Report on Nevados de Chillan (Chile) — 31 October-6 November 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 31 October-6 November 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on Nevados de Chillan (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 31 October-6 November 2018. 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) and ONEMI reported the continuing, slow growth of the lava dome in Nevados de Chillán’s Nicanor Crater during 30 October-6 November. Seismicity was characterized by moderate levels of long-period and tremor events, often associated with explosion signals. Gas emissions persisted, and sometimes contained ash. Periodic explosions sometimes ejected material that was deposited around the crater. At night incandescence emanated from the lava dome as well as from ejected ballistics. 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.
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.