Mount Bachelor, Oregon
Elevation: 9,064 feet (2,763 m)
Mount Bachelor (43.8-44N, 121.6-121.7W) is a broad shield volcano capped
by a steep-sided summit cone. It is part of the 25-km-long Mount
Bachelor volcanic chain, which contains numerous scoria cones with
related lava flows and two other shield volcanoes. The chain covers
about 250 km2 and constitutes a total magma volume of 30-50 km3.
Photograph of Mount Bachelor by Kyle Jones, August 1986.
Most eruptions in the Mount Bachelor volcanic chain were effusive but
minor explosive activity built cones of agglutinated spatter, bombs, and
scoria. Eruptions began about 18,000-15,000 years ago and constructed a
shield volcano capped by Sheridan Mountain. Kwolh Butte, the shield that
underlies Mount Bachelor, and most of the summit cone of Mount Bachelor
were formed by about 12,000 years ago. The most recent eruption was
about 8,000 to 10,000 years ago on the lower north flank of Mount
Bachelor. It produced a scoria cone and lava flows. Ash from the
climatic eruption of Mount Mazama blankets all volcanic deposits of the
Mount Bachelor volcanic chain, indicating activity had ceased by 6,845
years ago.
Additional information about Mount Bachelor is presented on the
Cascade Volcano Observatory homepage of the U.S. Geological Survey.
Source of Information:
Wood, C.A., and Kienle, J., 1993, Volcanoes of North America: Cambridge University Press, New York, 354 p.
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