Early Signs of Activity.

Located seventy miles from Portland, Oregon, in a sparsely populated region of southwestern Washington State, Mount St. Helens erupted in 1980 in one of the largest volcanic explosions in North American history. The mountain's last eruption had been recorded by the American soldier, explorer, and political leader John C. Fremont in 1857. Signs of significant seismic and volcanic activity began as early as 27 March 1980, when the first venting of smoke and ash began. As many as 250,000 residents in nearby counties, including several hundred loggers, forest rangers, and residents in the immediate vicinity of Mount St. Helens, were either evacuated or warned.

The Volcano Erupts.

At 8:32 A.M. on Sunday 18 May 1980 Mount St. Helens erupted. Millions of tons of earth were shot as high as 65,000 feet into the air. Heated rock and ash poured down the mountain's northern side. In a short...