Report on Villarrica (Chile) — 18 March-24 March 2015
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 March-24 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, 18 March-24 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)
OVDAS-SERNAGEOMIN reported that at night on 17 March explosions at Villarrica ejected tephra onto the flanks and produced nighttime incandescence. Pulsating ash plumes rose 300 m and drifted E. Seismicity increased and was characterized by low-magnitude tremor. The Alert Level was raised to Orange (the second highest level on a four-color scale) and the public was warned to stay outside of a 5-km radius around the crater and away from drainages. During 19-22 March pulsating plumes recorded by the webcam had a greater concentration of ash, and rose 100-500 m and drifted NE. Moderate levels of tremor were detected. Although cloud cover often prevented observations of the crater, incandescence was occasionally seen at night. During 22-24 March continued gas-and-ash emissions rose 400-500 m and drifted SW; the plumes were less dense, shorter, and contained less ash content. Incandescent material continued to be ejected from the crater, but with less frequency, and was deposited near the crater on the NE flank.
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.