USGS logo


The Climactic Eruption of May 18, 1980

Full fury

The climactic eruption in full fury in the late morning of May 18, 1980 (Photograph by Joseph Rosenbaum).

May 18, a Sunday, dawned bright and clear. At 7 a.m. Pacific Daylight Time (PDT), USGS volcanologist David A. Johnston, who had Saturday-night duty at an observation post about 6 miles north of the volcano, radioed in the results of some laser-beam measurements he had made moments earlier that morning. Even considering these measurements, the status of Mount St. Helens' activity that day showed no change from the pattern of the preceding month. Volcano-monitoring data--seismic, rate of bulge movement, sulfur-dioxide gas emission, and ground temperature--revealed no unusual changes that could be taken as warning signals for the catastrophe that would strike about an hour and a half later. About 20 seconds after 8:32 a.m. PDT, apparently in response to a magnitude 5.1 earthquake about 1 mile beneath the volcano, the bulged, unstable north flank of Mount St. Helens suddenly began to collapse, triggering a rapid and tragic train of events that resulted in widespread devastation and the loss of 57 people, including volcanologist Johnston.

Reawakening and Initial Activity

Debris avalanche


URL: <>
Contact: John Watson

Last updated: 06.25.97