Volcanic Advisory Issued For Mount St. Helens; U.S. Forest Service Closes Access

September 30, 2004

Volcanic Advisory Issued For Mount St. Helens; U.S. Forest Service Closes Access
September 30, 2004 – The U.S. Geological Survey issued a volcanic advisory Wednesday for Mount St. Helens with officials warning of a heightened possibility of a small to moderate eruption.

The volcano last erupted in 1980 in a nine-hour eruption that blew over or killed nearly 230 square miles of forest and sent a mushroom cloud of ash thousands of feet into the sky. That eruption killed 57 people.

Geologists have said that they cannot pinpoint when the eruption might occur, although it could happen today or a month from now.

"We think there is a heightened possibility that we could see an explosion," said Cynthia Gardner, acting scientist in charge at the Cascades Volcano Observatory. "We are expecting that either nothing could happen or perhaps we could have an explosive event."

She said if a small to moderate eruption occurred, rocks could be hurled up to 3 miles from the volcanic dome and ash could spew up to 10,000 feet in the air and be carried about 10 miles downwind.

The U.S. Forest Service has closed access into the crater and access to areas above 4,800 feet around Mount St. Helens. Trails on the north side of the crater have also been closed.

The advisory that was issued is the third of four levels — with the fourth being eruption.

"It’s a puzzle, and it’s keeping us on our toes," said U.S. Geological Survey geologist John Major. "It’s showing signs of an eruption, but not to the size and magnitude of 1980."

CNN reports that small quakes are not uncommon in the fall, as rainwater seeps into the ground and turns into steam when it reaches hot magma, scientists said. Magma is lava that has not yet escaped from the volcano.

If the steam has no outlet, they said, it can build until a small explosion occurs. But they can’t rule out the involvement of something other than steam.

Mount St. Helens has been an active volcano for about 40,000 years with intermittent periods of dormancy. The last 2,500 years, however, have seen shorter periods of dormancy and a change in the type of rocks expelled by the volcano.