Mount St. Helens spewed ash and steam miles into the air in two eruptions, dusting parts of two states with ash, and sending an 8-foot high wall of hot mud and melted snow down the nearby Toutle River, officials said today.
Fears of flooding prompted the evacuation of about 65 people, but no injuries were reported and evacuees were returning home.
A half-dozen geologists and volcanologists, brushing aside concerns of further blasts, set down in helicopters on Mount St. Helens to inspect its crater, glowing and steaming from its first explosive eruptions in 17 months.
While rumblings beneath the volcano eased after the blasts, scientists said the activity could persist for several days. Heavy steam rising about 2,500 feet above the crater and snowy weather made it impossible for scientists to determine any new growth of the crater's massive lava dome.
The first blast, at 7:28 p.m. Friday, shot an ash cloud to nearly nine miles above sea level--nearly seven miles above the top of the volcano--and the second blast six hours later sent an ash cloud about three miles into the air.
Earthmoving vehicles on the north fork of the Toutle River were tossed about like Tinkertoys by the force of the blast, but there were no reports of damage to homes.
Kathy Cashman of the U.S. Geological Survey said one large flow of mud, about 660 feet wide, swept out of the north side of the crater after the first eruption. The flow eventually broke into two parts, with one headed down the Toutle River and the other toward Spirit Lake.
The major damage visible from the air today appeared to be a wide channel gouged in an earthen retaining dam the Army Corps of Engineers built 12 miles northwest of the volcano to trap debris rolling down the mountain.
The 1:37 a.m. blast yesterday, which lasted three minutes, was much milder than Friday night's explosive outburst, said A.B. Adams of the University of Washington geophysics center in Seattle.
The eruptions were the first explosive bursts from the 8,400-foot high southwest Washington volcano since October, 1980, when the mountain erupted five times over three days. The volcano has experienced six nonexplosive eruptions, which contributed to the growth of its lava dome, since then.
On May 18, 1980, a cataclysmic eruption left 60 people dead or missing, flattened 150 square miles of timber and sent an ash cloud around the world.
Ash from the latest eruptions dusted parts of southwest Washington and northern Oregon up to 150 miles away.
"It looks like somebody gave us a heavy frost," said Oregon state trooper Mike Robinson.
Flight of commercial and private aircraft was kept at a 10-mile distance from the mountain in the first few hours after the ash plume was seen.