Report on Atka Volcanic Complex (United States) — May 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 5 (May 1986)
Managing Editor: Lindsay McClelland.
Atka Volcanic Complex (United States) Steam emission follows magnitude 7.7 earthquake
Please cite this report as:
Global Volcanism Program, 1986. Report on Atka Volcanic Complex (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:5. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198605-311160
Atka Volcanic Complex
52.331°N, 174.139°W; summit elev. 1518 m
All times are local (unless otherwise noted)
[On 6 May], James Dickson noted a 500-m vertical steam plume over the SE part of the summit [of Korovin]. On 23 May at about 1730, Aleutian Air pilot Thomas Madsen noted a 600-m steam plume containing traces of ash rising above the rim of a 240-m-deep crater in the SE part of the summit area. A shallow magnitude 7.7 earthquake centered roughly 100 km [SSW] of Korovin at [51.52°N, 174.78°W] occurred 7 May [at 2247 GMT].
John Reeder and Kirk Swanson climbed [Korovin] in July 1983, observing only minor steaming from deep within the crater, rising to only 60 m above its floor.
Geological Summary. The Atka Volcanic Complex consists of a central shield and Pleistocene caldera with several post-caldera volcanoes. A major dacitic explosive eruption accompanied formation of the caldera about 500,000 to 300,000 years ago. The most prominent of the post-caldera stratovolcanoes are Kliuchef and Sarichef, both of which may have been active in historical time. Sarichef has a symmetrical profile, but the less eroded Kliuchef is the source of most if not all historical eruptions. Kliuchef may have been active on occasion simultaneously with Korovin volcano to the north. Hot springs and fumaroles are located on the flanks of Mount Kliuchef and in a glacial valley SW of Kliuchef. Korovin, at the NE tip of Atka Island, is the most frequently active volcano of the complex, and contains a double summit with two craters. The NW summit has a small crater, but the 1-km-wide crater of the SE cone has an open cylindrical vent of widely variable depth that sometimes contains a crater lake or a high magma column. A fresh-looking cinder cone lies on the flank of the partially dissected Konia volcano, located on the SE flank of the dominantly basaltic Korovin. Some late-stage dacitic lava flows are present on both Korovin and Konia.
Information Contacts: J. Reeder, ADGGS; T. Miller and M.E. Yount, USGS Branch of Alaskan Geology, Anchorage.