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Report on Makushin (United States) — April 1987


Scientific Event Alert Network Bulletin, vol. 12, no. 4 (April 1987)
Managing Editor: Lindsay McClelland.

Makushin (United States) Correction: 2 March ash plume was from Akutan

Please cite this report as:

Global Volcanism Program, 1987. Report on Makushin (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198704-311310


United States

53.891°N, 166.923°W; summit elev. 1800 m

All times are local (unless otherwise noted)

The 2 March eruption plume [previously reported] was actually a plume from Akutan. Activity on 2 March was limited to a steam plume containing ash that extended at least 30 km E from the summit. Pilot H. Wilson (Peninsula Airways) observed several steam plumes rising at least 250 m above the summit and drifting at least 3 km WNW. He noted particulate matter, possibly ash, over snow in the summit region.

Geological Summary. The ice-covered Makushin volcano on northern Unalaska Island is capped by a 2.5 km caldera. Its broad, dome-like structure contrasts with the steep-sided profiles of most other Aleutian stratovolcanoes. Much of the edifice was formed during the Pleistocene, but the caldera (which formed about 8,000 years ago), Sugarloaf cone on the ENE flank, and a cluster of about a dozen explosion pits and cinder cones at Point Kadin on the WNW flank, are of Holocene age. A broad band of NE-SW-trending vents cuts across the volcano. The composite Pakushin cone, with multiple summit craters, lies 8 km SW. Table Top (Pleistocene, 68 +/- 14 ka) and Wide Bay (Holocene) cinder cones are about 20 km ENE on the peninsula across the bay from the City of Unalaska. Frequent explosive eruptions have occurred during the past 4,000 years, sometimes accompanied by pyroclastic flows and surges. Geothermal areas are found in the summit caldera and on the SE and E flanks. Small-to-moderate explosive eruptions have been recorded since 1786.

Information Contacts: J. Reeder, ADGGS; T. Miller, USGS Anchorage; W. Gould, NOAA/NESDIS.