Report on Atka Volcanic Complex (United States) — 8 March-14 March 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
8 March-14 March 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Atka Volcanic Complex (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 8 March-14 March 2006. Smithsonian Institution and US Geological Survey.
Atka Volcanic Complex
52.331°N, 174.139°W; summit elev. 1518 m
All times are local (unless otherwise noted)
AVO decreased the Concern Color Code at Korovin from Yellow to Green (the lowest level) on 8 March. After raising the Concern Color Code on 22 February in response to increased seismicity, the rate of micro-earthquakes stabilized and then declined. During 1-8 March, seismicity was near background levels and no unusual activity was seen on satellite imagery or by observers.
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.