Report on Cerro Hudson (Chile) — 30 November-6 December 2016
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 November-6 December 2016
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2016. Report on Cerro Hudson (Chile). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 30 November-6 December 2016. Smithsonian Institution and US Geological Survey.
45.9°S, 72.97°W; summit elev. 1905 m
All times are local (unless otherwise noted)
Based on OVDAS-SERNAGEOMIN notices from 1 and 30 November, ONEMI reported on 2 December that, although the rate of seismicity at Cerro Hudson had remained at normal levels and similar to previous periods, the magnitude of the highest energy events had steadily increased during the last months. Additionally the earthquakes were occurring in the same general area as those detected during the 2011 volcanic crisis. OVDAS-SERNAGEOMIN raised the Alert Level to Yellow (second highest level on a four-color scale), and ONEMI declared an Alert Level Yellow (the middle level on a three-color scale) for the communities of Aysén, Río Ibáñez, and Chile Chico.
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.