Mount Saint Helens - geography.

Mount Saint Helens - geography. Mount Saint Helens, active volcano, southwestern Washington, in the Cascade Range. The volcano, which had been dormant since 1857, began to show signs of renewed activity in early 1980 when a column of magma (molten rock) began pushing up inside the mountain, causing the north face of the mountain to bulge out. On May 18, 1980, an earthquake caused a landslide on the mountain's north face, taking off the top of the mountain. The landslide triggered the main eruption by "uncorking" the column of magma that had been building up. The eruption spewed a cloud of ash and gases as high as 19 km (12 mi). The release of the pressurized gases produced a turbulent blast of wind that knocked down trees and stripped their branches. The skies darkened as wind carried the ash-filled air over much of eastern Washington and beyond. The blast killed 57 people and damaged life in an area of some 180 sq km (some 70 sq mi), and a vast area was covered with ash and debris. As a result of the eruption, the mountain's elevation was decreased from 2,950 m (9,677 ft) to 2,550 m (8,365 ft). Minor eruptions occurred in 1982, 1986, and 2004-2005. Mount Saint Helens is slowly rebuilding itself as magma and ash fill in the crater left behind by the 1980 explosion. A dome of lava is rising within the crater. Scientists are monitoring the mountain closely, but they are unsure whether to expect a larger eruption during the next few years. The Mount Saint Helens National Volcanic Monument was established in the area surrounding the volcano in 1983. It includes visitors' centers with interpretive exhibits, hiking trails, and campgrounds. The area has been left as it appeared after the 1980 eruption, enabling scientists to study the return of plant and animal life to the scoured land. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.