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2014 study of St. Helens magma system will be among world’s largest

2014 study of volcano's magma system will be among world's largest

By Tom Vogt, Columbian Science, Military & History Reporter
Published: August 20, 2012, 5:00pm

Upgrades to equipment aim to get a pulse on Mount St. Helens

Researchers are setting the stage for an ambitious project in 2014 to investigate the system of magma flow underneath Mount St. Helens.

The National Science Foundation has already announced grants to several institutions for the study, but it will take about two years to set up the field work, said Vancouver scientist Seth Moran.

“It will be one of the biggest multi-disciplinary volcano imaging experiments in the world,” said Moran, a U.S. Geological Survey

seismologist with the Cascades Volcano Observatory in Vancouver. “One or two are being studied pretty thoroughly; this is the first one in the U.S.”

The three-year project will use several geological and geophysical investigation techniques featuring more than 3,000 seismic instruments — some of them arrayed dozens of miles from the peak.

The title of the NSF grant hints at the research goals: “Illuminating the Architecture of the Greater Mount St. Helens Magmatic System from Slab to Surface.”

“The ‘slab’ is the Juan de Fuca Plate. That is the engine providing all the energy for earthquakes” in this region, Moran explained. “The fluids coming from that slab are driving the vulcanism” in the Cascades.

Understanding the route of magma from the Juan de Fuca plate to the surface is fundamental to understanding volcanic activity, according to the National Science Foundation. Tracing the plumbing system beneath volcanoes will allow scientists to determine where and how magma flows are generated, as well as the shapes and sizes of pathways and reservoirs that are part of their path toward the surface.

That knowledge will help scientists make more informed predictions about volcanic events.

Mount St. Helens is an ideal setting, researchers say. Following its catastrophic eruption in 1980, it was the first volcano to be thoroughly monitored with modern instruments. Mount St. Helens still is active, ensuring the presence of magma in its system now. It’s also easily accessible and has a well-recorded history. And, there are long-standing relationships among the academic community, government agencies and land managers.

The instruments will include a network of 70 seismometers deployed for two years in a 30-mile radius pattern surrounding the volcano.

More than 3,000 seismic instruments will be part of an active-source experiment involving controlled explosions in 80-foot shafts drilled at several points around Mount St. Helens.

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“You put energy into the earth and see what comes back. It’s like a CAT scan” in a hospital, Moran said. “You take energy and put it through some body part, see what the energy looks like on the other side.”

Scientists can get some data from earthquakes, but “An earthquake translates into a fuzzy image,” Moran said. “With thumping, you know exactly what you put into the earth and where it happened.”

Other techniques will include magnetotellurics, which can image the earth’s electrical resistivity structure from near the surface to tens of thousands of feet below Mount St. Helens.

“Different rock types have different types of conductivity,” Moran said.

The number of instruments that will be used is a factor in the two-year run-up to the project.

“The equipment is coming from a pool of instruments that is made available to the nationwide academic community through a National Science Foundation instrument center in New Mexico,” Moran said. The center (Incorporated Research Institutions for Seismology) supplies about 70 experiments a year, he said.

“This will be a big one,” Moran said. “For enough instruments, we have to push it out two years.”

Geologists also will offer hands-on expertise, “coming in and providing reality,” Moran said. “Rocks tell you a lot about how they formed.”

The National Science Foundation will spend about $3 million on the project, according to a recent report from Rice University in Houston, one of the research partners.

The project also includes researchers from the University of Washington, Oregon State University and Columbia University in New York.

Columbian Science, Military & History Reporter