Mount St Helens
Mount St. Helens is an active volcano in America. The part of America it is in is the Skamania County, Washington, in Northwest United States. It is 96 miles south of Seattle, Washington, and 50 miles northeast of Portland, Oregon. Mount St Helens is a stratovolcano. It last eruption in July 10, 2008. It is 2,550 m high. It was first ascended in 1853. It is in the Cascade Range. Its first ascender was Thomas J. Dryer.
Mount St Helens was caused by the subduction of the Juan de Fuca plate under the North American plate. The collision of these two plates is called a collision instead of a destructive because they are both continental plates.
In 1980, a major eruption happened at Mount St. Helens. The eruption was the only significant one to occur in the 51 U.S. states since the 1915 eruption of Lassen Peak in California. The eruption was preceded by a two-month series of earthquakes caused by magma close to the volcanos surface that created a fracture system and a huge bulge to occur on the North side of the volcano. Prior to the eruption, USGS scientists convinced local authorities to close Mount St. Helens to the general public their work saved thousands of lives. An earthquake on May 18, 1980, caused the entire north face to slide away creating the largest landslide ever recorded. Because of this it exposed the molten rock in the volcano to lower pressure. This caused the rock to explode. An eruption rose 80,000 feet into the atmosphere. Also the snow on the volcano melted causing a mud slide that reached as far as the Columbia River, nearly 50 miles away.