Report on Nevados de Chillan (Chile) — 3 August-9 August 2016
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 3 August-9 August 2016
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2016. Report on Nevados de Chillan (Chile) (Sennert, S, ed.). Weekly Volcanic Activity Report, 3 August-9 August 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 the seismic stations monitoring Nevados de Chillán recorded an increase in seismic signals indicating explosions and increased emissions from new craters on the E side of Volcán Nuevo and the Volcán Arrau dome complex. During 1-9 August there were 11 explosions detected; the highest energy signal was recorded at 1656 on 8 August and was accompanied by an emission that rose 2 km. That same day the Buenos Aires VAAC reported that a gas-and-ash puff rose to an altitude of 4.2 km (14,000 ft) a.s.l. The Alert Level remained at Yellow, the middle level on a three-color scale, and the public was reminded not to approach the craters within a 3-km radius which had been extended due to the recent activity increase.
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.