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Deformation monitoring at Mount Rainier, using helicopter and EDM.
-- USGS Photo by Lyn Topinka, September 12, 1983

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USGS Spirit-Level tilt measurements at Mount Rainier. Using a triangular system of benchmarks, changes in the ground surface are recorded.
-- USGS Photo by Lyn Topinka, 1983

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Establishing baselines, deformation monitoring, Newberry Caldera.
-- USGS Photo by Lyn Topinka, August 20, 1985

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Global Positioning System (GPS) receiver at Cotopaxi Volcano, Ecuador. GPS uses data transmitted by orbiting satellites to locate points on the ground. The USGS has made baseline GPS measurements at several volcanoes in the United States and in Latin America. In the event of an awakening of one of these volcanoes, GPS receivers would be set up at these points again to determine whether or not measurable deformation had occurred and to monitor for precursory deformation that might herald an eruption.
-- USGS Photo by J. W. Ewert

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A "bulge" developed on the north side of Mount St. Helens as magma pushed up within the peak. Angle and slope-distance measurements to the bulge indicated it was growing at a rate of up to five feet (1.5 meters) per day. By May 17, part of the volcano's north side had been pushed upwards and outwards over 450 feet (135 meters). The view is from the northeast.
-- USGS Photo by Peter W. Lipman, April 27, 1980

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The U. S. Geological Survey has established both periodic and continuous 24-hour monitoring programs of Mount St. Helens to study and predict eruptions. In this slide, geologists use a steel tape to measure the distance across a crack on the crater floor. Widening of cracks is an indication that magma is rising and deforming the area, leading to an eruption. These cracks are generally radial to the dome, like spokes of a wheel.
-- USGS Photo by Lyn Topinka, May 12, 1981

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Geologists use a theodolite and EDM (Electronic Distance Meter) to measure angles and slope-distances to the lava dome. Changes in these angles and distances are used to calculate "deformation rates". An increase in deformation rates is an indication that magma is slowly entering the dome. Deformation rates often reach 30 feet per hour (10 m/hr) as magma rises and the dome expands before extrusion starts. During the winter months, the instrument stations often have to be dug out of the snow before measurements can be made.
-- USGS Photo by Lyn Topinka, May 26, 1984

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Geologists measure the strength of the magnetic field surrounding the dome. The strength of the field increases as the dome cools and magnetic minerals form. During the eruptions the strength usually changes rapidly as magma heats and deforms the dome.
-- USGS Photo by Lyn Topinka, June 18, 1984

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Geologists do precise leveling to measure changes in the slope of the crater floor, due to moving magma. Changes in slope are also measured electronically by tiltmeters. Tiltmeters allow 24-hour monitoring as the information is telemetered back to CVO. Other instruments such as displacement meters for measuring cracks, seismometers for measuring earthquakes, gas sensors for measuring gas concentrations, and magnetometers for measuring the magnetic field, are also used for 24-hour monitoring.
-- USGS Photo by Holly Martinson, May 1982

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In 1983, the U. S. Geological Survey extended both its periodic and its 24-hour monitoring programs to the top of Mount St. Helens' dome. In this aerial view, three geologists (middle bottom) are busy taking measurements to determine deformation rates.
-- USGS Photo by Lyn Topinka, April 18, 1988

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The U. S. Geological Survey also maintains a network of monitoring stations around the base of Mount St. Helens. Angle and distance measurements to the volcano's flanks are taken periodically to watch for any deformation similar to the 1980 bulge. Pictured here is an instrument station northeast of the volcano.
-- USGS Photo by Lyn Topinka, May 15, 1989

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Geologists use a theodolite and EDM to measure angles and slope-distances from Harrys Ridge (5 miles to the north) to Mount St. Helens crater and lava dome, 1981
-- ISGS Photo by Lyn Topinka, October 31, 1981

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Geologists measure angles and slope-distances from Harrys Ridge (5 miles to the north) to Mount St. Helens crater and lava dome, 1984
-- ISGS Photo by Lyn Topinka, March 22, 1984

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