Geologic Background:
The ice-covered, 2036-m Makushin volcano on
northern Unalaska Island is capped by a 2.5-km-wide
caldera. The broad, domical structure of Makushin
contrasts with the steep-sided profiles of most other
Aleutian stratovolcanoes. Much of the volcano was formed
during the Pleistocene, but the caldera, 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 satellitic vents cuts across the volcano
and a geothermal resource underlies the eastern flank.
Small-to-moderate explosive eruptions have been recorded
at Makushin since 1786.
Historic Activity:
- At least 16 eruptions since 1768.
Recent Activity:
- Last confirmed activity in 1980, but several reports
of increasing steam since then.
- Slight increase in small earthquakes during period
from July 2000 to June 2001
Data Sources:
- Smithsonian's SEAN Bulletin (V. 11, No. 4 to V. 12,
No. 4)
- Global Volcanism Network (V. 19, No. 1 to V. 26, No.
6).
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