A new geologic map at , scale depicts these deposits, these processes.
We correlate deposits by tephra layers calibrated by many radiocarbon dates. Augustine Volcano began erupting on the flank of a small island of Jurassic clastic-sedimentary rock before the late Wisconsin glaciation late Pleistocene. The oldest known effusions ranged from olivine basalt explosively propelled by steam, to highly explosive magmatic eruptions of dacite or rhyodacite shed as pumice flows.
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Late Wisconsin piedmont glaciers issuing from the mountainous western mainland surrounded the island while dacitic eruptive debris swept down the south volcano flank. Evidence is scant for eruptions between the late Wisconsin and about 2, yr B. On a few south-flank inliers, thick stratigraphically low pumiceous pyroclastic-flow and fall deposits probably represent this period from which we have no radiocarbon dates on Augustine Island. Eruptions between about 5, and 2, yr B. On Shuyak Island km southeast of Augustine, two distal fall ashes of Augustinian chemical provenance microprobe analysis of glass date respectively between about 5, and 5, yr B.
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An Augustine ash along Kamishak Creek 70 km southwest of Augustine dates between about 3, and 3, yr B. A probably Augustinian ash lying within peat near Homer dates to about 2, yr B. From before 2, yr B. During this period, numerous coarse debris avalanches swept beyond Augustine's coast, most. Rapid response of a hydrologic system to volcanic activity: Masaya volcano , Nicaragua. Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity.
Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano , Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent.
These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity.
We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic -hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool. This CD is the second in a series sponsored by the U. Department of Energy Office of Geothermal Technologies to collate Smithsonian data on Quaternary volcanism as a resource for the geothermal community.
It also has utility for those concerned with volcanic hazard and risk mitgation as well as an educational tool for those interested in Mexican volcanism. These include geographic and geologic data on individual volcanoes as well as a brief paragraph summarizing the geologic history along with tabular eruption chronologies, eruptive characteristics, and eruptive volumes, when known.
Volcano data are accessible from both geographical and alphabetical searches. A major component of the CD is more than digitized images illustrating the morphology of volcanic centers and eruption processes and deposits, providing a dramatic visual primer to the country's volcanoes.
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Images of specific eruptions can be directly linked to from the eruption chronology tables. Volcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano , Italia. We made a stratigraphic, structural and morphologic study of the Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist around the margin of the volcano.
These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of Amiata on its weak substratum, formed by the late Triassic evaporites Burano Anhydrites and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes Ligurian Complex. Regional doming created a slope in the basement facilitating the outward flow and spreading of the ductile layers forced by the volcanic load.
We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a set of solutions. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time.
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Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for spreading and formation of trains of adjacent diapirs.
As a feedback, the hot hydrothermal fluids decrease the shear strength of the anhydrites facilitating the spreading process. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays' exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks which host an extensive fresh. Oct 21, The results The F The San Francisco Volcanic Field SFVF , located in northern Arizona, USA, contains some of the youngest intracontinental volcanism within the United States and, given its recent eruptive history, presents an excellent opportunity to better understand how these systems behave.
Geophysical techniques such as magnetics, paleomagnetics, and seismic refraction can be used to understand eruptive behavior and image shallow subsurface structures. As such, they present an opportunity to understand eruptive processes associated with the monogenetic volcanism that is common within the SFVF. These techniques are especially beneficial in areas where erosion has not exposed shallow eruptive features within the volcano. These are thought to be some of the youngest volcanoes in the field and, as such, are well preserved.
Aside from being young, they both exhibit interesting features such as multiple vents, apparent vent alignment, and lack of erosional features that are present at many of the other volcanoes in the SFVF, making them ideal for this work. Initial results show that shallow subsurface basaltic masses can be located using geophysical techniques. These masses are interpreted as dikes or lava flows that are covered by younger scoria. Propagating dikes drive eruptions at monogenetic volcanoes , which often appear in aligned clusters.
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Locating these features will further the understanding of how magma is transported and how eruptions may have progressed. Full Text Available Volcanic hazards assessment tools are essential for risk mitigation of volcanic activities. A number of offline volcanic hazard assessment tools have been provided, but in most cases, they require relatively complex installation procedure and usage.
This situation causes limited usage of volcanic hazard assessment tools among volcanologists and volcanic hazards communities. In addition, volcanic eruption chronology and detailed database of each volcano in the world are essential key information for volcanic hazard assessment, but most of them are isolated and not connected to and with each other. The Volcanic Hazard Assessment Support System aims to implement a user-friendly, WebGIS-based, open-access online system for potential hazards assessment and risk-mitigation of Quaternary volcanoes in the world.
The users can get up-to-date information such as eruption chronology and geophysical monitoring data of a specific volcano using the direct link system to major volcano databases on the system. Currently, the system provides 3 simple, powerful and notable deterministic modeling simulation codes of volcanic processes, such as Energy Cone, Titan2D and Tephra2. The system provides deterministic tools because probabilistic assessment tools are normally much more computationally demanding. By using the volcano hazard assessment system, the area that would be affected by volcanic eruptions in any location near the volcano can be estimated using numerical simulations.
The system can be used to evaluate volcanic hazards and move this toward risk-potential by overlaying the estimated distribution of volcanic gravity flows or tephra falls on major roads, houses and evacuation areas using the GIS-enabled systems. The system is developed for all users in the world who need volcanic hazards assessment tools. The eruption of Chaiten Volcano Chile involved a variety of volcanic and associated hydrologic processes that damaged nearby forests. These processes included coarse gravel and fine silt to sand tephra fall, a laterally directed blast, fluvial deposition of remobilized tephra, a variety of low-temperature mass-movement processes, and a pyroclastic flow CO2 is a key chemical tracer for exploring volcanic degassing mechanisms of basaltic magmatic systems 1.
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The rate of CO2 release from sub-aerial volcanism is monitored via studies on volcanic plumes and fumaroles, but information is still sparse and incomplete for many regions of the globe, including the majority of the volcanoes in the Central American Volcanic Arc 2. Here, we use a combination of remote sensing techniques and in-situ measurements of volcanic gas plumes to provide a first estimate of the CO2 output from three degassing volcanoes in Central America: Turrialba, in Costa Rica, and Telica and San Cristobal, in Nicaragua.
SO2 concentrations in the near-vent plumes obtained via a temporary installed fully-automated Multi-GAS instrument 4. Distinct CO2 - SO2 - H2O proportions were observed at the three volcanoes , but still within the range of volcanic arc gas 5. These measurements contribute refining the current estimates of the total CO2 output from the Central American Volcanic Arc 7.
Symonds, R. Reviews in. Postshield stage transitional volcanism on Mahukona Volcano , Hawaii. These ages are younger than the inferred end of the tholeiitic shield stage and indicate that the volcano had entered the postshield alkalic stage before going extinct. Previously reported elevated helium isotopic ratios of lavas from one of these cones were incorrectly interpreted to indicate eruption during a preshield alkalic stage.
Consequently, high helium isotopic ratios are a poor indicator of eruptive stage, as they occur in preshield, shield, and postshield stage lavas. Loihi Seamount and Kilauea are the only known Hawaiian volcanoes where the volume of preshield alkalic stage lavas can be estimated. Springer-Verlag The eruption resulted in the worst volcanic disaster in the recorded history of Mexico, causing about 2, casualties, displacing thousands, and producing severe economic losses. Even when some villages were relocated after the eruption, many people still live and work in the vicinities of the volcano and may be affected in the case of a new eruption.
In fact, the fatalities reported in the first stage of the eruption were caused by roof collapse induced by ashfall and lithic ballistic projectiles. Different scenarios are defined based on the past activity of the volcano and parameterized by considering the maximum kinetic energy associated with ballistic projectiles ejected during previous eruptions. A ballistic model is used to reconstruct the "launching" kinetic energy of the projectiles observed in the field.
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These maps assist the responsible authorities to plan the definition and mitigation of restricted areas during volcanic crises. Sequential assimilation of volcanic monitoring data to quantify eruption potential: Application to Kerinci volcano. Quantifying the eruption potential of a restless volcano requires the ability to model parameters such as overpressure and calculate the host rock stress state as the system evolves. A critical challenge is developing a model-data fusion framework to take advantage of observational data and provide updates of the volcanic system through time.
The Ensemble Kalman Filter EnKF uses a Monte Carlo approach to assimilate volcanic monitoring data and update models of volcanic unrest, providing time-varying estimates of overpressure and stress. Although the EnKF has been proven effective to forecast volcanic deformation using synthetic InSAR and GPS data, until now, it has not been applied to assimilate data from an active volcanic system.
A two-sources analytical model is used to simulate the surface deformation of Kerinci volcano observed by InSAR time-series data and to predict the system evolution. A deep, deflating dike-like source reproduces the subsiding signal on the flanks of the volcano , and a shallow spherical McTigue source reproduces the central uplift.