Search results for "PLAN"
showing 10 items of 24706 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…
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…
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…
Dynamic Triggering of Mud Volcano Eruptions During the 2016-2017 Central Italy Seismic Sequence
2017
On 24 August 2016 a seismic event (Mw 6.0) was the first of the long Central Italy sequence (ongoing at the end of 2017) of medium-to-high magnitude earthquakes, with nine Mw ≥5 up to October 2017, and with about 74.000 seismic events registered after one year. The largest was the Mw 6.5 30 October 2016 event near Norcia. After the major seismic events, seventeen mud volcanoes erupted around Monteleone di Fermo village (Marche region). Mud volcano eruptions generally occurred a few hours to a few days after the main earthquakes, suggesting a seismic triggering. We analyzed the peak ground velocities (PGV) and dynamic stresses during the three largest earthquakes. We also evaluated the stati…
Is there a global carbonate layer in the oceanic mantle?
2021
co-auteur étranger; International audience; Previous modeling of carbonate subduction by high‐pressure experimentation has allowed to propose scenarios for bulk carbon return to the mantle, but the detailed transfer mechanisms have seldom been studied. We monitored carbonate – silicate reactions by combining high‐pressure experiments and synchrotron‐based x‐ray diffraction. Carbonates break down at moderate pressure and high temperature and CO2 is trapped at grain boundaries. Further isothermal compression yields melting, which may control continuous carbon introduction, first in the mantle wedge, and next, away from the wedge. Carbon presence has been discussed in a variety of magmatic con…
Vicarious Calibration of the Landsat 7 Thermal Infrared Band and LST Algorithm Validation of the ETM+ Instrument Using Three Global Atmospheric Profi…
2017
Due to problems in the thermal infrared sensor on-board the Landsat-8 satellite, Landsat-7 (L7) can be an interesting alternative source of thermal data because it is the only source of well-calibrated, free, high-resolution data. To contribute to the quality of thermal data, a vicarious calibration (VC) of the enhanced thematic mapper instrument and a validation of the single-channel general equation and the water vapor approach algorithm in conjunction with an inversion of the radiative transfer equation (RTE) have been performed during 2013–2015 over two Spanish test sites. For this purpose, three global atmospheric profile data sets were used to better characterize the error due to atmo…
Empirical and physical estimation of Canopy Water Content from CHRIS/PROBA data
2013
20 páginas, 4 tablas, 7 figuras.
Top-of-Atmosphere Retrieval of Multiple Crop Traits Using Variational Heteroscedastic Gaussian Processes within a Hybrid Workflow.
2021
In support of cropland monitoring, operational Copernicus Sentinel-2 (S2) data became available globally and can be explored for the retrieval of important crop traits. Based on a hybrid workflow, retrieval models for six essential biochemical and biophysical crop traits were developed for both S2 bottom-of-atmosphere (BOA) L2A and S2 top-of-atmosphere (TOA) L1C data. A variational heteroscedastic Gaussian process regression (VHGPR) algorithm was trained with simulations generated by the combined leaf-canopy reflectance model PROSAILat the BOA scale and further combined with the Second Simulation of a Satellite Signal in the Solar Spectrum (6SV) atmosphere model at the TOA scale. Establishe…