On the morning of May 18, 1980, an earthquake shook Mt. St. Helens and the mountain's north face collapsed in one of the largest debris avalanches ever recorded.
The slide uncorked the volcano, baring magma that exploded with 500 times the force of the Hiroshima bomb in the most destructive eruption in U.S. history.
The cataclysmic chain of events killed 57 people and thousands of animals, took out 250 homes, 47 bridges and 185 miles of highway, clogged rivers with sediment, flooded valleys and blocked the Columbia River shipping channel.
Forty years later, the destruction may not be over.
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