CONICET | Buscador de Institutos y Recursos Humanos

Copahue Volcano (37.9° S-71.2°W) is the most active volcano of Argentina. It is an active stratovolcano located in the Southern Volcanic Zone (SVZ), forming part of the Andean Ridge. 9 kilometers to the East of this volcano is situated Villa Caviahue. This small village of 800 inhabitants has the tourism as it´s main economic resource. It has andesitc to basaltic- andesitic composition and 9 aligned summit craters that during the last 250 years has experienced at least 13 phreatic and phreatomagmatic eruptions. All of these events had a Volcanic Explosivity Index ≤ 2 (Naranjo y Polanco, 2004). The Eastern crater is the active one and it contains a crater lake. According to Muñoz y Stern, (1988); Linares et al. (1999) this volcano began to build 1.2 m.a ago. Melnick et al. (2006) subdivided the evolution of Copahue volcano and it´s deposits in 3 stages according to their temporal relation with the last maximum glacial: pre, syn and postglacial. During field work in the Eastern flank of the Copahue volcano, pyroclastic rocks distributed in two different sectors and assignable to the preglacial stage were discovered. Genetically, one of these outcrops could be described as a high-grade welded andesitic ignimbrite with the presence of a welded vitrophyre basal level and an upper level with a high and uniform grade of welded both laterally and vertically. Meanwhile, the other outcrop could be genetically classified as a low-grade welded andesite ignimbrite. The presence of these outcrops, never before described for the Copahue volcano, could be showing the occurrence of more explosive eruptive phases (Subplinians to Plinian) than those currently known. However more studies are requiered, if this is confirmed, this contribution would be very important for the characterization of the hazards associated with the volcano and should be taken into consideration in the hazards map update.

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