Report on Villarrica (Chile) — 11 February-17 February 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 February-17 February 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, 11 February-17 February 2015. Smithsonian Institution and US Geological Survey.
39.42°S, 71.93°W; summit elev. 2847 m
All times are local (unless otherwise noted)
OVDAS-SERNAGEOMIN reported that activity significantly increased at Villarrica during 1-16 February, characterized by increased seismicity, crater incandescence, and explosions. On 6 February seismicity increased significantly, explosions occurred in the crater, and ash emissions rose above the crater rim. The Alert Level was raised to Yellow (the second lowest level on a four-color scale). DOAS (Differential Optical Absorption Spectrometry) data showed an average monthly sulfur dioxide emission value of 222 tons per day; a high value during this period of 450 tons per day was recorded on 11 February. The highest number of explosions, five per minute, during the period occurred on 16 February. Explosions ejected incandescent material out of the crater as far as 1 km onto the S flank. During an overflight on 16 February, supported by ONEMI, volcanologists observed the lava lake and recorded temperatures near 800 degrees Celsius, tephra in and around the active crater, and a diffuse layer of ash on the flanks.
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.