Mount Rainier Active Volcano
US Geological Survey
Mount Rainier Volcano - "The Mountain": (54 Miles From Olympia)
Mount Rainier, the highest (4,392 meters - 14,410 feet) and third-most voluminous volcano in the Cascades
after Mounts Shasta and Adams, dominates the Seattle-Tacoma area, where more than 1.5 million know it fondly as
The Mountain. The Mountain is, however, the most dangerous volcano in the range, owing to the large population
and to the huge area and volume of ice and snow on its flanks that could theoretically melt to generate debris flows
during cataclysmic eruptions. -- Swanson, et.al., 1989
Mount Rainier Dominates the Landscape: Mount Rainier volcano dominates the landscape of a large part of western
Washington. It stands nearly 3 miles higher than the lowlands to the west and 1.5 miles higher than the surrounding
mountains. The base of the volcano spreads over an area of about 100 square miles, and lava flows that radiate from
the base of the cone extend to distances of as much as 9 miles. The flanks of Mount Rainier are drained by five major
rivers and their tributaries. Clockwise from the northwest the major rivers are the Carbon, White, Cowlitz, Nisqually,
and Puyallup. Each river flows westerly through the Cascade Range and, with the exception of the Cowlitz, empties into
Puget Sound near Tacoma, Washington. The Cowlitz joins the Columbia River in the southwestern part of the State to flow
to the Pacific Ocean. -- Crandell, 1971
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Estimated Mud Flows
US Geological Survey
Eruptive Background: Mount Rainier is an active volcano that first erupted about half a million years ago. Because of
Rainier's great height and northerly location, glaciers have cut deeply into its lavas, making it appear deceptively
older than it actually is. Mount Rainier is known to have erupted as recently as in the 1840s, and large eruptions took
place as recently as about 1,000 and 2,300 years ago. Mount Rainier and other similar volcanoes in the Cascade Range,
such as Mount Adams and Mount Baker, erupt much less frequently than the more familiar Hawaiian volcanoes, but their
eruptions are vastly more destructive. Hot lava and rock debris from Rainier's eruptions have melted snow and glacier
ice and triggered debris flows (mudflows) - with a consistency of churning wet concrete - that have swept down all of
the river valleys that head on the volcano. Debris flows have also formed by collapse of unstable parts of the volcano
without accompanying eruptions. Some debris flows have traveled as far as the present margin of Puget Sound, and much
of the lowland to the east of Tacoma and the south of Seattle is formed of pre-historic debris from Mount Rainier --
Sisson, 1995-By National Park Service
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