Search results for "volcan"

Volcano seismicity and ground deformation unveil the gravity-driven magma discharge dynamics of a volcanic eruption.

2015

Effusive eruptions are explained as the mechanism by which volcanoes restore the equilibrium perturbed by magma rising in a chamber deep in the crust. Seismic, ground deformation and topographic measurements are compared with effusion rate during the 2007 Stromboli eruption, drawing an eruptive scenario that shifts our attention from the interior of the crust to the surface. The eruption is modelled as a gravity-driven drainage of magma stored in the volcanic edifice with a minor contribution of magma supplied at a steady rate from a deep reservoir. Here we show that the discharge rate can be predicted by the contraction of the volcano edifice and that the very-long-period seismicity migrat…

Mapping Susceptibility to Debris Flows Triggered by Tropical Storms: A Case Study of the San Vicente Volcano Area (El Salvador, CA)

2021

In this study, an inventory of storm-triggered debris flows performed in the area of the San Vicente volcano (El Salvador, CA) was used to calibrate predictive models and prepare a landslide susceptibility map. The storm event struck the area in November 2009 as the result of the simultaneous action of low-pressure system 96E and Hurricane Ida. Multivariate Adaptive Regression Splines (MARS) was employed to model the relationships between a set of environmental variables and the locations of the debris flows. Validation of the models was performed by splitting 100 random samples of event and non-event 10 m pixels into training and test subsets. The validation results revealed an excellent (…

Molecular and isotopic composition of free hydrocarbon gases from Sicily, Italy

2004

Chemical and isotopic data have been used as geochemical tracers for a genetic characterization of hydrocarbon gases from a total of eleven manifestations located in Eastern and Central-Southern Sicily (Italy). The molecular analysis shows that almost all the samples are enriched in methane (up to 93.2% Vol.), with the exception of four gas samples collected around Mt. Etna showing high mantle-derived CO2 content. Methane isotope signatures suggest that these are thermogenic gases or a mixture between thermogenic gases and microbial gases. Although samples from some mud volcanoes in Southern Sicily (Macalube di Aragona) show isotope signatures consistent with a mixing model between thermoge…

Composition and distribution of volcanic gases inside the Lakki Caldera (Nisyros, Greece): preliminary results

2013

Elemental and isotope covariation of noble gases in olivines and pyroxenes from Etnean volcanics erupted during 2001-2005, and genetic relation with …

2009

Revising midlatitude summer temperatures back to A.D. 600 based on a wood density network

2015

Annually resolved and millennium-long reconstructions of large-scale temperature variability are primarily composed of tree ring width (TRW) chronologies. Changes in ring width, however, have recently been shown to bias the ratio between low- and high-frequency signals. To overcome limitations in capturing the full spectrum of past temperature variability, we present a network of 15 maximum latewood density (MXD) chronologies distributed across the Northern Hemisphere extratropics. Independent subsets of continental-scale records consistently reveal high MXD before 1580 and after 1910, with below average values between these periods. Reconstructed extratropical summer temperatures reflect n…

External ballistic of volcanic explosions

1983

In order to determine the kinetic energy of an explosion it is necessary to know the initial velocities of ejected fragments. Calculations of initial velocities made earlier with few exceptions did not take into account the resistance of the air and therefore, greatly underestimated the initial velocities, and consequently the energy of the explosions. A solution of the inverse problem of ballistics which takes into account air resistance makes it possible to find precise values of initial velocities of ejection, determined from the distance of ejected fragments and their ballistic coefficients. The method makes it possible to determine the kinetic energy of explosions for eruptions which w…

Preliminary data on trace element emissions from Nyiragongo volcano (DR Congo)

2013

Intercomparison of gas emissions from the lava lakes of Nyiragongo and Nyamulagira, DR Congo

2015

From 25th of October to 5th of November 2014 field surveys were carried out at Nyiragongo and Nyamulagira volcanoes, DR Congo. These two volcanoes belong to the eight volcanoes in the Virunga volcanic chain. They have an altitude of about 3470 m.a.s.l. and 3060 m.a.s.l., respectively. The craters of the two volcanoes lie within a distance of less than 15 km and both have a diameter of about 1000 m and 2000 m, respectively showing a similar inner geometry containing several terraces inside. The lava lake of Nyamulagira is still under formation while Nyiragongo’s lava lake is known since more than 100 years with short interruptions after the eruptions in 1977 and 2002. However, also Nyamulagi…

Impacts of volcanic hazards on rural communities and adaptative strategies: A case study of the Virunga Volcanic Province (Democratic Republic of Con…

2023

co auteur étranger; International audience; Active volcanoes are a continuous threat for several regions worldwide and cause socio-economic and environmental issues, including the Virunga Volcanic Province (D.R. Congo). There, more than 2 million people are permanently exposed to the hazards of the most active volcanoes in Africa: Nyiragongo and Nyamulagira. However, there is a clear lack of information regarding the impacts of these hazards and how they may be affected by social vulnerability. In this study, a household survey based on semi-structural interviews was performed for rural communities in Virunga. This research aims to (i) investigate the impacts of volcanic hazards on rural co…