The Buenos Aires VAAC reported that on 26 November diffuse steam-and-gas emissions from Copahue, recorded by the ODVAS webcam and satellite images, possibly contained a small amount of ash. The plume rose to altitudes of 3.4-3.7 km (11,000-12,000 ft) a.s.l. and drifted 65 km E. On 30 November a pilot observation and webcam views revealed a diffuse and continuous plume near the summit. During 1-2 December a diffuse plume was detected in satellite images while the webcam recorded continuous ash emissions.

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.

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)