OVDAS-SERNAGEOMIN reported that seismicity at Copahue during 31 December, and 2 and 4-5 January indicated magma movement focused at 4 km below the crater and moving to shallower depths. On 5 January seismicity increased as well as gray emissions observed with a web camera. The Alert Level was raised to Orange. Incandescence on the crater was noted during 5-6 January, and plumes rose 200 m above the crater and drifted E during 5-7 January.

Based on analysis of satellite imagery, the Buenos Aires VAAC reported that on 2 January a diffuse gas-and-ash plume drifted 93 km NE and E. During 2-3 January web cameras near the volcano recorded steam-and-gas plumes drifting E and dissipating near the summit.

Geological Summary. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Sources: Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Nacional de Geología y Minería (SERNAGEOMIN)