Report on Villarrica (Chile) — January 1985
Scientific Event Alert Network Bulletin, vol. 10, no. 1 (January 1985)
Managing Editor: Lindsay McClelland.
Villarrica (Chile) Lava flow to N foot; lahar; pyroclastic cone collapses
Please cite this report as:
Global Volcanism Program, 1985. Report on Villarrica (Chile). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 10:1. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198501-357120.
39.42°S, 71.93°W; summit elev. 2847 m
All times are local (unless otherwise noted)
Between 16 November and 1 December, activity remained constant. The lava column maintained its pressure and level in the central crater, and there were small explosions and gas emissions. Strombolian activity increased 1-6 December. Tephra was ejected to about 100 m height every 10 minutes. Lava from the lake in the central crater continued to pour out slowly through the initial NE flank channel.
On 6 December between 1200 and 1500 there was a violent increase in the rate of lava production. Lava flowed out through a new channel NE toward the Río Correntoso (which turns NW and flows about 20 km into Lake Villarrica), reaching the base of the volcano. The activity generated a small lahar that flattened a small wooden bridge and affected houses beside the river. The volume of water returned to its normal level after 24 hours. An overflight of the crater revealed that the level of the lava lake was higher than before and the pyroclastic cone had grown higher than the central crater rim. Intense Strombolian activity continued 7-10 December. Pyroclastic material was ejected to 50-100 m height. Very liquid lava continued to pour out of the crater to the NE. Activity decreased gradually 11-19 December. Small explosions occurred 20 December but the pyroclastic cone and lava lake collapsed and effusive activity ended.
Explosive activity resumed 12 January between 1015 and 2300. A column of pyroclastics reached about 400 m height. A sequence of explosions ejected incandescent material to 100 m. On 18 January, the pyroclastic cone and lava lake in the central crater had completely collapsed.
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.
Information Contacts: O. González-Ferrán, Univ. de Chile, Santiago.