| Mount St. Helens volcano in southwest Washington transformed one of the most scenic alpine landscapes of the Cascade Range into a gray, barren wasteland in only a few minutes. A catastrophic landslide and explosive eruption on May 18, 1980, devastated 550 square kilometers of forest, sent damaging mudflows down rivers draining the volcano, and produced ash fallout hundreds of kilometers to the east. Four years after the volcano's reawakening, Mount St. Helens remains active, and the devastated landscape wrought by the May 18 eruption continues to pose flood hazards to communities downstream from the volcano. ... U.S. Geological Survey scientists at the David A. Johnston Cascades Volcano Observatory (CVO) in Vancouver, Washington, are studying the intermittent eruptive activity of Mount St. Helens and hazards posed by the effects of the May 18 eruption. Many different monitoring techniques and instruments are used to record the "daily pulse" of the volcano to evaluate the change of future eruptive activity and to investigate fundamental volcanic processes. Studies also are made of the river basins and the new lakes around the volcano and of the massive debris avalanche that slid off the mountain on May 18, 1980. These studies provide data to asses water-related hazards to downstream communities from increased sedimentation, erosion, and flooding along the Toutle and Cowlitz Rivers. Such hydrologic hazards likely will persist long after the decline of eruptive activity at Mount St. Helens. -- Brantley and Topinka, 1984 |
