Torres-Orozco, Rafael ; De Plaen, Raphael ; Capra, Lucia ; Marquez, Victor H. ; Sulpizio, Roberto ; Arambula, Raúl

Poster presented at AGU Fall Meeting, San Francisco on 2023-12-11

Abstract: Volcán de Colima, the most active andesitic stratovolcano in Mexico, last erupted explosively on July 10-11, 2015, producing pyroclastic density currents (PDCs) of different type. The July-10 PDCs formed dense block-and-ash flow deposits typical of Volcán de Colima's history of recurrent summit dome effusion and collapse. In contrast, the July-11 PDCs comprised hot and turbulent scoria-rich PDCs that were unforeseen, and whose triggers and precursors were unidentified. Here, chemical and microtextural analyses of the July-11 deposits via electron-microscopy and x-rays microtomography revealed that decompression of andesite magma at fluctuating rates (10-3-100 MPa s-1) from 2 km-depth triggered magma degassing and crystallization. The resulting extremely rheologically heterogeneous magma fragmented and powered the pulsating July-11 PDCs that released 100-300 m3 s-1 on surface. Seismic noise velocity variations identified in each day down to 2 km-depth support magma decompression from a shallow reservoir. The combined geological and seismological evidence suggest timescales of only hours to couple of days from conduit and dome cracking and collapse to magma decompression and eruption.

Keyword(s): Volcanology ; Eruption
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