Q:

When did Mount Saint Helens erupt?

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Quick Answer

Mount St. Helens' most significant eruption in modern times occurred on March 20, 1980. It was followed by additional eruptions between Dec. 7, 1989 to Jan. 6, 1990, Nov. 5, 1990 to Feb. 14, 1991, Oct.11, 2004, Mar. 8, 2005, and between Jan. 16, 2008 to July 10, 2008.

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When did Mount Saint Helens erupt?
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Full Answer

Prior to the 1980 eruption, recorded eruptions from 19th century include a major eruption in 1800, followed by smaller eruptions between 1831 to 1857. During that time, the largest eruption occurred in 1842. Other major eruptions date to 1480, 400 B.C., 1200 B.C., 1600 B.C., 1900 B.C. and 2500 B.C. It experienced a 2,000-year eruptive period beginning 20,000 years ago and another eruptive period that ended about 35,000 years ago.


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    How did Mount St. Helens form?

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    Mount St. Helens is a cinder cone volcano that formed through the gradual accumulation of cinders and ash at the base of the mountain. Unlike a shield volcano, such as Mauna Loa in Hawaii, cinder cones can rise sharply from the surrounding terrain and maintain a steep, angular profile throughout their existence.

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