VANCOUVER, Wash. - A steam-and-ash burst Thursday from Mount St. Helens caused a small mudflow from the volcano and lightly dusted parts of central Washington, authorities said.
Mud flowed out of the crater in a small channel, but sensors indicated it did not travel beyond the mountain, U.S. Geological Survey geologist Steve Brantley said.
The activity poses no danger to people living near the mountain, he said, and there is no evidence the southwest Washington volcano is building to a major eruption.
No plume from the volcano was reported by area pilots, but ash from the 5:24 a.m. blast was reported later in the day at several locations east of the mountain, Brantley said.
There have been a dozen such blasts in the past year and a half at the 8,366-foot volcano and about half of them generated ash plumes, he said.
A similar eruption Feb. 5 sent a plume to 18,000 feet.
Volcanic ash mixed with rainfall was reported in numerous towns in Yakima County on Thursday morning, said Don Thompson, director of the county's Office of Emergency Management.
Light ash was reported falling in a line stretching from Zillah to Prosser, about 100 miles east of St. Helens, Thompson said.
Ash also dusted portions of the Tri-Cities.
The area was blanketed by heavy ash during the volcano's 1980 eruption, but the present fallout was nothing like that disaster, he said.
"This is just a belch."
The ash-laden rainfall did not pose a danger, Thompson said. ``The only problem might be the possibility of scratching a windshield.''
Thurday's eruption destroyed two seismic stations in the crater.
They had just been replaced last week after being destroyed in the blast nine days ago.
The steam blasts are apparently caused by a buildup of gas or steam caused when melting water hits hot rocks.
Brantley said there probably will be more such blasts in coming weeks.
The May 18, 1980, eruption of Mount St. Helens leveled 230 square miles, left 57 people dead or missing and sent up an ash cloud that circled the globe.