Images

These pyroclastic-flow deposits of the climactic eruption of Mount Mazama, during which Crater Lake caldera formed, are eroded into spectacular spires at The Pinnacles on Wheeler Creek.

Lahars originating from Mount St. Helens after the 1980 eruption destroyed more than 200 homes and over 185 miles (300 kilometers) of roads. Pictured here is a damaged home along the South Fork Toutle River.

Between 1980 and 1986, Mount St. Helens' dome grew in different ways. From 1980 through 1982 the dome grew in periodic extrusions of stubby lava flows, called lobes. During this time frame Mount St. Helens' lobes grew at a rate of 3 to 10 feet per hour (1-3 meters/hour).

These measurements were used to study the erosion processes and to estimate the severity of the sedimentation problem. Rod person (lower left) and instrument persons (upper right) give scale.

U.S. Army Corps of Engineers preformed dredging projects on the Toutle, Cowlitz, and Columbia Rivers and by 1987 enough material had been removed to build a 12 lane highway, one-foot thick from New York, NY to San Francisco, CA.

Small phreatic eruption of Mount St. Helens in the spring of 1980, before the May 18, 1980 blast.

Measuring tilt in Timberline parking lot in early April 1980 during lightly falling snow.

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.