Presentamos una evaluación probabilística de los peligros volcánicos asociados a corrientes de densidad piroclástica (CDP) en el Complejo Volcánico San Salvador (CVSS). Este campo volcánico se compone por el estratovolcán El Boquerón (VB) y al menos 25 volcanes monogenéticos ubicados en los alrededoresde San Salvador, capital de El Salvador. En particular, definimos un conjunto de escenarios eruptivos, incluyendo desde eventos de pequeña escala con una incerteza significativa en la posición del centro de emisión hasta eventos de alta intensidad alimentados desde el cono central (i.e. VB). En el primer caso, adoptamos mapas ya publicados de probabilidad de apertura de nuevos centros eruptivos para la construcción de los mapas de peligro. La metodología adoptada se basa fundamentalmente en la modelación numérica. Específicamente, los modelos utilizados son las versiones co...

This study combines new noble gas data from fluid inclusions in minerals from Sabancaya, Ubinas, and El Misti (CVZ, Peru) and Villarica (South Chile, SVZ) with a revised noble gas compilation in the Andes, to identify systematic along arc variations in helium isotope compositions. We find 3He/4He ratios varying from 8.8 RA (Colombia) to 7.4 RA (Ecuador) within the NVZ, and only as high as 6.4 RA in the CVZ (RA is the atmospheric 3He/4He ratio of 1.39 × 10–6). These distinct isotope compositions cannot be explained by variable radiogenic 4He production via slab fluid transport of U and Th in the mantle wedge, since both NVZ and CVZ share similar slab sediment inputs (Th/La ≈ 0.08–0.13). Instead, the progressively more radiogenic 3He/4He signatures in Ecuador and Peru reflect 4He addition upon magma ascent/storage in the crust, this being especially thick in Peru (>70 km) and Ec...

The proximity of the major city of Arequipa to El Misti has focused attention on the hazards posed by the active volcano. Since its last major eruption in the fifteenth century, El Misti has experienced a series of modest phreatic eruptions and fluctuating fumarolic activity. Here, we present the first measurements of the compositions of gas emitted from the lava dome in the summit crater. The gas composition is found to be fairly dry with a H2O/SO2 molar ratio of 32 ± 3, a CO2/SO2 molar ratio of 2.7 ± 0.2, a H2S/SO2 molar ratio of 0.23 ± 0.02 and a H2/SO2 molar ratio of 0.012 ± 0.002. This magmatic gas signature with minimal evidence of hydrothermal or wall rock interaction points to a shallow magma source that is efficiently outgassing through a permeable conduit and lava dome. Field and satellite observations show no evolution of the lava dome over the last decade, indicating sust...