Report on Copahue (Chile-Argentina) — 23 September-29 September 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 23 September-29 September 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Copahue (Chile-Argentina). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 23 September-29 September 2020. 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 continuing activity at Copahue during 1-15 September. Webcams recorded gas-and-ash plumes rising as high as 1.1 km, sometimes associated with nighttime crater incandescence. The plumes drifted 6-15 km SW and SE. Sulfur dioxide emissions were high, averaging 1,499 tonnes per day (ranging from 1,148 to 1,850 tonnes per day), with a high value of 3,435 on 12 September. Two thermal anomalies were identified in satellite images. The Alert Level was remained at Yellow (the second lowest level on a four-color scale). ONEMI maintained the Yellow Alert (the middle level on a three-color scale) for residents of the Alto Biobío municipality and access to an area within 1 km of El Agrio Crater was restricted to the public.
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 since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.