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 Mount Rainier

Mount Rainier, Washington. Mount Rainier has not produced a significant eruption in the past 500 years, but scientists consider it to be one of the most hazardous volcanoes in the Cascades. Mount Rainier has 26 glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined. If only a small part of this ice were melted by volcanic activity, it would yield enough water to trigger enormous lahars.

Mount Rainier's potential for generating destructive mudflows is enhanced by its great height above surrounding valleys and its "soft" interior. The volcano stands about 3,000 meters above river valleys leading from its base. Volcanic heat and ground water have turned some of the volcano's originally hard lava into soft clay minerals, thereby weakening its internal structure. These conditions make Mount Rainier extremely susceptible to large landslides. Several have occurred in the past few thousand years, one as recently as about 600 years ago. These landslides, apparently containing great volumes of water, quickly turned into lahars as they rushed down river valleys.

Mount Rainier towers 3,000 meters above the surrounding valleys, all of which have been swept by lahars during the past 10,000 years. Future eruptions will probably trigger similar lahars. (Photograph by David Wieprecht.)

Maintained by John Watson
Updated 06.24.97

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