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Unformatted text preview: U.S. Department of the Interior U.S. Geological Survey Fact Sheet 2008–3062 2008 U.S. GEOLOGICAL SURVEY—REDUCING THE RISK FROM VOLCANO HAZARDS Mount Rainier—Living Safely With a Volcano in Your Backyard M ajestic Mount Rainier soars almost 3 miles (14,410 feet) above sea level and looms over the expanding suburbs of Seattle and Tacoma, Washington. Each year almost two million visitors come to Mount Rainier National Park to admire the volcano and its glaciers, alpine meadows, and forested ridges. However, the volcano’s beauty is deceptive— U.S. Geological Survey (USGS) research shows that Mount Rainier is one of our Nation’s most dangerous volcanoes. It has been the source of countless eruptions and volcanic mudflows (lahars) that have surged down valleys on its flanks and buried broad areas now densely populated. To help people live more safely with the volcano, USGS scientists are working closely with local communities, emergency managers, and the National Park Service. The flat floor of the Puyallup River valley near Orting, Washington, is formed by deposits of the 500-year-old Electron lahar, which surged down from Mount Rainier (in background). Lahars, or volcanic mudflows, are rapidly flowing slurries of mud and boulders that destroy or bury most manmade structures in their paths. Lahars from Mount Rainier can travel for tens of miles along river valleys and reach Puget Sound. (USGS photograph by D.E. Wieprecht.) Mount Rainier, an active volcano currently at rest between eruptions, is the highest peak in the Cascade Range. Its edifice, capped by snow and 25 glaciers, has been built up by untold eruptions over the past 500,000 years. It last erupted in 1894–95, when small summit explosions were reported by observers in Seattle and Tacoma. Mount Rainier’s next eruption might be of similar or larger size and could produce volcanic ash, lava flows, and avalanches of intensely hot rock and volcanic gases, called “pyroclastic flows.” Some of these events swiftly melt snow and ice and could produce torrents of meltwater that pick up loose rock and become rapidly flowing slurries of mud and boulders known as “lahars.” In contrast to lava flows and pyroclastic flows that are unlikely to extend farther than 10 miles from the volcano’s summit and remain within Mount Rainier National Park, the largest lahars can travel for tens of miles and reach Puget Sound. Volcanic ash will be distributed downwind, most often toward the east, away from Puget Sound’s large population centers. Airborne plumes of volcanic ash can greatly endan- ger aircraft in flight and seriously disrupt aviation operations. Although seldom life threatening, volcanic ash fallout on the ground can be a nuisance to residents, affect utility and transportation systems, and entail substantial clean-up costs. Armero, Colom- bia, was battered in 1985 by lahars generated by an eruption of gla- cier-clad Nevado del Ruiz volcano....
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This note was uploaded on 07/31/2011 for the course GLY 2030 taught by Professor Kruse,s during the Fall '08 term at University of South Florida.
- Fall '08