Mount St. Helens National Volcanic Monument Overview On May 18,
1980, the long-dormant Mount St. Helens erupted. Shaken by an
earthquake measuring 5.1 on the Richter scale, the north face of
this tall, symmetrical mountain collapsed in a massive avalanche
of rock debris. Within 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 eruption lasted nine
hours, but Mount St. Helens and the surrounding landscape were
dramatically changed within moments. A vast, gray landscape lay
where once the forested slopes of Mount St. Helens grew. Carved
out of the Gifford-Pinchot National Forest in 1982, the
110,000-acre National Volcanic Monument allows scientists and
visitors to see the changes in the landscape and the volcano.
Within the monument's bounds, the environment is left to respond
naturally to the disturbance. Observe how surviving plants and
animals rise out of the ash, colonizing plants catch hold of the
earth, and birds an