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Report on Nevados de Chillan (Chile) — 31 July-6 August 2019


Nevados de Chillan

Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
31 July-6 August 2019
Managing Editor: Sally Kuhn Sennert

Please cite this report as:

Global Volcanism Program, 2019. Report on Nevados de Chillan (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 31 July-6 August 2019. Smithsonian Institution and US Geological Survey.

Weekly Report (31 July-6 August 2019)

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


On 6 August ONEMI and SERNAGEOMIN reported that activity at Nevados de Chillán’s Nicanor Crater increased in the previous few days, characterized by an increase in the size and occurrence of explosions. Specifically, there were 129 explosive events recorded since 3 August. Dense gas-and-ash plumes rose as high as 1.6 km above the crater rim and ejected material onto the flanks. Crater incandescence was visible at night. A lahar traveled 1.5 km NNE. The Alert Level remained at Orange, the second highest level on a four-color scale, and residents were reminded not to approach the crater within 3 km. ONEMI maintained an Alert Level Yellow (the middle level on a three-color scale) for the communities of Pinto, Coihueco, and San Fabián.

Geological Summary. 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 dominantly andesitic Cerro Blanco (Volcán Nevado) stratovolcano is located at the NW end of the massif. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The Volcán Nuevo lava-dome complex formed during 1906-1945 on the NW flank of Viejo. The Volcán Arrau dome complex was then constructed on the SE side of Volcán Nuevo between 1973 and 1986, and eventually exceeded its height. Smaller domes or cones are present in the 5-km valley between the two major edifices.

Sources: Oficina Nacional de Emergencia-Ministerio del Interior (ONEMI), Servicio Nacional de Geología y Minería (SERNAGEOMIN)