Search results for "eta"
showing 10 items of 45767 documents
Planktic foraminiferal changes in the western Mediterranean Anthropocene
2021
The increase in anthropogenic induced warming over the last two centuries is impacting marine environment. Planktic foraminifera are a globally distributed calcifying marine zooplankton responding sensitively to changes in sea surface temperatures and interacting with the food web structure. Here, we study two high resolution multicore records from two western Mediterranean Sea regions (Alboran and Balearic basins), areas highly affected by both natural climate change and anthropogenic warming. Cores cover the time interval from the Medieval Climate Anomaly to present. Reconstructed sea surface temperatures are in good agreement with other results, tracing temperature changes through the Co…
Changes in SO2 Flux Regime at Mt. Etna Captured by Automatically Processed Ultraviolet Camera Data
2019
We used a one-year long SO2 flux record, which was obtained using a novel algorithm for real-time automatic processing of ultraviolet (UV) camera data, to characterize changes in degassing dynamics at the Mt. Etna volcano in 2016. These SO2 flux records, when combined with independent thermal and seismic evidence, allowed for capturing switches in activity from paroxysmal explosive eruptions to quiescent degassing. We found SO2 fluxes 1.5−2 times higher than the 2016 average (1588 tons/day) during the Etna’s May 16−25 eruptive paroxysmal activity, and mild but detectable SO2 flux increases more than one month before its onset. The SO2 flux typically peaked during a lava fo…
Pre- and syn-eruptive geochemistry of volcanic gases from Soufriere Hills of Montserrat, West Indies
1998
International audience; Soufriere Hills fumaroles contained magmaderived volatiles before and during the eruption initiated in 1995 but also preserved a typical and quite steady hydrothermal coinposition. Chemical changes due to increased boiling and a greater input of oxidizing magmatic gas occurred only at Galway's Soufriere, the most active fumarolic field. Hydrothermal buffering of the fumaroles has been favoured by their remote location (!-2 km) froin the eruptive vents and by a preferential degassing of the uprising magma through intrusive conduits under the crater. High temperature (720øC) gas collected froin the extruding lava dome in Feb. 1996 was chemically and isotopically repres…
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…
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…
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…
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…
Origin and Ion Charge State Evolution of Solar Wind Transients during 4 – 7 August 2011
2016
We present study of the complex event consisting of several solar wind transients detected by Advanced Composition Explorer (ACE) on 4 -- 7 August 2011, that caused a geomagnetic storm with Dst$=-$110 nT. The supposed coronal sources -- three flares and coronal mass ejections (CMEs) occurred on 2 -- 4 August 2011 in the active region (AR) 11261. To investigate the solar origin and formation of these transients we studied kinematic and thermodynamic properties of the expanding coronal structures using the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) EUV images and the differential emission measure (DEM) diagnostics. The Helioseismic and Magnetic Imager (HMI) magnetic fie…