Fast Facts

• The first sign of activity on the mountain occurred on March 16. 1980.
  
  
• Mount St. Helens' elevation before the eruption was 9,677 feet. Elevation after the eruption was 8,363 feet.
  
  
• The gigantic debris avalanche. Traveled at speeds ranging form 70mph to 150 mph and covered 23 square miles, burying 14 miles of the North Fork of the Toutle River Valley.
  
  
• The lateral blast traveled 17 miles, destroying 230 square miles of vegetation.
  
  
• The lateral blast moved at 300 MPH and sustained temperatures as high as 660 degrees fahrenheit The blast toppled enough trees to build 300,000 two-bedroom homes.
  
  
• The column of ash, rose over twelve miles, sending an estimated 520 million tons of ash into the eastern United States.
  
  
• The lahars of the eruption damaged 27 bridges and about 200 homes, in addition to reducing the Columbia River navigation channel form 40 to 14 feet, stranding 31 ships.
  
  
• 57 people died.
  
  
• 7,000 large mammals died in the blast along with 12 million salmon fingerlings.

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