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When did Mount St. Helens erupt?

Mount St. Helens, located in southwestern Washington state in the Cascade mountain range, erupted on May 18, 1980. Sixty-one people died as a result of the eruption. This was the first known volcanic eruption in the 48 contiguous United States (excluding Alaska and Hawaii) to claim a human life. Mount St. Helens is classified as a composite volcano (a steep-sided, often symmetrical cone constructed of alternating layers of lava flows, ash, and other volcanic debris). Composite volcanoes tend to erupt explosively.

Mount St. Helens and the other active volcanoes in the Cascade Mountains are a part of the ``Circle of Fire,'' a ring of active volcanoes that dot the lands bordering the Pacific Ocean.

There are active volcanoes in three other U.S. states besides Washington; they are California, Alaska, and Hawaii. Lassen Peak in California is one of several volcanoes in the...

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1. Characteristics
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