Mount St. Helens
Mount St. Helens was getting ready to burst for nearly two months before it exploded, not to mention the more than 120 years it lay dormant. While the eruption was anticipated, the manner in which it occurred was completely unprecedented. At 8:32 a.m. on May 18, 1980, a 5.1-magnitude earthquake triggered a sideways blast that swept the mountain's north face away into a cascading landslide that shot hot ash and stone out some 15 miles at speeds of at least 300 m.p.h. At the same time, a mushroom-shaped plume of ash shot 16 miles into the air, eventually covering three states. Complete darkness blanketed Spokane, Wash., a city about 250 miles northeast of the volcano. When the ash came down it fell in the form of black rain that literally coated the residents of Washington, Idaho and parts of Montana with a fine gray powder. Fifty-seven people and thousands of animals were killed, and some 200 square miles of trees were obliterated. In 1982, Congress and President Ronald Reagan designated the surrounding land as the Mount St. Helens National Volcanic Monument.