Report on Villarrica (Chile) — 28 September-4 October 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 28 September-4 October 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Villarrica (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 28 September-4 October 2011. Smithsonian Institution and US Geological Survey.
39.42°S, 71.93°W; summit elev. 2847 m
All times are local (unless otherwise noted)
According to Projecto Observación Visual Volcán Villarrica (POVI), an image from 17 September showed the inner SSW wall of the crater covered with snow and ice, and a thin layer of ash. A rapid rise in the level of the lava lake (in a pit about 40 m wide) on 19 September caused much of the snow and ice to melt, especially on the southern inner wall. Strombolian explosions from the crater were observed on 26 September, and tephra deposits on the E edge of the crater were noted. On 27 September incandescence from the lava lake were reflected in the cloud cover above.
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.