Venus - Volcanic features in Atla Region

NASA Technical Reports Server (NTRS)

1991-01-01

This Magellan image from the Atla region of Venus shows several types of volcanic features and superimposed surface fractures. The area in the image is approximately 350 kilometers (217 miles) across, centered at 9 degrees south latitude, 199 degrees east longitude. Lava flows emanating from circular pits or linear fissures form flower-shaped patterns in several areas. A collapse depression approximately 20 kilometers by 10 kilometers (12 by 6 miles) near the center of the image is drained by a lava channel approximately 40 kilometers (25 miles) long. Numerous surface fractures and graben (linear valleys) criss-cross the volcanic deposits in north to northeast trends. The fractures are not buried by the lavas, indicating that the tectonic activity post-dates most of the volcanic activity.

Satellite geological and geophysical remote sensing of Iceland

NASA Technical Reports Server (NTRS)

Williams, R. S., Jr. (Principal Investigator)

1978-01-01

The author has identified the following significant results. The ERTS imagery has sufficient resolution to map, from MSS color composites, areas of altered ground caused by high temperature geothermal activity at the Namafjall, Torfajokull, and Reykjanes geothermal areas. The major axes of the fallout pattern of tephra from the May - July 1970 volcanic eruption from Hekla Volcano can be mapped where sufficient depth of deposition was present to seriously affect the normal vegetation. Lava flows from the 1961 volcanic eruption at Askja; some of the lava flows from the 1947-48 eruption, and and all of the lava flows from the 1970 eruption at Hekla; and the areas covered by tephra and lava from the 1973 eruption on Heimaey could be delineated. Low sun angle imagery of less than 10 deg of snow covered terrain was particularly valuable in mapping structural and volcanic features concealed beneath glacial ice in the active volcanic zones of Iceland.

Volcanogenic fluorine in rainwater around active degassing volcanoes: Mt. Etna and Stromboli Island, Italy.

PubMed

Bellomo, S; D'Alessandro, W; Longo, M

2003-01-01

Many studies have assessed the strong influence of volcanic activity on the surrounding environment. This is particularly true for strong gas emitters such as Mt. Etna and Stromboli volcanoes. Among volcanic gases, fluorine compounds are potentially very harmful. Fluorine cycling through rainwater in the above volcanic areas was studied analysing more than 400 monthly bulk samples. Data indicate that only approximately 1% of fluorine emission through the plume is deposited on the two volcanic areas by meteoric precipitations. Although measured bulk rainwater fluorine fluxes are comparable to and sometimes higher than in heavily polluted areas, their influence on the surrounding vegetation is limited. Only annual crops, in fact, show some damage that could be an effect of fluorine deposition, indicating that long-living endemic plant species or varieties have developed some kind of resistance. Copyright 2002 Elsevier Science B.V.

Resilient plant-bird interactions in a volcanic island ecosystem: pollination of Japanese Camellia mediated by the Japanese White-eye.

PubMed

Abe, Harue; Ueno, Saneyoshi; Takahashi, Toshimori; Tsumura, Yoshihiko; Hasegawa, Masami

2013-01-01

Observations of interspecies interactions during volcanic activity provide important opportunities to study how organisms respond to environmental devastation. Japanese camellia (Camellia japonica L.) and its main avian pollinator, the Japanese White-eye (Zosterops japonica), offer an excellent example of such an interaction as key members of the biotic community on Miyake-jima, which erupted in 2000 and continues to emit volcanic gases. Both species exhibit higher resistance to volcanic damage than other species. We examined the effects of volcanic activity on this plant-pollinator system by estimating pollen flow and the genetic diversity of the next generation. The results showed that despite a decrease in Camellia flowers, the partitioning of allelic richness among mother-tree pollen pools and seeds decreased while the migration rate of pollen from outside the study plot and the pollen donor diversity within a fruit increased as the index of volcanic damage increased. In areas with low food (flower) density due to volcanic damage, Z. japonica ranged over larger areas to satisfy its energy needs rather than moving to areas with higher food density. Consequently, the genetic diversity of the seeds (the next plant generation) increased with the index of volcanic damage. The results were consistent with previously published data on the movement of Z. japonica based on radio tracking and the genetic diversity of Camellia pollen adhering to pollinators. Overall, our results indicated that compensation mechanisms ensured better pollination after volcanic disturbance.

A preliminary evaluation of ERTS-1 images on the volcanic areas of Southern Italy

NASA Technical Reports Server (NTRS)

Cassinis, R.; Lechi, G. M.

1973-01-01

The test site selected for the investigation covers nearly all the regions of active and quiescent volcanism in southern Italy, i.e. the eastern part of the island of Sicily, the Aeolian Islands and the area of Naples. The three active European volcanoes (Etna, Stromboli and Vesuvius) are included. The investigation is in the frame of a program for the surveillance of active volcanoes by geophysical (including remote sensing thermal methods) and geochemical methods. By the multispectral analysis of ERTS-1 data it is intended to study the spectral behavior of the volcanic materials as well as the major geological lineaments with special reference to those associated with the volcanic region. Secondary objectives are also the determination of the hydrographic network seasonal behavior and the relationship between the vegetation cover and the different type of soils and rocks.

Tectonics and Volcanism of East Africa as Seen Using Remote Sensing Imagery

NASA Technical Reports Server (NTRS)

Hutt, Duncan John

1996-01-01

The East African Rift is the largest area of active continental geology. The tectonics of this area has been studied with remote sensing data, including AVHRR, Landsat MSS and TM, SPOT, and electronic still camera from Shuttle. Lineation trends have been compared to centers of volcanic and earthquake activity as well as the trends shown on existing geologic maps. Remote sensing data can be used effectively to reveal and analyze significant tectonic features in this area.

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.

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.

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.

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

Magma-tectonic interactions in an area of active extension; a review of recent observations, models and interpretations from Iceland

NASA Astrophysics Data System (ADS)

Pedersen, Rikke; Sigmundsson, Freysteinn; Drouin, Vincent; Rafn Heimisson, Elías; Parks, Michelle; Dumont, Stéphanie; Árnadóttir, Þóra; Masterlark, Timothy; Ófeigsson, Benedíkt G.; Jónsdóttir, Kristín; Hooper, Andrew

2016-04-01

The geological setting of Iceland provides rich opportunities of studying magma-tectonic interactions, as it constitutes Earth's largest part of the mid-oceanic ridge system exposed above sea level. A series of volcanic and seismic zones accommodate the ~2 cm/year spreading between the North-American and Eurasian plates, and the Icelandic hot-spot conveniently provides the means of exposing this oceanic crust-forming setting above sea-level. Both extinct and active plumbing system structures can be studied in Iceland, as the deeply eroded tertiary areas provide views into the structures of extinct volcanic systems, and active processes can be inferred on in the many active volcanic systems. A variety of volcanic and tectonic processes cause the Icelandic crust to deform continuously, and the availability of contemporaneous measurements of crustal deformation and seismicity provide a powerful data set, when trying to obtain insight into the processes working at depth, such as magma migration through the uppermost lithosphere, magma induced host rock deformation and volcanic eruption locations and styles. The inferences geodetic and seismic datasets allow on the active plate spreading processes and subsurface magma movements in Iceland will be reviewed, in particular in relation to the Northern Volcanic Zone (NVZ). There the three phases of a rifting cycle (rifting, post-rifting, inter-rifting) have been observed. The NVZ is an extensional rift segment, bounded to the south by the Icelandic mantle plume, and to the north by the Tjörnes transform zone. The NVZ has typically been divided into five partly overlapping en-echelon fissure swarms, each with a central main volcanic production area. Most recently, additional insight into controlling factors during active rifting has been provided by the Bárðarbunga activity in 2014-2015 that included a major rifting event, the largest effusive eruption in Iceland since 1783, and a gradual caldera collapse. It is evident from available datasets that improved rifting-cycle models do need to incorporate realistic lithospheric properties, as well as the dynamic transport of magma, in order to reproduce the variety of observations, and provide means of forecasting large future dyking events and eruptions at active rifting segments.

Monitoring Colima Volcano, Mexico, using satellite data

NASA Technical Reports Server (NTRS)

Abrams, Michael; Glaze, Lori; Sheridan, Michael

1991-01-01

The Colima Volcanic Complex at the western end of the Mexican Volcanic Belt is the most active andesitic volcano in Mexico. Short-wavelength infrared data from the Landsat Thematic Mapper satellite were used to determine the temperature and fractional area of radiant picture elements for two January data acquisitions in 1985 and 1986. The 1986 data showed four 28.5 m by 28.5 m pixels (picture elements) whose hot subpixel components had temperatures ranging from 511-774 C and areas of 1.8-13 sq m. The 1985 data had no radiating areas above background temperatures. Ground observations and measurements in November 1985 and February 1986 reported the presence of hot fumaroles at the summit with temperatures of 135-895 C. This study demonstrates the utility of satellite data for monitoring volcanic activity.

Chronic exposure to volcanic air pollution and DNA damage in Furnas Volcano (São Miguel Island, Azores, Portugal) inhabitants

NASA Astrophysics Data System (ADS)

Linhares, Diana; Garcia, Patricia; Silva, Catarina; Ferreira, Teresa; Barroso, Joana; Camarinho, Ricardo; Rodrigues, Armindo

2015-04-01

Many studies in volcanic air pollution only have in consideration the acute toxic effects of gas or ash releases however the impact of chronic exposure to ground gas emissions in human health is yet poorly known. In the Azores archipelago (Portugal), São Miguel island has one of the most active and dangerous volcanoes: Furnas Volcano. Highly active fumarolic fields, hot springs and soil diffuse degassing phenomena are the main secondary volcanic phenomena that can be seen at the volcano surroundings. One of the main gases released in these diffuse degassing areas is radon (222Rn), which decay results in solid particles that readily settle within the airways. These decay particles emit alpha radiation that is capable of causing severe DNA damage that cumulatively can eventually cause cancer. Previous studies have established that chronic exposure to chromosome-damaging agents can lead to the formation of nuclear anomalies, such as micronuclei that is used for monitoring DNA damage in human populations. The present study was designed to evaluate whether chronic exposure to volcanic air pollution, associated to 222Rn, might result in DNA damage in human oral epithelial cells. A cross sectional study was performed in a study group of 142 individuals inhabiting an area where volcanic activity is marked by active fumarolic fields and soil degassing (hydrothermal area), and a reference group of 368 individuals inhabiting an area without these secondary manifestations of volcanism (non-hydrothermal area). For each individual, 1000 buccal epithelial cells were analyzed for the frequency of micronucleated cells (MNc) and the frequency of cells with other nuclear anomalies (ONA: pyknosis, karyolysis and karyorrhexis), by using the micronucleus assay. Information on lifestyle factors and an informed consent were obtained from each participant. Assessment of indoor radon was performed with the use of radon detectors. Data were analyzed with logistic regression models, adjusted for confounding factors (age, gender, smoking and drinking status, and number of cigarettes smoked per day). Results demonstrated that levels of radon in the environment were significantly different in study and reference groups (115 Bq/m3 vs. 47 Bq/m3, respectively; p<0.001); in winter, radon measurements reached the highest values both in the study and the reference groups (809 Bq/m3 vs. 56 Bq/m3, respectively). The frequency of MNc in the study group was significantly higher than in the reference group (2.93‰ vs. 2.58‰, respectively; p=0.002). The OR for formation of MNc in the hydrothermal area was 1.5 (95% CI 1.07-2.02). A moderate and positive correlation was found between the frequency of MNc and 222Rn (rs = 0.459, p<0.001). To our knowledge this is the first study that clearly associates the exposure of volcanogenic indoor radon in inhabitants of hydrothermal areas and the DNA damage in human oral epithelial cells, evidencing that volcanic air pollution is a risk factor of carcinogenesis. Although the present findings require confirmation in larger studies, bio-monitoring for DNA damage is recommended for inhabitants of localities with active volcanism and mitigation measures such as restriction of building in certain areas should be taken into consideration in these volcanically active areas.

Volcanic Supersites as cross-disciplinary laboratories

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Classifying Volcanic Activity Using an Empirical Decision Making Algorithm

NASA Astrophysics Data System (ADS)

Junek, W. N.; Jones, W. L.; Woods, M. T.

2012-12-01

Detection and classification of developing volcanic activity is vital to eruption forecasting. Timely information regarding an impending eruption would aid civil authorities in determining the proper response to a developing crisis. In this presentation, volcanic activity is characterized using an event tree classifier and a suite of empirical statistical models derived through logistic regression. Forecasts are reported in terms of the United States Geological Survey (USGS) volcano alert level system. The algorithm employs multidisciplinary data (e.g., seismic, GPS, InSAR) acquired by various volcano monitoring systems and source modeling information to forecast the likelihood that an eruption, with a volcanic explosivity index (VEI) > 1, will occur within a quantitatively constrained area. Logistic models are constructed from a sparse and geographically diverse dataset assembled from a collection of historic volcanic unrest episodes. Bootstrapping techniques are applied to the training data to allow for the estimation of robust logistic model coefficients. Cross validation produced a series of receiver operating characteristic (ROC) curves with areas ranging between 0.78-0.81, which indicates the algorithm has good predictive capabilities. The ROC curves also allowed for the determination of a false positive rate and optimum detection for each stage of the algorithm. Forecasts for historic volcanic unrest episodes in North America and Iceland were computed and are consistent with the actual outcome of the events.

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.

Relation of compositions of deep fluids in geothermal activity of Pleistocene-Holocene volcanic fields of Lesser Caucasus

NASA Astrophysics Data System (ADS)

Meliksetian, Khachatur; Lavrushin, Vassily; Shahinyan, Hrach; Aidarkozhina, Altin; Navasardyan, Gevorg; Ermakov, Alexander; Zakaryan, Shushan; Prasolov, Edward; Manucharyan, Davit; Gyulnazaryan, Shushan; Grigoryan, Edmond

2017-04-01

It is widely accepted, that geothermal activity in the conductive heat flow processes, such as volcanism and hydrothermal activity, is manifestation of the thermal mass transfer process in the Earth's crust, where geothermal and geochemical processes are closely connected. Therefore, geochemistry and isotope compositions of thermal mineral waters within and on periphery of volcanic clusters may represent key indicators for better understanding of geothermal activity in geodynamically active zones. Geochemical features of heat and mass transport in hydrothermal systems related to active volcanic and fault systems in continental collision related orogenic elevated plateaus such as Anatolian-Armenian-Iranian highlands are still poorly understood. In this contribution we attempt to fill these gaps in our knowledge of relations of geochemical and geothermal processes in collision zones. We present new data on chemical compositions, trace element geochemistry of thermal waters of Lesser Caucasus, (Armenia) as well as isotope analysis of free gases such as {}3He/{}4He, {}40Ar/{}36Ar, δ{}13?(CO{}2), nitrogen δ{}15N(N{}2) and oxygen and hydrogen isotopes in water phases (δD, δ{}18O). To reveal some specific features of formation of fluid systems related to thermal activity in the areas of collision related active volcanism and active geodynamics a complex geochemical (SiO{}2, K-Na, Na-Li, Li-Mg) and isotope geothermometers (δ{}18O(CaCO{}3) - δ{}18O(H{}2O)) were applied. The distribution of δ{}13?(??{}2) values in free gases of mineral waters of Armenia demonstrates that gases related to Quaternary volcanic fields are characterized by relatively light δ{}13?(CO{}2) values close to mantle derived gases, while on periphery of volcanic systems relatively heavy values of δ{}13?(CO{}2) indicate strong influence of metamorphic and sedimentary derived carbon dioxide. Distribution of nitrogen isotopes δ{}15N(N{}2) demonstrate an inverse correlation with δ{}13?(CO{}2) values and similarly to carbon dioxide indicate presence of metamorphic nitrogen on the periphery and strong influence of atmospheric (and mantle derived) nitrogen within volcanic fields. Results of geochemical and isotope investigations, as well as estimated temperatures of the formation of the mineral compositions of thermal waters demonstrate, that these studied hydrothermal systems originated within thermal anomaly fields associated with young (Pleistocene-Holocene) volcanic fields in Armenia. Basing on geochemical and isotope data, as well as on estimations of temperatures of water formation, calculated using various geothermometers, thermal anomaly fields, related to young volcanic activity and faults, within Armenian and neighboring areas of Lesser Caucasus are outlined. These results are used to reveal potential and promising areas for geothermal energy exploration in Armenia. This research is completed in framework of joint Armenian-Russian research grant funded by State Committee of Science of Armenia (grant #15RF-076) and Russian Foundation for Basic Research (grant#15-55-05069).

Tale of three prospects

USGS Publications Warehouse

Duffield, Wendell A.; ,

1992-01-01

Most high-temperature, hydrothermal-convection systems probably are heated by bodies of magma (and/or hot plutons), whose presence is suggested by geologically young, if not active volcanism. Study of a young volcanic area provides information about the general thermal status of the underlying heat source, and detailed information about the time-space-volume-composition (TSVC) characteristics for a volcanic area can help define temperature at least semi-quantitatively when interpreted within the framework of published magma-cooling models. Thus, TSVC study is a fairly powerful and cost effective tool in the pre-drilling phase of an exploration program in young volcanic terrane. Examples are described for Coso, California; Agua de Pau, Azores; and Tecuamburro, Guatemala.

Long-Term Acoustic Real-Time Sensor for Polar Areas (LARA)

DTIC Science & Technology

2015-09-30

segment in the northeast Pacific Ocean. Both areas have seafloor volcanic eruptions forecast for the near future, and the LARA moorings will allow us...time monitoring of deep-ocean seismic and volcanic activity (e.g., Dziak et al., 2012) - especially in areas where SOSUS coverage no longer exists...precursors and magma ascent before the April 2011 eruption at Axial Seamount. Nature Geoscience, 5, pp. 478-482. Klatt, O., Boebel, O., and Fahrbach, E

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.

Timing the evolution of a monogenetic volcanic field: Sierra Chichinautzin, Central Mexico

NASA Astrophysics Data System (ADS)

Jaimes-Viera, M. C.; Martin Del Pozzo, A. L.; Layer, P. W.; Benowitz, J. A.; Nieto-Torres, A.

2018-05-01

The unique nature of monogenetic volcanism has always raised questions about its origin, longevity and spatial distribution. Detailed temporal and spatial boundaries resulted from a morphometric study, mapping, relative dating, twenty-four new 40Ar/39Ar dates, and chemical analyses for the Sierra Chichinautzin, Central Mexico. Based on these results the monogenetic cones were divided into four groups: (1) Peñón Monogenetic Volcanic Group (PMVG); (2) Older Chichinautzin Monogenetic Volcanic Group (Older CMVG); (3) Younger Chichinautzin Monogenetic Volcanic Group (Younger CMVG) and (4) Sierra Santa Catarina Monogenetic Volcanic Group (SSC). The PMVG cover the largest area and marks the northern and southern boundaries of this field. The oldest monogenetic volcanism (PMVG; 1294 ± 36 to 765 ± 30 ka) started in the northern part of the area and the last eruption of this group occurred in the south. These basaltic-andesite cones are widely spaced and are aligned NE-SW (N60°E). After this activity, monogenetic volcanism stopped for 527 ka. Monogenetic volcanism was reactivated with the birth of the Tezoyuca 1 Volcano, marking the beginning of the second volcanic group (Older CMVG; 238 ± 51 to 95 ± 12 ka) in the southern part of the area. These andesitic to basaltic andesite cones plot into two groups, one with high MgO and Nb, and the other with low MgO and Nb, suggesting diverse magma sources. The eruption of the Older CMVG ended with the eruption of Malacatepec volcano and then monogenetic volcanism stopped again for 60 ka. At 35 ka, monogenetic volcanism started again, this time in the eastern part of the area, close to Popocatépetl volcano, forming the Younger CMVG (<35 ± 4 ka). These cones are aligned in an E-W direction. Geochemical composition of eruptive products of measured samples varies from basalts to dacites with low and high MgO. The Younger CMVG is considered still active since the last eruptions took place <2 ka. The SSC (132 ± 70 to 2 ± 56 ka) is located in the northern part of the area, in the old Chalco Lake and is separated by faults from the rest of the volcanic groups as a different range. The SSC formed closely spaced basaltic andesites to andesitic cones oriented NE-SW (N70°E). The SSC samples have high Zr, P2O5, and Nb, indicating a different magma source. The northern and southern spatial boundaries of the field (the surface area with monogenetic volcanoes) became smaller with time: 78 km for PMVG, 40 km for the Older CMVG and 25 km for the Younger CMVG, concentrating the volcanoes in the central part of the area. The alignment of the cones changed progressively from NNE-SSW to NE-SW to E-W through the time, associated with the changes in the stress field which appears also to have caused the gaps. Results suggest that the Sierra Chichinautzin is actually four different volcanic fields, some partially overlapping, instead of one as previously considered. The differences in age, emplacement orientation and geochemistry support this conclusion.

Monitoring the Sumatra volcanic arc with InSAR

NASA Astrophysics Data System (ADS)

Chaussard, E.; Hong, S.; Amelung, F.

2009-12-01

The Sumatra volcanic arc is the result of the subduction of the Indo-Australian plate under the Sunda plate. The arc consists of 35 known volcanic centers, subaerials on the west coast of the Sumatra and Andaman Islands and submarines between these islands. Six active centers are known in the Sumatra volcanic arc. Surface deformation in volcanic areas usually indicates movement of magma or hydrothermal fluids at depth. Here we present a satellite-based Interferometric synthetic aperture radar (InSAR) survey of the Sumatra volcanic arc using ALOS data. Spanning the years 2007 to beginning of 2009, our survey reveals the background level of activity of the 35 volcanoes. We processed data from 40 tracks (24 in descending orbit and 16 in ascending orbit) to cover the whole Sumatra arc. In the first results five of these six known active centers show no sign of activity: Dempo, Kaba, Marapi, Talang and Peuet. The remaining active volcano, Mount Kerinci, has an ambiguous signal. We used pair-wise logic and InSAR time series of the available ALOS data to determine if the observed InSAR signal is caused by ground deformation or by atmospheric delays.

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.

Mineralogy of Copper-Gold Deposit, Masjid Daghi Area, Jolfa, IRAN

NASA Astrophysics Data System (ADS)

Zenoozi, Roya

2010-05-01

The Copper-Gold deposit of Masjid Daghi area is located in the Jolfa quadrangle (scale 1:100,000), East Azerbaijan Province, north-west Iran. The deposit, hosting by sub-volcanic bodies comprise of quartz monzonite composition whose intruded the Tertiary volcanic and volcanic-sedimentary rocks and turbidities. The Tertiary volcanic rocks consist of andesite, trachy andesite and quartz andesite. These mineral-bearing bodies related to Late Eocene sub-volcanic activities which intrudded the Eocene volcanic rocks. Mineralography, XRD and SEM studies showed that the variations in mineralization of the area. The main agent of mineralization is the intrusion of Late Eocene sub volcanic bodies inside the Tertiary volcanic units. The mineralography studies revealed two main groups of mineralization as oxides and sulfides. The sulfide minerals formed as veins, vein lets and stock work.The economic minerals comprise of native gold, copper sulfides. The native gold occurring in siliceous veins and almost as inclusions inside the sulfides minerals such as chalcopyrite. The copper sulfides, contain pyrite, chalcopyrite and chalco-pyrrhoyite. Pyrite is main sulfide in the area and formed as disseminations, cavity filling and colloform. The amount of pyrite, chalcopyrite and chalco-pyrrhoyite increases with depth. Supergene alteration produced digenite, covellite, bornite, and malachite. The alteration occurred as potassic, phyllic, argillic and propylitic minerals. Furthermore, selective sercitic, sericitic-chloritic and alunitic alterations are seen around the mineralized veins. The mineralography studies indicate that pyrite is main mineral phase and native gold occurred in silicious vein almost as inclusions inside the sulfide mineral. Most of economic mineral formed as veins, vein lets, disseminated, cavity filling and colloform which related to intrusions of Late Eocene quartz monzonite bodies into the Eocene volcanic rocks and turbiditse. Some types of alterations such as potassic, phillic, argillic and prophylitic in the area and silicious alteration near the mineralized veins, indicate probable existence of porphyry copper ore and imply epithermal gold in the Jolfa area, north west of Iran. Key words: Masjid Dagi, Alteration, Pyrite, Sulfide, Mineralography, Stock work.

A comparison of the Landsat image and LAHARZ-simulated lahar inundation hazard zone by the 2010 Merapi eruption

NASA Astrophysics Data System (ADS)

Lee, Seul-Ki; Lee, Chang-Wook; Lee, Saro

2015-06-01

Located above the Java subduction zone, Merapi Volcano is an active stratovolcano with a volcanic activity cycle of 1-5 years. Most Merapi eruptions are relatively small with volcanic explosivity index (VEI) of 1-3. However, the most recent eruption, which occurred in 2010, was quite violent with a VEI of 4 and 386 people were killed. In this study, lahars and pyroclastic flow zones were detected using optical Landsat images and the lahar and pyroclastic flow zone simulated using the LAHARZ program. To detect areal extents of lahar and pyroclastic flows using Landsat images, supervised classification was performed after atmospheric correction by using a cosine of the solar zenith correction (COST) model. As a result, the extracted dimensions of pyroclastic flows are nearly identical to the Calatrava Volcanic Province (CVP) monthly reports. Then, areas of potential lahar and pyroclastic flow inundation based on flow volume using the LAHARZ program were simulated and mapped. Finally, the detected lahars and pyroclastic flow zones were compared with the simulated potential zones using LAHARZ program and verified. Results showed satisfactory similarity (55.63 %) between the detected and simulated zone. The simulated zones using the LAHARZ program can be used as an essential volcanic hazard map for preventing life and property damages for Merapi Volcano and other hazardous volcanic areas. Also, the LAHARZ program can be used to map volcano hazards in other hazardous volcanic areas.

Magma injection beneath the urban area of Naples: a new mechanism for the 2012-2013 volcanic unrest at Campi Flegrei caldera.

PubMed

D'Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

2015-08-17

We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km(3) of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area.

Field Testing and Performance Evaluation of the Long-Range Acoustic Real-Time Sensor for Polar Areas (LARA)

DTIC Science & Technology

2015-09-30

Valley Ridge segment in the northeast Pacific Ocean. Both areas have seafloor volcanic eruptions forecast for the near future, and the LARA moorings...useful for real-time monitoring of deep-ocean seismic and volcanic activity (e.g., Dziak et al., 2012) - especially in areas where SOSUS coverage no...2012): Seismic precursors and magma ascent before the April 2011 eruption at Axial Seamount. Nature Geoscience, 5, pp. 478-482. Klinck, H., and

Subsurface Structure Interpretation Beneath of Mt. Pandan Based on Gravity Data

NASA Astrophysics Data System (ADS)

Santoso, D.; Wahyudi, E. J.; Alawiyah, S.; Nugraha, A. D.; Widiyantoro, S.; Kadir, W. G. A.; Supendi, P.; Wiyono, S.; Zulkafriza

2017-04-01

Mt. Pandan is one of the volcano that state as dormant volcano. On the other hand, Smyth et al. (2008) defined that Mt. Pandan is an active volcano. This volcano is apart a volcanic chain in Java island which is trending east-west along the island. This volcanic chain known as present day volcanic arc. Mt. Wilis is located in the south and it relatively much bigger compare to Mt. Pandan. There were earthquakes activity experienced in the surrounding Mt. Pandan area in the past several years. This event is interesting, because Mt. Pandan is not classify as the active volcano according to the list of volcanoes in Indonesia. On the otherhand Smyth et. al. (2008) mentioned that G. Pandan as modern volcanic which is located in Kendeng Zone of East Java. Gravity measurement around Mt. Pandan area was done in order to understand subsurface structure of Mt. Pandan. Gravity interpretation results shows that there is a low density structure beneath Mt. Pandan. It could be interpreted as existing of magma body below the surface. Some indication of submagmatic activities were found as hot spring and warm ground. Therefore it could be concluded that there is a possibility of magmatic activity below the Mt. Pandan.

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.

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.

Effect of subglacial volcanism on changes in the West Antarctic Ice Sheet

NASA Technical Reports Server (NTRS)

Behrendt, John C.

1993-01-01

Rapid changes in the West Antarctic Ice Sheet (WAIS) may affect future global sea-level changes. Alley and Whillans note that 'the water responsible for separating the glacier from its bed is produced by frictional dissipation and geothermal heat,' but assume that changes in geothermal flux would ordinarily be expected to have slower effects than glaciological parameters. I suggest that episodic subglacial volcanism and geothermal heating may have significantly greater effects on the WAIS than is generally appreciated. The WAIS flows through the active, largely asiesmic West Antarctic rift system (WS), which defines the sub-sea-level bed of the glacier. Various lines of evidence summarized in Behrendt et al. (1991) indicate high heat flow and shallow asthenosphere beneath the extended, weak lithosphere underlying the WS and the WAIS. Behrendt and Cooper suggest a possible synergistic relation between Cenozoic tectonism, episodic mountain uplift and volcanism in the West Antarctic rift system, and the waxing and waning of the Antarctic ice sheet beginning about earliest Oligocene time. A few active volcanoes and late-Cenozoic volcanic rocks are exposed throughout the WS along both flanks, and geophysical data suggest their presence beneath the WAIS. No part of the rift system can be considered inactive. I propose that subglacial volcanic eruptions and ice flow across areas of locally (episodically?) high heat flow--including volcanically active areas--should be considered possibly to have a forcing effect on the thermal regime resulting in increased melting at the base of the ice streams.

Seismic structure beneath the Tengchong volcanic area (southwest China) from receiver function analysis

NASA Astrophysics Data System (ADS)

Xu, Yi; Li, Xuelei; Wang, Sheng

2018-05-01

Tengchong is a young volcanic area on the collision boundary between the Indian and Euro-Asian plates of the southeastern Tibetan margin. Holocene volcanoes are concentrated in the Tengchong basin, where they align an N-S trending string-like cluster. To study the magma activity and its relation with the volcanoes, we deployed a passive seismic observation across the volcanic area in northern Tengchong. Using tele-seismic data and receiver function technique, we determined the S-wave velocity structure beneath nine temporary stations. Results show that the Tengchong basin is underlain by prominent low-velocity zones that are associated with the magma chambers of the volcanoes. In the north, a small and less pronounced magma chamber lies beneath two crater lakes, with a depth range of 9-16 km and a lateral width of <8 km. To the south, an interconnected magma chamber is found between the Dayingshan (DYS) volcano and the Dakongshan (DKS) volcanic cluster, with a depth range of 6-15 km and a lateral width of <12 km. In the south, the Laoguipo (LGP) volcano is characterized by anomalous low velocities throughout the upper-mid crust. Combined with other studies, we infer that the DYS volcano shares the same magma chamber with the DKS volcanic cluster, whereas the heat flow beneath the LGP volcano belongs to another thermal system, probably relating to the magma activity beneath the Rehai geothermal field in the south or affected by the intersection between the Tengchong volcanic fault zone and the Dayingjiang fault zone. In addition, mantle intrusion has resulted in the Moho elevation beneath the DKS volcanic cluster, and the thick transition zones on the crust-mantle boundary imply a possible penetration of the heat flow from the uppermost mantle into the lower crust.

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.

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.

Active Volcanism on Io: Global Distribution and Variations in Activity

USGS Publications Warehouse

Lopes-Gautier, R.; McEwen, A.S.; Smythe, W.B.; Geissler, P.E.; Kamp, L.; Davies, A.G.; Spencer, J.R.; Keszthelyi, L.; Carlson, R.; Leader, F.E.; Mehlman, R.; Soderblom, L.

1999-01-01

Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the near-infrared mapping spectrometer (NIMS) for the first 10 orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI) and from groundbased observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager flybys in 1979. A total of 61 active volcanic centers have been identified from Voyager, groundbased, and Galileo observations. Of these, 41 are hot spots detected by NIMS and/or SSI. Another 25 locations were identified as possible active volcanic centers, mostly on the basis of observed surface changes. Hot spots are correlated with surface colors, particularly dark and red deposits, and generally anti-correlated with white, SO2-rich areas. Surface features corresponding to the hot spots, mostly calderas or flows, were identified from Galileo and Voyager images. Hot spot temperatures obtained from both NIMS and SSI are consistent with silicate volcanism, which appears to be widespread on Io. Two types of hot spot activity are present: persistent-type activity, lasting from months to years, and sporadic events, which may represent either short-lived activity or low-level activity that occasionally flares up. Sporadic events are not often detected, but may make an important contribution to Io's heat flow and resurfacing. The distribution of active volcanic centers on the surface does not show any clear correlation with latitude, longitude, Voyager-derived global topography, or heat flow patterns predicted by the asthenosphere and deep mantle tidal dissipation models. However, persistent hot spots and active plumes are concentrated toward lower latitudes, and this distribution favors the asthenosphere rather than the deep mantle tidal dissipation model. ?? 1999 Academic Press.

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.

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.

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.

Volcanic ash in ancient Maya ceramics of the limestone lowlands: implications for prehistoric volcanic activity in the Guatemala highlands

NASA Astrophysics Data System (ADS)

Ford, Anabel; Rose, William I.

1995-07-01

In the spirit of collaborative research, Glicken and Ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric Maya ceramics. Verification of the presence of glass shards and associated volcanic mineralogy in thin sections of Maya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonal wind rose patterns, target volcanoes include those from the area west of and including Guatemala City. Joint field research conducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala, 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits, was unsuccessful in discovering local volcanic ash deposits. The abundance of the ash in common Maya ceramic vessels coupled with the difficulties of long-distance procurement without draft animals lead Glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement; it literally dropped into their hands. A major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanic ash procurement, one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for the last half of the first millennium AD. Should this be documented through careful petrographic, microprobe and tephrachronological studies, a number of related archaeological phenomena would be explained. In addition, the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer time span than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper.

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.

Geodetic Volcano Monitoring Research in Canary Islands: Recent Results

NASA Astrophysics Data System (ADS)

Fernandez, J.; Gonzalez, P. J.; Arjona, A.; Camacho, A. G.; Prieto, J. F.; Seco, A.; Tizzani, P.; Manzo, M. R.; Lanari, R.; Blanco, P.; Mallorqui, J. J.

2009-05-01

The Canarian Archipelago is an oceanic island volcanic chain with a long-standing history of volcanic activity (> 40 Ma). It is located off the NW coast of the African continent, lying over a transitional crust of the Atlantic African passive margin. At least 12 eruptions have been occurred on the islands of Lanzarote, Tenerife and La Palma in the last 500 years. Volcanism manifest predominantly as basaltic strombolian monogenetic activity (whole archipelago) and central felsic volcanism (active only in Tenerife Island). We concentrate our studies in the two most active islands, Tenerife and La Palma. In these islands, we tested different methodologies of geodetic monitoring systems. We use a combination of ground- and space-based techniques. At Tenerife Island, a differential interferometric study was performed to detect areas of deformation. DInSAR detected two clear areas of deformation, using this results a survey-based GPS network was designed and optimized to control those deformations and the rest of the island. Finally, using SBAS DInSAR results weak spatial long- wavelength subsidence signals has been detected. At La Palma, the first DInSAR analysis have not shown any clear deformation, so a first time series analysis was performed detecting a clear subsidence signal at Teneguia volcano, as for Tenerife a GPS network was designed and optimized taking into account stable and deforming areas. After several years of activities, geodetic results served to study ground deformations caused by a wide variety of sources, such as changes in groundwater levels, volcanic activity, volcano-tectonics, gravitational loading, etc. These results proof that a combination of ground-based and space-based techniques is suitable tool for geodetic volcano monitoring in Canary Islands. Finally, we would like to strength that those results could have serious implications on the continuous geodetic monitoring system design and implementation for the Canary Islands which is under development nowadays.

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.

Assessing the long-term probabilistic volcanic hazard for tephra fallout in Reykjavik, Iceland: a preliminary multi-source analysis

NASA Astrophysics Data System (ADS)

Tonini, Roberto; Barsotti, Sara; Sandri, Laura; Tumi Guðmundsson, Magnús

2015-04-01

Icelandic volcanism is largely dominated by basaltic magma. Nevertheless the presence of glaciers over many Icelandic volcanic systems results in frequent phreatomagmatic eruptions and associated tephra production, making explosive eruptions the most common type of volcanic activity. Jökulhlaups are commonly considered as major volcanic hazard in Iceland for their high frequency and potentially very devastating local impact. Tephra fallout is also frequent and can impact larger areas. It is driven by the wind direction that can change with both altitude and season, making impossible to predict a priori where the tephra will be deposited during the next eruptions. Most of the volcanic activity in Iceland occurs in the central eastern part, over 100 km to the east of the main population centre around the capital Reykjavík. Therefore, the hazard from tephra fallout in Reykjavík is expected to be smaller than for communities settled near the main volcanic systems. However, within the framework of quantitative hazard and risk analyses, less frequent and/or less intense phenomena should not be neglected, since their risk evaluation depends on the effects suffered by the selected target. This is particularly true if the target is highly vulnerable, as large urban areas or important infrastructures. In this work we present the preliminary analysis aiming to perform a Probabilistic Volcanic Hazard Assessment (PVHA) for tephra fallout focused on the target area which includes the municipality of Reykjavík and the Keflavík international airport. This approach reverts the more common perspective where the hazard analysis is focused on the source (the volcanic system) and it follows a multi-source approach: indeed, the idea is to quantify, homogeneously, the hazard due to the main hazardous volcanoes that could pose a tephra fallout threat for the municipality of Reykjavík and the Keflavík airport. PVHA for each volcanic system is calculated independently and the results from all the PVHAs can be combined at the end. This will allow to: 1) possibly add the contribution of new volcanic systems, 2) compare and hierarchically rank the tephra fallout risk among both all the considered volcanoes and, possibly, other kinds of risk, and 3) quantitatively assess the overall tephra fallout hazard over the target area. As practical application, we selected a first subset consisting of the five most hazardous volcanic systems for tephra fallout that could affect the selected target area. These are the ones with the highest number of eruptions in the last 1100 years (Katla, Hekla, Grímsvötn) and the ones located closest to the target area (Reykjanes and Snæfellsjökull). PVHA is computed using the PyBetVH tool (an improvement of the Bayesian Event Tree for Volcanic Hazard -BET_VH- model) and tephra dispersal is modelled by means of VOL-CALPUFF numerical code. Katla volcanic system is used as pilot case study because of its eruptive history and behaviour are well known and documented. We found that some considerations and results derived from the study of Katla could be general and applied to the other considered volcanoes and, more in general, to other Icelandic volcanic systems. The work was financially supported by the European Science Foundation (ESF), in the framework of the Research Networking Programme MeMoVolc.

Magma injection beneath the urban area of Naples: a new mechanism for the 2012–2013 volcanic unrest at Campi Flegrei caldera

PubMed Central

D’Auria, Luca; Pepe, Susi; Castaldo, Raffaele; Giudicepietro, Flora; Macedonio, Giovanni; Ricciolino, Patrizia; Tizzani, Pietro; Casu, Francesco; Lanari, Riccardo; Manzo, Mariarosaria; Martini, Marcello; Sansosti, Eugenio; Zinno, Ivana

2015-01-01

We found the first evidence, in the last 30 years, of a renewed magmatic activity at Campi Flegrei caldera from January 2012 to June 2013. The ground deformation, observed through satellite interferometry and GPS measurements, have been interpreted as the effect of the intrusion at shallow depth (3090 ± 138 m) of 0.0042 ± 0.0002 km3 of magma within a sill. This interrupts about 28 years of dominant hydrothermal activity and occurs in the context of an unrest phase which began in 2005 and within a more general ground uplift that goes on since 1950. This discovery has implications on the evaluation of the volcanic risk and in the volcanic surveillance of this densely populated area. PMID:26279090

Io Shown in Lambertian Equal Area Projection and in Approximately Natural Color

NASA Image and Video Library

1998-06-04

NASA's Voyager 1 computer color mosaics, shown in approximately natural color and in Lambertian equal-area projections, show the Eastern (left) and Western (right) hemispheres of Io. This innermost of Jupiter's 4 major satellites is the most volcanically active object in the solar system. Io is 2263 mi (3640 km) in diameter, making it a little bigger than Earth's moon. Almost all the features visible here have volcanic origins, including several calderas and eruption plumes that were active at the time of the Voyager 1 encounter. http://photojournal.jpl.nasa.gov/catalog/PIA00318

Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy).

PubMed

Cardellini, C; Chiodini, G; Frondini, F; Avino, R; Bagnato, E; Caliro, S; Lelli, M; Rosiello, A

2017-07-28

In volcanoes with active hydrothermal systems, diffuse CO 2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO 2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO 2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO 2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO 2 tripled its extent. This expansion was accompanied by an increase of the background CO 2 flux, over most of the surveyed area (1.4 km 2 ), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO 2 increased up to values typical of persistently degassing active volcanoes (up to 3000 t d -1 ). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.

Potentially harmful elements released by volcanic ashes: Examples from the Mediterranean area

NASA Astrophysics Data System (ADS)

Cangemi, Marianna; Speziale, Sergio; Madonia, Paolo; D'Alessandro, Walter; Andronico, Daniele; Bellomo, Sergio; Brusca, Lorenzo; Kyriakopoulos, Konstantinos

2017-05-01

We have performed leaching experiments on the fine (< 2 mm) particulate sampled in seven active and quiescent volcanic systems in the Mediterranean area. We reacted the particulate both in pure water and in a synthetic gastric solution. The amount of As, Mn, Pb, Ba, U and Ni leached by pure water exceeded the MAC limits for drinking water in all the materials under investigation. We defined a tolerable ash intake index (TAI) to evaluate the impact of ash ingestion, and we find that 0.2 g and 12 g of ingested fine ash from Vesuvius and Vulcano are enough to exceed the safety limits for Pb and As. Six grams of fine ashes from Stromboli are sufficient to overstep the safety limits for As. Based on our mineralogical characterisation of the particulate, we expect that the submillimetric ash fraction, with a higher surface/volume ratio, releases a greater relative amount of trace metals, which are concentrated in the thin surface layer produced by the reaction of the pristine volcanic particles with coexisting volcanic gases. This means that our measurements represent lower bounds to the actual amount of metal released in aqueous solutions by the volcanic ashes from the locations under investigation. Our results place the first constraints on the mobilisation of toxic elements from volcanic ash, which are necessary to assess the associated potential health risk of volcanic areas.

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.

Structural analysis and thermal remote sensing of the Los Humeros Volcanic Complex: Implications for volcano structure and geothermal exploration

NASA Astrophysics Data System (ADS)

Norini, G.; Groppelli, G.; Sulpizio, R.; Carrasco-Núñez, G.; Dávila-Harris, P.; Pellicioli, C.; Zucca, F.; De Franco, R.

2015-08-01

The Los Humeros Volcanic Complex (LHVC) is an important geothermal target in the Trans-Mexican Volcanic Belt. Understanding the structure of the LHVC and its influence on the occurrence of thermal anomalies and hydrothermal fluids is important to get insights into the interplay between the volcano-tectonic setting and the characteristics of the geothermal resources in the area. In this study, we present a structural analysis of the LHVC, focused on Quaternary tectonic and volcano-tectonic features, including the areal distribution of monogenetic volcanic centers. Morphostructural analysis and structural field mapping revealed the geometry, kinematics and dynamics of the structural features in the study area. Also, thermal infrared remote sensing analysis has been applied to the LHVC for the first time, to map the main endogenous thermal anomalies. These data are integrated with newly proposed Unconformity Bounded Stratigraphic Units, to evaluate the implications for the structural behavior of the caldera complex and geothermal field. The LHVC is characterized by a multistage formation, with at least two major episodes of caldera collapse: Los Humeros Caldera (460 ka) and Los Potreros Caldera (100 ka). The study suggests that the geometry of the first collapse recalls a trap-door structure and impinges on a thick volcanic succession (10.5-1.55 Ma), now hosting the geothermal reservoir. The main ring-faults of the two calderas are buried and sealed by the widespread post-calderas volcanic products, and for this reason they probably do not have enough permeability to be the main conveyers of the hydrothermal fluid circulation. An active, previously unrecognized fault system of volcano-tectonic origin has been identified inside the Los Potreros Caldera. This fault system is the main geothermal target, probably originated by active resurgence of the caldera floor. The active fault system defines three distinct structural sectors in the caldera floor, where the occurrence of hydrothermal fluids is controlled by fault-induced secondary permeability. The resurgence of the caldera floor could be induced by an inferred magmatic intrusion, representing the heat source of the geothermal system and feeding the simultaneous monogenetic volcanic activity around the deforming area. The operation of the geothermal field and the plans for further exploration should focus on, both, the active resurgence fault system and the new endogenous thermal anomalies mapped outside the known boundaries of the geothermal field.

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).

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.

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.

Deformation patterns, magma supply, and magma storage at Karymsky Volcanic Center, Kamchatka, Russia, 2000-2010, revealed by InSAR

NASA Astrophysics Data System (ADS)

Ji, Lingyun; Izbekov, Pavel; Senyukov, Sergey; Lu, Zhong

2018-02-01

Under a complex geological region influenced by the subduction of the Pacific plate, Kamchatka Peninsula is one of the most active volcanic arcs in the Pacific Rim. Due to logistical difficulty in instrumentation, shallow magma plumbing systems beneath some of the Kamchatkan volcanoes are poorly understood. InSAR offers a safe and quick method for monitoring volcanic deformation with a high spatial resolution. In this study, a group of satellite radar interferograms that span the time interval from 2000 to 2010 shows eruptive and non-eruptive deformation at Karymsky Volcanic Center (KVC), Kamchatka, Russia. All the interferograms provide details of the activity around the KVC during 2000-2010, as follows: (1) from 2000 to 2004, the Karymsky-AN (Akademia Nauk) area deflated and the MS (Maly Semyachik) area inflated, (2) from 2004 to 2006, the Karymsky-AN area deflated with ongoing eruption, while the MS area subsided without eruption, (3) from 2006 to 2008, as with 2000-2004, the Karymsky-AN area deflated and the MS area inflated, (4) from 2008 to 2010, the Karymsky-AN area inflated up to 3 cm, and the MS area subsided. Point source models suggest that two magma reservoirs provide a good fit to the observed deformation. One source is located beneath the area between Karymsky and AN at a depth of approximately 7.0 km, and the other one is situated beneath MS at a depth of around 5.8 km. Synchronous deformation patterns suggest that two magma systems are fed from the same deep magma source and connected by a fracture zone. The InSAR results are consistent with GPS ground deformation measurements, seismic data, and petrological constraints.

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.

Validation of gravity data from the geopotential field model for subsurface investigation of the Cameroon Volcanic Line (Western Africa)

NASA Astrophysics Data System (ADS)

Marcel, Jean; Abate Essi, Jean Marcel; Nouck, Philippe Njandjock; Sanda, Oumarou; Manguelle-Dicoum, Eliézer

2018-03-01

Belonging to the Cameroon Volcanic Line (CVL), the western part of Cameroon is an active volcanic zone with volcanic eruptions and deadly gas emissions. The volcanic flows generally cover areas and bury structural features like faults. Terrestrial gravity surveys can hardly cover entirely this mountainous area due to difficult accessibility. The present work aims to evaluate gravity data derived from the geopotential field model, EGM2008 to investigate the subsurface of the CVL. The methodology involves upward continuation, horizontal gradient, maxima of horizontal gradient-upward continuation combination and Euler deconvolution techniques. The lineaments map inferred from this geopotential field model confirms several known lineaments and reveals new ones covered by lava flows. The known lineaments are interpreted as faults or geological contacts such as the Foumban fault and the Pan-African Belt-Congo craton contact. The lineaments highlighted coupled with the numerous maar lakes identified in this volcanic sector attest of the vulnerability of the CVL where special attention should be given for geohazard prevention.

Volcanic Structure of the Gakkel Ridge at 85°E

NASA Astrophysics Data System (ADS)

Willis, C.; Humphris, S.; Soule, S. A.; Reves-Sohn, R.; Shank, T.; Singh, H.

2007-12-01

We present an initial volcanologic interpretation of a magmatically-robust segment of the ultra-slow spreading (3- 7 mm/yr) Gakkel Ridge at 85°E in the eastern Arctic Basin based on surveys conducted during the July 2007 Arctic GAkkel Vents Expedition (AGAVE). A previous expedition (2001 AMORE) and seismic stations in the area found evidence for active hydrothermal circulation and seismicity that suggested volcanic activity may be ongoing at 85°E. We examine multi-beam bathymetric data, digital imagery, and rock and sediment samples in order to determine the nature of volcanic accretion that is occurring in this environment including the distribution of flow types and their relationship to features of the axial valley. Raw multi-beam bathymetric data was logged by the Kongsberg EM 120 1°x1° multi-beam echo sounder aboard the icbreaker IB Oden. Digital imagery was recorded on five video and still cameras mounted on the CAMPER fiber-optic wireline vehicle, which was towed 1-3m above the seafloor. Digital imagery was recorded on thirteen CAMPER drift-dives over interesting bathymetry including: a volcanic ridge in the axial valley named Duque's Hill, and Oden and Loke volcanoes that are part of the newly discovered Asgard volcanic chain. Talus, lava flows, and volcaniclastics were sampled with the clamshell grabber and slurp suction sampler on CAMPER. A variety of lava morphologies are identified in the imagery including large basalt pillows with buds and other surface ornamentation, lava tubes, lobates, sheet flows, and a thick cover of volcaniclastic sediment over extensive areas suggestive of explosive volcanic activity.

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.

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.

The Cretaceous Okhotsk-Chukotka Volcanic Belt (NE Russia): Geology, geochronology, magma output rates, and implications on the genesis of silicic LIPs

NASA Astrophysics Data System (ADS)

Tikhomirov, P. L.; Kalinina, E. A.; Moriguti, T.; Makishima, A.; Kobayashi, K.; Cherepanova, I. Yu.; Nakamura, E.

2012-04-01

The Cretaceous Okhotsk-Chukotka volcanic belt (OCVB) is a prominent subduction-related magmatic province, having the remarkably high proportion of silicic rocks (ca. 53% of the present-day crop area, and presumably over 70% of the total volcanic volume). Its estimated total extrusive volume ranges between 5.5 × 105 km3 (the most conservative estimate) and over 106 km3. This article presents a brief outline of the geology of OCVB, yet poorly described in international scientific literature, and results of a geochronological study on the northern part of the volcanic belt. On the base of new and published U-Pb and 40Ar/39Ar age determinations, a new chronological model is proposed. Our study indicates that the activity of the volcanic belt was highly discontinuous and comprised at least five main episodes at 106-98 Ma, 94-91 Ma, 89-87 Ma, 85.5-84 Ma, and 82-79 Ma. The new data allow a semi-quantitative estimate of the volcanic output rate for the observed part of the OCVB (area and volume approximately 105 km2 and 2.5 × 105 km3, respectively). The average extrusion rate for the entire lifetime of the volcanic belt ranges between 1.6 and 3.6 × 10- 5 km3yr- 1 km- 1, depending on the assumed average thickness of the volcanic pile; the optimal value is 2.6 × 10- 5 km3yr- 1 km- 1. Despite imprecise, such estimates infer the time-averaged volcanic productivity of the OCVB is similar to that of silicic LIPs and most active recent subduction-related volcanic areas of the Earth. However, the most extensive volcanic flare-ups at 89-87 and 85.5-84 Ma had higher rates of over 9.0 × 10- 5 km3yr- 1 km- 1. The main volumetric, temporal and compositional parameters of the OCVB are similar to those of silicic LIPs. This gives ground for discussion about the geodynamic setting of the latters, because the widely accepted definition of a LIP implies a strictly intraplate environment. Considering the genesis of the OCVB and other large provinces of silicic volcanism, we propose that residual thermal energy preserved in the continental crust after a previous major magmatic event may have been one of major reasons for high proportion of felsic rocks in a volcanic pile. In this scenario, underplating of mantle-derived basalts causes fast and extensive melting of still hot continental crust and generation of voluminous silicic magmas.

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.

High resolution seismic reflection survey in the Gulf of Pozzuoli, Naples, Italy. An example of preliminary interpretation of seismic profiles.

NASA Astrophysics Data System (ADS)

D'Aniello, Elena; di Fiore, Vincenzo; Sacchi, Marco; Rapolla, Antonio

2010-05-01

During the cruise CAFE_07 - Leg 3 conducted in the Gulf of Naples and Pozzuoli in January 2008, on board of the R/V URANIA of the CNR it was carried out the acquisition of a grid of ca. 800 km of high-resolution multichannel reflection seismic profiles (Sacchi et al., 2009; Di Fiore et al., 2009). The aim of the cruise was the understanding of the stratigraphic-structural setting of the Pozzuoli Bay area, with specific reference to the major offshore volcanic features, such as Nisida Bank, Pentapalummo Bank, M.Dolce-Pampano Bank and Miseno Bank and others. The Gulf of Pozzuoli is placed in the Volcanic district of Campi Flegrei, an area of active volcanism located at North West of Naples city, along the Tyrrhenian margin, in an extensional collapsed area called Campanian Plain, filled by siliciclastic, epiclastic and volcaniclastic sediments, deposited during Late Pliocene and Quaternary. Several studies present in literature suggest a relation between volcanic system of Campi Flegrei and faults system; in particular, at the Gulf of Pozzuoli we can observe some volcanic banks and submarine volcanic edifices, as Pentapalummo, Nisida and Miseno Banks, are aligned along the NE-SW trending Magnaghi-Sebeto fault line, that separates the Bay of Naples into two sectors: the first, at NW of the Bay, characterized by volcanism activity and magnetic anomalies and the second, at SE of the bay, involved only by sedimentary activity, with the exceptions of the circular anomalies in the offshore of Torre del Greco city (Bruno et al., 2003; Secomandi et al., 2003); other volcanic hights are instead positioned along NW-SE structural discontinuities (Bruno, 2004). The magnetic and gravimetric analysis of the Bay of Naples confirms the tectonic control of the Campanian volcanism: we can observe a good correspondence of high magnetic anomalies with the main volcanic structures at the North-Western side of the bay, just the Gulf of Pozzuoli, where both NE-SW and NW-SE normal faults were recognized. The correspondence between magnetic structures, interpreted as volcanic bodies, and the faults NE-SW and NW-SE trending, supports the hypothesis that the magma rises along normal faults cutting the carbonate platform. We here present two significant seismic profiles: their interpretation reveals a complex stratigraphic and structural setting, dominated by the occurrence of volcanic bodies and siliciclastic depositional units, mostly deriving from the dismantling of the adjacent vents and volcaniclastic units. The results of this preliminary research include the recognition of volcanic features and structures not yet described in the literature that may represent a relevant contribute to the understanding of the Late Quaternary evolution of the Campi Flegrei area. References: Bruno P.P., Rapolla A., Di Fiore V., 2003. Structural setting of the Bay of Naples (Italy) seismic reflection data: implications for Campanian volcanism. Tectonophysics, 372, 193-213. Bruno P.P., 2004. Structure and evolution of the Bay of Pozzuoli (Italy) using marine seismic reflection data: implication for collapse of the Campi Flegrei caldera. Bull. Volcanol., 66, 342-355. Di Fiore V., D'Aniello E., Rapolla A., Sacchi M., Secomandi M., Spiess V., 2009. Multichannel seismic survey in coastal Campania area by two different resolution sources. EGU General Assembly 2009, vol.11. Sacchi M., Alessio G., Aquino I., Esposito E., Molisso F., Nappi R., Porfido S., Violante C., 2008. Risultati preliminari della campagna oceanografica CAFE_07 - Leg 3 nei Golfi di Napoli e Pozzuoli, Mar Tirreno Orientale. Quaderni di Geofisica, n. 64. Secomandi M., Paoletti V., Aiello G., Fedi M., Marsella E., Ruggieri S., D'Argenio B., Rapolla A., 2003. Analysis of the magnetic anomaly field of the volcanic district of the Bay of Naples, Italy. Marine Geophysical Researches. 24: 207-221.

Interferometric investigations with the S1 constellation: an application to the Vesuvius/Campi Flegrei volcanic test site

NASA Astrophysics Data System (ADS)

Borgstrom, Sven; Del Gaudio, Carlo; De Martino, Prospero; Siniscalchi, Valeria; Prats-Iraola, Pau; Nannini, Matteo; Yague-Martinez, Nestor; Pinheiro, Muriel; Kim, Jun-Su; Vecchioli, Francesco; Minati, Federico; Costantini, Mario; Foumelis, Michael; Desnos, Yves-Louis

2017-04-01

The contribution focuses on the current status of the ESA study entitled "INSARAP Sentinel-1 Constellation Study" and investigates the interferometric performance of the S1A/S1B units. In particular, we refer to the Vesuvius/Campi Flegrei (Southern Italy) volcanic test site, where the continuous inflation (about 35 cm from 2011 to date) and the huge availability of ground-based geodetic data (continuous GPS - cGPS - leveling, tiltmetric, gravimetric, etc.) from the INGV-Osservatorio Vesuviano monitoring networks have allowed to get a clear deformation signal, besides the comparison between S1A/S1B and geodetic data. In this regard, the integration between InSAR and geodetic measurements is crucial for a continuous and extended monitoring of such an active volcanic area, as InSAR investigations allow to get an information on wide areas, whereas permanent networks (e.g., cGPS), allow to provide a continuous information complementing InSAR, which is limited by its revisiting time. Comparisons between S1 constellation data and geodetic measurements, with a particular focus on cGPS, will be presented, exploiting both LOS and inverted (E-W and vertical inversion) InSAR data starting from October, 2014. In addition, as a next step we are planning to model the deformation source of the area by exploiting the S1 time series results. Ultimately, very encouraging results suggest for a continuation of this activity also for the future, showing the great potential of S1 constellation data for monitoring active volcanic areas and, in general, to retrieve a very high quality deformation signal.

Volcano-ice-sea interaction in the Cerro Santa Marta area, northwest James Ross Island, Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Calabozo, Fernando M.; Strelin, Jorge A.; Orihashi, Yuji; Sumino, Hirochika; Keller, Randall A.

2015-05-01

We present here the results of detailed mapping, lithofacies analysis and stratigraphy of the Neogene James Ross Island Volcanic Group (Antarctic Peninsula) in the Cerro Santa Marta area (northwest of James Ross Island), in order to give constraints on the evolution of a glaciated volcanic island. Our field results included recognition and interpretation of seventeen volcanic and glacial lithofacies, together with their vertical and lateral arrangements, supported by four new unspiked K-Ar ages. This allowed us to conclude that the construction of the volcanic pile in this area took place during two main eruptive stages (Eruptive Stages 1 and 2), separated from the Cretaceous bedrock and from each other by two major glacial unconformities (U1 and U2). The U1 unconformity is related to Antarctic Peninsula Ice sheet expansion during the late Miocene (before 6.2 Ma) and deposition of glacial lithofacies in a glaciomarine setting. Following this glacial advance, Eruptive Stage 1 (6.2-4.6 Ma) volcanism started with subaerial extrusion of lava flows from an unrecognized vent north of the study area, with eruptions later fed from vent/s centered at Cerro Santa Marta volcano, where cinder cone deposits and a volcanic conduit/lava lake are preserved. These lava flows fed an extensive (> 7 km long) hyaloclastite delta system that was probably emplaced in a shallow marine environment. A second unconformity (U2) was related to expansion of a local ice cap, centered on James Ross Island, which truncated all the eruptive units of Eruptive Stage 1. Concomitant with glacier advance, renewed volcanic activity (Eruptive Stage 2) started after 4.6 Ma and volcanic products were fed again by Cerro Santa Marta vents. We infer that glaciovolcanic eruptions occurred under a moderately thin (~ 300 m) glacier, in good agreement with previous estimates of paleo-ice thickness for the James Ross Island area during the Pliocene.

Fine crustal and uppermost mantle S-wave velocity structure beneath the Tengchong volcanic area inferred from receiver function and surface-wave dispersion: constraints on magma chamber distribution

NASA Astrophysics Data System (ADS)

Li, Mengkui; Zhang, Shuangxi; Wu, Tengfei; Hua, Yujin; Zhang, Bo

2018-03-01

The Tengchong volcanic area is located in the southeastern margin of the collision zone between the Indian and Eurasian Plates. It is one of the youngest intraplate volcano groups in mainland China. Imaging the S-wave velocity structure of the crustal and uppermost mantle beneath the Tengchong volcanic area is an important means of improving our understanding of its volcanic activity and seismicity. In this study, we analyze teleseismic data from nine broadband seismic stations in the Tengchong Earthquake Monitoring Network. We then image the crustal and uppermost mantle S-wave velocity structure by joint analysis of receiver functions and surface-wave dispersion. The results reveal widely distributed low-velocity zones. We find four possible magma chambers in the upper-to-middle crust and one in the uppermost mantle. The chamber in the uppermost mantle locates in the depth range from 55 to 70 km. The four magma chambers in the crust occur at different depths, ranging from the depth of 7 to 25 km in general. They may be the heat sources for the high geothermal activity at the surface. Based on the fine crustal and uppermost mantle S-wave velocity structure, we propose a model for the distribution of the magma chambers.

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.

Earth Observation

NASA Image and Video Library

2013-06-11

ISS036-E-007165 (11 June 2013) --- Nevados de Chillan, Chile is featured in this image photographed by an Expedition 36 crew member on the International Space Station. This photograph highlights a large volcanic area located near the Chile-Argentina border. Like other historically active volcanoes in the central Andes ranges, the Nevados de Chillan were created by upwelling magma generated by eastward subduction of the dense oceanic crust of the Pacific basin beneath the less dense continental crust of South America. Rising magmas associated with this type of tectonic environment frequently erupt explosively, forming widespread ash and ignimbrite layers. They can also produce less explosive eruptions that form voluminous lava flows – layering together with explosively erupted deposits to build the classic cone-shaped edifice of a stratovolcano over geologic time. The Nevados de Chillan includes three distinct volcanic structures, built within three overlapping calderas that extend along a north-northwest to south-southeast line. The snow-capped volcanic complex sits within the glaciated terrain of the central Andes – glacial valleys are visible at upper left, upper right, and lower right. The northwestern end of the chain is occupied by the 3,212-meter-high Cerro Blanco (also known as Volcan Nevado). The 3,089-meter-high Volcan Viejo (also known as Volcan Chillan) sits at the southeastern end; this volcano was active during the 17th-19th centuries. A group of lava domes known as Volcan Nuevo formed to the northwest of Volcan Viejo between 1906-1945, followed by an even younger dome complex that formed between 1973-1986 (Volcan Arrau; not indicated on the image). The last reported volcanic activity at Nevados de Chillan took place in 2009 (according to the Smithsonian Institution’s Global Volcanism Network).

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.

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.

Probabilistic Hazard Estimation at a Densely Urbanised Area: the Neaples Volcanoes

NASA Astrophysics Data System (ADS)

de Natale, G.; Mastrolorenzo, G.; Panizza, A.; Pappalardo, L.; Claudia, T.

2005-12-01

The Neaples volcanic area (Southern Italy), including Vesuvius, Campi Flegrei caldera and Ischia island, is the highest risk one in the World, where more than 2 million people live within about 10 km from an active volcanic vent. Such an extreme risk calls for accurate methodologies aimed to quantify it, in a probabilistic way, considering all the available volcanological information as well as modelling results. In fact, simple hazard maps based on the observation of deposits from past eruptions have the major problem that eruptive history generally samples a very limited number of possible outcomes, thus resulting almost meaningless to get the event probability in the area. This work describes a methodology making the best use (from a Bayesian point of view) of volcanological data and modelling results, to compute probabilistic hazard maps from multi-vent explosive eruptions. The method, which follows an approach recently developed by the same authors for pyroclastic flows hazard, has been here improved and extended to compute also fall-out hazard. The application of the method to the Neapolitan volcanic area, including the densely populated city of Naples, allows, for the first time, to get a global picture of the areal distribution for the main hazards from multi-vent explosive eruptions. From a joint consideration of the hazard contributions from all the three volcanic areas, new insight on the volcanic hazard distribution emerges, which will have strong implications for urban and emergency planning in the area.

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.

The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: tectonically anomalous forearc volcanism in an urban setting

USGS Publications Warehouse

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

2009-01-01

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

Seismic signature of crustal magma and fluid from deep seismic sounding data across Tengchong volcanic area

NASA Astrophysics Data System (ADS)

Bai, Z. M.; Zhang, Z. Z.; Wang, C. Y.; Klemperer, S. L.

2012-04-01

The weakened lithosphere around eastern syntax of Tibet plateau has been revealed by the Average Pn and Sn velocities, the 3D upper mantle velocity variations of P wave and S wave, and the iimaging results of magnetotelluric data. Tengchong volcanic area is neighboring to core of eastern syntax and famous for its springs, volcanic-geothermal activities and remarkable seismicity in mainland China. To probe the deep environment for the Tengchong volcanic-geothermal activity a deep seismic sounding (DSS) project was carried out across the this area in 1999. In this paper the seismic signature of crustal magma and fluid is explored from the DSS data with the seismic attribute fusion (SAF) technique, hence four possible positions for magma generation together with some locations for porous and fractured fluid beneath the Tengchong volcanic area were disclosed from the final fusion image of multi seismic attributes. The adopted attributes include the Vp, Vs and Vp/Vs results derived from a new inversion method based on the No-Ray-Tomography technique, and the migrated instantaneous attributes of central frequency, bandwidth and high frequency energy of pressure wave. Moreover, the back-projected ones which are mainly consisted by the attenuation factor Qp , the delay-time of shear wave splitting, and the amplitude ratio between S wave and P wave + S wave were also considered in this fusion process. Our fusion image indicates such a mechanism for the surface springs: a large amount of heat and the fluid released by the crystallization of magma were transmitted upward into the fluid-filled rock, and the fluid upwells along some pipeline since the high pressure in deep, thus the widespread springs of Tengchong volcanic area were developed. Moreover, the fusion image, regional volcanic and geothermal activities, and the seismicity suggest that the main risk of volcanic eruption was concentrated to the south of Tengchong city, especially around the shot point (SP) Tuantian. There are typical tectonic and deep origin mechanisms for the moderate-strong earthquakes nearby SP Tuantian, and precaution should be added on this area in case of the potential earthquake. Our fusion image also clearly revealed that there exist two remarkable positions on the Moho discontinuity through which the heat from the upper mantle was transmitted upward, and this is attributed to the widely distributed hot material within the crust and upper mantle. We acknowledge the financial support of the Ministry of Land and Resources of China (SinoProbe-02-02), and the National Nature Science Foundation of China (No. 41074033 and No. 40830315). Key Words: Seismic Signature, Magma, Tengchong Volcanic Area, Deep Seismic Sounding, Seismic Attribute Fusion Li, Chang, van der Hilst, D., Meltzer, A.S., Engdahl, E.R., 2008. Subduction of the Indian lithosphere beneath the Tibetan Plateau and Burma. Earth Planet. Sci. Lett. 274. doi:10.1016/j.epsl.2008.07.016. Lebedev, S., van der Hilst, R.D., 2008. Global upper-mantle tomography with the automated multi-mode surface and S waveforms. Geophys. J. Int. 173 (2), 505-518. Wang C.Y. and Huangfu G.. 2004. Crustal structure in Tengchong Volcano-Geothermal Area, western Yunnan, China. Tectonophysics, 380: 69-87.

Studying monogenetic volcanoes with Terrestrial Laser Scanner: Case study at Croscat volcano (Garrotxa Volcanic Zone, Spain)

NASA Astrophysics Data System (ADS)

Geyer Traver, A.; Garcia-Selles, D.; Peddrazzi, D.; Barde-Cabusson, S.; Marti, J.; Muñoz, J.

2013-12-01

Monogenetic basaltic zones are common in many volcanic environments and may develop under very different geodynamic conditions. Despite existing clear similarities between the eruptive activity of different monogenetic volcanic fields, important distinctions may arise when investigating in detail the individual eruptive sequences. Interpretation of the deposits and consequently, the reconstruction and characterization of these eruptive sequences is crucial to evaluate the potential hazard in case of active areas. In diverse occasions, erosional processes (natural and/or anthropogenic) may partly destroy these relatively small-sized volcanic edifices exposing their internal parts. Furthermore, despite human activity in volcanic areas is sometimes unimportant due to the remote location of the monogenetic cones, there are places where this form of erosion is significant, e.g. Croscat volcano (Catalan Volcanic Field, Spain). In any case, when studying monogenetic volcanism, it is usual to find outcrops where the internal structure of the edifices is, for one or other reason, well exposed. However, the access to these outcrops may be extremely difficult or even impossible. During the last years, it has been demonstrated that the study of outcrops with problematic or completely restricted access can be carried out by means of digital representations of the outcrop surface. Digital outcrops make possible the study of those areas with natural access limitations or safety issues and may facilitate visualization of the features of interest over the entire outcrop, as long as the digital outcrop can be analysed while navigated in real- time, with optional displays for perspective, scale distortions, and attribute filtering. In particular, Terrestrial Laser Scanning (TSL) instruments using Light Detection And Ranging technology (LIDAR) are capable of capturing topographic details and achieve modelling accuracy within a few centimetres. The data obtained enables the creation of detailed 3-D terrain models of greater coverage and accuracy than conventional methods and with almost complete safety of the operators. Here we want to introduce the TSL methodology to the volcanological community. We show how data obtained with this tool may be useful, not only for volcano monitoring purposes, but also to perform the description of the internal structure of exposed volcanic edifices. A further useful application is the estimate of erosion rates and patterns that may be helpful in terms of hazard assessment or preservation of volcanic landscapes. We use as an example of application the Croscat volcano, a monogenetic edifice of the La Garrotxa volcanic field (Spain), which quarrying jobs have exposed the internal part of the volcano leading to a perfect view of its interior but making difficult the access to the upper parts. The Croscat volcano is additionally one of the most emblematic symbols of the La Garrotxa Volcanic Zone Natural Park being its preservation a main target of the park administration.

Potential hazards from future volcanic eruptions in California

USGS Publications Warehouse

Miller, C. Dan

1989-01-01

More than 500 volcanic vents have been identified in the State of California. At least 76 of these vents have erupted, some repeatedly, during the last 10,000 years. Past volcanic activity has ranged in scale and type from small rhyolitic and basaltic eruptions through large catastrophic rhyolitic eruptions. Sooner or later, volcanoes in California will erupt again, and they could have serious impacts on the health and safety of the State\\'s citizens as well as on its economy. This report describes the nature and probable distribution of potentially hazardous volcanic phenomena and their threat to people and property. It includes hazard-zonation maps that show areas relatively likely to be affected by future eruptions in California. The potentially more hazardous eruptions in the State are those that involve explosive eruption of large volumes of silicic magma. Such eruptions could occur at vents in as many as four areas in California. They could eject pumice high into the atmosphere above the volcano, produce destructive blasts, avalanches, or pyroclastic flows that reach distances of tens of kilometers from a vent, and produce mudflows and floods that reach to distances of hundreds of kilometers. Smaller eruptions produce similar, but less severe and less extensive, phenomena. Hazards are greatest close to a volcanic vent; the slopes on or near a volcano, and valleys leading away from it, are affected most often and most severely by such eruptions. In general, risk from volcanic phenomena decreases with increasing distance from a vent and, for most flowage processes, with increasing height above valley floors or fan surfaces. Tephra (ash) from explosive eruptions can affect wide areas downwind from a vent. In California, prevailing winds cause the 180-degree sector east of the volcano to be affected most often and most severely. Risk to life from ashfall decreases rapidly with increasing distance from a vent, but thin deposits of ash could disrupt communication, transportation, and utility systems at great distances, and over wide regions, in eastern California and adjacent states. Volcanic eruptions are certain to occur in California in the future and an be neither prevented nor stopped, but actions can be taken to limit damage from them. Reduction of risk to life and property can be effected by avoiding threatened areas and by taking protective measures to reduce the effects when and where vulnerable areas cannot be avoided. Monitoring of volcanic precursors generally can identify the locality of impending volcanic activity, even though it often does not pinpoint the nature or timing of an eruption, or even its certainty. Hazard-zonation maps can then be used to guide decisions regarding evacuation and other response activities. Thus, effective monitoring of volcanoes in the State, combined with preparation of contingency plans to deal with future eruptions, can help reduce risk to lives and property.

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.

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.

Barberton greenstone belt volcanism: Succession, style and petrogenesis

NASA Technical Reports Server (NTRS)

Byerly, G. R.; Lowe, D. R.

1986-01-01

The Barberton Mountain Land is an early Archean greenstone belt along the eastern margin of the Kaapvaal Craton of southern Africa. Detailed mapping in the southern portion of the belt leads to the conclusion that a substantial thickness is due to original deposition of volcanics and sediments. In the area mapped, a minimum thickness of 12km of predominantly mafic and ultramafic volcanics comprise the Komati, Hooggenoeg, and Kromberg Formations of the Onverwacht Group, and at least one km of predominantly pyroclastic and epiclastic sediments derived from dacitic volcanics comprise the Fig Tree Group. The Barberton greenstone belt formed primarily by ultramafic to mafic volcanism on a shallow marine platform which underwent little or no concurrent extension. Vents for this igneous activity were probably of the non-constructional fissure type. Dacitic volcanism occurred throughout the sequence in minor amounts. Large, constructional vent complexes were formed, and explosive eruptions widely dispersed pyroclastic debris. Only in the final stages of evolution of the belt did significant thrust-faulting occur, generally after, though perhaps overlapping with, the final stage of dacitic igneous activity. A discussion follows.

Dome collapse eruption in Tatun Volcanic Group near metropolitan Taipei, Taiwan at ~6 kyrs

NASA Astrophysics Data System (ADS)

Chen, C.; Lee, T.

2010-12-01

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

A GIS-based methodology for the estimation of potential volcanic damage and its application to Tenerife Island, Spain

NASA Astrophysics Data System (ADS)

Scaini, C.; Felpeto, A.; Martí, J.; Carniel, R.

2014-05-01

This paper presents a GIS-based methodology to estimate damages produced by volcanic eruptions. The methodology is constituted by four parts: definition and simulation of eruptive scenarios, exposure analysis, vulnerability assessment and estimation of expected damages. Multi-hazard eruptive scenarios are defined for the Teide-Pico Viejo active volcanic complex, and simulated through the VORIS tool. The exposure analysis identifies the elements exposed to the hazard at stake and focuses on the relevant assets for the study area. The vulnerability analysis is based on previous studies on the built environment and complemented with the analysis of transportation and urban infrastructures. Damage assessment is performed associating a qualitative damage rating to each combination of hazard and vulnerability. This operation consists in a GIS-based overlap, performed for each hazardous phenomenon considered and for each element. The methodology is then automated into a GIS-based tool using an ArcGIS® program. Given the eruptive scenarios and the characteristics of the exposed elements, the tool produces expected damage maps. The tool is applied to the Icod Valley (North of Tenerife Island) which is likely to be affected by volcanic phenomena in case of eruption from both the Teide-Pico Viejo volcanic complex and North-West basaltic rift. Results are thematic maps of vulnerability and damage that can be displayed at different levels of detail, depending on the user preferences. The aim of the tool is to facilitate territorial planning and risk management in active volcanic areas.

Mechanical interaction between volcanic systems in Libya

NASA Astrophysics Data System (ADS)

Elshaafi, Abdelsalam; Gudmundsson, Agust

2018-01-01

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

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.

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.

Statistical analysis of dispersal and deposition patterns of volcanic emissions from Mt. Sakurajima, Japan

NASA Astrophysics Data System (ADS)

Poulidis, Alexandros P.; Takemi, Tetsuya; Shimizu, Atsushi; Iguchi, Masato; Jenkins, Susanna F.

2018-04-01

With the eruption of Eyjafjallajökull (Iceland) in 2010, interest in the transport of volcanic ash after moderate to major eruptions has increased with regards to both the physical and the emergency hazard management aspects. However, there remain significant gaps in the understanding of the long-term behaviour of emissions from volcanoes with long periods of activity. Mt. Sakurajima (Japan) provides us with a rare opportunity to study such activity, due to its eruptive behaviour and dense observation network. In the 6-year period from 2009 to 2015, the volcano was erupting at an almost constant rate introducing approximately 500 kt of ash per month to the atmosphere. The long-term characteristics of the transport and deposition of ash and SO2 in the area surrounding the volcano are studied here using daily surface observations of suspended particulate matter (SPM) and SO2 and monthly ashfall values. Results reveal different dispersal patterns for SO2 and volcanic ash, suggesting volcanic emissions' separation in the long-term. Peak SO2 concentrations at different locations on the volcano vary up to 2 orders of magnitude and decrease steeply with distance. Airborne volcanic ash increases SPM concentrations uniformly across the area surrounding the volcano, with distance from the vent having a secondary effect. During the period studied here, the influence of volcanic emissions was identifiable both in SO2 and SPM concentrations which were, at times, over the recommended exposure limits defined by the Japanese government, European Union and the World Health Organisation. Depositional patterns of volcanic ash exhibit elements of seasonality, consistent with previous studies. Climatological and topographic effects are suspected to impact the deposition of volcanic ash away from the vent: for sampling stations located close to complex topographical elements, sharp changes in the deposition patterns were observed, with ash deposits for neighbouring stations as close as 5 km differing as much as an order of magnitude. Despite these effects, deposition was sufficiently approximated by an inverse power law relationship, the fidelity of which depended on the distance from the vent: for proximal to intermediate areas (<20 km), errors decrease with longer accumulation periods (tested here for 1-72 months), while the opposite was seen for deposition in distal areas (>20 km).

Development of mobile sensor for volcanic observation "HOMURA": Test campaigns for a long-term operation

NASA Astrophysics Data System (ADS)

Kaneko, K.; Iwahori, K.; Ito, K.; Sagi, H.

2016-12-01

Unmanned robots are useful to observe volcanic phenomena near active volcanic vents, to learn symptoms and transitions of eruptions, and to mitigate volcanic disasters. We have been trying to develop a practical UGV robot for flexible observation of active volcanic vents. We named this system "Homura". In this presentation, we report results of test campaigns of Homura for observation in a volcanic field. We have developed a prototype of Homura, which is a small robot vehicle with six wheels (75 x 43 x 31 cm and a weight of about 12 kg). It is remotely controlled with mobile phone radio waves; it can move in volcanic fields and send real time data of sensors (camera and gas sensors) equipped in the vehicle to the base station. Homura has a small solar panel (4 W). Power consumption of Homura is about 4 W in operation of sensors and less than 0.1 W in idle state, so that Homura can work outdoors for a long time by intermittent operation.We carried out two test campaigns of Homura at Iwo-yama to examine if Homura can work for a few month in natural volcanic fields (however, it had no solar panel in these campaigns). Iwo-yama is one of craters in the Kirishima volcanic field, SW Japan; the area within 1 km from the crater was an off-limit area from Oct., 2014 to May, 2015 and from Feb. to Mar., 2016 because of strong volcanic seismicity. On Feb. 19th, 2015 and Mar. 7th, 2016, we carried and put Homura at the rim of the crater. Unfortunately, mobile phone connectivity was not entirely stable around Iwo-yama. Then, we did not move Homura and only obtain real time data of the sensors. In the two campaigns, we operated Homura at our office for a few hours every day for 49 and 37 days, respectively. Although the weather was often bad (rain, fog, or cold temperature) during the campaigns, Homura perfectly worked. The results of these campaigns indicate that Homura is useful as s simple monitoring station in volcanic fields where mobile phone connection is available.

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).

Survey of possibility for volcanic energy development

NASA Astrophysics Data System (ADS)

1990-03-01

Volcanic areas, clarification of heat source structure, evaluation of resources and problems on utilization techniques were arranged to search the possibility of future volcanic heat source. It is necessary to improve the exploration accuracy by combining geophysical exploration with geological and geochemical surveys in order to explorate a magma reservoir. Especially, seismic exploration is effective. The surveying procedure is as follows: confirmation of magma existence and grasping the whole image, evaluation of resources, clarification of three-dimensional distribution of magma in a promising area, and heat structure survey by heat flow measurement and others to construct more accurate model for resources. This model is verified finally by practical drilling. Promising areas which are worthy of development, are active volcanic areas in Kyushu, Hakkoda nad Hokkaido. It is desirable to make drilling to the depth of 3 km or magma reservoir to develop the future heat source. It is also required to improve the thermal resistance and corrosion resistance of materials to be used. Heat extraction by a single well is most realistic and the closed coaxial double pipe heat exchanger or open heat exchanger in the well will be used to improve the extraction.

Health hazards and disaster potential of ground gas emissions at Furnas volcano, São Miguel, Azores

NASA Astrophysics Data System (ADS)

Baxter, Peter J.; Baubron, Jean-Claude; Coutinho, Rui

1999-09-01

A health hazard assessment of exposure to soil gases (carbon dioxide and radon) was undertaken in the village of Furnas, located in the caldera of an active volcano. A soil survey to map the area of soil gas flow was undertaken, gas emissions were monitored at fumaroles and in eight houses, and a preliminary radon survey of 23 houses in the main anomaly area was performed. Potential volcanic sources of toxic contamination of air, food, and water were also investigated, and ambient air quality was evaluated. About one-third (41 ha) of the houses were located in areas of elevated carbon dioxide soil degassing. Unventilated, confined spaces in some houses contained levels of carbon dioxide which could cause asphyxiation. Mean indoor radon levels exceeded UK and US action levels in the winter months. A tenfold increase in radon levels in one house over 2 h indicated that large and potentially lethal surges of carbon dioxide could occur without warning. Toxic exposures from the gaseous emissions and from contamination of soil and water were minimal, but sulphur dioxide levels were mildly elevated close to fumaroles. In contrast, evidence of dental fluorosis was manifested in the population of the nearby fishing village of Ribeira Quente where drinking water in the past had contained elevated levels of fluoride. The disaster potential of volcanic carbon dioxide in the area could also be associated with the hydrothermal system storing dissolved carbon dioxide beneath the village. Felt, or unfelt, seismic activity, or magma unrest, especially with a reawakening of explosive volcanic activity (30% probability in the next 100 years) could result in an increase in gas flow or even a gas burst from the hydrothermal system. A survey of all houses in Furnas is advised as structural measures to prevent the ingress of soil gases, including radon, were needed in some of the study houses. Evaluations of the human hazards of volcanic gases should be undertaken in all settlements in volcanic and hydrothermal areas associated with soil gas emissions.

Grain size and shape analysis of the AD 1226 tephra layer, Reykjanes volcanic system

NASA Astrophysics Data System (ADS)

Ösp Magnúsdóttir, Agnes; Höskuldsson, Ármann; Larsen, Guðrún; Tumi Guðmunsson, Magnús; Sigurgeirsson, Magnús Á.

2014-05-01

Recent explosive eruptions in Iceland have drawn attention to long range tephra transport in the atmosphere. In Iceland tephra forming explosion eruptions are frequent, due to abundance of water. However, the volcanism on the island is principally basaltic. Volcanism along the Reykjanes Peninsula is divided into five distinct volcanic systems. Volcano-tectonic activity within these systems is periodic, with recurrence intervals in the range of 1 ka. Last volcano-tectonic sequence began around AD 940, shortly after settlement of Iceland, and lasted through AD 1340. During this period activity was characterized by basaltic fissure eruptions. Furthermore, this activity period on the Reykjanes peninsula began within the eastern most volcanic system and gradually moved towards the west across the peninsula. The 1226 eruption was a basaltic fissure eruption with in the Reykjanes volcanic system. The eruption began on land and gradually progressed towards the SW until the volcanic fissure extended into the sea. Water-magma interaction changed the eruption from effusive into explosive forming the largest tephra layer on the peninsula. Due to its close proximity to the Keflavik international airport and that of the capital of Iceland it is important to get an insight into, the characteristics, generation and distribution of such tephra deposits. In this eruption the tephra produced had an approximate volume of 0.1 km3 and covered an area of some 3500 km2 within the 0.5 cm isopach. Total grain size distribution of this tephra layer will be presented along with analysis of principal grain shapes of the finer portion of the tephra layer as a function of distance from the source. The tephra grain size is dominated by particles finer than 1 millimeter with an almost complete absence of large grains independent of distance from the source. Comprehensive understanding of the characteristics of tephra generated in this eruption can help us to understand hazards posed by future eruptions of similar nature in the area.

Sustained effects of volcanic ash on biofilm stoichiometry, enzyme activity and community composition in North- Patagonia streams.

PubMed

Carrillo, Uara; Díaz-Villanueva, Verónica; Modenutti, Beatriz

2018-04-15

Volcanic eruptions are extreme perturbations that affect ecosystems. These events can also produce persistent effects in the environment for several years after the eruption, with increased concentrations of suspended particles and the introduction of elements in the water column. On 4th June 2011, the Puyehue-Cordón Caulle Volcanic Complex (40.59°S-72.11°W, 2200m.a.s.l.) erupted explosively in southern Chile. The area affected by the volcano was devastated; a thick layer of volcanic ash (up to 30cm) was deposited in areas 50 km east of the volcano towards Argentina. The aim of the present study was to evaluate the effect of volcanic ash deposits on stream ecosystems four years after the eruption, comparing biofilm stoichiometry, alkaline phosphatase activity, and primary producer's assemblage in streams which were severely affected by the volcano with unaffected streams. We confirmed in the laboratory that ash deposited in the catchment of affected streams still leach phosphorus (P) into the water four years after eruption. Results indicate that affected streams still receive volcanic particles and that these particles release P, thus stream water exhibits high P concentration. Biofilm P content was higher and the C:P ratio lower in affected streams compared to unaffected streams. As a consequence of less P in unaffected streams, the alkaline phosphatase activity was higher compared to affected streams. Cyanobacteria increased their abundances (99.9% of total algal biovolume) in the affected streams suggesting that the increase in P may positively affect this group. On the contrary, unaffected streams contained a diatom dominant biofilm. In this way, local heterogeneity was created between sub-catchments located within 30 km of each other. These types of events should be seen as opportunities to gather valuable ecological information about how severe disturbances, like volcanic eruptions, shape landscapes and lotic systems for several years after the event. Copyright © 2017 Elsevier B.V. All rights reserved.

Volcanic hotspots of the central and southern Andes as seen from space by ASTER and MODVOLC between the years 2000-2011

NASA Astrophysics Data System (ADS)

Jay, J.; Pritchard, M. E.; Mares, P. J.; Mnich, M. E.; Welch, M. D.; Melkonian, A. K.; Aguilera, F.; Naranjo, J.; Sunagua, M.; Clavero, J. E.

2011-12-01

We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for temperature anomalies between 2000-2011 from two different spacebourne sensors: 1) those automatically detected by the MODVOLC algorithm (Wright et al., 2004) from MODIS and 2) manually identified hotspots in nighttime images from ASTER. Based on previous work, we expected to find 8 thermal anomalies (volcanoes: Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Puyehue-Cordón Caulle, Chiliques). We document 31 volcanic areas with pixel integrated temperatures of 4 to more than 100 K above background in at least two images, and another 29 areas that have questionable hotspots with either smaller anomalies or a hotspot in only one image. Most of the thermal anomalies are related to known activity (lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to be active. A handful of volcanoes exhibit temporal variations in the magnitude and location of their temperature anomaly that can be related to both documented and undocumented pulses of activity. Our survey reveals that low amplitude volcanic hotspots detectable from space are more common than expected (based on lower resolution data) and that these features could be more widely used to monitor changes in the activity of remote volcanoes. We find that the shape, size, magnitude, and location on the volcano of the thermal anomaly vary significantly from volcano to volcano, and these variations should be considered when developing algorithms for hotspot identification and detection. We compare our thermal results to satellite InSAR measurements of volcanic deformation and find that there is no simple relationship between deformation and thermal anomalies - while 31 volcanoes have continuous hotspots, at least 17 volcanoes in the same area have exhibited deformation, and these lists do not completely overlap. In order to investigate the relationship between seismic and thermal volcanic activity, we examine seismic data for 5 of the volcanoes (Uturuncu, Olca-Paruma, Ollague, Irruputuncu, and Sol de Mañana) as well as seismological reports from the Chilean geological survey SERNAGEOMIN for 11 additional volcanoes. Although there were 7 earthquakes with Mw > 7 in our study area from 2000-2010, there is essentially no evidence from ASTER or MODVOLC that the thermal anomalies were affected by seismic shaking.

Bentonite chemical features as proxy of late Cretaceous provenance changes: A case study from the Western Interior Basin of Canada

NASA Astrophysics Data System (ADS)

Fanti, Federico

2009-05-01

Bentonite beds are fairly common in both marine and terrestrial Upper Cretaceous (Campanian-Maastrichtian) deposits of the Western Interior Basin of western Canada and northwestern United States. A detailed stratigraphic, sedimentologic, geochemical (X-ray fluorescence), and mineralogical (X-ray diffraction) study of twenty-one bentonites from the Puskwaskau and Wapiti formations in the Grande Prairie area (west-central Alberta, Canada) is here presented. Major and trace-element concentrations from altered volcanic ashes document the presence in the study area of predominantly trachyandesitic and rhyolitic volcanogenic products, resulted from intense volcanic arc to within-plate pyroclastic activity. Concentration values of high field strength elements (HFSE) and selected large ion lithophile elements (LILE) (e.g. Nb, Zr, Th, and Y) obtained by X-ray fluorescence spectroscopy strongly support the presence of multiple volcanic sources. Integrated paleoenvironmental and geochemical criteria for provenance determination indicate a bimodal occurrence of basic and acid volcanic products interpreted as reflection of source areas characterized by different tectonic setting and magmatic composition. A comparative analysis of geochemical compositions between Grande Prairie bentonites and 30 known volcanic beds from central and southern Alberta, Manitoba and Montana 1. documents a trend toward more acidic and alkali-depleted volcanic products during the late Campanian-early Maastrichtian interval, and 2. suggests a well constrained stratigraphic and geographic subdivision of the non-marine successions of the foreland basin on the basis of geochemical characteristic of volcanic ash beds. Furthermore, geochemical "fingerprints" of several decimeter to meter thick bentonite beds have been coupled with volcanic ash subsurface signature in order to investigate their role as marker beds. This multiple-approach provides a reliable tool for basin-scale identification and correlation of non-marine sedimentary successions.

Volcanic risk perception in the Campi Flegrei area

NASA Astrophysics Data System (ADS)

Ricci, T.; Barberi, F.; Davis, M. S.; Isaia, R.; Nave, R.

2013-03-01

The Campi Flegrei which includes part of the city of Naples, is an active volcanic system; its last eruption occurred in 1538 AD. More recently two significant crises occurred between 1969 and 72 and 1982-84 and were accompanied by ground movements (bradyseism) and seismic activity, forcing people of the town of Pozzuoli to be evacuated. Since 1984 development of a volcanic emergency plan has been underway. In 2000 Civil Protection published a risk map which defined the Red Zone, an area highly at risk from pyroclastic flows, which would need to be evacuated before an eruption. The first study to evaluate the volcanic risk perceptions of the people living within the Campi Flegrei area was completed in spring 2006, resulting in the largest sample ever studied on this topic except for one on Vesuvio area residents by Barberi et al. (2008). A 46 item questionnaire was distributed to 2000 of the approximately 300,000 residents of the Campi Flegrei Red Zone, which includes three towns and four neighborhoods within the city of Naples. A total of 1161 questionnaires were returned, for an overall response rate of 58%. Surveys were distributed to junior high and high school students, as well as to adult members of the general population. Results indicated that unlike issues such as crime, traffic, trash, and unemployment, volcanic hazards are not spontaneously mentioned as a major problem facing their community. However, when asked specific questions about volcanic risks, respondents believe that an eruption is likely and could have serious consequences for themselves and their communities and they are quite worried about the threat. Considering the events of 1969-72 and 1982-84, it was not surprising that respondents indicated earthquakes and ground deformations as more serious threats than eruptive phenomena. Of significant importance is that only 17% of the sample knows about the existence of the Emergency Plan, announced in 2001, and 65% said that they have not received enough information about the possible effects of an eruption. In addition, residents' sense of community was significantly positively correlated with both confidence in local authorities and Civil Protection as well as residents' feelings of self efficacy regarding their ability to protect themselves from a potential eruption. These results indicate that most residents of Campi Flegrei, while aware of the volcanic threat posed by Vesuvio, are not familiar with more local volcanic hazards in their area. This, coupled with little knowledge about the Emergency Plan and the very low level of information residents have about the effects of a possible eruption, suggests that authorities, in collaboration with the scientific community, should direct their efforts to better educate and inform the population about volcanic hazards and the Emergency Plan, and that such efforts could be facilitated by trying to encourage stronger community bonds.

Earth Observation taken during the Expedition 37 mission

NASA Image and Video Library

2013-09-30

ISS037-E-005089 (30 Sept. 2013) --- Ruapehu volcano and Tongariro volcanic complex in New Zealand are featured in this image photographed by an Expedition 37 crew member on the International Space Station. Mount Ruapehu is one of several volcanic centers on the North Island of New Zealand, but is the largest and historically most active. The 2,797-meter elevation volcano is also the highest mountain on North Island and is covered with snow on its upper slopes. Scientists believe while there are three summit craters that have been active during the last 10,000 years, South Crater is the only historically active one. This vent is currently filled with a lake (Crater Lake), visible at left; eruptions from the vent, mixed with water from the lake can lead to the formation of lahars – destructive gravity flows of mixed fluid and volcanic debris that form a hazard to ski areas on the upper slopes and lower river valleys. The most recent significant eruption of Ruapehu took place in 2007 and formed both an eruption plume and lahars. The volcano is surrounded by a 100-cubic-kilometer ring plain of volcaniclastic debris that appears dark grey in the image, whereas vegetated areas appear light to dark green. Located to the northeast of the Ruapehu volcanic structure, the Tongariro volcanic complex (lower right) is currently in an active eruptive phase – the previous eruptive phase ended in 1897. Explosive eruptions occurred in 2012, which have been followed by steam and gas plumes observed almost daily. According to scientists, the volcanic complex contains multiple cones constructed over the past 275,000 years. The most prominent of these, Mount Ngauruhoe, last erupted in 1975. Like Ruapehu, the upper slopes of both Ngauruhoe and the upper peaks of Tongariro are snow-covered. Scattered cloud cover is also visible near Tongariro at lower right.

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

Airborne EM survey in volcanoes : Application to a volcanic hazards assessment

NASA Astrophysics Data System (ADS)

Mogi, T.

2010-12-01

Airborne electromagnetics (AEM) is a useful tool for investigating subsurface structures of volcanoes because it can survey large areas involving inaccessible areas. Disadvantages include lower accuracy and limited depth of investigation. AEM has been widely used in mineral exploration in frontier areas, and have been applying to engineering and environmental fields, particularly in studies involving active volcanoes. AEM systems typically comprise a transmitter and a receiver on an aircraft or in a towed bird, and although effective for surveying large areas, their penetration depth is limited because the distance between the transmitter and receiver is small and higher-frequency signals are used. To explore deeper structures using AEM, a semi-airborne system called GRounded Electrical source Airborne Transient ElectroMagnetics (GREATEM) has been developed. The system uses a grounded-electrical-dipole as the transmitter and generates horizontal electric fields. The GREATEM technology, first proposed by Mogi et al. (1998), has recently been improved and used in practical surveys (Mogi et al., 2009). The GREATEM survey system was developed to increase the depth of investigation possible using AEM. The method was tested in some volcanoes at 2004-2005. Here I will talk about some results of typical AEM surveys and GREATEM surveys in some volcanoes in Japan to mitigate hazards associated with volcano eruption. Geologic hazards caused by volcanic eruptions can be mitigated by a combination of prediction, preparedness and land-use control. Risk management depends on the identification of hazard zones and forecasting of eruptions. Hazard zoning involves the mapping of deposits which have formed during particular phases of volcanic activity and their extrapolation to identify the area which would be likely to suffer a similar hazard at some future time. The mapping is usually performed by surface geological surveys of volcanic deposits. Resistivity mapping by AEM is useful tool to identify each volcanic deposit on the surface and at shallower depth as well. This suggests that more efficient hazard map involving subsurface information can be supplied by AEM resistivity mapping.

Infrasonic Influence of Volcanos

NASA Astrophysics Data System (ADS)

Hosman, Ashley

2014-03-01

My presentation will consist of a poster on the use of ring laser interferometers to detect infrasound. The research was performed during the summer of 2013 and it focused on the finding infrasound emissions created by volcanic activity. I will explain how a ring laser works and discuss how I analyze the collected data using Fast Fourier Transforms. Due to the extreme distances over which infrasound can travel, I will also stress the need to compare the detected responses to specific volcanic eruptions. Finally, I will purpose practical applications of my research. One of the more promising applications is to use ring lasers to detect volcanic activity in remote areas such as parts of the Aleutian Islands. There is considerable air traffic over the Aleutian Islands. Volcanic plumes are a significant aviation hazard and can damage jet engines to the extent that they will no longer operate. Thank you to the NSF ans NASA foundations for providing funding for this reseach.

Assessing qualitative long-term volcanic hazards at Lanzarote Island (Canary Islands)

NASA Astrophysics Data System (ADS)

Becerril, Laura; Martí, Joan; Bartolini, Stefania; Geyer, Adelina

2017-07-01

Conducting long-term hazard assessment in active volcanic areas is of primary importance for land-use planning and defining emergency plans able to be applied in case of a crisis. A definition of scenario hazard maps helps to mitigate the consequences of future eruptions by anticipating the events that may occur. Lanzarote is an active volcanic island that has hosted the largest (> 1.5 km3 DRE) and longest (6 years) eruption, the Timanfaya eruption (1730-1736), on the Canary Islands in historical times (last 600 years). This eruption brought severe economic losses and forced local people to migrate. In spite of all these facts, no comprehensive hazard assessment or hazard maps have been developed for the island. In this work, we present an integrated long-term volcanic hazard evaluation using a systematic methodology that includes spatial analysis and simulations of the most probable eruptive scenarios.

MINERVA: An INSAR Monitoring Service for Volcanic Hazard

NASA Astrophysics Data System (ADS)

Tampellini, M. L.; Sansosti, E.; Usai, S.; Lanari, R.; Borgstrom, S.; van Persie, M.; Ricciardi, G. P.; Maddalena, V.; Cicero, L.; Pepe, A.

2004-06-01

MINERVA (Monitoring by Interferometric SAR of Environmental Risk in Volcanic Areas) is a small scale service demonstration project financed by ESA in the Data User Programme framework. The objective of the project is the design, development and assessment of a demonstrative information service based on the interferometric processing of images acquired from either the ASAR instrument on board ENVISAT-I or SAR instruments on board ERS1/2. The system is based on a new approach for the processing of INSAR data, which allows to optimize the quality of interferograms spanning from 35 days up to several years, and to merge them to generate a single solution describing the temporal evolution of the ground deformations in the examined risk area. The system allows to update this solution each time a new SAR image is available, and constitutes therefore an innovative tool for monitoring of the ground displacements in risk areas. The system has been implemented and demonstrated at Osservatorio Vesuviano (Naples, Italy), which is the institution responsible for monitoring the volcanic phenomena in the Neapolitan volcanic district, and for alerting the Italian civil authorities (''Protezione Civile'') in case such monitoring activity reveals signals of imminent eruptions. In particular, the MINERVA system has been used to monitor the ground deformations at the Phlegrean Fields, a densely populated, high-hazard zone which is subject to alternate phases of uplift and subsidence, accompanied often by seismic activity.

Applying geophysical surveys for studying subsurface geology of monogenetic volcanic fields: the example of La Garrotxa Volcanic Field (NE of Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Bolós, Xavier; Barde-Cabusson, Stéphanie; Pedrazzi, Dario; Martí, Joan; Casas, Albert; Lovera, Raúl; Nadal-Sala, Daniel

2014-05-01

Improving knowledge of the shallowest part of the feeding system of monogenetic volcanoes and the relationship with the subsurface geology is an important task. We applied high-precision geophysical techniques that are self-potential and electrical resistivity tomography, for the exploration of the uppermost part of the substrate of La Garrotxa Volcanic Field, which is part of the European Cenozoic Rift System. Previous geophysical studies carried out in the same area at a less detailed scale were aimed at identifying deeper structures, and together constitute the basis to establish volcanic susceptibility in La Garrotxa. Self-potential study allowed identifying key areas where electrical resistivity tomography could be conducted. Dykes and faults associated with several monogenetic cones were identified through the generation of resistivity models. The combined results confirm that shallow tectonics controlling the distribution of the foci of eruptive activity in this volcanic zone mainly correspond to NNW-SSE and accessorily by NNE-SSW Neogene extensional fissures and faults and concretely show the associated magmatic intrusions. These studies show that previous alpine tectonic structures played no apparent role in controlling the loci of this volcanism. Furthermore, the results obtained show that the changes in eruption dynamics occurring at different vents located at relatively short distances in this volcanic area can be controlled by shallow stratigraphical, structural, and hydrogeological features underneath these monogenetic volcanoes. This study was partially funded by the Beca Ciutat d'Olot en Ciències Naturals and the European Commission (FT7 Theme: ENV.2011.1.3.3-1; Grant 282759: "VUELCO").

Fluid circulation and structural system of Cerritos Colorados geothermal field in La Primavera volcanic caldera (Mexico) inferred from geophysical surveys

NASA Astrophysics Data System (ADS)

Bolós, X.; Cifuentes-Nava, G.; Macias, J. L.; Sosa-Ceballos, G.; García-Tenorio, F.; Albor, M., III; Juarez, M.; Gamez, V.

2017-12-01

Hydrothermal activity in volcanic calderas is the consequence of energy transfer between deep magmatic chambers and subsurface layers saturated in water. This hydrothermal system is generated by convection of the groundwater supplied by meteoric water recharged and the ascent of hot volcanic gasses exsolved from deep magma reservoirs. Calderas are heterogeneous geological structures that due to their formation and evolution produced a complex stratigraphy. All of these heterogeneities can be affected by deformation and also by the presence of fractures and faults which constitute the main pathways whereby hydrothermal fluids can move easily through the surface as spring discharges and fumarolic activity. Geophysical methods have been used in the last decades to investigate the relationship between structural geology and hydrothermal systems in different volcanic areas around the world. In this work, we have focused on the role of subsurface structures to understand and localize the pathways of fluids related to the hydrothermal system of the Cerritos Colorados geothermal field. We focused in the central area of the caldera (P12 well and Cerritos Colorados graben), where active hydrothermal activity is evidenced by fumaroles, thermal anomalies, CO2 diffuse emission, and sulfur precipitation. We have applied a self-potential method (SP) that combined with temperature measurements that allowed to identify the main infiltration and ascending fluid zones in the area, and their specific surface temperature coinciding with fumarolic activity. From this data we an applied Electrical Resistivity Tomography (ERT) survey in two selected places. One ERT profile (1.2 km in length) was located in the P12 well area. A 3D resistivity model used with the equatorial method was carried out on the Cerritos Colorados graben area. Combining the results of the SP, TºC, and ERT data with a detailed structural map we identified the main degassing zones (i.e. fumaroles) that correspond to higher permeability zones located along normal and strike-slip faults. In conclusion, a strong structural control of the surface manifestation of these hydrothermal systems is deduced from our new data. Then, our results emphasize the importance of old structural boundaries that are controlled by intra-caldera tectonic structures.

Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

NASA Astrophysics Data System (ADS)

Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

2018-04-01

Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

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.

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.

Probabilistic constraints from existing and future radar imaging on volcanic activity on Venus

NASA Astrophysics Data System (ADS)

Lorenz, Ralph D.

2015-11-01

We explore the quantitative limits that may be placed on Venus' present-day volcanic activity by radar imaging of surface landforms. The apparent nondetection of new lava flows in the areas observed twice by Magellan suggests that there is a ~60% chance that the eruption rate is ~1 km3/yr or less, using the eruption history and area/volume flow geometry of terrestrial volcanoes (Etna, Mauna Loa and Merapi) as a guide. However, if the detection probability of an individual flow is low (e.g. ~10%) due to poor resolution or quality and unmodeled viewing geometry effects, the constraint (<10 km3/yr) is not useful. Imaging at Magellan resolution or better of only ~10% of the surface area of Venus on a new mission (30 years after Magellan) would yield better than 99% chance of detecting a new lava flow, even if the volcanic activity is at the low end of predictions (~0.01 km3/yr) and is expressed through a single volcano with a stochastic eruption history. Closer re-examination of Magellan data may be worthwhile, both to search for new features, and to establish formal (location-dependent) limits on activity against which data from future missions can be tested. While Magellan-future and future-future comparisons should offer much lower detection thresholds for erupted volumes, a probabilistic approach will be required to properly understand the implications.

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.

Lightning and electrical activity during the Shiveluch volcano eruption on 16 November 2014

NASA Astrophysics Data System (ADS)

Shevtsov, Boris M.; Firstov, Pavel P.; Cherneva, Nina V.; Holzworth, Robert H.; Akbashev, Renat R.

2016-03-01

According to World Wide Lightning Location Network (WWLLN) data, a sequence of lightning discharges was detected which occurred in the area of the explosive eruption of Shiveluch volcano on 16 November 2014 in Kamchatka. Information on the ash cloud motion was confirmed by the measurements of atmospheric electricity, satellite observations and meteorological and seismic data. It was concluded that WWLLN resolution is enough to detect the earlier stage of volcanic explosive eruption when electrification processes develop the most intensively. The lightning method has the undeniable advantage for the fast remote sensing of volcanic electric activity anywhere in the world. There is a good opportunity for the development of WWLLN technology to observe explosive volcanic eruptions.

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.

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.

Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA

USGS Publications Warehouse

Wicks, Charles W.; Dzurisin, Daniel; Ingebritsen, Steven E.; Thatcher, Wayne R.; Lu, Zhong; Iverson, Justin

2002-01-01

Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ~10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ~130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ~1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ~100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ~6.5 km.

The Cellular Automata for modelling of spreading of lava flow on the earth surface

NASA Astrophysics Data System (ADS)

Jarna, A.

2012-12-01

Volcanic risk assessment is a very important scientific, political and economic issue in densely populated areas close to active volcanoes. Development of effective tools for early prediction of a potential volcanic hazard and management of crises are paramount. However, to this date volcanic hazard maps represent the most appropriate way to illustrate the geographical area that can potentially be affected by a volcanic event. Volcanic hazard maps are usually produced by mapping out old volcanic deposits, however dynamic lava flow simulation gaining popularity and can give crucial information to corroborate other methodologies. The methodology which is used here for the generation of volcanic hazard maps is based on numerical simulation of eruptive processes by the principle of Cellular Automata (CA). The python script is integrated into ArcToolbox in ArcMap (ESRI) and the user can select several input and output parameters which influence surface morphology, size and shape of the flow, flow thickness, flow velocity and length of lava flows. Once the input parameters are selected, the software computes and generates hazard maps on the fly. The results can be exported to Google Maps (.klm format) to visualize the results of the computation. For validation of the simulation code are used data from a real lava flow. Comparison of the simulation results with real lava flows mapped out from satellite images will be presented.

Variations in eruptive style and depositional processes of Neoproterozoic terrestrial volcano-sedimentary successions in the Hamid area, North Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Khalaf, Ezz El Din Abdel Hakim

2013-07-01

Two contrasting Neoproterozoic volcano-sedimentary successions of ca. 600 m thickness were recognized in the Hamid area, Northeastern Desert, Egypt. A lower Hamid succession consists of alluvial sediments, coherent lava flows, pyroclastic fall and flow deposits. An upper Hamid succession includes deposits from pyroclastic density currents, sills, and dykes. Sedimentological studies at different scales in the Hamid area show a very complex interaction of fluvial, eruptive, and gravitational processes in time and space and thus provided meaningful insights into the evolution of the rift sedimentary environments and the identification of different stages of effusive activity, explosive activity, and relative quiescence, determining syn-eruptive and inter-eruptive rock units. The volcano-sedimentary deposits of the study area can be ascribed to 14 facies and 7 facies associations: (1) basin-border alluvial fan, (2) mixed sandy fluvial braid plain, (3) bed-load-dominated ephemeral lake, (4) lava flows and volcaniclastics, (5) pyroclastic fall deposits, (6) phreatomagmatic volcanic deposits, and (7) pyroclastic density current deposits. These systems are in part coeval and in part succeed each other, forming five phases of basin evolution: (i) an opening phase including alluvial fan and valley flooding together with a lacustrine period, (ii) a phase of effusive and explosive volcanism (pulsatory phase), (iii) a phase of predominant explosive and deposition from base surges (collapsing phase), and (iv) a phase of caldera eruption and ignimbrite-forming processes (climactic phase). The facies architectures record a change in volcanic activity from mainly phreatomagmatic eruptions, producing large volumes of lava flows and pyroclastics (pulsatory and collapsing phase), to highly explosive, pumice-rich plinian-type pyroclastic density current deposits (climactic phase). Hamid area is a small-volume volcano, however, its magma compositions, eruption styles, and inter-eruptive breaks suggest, that it closely resembles a volcanic architecture commonly associated with large, composite volcanoes.

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.

A consideration of the availableness of MODIS data to assess a volcanic ash fall

NASA Astrophysics Data System (ADS)

Tomiyama, N.; Yonezawa, C.; Yamakoshi, T.

It is important to grasp the situation of the ash fall at short interval for a volcanic disaster-prevention. Clouds and volcanic smokes reduce the opportunities to observe a volcano by a satellite's optical sensor. Therefore it is preferable to use data of a sensor that is able to observe same area with high frequency. MODIS sees every point on the earth every 1-2 days and provides NDVI data with 250m spatial resolutions. The purpose of this study is to consider the availableness of MODIS data to assess the situation of the volcanic ash fall. The test site is Miyake-jima, one of the active volcanic island in Japan. It is verified that a rate of change of NDVI between before and after erruptions correlates with the amounts of ash fall.

Volcanic Gas Emissions Mapping Using a Mass Spectrometer System

NASA Technical Reports Server (NTRS)

Griffin, Timothy P.; Diaz, J. Andres

2008-01-01

The visualization of hazardous gaseous emissions at volcanoes using in-situ mass spectrometry (MS) is a key step towards a better comprehension of the geophysical phenomena surrounding eruptive activity. In-Situ gas data consisting of helium, carbon dioxide, sulfur dioxide, and other gas species, were acquired with an MS system. MS and global position system (GPS) data were plotted on ground imagery, topography, and remote sensing data collected by a host of instruments during the second Costa Rica Airborne Research and Technology Applications (CARTA) mission This combination of gas and imaging data allowed 3-dimensional (3-D) visualization of the volcanic plume end the mapping of gas concentration at several volcanic structures and urban areas This combined set of data has demonstrated a better tool to assess hazardous conditions by visualizing and modeling of possible scenarios of volcanic activity. The MS system is used for in-situ measurement of three-dimensional gas concentrations at different volcanic locations with three different transportation platforms, aircraft, auto, and hand carried. The demonstration for urban contamination mapping is also presented as another possible use for the MS system.

Syn- and post-eruptive volcanic processes in the Yubileinaya kimberlite pipe, Yakutia, Russia, and implications for the emplacement of South African-style kimberlite pipes

NASA Astrophysics Data System (ADS)

Kurszlaukis, S.; Mahotkin, I.; Rotman, A. Y.; Kolesnikov, G. V.; Makovchuk, I. V.

2009-11-01

The Yubileinaya kimberlite pipe, with a surface area of 59 ha, is one of the largest pipes in the Yakutian kimberlite province. The Devonian pipe was emplaced under structural control into Lower Paleozoic karstic limestone. The pipe complex consists of several smaller precursor pipes which are cut by the large, round Main pipe. While the precursor pipes show many features typical for root zones, Main pipe is younger, cuts into the precursor pipes and exposes well-bedded volcaniclastic sediments. The maximum estimated erosion since emplacement is 250 m. Open pit mapping of a 180 m thick kimberlite sequence documents the waning phases of the volcanic activity in the kimberlite pipe and the onset of its crater infill by resedimentation. Three volcanic lithofacies types can be differentiated. The deepest and oldest facies type is a massive volcaniclastic rock ("AKB") only accessible in drill core. It is equivalent to Tuffisitic Kimberlite in South African pipes and thought to be related to the main volcanic phase which was characterized by violent explosions. The overlying lithofacies type comprises primary and resedimented volcaniclastic sediments as well as rock avalanche deposits sourced from the exposed maar crater collar. It represents the onset of sedimentation onto the crater floor during the waning phase of volcanic eruptions, where primary pyroclastic deposition was contemporaneous with resedimentation from the tephra wall and the widening maar crater. Ongoing volcanic activity is also testified by the presence of a vertical feeder conduit marking the area of the last volcanic eruption clouds piercing through the diatreme. This feeder conduit is overlain by the third and youngest lithofacies type which consists mainly of resedimented volcaniclastic material and lake beds. During the sedimentation of this facies, primary volcanic activity was only minor and finally absent and resedimentation processes dominated the crater infill. The Yubileinaya pipe complex exposes root zones, contact breccias as well as diatreme and crater infill sediments. It has all features typical of large South African-style pipes and much can be learned from Yubileinaya about the emplacement sequence and behaviour of these pipes. Emplacement of the pipe occurred over an extended time span with intermittent phases of volcanic quiescence and consolidation. The AKB reveals little direct evidence of what sort of emplacement process was dominant during the main period of volcanic activity. There is neither textural evidence that violent degassing of a juvenile gas phase has caused pipe excavation, nor that external water was present during the main phase of volcanic eruptions. However, there is clear evidence in rock textures that meteoric surface water was present during crater infill. Base surge deposits forming part of the bedded crater infill sequence indicate that water was present in the eruption clouds and, hence, the root zone of the pipe. There is no reason to assume that groundwater did not also have access to the ascending magma during the main phase of volcanic activity that excavated the pipe and formed the AKB.

An approach of understanding acid volcanics and tuffaceous volcaniclastics from field studies: A case from Tadpatri Formation, Proterozoic Cuddapah basin, Andhra Pradesh, India

NASA Astrophysics Data System (ADS)

Goswami, Sukanta; Upadhyay, P. K.; Bhagat, Sangeeta; Zakaulla, Syed; Bhatt, A. K.; Natarajan, V.; Dey, Sukanta

2018-03-01

The lower stratigraphic part of the Cuddapah basin is marked by mafic and felsic volcanism. Tadpatri Formation consists of a greater variety of rock types due to bimodal volcanism in the upper part. Presence of bimodal volcanism is an indication of continental rift setting. Various genetic processes involved in the formation of such volcanic sequence result in original textures which are classified into volcaniclastic and coherent categories. Detailed and systematic field works in Tadpatri-Tonduru transect of SW Cuddapah basin have provided information on the physical processes producing this diversity of rock types. Felsic volcanism is manifested here with features as finger print of past rhyolite-dacite eruptions. Acid volcanics, tuffs and associated shale of Tadpatri Formation are studied and mapped in the field. With supporting subordinate studies on geochemistry, mineralogy and petrogenesis of the volcanics to validate field features accurately, it is understood that volcanism was associated with rifting and shallow marine environmental condition. Four facies (i.e., surge, flow, fall and resedimented volcaniclastic) are demarcated to describe stratigraphic units and volcanic history of the mapped area. The present contribution focuses on the fundamental characterization and categorization of field-based features diagnostic of silica-rich volcanic activities in the Tadpatri Formation.

Analogue modelling of strike-slip fault propagation across a rheological/morphological crustal anisotropy: implications for the morphotectonic evolution of the Gloria Fault - Tore Madeira Rise area in NE Atlantic.

NASA Astrophysics Data System (ADS)

Tomás, Ricardo; Rosas, Filipe M.; Duarte, João C.; Terrinha, Pedro; Kullberg, Maria C.; Almeida, Jaime; Barata, Frederico; Carvalho, Bruno; Almeida, Pedro

2015-04-01

The Gloria Fault (GF) marks the E-W dextral transcurrent plate boundary between Eurasia and Africa in NE Atlantic, displaying complying high magnitude (historical and instrumental) seismic activity (e.g. M=7.1 in 1939 and M=8.4 in 1941, Bufforn et al., 1988), and cutting across a NNE-SSW 1000 km long bathymetric ridge: the so called Tore-Madeira Rise - TMR (rising in average 3km above the abyssal plain). The precise origin and tectono-magmatic evolution of the TMR is still not fully understood, although reported wide-angle refraction data points to a rheological configuration comprising an isostatically compensated thickened oceanic crust, possibly formed during a period of high accretion in the Mid-Atlantic Ridge (Pierce and Barton, 1991). Widespread evidence for volcanic activity has also been recognized, spanning from late Cretaceous to Present (Geldmacher et al. 2006, Merle et al. 2009), noticeably with the most recent volcanism (~500 Ky) occurring as tectonically aligned volcanic plugs, distributed along the E-W tectonic trend of the GF-related structures. To better understand the complex interference at play in this key area between the tectonic structures (essentially determined by the Gloria Fault system), the present and past magmatic activity and the resulting seafloor morphology, a series of dynamically scaled analogue modelling experiments have been conceived and carried out. The main focus of this experimental work was to decipher the potential influence of a rheological vs. morphological anisotropy (accounting for the TMR) on the lateral propagation of a major right-lateral strike-slip fault (representing the GF). The preliminary comparison of the obtained experimental results with the natural morphotectonic pattern in the study area reveals, not only a strong tectonic control of the ongoing volcanism, manifested by the observed preferred directions of aligned volcanic plugs, but also a so far unsuspected deflection/distributed pattern of several faults, and other GF-related structures, here interpreted as resulting from the specific rheological constrains (e.g. crustal soft anomalies) underlying the distributed volcanic activity throughout the TMR. Acknowledgments This work was sponsored by the Fundação para a Ciência e a Tecnologia (FCT) through project MODELINK EXPL/GEO-GEO/0714/2013.

Radium isotopes in groundwater around Fuji Volcano, Japan -application for groundwater dating on volcanic area-

NASA Astrophysics Data System (ADS)

Ohta, T.; Mahara, Y.

2010-12-01

Young groundwater dating less than 100 years is possible to be obtained from environmental radioactivity with short half life, 3H+3He, 85Kr, or chemical material, CFC-12. The 3H+3He dating method is excellent method to estimate the residence time of shallow groundwater. The one of advantage of the method is small sample volume. The 3He in groundwater is originated by 3 sources, tritiogenic He, mantle He, radiogenic He produced in rock. Especially, as the contribution of the mantle He is greater than the radiogenic and triogenic, when 3H+3He dating apply for groundwater dating on volcanic area, we have to determine ratio of 3 sources. On the other hand, as 85Kr is only originated from atmosphere, it is excellent groundwater dating tracer on volcanic area. However, as 85Kr is ultra low concentration in groundwater, 85Kr is needed to separate from large amount of ground water about 10^5 L. Young groundwater dating by these methods has both advantages and disadvantages, but the disadvantages of the individual methods can be offset by using multiple tracers. Development of a lot of groundwater dating techniques is desired. Therefore, an application of radium isotopes which is simple origin to groundwater dating on volcanic area was tried. Ra-228 and Ra-226 are progenies of Th and U, respectively. The 228Ra/226Ra in ground waters depends on the Th/U in the relevant rocks. As the 228Ra and 226Ra in shallow groundwater on volcanic area are originated from only rock, and the collection of radium isotopes from groundwater is easier than that of 85Kr, implying that it is possible to be good tracer for volcanic area. We aim that groundwater age obtain from 228Ra/226Ra in groundwater and relevant rock on volcanic area. We determined that 228Ra/226Ra observed with river waters and the relevant rocks. The method applied for Kakitagawa around Fuji Volcano, Japan. The relevant rock of Kakitagawa is Mishima lava flow. Our method compared with 3H+3He dating. The residence time of Kakitagawa river water estimated from the 228Ra/226Ra activity ratio in river water and relevant rock is from 12-20 years, and agree well with 3H+3He age, suggesting that 228Ra/226Ra of groundwater could be used as a tool of residence time estimation of groundwater on volcanic area.

A preparation zone for volcanic explosions beneath Naka-dake crater, Aso volcano, as inferred from magnetotelluric surveys

NASA Astrophysics Data System (ADS)

Kanda, Wataru; Tanaka, Yoshikazu; Utsugi, Mitsuru; Takakura, Shinichi; Hashimoto, Takeshi; Inoue, Hiroyuki

2008-11-01

The 1st crater of Naka-dake, Aso volcano, is one of the most active craters in Japan, and known to have a characteristic cycle of activity that consists of the formation of a crater lake, drying-up of the lake water, and finally a Strombolian-type eruption. Recent observations indicate an increase in eruptive activity including a decrease in the level of the lake water, mud eruptions, and red hot glows on the crater wall. Temporal variations in the geomagnetic field observed around the craters of Naka-dake also indicate that thermal demagnetization of the subsurface rocks has been occurring in shallow subsurface areas around the 1st crater. Volcanic explosions act to release the energy transferred from magma or volcanic fluids. Measurement of the subsurface electrical resistivity is a promising method in investigating the shallow structure of the volcanic edifices, where energy from various sources accumulates, and in investigating the behaviors of magma and volcanic fluids. We carried out audio-frequency magnetotelluric surveys around the craters of Naka-dake in 2004 and 2005 to determine the detailed electrical structure down to a depth of around 1 km. The main objective of this study is to identify the specific subsurface structure that acts to store energy as a preparation zone for volcanic eruption. Two-dimensional inversions were applied to four profiles across the craters, revealing a strongly conductive zone at several hundred meters depth beneath the 1st crater and surrounding area. In contrast, we found no such remarkable conductor at shallow depths beneath the 4th crater, which has been inactive for 70 years, finding instead a relatively resistive body. The distribution of the rotational invariant of the magnetotelluric impedance tensor is consistent with the inversion results. This unusual shallow structure probably reflects the existence of a supply path of high-temperature volcanic gases to the crater bottom. We propose that the upper part of the conductor identified beneath the 1st crater is mainly composed of hydrothermally altered zone that acts both as a cap to upwelling fluids supplied from deep-level magma and as a floor to infiltrating fluid from the crater lake. The relatively resistive body found beneath the 4th crater represents consolidated magma. These results suggest that the shallow conductor beneath the active crater is closely related to a component of the mechanism that controls volcanic activity within Naka-dake.

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.

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.

The 2016 Kumamoto-Oita earthquake sequence: aftershock seismicity gap and dynamic triggering in volcanic areas

NASA Astrophysics Data System (ADS)

Uchide, Takahiko; Horikawa, Haruo; Nakai, Misato; Matsushita, Reiken; Shigematsu, Norio; Ando, Ryosuke; Imanishi, Kazutoshi

2016-11-01

The 2016 Kumamoto-Oita earthquake sequence involving three large events ( M w ≥ 6) in the central Kyushu Island, southwest Japan, activated seismicities in two volcanic areas with unusual and puzzling spatial gaps after the largest earthquake ( M w 7.0) of April 16, 2016. We attempt to reveal the seismic process during the sequence by following seismological data analyses. Our hypocenter relocation result implies that the large events ruptured different faults of a complex fault system. A slip inversion analysis of the largest event indicates a large slip in the seismicity gap (Aso gap) in the caldera of Mt. Aso, which probably released accumulated stress and resulted in little aftershock production. We identified that the largest event dynamically triggered a mid-M6 event at Yufuin (80 km northeast of the epicenter), which is consistent with existence of the 20-km long zone where seismicity was activated and surface offset was observed. These findings will help us study the contribution of the identified complexity in fault geometries and the geotherm in the volcanic areas to the revealed seismic process and consequently improve our understanding of the seismo-volcano tectonics.[Figure not available: see fulltext.

VESUVIUS PENTALOGUE: Interdisciplinary Science for Disaster Resilience and Sustainability of Populations Surrounding Vesuvius

NASA Astrophysics Data System (ADS)

Dobran, F.

2015-12-01

VESUVIUS PENTALOGUE is an elaboration of VESUVIUS 2000 scientific initiative aimed at volcanic risk reduction in the Vesuvius area. Its 5 building blocks are: (1) The current strategy of volcanic risk management (massive deportation of population) is both problematic and unacceptable. (2) A continuing close habitation of the population with the volcano should be the crucial cultural point to be pursued. This can be accomplished through a redefinition of the danger zone around Summa-Vesuvius as follows: (a) An exclusion nucleus should be established that prohibits all future human settlements and discourage the existing ones; (b) A resilience belt, housing most of the current population, should be established; (c) A sustainable area should be established beyond the resilience belt, allowing for both sustainable practices and temporary resettlements of the "resilience belt" citizens. (3) The built environment construction codes for the population of the danger zone should be established by utilizing Plinian eruption scenarios, scenario-based seismic hazard assessment and zonation, (c) dynamic structural analyses, (d) global volcanic simulations modeling of thermo-fluid dynamic eruption processes. (4) The volcanic risk information and education should involve an effective volcanic risk information campaign and active public preparedness strategy. This should be implemented for the exclusion nucleus, resilience belt, and sustainable area regions surrounding Summa-Vesuvius. A Volcanic Risk Education Safety Program should be implemented in all schools located within each of the above areas surrounding the volcano. (5)The political Authorities and the scientific community should produce a "memorandum of understanding" that univocally establishes an effective collaboration, and periodic progress reports that keep the populations informed on the improvements leading to the realization of the above objectives. For further details see www.gvess.org.

Heavy metals in the volcanic environment and thyroid cancer.

PubMed

Vigneri, R; Malandrino, P; Gianì, F; Russo, M; Vigneri, P

2017-12-05

In the last two decades thyroid cancer incidence has increased worldwide more than any other cancer. Overdiagnosis of subclinical microcarcinomas has certainly contributed to this increase but many evidences indicate that a true increase, possibly due to environmental factors, has also occurred. Thyroid cancer incidence is markedly increased in volcanic areas. Thus, the volcanic environment is a good model to investigate the possible factors favoring thyroid cancer. In the volcanic area of Mt. Etna in Sicily, as well as in other volcanic areas, a non-anthropogenic pollution with heavy metals has been documented, a consequence of gas, ash and lava emission. Soil, water and atmosphere contamination, via the food chain, biocontaminate the residents as documented by high levels in the urines and the scalp hair compared to individuals living in adjacent non-volcanic areas. Trace amounts of metals are essential nutrients but, at higher concentrations, can be toxic for living cells. Metals can behave both as endocrine disruptors, perturbing the hormonal system, and as carcinogens, promoting malignant transformation. Similarly to other carcinogens, the transforming effect of heavy metals is higher in developing organisms as the fetus (contaminated via the mother) and individuals in early childhood. In the last decades environment metal pollution has greatly increased in industrialized countries. Although still within the "normal" limits for each single metal the hormesis effect (heavy metal activity at very low concentration because of biphasic, non linear cell response) and the possible potentiation effect resulting from the mixture of different metals acting synergistically can explain cell damage at very low concentrations. The effect of metals on the human thyroid is poorly studied: for some heavy metals no data are available. The scarce studies that have been performed mainly focus on metal effect as thyroid endocrine disruptors. The metal concentration in tissues has been rarely measured in the thyroid. Heavy metal accumulation and metabolism in the thyroid or the carcinogenic activity of different doses and different speciation of metals has not been investigated. These studies are now warranted to better understand thyroid biology and heavy metal role in human thyroid carcinogenesis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

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.

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.

Seventeen years of monitoring diffuse CO2 emission from the Tenerife North-West Rift Zone (NWRZ) volcano, Canary Islands

NASA Astrophysics Data System (ADS)

Padilla, Germán D.; Evans, Bethany J.; Provis, Aaron R.; Asensio, María; Alonso, Mar; Calvo, David; Hernández, Pedro; Pérez, Nemesio M.

2017-04-01

Tenerife together and Gran Canaria are the central islands of the Canarian archipelago, which have developed a central volcanic complex characterized by the eruption of differentiated magmas. Tenerife is the largest of the Canary Islands (2100 km2) and at present, the North-West Rift-Zone (NWRZ) is one of the most active volcanic structures of the three volcanic rift-zone of the island, which has hosted two historical eruptions (Arenas Negras in 1706 and Chinyero in 1909). In order to monitor the volcanic activity of NWRZ, since the year 2000, 49 soil CO2 efflux surveys have been performed at NWRZ (more than 300 observation sites each one) to evaluate the temporal an spatial variations of CO2 efflux and their relationships with the volcanic-seismic activity. Measurements were performed in accordance with the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO2 emission from the studied area, 100 simulations for each survey have been performed. We report herein the results of the last diffuse CO2 efflux surveys at the NWRZ undertaken in July and October 2016 to constrain the total CO2 output from the studied area. During July and October 2016 surveys, soil CO2 efflux values ranged from non-detectable up to 32.4 and 53.7 g m-2 d-1, respectively. The total diffuse CO2 output released to atmosphere were estimated at 255 ± 9 and 338 ± 18 t d-1, respectively, values higher than the background CO2 emission estimated on 144 t d-1. Since 2000, soil CO2 efflux values have ranged from non-detectable up to 141 g m-2 d-1, with the highest values measured in May 2005 whereas total CO2 output ranged between 52 and 867 t d-1. Long-term variations in the total CO2 output have shown a temporal correlation with the onsets of seismic activity at Tenerife, supporting unrest of the volcanic system, as is also suggested by anomalous seismic activity recorded in the studied area during April 22-29, 2004 and also during October 2-3, 2016. Spatial distribution of soil CO2 efflux values also showed changes in magnitude and amplitude, with higher CO2 efflux values measured along a trending WNW-ESE zone. Subsurface magma movement is proposed as a cause for the observed changes in the total output of diffuse CO2 emission as well as for the spatial distribution of soil CO2 efflux. The increasing trend of total CO2 output suggests increasing pressurization of the volcanic-hydrothermal system, a mechanism capable of triggering dyke intrusion along the NWRZ of Tenerife in the near future or futures changes in the seismicity. This study demonstrates the importance of performing soil CO2 efflux surveys as an effective surveillance volcanic tool.

Volcanology: Lessons learned from Synthetic Aperture Radar imagery

NASA Astrophysics Data System (ADS)

Pinel, V.; Poland, M. P.; Hooper, A.

2014-12-01

Twenty years of continuous Earth observation by satellite SAR have resulted in numerous new insights into active volcanism, including a better understanding of subsurface magma storage and transport, deposition of volcanic materials on the surface, and the structure and development of volcanic edifices. This massive archive of data has resulted in fundamental leaps in our understanding of how volcanoes work - for example, identifying magma accumulation at supposedly quiescent volcanoes, even in remote areas or in the absence of ground-based data. In addition, global compilations of volcanic activity facilitate comparison of deformation behavior between different volcanic arcs and statistical evaluation of the strong link between deformation and eruption. SAR data are also increasingly used in timely hazard evaluation thanks to decreases in data latency and growth in processing and analysis techniques. The existing archive of SAR imagery is on the cusp of being enhanced by a new generation of satellite SAR missions, in addition to ground-based and airborne SAR systems, which will provide enhanced temporal and spatial resolution, broader geographic coverage, and improved availability of data to the scientific community. Now is therefore an opportune time to review the contributions of SAR imagery to volcano science, monitoring, and hazard mitigation, and to explore the future potential for SAR in volcanology. Provided that the ever-growing volume of SAR data can be managed effectively, we expect the future application of SAR data to expand from being a research tool for analyzing volcanic activity after the fact, to being a monitoring and research tool capable of imaging a wide variety of processes on different temporal and spatial scales as those processes are occurring. These data can then be used to develop new models of how volcanoes work and to improve quantitative forecasts of volcanic activity as a means of mitigating risk from future eruptions.

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.

Recent and Hazardous Volcanic Activity Along the NW Rift Zone of Piton De La Fournaise Volcano, La Réunion Island

NASA Astrophysics Data System (ADS)

Walther, G.; Frese, I.; Di Muro, A.; Kueppers, U.; Michon, L.; Metrich, N.

2014-12-01

Shield volcanoes are a common feature of basaltic volcanism. Their volcanic activity is often confined to a summit crater area and rift systems, both characterized by constructive (scoria and cinder cones; lava flows) and destructive (pit craters; caldera collapse) phenomena. Piton de la Fournaise (PdF) shield volcano (La Réunion Island, Indian Ocean) is an ideal place to study these differences in eruptive behaviour. Besides the frequent eruptions in the central Enclos Fouqué caldera, hundreds of eruptive vents opened along three main rift zones cutting the edifice during the last 50 kyrs. Two short rift zones are characterized by weak seismicity and lateral magma transport at shallow depth (above sea level). Here we focus on the third and largest rift zone (15km wide, 20 km long), which extends in a north-westerly direction between PdF and nearby Piton des Neiges volcanic complex. It is typified by deep seismicity (up to 30 km), emitting mostly primitive magmas, testifying of high fluid pressures (up to 5 kbar) and large-volume eruptions. We present new field data (including stratigraphic logs, a geological map of the area, C-14 dating and geochemical analyses of the eruption products) on one of the youngest (~6kyrs) and largest lava field (Trous Blancs eruption). It extends for 24km from a height of 1800 m asl, passing Le Tampon and Saint Pierre cities, until reaching the coast. The source area of this huge lava flow has been identified in an alignment of four previously unidentified pit craters. The eruption initiated with intense fountaining activity, producing a m-thick bed of loose black scoria, which becomes densely welded in its upper part; followed by an alternation of volume rich lava effusions and strombolian activity, resulting in the emplacement of meter-thick, massive units of olivine-basalt alternating with coarse scoria beds in the proximal area. Activity ended with the emplacement of a dm-thick bed of glassy, dense scoria and a stratified lithic breccia, marking the pit crater foundering. Interestingly, this final stage compares well with the formation of pit craters on Kilauea volcano, Hawaii. Reoccurring of similar activity on the NW rift represents a major source of risk, for this now densely populated region (more than 150,000 people living in the affected area).

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.

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

Landslides density map of S. Miguel Island, Azores archipelago

NASA Astrophysics Data System (ADS)

Valadão, P.; Gaspar, J. L.; Queiroz, G.; Ferreira, T.

The Azores archipelago is located in the Atlantic Ocean and is composed of nine volcanic islands. S. Miguel, the largest one, is formed by three active, E-W trending, trachytic central volcanoes with caldera (Sete Cidades, Fogo and Furnas). Chains of basaltic cinder cones link those major volcanic structures. An inactive trachytic central volcano (Povoação) and an old basaltic volcanic complex (Nordeste) comprise the easternmost part of the island. Since the settlement of the island early in the 15th century, several destructive landslides triggered by catastrophic rainfall episodes, earthquakes and volcanic eruptions occurred in different areas of S. Miguel. One unique event killed thousands of people in 1522. Houses and bridges were destroyed, roads were cut, communications, water and energy supply systems became frequently disrupted and areas of fertile land were often buried by mud. Based on (1) historical documents, (2) aerial photographs and (3) field observations, landslide sites were plotted on a topographic map, in order to establish a landslide density map for the island. Data obtained showed that landslide hazard is higher on (1) the main central volcanoes where the thickness of unconsolidated pyroclastic deposits is considerable high and (2) the old basaltic volcanic complex, marked by deep gullies developed on thick sequences of lava flows. In these areas, caldera walls, fault scarps, steep valley margins and sea cliffs are potentially hazardous.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

The Late Ediacaran post-collisional volcano-sedimentary successions exposed in southern Sinai (Egypt) represent the last stage of magmatic activity associated with assembly of the northernmost segment of the Neoproterozoic Arabian-Nubian Shield. To clarify the age and tempo of post-collisional activity, three volcanic successions from southern Sinai were selected for the present study: the Sahiya, Iqna Shar'a and Meknas volcanics. They comprise a series of intermediate to silicic volcanic flows and their pyroclastic rocks. New zircon U-Pb dating by SIMS of the lava flows from the three successions yielded ages ranging between ca. 619 to 600 Ma. Combined with field evidence and the geochemical data, the obtained SIMS zircon ages enable us to recognize two phases of volcanic activity in southern Sinai at ca. 619-615 Ma and 606-600 Ma. Both age groups were found within the more northerly volcanic successions at Iqna Shar'a and Meknas and in both these sequences the younger phase uncomformably overlies the older phase. Only the older ages, ca. 615-619 Ma, were found in the Sahiya volcanics, exposed at the southern tip of Sinai. The ages of the youngest calc-alkaline volcanics in the study areas are similar to or slightly younger than the earliest phases of alkaline volcanism in southern Sinai, indicating coeval extrusion of calc-alkalic and alkalic A-type rocks. This observation corroborates similar observations documenting cogenetic calc-alkalic and alkalic plutons in the surrounding areas in southern Sinai. Geochemically, the volcanic rocks of the three successions display large silica variations and are mostly medium- to high-K calc-alkaline rocks. The first phase, from ca. 619-615 Ma, observed in all three volcanic suites, comprises basaltic andesite, andesite and dacite, whereas the second phase, from ca. 606-600 Ma and observed only in the northern volcanic suites (Iqna Shar'a and Meknas), comprises dacite, rhyodacite and rhyolite. In the Sahiya succession basal andesite and dacite have characteristics of low-silica adakitic rocks. The evolved rhyolites of the second phase have characteristics that are transitional to alkaline, A-type magmas but this is attributed to extensive fractionation and does not require a change in the tectonic regime. Although their eruption in a post-collisional setting, the Sahiya, Iqna Shar'a and Meknas volcanic suites all display geochemical fingerprints of subduction influence, interpreted to reflect remelting of previously formed arc material ca. 750-650 Ma in age. The formation of Late Ediacaran post-collisional lavas and tuffs in southern Sinai can be understood as a consequence of upwelling of hot asthenospheric material during thinning of the previously thickened lithosphere, leading to partial melting of mafic lower crust. The presence of inherited zircons indicates crustal contamination during evolution of the volcanic successions. Our results indicate that the studied volcanic successions correlate with the Dokhan volcanics of the northern Eastern Desert of Egypt. The earlier volcanic sequence also compares well with 625-600 Ma calc-alkaline plutonic rocks in the north Eastern Desert and Sinai, whereas the younger volcanic phase displays geochemical similarities with 610-585 Ma alkaline plutonic rocks in the north Eastern Desert and Sinai.

Development of mobile sensor for volcanic observation "HOMURA": Test campaign at Kirishima Iwo-yama, SW Japan

NASA Astrophysics Data System (ADS)

Kaneko, K.; Ito, K.; Iwahori, K.; Anbe, Y.

2015-12-01

Monitoring volcanoes near active craters is important to know symptoms and transitions of volcanic eruptions. In order to observe volcanic phenomena near craters according to the circumstance, monitoring system with unmanned robots are useful. We have been trying to develop a practical UGV-type robot, and have completed a prototype, which we named "Homura". Homura is a small-sized, vehicle-type robot with six wheels (750 x 430 x 310 mm in dimensions and a weight of about 12 kg). Homura is remotely controlled with mobile phone radio waves; it can move in volcanic fields and send real time data of sensors equipped in the vehicle to the base station. We carried out a test campaign of Homura from Feb. 19th to Apr. 8th, 2015 at Iwo-yama to examine if Homura can work for a few month in natural volcanic fields. Iwo-yama is one of craters in the Kirishima volcanic field, SW Japan; the area within 1 km from the crater was an off-limit area from Oct. 24th, 2014 to May 5th, 2015 because volcanic seismicity there was active and eruption might occur. On Feb. 19th, we carried and put Homura at the rim of the crater. Unfortunately, mobile phone connectivity was not entirely stable around Iwo-yama. Then, we decided not to move Homura and only to obtain real time data of the sensors (a camera, CO2 gas sensor, and thermometer). After we returned to our office, we operated Homura for one to two hours every day until Apr. 8th. Although the weather was often bad (rain, fog, or cold temperature) during the test campaign, we could completely operate Homura without any trouble. On Apr. 8th, the battery in Homura ran down. After we collected Homura from Iwo-yama and recharged the battery, Homura perfectly worked again. The results of this campaign indicate that Homura stably operates for a long time in volcanic field. Homura is useful as simple monitoring station in volcanic fields where mobile phone connection is available.

Earth Observations taken by Expedition 26 crewmember

NASA Image and Video Library

2011-01-11

ISS026-E-017074 (11 Jan. 2011) --- Emi Koussi volcano in Chad is featured in this image photographed by an Expedition 26 crew member on the International Space Station. The large Emi Koussi volcano is located in northern Chad at the southeastern end of the Tibesti Range. The dark volcanic rocks of the volcano provide a sharp contrast to the underlying tan and light brown sandstones exposed to the west, south, and east. Emi Koussi is a shield volcano formed from relatively low viscosity lavas—flowing more like motor oil as opposed to toothpaste—and explosively-erupted ignimbrites that produce a characteristic low and broad structure that covers a wide area (approximately 60 x 80 kilometers). This photograph highlights the entire volcanic structure; at 3,415 meters above sea level, Emi Koussi is the highest summit of the Sahara region. The summit area contains three calderas formed by powerful eruptions. Two older, and overlapping, calderas form a depression approximately 12 x 15 kilometers in area bounded by a distinct rim (center). According to scientists, the youngest and smallest caldera, Era Kohor, formed as a result of eruptive activity that occurred within the past 2 million years. Young volcanic features including lava flows and scoria cones are also thought to be less than 2 million years old. There are no historical records of eruptive activity at Emi Koussi, but there is an active thermal area on the southern flank of the volcano.

Tectonic Setting and Bimodal Magmatic Evolution of Eocene Volcanic Rocks of the Bijgerd-Kuh-e Kharchin area, Uromieh-Dokhtar Zone, Iran

NASA Astrophysics Data System (ADS)

Davarpanah, A.; Khalatbari-Jafari, M.; Babaie, H. A.; Krogstad, E. J.; Mobasher, K.; La Tour, T. E.; Deocampo, D. M.

2008-12-01

Geochemical composition and texture of the Middle and Late Eocene volcanic, volcaniclastic, and volcanic- sedimentary rocks in the Bijgerd-Kuh-e Kharchin area, northwest of Saveh, provide significant geochemical and geological clues for the tectonic and magmatic evolution of the Uromieh-Dokhtar volcanic-plutonic zone of Iran. The Middle Eocene volcanic rocks have an intermediate composition and include green tuff and tuffaceous sandstone with intercalated sandstone, sandy tuff, and shale. The shale has lenses of nummulite- bearing limestone with a Middle Eocene detrital age. The time between the Middle and Late Eocene volcanic activities in this area is marked by the presence of andesite and rhyolitic tuff. The Late Eocene succession is distinguished by the presence of four alternating levels (horizons) of intermediate lava and ignimbrite which we designate as Eig. The ignimbrites of the Eig sequence have a rhyolitic composition and include ignimbrite- breccia, ignimbrite-tuff, and ignimbrite-lava pairs. The volume of the felsic volcanic rocks in this sequence far exceeds that of the intermediate rocks, which makes it unlikely that they evolved through the magmatic differentiation of a basaltic magma. The presence of the nummulite-bearing limestone lenses, and sandstone and conglomerate interbeds between the ignimbrites, suggests a shallow marine environment for the pyroclastic deposition and probably the eruptions. The tuff and siltstone of the Est unit that sits above the first ignimbrite may represent deep water, Late Eocene deposit. Oligo-Miocene limestone of the Qom Formation unconformably overlies the uppermost Late Eocene ignimbrite. Washings from red marls give microfossils with Late Eocene age for the Eig sequence, which is synchronous with other paleontological evidence that puts the peak volcanic activity as Late Eocene in the Bijgerd-Kuh-e Kharchin area. Field and petrographic evidence for magma mixing/mingling is given by the presence of mafic- intermediate enclaves in the ignimbrite, hybrid breccias with felsic and mafic clasts, felsic pseudo-flames filled with intermediate lava, heterogeneity in the ignimbrite texture, and sieve texture and oscillatory zoning of plagioclase and opacitization of olivine in the intermediate lava. Geochemical analyses of the major and trace elements (including the REE) and rock texture and assemblages indicate the bimodal magmatic characteristics of the mafic-intermediate lavas and ignimbrites. The tuff and the breccia show a hybrid elemental distribution between those of rhyolite and basalt. The ignimbrites show more enriched compositions than those of the mafic and intermediate rocks on the chondrite-normalized trace element distribution diagram. The higher enrichment of the LREE in the ignimbrites may be due to a crustal contribution. The primitive mantle-normalized elemental distributions show a distinct depletion of Nb and Ti, which suggests a subduction-related volcanism during Eocene.

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".

Deposition and immersion-mode nucleation of ice by three distinct samples of volcanic ash

NASA Astrophysics Data System (ADS)

Schill, G. P.; Genareau, K.; Tolbert, M. A.

2015-07-01

Ice nucleation of volcanic ash controls both ash aggregation and cloud glaciation, which affect atmospheric transport and global climate. Previously, it has been suggested that there is one characteristic ice nucleation efficiency for all volcanic ash, regardless of its composition, when accounting for surface area; however, this claim is derived from data from only two volcanic eruptions. In this work, we have studied the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman microscopy coupled to an environmental cell. Ash from the Fuego (basaltic ash, Guatemala), Soufrière Hills (andesitic ash, Montserrat), and Taupo (Oruanui eruption, rhyolitic ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. In the present study, we find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice from 225 to 235 K at ice saturation ratios of 1.05 ± 0.01, comparable to the mineral dust proxy kaolinite. Since depositional ice nucleation will be more important at colder temperatures, fine volcanic ash may represent a global source of cold-cloud ice nuclei. For immersion freezing relevant to mixed-phase clouds, however, only the Oruanui ash exhibited appreciable heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

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

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.

Geothermal areas in Pakistan

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

Shuja, T.A.

1986-01-01

In this paper an attempt has been made to correlate the tectonic and geologic features with surface manifestations of geothermal activity in Pakistan to delineate prospective areas for exploration and development of geothermal energy. Underthrusting of the Arabian plate beneath the Eurasian plate has resulted in the formation of Chagai volcanic arc which extends into Iran. Quaternary volcanics in this environment, along with the presence of thermal springs, is an important geotectonic feature revealing the possible existence of geothermal fields. Geothermal activity in the northern areas of Pakistan, as evidenced by thermal springs, is the likely result of collision andmore » underthrusting of the Indian plate beneath the Eurasian plate. Numerous hot springs are found along the Main Mantle thrust and the Main Karakorum thrust in Chilas and Hunza areas respectively. The concentration of hot springs in Sind Province is also indicative of geothermal activity. A string of thermal seepages and springs following the alignment of the Syntaxial Bend in Punjab Province is also noteworthy from the geothermal viewpoint. In Baluchistan Province (southwest Pakistan), Hamun-e-Mushkel, a graben structure, also shows geothermal prospects on the basis of aeromagnetic studies.« less

The contribution of synchrotron X-ray computed microtomography to understanding volcanic processes.

PubMed

Polacci, Margherita; Mancini, Lucia; Baker, Don R

2010-03-01

A series of computed microtomography experiments are reported which were performed by using a third-generation synchrotron radiation source on volcanic rocks from various active hazardous volcanoes in Italy and other volcanic areas in the world. The applied technique allowed the internal structure of the investigated material to be accurately imaged at the micrometre scale and three-dimensional views of the investigated samples to be produced as well as three-dimensional quantitative measurements of textural features. The geometry of the vesicle (gas-filled void) network in volcanic products of both basaltic and trachytic compositions were particularly focused on, as vesicle textures are directly linked to the dynamics of volcano degassing. This investigation provided novel insights into modes of gas exsolution, transport and loss in magmas that were not recognized in previous studies using solely conventional two-dimensional imaging techniques. The results of this study are important to understanding the behaviour of volcanoes and can be combined with other geosciences disciplines to forecast their future activity.

Jovian dust streams: A monitor of Io's volcanic plume activity

USGS Publications Warehouse

Kruger, H.; Geissler, P.; Horanyi, M.; Graps, A.L.; Kempf, S.; Srama, R.; Moragas-Klostermeyer, G.; Moissl, R.; Johnson, T.V.; Grun, E.

2003-01-01

Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s-1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10-3 and 10 kg s-1, and is typically in the range of 0.1 to 1 kg s-1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes. Copyright 2003 by the American Geophysical Union.

Geochemical and Isotopic Evidences of the Magmatic Sources in the Eastern Sector of the Trans-Mexican Volcanic Belt: Xihuingo-Chichicuautla Volcanic Field

NASA Astrophysics Data System (ADS)

Valadez, S.; Martinez-serrano, R.; Juarez-Lopez, K.; Solis-Pichardo, G.; Perez-Arvizu, O.

2011-12-01

The study of magmatism in the Trans-Mexican Volcanic Belt (TMVB) has great importance due to several features such as its obliquity with respect to the Middle American Trench and its petrological and geochemical variability, which are not common in most typical volcanic arcs. Although several papers have contributed significantly to the understanding of most important magmatic processes in this province, there are still several questions such as the characterization of magmatic sources. In the present work, we provide new stratigraphic, petrographic, geochemical and Sr, Nd and Pb isotopic data as well as some K-Ar age determinations from the Xihuingo-Chichicuautla volcanic field (XCVF), located at the eastern part of the TMVB, with the aim to identify the magmatic sources that produced the main volcanic rocks. The volcanic structures in the XCVF are divided in two main groups according to the petrographic and geochemical compositions: 1) dacitic domes, andesitic lava flows and some dacitic-rhyolitic ignimbrites and 2) scoria cones, shield volcanoes and associated lava flows of basalt to basaltic-andesite composition. Distribution of most volcanic structures is probably controlled by NE-SW fault and fractures system. This fault system was studied by other authors who established that volcanic activity started ca. 13.5 Ma ago, followed by a volcanic hiatus of ca. 10 Ma, and the late volcanic activity began ca. 3 to 1 Ma. In this work we dated 2 rock samples by K-Ar method, which yielded ages of 402 and 871 Ka, which correspond to the most recent volcanic activity in this study area. The volcanic rocks of the XCVF display compositions from basalts to rhyolites but in general all rocks show trace element patterns typical of magmatic arcs. However, we can identify two main magmatic sources: a depleted magmatic source represented by dacitic-andesitic rocks which present a LILE enrichment with respect to HFSE indicating that a magmatic source was modified by fluids derived from the subduction processes. These magmas probably suffered fractional crystallization and minor assimilation in the continental crust. Sr, Nd isotopic compositions for this first group display the most radiogenic values (87Sr/86Sr from 0.7046 to 0.7047 and ɛNd from 2.2 to 2.8). The second source for the basaltic-andesite and basalt could be associated with an enriched mantle. These rocks present a minor LILE enrichment with respect to HSFE, and Sr and Nd isotopic values less radiogenic than the felsic rocks of the first group (87Sr/86Sr from 0.7040 to 0.7045 and ɛNd from 3.1 to 4.8). According to these evidences we can establish that the magmas emplaced in the study area were produced from a heterogeneous mantle source with complex magmatic processes combined with different interaction degrees between the magmas and continental crust.

Submarine Volcanic Morphology of Santorini Caldera, Greece

NASA Astrophysics Data System (ADS)

Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

2012-04-01

Santorini volcanic group form the central part of the modern Aegean volcanic arc, developed within the Hellenic arc and trench system, because of the ongoing subduction of the African plate beneath the European margin throughout Cenozoic. It comprises three distinct volcanic structures occurring along a NE-SW direction: Christianna form the southwestern part of the group, Santorini occupies the middle part and Koloumbo volcanic rift zone extends towards the northeastern part. The geology of the Santorini volcano has been described by a large number of researchers with petrological as well as geochronological data. The offshore area of the Santorini volcanic field has only recently been investigated with emphasis mainly inside the Santorini caldera and the submarine volcano of Kolumbo. In September 2011, cruise NA-014 on the E/V Nautilus carried out new surveys on the submarine volcanism of the study area, investigating the seafloor morphology with high-definition video imaging. Submarine hydrothermal vents were found on the seafloor of the northern basin of the Santorini caldera with no evidence of high temperature fluid discharges or massive sulphide formations, but only low temperature seeps characterized by meter-high mounds of bacteria-rich sediment. This vent field is located in line with the normal fault system of the Kolumbo rift, and also near the margin of a shallow intrusion that occurs within the sediments of the North Basin. Push cores have been collected and they will provide insights for their geochemical characteristics and their relationship to the active vents of the Kolumbo underwater volcano. Similar vent mounds occur in the South Basin, at shallow depths around the islets of Nea and Palaia Kameni. ROV exploration at the northern slopes of Nea Kameni revealed a fascinating underwater landscape of lava flows, lava spines and fractured lava blocks that have been formed as a result of 1707-1711 and 1925-1928 AD eruptions. A hummocky topography at the area that lies between the town of Fira on the main island of Santorini and Nea Kammeni has been revealed. The lower slopes were covered with landslide debris which consisted of lava blocks mostly mantled with soft sediment. At the upper slopes an abrupt cliff face was exposed that was highly indurated by biologic material. At the top of a volcanic dome, a crater with its deepest part at 43m, its rim at about 34m with an approximately 8m diameter was also found. Shimmery water with temperatures as much as 25°C above ambient was observed there but the source of venting has not yet been found. The combination of ROV video footage and multibeam data provide new information about the main morphological characteristics of Santorini Caldera which demonstrates the intense geodynamic processes occurring at the central part of the active Hellenic volcanic arc. These results will be useful for the interpretation of understanding the offshore volcanic area and its linkage with the onshore structures.

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.

Spatio-temporal evolution of the Tuxtla Volcanic Field

NASA Astrophysics Data System (ADS)

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

2010-12-01

Mapping of the Tuxtla Volcanic Field (TVF), located in Veracruz, Mexico, through the use of digital elevation models, aerial photography, and field confirmation has found 353 distinct cones, 4 large composite volcanoes, and 42 maars. Eruptive activity in the TVF began in the late Miocene, underwent a quiescent period approximately 2.6-0.8 Ma, and continues into historic times with the most recent eruption occurring at San Martín Tuxtla volcano in 1793. The covariance of the minimum cone separation in the TVF indicates that, despite the influence of clear vent alignments following regional faulting trends, the field as a whole is anticlustered. Dividing the cones by morphometric age shows that while the older cones have an anti-clustered distribution, the younger cones (<50 Ka) are clustered. The younger cones display a stronger spatial association with the Anegada fault than their predecessors, are more likely to form in aligned groups of similarly-sized cones, and are clustered in two areas: the area immediately surrounding San Martín Tuxtla and an area approximately 3 km east of Laguna Catemaco. These areas of concentrated volcanism roughly correspond to the locations of two gravity anomalies previously identified in the area. While the average height/width ratio is equal between the two clusters, the cones in the eastern group are significantly smaller than their counterparts in the western group. The maars of the TVF are mostly located within the younger volcanic series, west of Laguna Catemaco, and have an anticlustered distribution; many of the maars are evenly spaced along curved lines, where they are weakly grouped according to crater diameter. Results indicate volcanism TVF has undergone continued spatial restriction over time, concentrating in the western half of the TVF with the onset of the eruption of the younger volcanic series 0.8 Ma and further contracting along the principle fault system within the last 50 Ka.

Cumulative effects of volcanic ash on the food preferences of two Orthopteran species.

PubMed

Fernández-Arhex, Valeria; Amadio, Maria E; Bruzzone, Octavio A

2017-08-01

Inert dusts are an early form of insecticide which is still in use. One of the most common inert dusts is volcanic ash. In order to study the reaction of rangeland grasshoppers, Dichroplus vittigerum (Acrididae) and a katydid, Burgilis mendosensis (Phaneropteridae), to the presence of volcanic ash in their food sources and how this reaction changed as a function of time, we conducted paired preference tests between clean leaves of their preferred host plant and leaves exposed to volcanic ash of different grain size. The behavioral response was measured as the rating on the Thurstonian preference scale of leaves with ash in relation to clean leaves. The results showed that the avoidance of volcanic ash increased as a function of time in both species. Both species studied are occasionally exposed to volcanic activity, and come from an area in which a volcanic eruption had recently occurred. As their populations did not decrease after the ash fall, we propose that some behavioral responses such as avoidance of places with ash, works as tolerance mechanism to inert dusts exposure. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Geophysical exploration on the subsurface geology of La Garrotxa monogenetic volcanic field (NE Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Bolós, Xavier; Barde-Cabusson, Stéphanie; Pedrazzi, Dario; Martí, Joan; Casas, Albert; Lovera, Raúl; Nadal-Sala, Daniel

2014-11-01

We applied self-potential (SP) and electrical resistivity tomography (ERT) to the exploration of the uppermost part of the substrate geology and shallow structure of La Garrotxa monogenetic volcanic field, part of the European Neogene-Quaternary volcanic province. The aim of the study was to improve knowledge of the shallowest part of the feeding system of these monogenetic volcanoes and of its relationship with the subsurface geology. This study complements previous geophysical studies carried out at a less detailed scale and aimed at identifying deeper structures, and together will constitute the basis to establish volcanic susceptibility in La Garrotxa. SP study complemented previous smaller-scale studies and targeted key areas where ERT could be conducted. The main new results include the generation of resistivity models identifying dykes and faults associated with several monogenetic cones. The combined results confirm that shallow tectonics controlling the distribution of the foci of eruptive activity in this volcanic zone mainly correspond to NNW-SSE and accessorily by NNE-SSW Neogene extensional fissures and faults and concretely show the associated magmatic intrusions. These structures coincide with the deeper ones identified in previous studies, and show that previous Alpine tectonic structures played no apparent role in controlling the loci of this volcanism. Moreover, the results obtained show that the changes in eruption dynamics occurring at different vents located at relatively short distances in this volcanic area are controlled by shallow stratigraphical, structural and hydrogeological differences underneath these monogenetic volcanoes.

Morphostructural study and type of volcanism of submarine volcanoes over the Pitcairn hot spot in the South Pacific

NASA Astrophysics Data System (ADS)

Binard, Nicolas; Hékinian, Roger; Stoffers, Peter

1992-06-01

Undersea volcanoes found at about 80 km southeast of the island of Pitcairn, are believed to be the manifestation of a hot-spot activity located near 129°30'W 25°10'S, along the strike of the Mururoa-Gambier-Pitcairn volcanic alignment. Hydrothermal activities and recent volcanic flows were observed on the two largest (20 km in basal diameter) and shallowest (60 m and 450 m depth) volcanoes. More than twenty other smaller volcanic edifices ( < 500 m in height) were mapped during a Seabeam survey covering an area of about 8000 km 2. The edifices from the Pitcairn region are conical with a low degree of flatness (summit/basal diameters ratio <0.25), and consist of fresh alkali-enriched lava flows. The other truncated edifices with a high degree of flatness ( > 0.25) made up of ancient MORB-type tholeiitic rocks are inferred to be inherited from the EPR axial regions. The shallow volcanic activity which occurred on the two largest edifices are classified as: (1) reactive eruptions, with hydromagmatic activities, giving rise to volcanic ejecta, bombs, xenoliths, and ash, and (2) quiet eruptions which formed pillows and/or lobated lavas, and large massive flows. Intrusives (dyke and sill) were observed, cutting through the volcanic ejecta near the summit ( < 500 m depth) of the seamounts. The general structural orientations of the rift zones recognized from the bathymetry of individual volcanoes (N160°-180°, N80°, N30° and N120°) are comparable to those observed in the Society and Austral hot-spot regions. These orientations were inferred as corresponding to the structural discontinuities of the ancient oceanic crust, and to the regional stress field of the Pacific plate. Rock samples from the Pitcairn region consist of alkali-basalts, basanites, trachyandesites, and trachytes which are closer in chemical composition to some of the volcanics from the Society rather than to those from the Austral hot-spot regions.

Monitoring the UPS and Downs of Sumatra and Java with D-Insar Time-Series

NASA Astrophysics Data System (ADS)

Chaussard, E.; Amelung, F.

2010-12-01

We performed, for the first time, a global D-InSAR survey of the Indonesian islands of Sumatra and Java to define locations where deformation is occurring. The goals of this study are 1) to create an inventory of actively deforming volcanic centers and 2) monitor all types of ground motion. This work provides ground deformation data for previously unmonitored areas and can assist the Indonesian authorities to improve hazards assessment. The D-InSAR survey covers an area of about 500 000 km2 and 3000 km long on the islands of Sumatra, Java and Bali. We used ALOS data from 45 tracks and more than 1500 granules obtained from the Alaska Satellite Facility (ASF) through the US Government Research Consortium (USGRC). We completed more than 1000 interferograms spanning a period from the end of 2006 to the beginning of 2009. L-band SAR images enable deformation mapping at global scales even in highly vegetated areas where C-band signal experiences loss of coherence. To identify locations where ground deformations are occurring, we used multiple SAR acquisitions of the same area and performed time series analysis using the Small BAseline Subset (SBAS) method. Interferograms with a maximum spatial baseline of 3000 m were phase-unwrapped and subsequently inverted for the phase with respect to the first acquisition. Temporal coherence of each pixel is computed on the set of interferograms in order to select only pixels with high temporal coherence. The compiled InSAR velocity map reveals the background level of activity of the 84 volcanic centers constituting the Sumatra, Java and Bali volcanic arcs. We identified possible uplift at 6 volcanic centers: Agung (Bali), Lamongan (Java), Lawu (Java), Slamet (Java), Kerinci (Sumatra) and Sinabung (Sumatra). Moreover, we identified subsidence in 5 major cities and 1 coastal area. Subsidence rates range from 6 cm/yr in Medan, the largest city of Sumatra, to more than 15 cm/yr in Jakarta. These major subsidence areas are probably due to ground water extraction needed to support the increasing population and industrial activities.

Contribution of ground surface altitude difference to thermal anomaly detection using satellite images: Application to volcanic/geothermal complexes in the Andes of Central Chile

NASA Astrophysics Data System (ADS)

Gutiérrez, Francisco J.; Lemus, Martín; Parada, Miguel A.; Benavente, Oscar M.; Aguilera, Felipe A.

2012-09-01

Detection of thermal anomalies in volcanic-geothermal areas using remote sensing methodologies requires the subtraction of temperatures, not provided by geothermal manifestations (e.g. hot springs, fumaroles, active craters), from satellite image kinetic temperature, which is assumed to correspond to the ground surface temperature. Temperatures that have been subtracted in current models include those derived from the atmospheric transmittance, reflectance of the Earth's surface (albedo), topography effect, thermal inertia and geographic position effect. We propose a model that includes a new parameter (K) that accounts for the variation of temperature with ground surface altitude difference in areas where steep relief exists. The proposed model was developed and applied, using ASTER satellite images, in two Andean volcanic/geothermal complexes (Descabezado Grande-Cerro Azul Volcanic Complex and Planchón-Peteroa-Azufre Volcanic Complex) where field data of atmosphere and ground surface temperature as well as radiation for albedo calibration were obtained in 10 selected sites. The study area was divided into three zones (Northern, Central and Southern zones) where the thermal anomalies were obtained independently. K value calculated for night images of the three zones are better constrained and resulted to be very similar to the Environmental Lapse Rate (ELR) determined for a stable atmosphere (ELR > 7 °C/km). Using the proposed model, numerous thermal anomalies in areas of ≥ 90 m × 90 m were identified that were successfully cross-checked in the field. Night images provide more reliable information for thermal anomaly detection than day images because they record higher temperature contrast between geothermal areas and its surroundings and correspond to more stable atmospheric condition at the time of image acquisition.

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

Volcano hazards at Newberry Volcano, Oregon

USGS Publications Warehouse

Sherrod, David R.; Mastin, Larry G.; Scott, William E.; Schilling, Steven P.

1997-01-01

Newberry volcano is a broad shield volcano located in central Oregon. It has been built by thousands of eruptions, beginning about 600,000 years ago. At least 25 vents on the flanks and summit have been active during several eruptive episodes of the past 10,000 years. The most recent eruption 1,300 years ago produced the Big Obsidian Flow. Thus, the volcano's long history and recent activity indicate that Newberry will erupt in the future. The most-visited part of the volcano is Newberry Crater, a volcanic depression or caldera at the summit of the volcano. Seven campgrounds, two resorts, six summer homes, and two major lakes (East and Paulina Lakes) are nestled in the caldera. The caldera has been the focus of Newberry's volcanic activity for at least the past 10,000 years. Other eruptions during this time have occurred along a rift zone on the volcano's northwest flank and, to a lesser extent, the south flank. Many striking volcanic features lie in Newberry National Volcanic Monument, which is managed by the U.S. Forest Service. The monument includes the caldera and extends along the northwest rift zone to the Deschutes River. About 30 percent of the area within the monument is covered by volcanic products erupted during the past 10,000 years from Newberry volcano. Newberry volcano is presently quiet. Local earthquake activity (seismicity) has been trifling throughout historic time. Subterranean heat is still present, as indicated by hot springs in the caldera and high temperatures encountered during exploratory drilling for geothermal energy. This report describes the kinds of hazardous geologic events that might occur in the future at Newberry volcano. A hazard-zonation map is included to show the areas that will most likely be affected by renewed eruptions. In terms of our own lifetimes, volcanic events at Newberry are not of day-to-day concern because they occur so infrequently; however, the consequences of some types of eruptions can be severe. When Newberry volcano becomes restless, be it tomorrow or many years from now, the eruptive scenarios described herein can inform planners, emergency response personnel, and citizens about the kinds and sizes of events to expect.

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.

Multidisciplinary study (CO2 flux, ERT, self-potential, permeability and structural surveys) in Fondi di Baia, Astroni and Agnano volcanoes: insights for the structural architecture of the Campi Flegrei caldera (southern Italy)

NASA Astrophysics Data System (ADS)

Isaia, Roberto; Carapezza, Maria Luisa; Conti, Eric; Giulia Di Giuseppe, Maria; Lucchetti, Carlo; Prinzi, Ernesto; Ranaldi, Massimo; Tarchini, Luca; Tramparulo, Francesco; Troiano, Antonio; Vitale, Stefano; Cascella, Enrico; Castello, Nicola; Cicatiello, Alessandro; Maiolino, Marco; Puzio, Domenico; Tazza, Lucia; Villani, Roberto

2017-04-01

Recent volcanism at Campi Flegrei caldera produced more than 70 eruptions in the last 15 ka formed different volcanic edifices. The vent distribution was related to the main volcano-tectonic structure active in the caldera along which also concentrated part of the present hydrothermal and fumarolic activity, such as in the Solfatara area. In order to define the role of major faults in the Campi Flegrei Caldera, we analyzed some volcanic craters (Fondi di Baia and Astroni) and the Agnano caldera, by means of different geochemical and geophysical technics including CO2 flux, electrical resistivity (ERT), self-potential and permeability surveys. We provided some ERT profiles and different maps of geochemical and geophysical features. Major fault planes were identified comparing ERT imaging with alignments of anomalies in maps. The results can improve the knowledge on the present state of these volcanoes actually not fully monitored though included in the area with high probability of future vent opening within the Campi Flegrei caldera.

Surface temperature monitoring by integrating satellite data and ground thermal camera network on Solfatara Crater in Campi Flegrei volcanic area (Italy)

NASA Astrophysics Data System (ADS)

Buongiorno, M. F.; Musacchio, M.; Silvestri, M.; Vilardo, G.; Sansivero, F.; caPUTO, T.; bellucci Sessa, E.; Pieri, D. C.

2017-12-01

Current satellite missions providing imagery in the TIR region at high spatial resolution offer the possibility to estimate the surface temperature in volcanic area contributing in understanding the ongoing phenomena to mitigate the volcanic risk when population are exposed. The Campi Flegrei volcanic area (Italy) is part of the Napolitan volcanic district and its monitored by INGV ground networks including thermal cameras. TIRS on LANDSAT and ASTER on NASA-TERRA provide thermal IR channels to monitor the evolution of the surface temperatures on Campi Flegrei area. The spatial resolution of the TIR data is 100 m for LANDSAT8 and 90 m for ASTER, temporal resolution is 16 days for both satellites. TIRNet network has been developed by INGV for long-term volcanic surveillance of the Flegrei Fields through the acquisition of thermal infrared images. The system is currently comprised of 5 permanent stations equipped with FLIR A645SC thermo cameras with a 640x480 resolution IR sensor. To improve the systematic use of satellite data in the monitor procedures of Volcanic Observatories a suitable integration and validation strategy is needed, also considering that current satellite missions do not provide TIR data with optimal characteristics to observe small thermal anomalies that may indicate changes in the volcanic activity. The presented procedure has been applied to the analysis of Solfatara Crater and is based on 2 different steps: 1) parallel processing chains to produce ground temperature data both from satellite and ground cameras; 2) data integration and comparison. The ground cameras images generally correspond to views of portion of the crater slopes characterized by significant thermal anomalies due to fumarole fields. In order to compare the satellite and ground cameras it has been necessary to take into account the observation geometries. All thermal images of the TIRNet have been georeferenced to the UTM WGS84 system, a regular grid of 30x30 meters has been created to select polygonal areas corresponding only to the cells containing the georeferenced TIR images acquired by different TIRnet stations. Preliminary results of this integration approach has been analyzed in order to produce systematic reports to the Italian Civil Protection for the Napolitan Volcanoes.

Spatially Variable CO2 Degassing in the Main Ethiopian Rift: Implications for Magma Storage, Volatile Transport, and Rift-Related Emissions

NASA Astrophysics Data System (ADS)

Hunt, Jonathan A.; Zafu, Amdemichael; Mather, Tamsin A.; Pyle, David M.; Barry, Peter H.

2017-10-01

Deep carbon emissions from historically inactive volcanoes, hydrothermal, and tectonic structures are among the greatest unknowns in the long-term (˜Myr) carbon cycle. Recent estimates of diffuse CO2 flux from the Eastern Rift of the East African Rift System (EARS) suggest this could equal emissions from the entire mid-ocean ridge system. We report new CO2 surveys from the Main Ethiopian Rift (MER, northernmost EARS), and reassess the rift-related CO2 flux. Since degassing in the MER is concentrated in discrete areas of volcanic and off-edifice activity, characterization of such areas is important for extrapolation to a rift-scale budget. Locations of hot springs and fumaroles along the rift show numerous geothermal areas away from volcanic edifices. With these new data, we estimate total CO2 emissions from the central and northern MER as 0.52-4.36 Mt yr-1. Our extrapolated flux from the Eastern Rift is 3.9-32.7 Mt yr-1 CO2, overlapping with lower end of the range presented in recent estimates. By scaling, we suggest that 6-18 Mt yr-1 CO2 flux can be accounted for by magmatic extension, which implies an important role for volatile-enriched lithosphere, crustal assimilation, and/or additional magmatic intrusion to account for the upper range of flux estimates. Our results also have implications for the nature of volcanism in the MER. Many geothermal areas are found >10 km from the nearest volcanic center, suggesting ongoing hazards associated with regional volcanism.

Observed anomalous changes on diffuse CO2 emission at the summit crater of Teide volcano (Tenerife, Canary Islands, Spain): a geochemical evidence of volcanic unrest?

NASA Astrophysics Data System (ADS)

Perez, N. M.; Melián, G.; Asensio-Ramos, M.; Padrón, E.; Alonso Cótchico, M.; Hernández, P. A.; Rodríguez, F.; D'Auria, L.; García-Merino, M.; Padilla, G. D.; Burns, F.; Amonte, C.; García, E.; García-Hernández, R.; Barrancos, J.; Morales-Ocaña, C.; Calvo, D.; Vela, V.; Pérez, A.

2017-12-01

Tenerife (2034 km2) is the largest of the Canary Islands and hosts a central volcanic complex, Las Cañadas, which is characterized by the eruption of differentiated magmas. Laying inside Las Cañadas a twin stratovolcanoes system Pico Viejo and Teide, has been developed. Although Teide volcano shows weak fumarolic system, volcanic gas emissions observed in the summit area are mainly controlled by high rates of diffuse CO2 degassing. Soil CO2 efflux surveys have been performed at the summit crater of Teide volcano since 1999 according to the accumulation chamber method to monitor changes of volcanic activity. Soil CO2 efflux and soil temperature have been measured in sites homogeneously distributed within an area of about 6,972 m2 inside the summit crater. Historical seismic activity in Tenerife has been mainly characterized by low- to moderate-magnitude events (M <2.5), and most of epicenters clustered in an offshore area SE of Tenerife. Very few earthquakes have occurred in other areas, including Teide volcano. Since November 2016 more than 100 small magnitude earthquakes, with typical features of the microseismicity of hydrothermal systems, at depths usually ranging between 5 and 15 km located beneath Teide volcano have been recorded. On January 6th 2017 a M=2.5 earthquake was recorded in the area, being one of the strongest events recorded since 2004. Between October 11 and December 13, 2016, a continuous increase on the diffuse CO2 emission was registered preceding the occurrence of the 2.5 seismic event, from 21.3±2.0 to 101.7±20.7 t d-1. In Febraury 2017, the diffuse CO2 emission rate showed a maximum value (176±35 t/d) and has remained at relatively high values in the range 67-176 t/d. The observed increase on the diffuse CO2 emission, likely due to the increase of fluid pressure in the hydrothermal-magmatic system of Tenerife, might be a geochemical evidence of a future volcanic unrest at Tenerife Island.

Evidence for sub-lacustrine volcanic activity in Lake Bolsena (central Italy) revealed by high resolution seismic data sets

NASA Astrophysics Data System (ADS)

Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd; Schuerer, Anke

2017-06-01

The Bolsena caldera that formed between 0.6 and 0.2 Ma has a well preserved structural rim, which makes it an ideal site to study the tectonic and volcanic evolution of calderas. However, the main area is covered by a 150 m deep lake which makes it rather difficult to investigate the subsurface structure directly. To overcome this problem new high resolution hydro-acoustic surveys using a multichannel reflection seismic system and a sediment echo-sounder system were conducted in September 2012. As space was limited we used a rowing boat towed by a rubber boat to handle a 36 m long and 24 channel streamer to receive seismic reflections produced using a Mini GI-Gun (0.25 l). The subsurface structure of Lake Bolsena was imaged up to a sediment depth of 190 m, which is estimated to have filled over a period of 333 kyrs. However, massive pyroclastic flow deposits found in the deeper parts of the basin indicate an initial infill of volcanic deposits from two adjacent younger calderas, the Latera (W) and Montefiascone (SE) calderas. Our data suggest that the caldera has a long history of active volcanism, because the lacustrine sediments show post-sedimentary influences of geothermal fluids. We mapped several mound structures at various stratigraphic depths. Two volcanic structures outcrop at the modern lake surface implying recent activity. One of these structures is hardly covered by sediments and has a crater-like feature in its summit. The other structure shows a pockmark-like depression on top. Another observable feature is a partially sediment filled crater located in the western part of the lake which further implies the existence of a magma chamber located beneath the Bolsena caldera. Since the late Pleistocene and Holocene, the sedimentation was mainly hemipelagic evidenced by a sediment drape of up to 10 m thick sediment drape on the uppermost sediments. Beneath the drape we found evidence for a distal tephra layer likely related to an explosive eruption from the Campanian Volcanic Province occurring as the Neapolitan Yellow Tuff. Our new geophysical data set is a valuable record with a potential to constrain the sedimentary and volcanic evolution of the Vulsini Volcanic District in areas that have not been assessed previously due to logistical challenges of conducting surveys in water-filled settings.

Long-term Acoustic Real-Time Sensor for Polar Areas (LARA)

DTIC Science & Technology

2014-09-30

volcanic eruptions forecast for the near future, and the LARA moorings will allow us to observe the accuracy of these models in real-time. TRANSITIONS...systems at AUTEC and SCORE. In addition LARA technology will be useful for real-time monitoring of deep-ocean seismic and volcanic activity (e.g...M.J., Matsumoto, H., and Butterfield, D.A. (2012): Seismic precursors and magma ascent before the April 2011 eruption at Axial Seamount. Nature

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.

Igneous activity and related ore deposits in the western and southern Tushar Mountains, Marysvale volcanic field, west-central Utah

USGS Publications Warehouse

Steven, Thomas A.

1984-01-01

PART A: Igneous activity in the Marysvale volcanic field of western Utah can be separated into many episodes of extrusion, intrusion, and hydrothermal activity. The rocks of the western Tushar Mountains, near the western part of the volcanic field, include intermediate-composition, calc-alkalic volcanic rocks erupted from scattered volcanoes in Oligocene through earliest Miocene time and related monzonitic intrusions emplaced 24-23 m.y. ago. Beginning 22-21 m.y. ago and extending through much of the later Cenozoic, a bimodal basalt-rhyolite assemblage was erupted widely throughout the volcanic field. Only volcanic and intrusive rocks belonging to the rhyolitic end member of this bimodal assemblage are present in the western Tushar Mountains; most of these rocks either fill the Mount Belknap caldera (19 m.y. old) or are part of the rhyolite of Gillies Hill (9---8 m.y. old). Episodic hydrothermal activity altered and mineralized rocks at many places in the western Tushar Mountains during Miocene time. The earliest activity took place in and adjacent to monzonitic calcalkalic intrusions emplaced in the vicinity of Indian Creek and Cork Ridge. These rocks were widely propylitized, and gold-bearing quartz-pyrite-carbonate veins formed in local fractures. Hydrothermal activity associated with the Mount Belknap caldera mobilized and redeposited uranium contained in the caldera-fill rocks and formed primary concentrations of lithophile elements (including molybdenum and uranium) in the vicinity of intrusive bodies. Hydrothermal activity associated with the rhyolite of Gillies Hill altered and mineralized rocks at several places along the fault zone that marks the western margin of the Tushar Mountains; the zoned alunite and gold deposits at Sheep Rock, the gold deposit at the Sunday Mine, and an alunite deposit near Indian Creek were thus produced. Resetting of isotopic ages suggests that another center of hydrothermally altered rocks associated with a buried pluton about 16 m.y. old may exist near Indian Creek just west of the Mount Belknap caldera. Geophysical evidence confirms the probability of a buried pluton near Indian Creek, and also indicates that another buried pluton probably exists beneath the 9-m.y.-old mineralized area at Sheep Rock. The mineral potential of the different hydrothermal systems, and the types of minerals deposited probably vary considerably from one period of mineralization to another and from one depth environment to another within a given system. PART B: The Big John caldera, on the western flank of the Tushar Mountains in the Marysvale volcanic field in west-central Utah, formed 23-22 m.y. ago in response to ash-flow eruptions of the Delano Peak Tuff Member of the Bullion Canyon Volcanics. These eruptions were near the end of the period of Oligocene-early Miocene calc-alkalic igneous activity that built a broad volcanic plateau in this part of Utah. About 22 m.y. ago, the composition of rocks erupted changed to a bimodal assemblage of mafic and silicic volcanics that was erupted episodically through the remainder of Cenozoic time. The alkali rhyolites are uranium rich in part, and are associated with all the known uranium deposits in the Marysvale volcanic field. The Big John caldera was a broad drained basin whose floor was covered by a layer of stream gravels when ash flows from the western source area of the Mount Belknap Volcanics filled the caldera with the Joe Lott Tuff Member about 19 m.y. ago. Devitrified and zeolitized rocks in the caldera fill have lost one-quarter to one-half of the uranium contained in the original magma. This mobilized uranium probably moved into the hydrologic regime, and some may have been redeposited in stream gravels underlying the Joe Lott within the caldera, or in gravels filling the original drainage channel that extended south from the caldera.

Trace Element Geochemistry of Basaltic Tephra in Maar Cores; Implications for Centre Correlation, Field Evolution, and Mantle Source Characteristics of the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Hopkins, J. L.; Leonard, G.; Timm, C.; Wilson, C. J. N.; Neil, H.; Millet, M. A.

2014-12-01

Establishing volcanic hazard and risk management strategies hinges on a detailed understanding of the type, timing and tephra dispersal of past eruptions. In order to unravel the pyroclastic eruption history of a volcanic field, genetic links between the deposits and eruption source centre need to be established. The Auckland Volcanic Field (AVF; New Zealand) has been active for ca. 200 kyr and comprises ca. 53 individual centres covering an area of ca. 360km2. These centres show a range of sizes and eruptive styles from maar craters and tuff rings, to scoria cones and lava flows consistent with both phreatomagmatic and magmatic eruptions. Superimposition of the metropolitan area of Auckland (ca. 1.4 million inhabitants) on the volcanic field makes it critically important to assess the characteristics of the volcanic activity, on which to base assessment and management of the consequent hazards. Here we present a geochemical approach for correlating tephra deposits to their source centres. To acquire the most complete stratigraphic record of pyroclastic events, maar crater cores from different locations, covering various depths and thus ages across the field were selected. Magnetic susceptibility and x-ray density scanning of the cores was used to identify the basaltic tephra horizons, which were sampled and in-situ analysis of individual shards undertaken for major and trace elements using EPMA and LA-ICP-MS techniques, respectively. Our results show that tephra shard trace element ratios are comparable and complementary to the AVF whole rock database. The use of specific trace element ratios (e.g. Gd/Yb vs. Zr/Yb) allows us to fingerprint and cross correlate tephra horizons between cores and, when coupled with newly acquired 40Ar-39Ar age dating and eruption size estimates, correlate horizons to their source centres. This integrated style of study can provide valuable information to help volcanic hazard management and forecasting, and mitigation of related risks.

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

Submarine basaltic fountain eruptions in a back-arc basin during the opening of the Japan Sea

NASA Astrophysics Data System (ADS)

Hosoi, Jun; Amano, Kazuo

2017-11-01

Basaltic rock generated during the middle Miocene opening of the Japan Sea, is widely distributed on the back-arc side of the Japanese archipelago. Few studies have investigated on submarine volcanism related to opening of the Japan Sea. The present study aimed to reconstruct details of the subaqueous volcanism that formed the back-arc basin basalts (BABB) during this event, and to discuss the relationship between volcanism and the tectonics of back-arc opening, using facies analyses based on field investigation. The study area of the southern Dewa Hills contains well-exposed basalt related to the opening of the Japan Sea. Five types of basaltic rock facies are recognized: (1) coherent basalt, (2) massive platy basalt, (3) jigsaw-fit monomictic basaltic breccia, (4) massive or stratified coarse monomictic basaltic breccia with fluidal clasts, and (5) massive or stratified fine monomictic basaltic breccia. The basaltic rocks are mainly hyaloclastite. Based on facies distributions, we infer that volcanism occurred along fissures developed mainly at the center of the study area. Given that the rocks contain many fluidal clasts, submarine lava fountaining is inferred to have been the dominant eruption style. The basaltic rocks are interpreted as the products of back-arc volcanism that occurred by tensional stress related to opening of the Japan Sea, which drove strong tectonic subsidence and active lava fountain volcanism.

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.

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.

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.

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

Unraveling multiple provenance areas using sandstone petrofacies and geochemistry: An example in the southern flank of the Golfo San Jorge Basin (Patagonia, Argentina)

NASA Astrophysics Data System (ADS)

Limarino, Carlos Oscar; Giordano, Sergio Roberto

2016-03-01

The aim of this paper is to study the provenance of Late Cretaceous sandstones deposited along the south flank of the Golfo San Jorge Basin. For this purpose, detrital modes of three hundred thirty-seven sandstone samples collected in the Mina del Carmen, Bajo Barreal, and Cañadón Seco Formations were studied in ten oil fields. According to the modal composition of the sandstones, six petrofacies were defined allowing the identification of not only principal, but also secondary provenance areas. The QVM and VQM petrofacies are more than 20% metamorphic, sedimentary, and polycrystalline quartz clasts (Lm + Ls + Qpg > 20%), evidencing a secondary signal of basement supply masked by a predominant volcanic provenance. The petrofacies VP and VF are characterized by Lm + Ls + Qpg <20% and more than 20% total feldspar (Pm + Om >20%.), which indicate a supply of sediment from volcanic terrains and scarce derivation of materials from basement rocks. Based on the plagioclase/k-feldspar ratio, the VF petrofacies is interpreted to be dominated by the supply of sand grains from the Andean volcanic-arc, while VP is supposed have originated through the erosion of intermediate volcanic rock outcroppings in the Macizo del Deseado. Finally, both the VQ and QV petrofacies show Lm + Ls + Qpg <20% and Pm + Om<20%, indicating a provenance of volcanic areas coupled with minor contributions from basement rocks. During the Late Cretaceous, the Golfo San Jorge Basin underwent a sag phase that was characterized by very scarce volcanism and tectonic activity. Although these conditions did not favor defined patterns in the vertical stacking of petrofacies, the sandstones exhibit remarkable changes in their regional distribution, which were determined by the paleogeography of the basin and differences in basement composition within the source areas. Finally, a paleogeographic model for sediment circulation in the basin is proposed. This model recognizes the main fluvial dispersal trends that flowed northwest to southeast and transported large amounts of volcanic clasts (associated with petrofacies VF-VQ). To the extent that rivers flowed eastward, a secondary supply from the Precambrian basement, which were composed of low-to high-grade metamorphic rocks, was also important (petrofacies association VQM and QVM). The southwestern area of the basin is dominated by VP petrofacies that record the supply of plagioclase-rich volcanic clasts. This petrofacies likely corresponds to the erosion of Jurassic volcanic units that crop out in the Macizo del Deseado.

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.

Kula Geopark: Turkeys first European and Global Geopark

NASA Astrophysics Data System (ADS)

Gumus, Erdal; Zouros, Nickolas

2014-05-01

The Kula European and Global Geopark is situated in the Aegean Region of Turkey at Western Anatolia, within Manisa Province. The Geopark area covers 300 km2. The Kula Geopark area is the youngest volcanic region of Turkey where the volcanic activity continued up to prehistoric times. The outstanding volcanic structures of Kula Geopark area are well known at least for 2 thousand years. The great ancient Greek Geographer Strabo (63BC-24AD) in his majestic book "Geographica" named Kula as "Katakekaumene" (fire-born) because of the coal black lava. The geological significance and the cultural richness of Kula was mentioned by many foreign travellers and researchers like Charles Texier (1832) "Asia Minor" and Henry Washington's PhD thesis in 1893 where he named Kula basalts as "Kulaite". Kula Geopark area is awarded with high geodiversity representing 200 million years of earth history from Palaeozoic to Holocene including maars, monogenic cinder cones, successive lava flow plains, lava caves and tubes, craters, basalt columns, xenoliths, contact metamorphism, ash deposits, waterfalls in volcanic canyons, active karstic caves, badlands and fairy chimneys, mesa structures and schist tor, as far as 15 thousand years of fossil human foot prints preserved in volcanic ash. Kula Geopark is the land of miniature volcanoes where cinder cones are not higher than 150m. As a result, the geosites are easy to access and visiting the area requires very little risk, effort and time which makes the area excellent for geotourism and geoeducation. In addition to these outstanding natural and geological heritages, Kula Geopark reveals rich cultural, architectural historical, archaeological, and paleontological monuments. Kula represents well-preserved monuments of the 18th century Ottoman urban architecture in Turkey. The Kula Geopark Project was initiated in 2011 by PhD Erdal Gümüş with the support of the Kula Municipality. In September 2013 the Kula Geopark was certified as the first and only Turkish member of the European Geoparks Network and the Global Geoparks Network of UNESCO. As a result of the Kula Geopark Project, Turkey's first Geopark Visitor Centre the "Katakekaumene" and first thematic geotrail equipped with custom designed information sign and panels were established within Kula Geopark which offers regular indoor and outdoor geoeducational programs and activities. As a result of recognition of Kula Geopark as a EGN & GGN member, for the first time Turkey gained official position within European and Global Geoparks network represented by Kula Mayor Selim Aşkın and Kula Geopark Coordinator Erdal Gümüş. Keywords: Kula Geopark, Geosite, Geological Heritage, European Geoparks, Global Geoparks

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.

Etna_NETVIS: A dedicated tool for automatically pre-processing high frequency data useful to extract geometrical parameters and track the evolution of the lava field

NASA Astrophysics Data System (ADS)

Marsella, Maria; Junior Valentino D'Aranno, Peppe; De Bonis, Roberto; Nardinocchi, Carla; Scifoni, Silvia; Scutti, Marianna; Sonnessa, Alberico; Wahbeh, Wissam; Biale, Emilio; Coltelli, Mauro; Pecora, Emilio; Prestifilippo, Michele; Proietti, Cristina

2016-04-01

In volcanic areas, where it could be difficult to gain access to the most critical zones for carrying out direct surveys, digital photogrammetry techniques are rarely experimented, although in many cases they proved to have remarkable potentialities, as the possibility to follow the evolution of volcanic (fracturing, vent positions, lava fields, lava front positions) and deformation processes (inflation/deflation and instability phenomena induced by volcanic activity). These results can be obtained, in the framework of standard surveillance activities, by acquiring multi-temporal datasets including Digital Orthophotos (DO) and Digital Elevation Models (DEM) to be used for implementing a quantitative and comparative analysis. The frequency of the surveys can be intensified during emergency phases to implement a quasi real-time monitoring for supporting civil protection actions. The high level of accuracy and the short time required for image processing make digital photogrammetry a suitable tool for controlling the evolution of volcanic processes which are usually characterized by large and rapid mass displacements. In order to optimize and extend the existing permanent ground NEtwork of Thermal and VIsible Sensors located on Mt. Etna (Etna_NETVIS) and to improve the observation of the most active areas, an approach for monitoring surface sin-eruptive processes was implemented. A dedicated tool for automatically pre-processing high frequency data, useful to extract geometrical parameters as well as to track the evolution of the lava field, was developed and tested both in simulated and real scenarios. The tool allows to extract a coherent multi-temporal dataset of orthophotos useful to evaluate active flow area and to estimate effusion rates. Furthermore, Etna_NETVIS data were used to downscale the information derived from satellite data and/or to integrate the satellite datasets in case of incomplete coverage or missing acquisitions. This work was developed in the framework of the EU-FP7 project "MED-SUV" (MEDiterranean SUpersite Volcanoes).

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.

Geochemical and geochronological constrains on the Chiang Khong volcanic rocks (northwestern Thailand) and its tectonic implications

NASA Astrophysics Data System (ADS)

Qian, Xin; Feng, Qinglai; Chonglakmani, Chongpan; Monjai, Denchok

2013-12-01

Volcanic rocks in northwestern Thailand exposed dominantly in the Chiang Khong area, are commonly considered to be genetically linked to the tectonic evolution of the Paleo-Tethyan Ocean. The volcanic rocks consist mainly of andesitic to rhyolitic rocks and are traditionally mapped as Permian-Triassic sequences. Our zircon U-Pb geochronological results show that two andesitic samples (TL-1-B and TL-31-B), are representative of the Doi Yao volcanic zone, and give a mean weighted age of 241.2±4.6 Ma and 241.7±2.9 Ma, respectively. The rhyolitic sample (TL-32-B1) from the Doi Khun Ta Khuan volcanic zone erupted at 238.3±3.8 Ma. Such ages indicate that Chiang Khong volcanic rocks erputed during the early Middle Triassic period. Seven samples from the Doi Yao and Doi Khun Ta Khuan zones exhibit an affinity to arc volcanics. Three rhyolitic samples from the Chiang Khong area have a geochemical affinity to both arc and syn-collisional volcanic rocks. The Chiang Khong arc volcanic rocks can be geochemically compared with those in the Lampang area in northern Thailand, also consistent with those in Jinghong area of southwestern Yunnan. This indicates that the Chiang Rai arc-volcanic zone might northwardly link to the Lancangjiang volcanic zone in southwestern China.

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

Volcanic rocks and subglacial volcanism beneath the West Antarctic Ice Sheet in the West Antarctic Rift System, (WAIS) from aeromagnetic and radar ice sounding - Thiel Subglacial Volcano as possible source of the ash layer in the WAISCORE

NASA Astrophysics Data System (ADS)

Behrendt, J. C.

2012-12-01

Radar ice sounding and aeromagnetic surveys reported over the West Antarctic Ice Sheet (WAIS) have been interpreted as evidence of subglacial volcanic eruptions over a very extensive area (>500,000 km2 ) of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS reported from radar and aeromagnetic data. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km-width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Comparison of a carefully selected subset of ~400 of the >1000 high-amplitude anomalies in the CWA survey having topographic expression at the glacier bed, showed >80% had less than 200-m relief. About 18 high-amplitude subglacial magnetic sources also have high topography and bed relief (>600 m) interpreted as subaerially erupted volcanic peaks when the WAIS was absent, whose competent lava flows protected their edifices from erosion. All of these would have high elevation above sea-level, were the ice removed and glacial rebound to have occurred. Nine of these subaerially erupted volcanoes are concentrated in the WAIS divide area. Behrendt et al., 1998 interpreted a circular ring of positive magnetic anomalies overlying the WAIS divide as caused by a volcanic caldera. The area is characterized by high elevation bed topography. The negative regional magnetic anomaly surrounding the caldera anomalies was interpreted as the result of a shallow Curie isotherm. High heat flow inferred from temperature logging in the WAISCORE (G. Clow 2012, personal communication; Conway, 2011) and a prominent volcanic ash layer in the core (Dunbar, 2011) are consistent with the magnetic data. A prominent subaerially-erupted subglacial volcano, here named Mt Thiel, about 100 km distant to the NE, at approximately 78o 25' S, 111o 20' W, may be the source of the ash layer. This peak is characterized by a ~400-nT positive magnetic anomaly which Behrendt el, 2004, modeled as having apparent susceptibility contrasts of .034 and .15 SI. From its appearance (and the moat surrounding it), Mt. Thiel has subsided somewhat since initial eruption as is the case for Mt. Erebus and the Hawaiian Island chain. I suggest that Mt Thiel, about 100 km distance from the WAISCORE, may be the source of the ash layer. The present rapid changes in the WAIS resulting from global warming, could be accelerated by subglacial volcanism

A 3D model of crustal magnetization at the Pinacate Volcanic Field, NW Sonora, Mexico

NASA Astrophysics Data System (ADS)

García-Abdeslem, Juan; Calmus, Thierry

2015-08-01

The Pinacate Volcanic Field (PVF) is located near the western border of the southern Basin and Range province, in the State of Sonora NW Mexico, and within the Gulf of California Extensional Province. This volcanic field contains the shield volcano Santa Clara, which mainly consists of basaltic to trachytic volcanic rocks, and reaches an altitude of 1200 m. The PVF disrupts a series of discontinuous ranges of low topographic relief aligned in a NW direction, which consist mainly of Proterozoic metamorphic rocks and Proterozoic through Paleogene granitoids. The PVF covers an area of approximately 60 by 55 km, and includes more than 400 well-preserved cinder cones and vents and eight maar craters. It was active from about 1.7 Ma until about 13 ka. We have used the ages and magnetic polarities of the volcanic rocks, along with mapped magnetic anomalies and their inverse modeling to determine that the Pinacate Volcanic Field was formed during two volcanic episodes. The oldest one built the Santa Clara shield volcano of basaltic and trachytic composition, and occurred during the geomagnetic Matuyama Chron of reverse polarity, which also includes the normal polarity Jaramillo and Olduvai Subchrons, thus imprinting both normal and reverse magnetization in the volcanic products. The younger Pinacate series of basaltic composition represents monogenetic volcanic activity that extends all around the PVF and occurred during the subsequent geomagnetic Brunhes Chron of normal polarity. Magnetic anomalies toward the north of the Santa Clara volcano are the most intense in the PVF, and their inverse modeling indicates the presence of a large subsurface body magnetized in the present direction of the geomagnetic field. This suggests that the magma chambers at depth cooled below the Curie temperature during the Brunhes Chron.

Time Series Analysis OF SAR Image Fractal Maps: The Somma-Vesuvio Volcanic Complex Case Study

NASA Astrophysics Data System (ADS)

Pepe, Antonio; De Luca, Claudio; Di Martino, Gerardo; Iodice, Antonio; Manzo, Mariarosaria; Pepe, Susi; Riccio, Daniele; Ruello, Giuseppe; Sansosti, Eugenio; Zinno, Ivana

2016-04-01

The fractal dimension is a significant geophysical parameter describing natural surfaces representing the distribution of the roughness over different spatial scale; in case of volcanic structures, it has been related to the specific nature of materials and to the effects of active geodynamic processes. In this work, we present the analysis of the temporal behavior of the fractal dimension estimates generated from multi-pass SAR images relevant to the Somma-Vesuvio volcanic complex (South Italy). To this aim, we consider a Cosmo-SkyMed data-set of 42 stripmap images acquired from ascending orbits between October 2009 and December 2012. Starting from these images, we generate a three-dimensional stack composed by the corresponding fractal maps (ordered according to the acquisition dates), after a proper co-registration. The time-series of the pixel-by-pixel estimated fractal dimension values show that, over invariant natural areas, the fractal dimension values do not reveal significant changes; on the contrary, over urban areas, it correctly assumes values outside the natural surfaces fractality range and show strong fluctuations. As a final result of our analysis, we generate a fractal map that includes only the areas where the fractal dimension is considered reliable and stable (i.e., whose standard deviation computed over the time series is reasonably small). The so-obtained fractal dimension map is then used to identify areas that are homogeneous from a fractal viewpoint. Indeed, the analysis of this map reveals the presence of two distinctive landscape units corresponding to the Mt. Vesuvio and Gran Cono. The comparison with the (simplified) geological map clearly shows the presence in these two areas of volcanic products of different age. The presented fractal dimension map analysis demonstrates the ability to get a figure about the evolution degree of the monitored volcanic edifice and can be profitably extended in the future to other volcanic systems with very distinctive characteristics, with the aim to perform land classification, such as the identification of areas characterized by similar soil use, slopes and exposures.

Volcanic complexes in the eastern ridge of the Canary Islands: the Miocene activity of the island of Fuerteventura

NASA Astrophysics Data System (ADS)

Ancochea, E.; Brändle, J. L.; Cubas, C. R.; Hernán, F.; Huertas, M. J.

1996-03-01

Fuerteventura has been since early stages of its growth the result of three different adjacent large volcanic complexes: Southern, Central and Northern. The definition of these volcanic complexes and their respective growing episodes is based on volcano-stratigraphic, morphological and structural criteria, particularly radial dyke swarms. Each complex has its own prolonged history that might be longer than 10 m.y. During that time, several periods of activity alternating with gaps accompanied by important erosion took place. The evolution of each volcanic complex has been partially independent but all the three are affected by at least three Miocene tectonic phases that controlled considerably their activity. The volcanic complexes are deeply eroded and partially submerged. In the core of the Northern and the Central volcanic complexes there is a set of submarine and plutonic rocks intensely traversed by a dyke swarm, known as the Basal Complex. The Basal Complex has been interpreted in different ways but all previous authors have considered it to be prior to the subaerial shield stage of the island. Here we advance the idea that the Basal Complex represent the submarine growing stage of the volcanic complexes and the hypabyssal roots (plutons and dykes) of their successive subaerial growing episodes. Two seamounts situated nearby, southwest of the island, might be interpreted as remains of two other major volcanoes. These two volcanoes, together with those forming the present emerged island of Fuerteventura, and finally those of Famara and Los Ajaches situated further north on Lanzarote constitute a chain of volcanoes located along a lineation which is subparallel to the northwestern African coastline and which may relate to early Atlantic spreading trends in the area.

Diffuse CO_{2} degassing monitoring of the oceanic active volcanic island of El Hierro, Canary Islands, Spain

NASA Astrophysics Data System (ADS)

Hernández, Pedro A.; Norrie, Janice; Withoos, Yannick; García-Merino, Marta; Melián, Gladys; Padrón, Eleazar; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Pérez, Nemesio M.

2017-04-01

Even during repose periods, volcanoes release large amounts of gases from both visible (fumaroles, solfataras, plumes) and non-visible emanations (diffuse degassing). In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs, particularly in those volcanic areas where there are no visible volcanic-hydrothermal gas emissions. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. As CO2 travels upward by advective-diffusive transport mechanisms and manifests itself at the surface, changes in its flux pattern over time provide important information for monitoring volcanic and seismic activity. Since 1998, diffuse CO2 emission has been monitored at El Hierro Island, the smallest and south westernmost island of the Canarian archipelago with an area of 278 km2. As no visible emanations occur at the surface environment of El Hierro, diffuse degassing studies have become the most useful geochemical tool to monitor the volcanic activity in this volcanic island. The island experienced a volcano-seismic unrest that began in July 2011, characterized by the location of a large number of relatively small earthquakes (M<2.5) beneath El Hierro at depths between 8 and 15 km. On October 12, 2011, a submarine eruption was confirmed during the afternoon of October 12, 2011 by visual observations off the coast of El Hierro, about 2 km south of the small village of La Restinga in the southernmost part of the island. During the pre-eruptive and eruptive periods, the time series of the diffuse CO2 emission released by the whole island experienced two significant increases. The first started almost 2 weeks before the onset of the submarine eruption, reflecting a clear geochemical anomaly in CO2 emission, most likely due to increasing release of deep seated magmatic gases to the surface. The second one, between October 24 and November 27, 2011, before the most energetic seismic events of the volcanic-seismic unrest (Melián et al., 2014. J. Geophys. Res. Solid Earth, 119, 6976-6991). The highest CO2 degassing rate measured in the last three years (1684 t/d) was observed during a seismo-volcanic unrest. This value decreased until close to background value (˜422 t/d, Melián et al., 2014) contemporaneously with the decline of the seismic activity during the first half of 2013. The last diffuse CO2 degassing survey was carried out in the summer of 2016, showing a emission rate of 854 t/d. Discrete surveys of diffuse CO2 emission have provided important information to optimize the early warning system in the volcano monitoring programs of El Hierro and to monitor the evolution of an ongoing volcanic eruption, even though is a submarine eruption.

The distribution and tectonic framework of Late Paleozoic volcanoes in the Junggar basin and its adjacent area, NW China

NASA Astrophysics Data System (ADS)

Mao, X.; Li, J. H.

2012-04-01

We analyse the distribution and characteristics of 145 late Paleozoic volcanoes in north Xinjiang, NW China, including 32 volcanoes on the edge of the Junggar basin. These volcanoes are clustered and can be divided into calderas, volcanic domes, and volcanic necks. There are also 85 volcanoes inside the Junggar basin, which are dominantly distributed in the Ke-Bai fractured zone of the northwestern margin of Junggar Basin, 4 depressions (Dongdaohaizi Depression, Dishuiquan Depression, Sannan Depression and Wucaiwan Depression) and 7 uplifts (Baijiahai uplift, Beisantai uplift, Dibei uplift, Dinan uplift, Sangequan uplift, Shixi uplift and Xiayan uplift). The volcanoes inside the basin are principally controlled by Hercynian Fault Systems, along NE and nearly EW trending faults and most developed in the interjunctions of the faults. The long modification by late-stage weathering and leaching made the volcanoes difficult to identify. Remaining volcanic landforms, changing trends of the volcanic lithofacies and the typical volcanic rock, such as the crypto- explosive breccia, are the typical marks of the late Paleozoic volcanoes in the field; and the concealed volcanic edifices are identified by the techniques of seismic identification, such as seismic slicing, analysis of the attribute and tectonic trend plane. The ages of the volcanic rocks are focused on from 340 Ma to 320Ma and from 300 Ma to 295 Ma, corresponding to the subducting periods of West Junggar and East Junggar. From early Carboniferous to late Carboniferous, the volcanic activities in Junggar Basin and its adjacent areas show a variation trend from undersea to continental, from deep water to shallow water and from continental margin to intracontinental.

Earth Observation taken by the Expedition 19 crew

NASA Image and Video Library

2009-04-28

ISS019-E-011922 (28 April 2009) --- Mauna Kea Volcano in Hawaii is featured in this image photographed by an Expedition 19 crewmember on the International Space Station. The island of Hawaii is home to four volcanoes monitored by volcanologists ? Mauna Loa, Hualalai, Kilauea, and Mauna Kea. Mauna Kea is depicted in this view; of the four volcanoes, it is the only one that has not erupted during historical times. The Hawaiian Islands chain, together with the submerged Emperor Chain to the northwest, form an extended line of volcanic islands and seamounts that is thought to record passage of the Pacific Plate over a ?hotspot? (or thermal plume) in the Earth?s mantle. Areas of active volcanism in the southern Hawaiian Islands today mark the general location of the hotspot. This detailed photograph illustrates why the volcano is called Mauna Kea (?white mountain? in Hawaiian). While the neighboring Mauna Loa volcano is a classic shield volcano comprised of dark basaltic lava flows, Mauna Kea experienced more explosive activity during its last eruptive phase. This covered its basalt lava flows with pyroclastic deposits that are visible as the light brown area surrounding snow on the summit (center). Numerous small red to dark gray cinder cones are another distinctive feature of Mauna Loa. The cinder cones represent the most recent type of volcanic activity at the volcano. A small area of buildings and roadways at upper right is the Pohakuloa Training Area. This is the largest US Department of Defense facility in the state of Hawaii. The site is used for U.S. Army and Marine Corps exercises.

Volcanic hazards in Central America

USGS Publications Warehouse

Rose, William I.; Bluth, Gregg J.S.; Carr, Michael J.; Ewert, John W.; Patino, Lina C.; Vallance, James W.

2006-01-01

This volume is a sampling of current scientific work about volcanoes in Central America with specific application to hazards. The papers reflect a variety of international and interdisciplinary collaborations and employ new methods. The book will be of interest to a broad cross section of scientists, especially volcanologists. The volume also will interest students who aspire to work in the field of volcano hazards mitigation or who may want to work in one of Earth’s most volcanically active areas.

Conduits and dike distribution analysis in San Rafael Swell, Utah

NASA Astrophysics Data System (ADS)

Kiyosugi, K.; Connor, C.; Wetmore, P. H.; Ferwerda, B. P.; Germa, A.

2011-12-01

Volcanic fields generally consist of scattered monogenetic volcanoes, such as cinder cones and maars. The temporal and spatial distribution of monogenetic volcanoes and probability of future activity within volcanic fields is studied with the goals of understanding the origins of these volcano groups, and forecasting potential future volcanic hazards. The subsurface magmatic plumbing systems associated with volcanic fields, however, are rarely observed or studied. Therefore, we investigated a highly eroded and exposed magmatic plumbing system on the San Rafael Swell (UT) that consists of dikes, volcano conduits and sills. San Rafael Swell is part of the Colorado Plateau and is located east of the Rocky Mountain seismic belt and the Basin and Range. The overburden thickness at the time of mafic magma intrusion (Pliocene; ca. 4 Ma) into Jurassic sandstone is estimated to be ~800 m based on paleotopographical reconstructions. Based on a geologic map by P. Delaney and colleagues, and new field research, a total of 63 conduits are mapped in this former volcanic field. The conduits each reveal features of root zone and / or lower diatremes, including rapid dike expansion, peperite and brecciated intrusive and host rocks. Recrystallized baked zone of host rock is also observed around many conduits. Most conduits are basaltic or shonkinitic with thickness of >10 m and associated with feeder dikes intruded along N-S trend joints in the host rock, whereas two conduits are syenitic and suggesting development from underlying cognate sills. Conduit distribution, which is analyzed by a kernel function method with elliptical bandwidth, illustrates a N-S elongate higher conduit density area regardless of the azimuth of closely distributed conduits alignment (nearest neighbor distance <200 m). In addition, dike density was calculated as total dike length in unit area (km/km^2). Conduit and sill distribution is concordant with the high dike density area. Especially, the distribution of conduits is not random with respect to the dike distribution with greater than 99% confidence on the basis of the Kolmogorov-Smirnov test. On the other hand, dike density at each conduits location also suggests that there is no threshold of dike density for conduit formation. In other words, conduits may be possible to develop from even short mapped dikes in low dike density areas. These results show effectiveness of studying volcanic vent distribution to infer the size of magmatic system below volcanic fields and highlight the uncertainty of forecasting the location of new monogenetic volcanoes in active fields, which may be associated with a single dike intrusion.

Klyuchevskaya, Volcano, Kamchatka Peninsula, CIS

NASA Image and Video Library

1991-05-06

STS039-151-179 (28 April-6 May 1991) --- A large format frame of one of the USSR's volcanic complex (Kamchatka area) with the active volcano Klyuchevskaya (Kloo-chevs'-ska-ya), 15,584 feet in elevation. The last reported eruption of the volcano was on April 8, but an ash and steam plume extending to the south was observed by the STS-39 crew almost three weeks later. The south side of the volcano is dirty from the ash fall and landslide activity. The summit is clearly visible, as is the debris flow from an earlier eruption. Just north of the Kamchatka River is Shiveluch, a volcano which was active in early April. There are more than 100 volcanic edifices recognized on Kamchatka, with 15 classified as active.

First Evidence of Epithermal Gold Occurrences in the SE Afar Rift, Republic of Djibouti

NASA Astrophysics Data System (ADS)

Moussa, Nima; Fouquet, Yves; Caminiti, Antoine Marie; Le Gall, Bernard; Rolet, Joel; Bohn, Marcel; Etoubleau, Joel; Delacourt, Christophe; Jalludin, Mohamed

2010-05-01

The Republic of Djibouti, located at the SE part of the Afar volcanic Triangle, is characterized by intense tectonic and bimodal volcanic activity, and is emplaced over an earlier magmatic rift system, as old as 25-30 Ma. Each magmatic event is accompanied by hydrothermal activity. Few works have been so far published on hydrothermal mineralization in the Afar area. Mineralization generally occur as veins and are mainly associated with acidic volcanic intrusions along the fractures at the edges of grabens established during the last 4 Ma. Eighty samples from hydrothermal quartz ± carbonate veins and breccias were studied on 9 different sites representative of 4 main volcanic events ranging in age from early Miocene up to Present. Gold was found in excess of 200 ppb in 30% of the samples. Mineralogical analyses based on optical reflected light microscopy, X-Ray diffractometry, X-Ray fluorescence, inductively coupled plasma mass spectroscopy and electron microprobe, led us to identify two types of gold mineralization (i) native gold, electrum, hessite and sulfides (chalcopyrite, pyrite, bornite, ± sphalerite, and galena) in massive quartz breccias and banded chalcedony, (ii) gold, electrum, hematite, magnetite, trace minerals (argentite) and adularia in banded chalcedony. Another group without gold is characterized by quartz, pyrite ± goethite. Secondary minerals are characterized by goethite, native silver and native copper. Arsenic is enriched in pyrite in samples with a high gold content. The bimodal volcanism, the occurrence of adularia, the native gold and electrum in banded silica veins, are classically observed in neutral epithermal systems. The discovery of this type of mineralization in a recent-active continental rift system supplies new insights about hydrothermal processes associated with volcanic activity in a spreading context. Keywords: Republic of Djibouti, Afar Triangle, Hydrothermal, Epithermal system, Gold

Evaluating life-safety risk of fieldwork at New Zealand's active volcanoes

NASA Astrophysics Data System (ADS)

Deligne, Natalia; Jolly, Gill; Taig, Tony; Webb, Terry

2014-05-01

Volcano observatories monitor active or potentially active volcanoes. Although the number and scope of remote monitoring instruments and methods continues to grow, in-person field data collection is still required for comprehensive monitoring. Fieldwork anywhere, and especially in mountainous areas, contains an element of risk. However, on volcanoes with signs of unrest, there is an additional risk of volcanic activity escalating while on site, with potentially lethal consequences. As an employer, a volcano observatory is morally and sometimes legally obligated to take reasonable measures to ensure staff safety and to minimise occupational risk. Here we present how GNS Science evaluates life-safety risk for volcanologists engaged in fieldwork on New Zealand volcanoes with signs of volcanic unrest. Our method includes several key elements: (1) an expert elicitation for how likely an eruption is within a given time frame, (2) quantification of, based on historical data when possible, given a small, moderate, or large eruption, the likelihood of exposure to near-vent processes, ballistics, or surge at various distances from the vent, and (3) estimate of fatality rate given exposure to these volcanic hazards. The final product quantifies hourly fatality risk at various distances from a volcanic vent; various thresholds of risk (for example, zones with more than 10-5 hourly fatality risk) trigger different levels of required approval to undertake work. Although an element of risk will always be present when conducting fieldwork on potentially active volcanoes, this is a first step towards providing objective guidance for go/no go decisions for volcanic monitoring.

Episodes of fluvial and volcanic activity in Mangala Valles, Mars.

PubMed

Keske, Amber L; Hamilton, Christopher W; McEwen, Alfred S; Daubar, Ingrid J

2015-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400-500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.

Introduction to the 2012-2013 Tolbachik eruption special issue

NASA Astrophysics Data System (ADS)

Edwards, Benjamin R.; Belousov, Alexander; Belousova, Marina; Volynets, Anna

2015-12-01

The Tolbachik volcanic complex in central Kamchatka holds a special place in global volcanological studies. It is one of 4 areas of extensive historic volcanic activity in the northern part of the Central Kamchatka Depression (the others being Klyuchevskoy, Bezymianny, Shiveluch), and is part of the Klyuchevskoy volcanic group, which is one of the most active areas of volcanism on Earth. Tolbachik is especially well-known due largely to the massive 1975-1976 eruption that became known as the Great Tolbachik Fissure eruption (GTFE; Fedotov, 1983; Fedotov et al., 1984). This was one of the first eruptions in Russia to be predicted based on precursory seismic activity, based on M5 earthquakes approximately one week before the eruption started, and was intensively studied during its course by a large number of Russian scientists. A summary of those studies was published, first in Russian and then in English, and it became widely read for many reasons. One in particular is that the eruption was somewhat unusual for a subduction zone setting; although many subduction zone stratovolcanoes have associated basaltic tephra cone-lava fields, this was the first such Hawaiian-style eruption to be widely observed. After the end of the eruption in 1976, the complex showed no signs of activity until 27 November 2012, when increased seismic activity was registered by the Kamchatka Branch of the Russian Geophysical Survey and a red glow from the eruption site was first noticed through the snowstorm haze. This prompted them, and then the Kamchatka Volcanic Emergency Response Team (KVERT) to issue an alert that activity was coming from the south flank of Plosky Tolbachik volcano, the younger of two volcanic edifices (the older is Ostry Tolbachik) that together make up the bulk of the complex along with tephra cone-lava fields that lie along a NE-SW fissure zone that transects Plosky Tolbachik. The new eruption lasted for more than 250 days and, like the 1975-1976 eruption, was dominated by Hawaiian-style activity. With the start of the eruption coinciding with the onset of winter months in Kamchatka, field observations, while virtually continuous, were also not as numerous as those that documented the GTFE 36 years previously. Nonetheless the Institute of Volcanology and Seismology (IVS) in Petropavlovsk-Kamchatsky provided almost continuous field-based coverage throughout the eruption. Many of the research projects begun during the eruption comprise international teams of scientists who were able to partner with IVS through international funding, particularly through the United States National Science Foundation and the National Geographic Committee for Research.

GOSAT/TANSO-FTS Measurement of Volcanic and Geothermal CO2 Emissions

NASA Astrophysics Data System (ADS)

Schwandner, Florian M.; Carn, Simon A.; Newhall, Christopher G.

2010-05-01

Approximately one tenth of the Earth's human population lives in direct reach of volcanic hazards. Being able to provide sufficiently early and scientifically sound warning is a key to volcanic hazard mitigation. Quantitative time-series monitoring of volcanic CO2 emissions will likely play a key role in such early warning activities in the future. Impending volcanic eruptions or any potentially disastrous activity that involves movement of magma in the subsurface, is often preceded by an early increase of CO2 emissions. Conventionally, volcanic CO2 monitoring is done either in campaigns of soil emission measurements (grid of one-time measuring points) that are labor intensive and slow, or by ground-based remote FTIR measurements in emission plumes. These methods are not easily available at all sites of potential activity and prohibitively costly to employ on a large number of volcanoes. In addition, both of these ground-based approaches pose a significant risk to the workers conducting these measurements. Some aircraft-based measurements have been conducted as well in the past, however these are limited by the usually meager funding situation of individual observatories, the hazard such flights pose to equipment and crew, and by the inaccessibility of parts of the plume due to ash hazards. The core motivation for this study is therefore to develop a method for volcanic CO2 monitoring from space that will provide sufficient coverage, resolution, and data quality for an application to quantitative time series monitoring and correlation with other available datasets, from a safe distance and with potentially global reach. In summary, the purpose of the proposed research is to quantify volcanic CO2 emissions using satellite-borne observations. Quantitative estimates will be useful for warning of impending volcanic eruptions, and assessing the contribution of volcanic CO2 to global GHG. Our approach encompasses method development and testing for the detection of volcanic CO2 anomalies using GOSAT and correlation with Aura/OMI, AIRS, and ASTER determined SO2 fluxes and ground based monitoring of CO2 and other geophysical and geochemical parameters. This will provide the ground work for future higher spatial resolution satellite missions. This is a joint effort from two GOSAT-IBUKI data application projects: "Satellite-Borne Quantification of Carbon Dioxide Emissions from Volcanoes and Geothermal Areas" (PI Schwandner), and "Application of GOSAT/TANSO-FTS to the Measurement of Volcanic CO2 Emissions" (PI Carn).

Relationships between tectonism, volcano-tectonism and volcanism: the Ischia island (Italy) case.

NASA Astrophysics Data System (ADS)

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

2005-12-01

The resurgent calderas of Ischia, Campi Flegrei and Pantelleria are characterized by differentially displaced blocks, and distribution of later eruption vents in a well defined sector of the resurgent area. These features suggest a simple shearing block resurgence mechanism. Moreover, the studies carried out on Ischia and Campi Flegrei evidenced a very complex structural pattern due to deformation related to the local stress regime induced by magmatism and volcanism and also to reactivation of regional structures. In order to better define the relationships among tectonic, volcano-tectonic and caldera resurgence mechanism, a structural study has been carried out at Ischia, where the Mt. Epomeo has been uplifted of about 900 m in the past 30 ka. The measures taken on 1,400 planar surfaces (faults, joints and fracture cleavages) show that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcano-tectonism. The limit of the resurgent area is not defined towards the north, as beach deposits displaced at variable elevation by E-W and NW-SE trending faults, are exposed along the coastline. The western sector is bordered by inward-dipping, high-angle reverse faults, whose directions vary from N40E to NS and N50W from NW to SW of the block, testifying a compressional stress regime active in this area. These features are cut by late outward-dipping normal faults due to gravitational readjustment of the slopes. Vertical faults border the block at NE ad SW with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block, characterized by a tensile stress regime, has been deformed by N-S, N40-70E and N15W trending normal faults, with maximum elongation direction along N50W. The results of our study and the volcanological data of the past 3 ka, suggest that the eastern part of the resurgent block is the area with highest probability of vent opening in case of renewal of volcanism. Occurrence of landslides just before and after eruptions, suggest that resurgence occurs through discontinuous vertical movements which likely trigger the volcanic activity.

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.

Historic hydrovolcanism at Deception Island (Antarctica): implications for eruption hazards

NASA Astrophysics Data System (ADS)

Pedrazzi, Dario; Németh, Károly; Geyer, Adelina; Álvarez-Valero, Antonio M.; Aguirre-Díaz, Gerardo; Bartolini, Stefania

2018-01-01

Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the South Atlantic. Volcanic activity since the eighteenth century, along with the latest volcanic unrest episodes in the twentieth and twenty-first centuries, demonstrates that the volcanic system is still active and that future eruptions are likely. Despite its remote location, the South Shetland Islands are an important touristic destination during the austral summer. In addition, they host several research stations and three summer field camps. Deception Island is characterised by a Quaternary caldera system with a post-caldera succession and is considered to be part of an active, dispersed (monogenetic), volcanic field. Historical post-caldera volcanism on Deception Island involves monogenetic small-volume (VEI 2-3) eruptions such forming cones and various types of hydrovolcanic edifices. The scientific stations on the island were destroyed, or severely damaged, during the eruptions in 1967, 1969, and 1970 mainly due to explosive activity triggered by the interaction of rising (or erupting) magma with surface water, shallow groundwater, and ice. We conducted a detailed revision (field petrology and geochemistry) of the historical hydrovolcanic post-caldera eruptions of Deception Island with the aim to understand the dynamics of magma-water interaction, as well as characterise the most likely eruptive scenarios from future eruptions. We specifically focused on the Crimson Hill (estimated age between 1825 and 1829), and Kroner Lake (estimated age between 1829 and 1912) eruptions and 1967, 1969, and 1970 events by describing the eruption mechanisms related to the island's hydrovolcanic activity. Data suggest that the main hazards posed by volcanism on the island are due to fallout, ballistic blocks and bombs, and subordinate, dilute PDCs. In addition, Deception Island can be divided into five areas of expected activity due to magma-water interaction, providing additional data for correct hazard assessment on the island.

Earth Observations taken by the Expedition 17 Crew

NASA Image and Video Library

2008-06-18

ISS017-E-009598 (18 June 2008) --- The Sentinel Volcanic Field in Arizona is featured in this image photographed by an Expedition 17 crewmember on the International Space Station. This detailed view depicts a portion of the Gila River channel (center) between the Sentinel Volcanic Field and Oatman Mountain in south-central Arizona. The northernmost boundary of the Sentinel field is visible in the image, recognizable by the irregular flow fronts, or leading edge, of thin basalt lava flows erupted from low volcanic cones approximately 3.3--1.3 million years ago, according to scientists. Coloration of the lava flow tops ranges from dark brown exposed rock to a tan, carbonate-rich soil cover. Active agricultural fields along the Gila River are a rich green set against the surrounding desert. In contrast to the gentle topography of the Sentinel Volcanic Field, Oatman Mountain (upper left) rises from the Gila River channel to an elevation of approximately 560 meters. While Oatman Mountain is located close to the Sentinel field, it represents an earlier phase of volcanic activity in the area. Volcanic rocks comprising Oatman Mountain were more viscous, leading to shorter, stronger flows that are weathered into stream channels and scarps on the mountain slopes. The mountain is a popular hang gliding destination due to abundant thermal currents rising from the surrounding desert floor and lava surfaces.

Chronology of volcanic events in the eastern Philippine Sea

NASA Astrophysics Data System (ADS)

Meijer, Arend; Reagan, Mark; Ellis, Howard; Shafiqullah, Muhammad; Sutter, John; Damon, Paul; Kling, Stanley

Radiometric and paleontologic ages of samples from chiefly volcanic sections exposed on Guam, Saipan, and in the Palau Islands were determined to provide an improved temporal framework for tectonic and petrologic models for the evolution of the eastern Philippine Sea. The oldest arc related volcanic rocks found in this area are from the Facpi formation on Guam dated at 43.8±1.6 m.y. B.P. (late middle Eocene). Evidence for late Eocene, early Oligocene, and middle Miocene arc volcanism was also found in the Mariana fore arc. The Palau Islands contain volcanic units of late Eocene(?), early Oligocene and early Miocene age. A minimum age of 1.3±0.2 m.y. has been established for the Mariana active arc. Overall, the new data are consistent with Karig's (1971) model for the tectonic evolution of the eastern Philippine Sea. Whether or not arc volcanism and interarc basin spreading can take place at the same time has not been resolved, although no evidence of synchroneity has been found for at least the Parece Vela Basin—South Honshu Ridge arc system.

Arctic “ozone hole” in a cold volcanic stratosphere

PubMed Central

Tabazadeh, A.; Drdla, K.; Schoeberl, M. R.; Hamill, P.; Toon, O. B.

2002-01-01

Optical depth records indicate that volcanic aerosols from major eruptions often produce clouds that have greater surface area than typical Arctic polar stratospheric clouds (PSCs). A trajectory cloud–chemistry model is used to study how volcanic aerosols could affect springtime Arctic ozone loss processes, such as chlorine activation and denitrification, in a cold winter within the current range of natural variability. Several studies indicate that severe denitrification can increase Arctic ozone loss by up to 30%. We show large PSC particles that cause denitrification in a nonvolcanic stratosphere cannot efficiently form in a volcanic environment. However, volcanic aerosols, when present at low altitudes, where Arctic PSCs cannot form, can extend the vertical range of chemical ozone loss in the lower stratosphere. Chemical processing on volcanic aerosols over a 10-km altitude range could increase the current levels of springtime column ozone loss by up to 70% independent of denitrification. Climate models predict that the lower stratosphere is cooling as a result of greenhouse gas built-up in the troposphere. The magnitude of column ozone loss calculated here for the 1999–2000 Arctic winter, in an assumed volcanic state, is similar to that projected for a colder future nonvolcanic stratosphere in the 2010 decade. PMID:11854461

Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding - New evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices

USGS Publications Warehouse

Behrendt, John C.; Blankenship, D.D.; Morse, D.L.; Bell, R.E.

2004-01-01

Aeromagnetic and radar ice sounding results from the 1991-1997 Central West Antarctica (CWA) aerogeophysical survey over part of the West Antarctic Ice Sheet (WAIS) and subglacial area of the volcanically active West Antarctic rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography was protected from erosion by competent volcanic flows similar to prominent volcanic peaks that are exposed above the surface of the WAIS. Further, we infer these volcanoes as possibly erupted at a time when the WAIS was absent. In contrast, at the other extreme, there are a number of shallow-source, volcanic appearing magnetic anomalies overlying the very smooth bed topography in the survey area beneath Ice Stream D (Bindshadler Ice Stream); the glacial bed probably comprises a very thin layer of unconsolidated sediments (till). Probably, the volcanic edifices here were removed at a more rapid rate because of fast glacial flow. A few of the very shallow-source "volcanic" anomalies overlie the ice shelf just downstream of the grounding line of Ice Stream D, suggesting a causal relationship, if the volcanism is recent. ?? 2004 Elsevier B.V. All rights reserved.

Structural control of monogenetic volcanism in the Garrotxa volcanic field (Northeastern Spain) from gravity and self-potential measurements

NASA Astrophysics Data System (ADS)

Barde-Cabusson, S.; Gottsmann, J.; Martí, J.; Bolós, X.; Camacho, A. G.; Geyer, A.; Planagumà, Ll.; Ronchin, E.; Sánchez, A.

2014-01-01

We report new geophysical observations on the distribution of subsurface structures associated with monogenetic volcanism in the Garrotxa volcanic field (Northern Spain). As part of the Catalan Volcanic Zone, this Quaternary volcanic field is associated with the European rifts system. It contains the most recent and best preserved volcanic edifices of the Catalan Volcanic Zone with 38 monogenetic volcanoes identified in the Garrotxa Natural Park. We conducted new gravimetric and self-potential surveys to enhance our understanding of the relationship between the local geology and the spatial distribution of the monogenetic volcanoes. The main finding of this study is that the central part of the volcanic field is dominated by a broad negative Bouguer anomaly of around -0.5 mGal, within which a series of gravity minima are found with amplitudes of up to -2.3 mGal. Inverse modelling of the Bouguer data suggests that surficial low-density material dominates the volcanic field, most likely associated with effusive and explosive surface deposits. In contrast, an arcuate cluster of gravity minima to the NW of the Croscat volcano, the youngest volcano of this zone, is modelled by vertically extended low-density bodies, which we interpret as a complex ensemble of fault damage zones and the roots of young scoria cones. A ground-water infiltration zone identified by a self-potential anomaly is associated with a steep horizontal Bouguer gravity gradient and interpreted as a fault zone and/or magmatic fissure, which fed the most recent volcanic activity in the Garrotxa. Gravimetric and self-potential data are well correlated and indicate a control on the locations of scoria cones by NNE-SSW and NNW-SSE striking tectonic features, which intersect the main structural boundaries of the study area to the north and south. Our interpretation of the data is that faults facilitated magma ascent to the surface. Our findings have major implications for understanding the relationship between subsurface structures and potential future volcanic activity in the Garrotxa volcanic field.

Deriving spatial patterns from a novel database of volcanic rock geochemistry in the Virunga Volcanic Province, East African Rift

NASA Astrophysics Data System (ADS)

Poppe, Sam; Barette, Florian; Smets, Benoît; Benbakkar, Mhammed; Kervyn, Matthieu

2016-04-01

The Virunga Volcanic Province (VVP) is situated within the western branch of the East-African Rift. The geochemistry and petrology of its' volcanic products has been studied extensively in a fragmented manner. They represent a unique collection of silica-undersaturated, ultra-alkaline and ultra-potassic compositions, displaying marked geochemical variations over the area occupied by the VVP. We present a novel spatially-explicit database of existing whole-rock geochemical analyses of the VVP volcanics, compiled from international publications, (post-)colonial scientific reports and PhD theses. In the database, a total of 703 geochemical analyses of whole-rock samples collected from the 1950s until recently have been characterised with a geographical location, eruption source location, analytical results and uncertainty estimates for each of these categories. Comparative box plots and Kruskal-Wallis H tests on subsets of analyses with contrasting ages or analytical methods suggest that the overall database accuracy is consistent. We demonstrate how statistical techniques such as Principal Component Analysis (PCA) and subsequent cluster analysis allow the identification of clusters of samples with similar major-element compositions. The spatial patterns represented by the contrasting clusters show that both the historically active volcanoes represent compositional clusters which can be identified based on their contrasted silica and alkali contents. Furthermore, two sample clusters are interpreted to represent the most primitive, deep magma source within the VVP, different from the shallow magma reservoirs that feed the eight dominant large volcanoes. The samples from these two clusters systematically originate from locations which 1. are distal compared to the eight large volcanoes and 2. mostly coincide with the surface expressions of rift faults or NE-SW-oriented inherited Precambrian structures which were reactivated during rifting. The lava from the Mugogo eruption of 1957 belongs to these primitive clusters and is the only known to have erupted outside the current rift valley in historical times. We thus infer there is a distributed hazard of vent opening susceptibility additional to the susceptibility associated with the main Virunga edifices. This study suggests that the statistical analysis of such geochemical database may help to understand complex volcanic plumbing systems and the spatial distribution of volcanic hazards in active and poorly known volcanic areas such as the Virunga Volcanic Province.

Timing and compositional evolution of Late Pleistocene to Holocene volcanism within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia

NASA Astrophysics Data System (ADS)

Stelten, M. E.; Downs, D. T.; Dietterich, H. R.

2017-12-01

Harrat Rahat is one of the largest ( 20,000 km2) of 15 active Cenozoic volcanic fields that stretch 3,000 km along the western Arabian Peninsula from Yemen to Syria. The Harrat Rahat volcanic field is 310 km long (N-S) by 75 km wide (E-W), and is dominated by alkalic basalts with minor hawaiite, mugearite, benmoreite, and trachyte eruptives. The timing of volcanism within greater Harrat Rahat is poorly constrained, but field relations and geochronology indicate that northern Harrat Rahat hosted the most recent eruptions. To better constrain the timing and compositional evolution of Harrat Rahat during this recent phase, we present 743 geochemical analyses, 144 40Ar/39Ar ages, and 9 36Cl exposure ages for volcanic strata from northernmost Harrat Rahat. These data demonstrate that volcanism has been ongoing from at least 1.2 Ma to the present, with the most recent eruption known from historical accounts at 1256 CE. Basalt has erupted persistently from 1.2 Ma to the present, but more evolved volcanism has been episodic. Benmoreite erupted at 1.1 Ma and between 550 to 400 ka. Trachytic volcanism has only occurred over the past 150 ka, with the most recent eruption at 5 ka. Aside from the well-documented basaltic eruption at 1256 CE, prior workers interpreted 6 additional basaltic eruptions during the Holocene. However, our 36Cl exposure ages demonstrate that these erupted between 60 to 13 ka. Interestingly, in the northern part of our field area, where the spatial density of volcanic vents is low, young volcanism (<150 ka) is dominated by basaltic eruptions. Conversely, young volcanism in the southern part of our field area, where volcanic vent density is high, is dominated by trachyte. This observation is consistent with a process wherein the time-integrated effects of basaltic influx into the crust in the south produced a mafic intrusive complex, through which younger basaltic magmas cannot ascend. Instead, these magmas stall and produce trachyte, likely through fractional crystallization and/or partial melting of these stalled intrusions. Lesser basaltic input beneath the north end of the volcanic field failed to create a sizable intrusive complex, so basaltic magmas are able to ascend though the crust unimpeded.

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).

Volcanology: Lessons learned from Synthetic Aperture Radar imagery

USGS Publications Warehouse

Pinel, Virginie; Poland, Michael P.; Hooper, Andy

2014-01-01

Twenty years of continuous Earth observation by satellite SAR have resulted in numerous new insights into active volcanism, including a better understanding of subsurface magma storage and transport, deposition of volcanic materials on the surface, and the structure and development of volcanic edifices. This massive archive of data has resulted in fundamental leaps in our understanding of how volcanoes work – for example, identifying magma accumulation at supposedly quiescent volcanoes, even in remote areas or in the absence of ground-based data. In addition, global compilations of volcanic activity facilitate comparison of deformation behavior between different volcanic arcs and statistical evaluation of the strong link between deformation and eruption. SAR data are also increasingly used in timely hazard evaluation thanks to decreases in data latency and growth in processing and analysis techniques. The existing archive of SAR imagery is on the cusp of being enhanced by a new generation of satellite SAR missions, in addition to ground-based and airborne SAR systems, which will provide enhanced temporal and spatial resolution, broader geographic coverage, and improved availability of data to the scientific community. Now is therefore an opportune time to review the contributions of SAR imagery to volcano science, monitoring, and hazard mitigation, and to explore the future potential for SAR in volcanology. Provided that the ever-growing volume of SAR data can be managed effectively, we expect the future application of SAR data to expand from being a research tool for analyzing volcanic activity after the fact, to being a monitoring and research tool capable of imaging a wide variety of processes on different temporal and spatial scales as those processes are occurring. These data can then be used to develop new models of how volcanoes work and to improve quantitative forecasts of volcanic activity as a means of mitigating risk from future eruptions.

Structural Analysis of Mt. Epomeo Resurgent Block (ischia, Italy): Deformational Features, Uplifting Mechanism and Implications For Volcanic Hazard Assessment.

NASA Astrophysics Data System (ADS)

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

The studies carried out on the resurgent calderas of Campi Flegrei, Pantelleria and Is- chia, evidenced that the geometry of the resurgent blocks and the arial distribution of volcanic vents active after the caldera collapse, are not compatible with the commonly accepted resurgent dome model. For these areas a simple shearing block resurgence mechanism, that take in account all the geological and volcanological constraints, has been proposed. In order to define the structural setting of a resurgent block for which this mechanism has been proposed, a detailed structural study has been carried out on the island of Ischia, where the Mt. Epomeo was uplifted of about 900 m in the past 30 ka. The attitude of 1400 planar surfaces has been measured in 50 different sites around the resurgent block. These features have been distinguished in: a) faults; b) joints; c) fracture cleavages. It has been observed that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcan- otectonism. Northeastward the limit of the resurgent area is not defined, as along the coastline are exposed beach deposits displaced at variable elevation by E-W and NW- SE trending faults. The western sector is bordered by inward dipping, high angle re- verse faults, whose directions vary from N40E to NS and N50W from the northwestern to the southwestern parts of the block, testifying a compressional stress regime active in this area. These features are cut by late outward dipping normal faults due to grav- itational readjustment of the slopes. The northeastern and the southwestern sides are bordered by vertical faults with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block is characterized by a tensile stress regime and has been deformed by N-S, N40-70E and N15W trending normal faults, which demonstrates that the maximum elongation direction is N50W. The results of this study, together with the volcanological data available for the past 3 ka of activity, suggest that the eastern part of the resurgent block is the area with the highest probability of vent opening in case of renewal of 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.

Use of multiple in situ instruments and remote sensed satellite data for calibration tests at Solfatara (Campi Flegrei volcanic area)

NASA Astrophysics Data System (ADS)

Silvestri, Malvina; Musacchio, Massimo; Fabrizia Buongiorno, Maria; Doumaz, Fawzi; Andres Diaz, Jorge

2017-04-01

Monitoring natural hazards such as active volcanoes requires specific instruments to measure many parameters (gas emissions, surface temperatures, surface deformation etc.) to determine the activity level of a volcano. Volcanoes in most cases present difficult and dangerous environment for scientists who need to take in situ measurements. Remote Sensing systems on board of satellite permit to measure a large number of parameters especially during the eruptive events but still show large limits to monitor volcanic precursors and phenomena at local scale (gas species emitted by fumarole or summit craters degassing plumes and surface thermal changes of few degrees) for their specific risk. For such reason unmanned aircraft systems (UAS) mounting a variety of multigas sensors instruments (such as miniature mass spectrometer) or single specie sensors (such as electrochemical and IR sensors) allow a safe monitoring of volcanic activities. With this technology, it is possible to perform monitoring measurements of volcanic activity without risking the lives of scientists and personnel performing analysis during the field campaigns in areas of high volcanic activity and supporting the calibration and validation of satellite data measurements. These systems allowed the acquisition of real-time information such as temperature, pressure, relative humidity, SO2, H2S, CO2 contained in degassing plume and fumaroles, with GPS geolocation. The acquired data are both stored in the sensor and transmitted to a computer for real time viewing information. Information in the form of 3D concentration maps can be returned. The equipment used during the campaigns at Solfatara Volcano (in 2014, 2015 and 2016) was miniaturized instruments allowed measurements conducted either by flying drones over the fumarolic sites and by hand carrying into the fumaroles. We present the results of the field campaign held in different years at the Solfatara of Pozzuoli, near Naples, concerning measurements of CO2, H2S and SO2. The campaigns were carried out in collaboration with the University of Costa Rica and Jet Propulsion Laboratory of the California Institute of Technology (Pasadena, California) and has allowed the acquisition of a number of measures through scientific miniaturized multi-gas, thermal cameras and spectro-radiometer. The acquired measurements have also permitted the calibration and validation of satellite data as ASTER and LANDSAT8 (in collaboration with USGS). We believe that the rapid increasing of technology developments will permit the use UAS to integrate geophysical measurements and contribute to the necessary calibration and validation of current and future satellite missions dedicated to the measurements of surface temperatures and gas emissions in volcanic areas.

From "Volcanic Field" to "Volcanic Province": A Continuum of Spatial-Clustered Structures With Geological Significance or a Matter of Academic Snobbism?

NASA Astrophysics Data System (ADS)

Canon-Tapia, E.

2017-12-01

"Volcanic Field" is a term commonly used to describe a group of small, monogenetic and dominantly basaltic volcanoes, but that often includes groups of mixed monogenetic and polygenetic edifices. Besides ambiguities on the type of edifice that should be considered to form a VF, there is a lack of agreement concerning the number of volcanoes required to define a VF (ranging from five to over 1000), it is uncertain if the area covered by the volcanoes forming a VF must have a minimum number of volcanoes/unit area, or if the distance between adjacent structures needs to have a specific length. Furthermore, in many cases it is uncertain whether some area is occupied by two adjacent fields or if it is occupied by two subgroups belonging to a unique field. On the other hand, in analogy with the official definition of a geologic province, a "Volcanic Province" can be defined as a large region or area characterized by similar volcanic features, or by a history differing significantly from that of adjacent areas. Because neither the dimensions of the region nor the characteristics of the features to be used as reference are specified, there is an inherent ambiguity in this definition, which in some cases might become the source of unnecessary confusion. This work presents a review of the various ambiguities that remain unaddressed on the definition of a VF, and that bear some connection with the definition of VPs in general, with special interest in intraplate settings. It is shown that questions such as a) how many volcanoes are required to form a VF and b) when two "neighbor" volcanoes should not be considered to be part of the same field, can be adequately addressed by adopting the techniques of cluster analysis. Other parameters might not be as easy to address including aspects related to total volume of magma erupted, overall composition of the erupted products and age spans of activity and intermediate gaps. Based on the evidence presented, it is shown that there is a continuum of clustering structures at various spatial scales, some of which have direct geodynamic interpretations. Consequently, it is argued that the need of producing more rigorous definitions of a VF and a VP is not a matter of mere academic interest, but it is required as an aid to appreciate the different scales at which volcanic activity can self-organize at a planetary scale.

Self-sustained vibrations in volcanic areas extracted by Independent Component Analysis: a review and new results

NASA Astrophysics Data System (ADS)

de Lauro, E.; de Martino, S.; Falanga, M.; Palo, M.

2011-12-01

We investigate the physical processes associated with volcanic tremor and explosions. A volcano is a complex system where a fluid source interacts with the solid edifice so generating seismic waves in a regime of low turbulence. Although the complex behavior escapes a simple universal description, the phases of activity generate stable (self-sustained) oscillations that can be described as a non-linear dynamical system of low dimensionality. So, the system requires to be investigated with non-linear methods able to individuate, decompose, and extract the main characteristics of the phenomenon. Independent Component Analysis (ICA), an entropy-based technique is a good candidate for this purpose. Here, we review the results of ICA applied to seismic signals acquired in some volcanic areas. We emphasize analogies and differences among the self-oscillations individuated in three cases: Stromboli (Italy), Erebus (Antarctica) and Volcán de Colima (Mexico). The waveforms of the extracted independent components are specific for each volcano, whereas the similarity can be ascribed to a very general common source mechanism involving the interaction between gas/magma flow and solid structures (the volcanic edifice). Indeed, chocking phenomena or inhomogeneities in the volcanic cavity can play the same role in generating self-oscillations as the languid and the reed do in musical instruments. The understanding of these background oscillations is relevant not only for explaining the volcanic source process and to make a forecast into the future, but sheds light on the physics of complex systems developing low turbulence.

Late Pleistocene-Holocene volcanic activity in northern Victoria Land recorded in Ross Sea (Antarctica) marine sediments

NASA Astrophysics Data System (ADS)

Del Carlo, P.; Di Roberto, A.; Di Vincenzo, G.; Bertagnini, A.; Landi, P.; Pompilio, M.; Colizza, E.; Giordano, G.

2015-05-01

Eight pyroclastic fall deposits have been identified in cores of Late Pleistocene-Holocene marine sediments from the Ross Sea (Antarctica), and their components, granulometry and clast morphologies were analysed. Sedimentological, petrographic and geochemical analysis of clasts, with 40Ar-39Ar dating of alkali feldspar grains, indicate that during this period at least five explosive eruptions of mid to high intensity (plinian to subplinian) occurred, and that three of these eruptions took place from Mount Melbourne volcanic complex, between 137.1 ± 3.4 and 12 ka. Geochemical comparison of the studied tephra with micro- and crypto-tephra recovered from deep Antarctic ice cores and from nearby englacial tephra at Frontier Mountain indicates that eruptive activity in the Melbourne Volcanic Province of northern Victoria Land was intense during the Late Pleistocene-Holocene, but only a general area of provenance for the majority of the identified tephra can be identified.

Mount Rainier: learning to live with volcanic risk

USGS Publications Warehouse

Driedger, C.L.; Scott, K.M.

2002-01-01

Mount Rainier in Washington state is an active volcano reaching more than 2.7 miles (14,410 feet) above sea level. Its majestic edifice looms over expanding suburbs in the valleys that lead to nearby Puget Sound. USGS research over the last several decades indicates that Mount Rainier has been the source of many volcanic mudflows (lahars) that buried areas now densely populated. Now the USGS is working cooperatively with local communities to help people live more safely with the volcano.

Spatial and temporal variations of diffuse CO_{2} degassing at the Tenerife North-South Rift Zone (NSRZ) volcano (Canary Islands) during the period 2002-2016

NASA Astrophysics Data System (ADS)

Rodríguez, Fátima; McCollum, John J. K.; Orland, Elijah D. M.; Barrancos, José; Padilla, Germán D.; Calvo, David; Amonte, Cecilia; Pérez, Nemesio M.

2017-04-01

Subaerial volcanic activity on Tenerife (2034 km2), the largest island of the Canary archipelago, started 14 My ago and 4 volcanic eruptions have occurred in historical times during the last 300 years. The main volcano-structural and geomorphological features of Tenerife are (i) the central volcanic complex, nowadays formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and partially filled by post-caldera volcanic products and (ii) the triple junction-shaped rift system, formed by numerous aligned monogenetic cones. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 My (Dóniz et al., 2008). The North-South Rift Zone (NSRZ) of Tenerife comprises at least 139 cones. The main structural characteristic of the NSRZ of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Since there are currently no visible gas emissions at the NSRZ, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. Five diffuse CO2 degassing surveys have been carried out at NSRZ of Tenerife since 2002, the last one in the summer period of 2016, to evaluate the spatio-temporal variations of CO2 degassing as a volcanic surveillance tool for the NSRZ of Tenerife. At each survey, around 600 sampling sites were selected to cover homogenously the study area (325 km2) using the accumulation chamber method. The diffuse CO2 output ranged from 78 to 707 t/d in the study period, with the highest emission rate measured in 2015. The backgroung emission rate was estimated in 300 t/d. The last results the soil CO2 efflux values ranged from non-detectable up to 24.7 g m-2 d-1. The spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, showed the highest CO2 values as multiple isolated anomalies and did not show a clear relation with the main volcano-structural features of the area. The CO2 output released to the atmosphere in a diffuse way has been estimated at 524 t d-1, which represents a value lower than the previous one (707 t d-1 at summer of 2015) but higher than the background emission rate. These changes in the temporal series confirm the need of periodic diffuse emission surveys in the area as a powerful volcanic surveillance tool in volcanic systems where visible gas emanations are absent. References: Dóniz et al., 2008. J. Volcanol. Geotherm. Res. 173, 185.

Recurrence rate and magma effusion rate for the latest volcanism on Arsia Mons, Mars

NASA Astrophysics Data System (ADS)

Richardson, Jacob A.; Wilson, James A.; Connor, Charles B.; Bleacher, Jacob E.; Kiyosugi, Koji

2017-01-01

Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-km-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 km in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130 Ma. Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this approach to the 29 volcanic vents, volcanism likely began around 200-300 Ma then first peaked around 150 Ma, with an average production rate of 0.4 vents per Myr. The recurrence rate estimated including stratigraphic data is distinctly bimodal, with a second, lower peak in activity around 100 Ma. Volcanism then waned until the final vents were produced 10-90 Ma. Based on this model, volume flux is also bimodal, reached a peak rate of 1-8 km3 Myr-1 by 150 Ma and remained above half this rate until about 90 Ma, after which the volume flux diminished greatly. The onset of effusive volcanism from 200-150 Ma might be due to a transition of volcanic style away from explosive volcanism that emplaced tephra on the western flank of Arsia Mons, while the waning of volcanism after the 150 Ma peak might represent a larger-scale diminishing of volcanic activity at Arsia Mons related to the emplacement of flank apron lavas.

Recurrence Rate and Magma Effusion Rate for the Latest Volcanism on Arsia Mons, Mars

NASA Technical Reports Server (NTRS)

Richardson, Jacob A.; Wilson, James A.; Connor, Charles B.; Bleacher, Jacob E.; Kiyosugi, Koji

2016-01-01

Magmatism and volcanism have evolved the Martian lithosphere, surface, and climate throughout the history of Mars. Constraining the rates of magma generation and timing of volcanism on the surface clarifies the ways in which magma and volcanic activity have shaped these Martian systems. The ages of lava flows on other planets are often estimated using impact crater counts, assuming that the number and size-distribution of impact craters per unit area reflect the time the lava flow has been on the surface and exposed to potential impacts. Here we show that impact crater age model uncertainty is reduced by adding stratigraphic information observed at locations where neighboring lavas abut each other, and demonstrate the significance of this reduction in age uncertainty for understanding the history of a volcanic field comprising 29 vents in the 110-kilometer-diameter caldera of Arsia Mons, Mars. Each vent within this caldera produced lava flows several to tens of kilometers in length; these vents are likely among the youngest on Mars, since no impact craters in their lava flows are larger than 1 kilometer in diameter. First, we modeled the age of each vent with impact crater counts performed on their corresponding lava flows and found very large age uncertainties for the ages of individual vents, often spanning the estimated age for the entire volcanic field. The age model derived from impact crater counts alone is broad and unimodal, with estimated peak activity in the field around 130Ma (megaannum, 1 million years). Next we applied our volcano event age model (VEAM), which uses a directed graph of stratigraphic relationships and random sampling of the impact crater age determinations to create alternative age models. Monte Carlo simulation was used to create 10,000 possible vent age sets. The recurrence rate of volcanism is calculated for each possible age set, and these rates are combined to calculate the median recurrence rate of all simulations. Applying this approach to the 29 volcanic vents, volcanism likely began around 200-300Ma then first peaked around 150Ma, with an average production rate of 0.4 vents per Myr (million years). The recurrence rate estimated including stratigraphic data is distinctly bimodal, with a second, lower peak in activity around 100Ma. Volcanism then waned until the final vents were produced 10-90Ma. Based on this model, volume flux is also bimodal, reached a peak rate of 1-8 cubic kilometers per million years by 150Ma and remained above half this rate until about 90Ma, after which the volume flux diminished greatly. The onset of effusive volcanism from 200-150Ma might be due to a transition of volcanic style away from explosive volcanism that emplaced tephra on the western flank of Arsia Mons, while the waning of volcanism after the 150Ma peak might represent a larger-scale diminishing of volcanic activity at Arsia Mons related to the emplacement of flank apron lavas.

Frequency Based Volcanic Activity Detection through Remotely Sensed Data

NASA Astrophysics Data System (ADS)

Worden, A. K.; Dehn, J.; Webley, P. W.

2015-12-01

Satellite remote sensing has proved to offer a useful and relatively inexpensive method for monitoring large areas where field work is logistically unrealistic, and potentially dangerous. Current sensors are able to detect the majority of explosive volcanic activity; those that tend to effect and represent larger scale changes in the volcanic systems, eventually relating to ash producing periods of extended eruptive activity, and effusive activity. As new spaceborne sensors are developed, the ability to detect activity improves so that a system to gauge the frequency of volcanic activity can be used as a useful monitoring tool. Four volcanoes were chosen for development and testing of a method to monitor explosive activity: Stromboli (Italy); Shishaldin and Cleveland (Alaska, USA); and Karymsky (Kamchatka, Russia). Each volcano studied had similar but unique signatures of pre-cursory and eruptive activity. This study has shown that this monitoring tool could be applied to a wide range of volcanoes and still produce useful and robust data. Our method deals specifically with the detection of small scale explosive activity. The method described here could be useful in an operational setting, especially at remote volcanoes that have the potential to impact populations, infrastructure, and the aviation community. A number of important factors will affect the validity of application of this method. They are: (1) the availability of a continuous and continually populated dataset; (2) appropriate and reasonable sensor resolutions; (3) a recorded history of the volcano's previous activity; and, if available, (4) some ground-based monitoring system. We aim to develop the method further to be able to capture and evaluate the frequency of other volcanic processes such as lava flows, phreatomagmatic eruptions and dome growth and collapse. The work shown here has served to illustrate the capability of this method and monitoring tool for use at remote, un-instrumented volcanoes.

Effects of the Karacadag Volcanic Complex on the thermal structure and geothermal potential of southeast Anatolia

NASA Astrophysics Data System (ADS)

Bilim, Funda; Aydemir, Attila; Kosaroglu, Sinan; Bektas, Ozcan

2018-06-01

The Karacadag Volcanic Complex (KVC) is the largest volcanic unit in SE Turkey. It is also defined as a shield volcano on the northernmost part of the Arabian Plate. The main goal of this study is to investigate the geothermal potential of this region associated with the magnetic signature of this volcanic complex and surrounding area. Besides this primary objective, the possibility of there being volcanic intrusion into the buried fault zones under the volcanic cover are also investigated to determine the interrelations between the active tectonics and heat flow in the area. A spectral analysis method is applied to the magnetic anomalies of the volcanic rocks to identify the Curie point depth (CPD) and geothermal gradient, as well as to estimate heat flow and radiogenic heat production of radioactive minerals in the complex. A tilt angle map is also presented, in correlation with instrumentally recorded earthquake magnitudes, to indicate tectonic trends that are consistent with the maps of the thermal parameters in this study. In contrast with expectations for the KVC area, the region around Akcakale and Suruc Grabens is the most prolific zone for geothermal potential, despite them not showing strong magnetic anomalies. Curie point depths are shallow, down to 18 km, around the Akcakale Graben, and deeper, down to 22 km, around the Bitlis-Zagros Suture Zone where the geothermal gradients increase from 26 to 32 °C km-1 through the graben area. Heat flows in this zone are in the range from 75 to 90 mW m-2 depending on the thermal conductivity coefficient (2.3, 2.5, 2.7, and 3.0 W m-1 K-1) used. Radiogenic heat production values also indicate slightly changing spectra in the range 0.19 to 0.25 μW m-3). None of these parameters are focused around Mt. Karacadag. However, the earthquake epicenters (generally M ≤ 4) are aligned with the boundary faults of the Akcakale Graben where the CPD, geothermal gradient, and heat flow maps indicate relatively high potential. We thus suggest that this graben area would be good for future geothermal exploration. On the contrary, considering the low geothermal gradient and heat flow values, Mt. Karacadag can be accepted as being an extinct volcano, despite its apparent, high, magnetic anomalies.

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

Benkovitz, C.M.

Sulfur emissions from volcanoes are located in areas of volcanic activity, are extremely variable in time, and can be released anywhere from ground level to the stratosphere. Previous estimates of global sulfur emissions from all sources by various authors have included estimates for emissions from volcanic activity. In general, these global estimates of sulfur emissions from volcanoes are given as global totals for an ``average`` year. A project has been initiated at Brookhaven National Laboratory to compile inventories of sulfur emissions from volcanoes. In order to complement the GEIA inventories of anthropogenic sulfur emissions, which represent conditions circa specific years,more » sulfur emissions from volcanoes are being estimated for the years 1985 and 1990.« less

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.

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 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.

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.

People's behaviour in the face of volcanic hazards: Perspectives from Javanese communities, Indonesia

NASA Astrophysics Data System (ADS)

Lavigne, Franck; De Coster, Benjamin; Juvin, Nancy; Flohic, François; Gaillard, Jean-Christophe; Texier, Pauline; Morin, Julie; Sartohadi, Junun

2008-05-01

This paper is concerned with the way in which the Indonesian people living on the slopes or near active volcanoes behave in the face of volcanic threats. It explores the role of three factors in the shaping of this behaviour, e.g. risk perception, cultural beliefs and socio-economic constraints. The paper is mainly based on field data collected during the last 5 years on four volcanoes in Central Java, namely Sumbing, Sindoro, Dieng, and Merapi. The common assumption that hazard knowledge, risk perception and people's behaviour are closely related and conditional on volcanic activity is debatable in the Indonesian context. Factors that play a role in hazard knowledge—e.g. basic knowledge of volcanic processes, personal experience of volcanic crisis, time lapsed since the last volcanic eruption, etc.—differ from those that influence risk perception. Indeed, local people often underestimate the scientifically or statistically estimated risk. This poor risk perception is characterized by an approximate personal representation of the volcanic processes, an excess of trust in concrete countermeasures, the presence of a physical-visual obstructions, or cultural beliefs related to former eruptions. In addition, the commonly-acknowledged factors that influence hazard knowledge and/or risk perception may be at odds with the non hazard-related factors that prompt or force people to live in or to exploit areas at risk. These factors may be either socio-cultural—e.g., attachment to place, cultural beliefs, etc.—or social and socio-economical —e.g., standard of living, strength of people's livelihoods, well-being. These factors are fundamental in explaining the short-term behaviour in the face of a developing threat during a volcanic crisis.

[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.

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.

Modern volcanic activity on the Moon

NASA Astrophysics Data System (ADS)

Vidmachenko, A. P.

2018-05-01

Volcanic activity on the Moon began when its surface cooled, and the nucleus and mantle were clearly separated inside. Fragments of volcanic eruptions were discovered in the lunar soil, which was delivered to the Earth by "Apollo" spacecrafts. As shown by the analysis of some lunar meteorites, the first eruptions occurred 4.35 billion years ago. This is evidenced by the unique composition of the oxygen atoms for the Moon and on the radiocarbon analysis data. Well-visible on its surface, the dark "seas", which emerged shortly after the formation of the Moon, when the lowlands and large old craters were filled by liquid basaltic magma, rich in iron. The lunar "seas" are mostly on the visible side of the Moon, and cover almost a third of it; on the reverse side-the seas occupy less than 2%. Smooth surfaces of the seas mean that the lunar lava was very liquid. Therefore, at low gravity, it easily spread over a large area, almost without creating large cone-shaped peaks, but forming many small cone volcanic systems with an age of 3-4 billion years ago. On the images of the visible side of the Moon obtained with the help of the LRO, evidence is provided that volcanic eruptions on its surface were possible even a few million years ago.

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).

Bottom Characterization with High Resolution Sonar Data and Geochemical Analyses of an Uninvestigated Cone in Lagoa das Furnas on São Miguel Island, Azores Archipelago

NASA Astrophysics Data System (ADS)

Andersson, T.

2015-12-01

Lagoa das Furnas is a crater lake located in an area exposed to geohazards from earthquakes and volcanic activity on the island São Miguel in the Azores Archipelago. The Furnas volcanic center has a long history of earthquakes and volcanic activity. The area is relatively well studied except for the lake floor. Therefore, a high resolution geophysical and geological mapping survey was conducted at Lagoa das Furnas. Sidescan sonar was used to map the surface of the lake floor and single beam sonar was used to acquire sub-bottom profiles. In addition to the geophysical mapping, sediment surface sampling and core drilling were carried out followed by geochemical analyses of the retrieved material. The mapped data permitted a characterization of the floor of Lagoa das Furnas and revealed several volcanic features including fumarolic activity and a previously uninvestigated volcanic cone in the southern part of the lake. In order to unravel the origin of this cone several methods were applied, including analyses of tephra and minerals collected from the cone itself and from nearby deposits of two known eruptions, Furnas I and Furnas 1630. Sedimentological, petrological, geochemical and geochronological studies of pyroclastic deposits from the cone suggest a subaqueous eruption linked to the Furnas 1630 eruption. The chemistry of glass and crystal fragments sampled from the cone suggests that it is composed of more evolved magma than that of the main Furnas 1630, implying that the lake cone is likely a product of the last eruptional phase. According to historical records, two of three lakes were lost due the Furnas 1630 eruption. The results of this study show that the remaining lake is most likely Lagoa das Furnas, which consequently must have existed before the 1630 eruption.

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.

Mus musculus bone fluoride concentration as a useful biomarker for risk assessment of skeletal fluorosis in volcanic areas.

PubMed

Linhares, Diana; Camarinho, Ricardo; Garcia, Patrícia Ventura; Rodrigues, Armindo Dos Santos

2018-08-01

Fluoride is often found in elevated concentrations in volcanic areas due to the release of magmatic fluorine as hydrogen fluorine through volcanic degassing. The exposure to high levels of fluoride can affect the processes of bone formation and resorption causing skeletal fluorosis, a pathology that can easily be mistaken for other skeletal diseases. In this study, we aimed to determine if fluoride concentration in the femoral bone of wild populations of the house mouse (Mus musculus) is a good biomarker of exposure to active volcanic environments naturally enriched in fluoride, allowing their use in biomonitoring programs. The fluoride concentration of the whole femoral bone of 9 mice from Furnas (5 males and 4 females) and 33 mice from Rabo de Peixe (16 males and 17 females) was measured by the potentiometric method with a fluoride ion selective electrode. Fluoride in bones was significantly higher in the mice from Furnas when compared with the mice from Rabo de Peixe (616.5 ± 129.3 μg F/g vs. 253.8 ± 10.5 μg F/g). Accumulation rates were also significantly higher in the mice collected in Furnas when compared with Rabo de Peixe individuals (3.84 ± 0.52 μg F/day vs. 1.22 ± 0.06 μg F/day). The results demonstrate a significant association between exposure to fluoride in the active volcanic environment and fluoride content in bone, revealing that bone fluoride concentration is a suitable biomarker of chronic environmental exposure to fluoride. Copyright © 2018 Elsevier Ltd. All rights reserved.

Upward migration of the explosion sources at Sakurajima volcano, Japan, revield by a seismic network in the close vocinity of the summit crater

NASA Astrophysics Data System (ADS)

Ohminato, T.; Kaneko, T.; Koyama, T.; Watanabe, A.; Takeo, M.; Iguchi, M.

2011-12-01

Observations in the vicinity of summit area of active volcanoes are important not only for understanding physical processes in the volcanic conduit but also for eruption prediction and volcanic hazards mitigation. It is, however, challenging to install observation sensors near active vents because of the danger of sudden eruptions. We have been developing a volcano observation system based on an unmanned aerial vehicle (UAV) for safe observations near active volcanic vents. We deployed an unmanned autonomous helicopter which can aviate autonomously along a previously programmed path within a meter accuracy using real-time kinematics differential GPS equipment. The maximum flight time, flight distance, and payload are 90 minutes, 5km, and 10kg, respectively. By using the UAV, we installed seismic stations at the summit area of Sakurajima volcano, Japan. Since 2006, explosive eruptions have been continuing at the reopened Showa crater at the eastern flank near the summit of Sakurajima. Entering the area within 2 km from the active craters is prohibited, and thus there were no observation station in the summit area. From November 2nd to 12th, 2009, and from November 2nd to 12th, 2010, we conducted seismic station installation in Sakurajima summit area using UAV and successfully installed four seismic stations within 2km from the active craters. Since the installation of the seismic stations, we have succeeded in acquiring waveform data accompanying more than 500 moderate eruptions at Showa-crater. Except for the mechanical resonance contamination at 35Hz, the recorded waveforms are as good as that recorded at permanent stations in Sakurajima. Since the beginning of the observation in the vicinity of the summit crater, the normalized amplitudes of the signals accompanying eruptions at Showa crater had been almost steady. However, after early April 2011, gradual increase of the normalized amplitude started, and this increasing trend is continuing at the time of the abstract submission. This increasing trend of the normalized amplitude strongly suggests upward migration of the source of the explosive eruptions at Showa-crater. The upward migration may suggest further intensification of the activity of Sakurajima in the near future.

Potential Magma Chambers beneath the Tatun Volcanic Area, Taiwan: Results from Magnetotelluric Survey and Monitoring

NASA Astrophysics Data System (ADS)

Chen, C.

2013-12-01

Previous earthquakes analysis indicated existing seismicity anomaly beneath Tatun volcano, Taiwan, possibly caused by the fluid activity of the volcano. Helium isotope studies also indicated that over 60% of the fumarolic gases and vapors originated from deep mantle in the Tatun volcano area. The chemistry of the fumarolic gases and vapors and seismicity anomaly are important issues in view of possible magma chamber in the Tatun volcano, where is in the vicinity of metropolitan Taipei, only 15 km north of the capital city. In this study magnetotelluric (MT) soundings and monitoring were deployed to understand the geoelectric structures in the Tatun volcano as Electromagnetic methods are sensitive to conductivity contrasts and can be used as a supplementary tool to delineate reservoir boundaries. An anticline extending more than 10 km beneath the Chih-Shin-Shan and Da-You-Kan areas was recognized. Low resistivity at a shallow and highly porous layer 500m thick might indicate circulation of heated water. However, a high resistivity layer at depth between 2 and 6 km was detected. This layer could be associated with high micro-earthquakes zone. The characteristics of this layer produced by either the magma chamber or other geothermal activity were similar to that of some other active volcanic areas in the world. At 6 km underground was a dome structure of medium resistivity. This structure could be interpreted as a magma chamber in which the magma is possibly cooling down, as judged by its relatively high resistivity. The exact attributes of the magma chamber were not precisely determined from the limited MT soundings. At present, a joint monitors including seismic activity, ground deformation, volcanic gases, and changes in water levels and chemistry are conducted by universities and government agencies. When unusual activity is detected, a response team may do more ground surveys to better determine if an eruption is likely.

Cenozoic volcanic geology and probable age of inception of basin-range faulting in the southeasternmost Chocolate Mountains, California

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

Crowe, B.M.

1978-02-01

A complex sequence of Oligocene-age volcanic and volcaniclastic rocks form a major volcanic center in the Picacho area of the southeasternmost Chocolate Mountains, Imperial County, California. Basal-volcanic rocks consist of lava flows and flow breccia of trachybasalt, pyroxene rhyodacite, and pyroxene dacite (32 My old). These volcanic rocks locally overlie fanglomerate and rest unconformably on pre-Cenozoic basement rocks. South and southeast of a prominent arcuate fault zone in the central part of the area, the rhyolite ignimbrite (26 My old) forms a major ash-flow sheet. In the southwestern part of the Picacho area the rhyolite ignimbrite interfingers with and ismore » overlain by dacite flows and laharic breccia. The rhyolite ignimbrite and the dacite of Picacho Peak are overlapped by lava flows and breccia of pyroxene andesite (25 My old) that locally rest on pre-Cenozoic basement rocks. The volcanic rocks of the Picacho area form a slightly bimodal volcanic suite consisting chiefly of silicic volcanic rocks with subordinate andesite. Late Miocene augite-olivine basalt is most similar in major-element abundances to transitional alkali-olivine basalt of the Basin and Range province. Normal separation faults in the Picacho area trend northwest and north parallel to major linear mountain ranges in the region. The areal distribution of the 26-My-old rhyolite ignimbrite and the local presence of megabreccia and fanglomerate flanking probable paleohighs suggest that the ignimbrite was erupted over irregular topography controlled by northwest- and north-trending probable basin-range faults. These relations date the inception of faulting in southeasternmost California at pre-26 and probably pre-32 My ago. A transition of basaltic volcanism in the area is dated at 13 My ago. 9 figures, 2 tables.« less

3D seismic imaging of voluminous earliest Eocene buried lava fields and coastal escarpments off mid-Norway

NASA Astrophysics Data System (ADS)

Planke, Sverre; Millett, John M.; Maharjan, Dwarika; Jerram, Dougal A.; Mansour Abdelmalak, Mohamed

2017-04-01

Continental breakup between Greenland and NW Europe in the Paleogene was associated with massive basaltic volcanism, forming kilometer-thick sequences of flood basalts along the conjugate rifted margins. This event was temporarily associated with a warm world, the early Eocene greenhouse, and the short-lived Paleocene-Eocene Thermal Maximum (PETM). A 2500 km2 large industry-standard 3D seismic cube has recently been acquired on the Vøring Marginal High offshore mid-Norway to image sub-basalt sedimentary rocks. This cube also provides a unique opportunity for imaging top- and intra-basalt structures. Detailed seismic geomorphological interpretation of the Top basalt horizon reveal new insight into the late-stage development of the lava flow fields and the kilometer high coastal Vøring Escarpment. Subaerial lava flows with compressional ridges and inflated lava lobes cover the marginal high, with comparable structure and size to modern subaerial lava fields. Pitted surfaces, likely formed by lava emplaced in a wet environment, are present in the western part of the study area near the continent-ocean boundary. The prominent Vøring Escarpment formed when eastward-flowing lava reached the coastline. The escarpment morphology is influenced by pre-existing structural highs, and locally these highs are by-passed by the lava flows which are clearly deflected around them. Volcanogenic debris flows are well-imaged on the escarpment horizon along with large-scale slump blocks. Similar features exist in active volcanic environments, e.g. on the south coast of Hawaii. Numerous post-volcanic extensional faults and incised channels cut both into the marginal high and the escarpment, and show that the area was geologically active after the volcanism ceased. In conclusion, igneous seismic geomorphology and seismic volcanostratigraphy are two very powerful methods to understand the volcanic deposits and development of rifted margins, and the association of major volcanic events and global warming.

3-D modeling of magnetotelluric data in the Paniri-Toconce volcanic chain, Central Andes.

NASA Astrophysics Data System (ADS)

Mancini, R.; Brasse, H.; Diaz, D.

2017-12-01

The research is located in the San Pedro-Toconce volcanic chain in the central volcanic zone of the Andes, North Chile. This area is interesting because of its proximity to several active volcanic centers, the geysers field of El Tatio and the recently opened geothermal plant Cerro Pabellon. Thermobarometry studies made in the area point to magma accumulated at 8 km below Lavas de Chao, and depths greater than 24 km below Toconce and Cerro de Leon. Regional geophysical studies show a distribution of conductive bodies around the complex, but the resolution of these studies at shallow depths are not conclusive. Data from wells show the possible presence of a large geothermal system in the southwest part of the complex, with depths of 2 km. Twenty broadband magnetotelluric (MT) stations were measured in the vicinity of the complex and combined with 15 long period MT stations measured in the 1990s, aiming at characterizing the deep conductive structures previously observed in the area, with magmatic bodies associated with the adjacent volcanic system. The results of a 3-D inversion show several conductive anomalies around the complex. Analyses of conductivity together with the 3-D models obtained indicate the presence of a geothermal system to the southwest of the complex with maximum depths of about 5 km, and two possible magmatic chambers below Paniri volcano and between Paniri and San Pedro volcanoes. In addition, the presence of a highly conductive structure to the east is obtained, associated with the Altiplano-Puna magma body (APMB).

Volcano hazards at Fuego and Acatenango, Guatemala

USGS Publications Warehouse

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

2001-01-01

The Fuego-Acatenango massif comprises a string of five or more volcanic vents along a north-south trend that is perpendicular to that of the Central American arc in Guatemala. From north to south known centers of volcanism are Ancient Acatenango, Yepocapa, Pico Mayor de Acatenango, Meseta, and Fuego. Volcanism along the trend stretches back more than 200,000 years. Although many of the centers have been active contemporaneously, there is a general sequence of younger volcanism, from north to south along the trend. This massive volcano complex towers more than 3500 meters (m) above the Pacific coastal plain to the south and 2000 m above the Guatemalan Highlands to the north. The volcano complex comprises remnants of multiple eruptive centers, which periodically have collapsed to form huge debris avalanches. The largest of these avalanches extended more than 50 kilometers (km) from its source and covered more than 300 square km. The volcano has potential to produce huge debris avalanches that could inundate large areas of the Pacific coastal plain. In areas around the volcanoes and downslope toward the coastal plain, more than 100,000 people are potentially at risk from these and other flowage phenomena.

Application of ASAR-ENVISAT Data for Monitoring Andean Volcanic Activity : Results From Lastarria-Azufre Volcanic Complex (Chile-Argentina)

NASA Astrophysics Data System (ADS)

Froger, J.; Remy, D.; Bonvalot, S.; Franco Guerra, M.

2005-12-01

Since the pioneer study on Mount Etna by Massonnet et al., in 1995, several works have illustrated the promising potentiality of Synthetic Aperture Radar Interferometry (INSAR) for the monitoring of volcanoes. In the case of wide, remote or hazardous volcanic areas, in particular, INSAR represents a safer and more economic way to acquire measurements than from ground based geodetic networks. Here we present the preliminary results of an interferometric survey made with ASAR-ENVISAT data on a selection of South American volcanoes where deformation signals had been previously evidenced or are expected. An interesting result is the detection of a present-day active ground deformation on the Azufre-Lastarria area (Chile-Argentina) indicating that process, identified during 1998-2000 by Pritchard and Simmons (2004) from ERS data, is still active. The phase signal visible on ASAR interferograms (03/2003-06/2005) is roughly elliptical with a 45 km NNE-SSW major axis. Its amplitude increases as a function of time and is compatible with ground uplift in the line of sight of the satellite. The ASAR time series (up to 840 days, 7 ASAR images) indicates variable deformation rate that might confirm the hypothesis of a non uniform deformation process. We investigated the origin and the significance of the deformation using various source modelling strategies (analytical and numerical). The observed deformation can be explained by the infilling of an elliptical magmatic reservoir lying between 7 and 10 km depth. The deformation could represent the first stage of a new caldera forming as it is correlated with a large, although subtle, topographic depression surrounded by a crown of monogenetic centers. A short wavelength inflation has also been detected on Lastaria volcano. It could result from the on-going infilling of a small subsurface magmatic reservoir, eventually supplied by the deeper one. All these observations point out the need of a closer monitoring of this area in order to assess future volcanic hazard.

Volcanic Structures Within Niger and Dao Valles, Mars, and Implications for Outflow Channel Evolution and Hellas Basin Rim Development

NASA Astrophysics Data System (ADS)

Korteniemi, J.; Kukkonen, S.

2018-04-01

Outflow channel formation on the eastern Hellas rim region is traditionally thought to have been triggered by activity phases of the nearby volcanoes Hadriacus and Tyrrhenus Montes: As a result of volcanic heating subsurface volatiles were mobilized. It is, however, under debate, whether eastern Hellas volcanism was in fact more extensive, and if there were volcanic centers separate from the identified central volcanoes. This work describes previously unrecognized structures in the Niger-Dao Valles outflow channel complex. We interpret them as volcanic edifices: cones, a shield, and a caldera. The structures provide evidence of an additional volcanic center within the valles and indicate volcanic activity both prior to and following the formation of the outflow events. They expand the extent, type, and duration of volcanic activity in the Circum-Hellas Volcanic Province and provide new information on interaction between volcanism and fluvial activity.

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.

Cancer incidence among population utilizing geothermal hot water: a census-based cohort study.

PubMed

Kristbjornsdottir, Adalbjorg; Rafnsson, Vilhjalmur

2013-12-15

The aim of the study was to assess whether utilization of geothermal hot-water is associated with risk of cancer. The cohort from census was followed from 1981 to 2010 in nation-wide death and cancer registries. The moving apart of American-Eurasian tectonic plates, observed in Iceland, results in high volcanic activity. The definition of the study populations was based on geological information. The target population was inhabitants of communities located on bedrock younger than 3.3 million years, utilizing hot-water supply generated from geothermal wells since 1972. The two reference populations were inhabitants of communities without this hot-water supply located on areas with less volcanic/geothermal activity, and bedrock older than 3.3 million years. Hazard ratio (HR), and 95% confidence intervals (CI) were adjusted for age, gender, education, housing, reproductive factors and smoking. HR in the geothermal hot-water supply areas for all cancer was 1.15 (95% CI 1.05-1.25) as compared with nongeothermal areas. The HR for breast cancer was 1.40 (1.12-1.75), prostate cancer 1.61 (1.29-2.00), kidney cancer 1.64 (1.11-2.41), lymphatic and haematopoietic tissue cancers 1.45 (1.08-1.95), and for basal cell carcinoma (BCC) of the skin 1.46 (1.16-1.82). Positive exposure-response relations were observed between the risk of these cancers and the degree of volcanic/geothermal activity in the reference areas. Increased incidence of all cancers, breast, prostate, kidney cancer and BCC of the skin was found among the population utilizing geothermal hot-water for decades. More precise information on exposure is needed in future studies. Copyright © 2013 UICC.

Common features and peculiarities of the seismic activity at Phlegraean Fields, Long Valley, and Vesuvius

USGS Publications Warehouse

Marzocchi, W.; Vilardo, G.; Hill, D.P.; Ricciardi, G.P.; Ricco, C.

2001-01-01

We analyzed and compared the seismic activity that has occurred in the last two to three decades in three distinct volcanic areas: Phlegraean Fields, Italy; Vesuvius, Italy; and Long Valley, California. Our main goal is to identify and discuss common features and peculiarities in the temporal evolution of earthquake sequences that may reflect similarities and differences in the generating processes between these volcanic systems. In particular, we tried to characterize the time series of the number of events and of the seismic energy release in terms of stochastic, deterministic, and chaotic components. The time sequences from each area consist of thousands of earthquakes that allow a detailed quantitative analysis and comparison. The results obtained showed no evidence for either deterministic or chaotic components in the earthquake sequences in Long Valley caldera, which appears to be dominated by stochastic behavior. In contrast, earthquake sequences at Phlegrean Fields and Mount Vesuvius show a deterministic signal mainly consisting of a 24-hour periodicity. Our analysis suggests that the modulation in seismicity is in some way related to thermal diurnal processes, rather than luni-solar tidal effects. Independently from the process that generates these periodicities on the seismicity., it is suggested that the lack (or presence) of diurnal cycles is seismic swarms of volcanic areas could be closely linked to the presence (or lack) of magma motion.

Episodes of fluvial and volcanic activity in Mangala Valles, Mars

PubMed Central

Keske, Amber L.; Hamilton, Christopher W.; McEwen, Alfred S.; Daubar, Ingrid J.

2017-01-01

A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ~1 Ga, (2) emplacement of Tharsis lava flows in the valley from ~700 to 1000 Ma, (3) a megaflooding event at ~700–800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ~400–500 Ma, (5) another megaflooding event from ~400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ~300–350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ~300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars. PMID:29176911

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.

Automatized near-real-time short-term Probabilistic Volcanic Hazard Assessment of tephra dispersion before eruptions: BET_VHst for Vesuvius and Campi Flegrei during recent exercises

NASA Astrophysics Data System (ADS)

Selva, Jacopo; Costa, Antonio; Sandri, Laura; Rouwet, Dmtri; Tonini, Roberto; Macedonio, Giovanni; Marzocchi, Warner

2015-04-01

Probabilistic Volcanic Hazard Assessment (PVHA) represents the most complete scientific contribution for planning rational strategies aimed at mitigating the risk posed by volcanic activity at different time scales. The definition of the space-time window for PVHA is related to the kind of risk mitigation actions that are under consideration. Short temporal intervals (days to weeks) are important for short-term risk mitigation actions like the evacuation of a volcanic area. During volcanic unrest episodes or eruptions, it is of primary importance to produce short-term tephra fallout forecast, and frequently update it to account for the rapidly evolving situation. This information is obviously crucial for crisis management, since tephra may heavily affect building stability, public health, transportations and evacuation routes (airports, trains, road traffic) and lifelines (electric power supply). In this study, we propose a methodology named BET_VHst (Selva et al. 2014) for short-term PVHA of volcanic tephra dispersal based on automatic interpretation of measures from the monitoring system and physical models of tephra dispersal from all possible vent positions and eruptive sizes based on frequently updated meteorological forecasts. The large uncertainty at all the steps required for the analysis, both aleatory and epistemic, is treated by means of Bayesian inference and statistical mixing of long- and short-term analyses. The BET_VHst model is here presented through its implementation during two exercises organized for volcanoes in the Neapolitan area: MESIMEX for Mt. Vesuvius, and VUELCO for Campi Flegrei. References Selva J., Costa A., Sandri L., Macedonio G., Marzocchi W. (2014) Probabilistic short-term volcanic hazard in phases of unrest: a case study for tephra fallout, J. Geophys. Res., 119, doi: 10.1002/2014JB011252

Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

USGS Publications Warehouse

Vazquez, Jorge A.; Woolford, Jeff M

2015-01-01

The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

The North Tanzania Rift seen from multi geophysical tools: link between seismicity and resistivity

NASA Astrophysics Data System (ADS)

Gautier, S.; Plasman, M.; Tarits, P.; Hautot, S.; Tiberi, C.; Albaric, J.; Le Gall, B.; Deverchere, J.; Ebinger, C. J.; Roecker, S. W.; Ferdinand, R.; Muzuka, A.; Msabi, M.; Khalfan, M.; Gama, R.; Mulibo, G. D.

2016-12-01

The North Tanzania part of the East African Rift is the place of an incipient break up of the lithosphere. In this region, seismicity and volcanism seem strongly linked to the inherited structures, magmatic intrusion, and tectonic. Natron Lake is characterized by a shallow seismicity and present volcanic activity, whereas Manyara area is the location of a deeper seismicity and sparse volcanism. It is thus of prime interest to image the structure of this area to fully understand the role of each factor on the localisation of the current deformation at the surface. Since 2007 different multidisciplinary projects have taken place in this area to address this question. We present here a work based on a collaborative work between French, American and Tanzanian institutes that started in 2013. We have analysed more than a hundred teleseismic events and local seismicity to compute receiver function and local tomography. We combine this information with two MT profiles in order to image crustal and upper mantle structures. The resistivity deduced from the MT observations confirms the seismic results with a great difference within the crust and upper mantle between Natron and Manyara. The MT profiles evidence crustal structures such as major volcanic edifices, main tectonic units and interfaces. We discuss our combined images in terms of rift-craton interaction and magmatic intrusions.

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.

Different deformation patterns using GPS in the volcanic process of El Hierro (Canary Island) 2011-2013

NASA Astrophysics Data System (ADS)

García-Cañada, Laura; José García-Arias, María; Pereda de Pablo, Jorge; Lamolda, Héctor; López, Carmen

2014-05-01

Ground deformation is one of the most important parameter in volcano monitoring. The detected deformations in volcanic areas can be precursors of a volcanic activity and contribute with useful information to study the evolution of an unrest, eruption or any volcanic process. GPS is the most common technique used to measure volcano deformations. It can be used to detect slow displacement rates or much larger and faster deformations associated with any volcanic process. In volcanoes the deformation is expected to be a mixed of nature; during periods of quiescence it will be slow or not present, while increased activity slow displacement rates can be detected or much larger and faster deformations can be measure due to magma intrusion, for example in the hours to days prior a eruption beginning. In response to the anomalous seismicity detected at El Hierro in July 2011, the Instituto Geográfico Nacional (IGN) improved its volcano monitoring network in the island with continuous GPS that had been used to measure the ground deformation associated with the precursory unrest since summer 2011, submarine eruption (October 2011-March 2012) and the following unrest periods (2012-2013). The continuous GPS time series, together with other techniques, had been used to evaluate the activity and to detect changes in the process. We investigate changes in the direction and module of the deformation obtained by GPS and they show different patterns in every unrest period, very close to the seismicity locations and migrations.

Acute health effects associated with exposure to volcanic air pollution (vog) from increased activity at Kilauea Volcano in 2008.

PubMed

Longo, Bernadette M; Yang, Wei; Green, Joshua B; Crosby, Frederick L; Crosby, Vickie L

2010-01-01

In 2008, the Kilauea Volcano on the island of Hawai'i increased eruption activity and emissions of sulfurous volcanic air pollution called vog. The purpose of this study was to promptly assess for a relative increase in cases of medically diagnosed acute illnesses in an exposed Hawaiian community. Using a within-clinic retrospective cohort design, comparisons were made for visits of acute illnesses during the 14 wk prior to the increased volcanic emissions (low exposure) to 14 wk of high vog exposure when ambient sulfur dioxide was threefold higher and averaged 75 parts per billion volume per day. Logistic regression analysis estimated effect measures between the low- and high-exposure cohorts for age, gender, race, and smoking status. There were statistically significant positive associations between high vog exposure and visits for medically diagnosed cough, headache, acute pharyngitis, and acute airway problems. More than a sixfold increase in odds was estimated for visits with acute airway problems, primarily experienced by young Pacific Islanders. These findings suggest that the elevated volcanic emissions in 2008 were associated with increased morbidity of acute illnesses in age and racial subgroups of the general Hawaiian population. Continued investigation is crucial to fully assess the health impact of this natural source of sulfurous air pollution. Culturally appropriate primary- and secondary-level health prevention initiatives are recommended for populations in Hawai'i and volcanically active areas worldwide.

Radar Image, Hokkaido, Japan

NASA Image and Video Library

2000-05-18

The southeast part of the island of Hokkaido, Japan, is an area dominated by volcanoes and volcanic caldera. The active Usu Volcano is at the lower right edge of the circular Lake Toya-Ko and near the center of the image.

Anaglyph with Landsat Overlay, Kamchatka Peninsula, Russia

NASA Image and Video Library

2000-02-16

This 3-D anaglyph shows an area on the western side of the volcanically active Kamchatka Peninsula, Russia as seen by the instrument onboard NASA Shuttle Radar Topography Mission. 3D glasses are necessary to view this image.

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.

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.

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).

Risk-Free Volcano Observations Using an Unmanned Autonomous Helicopter: seismic observations near the active vent of Sakurajima volcano, Japan

NASA Astrophysics Data System (ADS)

Ohminato, T.; Kaneko, T.; Koyama, T.; Yasuda, A.; Watanabe, A.; Takeo, M.; Honda, Y.; Kajiwara, K.; Kanda, W.; Iguchi, M.; Yanagisawa, T.

2010-12-01

Observations in the vicinity of summit area of active volcanoes are important not only for understanding physical processes in the volcanic conduit but also for eruption prediction and volcanic hazards mitigation. It is, however, challenging to install observation sensors near active vents because of the danger of sudden eruptions. We need safe and efficient ways of installing sensors near the summit of active volcanoes. We have been developing an volcano observation system based on an unmanned autonomous vehicle (UAV) for risk-free volcano observations. Our UAV is an unmanned autonomous helicopter manufactured by Yamaha-Motor Co., Ltd. The UAV is 3.6m long and weighs 84kg with maximum payload of 10kg. The UAV can aviate autonomously along a previously programmed path within a meter accuracy using real-time kinematics differential GPS equipment. The maximum flight time and distance from the operator are 90 minutes and 5km, respectively. We have developed various types of volcano observation techniques adequate for the UAV, such as aeromagnetic survey, taking infrared and visible images from onboard high-resolution cameras, volcanic ash sampling in the vicinity of active vents. Recently, we have developed an earthquake observation module (EOM), which is exclusively designed for the UAV installation in the vicinity of active volcanic vent. In order to meet the various requirements for UAV installation, the EOM is very compact, light-weight (5-6kg), and is solar-powered. It is equipped with GPS for timing, a communication device using cellular-phone network, and triaxial accelerometers. Our first application of the EOM installation using the UAV is one of the most active volcanoes in Japan, Sakurajima volcano. Since 2006, explosive eruptions have been continuing at the reopened Showa crater at the eastern flank near the summit of Sakurajima. Entering the area within 2 km from the active craters is prohibited, and thus there were no observation station in the vicinity of active vents at the summit area. From November 2nd to 12th, 2009, we could successfully install four EOMs in the summit area within 2km from the active craters by using the UAV. Although the state of communication was not perfect since the installation points were outside of the service area of the cellular-phone network, we succeeded in retrieving the seismic waveform data accompanying moderate eruptions at Showa crater. Except for contamination by the mechanical resonance of the frame of EOM around 35 Hz, the recorded waveforms of the explosive eruptions are as good as the best permanent stations in Sakurajima. Preliminary results of the analyses show that the source location distribution of the explosion earthquakes at Showa crater is improved by the inclusion of the near source stations newly installed by using the UAV.

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

Three active volcanoes in China and their hazards

NASA Astrophysics Data System (ADS)

Wei, H.; Sparks, R. S. J.; Liu, R.; Fan, Q.; Wang, Y.; Hong, H.; Zhang, H.; Chen, H.; Jiang, C.; Dong, J.; Zheng, Y.; Pan, Y.

2003-02-01

The active volcanoes in China are located in the Changbaishan area, Jingbo Lake, Wudalianchi, Tengchong and Yutian. Several of these volcanoes have historical records of eruption and geochronological evidence of Holocene activity. Tianchi Volcano is a well-preserved Cenozoic polygenetic central volcano, and, due to its recent history of powerful explosive eruptions of felsic magmas, with over 100,000 people living on its flanks is a high-risk volcano. Explosive eruptions at 4000 and 1000 years BP involved plinian and ignimbrite phases. The Millennium eruption (1000 years BP) involved at least 20-30 km 3 of magma and was large enough to have a global impact. There are 14 Cenozoic monogenetic scoria cones and associated lavas with high-K basalt composition in the Wudalianchi volcanic field. The Laoheishan and Huoshaoshan cones and related lavas were formed in 1720-1721 and 1776 AD. There are three Holocene volcanoes, Dayingshan, Maanshan, and Heikongshan, among the 68 Quaternary volcanoes in the Tengchong volcanic province. Three of these volcanoes are identified as active, based on geothermal activity, geophysical evidence for magma, and dating of young volcanic rocks. Future eruptions of these Chinese volcanoes pose a significant threat to hundreds of thousands of people and are likely to cause substantial economic losses.

Constraints on the diversity and distribution of coral-reef assemblages in the volcanic Northern Mariana Islands

NASA Astrophysics Data System (ADS)

Houk, P.; Starmer, J.

2010-03-01

A central problem for jurisdictional scientists and managers is to reconcile how multiple environmental regimes, encompassing continuous, intermittent and human disturbances, influence pertinent ecological management targets. The presence of heterogeneous environments throughout the volcanic Northern Mariana Islands (NMI), coupled with the availability of descriptive physical data, form the basis examining environmental-ecological relationships. Since 2003, coral abundances and macrobiota (all visibly recognizable taxa greater than 2 cm) occurrences have been estimated at 42 reef slopes along the volcanic archipelago. Analyses showed that reef types acted as surrogates of coral growth capacity and the modern assemblages residing upon them, being highest and most favorable, respectively, where relatively high salinity levels, low-to-moderate wave exposure, and an absence of volcanic activity for ~90 years existed. However, island size was the greatest constraint on species richness overall, but relations with corals were dampened by volcanic activity and increased for sponges and algae where greater connection with the island aquifer existed (i.e., relatively low salinity levels). The number of years since volcanic activity has occurred was positively related to the residuals of species-area relationships and coral cover, with a ~90-year time frame predicted for recovery. Notably, no relationships with watershed characteristics or distance from CNMI’s main fishing port and coral-reef assemblages or species richness were found. Further examination of specific management concerns, such as fisheries and feral animal populations, should be designed to account for the inherent differences in driving environmental regimes. Management strategies focused upon conserving biodiversity and ecosystem function should be centered at the island level, matching the operational scale of dominant environmental-ecological relationships. Marine reserves represent a strategy pertinent for the remote NMI; a spatial structure is discussed.

A geochemical reconnaissance of the Alid volcanic center and geothermal system, Danakil depression, Eritrea

USGS Publications Warehouse

Lowenstern, J. B.; Janik, C.J.; Fournier, R.O.; Tesfai, T.; Duffield, W.A.; Clynne, M.A.; Smith, James G.; Woldegiorgis, L.; Weldemariam, K.; Kahsai, G.

1999-01-01

Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of ~10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.Geological and geochemical studies indicate that a high-temperature geothermal system underlies the Alid volcanic center in the northern Danakil depression of Eritrea. Alid is a very late-Pleistocene structural dome formed by shallow intrusion of rhyolitic magma, some of which vented as lavas and pyroclastic flows. Fumaroles and boiling pools distributed widely over an area of approx. 10 km2 on the northern half of Alid suggest that an active hydrothermal system underlies much of that part of the mountain. Geothermometers indicate that the fumarolic gases are derived from a geothermal system with temperatures >225??C. The isotopic composition of condensed fumarolic steam is consistent with these temperatures and implies that the source water is derived primarily from either lowland meteoric waters or fossil Red Sea water, or both. Some gases vented from the system (CO2, H2S and He) are largely magmatic in origin. Permeability beneath the volcanic center may be high, given the amount of intrusion-related deformation and the active normal faulting within the Danakil depression.

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.

New 40Ar / 39Ar age and geochemical data from seamounts in the Canary and Madeira volcanic provinces: Support for the mantle plume hypothesis

NASA Astrophysics Data System (ADS)

Geldmacher, J.; Hoernle, K.; Bogaard, P. v. d.; Duggen, S.; Werner, R.

2005-08-01

The role of mantle plumes in the formation of intraplate volcanic islands and seamount chains is being increasingly questioned. Particular examples are the abundant and somewhat irregularly distributed island and seamount volcanoes off the coast of northwest Africa. New 40Ar / 39Ar ages and Sr-Nd-Pb isotope geochemistry of volcanic rocks from seamounts northeast of the Madeira Islands (Seine and Unicorn) and northeast of the Canary Islands (Dacia and Anika), however, provide support for the plume hypothesis. The oldest ages of shield stage volcanism from Canary and Madeira volcanic provinces confirm progressions of increasing age to the northeast. Average volcanic age progression of ∼1.2 cm/a is consistent with rotation of the African plate at an angular velocity of ∼0.20° ± 0.05 /Ma around a common Euler pole at approximately 56° N, 45° W computed for the period of 0-35 Ma. A Euler pole at 35° N, 45° W is calculated for the time interval of 35-64 Ma. The isotope geochemistry further confirms that the Madeira and Canary provinces are derived from different sources, consistent with distinct plumes having formed each volcanic group. Conventional hotspot models, however, cannot easily explain the up to 40 m.y. long volcanic history at single volcanic centers, long gaps in volcanic activity, and the irregular distribution of islands and seamounts in the Canary province. A possible explanation could involve interaction of the Canary mantle plume with small-scale upper mantle processes such as edge-driven convection. Juxtaposition of plume and non-plume volcanism could also account for observed inconsistencies of the classical hotspot concept in other volcanic areas.

Evolution of major and trace elements and volatile contents of selected magmas in the Campi Flegrei and Procida volcanic fields, Italy, based on melt inclusion

NASA Astrophysics Data System (ADS)

Esposito, R.; Badescu, K.; Steele-MacInnis, M.; Lima, A.; De Vivo, B.; Cannatelli, C.; Manning, C. E.; Bodnar, R. J.

2017-12-01

The active Campi Flegrei (CF) volcanic field in southern Italy has been intensively studied owing to the volcanic risk to which the 1.5 million people in the area are exposed. The volcanic Island of Procida (IP) is located just southwest from CF but shows no signs of volcanic activity today. The IP volcanic products are the most primitive volcanic products of these two related volcanic fields. In this study, the major and minor element and volatile (H2O, CO2, S, Cl and F) compositions of melt inclusions (MI) hosted in sanidine, clinopyroxene, plagioclase and olivine were determined. MI data from this study and from the literature were compared with bulk rock data to test for agreement between MI compositions and compositions of CF and IP magmas determined by bulk rock analyses. Although MI compositions overlap with those of the bulk rock, some MI show anomalous compositions for one or a combination of Al2O3, FeO, P2O5, and TiO2. These MI represent melts produced by dissolution-reaction-mixing and were not included for the interpretation of volatile contents. Major elements and volatile concentrations of bubble-free MI that are interpreted to be representative of CF and IP were compared to crystal host compositions and to melt compositions obtained using rhyolite-MELTS simulations. Data suggest that less evolved magmas beneath the studied area crystallize either isobarically at ≥200 MPa (≥7.5 km) or polybarically during ascent to shallow depths under volatile-saturated conditions. Bubble-free MI representative of the least differentiated magmas can be divided into two groups. One group of MI is representative of simple fractional crystallization under volatile-saturated conditions from a primitive trachybasaltic melt. The other group of MI is representative of recharge of a primitive basaltic magma mixing with the preexisting primitive trachybasaltic magma before eruption. We suggest that the mixing process occurred at relatively great depth. Extensive isobaric crystallization of the trachybasaltic magmas beneath CF at 7.5 km may have generated trachy-phonolitic magmas, such as those associated with the Neapolitan Yellow Tuff that is characterized by a relatively high H2O content. These volatile saturated trachy-phonolitic magmas ascend through the crust and trigger high-magnitude eruptions.

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.

"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.

Characterization of fine volcanic ash from explosive eruption from Sakurajima volcano, South Japan

NASA Astrophysics Data System (ADS)

Nanayama, F.; Furukawa, R.; Ishizuka, Y.; Yamamoto, T.; Geshi, N.; Oishi, M.

2013-12-01

Explosive volcanic eruptions can affect infrastructure and ecosystem by their dispersion of the volcanic particle. Characterization of volcanic particle expelled by explosive eruption is crucial for evaluating for quantitative hazard assessment by future volcanic eruption. Especially for fine volcanic ash less than 64 micron in diameter, it can disperse vast area from the source volcano and be easily remobilized by surface wind and precipitation after the deposition. As fine volcanic ash is not preserved well at the earth surface and in strata except for enormously large scale volcanic eruption. In order to quantify quantitative characteristics of fine volcanic ash particle, we sampled volcanic ash directly falling from the eruption cloud from Showa crater, the most active vent of Sakurajima volcano, just before landing on ground. We newly adopted high precision digital microscope and particle grain size analyzer to develop hazard evaluation method of fine volcanic ash particle. Field survey was performed 5 sequential days in January, 2013 to take tamper-proof volcanic ash samples directly obtained from the eruption cloud of the Sakurajima volcano using disposable paper dishes and plastic pails. Samples were taken twice a day with time-stamp in 40 localities from 2.5 km to 43 km distant from the volcano. Japan Meteorological Agency reported 16 explosive eruptions of vulcanian style occurred during our survey and we took 140 samples of volcanic ash. Grain size distribution of volcanic ash was measured by particle grain size analyzer (Mophologi G3S) detecting each grain with parameters of particle diameter (0.3 micron - 1 mm), perimeter, length, area, circularity, convexity, solidity, and intensity. Component of volcanic ash was analyzed by CCD optical microscope (VHX-2000) which can take high resolution optical image with magnifying power of 100-2500. We discriminated each volcanic ash particle by color, texture of surface, and internal structure. Grain size distributions of volcanic ash from Sakurajima volcano have basically characteristics of unimodal and gaussian. Mode of distributions are 150 - 200 micron at 5 km and 70-80 micron at 20 km respectively from the Showa crater. Mode and deviation of the grain size distribution are function of distance from the source. Fine volcanic ash less than 1 micron in diameter is few and exists in every samples. Component of volcanic ash samples are dark-colored dense glass shard (ca. 50%), light-colored dense glass shard (10%), variously colored and vesiculated glass shard (10%), free crystal (20%), lithic fragment (10%), and altered fragment (less than 5%) which are mostly having similar ratio in every location suggesting single source process of the eruption. We also found fine volcanic ash samples less than 10 micron are frequently aggregated. The present study includes the result of "Research and Development of Margin Assessment Methodology of Decay Heat Removal Function against External Hazards" entrusted to Japan Atomic Energy Agency by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

Geochronologic evidence of a large magmatic province in northern Patagonia encompassing the Permian-Triassic boundary

NASA Astrophysics Data System (ADS)

Luppo, Tomás; López de Luchi, Mónica G.; Rapalini, Augusto E.; Martínez Dopico, Carmen I.; Fanning, Christopher M.

2018-03-01

The Los Menucos Complex (northern Patagonia) consists of ∼6 km thick succession of acidic and intermediate volcanic and pyroclastic products, which has been traditionally assigned to the Middle/Late Triassic. New U/Pb (SHRIMP) zircon crystallization ages of 257 ± 2 Ma at the base, 252 ± 2 Ma at an intermediate level and 248 ± 2 Ma near the top of the sequence, indicate that this volcanic event took place in about 10 Ma around the Permian-Triassic boundary. This volcanism can now be considered as the effusive terms of the neighboring and coeval La Esperanza Plutono-Volcanic Complex. This indicates that the climax of activity of a large magmatic province in northern Patagonia was coetaneous with the end-Permian mass extinctions. Likely correlation of La Esperanza- Los Menucos magmatic province with similar volcanic and plutonic rocks across other areas of northern Patagonia suggest a much larger extension than previously envisaged for this event. Its age, large volume and explosive nature suggest that the previously ignored potential role that this volcanism might have played in climatic deterioration around the Permian-Triassic boundary should be investigated.

Tertiary volcanic rocks and uranium in the Thomas Range and northern Drum Mountains, Juab County, Utah

USGS Publications Warehouse

Lindsey, David A.

1982-01-01

The Thomas Range and northern Drum Mountains have a history of volcanism, faulting, and mineralization that began about 42 m.y. (million years) ago. Volcanic activity and mineralization in the area can be divided into three stages according to the time-related occurrence of rock types, trace-element associations, and chemical composition of mineral deposits. Compositions of volcanic rocks changed abruptly from rhyodacite-quartz latite (42-39 m.y. ago) to rhyolite (38-32 m.y. ago) to alkali rhyolite (21 and 6-7 m.y. ago); these stages correspond to periods of chalcophile and siderophile metal mineralization, no mineralization(?), and lithophile metal mineralization, respectively. Angular unconformities record episodes of cauldron collapse and block faulting between the stages of volcanic activity and mineralization. The youngest angular unconformity formed between 21 and 7 m.y. ago during basin-and-range faulting. Early rhyodacite-quartz latite volcanism from composite volcanoes and fissures produced flows, breccias, and ash-flow tuff of the Drum Mountains Rhyodacite and Mt. Laird Tuff. Eruption of the Mt. Laird Tuff about 39 m.y. ago from an area north of Joy townsite was accompanied by collapse of the Thomas caldera. Part of the roof of the magma chamber did not collapse, or the magma was resurgent, as is indicated by porphyry dikes and plugs in the Drum Mountains. Chalcophile and siderophile metal mineralization, resulting in deposits of copper, gold, and manganese, accompanied early volcanism. Te middle stage of volcanic activity was characterized by explosive eruption of rhyolitic ash-flow tuffs and collapse of the Dugway Valley cauldron. Eruption of the Joy Tuff 38 m.y. ago was accompanied by subsidence of this cauldron and was followed by collapse and sliding of Paleozoic rocks from the west wall of the cauldron. Landslides in The Dell were covered by the Dell Tuff, erupted 32 m.y. ago from an unknown source to the east. An ash flow of the Needles Range(?) Formation was erupted 30-31 m.y. ago from an unknown source. Mineralization probably did not occur during the rhyolitic stage of volcanism. The last stage of volcanism was contemporaneous with basin-and-range faulting and was characterized by explosive eruption of ash and pumice, forming stratified tuff, and by quiet eruption of alkali rhyolite as viscous flows and domes. The first episode of alkali rhyolite volcanism deposited the beryllium tuff and porphyritic rhyolite members of the Spor Mountain Formation 21 m.y. ago. After a period of block faulting, the stratified tuff and alkali rhyolite of the Topaz Mountain Rhyolite were erupted 6-7 m.y. ago along faults and fault intersections. Erosion of Spor Mountain, as well as explosive eruptions through dolomite, provided abundant dolomite detritus to the beryllium tuff member. The alkali rhyolite of both formations is fluorine rich, as is evident from abundant topaz, and contains anomalous amounts of lithophile metals. Alkali rhyolite volcanism was accompanied by lithophile metal mineralization which deposited fluorite, beryllium, and uranium. The structure of the area is dominated by the Thomas caldera and the younger Dugway Valley cauldron, which is nested within the Thomas caldera; the Thomas caldera is surrounded by a rim of Paleozoic rocks at Spor Mountain and Paleozoic to Precambrian rocks in the Drum Mountains. The Joy fault and Dell fault system mark the ring-fracture zone of the Thomas caldera. These structural features began to form about 39 m.y. ago during eruption of the Mt. Laird Tuff and caldera subsidence. The Dugway Valley cauldron sank along a series of steplike normal faults southeast of Topaz Mountain in response to collapse of the magma chamber of the Joy Tuff. Caldera structure was modified by block faulting between 21 and 7 m.y. ago, the time of widespread extensional faulting in the Basin and Range Province. Vents erupted alkali rhyolite 6-7 m.y. ago along basin-and-range faults.

Thematic mapper studies of central Andean volcanoes

NASA Technical Reports Server (NTRS)

Francis, Peter W.

1987-01-01

A series of false color composite images covering the volcanic cordillera was written. Each image is 45 km (1536 x 1536 pixels) and was constructed using bands 7, 4, and 2 of the Thematic Mapper (TM) data. Approximately 100 images were prepared to date. A set of LANDSAT Multispectral Scanner (MSS) images was used in conjunction with the TM hardcopy to compile a computer data base of all volcanic structure in the Central Andean province. Over 500 individual structures were identified. About 75 major volcanoes were identified as active, or potentially active. A pilot study was begun combining Shuttle Imaging Radar (SIR) data with TM for a test area in north Chile and Bolivia.

Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

NASA Astrophysics Data System (ADS)

White, S. M.; Lee, A. J.; Rubin, K. H.

2015-12-01

Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active hydrothermal vents at either site. While these results do not support the idea of on-going and widespread volcanic activity associated with O-AMLs, a comprehensive survey may reveal smaller pockets of activity. A viable alternative is that off-axis activity is sparse and sporadic, perhaps focused by faults that tap into O-AML heat, and that O-AMLs warrant further investigation.

Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

NASA Astrophysics Data System (ADS)

West, A. J.; Torres, M. A.; Nealson, K. H.

2014-12-01

Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active hydrothermal vents at either site. While these results do not support the idea of on-going and widespread volcanic activity associated with O-AMLs, a comprehensive survey may reveal smaller pockets of activity. A viable alternative is that off-axis activity is sparse and sporadic, perhaps focused by faults that tap into O-AML heat, and that O-AMLs warrant further investigation.

The San Francisco volcanic field, Arizona

USGS Publications Warehouse

Priest, S.S.; Duffield, W.A.; Malis-Clark, Karen; Hendley, J. W.; Stauffer, P.H.

2001-01-01

Northern Arizona's San Francisco Volcanic Field, much of which lies within Coconino and Kaibab National Forests, is an area of young volcanoes along the southern margin of the Colorado Plateau. During its 6-million-year history, this field has produced more than 600 volcanoes. Their activity has created a topographically varied landscape with forests that extend from the Pi?on-Juniper up to the Bristlecone Pine life zones. The most prominent landmark is San Francisco Mountain, a stratovolcano that rises to 12,633 feet and serves as a scenic backdrop to the city of Flagstaff.

Lava Field, Syria

NASA Image and Video Library

2015-05-27

In southern Syria, the Azraq-Wadi as Sirhan Depression is the site of young volcanic activity, producing an extensive basaltic volcanic field. The north-northwest to south-southeast structural and fault control of the crust is evident in the straight alignment of numerous chains of cinder cones. At the top of the image, the northeast trending streaks are windblown sand deposits. The image was acquired May 20, 2009, covers an area of 46.5 x 67 km, and is located at 33.3 degrees north, 37.1 degrees east. http://photojournal.jpl.nasa.gov/catalog/PIA19479

Search for ongoing volcanic activity on Venus: Case study of Maat Mons, Sapas Mons and Ozza Mons volcanoes

NASA Astrophysics Data System (ADS)

Shalygin, E. V.; Basilevsky, A. T.; Markiewicz, W. J.; Titov, D. V.; Kreslavsky, M. A.; Roatsch, Th.

2012-12-01

We report on attempts to find the ongoing volcanic activity from near-infrared night-time observations with the Venus Monitoring Camera (VMC) onboard of Venus Express. Here we consider VMC images of the areas of Maat Mons volcano and its vicinities, which, as it follows from analysis of the Magellan data, show evidence of geologically very recent volcanism. Analysis of VMC images taken in 12 observation sessions during the time period from 31 October 2007 to 15 June 2009 did not reveal any suspicious high-emission spots which could be signatures of the presently ongoing volcanic eruptions. We compare this time sequence of observations with the history of eruptions of volcano Mauna Loa, Hawaii, in the 20th century. This comparison shows that if Maat Mons volcano had the eruption history similar to that of Mauna Loa, the probability to observe an eruption in this VMC observation sequence would be about 8%, meaning that the absence of detection does not mean that Maat is not active in the present epoch. These estimates do not consider the effect of absorption and blurring of the thermal radiation coming from Venus surface by the planet atmosphere and clouds, which decreases detectability of thermal signature of fresh lavas. To assess the role of this effect we simulated near-infrared images of the study area with artificially added circular and rectangular (with different aspect ratios) lava flows having surface temperature 1000 K and various areas. These simulations showed that 1 km2 lava flows should be marginally seen by VMC. An increase of the lava surface area to 2-3 km2 makes them visible on the plains and increase of the area to 4-5 km2 makes them visible even in deep rift zones. Typical individual lava flows on Mauna Loa are a few km2, however, they often have been formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower than 8%, but it is far from negligible. Our consideration suggests that further search of Maat Mons area and other areas including young rift zones makes sense and should be continued. More effective search could be done if observations simultaneously cover most part of the night side of Venus for relatively long (years) time of continuous observations.

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

Many volcanic craters and calderas are filled with large amounts of water that can pose significant flood hazards to downstream communities due to their high elevation and the potential for catastrophic releases of water. Recent reports pointed out the Baekdusan volcano that is located between the border of China and North Korea as a potential active volcano. Since Millennium Eruption around 1000 AD, smaller eruptions have occurred at roughly 100-year intervals, with the last one in 1903. Sudden release of huge volume of water stored in temporarily elevated caldera lakes are a recurrent feature of volcanic environments, due to the case with which outlet channels are blocked by and re-cut through, unwelded pyroclastic deposits. The volcano is showing signs of waking from a century-long slumber recently. Volcanic floods, including breakouts from volcanic lakes, can affect communities beyond the areas immediately affected by a volcanic eruption and cause significant hydrological hazards because floods from lake-filled calderas may be particularly large and high. Although a number of case studies have been presented in the literature, investigation of the underlying physical processes is required as well as a method for interpreting the process of the rapid release of water stored in a caldera lake. The development of various forecasting techniques to prevent and minimize economic and social damage is in urgent need. This study focuses on constructing a flood hazard map triggered by the magma effusion in the Baekdusan volcano. A physically-based uplift model was developed to compute the amount of water and time to peak flow. The ordinary differential equation was numerically solved using the finite difference method and Newton-Raphson iteration method was used to solve nonlinear equation. The magma effusion rate into the caldera lake is followed by examples at other volcanic activities. As a result, the hydrograph serves as an upper boundary condition when hydrodynamic model, called FLO-2D runs to simulate channel routing downstream to give the maximum water level. Once probable inundation areas are identified by the huge volume of water in the caldera lake, the unique geography, and the limited control capability, a potential hazard assessment can be represented. The study will contribute to build a geohazard map for the decision-makers and practitioners. Keywords: Volcanic flood, Caldera lake, Hazard assessment, Magma effusion Acknowledgement This research was supported by a grant [NEMA-BAEKDUSAN-2012-1-2] from the Volcanic Disaster Preparedness Research Center sponsored by National Emergency Management Agency of Korea.

Properties of volcanic soils in cold climate conditions

NASA Astrophysics Data System (ADS)

Kuznetsova, Elena

2017-04-01

Layers of volcanic ash and the Andosol soils derived from them may play an important role in preserving snow and ice as well as developing permafrost conditions in the immediate vicinity of volcanoes of high elevation or those situated at high latitudes, and land areas, often distant from volcanic activity that are either prone to permafrost or covered by snow and ice, but are affected by the deposition of subaerial ash. The special properties of volcanic ash that are responsible are critically reviewed particularly in relation to recent research in Kamchatka in the Far East of Russia. Of particular importance are the thermal properties and the unfrozen water contents of ash layers and the rate at which the weathering of volcanic glass takes place. Volcanic glass is the most easily weathered component of volcanic ejecta (Shoji et al., 1993; Kimble et al., 2000). There are many specific environmental conditions, including paleoclimate and present-day climate, the composition of volcanic tephra and glaciation history, which cause the differences in weathering and development of volcanic ash soils (Zehetner et al., 2003). The preservation of in situ, unweathered, and unaltered surficial ash-fall deposits in the cold regions has important implications for paleoclimate and glacial history. Ash-fall deposits, which trap and preserve the soils, sediments, and landforms on which they fall, can be used to resolve local climate conditions (temperature and moisture) at the ash site during ash-fall deposition. The preservation of detailed sedimentary features (e.g. bedding in the ash, sharpness of stratigraphic contacts) can tell us about their post-depositional history, whether they have been redeposited by wind or water, or overridden by glaciers (Marchant et al., 1996). Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite) but this takes place much slower in cold than under warmer climate conditions. Only few studies on weathering of volcanic ash and developing volcanic soils under cold climatic conditions were carried out, especially in areas with permafrost (Bäumler, 2003). Most of research on volcanic permafrost soils was done in Yukon (Canada), Kamchatka (Russia), and Antarctica, or on seasonal frost in mountain area in Iceland, Japan, New Zealand, and Ecuador. Soils of Iceland and Antarctica are used as terrestrial analogs to Martian soils (Gooding & Keil, 1978; Allen et al., 1981). The review of existing data demonstrates that there is a strong correlation between the thermal conductivity, the water-ice content, and the mineralogy of the weathered part of the volcanic ash, enhanced amount of amorphous clay minerals (allophane, palagonite) increase the proportion of unfrozen water and decrease thermal conductivity (Kuznetsova et al., 2012, 2013; Kuznetsova & Motenko, 2014), and amorphous silica does not alter to halloysite or other clay minerals even in ashes of Early Pleistocene age (Kamchatka) or Miocene and Pliocene deposits (Antarctica) due to cold temperatures. The significance of these findings is discussed in relation to the reconstruction of past climates and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

Drilling constraints on bimodal volcanism and subsequent formation of contrasted uppermost crustal compositions at the middle Okinawa Trough

NASA Astrophysics Data System (ADS)

Yamasaki, T.; Takaya, Y.; Mukae, N.; Nagase, T.; Tindell, T.; Totsuka, S.; Uno, Y.; Yonezu, K.; Nozaki, T.; Ishibashi, J. I.; Kumagai, H.; Maeda, L.; Shipboard Scientist, C.

2016-12-01

The Okinawa Trough (OT) is a young and actively spreading back-arc basin, extending behind the Ryukyu arc-trench system in the southeastern margin of the East China Sea. The OT is believed to be in an initial rifting stage (starting from 6-9 Ma), prior to the normal/stable seafloor spreading which constitutes the main stage of back-arc basin formation. Two drilling cruises ‒ the IODP Exp. 331 and SIP CK14-04 D/V Chikyu Cruise (Exp. 907) in 2010 and 2014 ‒ were conducted at the Iheya North Knoll, middle OT. The Iheya North Knoll is a domal volcanic complex consisting of small volcanic bodies. On these cruises, pumiceous gravel and altered rhyolitic rocks, as well as hemi-pelagic sediments, hydrothermal clay and Kuroko-type ores, were recovered from the upper 200 m of the crust. From Feb. 11, 2016 to Mar. 17, 2016, the SIP CK16-01 (Exp. 908) D/V Chikyu cruise was conducted at Iheya North Knoll and the sediment-covered rifting center of the Iheya-Minor Ridge area, middle OT. The Iheya-Minor ridge area is also an active hydrothermal field, located 25 km southeast of the Iheya North Knoll. In this area, basaltic rocks are widely distributed, and drilling has confirmed that the basaltic materials continue to 120 m below the seafloor. From an igneous petrological point of view, the volcanic rocks in the Okinawa Trough are characterized by bimodal basaltic and rhyolitic compositions, with a compositional gap between SiO2 = 56-66 wt%. The origin of the rhyolitic rock has been interpreted as magmatic differentiation of basaltic magma. However, the existence of an active basalt-hosted hydrothermal field in the Iheya-Minor ridge area suggests the presence of hot basaltic rocks at a shallow position in the crust, and reaching recharged seawater at this depth. Furthermore, the composition of felsic rocks just after the compositional gap (SiO2 = 67 wt%) is very similar to that of the minimum melt of a granitic system, and experimental partial melt of hydrous basalt. Therefore, the contrast in the uppermost crustal composition between very close ( 25 km) areas can reasonably be explained by re-melting of hydrothermally-altered basaltic rocks and production of felsic magma at the upper crustal level, and direct eruption of basaltic magma at the seafloor.

Hydration kinetics and morphology of cement pastes with pozzolanic volcanic ash studied via synchrotron-based techniques

DOE PAGES

Kupwade-Patil, Kunal; Chin, Stephanie; Ilavsky, Jan; ...

2017-10-13

Here, this study investigates the early ages of hydration behavior when basaltic volcanic ash was used as a partial substitute to ordinary Portland cement using ultra-small-angle X-ray scattering and wide-angle X-ray scattering (WAXS). The mix design consisted of 10, 30 and 50% substitution of Portland cement with two different-sized volcanic ashes. The data showed that substitution of volcanic ash above 30% results in excess unreacted volcanic ash, rather than additional pozzolanic reactions along longer length scales. WAXS studies revealed that addition of finely ground volcanic ash facilitated calcium-silicate-hydrate related phases, whereas inclusion of coarser volcanic ash caused domination by calcium-aluminum-silicate-hydratemore » and unreacted MgO phases, suggesting some volcanic ash remained unreacted throughout the hydration process. Addition of more than 30% volcanic ash leads to coarser morphology along with decreased surface area and higher intensity of scattering at early-age hydration. This suggests an abrupt dissolution indicated by changes in surface area due to the retarding gel formation that can have implication on early-age setting influencing the mechanical properties of the resulting cementitious matrix. The findings from this work show that the concentration of volcanic ash influences the specific surface area and morphology of hydration products during the early age of hydration. Therefore, natural pozzolanic volcanic ashes can be a viable substitute to Portland cement by providing environmental benefits in terms of lower-carbon footprint along with long-term durability.« less

Hydration kinetics and morphology of cement pastes with pozzolanic volcanic ash studied via synchrotron-based techniques

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

Kupwade-Patil, Kunal; Chin, Stephanie; Ilavsky, Jan

Here, this study investigates the early ages of hydration behavior when basaltic volcanic ash was used as a partial substitute to ordinary Portland cement using ultra-small-angle X-ray scattering and wide-angle X-ray scattering (WAXS). The mix design consisted of 10, 30 and 50% substitution of Portland cement with two different-sized volcanic ashes. The data showed that substitution of volcanic ash above 30% results in excess unreacted volcanic ash, rather than additional pozzolanic reactions along longer length scales. WAXS studies revealed that addition of finely ground volcanic ash facilitated calcium-silicate-hydrate related phases, whereas inclusion of coarser volcanic ash caused domination by calcium-aluminum-silicate-hydratemore » and unreacted MgO phases, suggesting some volcanic ash remained unreacted throughout the hydration process. Addition of more than 30% volcanic ash leads to coarser morphology along with decreased surface area and higher intensity of scattering at early-age hydration. This suggests an abrupt dissolution indicated by changes in surface area due to the retarding gel formation that can have implication on early-age setting influencing the mechanical properties of the resulting cementitious matrix. The findings from this work show that the concentration of volcanic ash influences the specific surface area and morphology of hydration products during the early age of hydration. Therefore, natural pozzolanic volcanic ashes can be a viable substitute to Portland cement by providing environmental benefits in terms of lower-carbon footprint along with long-term durability.« less

Spatial and temporal variations of diffuse CO_{2} degassing at the N-S volcanic rift-zone of Tenerife (Canary Islands, Spain) during 2002-2015 period

NASA Astrophysics Data System (ADS)

Alonso, Mar; Ingman, Dylan; Alexander, Scott; Barrancos, José; Rodríguez, Fátima; Melián, Gladys; Pérez, Nemesio M.

2016-04-01

Tenerife is the largest of the Canary Islands and, together with Gran Canaria Island, is the only one with a central volcanic complex that started to grow at about 3.5 Ma. Nowadays the central complex is formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and was partially filled by post-caldera volcanic products. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 Ma (Dóniz et al., 2008). Most of the monogenetic cones are aligned following a triple junction-shaped rift system, as result of inflation produced by the concentration of emission vents and dykes in bands at 120o to one another as a result of minimum stress fracturing of the crust by a mantle upwelling. The main structural characteristic of the southern volcanic rift (N-S) of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Four main volcanic successions in the southern volcanic rift zone of Tenerife, temporally separated by longer periods (˜70 - 250 ka) without volcanic activity, have been identified (Kröchert and Buchner, 2008). Since there are currently no visible gas emissions at the N-S rift, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. We report here the last results of diffuse CO2 efflux survey at the N-S rift of Tenerife, performed using the accumulation chamber method in the summer period of 2015. The objectives of the surveys were: (i) to constrain the total CO2 output from the studied area and (ii) to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for the N-S rift of Tenerife. Soil CO2 efflux values ranged from non-detectable up to 31.7 g m-2 d-1. A spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, did not show an apparent relation between higher diffuse CO2 emission values and the main N-S axis of the rift. The total CO2 output released to the atmosphere in a diffuse way has been estimated at 707 t d-1, which represents a value three times higher than the average of the three studies conducted previously. This observed increase suggests the occurrence of an episodic enhanced magmatic (endogenous) contribution. This also confirms the need of periodic diffuse emission surveys in the area as a powerful volcanic surveillance tool, mainly in volcanic systems where visible gas emanations are absent. References: Dóniz et al., 2008. J. Volcanol. Geotherm. Res. 173, 185. Kröchert and Buchner, 2008. Geol. Mag. 146, 161.

Satellite geological and geophysical remote sensing of Iceland

NASA Technical Reports Server (NTRS)

Williams, R. S., Jr. (Principal Investigator)

1974-01-01

The author has identified the following significant results. ERTS-1 imagery provides sufficient resolution to discern two effects of geothermal activity at the Namafjall geothermal area: snowmelt anomalies and delineation of altered ground. The fallout pattern of tephra from Hekla's 1970 volcanic eruption can be mapped where sufficient depth of deposition destroyed the vegetation. Lava flows from the volcanic eruptions at Askja and Hekla can be delineated. Low sun-angle imagery of snow-covered terrain has permitted the mapping of new structural and volcanic features beneath the icecaps. Coastline changes on the islands of Surtsey and Heimaey can be mapped. Variations of sediment plumes from glacial rivers on the south coast give a qualitative indication of seasonal changes in melting rates of glaciers. ERTS-1 imagery has been shown to be especially amenable to portrayal of changing glaciological phenomena: surging glaciers, collapse features in icecaps caused by subglacial volcanic (?) and geothermal activity and resulting jokulhlaups, and variations in size of glacier-margin lakes. A fifth vegetation class has now been added: lichen-covered bedrock. The high latitude permits more precise analysis of landforms, vegetation distribution, occurrence of snow cover, glaciers, and geologic structure.

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.

GeoBioScience: Red Wood Ants as Bioindicators for Active Tectonic Fault Systems in the West Eifel (Germany)

PubMed Central

Berberich, Gabriele; Schreiber, Ulrich

2013-01-01

Simple Summary In a 1.140 km² study area of the volcanic West Eifel, approx. 3,000 Red Wood Ant (RWA; Formica rufa-group) mounds had been identified and correlated with tectonically active gas-permeable faults, mostly strike-slip faults. Linear alignment of RWA mounds and soil gas anomalies distinctly indicate the course of these faults, while clusters of mounds indicate crosscut zones of fault systems, which can be correlated with voids caused by crustal block rotation. This demonstrates that RWA are bioindicators for identifying active fault systems and useful where information on the active regime is incomplete or the resolution by technical means is insufficient. Abstract In a 1.140 km² study area of the volcanic West Eifel, a comprehensive investigation established the correlation between red wood ant mound (RWA; Formica rufa-group) sites and active tectonic faults. The current stress field with a NW-SE-trending main stress direction opens pathways for geogenic gases and potential magmas following the same orientation. At the same time, Variscan and Mesozoic fault zones are reactivated. The results showed linear alignments and clusters of approx. 3,000 RWA mounds. While linear mound distribution correlate with strike-slip fault systems documented by quartz and ore veins and fault planes with slickensides, the clusters represent crosscut zones of dominant fault systems. Latter can be correlated with voids caused by crustal block rotation. Gas analyses from soil air, mineral springs and mofettes (CO2, Helium, Radon and H2S) reveal limiting concentrations for the spatial distribution of mounds and colonization. Striking is further the almost complete absence of RWA mounds in the core area of the Quaternary volcanic field. A possible cause can be found in occasionally occurring H2S in the fault systems, which is toxic at miniscule concentrations to the ants. Viewed overall, there is a strong relationship between RWA mounds and active tectonics in the West Eifel. PMID:26487413

Structural control on the CO2 release west of Mt. Epomeo resurgent block (Ischia, Italy)

NASA Astrophysics Data System (ADS)

de Vita, S.; Marotta, E.; Ventura, G.; Chiodini, G.

2003-04-01

Volcanism at Ischia started more than 150 ka B.P. and continued until the last eruption occurred in 1302 A.D. Ischia is dominated by the caldera forming eruption of Mt. Epomeo Green Tuff (55 ka), which was followed by block resurgence inside the caldera from 33 ka B.P. Resurgence influenced the volcanic activity determining the conditions for magma ascent mainly along the eastern edge of the resurgent block. The resurgent area has a poligonal shape resulting from reactivation of regional faults and by activation of faults related to volcanotectonism. The western sector is bordered by inward dipping, high angle strike-slip/reverse faults testifying a compressional stress regime in this area. These features are cut by late outward dipping normal faults due to gravitational stress. The activity of the volcanic system is testified by seismicity and thermal manifestations. Fumarolic activity concentrates along the faults that borders westward the Mt. Epomeo resurgent block, where the Green Tuff overlies fractured lavas. The structural data show that, outside the most active degassing zone, fractures show a NNW-SSE strike and dip toward Mt. Epomeo. These fractures delimit the northern sector of Mt. Epomeo and show strike and dip consistent with the inward dipping reverse faults. Inside the degassing area fractures show a NW-SE strike and dip outward Mt. Epomeo. These gravity-related faults cut the lavas where the hydrothermal circulation is active. The dip direction of the NW-SE striking fractures within the degassing zone is not consistent with that of the strike-slip/reverse faults (i.e. towards NE) but agrees well with that of the gravity-induced faults (dip direction towards SW). Inside the degassing zone, NW-SE striking faults with lengths not exceeding the hydrothermalized extension occur. This arrangement indicate that the syn-resurgence faults act as permeability barriers, whereas the youngest faults act as the main fluid pathway.

On the impact of different volcanic hot spot detection methods on eruption energy quantification

NASA Astrophysics Data System (ADS)

Pergola, Nicola; Coviello, Irina; Falconieri, Alfredo; Lacava, Teodosio; Marchese, Francesco; Tramutoli, Valerio

2016-04-01

Several studies have shown that sensors like the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) may be effectively used to identify volcanic hotspots. These sensors offer in fact some spectral channels in the Medium Infrared (MIR) and Thermal Infrared (TIR) bands together with a good compromise between spatial and temporal resolution suited to study and monitor thermal volcanic activity. Many algorithms were developed to identify volcanic thermal anomalies from space with some of them that were extensively tested in very different geographich areas. In this work, we analyze the volcanic radiative power (VRP) representing one of parameters of major interest for volcanologists that may be estimated by satellite. In particular, we compare the radiative power estimations driven by some well-established state of the art hotspot detection methods (e.g. RSTVOLC, MODVOLC, HOTSAT). Differences in terms of radiative power estimations achieved during recent Mt. Etna (Italy) eruptions will be evaluated, assessing how much the VRP retrieved during effusive eruptions is affected by the sensitivity of hotspot detection methods.

Loki Patera

NASA Image and Video Library

1998-06-04

A huge area of Io's volcanic plains is shown in this Voyager 1 image mosaic. Numerous volcanic calderas and lava flows are visible here. Loki Patera, an active lava lake, is the large shield-shaped black feature. Heat emitted from Loki can be seen through telescopes all the way from Earth. These telescopic observations tell us that Loki has been active continuously (or at least every time astronomers have looked) since the Voyager 1 flyby in March 1979. The composition of Io's volcanic plains and lava flows has not been determined, but they could consist dominantly of sulfur with surface frosts of sulfur dioxide or of silicates (such as basalts) encrusted with sulfur and sulfur dioxide condensates. The bright whitish patches probably consist of freshly deposited SO2 frost. The black spots, including Loki, are probably hot sulfur lava, which may remain molten by intrusions of molten silicate magma, coming up from deeper within Io. The ultimate source of heat that keeps Io active is tidal frictional heating due to the continual flexure of Io by the gravity of Jupiter and Europa, another of Jupiter's satellites. http://photojournal.jpl.nasa.gov/catalog/PIA00320

Gravity modeling finds a large magma body in the deep crust below the Gulf of Naples, Italy.

PubMed

Fedi, M; Cella, F; D'Antonio, M; Florio, G; Paoletti, V; Morra, V

2018-05-29

We analyze a wide gravity low in the Campania Active Volcanic Area and interpret it by a large and deep source distribution of partially molten, low-density material from about 8 to 30 km depth. Given the complex spatial-temporal distribution of explosive volcanism in the area, we model the gravity data consistently with several volcanological and petrological constraints. We propose two possible models: one accounts for the coexistence, within the lower/intermediate crust, of large amounts of melts and cumulates besides country rocks. It implies a layered distribution of densities and, thus, a variation with depth of percentages of silicate liquids, cumulates and country rocks. The other reflects a fractal density distribution, based on the scaling exponent estimated from the gravity data. According to this model, the gravity low would be related to a distribution of melt pockets within solid rocks. Both density distributions account for the available volcanological and seismic constraints and can be considered as end-members of possible models compatible with gravity data. Such results agree with the general views about the roots of large areas of ignimbritic volcanism worldwide. Given the prolonged history of magmatism in the Campania area since Pliocene times, we interpret the detected low-density body as a developing batholith.

Identification of geothermal system using 2D audio magnetotelluric method in Telomoyo volcanic area

NASA Astrophysics Data System (ADS)

Romadlon, Arriqo'Fauqi; Niasari, Sintia Windhi

2017-07-01

Geothermal area of Candi Umbul Telomoyo is one of geothermal fields in Indonesia. This geothermal field is located in the Grabag district, Magelang, Central Java. This geothermal field was formed in a volcanic quarter. The main aim in this study is to identify geothermal system at Telomoyo volcanic area through synthetic model analysis. There are surface manifestations such as warm springs and altered rocks. Results of geochemistry study showed reservoir's temperature was 230°C. The Warm spring in Candi Umbul was the outflow zone of the Telomoyo geothermal system. The Telomoyo geothermal system was indicated chloride-bicarbonate type of warm spring. In addition, the results of geological mapping indicate that the dominant fault structure has southwest-northeast orientation. The fault was caused by the volcanic activity of mount Telomoyo. In this research conducted data analysis from synthetics model. It aims to estimate the response of magnetotelluric methods in various models of geothermal systems. In this study, we assumed three models of geothermal system in Candi Umbul-Telomoyo area. From the data analysis it was known that the model 1 and model 2 can be distinguished if the measurements were conducted in a frequency range of 0.01 Hz to 1000 Hz. In response of tipper (Hz) had a small value on all models at all measurement points, so the tipper cannot distinguish between model 1, model 2 and model 3. From this analysis was known that TM mode is more sensitive than TE mode at the resistivity and phase responses.

Io - A volcanic flow model for the hot spot emission spectrum and a thermostatic mechanism

NASA Technical Reports Server (NTRS)

Sinton, V. M.

1982-01-01

The hot spots of Io are modeled as a steady state of active areas at 600 K, continuing creation of new lava flows and calderas, cooling off of recent flows and calderas, and the cessation of radiation of old flows and calderas from the accumulation of insulation added by resurfacing. There are three adjustable parameters in this model: the area of active sources at 600 K, the rate of production of new area that is cooling, and the temperature of cessation of emission as the result of resurfacing. The resurfacing rate sets constrains on this last parameter. The emission spectrum computed with reasonable values for these parameters is an excellent match to the spectrum from recent observations. A thermostatic mechanism is described whereby the volcanic activity is turned on for a long period of time and is then turned off for a nearly equal period. As a result the presently observed internal heat flow of approximately 1.5 W/sq m may be as much as twice the rate of production of internal heat. Thus the restrictions placed on theories of tidal dissipation by the observed heat flow may be partially relieved.

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.

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).

Multiteide Project: Multiparametric characterization of the activity of Teide-Pico Viejo volcanic system

NASA Astrophysics Data System (ADS)

Domínguez Cerdeña, Itahiza; Villasante-Marcos, Victor; Meletlidis, Stavros; Sainz-Maza, Sergio; Abella, Rafael; Torres, Pedro A.; Sánchez, Nieves; Luengo-Oroz, Natividad; José Blanco, María; García-Cañada, Laura; Pereda de Pablo, Jorge; Lamolda, Héctor; Moure, David; Del Fresno, Carmen; Finizola, Anthony; Felepto, Alicia

2017-04-01

Teide-Pico Viejo complex stands for one of the major natural volcanic hazards in the Canary Islands, due to the expected types of eruptions in the area and the high number of inhabitants in Tenerife Island. Therefore, it is necessary to have a volcanic alert system able to afford a precise assessment of the current state of the complex. For this purpose, the knowledge of the expected signals at each volcanic activity level is required. Moreover, the external effects that can affect the measurements shall be distinguished, external influences as the atmosphere are qualitatively known but have not been quantified yet. The objective of the project is to collect, analyze and jointly and continuously evaluate over time geophysical, geodetic, geochemical and meteorological data from the Teide-Pico Viejo complex and its surroundings. A continuous multiparametric network have been deployed in the area, which, together with the data provided by the Volcano Monitoring Network of the Instituto Geográfico Nacional (IGN) and data from other institutions will provide a comprehensive set of data with high resolution in both space and time. This multiparametric network includes a seismic array, two self-potential lines for continuous measurements, five magnetometers and two weather stations. The network will be complemented with 8 CGPS stations, one tiltmeter, 10 seismic stations, and four thermometric stations on the fumaroles of Teide volcano that IGN already manage in Tenerife. The data will be completed with the results from different repeated surveys of self potential, soil temperature and CO2 diffuse flux in several pre-established areas on top of Teide throughout the entire duration of project. During the project, new computation tools will be developed to study the correlation between the different parameters analyzed. The results obtained will characterize the possible seasonal fluctuations of each parameter and the variations related to meteorological phenomena. In addition, they will allow identifying the response of all the analyzed parameters to specific events that are traditionally studied with a single technique, such as short episodes of tremor (sporadically registered in Teide-Pico Viejo surroundings) or changes in activity of the hydrothermal system of the volcanic complex. We present here the first multiparametric results obtained from the project, including locations with the seismic array, CO2 and temperature maps of Teide fumaroles zones and magnetometric measurements.

Diffuse Carbon Dioxide Degassing Monitoring at Santa Ana-Izalco-Coatepeque Volcanic System, El Salvador, Central America

NASA Astrophysics Data System (ADS)

Olmos, R.; Barahona, F.; Cartagena, R.; Soriano, T.; Salazar, J.; Hernandez, P.; Perez, N.; Notsu, K.; Lopez, D.

2001-12-01

Santa Ana volcanic complex (0.22 Ma), located 40 Km west of San Salvador, comprises Santa Ana, Izalco, and Cerro Verde stratovolcanoes, the Coatepeque collapse caldera, as well as several cinder cones and explosion craters. Most recent activity has occurred at Izalco (1966) and Santa Ana which shows a permanent acidic crater lake with an intense fumarolic activity. In addition, Santa Ana exhibits a SO2-rich rising plume though no local seismicity has been reported. Weak fumarolic activity is also present at two locations within the Santa Ana volcanic complex: the summit crater of Izalco and Cerro Pacho at Coatepeque caldera. Other important structural features of this volcanic complex are two fault/fissure systems running NNW-SSE that can be identified by the alignment of the stratovolcanoes and numerous cinder cones and explosion craters. In January 2001, a 7.6 magnitude earthquake occurred about 150 Km SE of Santa Ana volcano. A soil gas and CO2 efflux survey was performed to evaluate the impact of this seismic event upon the diffuse degassing rates in Santa Ana volcanic complex in March 2001. A total of 450 soil gas and diffuse CO2 efflux measurements were carried out covering an area of 209.5 Km2. CO2 efflux ranged from non-detectable values to 293 gm-2d-1, with a median of 8.9 gm-2d-1 and an upper quartile of 5.2 gm-2d-1. The CO2 efflux spatial distribution reveals the existence of areas with CO2 efflux higher than 60 gm-2d-1 associated to the fault/fissure systems of NNW-SSE orientation. One of these areas, Cerro Pacho, was selected for the continuous monitoring of diffuse CO2 efflux in late May 2001. Secular variations of diffuse CO2 efflux ranged from 27.4 to 329 gm-2d-1 with a median of 130 gm-2d-1 and a quartile range of 59.3 gm-2d-1. An increasing trend of 43 gm-2d-1 was observed between May and August 2001 overlapped to high-frequency minor fluctuations related to meteorological variables' changes. However, a larger observation time-span is needed to understand the influence of the rainy-season and meteorological parameters in the observed CO2 efflux time series.

Earthquake swarm in the non-volcanic area north of Harrat Lunayyir, western Saudi Arabia: observations and imaging

NASA Astrophysics Data System (ADS)

Youssof, M.; Mai, P. M.; Parisi, L.; Tang, Z.; Zahran, H. M.; El-Hadidy, S. Y.; Al-Raddadi, W.; Sami, M.; El-Hadidy, M. S. Y.

2017-12-01

We report on an unusual earthquake swarm in a non-volcanic area of western Saudi Arabia. Since March 2017, hundreds of earthquakes were recorded, reaching magnitude Ml 3.7, which occurred within a very narrowly defined rock volume. The seismicity is shallow, mostly between 4 to 8 km depths, with some events reaching as deep as 16 km. One set of events aligns into a well-defined horizontal tube of 2 km height, 1 km width, and 4-5 km E-W extent. Other event clusters exist, but are less well-defined. The focal mechanism solutions of the largest earthquakes indicate normal faulting, which agree with the regional stress field. The earthquake swarm occurs 75 km NW of Harrat Lunayyir. However, the area of interest doesn't seem to be associated with the well-known volcanic area of Harrat Lunayyir, which experienced a magmatic dike intrusion in 2009 with intense seismic activity (including a surface rupturing Mw 5.7 earthquake). Furthermore, the study area is characterized by a complex shear system, which host gold mineralization. Therefore, the exact origin of the swarm sequence is enigmatic as it's the first of its kind in this region. By using continuous seismological data recorded by the Saudi Geological Survey (SGS) that operates three permanent seismic stations and a temporary network of 11 broadband sensors, we analyze the seismic patterns in space and time. For the verified detected events, we assemble the body wave arrival times that are inverted for the velocity structures along with events hypocenters to investigate possible causes of this swarm sequence, that is, whether the activity is of tectonic- or hydro-thermal origin.

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

New seismo-stratigraphic and marine magnetic data of the Gulf of Pozzuoli (Naples Bay, Tyrrhenian Sea, Italy): inferences for the tectonic and magmatic events of the Phlegrean Fields volcanic complex (Campania)

NASA Astrophysics Data System (ADS)

Aiello, Gemma; Marsella, Ennio; Fiore, Vincenzo Di

2012-06-01

A detailed reconstruction of the stratigraphic and tectonic setting of the Gulf of Pozzuoli (Naples Bay) is provided on the basis of newly acquired single channel seismic profiles coupled with already recorded marine magnetics gathering the volcanic nature of some seismic units. Inferences for the tectonic and magmatic setting of the Phlegrean Fields volcanic complex, a volcanic district surrounding the western part of the Gulf of Naples, where volcanism has been active since at least 50 ka, are also discussed. The Gulf of Pozzuoli represents the submerged border of the Phlegrean caldera, resulting from the volcano-tectonic collapse induced from the pyroclastic flow deposits of the Campanian Ignimbrite (35 ka). Several morpho-depositional units have been identified, i.e., the inner continental shelf, the central basin, the submerged volcanic banks and the outer continental shelf. The stratigraphic relationships between the Quaternary volcanic units related to the offshore caldera border and the overlying deposits of the Late Quaternary depositional sequence in the Gulf of Pozzuoli have been highlighted. Fourteen main seismic units, both volcanic and sedimentary, tectonically controlled due to contemporaneous folding and normal faulting have been revealed by geological interpretation. Volcanic dykes, characterized by acoustically transparent sub-vertical bodies, locally bounded by normal faults, testify to the magma uprising in correspondence with extensional structures. A large field of tuff cones interlayered with marine deposits off the island of Nisida, on the western rim of the gulf, is related to the emplacement of the Neapolitan Yellow Tuff deposits. A thick volcanic unit, exposed over a large area off the Capo Miseno volcanic edifice is connected with the Bacoli-Isola Pennata-Capo Miseno yellow tuffs, cropping out in the northern Phlegrean Fields.

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

NASA Astrophysics Data System (ADS)

Tormey, Daniel

2010-11-01

Glaciated mountains are among the most sensitive environments to climatic changes, and recent work has shown that large-scale glacial melting, including at the end of the Pleistocene, caused a significant increase in the incidence of large volcanic sector collapse and debris flows on then-active volcanoes. With current accelerated rates of glacial melting, glaciated active volcanoes are at an increasing risk of sector collapse, debris flow and landslide. These catastrophic events are Earth's most damaging erosion phenomenon, causing extensive property damage and loss of life. This paper illustrates these effects in well-studied settings, focusing on the end-Pleistocene to Holocene glaciovolcanic growth and destruction of the cone of the active volcano Planchon-Peteroa in the Andean Southern Volcanic Zone at latitude 35° 15' S, along the border between Chile and Argentina. The development of the volcano over the last 14,000 years illustrates how glacial melting and magmatic activity can trigger landslides and sector collapses. Planchon had a large sector collapse that produced a highly mobile and erosive debris avalanche 11,000 years BP, and other slope instabilities during the end-Pleistocene/early Holocene deglaciation. The summit amphitheater left after the sector collapse was subject to alternating periods of glaciation and melting-induced lake formation. Breaching of the moraine dams then formed lahars and landslides originating at the western edge of the summit amphitheater, and the deposits are preserved along the western flank of the volcano. Deep incision of moraine deposits further down the western slope of the volcano indicates that the lahars and landslides were water-rich and had high erosive power. As illustrated by Planchon-Peteroa, the interplay among glacial growth and melting, magmatic activity, and slope stability is complex, but must be accounted for in volcanic hazard assessment. Planchon-Peteroa currently has the southernmost temperate zone mountain glacier in the Andes. Accelerated glacial melting at present rates of climate change could lead to a recurrence of many of these post-Pleistocene events. A framework for augmenting hazard assessments and countermeasures is also proposed based on the types of hazards presented by accelerated glacial melting. Glacial melting may lead to volcanic hazards in areas not previously considered at risk, and hence there may be a low level of preparedness. Compared to the end-Pleistocene accelerated glacial melting and sector collapses, present-day glacial melting in volcanic terrain has the potential to affect large human populations. Human settlements, hydropower production, forestry, mining and wilderness tourism are all concentrated near some glaciated volcanic areas. For example, the area covered by the debris avalanche from Volcan Planchon currently supports a rich agricultural economy in Chile. Effective risk management is needed to address the issues of changing patterns in vulnerability, the nature and redistribution of hazards, and the potential socioeconomic consequences of glaciovolcanic events. Since these events are infrequent, local communities frequently do not have a memory of past occurrences, and therefore have a low awareness of the potential effects. Systematic and structured impact assessment allows objective risk analysis, uncertainty analysis, and a framework for balancing countermeasures and contingency measures with public need and acceptance. An impact assessment approach similar to that used in land use planning is presented here, with the following major elements: (i) hazard characterization; (ii) consequence characterization; (iii) risk assessment; (iv) risk control and countermeasures; and (v) risk communication. The emphasis is on effective risk communication, supported by facts, in order to address the increased hazards posed by accelerated glacial melting on volcanic cone stability. Decision makers must then weigh societal acceptance of the risk control and countermeasures against their costs and consequences.

Kolumbo submarine volcano (Greece): An active window into the Aegean subduction system.

PubMed

Rizzo, Andrea Luca; Caracausi, Antonio; Chavagnac, Valèrie; Nomikou, Paraskevi; Polymenakou, Paraskevi N; Mandalakis, Manolis; Kotoulas, Georgios; Magoulas, Antonios; Castillo, Alain; Lampridou, Danai

2016-06-17

Submarine volcanism represents ~80% of the volcanic activity on Earth and is an important source of mantle-derived gases. These gases are of basic importance for the comprehension of mantle characteristics in areas where subaerial volcanism is missing or strongly modified by the presence of crustal/atmospheric components. Though, the study of submarine volcanism remains a challenge due to their hazardousness and sea-depth. Here, we report (3)He/(4)He measurements in CO2-dominated gases discharged at 500 m below sea level from the high-temperature (~220 °C) hydrothermal system of the Kolumbo submarine volcano (Greece), located 7 km northeast off Santorini Island in the central part of the Hellenic Volcanic Arc (HVA). We highlight that the mantle below Kolumbo and Santorini has a (3)He/(4)He signature of at least 7.0 Ra (being Ra the (3)He/(4)He ratio of atmospheric He equal to 1.39×10(-6)), 3 Ra units higher than actually known for gases-rocks from Santorini. This ratio is also the highest measured across the HVA and is indicative of the direct degassing of a Mid-Ocean-Ridge-Basalts (MORB)-like mantle through lithospheric faults. We finally highlight that the degassing of high-temperature fluids with a MORB-like (3)He/(4)He ratio corroborates a vigorous outgassing of mantle-derived volatiles with potential hazard at the Kolumbo submarine volcano.

The Chahnaly low sulfidation epithermal gold deposit, western Makran volcanic arc, southeastern Iran

USGS Publications Warehouse

Sholeh, Ali; Rastad, Ebrahim; Huston, David L.; Gemmell, J. Bruce; Taylor, Ryan D.

2016-01-01

The Chahnaly Au deposit formed during the early stages of magmatism. LA-ICP-MS zircon U-Pb geochronology of host andesite and 40Ar/39Ar dating of two samples of gold-associated adularia show that the ore-stage adularia (19.83 ± 0.10 and 19.2 ± 0.5 Ma) is younger, by as much as 1.5 million years, than the volcanic host rock (20.32 ± 0.4 Ma). Therefore, either hydrothermal activity continued well after volcanism or a second magmatic event rejuvenated hydrothermal activity. This second magmatic event may be related to eruption of porphyritic andesite at ~20.32 ± 0.40 Ma, which is within error of ~19.83 ± 0.10 Ma adularia. The new LA-ICP-MS zircon U-Pb host rock and vein adularia 40Ar/39Ar ages suggest that early Miocene magmatism and mineralization in the Bazman area is of a similar age to that of the Saindak porphyry and Tanjeel porphyry center of the giant Reko Diq deposit. This confirms the existence of early Miocene arc magmatism and mineralization along the Iranian part of the Makran volcanic arc. Ore, alteration mineralogy, and alteration patterns indicate that the Chahnaly deposit is a typical low-sulfidation epithermal Au deposit, located in a poorly explored part of the Makran volcanic arc in Iran.                   

Petrogenesis of Tertiary continental intra-plate lavas between Siebengebirge and Westerwald, Germany: Constraints from trace element systematics and Nd, Sr and Pb isotopes

NASA Astrophysics Data System (ADS)

Schubert, S.; Jung, S.; Pfänder, J. A.; Hauff, F.; Garbe-Schönberg, D.

2015-10-01

New 39Ar/40Ar ages and major- and trace-element and radiogenic isotope data are presented for basanites and alkali basalts from the transition area between the Westerwald and Siebengebirge volcanic fields (Germany) that belongs to the Central European Volcanic Province (CEVP). The 39Ar/40Ar ages indicate ages of c. 24 and c. 5 Ma which are fully compatible with previous K/Ar ages indicating that the evolution of this volcanic field belongs to the Westerwald area (28-22 Ma and 5 Ma) rather than to the Siebengebirge area (26-23 Ma). Based on the occurrence of > 30 isolated volcanic plugs with a simple igneous history, this volcanic field can be viewed as a monogenetic volcanic field. Compositions of some basanites are primitive, whereas others and the alkali basalts show decreasing Cr and Ni contents and CaO/Al2O3 ratios. However, increasing TiO2, Al2O3 and incompatible elements (Sr, Zr, Y, Hf, Ta) concentrations with decreasing MgO indicating fractionation of mainly olivine with minor amounts of clinopyroxene and spinel can be noticed. Rare earth element systematics suggest that most of the alkaline rocks are generated by different degrees of melting (5%-10%) of a garnet-bearing peridotite containing some residual amphibole. Negative anomalies of Rb and K in primitive mantle-normalized diagrams and a lack of Ba/Rb fractionation suggest that amphibole was the major OH-bearing mineral phase in the mantle. The alkaline rocks have a restricted range in 87Sr/86Sr and 143Nd/144Nd ratios ranging from 0.7033 to 0.7044 and from 0.51275 to 0.51285, respectively. Lead isotope compositions (206Pb/204Pb: 19.21-19.65; 207Pb/204Pb: 15.62-15.67; 208Pb/204Pb: 39.10-39.46) of the alkaline rocks are within the range of most OIB in which the higher values approach the composition of the European Asthenospheric Reservoir (EAR). The correlation between Sr and Nd isotopes and trace element constraints (Ce/Pb; Nb/U) indicates that for some samples interaction with crustal rocks during fractionation has occurred. Miocene intraplate basaltic volcanism in the area probably occurred as a result of minor "baby plume" activity. Each volcanic plug records evidence of a specific stage of fractionation with or without assimilation; however, in summary the lavas plot on a single fractionation path. This implies that during evolution of the volcanic field initial melting took place in the asthenosphere or at the lithosphere-asthenosphere interface. The melts moved through the lithospheric mantle and stagnated at crustal levels, however the observed fractionation paths suggest that they were fed from a single reservoir. This model, which involves small-scale plume impact followed by asthenosphere-lithosphere interaction together with minor crustal contamination, should also be applicable to other intra-continental rift-related areas.

Embedded ARM system for volcano monitoring in remote areas: application to the active volcano on Deception Island (Antarctica).

PubMed

Peci, Luis Miguel; Berrocoso, Manuel; Fernández-Ros, Alberto; García, Alicia; Marrero, José Manuel; Ortiz, Ramón

2014-01-02

This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARM™ processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (Debian™) as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS) described has been deployed on the active Deception Island (Antarctica) volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands) in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis.

Embedded ARM System for Volcano Monitoring in Remote Areas: Application to the Active Volcano on Deception Island (Antarctica)

PubMed Central

Peci, Luis Miguel; Berrocoso, Manuel; Fernández-Ros, Alberto; García, Alicia; Marrero, José Manuel; Ortiz, Ramón

2014-01-01

This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARM™™ processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (Debian™) as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS) described has been deployed on the active Deception Island (Antarctica) volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands) in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis. PMID:24451461

New chronological and geochemical constraints on the genesis and geological evolution of Ponza and Palmarola Volcanic Islands (Tyrrhenian Sea, Italy)

NASA Astrophysics Data System (ADS)

Cadoux, Anita; Pinti, Daniele L.; Aznar, Cyril; Chiesa, Sergio; Gillot, Pierre-Yves

2005-04-01

A new geochronological and geochemical study of the volcanic rocks of the Ponza and Palmarola Islands, Pontine Archipelago, has been carried out. This archipelago is located along the boundary between the Italian continental shelf and the opening Tyrrhenian basin. It is a key area to study volcanism related to the opening of the Tyrrhenian Sea. Ponza is the oldest felsic magmatic manifestation in the central Tyrrhenian area. Previous studies suggested that Ponza volcanic activity began before 5 Ma. Twenty-five new K-Ar ages constrain the volcanic activity (rhyolitic hyaloclastites and dykes) to the last 4.2 Ma, with two episodes of quiescence between 3.7 and 3.2 Ma and between 2.9 and 1.0 Ma. A new volcanic episode dated at 3.2-2.9 Ma has been identified on the central and southern Ponza, with emplacement of pyroclastic units. At 1.0 Ma, a trachytic episode ended the volcanic activity. The near island of Palmarola exhibits rhyolitic hyaloclastites and domes dated between 1.6 and 1.5 Ma, indicating that the island was entirely built during the Early Pleistocene in a short span of time of ca. 120 ka. Although only 6-8 km apart, the two islands display significantly different geochemical signatures. Ponza rhyolites show major and trace element compositions representative of orogenic magmas of subduction/collision zones: high-K calc-alkaline and metaluminous rhyolites (Agpaitic Index [AI] and Alumina Saturation Index [ASI] <1), high LILE/HFSE (Th/Ta=16-21) and LREE/HFSE ratios (La/Nb>3), and Nb-Ta negative anomalies. In Palmarola, the orogenic character is also present, but much less marked than in Ponza: rhyolites have a peralkaline character (AI>1), lower LILE/HFSE (Th/Ta=11-15), low LREE/HFSE ratios (La/Nb=1-2) close to those of anorogenic lavas, and the Nb-Ta negative anomalies are almost absent. Y/Nb ratios indicate different magmatic sources, one similar to island-arc or active continental margin basalts for Ponza rhyolites, and the others probably involving an OIB type component for Palmarola rhyolites and Ponza trachytes. Palmarola volcanics represent a transitional magmatism: although a preserved collisional geochemical imprint, they show geochemical features approaching those of anorogenic lavas erupted in a within-plate context. The change of magmatism evidenced in this study can be related to the tectonic evolution of the area. Indeed, Hf, Ta and Rb contents suggest that the oldest Pliocene rhyolites of Ponza would emplace in a syn- to late-collisional setting, while the younger Pleistocene rhyolites of Palmarola would be emplaced in a post-collisional setting in which the orogenic character (Th/Ta) decreases and mantle influence (Nb/Ta) increases. Geochemical modeling strongly suggests that the Palmarola rhyolites represent the waning stages of a subduction-related magmatism. The K-Ar datings allow us to estimate precisely the transition of magmatism to last less than 1.3 Ma. The transitional magmas may be the result of the upwelling of asthenospheric mantle inducing melting of a metasomatized lithospheric mantle and the mixing between these two sources. This upwelling could occur during the extension of the Tyrrhenian basin, caused by the slab retreat and steepening, or during a process of slab break-off starting in the Pliocene.

Submarine volcanic features west of Kealakekua Bay, Hawaii

USGS Publications Warehouse

Fornari, D.J.; Lockwood, J.P.; Lipman, P.W.; Rawson, M.; Malahoff, A.

1980-01-01

Visual observations of submarine volcanic vents were made from the submersible vehicle DSV "Sea Cliff" in water depths between 1310 and 690 m, west of Kealakekua Bay, Hawaii. Glass-rich, shelly submarine lavas surround circular 1- to 3-m-diameter volcanic vents between 1050 and 690 m depth in an area west-northwest of the southernpoint (Keei Pt.) of Kealakekua Bay. Eye-witness accounts indicate that this area was the site of a submarine eruption on February 24, 1877. Chemical analyses of lavas from these possible seafloor vent areas indicate that the eruptive products are very similar in composition to volcanic rocks produced by historic eruptions of Mauna Loa volcano. ?? 1980.

Geological and geochemical studies in the Robinson Mining District, White Pine County, Nevada, using Skylab S190A imagery

NASA Technical Reports Server (NTRS)

Jensen, M. L. (Principal Investigator); Rogers, R. J.; Erickson, M. P.

1973-01-01

The author has identified the following significant results. In the Robinson mining district which included the Ruth porphyry copper mines, three large positive aeromagnetic anomalies exist over a Tertiary volcanic area north west of Ruth. Prior studies of this area have suggested that the volcanics may or may not be the cause of the anomalies. Skylab Sl90A imagery, however, indicates possible outcrops in the volcanic area of the Paleozoic sediments. Field studies or ground truth verify the existence of these inliers suggesting that the magnetic anomaly may be the result of a buried intrusive body for which potential mineralization has been covered by the post-ore blanket of volcanics. The area is being mapped in more detail and samples of mercury-bearing soil-gas area being collected within and outside the area.

Volcanisme, activité anthropique et circulation des masses océaniques : leur influence respective sur la distribution des populations d'ostracodes dans la baie de Kagoshima (île de Kyushu, Japon)Impact of volcanism, human activities, and water mass circulation on the distribution of ostracod populations in Kagoshima Bay (Kyushu Island, southern Japan)

NASA Astrophysics Data System (ADS)

Bodergat, Anne-Marie; Oki, Kimihiko; Ishizaki, Kunihiro; Rio, Michel

2002-11-01

The distribution of ostracod populations in Kagoshima Bay (Japan) is analysed with reference to different environmental parameters. The bay is an area of volcanic activity of Sakurajima volcano under the influence of the Kuroshio Current. Most of the Head environment is occupied by an acidic water mass. Numbers of individual and species decrease from the Mouth of the bay towards the Basin and Head environments. In this latter, acidic water mass has a drastic effect on ostracod populations, whereas volcanic ashes and domestic inputs are not hostile. Ostracod distribution is influenced by the quality and structure of water masses. To cite this article: A.-M. Bodergat et al., C. R. Geoscience 334 (2002) 1053-1059.

Living through a volcanic eruption: Understanding the experience of survivors as a phenomenological existential phenomenon.

PubMed

Warsini, Sri; Mills, Jane; West, Caryn; Usher, Kim

2016-06-01

Mount Merapi in Indonesia is the most active volcano in the world with its 4-6-year eruption cycle. The mountain and surrounding areas are populated by hundreds of thousands of people who live near the volcano despite the danger posed to their wellbeing. The aim of this study was to explore the lived experience of people who survived the most recent eruption of Mount Merapi, which took place in 2010. Investigators conducted interviews with 20 participants to generate textual data that were coded and themed. Three themes linked to the phenomenological existential experience (temporality and relationality) of living through a volcanic eruption emerged from the data. These themes were: connectivity, disconnection and reconnection. Results indicate that the close relationship individuals have with Mount Merapi and others in their neighbourhood outweighs the risk of living in the shadow of an active volcano. This is the first study to analyze the phenomenological existential elements of living through a volcanic eruption. © 2016 Australian College of Mental Health Nurses Inc.

Long- and short-term temporal variations of the diffuse CO2 emission from Timanfaya volcano, Lanzarote, Canary Islands

NASA Astrophysics Data System (ADS)

Hernández, P. A.; Padilla, G.; Calvo, D.; Padrón, E.; Melian, G.; Dionis, S.; Nolasco, D.; Barrancos, J.; Rodríguez, F.; Pérez, N.

2012-04-01

Lanzarote Island is an emergent part of the East Canary Ridge and it is situated approximately 100 km from the NW coast of Morocco, covering an area of about 795km2. The largest historical eruption of the Canary Islands, Timanfaya, took place during 1730-36 in this island when long-term eruptions from a NE-SW-trending fissure formed the Montañas del Fuego. The last eruption at Lanzarote Island occurred during 1824, Tinguaton volcano, and produced a much smaller lava flow that reached the SW coast. At present, one of the most prominent phenomena at Timanfaya volcanic field is the high maintained superficial temperatures occurring in the area since the 1730 volcanic eruption. The maximum temperatures recorded in this zone are 605°C, taken in a slightly inclined well 13 m deep. Since fumarolic activity is absent at the surface environment of Lanzarote, to study the diffuse CO2 emission becomes an ideal geochemical tool for monitoring its volcanic activity. Soil CO2 efflux surveys were conducted throughout Timanfaya volcanic field and surrounding areas during the summer periods of 2006, 2007, 2008, 2009, fall period of 2010 and winter, spring and summer periods of 2011 to investigate long and short-term temporal variations of the diffuse CO2 emission from Timanfaya volcano. Soil CO2 efflux surveys were undertaken at Timanfaya volcanic field always under stable weather conditions to minimize effects of meteorological conditions on the CO2 at the soil atmosphere. Approximately 370-430 sampling sites were selected at the surface environment of Timanfaya to obtain an even distribution of the sampling points over the study area. The accumulation chamber method (Parkinson et al., 1981) was used to perform soil CO2 efflux measurements in-situ by means of a portable non dispersive infrared (NDIR) CO2 analyzer, which was interfaced to a hand size computer that runs data acquisition software. At each sampling site, soil temperature at 15 and 40cm depth was also measured by means of a thermocouple together with soil gas samples collected during the campaign of 2010 to evaluate the chemical and isotopic composition of soil gases. Diffuse CO2 emission values have ranged between non detectable values to 34 g m-2 d-1, and most of the study area have shown relatively low values, around the detection limit of the instrument (~0,5 g m-2 d-1). Higher soil CO2 diffuse emission values were observed where thermal anomalies occur, indicating a convective mechanism transport of gas from depth at these areas. Total CO2 outputs of the study area have been estimated in the range 41-518 t d-1 during the study period. Long-term temporal variation on total CO2 diffuse emission shows a peak recorded on winter 2011, suggesting a seasonal control on the CO2 emission. As part of the volcanic surveillance program and to understand the dynamics of CO2 diffuse emission at Timanfaya volcanic zone, an automatic geochemical station was installed in July 2010 to monitor the CO2 emission and investigate the short-term temporal variation. Time series of soil CO2 efflux shows also a close relationship with seasonal changes mainly due to rainfall.

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.

Autonomous Sensorweb Operations for Integrated Space, In-Situ Monitoring of Volcanic Activity

NASA Technical Reports Server (NTRS)

Chien, Steve A.; Doubleday, Joshua; Kedar, Sharon; Davies, Ashley G.; Lahusen, Richard; Song, Wenzhan; Shirazi, Behrooz; Mandl, Daniel; Frye, Stuart

2010-01-01

We have deployed and demonstrated operations of an integrated space in-situ sensorweb for monitoring volcanic activity. This sensorweb includes a network of ground sensors deployed to the Mount Saint Helens volcano as well as the Earth Observing One spacecraft. The ground operations and space operations are interlinked in that ground-based intelligent event detections can cause the space segment to acquire additional data via observation requests and space-based data acquisitions (thermal imagery) can trigger reconfigurations of the ground network to allocate increased bandwidth to areas of the network best situated to observe the activity. The space-based operations are enabled by an automated mission planning and tasking capability which utilizes several Opengeospatial Consortium (OGC) Sensorweb Enablement (SWE) standards which enable acquiring data, alerts, and tasking using web services. The ground-based segment also supports similar protocols to enable seamless tasking and data delivery. The space-based segment also supports onboard development of data products (thermal summary images indicating areas of activity, quicklook context images, and thermal activity alerts). These onboard developed products have reduced data volume (compared to the complete images) which enables them to be transmitted to the ground more rapidly in engineering channels.

Newberry Volcano—Central Oregon's Sleeping Giant

USGS Publications Warehouse

Donnelly-Nolan, Julie M.; Stovall, Wendy K.; Ramsey, David W.; Ewert, John W.; Jensen, Robert A.

2011-01-01

Hidden in plain sight, Oregon's massive Newberry Volcano is the largest volcano in the Cascades volcanic arc and covers an area the size of Rhode Island. Unlike familiar cone-shaped Cascades volcanoes, Newberry was built into the shape of a broad shield by repeated eruptions over 400,000 years. About 75,000 years ago a major explosion and collapse event created a large volcanic depression (caldera) at its summit. Newberry last erupted about 1,300 years ago, and present-day hot springs and geologically young lava flows indicate that it could reawaken at any time. Because of its proximity to nearby communities, frequency and size of past eruptions, and geologic youthfulness, U.S. Geological Survey scientists are working to better understand volcanic activity at Newberry and closely monitor the volcano for signs of unrest.

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

NASA Astrophysics Data System (ADS)

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

2007-05-01

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

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.

3-D density modeling of Mt. Paekdu (N Korea/China) stratovolcano and its evolution by a combination of EGM2008/terrestrial gravity field

NASA Astrophysics Data System (ADS)

Götze, Hans-Jürgen; Choi, Sungchan

2015-04-01

We combined the global gravity dataset EGM2008 and a local terrestrial gravity data survey to conduct constrained 3-D crustal density modeling of a strato-volcanic complex and the surrounding area located close to the border of North Korea and China. The independent geophysical (seismic, seismology, geochemistry) and petrological constraints will be presented together with the preprocessing of data base by curvature analysis and Euler deconvolution. The multiple data base is used to assist a general interpretation of the investigated area, and the 3D density model (modelled by the in-house IGMAS+ software). Mt. Paekdu is characterized by a low of Bouguer anomaly of some -110 × 10-5 m/s2, which is caused by the combined gravity effects of (1) Moho depth of about 40 km, (2) a zone with both lower P-wave velocity and density than the surrounding, (3) low density volcanic rocks at the surface, and (4) the presence of a magma chamber that has not previously been identified. The terrestrial gravity field measured along the seismic profile shows a remarkable anomaly descending from the southern- to the northern flank of the Mt. Paekdu volcano, which should be a typical anomaly pattern generally observed over the active volcanic area in the world (e.g. the Yellow Stone volcano). The trend is interpreted to be caused by a prominent density difference between a serious of high density mid crustal sill beneath the southern flank and a predicted partial melted zone locating in the northern flank. With the help of several geoscientific observations (seismic, electromagnetic, gravity and geochemistry) and the 3D density model we conclude that a high density sill was formed in Pliocene and early Pleistocene after pre-shield plateau-forming eruption. Since the Pliocene, volcanic activity in the Mt. Paekdu region might be migrated from the southeastern of North Korea to the northwest, following the path of NW-SE-trending faults. Recently observed seismic tremors can be explained by the vertical movement of the partial melted magma chamber beneath the northern part of the Mt. Baekdu volcanic area, which is confirmed by vertical stress change calculation.

High resolution bathymetric and sonar images of a ridge southeast of Terceira Island (Azores plateau)

NASA Astrophysics Data System (ADS)

Lourenço, N.; Miranda, J. M.; Luis, J.; Silva, I.; Goslin, J.; Ligi, M.

2003-04-01

The Terceira rift is a oblique ultra-slow spreading system where a transtensive regime results from differential movement between Eurasian and African plates. So far no classical ridge segmentation pattern has here been observed. The predominant morphological features are fault controlled rhombic shaped basins and volcanism related morphologies like circular seamounts and volcanic ridges. We present SIMRAD EM300 (bathymetry + backscatter) images acquired over one of these ridges located SE of Terceira Island, during the SIRENA cruise (PI J. Goslin), which complements previous TOBI mosaics performed over the same area during the AZZORRE99 cruise (PI M. Ligi). The ridge presents a NW-SE orientation, it is seismically active (a seismic crisis was documented in 1997) and corresponds to the southern branch of a V shape bathymetric feature enclosing the Terceira Island and which tip is located west of the Island near the 1998 Serreta ridge eruption site. NE of the ridge, the core of the V, corresponds to the North Hirondelle basin. All this area corresponds mainly to Brunhes magnetic epoch. The new bathymetry maps reveal a partition between tectonic processes, centred in the ridge, and volcanism present at the bottom of the North Hirondelle basin. The ridge high backscatter surface is cut by a set of sub-parallel anastomosed normal faults striking between N130º and N150º. Some faults present horse-tail terminations. Fault splays sometimes link to neighbour faults defining extensional duplexes and fault wedge basins and highs of rhombic shape. The faulting geometry suggests that a left-lateral strike slip component should be present. The top of the ridge consists on an arched demi-.horst, and it is probably a volcanic structure remnant (caldera system?), existing prior to onset of the tectonic stage in the ridge. Both ridge flanks display gullies and mass wasting fans at the base of the slope. The ridge vicinities are almost exclusively composed of a grayish homogeneous acoustic facies interpreted as pelagic and volcanic sediment. The numerous untectonized volcanic cones present to NE, in the northern flank of the North Hirondelle basin, align-up with the three volcanic systems of the Terceira Island (progressively less eroded towards west) and the Serreta ridge, thus suggesting propagation of a melt/thermal anomaly westwards through time. This volcanic area contrasts strongly with the highly fractured pattern observed in the ridge.

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.

The distribution and hydrogeological controls of fluoride in the groundwater of central Ethiopian rift and adjacent highlands

NASA Astrophysics Data System (ADS)

Ayenew, Tenalem

2008-05-01

Occurrence of fluoride (F) in groundwater has drawn worldwide attention, since it has considerable impact on human health. In Ethiopia high concentrations of F in groundwaters used for community water supply have resulted in extensive dental and skeletal fluorosis. As a part of a broader study, the distribution of F in groundwater has been investigated, and compared with bedrock geology and pertinent hydrochemical variables. The result indicates extreme spatial variations. High F concentration is often associated with active and sub-active regional thermal fields and acidic volcanics within high temperature rift floor. Variations in F can also be related to changes in calcium concentration resulting from dissolution of calcium minerals and mixing with waters of different chemical composition originated from variable hydrogeological environment across the rift valley. The concentration of F dramatically declines from the rift towards the highlands with the exception of scattered points associated with thermal springs confined in local volcanic centers. There are also interactions of F-rich alkaline lakes and the surrounding groundwater. Meteoric waters recharging volcanic aquifers become enriched with respect to F along the groundwater flow path from highland recharge areas to rift discharge areas. Locally wells drilled along large rift faults acting as conduits of fresh highland waters show relatively lower F. These areas are likely to be possible sources of better quality waters within the rift. The result of this study has important implications on site selection for water well drilling.

Environmental monitoring of El Hierro Island submarine volcano, by combining low and high resolution satellite imagery

NASA Astrophysics Data System (ADS)

Eugenio, F.; Martin, J.; Marcello, J.; Fraile-Nuez, E.

2014-06-01

El Hierro Island, located at the Canary Islands Archipelago in the Atlantic coast of North Africa, has been rocked by thousands of tremors and earthquakes since July 2011. Finally, an underwater volcanic eruption started 300 m below sea level on October 10, 2011. Since then, regular multidisciplinary monitoring has been carried out in order to quantify the environmental impacts caused by the submarine eruption. Thanks to this natural tracer release, multisensorial satellite imagery obtained from MODIS and MERIS sensors have been processed to monitor the volcano activity and to provide information on the concentration of biological, chemical and physical marine parameters. Specifically, low resolution satellite estimations of optimal diffuse attenuation coefficient (Kd) and chlorophyll-a (Chl-a) concentration under these abnormal conditions have been assessed. These remote sensing data have played a fundamental role during field campaigns guiding the oceanographic vessel to the appropriate sampling areas. In addition, to analyze El Hierro submarine volcano area, WorldView-2 high resolution satellite spectral bands were atmospherically and deglinted processed prior to obtain a high-resolution optimal diffuse attenuation coefficient model. This novel algorithm was developed using a matchup data set with MERIS and MODIS data, in situ transmittances measurements and a seawater radiative transfer model. Multisensor and multitemporal imagery processed from satellite remote sensing sensors have demonstrated to be a powerful tool for monitoring the submarine volcanic activities, such as discolored seawater, floating material and volcanic plume, having shown the capabilities to improve the understanding of submarine volcanic processes.

A remote sensing assessment of the impact of the 2010 Maule, Chile earthquake (Mw 8.8) on the volcanoes of the southern Andes

NASA Astrophysics Data System (ADS)

Pritchard, M. E.; Welch, M.; Jay, J.; Button, N.

2011-12-01

There are tantalizing, but controversial, indications that great earthquakes affect arc-wide volcanic activity. For example, analysis of historic eruptions at volcanoes of the southern Andes has shown that 3-4 eruptions were likely seismically triggered by Mw > 8 earthquakes in the Chile subduction zone -- particularly the 1906 and 1960 earthquakes (e.g., Watt et al., 2009). However, the 27 February 2010 Mw 8.8 Maule, Chile earthquake that ruptured the subduction zone between the 1960 and 1906 earthquakes does not appear to have triggered 3-4 volcanic eruptions in the same area in the 12 months after the event. In an effort to understand the relation between a large earthquake and volcanic unrest, we use a variety of satellite instruments to look for more subtle (i.e., not leading to eruption), but detectable change in thermal or deformation activity at the volcanoes of the southern Andes after the Maule earthquake and its aftershocks. For all of the volcanoes in the catalog of the Smithsonian Institution (approximately 80), we use nighttime MODIS and ASTER data to assess the thermal activity and ALOS InSAR data to characterize the surface deformation before and after the earthquake. The ALOS InSAR data are not ideal for detecting changes in deformation before and after the earthquake because of the small number of acquisitions in austral summer as well as ionospheric and tropospheric artifacts. We estimate that we could detect deformation > 5 cm/year. Similarly, the ASTER and MODIS data suffer respectively from poor temporal and spatial resolution of thermal anomalies. We update previous InSAR work that identified at least 8 areas of volcanic deformation in the southern Andes related to eruptive processes, subsidence of past lava flows, or surface uplift not associated with an eruption (Fournier et al., 2010). Of greatest interest are the two volcanic areas with the largest deformation signals between 2007-2008 (both > 15 cm/yr in the radar line of sight): Laguna del Maule and Cordón Caulle (which began a major eruption in June, 2011). The deformation rate at Laguna del Maule continues through 2011 at a similar high rate, accumulating more than 60 cm of vertical deformation since 2007 -- making it one of the largest deformation signals without recent eruption yet observed. The rate of uplift at Laguna del Maule seems to be unchanged before and after the 2010 Maule earthquake. The spatial and temporal deformation at Cordón Caulle is complex as noted by Fournier et al., 2010, but does not appear to have been changed by the Maule earthquake either. The reasons that the 2010 Maule earthquake did not strongly affect the closest volcanic arc in the southern Andes remains a mystery. Comparison with the 2004 Sumatra (Mw 9.2) and the 2011 Japan (Mw 9.0) earthquakes and their closest volcanic arcs could provide clues to the elusive links between large earthquakes and volcanic unrest.

MOUNT SHASTA WILDERNESS STUDY AREA, CALIFORNIA.

USGS Publications Warehouse

Christiansen, Robert L.; Tuchek, Ernest T.

1984-01-01

The Mount Shasta Wilderness lies wholly on the slopes and summit area of Mount Shasta and consists almost entirely of the products of geologically young volcanism. Small deposits of volcanic cinders and pumice are present. The volcanic system of Mount Shasta is judged to have probable resource potential for geothermal energy but that potential is least within the wilderness study area boundaries. Because any geothermal energy resource beneath the volcano would lie at considerable depths, exploration or development would be most likely at lower altitudes on the gentler slopes outside the study area.

Negative magnetic anomaly over Mt. Resnik, a subaerially erupted volcanic peak beneath the West Antarctic Ice Sheet

USGS Publications Warehouse

Behrendt, John C.; Finn, C.; Morse, D.L.; Blankenship, D.D.

2006-01-01

Mt. Resnik is one of the previously reported 18 subaerially erupted volcanoes (in the West Antarctic rift system), which have high elevation and high bed relief beneath the WAIS in the Central West Antarctica (CWA) aerogeophysical survey. Mt. Resnik lies 300 m below the surface of the West Antarctic Ice Sheet (WAIS); it has 1.6 km topographic relief, and a conical form defined by radar ice-sounding of bed topography. It has an associated complex negative magnetic anomaly revealed by the CWA survey. We calculated and interpreted magnetic models fit to the Mt. Resnik anomaly as a volcanic source comprising both reversely and normally magnetized (in the present field direction) volcanic flows, 0.5-2.5-km thick, erupted subaerially during a time of magnetic field reversal. The Mt. Resnik 305-nT anomaly is part of an approximately 50- by 40-km positive anomaly complex extending about 30 km to the west of the Mt. Resnik peak, associated with an underlying source complex of about the same area, whose top is at the bed of the WAIS. The bed relief of this shallow source complex has a maximum of only about 400 m, whereas the modeled source is >3 km thick. From the spatial relationship we interpret that this source and Mt Resnik are approximately contemporaneous. Any subglacially (older?) erupted edifices comprising hyaloclastite or other volcanic debris, which formerly overlaid the source to the west, were removed by the moving WAIS into which they were injected as is the general case for the ???1000 volcanic centers at the base of the WAIS. The presence of the magnetic field reversal modeled for Mt. Resnik may represent the Bruhnes-Matayama reversal at 780 ka (or an earlier reversal). There are ???100 short-wavelength, steep-gradient, negative magnetic anomalies observed over the West Antarctic Ice Sheet (WAIS), or about 10% of the approximately 1000 short-wavelength, shallow-source, high-amplitude (50- >1000 nT) "volcanic" magnetic anomalies in the CWA survey. These negative anomalies indicate volcanic activity during a period of magnetic reversal and therefore must also be at least 780 ka. The spatial extent and volume of volcanism can now be reassessed for the 1.2 ?? 106 km2 region of the WAIS characterized by magnetic anomalies defining interpreted volcanic centers associated with the West Antarctic rift system. The CWA covers an area of 3.54 ?? 105 km2; forty-four percent of that area exhibits short-wavelength, high-amplitude anomalies indicative of volcanic centers and subvolcanic intrusions. This equates to an area of 0.51 ?? 105 km2 and a volume of 106 km3 beneath the ice-covered West Antarctic rift system, of sufficient extent to be classified as a large igneous province interpreted to be of Oligocene to recent age.

GlobVolcano pre-operational services for global monitoring active volcanoes

NASA Astrophysics Data System (ADS)

Tampellini, Lucia; Ratti, Raffaella; Borgström, Sven; Seifert, Frank Martin; Peltier, Aline; Kaminski, Edouard; Bianchi, Marco; Branson, Wendy; Ferrucci, Fabrizio; Hirn, Barbara; van der Voet, Paul; van Geffen, J.

2010-05-01

The GlobVolcano project (2007-2010) is part of the Data User Element programme of the European Space Agency (ESA). The project aims at demonstrating Earth Observation (EO) based integrated services to support the Volcano Observatories and other mandate users (e.g. Civil Protection) in their monitoring activities. The information services are assessed in close cooperation with the user organizations for different types of volcano, from various geographical areas in various climatic zones. In a first phase, a complete information system has been designed, implemented and validated, involving a limited number of test areas and respective user organizations. In the currently on-going second phase, GlobVolcano is delivering pre-operational services over 15 volcanic sites located in three continents and as many user organizations are involved and cooperating with the project team. The set of GlobVolcano offered EO based information products is composed as follows: Deformation Mapping DInSAR (Differential Synthetic Aperture Radar Interferometry) has been used to study a wide range of surface displacements related to different phenomena (e.g. seismic faults, volcanoes, landslides) at a spatial resolution of less than 100 m and cm-level precision. Permanent Scatterers SAR Interferometry method (PSInSARTM) has been introduced by Politecnico of Milano as an advanced InSAR technique capable of measuring millimetre scale displacements of individual radar targets on the ground by using multi-temporal data-sets, estimating and removing the atmospheric components. Other techniques (e.g. CTM) have followed similar strategies and have shown promising results in different scenarios. Different processing approaches have been adopted, according to data availability, characteristic of the area and dynamic characteristics of the volcano. Conventional DInSAR: Colima (Mexico), Nyiragongo (Congo), Pico (Azores), Areanal (Costa Rica) PSInSARTM: Piton de la Fournaise (La Reunion Island), Stromboli and Volcano (Italy), Hilo (Hawai), Mt. St. Helens (United States), CTM (Coherent Target Monitoring): Cumbre Vieja (La Palma) To generate products either Envisat ASAR, Radarsat 1or ALOS PALSAR data have been used. Surface Thermal Anomalies Volcanic hot-spots detection, radiant flux and effusion rate (where applicable) calculation of high temperature surface thermal anomalies such as active lava flow, strombolian activity, lava dome, pyroclastic flow and lava lake can be performed through MODIS (Terra / Aqua) MIR and TIR channels, or ASTER (Terra), HRVIR/HRGT (SPOT4/5) and Landsat family SWIR channels analysis. ASTER and Landsat TIR channels allow relative radiant flux calculation of low temperature anomalies such as lava and pyroclastic flow cooling, crater lake and low temperature fumarolic fields. MODIS, ASTER and SPOT data are processed to detect and measure the following volcanic surface phenomena: Effusive activity Piton de la Fournaise (Reunion Island); Mt Etna (Italy). Lava dome growths, collapses and related pyroclastic flows Soufrière Hills (Montserrat); Arenal - (Costa Rica). Permanent crater lake and ephemeral lava lake Karthala (Comores Islands). Strombolian activity Stromboli (Italy). Low temperature fumarolic fields Nisyros (Greece), Vulcano (Italy), Mauna Loa (Hawaii). Volcanic Emission The Volcanic Emission Service is provided to the users by a link to GSE-PROMOTE - Support to Aviation Control Service (SACS). The aim of the service is to deliver in near-real-time data derived from satellite measurements regarding SO2 emissions (SO2 vertical column density - Dobson Unit [DU]) possibly related to volcanic eruptions and to track the ash injected into the atmosphere during a volcanic eruption. SO2 measurements are derived from different satellite instruments, such as SCIAMACHY, OMI and GOME-2. The tracking of volcanic ash is accomplished by using SEVIRI-MSG data and, in particular, the following channels VIS 0.6 and IR 3.9, and along with IR8.7, IR 10.8 and IR 12.0. The GlobVolcano information system and its current experimentation represent a significant step ahead towards the implementation of an operational, global observatory of volcanoes by the synergetic use of data from available Earth Observation satellites.

Volcanoes: Nature's Caldrons Challenge Geochemists.

ERIC Educational Resources Information Center

Zurer, Pamela S.

1984-01-01

Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

Search for ongoing volcanic activity on Venus: Case study of Maat Mons, Sapas Mons and Ozza Mons

NASA Astrophysics Data System (ADS)

Basilevsky, A. T.; Shalygin, E. V.; Markiewicz, W. J.; Titov, D. V.; Roatsch, Th.; Kreslavsky, M. A.

2012-04-01

Maat Mons volcano and its vicinities show evidence of geologically very recent volcanism. We consider Venus Monitoring Camera (VMC) night-side images of this area. Analysis of VMC images taken in 12 observation sessions during the time period from 31 Oct 2007 to 15 Jun 2009 did not reveal any suspicious high-emission spots which could be signatures of the presently ongoing volcanic eruptions. If Maat Mons volcano had the eruption history similar to that of Mauna Loa, Hawaii, in the 20th century, the probability to observe an eruption in this VMC observation sequence would be about 8%, meaning that the absence of detection does not mean that Maat is not active in the present epoch. Blurring of the thermal radiation coming from Venus surface by the planet atmosphere decreases detectability of thermal signature of fresh lavas. We simulated near-infrared images of the study area with artificially added lava flows having surface temperature 1000 K and various areas. These simulations showed that 1 km2 lava flows should be marginally seen by VMC. An increase of the lava surface area to 2 - 3 km2 makes them visible on the plains and increase of the area to 4 - 5 km2 makes them visible even in deep rift zones. Typical individual lava flows on Mauna Loa are a few km2, however, they often have been formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower than 8%, but it is far from negligible. Our consideration suggests that further search of Maat Mons area and other areas including young rift zones makes sense and should be continued. More effective search could be done if observations simultaneously cover most part of the night side of Venus for relatively long (years) time of continuous observations.

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.

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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