Report on Cerro Hudson (Chile) — 2 November-8 November 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 2 November-8 November 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Cerro Hudson (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 2 November-8 November 2011. Smithsonian Institution and US Geological Survey.
45.9°S, 72.97°W; summit elev. 1905 m
All times are local (unless otherwise noted)
On 2 November, OVDAS-SERNAGEOMIN reported that the Alert Level for Cerro Hudson was lowered to Yellow, Level 4, noting that the eruption that began on 26 October had ceased. ONEMI reported that the 140 evacuees were permitted to return home. Analysis of ash deposited on the edge of the crater during the eruption indicated the presence of juvenile basalt. During 1-6 November between 16 and 110 earthquakes per day were recorded and satellite images showed drifting plumes daily.
Geologic Background. The ice-filled, 10-km-wide caldera of the remote Cerro Hudson volcano was not recognized until its first 20th-century eruption in 1971. It is the southernmost volcano in the Chilean Andes related to subduction of the Nazca plate beneath the South American plate. The massive volcano covers an area of 300 km2. The compound caldera is drained through a breach on its NW rim, which has been the source of mudflows down the Río de Los Huemeles. Two cinder cones occur N of the volcano and others occupy the SW and SE flanks. This volcano has been the source of several major Holocene explosive eruptions. An eruption about 6700 years ago was one of the largest known in the southern Andes during the Holocene; another eruption about 3600 years ago also produced more than 10 km3 of tephra. An eruption in 1991 was Chile's second largest of the 20th century and formed a new 800-m-wide crater in the SW portion of the caldera.