Report on Atka Volcanic Complex (United States) — 23 February-1 March 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
23 February-1 March 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Atka Volcanic Complex (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 23 February-1 March 2005. 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)
On 24 February AVO raised the Concern Color Code at Korovin volcano from Green to Yellow after receiving a report that ash and steam were emitted from Korovin on 23 February around 1900. According to residents of Atka village near the volcano, the initial ash burst rose to a height of ~ 2.4 km a.s.l. and drifted E. It was followed by several smaller ash-and-steam bursts. No ashfall was reported in Atka village, nor were there reports of accompanying volcanic odors, earthquakes, or larger volcanic explosions. Satellite images of the volcano did not clearly show the presence of ash or any thermal anomalies. On the morning of 24 February the volcano was steaming. AVO warned that low-level steam-and-ash emissions may continue and could pose a hazard to people and low- to medium-flying aircraft in the vicinity of the volcano. They further warned that if the eruption continues and begins to intensify, light ash fall could occur on parts of Atka Island, including the village of Atka.
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.