continental to oceanic lithosphere about the Bay of Plenty coast (NE New Zealand). Removal of these broad regional trends reveals the presence of a triangular shaped area, within the lines Taranaki-Coromandel and Taranaki - White Island, with negative anomalies between -30 and 60 mGal and positive anomalies around 10 mGal along the margins. This area, commonly referred to as the Central Volcanic Region (CVR) represents the continental continuation of the Lau-Havre, oceanic, back-arc rift basin. The Taupo Volcanic Zone forms the active eastern half of the CVR, where anomalously high heat output, geothermal activity and active volcanism occur. The new gravity model includes the presence of a 90km wide, ca. 10 km thick rift pillow of new underplated, lower crust between the depths of 15 and 25 km. A positive density contrast of 300 kg/m3 for this body is consistent with the observed seismic velocities (6.8 ≤ Vp ≤ 7.1 km/s). A ca. 2.5 km deep basin dominates the upper crustal structure and is about 50 km wide, infilled by low density volcaniclastics, with adopted average negative densities of -425 kg/m3. In the mid-crustal region, between 2.5 and 15 km depth, isostatic compensation requires a small density contrast of -110 kg/m3. This density contrast, with respect to a standard crustal model, can be ascribed to the presence of low density intrusives, within the old and now stretched crust. On the basis of this new crustal structure model we estimate a stretching factor (ß) for the old crust of 2-2.4. The intruded mid crust and the underplated new crust are most likely the primary sources of the impressive 4 GW heat output of the CVR.

Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - I: model and the case of Tenerife Island

NASA Astrophysics Data System (ADS)

Prudencio, Janire; Del Pezzo, Edoardo; García-Yeguas, Araceli; Ibáñez, Jesús M.

2013-12-01

The complex volcanic system of Tenerife Island is known to have a highly heterogeneous character, as recently confirmed by velocity tomography. We present new information derived from intrinsic quality factor inverse maps (Qi-1), scattering quality factor inverse maps (Qs-1) and total quality factor inverse maps (Qt-1) obtained for the same region. The data set used in this work is the result of the analysis of an active seismic experiment carried out, using offshore shots (air guns) recorded at over 85 onshore seismic stations. The estimates of the attenuation parameters are based on the assumption that the seismogram energy envelopes are determined by seismic energy diffusion processes occurring inside the island. Diffusion model parameters, proportional to Qi-1 and to Qs-1, are estimated from the inversion of the energy envelopes for any source-receiver couple. They are then weighted with a new graphical approach based on a Gaussian space probability function, which allowed us to create `2-D probabilistic maps' representing the space distribution of the attenuation parameters. The 2-D images obtained reveal the existence of a zone in the centre of the island characterized by the lowest attenuation effects. This effect is interpreted as highly rigid and cooled rocks. This low-attenuation region is bordered by zones of high attenuation, associated with the recent historical volcanic activity. We calculate the transport mean free path obtaining a value of around 4 km for the frequency range 6-12 Hz. This result is two orders of magnitude smaller than values calculated for the crust of the Earth. An absorption length between 10 and 14 km is associated with the average intrinsic attenuation parameter. These values, while small in the context of tectonic regions, are greater than those obtained in volcanic regions such as Vesuvius or Merapi. Such differences may be explained by the magnitude of the region of study, over three times larger than the aforementioned study areas. This also implies deeper sampling of the crust, which is evidenced by a change in the values of seismic attenuation. One important observation is that scattering attenuation dominates over the intrinsic effects, Qi being at least twice the value of Qs.

Geochemical characterization of a Quaternary monogenetic volcano in Erciyes Volcanic Complex: Cora Maar (Central Anatolian Volcanic Province, Turkey)

NASA Astrophysics Data System (ADS)

Gencalioglu-Kuscu, Gonca

2011-11-01

Central Anatolian Volcanic Province (CAVP) is a fine example of Neogene-Quaternary post-collisional volcanism in the Alpine-Mediterranean region. Volcanism in the Alpine-Mediterranean region comprises tholeiitic, transitional, calc-alkaline, and shoshonitic types with an "orogenic" fingerprint. Following the orogenic volcanism, subordinate, within-plate alkali basalts ( sl) showing little or no orogenic signature are generally reported in the region. CAVP is mainly characterized by widespread calc-alkaline andesitic-dacitic volcanism with orogenic trace element signature, reflecting enrichment of their source regions by subduction-related fluids. Cora Maar (CM) located within the Erciyes pull-apart basin, is an example to numerous Quaternary monogenetic volcanoes of the CAVP, generally considered to be alkaline. Major and trace element geochemical and geochronological data for the CM are presented in comparison with other CAVP monogenetic volcanoes. CM scoria is basaltic andesitic, transitional-calc-alkaline in nature, and characterized by negative Nb-Ta, Ba, P and Ti anomalies in mantle-normalized patterns. Unlike the "alkaline" basalts of the Mediterranean region, other late-stage basalts from the CAVP monogenetic volcanoes are classified as tholeiitic, transitional and mildly alkaline. They display the same negative anomalies and incompatible element ratios as CM samples. In this respect, CM is comparable to other CAVP monogenetic basalts ( sl), but different from the Meditterranean intraplate alkali basalts. Several lines of evidence suggest derivation of CM and other CAVP monogenetic basalts from shallow depths within the lithospheric mantle, that is from a garnet-free source. In a wider regional context, CAVP basalts ( sl) are comparable to Apuseni (Romania) and Big Pine (Western Great Basin, USA) volcanics, except the former have depleted Ba contents. This is a common feature for the CAVP volcanics and might be related to crustal contamination or source characteristics. Indeed, HFS and other incompatible element ratios suggest the role of crustal contamination in the genesis of the CAVP monogenetic basalts.

Volcanic passive margins: another way to break up continents

PubMed Central

Geoffroy, L.; Burov, E. B.; Werner, P.

2015-01-01

Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle. PMID:26442807

Volcanic passive margins: another way to break up continents.

PubMed

Geoffroy, L; Burov, E B; Werner, P

2015-10-07

Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

The LUSI Seismic Experiment: Deployment of a Seismic Network around LUSI, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Haryanto, Iyan; Masturyono, Masturyono; Hadi, Soffian; Rohadi, Suprianto; Suardi, Iman; Rudiyanto, Ariska; Pranata, Bayu

2015-04-01

The spectacular Lusi eruption started in northeast Java, Indonesia the 29 of May 2006 following a M6.3 earthquake striking the island. Initially, several gas and mud eruption sites appeared along the reactivated strike-slip Watukosek fault system and within weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. Lusi is located few kilometres to the NE of the Arjuno-Welirang volcanic complex. Lusi sits upon the Watukosek fault system. From this volcanic complex originates the Watukosek fault system that was reactivated by the M6.3 earthquake in 2006 and is still periodically reactivated by the frequent seismicity. To date Lusi is still active and erupting gas, water, mud and clasts. Gas and water data show that the Lusi plumbing system is connected with the neighbouring Arjuno-Welirang volcanic complex. This makes the Lusi eruption a "sedimentary hosted geothermal system". To verify and characterise the occurrence of seismic activity and how this perturbs the connected Watukosek fault, the Arjuno-Welirang volcanic system and the ongoing Lusi eruption, we deployed 30 seismic stations (short-period and broadband) in this region of the East Java basin. The seismic stations are more densely distributed around LUSI and the Watukosek fault zone that stretches between Lusi and the Arjuno Welirang (AW) complex. Fewer stations are positioned around the volcanic arc. Our study sheds light on the seismic activity along the Watukosek fault system and describes the waveforms associated to the geysering activity of Lusi. The initial network aims to locate small event that may not be captured by the Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) seismic network and it will be crucial to design the second phase of the seismic experiment that will consist of a local earthquake tomography of the Lusi-Arjuno Welirang region and temporal variations of vp/vs ratios. Such variations will then be ideally related to large-magnitude seismic events. This project is an unprecedented monitoring of a multi component system including an Lusi active eruption, an unlocked strike slip fault, a neighbouring volcanic arc all affected by frequent seismicity. Our study will also provide a large dataset for a qualitative analysis of earthquake triggering studies, earthquake-volcano and earthquake-earthquake interactions. The seismic experiment suggested in this study enforces our knowledge about Lusi and will represent a step further towards the reconstruction of a society devastated by Lusi disaster.

Horizontal and Vertical Distributions of SO2 Observed During the PEACE Missions

NASA Astrophysics Data System (ADS)

Tanimoto, H.; Hatakeyama, S.; Takami, A.; Kita, K.

2002-12-01

Measurements of sulfur dioxide (SO2) were made by a significantly modified pulsed-fluorescence analyzer during the PEACE (Pacific Exploration of Asian Continental Emission) B aircraft missions, which were conducted over the East Asian Pacific rim/Western Pacific region in spring 2002. The SO2 data are successfully obtained up to approximately 5 km during the whole flights. The mixing ratios of SO2 show a large variability ranging from <100 pptv to 15 ppbv. The SO2 variability is mainly controlled by the switching of continental and maritime air masses. Enhanced SO2 levels due to _gfresh_h continental outflow events are found below 2 km regions over the Sea of Japan. Several plumes, whose mixing ratios elevated as high as >10 ppbv, are attributed to emissions from volcanic islands around Japan. Although the continental emissions and outflow make large contribution to the mixing ratio levels, variations, and distributions of SO2 around the East Asian continental rim and the western Pacific regions, volcanic activities also significantly inject large amount of SO2 into the lower atmosphere of the regions. The SO2 data are compared with those from PEACE-A and previous campaigns (e.g., PEM-West A and B, PEACAMPOT). Relative importance of the contribution from anthropogenic and volcanic emissions on the SO2 distributions in this region is discussed.

Volcanic hazard assessment for the Canary Islands (Spain) using extreme value theory, and the recent volcanic eruption of El Hierro

NASA Astrophysics Data System (ADS)

Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.

2012-04-01

The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 years, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterise the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. Shortly after the publication of this method an eruption in the island of El Hierro took place for the first time in historical times, supporting our method and contributing towards the validation of our results.

Sulfur mass loading of the atmosphere from volcanic eruptions: Calibration of the ice core record on basis of sulfate aerosol deposition in polar regions from the 1982 El Chichon eruption

NASA Technical Reports Server (NTRS)

Sigurdsson, Haraldur; Laj, Paolo

1990-01-01

Major volcanic eruptions disperse large quantities of sulfur compound throughout the Earth's atmosphere. The sulfuric acid aerosols resulting from such eruptions are scavenged by snow within the polar regions and appear in polar ice cores as elevated acidity layers. Glacio-chemical studies of ice cores can, thus, provide a record of past volcanism, as well as the means for understanding the fate of volcanic sulfur in the atmosphere. The primary objectives of this project are to study the chemistry and physical properties of volcanic fallout in a Greenland Ice Core in order to evaluate the impact of the volcanic gases on the atmospheric chemistry and the total atmospheric mass of volcanic aerosols emitted by major volcanic eruptions. We propose to compare the ice core record to other atmospheric records performed during the last 10 years to investigate transport and deposition of volcanic materials.

New constraints on the pyroclastic eruptive history of the Campanian volcanic Plain (Italy)

USGS Publications Warehouse

de Vivo, B.; Rolandi, G.; Gans, P.B.; Calvert, A.; Bohrson, W.A.; Spera, F.J.; Belkin, H.E.

2001-01-01

The ∼ 150 km3 (DRE) trachytic Campanian Ignimbrite, which is situated north-west of Naples, Italy, is one of the largest eruptions in the Mediterranean region in the last 200 ky. Despite centuries of investigation, the age and eruptive history of the Campanian Ignimbrite is still debated, as is the chronology of other significant volcanic events of the Campanian Plain within the last 200–300 ky. New 40Ar/39Ar geochronology defines the age of the Campanian Ignimbrite at 39.28 ± 0.11 ka, about 2 ky older than the previous best estimate. Based on the distribution of the Campanian Ignimbrite and associated uppermost proximal lithic and polyclastic breccias, we suggest that the Campanian Ignimbrite magma was emitted from fissures activated along neotectonic Apennine faults rather than from ring fractures defining a Campi Flegrei caldera. Significantly, new volcanological, geochronological, and geochemical data distinguish previously unrecognized ignimbrite deposits in the Campanian Plain, accurately dated between 157 and 205 ka. These ages, coupled with a xenocrystic sanidine component > 315 ka, extend the volcanic history of this region by over 200 ky. Recent work also identifies a pyroclastic deposit, dated at 18.0 ka, outside of the topographic Campi Flegrei basin, expanding the spatial distribution of post-Campanian Ignimbrite deposits. These new discoveries emphasize the importance of continued investigation of the ages, distribution, volumes, and eruption dynamics of volcanic events associated with the Campanian Plain. Such information is critical for accurate assessment of the volcanic hazards associated with potentially large-volume explosive eruptions in close proximity to the densely populated Neapolitan region.

The interaction between parent material, climate and volcanism as the major soil forming factor in the Ecuadorian high Andes region

NASA Astrophysics Data System (ADS)

Buytaert, W.; Duyck, H.; Dercon, G.; Deckers, J.; Wyseure, G.

2003-04-01

The high Andes region of Ecuador and Colombia (>3500m a.s.l.) is covered by the so-called páramo ecosystem, characterised by a cold climate, a typical grass or small shrub vegetation and volcanic soils. Soil profiles of the paramo in the Austro Ecuatoriano, South Ecuador, were studied in order to reveal genetic relationships with geology, volcanic ash deposits, climate and land use. A gradual diminuation of Andic properties was found, related to the distance of the pedon to the active volcanoes of the Northern Volcanic Zone of the Andes. Pedons in the north of the region, closer to these volcanoes (Sangay, Tungurahua) are classified as non-allophanic Histic Andosols. The influence of the vicinity of the volcanoes leads to a higher oxalate extractable aluminium and iron. The genesis of the Andosols seems to be strongly related to the presence and thickness of volcanic ash depositions. The limit of these depositions is situated south of the city of Cuenca. Pedons further to the south are classified as Histosols. However, they also have clear Andic properties. Several differences in chemical properties between the Western and Eastern cordilleras where found, that are most probable related with a difference in mother material, and maybe also a different climatic regime. Correlation of the chemical properties with land use reveals that no chemical differences can be found that are invoked by occupying natural Andosols for agricultural purposes, within the first five years of cultivation. At last, the conclusions were used to revisit the World Reference Base for Soil Resources in order to sharpen up differenciation between Andosols and Histosols.

Seismic velocity structure of the slab and continental plate in the region of the 1960 Valdivia (Chile) slip maximum — Insights into fluid release and plate coupling

NASA Astrophysics Data System (ADS)

Dzierma, Yvonne; Rabbel, Wolfgang; Thorwart, Martin; Koulakov, Ivan; Wehrmann, Heidi; Hoernle, Kaj; Comte, Diana

2012-05-01

The south-central Chilean subduction zone has witnessed some of the largest earthquakes in history, making this region particularly important for understanding plate coupling. Here we present the results of a local earthquake tomography study from a temporary local seismic network in the Villarrica region between 39 and 40°S, where the largest coseismic displacement of the 1960 Valdivia earthquake occurred. A low-velocity anomaly and high Vp/Vs values occur under the coastal region, indicating mantle serpentinisation and/or underthrusting of forearc material. Further east, a high-velocity anomaly is observed, interpreted as "normal" high-velocity mantle. Under the active volcanic arc a low-velocity anomaly together with high Vp/Vs ratios (1.8 and higher) likely images fluid ascent beneath the volcanoes. Close to the subducting Valdivia Fracture Zone, the coastal low-velocity anomaly extends further inland, where it interrupts and shifts the high-velocity anomalies associated with "normal" fast mantle velocities. This may indicate enhanced fluid presence along this part of the margin, probably caused by a stronger hydration of the incoming plate along the Valdivia Fracture Zone. This is consistent with geochemical fluid proxies (U/Th, Pb/Ce, Ba/Nb) in young volcanic rocks displaying peak values along the volcanic front at Llaima and Villarrica Volcanoes, and with recent GPS measurements, which suggested a local reduction in plate coupling in this region. The shift in the high-velocity anomaly underlying the central part may be caused by a north to south decrease in plate age and hydration across the Valdivia Fracture Zone, and may explain why a Central Valley is absent in this segment of the margin. The low La/Yb ratios in the volcanic rocks from Villarrica and Llaima suggest that the high slab-derived fluid flux causes elevated degrees of melting beneath these volcanoes, providing an explanation as to why these are amongst the most active volcanoes in South America.

Volcanism in Northwest Ishtar Terra, Venus

NASA Astrophysics Data System (ADS)

Gaddis, Lisa R.; Greeley, Ronald

1990-10-01

Evidence is presented for a previously undocumented volcanic complex in the highlands of NW Ishtar Terra (74 deg N, 313 deg E). The proposed valcanic center is in mountainous banded terrain thought to have been formed by regional compression. Data used include Soviet Venera 15/16 radar images and topography (Fotokarta Veneri B-4, 1987). An attempt is made to assess the place of this feature in the framework of known volcanic landforms of the Lakshmi Planum and to examine the relationships between volcanism and tectonism in this region.

The nature of magmatism at Palinpinon geothermal field, Negros Island, Philippines: implications for geothermal activity and regional tectonics

NASA Astrophysics Data System (ADS)

Rae, Andrew J.; Cooke, David R.; Phillips, David; Zaide-Delfin, Maribel

2004-01-01

The Palinpinon geothermal field, Negros Island, Philippines is a high-temperature, liquid-dominated geothermal system in an active island-arc volcanic setting. This paper presents a regional context for the Palinpinon geology, discusses the petrogenetic evolution of magmatism in the district and assesses the genetic relationships between intrusion and geothermal circulation. The oldest rock formation, the Lower Puhagan Volcanic Formation (Middle Miocene), is part of a volcanic sequence that is traceable throughout the Visayas region and is related to subduction of the Sulu Sea oceanic basin in a southeasterly direction beneath the Sulu arc. Late Miocene to Early Pliocene times mark a period of regional subsidence and marine sedimentation. A thick sequence of calcareous sediments (Okoy Formation) was deposited during this period. Magmatism in Early Pliocene to Recent times coincided with commencement of subduction at the Negros-Sulu Arc. This produced basaltic andesites and andesites belonging to the Southern Negros and Cuernos Volcanic Formations. During this time the Puhagan dikes and the Nasuji Pluton intruded Middle Miocene, Late Miocene and Early-Late Pliocene formations. Based on radiogenic ( 40Ar/ 39Ar) dating of hornblende, the Puhagan dikes are 4.1-4.2 Ma and the Nasuji Pluton 0.3-0.7 Ma. This age difference confirms these intrusions are not genetically related. The Early Pliocene age of the Puhagan dikes also confirms they are not the heat source for the current geothermal system and that a much younger intrusion is situated beyond drill depths. Igneous rock formations in southern Negros are the products of regional island-arc magmatism with medium K, calc-alkaline, basaltic to dacitic compositions. Their adakitic affinity implies that the melting of subducted oceanic basalt has influenced magmatism in this region. Considering the regional tectonic history the most likely scenarios for the generation of slab melts are: (1) during the Middle Miocene, by the melting of relatively young (<20 Ma) oceanic crust; (2) during Early Pliocene times, by the initiation of subduction along the Negros-Sulu Trench; and (3) during Late Pliocene times, by the melting of young (<10-20 Ma) oceanic crust. The adakitic composition of the magmas at Palinpinon has promoted the formation of a porphyry copper-style magmatic-hydrothermal system that is comparable to mineralised porphyry deposits elsewhere in the Philippines.

Structural and lithologic constraints to mineralization in Aurora, Nevada and Bodie, California mining districts, observed with aerospace geophysical data

NASA Astrophysics Data System (ADS)

Smailbegovic, Amer

This study used a multifaceted approach to investigate the geology and metallogenesis of the Bodie Hills region and the Aurora mining district. The factors influencing regional- and local-scale metallogenesis are compared and discussed in context of the various datasets, analysis techniques and methodologies. The Aurora and Bodie mining districts are located in the Miocene volcanics of the Bodie Hills, north of Mono Lake, on the opposite sides of the Nevada-California state line. From the standpoint of economic geology, both deposits are structurally controlled, low-sulfidation, quartz-adularia-sericite precious metal vein deposits with an extensive alteration halo. The area has been exploited since late 1870s by both underground and minor open pit operations (Aurora), exposing portions of altered andesites, rhyolite flows and tuffs and quartz-adularia-sericite veins. Much of the previous geologic mapping and explanation in Aurora was ad-hoc and primarily in support of the mining operations, without particular interest paid to the system as a whole. Using detailed field mapping and interpretation of the deposit in Bodie as a guide, a combined array of geophysical data in conjunction with traditional field mapping and GIS-based Weights of Evidence (WofE) modeling was utilized to attain better understanding of the Aurora district and both districts in the local and regional framework. The gravity data suggests a NE-trending, positive anomaly, resulting from a density contrast between the presumably uplifted pre-Tertiary basement and Miocene volcanic assemblage in the Bodie Hills. The aeromagnetic data are dominated by the strong signature of the Miocene volcanism (vents, flows, etc.) and suggests that the volcanic activity is concentrated along the northeasterly corridor of basement uplift. Multispectral, spaceborne imagery (Landsat ETM, ASTER) shows the regional structural setting, which is dominated by NNE and NE-trending lineaments and major alteration trends in the Bodie Hills. The high-resolution, narrow-swath, hyperspectral data obtained from high and low altitude AVIRIS targeted on the individual districts, allows identification of hydrothermal alteration assemblages, potential structural mineralization conduits and surface manifestations of mineralization. Individual segments of the regional-to-local geophysical survey are field checked and spatially integrated using WofE. The interpretation and WofE modeling of the geophysical data and detailed geologic field mapping reveal a close relationship between the basement uplift (source for metals), NE-trending structures (conduits), volcanic activity (energy), hydrothermal activity (genesis) and mineralization in Aurora and Bodie. This study confirms that Aurora represents a low-sulfidation system hosted in a strike-slip influenced dilational vein system, which may be genetically associated with the initial phase of Miocene extension and stress accommodation in Western Great Basin during 15--8 Ma.

DOE Office of Scientific and Technical Information (OSTI.GOV)

F. Perry

Studies of volcanic risk to the proposed high-level radioactive waste repository at Yucca Mountain have been ongoing for 25 years. These studies are required because three episodes of small-volume, alkalic basaltic volcanism have occurred within 50 km of Yucca Mountain during the Quaternary. Probabilistic hazard estimates for the proposed repository depend on the recurrence rate and spatial distribution of past episodes of volcanism in the region. Several independent research groups have published estimates of the annual probability of a future volcanic disruption of the proposed repository, most of which fall in the range of 10{sup -7} to 10{sup -9} permore » year; similar conclusions were reached. through an extensive expert elicitation sponsored by the Department of Energy in 1995-1996. The estimated probability values are dominated by a regional recurrence rate of 10{sup -5} to 10{sup -6} volcanic events per year (equating to recurrence intervals of several hundred thousand years). The recurrence rate, as well as the spatial density of volcanoes, is low compared to most other basaltic volcanic fields in the western United States, factors that may be related to both the tectonic history of the region and a lithospheric mantle source that is relatively cold and not prone to melting. The link between volcanism and tectonism in the Yucca Mountain region is not well understood beyond a general association between volcanism and regional extension, although areas of locally high extension within the region may control the location of some volcanoes. Recently, new geologic data or hypotheses have emerged that could potentially increase past estimates of the recurrence rate, and thus the probability of repository disruption. These are (1) hypothesized episodes of anomalously high strain rate, (2) hypothesized presence of a regional mantle hotspot, and (3) new aeromagnetic data suggesting as many as twelve previously unrecognized volcanoes buried in alluvial-filled basins near Yucca Mountain.« less

Hot spots on Io: Initial results from Galileo's near infrared mapping spectrometer

USGS Publications Warehouse

Lopes-Gautier, R.; Davies, A.G.; Carlson, R.; Smythe, W.; Kamp, L.; Soderblom, L.; Leader, F.E.; Mehlman, R.

1997-01-01

The Near-Infrared Mapping Spectrometer on Galileo has monitored the volcanic activity on Io since June 28, 1996. This paper presents preliminary analysis of NIMS thermal data for the first four orbits of the Galileo mission. NIMS has detected 18 new hot spots and 12 others which were previously known to be active. The distribution of the hot spots on Io's surface may not be random, as hot spots surround the two bright, SO2-rich regions of Bosphorus Regio and Colchis Regio. Most hot spots seem to be persistently active from orbit to orbit and 10 of those detected were active in 1979 during the Voyager encounters. We report the distribution of hot spot temperatures and find that they are consistent with silicate volcanism. Copyright 1997 by the American Geophysical Union.

Polarization anisotropy for monitoring seismogenic and volcanic zones- application to Mount Fuji at the time of the 2011 Tohoku earthquake

NASA Astrophysics Data System (ADS)

Saade, Maria; Montagner, Jean-Paul; Araragi, Kohtaro; Roux, Philippe; Brenguier, Florent

2017-04-01

In active regions (seismogenic and volcanic zones), the polarization of surface waves is mainly related to seismic anisotropy. It can be derived by using seismic interferometry. We use continuous data recorded in the area around Mount Fuji, covering the year 2011 in which the Tohoku-Oki earthquake, Japan (Mw=9.0) occurred. Previously, seismic velocity measurements done using cross-correlations of seismic noise, revealed that the Tohoku-Oki earthquake also affected the velocity structure of volcanic zones such as the Mount Fuji area (Brenguier et al. 2014). In fact, seismic velocity dropped by 0.1% in the shallow depth (<10km) underneath the area of Mount Fuji due to the high sensitivity of the volcanic crust and the presence of pressurized fluids in the volcanic fissures. Results of this study show that the orientation of seismic anisotropy has significantly changed at the time of the earthquake inducing strong and rapid deviations of the horizontal polarization of surface waves. These changes might be due to a change in the alignment of cracks when subject to a co-seismic stress perturbation.

Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years.

PubMed

Ning, Liang; Liu, Jian; Sun, Weiyi

2017-02-16

Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901-1935 and 1963-1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936-1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM.

Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years

NASA Astrophysics Data System (ADS)

Ning, Liang; Liu, Jian; Sun, Weiyi

2017-02-01

Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901-1935 and 1963-1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936-1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM.

Influence of volcanic activity and anthropic impact in the trace element contents of fishes from the North Patagonia in a global context.

PubMed

Bubach, D F; Macchi, P J; Pérez Catán, S

2015-11-01

The elemental contents in salmonid muscle and liver tissues from different lakes around the world were investigated. Fish from pristine areas were compared with those fishes from impacted environments, both by volcanic and anthropogenic activities. Within the data, special attention was given to fishes from the Andean Patagonian lakes in two contexts: local and global. The local evaluation includes geological and limnological parameters and diet composition which were obtained through a data search from published works. The volcanic influence in Andean Patagonian lakes was mainly observed by an increase of cesium (Cs) and rubidium (Rb) concentrations in fishes, influenced by calcium (Ca) and potassium (K) water contents. Zinc (Zn), selenium (Se), iron (Fe), silver (Ag), and mercury (Hg) contents in fishes showed the effect of the geological substratum, and some limnological parameters. The diet composition was another factor which affects the elemental concentration in fishes. The analyzed data showed that the fishes from Andean Patagonian lakes had elemental content patterns corresponding to those of pristine regions with volcanic influence. Selenium and Ag contents from Andean Patagonian fishes were the highest reported.

Mid-tertiary volcano-tectonic development of the Southwestern Cordillera of North America

NASA Technical Reports Server (NTRS)

Nelson, Kerri L.

1987-01-01

In the Southwestern Cordillera (SC) of North America, volcanic style changed from dominantly calcalkaline stratovolcanoes to caldera-related magmatism during the mid-Tertiary. The dominant tectonic process affecting the region during this time was convergence of the Farallon and North American Plates. The change in style of volcanism indicates a change in the operative stress regime: compressional for the earlier calcalkaline volcanism and tensional for development of the calderas. The development of the centers were compared to evaluate the volcano-tectonic relationship of caldera development within and between centers and determine the relationships between the earlier calcalkaline and later caldera-style volcanisms. The calderas exhibit three distinct stages of development that are closely associated with the East Pacific Rise/trench collision. The spatial and temporal association of the calcalkaline and caldera-related volcanism argues for the SC representing a region of continued arc magnetism in which the style of volcanism varied in response to differences in regional stresses.

Hunting for the Tristan mantle plume - An upper mantle tomography around the volcanic island of Tristan da Cunha

NASA Astrophysics Data System (ADS)

Schlömer, Antje; Geissler, Wolfram H.; Jokat, Wilfried; Jegen, Marion

2017-03-01

The active volcanic island Tristan da Cunha, located at the southwestern and youngest end of the Walvis Ridge - Tristan/Gough hotspot track, is believed to be the surface expression of a huge thermal mantle anomaly. While several criteria for the diagnosis of a classical hotspot track are met, the Tristan region also shows some peculiarities. Consequently, it is vigorously debated if the active volcanism in this region is the expression of a deep mantle plume, or if it is caused by shallow plate tectonics and the interaction with the nearby Mid-Atlantic Ridge. Because of a lack of geophysical data in the study area, no model or assumption has been completely confirmed. We present the first amphibian P-wave finite-frequency travel time tomography of the Tristan da Cunha region, based on cross-correlated travel time residuals of teleseismic earthquakes recorded by 24 ocean-bottom seismometers. The data can be used to image a low velocity structure southwest of the island. The feature is cylindrical with a radius of ∼100 km down to a depth of 250 km. We relate this structure to the origin of Tristan da Cunha and name it the Tristan conduit. Below 250 km the low velocity structure ramifies into narrow veins, each with a radius of ∼50 km. Furthermore, we imaged a linkage between young seamounts southeast of Tristan da Cunha and the Tristan conduit.

Volcanic deformation sources associated with Fogo 2011-2012 unrest, Azores - The first modelling result

NASA Astrophysics Data System (ADS)

Okada, Jun; Araújo, João; Bonforte, Alessandro; Guglielmino, Francesco; Lorenzo, Maria; Ferreira, Teresa

2016-04-01

Volcanic deformation is often observed at many active volcanoes in the world by using space geodesy techniques, namely GNSS and InSAR. More difficulties in judgement if eruptions are imminent or not arise when such phenomenon occurs at dormant volcanoes due to the lack of eruption experiences with monitoring data. The eruption triggering mechanism is still controversial at many cases, but many attempts to image deformation sources beneath volcanoes have been made using geophysical inversion techniques. In this study, we show the case study of Fogo (Água de Pau) volcano, S. Miguel Island, Azores which represents over 450 years of eruption dormancy since 1563-1564. In the recent decades Fogo has exhibited three prominent unrest episodes (1989, 2003-2006, and 2011-2012). The lack of geochemical and hydrothermal evidences for a magmatic intrusion during those episodes does not encourage discussions on resuming volcanic activity of Fogo. However, the inflation/uplift are evident on the edifices at least for the last two unrest episodes based on GPS data by Trota et al. (2009) and Okada et al. (2015), respectively. The preliminary deformation modelling based on repeated GPS campaign data suggested a shallow expanding spheroid (Trota et al. 2009) or a single Mogi sources beneath the summit caldera. We performed a more integrated inversion for the 2011-2012 episode using a genetic algorithm optimizing the source parameters. The best fit model agrees well with the regional/local tectonic lineament suggesting the close relation between the volcanic sources and the regional/local tectonics. The regional extensional stress (between Eurasia and Nubia plates) may play important roles for the ascent of volcanic fluids at Fogo volcano. We do not discard the possibility that Fogo may have been preparing for eruptions by intermittent ascents of magma at shallow crust (i.e. experiencing "failed eruptions") during the apparent dormant period. As a local monitoring agency, CIVISA (Center for Information and Seismovolcanic Surveillance of the Azores) continues to monitor Fogo's deformation in order to track changes in the source processes (source position and geometry, volume, pressure, etc.) as well as Fogo's seismicity and geochemistry.

Abstracts for the October 2012 meeting on Volcanism in the American Southwest, Flagstaff, Arizona

USGS Publications Warehouse

Lowenstern, Jacob B.

2013-01-01

Though volcanic eruptions are comparatively rare in the American Southwest, the States of Arizona, Colorado, New Mexico, Nevada, and Utah host Holocene volcanic eruption deposits and are vulnerable to future volcanic activity. Compared with other parts of the western United States, comparatively little research has been focused on this area, and eruption probabilities are poorly constrained. Monitoring infrastructure consists of a variety of local seismic networks, and ”backbone“ geodetic networks with little integration. Emergency response planning for volcanic unrest has received little attention by either Federal or State agencies. On October 18–20, 2012, 90 people met at the U.S. Geological Survey campus in Flagstaff, Arizona, providing an opportunity for volcanologists, land managers, and emergency responders to meet, converse, and begin to plan protocols for any future activity. Geologists contributed data on recent findings of eruptive ages, eruption probabilities, and hazards extents (plume heights, ash dispersal). Geophysicists discussed evidence for magma intrusions from seismic, geodetic, and other geophysical techniques. Network operators publicized their recent work and the relevance of their equipment to volcanic regions. Land managers and emergency responders shared their experiences with emergency planning for earthquakes. The meeting was organized out of the recognition that little attention had been paid to planning for or mitigation of volcanic hazards in the American Southwest. Moreover, few geological meetings have hosted a session specifically devoted to this topic. This volume represents one official outcome of the meeting—a collection of abstracts related to talks and poster presentations shared during the first two days of the meeting. In addition, this report includes the meeting agenda as a record of the proceedings. One additional intended outcome will be greater discussion and coordination among emergency responders, geologists, geophysicists, and land managers regarding geologic hazards in the Southwest.

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

NASA Astrophysics Data System (ADS)

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.

Petrology and petrogenesis of the Eocene Volcanic rocks in Yildizeli area (Sivas), Central Anatolia, Turkey

NASA Astrophysics Data System (ADS)

Doğa Topbay, C.; Karacık, Zekiye; Genç, S. Can; Göçmengil, Gönenç

2015-04-01

Yıldızeli region to the south of İzmir Ankara Erzincan suture zone is situated on the large Sivas Tertiary sedimentary basin. After the northern branch of the Neotethyan Ocean was northerly consumed beneath the Sakarya Continent, a continent - continent collision occurred between the Anatolide- Tauride platform and Pontides and followed a severe intermediate magmatism during the Late Cretaceous- Tertiary period. This created an east-west trending volcanic belt along the whole Pontide range. In the previous studies different models are suggested for the Eocene volcanic succession such as post-collisional, delamination and slab-breakoff models as well as the arc model for its westernmost parts. We will present our field and geochemical data obtained from the Yıldızeli and its surroundings for its petrogenesis, and will discuss the tectonic model(s) on the basis of their geochemical/petrological aspects. Cenozoic volcanic sequences of Yıldızeli region which is the main subject of this study, overlie Pre-Mesozoic crustal meta-sedimentary group of Kırşehir Massif, Ophiolitic mélange and Cretaceous- Paleocene? flysch-like sequences. In the northern part of Yıldızeli region, north vergent thrust fault trending E-W seperates the ophiolitic mélange complex from the Upper Cretaceous-Paleocene and Tertiary formations. Volcano-sedimentary units, Eocene in age, of the Yıldızeli (Sivas-Turkey) which are intercalated with sedimentary deposits related to the collision of Anatolide-Tauride and a simultaneous volcanic activity (i.e. the Yıldızeli volcanics), exposed throughout a wide zone along E-W orientation. Yıldızeli volcanics consist of basalts, basaltic-andesites and andesitic lavas intercalated flow breccias and epiclastic, pyroclastic deposits. Basaltic andesite lavas contain Ca-rich plagioclase + clinopyroxene ± olivine with minor amounts of opaque minerals in a matrix comprised of microlites and glass; andesitic lavas are generally contain Ca-Na plagioclase + hornblend ± pyroxene ± biotite + opaques in a matrix comprised of mostly glass, microlites or crypto to micro crystalline feldspars. All the lavas show mainly pilotaxitic, intersertal, cumulophyric and poikilitic textures. Geochemically, Yıldızeli lavas ranging in composition from basalt to trachyandesite displaying the calc-alkaline affinity with medium-K and shoshonitic character. All intermediate and basic volcanic rocks show enrichment in large ion lithophile elements (LILE) and light rare earth elements (LREE) relative to the high field strength elements (HFSE) such as Nb, Ta, Zr and Ti. Volcanic rocks of the Yıldızeli region display the following range in Sr and Nd initial isotope ratios: 87Sr/86Sr = 0.704389 to 0.706291 and 143Nd/144Nd = 0.512671. The major- trace element geochemistry and isotopic values suggest that Yıldızeli volcanics derived possibly from a mantle source which was modified by subduction related fluids or was contaminated by the continental crustal components.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fedotov, S.A.

Using geophysical data, the mechanism of deep-seated magmatic and volcanic activity was studied in the region of the island arcs and associated structures. Data on magmatic activity below the volcanic belt of East Kamchatka, obtained during geophysical investigations, mainly during detailed seismological investigations and deep seismic sounding, provide evidence for an association between the volcanoes and the processes in the Pacific Ocean focal layer of earthquakes, and for the accumulation of magmas below the volcanic belt at depths less than 60 km. Anomalous columnar bodies more than 5 to 7 km across were found linking the volcanoes with the focalmore » layer. There was also a very large concentration of convective heat flow and volatiles in the magma columns feeding the volcanoes. As to the role of different forces in the uprise of magmas into the volcanoes, hydrostatic forces probably predominate in the asthenosphere, supplemented by tectonic pressure in the lithosphere and forces associated with boiling of magmas during release of volatiles in the crust, especially in its upper layers.« less

Catalogue of satellite photography of the active volcanoes of the world

NASA Technical Reports Server (NTRS)

Heiken, G.

1976-01-01

A catalogue is presented of active volcanoes as viewed from Earth-orbiting satellites. The listing was prepared of photographs, which have been screened for quality, selected from the earth resources technology satellite (ERTS) and Skylab, Apollo and Gemini spacecraft. There is photography of nearly every active volcano in the world; the photographs are particularly useful for regional studies of volcanic fields.

Status of volcanism studies for the Yucca Mountain Site Characterization Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowe, B.; Perry, F.; Murrell, M.

1995-02-01

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

Crustal and upper mantle velocity structure of the Hoggar swell (Central Sahara, Algeria)

NASA Astrophysics Data System (ADS)

Ayadi, A.; Dorbath, C.; Lesquer, A.; Bezzeghoud, M.

2000-02-01

The Hoggar region is known as one of the most important swells in the African continent. Its altitude culminates at 2908 m in the Tahat hill (Atakor). The Hoggar and other massifs of central Africa (Aı̈r, Eghei, Tibesti, Darfur, Cameroon mount, …) form a system of domal uplifts with similar scale, morphology and volcanic activity. The knowledge of the structure beneath the Hoggar swell will help us to understand the origin of continental swells. In order to get an image of the lithosphere in this region, we have performed a teleseismic field experiment. The 33 short-period seismic stations have been maintained for 2 1/2 month along a 700-km long NNW-SSW profile. This experiment crossed the Central Hoggar and extended northward into the In-Salah Sahara basin which is characterized by high heat flow values of deep origin. The high quality of the data recorded during this experiment allows us to perform a velocity inversion. The Hoggar appears to be characterized by lower mantle velocities. The anomalous zone extends from the upper lithosphere to the mantle. The weak velocity contrast is interpreted in agreement with gravity, geothermal and petrological data as due to extensive mantle modifications inherited from Cenozoic volcanic activity. It confirms that the Hoggar swell is not due to a large-scale uplift of hot asthenospheric materials but corresponds to a now cooled-off modified mantle. On the contrary, local low-velocity zones associated with the Atakor and Tahalra volcanic districts show that hot materials still exist at depths in relation with recent basaltic volcanism.

Volcanism and Subduction: The Kamchatka Region

NASA Astrophysics Data System (ADS)

Eichelberger, John; Gordeev, Evgenii; Izbekov, Pavel; Kasahara, Minoru; Lees, Jonathan

The Kamchatka Peninsula and contiguous North Pacific Rim is among the most active regions in the world. Kamchatka itself contains 29 active volcanoes, 4 now in a state of semi-continuous eruption, and I has experienced 14 magnitude 7 or greater earthquakes since accurate recording began in 1962. At its heart is the uniquely acute subduction cusp where the Kamchatka and Aleutian Arcs and Emperor Seamount Chain meet. Volcanism and Subduction covers coupled magmatism and tectonics in this spectacular region, where the torn North Pacific slab dives into hot mantle. Senior Russian and American authors grapple with the dynamics of the cusp with perspectives from the west and east of it, respectively, while careful tephrostratigraphy yields a remarkably precise record of behavior of storied volcanoes such as Kliuchevskoi and Shiveluch. Towards the south, Japanese researchers elucidate subduction earthquake processes with unprecedented geodetic resolution. Looking eastward, new insights on caldera formation, monitoring, and magma ascent are presented for the Aleutians. This is one of the first books of its kind printed in the English language. Students and scientists beginning research in the region will find in this book a useful context and introduction to the region's scientific leaders. Others who wish to apply lessons learned in the North Pacific to their areas of interest will find the volume a valuable reference.

Management of the volcanic crises of Galeras volcano: Social, economic and institutional aspects

NASA Astrophysics Data System (ADS)

Cardona, Omar D.

1997-05-01

This paper presents a summary of the institutional management of the volcanic hazard and risk in the areas that surround Galeras volcano, Colombia, during its recent activity. The social and economic problems discussed have stemmed from difficulties in forecasting the behavior of the volcano and the inadequate management of the warnings by various government bodies and the media. The Galeras situation had economic, social, and psychological effects that contributed to resistance in implementing mitigation measures. Furthermore, the political authorities were reluctant to accept the volcanic risk. At regional and local levels, certain business organizations and a large part of the population also were inadequately prepared to accept the risk, despite the effort and insistence at the national level to implement a volcano emergency preparedness plan.

MPF model ages of the Rembrandt basin and scarp system, Mercury.

NASA Astrophysics Data System (ADS)

Ferrari, Sabrina; Massironi, Matteo; Marchi, Simone; Byrne, Paul K.; Klimczak, Christian; Cremonese, Gabriele

2013-04-01

The 715-km-diameter Rembrandt basin is the largest well-preserved impact feature of the southern hemisphere of Mercury [1] (Fig. 1), and was imaged for the first time during the second flyby of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission [2]. Much of the basin interior is covered by smooth, high-reflectance plains interpreted to be of volcanic origin [1-3] that host sets of contractional and extensional tectonic structures. Notably, Rembrandt basin and its smooth plains are cross-cut by a 1,000-km-long reverse fault system [1-5] that trends ~E-W, bending toward the north within the basin. The individual faults of this system accommodated crustal shortening that resulted from global contraction as Mercury's interior cooled [1]. The current shape of the reverse fault system may have been influenced by the formation of the Rembrandt basin [5]. The emplacement of the interior smooth plains predates both the basin-related tectonism and the final development of the giant scarp, which is suggestive of either short-lived volcanic activity immediately after basin formation or a later volcanic phase set against prolonged tectonic activity. In order to quantify the duration of volcanic and tectonic activity in and around Rembrandt basin, we determined the crater count-derived ages of the involved terrains by means of the Model Production Function (MPF) chronology of Mercury [6-8], which is rely on the knowledge of the impactors flux on the planet. Crater chronology allowed us to constrain the Rembrandt basin formation to the early Calorian period and a widespread resurfacing up to 3.5 Ga ago. The volcanic activity affected both the basin and its surroundings, but ended prior to some basin-related and regional faulting. Hence, if the giant scarp begun to develop even before the basin formation (as suggested by its length-displacement profile across the basin itself, [5]) the regional tectonic activity along this structure might have started even before the Late Heavy Bombardment period and lasted for more than 300 Ma, when the volcanic activity in this part of hermean surface was already accomplished. [1] Watters T. R. et al. (2009) Science, 324, 618. [2] Solomon S. C. et al. (2008) Science, 321, 59. [3] Denevi B. W. et al. (2009) Science, 324, 613. [4] Byrne P. K. et al. (2012) LPS, 43, abstract 1722. [5] Ferrari S. et al. (2012) EPSC, 7, abstract 2012-874. [6] Marchi S. et al. (2009) The Astron. Jour., 137, 4936. [7] Massironi M. et al. (2009) Geophys. Res. Lett., 36, L21204. [8] Marchi S. et al. (2011) Plaet. Space Sci., 59, 1968.

Geology Report: Area 3 Radioactive Waste Management Site DOE/Nevada Test Site, Nye County, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

NSTec Environmental Management

2006-07-01

Surficial geologic studies near the Area 3 Radioactive Waste Management Site (RWMS) were conducted as part of a site characterization program. Studies included evaluation of the potential for future volcanism and Area 3 fault activity that could impact waste disposal operations at the Area 3 RWMS. Future volcanic activity could lead to disruption of the Area 3 RWMS. Local and regional studies of volcanic risk indicate that major changes in regional volcanic activity within the next 1,000 years are not likely. Mapped basalts of Paiute Ridge, Nye Canyon, and nearby Scarp Canyon are Miocene in age. There is a lackmore » of evidence for post-Miocene volcanism in the subsurface of Yucca Flat, and the hazard of basaltic volcanism at the Area 3 RWMS, within the 1,000-year regulatory period, is very low and not a forseeable future event. Studies included a literature review and data analysis to evaluate unclassified published and unpublished information regarding the Area 3 and East Branch Area 3 faults mapped in Area 3 and southern Area 7. Two trenches were excavated along the Area 3 fault to search for evidence of near-surface movement prior to nuclear testing. Allostratigraphic units and fractures were mapped in Trenches ST02 and ST03. The Area 3 fault is a plane of weakness that has undergone strain resulting from stress imposed by natural events and underground nuclear testing. No major vertical displacement on the Area 3 fault since the Early Holocene, and probably since the Middle Pleistocene, can be demonstrated. The lack of major displacement within this time frame and minimal vertical extent of minor fractures suggest that waste disposal operations at the Area 3 RWMS will not be impacted substantially by the Area 3 fault, within the regulatory compliance period. A geomorphic surface map of Yucca Flat utilizes the recent geomorphology and soil characterization work done in adjacent northern Frenchman Flat. The approach taken was to adopt the map unit boundaries (line work) of Swadley and Hoover (1990) and re-label these with map unit designations like those in northern Frenchman Flat (Huckins-Gang et al, 1995a,b,c; Snyder et al, 1995a,b,c,d).« less

Volcanism in Northwest Ishtar Terra, Venus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaddis, L.R.; Greeley, R.

Evidence is presented for a previously undocumented volcanic complex in the highlands of NW Ishtar Terra (74 deg N, 313 deg E). The proposed valcanic center is in mountainous banded terrain thought to have been formed by regional compression. Data used include Soviet Venera 15/16 radar images and topography (Fotokarta Veneri B-4, 1987). An attempt is made to assess the place of this feature in the framework of known volcanic landforms of the Lakshmi Planum and to examine the relationships between volcanism and tectonism in this region. 38 refs.

Modeling Seasonal Thermal Radiance Cycles for Change Detection at Volcanic / Geothermal Areas

NASA Astrophysics Data System (ADS)

Vaughan, R.; Beuttel, B. S.

2013-12-01

Remote sensing observations of thermal features associated with (and often preceding) volcanic activity have been used for decades to detect and monitor volcanism. However, anomalous thermal precursors to volcanic eruptions are usually only recognized retrospectively. One of the reasons for this is that precursor thermal activity is often too subtle in magnitude (spatially, temporally, or in absolute temperature) to be unambiguously detected in time to issue warnings or forecasts. Part of the reason for this is the trade-off between high spatial and high temporal resolution associated with satellite imaging systems. Thus, the goal of this work has been to develop some techniques for using high-temporal-resolution, coarse-spatial-resolution imagery to try to detect subtle thermal anomalies. To identify anomalies, background thermal activity must first be characterized. Every active, or potentially active, volcano has a unique thermal history that provides information about normal background thermal activity due to seasonal or diurnal variations. Understanding these normal variations allows recognition of anomalous activity that may be due to volcanic / hydrothermal processes - ultimately with a lead time that may be sufficient to issue eruption warnings or forecasts. Archived MODIS data, acquired ~daily from 2000 to 2012, were used to investigate seasonal thermal cycles at three volcanic areas with different types of thermal features: Mount St. Helens, which had a dacite dome-building eruption from 2004-2008; Mount Ruapehu, which has a 500-m diameter active summit crater lake; and Yellowstone, which is a large active geothermal system that has hundreds of hot springs and fumarole fields spread out over a very large area. The focus has been on using MODIS 1-km sensor radiance data in the MIR and TIR wavelength regions that are sensitive to thermal emission from features that range in temperature from hundreds of °C, down to tens of °C (below the boiling temperature of water). To detect such features it is best to use data acquired at night, as this maximizes the delta T between the thermal target and non-thermal background and minimizes the effects of the Sun. Decadal time-series plots of nighttime MODIS sensor radiance data over the target areas show that seasonal thermal cycles due to varying solar incidence angle can be modeled with a sine function and removed to reveal subtle changes in TIR radiance. The seasonal sine function is unique to each volcanic / geothermal area and can be modeled iteratively using a least squares fit to the cloud of radiance data. The sine function model can also be used to generate a first-order cloud cover approximation for the nighttime TIR data. This work helps establish a framework for improved thermal alarm algorithms, automated thermal detection methods, and operational monitoring techniques for active, or potentially active, volcanoes throughout the world. This type of background study is a step toward establishing a global volcanic eruption forecasting system using satellite-based remote sensing data that are sensitive to subtle precursor thermal anomalies.

Atla Regio, Venus: Geology and origin of a major equatorial volcanic rise

NASA Technical Reports Server (NTRS)

Senske, D. A.; Head, James W., III

1992-01-01

Regional volcanic rises form a major part of the highlands in the equatorial region of Venus. These broad domical uplands, 1000 to 3000 km across, contain centers of volcanism forming large edifices and are associated with extension and rifting. Two classes of rises are observed: (1) those that are dominated by tectonism, acting as major centers for converging rifts such as Beta Regio and Alta Regio, and are termed tectonic junctions; and (2) those forming uplands characterized primarily by large-scale volcanism forming edifices. Western Eistla Regio and Bell Regio, where zones of extension and rifting are less developed. Within this second class of features the edifices are typically found at the end of a single rift, or are associated with a linear belt of deformation. We examine the geologic characteristics of the tectonic junction at Alta Regio, concentrating on documenting the styles of volcanism and assessing mechanisms for the formation of regional topography.

Field Trip Guide to Serpentinite, Silica-Carbonate Alteration, and Related Hydrothermal Activity in the Clear Lake Region, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fraser Goff; George Guthrie

1999-06-01

This guide is designed to familiarize scientists with the geology, structure, alteration, and fluids typical of California serpentinites for purposes of carbon dioxide sequestration (Lackner et al., 1995). Goff et al. (1997) and Goff and Lackner (1998) describe the geology and geochemistry of some of the serpentinites from this area. Mechanisms of silica-carbonate alteration were outlined by Barnes et al. (1973). Donnelly-Nolan et al. (1993) most recently reviewed relations between regional hydrothermal alteration and Quarternary volcanic activity. Stanley et al. (1998) summarized geophysical characteristics of the region.

Volcanism Studies: Final Report for the Yucca Mountain Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

1998-12-01

This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period ofmore » a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is defined and described as one of many alternative models of the structural controls of the distribution of Plio-Quaternary basalt centers in the YMR. Geophysical data are described for the YMR and are used as an aid to understand the distribution of basaltic volcanic centers. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. Geochemical and isotopic data are presented for post-Miocene basalts of the Yucca Mountain region. Alternative petrogenetic models are assessed for the formation of the Lathrop Wells volcanic center. Based on geochemical data, basaltic ash in fault trenches near Yucca Mountain is shown to have originated from the Lathrop Wells center. Chapter 5 synthesizes eruptive and subsurface effects of basaltic volcanism on a potential repository and summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Chapter 6 synthesizes current knowledge of the probability of disruption of a potential repository at Yucca Mountain. In 1996, an Expert Elicitation panel was convened by DOE that independently conducted PVHA for the Yucca Mountain site. Chapter 6 does not attempt to revise this PVHA; instead, it further examines the sensitivity of variables in PVHA. The approaches and results of PVHA by the expert judgment panel are evaluated and incorporated throughout this chapter. The disruption ratio (E2) is completely re-evaluated using simulation modeling that describes volcanic events based on the geometry of basaltic feeder dikes. New estimates of probability bounds are developed. These comparisons show that it is physically implausible for the probability of magmatic disruption of the Yucca Mountain site to be > than about 7 x 10{sup {minus}8} events yr{sup {minus}1} . Simple probability estimates are used to assess possible implications of not drilling aeromagnetic anomalies in the Amargosa Valley. The sensitivity of the disruption probability to the location of northeast boundaries of volcanic zones near the Yucca Mountain sit« less

Structural controls on the spatial distribution and geochemical composition of volcanism in a continental rift zone; an example from Owens Valley, eastern California

NASA Astrophysics Data System (ADS)

Haproff, P. J.; Yin, A.

2014-12-01

Bimodal volcanism is common in continental rift zones. Structural controls to the emplacement and compositions of magmas, however, are not well understood. To address this issue, we examine the location, age, and geochemistry of active volcanic centers, and geometry and kinematics of rift-related faults across the active transtensional Owens Valley rift zone. Building on existing studies, we postulate that the spatial distribution and geochemical composition of volcanism are controlled by motion along rift-bounding fault systems. Along-strike variation in fault geometry and characteristics of active volcanism allow us to divide Owens Valley into three segments: southern, northern, and central. The southern segment of Owens Valley is a simple shear, asymmetric rift bounded to the west by the east-dipping Sierra Nevada frontal fault (SNFF). Active vents of Coso volcanic field are distributed along the eastern rift shoulder and characterized by the eruption of bimodal lavas. The SNFF within this segment is low-angle and penetrates through the lithosphere and into the ductile asthenosphere, allowing for mantle-derived magma to migrate across the weakest part of the fault zone beneath the eastern rift shoulder. Magma thermally weakens wall rocks and eventually stalls in the crust where the melt develops a greater felsic component prior to eruption. The northern segment of Owens Valley displays similar structural geometry, as the west-dipping White Mountains fault (WMF) is listric at depth and offsets the crust and mantle lithosphere, allowing for vertical transport of magma and reservoir emplacement within the crust. Bimodal lavas periodically erupted in the Long Valley Caldera region along the western rift shoulder. The central segment of Owens Valley is a pure shear, symmetric graben generated by motion along the SNFF and WMF. The subvertical, right-slip Owens Valley fault (OVF) strikes along the axis of the valley and penetrates through the lithosphere into the asthenosphere. Volcanic centers of Big Pine volcanic field are located along the trace of the OVF and characterized by mafic eruptions. The OVF is interpreted to provide a subvertical conduit for asthenospheric magma to migrate across the LAB and Moho and erupt on the rift surface without significant contamination with felsic crust.

Contrasting modes of rifting: The Benue Trough and Cameroon Volcanic Line, West Africa

NASA Astrophysics Data System (ADS)

Okereke, C. S.

1988-08-01

The Benue trough of west Africa is commonly believed to be a rift feature that originated in the Cretaceous at about the time that Africa and South America began to separate. Bouguer gravity and available geological data in the trough indicate that its formation was probably the result of regional horizontal stresses in the lithosphere, causing crustal extension and surface subsidence. By contrast, the data for the adjoining Cameroon volcanic line suggests that the associated tensional stresses relate to mantle upwarp causing thinning of the lithosphere and regional crustal uplift similar to that associated with the Kenya rift. Thus the association of passive and active rifts seen in the Afro-Arabia rift system is also a feature of the Cretaceous rift system in west Africa.

Application of Earthquake Subspace Detectors at Kilauea and Mauna Loa Volcanoes, Hawai`i

NASA Astrophysics Data System (ADS)

Okubo, P.; Benz, H.; Yeck, W.

2016-12-01

Recent studies have demonstrated the capabilities of earthquake subspace detectors for detailed cataloging and tracking of seismicity in a number of regions and settings. We are exploring the application of subspace detectors at the United States Geological Survey's Hawaiian Volcano Observatory (HVO) to analyze seismicity at Kilauea and Mauna Loa volcanoes. Elevated levels of microseismicity and occasional swarms of earthquakes associated with active volcanism here present cataloging challenges due the sheer numbers of earthquakes and an intrinsically low signal-to-noise environment featuring oceanic microseism and volcanic tremor in the ambient seismic background. With high-quality continuous recording of seismic data at HVO, we apply subspace detectors (Harris and Dodge, 2011, Bull. Seismol. Soc. Am., doi: 10.1785/0120100103) during intervals of noteworthy seismicity. Waveform templates are drawn from Magnitude 2 and larger earthquakes within clusters of earthquakes cataloged in the HVO seismic database. At Kilauea, we focus on seismic swarms in the summit caldera region where, despite continuing eruptions from vents in the summit region and in the east rift zone, geodetic measurements reflect a relatively inflated volcanic state. We also focus on seismicity beneath and adjacent to Mauna Loa's summit caldera that appears to be associated with geodetic expressions of gradual volcanic inflation, and where precursory seismicity clustered prior to both Mauna Loa's most recent eruptions in 1975 and 1984. We recover several times more earthquakes with the subspace detectors - down to roughly 2 magnitude units below the templates, based on relative amplitudes - compared to the numbers of cataloged earthquakes. The increased numbers of detected earthquakes in these clusters, and the ability to associate and locate them, allow us to infer details of the spatial and temporal distributions and possible variations in stresses within these key regions of the volcanoes.

Lithospheric controls on magma composition along Earth's longest continental hotspot track.

PubMed

Davies, D R; Rawlinson, N; Iaffaldano, G; Campbell, I H

2015-09-24

Hotspots are anomalous regions of volcanism at Earth's surface that show no obvious association with tectonic plate boundaries. Classic examples include the Hawaiian-Emperor chain and the Yellowstone-Snake River Plain province. The majority are believed to form as Earth's tectonic plates move over long-lived mantle plumes: buoyant upwellings that bring hot material from Earth's deep mantle to its surface. It has long been recognized that lithospheric thickness limits the rise height of plumes and, thereby, their minimum melting pressure. It should, therefore, have a controlling influence on the geochemistry of plume-related magmas, although unambiguous evidence of this has, so far, been lacking. Here we integrate observational constraints from surface geology, geochronology, plate-motion reconstructions, geochemistry and seismology to ascertain plume melting depths beneath Earth's longest continental hotspot track, a 2,000-kilometre-long track in eastern Australia that displays a record of volcanic activity between 33 and 9 million years ago, which we call the Cosgrove track. Our analyses highlight a strong correlation between lithospheric thickness and magma composition along this track, with: (1) standard basaltic compositions in regions where lithospheric thickness is less than 110 kilometres; (2) volcanic gaps in regions where lithospheric thickness exceeds 150 kilometres; and (3) low-volume, leucitite-bearing volcanism in regions of intermediate lithospheric thickness. Trace-element concentrations from samples along this track support the notion that these compositional variations result from different degrees of partial melting, which is controlled by the thickness of overlying lithosphere. Our results place the first observational constraints on the sub-continental melting depth of mantle plumes and provide direct evidence that lithospheric thickness has a dominant influence on the volume and chemical composition of plume-derived magmas.

Discovering Volcanoes in the Azores - A Field Trip

NASA Astrophysics Data System (ADS)

Brandão, Susana; Fernandes, Fátima

2013-04-01

The Azores islands are located in the North Atlantic Ocean near a triple junction, between the African, Eurasian and North American plates, at about 1500 km from the European continent and 3900 km from the North America east coast. It is formed by nine volcanic islands and a few islets dispersed along a 600 km NW-SE direction axis. The complex geological and geodynamic setting of the Azores explains its significant seismic and volcanic activity, including eruptions and degassing processes. Important landslides triggered either by earthquakes, volcanic eruptions, extreme meteorological conditions and/or coastal erosion processes frequently affect the islands, and tsunamis related with earthquakes and landslides were reported to have occurred in the past. The national curriculum for the school subject of Biology and Geology sees the Azores as a laboratory for the earth sciences and many topics revolve around it. For these reasons, we organised a field trip to the island of São Miguel, with pupils of the 11th grade who live in the Portuguese mainland, in a region that is geologically very different. During the six days of this trip, we attended training sessions in the Centre for Volcanology and Geological Risks Assessment (CVARG) of the Azores University. This multidisciplinary research unit organises activities around the prediction and prevention of disasters and natural hazards in the fields of volcanology and correlated phenomena, including volcanic eruptions, earthquakes, volcanic fumes, air pollution and water contaminants, landslides, floods and tsunamis, among others. The pupils explored volcanic calderas, lava caves, fumaroles and hot springs. They also collected and analysed extremophile bacteria that live in local hot springs.

Detecting the brightness temperature from Landsat-8 thermal infra red scanner preceding the Rinjani strombolian eruption 2015

NASA Astrophysics Data System (ADS)

Suwarsono, Hidayat, Suprapto, Totok; Prasasti, Indah; Parwati, Rokhis Khomarudin, M.

2017-07-01

At the end of October to early November 2015, Rinjani Volcano that is located in Lombok Island was erupted and has catapulted the ash, pyroclastic and lava flow. The dispersion of this volcanic ash in the atmosphere has been disrupting flights and the three closest airports to be closed for a while. The existence of Rinjani Volcano geographically plays an important role in the survival of life on the island of Lombok, because large areas of land on the island are a part of the Rinjani Volcano landscape. Based on the experience of violent eruptions that have occurred in the 13th century ago, the monitoring of the volcanism activity of this volcano needs to be done intensively and continuously. This is something important to do an early detection efforts of the volcanic eruption. These efforts need to be done as a preparedness effort in order to minimize adverse impacts that may occur as a result of this eruption. This research tries to detect the volcanic eruption precursor based on changes in temperature conditions of the crater and the surrounding area. We use the medium resolution satellite data, Thermal Infra Red Scanner (TIRS), on board Landsat-8, to monitor the brightness temperature as a representative of surface temperature of the volcanic region. The results showed that the brightness temperature derived from Landsat-8 TIRS is very usefull to predict the strombolian eruption which will occur in the near future. The use of multitemporal image data is important to understand the dynamics of volcanism activity over time.

A Subduction Factory Laboratory: Tectonics of the Southern Mariana Convergent Margin

NASA Astrophysics Data System (ADS)

Fryer, P.; Martinez, F.; Becker, N.; Appelgate, B.; Hawkins, J.; Ishihara, T.

2001-12-01

Recent MR-1 side-scan sonar mapping, gravity and magnetics surveys, and sea floor sampling of the southernmost portion of the Mariana region reveal a convergent margin subject to complexly interacting stresses. The backarc spreading center and the crust it has produced is inflated as a consequence of proximity of the arc and backarc basin magma sources. The formation of backarc basin crust dates from only 3 m.y. ago based on interpretations of magnetics data. The westward extension of the more recent arc volcanic centers beyond Guam shows a general diminishing of arc volcanic centers and a coalescing with the spreading center in a zone of transition from magmatic to amagmatic extension. Magnetic and gravity data are consistent with this tectonic interpretation. It is possible, however, that newly imaged volcanoes on the West Mariana ridge may be active. They show high-backscatter characteristics on sonar imagery and coincide with the typical depths to slab for magma generation in subduction zones. The distance to trench axis and the level of seismic activity in the region is consistent with volcanic activity on this portion of the "remnant arc." If our hypothesis is correct, then the southern Mariana system preserves the transition from remnant arc through extension and formation of a backarc basin spreading center, to the reestablishment of a new active volcanic arc. It thus provides a natural laboratory for the simultaneous study of all of the fundamental processes of the Subduction Factory. In addition, the forearc is deeply dissected by profound faulting that exposes the structure of the arc massif along faults with throws of up to 4 km. There are several stair-stepping antithetic normal faults in the forearc south of Guam that expose intermediate depth (up to approximately 15 km) plutonics of arc origin, providing a potential record of the most complete crustal section through the arc substructure known to be exposed in an active arc. Finally, the deeply-excised forearc of the southeastern corner of the system is underlain by a subducting plate that has likely been torn, which dips more steeply to the west of the proposed tear, and which may thus provide an excellent location for the study of mantle flow in association with disruption of subducting slabs. Pacific mantle may be leaking westward past the slab, invading the backarc region. The backarc magmas of the Izu-Bonin-Mariana system have been characterized as of Indian Ocean mantle composition. The rapid rate of volcanism along the southern backarc spreading center may make it possible to trace the incursion rate of Pacific mantle across this boundary.

Correlating the electrification of volcanic plumes with ashfall textures at Sakurajima Volcano, Japan

NASA Astrophysics Data System (ADS)

Smith, Cassandra M.; Van Eaton, Alexa R.; Charbonnier, Sylvain; McNutt, Stephen R.; Behnke, Sonja A.; Thomas, Ronald J.; Edens, Harald E.; Thompson, Glenn

2018-06-01

Volcanic lightning detection has become a useful resource for monitoring remote, under-instrumented volcanoes. Previous studies have shown that the behavior of volcanic plume electrification responds to changes in the eruptive processes and products. However, there has not yet been a study to quantify the links between ash textures and plume electrification during an actively monitored eruption. In this study, we examine a sequence of vulcanian eruptions from Sakurajima Volcano in Japan to compare ash textural properties (grain size, shape, componentry, and groundmass crystallinity) to plume electrification using a lightning mapping array and other monitoring data. We show that the presence of the continual radio frequency (CRF) signal is more likely to occur during eruptions that produce large seismic amplitudes (>7 μm) and glass-rich volcanic ash with more equant particle shapes. We show that CRF is generated during energetic, impulsive eruptions, where charge buildup is enhanced by secondary fragmentation (milling) as particles travel out of the conduit and into the gas-thrust region of the plume. We show that the CRF signal is influenced by a different electrification process than later volcanic lightning. By using volcanic CRF and lightning to better understand the eruptive event and its products these key observations will help the monitoring community better utilize volcanic electrification as a method for monitoring and understanding ongoing explosive eruptions.

Earthquake swarms and local crustal spreading along major strike-slip faults in California

USGS Publications Warehouse

Weaver, C.S.; Hill, D.P.

1978-01-01

Earthquake swarms in California are often localized to areas within dextral offsets in the linear trend in active fault strands, suggesting a relation between earthquake swarms and local crustal spreading. Local crustal spereading is required by the geometry of dextral offsets when, as in the San Andreas system, faults have dominantly strike-slip motion with right-lateral displacement. Three clear examples of this relation occur in the Imperial Valley, Coso Hot Springs, and the Danville region, all in California. The first two of these areas are known for their Holocene volcanism and geothermal potential, which is consistent with crustal spreading and magmatic intrusion. The third example, however, shows no evidence for volcanism or geothermal activity at the surface. ?? 1978 Birkha??user Verlag.

Lunar Sample Return Missions Using a Tele-Robotic Lander

NASA Astrophysics Data System (ADS)

Downes, H.; Crawford, I. A.; Alexander, L.

2018-02-01

Deep Space Gateway would allow tele-robotic landers and rovers to access regions of the Moon which have not been previously sampled. Scientific questions, e.g., the nature and duration of volcanic activity and the composition of the mantle/lower crust, could be addressed.

Seismic evidence for a cold serpentinized mantle wedge beneath Mount St Helens

PubMed Central

Hansen, S. M.; Schmandt, B.; Levander, A.; Kiser, E.; Vidale, J. E.; Abers, G. A.; Creager, K. C.

2016-01-01

Mount St Helens is the most active volcano within the Cascade arc; however, its location is unusual because it lies 50 km west of the main axis of arc volcanism. Subduction zone thermal models indicate that the down-going slab is decoupled from the overriding mantle wedge beneath the forearc, resulting in a cold mantle wedge that is unlikely to generate melt. Consequently, the forearc location of Mount St Helens raises questions regarding the extent of the cold mantle wedge and the source region of melts that are responsible for volcanism. Here using, high-resolution active-source seismic data, we show that Mount St Helens sits atop a sharp lateral boundary in Moho reflectivity. Weak-to-absent PmP reflections to the west are attributed to serpentinite in the mantle-wedge, which requires a cold hydrated mantle wedge beneath Mount St Helens (<∼700 °C). These results suggest that the melt source region lies east towards Mount Adams. PMID:27802263

A LiDAR Survey of an Exposed Magma Plumbing System in the San Rafael Desert, Utah

NASA Astrophysics Data System (ADS)

Richardson, J. A.; Kinman, S.; Connor, L.; Connor, C.; Wetmore, P. H.

2013-12-01

Fields of dozens to hundreds of volcanoes are a common occurrence on Earth and are created due to distributed-style volcanism often referred to as "monogenetic." These volcanic fields represent a significant hazard on both local and regional scales. While it is important to understand the physical states of active volcanic fields, it is difficult or impossible to directly observe active magma emplacement. Because of this, observing an exposed magmatic plumbing system may enable further efforts to describe active volcanic fields. The magmatic plumbing system of a Pliocene-aged monogenetic volcanic field is currently exposed as a sill and dike swarm in the San Rafael Desert of Central Utah. Alkali diabase and shonkinitic sills and dikes in this region intruded into Mesozoic sedimentary units of the Colorado Plateau and now make up the most erosion resistant units, forming mesas, ridges, and small peaks associated with sills, dikes, and plug-like bodies respectively. Diez et al. (Lithosphere, 2009) and Kiyosugi et al. (Geology, 2012) provide evidence that each cylindrical plug-like body represents a conduit that once fed one volcano. The approximate original depth of the currently exposed swarm is estimated to be 0.8 km. Volcanic and sedimentary materials may be discriminated at very high resolution with the use of Light Detection and Ranging (LiDAR). LiDAR produces a three dimensional point cloud, where each point has an associated return intensity. High resolution, bare earth digital elevation models (DEMs) can be produced after vegetation is identified and removed from the dataset. The return intensity at each point can enable classification as either sedimentary or volcanic rock. A Terrestrial LiDAR Survey (TLS) has been carried out to map a large hill with at least one volcanic conduit at its core. This survey implements a RIEGL VZ-400 3D Laser Scanner, which successfully maps solid objects in line-of-sight and within 600 meters. The laser used has a near infrared wavelength. The scanner is set up at 11 scan positions around the conduit edifice, enabling the creation of a 3D point cloud for the edifice and surrounding surface geology. Vegetation is then removed and the point cloud is georeferenced to create a bare earth DEM. Points are assigned RGB color values using calibrated photographs taken coincident to the laser scanning. With the processed LiDAR point cloud, volcanic and sedimentary materials may be discriminated by return intensity and RGB color values. We find that intrusive material returns a demonstrably lower intensity signal than the lighter sedimentary units. Along with field mapping during the TLS, this information can provide high resolution detail of the local magma plumbing system. Exposed dikes, sills, and conduits mapped by this survey are extrapolated into a 3D space from the top of the edifice the base election of the survey to provide a first-order estimate of the final intrusive volume of the now eroded volcanic field in this location.

Faults and volcanoes: Main volcanic structures in the Acambay Graben, Mexico

NASA Astrophysics Data System (ADS)

Aguirre-Diaz, G. J.; Pedrazzi, D.; Suñe-Puchol, I.; Lacan, P.

2016-12-01

The Mexican Volcanic Belt (MVB) province is best known by the major stratovolcanoes, such as Popocatepetl and Colima, but most of the province is formed by modest size stratovolcanoes and monogenetic cones. Regional fault systems were developed together with the building of the volcanic province; the most notorious one is Chapala-Tula Fault System (CTFS), which runs parallel to the central sector of the MVB, and thus it is also referred to as the Intra-Arc fault system. Acambay graben (AG) is part of this central system. It is a 20 x 70 km depression located 100 km to the NW of Mexico City, at the easternmost end of the E-W trending CTFS, and was formed as the result of NS to NE oriented extension. Seismically active normal faults, such as the Acambay-Tixmadejé fault, with a mB =7 earthquake in 1912, delimit the AG. The graben includes several volcanic structures and associated deposits ranging in age from Miocene to 3 ka. The main structures are two stratovolcanoes, Altamirano (900 m high) and Temascalcingo (800 m high). There are also several Miocene-Pliocene lava domes, and Quaternary small cinder cones and shield volcanoes. Faulting of the Acambay graben affects all these volcanic forms, but depending on their ages, the volcanoes are cut by several faults or by a few. That is the case of Altamirano and Temascalcingo volcanoes, where the former is almost unaffected whereas the latter is highly dissected by faults. Altamirano is younger than Temascalcingo; youngest pyroclastic deposits from Altamirano are dated at 12-3 ka, and those from Temascalcingo at 40-25 ka (radiocarbon ages). The relatively young ages found in volcanic deposits within the Acambay graben raise the volcanic danger level in this area, originally marked as an inactive volcanic zone, but activity could restart at any time. Supported by DGAPA-PAPIIT-UNAM grant IN-104615.

Fault propagation folds induced by gravitational failure and slumping of the Central Costa Rica volcanic range: Implications for large terrestrial and Martian volcanic edifices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borgia, A.; Burr, J.; Montero, W.

1990-08-30

Long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress. In contrast, the ridges bordering the Central Costa Rica volcanic range (CCRVR) are the topographic expression of hanging wall asymmetric angular anticlines overlying low-angle thrust faults at the base of the range. These faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20,000 years. These anticlines are hypothesized to occur alongmore » the base of the volcano, where the thrust faults ramp up toward the sea bottom. Ridges and scarps between 2,000 and 5,000 m below sea level are interpreted as the topographic expression of these folds. The authors further suggest that the scarps of the CCRVR and valid scaled terrestrial analogs of the perimeter scarp of the Martian volcano Olympus Mons. They suggest that the crust below Olympus Mons has failed under the load of the volcano, triggering the radial slumping of the flanks of the volcano on basal thrusts. The thrusting would have, in turn, formed the anticlinal ridges and scarps that surround the edifice. The thrust faults may extend all the way to the base of the Martian crust (about 40 km), and they may have been active until almost the end of the volcanic activity. They suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices. In the CCRVR this slumping of the flanks is a slow intermittent process, but it could evolve to rapid massive avalanching leading to catastrophic eruptions. Thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards.« less

The influence of regional extensional tectonic stress on the eruptive behaviour of subduction-zone volcanoes

NASA Astrophysics Data System (ADS)

Tost, M.; Cronin, S. J.

2015-12-01

Regional tectonic stress is considered a trigger mechanism for explosive volcanic activity, but the related mechanisms at depth are not well understood. The unique geological setting of Ruapehu, New Zealand, allows investigation on the effect of enhanced regional extensional crustal tension on the eruptive behaviour of subduction-zone volcanoes. The composite cone is located at the southwestern terminus of the Taupo Volcanic Zone, one of the most active silicic magma systems on Earth, which extends through the central part of New Zealand's North Island. Rhyolitic caldera eruptions are limited to its central part where crustal extension is highest, whereas lower extension and additional dextral shear dominate in the southwestern and northeastern segments characterized by andesitic volcanism. South of Ruapehu, the intra-arc rift zone traverses into a compressional geological setting with updoming marine sequences dissected by reverse and normal faults. The current eruptive behaviour of Ruapehu is dominated by small-scaled vulcanian eruptions, but our studies indicate that subplinian to plinian eruptions have frequently occurred since ≥340 ka and were usually preceded by major rhyolitic caldera unrest in the Taupo Volcanic Zone. Pre-existing structures related to the NNW-SSE trending subduction-zone setting are thought to extend at depth and create preferred pathways for the silicic magma bodies, which may facilitate the development of large (>100 km3) dyke-like upper-crustal storage systems prior to major caldera activity. This may cause enhanced extensional stress throughout the entire intra-arc setting, including the Ruapehu area. During periods of caldera dormancy, the thick crust underlying the volcano and the enhanced dextral share rate likely impede ascent of larger andesitic magma bodies, and storage of andesitic melts dominantly occurs within small-scaled magma bodies at middle- to lower-crustal levels. During episodes of major caldera unrest, ascent and storage of voluminous rhyolitic magma bodies at upper crustal levels may cause the extensional stress to supercede the dextral shear rate in the Ruapehu area, facilitating ascent of larger andesitic magma bodies at depth, and changing the volcano's eruptive behaviour from dominantly vulcanian to violently subplinian/plinian.

California's Vulnerability to Volcanic Hazards: What's at Risk?

NASA Astrophysics Data System (ADS)

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

2015-12-01

California is a leader in comprehensive planning for devastating earthquakes, landslides, floods, and tsunamis. Far less attention, however, has focused on the potentially devastating impact of volcanic eruptions, despite the fact that they occur in the State about as frequently as the largest earthquakes on the San Andreas Fault Zone. At least 10 eruptions have occurred in the past 1,000 years—most recently in northern California (Lassen Peak 1914 to 1917)—and future volcanic eruptions are inevitable. The likelihood of renewed volcanism in California is about one in a few hundred to one in a few thousand annually. Eight young volcanoes, ranked as Moderate to Very High Threat [1] are dispersed throughout the State. Partially molten rock (magma) resides beneath at least seven of these—Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, and Salton Buttes— causing earthquakes, toxic gas emissions, hydrothermal activity, and (or) ground deformation. Understanding the hazards and identifying what is at risk are the first steps in building community resilience to volcanic disasters. This study, prepared in collaboration with the State of California Governor's Office of Emergency Management and the California Geological Survey, provides a broad perspective on the State's exposure to volcano hazards by integrating mapped volcano hazard zones with geospatial data on at-risk populations, infrastructure, and resources. The study reveals that ~ 16 million acres fall within California's volcano hazard zones, along with ~ 190 thousand permanent and 22 million transitory populations. Additionally, far-field disruption to key water delivery systems, agriculture, utilities, and air traffic is likely. Further site- and sector-specific analyses will lead to improved hazard mitigation efforts and more effective disaster response and recovery. [1] "Volcanic Threat and Monitoring Capabilities in the United States," http://pubs.usgs.gov/of/2005/1164/

Lidar detection of carbon dioxide in volcanic plumes

NASA Astrophysics Data System (ADS)

Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Maio, Giovanni; Del Franco, Mario; Aiuppa, Alessandro

2015-06-01

Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. Two differential absorption lidar instruments will be presented in this paper: BILLI (BrIdge voLcanic LIdar), based on injection seeded Nd:YAG laser, double grating dye laser, difference frequency mixing (DFM) and optical parametric amplifier (OPA), and VULLI (VULcamed Lidar), based on injection seeded Nd:YAG laser and optical parametric oscillator (OPO). The first one is funded by the ERC (European Research Council) project BRIDGE and the second one by the ERDF (European Regional Development Fund) project VULCAMED. While VULLI has not yet been tested in a volcanic site, BILLI scanned the gas emitted by Pozzuoli Solfatara (Campi Flegrei volcanic area, Naples, Italy) during a field campaign carried out from 13 to 17 October 2014. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater area. Lidar measurements were in good agreement with well-established techniques, based on different operating principles. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar, representing the first direct measurement of this kind ever performed on an active volcano and showing the high potential of laser remote sensing in geophysical research.

Volcanic and nonvolcanic rifted margins of the Red Sea and Gulf of Aden: Crustal cooling and margin evolution in Yemen

NASA Astrophysics Data System (ADS)

Menzies, Martin; Gallagher, Kerry; Yelland, Andrew; Hurford, Anthony J.

1997-06-01

New apatite fission track (AFT) data from the southern Red Sea volcanic and the Gulf of Aden nonvolcanic margins provide important constraints on the timing of crustal cooling relative to periods of volcanism and lithosphere extension. The AFT data define several regions of extension immediately adjacent to the Red Sea margin with AFT ages < 25 Ma and track-length distributions consistent with rapid cooling. Elevated Precambrian basement highs on the rift shoulder have AFT ages ≫ 100 Ma and track-length distributions indicative of a complex pre-rift history. An intervening area along the Red Sea and Gulf of Aden margins, and inland along the Balhaf graben (Jurassic rift), has AFT ages of 25-100 Ma. and track-length distributions indicative of rapid cooling. Elevated Precambrian basement highs are juxtaposed against topographically lower extended coastal terranes with sharp contrasts in AFT ages and track-length distributions, pointing to possible reactivation in the Tertiary of lineaments of Precambrian and Jurassic age. Integration of field observations with AFT data and 40Ar/ 39Ar data indicates that, on the Red Sea volcanic margin, surface uplift was initiated immediately prior to volcanism and that cooling was synchronous with widespread extension and an apparent hiatus in voluminous volcanic activity.

Origin and potential geothermal significance of China Hat and other late Pleistocene topaz rhyolite lava domes of the Blackfoot Volcanic Field, SE Idaho

NASA Astrophysics Data System (ADS)

McCurry, M. O.; Pearson, D. M.; Welhan, J. A.; Kobs-Nawotniak, S. E.; Fisher, M. A.

2014-12-01

The Snake River Plain and neighboring regions are well known for their high heat flow and robust Neogene-Quaternary tectonic and magmatic activity. Interestingly, however, there are comparatively few surficial manifestations of geothermal activity. This study is part of a renewed examination of this region as a possible hidden or blind geothermal resource. We present a testable, integrated volcanological, petrogenetic, tectonic and hydrothermal conceptual model for 57 ka China Hat and cogenetic topaz rhyolite lava domes of the Blackfoot Volcanic Field. This field is well suited for analysis as a blind resource because of its distinctive combination of (1) young bimodal volcanism, petrogenetic evidence of shallow magma storage and evolution, presence of coeval extension, voluminous travertine deposits, and C- and He-isotopic evidence of active magma degassing; (2) a paucity of hot springs or other obvious indicators of a geothermal resource in the immediate vicinity of the lava domes; and (3) proximity to a region of high crustal heat flow, high-T geothermal fluids at 2.5-5 km depth and micro-seismicity characterized by its swarming nature. Eruptions of both basalt and rhyolite commonly evolve from minor phreatomagmatic to effusive. In our model, transport of both magmatic and possible deep crustal aqueous fluids may be controlled by preexisting crustal structures, including west-dipping thrust faults. Geochemical evolution of rhyolite magma is dominated by mid- to upper-crustal fractional crystallization (with pre-eruption storage and phenocryst formation at ~14 km). Approximately 1.2 km3 of topaz rhyolite have been erupted since 1.4 Ma, yielding an average eruption rate of 0.8 km3/m.y. Given reasonable assumptions of magma cumulate formation and eruption rates, and initial and final volatile concentrations, we infer average H2O and CO2 volatile fluxes from the rhyolite source region of ~2MT/year and 340 T/day, respectively. Lithium flux may be comparable to CO2.

­­­­High-Resolution Mapping of Kick`em Jenny Submarine Volcano and Associated Landslides

NASA Astrophysics Data System (ADS)

Ruchala, T. L.; Carey, S.; Hart, L.; Chen, M.; Scott, C.; Tominaga, M.; Dondin, F. J. Y.; Fujii, M.

2016-02-01

To understand the physical and geological processes that drive the volcanism and control the morphology of Kick`em Jenny (KEJ) volcano, the only active submarine volcano in the in the Lesser Antilles volcanic arc, we conducted near-source, high-resolution mapping of KEJ and its subsurface using the Remotely Operated Vehicle (ROV) Hercules during cruise NA054 of the E/V Nautilus (Sept.-Oct. 2014). Shipboard bathymetric data (EM302 system) and slope analysis maps were used to decipher the detailed seafloor morphology surrounding KEJ. Multiple generations of submarine landslides and canyons were observed, suggesting the area has been hosting dynamic sediment transport systems at multiple scales over time. Some of them might have been associated by past eruptions. Clear contacts between partially lithified carbonate sediments and volcanic formations were identified from ROV videos at the middle of the landslide slope face. Detailed observations of facies on these exposures provide constraints on the time intervals between landslide events along the western slope of KEJ. ROV video imagery also identified outcrops of columnar basalts located in the middle of the landslide deposits. These are similar in appearance to those observed in the KEJ crater during previous ROV dives, indicating a possible travel distance of volcanic materials from the crater region along landslide path. High-resolution photo mosaics, bathymetry, and magnetic data acquired by ROV Hercules were used to investigate geological processes and the possible volcanic source of landslide material within the KEJ crater. Mapping in the northwestern part of the crater floor revealed distinctive regions, including (i) microbial mats, (ii) active hydrothermal vent sites; (iii) landforms curved by channelized bottom current where seafloor is outcropped; and (iv) coarse scree the distribution of which may correlate with the distance from the crater rim. Near-bottom magnetic profiles show coherent magnetic signatures with correlatable high amplitude anomalies located in the middle of the KEJ crater.

Late Miocene (Proto-Gulf) Extension and Magmatism on the Sonoran Margin

NASA Astrophysics Data System (ADS)

Gans, P.; MacMillan, I.; Roldan-Quintana, J.

2003-12-01

Constraints on the magnitude and character of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California extensional province are key to understanding how and when Baja California was captured by the Pacific plate and how strain was partitioned during the early stages of this transtensional rift system. Our new geologic mapping in southwestern Sonora and 40Ar/39Ar dating of pre-, syn-, and post-tectonic volcanic units indicate that late Miocene deformation and volcanic activity were largely restricted to a NW-trending, 100-120 km wide belt adjacent to the coast. Inboard of this belt, NW-SE extension is mainly older (>15 Ma) and occurred in an intra-arc or back-arc setting. Proto-Gulf deformation within the coastal belt was profoundly transtensional, with NW-striking, dextral strike slip faults operating in concert with N-S and NNE-striking normal and oblique slip faults to produce an inferred NW or NNW tectonic transport direction. The total amount of late Miocene NW directed dextral shear within the coastal belt is still poorly constrained, but may exceed 100 km. The locus of deformation and volcanic activity migrated westward or northwestward within the Sonoran coastal belt. in the eastern portion (Sierra Libre and Sierra El Bacatete) major volcanic activity commenced at ˜13.0 Ma and peaked at 12.0 Ma, and major faulting and tilting is bracketed between 12.0 and 10.6 Ma. Further west in the Sierra El Aguaje/San Carlos region, major volcanic activity commenced at 11.5 Ma and peaked at 10.5 Ma, and most faulting and tilting is bracketed between 10.7 and 9.3 Ma. On the coastal mountains northwest of San Carlos, rift related faulting and tilting continued after 8.5 Ma. Voluminous late Miocene (13-8 Ma) volcanic rocks within the Sonoran coastal belt were erupted from numerous centers (e.g. Sierra Libre, Guaymas, Sierra El Aguaje). These thick volcanic sections are compositionally diverse (basalt to rhyolite, with abundant dacite and andesite), and are intimately associated in space and time with tectonic activity. Overall, the Sonoran coastal belt provides a spectacular example of distributed transtension and associated magmatism that ultimately led to rupturing of the continental lithosphere.

SYSTHESIS OF VOLCANISM STUDIES FOR THE YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perry, F. V.; Crowe, G. A.; Valentine, G. A.

1997-09-23

This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certaintymore » but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. Geochemical and isotopic data are presented for post-Miocene basalts of the Yucca Mountain region. Alternative petrogenetic models are assessed for the formation of the Lathrop Wells volcanic center. Based on geochemical data, basaltic ash in fault trenches near Yucca Mountain is shown to have originated from the Lathrop Wells center. Chapter 5 synthesizes eruptive and subsurface effects of basaltic volcanism on a potential repository and summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Chapter 6 synthesizes current knowledge of the probability of disruption of a potential repository at Yucca Mountain. In 1996, an Expert Elicitation panel was convened by DOE that independently conducted PVHA for the Yucca Mountain site. Chapter 6 does not attempt to revise this PVHA; instead, it further examines the sensitivity of variables in PVHA. The approaches and results of PVHA by the expert judgment panel are evaluated and incorporated throughout this chapter. The disruption ratio (E2) is completely re-evaluated using simulation modeling that describes volcanic events based on the geometry of basaltic feeder dikes. New estimates of probability bounds are developed. These comparisons show that it is physically implausible for the probability of magmatic disruption of the Yucca Mountain site to be greater than 10{sup -7} events per year. Bounding probability estimates are used to assess possible implications of not drilling aeromagnetic anomalies in the Arnargosa Valley and Crater Flat. The results of simulation modeling are used to assess the sensitivity of the disruption probability for the location of northeast boundaries of volcanic zones near the Yucca Mountain site. A new section on modeling of radiological releases associated with surface and subsurface magmatic activity has been added to chapter 6. The modeling results are consistent with past total system performance assessments that show future volcanic and magmatic events are not significant components of repository performance and volcanism is not a priority issue for performance assessment studies.« less

Vegetation component of geothermal EIS studies: Introduced plants, ecosystem stability, and geothermal development

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

This paper contributes new information about the impacts from introduced plant invasions on the native Hawaiian vegetation as consequences of land disturbance and geothermal development activities. In this regard, most geothermal development is expected to act as another recurring source of physical disturbance which favors the spread and maintenance of introduced organisms throughout the region. Where geothermal exploration and development activities extend beyond existing agricultural and residential development, they will become the initial or sole source of disturbance to the naturalized vegetation of the area. Kilauea has a unique ecosystem adapted to the dynamics of a volcanically active landscape. Themore » characteristics of this ecosystem need to be realized in order to understand the major threats to the ecosystem and to evaluate the effects of and mitigation for geothermal development in Puna. The native Puna vegetation is well adapted to disturbances associated with volcanic eruption, but it is ill-adapted to compete with alien plant species in secondary disturbances produced by human activities. Introduced plant and animal species have become a major threat to the continued presence of the native biota in the Puna region of reference.« less

Geomorphological insights on human-volcano interactions and use of volcanic materials in pre-Hispanic cultures of Costa Rica through the Holocene

NASA Astrophysics Data System (ADS)

Ruiz, Paulo; Mana, Sara; Gutiérrez, Amalia; Alarcón, Gerardo; Garro, José; Soto, Gerardo J.

2018-02-01

Critical Zones in tropical environments, especially near active volcanoes, are rich in resources such as water, food and construction materials. In Central America, people have lived near volcanic centers for thousands of years and learned to take advantage of these resources. Understanding how pre-Hispanic societies lived in this type of Critical Zones and interacted with volcanoes, provides us with insights on how to reduce the negative impact derived from volcanic activity in modern cities. In this multidisciplinary approach we focus on two case studies in Costa Rica near Poás and Turrialba volcanoes, which are currently active, in order to obtain a comprehensive view of human-volcano interactions through time. We use a methodology based on historical accounts, geological and archaeological fieldwork, geomorphological characterization based on remote sensing techniques and past (pre-Hispanic), and present land use analysis. The northern Poás region represents a case of a poorly developed pre-Hispanic society, which subsisted mainly on hunting and gathering activities, had no permanent settlements and was probably affected by the activity of the Hule and Río Cuarto maars. In spite of their vulnerability and lack of infrastructure, they used geomorphology to their advantage, achieving natural protection. Conversely, the Guayabo National Monument near Turrialba Volcano represents a cultural peak in pre-Hispanic societies in Costa Rica. Archaeological remains and structures at this site indicate that this society had a good understanding of physical and geological processes and was therefore able to take advantage of natural resources for water and food supply, construction, and protection as well as hazard prevention and mitigation. The use of new technologies, some accessible and low-cost such as Google Earth and others with restricted access and higher costs such as LiDAR, allowed us to complete a rapid and efficient characterization of land use and geomorphological features of the study area. This study helps to establish how some locations near volcanic edifices are more prone the effects of volcanic hazards than others and why this data should be included in volcanic risk assessment and land planning processes.

Geodynamic features along the Christianna-Santorini-Kolumbo tectonic line (South Aegean Sea, Greece)

NASA Astrophysics Data System (ADS)

Nomikou, Paraskevi; Papanikolaou, Dimitrios; Carey, Steve; Bejelou, Konstantina; Sakellariou, Dimitris; Kilias, Stefanos; Camilli, Rich; Escartin, Javier; Bell, Kathrine; Parks, Michelle

2013-04-01

Numerous oceanographic surveys have been conducted in Santorini Volcanic Group (South Aegean Sea) since 2001, revealing the spectacular morphology of the seafloor (multibeam data) and the sub-seafloor stratigraphic horizons (seismic profiles). Technological advancements in seafloor exploration such as ROVs and a submersible, enabled us to observe products of submarine volcanism that were previously inaccessible. In addition, gravity and box coring, geological and biological samples have been collected from selected areas for further analysis. The offshore geophysical survey in Santorini shows that recent volcanism occurred along a NE-SW tectonic zone named as Christianna-Santorini-Kolumbo (CSK) line. Christiana islets and three newly discovered submarine volcanic domes, with small colonies of yellow, presumably sulfur-reducing hydrothermal bacteria, occur in the southwestern part of the line. The presently active intra caldera volcanic domes of Palea and Nea Kameni islands and the low temperature (17-24°C) vent mounds covered by yellowish bacterial mat occupy the middle part of the line. The Santorini vent field is linked with the Kolumbo normal fault onshore which is likely controlling the pathways of hydrothermal circulation within the caldera. The most prominent feature at the NE part of this zone, is Kolumbo submarine volcanic chain which is extended 20Km with several volcanic domes aligned along this direction. The Kolumbo volcano had an explosive eruption in 1650 that killed 70 people on Santorini. The hydrothermal vent field in the crater floor of Kolumbo consists dominantly of active and inactive sulfide-sulfate structures in the form of vertical spires and pinnacles, mounds and flanges along a NE-SW trend, with temperatures up to 220°C and vigorous CO2 gas emission. For several years, the highest frequency of earthquakes was concentrated mainly in the vicinity of Kolumbo volcano. However, during 2011-2012 both seismic and geodetic unrest began abruptly inside Santorini caldera related to a shallow magmatic intrusion indicated by inflation. Recently, several earthquakes occurred in the region south of Christianna at the SW edge of the CSK line. This CSK line has possibly fed the post-caldera eruptions and is the main path for fluid circulation. In conclusion, the CSK tectonic line displays a special character in terms of morphology, volcanism, hydrothermal activity, seismicity and tectonic structure. It may cause important geohazards to the highly touristic Santorini island. Further seafloor investigations along this active line can provide insights into the overall geodynamic activity and aid the archipelago's hazard preparedness.

NASA MEVTV Program Working Group Meeting: Volcanism on Mars

NASA Technical Reports Server (NTRS)

1988-01-01

The purpose of this working group meeting is to focus predominantly on volcanism on Mars, prior to considering the more complex issues of interactions between volcanism and tectonism or between volcanism and global or regional volatile evolution. It is also hoped that the topical areas of research identified will aid the planetary geology community in understanding volcanism on Mars and its relationship to other physical processes.

Lunar cryptomare: Analysis of mineralogy and distribution of ancient volcanic deposits

NASA Astrophysics Data System (ADS)

Whitten, J.; Head, J. W.; Pieters, C. M.; Kreslavsky, M. A.; Hiesinger, H.

2012-12-01

Early volcanic deposits have been almost completely erased by plate tectonics on Earth, but they remain relatively well preserved on some of the other terrestrial planetary bodies, especially the Moon. Ancient volcanic smooth plains on the Moon are referred to as cryptomaria [Head and Wilson, 1992], described as smooth volcanic deposits that have been covered post-emplacement with high albedo feldspathic regolith. Identification of cryptomare deposits is facilitated by the presence of dark-halo craters, which are typically simple craters excavating mafic material from below the feldspathic light plains regolith layer [e.g., Schultz and Spudis, 1979], and highly mafic soils. Isotopic age data from the Apollo and lunar meteorite sample collections combined with crater statistics and stratigraphic relationships indicate that cryptomare deposits were emplaced around the period of latest basin formation. Many questions about cryptomare deposits remain: Were they emplaced in ancient lunar basins or are they associated with intercrater areas? What is their areal extent? What is the mineralogy of these deposits? Does it vary spatially or temporally? Analysis with the highest resolution datasets could address several of these questions and help to refine our knowledge of the extent and character of early lunar volcanism. For this study cryptomare to the west of Oceanus Procellarum, as well as other previously identified regions (e.g., Mendel-Ryberg, Tsiolkovskiy, etc.), were selected for analysis based on their different geologic settings. To better understand early eruption conditions it is important to compare deposit locations and look for trends in geologic setting. Analysis of previously mapped cryptomare in the Schiller-Schickard region has established a method for deposit identification and is applied in this study to map and characterize the composition of the early volcanic deposits in other areas of the Moon [Whitten et al., 2012]. Lunar Orbiter Laser Altimeter (LOLA) data are being used to understand the geologic context and surface roughness of these ancient volcanic deposits and Lunar Reconnaissance Orbiter Camera (LROC) image data are used to identify the exposure of lower albedo material or small dark-halo craters and also to help narrow down the boundary of the cryptomare deposits. In addition to topographic and image data, mineralogy data from the Moon Mineralogy Mapper (M3) instrument are being used to identify cryptomare deposits and to measure the compositional variability of the exposed mafic regions in these deposits. The measured mineral compositions of cryptomare deposits from dark-halo craters are compared with spectra collected from exposed mare deposits to determine if there are observable compositional differences. Our analyses support previous interpretations in the Schiller-Schickard region that suggest that the composition of volcanic deposits did not changed significantly during the ≥100 Ma of volcanic activity and that at least some of the cryptomare deposits in the region were emplaced in the Schiller-Zucchius basin. References Head, J.W. and L. Wilson, (1992) GCA, 55, 2155-2175. Schultz, P.H. and P.D. Spudis, (1079) Proc. Lunar Planet. Sci. Conf., 10th, 2899-2918. Whitten, J.L., J.W. Head, C.M. Pieters and H. Hiesinger, (2012) Lunar Sci. Forum, Abstract #592.

Petrogenesis of mid-Miocene rhyolites from the Idaho-Oregon-Nevada region, USA: Implications from feldspar Sr and Pb isotope data

NASA Astrophysics Data System (ADS)

Wypych, A.; Hart, W. K.

2012-12-01

The Idaho-Oregon-Nevada (ION) region provides an excellent natural laboratory for studying the complex processes that form continental crust. During the Oligocene-Miocene, the ION region underwent widespread extension and volcanism with bimodal (silicic and mafic) volcanism dominating the mid-Miocene [1]. This bimodal volcanism is temporally related to the main Columbia River flood basalt activity to the north, and initiated with mafic eruptions at ~17 Ma, followed closely by silicic magmatism at ~16.5 Ma. This intimate link between mafic and silicic activity continued until ~13 Ma. The ION region is situated on a boundary between Proterozoic cratonic lithosphere to the east and Mesozoic accreted terrains to the west as defined by Sr and Nd isotopic compositions. In this region, however, the boundary is not sharp and distinctive, but rather forms a heterogeneous "transitional zone" between the two lithospheric domains. Another feature adding to the complexity of this region is the fact that it lies at the junction of two major volcanic trends: the Snake River Plain- Yellowstone (SRP-Y) progressing in time and space to the northeast and the High Lava Plains - Newberry (HPL-N) progressing to the northwest. The ION region volcanism as well as the SRP-Y and HLP-N volcanic trends is caused by mantle upwelling behind the subducting Juan de Fuca slab, voluminous mafic magma injections into the crust, melting of spatially, temporally, and compositionally heterogeneous crust, and mixing of the primitive and more evolved products [1,2,3]. An ongoing petrographic, major and trace element and Sr-Nd-Pb-Hf isotope investigation of 24 pairs of glass separates and whole rock samples from five ION silicic centers representing a west (off-craton) to east (on-craton) transect across this zone of transitional lithosphere provides evidence of open system processes involved in the production of the silicic material as well as spatial, temporal and compositional diversity within and between the silicic centers [4]. The samples demonstrate involvement of fractional crystallization of less evolved mafic material along with assimilation of partial crustal melts, however the degree of involvement of each process remains difficult to quantify, as do the contributions from mantle and crustal reservoirs. To further investigate these issues, we here present petrological, major and trace element, along with lead and strontium isotopic examination of feldspar crystals from three selected silicic centers: 1) westernmost, off-craton, 2) central region of transitional lithosphere, and 3) eastern transition zone to on-craton. The textural evidence for open system behavior is only partially supported by bulk feldspar Pb and Sr isotopic compositions where the differences between whole rock, glass and crystal separate aliquots of the same eruptive units are a maximum of 0.3 in 208Pb/204Pb, 0.2 in 206Pb/204Pb and 0.002 in 87Sr/86Sr. Models combining these results with the spatial availability of geochemically distinct magma source reservoirs will be discussed. [1] Brueseke et al. (2008) Bull. Volc. 70, 343-360. [2] Nash et al. (2006) Earth Plant. Sci. Lett. 247, 143-156. [3] Christiansen and McCurry (2008) Bull. Volc., 70, 251-267. [4] Wypych and Hart (2011) Min. Magazine, 75 (3), 2186.

The Distribution of Subsurface Water at Hadriaca and Tyrrhena Paterae and Surrounding Areas on Mars from Impact Crater Morphology

NASA Astrophysics Data System (ADS)

Lancaster, M. G.; Guest, J. E.

1996-03-01

It is well established that the surface of Mars exhibits abundant evidence for the presence of either liquid or frozen water during the course of Martian history. The origin, location, extent and transport of this water is of critical importance in the understanding of Martian geology and climate. In particular, the fluid appearance of rampart crater ejecta has been cited as evidence for subsurface ice at the time of impact. Ejecta morphology has proven to be a useful tool for studying the distribution of subsurface ice on Mars. It is possible that in some regions the concentration and distribution of subsurface ice has been affected by volcanic processes, either in the melting and/or mobilisation of existing subsurface water, and/or in the injection of juvenile water into the martian crust. The presence of water may also have affected the style of volcanic eruptions on Mars, increasing the volatile content of rising magmas and generating explosive activity. We are currently investigating the abundance and role of water in the evolution of the volcanoes Hadriaca and Tyrrhena Patera and surrounding highlands northeast of the Hellas Basin. The morphology of these volcanoes has been attributed to explosive volcanism, and to the presence of substantial amounts of water in the regolith at the time of their eruption. The location of Hadriaca Patera in a region containing channelled plains, debris flows, and pitted plains, together with the style of erosion of the volcano flanks suggests presence of volatile-rich surface materials or fluvial or periglacial activity. This work is a continuation of research undertaken by Cave in the Elysium Mons Region, where ice was found to be enriched at depth in the Elysium Lavas. We are performing a similar analysis for the volcanics of Hadriaca and Tyrrhena Paterae. A database containing information on the location, size, morphology, ejecta characteristics and degradation state of several hundred impact craters displaying ejecta in the region of Mars between the equator and 40 degrees S, and from 225 degrees to 275 degrees W is therefore being compiled.

Late Mesozoic-Cenozoic intraplate magmatism in Central Asia and its relation with mantle diapirism: Evidence from the South Khangai volcanic region, Mongolia

NASA Astrophysics Data System (ADS)

Yarmolyuk, Vladimir V.; Kudryashova, Ekaterina A.; Kozlovsky, Alexander M.; Lebedev, Vladimir A.; Savatenkov, Valery M.

2015-11-01

The South Khangai volcanic region (SKVR) comprises fields of Late Mesozoic-Cenozoic volcanic rocks scattered over southern and central Mongolia. Evolution of the region from the Late Jurassic to the Late Cenozoic includes 13 successive igneous episodes that are more or less evenly distributed in time. Major patterns in the distribution of different-aged volcanic complexes were controlled by a systematic temporal migration of volcanic centers over the region. The total length of their trajectory exceeds 1600 km. Principle characteristics of local magmatism are determined. The composition of igneous rocks varies from basanites to rhyolites (predominantly, high-K rocks), with geochemistry close to that of OIB. The rock composition, however, underwent transformations in the Mesozoic-Cenozoic. Rejuvenation of mafic rocks is accompanied by decrease in the contents of HREE and increase of Nb and Ta. According to isotope data, the SKVR magmatic melts were derived from three isotope sources that differed in the Sr, Nd, and Pb isotopic compositions and successively alternated in time. In the Early Cretaceous, the predominant source composition was controlled by interaction of the EMII- and PREMA-type mantle materials. The PREMA-type mantle material dominated quantitatively in the Late Cretaceous and initial Early Cenozoic. From the latest Early Cenozoic to Late Cenozoic, the magma source also contained the EMI-type material along with the PREMA-type. The structural fabric, rock composition, major evolutionary pattern, and inner structure of SKVR generally comply with the criteria used to distinguish the mantle plume-related regions. Analogous features can be seen in other regions of recent volcanism in Central Asia (South Baikal, Udokan, Vitim, and Tok Stanovik). The structural autonomy of these regions suggests that distribution of the Late Mesozoic-Cenozoic volcanism in Central Asia was controlled by a group of relatively small hot finger-type mantle plumes associated with the common hot mantle field of Central Asia.

Using Intensive Variables to Constrain Magma Source Regions

NASA Astrophysics Data System (ADS)

Edwards, B. R.; Russell, J. K.

2006-05-01

In the modern world of petrology, magma source region characterization is commonly the realm of trace element and isotopic geochemistry. However, major element analyses of rocks representing magmatic compositions can also be used to constrain source region charactertistics, which enhance the results of isotopic and trace element studies. We show examples from the northern Cordilleran volcanic province (NCVP), in the Canadian Cordillera, where estimations of thermodynamic intensive variables are used to resolve different source regions for mafic alkaline magmas. We have taken a non-traditional approach to using the compositions of three groups of mafic, alkaline rocks to characterize the source regions of magmas erupted in the NCVP. Based on measured Fe2O3 and FeO in rocks from different locations, the Atlin volcanic district (AVD), the Fort Selkirk volcanic complex (FSVC), the West Tuya volcanic field, (WTVF), we have estimated oxygen fugacities (fO2) for the source regions of magmas based on the model of Kress and Carmichael (1991) and the computational package MELTS/pMelts (Ghiorso and Sack, 1995; Ghiorso et al., 2002). We also have used Melts/pMelts to estimate liquidus conditions for the compositions represented by the samples as well as activities of major element components. The results of our calculations are useful for distinguishing between three presumably different magma series: alkaline basalts, basanites, and nephelinites (Francis and Ludden, 1990; 1995). Calculated intensive variables (fO2, activities SiO2, KAlSiO4, Na2SiO3) show clear separation of the samples into two groups: i) nephelinites and ii) basanites/alkaline basalts. The separation is especially evident on plots of log fO2 versus activity SiO2. The source region for nephelinitic magmas in the AVD is up to 2 log units more oxidized than that for the basanites/basalts as well as having a distinctly lower range of activities of SiO2. Accepting that our assumptions about the magmas representing source region conditions are valid, these thermodynamic constraints on the source regions clearly indicate two things: the nephelinites and basanites/basalts could not have originated from the same source regions, and the basanites and basalts could have originated from the same source regions. We suggest that computation of intensive variables for magma source regions is a logical complement to standard trace element and isotopic studies. -Francis, D. and Ludden, J., (1990) The mantle source for olivine nephelinite, basanite and alkaline olivine basalts at Fort Selkirk, Yukon, Canada: Journal of Petrology, 31, p. 371-400. -Francis, D. and Ludden, J., (1995) The signature of amphibole in mafic alkaline lavas, a study in the northern Canadian Cordillera: Journal of Petrology, 36, p. 1171-1191. -Ghiorso, MS., and Sack, RO. (1995) Chemical Mass Transfer in Magmatic Processes. IV. A Revised and Internally Consistent Thermodynamic Model for the Interpolation and Extrapolation of Liquid-Solid Equilibria in Magmatic Systems at Elevated Temperatures and Pressures. Contributions to Mineralogy and Petrology, 119, 197-212. -Ghiorso, MS., Hirschmann, MM., Reiners, PW., and Kress, VC. III (2002) The pMELTS: An revision of MELTS aimed at improving calculation of phase relations and major element partitioning involved in partial melting of the mantle at pressures up to 3 GPa. Geochemistry, Geophysics, Geosystems 3(5), 10.1029/2001GC000217.

The Mountains of Io: Global and Geological Perspectives from Voyager and Galileo

NASA Technical Reports Server (NTRS)

Schenk, Paul; Hargitai, Henrik; Wilson, Ronda; McEwen, Alfred; Thomas, Peter; Bredekamp, Joe (Technical Monitor)

2001-01-01

To search for local and global scale geologic associations that may be related to the internal dynamics of Io, we have completed a global catalog of all mountains and volcanic centers. We have identified 115 mountain structures (covering approx. 3% of the surface) and 541 volcanic centers, including paterae (calderas and dark spots) and shield volcanoes. The average length of an Ionian mountain is 157 km, with the longest being 570 km. The mean height of Ionian mountains is 6.3 km, and the highest known mountain is Boosaule Montes (17.5 +/- 3 km). Five basic morphologic types of mountains have been identified; mesa, plateau peak, ridge, and massif. Very few mountains bear any physical similarity. to classic volcanic landforms, but many resemble flatiron mountains on Earth and are interpreted as tilted crustal blocks. This would be consistent with the hypothesis that most mountains are thrust blocks formed as a result of compressive stresses built up in the lower crust due to the global subsidence of volcanic layers as they are buried over time. More than one mechanism may be responsible for all Ionian mountains, however. The proximity of some mountains to paterae may indicate a direct link between some mountains and volcanism, although it is not always clear which came first. In contrast to earlier studies, a pronounced bimodal pattern is observed in the global distribution of both mountains and volcanic centers. The regions of highest areal densities of volcanic centers are near the sub- and anti-Jovian regions, but are offset roughly 90deg in longitude from the two, regions of greatest concentration of mountains. This anticorrelation may indicate the overprinting of a second stress field on the global compressive stresses due to subsidence. The bimodal distribution of volcanic centers and mountains is consistent with models of asthenospheric tidal heating and internal convection developed by Tackley et al.Over regions of mantle upwelling, compressive stresses in the lower crust induced by global subsidence might be reduced, encouraging volcanism and discouraging mountain building. In regions of mantle downwelling, these compressive stresses in the lower crust might be increased, discouraging volcanism and encouraging mountain building. Alternatively, the global pattern may be related to possible (but undocumented) nonsynchronous rotation of lo, which would produce two regions each of compression and extension in the crust. Evidence of layering and of mass wasting, including landslides, block sliding, debris aprons and downslope creep, on Ionian mountains suggests that the crust of Io is essentially a layered stack of partially consolidated volcanic lavas and plume deposits, becoming more consolidated with depth. The lower crust especially may also be ductily deformed, punctuated by volcanic intrusions and faulting at paterae, and broken into blocks, some of which have been uplifted to form mountains.

The NASA ASTER Urgent Request Program: The Last Eight Plus Years of Monitoring Kamchatka's Volcanoes From Space

NASA Astrophysics Data System (ADS)

Ramsey, M.; Wessels, R.; Dehn, J.; Duda, K.; Harris, A.; Watson, M.

2008-12-01

From soon after its launch in December 1999, the ASTER sensor on the NASA Terra satellite has been acquiring data of volcanic eruptions and other natural disasters around the world. ASTER has the capability to acquire high spatial resolution data from the visible to thermal infrared wavelength region. Those data, in conjunction with its ability to generate digital elevation models (DEMs), makes ASTER particularly useful for numerous aspects of volcanic remote sensing. However, the nature of the ASTER scheduling/data collection/calibration pathway makes rapid observations of hazard locations nearly impossible. The sensor's acquisitions are scheduled in advance and the data are processed and calibrated in Japan prior to archiving in the United States. This can produce a lag of at least several days from the initial request to data scheduling and another several days after acquisition until the data are available. However, there exists a manual "rapid response" mode that provides faster data scheduling, processing and availability. This mode has now been semi-automated and linked to larger-scale and more rapid monitoring alert system. The first phase has been to integrate with the Alaska Volcano Observatory's current near-real-time satellite monitoring system, which relies on high temporal/low spatial resolution orbital data. This phase of the project has focused on eruptions in the north Pacific region, and in particular over Kamchatka, Russia. Several beneficial factors have combined that resulted in over 1350 ASTER images being acquired for the five most thermally-active Kamchatka volcanoes (Bezymianny, Karimsky, Kluichevskoi, Sheveluch and Tolbachik). These factors include the orbital alignment of Terra, the high latitude of the peninsula, and the many eruptions and volcanic activity in Kamchatka. From the inception of the automated rapid response program in 2003, an additional 350 scenes have been acquired over the Kamchatka volcanoes, which have targeted both small-scale activity and larger eruptions for science and hazard response. Numerous eruptions have been observed that displayed varying volcanic styles including basaltic lava flow emplacement, silicic lava dome growth, pyroclastic flow production, volcanic ash plume production, fumarolic activity, and geothermal emission. The focus of this presentation is to summarize the current ASTER rapid response program in Kamchatka, focus on two specific eruptions of Sheveluch volcano, and discuss the future expansion plans for global hazard response.

Total electron content anomalies associated with global VEI4 + volcanic eruptions during 2002-2015

NASA Astrophysics Data System (ADS)

Li, Wang; Guo, Jinyun; Yue, Jianping; Shen, Yi; Yang, Yang

2016-10-01

In previous studies, little attention has been paid to the total electron content (TEC) anomalies preceding the volcanic eruption. We analyze the coupling relationship between volcanic eruption and TEC anomalies, and discuss the spatial distribution of TEC anomalies associated with volcanic geographical location. We utilize the global ionosphere map (GIM) data from the Center for Orbit Determination in Europe (CODE) to analyze TEC variations before the global volcanic eruptions indicated by VEI (Volcanic Explosivity Index) 4 + from 2002 to 2015 with the sliding interquartile range method. The results indicate the occurrence rate of TEC anomalies before great volcanic eruptions is related with the volcanic type and geographical position. The occurrence rate of TEC anomalies before stratovolcano and caldera eruptions is higher than that before shield and pyroclastic shield eruptions, and the occurrence rate of TEC anomalies has a descending trend from low latitudes to high latitudes. The TEC anomalies before the volcanic eruptions in low-mid latitudes are within the volcanic affected areas, but do not coincide with the volcanic foci. The corresponding TEC anomalies could be observed in the conjugated region, and all the TEC anomalies in the volcanic affected areas are usually close to bounds of equatorial anomaly zones. However, the TEC anomalies preceding these eruptions in high latitudes usually surround the volcano, and no TEC anomalies appear in the conjugated region. These conclusions have potential applications to the prediction of great volcanic eruptions in the future.

Map of Io Volcanic Heat Flow

NASA Image and Video Library

2015-09-15

This frame from an animation shows Jupiter volcanic moon Io as seen by NASA Voyager and Galileo spacecraft (at left) and the pattern of heat flow from 242 active volcanoes (at right). The red and yellow areas are places where local heat flow is greatest -- the result of magma erupting from Io's molten interior onto the surface. The map is the result of analyzing decades of observations from spacecraft and ground-based telescopes. It shows Io's usual volcanic thermal emission, excluding the occasional massive but transient "outburst" eruption; in other words, this is what Io looks like most of the time. This heat flow map will be used to test models of interior heating. The map shows that areas of enhanced volcanic heat flow are not necessarily correlated with the number of volcanoes in a particular region and are poorly correlated with expected patterns of heat flow from current models of tidal heating -- something that is yet to be explained. This research is published in association with a 2015 paper in the journal Icarus by A. Davies et al., titled "Map of Io's Volcanic Heat Flow," (http://dx.doi.org/10.1016/j.icarus.2015.08.003.) http://photojournal.jpl.nasa.gov/catalog/PIA19655

The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism

NASA Astrophysics Data System (ADS)

Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.

2001-12-01

The awesome power and intricate inner workings of volcanoes have made them a popular subject with scientists and the general public alike. About 1500 known volcanoes have been active on Earth during the Holocene, approximately 50 of which erupt per year. With so much activity occurring around the world, often in remote locations, it can be difficult to find up-to-date information about current volcanism from a reliable source. To satisfy the desire for timely volcano-related information the Smithsonian Institution and US Geological Survey combined their strengths to create the Weekly Volcanic Activity Report. The Smithsonian's Global Volcanism Program (GVP) has developed a network of correspondents while reporting worldwide volcanism for over 30 years in their monthly Bulletin of the Global Volcanism Network. The US Geological Survey's Volcano Hazards Program studies and monitors volcanoes in the United States and responds (upon invitation) to selected volcanic crises in other countries. The Weekly Volcanic Activity Report is one of the most popular sites on both organization's websites. The core of the Weekly Volcanic Activity Report is the brief summaries of current volcanic activity around the world. In addition to discussing various types of volcanism, the summaries also describe precursory activity (e.g. volcanic seismicity, deformation, and gas emissions), secondary activity (e.g. debris flows, mass wasting, and rockfalls), volcanic ash hazards to aviation, and preventative measures. The summaries are supplemented by links to definitions of technical terms found in the USGS photoglossary of volcano terms, links to information sources, and background information about reported volcanoes. The site also includes maps that highlight the location of reported volcanoes, an archive of weekly reports sorted by volcano and date, and links to commonly used acronyms. Since the Weekly Volcanic Activity Report's inception in November 2000, activity has been reported at over 60 volcanoes, with an average of 10 volcanoes discussed each week. Notable volcanic activity during November 2000-November 2001 included an eruption beginning on 6 February at Nyamuragira in the Democratic Republic of the Congo; it issued low-viscosity lava flows that traveled towards inhabited towns, and also produced ash clouds that adversely effected the health of residents and livestock near the volcano. Eruptions at Mayon in the Philippines on 24 June and 25 July caused local authorities to raise the alert to the highest level, close area airports, and evacuate thousands of residents near the volcano. Most recently a large flank eruption at Etna in Italy began on 17 July and gained worldwide attention as extensive lava flows threatened a small town and a tourist complex. While the information found in the Weekly Volcanic Activity Report, ranging from large eruptions to small precursory events, is of interest to the general public, it has also proven to be a valuable resource to volcano observatory staff, universities, researchers, secondary schools, and the aviation community.

Remote Triggering of Microearthquakes in the Piton de la Fournaise and Changbaishan Volcanoes

NASA Astrophysics Data System (ADS)

Li, C.; Liu, G.; Peng, Z.; Brenguier, F.; Dufek, J.

2015-12-01

Large earthquakes are capable of triggering seismic, aseismic and hydrological responses at long-range distances. In particular, recent studies have shown that microearthquakes are mostly triggered in volcanic/geothermal regions. However, it is still not clear how widespread the phenomenon is, and whether there are any causal links between large earthquakes and subsequent volcanic unrest/eruptions. In this study we conduct a systematic search for remotely triggered activity at the Piton de la Fournaise (PdlF) and Changbaishan (CBS) volcanoes. The PdlF is a shield volcano located on the east-southern part of the Reunion Island in Indian Ocean. It is one of the most active volcanoes around the world. The CBS volcano is an intraplate stratovolcano on the border between China and North Korea, and it was active with a major eruption around 1100 years ago and has been since dormant from AD 1903, however, it showed signals of unrest recently. We choose these regions because they are well instrumented and spatially close to recent large earthquakes, such as the 2004/12/26 Mw9.1 Sumatra, 2011/03/11 Mw9.0 Tohoku, and the 2012/04/11 Mw8.6 Indian Ocean Earthquakes. By examining continuous waveforms a few hours before and after many earthquakes since 2000, we find many cases of remote triggering around the CBS volcano. In comparison, we only identify a few cases of remotely triggered seismicity around the PdlF volcano, including the 2004 Sumatra earthquake. Notably, the 2012 Indian Ocean earthquake and its M8.2 aftershock did not trigger any clear increase of seismicity, at least during their surface waves. Our next step is to apply a waveform matching method to automatically detect volcano-seismicity in both regions, and then use them to better understand potential interactions between large earthquakes and volcanic activities.

Influences of volcano eruptions on Asian Summer Monsoon over the last 110 years

PubMed Central

Ning, Liang; Liu, Jian; Sun, Weiyi

2017-01-01

Asian summer monsoon (ASM) precipitation is the primary water resource for agriculture in many Asian countries that have experienced rapid economic growth in recent decades, thus implying the necessity for further investigations on both the internal variability of the ASM and the influence of external factors on the ASM. Using long-term high-resolution (0.5° × 0.5°) observed precipitation data, contrary to previous studies on inter-annual timescale, we showed that over the last 110 years, volcanic eruptions have influenced ASM variations on an inter-decadal timescale via teleconnections with the Atlantic Multi-decadal Oscillation (AMO). This relationship was also confirmed by Coupled Model Intercomparison Program Phase 5 (CMIP5) model simulations. During the active volcanic eruption periods (1901–1935 and 1963–1993), significantly lower ASM precipitation was observed compared with that during the inactive volcanic eruption period (1936–1962). We found that during active volcanic eruption periods, which correspond to a negative AMO state, there is an anomalously weakened Walker circulation over the tropical Pacific that transports less moisture to the ASM region and subsequently reduces ASM precipitation. This new finding may help improve decadal predictions of future changes in the ASM. PMID:28205603

Multi-scale seismic tomography of the Merapi-Merbabu volcanic complex, Indonesia

NASA Astrophysics Data System (ADS)

Mujid Abdullah, Nur; Valette, Bernard; Potin, Bertrand; Ramdhan, Mohamad

2017-04-01

Merapi-Merbabu volcanic complex is the most active volcano located on Java Island, Indonesia, where the Indian plate subducts beneath Eurasian plate. We present a preliminary study of a multi-scale seismic tomography of the substructures of the volcanic complex. The main objective of our study is to image the feeding paths of the volcanic complex at an intermediate scale by using the data from the dense network (about 5 km spacing) constituted by 53 stations of the French-Indonesian DOMERAPI experiment complemented by the data of the German-Indonesian MERAMEX project (134 stations) and of the Indonesia Tsunami Early Warning System (InaTEWS) located in the vicinity of the complex. The inversion was performed using the INSIGHT algorithm, which follows a non-linear least squares approach based on a stochastic description of data and model. In total, 1883 events and 41846 phases (26647 P and 15199 S) have been processed, and a two-scale approach was adopted. The model obtained at regional scale is consistent with the previous studies. We selected the most reliable regional model as a prior model for the local tomography performed with a variant of the INSIGHT code. The algorithm of this code is based on the fact that inverting differences of data when transporting the errors in probability is equivalent to inverting initial data while introducing specific correlation terms in the data covariance matrix. The local tomography provides images of the substructure of the volcanic complex with a sufficiently good resolution to allow identification of a probable magma chamber at about 20 km.

Regional geology and geophysics of the Jemez Mountains

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, F.G.

1973-08-01

The western margin of the Rocky Mountain tectonic belt is the initial site for the Los Alamos Geothermal Project. lgneous activity in the area culminated with the formation of a collapsed volcanic caldera and the deposition of thick beds of tuff. Geophysical studies indicate that the region is one of relatively highterrestrial heat flow, low-crustal density, low-crustal seismic velocities, low-crustal magnetoelectric impedance, and thin crust. 34 references. (auth)

Northeastern Brazilian margin: Regional tectonic evolution based on integrated analysis of seismic reflection and potential field data and modelling

NASA Astrophysics Data System (ADS)

Blaich, Olav A.; Tsikalas, Filippos; Faleide, Jan Inge

2008-10-01

Integration of regional seismic reflection and potential field data along the northeastern Brazilian margin, complemented by crustal-scale gravity modelling, is used to reveal and illustrate onshore-offshore crustal structure correlation, the character of the continent-ocean boundary, and the relationship of crustal structure to regional variation of potential field anomalies. The study reveals distinct along-margin structural and magmatic changes that are spatially related to a number of conjugate Brazil-West Africa transfer systems, governing the margin segmentation and evolution. Several conceptual tectonic models are invoked to explain the structural evolution of the different margin segments in a conjugate margin context. Furthermore, the constructed transects, the observed and modelled Moho relief, and the potential field anomalies indicate that the Recôncavo, Tucano and Jatobá rift system may reflect a polyphase deformation rifting-mode associated with a complex time-dependent thermal structure of the lithosphere. The constructed transects and available seismic reflection profiles, indicate that the northern part of the study area lacks major breakup-related magmatic activity, suggesting a rifted non-volcanic margin affinity. In contrast, the southern part of the study area is characterized by abrupt crustal thinning and evidence for breakup magmatic activity, suggesting that this region evolved, partially, with a rifted volcanic margin affinity and character.

Aeromagnetic Study of the Nortern Acambay Graben and Amealco Caldera, Central Mexican Volcanic Belt

NASA Astrophysics Data System (ADS)

Gonzalez, T.

2011-12-01

The Mexican Volcanic Belt (MVB) is characterized by E-W striking faults which form a series of en echelon graben along its length. In the central region of the MVB is located the Acambay graben an intra-arc tectonic depression structure, of apparent Quaternary age, which gives rise to pronounced scarps over a distance of about 80 Km. and 15 to 35 Km wide. The general arrangement of the faults that constitute the Acambay graben shows E-W trend which defines the fronts of the graben exhibits a major fault discontinuity. The graben is limited of the north by the Acambay- Tixmadeje and Epitafio Huerta faults and in the south by the Pastores and Venta de Bravo faults.. In the northern wall in the graben is located the Amealco caldera. This volcanic center (approximately 10 km in diameter) was formed by several discrete volcanic events, which produced an ignimbrite which covers the area. It is partially cut by a regional fault and the southern portion of the Amealco Caldera was displaced by a normal faulting along a segment of the Epitafio Huerta system. Continued tectonic activity in the Acambay area is confirmed by recent seismic episodes The Amealco tuff is the most important volcanic unit because of its volume and distribution. Aeromagnetic data was obtained and analyzed the anomalies. The anomaly map was compared with the surface geology and larger anomalies were correlated with major volcanic features. Since our main interest was in mapping the subsurface intrusive and volcanic bodies, the total field magnetic anomalies were reduced to the pole by using the double integral Fourier method. The reduced to the pole anomaly map results in a simplified pattern of isolated positive and negative anomalies, which show an improved correlation with all major volcanic structures. For the analysis and interpretation of the anomalies, the reduced to the pole anomalies were continued upward at various reference levels. These operations result in smoothing of the anomaly field by the filtering of high frequency anomalies that may be related to shallow sources.

The Zamama-Thor region of Io: Insights from a synthesis of mapping, topography, and Galileo spacecraft data

USGS Publications Warehouse

Williams, D.A.; Keszthelyi, L.P.; Schenk, P.M.; Milazzo, M.P.; Lopes, R.M.C.; Rathbun, J.A.; Greeley, R.

2005-01-01

We have studied data from the Galileo spacecraft's three remote sensing instruments (Solid-State Imager (SSI), Near-Infrared Mapping Spectrometer (NIMS), and Photopolarimeter-Radiometer (PPR)) covering the Zamama - Thor region of Io's antijovian hemisphere, and produced a geomorphological map of this region. This is the third of three regional maps we are producing from the Galileo spacecraft data. Our goal is to assess the variety of volcanic and tectonic materials and their interrelationships on Io using planetary mapping techniques, supplemented with all available Galileo remote sensing data. Based on the Galileo data analysis and our mapping, we have determined that the most recent geologic activity in the Zamama - Thor region has been dominated by two sites of large-scale volcanic surface changes. The Zamama Eruptive Center is a site of both explosive and effusive eruptions, which emanate from two relatively steep edifices (Zamama Tholi A and B) that appear to be built by both silicate and sulfur volcanism. A ???100-km long flow field formed sometime after the 1979 Voyager flybys, which appears to be a site of promethean-style compound flows, flow-front SO2 plumes, and adjacent sulfur flows. Larger, possibly stealthy, plumes have on at least one occasion during the Galileo mission tapped a source that probably includes S and/or Cl to produce a red pyroclastic deposit from the same vent from which silicate lavas were erupted. The Thor Eruptive Center, which may have been active prior to Voyager, became active again during the Galileo mission between May and August 2001. A pillanian-style eruption at Thor included the tallest plume observed to date on Io (at least 500 km high) and new dark lava flows. The plume produced a central dark pyroclastic deposit (probably silicate-rich) and an outlying white diffuse ring that is SO2-rich. Mapping shows that several of th000e new dark lava flows around the plume vent have reoccupied sites of earlier flows. Unlike most of the other pillanian eruptions observed during the Galileo mission, the 2001 Thor eruption did not produce a large red ring deposit, indicating a relative lack of S and/or Cl gases interacting with the magma during that eruption. Between these two eruptive centers are two paterae, Thomagata and Reshef. Thomagata Patera is located on a large shield-like mesa and shows no signs of activity. In contrast, Reshef Patera is located on a large, irregular mesa that is apparently undergoing degradation through erosion (perhaps from SO2 -sapping or chemical decomposition of sulfur-rich material) from multiple secondary volcanic centers. ?? 2005 Elsevier Inc. All rights reserved.

The Southern Washington Cascades magmatic system imaged with magnetotellurics

NASA Astrophysics Data System (ADS)

Bowles-martinez, E.; Bedrosian, P.; Schultz, A.; Hill, G. J.; Peacock, J.

2016-12-01

The goal of the interdisciplinary iMUSH project (Imaging Magma Under Saint Helens) is to image the magmatic system of Mount Saint Helens (MSH), and to determine the relationship of this system to the greater Cascades volcanic arc. We are especially interested in an anomalously conductive crustal zone between MSH and Mount Adams known as the Southern Washington Cascades Conductor (SWCC), which early studies interpreted as accreted sediments, but more recently has been interpreted as a broad region of partial melt. MSH is located 50 km west of the main arc and is the most active of the Cascade volcanoes. Its 1980 eruption highlighted the need to understand this potentially hazardous volcanic system. We use wideband magnetotelluric (MT) data collected in 2014-2015 along with data from earlier studies to create a 3D model of the electrical resistivity throughout the region, covering MSH as well as Mount Adams and Mount Rainier along the main volcanic arc. We look at not only the volcanoes themselves, but also their relationship to one another and to regional geologic structures. Preliminary modeling identifies several conductive features, including a mid-crustal conductive region between MSH and Mount Adams that passes below Indian Heaven Volcanic Field and coincides with a region with a high Vp/Vs ratio identified in the seismic component of iMUSH. This suggests that it could be magmatic, but does not preclude the possibility of conductive sediments. Synthesis of seismic and MT data to address this question is ongoing. We also note a conductive zone running north-south just west of MSH that is likely associated with fluids within faults of the Saint Helens Seismic Zone. We finally note that curvature of the conductive lineament that defines the main Cascade arc suggests that the boundary of magmatism is influenced by compression within the Yakima Fold and Thrust Belt, east and southeast of Mount Adams.

Morphology of Some Small Mars North-Polar Volcanic Edifices from Viking Images and MOLA Topography

NASA Technical Reports Server (NTRS)

Wright, H. M.; Sakimoto, S. E. H.; Garvin, J. B.

2000-01-01

Studied features in the northern near polar regions of Mars have morphologies suggesting volcanic origin. The results of this study suggest that these features may represent martian effusive shield volcanics.

Lakshmi Planum: A distinctive highland volcanic province

NASA Astrophysics Data System (ADS)

Roberts, Kari M.; Head, James W.

Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region.

Lakshmi Planum: A distinctive highland volcanic province

NASA Technical Reports Server (NTRS)

Roberts, Kari M.; Head, James W.

1989-01-01

Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region.

Lakshmi Planum, Venus - Characteristics and models of origin

NASA Technical Reports Server (NTRS)

Roberts, Kari M.; Head, James W.

1990-01-01

The distinctive and unique Venusian geological structure, Lakshmi Planum, is an expansive relatively smooth flat plateau containing two large shield volcanos and abundant volcanic plains in the midst of a region of extreme relief. The characteristics which distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio, are identified. These include its high altitude and plateaulike nature; the presence of two very large low shield structures with distinctive central paterae and long radiating flows; and its compressional tectonic environment. The detailed nature and significance of the volcanic deposits on Lakshmi are determined; the erruption styles and conditions are interpreted; and the link between the observed volcanism and tectonic environment of the region is discussed. Models for the formation of Lakshmi Planum are presented and evaluated.

Lakshmi Planum, Venus - Characteristics and models of origin

NASA Astrophysics Data System (ADS)

Roberts, Kari M.; Head, James W.

1990-12-01

The distinctive and unique Venusian geological structure, Lakshmi Planum, is an expansive relatively smooth flat plateau containing two large shield volcanos and abundant volcanic plains in the midst of a region of extreme relief. The characteristics which distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio, are identified. These include its high altitude and plateaulike nature; the presence of two very large low shield structures with distinctive central paterae and long radiating flows; and its compressional tectonic environment. The detailed nature and significance of the volcanic deposits on Lakshmi are determined; the erruption styles and conditions are interpreted; and the link between the observed volcanism and tectonic environment of the region is discussed. Models for the formation of Lakshmi Planum are presented and evaluated.

Assessing future vent opening locations at the Somma-Vesuvio volcanic complex: 1. A new information geodatabase with uncertainty characterizations

NASA Astrophysics Data System (ADS)

Tadini, A.; Bisson, M.; Neri, A.; Cioni, R.; Bevilacqua, A.; Aspinall, W. P.

2017-06-01

This study presents new and revised data sets about the spatial distribution of past volcanic vents, eruptive fissures, and regional/local structures of the Somma-Vesuvio volcanic system (Italy). The innovative features of the study are the identification and quantification of important sources of uncertainty affecting interpretations of the data sets. In this regard, the spatial uncertainty of each feature is modeled by an uncertainty area, i.e., a geometric element typically represented by a polygon drawn around points or lines. The new data sets have been assembled as an updatable geodatabase that integrates and complements existing databases for Somma-Vesuvio. The data are organized into 4 data sets and stored as 11 feature classes (points and lines for feature locations and polygons for the associated uncertainty areas), totaling more than 1700 elements. More specifically, volcanic vent and eruptive fissure elements are subdivided into feature classes according to their associated eruptive styles: (i) Plinian and sub-Plinian eruptions (i.e., large- or medium-scale explosive activity); (ii) violent Strombolian and continuous ash emission eruptions (i.e., small-scale explosive activity); and (iii) effusive eruptions (including eruptions from both parasitic vents and eruptive fissures). Regional and local structures (i.e., deep faults) are represented as linear feature classes. To support interpretation of the eruption data, additional data sets are provided for Somma-Vesuvio geological units and caldera morphological features. In the companion paper, the data presented here, and the associated uncertainties, are used to develop a first vent opening probability map for the Somma-Vesuvio caldera, with specific attention focused on large or medium explosive events.

"Curso de Vulcanología General": Web-education efforts on volcanic hazards for the Latin American region from Mexico.

NASA Astrophysics Data System (ADS)

Delgado, Hugo

2016-04-01

Education of volcanic hazards is a never-ending task in countries where volcanoes erupt very frequently as they do in the Latin American region (LAR). Eleven countries in the LAR have active volcanoes within their territories and some volcanoes are located in between countries so the volcanic hazards associated to the eruption of those volcanoes affect more than one country. Besides, countries without volcanoes within their territory (i. e. Belize, Honduras or Brazil) can be impacted as well. Personnel working at several volcano observatories in the LAR need training in Volcanology and, more importantly, in Volcanic Hazards. Unfortunately, Volcanology is a discipline that is not taught at universities of some countries. Even worse, Earth Sciences are not even taught at high education centers in some countries of the LAR. Thus, there is an important need for the acquisition of volcanological knowledge by the personnel working at volcano observatories but there are no possibilities for them to study at their countries or they are impended for travel abroad for training. The international course: "Curso de Vulcanología General" taught from Mexico City at the Universidad Nacional Autónoma de México (UNAM) has been successfully implemented and has been active over the last five years. Nearly 700 students have participated in this course although only ~150 have been awarded the certificate UNAM grants to the students who have concluded the course successfully. This course has been sponsored by UNAM, ALVO (Latin American Volcanological Association) and IAVCEI (International Association of Volcanology and Chemistry of the Earth's Interior). More than 50 lecturers from LAR, Europe and US have been involved in these courses. Here, Reflections on the course, the opportunities sparkled, the educational tools, benefits, statistics and virtues of the course are presented.

Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S)

NASA Astrophysics Data System (ADS)

Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.

2006-11-01

This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

Slab dehydration in Cascadia and its relationship to volcanism, seismicity, and non-volcanic tremor

NASA Astrophysics Data System (ADS)

Delph, J. R.; Levander, A.; Niu, F.

2017-12-01

The characteristics of subduction beneath the Pacific Northwest (Cascadia) are variable along strike, leading to the segmentation of Cascadia into 3 general zones: Klamath, Siletzia, and Wrangelia. These zones show marked differences in tremor density, earthquake density, seismicity rates, and the locus and amount of volcanism in the subduction-related volcanic arc. To better understand what controls these variations, we have constructed a 3D shear-wave velocity model of the upper 80 km along the Cascadia margin from the joint inversion of CCP-derived receiver functions and ambient noise surface wave data using 900 temporary and permanent broadband seismic stations. With this model, we can investigate variations in the seismic structure of the downgoing oceanic lithosphere and overlying mantle wedge, the character of the crust-mantle transition beneath the volcanic arc, and local to regional variations in crustal structure. From these results, we infer the presence and distribution of fluids released from the subducting slab and how they affect the seismic structure of the overriding lithosphere. In the Klamath and Wrangelia zones, high seismicity rates in the subducting plate and high tremor density correlate with low shear velocities in the overriding plate's forearc and relatively little arc volcanism. While the cause of tremor is debated, intermediate depth earthquakes are generally thought to be due to metamorphic dehydration reactions resulting from the dewatering of the downgoing slab. Thus, the seismic characteristics of these zones combined with rather sparse arc volcanism may indicate that the slab has largely dewatered by the time it reaches sub-arc depths. Some of the water released during earthquakes (and possibly tremor) may percolate into the overriding plate, leading to slow seismic velocities in the forearc. In contrast, Siletzia shows relatively low seismicity rates and tremor density, with relatively higher shear velocities in the forearc. Siletzia also contains most of the young arc volcanoes in the Cascades, indicating that water is retained in the slab to depths where it can feed arc volcanism. Thus, the along strike variations in volcanic activity and seismic activity in Cascadia appear to be related to variations in depth of dewatering of the downgoing oceanic lithosphere.

Volcanic Hazards Survey in the Trans Mexican Volcanic Belt

NASA Technical Reports Server (NTRS)

Abrams, Michael; Siebe, Claus; Macias, Jose Luis

1996-01-01

We have assembled a digital mosaic of 11 Landsat Thematic images to serve as a mapping base for reconnaissance activities within the Trans Mexican Volcanic Belt. This will aid us in interpretation and in the evaluation of potential activity of all the volcanic centers there. One result is a volcanic hazards map of the area.

Characteristics of Volcanic Stratospheric Aerosol Layer Observed by CALIOP and Ground Based Lidar at Equatorial Atmosphere Radar Site

NASA Astrophysics Data System (ADS)

Abo, Makoto; Shibata, Yasukuni; Nagasawa, Chikao

2018-04-01

We investigated the relation between major tropical volcanic eruptions in the equatorial region and the stratospheric aerosol data, which have been collected by the ground based lidar observations at at Equatorial Atmosphere Radar site between 2004 and 2015 and the CALIOP observations in low latitude between 2006 and 2015. We found characteristic dynamic behavior of volcanic stratospheric aerosol layers over equatorial region.

Geologic map of the Ganiki Planitia quadrangle (V-14), Venus

USGS Publications Warehouse

Grosfils, Eric B.; Long, Sylvan M.; Venechuk, Elizabeth M.; Hurwitz, Debra M.; Richards, Joseph W.; Drury, Dorothy E.; Hardin, Johanna

2011-01-01

The Ganiki Planitia (V-14) quadrangle on Venus, which extends from 25° N. to 50° N. and from 180° E. to 210° E., derives its name from the extensive suite of plains that dominates the geology of the northern part of the region. With a surface area of nearly 6.5 x 106 km2 (roughly two-thirds that of the United States), the quadrangle is located northwest of the Beta-Atla-Themis volcanic zone and southeast of the Atalanta Planitia lowlands, areas proposed to be the result of large scale mantle upwelling and downwelling, respectively. The region immediately south of Ganiki Planitia is dominated by Atla Regio, a major volcanic rise beneath which localized upwelling appears to be ongoing, whereas the area just to the north is dominated by the orderly system of north-trending deformation belts that characterize Vinmara Planitia. The Ganiki Planitia quadrangle thus lies at the intersection between several physiographic regions where extensive mantle flow-induced tectonic and volcanic processes are thought to have occurred. The geology of the V-14 quadrangle is characterized by a complex array of volcanic, tectonic, and impact-derived features. There are eleven impact craters with diameters from 4 to 64 km, as well as four diffuse 'splotch' features interpreted to be the product of near-surface bolide explosions. Tectonic activity has produced heavily deformed tesserae, belts of complex deformation and rifts as well as a distributed system of fractures and wrinkle ridges. Volcanic activity has produced extensive regional plains deposits, and in the northwest corner of the quadrangle these plains host the initial (or terminal) 700 km of the Baltis Vallis canali, an enigmatic volcanic feature with a net length of ~7,000 km that is the longest channel on Venus. Major volcanic centers in V-14 include eight large volcanoes and eight coronae; all but one of these sixteen features was noted during a previous global survey. The V-14 quadrangle contains an abundance of minor volcanic features including individual shield volcanoes and localized fissure eruptions as well as many small annular structures and domes, which often serve as the source for local lava flows. The topographic and geophysical characteristics of the Ganiki Planitia quadrangle are less complex than the surface geology, but they yield equally valuable information about the region’s formation and evolution. Referenced to the mean planetary radius of 6051.84 km, the average elevation in the quadrangle is -0.26±0.86 km (2σ) with a full range of -2.58 km to 1.85 km. The highest 2.5 percent of elevations in the quadrangle (above 0.60 km) are associated primarily with the major tessera blocks and the peaks of a few volcanic edifices, whereas the lowest 2.5 percent (below -1.12 km) mostly occur within corona interiors and in the northwest corner of the quadrangle where the plains begin to merge into the Atalanta Planitia lowlands. At the ~4.6 km/pixel scale of the topography data, the mean point-to-point topographic slope is 0.63° and topographic slopes greater than 2° cover less than 5 percent of the region. Overall, the topography of the Ganiki Planitia quadrangle can be characterized as flat, low lying, and nearly devoid of abrupt topographic variation. Complementing this gentle topography, the geoid anomaly has a generally linear gradient that decreases north-northwest from a high of ~20 m at the southern edge of the quadrangle (the northern border of the Atla Regio anomaly) to a low of -30 to -40 m along the northern edge (Konopliv and others, 1999). The vertical component of the gravity anomaly varies from ~50 mGal to -40 mGal, and integrated analysis of the gravity and topography data indicates that dynamically supported regions and areas of thickened crust are both present within the quadrangle. Because the Ganiki Planitia quadrangle is a plains-dominated lowland area that lies between several major physiographic provinces (namely, Atla Regio, Atalanta Planitia, and Vinmara Planitia), a geologic map of the region may yield insight into a wide array of important problems in Venusian geology. The current mapping effort and analysis complements previous efforts to characterize aspects of the region’s geology, for example stratigraphy near parabolic halo crater sites, volcanic plains emplacement, wrinkle ridges, volcanic feature distribution, volcano deformation, coronae characteristics, lithospheric flexure, and various features along a 30±7.58° N. geotraverse. Our current research focuses on addressing four specific questions. Has the dominant style of volcanic expression within the quadrangle varied in a systematic fashion over time? Does the tectonic deformation within the quadrangle record significant regional patterns that vary spatially or temporally, and if so what are the scales, orientations and sources of the stress fields driving this deformation? If mantle upwelling and downwelling have played a significant role in the formation of Atla Regio and Atalanta Planitia as has been proposed, does the geology of Ganiki Planitia record evidence of northwest-directed lateral mantle flow connecting the two sites? Finally, can integration of the tectonic and volcanic histories preserved within the quadrangle help constrain competing resurfacing models for Venus?

S-wave attenuation structure beneath the northern Izu-Bonin arc

NASA Astrophysics Data System (ADS)

Takahashi, Tsutomu; Obana, Koichiro; Kodaira, Shuichi

2016-04-01

To understand temperature structure or magma distribution in the crust and uppermost mantle, it is essential to know their attenuation structure. This study estimated the 3-D S-wave attenuation structure in the crust and uppermost mantle at the northern Izu-Bonin arc, taking into account the apparent attenuation due to multiple forward scattering. In the uppermost mantle, two areas of high seismic attenuation (high Q -1) imaged beneath the volcanic front were mostly colocated with low-velocity anomalies. This coincidence suggests that these high- Q -1 areas in low-velocity zones are the most likely candidates for high-temperature regions beneath volcanoes. The distribution of random inhomogeneities indicated the presence of three anomalies beneath the volcanic front: Two were in high- Q -1 areas but the third was in a moderate- Q -1 area, indicating a low correlation between random inhomogeneities and Q -1. All three anomalies of random inhomogeneities were rich in short-wavelength spectra. The most probable interpretation of such spectra is the presence of volcanic rock, which would be related to accumulated magma intrusion during episodes of volcanic activity. Therefore, the different distributions of Q -1 and random inhomogeneities imply that the positions of hot regions in the uppermost mantle beneath this arc have changed temporally; therefore, they may provide important constraints on the evolutionary processes of arc crust and volcanoes.

An assessment of the crustal remelting hypothesis for volcanism in the Freyja Montes deformation zone

NASA Astrophysics Data System (ADS)

Namiki, Noriyuki; Solomon, Sean C.

1991-06-01

The linear mountain belts of Ishtar Terra on Venus are notable for their topographic relief and slope and for the intensity of surface deformation. The mountains surround the highland plain Lakshmi Planum, the site of two major paterae and numerous other volcanic features and deposits, and evidence is widespread for volcanism within the mountains and in terrain immediately outward of the mountain belt units. While two hypotheses for magmatism can be distinguished on the basis of the chemistry of the melts, chemical data are presently lacking for the Ishtar region. The competing hypotheses for magmatism in Western Ishtar Terra can also be tested with thermal models, given a kinematic or dynamic model for the evolution of the region. The crustal remelting hypothesis is assessed, using the kinematic scenario of Head for the evolution of Freyja Montes. In that scenario, Freyja Montes formed by a sequence of large scale underthrusts of the lithosphere of the North Polar Plains beneath Ishtar Terra, with successive blocks of underthrust crust sutured in imbricate fashion onto the thickened crust of Lakshmi Planum and the mantle portion of underthrusting lithosphere episodically detached. The numerical experiments thus show that volcanic activity associated with the formation of the Frejya Montes deformation zone can be explained by crustal melting, due either to direct contact of crustal material with the hot asthenosphere or to heat generation in a thickened crustal layer.

The Midway sequence: A Timiskaming-type, pull-apart basin deposit in the western Wawa subprovince, Minnesota

USGS Publications Warehouse

Jirsa, M.A.

2000-01-01

The Midway sequence is an assemblage of subaerially deposited clastic and volcanic rocks that forms a narrow wedge within Neoarchean greenstone of the western Wawa subprovince of the Superior Province. Volcanic conglomerate in the Midway sequence contains clasts of stratigraphically older greenstone, together with clasts of a distinctive hornblende-phyric trachyandesite that is not represented among the older greenstone flows. The trachyandesite forms flows and pyroclastic units that are interbedded with lenticular deposits of volcanic conglomerate in a manner interpreted to indicate approximately coeval volcanism and alluvial fan - Fluvial sedimentation within a linear, restricted, and tectonically active depocentre. The Midway sequence unconformably overlies greenstone on one side and is bounded by a regional-scale, strike-slip fault on the other. Structural analyses show that the Midway sequence was deposited after an early, precleavage folding event (D1) in greenstone, but before the regional metamorphic cleavage-forming D2 deformation. Lithologic and structural attributes are consistent with deposition in a strike-slip "pull-apart" basin. The stratigraphic and structural characteristics of the Midway sequence are generally similar to those of the Timiskaming Group and Timiskaming-type rocks in Canada, and more specifically to those of the Shebandowan Group in the Thunder Bay district. This similarity implies that the latest Archean tectonic and magmatic history of the western Wawa subprovince may have been nearly synchronous over great distances.

Subaqueous volcanism in the Etnean area: evidence for hydromagmatic activity and regional uplift inferred from the Castle Rock of Acicastello

NASA Astrophysics Data System (ADS)

Corsaro, R. A.; Cristofolini, R.

2000-01-01

The subalkaline rocks outcropping at the Acicastello Castle Rock, Catania, Sicily, and on its abrasion platforms, are related to the oldest Etnean volcanism (500-300 ka; [Gillot, P.Y., Kieffer, G., Romano, R., 1994. The evolution of Mount Etna in the light of potassium-argon dating. Acta Vulcanol. 5, 81-87.]). Here, submarine lavas with pillows closely packed onto each other are associated with heterogeneous and poorly sorted volcaniclastic breccia levels with sub-vertical sharp boundaries. The present-day attitude was previously interpreted as due to a local tilt [Di Re, M., 1963. Hyaloclastites and pillow-lavas of Acicastello (Mt. Etna). Bull. Volcanol. 25, 281-284.; Kieffer, G., 1985. Evolution structurale et dynamique d'un grand volcan polygenique: stades d'edification et activitè actuelle de l'Etna (Sicile). Clermont Ferrand IIDoctorat Etat Tesi, Clermont Ferrand II.], or to the seaward sliding of the entire eastern Etnean flank [Borgia, A., Ferrari, L., Pasquarè, G., 1992. Importance of gravitational spreading in the tectonic and volcanic evolution of Mount Etna. Nature 357, 231-235.], on the assumption of originally horizontal boundaries. On the contrary, our observations do not match the hypothesis of a significantly tilted succession and lead us to conclude that, apart from the strong regional uplift, the present Castle Rock exposure did not suffer any substantial change of its attitude.

Volcanic rises on Venus: Geology, formation, and sequence of evolution

NASA Technical Reports Server (NTRS)

Senske, D. A.; Stofan, E. R.; Bindschadler, D. L.; Smrekar, S. E.

1993-01-01

Large centers of volcanism on Venus are concentrated primarily in the equatorial region of the planet and are associated with regional topographic rises. Analysis of both radar images and geophysical data suggest that these uplands are sites of mantle upwelling. Magellan radar imaging provides a globally contiguous data set from which the geology of these regions is evaluated and compared. In addition, high resolution gravity data currently being collected provide a basis to assess the relationship between these uplands and processes in the planet's interior. Studies of the geology of the three largest volcanic highlands (Beta Regio, Atla Regio, Western Eistla Regio) show them to be distinct, having a range of volcanic and tectonic characteristics. In addition to these large areas, a number of smaller uplands are identified and are being analyzed (Bell Regio, Imdr Regio, Dione Regio (Ushas, Innini, and Hathor Montes), and Themis Regio). To understand better the mechanisms by which these volcanic rises form and evolve, we assess their geologic and geophysical characteristics.

Quantification of carbon dioxide emissions of Ciomadul, the youngest volcano of the Carpathian-Pannonian Region (Eastern-Central Europe, Romania)

NASA Astrophysics Data System (ADS)

Kis, Boglárka-Mercédesz; Ionescu, Artur; Cardellini, Carlo; Harangi, Szabolcs; Baciu, Călin; Caracausi, Antonio; Viveiros, Fátima

2017-07-01

We provide the first high-resolution CO2 flux data for the Neogene to Quaternary volcanic regions of the entire Carpathian-Pannonian Region, Eastern-Central Europe, and estimate the CO2 emission of the seemingly inactive Ciomadul volcanic complex, the youngest volcano of this area. Our estimate includes data from focused and diffuse CO2 emissions from soil. The CO2 fluxes of focused emissions range between 277 and 8172 g d- 1, corresponding to a CO2 output into the atmosphere between 0.1 and 2.98 t per year. The investigated areas for diffuse soil gas emissions were characterized by wide range of CO2 flux values, at Apor Baths, ranging from 1.7 × 101 to 8.2 × 104 g m- 2 d- 1, while at Lăzărești ranging between 1.43 and 3.8 × 104 g m- 2 d- 1. The highest CO2 focused gas fluxes at Ciomadul were found at the periphery of the youngest volcanic complex, which could be explained either by tectonic control across the brittle older volcanic edifices or by degassing from a deeper crustal zone resulting in CO2 flux at the periphery of the supposed melt-bearing magma body beneath Ciomadul. The estimate of the total CO2 output in the area is 8.70 × 103 t y- 1, and it is consistent with other long (> 10 kyr) dormant volcanoes with similar age worldwide, such as in Italy and USA. Taking into account the isotopic composition of the gases that indicate deep origin of the CO2 emissions, this yields further support that Ciomadul may be considered indeed a dormant, or PAMS volcano (volcano with potentially active magma storage) rather than an inactive one. Furthermore, hazard of CO2 outpourings has to be taken into account and it has to be communicated to the visitors. Finally, we suggest that CO2 output of dormant volcanic systems has to be also accounted in the estimation of the global volcanic CO2 budget.

Reconstructing the Vulcano Island evolution from 3D modeling of magnetic signatures

NASA Astrophysics Data System (ADS)

Napoli, Rosalba; Currenti, Gilda

2016-06-01

High-resolution ground and marine magnetic data are exploited for a detailed definition of a 3D model of the Vulcano Island volcanic complex. The resulting 3D magnetic imaging, obtained by 3-D inverse modeling technique, has delivered useful constraints both to reconstruct the Vulcano Island evolution and to be used as input data for volcanic hazard assessment models. Our results constrained the depth and geometry of the main geo-structural features revealing more subsurface volcanic structures than exposed ones and allowing to elucidate the relationships between them. The recognition of two different magnetization sectors, approximatively coincident with the structural depressions of Piano caldera, in the southern half of the island, and La Fossa caldera at the north, suggests a complex structural and volcanic evolution. Magnetic highs identified across the southern half of the island reflect the main crystallized feeding systems, intrusions and buried vents, whose NNW-SSE preferential alignment highlights the role of the NNW-SSE Tindari-Letojanni regional system from the initial activity of the submarine edifice, to the more recent activity of the Vulcano complex. The low magnetization area, in the middle part of the island may result from hydrothermally altered rocks. Their presence not only in the central part of the volcano edifice but also in other peripheral areas, is a sign of a more diffuse historical hydrothermal activity than in present days. Moreover, the high magnetization heterogeneity within the upper flanks of La Fossa cone edifice is an imprint of a composite distribution of unaltered and altered rocks with different mechanical properties, which poses in this area a high risk level for failure processes especially during volcanic or hydrothermal crisis.

Monogenetic Volcano Clusters within the wider Michoacán-Guanajuato Volcanic Field (México) and their Significance

NASA Astrophysics Data System (ADS)

Siebe, C.

2017-12-01

The Trans-Mexican Volcanic Belt, one of the most complex and active continental arcs worldwide, displays several volcanic fields dominated by monogenetic volcanoes. Of these, the Plio-Quaternary Michoacán-Guanajuato Volcanic Field (MGVF) situated in central Mexico, is the largest monogenetic volcanic field in the world and includes more than 1000 scoria cones and associated lava flows and about 400 medium-sized volcanoes (Mexican shields). The smaller monogenetic vents occur either isolated or form small clusters within the wider MGVF. The recent identification of small clusters comprising several monogenetic volcanoes that erupted in a sequence of geologically short time intervals (hundreds to few thousands of years) in small areas within the much wider MGVF opens several questions in regard to future volcanic hazard assessments in this region: Are the youngest (Holocene) clusters still "active" and is a new eruption likely to occur within their surroundings? How long are such clusters "active"? Will the next monogenetic eruption in the MGVF be a single short-lived isolated eruption, or the beginning of a cluster? Furthermore, is it possible that the historic eruptions of Jorullo (1759) and Paricutin (1943) represent each the beginning of a cluster and should a new eruption in their proximity be expected in the future? In order to address these questions, two Holocene clusters, namely Tacámbaro and Malpaís de Zacapu are currently under study and preliminary results will be presented. Each comprises four monogenetic vents that erupted in a sequence of geologically short time intervals (hundreds to few thousands of years) within a small area (few tens of km2) Geologic mapping, geochemical analyses, radiometric dating, and paleomagnetic studies will help to establish the sequence of eruption of the different vents, and shed more light on the conditions that allow several magma sources to be formed and then tapped in close temporal and spatial proximity to each other and produce such small "flare-ups".

40Ar/39Ar geochronology, paleomagnetism, and evolution of the Boring volcanic field, Oregon and Washington, USA

USGS Publications Warehouse

Fleck, Robert J.; Hagstrum, Jonathan T.; Calvert, Andrew T.; Evarts, Russell C.; Conrey, Richard M.

2014-01-01

The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.

Geologic and Geophysical Framework of the Santa Rosa 7.5' Quadrangle, Sonoma County, California

USGS Publications Warehouse

McLaughlin, R.J.; Langenheim, V.E.; Sarna-Wojcicki, A. M.; Fleck, R.J.; McPhee, D.K.; Roberts, C.W.; McCabe, C.A.; Wan, Elmira

2008-01-01

The geologic and geophysical maps of Santa Rosa 7.5? quadrangle and accompanying structure sections portray the sedimentary and volcanic stratigraphy and crustal structure of the Santa Rosa 7.5? quadrangle and provide a context for interpreting the evolution of volcanism and active faulting in this region. The quadrangle is located in the California Coast Ranges north of San Francisco Bay and is traversed by the active Rodgers Creek, Healdsburg and Maacama Fault Zones. The geologic and geophysical data presented in this report, are substantial improvements over previous geologic and geophysical maps of the Santa Rosa area, allowing us to address important geologic issues. First, the geologic mapping is integrated with gravity and magnetic data, allowing us to depict the thicknesses of Cenozoic deposits, the depth and configuration of the Mesozoic basement surface, and the geometry of fault structures beneath this region to depths of several kilometers. This information has important implications for constraining the geometries of major active faults and for understanding and predicting the distribution and intensity of damage from ground shaking during earthquakes. Secondly, the geologic map and the accompanying description of the area describe in detail the distribution, geometry and complexity of faulting associated with the Rodgers Creek, Healdsburg and Bennett Valley Fault Zones and associated faults in the Santa Rosa quadrangle. The timing of fault movements is constrained by new 40Ar/39Ar ages and tephrochronologic correlations. These new data provide a better understanding of the stratigraphy of the extensive sedimentary and volcanic cover in the area and, in particular, clarify the formational affinities of Pliocene and Pleistocene nonmarine sedimentary units in the map area. Thirdly, the geophysics, particularly gravity data, indicate the locations of thick sections of sedimentary and volcanic fill within ground water basins of the Santa Rosa plain and Rincon, Bennett, and northwestern Sonoma Valleys, providing geohydrologists a more realistic framework for groundwater flow models.

Geology and geochemistry of volcanic centers within the eastern half of the Sonoma volcanic field, northern San Francisco Bay region, California

USGS Publications Warehouse

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

2011-01-01

The volcanic fields in the California Coast Ranges north of San Francisco Bay are temporally and spatially associated with the northward migration of the Mendocino triple junction and the transition from subduction and associated arc volcanism to a slab window tectonic environment. Our geochemical analyses from the Sonoma volcanic field highlight the geochemical diversity of these volcanic rocks, allowing us to clearly distinguish these volcanic rocks from those of the roughly coeval ancestral Cascades magmatic arc to the west, and also to compare rocks of the Sonoma volcanic field to rocks from other slab window settings.

Philippine geothermal resources: General geological setting and development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datuin, R.T.; Troncales, A.C.

1986-01-01

The Phillippine Archipelago has a composite geologic structure arising from the multi-stage development of volcanic-tectonic events evidenced by volcanism and seismic activity occurring along the active blocks of the major structural lines which traverse most of the major islands of the Phillipines. The widespread volcanic activity located along the active tectonic block has generated regions of high heat flow, where a vast number of potential rich geothermal resources could be exploited as an alternative source of energy. As part of a systematic geothermal development program launched by the Philippine government after the successful pilot study at the Tiwi geothermal fieldmore » in 1967 by the Commission on Volcanology (now called the Philippine Institute of Volcanology-PIV), the Philippines developed four geothermal fields in the period 1972-84. These four areas, Tiwi in Albay, Mak-Ban in Laguna, Tongonan in Leyte, and Palinpinon in Southern Negros, have already contributed 891 MW installed capacity to the total electrical power supply of the country, which is mainly dependent on oil resources. The Philippines envisaged that, with its accelerated geothermal energy programme, it would be able to achieve its target of reducing the country's dependence on imported fossil fuel by about 20% within the next decade through the utilization of its vast geothermal energy resources.« less

Rayleigh Wave Phase Velocities Beneath the Central and Southern East African Rift System

NASA Astrophysics Data System (ADS)

Adams, A. N.; Miller, J. C.

2017-12-01

This study uses the Automated Generalized Seismological Data Function (AGSDF) method to develop a model of Rayleigh wave phase velocities in the central and southern portions of the East African Rift System (EARS). These phase velocity models at periods of 20-100s lend insight into the lithospheric structures associated with surficial rifting and volcanism, as well as basement structures that pre-date and affect the course of rifting. A large dataset of >700 earthquakes is used, comprised of Mw=6.0+ events that occurred between the years 1995 and 2016. These events were recorded by a composite array of 176 stations from twelve non-contemporaneous seismic networks, each with a distinctive array geometry and station spacing. Several first-order features are resolved in this phase velocity model, confirming findings from previous studies. (1) Low velocities are observed in isolated regions along the Western Rift Branch and across the Eastern Rift Branch, corresponding to areas of active volcanism. (2) Two linear low velocity zones are imaged trending southeast and southwest from the Eastern Rift Branch in Tanzania, corresponding with areas of seismic activity and indicating possible incipient rifting. (3) High velocity regions are observed beneath both the Tanzania Craton and the Bangweulu Block. Furthermore, this model indicates several new findings. (1) High velocities beneath the Bangweulu Block extend to longer periods than those found beneath the Tanzania Craton, perhaps indicating that rifting processes have not altered the Bangweulu Block as extensively as the Tanzania Craton. (2) At long periods, the fast velocities beneath the Bangweulu Block extend eastwards beyond the surficial boundaries, to and possibly across the Malawi Rift. This may suggest the presence of older, thick blocks of lithosphere in regions where they are not exposed at the surface. (3) Finally, while the findings of this study correspond well with previous studies in regions of overlapping data, the greatest deviations, as well as the highest standard deviation in measurements, are found in volcanically active regions characterized by high anisotropy, suggesting that the influence of seismic anisotropy may have vary significantly between tomography methods.

Field-trip guides to selected volcanoes and volcanic landscapes of the western United States

USGS Publications Warehouse

,

2017-06-23

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

Increased thyroid cancer incidence in a basaltic volcanic area is associated with non-anthropogenic pollution and biocontamination.

PubMed

Malandrino, Pasqualino; Russo, Marco; Ronchi, Anna; Minoia, Claudio; Cataldo, Daniela; Regalbuto, Concetto; Giordano, Carla; Attard, Marco; Squatrito, Sebastiano; Trimarchi, Francesco; Vigneri, Riccardo

2016-08-01

The increased thyroid cancer incidence in volcanic areas suggests an environmental effect of volcanic-originated carcinogens. To address this problem, we evaluated environmental pollution and biocontamination in a volcanic area of Sicily with increased thyroid cancer incidence. Thyroid cancer epidemiology was obtained from the Sicilian Regional Registry for Thyroid Cancer. Twenty-seven trace elements were measured by quadrupole mass spectrometry in the drinking water and lichens (to characterize environmental pollution) and in the urine of residents (to identify biocontamination) in the Mt. Etna volcanic area and in adjacent control areas. Thyroid cancer incidence was 18.5 and 9.6/10(5) inhabitants in the volcanic and the control areas, respectively. The increase was exclusively due to the papillary histotype. Compared with control areas, in the volcanic area many trace elements were increased in both drinking water and lichens, indicating both water and atmospheric pollution. Differences were greater for water. Additionally, in the urine of the residents of the volcanic area, the average levels of many trace elements were significantly increased, with values higher two-fold or more than in residents of the control area: cadmium (×2.1), mercury (×2.6), manganese (×3.0), palladium (×9.0), thallium (×2.0), uranium (×2.0), vanadium (×8.0), and tungsten (×2.4). Urine concentrations were significantly correlated with values in water but not in lichens. Our findings reveal a complex non-anthropogenic biocontamination with many trace elements in residents of an active volcanic area where thyroid cancer incidence is increased. The possible carcinogenic effect of these chemicals on the thyroid and other tissues cannot be excluded and should be investigated.

Initiation and Along-Axis Segmentation of Seaward-Dipping Volcanic Sequences Captured in Afar

NASA Astrophysics Data System (ADS)

Ebinger, C.; Wolfenden, E.; Yirgu, G.; Keir, D.

2003-12-01

The Afar triple junction zone provides a unique opportunity to examine the early development of magmatic margins, as respective limbs of the triple junction capture different stages of the breakup process. Initial rifting in the southernmost Red Sea occurred concurrent with, or soon after flood basaltic magmatism at ~31 Ma in the Ethiopia-Yemen plume province, whereas the northern part of the Main Ethiopian rift initiated after 12 Ma. Both rift systems initiated with the development of high-angle border fault systems bounding broad basins, but 8-10 My after rifting we see riftward migration of strain from the western border fault to narrow zones of increasingly more basaltic magmatism. These localised zones of faulting and volcanism (magmatic segments) show a segmentation independent of the border fault segmentation. The much older, more evolved magmatic segments in the southern Red Sea, where not onlapped by Pliocene-Recent sedimentary strata, dip steeply riftward and define a regional eastward flexure into transitional oceanic crust, as indicated by gravity models constrained by seismic refraction and receiver function data. The southern Red Sea magmatic segments have been abandoned in Pliocene-Recent triple junction reorganisations, whereas the process of seaward-dipping volcanic sequence emplacement is ongoing in the seismically and volcanically active Main Ethiopian rift. Field, remote sensing, gravity, and seismicity data from the Main Ethiopian and southern Red Sea rifts indicate that seaward-dipping volcanic sequences initiate in moderately stretched continental crust above a narrow zone of dike-intrusion. Our comparison of active and ancient magmatic segments show that they are the precursors to seaward-dipping volcanic sequences analogous to those seen on passive continental margins, and provides insights into the initiation of along-axis segmentation of seafloor-spreading centers.

Imaging subsurface density structure in Luynnier volcanic field, Saudi Arabia, using 3D gravity inversion technique

NASA Astrophysics Data System (ADS)

Aboud, Essam; El-shrief, Adel; Alqahtani, Faisal; Mogren, Saad

2017-04-01

On 19 May, 2009, an earthquake of magnitude (M=5.4) shocked the most volcanically active recent basaltic fields, Luynnier volcanic field, northwestern Saudi Arabia. This event was the largest recorded one since long time ago. Government evacuated the surrounding residents around the epicenter for over 3 months away from any future volcanic activity. The seismic event caused damages to buildings in the village around the epicenter and resulted in surface fissure trending in NNW-SSE direction with about 8 km length. Seismologists from Saudi Geological Survey (SGS) worked out on locating the epicenter and the cause of this earthquake. They collected seismic data from Saudi Geological Surveys Station Network as well as installed broadband seismic stations around the region of the earthquake. They finally concluded that the main cause of the M=5.4 event is dike intrusion at depth of about 5 km (not reached to the surface). In the present work, we carried out detailed ground/airborne gravity survey around the surficial fissure to image the subsurface volcanic structure where about 380 gravity stations were recorded covering the main fissure in an area of 600 km2. Gravity data was analyzed using CET edge detection tools and 3D inversion technique. The results revealed that, there is a magma chamber/body beneath the surface at 5-20 km depth and the main reason for the M=5.4 earthquake is tectonic settings of the Red Sea. Additionally, the area is characterized by set of faults trending in NW direction, parallel to the Red Sea, and most of the volcanic cones were located on faults/contacts implying that, they are structurally controlled. The 8-km surficial crack is extended SE underneath the surface.

SMED - Sulphur MEditerranean Dispersion

NASA Astrophysics Data System (ADS)

Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

2016-04-01

Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model (FLEXPART) for inspecting the transport and dispersion of volcanic plume over the Mediterranean region and the radiative transfer model UVSPEC for inspecting radiative forcing of volcanic sulphates over the Mediterranean region. Preliminary results exploring the Central-Southern Mediterranean, reveal that thought only 2 -7% of Mt. Etna's volcanic clouds disperses over this region, volcanic impact might be relevant in both SO2 abundances and sulphate-volcanogenic derived aerosol.

2010 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: summary of events and response of the Alaska Volcano Observatory

USGS Publications Warehouse

Neal, Christina A.; Herrick, Julie; Girina, O.A.; Chibisova, Marina; Rybin, Alexander; McGimsey, Robert G.; Dixon, Jim

2014-01-01

The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest at 12 volcanic centers in Alaska during 2010. The most notable volcanic activity consisted of intermittent ash emissions from long-active Cleveland volcano in the Aleutian Islands. AVO staff also participated in hazard communication regarding eruptions or unrest at seven volcanoes in Russia as part of an ongoing collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

Constraining Silicate Weathering Processes in an Active Volcanic Complex: Implications for the Long-term Carbon Cycle

NASA Astrophysics Data System (ADS)

Washington, K.; West, A. J.; Hartmann, J.; Amann, T.; Hosono, T.; Ide, K.

2017-12-01

While analyzing geochemical archives and carbon cycle modelling can further our understanding of the role of silicate weathering as a sink in the long-term carbon cycle, it is necessary to study modern weathering processes to inform these efforts. A recent compilation of data from rivers draining basaltic catchments estimates that rock weathering in active volcanic fields (AVFs) consumes atmospheric CO2 approximately three times faster than in inactive volcanic fields (IVFs), suggesting that the eruption and subsequent weathering of large igneous provinces likely played a major role in the carbon cycle in the geologic past [1]. The study demonstrates a significant correlation between catchment mean annual temperature (MAT) and atmospheric CO2 consumption rate for IVFs. However CO2 consumption due to weathering of AVFs is not correlated with MAT as the relationship is complicated by variability in hydrothermal fluxes, reactive surface area, and groundwater flow paths. To investigate the controls on weathering processes in AVFs, we present data for dissolved and solid weathering products from Mount Aso Caldera, Japan. Aso Caldera is an ideal site for studying the how the chemistry of rivers draining an AVF is impacted by high-temperature water/rock interactions, volcanic ash weathering, and varied groundwater flow paths and residence times. Samples were collected over five field seasons from two rivers and their tributaries, cold groundwater springs, and thermal springs. These samples capture the region's temperature and precipitation seasonality. Solid samples of unaltered volcanic rocks, hydrothermally-altered materials, volcanic ash, a soil profile, and suspended and bedload river sediments were also collected. The hydrochemistry of dissolved phases were analyzed at the University of Hamburg, while the mineralogy and geochemical compositions of solid phases were analyzed at the Natural History Museum of Los Angeles. This work will be discussed in the context of volcanic activity and associated silicate weathering in the geologic past. [1] Li, G., J. Hartmann, L. A. Derry, A. J. West, C.-F. You, X. Long, T. Zhan, L. Li, G. Li, and W. Qiu (2016), Temperature dependence of basalt weathering, Earth Planet. Sci. Lett., 443, 59-69.

A new comprehensive database of global volcanic gas analyses

NASA Astrophysics Data System (ADS)

Clor, L. E.; Fischer, T. P.; Lehnert, K. A.; McCormick, B.; Hauri, E. H.

2013-12-01

Volcanic volatiles are the driving force behind eruptions, powerful indicators of magma provenance, present localized hazards, and have implications for climate. Studies of volcanic emissions are necessary for understanding volatile cycling from the mantle to the atmosphere. Gas compositions vary with volcanic activity, making it important to track their chemical variability over time. As studies become increasingly interdisciplinary, it is critical to have a mechanism to integrate decades of gas studies across disciplines. Despite the value of this research to a variety of fields, there is currently no integrated network to house all volcanic and hydrothermal gas data, making spatial, temporal, and interdisciplinary comparison studies time-consuming. To remedy this, we are working to establish a comprehensive database of volcanic gas emissions and compositions worldwide, as part of the Deep Carbon Observatory's DECADE (Deep Carbon Degassing) initiative. Volcanic gas data have been divided into two broad categories: 1) chemical analyses from samples collected directly at the volcanic source, and 2) measurements of gas concentrations and fluxes, such as remotely by mini-DOAS or satellite, or in-plume such as by multiGAS. The gas flux database effort is realized by the Global Volcanism Program of the Smithsonian Institution (abstract by Brendan McCormick, this meeting). The direct-sampling data is the subject of this presentation. Data from direct techniques include samples of gases collected at the volcanic source from fumaroles and springs, tephras analyzed for gas contents, filter pack samples of gases collected in a plume, and any other data types that involve collection of a sample. Data are incorporated into the existing framework of the Petrological Database, PetDB. Association with PetDB is advantageous as it will allow volcanic gas data to be linked to chemical data from lava or tephra samples, forming more complete ties between the eruptive products and the source magma. Eventually our goal is to have a seamless gas database that allows the user to easily access all gas data ever collected at volcanoes. This database will be useful in a variety of science applications: 1) correlating volcanic gas composition to volcanic activity; 2) establishing a characteristic gas composition or total volatile budget for a volcano or region in studies of global chemical cycles; 3) better quantifying the flux and source of volcanic carbon to the atmosphere. The World Organization of Volcano Observatories is populating a volcano monitoring database, WOVOdat, which centers on data collected during times of volcanic unrest for monitoring and hazard purposes. The focus of our database is to gain insight into volcanic degassing specifically, during both eruptive and quiescent times. Coordination of the new database with WOVOdat will allow comparison studies of gas compositions with seismic and other monitoring data during times of unrest, as well as promote comprehensive and cross-disciplinary questions about volcanic degassing.

Geologic Mapping of the Chaac-Camaxtli Region of Io from Galileo Imaging Data

NASA Technical Reports Server (NTRS)

Williams, David A.; Radebaugh, Jani; Keszthelyi, Laszlo P.; McEwen, Alfred S.; Lopes, Rosaly M. C.; Doute, Sylvain; Greekely, Ronald

2003-01-01

We produced a geologic/geomorphologic map of the Chaac-Camaxtli region of Io's leading anti-Jovian hemisphere using regional resolution ( 186 m/pixel) Galileo imaging data collected during orbit I27 (February 2000) integrated with lower resolution (1.4 km/pixel) color data, along with other Galileo imaging and spectral data. This is the first regional map of Io made from Galileo data. Nine color and geomorphologic units have been mapped, and the close proximity of dark and various colored bright materials suggests that there is an intimate interaction between (presumably) silicate magmas and sulfur-bearing volatile materials that produced a variety of explosive and effusive deposits in the recent geologic past. This region of Io is dominated by 11 volcanic centers, most of which are paterae that are analogous in morphology to terrestrial calderas but larger in size. Mapping of structural features indicates that most of the active regions occur in topographic lows, and less active or inactive paterae are associated with topographic highs. This indicates that crustal thickness variations influence magma access to the surface. Surface changes in this region since the Voyager flybys are relatively minor (additional bright and dark flows, color changes), although several active vents have migrated within paterae. This observation, along with the identification of the relatively regular spacing of paterae (approx. 100 - 150 km) along a line, may indicate there are multiple interlacing fractures in the crust that serve as magma conduits from the interior. This connection between volcanism and tectonism may have implications for tidal heating mechanisms and their effect on Io's lithosphere. Some inactive patera floors may be evolving into bright plains material, which, if composed of silicates, might explain the strength of Io's crust to support steep patera walls and tall mountains.

Geologic Mapping of the Chaac-Camaxtli Region of Io from Galileo Imaging Data

NASA Technical Reports Server (NTRS)

Williams, David A.; Radebaugh, Jani; Keszthelyi, Laszlo P.; McEwen, Alfred S.; Lopes, Rosaly M. C.; Doute, Sylvain; Greeley, Ronald

2002-01-01

We produced a geologic/geomorphologic map of the Chaac-Camaxtli region of Io's leading anti-Jovian hemisphere using regional resolution (186 m/pixel) Galileo imaging data collected during orbit I27 (February 2000) integrated with lower resolution (1.4 km/pixel) color data, along with other Galileo imaging and spectral data. This is the first regional map of Io made from Galileo data. Nine color and geomorphologic units have been mapped, and the close proximity of dark and various colored bright materials suggests that there is an intimate interaction between (presumably) silicate magmas and sulfur-bearing volatile materials that produced a variety of explosive and effusive deposits in the recent geologic past. This region of Io is dominated by 11 volcanic centers, most of which are paterae that are analogous in morphology to terrestrial calderas but larger in size. Mapping of structural features indicates that most of the active regions occur in topographic lows, and less active or inactive paterae are associated with topographic highs. This indicates that crustal thickness variations influence magma access to the surface. Surface changes in this region since the Voyager flybys (1979) are relatively minor (additional bright and dark flows, color changes), although several active vents have migrated within paterae. This observation, along with the identification of the relatively regular spacing of paterae (approx. 100- 150 km) along a line, may indicate there are multiple interlacing fractures in the crust that serve as magma conduits from the interior. This connection between volcanism and tectonism may have implications for tidal heating mechanisms and their effect on Io's lithosphere. Some inactive patera floors may be evolving into bright plains material, which, if composed of silicates, might explain the strength of Io's crust to support steep patera walls and tall mountains.

Application of the probabilistic model BET_UNREST during a volcanic unrest simulation exercise in Dominica, Lesser Antilles

NASA Astrophysics Data System (ADS)

Constantinescu, Robert; Robertson, Richard; Lindsay, Jan M.; Tonini, Roberto; Sandri, Laura; Rouwet, Dmitri; Smith, Patrick; Stewart, Roderick

2016-11-01

We report on the first "real-time" application of the BET_UNREST (Bayesian Event Tree for Volcanic Unrest) probabilistic model, during a VUELCO Simulation Exercise carried out on the island of Dominica, Lesser Antilles, in May 2015. Dominica has a concentration of nine potentially active volcanic centers and frequent volcanic earthquake swarms at shallow depths, intense geothermal activity, and recent phreatic explosions (1997) indicate the region is still active. The exercise scenario was developed in secret by a team of scientists from The University of the West Indies (Trinidad and Tobago) and University of Auckland (New Zealand). The simulated unrest activity was provided to the exercise's Scientific Team in three "phases" through exercise injects comprising processed monitoring data. We applied the newly created BET_UNREST model through its software implementation PyBetUnrest, to estimate the probabilities of having (i) unrest of (ii) magmatic, hydrothermal or tectonic origin, which may or may not lead to (iii) an eruption. The probabilities obtained for each simulated phase raised controversy and intense deliberations among the members of the Scientific Team. The results were often considered to be "too high" and were not included in any of the reports presented to ODM (Office for Disaster Management) revealing interesting crisis communication challenges. We concluded that the PyBetUnrest application itself was successful and brought the tool one step closer to a full implementation. However, as with any newly proposed method, it needs more testing, and in order to be able to use it in the future, we make a series of recommendations for future applications.

A Reappraisal of Seismicity and Eruptions of Pantelleria Island and the Sicily Channel (Italy)

NASA Astrophysics Data System (ADS)

Spampinato, Salvatore; Ursino, Andrea; Barbano, Maria Serafina; Pirrotta, Claudia; Rapisarda, Salvatore; Larocca, Graziano; Platania, Pier Raffaele

2017-07-01

Three main tectonic depressions (the Pantelleria, Linosa and Malta troughs), the expression of a continental rift, characterize the Sicily Channel, a region with recent volcanic activity attested by the Pantelleria and Linosa volcanic islands, as well as numerous seamounts. To understand the seismic and eruptive behaviour of this area, we compare historical and instrumental seismicity retrieved from catalogues with recordings from both a mobile seismic network and a permanent station deployed at Pantelleria. A review of historical eruptions affecting the Sicily Channel is also presented. Recent instrumental seismicity shows that the Sicily Channel is characterized by a low level of seismicity, with earthquakes mainly occurring as isolated events, rather than swarms as observed during the few documented eruptive periods. The results of a seismic survey in 2006-2007, as well as the signals recorded by a permanent station in 2010-2014, enable stating that also Pantelleria is characterized by a very low rate of seismicity. The available, though scant, historical information suggests a recurrence time of about a century for the volcanic activity and that eruptions are usually preceded by seismic swarms. In the only historical known eruption of Pantelleria, in addition to shocks, uplifting and increasing fumarole activity, were observed. Notwithstanding the lack of eruptions over the past century, and despite the low recent seismic rate, we believe that the geophysical monitoring of the Sicily Channel needs improving since it is an area of potentially high seismic and volcanic hazard given the presence of several active submarine eruptive centres.

Young Lunar Volcanism: Irregular Mae Patches as Drained Lava Ponds and Inflated Flows

NASA Technical Reports Server (NTRS)

Stopar, J. D.; Robinson, M. S.; van der Bogert, C. H.; Hiesinger, H.; Ostrach, L. R.; Giguere, T. A.; Lawrence, S. J.

2017-01-01

Irregular mare patches (IMPs) were previously proposed as sites of young lunar volcanism and/or endogenic activity [1-3], raising the possibility that volcanism on the Moon may not have ended approximately 1 Ga as determined from surface ages [4]. The wide-spread occurrence of more than 70 IMPs on the lunar nearside suggests a correlation with Th-rich PKT regions and a basaltic composition [1,2]. IMPs exhibit at least two types of deposit morphologies: (a) dome-like, steep-sided and smooth mounds and (b) low-relief ropy (LRR) to hummocky (LRH) materials (Fig. 1). Morphologic indicators such as steep (>40 deg) margin slopes across distances <10 m and crisp boundaries imply ages less than a few 100 Ma [e.g.,1-3]. The IMPs also have relatively few superposed craters >10 m in diameter, and young absolute model ages, which when combined with their superposition on young crater deposits like the continuous ejecta of Aristarchus crater, imply ages approximately 10 Ma to 100 Ma [1,2]. However, the mounds do not exhibit blocky crater morphologies, nor fracturing typical of young volcanic deposits, and the mound texture resembles that of mature regolith [e.g., 2,5], implying a much older age (approximately 3.5 Ga). These contrasting indicators have led to the proposal of widely varying formation mechanisms that range from ancient volcanism modified by recent tectonism [6] or outgassing [3,7], ancient volcanism of atypical materials [8], to Copernican-era volcanism [1,2].

Alignments of volcanic features in the southern hemisphere of Mars produced by migrating mantle plumes

NASA Astrophysics Data System (ADS)

Leone, Giovanni

2016-01-01

Mars shows alignments of volcanic landforms in its southern hemisphere, starting from the equatorial regions and converging towards the South Pole, and visible at global scale. These composite alignments of volcanoes, calderas, shields, vents, heads of valley networks and massifs between the equatorial regions and the southern polar region define twelve different lines, fitted by rhumb lines (loxodromes), that I propose to be the traces of mantle plumes. The morphology of the volcanic centres changes along some of the alignments suggesting different processes of magma emplacement and eruptive style. The diameters of the volcanic centres and of the volcanic provinces are largest at Tharsis and Elysium, directly proportional to the number of alignments starting from them. A minor presence of unaligned volcanic features is observed on the northern lowlands and on the highlands outside the 12 major alignments. The heads of channels commonly interpreted as fluvial valleys are aligned with the other volcanic centres; unaltered olivine is present along their bed-floors, raising severe doubts as to their aqueous origin. Several hypotheses have tried to explain the formation of Tharsis with the migration of a single mantle plume under the Martian lithosphere, but the discovery of twelve alignments, six starting from Tharsis, favours the hypothesis of several mantle plumes as predicted by the model of the Southern Polar Giant Impact (SPGI) and provides a new view on the formation of the volcanic provinces of Mars.

Catastrophic volcanism

NASA Technical Reports Server (NTRS)

Lipman, Peter W.

1988-01-01

Since primitive times, catastrophes due to volcanic activity have been vivid in the mind of man, who knew that his activities in many parts of the world were threatened by lava flows, mudflows, and ash falls. Within the present century, increasingly complex interactions between volcanism and the environment, on scales not previously experienced historically, have been detected or suspected from geologic observations. These include enormous hot pyroclastic flows associated with collapse at source calderas and fed by eruption columns that reached the stratosphere, relations between huge flood basalt eruptions at hotspots and the rifting of continents, devastating laterally-directed volcanic blasts and pyroclastic surges, great volcanic-generated tsunamis, climate modification from volcanic release of ash and sulfur aerosols into the upper atmosphere, modification of ocean circulation by volcanic constructs and attendent climatic implications, global pulsations in intensity of volcanic activity, and perhaps triggering of some intense terrestrial volcanism by planetary impacts. Complex feedback between volcanic activity and additional seemingly unrelated terrestrial processes likely remains unrecognized. Only recently has it become possible to begin to evaluate the degree to which such large-scale volcanic processes may have been important in triggering or modulating the tempo of faunal extinctions and other evolutionary events. In this overview, such processes are examined from the viewpoint of a field volcanologist, rather than as a previous participant in controversies concerning the interrelations between extinctions, impacts, and volcanism.

Earth observation taken by the Expedition 29 crew

NASA Image and Video Library

2011-10-07

ISS029-E-020003 (7 Oct. 2011) --- Parinacota Volcano in the Chile-Bolivia border region, South America is featured in this image photographed by an Expedition 29 crew member on the International Space Station. Volcan Parinacota (?flamingo lake? in the regional Aymara language) is a potentially active stratovolcano located on the Altiplano, a high plateau situated within the Andes Mountains of west-central South America. While no direct observations of eruptive activity are recorded, surface exposure age-dating of lava flows suggests that activity occurred as recently as 290 AD approximately 300 years, according to scientists. Local Aymara stories also suggest that the volcano has erupted during the past 1,000 years. This detailed photograph highlights the symmetrical cone of Parinacota, with its well-developed summit crater (elevation 6,348 meters above sea level) at center. Dark brown to dark gray surfaces to the east and west of the summit include lava flows, pyroclastic deposits, and ash. A companion volcano, Pomerape, is located across a low saddle to the north ? scientists believe this volcano last erupted during the Pleistocene Epoch (extending from approximately 3 million to 12,000 years ago). The summits of both volcanoes are covered by white permanent snowpack and small glaciers. Together, the two volcanoes form the Nevados de Payachata volcanic area. Eruptive activity at Parinacota has directly influenced development of the local landscape beyond the emplacement of volcanic deposits ? approximately 8,000 years ago the western flank of the volcano collapsed, creating a debris avalanche that traveled 22 kilometers to the west. This debris avalanche blocked drainages, leading to the formation of Lake Chungara to the south (upper right). The uneven, hummocky surface of the debris avalanche deposit provides ample catchments for water, as evidenced by the numerous small ponds and Cotacotani Lake to the west.

Hydrogeochemical Investigation of Recharge Pathways to Intermediate and Regional Groundwater in Canon de Valle and Technical Area 16, Los Alamos National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brady, Brendan W.

In aquifers consisting of fractured or porous igneous rocks, as well as conglomerate and sandstone products of volcanic formations, silicate minerals actively dissolve and precipitate (Eby, 2004; Eriksson, 1985; Drever, 1982). Dissolution of hydrated volcanic glass is also known to influence the character of groundwater to which it is exposed (White et al., 1980). Hydrochemical evolution, within saturated zones of volcanic formations, is modeled here as a means to resolve the sources feeding a perched groundwater zone. By observation of solute mass balances in groundwater, together with rock chemistry, this study characterizes the chemical weathering processes active along recharge pathwaysmore » in a mountain front system. Inverse mass balance modeling, which accounts for mass fluxes between solid phases and solution, is used to contrive sets of quantitative reactions that explain chemical variability of water between sampling points. Model results are used, together with chloride mass balance estimation, to evaluate subsurface mixing scenarios generated by further modeling. Final model simulations estimate contributions of mountain block and local recharge to various contaminated zones.« less

Progress in Near Real-Time Volcanic Cloud Observations Using Satellite UV Instruments

NASA Astrophysics Data System (ADS)

Krotkov, N. A.; Yang, K.; Vicente, G.; Hughes, E. J.; Carn, S. A.; Krueger, A. J.

2011-12-01

Volcanic clouds from explosive eruptions can wreak havoc in many parts of the world, as exemplified by the 2010 eruption at the Eyjafjöll volcano in Iceland, which caused widespread disruption to air traffic and resulted in economic impacts across the globe. A suite of satellite-based systems offer the most effective means to monitor active volcanoes and to track the movement of volcanic clouds globally, providing critical information for aviation hazard mitigation. Satellite UV sensors, as part of this suite, have a long history of making unique near-real time (NRT) measurements of sulfur dioxide (SO2) and ash (aerosol Index) in volcanic clouds to supplement operational volcanic ash monitoring. Recently a NASA application project has shown that the use of near real-time (NRT,i.e., not older than 3 h) Aura/OMI satellite data produces a marked improvement in volcanic cloud detection using SO2 combined with Aerosol Index (AI) as a marker for ash. An operational online NRT OMI AI and SO2 image and data product distribution system was developed in collaboration with the NOAA Office of Satellite Data Processing and Distribution. Automated volcanic eruption alarms, and the production of volcanic cloud subsets for multiple regions are provided through the NOAA website. The data provide valuable information in support of the U.S. Federal Aviation Administration goal of a safe and efficient National Air Space. In this presentation, we will highlight the advantages of UV techniques and describe the advances in volcanic SO2 plume height estimation and enhanced volcanic ash detection using hyper-spectral UV measurements, illustrated with Aura/OMI observations of recent eruptions. We will share our plan to provide near-real-time volcanic cloud monitoring service using the Ozone Mapping and Profiler Suite (OMPS) on the Joint Polar Satellite System (JPSS).

Volcanic Forcing of Global Warming during the Pleistocene?

NASA Astrophysics Data System (ADS)

Ericson, J. E.

2002-12-01

The volcanic forcing hypothesis is a new model of global climatic change that may have significance for the history of the Earth and palaeoclimate. The rapid injection of CO2 into the atmosphere during volcanic eruption through underlying massive carbonate appears to trigger global warming through the emission of this greenhouse gas. The record of eruptions (10-20 Kya) of 6 volcanoes overlying 900-10,000 meters of carbonate of the Cordillerian geosyncline in the American Southwest is synchronous with the Late Pleistocene marine transgression record. The record of volcanic eruptions through massive carbonates (20-71 Kya) in Italy, Indonesia and the American Southwest appears to be synchronous with the Wisconsin interstadial events. The extension of the volcanic eruption and climatic records to 71 Kya and inclusion of other volcanic regions represents additional supporting of evidence of the volcanic forcing hypothesis. As an example of these processes, the thermal dissociation of carbonate by magma forming a volcanic conduit (0.4 km high, 0.5 km radius) and subsequent release of carbon dioxide would increase the atmospheric carbon dioxide by 25%. The emitted CO2 would trigger a series of other processes, ocean-atmospheric CO2 exchange, increased photosynthesis and changes with terrestrial biome and global warming. [Recent field reconnaissance of Sunset Crater (erupted 1064-65 AD) indicates the evidence for thermal dissolution of limestone during basaltic extrusion.] Carbon dioxide emitted from volcanic-carbonate sources meets several observed conditions: a rapid increase (<20 years) in atmospheric carbon dioxide, abrupt increases of marine (isotopic) carbon, dilution of atmospheric radiocarbon activity independent of fluctuations of the geomagnetic field and cosmic ray fluxes, temporal covariation of sulfate, Ca+2, and CO2 in ice core records and random, interstadial events during glaciation. Volcanic forcing hypothesis represents a new model and synthesis of natural processes involving recycling of marine carbonate through volcanic eruption leading to global warming.

Gish Bar Patera, Io: Geology and Volcanic Activity, 1996-2001

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

Quaternary fault-controlled volcanic vents and crustal thinning: new insights from the magma-rich Tyrrhenian passive margin (Italy)

NASA Astrophysics Data System (ADS)

Cardello, Giovanni Luca; Conti, Alessia; Consorti, Lorenzo; Do Couto, Damien

2017-04-01

The discover of monogenic Quaternary volcanic vents, that were recently mapped along major fault zones both inland and offshore the Tyrrhenian magma-rich passive margin, poses questions about: timing and role they had into Plio-Pleistocene crustal thinning with relevant consequences for the hazard assessment of an area inhabited by some 0.5 million people. The present-day margin is stretched over 100 km between the Volsci Range (VR) and the Pontian escarpment, being defined by moderate shallow seismicity (Mw≤4.6), relative high geothermal gradient and ongoing hydrothermal activity. Although major central volcanoes (e.g., Colli Albani), occurring at major fault intersections are well studied, smaller volcanic fields were so far unconstrained. Both field survey in the VR and offshore high-resolution geophysical data, allow us to: 1) better define the anatomy of the poorly known VR volcanic field; 2) furnish new insights on the regional Quaternary dynamics; 3) propose modes and reason of magma emplacement. The VR is composed of about 40 punctual and linear monogenic and mostly phreatomagmatic vents occurring at the edges of the Apennine carbonate fold-and-thrust belt and within the VR backbone. Volcanites are characterized by zeolitized to incoherent tuffs and surge deposits locally covered by lavas and slope deposits. Most explosive units host carbonate-rich lithics with different degrees of rounding and decarbonation, which frequently belong to Albian-Cenomanian aquifers. By comparing cross-section with lithic analyses we demonstrate that fragmentation, transport, progressive disintegration and decarbonation occur at multiple depths, depending on the fold-and-thrust belt setting. Thus, along the same vent zone, juvenile lithic composition proves repeated fragmentation within pressured-aquifers, testifying for fissural activity with implications for local seismic and volcanic assessment. Pyroclastic deposits occur as well in the Pontina and Fondi coastal plains at shallow depth suggesting recent (<10 kyr) and possibly local eruptions. Offshore, 25 km north of Ventotene, a middle Pleistocene 200 m-high truncated volcano was found partially covered by middle to recent deposits. It is delimited by well defined WNW-striking fault-controlled escarpment dissected by NE-striking faults. As on the Ponza-Zannone high, volcanic complex occur on a horst intersecting the two main regional trends, possibly associated with younger SE-stretching. Quaternary stretching rotation occurs as a response to Tyrrhenian back-arc opening and contemporaneous inarching of the Apennine front. In this frame, frontal to lateral slab tearing and retreat is tracked by E-rejuvenated volcanic activity along the Palmarola-Vesuvius lineament. In conclusion, we argue about the role NE-dipping crustal detachment(s) may have played into crustal thinning, driving and occasionally hampering magma-emplacement.

Io - Volcanic Eruption

NASA Technical Reports Server (NTRS)

1979-01-01

This photo of a volcanic eruption on Jupiter's satellite Io (dark fountain-like feature near the limb) was taken March 4, 1979, about 12 hours before Voyager 1's closest approach to Jupiter. This and the accompanying photo present the evidence for the first active volcanic eruption ever observed on another body in the solar system. This photo taken from a distance of 310,000 miles (499,000 kilometers), shows a plume-like structure rising more than 60 miles (100 kilometers) above the surface, a cloud of material being produced by an active eruption. At least four eruptions have been identified on Voyager 1 pictures and many more may yet be discovered on closer analysis. On a nearly airless body like Io, particulate material thrown out of a volcano follows a ballistic trajectory, accounting for the dome-like shape of the top of the cloud, formed as particles reach the top of their flight path and begin to fall back. Spherical expansion of outflowing gas forms an even larger cloud surrounding the dust. Several regions have been identified by the infrared instrument on Voyager 1 as being several hundred degrees Fahrenheit warmer than surrounding terrain, and correlated with the eruptions. The fact that several eruptions appear to be going on simultaneously makes Io the most active surface in the solar system and suggests to scientists that Io is undergoing continuous volcanism, revising downward the age of Io's surface once again. JPL manages and controls the Voyager Project for NASA's Office of Space Science.

Imaging an off-axis volcanic field in the Main Ethiopian Rift using 3-D magnetotellurics

NASA Astrophysics Data System (ADS)

Huebert, J.; Whaler, K. A.; Fisseha, S.; Hogg, C.

2017-12-01

In active continental rifts, asthenospheric upwelling and crustal thinning result in the ascent of melt through the crust to the surface. In the Main Ethiopian Rift (MER), most volcanic activity is located in magmatic segments in the rift centre, but there are areas of significant off-axis magmatism as well. The Butajira volcanic field is part of the Silti Debre Zeyt Fault (SDZF) zone in the western Main Ethiopian Rift. It is characterized by densely clustered volcanic vents (mostly scoria cones) and by limited seismic activity, which is mainly located along the big border faults that form the edge of a steep escarpment. Seismic P-Wave tomography reveals a crustal low velocity anomaly in this area. We present newly collected Magnetotelluric (MT) data to image the electrical conductivity structure of the area. We deployed 12 LMT instruments and 27 broadband stations in the western flank of the rift to further investigate the along-rift and depth extent of a highly conductive region under the SDZF which was previously identified by MT data collected on the central volcano Aluto and along a cross-rift transverse. This large conductor was interpreted as potential pathways for magma and fluid in the crust. MT Stations were positioned in five NW-SE running 50 km long profiles, covering overall 100km along the rift and providing good coverage for a 3-D inversion of the data to image this enigmatic area of the MER.

Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): part 2--morphological and mineralogical features.

PubMed

Calabrese, S; D'Alessandro, W

2015-01-01

Volcanic emissions were studied at Mount Etna (Italy) by using moss-bags technique. Mosses were exposed around the volcano at different distances from the active vents to evaluate the impact of volcanic emissions in the atmosphere. Morphology and mineralogy of volcanic particulate intercepted by mosses were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Particles emitted during passive degassing activity from the two active vents, Bocca Nuova and North East Crater (BNC and NEC), were identified as silicates, sulfates and halide compounds. In addition to volcanic particles, we found evidences also of geogenic, anthropogenic and marine spray input. The study has shown the robustness of this active biomonitoring technique to collect particles, very useful in active volcanic areas characterized by continuous degassing and often not easily accessible to apply conventional sampling techniques. Copyright © 2014 Elsevier Ltd. All rights reserved.

Violent Explosive Eruptions in the Ararat Valley, Armenia and Associated Volcanic Hazards

NASA Astrophysics Data System (ADS)

Meliksetian, Khachatur; Savov, Ivan; Connor, Charles; Gevorgyan, Hripsime; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Jrbashyan, Ruben; Ghukasyan, Yura

2016-04-01

The Anatolian-Armenian-Iranian volcanically active orogenic plateau is located in the collision zone between the Arabian and Eurasian plates. The majority of regional geodynamic and petrologic models of collision-related magmatism use the model proposed by Keskin (2003), where volcanism is driven by Neo-Tethyan slab break-off, however an updated model by Neill et al. (2015) and Skolbeltsyn et al.(2014) comprise break-off of two slabs. One of the significant (and understudied) features of the regionally extensive collision zone volcanism is the diversity of eruption styles and also the presence of large number of highly explosive (Plinian) eruptions with VEI≥5 during the Middle-Upper Pleistocene. Geological records of the Ararat depression include several generations of thick low aspect ratio Quaternary ignimbrites erupted from Aragats volcano, as well as up to 3 m thick ash and pumice fall deposit from the Holocene-historically active Ararat volcano. The Ararat tephra fall deposit is studied at 12 newly discovered outcrops covering an area ˜1000 km2. It is noteworthy, that the Ararat tephra deposits are loose and unwelded and observed only in cross-sections in small depressions or in areas where they were rapidly covered by younger, colluvium deposits, presumably of Holocene age. Therefore, the spatial extent of the explosive deposits of Ararat is much bigger but not well preserved due to rapid erosion. Whole rock elemental, isotope (Sr, Nd) and mineral chemistry data demonstrate significant difference in the magma sources of the large Aragats and Ararat stratovolcanoes. Lavas and pyroclastic products of Aragats are high K calc-alkaline, and nearly always deprived from H2O rich phases such as amphibole. In contrasts lavas and pyroclastic products from Ararat are medium K calc-alkaline and volatile-rich (>4.6 wt% H2O and amphibole bearing) magmas. Here we shall attempt to reveal possible geochemical triggers of explosive eruptions in these volcanoes and assess volcanic hazards for the region of Ararat valley based on numerical simulations. Our work is important as Ararat Valley host the capital city of Yerevan (population ˜ 1.4 million) and also the currently operating Armenian Nuclear Power Plant at Metsamor. References Keskin,2003. GRL 30, 1-4; Neill et al., 2015 Chemical Geology, 403, p. 24-41; Skolbeltsyn et al. 2014. Tectonics 33, 207-221.

Cenozoic tectonic reorganizations of the Death Valley region, southeast California and southwest Nevada

USGS Publications Warehouse

Fridrich, Christopher J.; Thompson, Ren A.

2011-01-01

The Death Valley region, of southeast California and southwest Nevada, is distinct relative to adjacent regions in its structural style and resulting topography, as well as in the timing of basin-range extension. Cenozoic basin-fill strata, ranging in age from greater than or equal to 40 to approximately 2 million years are common within mountain-range uplifts in this region. The tectonic fragmentation and local uplift of these abandoned basin-fills indicate a multistage history of basin-range tectonism. Additionally, the oldest of these strata record an earlier, pre-basin-range interval of weak extension that formed broad shallow basins that trapped sediments, without forming basin-range topography. The Cenozoic basin-fill strata record distinct stratigraphic breaks that regionally cluster into tight age ranges, constrained by well-dated interbedded volcanic units. Many of these stratigraphic breaks are long recognized formation boundaries. Most are angular unconformities that coincide with abrupt changes in depositional environment. Deposits that bound these unconformities indicate they are weakly diachronous; they span about 1 to 2 million years and generally decrease in age to the west within individual basins and regionally, across basin boundaries. Across these unconformities, major changes are found in the distribution and provenance of basin-fill strata, and in patterns of internal facies. These features indicate rapid, regionally coordinated changes in strain patterns defined by major active basin-bounding faults, coincident with step-wise migrations of the belt of active basin-range tectonism. The regionally correlative unconformities thus record short intervals of radical tectonic change, here termed "tectonic reorganizations." The intervening, longer (about 3- to 5-million-year) interval of gradual, monotonic evolution in the locus and style of tectonism are called "tectonic stages." The belt of active tectonism in the Death Valley region has abruptly stepped westward during three successive tectonic reorganizations that intervened between four stages of basin-range tectonism, the youngest of which is ongoing. These three tectonic reorganizations also intervened between four stages of volcanic activity, each of which has been distinct in the compositions of magmas erupted, in eruption rates, and in the locus of volcanic activity—which has stepped progressively westward, in close coordination with the step-wise migrations in the locus of basin-range extension. The timing of the Cenozoic tectonic reorganizations in the Death Valley region correlates closely with the documented timing of episodic reorganizations of the boundary between the Pacific and North American plates, to the west and southwest. This supports models that explain the widely distributed transtensional tectonism in southwestern North America since approximately 40 million years ago as resulting from traction imposed by the adjacent, divergent Pacific plate.

Atmospheric control on ground and space based early warning system for hazard linked to ash injection into the atmosphere

NASA Astrophysics Data System (ADS)

Caudron, Corentin; Taisne, Benoit; Whelley, Patrick; Garces, Milton; Le Pichon, Alexis

2014-05-01

Violent volcanic eruptions are common in the Southeast Asia which is bordered by active subduction zones with hundreds of active volcanoes. The physical conditions at the eruptive vent are difficult to estimate, especially when there are only a few sensors distributed around the volcano. New methods are therefore required to tackle this problem. Among them, satellite imagery and infrasound may rapidly provide information on strong eruptions triggered at volcanoes which are not closely monitored by on-site instruments. The deployment of an infrasonic array located at Singapore will increase the detection capability of the existing IMS network. In addition, the location of Singapore with respect to those volcanoes makes it the perfect site to identify erupting blasts based on the wavefront characteristics of the recorded signal. There are ~750 active or potentially active volcanoes within 4000 kilometers of Singapore. They have been combined into 23 volcanic zones that have clear azimuth with respect to Singapore. Each of those zones has been assessed for probabilities of eruptive styles, from moderate (Volcanic Explosivity Index of 3) to cataclysmic (VEI 8) based on remote morphologic analysis. Ash dispersal models have been run using wind velocity profiles from 2010 to 2012 and hypothetical eruption scenarios for a range of eruption explosivities. Results can be used to estimate the likelihood of volcanic ash at any location in SE Asia. Seasonal changes in atmospheric conditions will strongly affect the potential to detect small volcanic eruptions with infrasound and clouds can hide eruption plumes from satellites. We use the average cloud cover for each zone to estimate the probability of eruption detection from space, and atmospheric models to estimate the probability of eruption detection with infrasound. Using remote sensing in conjunction with infrasound improves detection capabilities as each method is capable of detecting eruptions when the other is 'blind' or 'defened' by adverse atmospheric conditions. According to its location, each volcanic zone will be associated with a threshold value (minimum VEI detectable) depending on the seasonality of the wind velocity profile in the region and the cloud cover.

Sakura-jima volcano in Japan as seen from STS-66 Atlantis

NASA Technical Reports Server (NTRS)

1994-01-01

One of the world's most active volcanoes, Sakura-jima in southern-most Kyushu, Japan, erupts dozens of times a year. Volcanic eruptions are so much a part of of daily life in the city of Kagoshima (across the bay and west of Sakura-jima), that school children wear hard hats to school. This photo provides a nice clear view of Sakura-jima on a quiet day - only a plume of steam rises from the summit crater. The summit region is covered with gray ash from the frequent eruptions, and some of the rivers cutting down the mountain (especially the western drainages) appear to be filled with volcanic debris.

Sakura-jima volcano in Japan as seen from STS-66 Atlantis

NASA Image and Video Library

1994-11-14

One of the world's most active volcanoes, Sakura-jima in southern-most Kyushu, Japan, erupts dozens of times a year. Volcanic eruptions are so much a part of of daily life in the city of Kagoshima (across the bay and west of Sakura-jima), that school children wear hard hats to school. This photo provides a nice clear view of Sakura-jima on a quiet day - only a plume of steam rises from the summit crater. The summit region is covered with gray ash from the frequent eruptions, and some of the rivers cutting down the mountain (especially the western drainages) appear to be filled with volcanic debris.

The structural-functional organization of thermotolerant complexes of actinomycetes in desert and volcanic soils

NASA Astrophysics Data System (ADS)

Zenova, G. M.; Kurapova, A. I.; Lysenko, A. M.; Zvyagintsev, D. G.

2009-05-01

It has been found that the number of thermotolerant actinomycetes in strongly heated soils of deserts and volcanic regions is comparable to or exceeds the number of mesophilic actinomycetes. Among the latter group, streptomyces usually predominate; among thermotolerant actinomycetes, representatives of the Micromonospora, Streptosporangium, Actinomadura, Saccharopolyspora, Microtetraspora, and Microbispora genera are identified. Thermotolerant actinomycetes display the full cycle of their development in these soils. The method of fluorescent in situ hybridization has made it possible to determine that mycelial forms predominate among the metabolically active representatives of Actinobacteria; their portion increases with the rise in the temperature of soil incubation.

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

NASA Astrophysics Data System (ADS)

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

2012-12-01

The Ceboruco Volcano (21° 7.688 N, 104° 30.773 W) is located in the northwestern part of the Tepic-Zacoalco graben. Its volcanic activity can be divided in four eruptive cycles differentiated by their VEI and chemical variations as well. As a result of andesitic effusive activity, the "paleo-Ceboruco" edifice was constructed during the first cycle. The end of this cycle is defined by a plinian eruption (VEI between 3 and 4) which occurred some 1020 years ago and formed the external caldera. During the second cycle an andesitic dome built up in the interior of the caldera. The dome collapsed and formed the internal caldera. The third cycle is represented by andesitic lava flows which partially cover the northern and south-southwestern part of the edifice. The last cycle is represented by the andesitic lava flows of the nineteenth century located in the southwestern flank of the volcano. Actually, moderate fumarolic activity occurs in the upper part of the volcano showing temperatures ranging between 20° and 120°C. Some volcanic high frequency tremors have also been registered near the edifice. Shows the updating of the volcanic hazard maps published in 1998, where we identify with SPOT satellite imagery and Google Earth, change in the land use on the slope of volcano, the expansion of the agricultural frontier on the east sides of the Ceboruco volcano. The population inhabiting the area is 70,224 people in 2010, concentrated in 107 localities and growing at an annual rate of 0.37%, also the region that has shown an increased in the vulnerability for the development of economic activities, supported by highway, high road, railroad, and the construction of new highway to Puerto Vallarta, which is built in the southeast sector of the volcano and electrical infrastructure that connect the Cajon and Yesca Dams to Guadalajara city. The most important economic activity in the area is agriculture, with crops of sugar cane (Saccharum officinarum), corn, and jamaica (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.

Regional Tectonic Control of Tertiary Mineralization and Recent Faulting in the Southern Basin-Range Province, an Application of ERTS-1 Data

NASA Technical Reports Server (NTRS)

Bechtold, I. C.; Liggett, M. A.; Childs, J. F.

1973-01-01

Research based on ERTS-1 MSS imagery and field work in the southern Basin-Range Province of California, Nevada and Arizona has shown regional tectonic control of volcanism, plutonism, mineralization and faulting. This paper covers an area centered on the Colorado River between 34 15' N and 36 45' N. During the mid-Tertiary, the area was the site of plutonism and genetically related volcanism fed by fissure systems now exposed as dike swarms. Dikes, elongate plutons, and coeval normal faults trend generally northward and are believed to have resulted from east-west crustal extension. In the extensional province, gold silver mineralization is closely related to Tertiary igneous activity. Similarities in ore, structural setting, and rock types define a metallogenic district of high potential for exploration. The ERTS imagery also provides a basis for regional inventory of small faults which cut alluvium. This capability for efficient regional surveys of Recent faulting should be considered in land use planning, geologic hazards study, civil engineering and hydrology.

Coincidences in time of the Imbrium Basin impact and Apollo 15 KREEP volcanic series: Impact-induced melting?

NASA Technical Reports Server (NTRS)

Ryder, Graham

1992-01-01

On the Earth there may be no firm evidence that impacts can induce volcanic activity. However, the Moon does provide a very likely example of volcanism induced by an immense impact: the Imbrium Basin-forming event was immediately succeeded by a crustal partial melting event that released KREEP lava flows over a wide area. These two events are presently indistinguishable in radiometric age. The sample record indicates that such KREEP volcanism had not occurred in the region prior to that time, and never occurred again. Such coincidence in time implies a genetic relationship between the two events, and impact-induced partial melting appears to be the only candidate process. This conclusion rests essentially on the arguments that: (1) the Imbrium Basin event took place 3.86 +/- 0.02 Ga ago; (2) the Apennine Bench Formation postdates Imbrium; (3) the Apollo 15 KREEP basalts are 3.85 +/- 0.03 Ga old; (4) the Apollo 15 KREEP basalts are derived from the Apennine Bench Formation; and (5) the Apollo 15 KREEP basalts are volcanic. Thus, the Apollo 15 KREEP basalts represent a unique volcanic unit that immediately postdates the Imbrium event (within 20 Ma, possibly much less). The evidence for the links in the argument are sketched, and some implications for initial conditions are described. Ramifications of the process for the early history of the Earth are briefly explored.

Andean analogue for Late Carboniferous volcanic arc and arc flank environments of the western New England Orogen, New South Wales, Australia

NASA Astrophysics Data System (ADS)

McPhei, J.

1987-07-01

Late Carboniferous continental conglomerates interbedded with silicic ignimbrite sheets outcrop along more than 400 km of the western margin of the southern portion of the New England Orogen. Farther east, the coeval sedimentary facies are volcanogenic shallow marine and turbidite deposits. The volcanic source terrain, no longer exposed, was located to the west of the existing conglomerate-ignimbrite sequences and was underlain by continental crust which is, in part, represented by the northern Lachlan Fold Belt. The regional Late Carboniferous palaeogeography was similar to that of the present-day western continental margin of South America. The geology of the oceanward-flank of the Andean arc in northern Chile and a section of the Late Carboniferous continental sequence near Currabubula are comparable in detail. The Andean stratovolcanoes and ignimbrite centres thus provide the means of reconstruction of the Late Carboniferous volcanic source terrain. The geological record of both of these continental margin volcanic arcs, preserved in deposits of the arc flanks, is shaped by volcanism, especially the eruption of voluminous ignimbrites, and by uplift, deformation and glaciation centered on the arc. For the arc sections considered, diversity in the flank sequences arises because these controls vary in importance spatially and during the life of the arc (20-30 Ma). For the entire Andean arc, arc-parallel variations in the sites of active volcanism and its character appear to be related to differences in the continental crust thickness and the circumstances of subduction of oceanic crust, particularly the dip of the Benioff Zone. By analogy, variation in the age, duration and style of volcanic activity along the late Palaeozoic magmatic arc of the western New England Orogen perhaps reflects the former existence of significant differences in crust thickness and in the angle of subduction.

From middle Miocene to late Quaternary spatial and temporal evolution of Cappadocian Volcanism

NASA Astrophysics Data System (ADS)

Aydar, E.; Cubukcu, E.; Ersoy, O.; Kabadayı, E.; Duncan, R.

2009-04-01

Cappadocian Volcanism, Central Turkey was active from Miocene to upper Holocene, originating from varying sources and presents various dynamics. Central Anatolia constitutes a plateau reaching to 1100-1200 meters from the sea level. From Miocene to Quaternary, the volcanism and/or its relationships with local tectonic targeted in numerous works. Those works can be classified as follows: (i) volcanism-tectonic relationship (Pasquare et al, 1988; Toprak and Goncuoglu, 1993; Toprak, 1998, Dhont et al, 1998; Froger et al, 1998), (ii) volcanological, petrological, geochemical works on stratovolcanoes, monogenetic vents, ignimbrites (Batum, 1978; Ercan, 1985; Aydar, 1992; Aydar and Gourgaud, 1993; Aydar et al, 1994; Aydar et al, 1995; Le Pennec et al, 1994; Druitt et al, 1995; Aydar and Gourgaud, 1998; Deniel et al, 1998, Temel, 1998; Kuzucuoglu et al, 1998; Mouralis et al, 2002; Sen et al, 2003) (iii) Geophysical works on the missing calderas (Ongur, 1978; Ekingen, 1982; Froger et al,1998). Cappadocian landscape is made principally of eroded ignimbirites forming fair chimneys. Apart from the ignimbrites, Cappadocia bears several stratovolcanoes (Mt Erciyes, Mt. Hasan) and numerous monogenetic vents (cinder cones, maars, domes) and some andesitic dacitic relicts of lava fields intercalated within the ignimbritic sequence. Although the stratovolcanoes have some historical activities, their initial eruptions occured in Miocene (Kecikalesi stage of Mt Hasan- 13 My), Pliocene (Kocdag stage of Mt Erciyes). The monogenetic vents demonstrate interestingly bi-modal character which is typically found in rifted regions of the world. Origin of this young volcanism is proposed as collision related transitional alkaline-calcalkaline association (Aydar, 1992, Deniel et al, 1998), is also linked to the subduction (Olanca, 1994). Our preliminary data on the Quaternary rhyolitic glass combined with chemical analysis of the Miocene volcanics exhibit that a slight transition from peraluminious to metaluminious toward a rough peralkaline character of volcanics with time. A Rifting (?) occurs and its evolution is unknown and in the frame of this work, a detailed geochronology and geochemistry will be proposed.

Venus - Dead or alive?

NASA Technical Reports Server (NTRS)

Taylor, Harry A., Jr.; Cloutier, Paul A.

1986-01-01

In situ nightside electric field observations from the Pioneer Venus Orbiter have been interpreted as evidence of extensive lightning in the lower atmosphere of Venus. The scenario, including proposed evidence of clustering of lightning over surface highland regions, has encouraged the acceptance of currently active volcanic output as part of several investigations of the dynamics and chemistry of the atmosphere and the geology of the planet. However, the correlation between the 100-hertz electric field events attributed to lightning and nightside ionization troughs resulting from the interaction of the solar wind with the ionosphere indicates that the noise results from locally generated plasma instabilities and not from any behavior of the lower atmosphere. Furthemore, analysis of the spatial distribution of the noise shows that it is not clustered over highland topography, but rather occurs at random throughout the latitude and longitude regions sampled by the orbiter during the first 5 years of operation, from 1978 to 1984. Thus the electric field observations do not identify lightning and do not provide a basis for inferring the presence of currently active volcanic output. In the absence of known evidence to the contrary, it appears that Venus is no longer active.

Seismotectonic features of the African plate: the possible dislocation of a continent

NASA Astrophysics Data System (ADS)

Meghraoui, Mustapha

2014-05-01

The African continent is made of seismically active structures with active deformation in between main substratum shields considered as stable continental interiors. Seismically active regions are primarily located along rift zones, thrust and fold mountain belts, transform faults and volcanic fields. The active tectonic structures generated large and destructive earthquakes in the past with significant damage and economic losses in Africa. Although some regions of the continent show a low-level of seismic activity, several large earthquakes (with M > 7) have occurred in the past. The presence of major active faults that generate destructive earthquakes is among the most important geological and geophysical hazards for the continent. National and International scientific projects dealing with the seismic hazards assessment are increasing in seismically active regions in Africa. The UNESCO-SIDA/IGCP (Project 601 http://eost.u-strasbg.fr/~igcp601/) support the preparation and implementation of the "Seismotectonic Map of Africa". Therefore, new seismotectonic data with the regional analysis of earthquake hazards became necessary as a basis for a mitigation of the earthquake damage. A database in historical and instrumental seismicity, active tectonics, stress tensor distribution, earthquake geology and paleoseismology, active deformation, earthquake geodesy (GPS) and gravity, crustal structure studies, magnetic and structural segmentation, volcanic fields, collision tectonics and rifting processes is prepared to constrain the geodynamic evolution of the continent. Taking into account the geological, tectonic and geophysical characteristics, we define six seismotectonic provinces that characterize the crustal deformation. With the previously identified Somalia tectonic block, the seismotectonic and geophysical framework of the continent reveal the existence of the Cameroon volcanic line, the South African tectonic block with transform faulting and Cape folding system, the Libyan rifting and Maghreb thrusting. Although bearing a relatively slow deformation with regards to the East Africa Rift System, the Nubia plate previously considered as a homogeneous tectonic block appears to be dislocating progressively also forming a system of microplates. A synthesis of earthquake studies and regional deformation exposed in a seismotectonic map hitherto serves as a basis for the seismic hazard evaluations and the reduction of seismic risks. * IGCP/SIDA: International Geoscience Program/Swedish International Cooperation Authority http://www.unesco.org/science/IGCP IGCP-601 Working Group: Paulina Amponsah (Ghana Atomic Energy Commission), Atalay Ayele (Addis Ababa University, Ethiopia), Bekoa Ateba (Inst. of Geol. and Min. Res., Buea, Cameroon), Abdelhakim Ayadi (CRAAG, Algeria), Abdunnur Bensuleman (University of Tripoli, Libya), Damien Delvaux (Royal Museum for Central Africa, Tervuren, Belgium), Mohamed El Gabry (National Research Institute of Geophysics, Cairo, Egypt), Rui-Manuel Fernandes (Universidade da Beira Interior, Portugal), Mustapha Meghraoui (IPG Strasbourg, France), Vunganai Midzi & Magda Roos (Council for Geoscience, Pretoria, South Africa), and Youssef Timoulali (CNRST, Rabat, Morocco).

2005 Volcanic Activity in Alaska, Kamchatka, and the Kurile Islands: Summary of Events and Response of the Alaska Volcano Observatory

USGS Publications Warehouse

McGimsey, R.G.; Neal, C.A.; Dixon, J.P.; Ushakov, Sergey

2008-01-01

The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity at or near 16 volcanoes in Alaska during 2005, including the high profile precursory activity associated with the 2005?06 eruption of Augustine Volcano. AVO continues to participate in distributing information about eruptive activity on the Kamchatka Peninsula, Russia, and in the Kurile Islands of the Russian Far East, in conjunction with the Kamchatkan Volcanic Eruption Response Team (KVERT) and the Sakhalin Volcanic Eruption Response Team (SVERT), respectively. In 2005, AVO helped broadcast alerts about activity at 8 Russian volcanoes. The most serious hazard posed from volcanic eruptions in Alaska, Kamchatka, or the Kurile Islands is the placement of ash into the atmosphere at altitudes traversed by jet aircraft along the North Pacific and Russian Trans East air routes. AVO, KVERT, and SVERT work collaboratively with the National Weather Service, Federal Aviation Administration, and the Volcanic Ash Advisory Centers to provide timely warnings of volcanic eruptions and the production and movement of ash clouds.

Yardang-Sculpted Deposits from Apollonaris Patera

NASA Image and Video Library

2015-08-12

This observation from NASA Mars Reconnaissance Orbiter spacecraft shows a terrain of relatively smooth region that transitions into sharp ridges called yardangs on Apollonaris Patera. These ridges, aligned in the nearly same direction, are called yardangs. Yardangs are not unique to Mars. Many yardangs can be found on Earth, in very dry regions with strong prevailing winds. Yardangs are formed when a surface that is composed of materials of differing strengths (i.e., of both harder and softer materials) is shaped by the abrasive action of sand and dust carried by the wind. In this case, and given the proximity of the Apollonaris Patera volcanic center, we think that these wind-carved deposits are comprised of volcanic ash and pyroclastics that erupted from Apollonaris when it was last active in the not-too-distant geologic past. Over time, the softer materials (likely volcanic ash) were eroded away, leaving behind the harder materials in the form of elongated ridges that are parallel to the direction of the prevailing wind. The end result is a stunning, out-of-this-world display of yardangs, sculpted with the artistic chisel of the Martian wind. http://photojournal.jpl.nasa.gov/catalog/PIA19869

Volcanic activity at Tvashtar Catena, Io

USGS Publications Warehouse

Milazzo, M.P.; Keszthelyi, L.P.; Radebaugh, J.; Davies, A.G.; Turtle, E.P.; Geissler, P.; Klaasen, K.P.; Rathbun, J.A.; McEwen, A.S.

2005-01-01

Galileo's Solid State Imager (SSI) observed Tvashtar Catena four times between November 1999 and October 2001, providing a unique look at a distinctive high latitude volcanic complex on Io. The first observation (orbit I25, November 1999) resolved, for the first time, an active extraterrestrial fissure eruption; the brightness temperature was at least 1300 K. The second observation (orbit I27, February 2000) showed a large (??? 500 km 2) region with many, small, hot, regions of active lava. The third observation was taken in conjunction with Cassini imaging in December 2000 and showed a Pele-like, annular plume deposit. The Cassini images revealed an ???400 km high Pele-type plume above Tvashtar Catena. The final Galileo SSI observation of Tvashtar (orbit I32, October 2001), revealed that obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. In this paper, we primarily analyze the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of simple advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping eruptions. The highest reliable color temperature is ???1300 K. Although higher temperatures cannot be ruled out, they do not need to be invoked to fit the observed data. The total power output from the active lavas in February 2000 was at least 1011 W. ?? 2005 Elsevier Inc. All rights reserved.

Systematic Satellite Observations of the Impact of Aerosols from Passive Volcanic Degassing on Local Cloud Properties

NASA Technical Reports Server (NTRS)

Ebmeier, S.K.; Sayer, Andrew M.; Grainger, R. G.; Mather, T. A.; Carboni, E.

2014-01-01

The impact of volcanic emissions, especially from passive degassing and minor explosions, is a source of uncertainty in estimations of aerosol indirect effects. Observations of the impact of volcanic aerosol on clouds contribute to our understanding of both present-day atmospheric properties and of the pre-industrial baseline necessary to assess aerosol radiative forcing. We present systematic measurements over several years at multiple active and inactive volcanic islands in regions of low present-day aerosol burden. The timeaveraged indirect aerosol effects within 200 kilometers downwind of island volcanoes are observed using Moderate Resolution Imaging Spectroradiometer (MODIS, 2002-2013) and Advanced Along-Track Scanning Radiometer (AATSR, 2002- 2008) data. Retrievals of aerosol and cloud properties at Kilauea (Hawaii), Yasur (Vanuatu) and Piton de la Fournaise (la Reunion) are rotated about the volcanic vent to be parallel to wind direction, so that upwind and downwind retrievals can be compared. The emissions from all three volcanoes - including those from passive degassing, Strombolian activity and minor explosions - lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference ranging from 2 - 8 micrometers at the different volcanoes in different seasons. Estimations of the difference in Top of Atmosphere upward Short Wave flux upwind and downwind of the active volcanoes from NASA's Clouds and the Earth's Radiant Energy System (CERES) suggest a downwind elevation of between 10 and 45 Watts per square meter at distances of 150 - 400 kilometers from the volcano, with much greater local (less than 80 kilometers) effects. Comparison of these observations with cloud properties at isolated islands without degassing or erupting volcanoes suggests that these patterns are not purely orographic in origin. Our observations of unpolluted, isolated marine settings may capture processes similar to those in the pre-industrial marine atmosphere.

Geology of the Uranius Group Volcanic Constructs: Uranius Patera, Ceraunius Tholus, and Uranius Tholus

USGS Publications Warehouse

Plescia, J.B.

2000-01-01

Uranius Patera, Ceraunius Tholus, and Uranius Tholus (three small constructs in the northeast Tharsis region) date to the Late Hesperian Epoch and define the earliest phases of constructional volcanism in the Tharsis province. All three volcanoes are interpreted as shields, built by effusive eruptions of low-viscosity lavas, presumably basalt. Ceraunius Tholus and Uranius Tholus also record pyroclastic volcanism in the form of mantling deposits on their flanks; Uranius Patera either did not experience pyroclastic volcanism or the deposits were subsequently buried by later effusive eruptions. Troughs observed on the flanks of Ceraunius Tholus and Uranius Tholus are interpreted to have been formed by fluvial surface runoff. These constructs are coeval with other small edifices in western Tharsis province and are coeval with plains volcanism in the southern Tharsis, Syria, and Sinai regions. ?? 2000 Academic Press.

Geologic map of the northern plains of Mars

USGS Publications Warehouse

Tanaka, Kenneth L.; Skinner, James A.; Hare, Trent M.

2005-01-01

The northern plains of Mars cover nearly a third of the planet and constitute the planet's broadest region of lowlands. Apparently formed early in Mars' history, the northern lowlands served as a repository both for sediments shed from the adjacent ancient highlands and for volcanic flows and deposits from sources within and near the lowlands. Geomorphic evidence for extensive tectonic deformation and reworking of surface materials through release of volatiles occurs throughout the northern plains. In the polar region, Planum Boreum contains evidence for the accumulation of ice and dust, and surrounding dune fields suggest widespread aeolian transport and erosion. The most recent regional- and global-scale maps describing the geology of the northern plains are largely based on Viking Orbiter image data (Dial, 1984; Witbeck and Underwood, 1984; Scott and Tanaka, 1986; Greeley and Guest, 1987; Tanaka and Scott, 1987; Tanaka and others, 1992a; Rotto and Tanaka, 1995; Crumpler and others, 2001; McGill, 2002). These maps reveal highland, plains, volcanic, and polar units based on morphologic character, albedo, and relative ages using local stratigraphic relations and crater counts. This geologic map of the northern plains is the first published map that covers a significant part of Mars using topography and image data from both the Mars Global Surveyor and Mars Odyssey missions. The new data provide a fresh perspective on the geology of the region that reveals many previously unrecognizable units, features, and temporal relations. In addition, we adapted and instituted terrestrial mapping methods and stratigraphic conventions that we think result in a clearer and more objective map. We focus on mapping with the intent of reconstructing the history of geologic activity within the northern plains, including deposition, volcanism, erosion, tectonism, impact cratering, and other processes with the aid of comprehensive crater-density determinations. Mapped areas include all plains regions within the northern hemisphere of Mars, as well as an approximately 300-km-wide strip of cratered highland and volcanic regions, which border the plains. Note that not all of the contiguous northern plains are mapped, because some minor parts of Elysium and Amazonis Planitiae lie south of the equator.

Lunar volcanism produced a transient atmosphere around the ancient Moon

NASA Astrophysics Data System (ADS)

Needham, Debra H.; Kring, David A.

2017-11-01

Studies of the lunar atmosphere have shown it to be a stable, low-density surface boundary exosphere for the last 3 billion years. However, substantial volcanic activity on the Moon prior to 3 Ga may have released sufficient volatiles to form a transient, more prominent atmosphere. Here, we calculate the volume of mare basalt emplaced as a function of time, then estimate the corresponding production of volatiles released during the mare basalt-forming eruptions. Results indicate that during peak mare emplacement and volatile release ∼3.5 Ga, the maximum atmospheric pressure at the lunar surface could have reached ∼1 kPa, or ∼1.5 times higher than Mars' current atmospheric surface pressure. This lunar atmosphere may have taken ∼70 million years to fully dissipate. Most of the volatiles released by mare basalts would have been lost to space, but some may have been sequestered in permanently shadowed regions on the lunar surface. If only 0.1% of the mare water vented during these eruptions remains in the polar regions of the Moon, volcanically-derived volatiles could account for all hydrogen deposits - suspected to be water - currently observed in the Moon's permanently shadowed regions. Future missions to such locations may encounter evidence of not only asteroidal, cometary, and solar wind-derived volatiles, but also volatiles vented from the interior of the Moon.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

Aerogeophysical evidence for active volcanism beneath the West Antarctic Ice Sheet

NASA Technical Reports Server (NTRS)

Blankenship, Donald D.; Bell, Robin E.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.

1993-01-01

Although it is widely understood that the collapse of the West Antarctic Ice Sheet (WAIS) would cause a global sea-level rise of 6 m, there continues to be considerable debate about the response of this ice sheet to climate change. The stability of the WAIS, which is characterized by a bed grounded well below sea level, may depend on geologically controlled conditions at the base, which are independent of climate. Ice streams moving up to 750 m/yr disperse material from the interior through to the oceans. As these ice streams tend to buffer the reservoir of slow-moving inland ice from exposure to oceanic degradation, understanding the ice-streaming process is important for evaluating WAIS stability. There is strong evidence that ice streams slide on a lubricating layer of water-saturated till. Development of this basal layer requires both water and easily eroded sediments. Active lithospheric extension may elevate regional heat flux, increase basal melting, and trigger ice streaming. If a geologically defined boundary with a sharp contrast in geothermal flux exists beneath the WAIS, ice streams may only be capable of operating as a buffer over a restricted region. Should ocean waters penetrate beyond this boundary, the ice-stream buffer would disappear, possibly triggering a collapse of the inland ice reservoir. Aerogeophysical evidence for active volcanism and elevated heat flux beneath the WAIS near the critical region where ice streaming begins is presented.

Subaerial records of large-scale explosive volcanism and tsunami along an oceanic arc, Tonga, SW Pacific

NASA Astrophysics Data System (ADS)

Cronin, S. J.; Smith, I. E.

2015-12-01

We present a new chronology of major terrestrial eruptions and tsunami events for the central Tongan Arc. The active Tonga-Kermadec oceanic arc extends 2500 km northward of New Zealand and hosts many tens of submarine volcanoes with around a dozen forming islands. Despite its obious volcanic setting, the impacts of explosive volcanism and volcano-tectonic related tsunami are an often overlooked in archaeological and paleo-botanical histories, mainly due the lack of good Holocene subaerial exposures. The inhabited small uplifted coral platform islands east of the volcanic arc in Tonga collectively cover only <550 km2. Inspired by local mythology of gods flying overhead with baskets of ash, and an analysis of the high-level wind distribution patterns, lake and wetland sites were investigated along the Tongan chain. In most cases former lagoon basins lifted above sea-level by a combination of tectonic rise and the lowering of mean sea levels by around 2 m since the Mid-Holocene form closed lake or swampy depressions. Coring reveaed between 6 and 20 mineral layers at each site, withn humic sediment or peat. Over thirty new radiocarbon dates were collected to develop a chronology for the sequences and the mineral layers were examined mineralogically and geochemically. These sites reveal mainly tephra fall layers of <6500 cal. years B.P., including several very large and regionally significant tephras. Erupted compositions range from basaltic to dacitic, with some showing compositional change during eruption. In addition, some large eruptions appear to have generated regionally significant tsunami, represented by characteristically mixed sandy layers with lithologies including shell fragment, foraminifera and volcanic particles.

How wide is the East African Rift system?

NASA Astrophysics Data System (ADS)

Pierre, S.; Ebinger, C.; Naum, J.

2017-12-01

There has been a longstanding observation that earthquakes and volcanoes occur mostly at the edges of rigid tectonic plates, but that pattern changes during continental rifting where new plate boundaries are forming. The seismically and volcanically active East African rift system provides an opportunity to evaluate rigid plate tectonic models. The objective of this research is to evaluate the geographic spread of earthquakes and volcanoes across the African plate, including areas interpreted as smaller microplates in East Africa. The National Earthquake Information Center catalog of earthquakes spanning the time period 1976 to July 2017 and the Smithsonian Institution Global Volcanism Program catalogue of Holocene volcanoes were displayed using the open source Geographic Information System package GMT, using command line scripts. Earthquake moment tensors from the Global CMT project were also displayed with locations of earthquakes and volcanoes. We converted all of the earthquake magnitudes to moment magnitude (Mw) for comparison of energy release in different rift sectors. A first-order observation is that earthquakes and volcanoes occur across most of the continental region, and in parts of the oceanic region offshore East Africa. The pattern of earthquakes and volcanoes suggests that the African plate is breaking into smaller plates surrounding by zones of earthquakes and volcanoes, such as the Comoros-Davie Ridge-Madagascar seismo-volcanic zone, and the Southwestern rift zone. A comparison of the geographic distribution of earthquakes and volcanoes from places such as the Malawi rift, which has only one isolated volcanic province, and the Eastern rift, which has volcanoes along its length showed differences in the magnitude frequency distributions, which appear to correlate with the presence or absence of volcanism.

A geochemical and geochronological section through the Eastern Aegean

NASA Astrophysics Data System (ADS)

Boehm, Katharina; Kuiper, Klaudia; Vroon, Pieter; Wijbrans, Jan

2017-04-01

The convergence of Africa and Eurasia and the subduction of a oceanic lithosphere of narrow basins between Gondwana terranes has controlled the geological evolution of the Eastern Mediterranean region since the Cretaceous. This resulted in back-arc extension and lithospheric thinning caused by slab roll-back together with the westward extrusion of Anatolia, in the southwards retreat and stepwise development of the subduction system and also in a low velocity seismic anomaly gap between the Cyprus and Hellenic slab and other slab segments. However, the exact timing of all these events in the Eastern Mediterranean region is still a matter of debate, and the purpose of this study is therefore to disentangle when terrains collided and slab detached in the last 30Ma. In a N-S transect magmatic rocks of the Aegean plate are studied, including volcanics from the islands Nisyros, Kos, Patmos, Chios, Lesbos and Samothraki. Major- and trace elements as well as Sr-Nd-Hf-Pb-O isotopes are used to interpret the different features of the Aegean subduction zone. With this geochemical approach the extend of upwelling hot asthenospheric material from the slab tear can be traced in the recent to Eocene volcanic rocks. The volcanic rocks give a wide scatter in classification diagrams and pose for example the question how the sodium rich volcanic products of Patmos can be explained. On the other hand Chios seems to play a key role around 15 Ma years in a phase of relatively low volcanic activity. To get a reliable timeline of the subduction in the Aegean since the Eocene we are aiming to tie our chemical and isotopic data to parallel obtained geochronological ages. New 40Ar/39Ar data will allow us to get the needed resolution for this time span and material.

P-wave tomography of Northeast Asia: Constraints on the western Pacific plate subduction and mantle dynamics

NASA Astrophysics Data System (ADS)

Ma, Jincheng; Tian, You; Liu, Cai; Zhao, Dapeng; Feng, Xuan; Zhu, Hongxiang

2018-01-01

A high-resolution model of 3-D P-wave velocity structure beneath Northeast Asia and adjacent regions is determined by using 244,180 arrival times of 14,163 local and regional earthquakes and 319,857 relative travel-time residuals of 9988 teleseismic events recorded at ∼2100 seismic stations in the study region. Our tomographic results reveal the subducting Pacific slab clearly as a prominent high-velocity anomaly from the Japan Trench to the North-South Gravity lineament (NSGL) in East China. The NSGL is roughly coincident with the western edge of the stagnant Pacific slab in the mantle transition zone (MTZ). The subducting Pacific slab has partly sunk into the lower mantle beneath Northeast China, but under the Sino-Korean Craton the slab lies horizontally in the MTZ. The NSGL, as an important tectonic line in Mainland China, is marked by sharp differences in the surface topography, gravity anomaly, crustal and lithospheric thickness and mantle seismic velocity from the east to the west. These features of the NSGL and large-scale hot and wet upwelling in the big mantle wedge (BMW) in the east of the NSGL are all related to the subduction processes of the Western Pacific plate. The Changbai intraplate volcanic group is underlain by a striking low-velocity anomaly from the upper MTZ and the BMW up to the surface, and deep earthquakes (410-650 km depths) occur actively in the subducting Pacific slab to the east of the Changbai volcano. We propose that the Changbai volcanic group is caused by upwelling of hot and wet asthenospheric materials and active convection in the BMW. The formation of other volcanic groups in the east of the NSGL is also associated with the subduction-driven corner flow in the BMW.

The NOAA/PMEL Vents Program - 1983 to 2013: A History of Deep-Sea Volcanic and Hydrothermal Exploration and Research

NASA Astrophysics Data System (ADS)

Hammond, S. R.; Baker, E. T.; Embley, R. W.

2015-12-01

Inspiration for the Vents program arose from two serendipitous events: the discovery of seafloor spreading-center hydrothermal venting on the Galápagos Rift in 1977, and NOAA's deployment of the first US civilian research multibeam bathymetric sonar on the NOAA Ship Surveyor in 1979. Multibeam mapping in the NE Pacific revealed an unprecedented and revolutionary perspective of the Gorda and Juan de Fuca spreading centers, thus stimulating a successful exploration for volcanic and hydrothermal activity at numerous locations along both. After the 1986 discovery of the first "megaplume,", quickly recognized as the water column manifestation of a deep submarine volcanic eruption, the Vents program embarked on a multi-decadal effort to discover and understand local-, regional-, and, ultimately, global-scale physical, chemical, and biological ocean environmental impacts of submarine volcanism and hydrothermal venting. The Vents program made scores of scientific discoveries, many of which owed their success to the program's equally innovative and productive technological prowess. These discoveries were documented in hundreds of peer-reviewed papers by Vents researchers and their colleagues around the world. An emblematic success was the internationally recognized, first-ever detection, location, and study of an active deep volcanic eruption in 1993. To continue the Vents mission and further enhance its effectiveness in marine science and technology innovation, the program was reorganized in 2014 into two distinct, but closely linked, programs: Earth-Oceans Interactions and Acoustics. Both are currently engaged in expeditions and projects that maintain the Vents tradition of pioneering ocean exploration and research.

Systematic Satellite Observations of the Impact of Aerosols from Passive Volcanic Degassing on Local Cloud Properties

NASA Technical Reports Server (NTRS)

Ebmeier, S. K.; Sayer, A. M.; Grainger, R. G.; Mather, T. A.; Carboni, E.

2014-01-01

The impact of volcanic emissions is a significant source of uncertainty in estimations of aerosol indirect radiative forcing, especially with respect to emissions from passive de-gassing and minor explosions. Understanding the impact of volcanic emissions on indirect radiative forcing is important assessing present day atmospheric properties and also to define the pre-industrial baseline to assess anthropogenic perturbations. We present observations of the time-averaged indirect aerosol effect within 200 km downwind of isolated island volcanoes in regions of low present-day aerosol burden using MODIS and AATSR data. Retrievals of aerosol and cloud properties at Kilauea (Hawaii), Yasur (Vanuatu) and Piton de la Fournaise (Reunion) are rotated about the volcanic vent according to wind direction, so that retrievals downwind of the volcano can be averaged to improve signal to noise ratio. The emissions from all three volcanoes, including those from passive degassing, strombolian activity and minor explosions lead to measurably increased aerosol optical depth downwind of the active vent. Average cloud droplet effective radius is lower downwind of the volcano in all cases, with the peak difference in effective radius ranging from 48 microns at the different volcanoes. A comparison of these observations with cloud properties at isolated islands with no significant source of aerosol suggests that these patterns are not purely orographic in origin. This approach sets out a first step for the systematic measurement of the effects of present day low altitude volcanic emissions on cloud properties, and our observations of unpolluted, isolated marine settings may capture processes similar to those in the preindustrial marine atmosphere.

Regional Climate Response to Volcanic Radiative Forcing in Middle East and North Africa

NASA Astrophysics Data System (ADS)

Stenchikov, G.; Dogar, M.

2012-04-01

We have tested the regional climate sensitivity in the Middle East and North Africa (MENA) to radiation perturbations caused by the large explosive equatorial volcanic eruptions of the second part of 20th century, El Chichon and Pinatubo occurred, respectively, in 1982 and 1991. The observations and reanalysis data show that the surface volcanic cooling in the MENA region is two-three times larger than the global mean response to volcanic forcing. The Red Sea surface temperature appears to be also very sensitive to the external radiative impact. E.g., the sea surface cooling, associated with the 1991 Pinatubo eruption, caused deep water mixing and coral bleaching for a few years. To better quantify these effects we use the Geophysical Fluid Dynamics Laboratory global High Resolution Atmospheric Model (HIRAM) to conduct simulations of both the El Chichon and Pinatubo impacts with the effectively 25-km grid spacing. We find that the circulation changes associated with the positive phase of the arctic oscillation amplified the winter temperature anomalies in 1982-1984 and 1991-1993. The dynamic response to volcanic cooling also is characterized by the southward shift of the inter-tropical convergence zone in summer and associated impact on the precipitation patterns. Thus, these results suggest that the climate regime in the MENA region is highly sensitive to external forcing. This is important for better understanding of the climate variability and change in this region.

How will melting of ice affect volcanic hazards in the twenty-first century?

PubMed

Tuffen, Hugh

2010-05-28

Glaciers and ice sheets on many active volcanoes are rapidly receding. There is compelling evidence that melting of ice during the last deglaciation triggered a dramatic acceleration in volcanic activity. Will melting of ice this century, which is associated with climate change, similarly affect volcanic activity and associated hazards? This paper provides a critical overview of the evidence that current melting of ice will increase the frequency or size of hazardous volcanic eruptions. Many aspects of the link between ice recession and accelerated volcanic activity remain poorly understood. Key questions include how rapidly volcanic systems react to melting of ice, whether volcanoes are sensitive to small changes in ice thickness and how recession of ice affects the generation, storage and eruption of magma at stratovolcanoes. A greater frequency of collapse events at glaciated stratovolcanoes can be expected in the near future, and there is strong potential for positive feedbacks between melting of ice and enhanced volcanism. Nonetheless, much further research is required to remove current uncertainties about the implications of climate change for volcanic hazards in the twenty-first century.

Tectonics and volcanism of Eastern Aphrodite Terra: No subduction, no spreading

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Characteristics and management of the 2006-2008 volcanic crisis at the Ubinas volcano (Peru)

NASA Astrophysics Data System (ADS)

Rivera, Marco; Thouret, Jean-Claude; Mariño, Jersy; Berolatti, Rossemary; Fuentes, José

2010-12-01

Ubinas volcano is located 75 km East of Arequipa and ca. 5000 people are living within 12 km from the summit. This composite cone is considered the most active volcano in southern Peru owing to its 24 low to moderate magnitude (VEI 1-3) eruptions in the past 500 years. The onset of the most recent eruptive episode occurred on 27 March 2006, following 8 months of heightened fumarolic activity. Vulcanian explosions occurred between 14 April 2006 and September 2007, at a time ejecting blocks up to 40 cm in diameter to distances of 2 km. Ash columns commonly rose to 3.5 km above the caldera rim and dispersed fine ash and aerosols to distances of 80 km between April 2006 and April 2007. Until April 2007, the total volume of ash was estimated at 0.004 km 3, suggesting that the volume of fresh magma was small. Ash fallout has affected residents, livestock, water supplies, and crop cultivation within an area of ca. 100 km 2 around the volcano. Continuous degassing and intermittent mild vulcanian explosions lasted until the end of 2008. Shortly after the initial explosions on mid April 2006 that spread ash fallout within 7 km of the volcano, an integrated Scientific Committee including three Peruvian institutes affiliated to the Regional Committee of Civil Defense for Moquegua, aided by members of the international cooperation, worked together to: i) elaborate and publish volcanic hazard maps; ii) inform and educate the population; and iii) advise regional authorities in regard to the management of the volcanic crisis and the preparation of contingency plans. Although the 2006-2008 volcanic crisis has been moderate, its management has been a difficult task even though less than 5000 people now live around the Ubinas volcano. However, the successful management has provided experience and skills to the scientific community. This volcanic crisis was not the first one that Peru has experienced but the 2006-2008 experience is the first long-lasting crisis that the Peruvian civil authorities have had to cope with, including attempts to utilize a new alert-level scheme and communications system, and the successful evacuation of 1150 people. Lessons learned can be applied to future volcanic crises in southern Peru, particularly in the case of reawakening of El Misti volcano nearby Arequipa.

Fluid and Melt Inclusions as a tool to understand two high risk volcanic systems: Vesuvius and Campi Flegrei

NASA Astrophysics Data System (ADS)

De Vivo, B.

2017-12-01

In the Campania region (Southern Italy) major active volcanic systems occur in the greater metropolitan area of Naples: Mt. Somma-Vesuvius (SV) and the Campi Flegrei (CF). These volcanic systems have been studied for centuries, yet significant differences of opinions exist about their origins and behaviors. Here, I present some alternative views on issues based on more than 25 years of research, focusing the attention on role played by fluids and magmas based on fluid inclusions (FI) and melt inclusions (MI). In particular, FI and MI data from the Neapolitan volcanoes provide valuable information on the nature of fluid and melt phases trapped during the late evolutionary stages of the alkaline magmatic rocks; such data from past eruptions might be applied to predict the imminence of volcanic eruptions and help protect the population from such hazards. In my and my collaborator studies, FI and MI data have been also used to address the problem of bradyseism in the CF. Using FI and MI, to explain the bradyseism phenomena at CF, my collaborators and I described a new model that involves only hydrothermal fluids of magmatic or meteoric/marine origin with no direct involvement of the magma, other than as a heat source to explain the ground deformation. My collaborators and I explain the bradyseism as a purely hydrothermal model, using processes in porphyry systems as an analogue to those of the CF. SV activity is characterized by cyclic events, and in terms of volcanic risk assessment, a crucial aspect to understand is when a potential next explosive eruption might occur. Evaluating volcanic hazards requires knowledge of the processes that trigger eruptions and the nature and timing of geophysical/geochemical signals related to these processes. One approach to addressing this need is to link observable signals to pre-eruptive magmatic events deduced from studies of erupted magmas. I believe that a way to work in this direction is to determine the residence time, through MI diffusion profiles, of crystals in the magma chamber before an explosive event. I think that working on the crystals residence time of the many plinian eruptions we know to have occurred in SV history, could help us to understand better the relationships between tectonic, regional, event and explosive eruptions.

Crustal Structure of the Tengchong Intra-plate Volcanic Area

NASA Astrophysics Data System (ADS)

Qian, Rongyi; Tong, Vincent C. H.

2015-09-01

We here provide an overview of our current understanding of the crustal structure of Tengchong in southwest China, a key intra-plate volcanic area along the Himalayan geothermal belt. Given that there is hitherto a lack of information about the near-surface structure of intra-plate volcanic areas, we present the first seismic reflection and velocity constraints on the shallow crust between intra-plate volcanoes. Our near-surface seismic images reveal the existence of dome-shaped seismic reflectors (DSRs) in the shallow crust between intra-plate volcanic clusters in Tengchong. The two DSRs are both ~2 km wide, and the shallowest parts of the DSRs are found at the depth of 200-300 m. The velocity model shows that the shallow low-velocity layer (<4 km/s) is anomalously thick (~1 km) in the region where the DSRs are observed. The presence of DSRs indicates significant levels of intra-plate magmatism beneath the along-axis gap separating two volcano clusters. Along-axis gaps between volcano clusters are therefore not necessarily an indicator of lower levels of magmatism. The seismic images obtained in this technically challenging area for controlled-source seismology allow us to conclude that shallow crustal structures are crucial for understanding the along-axis variations of magmatism and hydrothermal activities in intra-plate volcanic areas.

The VeTOOLS Project: an example of how to strengthen collaboration between scientists and Civil Protections in disaster risk reduction

NASA Astrophysics Data System (ADS)

Marti, Joan; Bartolini, Stefania; Becerril, Laura

2016-04-01

VeTOOLS is a project funded by the European Commission's Humanitarian Aid and Civil Protection department (ECHO), and aims at creating an integrated software platform specially designed to assess and manage volcanic risk. The project facilitates interaction and cooperation between scientists and Civil Protection Agencies in order to share, unify, and exchange procedures, methodologies and technologies to effectively reduce the impacts of volcanic disasters. The project aims at 1) improving and developing volcanic risk assessment and management capacities in active volcanic regions; 2) developing universal methodologies, scenario definitions, response strategies and alert protocols to cope with the full range of volcanic threats; 4) improving quantitative methods and tools for vulnerability and risk assessment; and 5) defining thresholds and protocols for civil protection. With these objectives, the VeTOOLS project points to two of the Sendai Framework resolutions for implementing it: i) Provide guidance on methodologies and standards for risk assessments, disaster risk modelling and the use of data; ii) Promote and support the availability and application of science and technology to decision-making, and offers a good example on how a close collaboration between science and civil protection is an effective way to contribute to DRR. European Commission ECHO Grant SI2.695524

Large shield volcanos on Venus: The effect of neutral buoyancy zone development on evolution and altitude distribution

NASA Technical Reports Server (NTRS)

Keddie, S.; Head, James W., III

1992-01-01

The Magellan mission to Venus has emphasized the importance of volcanism in shaping the surface of the planet. Volcanic plains make up 80 percent of the terrain and hundreds of regions of localized eruptions have been identified. Large volcanos, defined as edifices with diameters greater than 100 km, are the sites of some of the most voluminous eruptions. Head et al. have identified 158 of these structures. Their spatial distribution is neither random nor arranged in linear chains as on the Earth; large volcanos on Venus are concentrated in two large, near-equatorial clusters that are also the site of many other forms of volcanic activity. The set of conditions that must be met on Venus that controls the change from widespread, distributed volcanism to focused, shield-building volcanism is not well understood. Future studies of transitional features will help to address this problem. It is likely, however, that the formation and evolution of a neutral buoyancy zone (NBZ) plays an important role in both determining the style of the volcanism and the development of the volcanic feature once it has begun to erupt. Head and Wilson have suggested that the high surface pressure on Venus may inhibit volatile exsolution, which may influence the density distribution of the upper crust and hence control the nature and location of a NBZ. The extreme variations in pressure with elevation may result in significantly different characteristics of such a NBZ at different locations on the planet. In order to test these ideas regarding the importance of NBZ development in the evolution of a large shield and to determine the style of volcanism, three large volcanos that occur at different basal elevations were examined and the distribution of large volcanos as a function of altitude was determined.

Earth Observation

NASA Image and Video Library

2013-09-03

ISS036-E-039778 (3 Sept. 2013) --- Caldera lakes to the northwest of Rome, Italy are featured in this image photographed by an Expedition 36 crew member on the International Space Station. The Lazio region of central Italy has many landforms of volcanic origin, including several large lakes that mark the locations of ancient volcanoes. This photograph highlights two such lakes, Lago di Vico and Lago Bracciano, located to the northwest of the capital city of Rome. Both lakes are located within calderas, large depressions that form after violent explosive eruptions empty a volcano’s underlying magma chamber. Any remnants of the volcanic edifice can then collapse into the newly-formed void space, leading to the creation of large depressions. These depressions can then fill partially or completely with water, forming permanent lakes. Lago Bracciano (left) is the larger of the two lakes highlighted in the image; it is approximately eight kilometers wide at its widest point, and is located 32 kilometers northwest of Rome. According to scientists, the volcanic activity that led to the formation of Lago Bracciano began approximately 600,000 years ago and continued to approximately 40,000 years ago as part of the formation of the Sabatini volcanic complex. While part of the lake formation was due to caldera collapse of part of a large magma chamber, the current depression was also formed by movement along numerous faults in the area – a process known as volcano-tectonic collapse. Located approximately 24 kilometers to the north-northwest of Lago Bracciano, Lago di Vico (right) occupies part of a caldera associated with eruptive activity that began approximately 800,000 years ago and continued until approximately 90,000 years ago. The caldera formed largely by the catastrophic eruption of the ancestral Vico volcano approximately 200,000-150,000 years ago. The final phase of volcanic activity in the caldera led to the formation of a small lava cone in the northeast quadrant known as Mount Venus. The extent of the lakes of Bracciano and Vico are readily apparent in this image due to sunglint – light reflecting back towards the observer from the water surfaces. This reflection gives a mirror-like sheen to the water surfaces in the image. Dark green forested areas associated with parks are visible near both lakes, while light gray to white regions indicate built areas - such as the city of Viterbo at right - and tilled fields (bottom center).

Larger benthic foraminiferal turnover across the Eocene-Oligocene transition at Siwa Oasis, Western Desert, Egypt

NASA Astrophysics Data System (ADS)

Orabi, H.; El Beshtawy, M.; Osman, R.; Gadallah, M.

2015-05-01

In the Eocene part of the Siwa Oasis, the larger foraminifera are represented by the genera Nummulites, Arxina, Operculina, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella, Gaziryina and Discocyclina in order of abundance. Operculina continues up to the early Oligocene as modern representatives in tropical regions, while the other genera became extinct. Nevertheless, the most common larger foraminiferal genus Lepidocyclina (Nephrolepidina) appears only in the lowermost Oligocene. In spite of the Eocene-Oligocene (E/O) transition is thought to have been attended by major continental cooling at northern middle and high latitudes, we discover that at the Siwa Oasis, there is a clear warming trend from the late Eocene (extinction level of Nummulites, Sphaerogypsina, Asterocyclina, Grzybowskia, Silvestriella and Discocyclina) to the early Oligocene is observed due to the high abundance of Operculina and occurrence of kaolinite and gypsiferous shale deposits in both Qatrani and El Qara formations (Oligocene) at this transition. The El Qara Formation is a new rock unit proposed herein for the Oligocene (Rupelian age) in the first time. Several episodes of volcanic activity occurred in Egypt during the Cenozoic. Mid Tertiary volcanicity was widespread and a number of successive volcanic pulses are starting in the late Eocene. The release of mantle CO2 from this very active volcanic episode may have in fact directly caused the warm Eocene-Oligocene greenhouse climate effect.

A Proposed Community Network For Monitoring Volcanic Emissions In Saint Lucia, Lesser Antilles

NASA Astrophysics Data System (ADS)

Joseph, E. P.; Beckles, D. M.; Robertson, R. E.; Latchman, J. L.; Edwards, S.

2013-12-01

Systematic geochemical monitoring of volcanic systems in the English-speaking islands of the Lesser Antilles was initiated by the UWI Seismic Research Centre (SRC) in 2000, as part of its volcanic surveillance programme for the English-speaking islands of the Lesser Antilles. This programme provided the first time-series observations used for the purpose of volcano monitoring in Dominica and Saint Lucia, permitted the characterization of the geothermal fluids associated with them, and established baseline studies for understanding of the hydrothermal systems during periods of quiescence (Joseph et al., 2011; Joseph et al., 2013). As part of efforts to improve and expand the capacity of SRC to provide volcanic surveillance through its geothermal monitoring programme, it is necessary to develop economically sustainable options for the monitoring of volcanic emissions/pollutants. Towards this effort we intend to work in collaboration with local authorities in Saint Lucia, to develop a monitoring network for quantifying the background exposure levels of ambient concentrations of volcanic pollutants, SO2 in air and As in waters (as health significant marker elements in the geothermal emissions) that would serve as a model for the emissions monitoring network for other volcanic islands. This programme would facilitate the building of local capacity and training to monitor the hazardous exposure, through the application and transfer of a regionally available low-cost and low-technology SO2 measurement/detection system in Saint Lucia. Existing monitoring technologies to inform evidence based health practices are too costly for small island Caribbean states, and no government policies or health services measures currently exist to address/mitigate these influences. Gases, aerosols and toxic elements from eruptive and non-eruptive volcanic activity are known to adversely affect human health and the environment (Baxter, 2000; Zhang et al., 2008). Investigations into the impact of volcanic emissions on health have been almost exclusively focused on acute responses, or the effects of one-off eruptions (Horwell and Baxter, 2006). However, little attention has been paid to any long-term impacts on human health in the population centers around volcanoes as a result of exposure to passive emissions from active geothermal systems. The role of volcano tourism is also recognized as an important contributor to the economy of volcanic islands in the Lesser Antilles. However, if it is to be promoted as a sustainable sector of the tourism industry tourists, tour guides, and vendors must be made aware of the potential health hazards facing them in volcanic environments.

Timing and development of the Heise volcanic field, Snake River Plain, Idaho, western USA

USGS Publications Warehouse

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

2005-01-01

The Snake River Plain (SRP) developed over the last 16 Ma as a bimodal volcanic province in response to the southwest movement of the North American plate over a fixed melting anomaly. Volcanism along the SRP is dominated by eruptions of explosive high-silica rhyolites and represents some of the largest eruptions known. Basaltic eruptions represent the final stages of volcanism, forming a thin cap above voluminous rhyolitic deposits. Volcanism progressed, generally from west to east, along the plain episodically in successive volcanic fields comprised of nested caldera complexes with major caldera-forming eruptions within a particular field separated by ca. 0.5-1 Ma, similar to, and in continuation with, the present-day Yellowstone Plateau volcanic field. Passage of the North American plate over the melting anomaly at a particular point in time and space was accompanied by uplift, regional tectonism, massive explosive eruptions, and caldera subsidence, and followed by basaltic volcanism and general subsidence. The Heise volcan ic field in the eastern SRP, Idaho, represents an adjacent and slightly older field immediately to the southwest of the Yellowstone Plateau volcanic field. Five large-volume (>0.5 km3) rhyolitic ignimbrites constitute a time-stratigraphic framework of late Miocene to early Pliocene volcanism for the study region. Field relations and high-precision 40Ar/39Ar age determinations establish that four of these regional ignimbrites were erupted from the Heise volcanic field and form the framework of the Heise Group. These are the Blacktail Creek Tuff (6.62 ?? 0.03 Ma), Walcott Tuff (6.27 ?? 0.04 Ma), Conant Creek Tuff (5.51 ?? 0.13 Ma), and Kilgore Tuff (4.45 ?? 0.05 Ma; all errors reported at ?? 2??). The fifth widespread ignimbrite in the regions is the Arbon Valley Tuff Member of the Starlight Formation (10.21 ?? 0.03 Ma), which erupted from a caldera source outside of the Heise volcanic field. These results establish the Conant Creek Tuff as a distinct and widespread ignimbrite in the Heise volcanic field, eliminating former confusion resulting from previous discordant K/Ar and fission-track dates. New 40Ar/39Ar determinations, when combined wi th geochemical, lithologic geophysical, and field data, define the volcanic and tectonic history of the Heise volcanic field and surrounding areas. Volcanic units erupted from the Heise volcanic field also provide temporal control for tectonic events associated with late Cenozoic extension in the Snake Range and with uplift of the Teton Range, Wyoming. In the Snake Range, movement of large (???0.10 km3) slide blocks of Mississippian limestone exposed 50 km to the east of the Heise field occurred between 6.3 and 5.5 Ma and may have been catastrophically triggered by the caldera eruption of the 5.51 ?? 0.13-Ma Conant Creek Tuff. This slide block movement of ???300 vertical meters indicates that the Snake Range had significant relief by at least 5.5 Ma. In Jackson Hole, the distribution of outflow facies of the 4.45 ?? 0.05-Ma Kilgore caldera in the Heise volcanic field on the eastern SRP indicates that the northern Teton Range was not a significant topographic feature at this time. ?? 2005 Geological Society of America.

Investigation of the Volcano-tectonic dynamics of Vulcano Island by long-term (40 years) geophysical data

NASA Astrophysics Data System (ADS)

Bonforte, Alessandro; Alparone, Salvatore; Gambino, Salvatore; Guglielmino, Francesco; Obrizzo, Francesco; Velardita, Rosanna

2015-04-01

Vulcano island is a composite volcanic edifice located in the south-central sector of the Aeolian Archipelago (Tyrrhenian Sea, Italy). It is the southernmost tip of the southern branch of the Y-shaped archipelago; in particular, it is part of the bigger Lipari-Vulcano volcanic complex that comprises the two southernmost islands of the archipelago. This branch of the archipelago is NNW-SSE oriented and represent the off-shore prolongation of the Tindari-Letojanni tectonic lineament in the NE Sicily, splitting the Appennine chain on the west, from the Calabrian arc on the East. N-S compression seems to affect the western side of this NNW-SSE lineament, while extension affects the eastern one, with active volcanism and a NW dipping Benioff plane. Historic activity at Vulcano has been characterized by frequent transitions from phereatomagmatic to minor magmatic activity. The last eruption in 1888-90 was characterized by energetic explosive pulses and defines the so-called "vulcanian" type of activity. Since then, volcanic activity has taken the form of fumarolic emanations of variable intensity and temperature, mainly concentrated at "La Fossa" crater, with maximum temperatures ranging between 200° and 300° C; temperature increases and changes in the gas chemistry, were often observed. The most recent episode began in the 80's when fumarole temperature progressively increased to 690°C in May 1993. Vulcano is active and this favoured monitoring and research studies, in particular focussed on the most recent structures. In the frame of DPC-INGV "V3" project, we investigate the dynamics of the island through ca. 40 years of ground deformation and seismicity data collected by the discrete and continuous INGV monitoring networks. We considered levelling, GPS, EDM, seismic and tilt data. EDM and levelling measurements began in the middle 1970s and since the late 1990s the same EDM network has been surveyed by GPS. By combining and comparing geodetic data and seismicity we are able to distinguish three different scales of phenomena: the first one seems to be linked to the regional tectonics, with a general transpressive kinematics; the second one affects the northern half of the island and could be related to the caldera dynamics; the third one affects only the cone of La Fossa. Regional tectonic stress seems to play an important role in the transition of the volcanic system from a phase of stability to a phase of unrest, inducing the heating and the expansion of shallow hydrothermal fluids. Current local ground deformation at Vulcano may be linked to the geothermal system rather than magmatic sources.

Climatic impact of volcanic eruptions

NASA Technical Reports Server (NTRS)

Rampino, Michael R.

1991-01-01

Studies have attempted to 'isolate' the volcanic signal in noisy temperature data. This assumes that it is possible to isolate a distinct volcanic signal in a record that may have a combination of forcings (ENSO, solar variability, random fluctuations, volcanism) that all interact. The key to discovering the greatest effects of volcanoes on short-term climate may be to concentrate on temperatures in regions where the effects of aerosol clouds may be amplified by perturbed atmospheric circulation patterns. This is especially true in subpolar and midlatitude areas affected by changes in the position of the polar front. Such climatic perturbation can be detected in proxy evidence such as decrease in tree-ring widths and frost rings, changes in the treeline, weather anomalies, severity of sea-ice in polar and subpolar regions, and poor grain yields and crop failures. In low latitudes, sudden temperature drops were correlated with the passage overhead of the volcanic dust cloud (Stothers, 1984). For some eruptions, such as Tambora, 1815, these kinds of proxy and anectdotal information were summarized in great detail in a number of papers and books (e.g., Post, 1978; Stothers, 1984; Stommel and Stommel, 1986; C. R. Harrington, in press). These studies lead to the general conclusion that regional effects on climate, sometimes quite severe, may be the major impact of large historical volcanic aerosol clouds.

An investigation into the utilization of HCMM thermal data for the descrimination of volcanic and Eolian geological units. [Craters of the Moon volcanic field, Idaho; San Francisco volcanic field, Arizona; High Desert, California; and the Cascade Range, California and Oregon

NASA Technical Reports Server (NTRS)

Head, J. W., III (Principal Investigator)

1982-01-01

Analysis of HCMM data shows that the resolution provided by the thermal data is inadequate to permit the identification of individual lava flows within the volcanic test sites. Thermal data of southern California reveals that dune complexes at Kelso and Algodomes are found to be too small to permit adequate investigation of their structure. As part of the study of the San Francisco volcanic field, marked variations in the thermal properties of the region between Flagstaff and the Utah State border were observed. Several well-defined units within the Grand Canyon and the Colorado Plateau were recognized and appear to be very suitable for analysis with HCMM, SEASAT and LANDSAT images. Although individual volcanic constructs within the Cascade Range are too small to permit detailed characterization with the thermal data, the regional volcano/tectonic setting offers a good opportunity for comparing the possible thermal distinction between this area and sedimentary fold belts such as those found in the eastern United States. Strong intra-regional variations in vegetation cover were also tentatively identified for the Oregon test site.

Systematic change in global patterns of streamflow following volcanic eruptions.

PubMed

Iles, Carley E; Hegerl, Gabriele C

2015-11-01

Following large explosive volcanic eruptions precipitation decreases over much of the globe1-6, particularly in climatologically wet regions4,5. Stratospheric volcanic aerosols reflect sunlight, which reduces evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity7. Circulation changes modulate this global precipitation reduction on regional scales1,8-10. Despite the importance of rivers to people, it has been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse observational records of streamflow volume for fifty large rivers from around the world which cover between two and 6 major volcanic eruptions in the 20 th and late 19 th century. We find statistically significant reductions in flow following eruptions for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. When data from neighbouring rivers are combined - based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions - a significant (p<0.1) decrease in streamflow following eruptions is detected in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This suggests that future volcanic eruptions could substantially affect global water availability.

Systematic change in global patterns of streamflow following volcanic eruptions

PubMed Central

Iles, Carley E.; Hegerl, Gabriele C.

2016-01-01

Following large explosive volcanic eruptions precipitation decreases over much of the globe1–6, particularly in climatologically wet regions4,5. Stratospheric volcanic aerosols reflect sunlight, which reduces evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity7. Circulation changes modulate this global precipitation reduction on regional scales1,8–10. Despite the importance of rivers to people, it has been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse observational records of streamflow volume for fifty large rivers from around the world which cover between two and 6 major volcanic eruptions in the 20th and late 19th century. We find statistically significant reductions in flow following eruptions for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. When data from neighbouring rivers are combined - based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions – a significant (p<0.1) decrease in streamflow following eruptions is detected in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This suggests that future volcanic eruptions could substantially affect global water availability. PMID:27279897

Large Volcanic Rises on Venus

NASA Technical Reports Server (NTRS)

Smrekar, Suzanne E.; Kiefer, Walter S.; Stofan, Ellen R.

1997-01-01

Large volcanic rises on Venus have been interpreted as hotspots, or the surface manifestation of mantle upwelling, on the basis of their broad topographic rises, abundant volcanism, and large positive gravity anomalies. Hotspots offer an important opportunity to study the behavior of the lithosphere in response to mantle forces. In addition to the four previously known hotspots, Atla, Bell, Beta, and western Eistla Regiones, five new probable hotspots, Dione, central Eistla, eastern Eistla, Imdr, and Themis, have been identified in the Magellan radar, gravity and topography data. These nine regions exhibit a wider range of volcano-tectonic characteristics than previously recognized for venusian hotspots, and have been classified as rift-dominated (Atla, Beta), coronae-dominated (central and eastern Eistla, Themis), or volcano-dominated (Bell, Dione, western Eistla, Imdr). The apparent depths of compensation for these regions ranges from 65 to 260 km. New estimates of the elastic thickness, using the 90 deg and order spherical harmonic field, are 15-40 km at Bell Regio, and 25 km at western Eistla Regio. Phillips et al. find a value of 30 km at Atla Regio. Numerous models of lithospheric and mantle behavior have been proposed to interpret the gravity and topography signature of the hotspots, with most studies focusing on Atla or Beta Regiones. Convective models with Earth-like parameters result in estimates of the thickness of the thermal lithosphere of approximately 100 km. Models of stagnant lid convection or thermal thinning infer the thickness of the thermal lithosphere to be 300 km or more. Without additional constraints, any of the model fits are equally valid. The thinner thermal lithosphere estimates are most consistent with the volcanic and tectonic characteristics of the hotspots. Estimates of the thermal gradient based on estimates of the elastic thickness also support a relatively thin lithosphere (Phillips et al.). The advantage of larger estimates of the thermal lithospheric thickness is that they provide an explanation for the apparently modest levels of geologic activity on Venus over the last half billion years.

Volcanic hazard assessment for the Canary Islands (Spain) using extreme value theory

NASA Astrophysics Data System (ADS)

Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.

2011-10-01

The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 yr, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterize the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. This is done in three steps: First, we analyze the historical eruptive series to assess independence and homogeneity of the process. Second, we perform a Weibull analysis of the distribution of repose time between successive eruptions. Third, we analyze the non-homogeneous Poisson process with a generalized Pareto distribution as the intensity function.

Internal Structure of the Tuxtla Volcanic Field, Eastern mexico, Derived from Gravity and Aeromagnetic data.

NASA Astrophysics Data System (ADS)

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

2016-12-01

The TVF is a basaltic volcanic field located in the western margin of the Gulf of Mexico in the Mexican State of Veracruz, about 230 km to the SSE of the easternmost tip of the Trans-Mexican Volcanic Belt, and about the same distance from El Chichon volcano, in the Chiapanecan Volcanic Arc, to the SE. It is separated from both volcanic chains also in composition as its rocks are predominantly alkaline. These characteristics prompt questions about its origin, more so since, one of the large volcanoes of the field, San Martin Tuxtla, erupted in 1793 CE. The TVF stands out from the lowlands of the Veracruz margins and is approximately surrounded by the 100 m contour line, while the surrounding areas along the Gulf of Mexico shoreline lie below this contour. Assuming that the rocks above this contour were deposited by the volcanic activity in the area, a good estimate of its volume is obtained by calculating the amount of material contained above this contour. We performed this calculation from the digital elevation model of the area received from restitutions carried out by Mexicós National Institute of Statistics, Geography, and Informatics (Spanish acronym: INEGI). We obtained a total amount of 1300 km3 for this volume. To understand more about the volcanism that has deposited this volume of products, we analyzed the gravimetric and aeromagnetic anomalies of the area and obtained a density model of the causative body. We got a body with a somewhat flattened top at 16 km below sea level from the inversion of the regional. Three separate slender bodies with tops 6 km deep were obtained from the inversion of the residual. The gravity and magnetic anomalies, as well as the inferred source bodies that produce those geophysical anomalies, lie between two large regional faults (Sontecomapan and Catemaco faults), which are proposed as flower structures associated with an inferred deep-seated fault termed the Veracruz Fault. We suggest that the process leading to the formation of the TVF is that of underplating as in several global examples examined by Thybo and Artemieva (Tectonophysics 609, 605-619,2013).

Magmatism and Dynamic Topography of Libya and Tibesti, North Africa

NASA Astrophysics Data System (ADS)

Ball, P.; White, N. J.; Maclennan, J.; Stuart, F. M.

2016-12-01

In the continents, dynamic topography is difficult to determine because the density structure of the lithosphere is poorly known. It is generally agreed that hot upwelling mantle produces dynamic uplift whilst cold downwelling mantle causes regional subsidence. Calculating asthenospheric potential temperatures from basalts provides one important constraint on dynamic uplift at the present day and in the geologic record. The spatial and temporal distribution of eruptive products together with the compositional variation of lavas allows the origin of continental volcanic events to be interpreted. The Cenozoic Libyan volcanic field is characterized by a series of long wavelength topographic swells that may reflect sub-lithospheric dynamic processes. Admittance analysis of gravity and topographic data as well as seismic tomographic imaging suggest that a low density anomaly sits beneath the lithospheric plate. A new regional basaltic database of 188 XRF and ICP-MS analyses together with 39 40Ar-39Ar dates has been assembled. The Libyan volcanic field has been active from at least 17 Ma until the present day. Inverse modeling of rare earth elemental distributions shows that Libyan basalts were generated by melting of a predominantly anhydrous mixed peridotitic mantle source with an asthenospheric potential temperature of 1400 oC. Our results suggest that the existence and distribution of volcanism is caused by the combination of warm, upwelling asthenospheric mantle and thinner (< 100 km) lithosphere beneath Libya whereby melts may ascend to the surface through metasomatized lithospheric channels.

Mapping Intraplate Volcanic Fields: A Case Study from Harrat Rahat, Saudi Arabia

NASA Astrophysics Data System (ADS)

Downs, D. T.; Stelten, M. E.; Champion, D. E.; Dietterich, H. R.

2017-12-01

Continental intraplate mafic volcanoes are typically small-volume (<1 km3), but are one of the most prevalent volcanic landforms on Earth, particularly in the >200 volcanic fields proposed to be active worldwide during the Holocene. Their small individual eruption volumes make any hazards low, however their high prevalence offsets this by raising the risk to populations and infrastructure. The western Arabian Plate hosts at least 15 continental, intra-plate volcanic fields that stretch >3,000 km south to north from Yemen to Turkey. In total, these volcanic fields comprise one of the largest alkali basalt volcanic provinces on Earth, covering an area of 180,000 km2. With a total volume of 20,000 km3, Harrat Rahat in western Saudi Arabia is one of the largest of these volcanic fields. Our study focused on mapping the northern third of the Harrat Rahat volcanic field using a multidisciplinary approach. We have discriminated >200 individual eruptive units, mainly basaltic lava flows throughout Harrat Rahat that are distinguished through a combination of field observations, petrography, geochemistry, paleomagnetism, and 40Ar/39Ar radiometric and 36Cl cosmogenic surface-exposure dating. We have compiled these results into a high-resolution geologic map, which provides new information about the timing, compositions, and eruptive processes of Quaternary volcanism in Harrat Rahat. For example, prior mapping and geochronology undertaken during the 1980s suggested that the majority of mafic and silicic volcanics erupted during the Miocene and Pliocene, whereas several of the youngest-appearing lava flows were interpreted to be Neolithic ( 7,000 to 4,500 years BP) to post-Neolithic. New mapping and age-constrained stratigraphic relations indicate that all exposed volcanic units within the northern third of Harrat Rahat erupted during the Pleistocene, with the exception of a single Holocene eruption in 1256 AD. This new multidisciplinary mapping is critical for understanding the overall spatial, temporal, and compositional evolution of Harrat Rahat, timescales of magmatic processes in the mantle and crust, and understanding hazards and risks associated with the varied styles of volcanism in the region.

Tectonic controls on the genesis of ignimbrites from the Campanian Volcanic Zone, southern Italy

USGS Publications Warehouse

Rolandi, G.; Bellucci, F.; Heizler, M.T.; Belkin, H.E.; de Vivo, B.

2003-01-01

The Campanian Plain is an 80 x 30 km region of southern Italy, bordered by the Apennine Chain, that has experienced subsidence during the Quaternary. This region, volcanologically active in the last 600 ka, has been identified as the Campanian Volcanic Zone (CVZ). The products of three periods of trachytic ignimbrite volcanism (289-246 ka, 157 ka and 106 ka) have been identified in the Apennine area in the last 300 ka. These deposits probably represent distal ash flow units of ignimbrite eruptions which occurred throughout the CVZ. The resulting deposits are interstratified with marine sediments indicating that periods of repeated volcano-tectonic emergence and subsidence may have occurred in the past. The eruption, defined as the Campanian Ignimbrite (CI), with the largest volume (310 km3), occurred in the CVZ 39 ka ago. The products of the CI eruption consist of two units (unit-1 and unit-2) formed from a single compositionally zoned magma body. Slightly different in composition, three trachytic melts constitute the two units. Unit-1 type A is an acid trachyte, type B is a trachyte and type C of unit-2 is a mafic trachyte. The CI, vented from pre-existing neotectonic faults, formed during the Apennine uplift, Initially the venting of volatile-rich type A magma deposited the products to the N-NE of the CVZ. During the eruption, the Acerra graben already affected by a NE-SW fault system, was transected by E-W faults, forming a cross-graben that extended to the gulf of Naples. E-W faults were then further dislocated by NE-SW transcurrent movements. This additional collapse significantly influenced the deposition of the B-type magma of unit-1, and the C-type magma of unit-2 toward the E-SE and S, in the Bay of Naples. The pumice fall deposit underlying the CI deposits, until now thought to be associated with the CI eruption, is not a strict transition from plinian to CI-forming activity. It is derived instead from an independent source probably located near the Naples area. This initial volcanic activity is assumed to be a precursor to the CI trachytic eruptions, which vented along regional faults.

Crustal evolution in Asia: Correlations and connections

NASA Astrophysics Data System (ADS)

Tsunogae, Toshiaki; Kwon, Sanghoon; Santosh, M.

2016-11-01

The Asian region records multiple subduction, accretion and collision processes related to the breakup of Gondwana and Pangea, and the ongoing formation of the future supercontinent Amasia. The oldest geological record of Asia is preserved in Archean crustal fragments which were welded together by later collisional events related to the assembly of several supercontinents. The Asian region also records recent geological events such as volcanic activities and mega-earthquakes related to subduction of oceanic plates along active continental margins and collision of microplates. This region is thus regarded as an excellent field laboratory for examining the evolution of continental crust and cratons, formation and destruction of continents and supercontinents, and related metallogenic and surface environmental processes.

Living With Volcanic Risk in the Cascades

USGS Publications Warehouse

Dzurisin, Daniel; Stauffer, Peter H.; Hendley, James W.

1997-01-01

The Cascade Range of the Pacific Northwest has more than a dozen potentially active volcanoes. Cascade volcanoes tend to erupt explosively, and on average two eruptions occur per century?the most recent were at Mount St. Helens, Washington (1980?86 and 2004?8), and Lassen Peak, California (1914?17). To help protect the Pacific Northwest?s rapidly expanding population, USGS scientists at the Cascades Volcano Observatory in Vancouver, Washington, monitor and assess the hazards posed by the region?s volcanoes.

Evolution of volcanic and tectonic features in caldera settings and their importance in the localization of ore deposits

USGS Publications Warehouse

Rytuba, J.J.

1994-01-01

Many calderas are located along regionally important fault zones that are intermittently active before and after the caldera cycle. In mineralized calderas, the ore deposits are controlled by structures developed during caldera formation and by regional faults which intersect and reactivate the caldera-related structures. The paper discusses the importance of the different stages of caldera formation in connection with the localization of ore deposits. -from Author

Geometric Comparisons of Selected Small Topographically Fresh Volcanoes in the Borealis and Elysium Planitia Volcanic Fields, Mars: Implications for Eruptive Styles

NASA Technical Reports Server (NTRS)

Taylor, K.; Sakimoto, S. E. H.; Mitchell, D.

2002-01-01

MOLA (Mars Orbiter Laser Altimeter) data from small, topographically fresh volcanoes from the Elysium and Borealis regions were gridded and analyzed using GMT (Generic Mapping Tools) programs. Results compare eruptive styles of the two regions, and draw conclusions about the different volcanic regions. Additional information is contained in the original extended abstract.

A geo-spatial data management system for potentially active volcanoes—GEOWARN project

NASA Astrophysics Data System (ADS)

Gogu, Radu C.; Dietrich, Volker J.; Jenny, Bernhard; Schwandner, Florian M.; Hurni, Lorenz

2006-02-01

Integrated studies of active volcanic systems for the purpose of long-term monitoring and forecast and short-term eruption prediction require large numbers of data-sets from various disciplines. A modern database concept has been developed for managing and analyzing multi-disciplinary volcanological data-sets. The GEOWARN project (choosing the "Kos-Yali-Nisyros-Tilos volcanic field, Greece" and the "Campi Flegrei, Italy" as test sites) is oriented toward potentially active volcanoes situated in regions of high geodynamic unrest. This article describes the volcanological database of the spatial and temporal data acquired within the GEOWARN project. As a first step, a spatial database embedded in a Geographic Information System (GIS) environment was created. Digital data of different spatial resolution, and time-series data collected at different intervals or periods, were unified in a common, four-dimensional representation of space and time. The database scheme comprises various information layers containing geographic data (e.g. seafloor and land digital elevation model, satellite imagery, anthropogenic structures, land-use), geophysical data (e.g. from active and passive seismicity, gravity, tomography, SAR interferometry, thermal imagery, differential GPS), geological data (e.g. lithology, structural geology, oceanography), and geochemical data (e.g. from hydrothermal fluid chemistry and diffuse degassing features). As a second step based on the presented database, spatial data analysis has been performed using custom-programmed interfaces that execute query scripts resulting in a graphical visualization of data. These query tools were designed and compiled following scenarios of known "behavior" patterns of dormant volcanoes and first candidate signs of potential unrest. The spatial database and query approach is intended to facilitate scientific research on volcanic processes and phenomena, and volcanic surveillance.

Seismic image of a CO2 reservoir beneath a seismically active volcano

USGS Publications Warehouse

Julian, B.R.; Pitt, A.M.; Foulger, G.R.

1998-01-01

Mammoth Mountain is a seismically active volcano 200 000 to 50 000 years old, situated on the southwestern rim of Long Valley caldera, California. Since 1989 it has shown evidence of unrest in the form of earthquake swarms (Hill et al. 1990), volcanic 'long-period' earthquakes (Pitt and Hill 1994), increased output of magmatic 3He (Sorey et al. 1993) and the emission of about 500 tonnes day-1 of CO2 (Farrar et al. 1995; Hill 1996; M. Sorey, personal communication, 1997) which has killed trees and poses a threat to human safety. Local-earthquake tomography shows that in mid-1989 areas of subsequent tree-kill were underlain by extensive regions where the ratio of the compressional and shear elastic-wave speeds Vp/VS was about 9% lower than in the surrounding rocks. Theory (Mavko and Mukerji 1995), experiment (Ito, DeVilbiss and Nur 1979) and experience at other geothermal/volcanic areas (Julian et al. 1996) and at petroleum reservoirs (Harris et al. 1996) indicate that Vp/VS is sensitive to pore-fluid compressibility, through its effect on Vp. The observed Vp/VS anomaly is probably caused directly by CO2, and seismic Vp/VS tomography is thus a promising tool for monitoring gas concentration and movement in volcanoes, which may in turn be related to volcanic activity.

Earthquake dynamics. Mapping pressurized volcanic fluids from induced crustal seismic velocity drops.

PubMed

Brenguier, F; Campillo, M; Takeda, T; Aoki, Y; Shapiro, N M; Briand, X; Emoto, K; Miyake, H

2014-07-04

Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems. Copyright © 2014, American Association for the Advancement of Science.

Acquisition, capitalization, modeling and sharing of volcanic and seismic monitoring data at La Réunion Island

NASA Astrophysics Data System (ADS)

Boissier, Patrice; Di Muro, Andrea; Henriette, Laura; Rivière, Audrey; Roult, Geneviève; Agrinier, Pierre; Beauducel, François; Davoine, Paule-Annick; Dyon, Joël; Ferrazzini, Valérie; Kowalski, Philippe; Lemarchand, Arnaud; Nercessian, Alexandre; Peltier, Aline; Shapiro, Nikolai; Staudacher, Thomas; Villeneuve, Nicolas

2014-05-01

Piton de la Fournaise is one of the most active volcano in the world with an average of one eruption every 9 months, and rest periods of short duration (only 2 periods exceeded 5 years during the last 50 years). Even if 97 percent of the recent volcanic activity took place within the uninhabited Enclos Fouque caldera; only 3 eruptions occurred outside of the caldera, threatening inhabited areas. The distal 1977 eruption (NE rift), the lave flows of which passed through Piton Sainte-Rose village, destroying houses and forced the evacuation of part of the population, triggered an awareness of volcanic risk at Piton de la Fournaise and led to the creation of the Piton de la Fournaise Volcano Observatory (OVPF - IPGP) in 1979. During thirty-five years, the continuous monitoring networks (geophysical and geochemical), measurements campaigns and phenomenological observation (e.g. imaging and films in the visible and infrared) have built an extraordinary amount of heterogeneous data in terms of format (digital and analog) and storage supports (paper, magnetic tape, floppy disk, etc.). With the aim to structure and distribute the data acquired since its establishment the OVPF conceived an innovative project for "Acquisition, capitalization, modeling and sharing of volcanic and seismic monitoring data at La Reunion Island". The project is funded by the European Regional Development Fund - Convergence (2007-2013) and supported by the local government (Region Reunion). The project is structured around two main parts : - Action 1: acquisition, digitizing and data backup, - Action 2: development of an Information System. On one hand, the project has the ultimate goal to facilitate the distribution of high quality data and long time series to the largest number of beneficiaries of the local, national and international scientific community and of the public and private sectors through IPGP Internet portals (IPGP Data Center and VOLOBSIS). On the other hand, the information system will allow a complete and modern analysis of all the datasets acquired by the OVPF (notably through the WebObs system), and thus improve the understanding of volcanism and seismicity at La Reunion Island.

Stable isotope geochemistry of fumaroles: an insight into volcanic surveillance

NASA Astrophysics Data System (ADS)

Panichi, C.; La Ruffa, G.

2001-12-01

In active volcanic environments magmatic water may accumulate in the volcanic-hosted geothermal systems, or, more rarely may reach the surface along deep fractures inside the volcano crater. Knowledge of magmatic contribution to emerging fluids in volcanic active areas is critical to understanding the chemical evolution of the magma, the conditions in which it exists in the crust, and the mechanisms by which it erupts in the crust. The source of volatiles (especially water) is also of interest when eruptions are driven by the expansion of hydrothermal fluids against atmospheric pressure, without the involvement of fresh magma ('hydrothermal' or 'phreatomagmatic' eruptions). In both cases the occurrence of volcanic and/or phreatic activities is likely to be preceded by substantial isotopic and chemical changes in the crater fumarolic systems. H and O isotopic composition of condensed water from crater fumaroles appear to be able to give strong evidence for the existence of magmatic waters in the high-temperature manifestations of the volcanic systems. Isotopic data and specific hydrological models from seven different volcanic systems (Galeras Volcano, Colombia, Kilauea Volcano, Hawaii, Kudryvy Volcano, Kuril volcanic arc, Mt St Helens, USA; Guagua Pichincha, Ecuador; Vulcano island, Italy; the Aegean Volcanic Arc, Greece) are discussed in order to highlight the possibility to use those isotopic parameters in the assessment of the environmental risks of an active volcanic area.

Structural controls on fluid circulation at the Caviahue-Copahue Volcanic Complex (CCVC) geothermal area (Chile-Argentina), revealed by soil CO2 and temperature, self-potential, and helium isotopes

NASA Astrophysics Data System (ADS)

Roulleau, Emilie; Bravo, Francisco; Pinti, Daniele L.; Barde-Cabusson, Stéphanie; Pizarro, Marcela; Tardani, Daniele; Muñoz, Carlos; Sanchez, Juan; Sano, Yuji; Takahata, Naoto; de la Cal, Federico; Esteban, Carlos; Morata, Diego

2017-07-01

Natural geothermal systems are limited areas characterized by anomalously high heat flow caused by recent tectonic or magmatic activity. The heat source at depth is the result of the emplacement of magma bodies, controlled by the regional volcano-tectonic setting. In contrast, at a local scale a well-developed fault-fracture network favors the development of hydrothermal cells, and promotes the vertical advection of fluids and heat. The Southern Volcanic Zone (SVZ), straddling Chile and Argentina, has an important, yet unexplored and undeveloped geothermal potential. Studies on the lithological and tectonic controls of the hydrothermal circulation are therefore important for a correct assessment of the geothermal potential of the region. Here, new and dense self-potential (SP), soil CO2 and temperature (T) measurements, and helium isotope data measured in fumaroles and thermal springs from the geothermal area located in the north-eastern flank of the Copahue volcanic edifice, within the Caviahue Caldera (the Caviahue-Copahue Volcanic Complex - CCVC) are presented. Our results allowed to the constraint of the structural origin of the active thermal areas and the understanding of the evolution of the geothermal system. NE-striking faults in the area, characterized by a combination of SP, CO2, and T maxima and high 3He/4He ratios (up to 8.16 ± 0.21Ra, whereas atmospheric Ra is 1.382 × 10- 6), promote the formation of vertical permeability preferential pathways for fluid circulation. WNW-striking faults represent low-permeability pathways for hydrothermal fluid ascent, but promote infiltration of meteoric water at shallow depths, which dilute the hydrothermal input. The region is scattered with SP, CO2, and T minima, representing self-sealed zones characterized by impermeable altered rocks at depth, which create local barriers for fluid ascent. The NE-striking faults seem to be associated with the upflowing zones of the geothermal system, where the boiling process produces a high vapor-dominated zone close to the surface, whereas the WNW-striking faults could act as a boundary of the Copahue geothermal area to the south.

Numerical Tsunami Hazard Assessment of the Only Active Lesser Antilles Arc Submarine Volcano: Kick 'em Jenny.

NASA Astrophysics Data System (ADS)

Dondin, F. J. Y.; Dorville, J. F. M.; Robertson, R. E. A.

2015-12-01

The Lesser Antilles Volcanic Arc has potentially been hit by prehistorical regional tsunamis generated by voluminous volcanic landslides (volume > 1 km3) among the 53 events recognized so far. No field evidence of these tsunamis are found in the vincity of the sources. Such a scenario taking place nowadays would trigger hazardous tsunami waves bearing potentially catastrophic consequences for the closest islands and regional offshore oil platforms.Here we applied a complete hazard assessment method on the only active submarine volcano of the arc Kick 'em Jenny (KeJ). KeJ is the southernmost edifice with recognized associated volcanic landslide deposits. From the three identified landslide episodes one is associated with a collapse volume ca. 4.4 km3. Numerical simulations considering a single pulse collapse revealed that this episode would have produced a regional tsunami. An edifice current volume estimate is ca. 1.5 km3.Previous study exists in relationship to assessment of regional tsunami hazard related to shoreline surface elevation (run-up) in the case of a potential flank collapse scenario at KeJ. However this assessment was based on inferred volume of collapse material. We aim to firstly quantify potential initial volumes of collapse material using relative slope instability analysis (RSIA); secondly to assess first order run-ups and maximum inland inundation distance for Barbados and Trinidad and Tobago, i.e. two important economic centers of the Lesser Antilles. In this framework we present for seven geomechanical models tested in the RSIA step maps of critical failure surface associated with factor of stability (Fs) for twelve sectors of 30° each; then we introduce maps of expected potential run-ups (run-up × the probability of failure at a sector) at the shoreline.The RSIA evaluates critical potential failure surface associated with Fs <1 as compared to areas of deficit/surplus of mass/volume identified on the volcanic edifice using (VolcanoFit 2.0 & SSAP 4.5). Tsunami sources characteristics are retrieved from numerical simulation using an hydraulic equations-based code (VolcFlow-Matlab). The tsunami propagation towards the coasts is computed using the open source a Boussinesq equations-based code (FUNWAVE) taking into account high order non linear effects including dissipation.

Lazufre volcanic complex, Chile: attempts to image a large scale magmatic inflation body using regional and teleseismic broadband recordings

NASA Astrophysics Data System (ADS)

Heimann, Sebastian; Trabs, Stefan; Dahm, Torsten

2013-04-01

The Lazufre volcanic area around Lastarria and Cordon del Azufre in the central Andes is the second largest area of presently active volcano related uplift woldwide. A magma reservoir or sill layer, filling in about 10 km depth, is thought to be causative for inflation of an area of more than 1800 km2 (more than four times larger than the total area of the city of Vienna). Uplift rates of up to 3.2 cm/yr were found from InSAR measurements during the past two decades. In 2008, we deployed a network of 17 broadband seismometers in and around the area of active uplift for a period of 2 months. Hundreds of regional and several teleseismic earthquakes were recorded during the experiment. Recorded seismograms show strong anomalies in the region of maximum uplift. We tried to apply (1) tomography with regional events and (2) the receiver function technique with teleseismic events in order to interprete the recorded anomalies. Due to the relatively short dataset and the very heterogeneous structure beneath Lazufre, both techniques could only be applied with limited success. (1) To gain a full tomographic image of the deep underground, ray coverage was not dense enough. However, recorded delay times and amplitude decreases for rays passing through the inflation center carry valuable information. (2) Receiver functions were strongly influenced by 3D structure and could not be intepreted using standard techniques. Nevertheless, careful data selection and comparison with modelling results led to conclusions. In combination, our results allow for some insights into the volcanic complex. We can confirm the presence of molten or partially molten material at a depth of 8 km in the center and 12 km in the outer parts and can derive constraints on the lateral extent of the intrusion. We also find evidence for a huge low velocity zone at greater depth.

Geomorphological evolution of landslides near an active normal fault in northern Taiwan, as revealed by lidar and unmanned aircraft system data

NASA Astrophysics Data System (ADS)

Chang, Kuo-Jen; Chan, Yu-Chang; Chen, Rou-Fei; Hsieh, Yu-Chung

2018-03-01

Several remote sensing techniques, namely traditional aerial photographs, an unmanned aircraft system (UAS), and airborne lidar, were used in this study to decipher the morphological features of obscure landslides in volcanic regions and how the observed features may be used for understanding landslide occurrence and potential hazard. A morphological reconstruction method was proposed to assess landslide morphology based on the dome-shaped topography of the volcanic edifice and the nature of its morphological evolution. Two large-scale landslides in the Tatun volcano group in northern Taiwan were targeted to more accurately characterize the landslide morphology through airborne lidar and UAS-derived digital terrain models and images. With the proposed reconstruction method, the depleted volume of the two landslides was estimated to be at least 820 ± 20 × 106 m3. Normal faulting in the region likely played a role in triggering the two landslides, because there are extensive geological and historical records of an active normal fault in this region. The subsequent geomorphological evolution of the two landslides is thus inferred to account for the observed morphological and tectonic features that are indicative of resulting in large and life-threatening landslides, as characterized using the recent remote sensing techniques.

Tectono-stratigraphic evolution of the Comondú Group from Bahía de La Paz to Loreto, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Drake, William R.; Umhoefer, Paul J.; Griffiths, Alexis; Vlad, Ann; Peters, Lisa; McIntosh, William

2017-11-01

The late Oligocene to mid-Miocene volcanic and volcaniclastic rocks of the Comondú Group are well exposed along the Main Rift Escarpment of Baja California Sur from the Bahía de La Paz region to Bahía Concepción. New mapping and stratigraphic analysis of the Comondú Group from Bahía de La Paz to Loreto reveal facies trends and correlations that form the foundation for a continuous stratigraphic framework for the Comondú Group along a 300 km-long transect on the eastern coast of the Baja California peninsula. Broad but distinct lithostratigraphic trends, alluvial fan facies, and volcanic and volcaniclastic facies record an overall coarsening-upwards package that includes ignimbrite deposits within increasingly proximal alluvial fan deposits, both derived from the east. Geochronology of the unit, including 32 isotope ages and 12 previously unpublished 40Ar/39Ar ages, provide the timing of four main increasingly proximal depositional events. Non-marine sandstone, defining the base of the Comondú Group, was first deposited between 26 Ma and 24 Ma. Emplacement of rhyolitic ignimbrites initiated between 24 Ma and 23 Ma and marked a westward expansion of volcanic activity affiliated with the Sierra Madre Occidental ignimbrite sequences in southern Sinaloa, western Durango, and northern Nayarit. A change in volcanism occurred at 19 Ma to 18 Ma with more ignimbrites, increased intermediate compositions, and the appearance of local vents and proximal volcanic facies. A final localized change of volcanism occurred from 14 to 12 Ma in the Loreto area with an increase of proximal alluvial fan deposits and local volcanoes in the Upper Comondú Group. The bulk of the Upper Comondú Group is absent south of the Loreto area and has either been removed by erosion as a source for the Magdalena Fan in the Pacific Ocean, or was focused primarily in the Loreto area and northward. We use a pre-rift tectonic reconstruction of the Gulf of California to align broad stratigraphic trends along the peninsula, the Gulf conjugate margins, and within the Gulf. The Cascadia arc of Oregon and northern California may be a modern analog for the Comondú Group with a linear volcanic arc formed above shrinking subducting microplates, and a broad backarc region of moderate extension and scattered volcanism.

Laboratory simulations of volcanic ash charging and conditions for volcanic lightning on Venus

NASA Astrophysics Data System (ADS)

Airey, Martin; Warriner-Bacon, Elliot; Aplin, Karen

2017-04-01

Lightning may be important in the emergence of life on Earth and elsewhere, as significant chemical reactions occur in the superheated region around the lightning channel. This, combined with the availability of phosphates in volcanic clouds, suggests that volcanic lightning could have been the catalyst for the formation of biological compounds on the early Earth [1]. In addition to meteorological lightning, volcanic activity also generates electrical discharges within charged ash plumes, which can be a significant contributor to atmospheric electricity on geologically active planets. The physical properties of other planetary atmospheres, such as that of Venus, have an effect on the processes that lead to the generation of volcanic lightning. Volcanism is known to have occurred on Venus in the past, and recent observations made by ESA's Venus Express satellite have provided evidence for currently active volcanism [2-4], and lightning discharges [e.g. 5]. Venusian lightning could potentially be volcanic in origin, since no meteorological mechanisms are known to separate charge effectively in its clouds [6]. The hunt for further evidence for lightning at Venus is ongoing, for example by means of the Lightning and Airglow Camera (LAC) [7] on Akatsuki, the current JAXA mission at Venus. Our laboratory experiments simulate ash generation and measure electrical charging of the ash under typical atmospheric conditions on Earth and Venus. The study uses a 1 litre chamber, which, when pressurised and heated, can simulate the high-pressure, high-temperature, carbon dioxide-dominated atmosphere of Venus at 10 km altitude ( 5 MPa, 650 K). A key finding of previous work [8] is that ash plume-forming eruptions are more likely to occur at higher altitudes such as these on Venus. The chamber contains temperature/pressure monitoring and logging equipment, a rock collision apparatus (based on [9]) to generate the charged rock fragments, and charge measurement electrodes connected to a high-precision electrometer. The separate effects of varying the atmospheric composition, temperature, and pressure on the charges attained and the relationship between particle size and charge polarity will be addressed, and the implications discussed. The key questions considered here are: (a) is volcanic activity a feasible mechanism for lightning generation on Venus, (b) how do the extreme environmental conditions on Venus affect the mechanisms required to generate lightning, (c) what are the implications for volcanic lightning's role in the emergence of life on other planets? [1] Navarro-Gonzalez, R. and Segura, A., (2001) Volcanic lightning and the availability of reactive nitrogen and phosphorus for chemical evolution. [2] Marcq, E., et al. (2012) Nature Geoscience, 1-4 [3] Shalygin, E.V., et al. (2015) Geophys. Res. Lett., 42 [4] Smrekar, S.E., et al. (2010) Science, 328, 5978, 605-608 [5] Russell, C.T., et al. (2008) Journal of Geophysical Research-Planets, 113 [6] Aplin, K.L. and Fischer, G. (In press) Weather, (preprint at https://arxiv.org/abs/1606.03285) [7] Takahashi, Y., et al. (2008) Space Sci. Rev., 137, 1-4, 317-334 [8] Airey, M.W., et al. (2015) Planetary and Space Science, 113-114, 33-48 [9] James, M.R., et al. (2000) Journal of Geophysical Research-Solid Earth, 105, B7, 16641-16649

Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (western Turkey) using cosmogenic 3He and 10Be

NASA Astrophysics Data System (ADS)

Heineke, Caroline; Niedermann, Samuel; Hetzel, Ralf; Akal, Cüneyt

2015-04-01

The Kula volcanic field is the youngest volcanic province in western Anatolia and covers an area of about 600 km2 around the town Kula (Richardson-Bunbury, 1996). Its alkali basalts formed by melting of an isotopically depleted mantle in a region of long-lived continental extension and asthenospheric upwelling (Prelevic et al., 2012). Based on morphological criteria and 40Ar/39Ar dating, four phases of Quaternary activity have been distinguished in the Kula volcanic field (Richardson-Bunbury, 1996; Westaway et al., 2006). The youngest lava flows are thought to be Holocene in age, but so far only one sample from this group was dated by 40Ar/39Ar at 7±2 ka (Westaway et al., 2006). In this study, we analysed cosmogenic 3He in olivine phenocrysts from three basalt flows and one cinder cone to resolve the Holocene history of volcanic eruptions in more detail. In addition, we applied 10Be exposure dating to two quartz-bearing xenoliths found at the surface of one flow and at the top of one cinder cone. The exposure ages fall in the range between ~500 and ~3000 years, demonstrating that the youngest volcanic activity is Late Holocene in age and therefore distinctly younger than previously envisaged. Our results show that the Late Holocene lava flows are not coeval but formed over a period of a few thousand years. We conclude that surface exposure dating of very young volcanic rocks provides a powerful alternative to 40Ar/39Ar dating. References Prelevic, D., Akal, C. Foley, S.F., Romer, R.L., Stracke, A. and van den Bogaard, P. (2012). Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey. Journal of Petrology, 53, 1019-1055. Richardson-Bunbury, J.M. (1996). The Kula Volcanic Field, western Turkey: the development of a Holocene alkali basalt province and the adjacent normal-faulting graben. Geological Magazine, 133, 275-283. Westaway, R., Guillou, H., Yurtmen, S., Beck, A., Bridgland, D., Demir, T., Scaillet, S. and Rowbotham, G. (2006). Late Cenozoic uplift of western Turkey: Improved dating of the Kula Quaternary volcanic field and numerical modelling of the Gediz River terrace staircase. Global and Planetary Change, 51, 131-171.

Developing International Guidelines on Volcanic Hazard Assessments for Nuclear Facilities

NASA Astrophysics Data System (ADS)

Connor, Charles

2014-05-01

Worldwide, tremendous progress has been made in recent decades in forecasting volcanic events, such as episodes of volcanic unrest, eruptions, and the potential impacts of eruptions. Generally these forecasts are divided into two categories. Short-term forecasts are prepared in response to unrest at volcanoes, rely on geophysical monitoring and related observations, and have the goal of forecasting events on timescales of hours to weeks to provide time for evacuation of people, shutdown of facilities, and implementation of related safety measures. Long-term forecasts are prepared to better understand the potential impacts of volcanism in the future and to plan for potential volcanic activity. Long-term forecasts are particularly useful to better understand and communicate the potential consequences of volcanic events for populated areas around volcanoes and for siting critical infrastructure, such as nuclear facilities. Recent work by an international team, through the auspices of the International Atomic Energy Agency, has focused on developing guidelines for long-term volcanic hazard assessments. These guidelines have now been implemented for hazard assessment for nuclear facilities in nations including Indonesia, the Philippines, Armenia, Chile, and the United States. One any time scale, all volcanic hazard assessments rely on a geologically reasonable conceptual model of volcanism. Such conceptual models are usually built upon years or decades of geological studies of specific volcanic systems, analogous systems, and development of a process-level understanding of volcanic activity. Conceptual models are used to bound potential rates of volcanic activity, potential magnitudes of eruptions, and to understand temporal and spatial trends in volcanic activity. It is these conceptual models that provide essential justification for assumptions made in statistical model development and the application of numerical models to generate quantitative forecasts. It is a tremendous challenge in quantitative volcanic hazard assessments to encompass alternative conceptual models, and to create models that are robust to evolving understanding of specific volcanic systems by the scientific community. A central question in volcanic hazards forecasts is quantifying rates of volcanic activity. Especially for long-dormant volcanic systems, data from the geologic record may be sparse, individual events may be missing or unrecognized in the geologic record, patterns of activity may be episodic or otherwise nonstationary. This leads to uncertainty in forecasting long-term rates of activity. Hazard assessments strive to quantify such uncertainty, for example by comparing observed rates of activity with alternative parametric and nonparametric models. Numerical models are presented that characterize the spatial distribution of potential volcanic events. These spatial density models serve as the basis for application of numerical models of specific phenomena such as development of lava flow, tephra fallout, and a host of other volcanic phenomena. Monte Carlo techniques (random sampling, stratified sampling, importance sampling) are methods used to sample vent location and other key eruption parameters, such as eruption volume, magma rheology, and eruption column height for probabilistic models. The development of coupled scenarios (e.g., the probability of tephra accumulation on a slope resulting in subsequent debris flows) is also assessed through these methods, usually with the aid of event trees. The primary products of long-term forecasts are a statistical model of the conditional probability of the potential effects of volcanism, should an eruption occur, and the probability of such activity occurring. It is emphasized that hazard forecasting is an iterative process, and board consideration must be given to alternative conceptual models of volcanism, weighting of volcanological data in the analyses, and alternative statistical and numerical models. This structure is amenable to expert elicitation in order to weight alternative models and to explore alternative scenarios.

The Volcanic History of Mars and Influences on Carbon Outgassing

NASA Astrophysics Data System (ADS)

Bleacher, J. E.; Whelley, P.

2015-12-01

Exploration of Mars has revealed some of the most impressive volcanic landforms found throughout the solar system. Volatiles outgassed from volcanoes were likely to have strongly influenced atmospheric chemistry and affected the martian climate. On Earth the role of carbon involved in volcanic outgassing is strongly influenced by tectonic setting, with the greatest weight percent contributions coming from partial mantle melts associated with hot spot volcanism. Most martian volcanic centers appear to represent this style of volcanism. Thus, one important factor in understanding the martian carbon cycle through time is understanding this volatile's link to the planet's volcanic history. The identified volcanic constructs on Mars are not unlike those of the Earth suggesting similar magmatic and eruptive processes. However, the dimensions of many martian volcanic features are significantly larger. The distribution of volcanoes and volcanic deposits on Mars are not spatially or temporally uniform. Large volcanoes (> 100 km diameter) are spatially concentrated in volcanic provinces that likely represent focused upwellings or zones of crustal weakness that enabled magma ascension. Smaller (10s km diameters) volcanoes such as cones, low shields and fissures are often grouped into fields and their lava flows coalesce to produce low slope plains. In some cases plains lava fields are quite extensive with little to no evidence for the volcanic constructs. Although martian volcanism appears to have been dominated by effusive eruptions with likely contributions from passive degassing from the interior, explosive volcanic centers and deposits are known to exist. After the development of a martian crust the planet's volcanic style appears to have evolved from early explosive activity to effusive activity centered at major volcanoes to effusive distributed activity in fields. However, questions remain as to whether or not these styles significantly overlapped in time and if so, why? As scientists continue to learn more about carbon's role in terrestrial volcanism, it is reasonable to question how and how much carbon was involved in different styles of martian volcanic activity and how carbon and other volatiles have affected the martian atmosphere and climate through time.

Seismicity of the Earth 1900-2010 Mexico and vicinity

USGS Publications Warehouse

Rhea, Susan; Dart, Richard L.; Villaseñor, Antonio; Hayes, Gavin P.; Tarr, Arthur C.; Furlong, Kevin P.; Benz, Harley M.

2011-01-01

Mexico, located in one of the world's most seismically active regions, lies on three large tectonic plates: the North American plate, Pacific plate, and Cocos plate. The relative motion of these tectonic plates causes frequent earthquakes and active volcanism and mountain building. Mexico's most seismically active region is in southern Mexico where the Cocos plate is subducting northwestward beneath Mexico creating the deep Middle America trench. The Gulf of California, which extends from approximately the northern terminus of the Middle America trench to the U.S.-Mexico border, overlies the plate boundary between the Pacific and North American plates where the Pacific plate is moving northwestward relative to the North American plate. This region of transform faulting is the southern extension of the well-known San Andreas Fault system.

Geochemical Overview of the East African Rift System

NASA Astrophysics Data System (ADS)

Furman, T.

2003-12-01

Mafic volcanics of the East African Rift System (EARS) record a protracted history of continental extension that is linked to mantle plume activity. The modern EARS traverses two post-Miocene topographic domes separated by a region of polyphase extension in northern Kenya and southern Ethiopia. Basaltic magmatism commenced ˜45 Ma in this highly extended region, while the onset of plume-related activity took place ˜30 Ma with eruption of flood basalts in central Ethiopia. A spatial and temporal synthesis of EARS volcanic geochemistry shows progressive lithospheric removal (by erosion and melting) as the degree of rifting increases, with basalts in the most highly extended areas recording melting of depleted asthenosphere. Plume contributions are indicated locally in the northern half of the EARS, but are absent from the southern half. The geochemical signatures are compatible with a physical model in which the entire EARS is fed by a discontinuous plume emanating from the core-mantle boundary as the South African Superswell. Quaternary basaltic lavas erupted in the Afar triangle, Red Sea and Gulf of Aden define the geochemical signature attributed to the Afar plume (87Sr/86Sr 0.7034-0.7037, 143Nd/144Nd 0.5129-0.5130; La/Nb 0.6-0.9; Nb/U 40-50). These suites commonly record mixing with ambient upper mantle having less radiogenic isotopes but generally overlapping incompatible trace element abundances. Within the Ethiopian dome both lithospheric and sub-lithoshperic contributions can be documented clearly; lithospheric contributions are manifest in more radiogenic isotope values (87Sr/86Sr up to 0.7050) and distinctive trace element abundances (e.g., La/Nb <2.0, Nb/U > 10). The degree of lithospheric contribution is lowest within the active Main Ethiopian Rift and increases towards the southern margin of the dome. The estimated depth of melting (65-75 km) is consistent with geophysical observations of lithospheric thickness. In regions of prolonged volcanism the lithospheric contributions and estimated melting depths decrease through time, corresponding to a higher degree of rifting. In the Kenyan dome, including the western rift, the degree of extension is low and lithospheric melting is the dominant source for basaltic magmatism. Mafic lavas from these regions have generally lower MgO but higher contents of alkalis, P2O5 and many incompatible trace elements than are observed in the Ethiopian Rift. High values of 87Sr/86Sr, 207Pb/204Pb and Zr/Hf relative to other parts of the EARS indicate melting of metasomatized lithosphere. Melting in this area occurs at depths up to 100+ km, consistent with the thick crustal section observed seismically. Between the topographic domes, basalts from the Turkana region record melting at shallow levels ( ˜35 km) consistent with seismic evidence for nearly complete rifting of the crustal section. The geochemistry of these lavas is dominated by asthenospheric source materials, with only minor lithospheric involvement. Temporal evolution of EARS geochemistry reflects progressive rifting of the thick craton. This change is manifest within lavas that are interpreted as plume-derived, as Tb/Yb values decrease from 30 Ma through the present. The modern thermal anomaly associated with Afar volcanism does not appear to extend below the shallow mantle, but may reflect a large blob of deep mantle material that became stuck to Africa 30 Ma and has contributed to regional volcanism ever since. Relative contributions from this deep mantle source, shallow asthenosphere and lithosphere are controlled by the extent of rifting and cannot be predicted solely on the basis of surface topography.

The Aysen (Southern Chile) 2007 Seismic Swarm: Volcanic or Tectonic Origin?

NASA Astrophysics Data System (ADS)

Comte, D.; Gallego, A.; Russo, R.; Mocanu, V.; Murdie, R.; Vandecar, J.

2007-05-01

The Aysen seismic swarm began January 23, 2007, with a magnitude 5.2 (USGS) earthquake and, after an apparent decrease in activity, continued with a magnitude 5.6 event on February 26. The swarm is characterized by numerous felt earthquakes of small to moderate magnitude, located at crustal depths beneath the Aysen Canal, a prominent fiord of the Chilean littoral. The region is characterized by the subduction of an active oceanic spreading ridge: the Chile Ridge, the divergent Nazca-Antarctic plate boundary, is currently subducting beneath continental South America along the Chile Trench at approximately 46.5°S, forming a plate triple junction in the vicinity of the Taitao Peninsula, somewhat south and west of the swarm. Also, the Liquine-Ofqui dextral strike- slip fault traverses the Aysen Canal in the vicinity of the swarm. This fault has been interpreted as a 1000 km long dextral intra-arc strike-slip fault zone, consisting of two major strands which extend north from the Chile Margin triple junction. The Liquiñe-Ofqui system is marked by several pull-apart basins along its trace through the area. Seismic activity along the Liquiñe-Ofqui fault zone has been poorly studied to date, largely because teleseismic events clearly related to the fault have been few, and southern hemisphere seismic stations are lacking. However, we deployed a dense temporary broad-band seismic network both onland and on the islands in the Aysen region, which allowed us to capture the initial phases of the swarm on some 20 stations, and to determine the background seismicity patterns in this area for the two years preceding the swarm. The swarm could be caused by several processes: the spatial and depth distribution of the events suggests that they are well correlated with reactivation of the southern end of the Liquiñe-Ofqui fault, as defined by geologic studies and onshore gravity data collected in southern Chile. The swarm may be related to formation of new volcanic center between Volcan Hudson (last erupted 1991) and Volcan Maca. Given uncertainties in the event locations, the 2007 seismic swarm could also result from a combination of tectonic motions on the Liquiñe-Ofqui fault system and magmatic arc activity. The two earthquakes with magnitudes over 5 and the numerous felt earthquake of the swarm clearly indicate that seismic hazard estimations in this previously quiescent region must be re-estimated.

Geothermal Energy in the Pacific Region

DTIC Science & Technology

1975-05-01

drilled at Kilauea Volcano , on 0 the Island of Hawaii , by the Colorado Sohool of Mines under a National Science Foundation grant. A second test well has...34•olombia belt of active volcanoes where dacite is commonly reported. The simatic Pacific Basin harbors several areas of active volcanism: Hawaii , Galapagos...reef-capped volcanoes . Numerous articles have been written on many aspects of the geology of Hawaii and notable books include Macdonald and hbbott (1970

The Long Valley Caldera GIS database

USGS Publications Warehouse

Battaglia, Maurizio; Williams, M.J.; Venezky, D.Y.; Hill, D.P.; Langbein, J.O.; Farrar, C.D.; Howle, J.F.; Sneed, M.; Segall, P.

2003-01-01

This database provides an overview of the studies being conducted by the Long Valley Observatory in eastern California from 1975 to 2001. The database includes geologic, monitoring, and topographic datasets related to Long Valley caldera. The CD-ROM contains a scan of the original geologic map of the Long Valley region by R. Bailey. Real-time data of the current activity of the caldera (including earthquakes, ground deformation and the release of volcanic gas), information about volcanic hazards and the USGS response plan are available online at the Long Valley observatory web page (http://lvo.wr.usgs.gov). If you have any comments or questions about this database, please contact the Scientist in Charge of the Long Valley observatory.

Toward Assessing the Causes of Volcanic Diversity in the Cascades Arc

NASA Astrophysics Data System (ADS)

Till, C. B.; Kent, A. J.; Abers, G. A.; Pitcher, B.; Janiszewski, H. A.; Schmandt, B.

2017-12-01

A fundamental unanswered question in subduction system science is the cause of the observed diversity in volcanic arc style at an arc-segment to whole-arc scale. Specifically, we have yet to distinguish the predominant mantle and crustal processes responsible for the diversity of arc volcanic phenomenon, including the presence of central volcanoes vs. dispersed volcanism; episodicity in volcanic fluxes in time and space; variations in magma chemistry; and differences in the extent of magmatic focusing. Here we present a thought experiment using currently available data to estimate the relative role of crustal magmatic processes in producing the observed variations in Cascades arc volcanism. A compilation of available major element compositions of Quaternary arc volcanism and estimates of eruptive volumes are used to examine variations in the composition of arc magmas along strike. We then calculate the Quaternary volcanic heat flux into the crust, assuming steady state, required to produce the observed distribution of compositions via crystallization of mantle-derived primitive magmas vs. crustal melting using experiment constraints on possible liquid lines of descent and crustal melting scenarios. For pure crystallization, heat input into the crust scales with silica content, with dacitic to rhyolite compositions producing significantly greater latent heat relative to basalts to andesites. In contrast, the heat required to melt lower crustal amphibolite decreases with increasing silica and is likely provided by the latent heat of crystallization. Thus we develop maximum and minimum estimates for heat added to the crust at a given SiO2 range. When volumes are considered, we find that the average Quaternary volcanic heat flux at latitudes south of South Sister to be more than twice that to the north. Distributed mafic volcanism produces only a quarter to half the heat flux calculated for the main edifices at a given latitude because of their lesser eruptive volumes and quantities of evolved magma. When we compare our Quaternary heat flux calculations to a variety of geophysical observations, we find that regions of calculated higher volcanic heat flux coincide with regions of significantly lower crustal seismic wave speeds beneath and behind the arc, as well as with regions of significantly higher heat flow.

Volcanic unrest in Kenya: geological history from a satellite perspective

NASA Astrophysics Data System (ADS)

Robertson, E.; Biggs, J.; Edmonds, M.; Vye-Brown, C.

2013-12-01

The East African Rift (EAR) system is a 5,000 km long series of fault bounded depressions that run from Djibouti to Mozambique. In the Kenyan Rift, fourteen Quaternary volcanoes lie along the central rift axis. These volcanoes are principally composed of trachyte pyroclastics and trachyte and basaltic lavas forming low-angle multi-vent edifices. Between 1997 and 2008, geodetic activity has been observed at five Kenyan volcanoes, all of which have undergone periods of caldera collapse and explosive activity. We present a remote-sensing study to investigate the temporal and spatial development of volcanic activity at Longonot volcano. High-resolution mapping using ArcGIS and an immersive 3D visualisation suite (GeovisionaryTM) has been used with imagery derived from ASTER, SPOT5 and GDEM data to identify boundaries of eruptive units and establish relative age in order to add further detail to Longonot's recent eruptive history. Mapping of the deposits at Longonot is key to understand the recent geological history and forms the basis for future volcanic hazard research to inform risk assessments and mitigation programs in Kenya. Calderas at Kenyan volcanoes are elliptical in plan view and we use high-resolution imagery to investigate the regional stresses and structural control leading to the formation of these elliptical calderas. We find that volcanoes in the central and northern segments of the Kenyan rift are elongated nearly parallel to the direction of least horizontal compressive stress, likely as a reflection of the direction of the plate motion vector at the time of caldera collapse. The southern volcanoes however are elongated at an acute angle to the plate motion vector, most likely as a result of oblique opening of the Kenyan rift in this region.

Paleomagnetism in the Determination of the Emplacement Temperature of Cerro Colorado Tuff Cone, El Pinacate Volcanic Field, Sonora, Mexico.

NASA Astrophysics Data System (ADS)

Rodriguez Trejo, A.; Alva-Valdivia, L. M.; Vidal Solano, J. R.; Garcia Amador, B.; Gonzalez-Rangel, J. A.

2014-12-01

Cerro Colorado Maar is located at the World Heritage Site, biosphere reserve El Pinacate and Gran Desierto del Altar, at the NNW region of Sonora, Mexico (in El Pinacate Volcanic Field). It is a tuff cone, about 1 km diameter, result of several phreatomagmatic episodes during the late Quaternary. We report paleomagnetic and rock magnetic properties from fusiform volcanic bombs obtained from the borders of Cerro Colorado. This study is based in the thermoremanent magnetization TRM normally acquired by volcanic rocks, which can be used to estimate the emplacement temperature range. We performed the experiments on 20 lithic fragments (10 cm to 20 cm approximately), taking 6-8 paleomagnetic cores from each. Rock magnetic experiments (magnetic susceptibility vs. temperature (k-T), hysteresis curves and FORC analysis, shows that the main magnetic mineral carriers of magnetization are titanomagnetite and titanohematite in different levels of intergrowth. The k-T curves suggest in many cases, only one magnetic phase, but also in other cases a second magnetic phase. Thermal demagnetization was used to demagnetize the specimens in detailed short steps and make a well-defined emplacement temperature determination ranges. We found that temperature emplacement determination range for these two magnetic phases is between 350-450 °C, and 550-580 °C, respectively. These results are consistent with those expected in an eruption of Surtsey type, showing a distinct volcanic activity compared to the other craters from El Pinacate volcanic field.

Electrical resistivity structure beneath the Hangai Dome, Mongolia: intraplate volcanism and deformation imaged with magnetotelluric data

NASA Astrophysics Data System (ADS)

Comeau, M. J.; Becken, M.; Kaeufl, J.; Kuvshinov, A. V.; Kamm, J.; Grayver, A.; Demberel, S.; Usnikh, S. U.; Batmagnai, E.; Tserendug, S.

2017-12-01

The Hangai Dome in central Mongolia is characterized by intraplate volcanism on a high-elevation intra-continental plateau. Volcanism dates from the Oligocene to the Holocene and is thought to be coincident with the onset of the uplift of the Hangai Dome, indicating that the processes may be linked. However, the processes and driving mechanisms responsible for creating this region remain largely unexplained, due in part to a lack of high-resolution geophysical data over the area. An extensive magnetotelluric (MT) data set was collected over the Hangai Dome in 2016 and 2017, with broadband data (0.002 - 5,000 s) collected at a total of 294 sites. This data set consists of a large array ( 50 km site spacing) and several long ( 600 km) and dense ( 5 km site spacing) profiles that cross the uplifted Hangai Dome. Additionally, they cross the bounding faults of the Hangai block, the Bulnay fault in the north and the Bogd fault of the Gobi-Altai in the south, which have had several M>8 earthquakes in the past century. These MT data have been used to generate electrical resistivity models of the crust and upper mantle in this region. Anomalous, low resistivity ( 30 ohm-m) zones in the lower crust ( 25 - 50 km depth) are spatially associated with the surface expressions of volcanism and modern-day hydrothermal activity. These zones indicate the presence of local accumulations of fluids below the brittle-ductile transition zone. Interestingly, this feature terminates sharply at the South Hangai Fault Zone. Furthermore, lower resistivity pathways in the upper crust (0 - 25 km depth) connect the deeper features to the surface. This is prominently observed below the Hangai's youngest volcanic zones of Tariat/Khorgo and Chuluut, as well as the hot spring area of Tsenkher, near Tsetserleg. Additionally, an electrical signature can be associated with known fault zones and mineralized zones (such as the Bayankhongor mineral belt). An anomalous low-resistivity zone in the upper mantle ( 70 - 100 km) directly below the Hangai Dome can be explained by the presence of a small amount of partial melt. This zone likely represents the region of melt generation for intraplate volcanism and gives evidence for a small-scale (<100 km) asthenospheric upwelling, which contributes to intraplate deformation.

MED SUV TASK 6.3 Capacity building and interaction with decision makers: Improving volcanic risk communication through volcanic hazard tools evaluation, Campi Flegrei Caldera case study (Italy)

NASA Astrophysics Data System (ADS)

Nave, Rosella; Isaia, Roberto; Sandri, Laura; Cristiani, Chiara

2016-04-01

In the communication chain between scientists and decision makers (end users), scientific outputs, as maps, are a fundamental source of information on hazards zoning and the related at risk areas definition. Anyway the relationship between volcanic phenomena, their probability and potential impact can be complex and the geospatial information not easily decoded or understood by not experts even if decision makers. Focusing on volcanic hazard the goal of MED SUV WP6 Task 3 is to improve the communication efficacy of scientific outputs, to contribute in filling the gap between scientists and decision-makers. Campi Flegrei caldera, in Neapolitan area has been chosen as the pilot research area where to apply an evaluation/validation procedure to provide a robust evaluation of the volcanic maps and its validation resulting from end users response. The selected sample involved are decision makers and officials from Campanian Region Civil Protection and municipalities included in Campi Flegrei RED ZONE, the area exposed to risk from to pyroclastic currents hazard. Semi-structured interviews, with a sample of decision makers and civil protection officials have been conducted to acquire both quantitative and qualitative data. The tested maps have been: the official Campi Flegrei Caldera RED ZONE map, three maps produced by overlapping the Red Zone limit on Orthophoto, DTM and Contour map, as well as other maps included a probabilistic one, showing volcanological data used to border the Red Zone. The outcomes' analysis have assessed level of respondents' understanding of content as displayed, and their needs in representing the complex information embedded in volcanic hazard. The final output has been the development of a leaflet as "guidelines" that can support decision makers and officials in understanding volcanic hazard and risk maps, and also in using them as a communication tool in information program for the population at risk. The same evaluation /validation process has been applied also on the scientific output of MED-SUV WP6, as a tool for the short-term probabilistic volcanic hazard assessment. For the Campi Flegrei volcanic system, the expected tool has been implemented to compute hazard curves, hazard maps and probability maps for tephra fallout on a target grid covering the Campania region. This allows the end user to visualize the hazard from tephra fallout and its uncertainty. The response of end-users to such products will help to determine to what extent end-users understand them, find them useful, and match their requirements. In order to involve also Etna area in WP6 TASK 3 activities, a questionnaire developed in the VUELCO project (Volcanic Unrest in Europe and Latin America) has been proposed to Sicily Civil Protection officials having decision-making responsibility in case of volcanic unrest at Etna and Stromboli, to survey their opinions and requirements also in case of volcanic unrest

A methodology to track temporal dynamics and rainfall thresholds of landslide processes in the East African Rift

NASA Astrophysics Data System (ADS)

Monsieurs, Elise; Jacobs, Liesbet; Kervyn, François; Kirschbaum, Dalia; d'Oreye, Nicolas; Derauw, Dominique; Kervyn, Matthieu; Nobile, Adriano; Trefois, Philippe; Dewitte, Olivier

2015-04-01

The East African rift valley is a major tectonic feature that shapes Central Africa and defines linear-shaped lowlands between highland ranges due to the action of geologic faults associated to earthquakes and volcanism. The region of interest, covering the Virunga Volcanic Province in eastern DRC, western Rwanda and Burundi, and southwest Uganda, is threatened by a rare combination of several types of geohazards, while it is also one of the most densely populated region of Africa. These geohazards can globally be classified as seismic, volcanic and landslide hazards. Landslides, include a wide range of ground movements, such as rock falls, deep failure of slopes and shallow debris flows. Landslides are possibly the most important geohazard in terms of recurring impact on the populations, causing fatalities every year and resulting in structural and functional damage to infrastructure and private properties, as well as serious disruptions of the organization of societies. Many landslides are observed each year in the whole region, and their occurrence is clearly linked to complex topographic, lithologic and vegetation signatures coupled with heavy rainfall events, which is the main triggering factor. The source mechanisms underlying landslide triggering and dynamics in the region of interest are still poorly understood, even though in recent years, some progress has been made towards appropriate data collection. Taking into account difficulties of field accessibility, we present a methodology to study landslide processes by multi-scale and multi-sensor remote sensing data from very high to low resolution (Pléiades, TRMM, CosmoSkyMed, Sentinel). The research will address the evolution over time of such data combined with other earth observations (seismic ground based networks, catalogues, rain gauge networks, GPS surveying, field observations) to detect and study landslide occurrence, dynamics and evolution. This research aims to get insights into the rainfall thresholds that trigger and control the different types of landslide in this region of the East African Rift. A specific attention will be given to the landslide processes in relation to volcanic activity and earthquakes.

Incorporating Community Knowledge to Lahar Hazard Maps: Canton Buenos Aires Case Study, at Santa Ana (Ilamatepec) Volcano

NASA Astrophysics Data System (ADS)

Bajo, J. V.; Martinez-Hackert, B.; Polio, C.; Gutierrez, E.

2015-12-01

Santa Ana (Ilamatepec) Volcano is an active composite volcano located in the Apaneca Volcanic Field located in western part of El Salvador, Central America. The volcano is surrounded by rural communities in its proximal areas and the second (Santa Ana, 13 km) and fourth (Sonsosante, 15 km) largest cities of the country. On October 1st, 2005, the volcano erupted after months of increased activity. Following the eruption, volcanic mitigation projects were conducted in the region, but the communities had little or no input on them. This project consisted in the creation of lahar volcanic hazard map for the Canton Buanos Aires on the northern part of the volcano by incorporating the community's knowledge from prior events to model parameters and results. The work with the community consisted in several meetings where the community members recounted past events. They were asked to map the outcomes of those events using either a topographic map of the area, a Google Earth image, or a blank paper poster size. These maps have been used to identify hazard and vulnerable areas, and for model validation. These maps were presented to the communities and they accepted their results and the maps.

KAr ages, chemical composition and geothermal significance of cenozoic basalt near the Jordan rift

USGS Publications Warehouse

Duffield, W.A.; McKee, E.H.; El, Salem F.; Teimeh, M.

1988-01-01

Late Cenozoic mafic lavas crop out locally along the Jordan rift. Some of these lavas are spatially associated with thermal springs, and this association has prompted some workers to hypothesize that the hot water derives its thermal energy from the shallow, still hot intrusive roots of the volcanic rocks. However, all of the volcanic rocks appear to represent mantle-derived mafic magma that rose rather quickly to the Earth's surface, without filling crustal reservoirs within which differentiation would have produced evolved, derivative products. Moreover, the lavas are too old and of too small a volume to represent the surface expression of an active reservoir of magma within the crust. These interpretations of the volcanic geology are consistent with conclusions drawn from the chemistry of the thermal water; the water has equilibrated with host rocks at no more than 110??C, probably at depths of 2-3 km. Thus, thermal springs along the Jordan rift appear to reflect heating during circulation through a regional regime of average crustal heat flow (Galanis et at., 1986). The magmatic activity may only be a second or third order contributor to this heat flow. ?? 1988.

Spatiotemporal analysis and interpretation of 2003-2013 ground deformation at Campi Flegrei, Italy, observed by advanced DInSAR

NASA Astrophysics Data System (ADS)

Tiampo, Kristy; Samsonov, Sergey; González, Pablo; Fernández, Jose; Camacho, Antonio

2014-05-01

Studies identify Campi Flegrei caldera as one of the highest risk volcanic areas in the world because of its close proximity to the city of Naples, the third largest municipality in Italy with population close to 1 million inhabitants, making it one of the most dangerous volcanic areas on Earth (Orsi et al., 2004; De Natale et al., 2006; Isaia et al., 2009). The last major eruption occurred at Monte Nuovo in 1538, following a short term of ground uplift which interrupted a period of secular subsidence that continued after the eruption. Since that time, Campi Flegrei caldera has undergone frequent episodes of ground uplift and subsidence, with uplift phases accompanied by seismic activity (Troise et al., 2007). Well-established volcanic surveillance networks monitor changes in seismicity, gas emissions and active ground deformation occurring in volcanic areas as indicators of renewed volcanic/magmatic activities, potentially culminating in eruption. Since 1988, secular subsidence has continued at the historic rate of approximately 1.5 cm/yr. Surveys revealed significant gravity changes between 1981 and 2001, likely the result of dynamic changes in the subsurface magmatic reservoir (Dvorak & Berrino, 1991; Fernández et al., 2001; Gottsmann et al., 2003), changes within the subsurface hydrothermal systems (Bonafede & Mazzanti, 1998), or a combination (Gottsmann et al., 2005, 2006). In this study we apply the advanced Multidimensional SBAS (MSBAS) InSAR technique to measure ground deformation with high temporal and spatial resolution, and with high precision. We used 2003-2010 ENVISAT and 2009-2013 RADARSAT-2 satellite radar images and produced time series for the vertical and horizontal (east-west) components of deformation. Ground deformation results cover the entire Naples Bay area and, in particular, Campi Flegrei. Starting from June of 2010 we observe a moderate uplift at Campi Flegrei caldera. The rate of uplift substantially increased in 2011 and further accelerated in 2012. Between 2010 and 2013, the maximum cumulative uplift reached about 13 cm. Horizontal motions of up to 7 cm also were observed. We model the observed ground deformation in order to determine source parameters and the implication for volcanic hazard reduction in the Campi Flegrei region.

Earth's Volcanoes and their Eruptions; the 3rd edition of the Smithsonian Institution's Volcanoes of the World

NASA Astrophysics Data System (ADS)

Siebert, L.; Simkin, T.; Kimberly, P.

2010-12-01

The 3rd edition of the Smithsonian Institution’s Volcanoes of the World incorporates data on the world’s volcanoes and their eruptions compiled since 1968 by the Institution’s Global Volcanism Program (GVP). Published this Fall jointly by the Smithsonian and the University of California Press, it supplements data from the 1994 2nd edition and includes new data on the number of people living in proximity to volcanoes, the dominant rock lithologies at each volcano, Holocene caldera-forming eruptions, and preliminary lists of Pleistocene volcanoes and large-volume Pleistocene eruptions. The 3rd edition contains data on nearly 1550 volcanoes of known or possible Holocene age, including chronologies, characteristics, and magnitudes for >10,400 Holocene eruptions. The standard 20 eruptive characteristics of the IAVCEI volcano catalog series have been modified to include dated vertical edifice collapse events due to magma chamber evacuation following large-volume explosive eruptions or mafic lava effusion, and lateral sector collapse. Data from previous editions of Volcanoes of the World are also supplemented by listings of up to the 5 most dominant lithologies at each volcano, along with data on population living within 5, 10, 30, and 100 km radii of each volcano or volcanic field. Population data indicate that the most populated regions also contain the most frequently active volcanoes. Eruption data document lava and tephra volumes and Volcanic Explosivity Index (VEI) assignments for >7800 eruptions. Interpretation of VRF data has led to documentation of global eruption rates and the power law relationship between magnitude and frequency of volcanic eruptions. Data with volcanic hazards implications include those on fatalities and evacuations and the rate at which eruptions reach their climax. In recognition of the hazards implications of potential resumption of activity at pre-Holocene volcanoes, the 3rd edition includes very preliminary lists of Pleistocene volcanoes and large-volume Pleistocene eruptions, the latter in collaboration with the VOGRIPA project of Steve Sparks and colleagues. The GVP volcano and eruption data derive both from the retrospective perspective of the volcanological and other literature and documentation of contemporary eruptions and volcanic unrest in the Smithsonian’s monthly bulletin and Weekly Volcanic Activity Reports compiled since 2000 in collaboration with the USGS.

Morpho-structural evolution of a volcanic island developed inside an active oceanic rift: S. Miguel Island (Terceira Rift, Azores)

NASA Astrophysics Data System (ADS)

Sibrant, A. L. R.; Hildenbrand, A.; Marques, F. O.; Weiss, B.; Boulesteix, T.; Hübscher, C.; Lüdmann, T.; Costa, A. C. G.; Catalão, J. C.

2015-08-01

The evolution of volcanic islands is generally marked by fast construction phases alternating with destruction by a variety of mass-wasting processes. More specifically, volcanic islands located in areas of intense regional deformation can be particularly prone to gravitational destabilisation. The island of S. Miguel (Azores) has developed during the last 1 Myr inside the active Terceira Rift, a major tectonic structure materializing the present boundary between the Eurasian and Nubian lithospheric plates. In this work, we depict the evolution of the island, based on high-resolution DEM data, stratigraphic and structural analyses, high-precision K-Ar dating on separated mineral phases, and offshore data (bathymetry and seismic profiles). The new results indicate that: (1) the oldest volcanic complex (Nordeste), composing the easternmost part of the island, was dominantly active between ca. 850 and 750 ka, and was subsequently affected by a major south-directed flank collapse. (2) Between at least 500 ka and 250 ka, the landslide depression was massively filled by a thick lava succession erupted from volcanic cones and domes distributed along the main E-W collapse scar. (3) Since 250 kyr, the western part of this succession (Furnas area) was affected by multiple vertical collapses; associated plinian eruptions produced large pyroclastic deposits, here dated at ca. 60 ka and less than 25 ka. (4) During the same period, the eastern part of the landslide scar was enlarged by retrogressive erosion, producing the large Povoação valley, which was gradually filled by sediments and young volcanic products. (5) The Fogo volcano, in the middle of S. Miguel, is here dated between ca. 270 and 17 ka, and was affected by, at least, one southwards flank collapse. (6) The Sete Cidades volcano, in the western end of the island, is here dated between ca. 91 and 13 ka, and experienced mutliple caldera collapses; a landslide to the North is also suspected from the presence of a subtle morphologic scar covered by recent lava flows erupted from alignments of basaltic strombolian cones. The predominance of the N150° and N75° trends in the island suggest that the tectonics of the Terceira Rift controlled the location and the distribution of the volcanism, and to some extent the various destruction events.

Magmatism at the Eurasian–North American modern plate boundary: Constraints from alkaline volcanism in the Chersky Belt (Yakutia)

PubMed Central

Tschegg, Cornelius; Bizimis, Michael; Schneider, David; Akinin, Vyacheslav V.; Ntaflos, Theodoros

2011-01-01

The Chersky seismic belt (NE-Russia) forms the modern plate boundary of the Eurasian−North American continental plate. The geodynamic evolution of this continent−continent setting is highly complex and remains a matter of debate, as the extent and influence of the Mid-Arctic Ocean spreading center on the North Asian continent since the Eocene remains unclear. The progression from a tensional stress regime to a modern day transpressional one in the Chersky seismic belt, makes the understanding even more complicated. The alkaline volcanism that has erupted along the Chersky range from Eocene through to the Recent can provide constraints on the geodynamic evolution of this continental boundary, however, the source and petrogenetic evolution of these volcanic rocks and their initiating mechanisms are poorly understood. We studied basanites of the central Chersky belt, which are thought to represent the first alkaline volcanic activity in the area, after initial opening of the Arctic Ocean basin. We present mineral and bulk rock geochemical data as well as Sr–Nd–Pb–Hf isotopes of the alkaline suite of rocks combined with new precise K–Ar and 40Ar/39Ar dating, and discuss an integrated tectono-magmatic model for the Chersky belt. Our findings show that the basanites were generated from a homogeneous asthenospheric mantle reservoir with an EM-1 isotopic flavor, under relatively ‘dry’ conditions at segregation depths around 110 km and temperatures of ~ 1500 °C. Trace element and isotope systematics combined with mantle potential temperature estimates offer no confirmation of magmatism related to subduction or plume activity. Mineral geochemical and petrographical observations together with bulk geochemical evidence indicate a rapid ascent of melts and high cooling rates after emplacement in the continental crust. Our preferred model is that volcanism was triggered by extension and thinning of the lithosphere combined with adiabatic upwelling of the underlying mantle at 37 Ma. This suggests that at that time, rift tectonics in the Mid-Arctic Ocean most likely had also affected the North-Asian continent, causing volcanic activity in the Chersky belt, before the regional geodynamic regime changed from a tensional to compressional. Our conclusions contribute not only to the understanding of volcanism in the Chersky seismic belt (NE-Russia) but also to general aspects of plate dynamics between the Eurasian and North American continent. PMID:26523071

Magmatism at the Eurasian-North American modern plate boundary: Constraints from alkaline volcanism in the Chersky Belt (Yakutia).

PubMed

Tschegg, Cornelius; Bizimis, Michael; Schneider, David; Akinin, Vyacheslav V; Ntaflos, Theodoros

2011-07-01

The Chersky seismic belt (NE-Russia) forms the modern plate boundary of the Eurasian-North American continental plate. The geodynamic evolution of this continent-continent setting is highly complex and remains a matter of debate, as the extent and influence of the Mid-Arctic Ocean spreading center on the North Asian continent since the Eocene remains unclear. The progression from a tensional stress regime to a modern day transpressional one in the Chersky seismic belt, makes the understanding even more complicated. The alkaline volcanism that has erupted along the Chersky range from Eocene through to the Recent can provide constraints on the geodynamic evolution of this continental boundary, however, the source and petrogenetic evolution of these volcanic rocks and their initiating mechanisms are poorly understood. We studied basanites of the central Chersky belt, which are thought to represent the first alkaline volcanic activity in the area, after initial opening of the Arctic Ocean basin. We present mineral and bulk rock geochemical data as well as Sr-Nd-Pb-Hf isotopes of the alkaline suite of rocks combined with new precise K-Ar and 40 Ar/ 39 Ar dating, and discuss an integrated tectono-magmatic model for the Chersky belt. Our findings show that the basanites were generated from a homogeneous asthenospheric mantle reservoir with an EM-1 isotopic flavor, under relatively 'dry' conditions at segregation depths around 110 km and temperatures of ~ 1500 °C. Trace element and isotope systematics combined with mantle potential temperature estimates offer no confirmation of magmatism related to subduction or plume activity. Mineral geochemical and petrographical observations together with bulk geochemical evidence indicate a rapid ascent of melts and high cooling rates after emplacement in the continental crust. Our preferred model is that volcanism was triggered by extension and thinning of the lithosphere combined with adiabatic upwelling of the underlying mantle at 37 Ma. This suggests that at that time, rift tectonics in the Mid-Arctic Ocean most likely had also affected the North-Asian continent, causing volcanic activity in the Chersky belt, before the regional geodynamic regime changed from a tensional to compressional. Our conclusions contribute not only to the understanding of volcanism in the Chersky seismic belt (NE-Russia) but also to general aspects of plate dynamics between the Eurasian and North American continent.

Late Cenozoic calc-alkaline volcanism over the Payenia shallow subduction zone, South-Central Andean back-arc (34°30‧-37°S), Argentina

NASA Astrophysics Data System (ADS)

Litvak, Vanesa D.; Spagnuolo, Mauro G.; Folguera, Andrés; Poma, Stella; Jones, Rosemary E.; Ramos, Víctor A.

2015-12-01

A series of mesosilicic volcanic centers have been studied on the San Rafael Block (SRB), 300 km to the east of the present-day volcanic arc. K-Ar ages indicate that this magmatic activity was developed in at least two stages: the older volcanic centers (˜15-10 Ma) are located in the central and westernmost part of the SRB (around 36°S and 69°W) and the younger centers (8-3.5 Ma) are located in an eastern position (around 36°S and 69°30‧W) with respect to the older group. These volcanic rocks have andesitic to dacitic compositions and correspond to a high-K calc-alkaline sequence as shown by their SiO2, K2O and FeO/MgO contents. Elevated Ba/La, Ba/Ta and La/Ta ratios show an arc-like signature, and primitive mantle normalized trace element diagrams show typical depletions of high field strength elements (HFSE) relative to large ion lithophile elements (LILE). Rare earth element (REE) patterns suggest pyroxene and amphibole crystallization. Geochemical data obtained for SRB volcanic rocks support the proposal for a shallow subduction zone for the latest Miocene between 34°30″-37°S. Regionally, SRB volcanism is associated with a mid-Miocene to early Pliocene eastward arc migration caused by the shallowing of the subducting slab in the South-Central Andes at these latitudes, which represents the evolution of the Payenia shallow subduction segment. Overall, middle Miocene to early Pliocene volcanism located in the Payenia back-arc shows evidence for the influence of slab-related components. The younger (8-3.5 Ma) San Rafael volcanic rocks indicate the maximum slab shallowing and the easternmost extent of slab influence in the back-arc.

Volcanic risk perception of young people in the urban areas of Vesuvius: Comparisons with other volcanic areas and implications for emergency management

USGS Publications Warehouse

Carlino, S.; Somma, R.; Mayberry, G.C.

2008-01-01

More than 600 000 people are exposed to volcanic risk in the urban areas near the volcano, Vesuvius, and may need to be evacuated if there is renewed volcanic activity. The success of a future evacuation will strongly depend on the level of risk perception and preparedness of the at-risk communities during the current period of quiescence. The volcanic risk perception and preparedness of young people is of particular importance because hazard education programs in schools have been shown to increase the clarity of risk perception and students often share their knowledge with their parents. In order to evaluate young people's risk perception and preparedness for a volcanic crisis, a multiple choice questionnaire was distributed to 400 high-school students in three municipalities located close to the volcano. The overall results suggest that despite a 60-year period of quiescence at Vesuvius, the interviewed students have an accurate perception of the level of volcanic risk. On the other hand, the respondents demonstrate a clear lack of understanding of volcanic processes and their related hazards. Also, the interviewed students show high levels of fear, poor perceived ability to protect themselves from the effects of a future eruption, and insufficient knowledge of the National Emergency Plan for Vesuvian Area (NEPVA). The latter result suggests that in comparison with volcanic crises in other regions, during a future eruption of Vesuvius, there may not be enough time to educate the large number of people living near the volcano about how to appropriately respond. The inadequate risk education and preparedness of respondents implies that a strong effort is needed to improve communication strategies in order to facilitate successful evacuations. Therefore, it is important to take advantage of the present period of quiescence at Vesuvius to improve the accuracy of risk perception of youth in local communities. ?? 2008.

Sensitivity of the regional climate in the Middle East and North Africa to volcanic perturbations

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

Intra-arc Seismicity: Geometry and Kinematic Constraints of Active Faulting along Northern Liquiñe-Ofqui and Andean Transverse Fault Systems [38º and 40ºS, Southern Andes

NASA Astrophysics Data System (ADS)

Sielfeld, G.; Lange, D.; Cembrano, J. M.

2017-12-01

Intra-arc crustal seismicity documents the schizosphere tectonic state along active magmatic arcs. At oblique-convergent margins, a significant portion of bulk transpressional deformation is accommodated in intra-arc regions, as a consequence of stress and strain partitioning. Simultaneously, crustal fluid migration mechanisms may be controlled by the geometry and kinematics of crustal high strain domains. In such domains shallow earthquakes have been associated with either margin-parallel strike-slip faults or to volcano-tectonic activity. However, very little is known on the nature and kinematics of Southern Andes intra-arc crustal seismicity and its relation with crustal faults. Here we present results of a passive seismicity study based on 16 months of data collected from 33 seismometers deployed along the intra-arc region of Southern Andes between 38˚S and 40˚S. This region is characterized by a long-lived interplay among margin-parallel strike-slip faults (Liquiñe-Ofqui Fault System, LOFS), second order Andean-transverse-faults (ATF), volcanism and hydrothermal activity. Seismic signals recorded by our network document small magnitude (0.2P and 2,796 S phase arrival times have been located with NonLinLoc. First arrival polarities and amplitude ratios of well-constrained events, were used for focal mechanism inversion. Local seismicity occurs at shallow levels down to depth of ca. 16 km, associated either with stratovolcanoes or to master, N10˚E, and subsidiary, NE to ENE, striking branches of the LOFS. Strike-slip focal mechanisms are consistent with the long-term kinematics documented by field structural-geology studies. Unexpected, well-defined NW-SE elongated clusters are also reported. In particular, a 72-hour-long, N60˚W-oriented seismicity swarm took place at Caburgua Lake area, describing a ca. 36x12x1km3 faulting crustal volume. Results imply a unique snapshot on shallow crustal tectonics, contributing to the understanding of faulting processes in volcanic arcs and ultimately, providing useful knowledge to improve the quality of hazard assessment communities emplaced in Southern Andes volcanic arc.

Crustal Seismicity and 3-D Velocity Structure in the Principal Cordillera of Central Chile (33- 34.5 S, 69.5-71 W): Implications on Andean Geodynamic and Seismic Hazard

NASA Astrophysics Data System (ADS)

Pardo, M.; Monfret, T.; Vera, E.; Yañez, G.; Eisenberg, A.

2007-12-01

Based on data from a dense local temporary seismological network, crustal seismicity is characterized, and a 3- D body wave velocity structure is obtained by tomographic inversion down to the subducted slab. In the framework of Fondecyt 1050758, GeoAzur-IRD and ACT-18 projects, 35 broadband and short period instruments, were deployed in the studied zone for 135 days recording in continuous mode. At this zone the Andean active volcanism reappears after a gap of volcanic activity since late Miocene occurring north of 33 S due to the Central Chile flat slab subduction zone. Crustal seismicity in the depth range 0-30 km is well correlated with known geological faults that become now important in the assessment of the regional seismic hazard. This seismicity also clusters around the giant porphyry cooper deposits in the region (Rio Blanco, El Teniente), and are neither related to mine-blasts nor induced by mining activity. Moreover, the local 3-D velocity structure shows that the zone surrounding each deposit is characterized by high Vp/Vs greater than 1.8, which may indicate fluid phases located in the weakest and more fractured zone of the crust. The body wave velocity pattern shown at depth by the local tomography indicates channels of high Vp/Vs connecting the subducted slab with the surface at places where active volcanism is present, suggesting upward migration of hydrous or melted rocks. This pattern agrees with the one observed with a previous regional tomography that includes this zone, while this Vp/Vs pattern tends to be horizontal at the flat slab zone. At depths of 20-25 km, a layer of high Vp/Vs is observed beneath the Andes Cordillera that could be associated to changes in the rheological properties between the upper and lower crust, or to accumulation of magma. The average stress tensor, derived from focal mechanisms, indicate that the Andean zone is under compression in the plate convergence direction.

The Western Arabian intracontinental volcanic fields as a potential UNESCO World Heritage site

NASA Astrophysics Data System (ADS)

Németh, Károly; Moufti, Mohammed R.

2017-04-01

UNESCO promotes conservation of the geological and geomoprhological heritage through promotion of protection of these sites and development of educational programs under the umbrella of geoparks among the most globally significant ones labelled as UNESCO Global Geoparks. UNESCO also maintains a call to list those natural sites that provide universal outstanding values to demonstrate geological features or their relevance to our understanding the evolution of Earth. Volcanoes currently got a surge in nomination to be UNESCO World Heritage sites. Volcanic fields in the contrary fell in a grey area of nominations as they represents the most common manifestation of volcanism on Earth hence they are difficult to view as having outstanding universal values. A nearly 2500-km long 300-km wide region of dispersed volcanoes located in the Western Arabian Penninsula mostly in the Kingdom of Saudi Arabia form a near-continuous location that carries universal outstanding value as one of the most representative manifestation of dispersed intracontinental volcanism on Earth to be nominated as an UNESCO World Heritage site. The volcanic fields formed in the last 20 Ma along the Red Sea as group of simple basaltic to more mature and long-lived basalt to trachyte-to-rhyolite volcanic fields each carries high geoheritage values. While these volcanic fields are dominated by scoria and spatter cones and transitional lava fields, there are phreatomagmatic volcanoes among them such as maars and tuff rings. Phreatomagmatism is more evident in association with small volcanic edifices that were fed by primitive magmas, while phreatomagmatic influences during the course of a larger volume eruption are also known in association with the silicic eruptive centres in the harrats of Rahat, Kishb and Khaybar. Three of the volcanic fields are clearly bimodal and host small-volume relatively short-lived lava domes and associated block-and-ash fans providing a unique volcanic landscape commonly not considerred to be associated with dispersed intracontinental volcanic fields. In addition the nominated volcanic region also hosts the largest and youngest historic eruption (Al Madinah Eruption) in Western Saudi Arabia took place at 1256-AD, lasted 52 days and produced at least 0.29-km3 of pahoehoe-to-aa transitional lava fields that were emitted through a 2.3 km-long fissure and associated spatter-to-scoria cone complexes. The Western Arabian intracontinental volcanic fields provide the best exposed and most diverse type of intracontinental volcanic fields on Earth that also occupies the largest surface area. In addition, this chain of volcanic fields are also host significant archaeological and human occupation sites help to understand early human evolution as well as hosting several historic locations with high cultural heritage values. These generally intact and well-exposed volcanic zones hosting globally unique geoheritage sites can form the basis of complex geoeducational programs through the establishment of various volcanic geoparks in the region that can link together a UNESCO World Heritage Site on the basis of their global universal volcanic geoheritage values.

Meteorological Controls on Local and Regional Volcanic Ash Dispersal.

PubMed

Poulidis, Alexandros P; Phillips, Jeremy C; Renfrew, Ian A; Barclay, Jenni; Hogg, Andrew; Jenkins, Susanna F; Robertson, Richard; Pyle, David M

2018-05-02

Volcanic ash has the capacity to impact human health, livestock, crops and infrastructure, including international air traffic. For recent major eruptions, information on the volcanic ash plume has been combined with relatively coarse-resolution meteorological model output to provide simulations of regional ash dispersal, with reasonable success on the scale of hundreds of kilometres. However, to predict and mitigate these impacts locally, significant improvements in modelling capability are required. Here, we present results from a dynamic meteorological-ash-dispersion model configured with sufficient resolution to represent local topographic and convectively-forced flows. We focus on an archetypal volcanic setting, Soufrière, St Vincent, and use the exceptional historical records of the 1902 and 1979 eruptions to challenge our simulations. We find that the evolution and characteristics of ash deposition on St Vincent and nearby islands can be accurately simulated when the wind shear associated with the trade wind inversion and topographically-forced flows are represented. The wind shear plays a primary role and topographic flows a secondary role on ash distribution on local to regional scales. We propose a new explanation for the downwind ash deposition maxima, commonly observed in volcanic eruptions, as resulting from the detailed forcing of mesoscale meteorology on the ash plume.

Experimental study on the effect of calcination on the volcanic ash activity of diatomite

NASA Astrophysics Data System (ADS)

Xiao, Liguang; Pang, Bo

2017-09-01

The volcanic ash activity of diatomite was studied under the conditions of aerobic calcination and vacuum calcination by the combined water rate method, it was characterized by XRD, BET and SEM. The results showed that the volcanic ash activity of diatomite under vacuum conditions was higher than that of aerobic calcination, 600°C vacuum calcination 2h, the combined water rate of diatomite-Ca(OH)2-H2O system was increased from 6.24% to 71.43%, the volcanic ash activity reached the maximum value, the specific surface

Large-scale volcanism associated with coronae on Venus

NASA Technical Reports Server (NTRS)

Roberts, K. Magee; Head, James W.

1993-01-01

The formation and evolution of coronae on Venus are thought to be the result of mantle upwellings against the crust and lithosphere and subsequent gravitational relaxation. A variety of other features on Venus have been linked to processes associated with mantle upwelling, including shield volcanoes on large regional rises such as Beta, Atla and Western Eistla Regiones and extensive flow fields such as Mylitta and Kaiwan Fluctus near the Lada Terra/Lavinia Planitia boundary. Of these features, coronae appear to possess the smallest amounts of associated volcanism, although volcanism associated with coronae has only been qualitatively examined. An initial survey of coronae based on recent Magellan data indicated that only 9 percent of all coronae are associated with substantial amounts of volcanism, including interior calderas or edifices greater than 50 km in diameter and extensive, exterior radial flow fields. Sixty-eight percent of all coronae were found to have lesser amounts of volcanism, including interior flooding and associated volcanic domes and small shields; the remaining coronae were considered deficient in associated volcanism. It is possible that coronae are related to mantle plumes or diapirs that are lower in volume or in partial melt than those associated with the large shields or flow fields. Regional tectonics or variations in local crustal and thermal structure may also be significant in determining the amount of volcanism produced from an upwelling. It is also possible that flow fields associated with some coronae are sheet-like in nature and may not be readily identified. If coronae are associated with volcanic flow fields, then they may be a significant contributor to plains formation on Venus, as they number over 300 and are widely distributed across the planet. As a continuation of our analysis of large-scale volcanism on Venus, we have reexamined the known population of coronae and assessed quantitatively the scale of volcanism associated with them. In particular, we have examined the percentage of coronae associated with volcanic flow fields (i.e., a collection of digitate or sheet-like lava flows extending from the corona interior or annulus); the range in scale of these flow fields; the variations in diameter, structure and stratigraphy of coronae with flow fields; and the global distribution of coronae associated with flow fields.

Antarctic volcanoes: A remote but significant hazard

NASA Astrophysics Data System (ADS)

Geyer, Adelina; Martí, Alex; Folch, Arnau; Giralt, Santiago

2017-04-01

Ash emitted during explosive volcanic eruptions can be dispersed over massive areas of the globe, posing a threat to both human health and infrastructures, such as the air traffic. Some of the last eruptions occurred during this decade (e.g. 14/04/2010 - Eyjafjallajökull, Iceland; 24/05/2011-Grímsvötn, Iceland; 05/06/2011-Puyehue-Cordón Caulle, Chile) have strongly affected the air traffic in different areas of the world, leading to economic losses of billions of euros. From the tens of volcanoes located in Antarctica, at least nine are known to be active and five of them have reported volcanic activity in historical times. However, until now, no attention has been paid to the possible social, economical and environmental consequences of an eruption that would occur on high southern latitudes, perhaps because it is considered that its impacts would be minor or local, and mainly restricted to the practically inhabited Antarctic continent. We show here, as a case study and using climate models, how volcanic ash emitted during a regular eruption of one of the most active volcanoes in Antarctica, Deception Island (South Shetland Islands), could reach the African continent as well as Australia and South America. The volcanic cloud could strongly affect the air traffic not only in the region and at high southern latitudes, but also the flights connecting Africa, South America and Oceania. Results obtained are crucial to understand the patterns of volcanic ash distribution at high southern latitudes with obvious implications for tephrostratigraphical and chronological studies that provide valuable isochrones with which to synchronize palaeoclimate records. This research was partially funded by the MINECO grants VOLCLIMA (CGL2015-72629-EXP)and POSVOLDEC(CTM2016-79617-P)(AEI/FEDER, UE), the Ramón y Cajal research program (RYC-2012-11024) and the NEMOH European project (REA grant 34 agreement n° 289976).

Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

USGS Publications Warehouse

Pearson, S.C.P.; Connor, C.B.; Sanford, W.E.

2008-01-01

Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

A new sulfur and carbon degassing inventory for the Southern Central American Volcanic Arc: The importance of accurate time-series datasets and possible tectonic processes responsible for temporal variations in arc-scale volatile emissions

USGS Publications Warehouse

de Moor, Maarten; Kern, Christoph; Avard, Geoffroy; Muller, Cyril; Aiuppa, Sandro; Saballos, Armando; Ibarra, Martha; LaFemina, Peter; Protti, Mario; Fischer, Tobias

2017-01-01

This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015–2016. We report ∼300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ∼500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972–2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015–2016 than in any period since ∼1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time‐series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short‐lived degassing events and arc systems likely display significant short‐term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

Carbon isotope systematics of Turrialba volcano, Costa Rica, using a portable cavity ring-down spectrometer

NASA Astrophysics Data System (ADS)

Malowany, K. S.; Stix, J.; de Moor, J. M.; Chu, K.; Lacrampe-Couloume, G.; Sherwood Lollar, B.

2017-07-01

Over the past two decades, activity at Turrialba volcano, Costa Rica, has shifted from hydrothermal to increasingly magmatic in character, with enhanced degassing and eruption potential. We have conducted a survey of the δ13C signatures of gases at Turrialba using a portable field-based CRDS with comparison to standard IRMS techniques. Our δ13C results of the volcanic plume, high-temperature vents, and soil gases reveal isotopic heterogeneity in the CO2 gas composition at Turrialba prior to its recent phase of eruptive activity. The isotopic value of the regional fault system, Falla Ariete (-3.4 ± 0.1‰), is in distinct contrast with the Central crater gases (-3.9 ± 0.1‰) and the 2012 high-temperature vent (-4.4 ± 0.2‰), an indication that spatial variability in δ13C may be linked to hydrothermal transport of volcanic gases, heterogeneities in the source composition, or magmatic degassing. Isotopic values of CO2 samples collected in the plume vary from δ13C of -5.2 to -10.0‰, indicative of mixing between atmospheric CO2 (-9.2 ± 0.1‰), and a volcanic source. We compare the Keeling method to a traditional mixing model (hyperbolic mixing curve) to estimate the volcanic source composition at Turrialba from the plume measurements. The predicted source compositions from the Keeling and hyperbolic methods (-3.0 ± 0.5‰ and -3.9 ± 0.4‰, respectively) illustrate two potential interpretations of the volcanic source at Turrialba. As of the 29 October 2014, Turrialba has entered a new eruptive period, and continued monitoring of the summit gases for δ13C should be conducted to better understand the dominant processes controlling δ13C fractionation at Turrialba.

A New Sulfur and Carbon Degassing Inventory for the Southern Central American Volcanic Arc: The Importance of Accurate Time-Series Data Sets and Possible Tectonic Processes Responsible for Temporal Variations in Arc-Scale Volatile Emissions

NASA Astrophysics Data System (ADS)

de Moor, J. M.; Kern, C.; Avard, G.; Muller, C.; Aiuppa, A.; Saballos, A.; Ibarra, M.; LaFemina, P.; Protti, M.; Fischer, T. P.

2017-12-01

This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015-2016. We report ˜300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ˜500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972-2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015-2016 than in any period since ˜1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time-series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short-lived degassing events and arc systems likely display significant short-term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

Spreading of Somma-Vesuvio Volcanic Complex: is the Hazard for Plinian Eruptions being reduced?

NASA Astrophysics Data System (ADS)

Borgia, A.; Tizzani, P.; Solaro, G.; Luongo, G.; Fusi, N.

2003-12-01

Contrary to what is the common knowledge, a detailed structural study of active faulting and rifting of the summit area of Somma-Vesuvio volcanic complex, combined with INSAR, levelling data and seismic profiling at sea suggests that the present-day long-term dynamic behaviour of the complex and of its summit caldera is characterized by volcanic spreading. The structural evolution is controlled by a number of asymmetric, intersecting leaf-grabens. The boundary faults of these grabens intersect at different angles the Somma caldera walls generating a set of wedge-horsts. While normal faulting characterizes the Somma caldera walls, the lavas of the past 150 years, infilling the caldera, have been rifted all around the southern, eastern and northern base of Vesuvio's cone, which, in turn, is being displaced seaward. Associated to the subsidence and extension of the summit area, relative uplift occurs along the coast; in addition, deformation of recent sediments 6-18 km offshore also indicate compression and uplift, which appears to be unrelated to regional tectonics. A preliminary evaluation indicates that rifting of the lavas is in the order of 1-2 mm/a with a southwestward average direction of displacement. Based on these data, we suggest that a wide sector of Somma-Vesuvio is spreading on its plastic sedimentary substratum, which have been identified by drilling. Volcanic spreading appears to have controlled the magmatic evolution and the energy decrease of major historic explosive eruptions since 79 AD. If our interpretation is correct, major plinian eruptions should not occur in the near future. On the other hand, rifting around the caldera suggests that volcanic activity could soon be renewed.

Characterize Framework for Igneous Activity at Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

F. Perry; B. Youngs

2000-11-06

The purpose of this Analysis/Model (AMR) report is twofold. (1) The first is to present a conceptual framework of igneous activity in the Yucca Mountain region (YMR) consistent with the volcanic and tectonic history of this region and the assessment of this history by experts who participated in the Probabilistic Volcanic Hazard Analysis (PVHA) (CRWMS M&O 1996). Conceptual models presented in the PVHA are summarized and extended in areas in which new information has been presented. Alternative conceptual models are discussed as well as their impact on probability models. The relationship between volcanic source zones defined in the PVHA andmore » structural features of the YMR are described based on discussions in the PVHA and studies presented since the PVHA. (2) The second purpose of the AMR is to present probability calculations based on PVHA outputs. Probability distributions are presented for the length and orientation of volcanic dikes within the repository footprint and for the number of eruptive centers located within the repository footprint (conditional on the dike intersecting the repository). The probability of intersection of a basaltic dike within the repository footprint was calculated in the AMR ''Characterize Framework for Igneous Activity at Yucca Mountain, Nevada'' (CRWMS M&O 2000g) based on the repository footprint known as the Enhanced Design Alternative [EDA II, Design B (CRWMS M&O 1999a; Wilkins and Heath 1999)]. Then, the ''Site Recommendation Design Baseline'' (CRWMS M&O 2000a) initiated a change in the repository design, which is described in the ''Site Recommendation Subsurface Layout'' (CRWMS M&O 2000b). Consequently, the probability of intersection of a basaltic dike within the repository footprint has also been calculated for the current repository footprint, which is called the 70,000 Metric Tons of Uranium (MTU) No-Backfill Layout (CRWMS M&O 2000b). The calculations for both footprints are presented in this AMR. In addition, the probability of an eruptive center(s) forming within the repository footprint is calculated and presented in this AMR for both repository footprint designs. This latter type of calculation was not included in the PVHA.« less

The Southern Andes of South America as seen from STS-60

NASA Image and Video Library

1994-02-09

STS060-85-000AH (3-11 Feb 1994) --- This view is centered at about 44 degrees south along the Chilean continental margin of South America. The dark-colored coastal region is heavily forested by dense old-growth forests that are now being cut, but east of the mountains in Argentina the dry climate supports very little vegetation. This desert region known as Patagonia appears as light brown colors. The coastline is especially dramatic because it is shaped by the tortuous channels carved by glaciers which have left fjords. These fjords have effectively cut across the continental divide, and are bordered by active volcanoes which reach elevations between 2, 000 - 3,000 meters. The prominent volcanic peak in the center of the frame is Mt. Melimoya. To the north is a long, snow-covered volcanic ridge called Cerro Yantales. Cerro Yantales recently reported greatly increased fumarolic activity, including the emission of yellow gases near the summit. Russian and American scientists will use this photography to look for further evidence of increased activity like snow melt around the peak. Other Russian and American scientists are particularly interested in mapping the summertime snowline and firm (permanent snow field) elevations as early indications of any potential climatic variation in the making.

Detecting hidden volcanic explosions from Mt. Cleveland Volcano, Alaska with infrasound and ground-couples airwaves

USGS Publications Warehouse

De Angelis, Slivio; Fee, David; Haney, Matthew; Schneider, David

2012-01-01

In Alaska, where many active volcanoes exist without ground-based instrumentation, the use of techniques suitable for distant monitoring is pivotal. In this study we report regional-scale seismic and infrasound observations of volcanic activity at Mt. Cleveland between December 2011 and August 2012. During this period, twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent, and ground-coupled acoustic waves were recorded at seismic stations across the Aleutian Arc. Several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data. However, many explosions eluded initial, automated, analyses of satellite data due to poor weather conditions. Infrasound and seismic monitoring provided effective means for detecting these hidden events. We present results from the implementation of automatic infrasound and seismo-acoustic eruption detection algorithms, and review the challenges of real-time volcano monitoring operations in remote regions. We also model acoustic propagation in the Northern Pacific, showing how tropospheric ducting effects allow infrasound to travel long distances across the Aleutian Arc. The successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the Aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.

Interactions of tectonic, igneous, and hydraulic processes in the North Tharsis Region of Mars

NASA Technical Reports Server (NTRS)

Davis, P. A.; Tanaka, Kenneth L.; Golombek, M. P.; Plescia, J. B.

1991-01-01

Recent work on the north Tharsis of Mars has revealed a complex geologic history involving volcanism, tectonism, flooding, and mass wasting. Our detailed photogeologic analysis of this region found many previously unreported volcanic vents, volcaniclastic flows, irregular cracks, and minor pit chains; additional evidence that volcanic tectonic processes dominated this region throughout Martian geologic time; and the local involvement of these processes with surface and near surface water. Also, photoclinometric profiles were obtained within the region of troughs, simple grabens, and pit chains, as well as average spacings of pits along pit chains. These data were used together with techniques to estimate depths of crustal mechanical discontinuities that may have controlled the development of these features. In turn, such discontinuities may be controlled by stratigraphy, presence of water or ice, or chemical cementation.

Repeat terrestrial lidar mapping of the new volcanic vent at Holuhraun, Iceland

NASA Astrophysics Data System (ADS)

Richardson, J. A.; Whelley, P.; Sutton, S.; Needham, D. H.; Byrne, S.; Hamilton, C.

2016-12-01

The locations and morphologies of volcanic vents are essential observations that inform models of volcanic processes on Earth and other planets. Post-eruption morphologic changes at vents are important to characterize in order to more confidently use data gathered from mapping volcanic terrains. We present two terrestrial lidar surveys of the recently formed volcanic vent that fed the Holuhraun lava flow in the Northeastern Region of Iceland. While many studies have measured erosion rate at older volcanic vents, these surveys were performed 6 and 18 months after the end of the eruption and present an opportunity to measure morphologic changes at a brand-new vent. The Holuhraun eruption began in August 2014 by effusing lava through a fissure and continued until February 2015, emplacing approximately 1.4 km³ of lava over nearly 85 km². During the eruption the predominant activity at the northern end of the fissure produced a large (50 m high, 500 m long) cinder-canyon with scoria covered flanks. Lava ponded within this vent and drained to form a primary channel to the northeast. As lava drained through the channel, high stands of lava were preserved as "bathtub rings" on the walls of the vent. Following the cessation of activity at Holuhraun, two lidar surveys were carried out inside the vent, in August 2015 and August 2016. A Riegl VZ-400 scanner was used to collect the point cloud data, which give a precise 3D model of the vent with relative accuracy of 15 cm between scan positions. Differences between the two 3D point clouds are used to distinguish between flow emplacement and post-flow modifications to the surface, and to quantify the surface erosion rate experienced by the young vent. Near-infrared (1550 nm wavelength) reflectance values can also be correlated to lava textures and materials within the vent, providing additional information about how the vent was built syn-eruption and how it degrades post-eruption.

The structural architecture of the Los Humeros volcanic complex and geothermal field, Trans-Mexican Volcanic Belt, Central Mexico

NASA Astrophysics Data System (ADS)

Norini, Gianluca; Groppelli, Gianluca; Sulpizio, Roberto; Carrasco Núñez, Gerardo; Davila Harris, Pablo

2014-05-01

The development of geothermal energy in Mexico is a very important goal, given the presence of a large heat anomaly, associated with the Trans-Mexican Volcanic Belt, the renewability of the resource and the low environmental impact. The Quaternary Los Humeros volcanic complex is an important geothermal target, whose evolution involved at least two caldera events, that alternated with other explosive and effusive activity. The first caldera forming event was the 460 ka eruption that produced the Xaltipan ignimbrite and formed a 15-20 km wide caldera. The second collapse event occurred 100 ka with the formation of the Zaragoza ignimbrite and a nested 8-10 km wide caldera. The whole volcano structure, the style of the collapses and the exact location of the calderas scarps and ring faults are still a matter of debate. The Los Humeros volcano hosts the productive Los Humeros Geothermal Field, with an installed capacity of 40 MW and additional 75 MW power plants under construction. Recent models of the geothermal reservoir predict the existence of at least two reservoirs in the geothermal system, separated by impermeable rock units. Hydraulic connectivity and hydrothermal fluids circulation occurs through faults and fractures, allowing deep steam to ascend while condensate flows descend. As a consequence, the plans for the exploration and exploitation of the geothermal reservoir have been based on the identification of the main channels for the circulation of hydrothermal fluids, constituted by faults, so that the full comprehension of the structural architecture of the caldera is crucial to improve the efficiency and minimize the costs of the geothermal field operation. In this study, we present an analysis of the Los Humeros volcanic complex focused on the Quaternary tectonic and volcanotectonics features, like fault scarps and aligned/elongated monogenetic volcanic centres. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the structural features of the studied area. The integration of these structural data with available stratigraphy, geological maps and well logs is used to propose a new model of the caldera and geothermal field. As a result of our study, we interpret the Xaltipan and Zaragoza calderas mainly as trap-door structures. These calderas affected a cone-shaped volcanic sequence, formed mainly by effusive products emitted in the pre-caldera forming phase and now hosting the geothermal reservoir (11-1.5 Ma). The main ring faults of the two calderas are buried and sealed by widespread post-calderas volcanic products, and for this reason probably do not have enough secondary permeability to be main channels for hydrothermal fluid circulation. Active, fast-moving subvertical faults have been identified inside the Zaragoza caldera depression. These structures affect recent post-caldera pyroclastic deposits and probably are related both to active resurgence inside the caldera and to regional faults NW-SE striking. The presence of active faults generating high secondary permeability is the most important structural element shaping the geothermal reservoir. Future plans of expansion of the geothermal field should focus on these active faults, considering their geometry at depth and the whole structural architecture of the Los Humeros volcanic complex.

Cenozoic changes in atmospheric lead recorded in central Pacific ferromanganese crusts

NASA Astrophysics Data System (ADS)

Klemm, Veronika; Reynolds, Ben; Frank, Martin; Pettke, Thomas; Halliday, Alex N.

2007-01-01

The possible sources of pre-anthropogenic Pb contributed to the world's oceans have been the focus of considerable study. The role of eolian dust versus riverine inputs has been of particular interest. With better calibration of isotopic records from central Pacific ferromanganese crusts using Os isotope stratigraphy it now appears that deep water Pb isotopic compositions were effectively homogeneous over a distance of 5000 km for the past 80 Myr. The composition shifted slightly from high 206Pb/ 204Pb ratios in the range of 18.87 ± 0.02 before 65 Ma to lower values of 18.62 ± 0.02 by 45 Ma and then gradually increased again very slightly to the present day ratio of 18.67 ± 0.02. The regional homogeneity provides evidence of a dominant well-mixed atmospheric source the most likely candidate for which is volcanic aerosols contributed either directly or as soluble condensates on eolian dust. The slight shift in Pb isotope composition of deep waters in the central Pacific between 65 and 45 Ma may be the result of a regional- or perhaps global-scale change in the sources of volcanic exhalations and volcanic activity caused by an increase in the importance of melting and assimilation of older continental crustal components over the Cenozoic.

The frequency of explosive volcanic eruptions in Southeast Asia.

PubMed

Whelley, Patrick L; Newhall, Christopher G; Bradley, Kyle E

There are ~750 active and potentially active volcanoes in Southeast Asia. Ash from eruptions of volcanic explosivity index 3 (VEI 3) and smaller pose mostly local hazards while eruptions of VEI ≥ 4 could disrupt trade, travel, and daily life in large parts of the region. We classify Southeast Asian volcanoes into five groups, using their morphology and, where known, their eruptive history and degassing style. Because the eruptive histories of most volcanoes in Southeast Asia are poorly constrained, we assume that volcanoes with similar morphologies have had similar eruption histories. Eruption histories of well-studied examples of each morphologic class serve as proxy histories for understudied volcanoes in the class. From known and proxy eruptive histories, we estimate that decadal probabilities of VEI 4-8 eruptions in Southeast Asia are nearly 1.0, ~0.6, ~0.15, ~0.012, and ~0.001, respectively.

Volcano-rift interaction on Venus: initial results from the Beta-Atla-Themis region.

NASA Astrophysics Data System (ADS)

Lopez, I.; Martin-Gonzalez, F.; Marquez, A.; de Pablo, M. A.; Carreno, F.

Extensional deformation and volcanism are widespread and geographically related processes on the surface of Venus (e.g. Head et al., 1992; Solomon et al., 1992). We report the initial results of an ongoing study on the interaction between fracture belts (chasmata and fossae) and large to intermediate-size volcanoes on Venus. The initial work focused in Beta-Atla-Themis, a region centered at ˜ 250o of longitude that covers ˜ 20 percent of the surface of the planet in which concentration of volcanic centers and fracture belts exceeds the global mean density (e.g. Crumpler et al., 1993). We carried out a survey of the volcanic features located in and close to fracture belts using existing volcano databases (Crumpler and Aubele, 2000) updated during this initial stage of our study through the analysis of full-resolution Magellan radar images for the studied region. We identified over a hundred volcanic features of different size and type (large volcanoes, intermediate-size volcanoes, steep-side domes and modified or fluted edifices) located in or near fracture belts. In this initial work, we have also established the time relationship that exist between each volcanic feature and the fracture belts and found that volcanic edifices predate, postdate or develop contemporaneously to extensional fracturing. Detailed structural mapping of locations where extensional fracturing and the formation of volcanoes is related is being carried out. In these geological settings the fracture patterns resulting from the interaction between both processes can help to constrain the different processes that operate during volcano growth (i.e. dike intrusion, chamber inflation, volcanic sagging and volcanic spreading) and its interaction with the regional stress fields responsible for the fracture belts. References: - Crumpler L.S. and J.C. Aubele (2000). Volcanism on Venus. In Encyclopedia of volcanoes, (Sigurdsson, H, B. Houghton, S.R. McNutt, H. Rymer, J. Stix, eds), p.727- 770. Academic Press. - Crumpler, L.S., J.W. Head and J.C. Aubele (1993). Relation of mayor volcanic center concentration on Venus to global tectonic patterns. Science, 261, p.591-595. - Head, J.W., L.S. Crumpler, J.C. Aubele, J.E. Guest and R.S. Saunders (1992). Venus volcanism: Classification of volcanic features and structures, associations, and global 1 distribution from Magellan data. J. Geophys. Res., 97, p.13153-13197. - Solomon S.C., S.E. Smrekar, D.L. Bindschadler, R.E. Grimm, W.M. Kaula, G.E. McGill, R.J. Phillips, R.S. Saunders, G. Schubert, S.W, Squyres and E.R. Stofan (1992). Venus tectonics: An overview of Magellan observations. J. Geophys. Res., 97, p.13199-13255. 2

Volcanism and hydrothermalism on a hotspot-influenced ridge: Comparing Reykjanes Peninsula and Reykjanes Ridge, Iceland

NASA Astrophysics Data System (ADS)

Pałgan, Dominik; Devey, Colin W.; Yeo, Isobel A.

2017-12-01

Current estimates indicate that the number of high-temperature vents (one of the primary pathways for the heat extraction from the Earth's mantle) - at least 1 per 100 km of axial length - scales with spreading rate and should scale with crustal thickness. But up to present, shallow ridge axes underlain by thick crust show anomalously low incidences of high-temperature activity. Here we compare the Reykjanes Ridge, an abnormally shallow ridge with thick crust and only one high-temperature vent known over 900 km axial length, to the adjacent subaerial Reykjanes Peninsula (RP), which is characterized by high-temperature geothermal sites confined to four volcanic systems transected by fissure swarms with young (Holocene) volcanic activity, multiple faults, cracks and fissures, and continuous seismic activity. New high-resolution bathymetry (gridded at 60 m) of the Reykjanes Ridge between 62°30‧N and 63°30‧N shows seven Axial Volcanic Ridges (AVR) that, based on their morphology, geometry and tectonic regime, are analogues for the volcanic systems and fissure swarms on land. We investigate in detail the volcano-tectonic features of all mapped AVRs and show that they do not fit with the previously suggested 4-stage evolution model for AVR construction. Instead, we suggest that AVR morphology reflects the robust or weak melt supply to the system and two (or more) eruption mechanisms may co-exist on one AVR (in contrast to 4-stage evolution model). Our interpretations indicate that, unlike on the Reykjanes Peninsula, faults on and around AVRs do not cluster in orientation domains but all are subparallel to the overall strike of AVRs (orthogonal to spreading direction). High abundance of seamounts shows that the region centered at 62°47‧N and 25°04‧W (between AVR-5 and -6) is volcanically robust while the highest fault density implies that AVR-1 and southern part of AVR-6 rather undergo period of melt starvation. Based on our observations and interpretations we expect all of the AVRs on Reykjanes Ridge to be hydrothermally active but morphological and hydrographic settings of this ridge may cause hydrothermal plumes to be quickly dispersed and diluted due to exposure to strong bottom currents. Therefore, combined CTD and autonomous vehicles surveys are probably the most efficient methods for hydrothermal exploration along the Reykjanes Ridge.

The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions

NASA Astrophysics Data System (ADS)

Pouclet, A.; Bellon, H.; Bram, K.

2016-09-01

The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time. The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the presence of phlogopite and the local existence of a metasomatized mantle. A carbonatite contribution is evidenced in the Nyiragongo lavas. New K-Ar ages date around 21 Ma the earliest volcanic activity made of nephelinites. A sodic alkaline volcanism took place between 13 and 9 Ma at the western side of the Virunga during the doming stage of the rift and before the formation of the rift valley. In the South-Kivu area, the first lavas were tholeiitic and dated at 11 Ma. The rift valley subsidence began around 8-7 Ma. The tholeiitic lavas were progressively replaced by alkali basaltic lavas until to 2.6 Ma. Renewal of the basaltic volcanism happened at ca. 1.7 Ma on a western step of the rift. In the Virunga area, the potassic volcanism appeared ca. 2.6 Ma along a NE-SW fault zone and then migrated both to the east and west, in jumping to oblique tension gashes. The uncommon magmatic evolution and the high diversity of volcanic rocks of the Kivu rift are explained by varying transtensional constraints during the rift history.

Kamchatkan Volcanic Eruption Response Team (KVERT), Russia: preventing the danger of volcanic eruptions to aviation.

NASA Astrophysics Data System (ADS)

Girina, O.; Neal, Ch.

2012-04-01

The Kamchatkan Volcanic Eruption Response Team (KVERT) has been a collaborative project of scientists from the Institute of Volcanology and Seismology, the Kamchatka Branch of Geophysical Surveys, and the Alaska Volcano Observatory (IVS, KB GS and AVO). The purpose of KVERT is to reduce the risk of costly, damaging, and possibly deadly encounters of aircraft with volcanic ash clouds. To reduce this risk, KVERT collects all possible volcanic information and issues eruption alerts to aviation and other emergency officials. KVERT was founded by Institute of Volcanic Geology and Geochemistry FED RAS in 1993 (in 2004, IVGG merged with the Institute of Volcanology to become IVS). KVERT analyzes volcano monitoring data (seismic, satellite, visual and video, and pilot reports), assigns the Aviation Color Code, and issues reports on eruptive activity and unrest at Kamchatkan (since 1993) and Northern Kurile (since 2003) volcanoes. KVERT receives seismic monitoring data from KB GS (the Laboratory for Seismic and Volcanic Activity). KB GS maintains telemetered seismic stations to investigate 11 of the most active volcanoes in Kamchatka. Data are received around the clock and analysts evaluate data each day for every monitored volcano. Satellite data are provided from several sources to KVERT. AVO conducts satellite analysis of the Kuriles, Kamchatka, and Alaska as part of it daily monitoring and sends the interpretation to KVERT staff. KVERT interprets MODIS and MTSAT images and processes AVHRR data to look for evidence of volcanic ash and thermal anomalies. KVERT obtains visual volcanic information from volcanologist's field trips, web-cameras that monitor Klyuchevskoy (established in 2000), Sheveluch (2002), Bezymianny (2003), Koryaksky (2009), Avachinsky (2009), Kizimen (2011), and Gorely (2011) volcanoes, and pilots. KVERT staff work closely with staff of AVO, AMC (Airport Meteorological Center) at Yelizovo Airport and the Tokyo Volcanic Ash Advisory Center (VAAC), the Anchorage VAAC, the Washington VAAC, the Montreal VAAC, and the Darwin VAAC to release timely eruption warnings. Urgent information is sent by email to government agencies, aviation services, and scientists (>300 users) located throughout the North Pacific region. KVERT staff also notify AMC and other emergency agencies in Kamchatka by telephone. VONA/KVERT Information Releases (VONA - Volcano Observatory Notice for Aviation) are formal written notifications that are sent by email to these same users to announce Aviation Color Code changes and significant changes in activity. These statements are posted on the KVERT (http://www.kscnet.ru/ivs/kvert/) and the AVO (http://www.avo.alaska.edu) web site. During the period of 2009-2011, eruptions of 6 of Kamchatkan volcanoes were potentially dangerous for aviation: three significant events occurred at Bezymianny (2009, 2010 and 2011), one protracted eruption at Klyuchevskoy (from 2009 till 2010), three short events at Koryaksky (2009) and an ongoing explosive-effusive eruption at Kizimen (2010-2012). Eruptions of Karymsky and Sheveluch volcanoes have continued essentially uninterrupted throughout the period 2009-2011 and have also posed a hazard to aviation intermittently. Very strong explosive eruption of Sheveluch occurred on October 27-28, 2010.

TECTONIC VERSUS VOLCANIC ORIGIN OF THE SUMMIT DEPRESSION AT MEDICINE LAKE VOLCANO, CALIFORNIA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark Leon Gwynn

Medicine Lake Volcano is a Quaternary shield volcano located in a tectonically complex and active zone at the transition between the Basin and Range Province and the Cascade Range of the Pacific Province. The volcano is topped by a 7x12 km elliptical depression surrounded by a discontinuous constructional ring of basaltic to rhyolitic lava flows. This thesis explores the possibility that the depression may have formed due to regional extension (rift basin) or dextral shear (pull-apart basin) rather than through caldera collapse and examines the relationship between regional tectonics and localized volcanism. Existing data consisting of temperature and magnetotelluric surveys,more » alteration mineral studies, and core logging were compiled and supplemented with additional core logging, field observations, and fault striae studies in paleomagnetically oriented core samples. These results were then synthesized with regional fault data from existing maps and databases. Faulting patterns near the caldera, extension directions derived from fault striae P and T axes, and three-dimensional temperature and alteration mineral models are consistent with slip across arcuate ring faults related to magma chamber deflation during flank eruptions and/or a pyroclastic eruption at about 180 ka. These results are not consistent with a rift or pull-apart basin. Limited subsidence can be attributed to the relatively small volume of ash-flow tuff released by the only known major pyroclastic eruption and is inconsistent with the observed topographic relief. The additional relief can be explained by constructional volcanism. Striae from unoriented and oriented core, augmented by striae measurements in outcrop suggest that Walker Lane dextral shear, which can be reasonably projected from the southeast, has probably propagated into the Medicine Lake area. Most volcanic vents across Medicine Lake Volcano strike north-south, suggesting they are controlled by crustal weakness related to Basin and Range extension. Interaction of dextral shear, Basin and Range extension, and the zone of crustal weakness expressed as the Mount Shasta-Medicine Lake volcanic highland controlled the location and initiation of Medicine Lake Volcano at about 500 ka.« less

Tectonic versus volcanic origin of the summit depression at Medicine Lake Volcano, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark Leon Gwynn

Medicine Lake Volcano is a Quaternary shield volcano located in a tectonically complex and active zone at the transition between the Basin and Range Province and the Cascade Range of the Pacific Province. The volcano is topped by a 7x12 km elliptical depression surrounded by a discontinuous constructional ring of basaltic to rhyolitic lava flows. This thesis explores the possibility that the depression may have formed due to regional extension (rift basin) or dextral shear (pull-apart basin) rather than through caldera collapse and examines the relationship between regional tectonics and localized volcanism. Existing data consisting of temperature and magnetotelluric surveys,more » alteration mineral studies, and core logging were compiled and supplemented with additional core logging, field observations, and fault striae studies in paleomagnetically oriented core samples. These results were then synthesized with regional fault data from existing maps and databases. Faulting patterns near the caldera, extension directions derived from fault striae P and T axes, and three-dimensional temperature and alteration mineral models are consistent with slip across arcuate ring faults related to magma chamber deflation during flank eruptions and/or a pyroclastic eruption at about 180 ka. These results are not consistent with a rift or pull-apart basin. Limited subsidence can be attributed to the relatively small volume of ash-flow tuff released by the only known major pyroclastic eruption and is inconsistent with the observed topographic relief. The additional relief can be explained by constructional volcanism. Striae from unoriented and oriented core, augmented by striae measurements in outcrop suggest that Walker Lane dextral shear, which can be reasonably projected from the southeast, has probably propagated into the Medicine Lake area. Most volcanic vents across Medicine Lake Volcano strike north-south, suggesting they are controlled by crustal weakness related to Basin and Range extension. Interaction of dextral shear, Basin and Range extension, and the zone of crustal weakness expressed as the Mount Shasta-Medicine Lake volcanic highland controlled the location and initiation of Medicine Lake Volcano at about 500 ka.« less

Venus lives!. [evidence for active volcanoes

NASA Technical Reports Server (NTRS)

Wood, Charles A.; Francis, Peter W.

1988-01-01

Observational evidence which supports the contention that Venus is a volcanically and tectonically active planet is discussed. It is argued that, although there are no observations to date that would prove that Venus has been volcanically active during the last decade, planetological studies presented evidence for youthful volcanic mountains on Venus: the surface of the northern quarter of Venus is considered to be younger than 1 Gy, and some units are likely to be much younger. Because of the small sizes of likely volcanic manifestations and the long intervals expected between eruptions, it is unlikely that any direct evidence of eruptions will be detected with existing and planned spacecraft. It is suggested that future studies of the dynamics and the chemical mixing of the Venusian atmosphere might supply an unequivocal evidence for active volcanism on this planet.

Magmatism and the Shallowing of the Chilean Flatslab in the Central Andes

NASA Astrophysics Data System (ADS)

Kay, S. M.

2014-12-01

The magmatic history of the flatslab region between the Central and Southern Andean volcanic zones reflects shallowing of the slab, lithospheric thinning, narrowing of the asthenospheric wedge, crustal thickening and forearc removal by subduction erosion. Newly revised contours on the northern margin of the modern flatslab (Mulcahy et al. 2014) show the flattest part extends from ~28° to 33°S and is bounded by Pleistocene volcanic activity. An eastward broadening of the magmatic arc began after 18 Ma as westward drift of South America accelerated, but the most distinctive retroarc magmatism occurred after near normal subduction of the southward drifting Juan Fernandez Ridge began at ~11 Ma and ended as magmatism ceased in the Pampean ranges, ~ 700 km east of the trench at ~4.7 Ma. Recent seismic work in the retroarc area indicate a ~60 km thick crust under the Precordillera fold-thrust belt with transitions at ~20 and ~40 km that are considered to be the top of crystalline basement and an eclogitic facies transition. Chemical constraints from ~15-7 Ma magmatic rocks suggest eclogization is related to crustal thickening over the shallowing slab in accord with field relations for major thrusting in the region by ~8-7 Ma. High Ba/Th ratios in <9 Ma volcanic rocks are interpreted to reflect phengite breakdown in the mantle wedge with the fluids facilitating eclogization of the lower crust. Evidence for mantle melt contributions in the magmas up until ~7 Ma comes from more primitive isotopic values in 1088-1251 Ma amphibolite and granulite facies xenoliths (eNd = 0 to -3; 87Sr/86Sr =704-0.710) than in Miocene volcanic rocks (eNd = 0-1.7; 0.70325-0.70345; zircon eHf ~ 0). From ~8 to 3 Ma, the active volcanic arc front near 28°S and 33°S was translated ~ 40-50 km eastward in a suspected response to forearc removal by subduction erosion. Given the position of the arc and distance to the trench, the same amount of forearc was likely removed in the intervening flatslab region. Trapping of subducted forearc material in the mantle wedge could help to explain a low Vp/Vs ratios (1.65-1.72, Wagner et al. 2008 ) in the mantle wedge above the flat-slab as a low Vp could result from orthopyroxene formation by reaction of silicic material with the mantle wedge and a high Vs can be explained by the current slab being too cool to hydrate the mantle wedge.

Winds, Eddies and Flow through Straits

DTIC Science & Technology

2010-01-01

driven origin of the Philippine dipole eddies. By contrast, in other volcanic island regions of the world (including the Hawaiian, Cabo Verde, and... volcanic island regions of the world. By contrast in the Hawaiian, Cabo Verde and Canary Islands, the driving mechanism in the eddy dynamics is...J. Aristegui, and F. Herrera (2000), Lee region of Gran Canaria , J. Geophys. Res., 105(C7), 17173-17193. Chang, C.-P., Z. Wang, and H. Hendon

In vitro evaluation of pulmonary deposition of airborne volcanic ash

NASA Astrophysics Data System (ADS)

Lähde, Anna; Sæunn Gudmundsdottir, Sigurbjörg; Joutsensaari, Jorma; Tapper, Unto; Ruusunen, Jarno; Ihalainen, Mika; Karhunen, Tommi; Torvela, Tiina; Jokiniemi, Jorma; Järvinen, Kristiina; Gíslason, Sigurður Reynir; Briem, Haraldur; Gizurarson, Sveinbjörn

2013-05-01

There has been an increasing interest in the effects of volcanic eruption on the environment, climate, and health following two recent volcanic eruptions in Iceland. Although health issues are mainly focused on subjects living close to the eruption due to the high concentration of airborne ash and gasses in close vicinity to the volcanoes, the ash may also reach high altitude and get distributed thousands of kilometers away from the volcano. Ash particles used in the studies were collected at the Eyjafjallajökull and Grímsvötn eruption sites. The composition, size, density and morphology of the particles were analyzed and the effect of particle properties on the re-dispersion and lung deposition were studied. The aerodynamic size and morphology of the particles were consistent with field measurement results obtained during the eruptions. Due to their size and structure, the ash particles can be re-suspended and transported into the lungs. The total surface area of submicron ash particles deposited into the alveolar and tracheobronchial regions of the lungs were 3-9% and 1-2%, respectively. Although the main fraction of the surface area is deposited in the head airways region, a significant amount of particles can deposit into the alveolar and tracheobronchial regions. The results indicate that a substantial increase in the concentration of respirable airborne ash particles and associated health hazard can take place if the deposited ash particles are re-suspended under dry, windy conditions or by outdoor human activity.

Genetic structure of Dendroctonus mexicanus (Coleoptera: Curculionidae: Scolytinae) in the trans-Mexican volcanic belt.

Treesearch

Gerardo Zúniga; Ramón Cisneros; Yolanda Salinas-Moreno; Jane L. Hayes; John E. Rinehart

2006-01-01

It is assumed that geographic isolation of Dendroctonus Erichson species populations or their plant hosts determines genetic structure. This structure can be analyzed with respect to the biogeographic pattern that describes the species in a region. The Trans-Mexican Volcanic Belt (TMVB) is located between the Neartic and Neotropical regions and is...

Western US volcanism due to intruding oceanic mantle driven by ancient Farallon slabs

NASA Astrophysics Data System (ADS)

Zhou, Quan; Liu, Lijun; Hu, Jiashun

2018-01-01

The origin of late Cenozoic intraplate volcanism over the western United States is debated. One important reason is the lack of a clear understanding of the mantle dynamics during this volcanic history. Here we reconstruct the mantle thermal states beneath North America since 20 million years ago using a hybrid inverse geodynamic model with data assimilation. The model simultaneously satisfies the past subduction kinematics, present mantle tomographic image and the volcanic history. We find that volcanism in both the Yellowstone volcanic province and the Basin and Range province corresponds to a similar eastward-intruding mantle derived from beneath the Pacific Ocean and driven mostly by the sinking Farallon slab below the central-eastern United States. The hot mantle that forms the Columbia River flood basalt and subsequent Yellowstone-Newberry hotspot tracks first enters the western United States through tears within the Juan de Fuca slab. Subsequent coexistence of the westward asthenospheric flow above the retreating Juan de Fuca slab and eastward-propagating mantle beyond the back-arc region reproduces the bifurcating hotspot chains. A similar but weaker heat source intrudes below the Basin and Range around the southern edge of the slab, and can explain the diffuse basaltic volcanism in this region. According to our models, the putative Yellowstone plume contributes little to the formation of the Yellowstone volcanic province.

Coupled geohazards at Southern Andes (Copahue-Lanín volcanoes): Chile's GEO supersite proposal

NASA Astrophysics Data System (ADS)

Lara, Luis E.; Cordova, Loreto

2017-04-01

Southern Andes are a young and active mountain belt where volcanism and tectonic processes (and those related to the hydrometeorological conditions controlled by this geological setting) pose a significant threat to the growing communities nearby. This proposal focus on a ca. 200 km long segment of the Southern Andes where 9 stratovolcanoes and 2 distributed volcanic fields are located, just along a tectonic corridor defined by the northern segment of the Liquiñe-Ofqui Faul System (LOFS), a long-lived active strike-slip fault running for 1200 km. Volcanoes in this area take part of the central province of the Andean Southern Volcanic Zone (37-41°S), particularly the northermost portion that is limited at the south by an Andean tranverse fault (Lanalhue Fault, which define the Villarrica-Lanin volcanic chain) and run along the horse-tail array of the LOFS to the north. Most of the stravolcanoes are atop of the LOFS main branch with only 3 exceptions (Callaqui, Tolhuaca and Lanín) 15-20 km away, but related to transverse faults. Hazards in the segment derive from the activity of some of the most active volcanoes in South America (e.g., Villarrica, Llaima), others with long-lasting weak activity (e.g., Copahue) or some volcanoes with low frequency but high magnitude eruptions in the geological record. Only since the beggining of the 20th century 80 eruptions have been recorded in this area. In addition, activity of the LOFS has been detected prior to some eruptions and coeval with some others (e.g., Lonquimay 1989). A strong two-way coupling between tectonics and volcanism has been proposed for the segment but only recently detected by geophysical techniques or numerical modelling. Tectonic triggered landslides are frequent in this region together with debris flows at erupting ice-covered volcanoes or stream headed at high altitude basins. The latter scenario seems to be worst at present because of global climate change. Ground-based monitoring networks for both volcanism (the so-called Red Nacional de Vigilancia Volcánica at Sernageomin) and tectonics (Centro Sismólogico Nacional at Universidad de Chile) allow a good complement with space-borne data (e.g., we observed deformation by GPS and InSAR at Villarrica volcano related to the March 3, 2015 eruption) in order to promote basic and applied research for a successful national strategy of disaster risk reduction. In addition, at least 3 active national research grants focus in this area and a number of young scientists are working there. Thus, we propose the Copahue-Lanín (37.5-39.5°S) segment of the Southern Volcanic Zone as a Geohazards Supersite and look forward for an enhanced engagement of the scientific community in this area.

U-Pb zircon geochronology of the Paleogene - Neogene volcanism in the NW Anatolia: Its implications for the Late Mesozoic-Cenozoic geodynamic evolution of the Aegean

NASA Astrophysics Data System (ADS)

Ersoy, E. Yalçın; Akal, Cüneyt; Genç, Ş. Can; Candan, Osman; Palmer, Martin R.; Prelević, Dejan; Uysal, İbrahim; Mertz-Kraus, Regina

2017-10-01

The northern Aegean region was shaped by subduction, obduction, collision, and post-collisional extension processes. Two areas in this region, the Rhodope-Thrace-Biga Peninsula to the west and Armutlu-Almacık-Nallıhan (the Central Sakarya) to the east, are characterized by extensive Eocene to Miocene post-collisional magmatic associations. We suggest that comparison of the Cenozoic magmatic events of these two regions may provide insights into the Late Mesozoic to Cenozoic tectonic evolution of the Aegean. With this aim, we present an improved Cenozoic stratigraphy of the Biga Peninsula derived from a new comprehensive set of U-Pb zircon age data obtained from the Eocene to Miocene volcanic units in the region. The compiled radiometric age data show that calc-alkaline volcanic activity occurred at 43-15 Ma in the Biga Peninsula, 43-17 Ma in the Rhodope and Thrace regions, and 53-38 Ma in the Armutlu-Almacık-Nallıhan region, which are slightly overlapping. We discuss the possible cause for the distinct Cenozoic geodynamic evolution of the eastern and western parts of the region, and propose that the Rhodope, Thrace and Biga regions in the north Aegean share the same Late Mesozoic to Cenozoic geodynamic evolution, which is consistent with continuous subduction, crustal accretion, southwestward trench migration and accompanying extension; all preceded by the Late Cretaceous - Paleocene collision along the Vardar suture zone. In contrast, the Armutlu-Almacık-Nallıhan region was shaped by slab break-off and related processes following the Late Cretaceous - Paleocene collision along the İzmir-Ankara suture zone. The eastern and western parts of the region are presently separated by a northeast-southwest trending transfer zone that was likely originally present as a transform fault in the subducted Tethys oceanic crust, and demonstrates that the regional geodynamic evolution can be strongly influenced by the geographical distribution of geologic features on the subducting plate.

Ice in Volcanic Clouds

NASA Astrophysics Data System (ADS)

Few, A. A.

2010-12-01

It is widely recognized that lightning activity in thunderstorm clouds is associated with ice in the clouds. In volcanic plumes the lower electrical discharges near the vent are clearly not associated with ice; however, the electrical discharges from the upper volcanic clouds very likely are associated with ice. There is ample water in volcanic plumes and clouds. The explosive volcanic eruption is produced by volatile components in the rising magma. Researchers estimate that the water content of the volatiles is up to 99% by mole; other gases are mainly sulfur and chlorine species. These volatiles carry with them a wide range of hot magma melts and solids, importantly silicate particles and tephra. The more massive components fall out near the vent carrying with them much of the heat from the plume; these large components are not in thermodynamic equilibrium with the gases, ash, and lapilli; thus the heat removed does not lower the temperature of the materials carried aloft in the plume. Upward motion is initially provided by the thrust from the volcanic eruption, then by buoyancy of the hot plume. The rising plume is cooled by entrainment of environmental air, which contains water, and by adiabatic expansion; the plume transitions into a volcanic cloud. Further lifting and cooling produces supercooled water droplets (T ~ -5 C) in a limited zone (z ~ 9 km) before the fast updraft (~ 60 m/s) rapidly transforms them into ice. Computer models of volcanic clouds that include water and ice microphysics indicate that the latent heat of condensation is not significant in cloud dynamics because it occurs in a region where buoyancy is provided by the original hot plume material. The latent heat of ice formation occurs at higher and colder levels and seems to contribute to the final lifting of the cloud top by ~1.5km. Laboratory results indicate that the fine silicate ash particles, which are abundant, are good ice nuclei, IN. Because of the abundance of the silicate ash, modelers conclude that there are many small ice particles in a volcanic clouds compared to thunderstorm clouds where the scarcity of IN produce fewer but larger ice particles. Another microphysical difference is that in the water phase (drops or ice surface) adsorption of sulfur and chlorine gases is enhanced and the freezing temperature lowered. During diffusion growth of ice particles sulfur dioxide can be incorporated in the ice. The sulfur dioxide sequestered by the ice can be converted to sulfate and transported into the stratosphere and released when the ice sublimates. Do these microphysical differences significantly alter the electrical charging mechanisms that exist in thunderstorm clouds? Observations of the lightning discharges associated with the upper regions of volcanic clouds seem to indicate that the charging mechanisms are essentially the same.

Geology, geochronology, and paleogeography of the southern Sonoma volcanic field and adjacent areas, northern San Francisco Bay region, California

USGS Publications Warehouse

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

2011-01-01

Recent geologic mapping in the northern San Francisco Bay region (California, USA) supported by radiometric dating and tephrochronologic correlations, provides insights into the framework geology, stratigraphy, tectonic evolution, and geologic history of this part of the San Andreas transform plate boundary. There are 25 new and existing radiometric dates that define three temporally distinct volcanic packages along the north margin of San Pablo Bay, i.e., the Burdell Mountain Volcanics (11.1 Ma), the Tolay Volcanics (ca. 10–8 Ma), and the Sonoma Volcanics (ca. 8–2.5 Ma). The Burdell Mountain and the Tolay Volcanics are allochthonous, having been displaced from the Quien Sabe Volcanics and the Berkeley Hills Volcanics, respectively. Two samples from a core of the Tolay Volcanics taken from the Murphy #1 well in the Petaluma oilfield yielded ages of 8.99 ± 0.06 and 9.13 ± 0.06 Ma, demonstrating that volcanic rocks exposed along Tolay Creek near Sears Point previously thought to be a separate unit, the Donnell Ranch volcanics, are part of the Tolay Volcanics. Other new dates reported herein show that volcanic rocks in the Meacham Hill area and extending southwest to the Burdell Mountain fault are also part of the Tolay Volcanics. In the Sonoma volcanic field, strongly bimodal volcanic sequences are intercalated with sediments. In the Mayacmas Mountains a belt of eruptive centers youngs to the north. The youngest of these volcanic centers at Sugarloaf Ridge, which lithologically, chemically, and temporally matches the Napa Valley eruptive center, was apparently displaced 30 km to the northwest by movement along the Carneros and West Napa faults. The older parts of the Sonoma Volcanics have been displaced at least 28 km along the Rodgers Creek fault since ca. 7 Ma. The Petaluma Formation also youngs to the north along the Rodgers Creek–Hayward fault and the Bennett Valley fault. The Petaluma basin formed as part of the Contra Costa basin in the Late Miocene and was displaced to its present location along the Rodgers Creek–Hayward and older faults. The Tolay fault, previously thought to be a major dextral fault, is part of a fold-and-thrust belt that does not exhibit lateral displacement.

Magma genesis of the acidic volcanism in the intra-arc rift zone of the Izu volcanic arc, Japan

NASA Astrophysics Data System (ADS)

Haraguchi, S.; Tokuyama, H.; Ishii, T.

2010-12-01

The Izu volcanic arc extends over 550 km from the Izu Peninsula, Japan, to the Nishinoshima Trough or Sofugan tectonic line. It is the northernmost segment of the Izu-Bonin-Mariana arc system, which is located at the eastern side of the Philippine Sea Plate. The recent magmatism of the Izu arc is bimodal and characterized by basalt and rhyolite (e.g. Tamura and Tatsumi 2002). In the southern Izu arc, volcanic front from the Aogashima to the Torishima islands is characterized by submarine calderas and acidic volcanisms. The intra-arc rifting, characterized by back-arc depressions, small volcanic knolls and ridges, is active in this region. Volcanic rocks were obtained in 1995 during a research cruise of the R/V MOANA WAVE (Hawaii University, cruise MW9507). Geochemical variation of volcanic rocks and magma genesis was studied by Hochstaedter et al. (2000, 2001), Machida et al (2008), etc. These studies focused magma and mantle dynamics of basaltic volcanism in the wedge mantle. Acidic volcanic rocks were also dredged during the curies MW9507. However, studies of these acidic volcanics were rare. Herein, we present petrographical and chemical analyses of these acidic rocks, and compare these results with those of other acidic rocks in the Izu arc and lab experiments, and propose a model of magma genesis in a context of acidic volcanism. Dredge sites by the cruise MW9507 are 120, and about 50 sites are in the rift zone. Recovered rocks are dominated by the bimodal assemblage of basalt-basaltic andesite and dacite-rhyolite. The most abundant phase is olivine basalt, less than 50 wt% SiO2. Andesites are minor in volume and compositional gap from 56 to 65 wt% SiO2 exists. The across-arc variation of the HFSE contents and ratios, such as Zr/Y and Nb/Zr of rhyolites exhibit depleted in the volcanic front side and enriched in reararc side. This characteristic is similar to basaltic volcanism pointed out by Hochstaedter et al (2000). The petrographical features of rhyolites exhibit massive or flow textures, and aphyric or rare phyric. Phenocrysts are mainly plagioclase and quartz. Colored minerals are rare and observed mainly orthopyroxene. Amphibole and biotite are not observed. The phenocryst and groundmass mineral compositions of rhyolites exhibit felsic characteristics and narrow ranges. These mineral compositions are not overlapped on those of andesites and basalts. Acidic volcanism in the Izu arc is considered to partial melting of arc middle to lower crust (e.g. Tamura and Tatsumi, 2003) because rhyolite exhibits similar composition to melting experimental results of basaltic or andesitic parental material under anhydrous, low pressure and low temperature (e.g. Shukuno et al., 2006). Compare to these experiments, we consider that parent material of acidic volcanics in the rift zone is andesitic middle crust, and this crust exhibits depleted in the front side and enriched in the reararc side caused by across-arc variation of basaltic volcanism. During the rifting activity, rhyolitic magma was produced by melting of this andesitic middle crust by heating from magma and decompression, and produced rhyolites exhibit enriched in reararc side and depleted in front side.

Patterns in the Physical, Chemical, and Biological Composition of Icelandic Lakes and the Dominant Factors Controlling Variability Across Watersheds

NASA Astrophysics Data System (ADS)

Greco, A.; Strock, K.; Edwards, B. R.

2017-12-01

Fourteen lakes were sampled in the southern and western area of Iceland in June of 2017. The southern systems, within the Eastern Volcanic Zone, have minimal soil development and active volcanoes that produce ash input to lakes. Lakes in the Western Volcanic Zone were more diverse and located in older bedrock with more extensively weathered soil. Physical variables (temperature, oxygen concentration, and water clarity), chemical variables (pH, conductivity, dissolved and total nitrogen and phosphorus concentrations, and dissolved organic carbon concentration), and biological variables (algal biomass) were compared across the lakes sampled in these geographic regions. There was a large range in lake characteristics, including five to eighteen times higher algal biomass in the southern systems that experience active ash input to lakes. The lakes located in the Eastern Volcanic Zone also had higher conductivity and lower pH, especially in systems receiving substantial geothermal input. These results were analyzed in the context of more extensive lake sampling efforts across Iceland (46 lakes) to determine defining characteristics of lakes in each region and to identify variables that drive heterogeneous patterns in physical, chemical, and biological lake features within each region. Coastal systems, characterized by high conductivity, and glacially-fed systems, characterized by high iron concentrations, were unique from lakes in all other regions. Clustering and principal component analyses revealed that lake type (plateau, valley, spring-fed, and direct-runoff) was not the primary factor explaining variability in lake chemistry outside of the coastal and glacial lake types. Instead, lakes differentiated along a gradient of iron concentration and total nitrogen concentration. The physical and chemical properties of subarctic lakes are especially susceptible to both natural and human-induced environmental impacts. However, relatively little is known about the contemporary physical and chemical properties of Icelandic lakes, despite their abundance and importance as freshwater resources. Here we report an analysis of the physical, chemical, and biological characteristics of a set of subarctic lakes and use spatial Information to infer controls on lake heterogeneity within and across regions.

Integrating Multiple Space Ground Sensors to Track Volcanic Activity

NASA Technical Reports Server (NTRS)

Chien, Steve; Davies, Ashley; Doubleday, Joshua; Tran, Daniel; Jones, Samuel; Kjartansson, Einar; Thorsteinsson, Hrobjartur; Vogfjord, Kristin; Guomundsson, Magnus; Thordarson, Thor;

The 2007 Nazko, British Columbia, earthquake sequence: Injection of magma deep in the crust beneath the Anahim volcanic belt

USGS Publications Warehouse

Cassidy, J.F.; Balfour, N.; Hickson, C.; Kao, H.; White, Rickie; Caplan-Auerbach, J.; Mazzotti, S.; Rogers, Gary C.; Al-Khoubbi, I.; Bird, A.L.; Esteban, L.; Kelman, M.; Hutchinson, J.; McCormack, D.

2011-01-01

On 9 October 2007, an unusual sequence of earthquakes began in central British Columbia about 20 km west of the Nazko cone, the most recent (circa 7200 yr) volcanic center in the Anahim volcanic belt. Within 25 hr, eight earthquakes of magnitude 2.3-2.9 occurred in a region where no earthquakes had previously been recorded. During the next three weeks, more than 800 microearthquakes were located (and many more detected), most at a depth of 25-31 km and within a radius of about 5 km. After about two months, almost all activity ceased. The clear P- and S-wave arrivals indicated that these were high-frequency (volcanic-tectonic) earthquakes and the b value of 1.9 that we calculated is anomalous for crustal earthquakes but consistent with volcanic-related events. Analysis of receiver functions at a station immediately above the seismicity indicated a Moho near 30 km depth. Precise relocation of the seismicity using a double-difference method suggested a horizontal migration at the rate of about 0:5 km=d, with almost all events within the lowermost crust. Neither harmonic tremor nor long-period events were observed; however, some spasmodic bursts were recorded and determined to be colocated with the earthquake hypocenters. These observations are all very similar to a deep earthquake sequence recorded beneath Lake Tahoe, California, in 2003-2004. Based on these remarkable similarities, we interpret the Nazko sequence as an indication of an injection of magma into the lower crust beneath the Anahim volcanic belt. This magma injection fractures rock, producing high-frequency, volcanic-tectonic earthquakes and spasmodic bursts.

Geologic Evolution of Eastern Hellas, Mars: Styles and Timing of Volatile-driven Activity

NASA Technical Reports Server (NTRS)

Crown, David A.; Bleamaster, Leslie F., III; Mest, Scott C.

2004-01-01

The east rim of the Hellas basin and the surrounding highlands comprise a geologically significant region for evaluating volatile abundance, volatile distribution and cycling, and potential changes in Martian environmental conditions. This region of the Martian surface exhibits landforms shaped by a diversity of geologic processes and has a well-preserved geologic record, with exposures of Noachian, Hesperian, and Amazonian units, as well as spans a wide range in both latitude and elevation due to the magnitude of Hellas basin. In addition, geologically contemporaneous volcanism and volatile-driven activity in the circum-Hellas highlands provide important ingredients for creating habitats for potential Martian life.

Volcanic ash as an oceanic iron source and sink

NASA Astrophysics Data System (ADS)

Rogan, Nicholas; Achterberg, Eric P.; Le Moigne, Frédéric A. C.; Marsay, Chris M.; Tagliabue, Alessandro; Williams, Richard G.

2016-03-01

Volcanic ash deposition to the ocean forms a natural source of iron (Fe) to surface water microbial communities. Inputs of lithogenic material may also facilitate Fe removal through scavenging. Combining dissolved Fe (dFe) and thorium-234 observations alongside modeling, we investigate scavenging of Fe in the North Atlantic following the Eyjafjallajökull volcanic eruption. Under typical conditions biogenic particles dominate scavenging, whereas ash particles dominate during the eruption. The size of particles is important as smaller scavenging particles can become saturated with surface-associated ions. Model simulations indicate that ash deposition associated with Eyjafjallajökull likely led to net Fe removal. Our model suggests a threefold greater stimulation of biological activity if ash deposition had occurred later in the growing season when the region was Fe limited. The implications of ash particle scavenging, eruption timing, and particle saturation need to be considered when assessing the impact of ash deposition on the ocean Fe cycle and productivity.

Paleomagnetic investigation of some volcanic rocks from the McMurdo volcanic province, Antarctica

USGS Publications Warehouse

Mankinen, E.A.; Cox, A.

1988-01-01

Paleomagnetic data for lava flows from sporadic but long-lived eruptions in the McMurdo Sound region are combined with previously published geologic and geochronologic data to determine the general eruptive sequence of the area. Lava flows in the Walcott Bay area were erupted during the Gauss Normal, Matuyama Reversed, and Brunhes Normal Polarity Chrons. The youngest flows on Black Island probably erupted near the boundary between the Gilbert and Gauss chrons. The most recent activity was concentrated on the volcanic edifices of Mounts Morning and Discovery and on Ross Island sampled during this study with those of eight flows that were published previously yields a mean paleomagnetic pole at 87.3??N, 317.3??E (??95 = 6.3??). The ancient geomagnetic field dispersion about this mean pole is 23.5??, with upper and lower limits of 95% confidence equal to 27.4?? and 20.5??, respectively. This value probably is a reasonable estimate of secular variation for the Antarctic continent during Pliocene and Pleistocene time. -Authors

Natural Environmental Hazards Reflected in High-Altitude Patagonian Lake Sediments (lake Caviahue, Argentina)

NASA Astrophysics Data System (ADS)

Müller, Anne; Scharf, Burkhard; von Tümpling, Wolf; Pirrung, Michael

2009-03-01

Two 6-m long sediment cores drilled in the two basins of Lake Caviahue give new evidence of the impact of natural hazards such as ash fallouts linked to nearby volcanic eruptions in the ecologically sensitive environment of the high-altitude region of the Argentinan Patagonian Andes. The two cores show distinct signals of changes in autochthonous productivity and terrigenous input into the lake from ash fallout as well as from river load and shore erosion. Multiproxy records of the sediments indicate whether these changes can be related to volcanic activity. High values of magnetic susceptibility in the cores reflect periods of basaltic ash fallouts during eruptions of the nearby Copahue Volcano. The southern basin is located in the prevalent direction of ash fallouts and has been affected by these volcanic inputs more intensely than the northern basin of the lake. In contrast, sedimentation and authochthonous productivity in the northern basin are strongly affected by fluvial inputs such as suspended river load and acidic stream waters.

Natural Environmental Hazards Reflected in High-Altitude Patagonian Lake Sediments (Lake Caviahue, Argentina)

NASA Astrophysics Data System (ADS)

Mueller, A.; Pirrung, M.; Scharf, B.; von Tuempling, W.

2007-05-01

Two 6-m long sediment cores drilled in the two basins of Lake Caviahue give new evidence of the impact of natural hazards such as ash fallouts linked to nearby volcanic eruptions in the ecologically sensitive environment of the high-altitude region of the Argentinan Patagonian Andes. The two cores show distinct signals of changes in autochthonous productivity and terrigenous input into the lake from ash fallout, river load and shore erosion. Multiproxy records of the sediments indicate whether these changes can be related to volcanic activity. High values of magnetic susceptibility in the cores reflect periods of basaltic ash fallouts during eruptions of the nearby Copahue volcano. The southern basin is located in the prevalent direction of ash fallouts and has been affected by these volcanic inputs more intensely than the northern basin of the lake. In contrast, sedimentation and authochthonous productivity in the northern basin are strongly affected by fluvial inputs such as suspended river load and acidic stream waters.

Inventory of gas flux measurements from volcanoes of the global Network for Observation of Volcanic and Atmospheric Change (NOVAC)

NASA Astrophysics Data System (ADS)

Galle, B.; Arellano, S.; Norman, P.; Conde, V.

2012-04-01

NOVAC, the Network for Observation of Volcanic and Atmospheric Change, was initiated in 2005 as a 5-year-long project financed by the European Union. Its main purpose is to create a global network for the monitoring and research of volcanic atmospheric plumes and related geophysical phenomena by using state-of-the-art spectroscopic remote sensing technology. Up to 2012, 64 instruments have been installed at 24 volcanoes in 13 countries of Latin America, Italy, Democratic Republic of Congo, Reunion, Iceland, and Philippines, and efforts are being done to expand the network to other active volcanic zones. NOVAC has been a pioneer initiative in the community of volcanologists and embraces the objectives of the Word Organization of Volcano Observatories (WOVO) and the Global Earth Observation System of Systems (GEOSS). In this contribution, we present the results of the measurements of SO2 gas fluxes carried out within NOVAC, which for some volcanoes represent a record of more than 7 years of continuous monitoring. The network comprises some of the most strongly degassing volcanoes in the world, covering a broad range of tectonic settings, levels of unrest, and potential risk. We show a global perspective of the output of volcanic gas from the covered regions, specific trends of degassing for a few selected volcanoes, and the significance of the database for further studies in volcanology and other geosciences.

Investigating Crustal Scale Fault Systems Controlling Volcanic and Hydrothermal Fluid Processes in the South-Central Andes, First Results from a Magnetotelluric Survey

NASA Astrophysics Data System (ADS)

Pearce, R.; Mitchell, T. M.; Moorkamp, M.; Araya, J.; Cembrano, J. M.; Yanez, G. A.; Hammond, J. O. S.

2017-12-01

At convergent plate boundaries, volcanic orogeny is largely controlled by major thrust fault systems that act as magmatic and hydrothermal fluid conduits through the crust. In the south-central Andes, the volcanically and seismically active Tinguiririca and Planchon-Peteroa volcanoes are considered to be tectonically related to the major El Fierro thrust fault system. These large scale reverse faults are characterized by 500 - 1000m wide hydrothermally altered fault cores, which possess a distinct conductive signature relative to surrounding lithology. In order to establish the subsurface architecture of these fault systems, such conductivity contrasts can be detected using the magnetotelluric method. In this study, LEMI fluxgate-magnetometer long-period and Metronix broadband MT data were collected at 21 sites in a 40km2 survey grid that surrounds this fault system and associated volcanic complexes. Multi-remote referencing techniques is used together with robust processing to obtain reliable impedance estimates between 100 Hz and 1,000s. Our preliminary inversion results provide evidence of structures within the 10 - 20 km depth range that are attributed to this fault system. Further inversions will be conducted to determine the approximate depth extent of these features, and ultimately provide constraints for future geophysical studies aimed to deduce the role of these faults in volcanic orogeny and hydrothermal fluid migration processes in this region of the Andes.

Soil CO2 flux baseline in an urban monogenetic volcanic field: the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Mazot, Agnès; Smid, Elaine R.; Schwendenmann, Luitgard; Delgado-Granados, Hugo; Lindsay, Jan

2013-11-01

The Auckland Volcanic Field (AVF) is a dormant monogenetic basaltic field located in Auckland, New Zealand. Though soil gas CO2 fluxes are routinely used to monitor volcanic regions, there have been no published studies of soil CO2 flux or soil gas CO2 concentrations in the AVF to date or many other monogenetic fields worldwide. We measured soil gas CO2 fluxes and soil gas CO2 concentrations in 2010 and 2012 in varying settings, seasons, and times of day to establish a baseline soil CO2 flux and to determine the major sources of and controlling influences on Auckland's soil CO2 flux. Soil CO2 flux measurements varied from 0 to 203 g m-2 day-1, with an average of 27.1 g m-2 day-1. Higher fluxes were attributed to varying land use properties (e.g., landfill). Using a graphical statistical approach, two populations of CO2 fluxes were identified. Isotope analyses of δ13CO2 confirmed that the source of CO2 in the AVF is biogenic with no volcanic component. These data may be used to assist with eruption forecasting in the event of precursory activity in the AVF, and highlight the importance of knowing land use history when assessing soil gas CO2 fluxes in urban environments.