The magnitude and impact of the 431 CE Tierra Blanca Joven eruption of Ilopango, El Salvador.

The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is >7,000 km from Ilopango; and calculated that between 37 and 82 km of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods.

Alluvial and gypsum karst geological transition favors spreading arsenic contamination in Matehuala, Mexico.

Arsenic transport in alluvial aquifers is usually constrained due to arsenic adsorption on iron oxides. In karstic aquifers, however, arsenic contamination may spread to further extensions mainly due to favorable hydrogeochemical conditions. In this study, we i) determined the spatial and temporal behavior of arsenic in water in an alluvial-karstic geological setting using field and literature data, ii) established whether a contaminated aquifer exists using field and literature piezometric data and geophysical analysis, iii) studied the local geology and associated arsenic contaminated water sources to specific aquifers, iv) revealed and modeled subsoil stratigraphy, and v) established the extent of arsenic exposure to the population.