The Mount St. Helens Eruption

Mount St. Helens erupted on the morning of May 18, 1980 in an explosion that remains the most destructive volcanic event in the recorded history of the contiguous United States. A magnitude 5.1 earthquake triggered the collapse of the mountain's north face, the largest landslide in recorded history, which released the pressure on a lateral blast that flattened 230 square miles of forest in minutes. The eruption removed 1,314 feet from the mountain's summit, reduced it from Washington's fifth tallest peak to its thirtieth, and released energy equivalent to 1,600 atomic bombs. Fifty-seven people were killed.

Source: USGS