Images

The volume of the debris avalanche was nearly 2/3 cubic miles (2.5 cubic kilometers) of debris avalanche that slid from the volcano on May 18, 1980. That is enough material to cover Washington, D.C. to a depth of 14 feet (4 meters). The avalanche traveled approximately 15 miles (24 kilometers) downstream at a velocity exceeding 150 miles per hour (240 km/hr).

This October dome was taller than a nine-story building and wider than the length of three football fields. This dome was not the first dome to grow in the crater. In June and August 1980, two domes formed, only to be blasted away by the explosive events of July 22 and October 16.

Nearly 135 miles (220 kilometers) of river channels surrounding the volcano were affected by the lahars of May 18, 1980. A mudline left behind on trees shows depths reached by the mud.

Pumice blocks at the toe of a pyroclastic flow from the 1980 eruption sequence at Mount St. Helens.

Many smaller animals, such as gophers, mice, frogs, fish, and insects were hibernating below ground or under water on May 18, 1980, and they survived the blast. Larger animals such as bear (whose tracks are shown here), elk, deer, and coyotes have been moving back into the area as their food supplies increase.

This lake was once surrounded by lush forest and is within the area devastated by the directed blast, covered by ash and tephra, then inundated by pyroclastic flows. Remnants of the forest float on the surface of the lake. Mount Rainier (4,392 m or 14,410 ft) is in the distance. The view is from the south.

The direction of the blast, shown here from left to right, is apparent in the alignment of the downed trees. Over four billion board feet of usable timber, enough to build 150,000 homes, was damaged or destroyed.

For weeks volcanic ash covered the landscape around the volcano and for several hundred miles downwind to the east. Noticeable ash fell in eleven states. The total volume of ash (before its compaction by rainfall) was approximately 0.26 cubic mile (1.01 cubic kilometers), or, enough ash to cover a football field to a depth of 150 miles (240 kilometers).

Muddy River bridge crossing destruction from May 18, 1980 Mount St. Helens lahars.

After the May 18, 1980 eruption, Mount St. Helens' elevation was only 8,364 feet (2,550 meters) and the volcano had a one-mile-wide (1.5 kilometers) and approximately 600 m (2000 ft) deep horseshoe-shaped crater. View here is from the northwest.

Mount St. Helens soon after the May 18, 1980 eruption, as viewed from Johnston's Ridge.

Mount St. Helens soon after the May 18, 1980 eruption, as viewed from Johnston's Ridge.

Blowdown of trees from the shock-wave of the directed (lateral) blast from the May 18, 1980 eruption of Mount St. Helens. Elk Rock is the peak with a singed area on the left.

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.

During the May 18, 1980 eruption, at least 17 separate pyroclastic flows descended the flanks of Mount St. Helens. Pyroclastic flows typically move at speeds of over 60 miles per hour (100 kilometers/hour) and reach temperatures of over 800 Degrees Fahrenheit (400 degrees Celsius).

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.

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