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I Saw It Blow!

On May 18, 1980, Mount St. Helens erupted, being the "deadliest and most economically destructive volcanic event in the history of the United States":

  • 57 people were killed
  • 250 homes, 47 bridges, 15 miles of railways, and 185 miles of highway were destroyed
  • The massive debris avalanche (about 2.9 cubic kilometers) reduced the elevation of the mountain's summit from 9,677 feet to 8,365 feet
  • A great amount of ash (1 cubic kilometer) was ejected into the air and spread world-wide
Question: Considering just the State of Washington, what should have been the thickness of the layer of ash if all of the ash was distributed on the State's land evenly?

Source: Adaptation of Science News, January 29, 2005, p. 76