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One of the things moving magma tends to do, is that it tends to deform the surface of the Earth. It tends to cause the surface to bulge upward or to spread apart.
One of the instruments we use to measure deformation is a tiltmeter. A tiltmeter measures very subtle changes in the surface of the Earth -- as magma accumulates beneath a station or moves upward, for example.
Another instrument we use is the Global Positioning System or GPS. We put several of them out on the volcano. We record signals from satellites orbiting above the earth and we look for movement of one of the station with respect to the other.
As the ground deforms, the volcano changes its shape, those stations move; and that tells us something about what is going on beneath the surface.
Title: Volcano Monitoring Animations #1: Volcano Deformation
Moving magma can deform the surface of the Earth. This animation shows how a tiltmeter and GPS are used to detect the subtle signs that tell scientists something about what is going on beneath the surface.
Location: Vancouver, WA, USA
Date Taken: 1/1/2012
Video Producer: Jenda Johnson , U.S. Geological Survey-Cascades Volcano Observatory
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Additional Video Credits:
This animation was created for the Mount St. Helens Visitor Center in collaboration with the U.S. Geological Survey and the U.S. Forest Service. Animation by Jenda Johnson, narration by Dan Dzurisin, geologist, USGS-Cascades Volcano Observatory.
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