If you're hiking in the Mount St. Helens National Volcanic Monument in July or August, and you feel the earth rumble briefly, it could just be scientists trying to plumb the depths of the Northwest’s most active volcano.
Scientists are peppering Mount St. Helens with thousands of sensitive instruments this summer to understand what makes the volcano tick.
The seismometers and magnetic devices will measure underground vibrations and electromagnetic fields up to 100 miles underground.
Scientists hope the data will provide a map of where molten magma is pooled and how it moves toward the surface before an eruption.
This summer’s work will cost about $3 million.
The Imaging Magma Under St. Helens project involves five universities and the U.S. Geological Survey.
Seismologist John Vidale with the University of Washington said scientists currently have a fair understanding of how magma behaves in the top few miles beneath Saint Helens. They believe magma pools in a chamber 2 to 5 miles beneath the surface.
“Beneath that, it’s basically a mystery,” Vidale said.
The new research could eventually help scientists make better forecasts of St. Helens' eruptions, like the one that killed 57 people in 1980.
“We’d like, once we’re done with this, perhaps, to move on to Mount Hood or Mount Rainier, the volcanoes that are near Portland and Seattle, because they’re also full of mysteries,” Vidale said.
Researchers from Rice University in Houston plan to set off up to 24 underground explosions on Mount St. Helens in July and August. A grid of 3,500 seismometers, covering an area around the volcano 75 miles wide, will measure the resulting vibrations. All that data will let scientists draw a 3-D picture of the volcano's inner workings.
"It's akin to a CAT scan of the volcano," said Rice University seismologist Alan Levander.
Levander said the explosive charges of up to a ton each will be buried about 80 feet underground and will cause no damage at the surface. He said only people standing within a few hundred yards would even notice a brief rumble.
“It’s like standing on a bridge when a truck goes by,” he said.