Mount St. Helens timeline

The Associated Press

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1979 — The mountain is a recreational haven. Half a million people a year visit the Spirit Lake area below the cone-shaped, 9,677-foot summit.

March 1980 — The volcano begins to show signs of unrest. Earthquakes and steam eruptions continue for several weeks.

8:32 a.m., May 18, 1980 — A 5.1-magnitude earthquake about a mile below the summit triggers a massive eruption and landslide, flattening 230 square miles of forest northwest of the summit and resulting in the deaths of 57 people. A plume of ash extends 15 miles into the sky and coats towns 250 miles away.

Summer 1980-October 1986 — Repeated minor eruptions build a 925-foot-tall dome of hardened lava inside the crater left by the eruption.

1982 — Congress and President Reagan create the 110,000-acre National Volcanic Monument for research, recreation and education. Inside the monument, the environment is left to respond naturally to the disturbance.

1990-present — Steady progression in the variety and number of plants and animals returning to the blast zone.

1998 — First major seismic activity since 1986, with earthquakes located as deep as 6 miles forcing magma to within about a mile of the dome, scientists believe.

2001 — Another flurry of small earthquakes, but once again, no magma surfaces.

Sept. 23, 2004 — The first of thousands of tiny, shallow earthquakes are recorded at St. Helens.

Sunday — The U.S. Geological Survey declares a notice of volcanic unrest, closing the crater and upper flanks of the volcano to hikers and climbers.

Wednesday — Earthquakes increase to about four per minute, ranging in magnitude from 2.0-2.8. The USGS raises its warning system to the third of four levels and warns that a blast could send rocks and ash 3 miles from the summit.

Friday — Mountain briefly belches out a plume of smoke and ash. Quakes subside.

Copyright © 2004 The Seattle Times Company

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