Unit on volcano helps scientists track drifting plates
Friday, February 4, 2005 7:22 AM PST
By Courtney Sherwood
Printable version
E-mail this articleMount St. Helens is now part of the world's biggest-ever attempt to understand what's really happening under the surface of the earth, all thanks to a small piece of equipment called a global positioning system unit.
The mountain now has a small part to play as part of the $220 million Earthscope project, a Congressionally funded effort to understand how earthquakes and volcanoes work.
A global positioning system unit placed on Mount St. Helens flanks Tuesday has joined six other GPS units on and around the volcano.
Using satellites circling the planet, the GPS units can track movements as little as a millimeter. From those movements, scientists hope learn more about how the planet works.
"Think of it all as providing an MRI," said Chuck Meertens, one of the leaders of the effort. "We'll image what's going on in the earth."
Each unit sends signals about its location and movement to Colorado-based UNAVCO, which is gathering information from dozens of sites around the western United States.
Eventually, 870 GPS units will be deployed around the western U.S., said Meertens, facilities manager for UNAVCO.
Southwest Washington is shifting about one to two centimeters in a year, measurements of the region reveal.
"The entire western United States is deforming," Meertens said Thursday.
Under the earth's seemingly-stable crust, distinct slabs called tectonic plates move and rub against each other, causing earthquakes and volcanic eruptions. Plate collisions build mountains over eons or cause devastating earthquakes without a moment's notice.
Off the Pacific Northwest Coast, in an area called the Cascadia Subduction Zone, the oceanic Juan de Fuca plate is colliding with the North American plate, the book "Volcanoes of the Cascades" reports.
As the plates shove against each other, the North American Plate is being forced up and to the east, according to the book. Eventually, this zone will trigger a massive earthquake like the one in the Indian Ocean off Indonesia Dec. 26, scientists say.
"The whole point of this project is to measure the changes in the earth and measure plate boundary changes," Meertens said. "We want to really understand the physics of what's going on."
While UNAVCO focuses on GPS units, other Earthscope groups are working to deploy 2,000 seismometers to measure earthquakes within the earth's surface.
A third project is drilling through California's famous San Andreas fault zone to measure and observe the collision of two of the earth's plates along an active fault line. The San Andreas fault caused the great 1906 San Francisco earthquake.
Volcanoes are of particular interest to the scientists working on Earthscope, Meertens said.
Scientists believe the hot molten rock that creates volcanoes oozes from below the earth's crust to the planets' surface because of high pressure that forms when plates collide, according to "Volcanoes of the Cascades."
In addition to Mount St. Helens, UNAVCO is collecting GPS signals from several volcanos in Alaska, Meertens said.
The Earthscope project was not the only source of new scientific endeavor at Mount St. Helens this week.
USGS scientists put a GPS unit and a seismic monitor on the growing lava dome inside the volcano's crater Thursday. This equipment replaces devices destroyed in a Jan. 16 blast that flung foot-wide rocks against the crater walls.
Scientists hope the new monitors will help them learn to predict future blasts, said USGS hydrologist and outreach coordinator Carolyn Driedger.
The GPS unit will also help scientists measure the movement and growth of the lava dome as the volcano continues to erupt..
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