OVDAS-SERNAGEOMIN reported that during 4-11 June white plumes recorded by a web camera rose at most 200 m above Copahue and drifted N and E. During 4-5 June seismicity had decreased with respect to the previous 24-hour period; the majority of the signals were low-magnitude hybrid events, detected at an average rate of 42 per hour. During 5-6 June seismicity was similar to the previous period, with an average of 50 events per hour being detected. Seismicity increased during 6-7 June; an average of 84 events per hour was detected. During 7-8 June seismicity fluctuated with a high average of 124 events per hour then decreased to a low average of 8 events per hour; the overall average was 62 events per hour. Seismicity decreased during 8-9 June; only 5 events per hour were detected. On 9 June OVDAS-SERNAGEOMIN scientists aboard an overflight to locate sites for the installation of three additional seismic stations observed fumaroles inside Del Agrio Crater, and gas emissions that rose at most 200 m and drifted NE. They noted that no lava dome was present. During 9-10 June the number of earthquakes increased to an average of 20 events per hour. The Alert Level remained at Orange.

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)