Mt. St. Helens, the volatile mountain that blew its top in spectacular fashion 24 years ago, has been grumbling again, and scientists said Wednesday a small-to-moderate eruption was possible in the next few days.
Such an event could spew rock and ash thousands of feet, but the fallout likely would not go beyond the volcano’s crater or flanks. At worst, scientists say, some debris could travel as far as 3 miles–nowhere near the closest towns of Cougar and Toutle.
Seismologists monitoring the volcano on Wednesday afternoon raised the alert level to “volcano advisory”–level 2 on a 3-step scale–after a series of small earthquakes indicated the mountain was, in the words of local seismologist Seth Moran, “ramping up.”
Moran said a hardened dome of lava inside the crater also appeared to be growing, meaning gases or molten rock could be building just below the surface. The lava dome, now about 900 feet tall, grew inside the crater in the years after the May 18, 1980, eruption that killed 57 people and razed 150 square miles of forest.
The eruption blew off the top 1,300 feet of the mountain and caused one of the largest recorded landslides in history. Ash from the explosion eventually circled the globe.
That type of eruption “is not in the cards this time,” said Steve Malone, a seismologist at the University of Washington. But he and the other scientists noted that predicting volcanic eruptions is an inexact science.
“We’re not guaranteeing an eruption,” said Cynthia Gardner, a research geologist for the Cascades Volcano Observatory in Vancouver, Wash. The observatory is operated by the U.S. Geological Survey.
The U.S. Forest Service has closed hiking trails near the crater and above the 4,800-foot level of the mountain, which rises 8,364 feet. The Weyerhaeuser Corp., which owns 435,000 acres surrounding the mountain, closed off areas within a 12-mile radius of the volcano.
Last Thursday, instruments began detecting intermittent swarms of earthquakes beneath the surface of the crater. By Tuesday, the quakes–the largest measuring 2 to 2.8–were coming at a rate of two to three per minute.
“Most of these earthquakes are very, very small. You wouldn’t feel them even if you were standing right on top of them,” Moran said.
After a quiet period Tuesday evening, the quakes began again early Wednesday and lasted nearly 8 hours, Moran said at a briefing in Vancouver. He said the swarms were accelerating “in both frequency and intensity.” During that period, instruments recorded up to four quakes per minute.
Meanwhile, officials at the Mt. St. Helens visitor center, which has remained opened, have reported a noticeable increase in tourists since last Thursday. Instead of being frightened away, people seem to be drawn toward the volcano.
“There’s nothing more alluring than a volcano, and there’s nothing more alluring than a volcano that looks like it might erupt,” Gardner said.
