Report on Copahue (Chile-Argentina) — 25 November-1 December 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 November-1 December 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Copahue (Chile-Argentina). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 November-1 December 2015. Smithsonian Institution and US Geological Survey.
37.856°S, 71.183°W; summit elev. 2953 m
All times are local (unless otherwise noted)
SERNAGEOMIN reported that during 16-30 November continuous ash emissions from explosions at Copahue's El Agrio crater were recorded by the webcam; plumes rose as high as 1.3 km above the crater on 29 November. Satellite images detected ash plumes drifting as far as 560 km SE and ESE. During an overflight on 28 November scientists observed the absence of the acidic lake and a growing pyroclastic cone. Impact craters from ballistics ejected during minor explosions were within a radius of 300 m of El Agrio. Satellite images detected a thermal anomaly during 28-29 November. The Alert Level remained at Yellow; SERNAGEOMIN recommended no entry into a restricted area within 1.5 km of the crater. ONEMI maintained Level Yellow for the community of Alto Biobío (40 km W) in the Biobío region (since 3 June 2013).
Geologic Background. 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 at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.