Report on El Chichon (Mexico) — August 1982
Scientific Event Alert Network Bulletin, vol. 7, no. 8 (August 1982)
Managing Editor: Lindsay McClelland..
El Chichon (Mexico) Bulk of stratospheric cloud remains at low N latitudes
Please cite this report as:
Global Volcanism Program, 1982. Report on El Chichon (Mexico). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 7:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198208-341120.
17.36°N, 93.228°W; summit elev. 1150 m
All times are local (unless otherwise noted)
Seismicity continued to decline in August and no eruptive activity has been reported. There was a large increase in the volume of radon emitted after the initial explosion 28 March, but it has been declining since then.
Geologic Background. El Chichón is a small, but powerful trachyandesitic tuff cone and lava dome complex that occupies an isolated part of the Chiapas region in SE México far from other Holocene volcanoes. Prior to 1982, this relatively unknown volcano was heavily forested and of no greater height than adjacent nonvolcanic peaks. The largest dome, the former summit of the volcano, was constructed within a 1.6 x 2 km summit crater created about 220,000 years ago. Two other large craters are located on the SW and SE flanks; a lava dome fills the SW crater, and an older dome is located on the NW flank. More than ten large explosive eruptions have occurred since the mid-Holocene. The powerful 1982 explosive eruptions of high-sulfur, anhydrite-bearing magma destroyed the summit lava dome and were accompanied by pyroclastic flows and surges that devastated an area extending about 8 km around the volcano. The eruptions created a new 1-km-wide, 300-m-deep crater that now contains an acidic crater lake.
Information Contacts: S. de la Cruz-Reyna, UNAM, México.