Images

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.

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.

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.

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.

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.

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.

Steam-blast eruption from summit crater of Mount St. Helens. Aerial view, April 6, looking southwest, showing a roiling, gray-brown, ash-laden cloud that envelops and almost completely hides an initial fingerlike ash column, and an upper white cloud formed by atmospheric condensation of water vapor in the convectively rising top of the eruptive column.

View looking west of Mount St. Helens' summit after several small explosive eruptions. The smaller of the two pit craters was formed first on March 27. Subsequent eruptions opened the farther crater.

Ash covered snow is a result of wind direction, resulting in left portion of cone free of ash while the right portion is covered. Snowstorms later covered these ash layers, which in turn were covered by new ash. The result was many alternating layers of snow and ash.

View from the northwest of a phreatic eruption on Mount St. Helens pre- May 18, 1980 eruption.

View from the north of Mount St. Helens' eruption and first crater.

An east-west fault across middle of summit area and an uplift or bulge on upper north flank of the volcano are also visible in this photo.

Although seismic activity began under Mount St. Helens on March 20, this overflight showed no unusual features except numerous tracks of earthquake-triggered snow avalanches. No evidence of fracturing of summit area was detected during careful visual observations on the afternoon of March 24, 1980.