Facts About Mount Saint Helens

Mount Saint Helens is probably one of the most celebrated volcanoes in the United States, along with Hawaii's Mauna Loa, which is itself the most massive volcano on the earth. Mount St. Helens is still active, after its last fierce eruption in 1980. It is a stratovolcano placed in Skamania County, Washington. It is placed in the Cascade Mountain Range, and is known as a part of the Cascade Volcanic Arc. This is a small segment of the pacific Ring of Fire that includes over 160 active volcanoes.

Facts About Mount Saint Helens

Facts About Mount Saint Helens

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Facts About Mount Saint Helens

Facts About Mount Saint Helens

When someone says "Mount Saint Helens", you will probably immediately think of the massive eruption on May 18, 1980. This was the most economically destructive and deadliest volcanic event in the history of the United States. It killed fifty-seven people; it destroyed 185 miles of highway, 15 miles or rail roadways, 47 bridges and 250 homes.

The eruption caused a huge avalanche of debris, which reduced the elevation of the summit from 9677 feet to 8365 feet. It replaced the summit with a one mile wide horse-shoe-shaped crater. In the aftermath was created the Mount St Helens National Volcanic Monument, to support the volcano and allow it to be studied.

Mount Saint Helens is a large eruptive cone that is made of lava rock interspersed with pumice, ash and other deposits. The mountain has layers of andesite and basalt straight through which lava has erupted. There were two dacite domes on Mount Saint Helens before 1980, but both were destroyed in that eruption.

When this volcano erupted, the whole mountain was shaken by a 5.1 earthquake, and the entire north face of the mountain collapsed in a rock and debris avalanche. Approximately 230 miles of forest land was blown over or buried under volcanic deposits. Simultaneously, a massive cloud of ash rose skyward and drifted downwind, which turned day into night for citizen in the immediate area. The eruption lasted nine hours, and Mount Saint Helens and the surrounding area were changed within the first moments.

Mount Saint Helens is young when compared to the other not-as celebrated volcanoes in the Cascade range. It was only formed within the past 40,000 years. This volcano is the most active in the range within the last 10,000 years or so.

Before the eruption in 1980, Mount Saint Helens was the 5th highest mountain peak in the state of Washington. It was called Mt Fuji of America, and, with its snow-covered symmetrical dome, it stood out prominently from the hills around it. Its peak rose higher than 5,000 feet above its base, where the lower parts would merge with adjacent ridges.

The streams that begin high atop the volcano enter the main river systems on either side of the mountain. These streams are fed by much snow and rain, as the average yearly rainfall in the area is about 140 inches. The sometimes lazy flow of the rivers belies the power that lies below the earth's surface.

Facts About Mount Saint Helens

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