SERNAGEOMIN and SEGEMAR reported increased activity at Copahue during 9-10 August, characterized as increased gas emissions, ash emissions, and crater incandescence. During the morning of 9 August gas-and-steam emissions increased and sulfur dioxide flux was as high as 7,200 tons per day. Crater incandescence was visible in nighttime webcam views and was intense during the early hours of 10 August. An ash plume rose 300 m above the crater rim and drifted N and NNW. Seismicity remained stable; data suggested no rising magma. The Alert Level remained at Green (the lowest level on a four-color scale).

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: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Servicio Geológico Minero Argentino (SEGEMAR)