Search results for "Earth"
showing 10 items of 12204 documents
Sustaining persistent lava lakes: Observations from high-resolution gas measurements at Villarrica volcano, Chile
2016
International audience; Active lava lakes – as the exposed upper part of magmatic columns – are prime locations to investigate the conduit flow processes operating at active, degassing volcanoes. Persistent lava lakes require a constant influx of heat to sustain a molten state at the Earth's surface. Several mechanisms have been proposed to explain how such heat transfer can operate efficiently. These models make contrasting predictions with respect to the flow dynamics in volcanic conduits and should result in dissimilar volatile emissions at the surface. Here we look at high-frequency SO2 fluxes, plume composition, thermal emissions and aerial video footage from the Villarrica lava lake i…
Prodigious emission rates and magma degassing budget of major, trace and radioactive volatile species from Ambrym basaltic volcano, Vanuatu island Arc
2016
Abstract Ambrym volcano, in the Vanuatu arc, is one of the most active volcanoes of the Southwest Pacific region, where persistent lava lake and/or Strombolian activity sustains voluminous gas plume emissions. Here we report on the first comprehensive budget for the discharge of major, minor, trace and radioactive volatile species from Ambrym volcano, as well as the first data for volatiles dissolved in its basaltic magma (olivine-hosted melt inclusions). In situ MultiGAS analysis of H 2 O, CO 2 , SO 2 and H 2 S in crater rim emissions, coupled with filter-pack determination of SO 2 , halogens, stable and radioactive metals demonstrates a common magmatic source for volcanic gases emitted by…
Using mosses as biomonitors to study trace element emissions and their distribution in six different volcanic areas
2017
Volcanoes emit SO2, CO2, and H2S, but also trace elements gases and particles such as As, Cd, Cr, Cu, Hg, Ni, Pb, and Sb. Active moss bag biomonitoring, an easy to apply and low budget method, was used to determine trace element release from volcanic areas of different geological context and climates. Exposure height variations (0.7â1.6 m above ground) due to different availability of natural tie points did not affect the results. Accumulation was linear for exposure durations from three days to nine weeks, so values were comparable by normalization to moss exposure time. Uncovered moss bags showed higher accumulation than co-exposed covered ones because of additional dust and wet deposit…
Thematic vent opening probability maps and hazard assessment of small-scale pyroclastic density currents in the San Salvador volcanic complex (El Sal…
2021
The San Salvador volcanic complex (El Salvador) and Nejapa-Chiltepe volcanic complex (Nicaragua) have been characterized by a significant variability in eruption style and vent location. Densely inhabited cities are built on them and their surroundings, including the metropolitan areas of San Salvador (∼2.4 million people) and Managua (∼1.4 million people), respectively. In this study we present novel vent opening probability maps for these volcanic complexes, which are based on a multi-model approach that relies on kernel density estimators. In particular, we present thematic vent opening maps, i.e., we consider different hazardous phenomena separately, including lava emission, small-scale…
Forecasting Effusive Dynamics and Decompression Rates by Magmastatic Model at Open-vent Volcanoes
2017
AbstractEffusive eruptions at open-conduit volcanoes are interpreted as reactions to a disequilibrium induced by the increase in magma supply. By comparing four of the most recent effusive eruptions at Stromboli volcano (Italy), we show how the volumes of lava discharged during each eruption are linearly correlated to the topographic positions of the effusive vents. This correlation cannot be explained by an excess of pressure within a deep magma chamber and raises questions about the actual contributions of deep magma dynamics. We derive a general model based on the discharge of a shallow reservoir and the magmastatic crustal load above the vent, to explain the linear link. In addition, we…
Shallow vent architecture during hybrid explosive-effusive activity at Cordón Caulle (Chile, 2011-12): Evidence from direct observations and pyroclas…
2013
International audience; In June 2011, an eruption of rhyolite magma began at the Puyehue-Cordón Caulle volcanic complex, southern Chile. By January 2012, explosive activity had declined from sustained pyroclastic (Plinian to sub-Plinian) fountaining to mixed gas and ash jetting punctuated by Vulcanian blasts. This explosive activity was accompanied by synchronous effusion of obsidian lava in a hybrid explosive-effusive eruption. Fortuitous climatic conditions permitted ground-based observation and video recording of transient vent dynamics as well as real-time collection of proximal juvenile ash as it sedimented from the active plume. The main eruptive vent complex and site of lava effusion…
The Permeability Evolution of Tuffisites and Implications for Outgassing Through Dense Rhyolitic Magma
2019
There is growing evidence that outgassing through transient fracture networks exerts an important control on conduit processes and explosive‐effusive activity during silicic eruptions. Indeed, the first modern observations of rhyolitic eruptions have revealed that degassed lava effusion may depend upon outgassing during simultaneous pyroclastic venting. The outgassing is thought to occur as gas and pyroclastic debris are discharged through shallow fracture networks within otherwise low‐permeability, conduit‐plugging lava domes. However, this discharge is only transient, as these fractures become clogged and eventually blocked by the accumulation and sintering of hot, melt‐rich pyroclastic d…
Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)
2017
International audience; Basaltic magma chambers are often characterized by emptying and refilling cycles that influence their evolution in space and time, and the associated eruptive activity. During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system (>240×106 m3>240×106 m3) and resulted in collapse of the 1-km-wide summit crater. Following these major events, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composi…
Sedimentation close to the active Medlicott Wadia Thrust (Western Himalaya): how to estimate climatic base level changes and tectonics.
2017
16 pages; International audience; The Medlicott-Wadia Thrust (MWT) is one of the major active out-of-sequence thrusts in the Himalaya. Studies on Quaternary terraces in its vicinity have been performed using sedimentological, geomorphic and geochronological methods. We focus on the Riasi zone, south of the Pir Panjal range, in the Jammu and Kashmir region of India. The sedimentary units of Quaternary landforms have been mapped as a function of their location with respect to the thrust faults, their relative chronology, and their lithology. Three aggrading sedimentary units, five thin units above strath surfaces at the footwall of the fault system, and seven thin units above strath surfaces …
Calculating pressure with elastic geobarometry: A comparison of different elastic solutions with application to a calc-silicate gneiss from the Rhodo…
2020
Abstract Raman elastic geobarometry has increasingly been used complementary to metamorphic phase equilibria to estimate the conditions of recrystallization in metamorphic rocks. The procedure of applying Raman elastic barometry to host-inclusion mineral systems requires several steps that involve various assumptions. One of the most essential assumptions is that the mineral host-inclusion system behaves in an elastic and reversible manner. We discuss the discrepant results obtained by different authors employing different analytical solutions for elasticity and explore the assumptions lying behind each method. Furthermore, we evaluate numerically linear and non-linear elastic solutions and…