Images

Pyroclastic flow during August 7, 1980, Mount St. Helens eruption. The view is from Johnston Ridge, located 8 km (5 mi) north of Mount St. Helens.

July 22, 1980 eruption of Mount St. Helens sent pumice and ash 6 to 11 mi (10-18 km) into the air, and was visible in Seattle, Washington (100 mi/160 km north).

The Washington State Highway 99 (Old Pacific Highway) Bridge survived the May 18, 1980 lahar. Here, the front of the mudflow from the South Fork Toutle River passed by at about 1:00 p.m. P.D.T. on May 18; the mudflow from the North Fork of the Toutle River arrived at about 8:30 p.m. High-mudflow marks may still be visible on nearby trees.

Mudline left on tree by May 18, 1980 lahars from Mount St. Helens near the Old Highway 99 bridge across Toutle River, geologist 6 ft tall.

Ash from the May 18, 1980 eruption of Mount St. Helens covering the ground and road at a farm in Connell, Washington, approximately 300 km (180 mi) from the volcano.

For more than nine hours a vigorous plume of ash erupted, eventually reaching 20-25 km (12-15 mi) above sea level. By early May 19, the devastating eruption was over.

On May 18, 1980, at 8:32 a.m. Pacific Daylight Time, a magnitude 5.1 earthquake shook Mount St. Helens. The bulge and surrounding area slid away in a gigantic rockslide and debris avalanche, releasing pressure, and triggering a major pumice and ash eruption of the volcano. Thirteen-hundred feet (400 meters) of the peak collapsed or blew outwards.

The May 18, 1980 eruption of Mount St. Helens, Washington, generated lahars that swept down river valleys. The St. Helens bridge on Highway 504 was carried over a quarter-mile (a half-kilometer) downstream and partially buried.  The USGS Cascades Volcano Observatory continues to monitor Mount St. Helens and other very high threat volcanoes. Photo by R.L.

May 18, 1980 eruption of Mount St. Helens from southwest. Note the pyroclastic density currents spilling over the crater rim.

Plinian eruption column from May 18, 1980 Mount St. Helens. Aerial view from the Southwest.

Plinian column from May 18, 1980 eruption of Mount St. Helens. Aerial view from southwest. Mount Adams is in the background (right).

Plinian column of ash, steam, water, and debris viewed from the south of the Mount St.Helens May 18, 1980 eruption. This column reached a height of 60,000 ft (18,288 m).

Mount St. Helens on May 17, 1980, one day before the devastating eruption. The view is from Johnston's Ridge, six miles (10 kilometers) northwest of the volcano.

David Johnston at Coldwater II, 1900 hours, May 17, 1980. Dave did not survive the next day's eruption. Coldwater II would eventually be re-named "Johnston Ridge" in honor of Dave.

Bulge on the north slope of Mount St. Helens before the May 18, 1980 eruption. Sugar Bowl on left (east) side of bulge and Goat Rocks on right (west) side, viewed from the air.

A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 meters) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 meters).

Steaming Mount St. Helens as seen from Interstate 5, at Chehelis, Washington.

Mount St. Helens prior to the catastrophic eruption of May 18, 1980. Streams and lava flows also visible. View is looking southerly from oblique aerial view. Mount Hood in distance.

On March 20, 1980, after a quiet period of 123 years, earthquake activity once again began under Mount St. Helens volcano. Seven days later, on March 27, small phreatic (steam) explosions began.

Spirit Lake before the big May 18, 1980, eruption of Mount St. Helenes. View from the south. Mount Rainier, is in the distance.

View from the west of the top of Mount St. Helens showing a graben and new crater.