USGS/Cascades Volcano Observatory, Vancouver, Washington
REPORT:
Volcano Hazards in the Three Sisters Region, Oregon
--
W.E. Scott, R.M. Iverson, S.P. Schilling, and B.J. Fischer,
2001,
Volcano Hazards in the Three Sisters Region, Oregon:
U.S. Geological Survey Open-File Report 99-437
Introduction
Introduction
Large snow-covered volcanoes of the Three
Sisters volcanic center dominate Central Oregon's
landscape between Santiam Pass in the north and
Willamette Pass in the south, an area of
widespread volcanic activity that for purposes of
this report we call the Three Sisters region.
Rapidly developing areas in Deschutes County
occupy the eastern border of the region, and
westward several small communities dot the
McKenzie River valley along its course to the
Eugene-Springfield metropolitan area. Three
Sisters volcanic center, one of three volcanic
centers in Central Oregon along with Newberry
volcano and Mount Jefferson, has erupted
repeatedly for hundreds of thousands of years,
most recently about 1,500 years ago. When a
volcano erupts again in the Three Sisters region,
areas close to the erupting vent will be severely
affected. Even areas tens of kilometers (or miles)
downstream along the valleys that head near the
vent may be at risk, as may be areas hundreds of
kilometers (miles) downwind. Moreover, areas
along valleys that head on slopes of large, steep
volcanoes can be affected by landslides, floods,
and debris flows that can occur without eruptive
activity. This report describes the kinds of
hazardous geologic events that have occurred in
the Three Sisters region in the past and shows, in
the accompanying volcano-hazard-zonation map,
which areas will likely be at risk during future
such events.
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03/03/06, Lyn Topinka