Tefras emitidas durante la fase inicial hidromagmática (julio de 2012) del ciclo eruptivo 2012-actual (2016) del volcán Copahue (Andes del Sur)

Abstract

Copahue volcano has a record of historical eruptions of low intensity which have mainly been characterized from the events ob-served in last decades. Significant changes in several parameters associated with the volcano activity were observed since the end of 2011. After 12 years of quiescence, on July 2012, the volcano started a new eruptive period. In this work, the characterization of the pyroclastic products emitted on 19th July 2012 is presented. Although the limited dispersion of the event, its study is central in the definition of the character of the initial phase of the eruptive cycle. A high proportion of lithics and the presence of juvenile first-cycled vitroclasts studied in detail allow us to characterize the eruptive mechanism, consistent with a phreatomagmatic erup-tion. A distinctive feature of the tephra is the presence of pyroclastic sulfur. Although these kinds of particles have been identified in previous eruptions, its presence is crucial revealing the existence of molten sulfur under the crater lake. The participation of this precipitated material allow us to infer its influence in the eruptive mechanism.