Monitoring Volcano Ground Deformation and Seismicity

Pictured above: Earth scientists employing an electronic distance meter that uses lasers to measure changes in the Earth's shape.

Magma and volcanic gas must first force their way up through shallow underground fractures and passageways before an eruption, generally producing earthquakes. Therefore, seismic activity beneath a volcano almost always increases and the volcano's surface often changes shape preceding volcanic activity. A variety of methods are used to monitor a volcano's deformation and seismicity. Whatever the method, our goal is the same: to determine the changes occurring at a volcano that help us provide eruption warnings and to understand how volcanoes work.

Pictured above: A USGS scientist installing a Global Positioning System (GPS) receiver.

Precise Measurements:

Hawai`i Volcanoes National Park: USGS monitors ground deformation and seismicity at Kilauea, the world's most active volcano. During a brief eruptive episode of Kilauea Volcano that began on January 30, 1997, continuously recording GPS receivers measured significant ground deformation near the eruption site

Pictured above: Lava fountains erupting at Kilauea Volcano.

Regional Changes in Elevation:

Satellite interferometric synthetic aperture radar (InSAR) measures deformation over large regions such as the Yellowstone Caldera.

Monitoring Ground-shaking:

Seismometers detect patterns of ground-shaking. Different geologic events generate unique patterns. The red lines in the figure illustrate representative patterns that we can learn to recognize and identify. The patterns in this figure represent seismic events at Mount Rainier.