Fallout deposits of the 22–23 April 2015 eruption of Calbuco volcano, Southern Andes
Segura, A., Castruccio, A., Clavero, J., Le Pennec, J. L., Roche, O., Samaniego, P., Droguett, B., Romero, J.
Abstract
Stratigraphy, petrography, grain size, geochemistry and volume of the fallout deposit of the 2015 eruption, dispersed to the NE. Four layers associated with two pulses are distinguished; the total volume is estimated at 0.38 km³ (0.15 km³ DRE).
Layers 0 and 1 correspond to the first pulse (22 April) and layers 2 and 3 to the second (23 April). The material is medium-K basaltic andesite (54.6–55.5 wt% SiO₂) with andesitic to dacitic glass. The maximum thickness measured was 54 cm, 5 km from the crater.
Using 96 control points, three volume calculation methods (Weibull, exponential and power law) are compared; the Weibull fit is considered the most representative. The second pulse marks a change in eruptive style, with more pyroclastic density currents and greater fragmentation.
