Report on Nevados de Chillan (Chile) — 29 January-4 February 2020
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 January-4 February 2020
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2020. Report on Nevados de Chillan (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 January-4 February 2020. Smithsonian Institution and US Geological Survey.
Nevados de Chillan
36.868°S, 71.378°W; summit elev. 3180 m
All times are local (unless otherwise noted)
SERNAGEOMIN reported that during 28 January-4 February white gas plumes from Nevados de Chillán’s Nicanor Crater rose as high as 900 m above the rim and drifted E, ESE, and SE. Minor explosions during 28-29 January ejected incandescent blocks that were visible at night. At 1356 on 30 January an explosion generated a gas-and-ash plume that rose 3.4 km above the crater rim; parts of the plume collapsed, generating pyroclastic flows that traveled NE and SE. Two thermal anomalies were identified in satellite images, one from vent CE4 (November 2019) and the second from a new vent named CE5, formed 60 m NW of the center of CE4. There had been no advancement of the lava flows (L1, L2, L3, and L4) since 24 November 2019. The number of long-period earthquakes and tremor associated with explosions both considerably decreased after December 2019. The volcano Alert Level remained at Orange, the second highest level on a four-color scale. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián, and stated that the public should stay at least 3 km away from the crater on the SW flank and 5 km away on the ENE flank.
Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.