Mount St. Helens

Mount St. Helens is an active stratovolcano in Skamania County, Washington, in the Pacific Northwest region of the United States. It is located 96 miles (154 km) south of Seattle and 53 miles (85 km) northeast of Portland, Oregon. The mountain is part of the Cascade Range and was initially known as Louwala-Clough which means "smoking or fire mountain" in the language of the Klickitats. It was named for British diplomat Lord St Helens who was a friend of George Vancouver, an explorer who made a survey of the area in the late 18th century.

Related Topics:
Stratovolcano - Skamania County - Washington - Pacific Northwest - United States - Seattle - Portland, Oregon - Cascade Range - Klickitat - Lord St Helens - George Vancouver

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It is most famous for a catastrophic eruption on May 18, 1980. That eruption was the most deadly and economically destructive volcanic eruption in the history of the United States. Fifty-seven people were killed and 200 homes, 47 bridges, 15 miles (24 km) of railways and 185 miles (300 km) of highway were destroyed. The eruption blew off the top of the mountain, reducing its summit from 9,677 feet (2,950 m) to 8,364 feet (2,550 m) in elevation and replacing it with a mile-wide (1.5 km-wide) horseshoe-shaped crater (see geology section or 1980 eruption of Mount St. Helens for more detail).

Related Topics:
May 18 - 1980 - Feet - M - 1980 eruption of Mount St. Helens

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Like most other volcanoes in the Cascade Range, St. Helens is a great cone of rubble consisting of lava rock interlayered with ash, pumice and other deposits. Volcanic cones of this internal structure are called composite cones or stratovolcanoes. Mount St. Helens includes layers of basalt and andesite through which several domes of dacite lava have erupted. The largest of the dacite domes formed the previous summit; another formed Goat Rocks dome on the northern flank. These were destroyed in St. Helens' 1980 eruption.

Related Topics:
Lava - Ash - Pumice - Stratovolcano - Basalt - Andesite - Dacite - Goat Rocks

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