SERNAGEOMIN reported that on 15 October gray ash plumes rose 300 m above Copahue’s El Agrio Crater and four explosions were recorded. Plumes on 17 October were generally white and rose 100 m; no explosions were detected. Seismicity was low on 18 October. Plumes on 19 October rose 300 m. Six explosions associated with ash emissions were recorded. Incandescence from the crater was detected in the evening. On 20 October the network recorded 12 explosions with associated ash emissions. During 20-21 October plumes rose 200 m, and crater incandescence at night was noted. SERNAGEOMIN maintained the Alert Level at Orange, and ONEMI maintained Level Yellow for Alto Biobío (40 km W) in the Biobío region (since 3 June 2013).

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: Servicio Nacional de Geología y Minería (SERNAGEOMIN)