__1980: __Washington state's Mount St. Helens volcano explodes in a cataclysm that pulverizes its top 1,300 feet, deforests nearby valleys, sends ash 12 miles into the air and kills 57 people. The picture-perfect snow-capped peak becomes the center of a bleak, gray mudscape.

The volcano, about 55 miles northeast of Portland, Oregon, had lain dormant since 1857. The 9,677-foot peak and the surrounding valleys, lakes and forests were popular destinations for mountain climbers, backpackers, day hikers, boaters, fishermen and those who just wanted to sit back and take in the sylvan splendor.

Volcanologists started detecting swarms of small earthquakes emanating from the volcano's insides on March 20, 1980. Snow avalanches began on March 24, and the crater started steaming on March 27. A series of explosions from March 28 to 30 was heard 20 miles away and sent ash drifting 100 miles away.

The volcano was no longer sleeping.

Fearing snow avalanches and mudslides, the National Forest Service closed the area to visitors and allowed loggers to use the area on a no-overnight basis. Stereoscopic aerial photography in early April showed that the mountain was inflating, with parts of the crater rim 250 feet higher than they'd been before. Ominously, the north slopes were pushing out sideways as well, displaced 300 feet or more.

Earthquakes — up to magnitude 4.9 — continued, and St. Helens began a second set of steam and ash explosions May 7. A few property owners chose to stay put. Doughty old Harry Truman, owner of the Spirit Lake Resort, said he'd trust the mountain and if she wanted to take him, so be it.

Geologists and journalists swarmed into the area, too. U.S. Geological Survey volcanologist David Johnston took an observation post on a ridge 5 miles from the peak, That seemed far enough for safety.

St. Helens' big boom came on Sunday morning, May 18, at 8:32 a.m. The entire north face of the mountain, it turned out, was made of crumbly rock riddled with cracks and fissures. So St. Helens didn't blow up exactly. It blew north and up.

A magnitude 5.0 quake shook a block of the mountain loose, setting off a landslide half a mile wide and a mile from top to bottom. With the side, rather than the top, of the volcano open and exposed, searing volcanic gas and steam from its innards shot up and out. That blast seared the landscape and blew huge trees down like matchsticks up to 17 miles away.

Hot ash and rock billowed into the sky and spread for hundreds of miles. But there was enough ash and debris at ground level to melt the mountain's snow and glaciers and create surging mudflows that filled the valleys below.

David Johnston was lost in the blast. Harry Truman was buried in the mudflow. Other photographers and observers perished as well. Downstream, emergency workers rescued about 200 people from the mudflows, but 57 people lost their lives.

Some people have returned to rebuild in the devastated valleys. Plants and animals have gradually re-colonized parts of the blown-down forests and mud-filled valleys. And the the Forest Service and Geological Survey keep a watchful eye on the mountain.

Source: Mount St. Helens - The Volcano; National Geographic, January 1981

Photo: Driftwood still clogs parts of Spirit Lake in 2005, a quarter century after the eruption.

Photographer: Ken Lambert/AP

See Also:- Mount St. Helens Eruption: May 18, 1980