18 May 1980 Mt St. Helens erupts
At 8.32 am, the volcano erupted. and with an earthquake measuring 5.1 on the Richter scale, the north face of the mountain collapsed in a massive rock debris avalanche. In a few moments this slab of rock and ice slammed into Spirit Lake, crossed a ridge 1,300 feet high, and roared 14 miles down the Toutle River.
The avalanche rapidly released pressurized gases within the volcano. A tremendous lateral explosion ripped through the avalanche and developed into a turbulent, stone-filled wind that swept over ridges and toppled trees. Nearly 150 square miles of forest was blown over or left dead and standing.
At the same time a mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night as dark, grey ash fell over eastern Washington and beyond. Wet, cement-like slurries of rock and mud scoured all sides of the volcano. The eruption lasted 9 hours, but Mount St. Helens and the surrounding landscape were dramatically changed within moments.
A vast, grey landscape lay where once the forested slopes of Mount St. Helens grew. In 1982 the President and Congress created the 110,000-acre NationalVolcanicMonument for research, recreation, and education. Inside the Monument, the environment is left to respond naturally to the disturbance.