St. Helens could erupt today

Professor says it won't be as large as 1980 eruption

By Ryan Smith

Mount St. Helens literally rumbled back to life this week after more than a decade of inactivity when a series of earthquakes and tremors led to the mountain spewing steam and ash 10,000 feet into the air.

While small earthquakes of magnitude 3 or less have been occurring since Wednesday, two tremors on Friday and early Sunday have scientists believing an eruption of lava is imminent—possibly as early as today.

The United States Geological Survey reported on its Web site that immediately after the steam emission Friday afternoon, seismic activity changed from rock breakage events, such as earthquakes, to continuous low-frequency tremors.

“With harmonic tremors, it’s kind of like pipes shaking back and forth while magma moves up,” said Keith Putirka, a volcanologist and assistant professor of earth and environmental sciences at Fresno State. “It’s sort of like when you turn the water on in your house and the pipes shake as the water moves through the pipes.

“These are things that tell us magma is on the way.”

Putirka said an eruption depends on whether these harmonic tremors continue to occur. However, he said, at the pace they are occurring right now, an eruption quite possibly could occur within hours.
The last time Mount St. Helens erupted was on May 18, 1980. The eruption destroyed 230 square miles of forest, showered cities more than 250 miles away with ash and killed 57 people.

The volcano continued to erupt through 1986, piling layers of lava one on top of the next until it formed a lava dome across the top of the mountain.

Activity started again in 1998 when magma rose from about six miles to one mile below the surface, though it never erupted. The volcano has been relatively inactive until this week.

“There is certainly a very good chance that it could erupt,” Putirka said. “Mount St. Helens is probably one of the most active volcanoes in the Cascade Range. It is not surprising that it has been dormant for years only for it to act up again.”

While scientists can’t say for certain when or how large the eruption will be, if it erupts at all, many believe that the eruption won’t be as big as the one in 1980.

“The USGS doesn’t necessarily know what is going to happen,” Putirka said. “From what we’ve seen so far, it basically means things are active—stuff is just re-adjusting.”