First evidence of hydromagmatism at Colima volcano (Mexico)

Here we report for the first time evidences of hydromagmatism at Colima volcano (western sector of Trans-Mexican Volcanic Belt). The studied location exposes 9 m of fine ash deposits dated at around 15 cal kyr BP by C-14 measurement on organic matter collected at the very base of the stratigraphic succession. The ash deposits rest directly on the top of a debris avalanche deposit. The morphology and grain size distribution of ash samples from the basal part of the stratigraphic succession testify for an explosive magma-water interaction, which produced finely bedded layers with blocky fragments characterized by adhering particles, quenching cracks and chemical pitting. The availability of ground water was hypothesized to be in close relationship with the amelioration of climate conditions at the end of the Last Glacial period, with rising temperatures that induced melting of glaciers and snow previously accumulated on the volcano summit slopes. This recognition demonstrates how, even a "dry" volcano like Colima, can experience hydromagmatism under adequate climatic conditions. (C) 2012 Published by Elsevier B.V.