Report on Nevados de Chillan (Chile) — 30 December-5 January 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 December-5 January 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Nevados de Chillan (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 30 December-5 January 2016. 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)
Servicio Nacional de Geología and Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS) reported that increasing seismicity at Nevados de Chillán and increased activity of the hydrothermal system prompted an Alert Level increase to Yellow, on a three-color scale. During 1-31 December the seismic network recorded 1,259 seismic events, including 186 volcano-tectonic events with a maximum local M (LM) of 1.8 located 17 km NNW at a depth of 4 km, 1,030 long-period earthquakes with a maximum LM 1.7, 40 short episodes of spasmodic tremor, and three tornillo-type events. The webcam recorded a small white plume rising from the crater on 9 December.
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.