2012 Copahue volcano eruption: characterization of ejected material

CASELLI A; ALBITE J; DAGA R; AGUSTO M

BOLLETTINO DI GEOFISICA TEORICA ED APPLICATA

ISTITUTO NAZIONALE DI OCEANOGRAFIA E DI GEOFISICA

Lugar: Trieste; Año: 2013 vol. 54 p. 140 - 144

0006-6729

The Caviahue-Copahue Volcanic Complex (CCVC; Argentina-Chile), is located on the west border of Argentina, in the Neuquén province, on the Andes Range nearby the boundary with Chile, and belongs to the Southern Andean Volcanic Zone (SVZ: 33.3º- 46ºS). It is composed by the Copahue polygenic fissural stratovolcano (37º45?S-71º10.2?W, 2977 m a.s.l.) and the Caviahue squared caldera. The volcano-tectonic activity in this area started in the Pliocene and it was mainly characterized by intense eruptions producing andesitic to basaltic-andesitic pyroclastic and lava lows. The crater currently hosts a hot and acidic crater lake. The last eruptive cycle took place from the easternmost crater in 2000 and 2012. On July 19, 2012 a phreatic explosion occurred with emission of pyroclastic material, producing a small plume that extended 18 km on ESE direction. A sample of this event, recovered from the crater, was constituted mainly by sulphur pyroclasts, with low proportion of pumice and scoriae fragments, irregular argillaceous white material and accidental/accessory fragments. Sulphur pyroclastic material have variable sizes, mostly globular morphology with vesicles, like perfect spheres or elongated forms in some cases, and like deformed ?drops? in others. On December 22, 2012 a new magmatic pulse initiated with a rapid vaporization of the crater lake and a phreatic eruption. Minutes later it became in phreatomagmatic with convective cloud generation and ballistic emission of blocks and bombs, and pyroclastic fall of ash, mainly dark brown pumice fragments, from the plume. Several hours later the eruptive phase turned to vulcanian-strombolian style, with emission of elongated volcanic bombs. This eruption produced a plume that extended 200 km SSW direction.