Images

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.

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.

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

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.

Before the devastating May 18, 1980 eruption, Mount St. Helens was considered to be one of the most beautiful and most frequently-climbed peaks in the Cascade Range. Spirit Lake was a vacation area offering hiking, camping, boating, and fishing.

Mount St. Helens one year prior to the May 18, 1980, catastrophic eruption, showing glaciers at the summit.

Summit region (Kalama age–1479 to 1720 C.E.) of Mount St. Helens looking northeast. Spirit Lake and Mount Adams in background. September 28, 1979.

Worm Complex on the southeast flank of Mount St. Helens—Middle Kalama lava flows in center of image. Photo from September 28, 1979. Click to view larger image.

East Dome erupted during Sugar Bowl time (C.E. 850-900) east flank view of Mount St. Helens. Kalama age (erupted about 1535) andesite flows surround dome.

Studebaker Ridge formed during the Tertiary geologic time period (65 million to 2.6 million years ago). The pyroclastic surge from the May 18, 1980 eruption destroyed the trees on the ridge.

Before the eruption of May 18, 1980, Mount St. Helens' elevation was 2,950 m (9,677 ft). View from the west, Mount Adams in distance. S. Fork Toutle River is valley in center of photo.

Mount Adams elevation is 3,745 m (12, 286 ft). Mount St. Helens was the smallest of five major volcanic peaks in Washington State.