Villarrica, Chile

Characterization of the Chaimilla tephra fall deposit - L. Costantini, C. Bonadonna, L. Pioli and J. Clavero

Villarrica is the most active volcano of the Southern Andes in historical times and it started its activity approximately 600 ka ago. Although its historical eruptive activity has been mainly effusive and slightly explosive, it also had a strong explosive behaviour, marked by two ignimbrite eruptions (Licán and Pucón ignimbrites) at ca. 13.5 and 3.7 ka.

Immediately after the caldera-forming Pucón ignimbrite eruption (3700 BP), a new cone started to build with a series of highly explosive eruptions, which generated the Chaimilla tephra fallout deposit. This is mainly distributed towards the eastern and northern flanks of the Villarica volcano and has a basaltic andesite chemical composition. It is constituted of two main beds separated by thin but well dispersed pyroclastic flow layers. The Chaimilla deposit present a complex internal stratigraphy, which varies from lithic- and dense juvenile-rich base to lithic-poor, highly vesiculated scoria fall layers.

Photos of a) Lower unit and b) Upper unit of Chaimilla deposit of Villarica volcano, Chile.

The aim of this project is to characterize the dispersal and physical parameters of this eruption as well as the chemical analysis and microtextures of the juvenile products in order to investigate the eruptive dynamic and possible trigger mechanism for this unusual, highly explosive eruptive style at Villarrica volcano.