Report on Villarrica (Chile) — 4 March-10 March 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 March-10 March 2015
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2015. Report on Villarrica (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 March-10 March 2015. Smithsonian Institution and US Geological Survey.
39.42°S, 71.93°W; summit elev. 2847 m
All times are local (unless otherwise noted)
Based on OVDAS-SERNAGEOMIN data, representatives from ONEMI, SERNAGEOMIN, Sistema Nacional de Protección Civil, and others reduced the exclusion zone around Villarrica to 5 km on 5 March. OVDAS-SERNAGEOMIN reported that the Alert Level for Villarrica was lowered to Orange (the second highest level on a four-color scale) on 6 March, citing that seismicity had declined to below baseline levels and visual observations indicated no active lava lake. During an overflight on 9 March scientists observed subsidence of material in the crater which partially obscured the conduit. Weak degassing was also noted. On 10 March the Alert Level was lowered to Yellow; OVDAS-SERNAGEOMIN warned of avalanches of unconsolidated material and maintained an exclusion zone of 3 km.
Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.