The lava dome at Mount St. Helens grew episodically between October 1980 and October 1986, and throughout this period, many techniques and procedures were established to help monitor, study, and predict dome-building episodes. These included measurement of displacements on radial cracks and thrust faults on the crater floor and dome, leveling the crater floor, and repeated occupation of trilateration and distance-measuring networks on the crater floor and dome. Displacement meters were also installed to continually monitor radial cracks on the crater floor and dome. Distance-measuring networks became one of the most reliable methods used for predicting dome-building episodes. New and old methods have been adopted to establish and measure such networks. The use of both distances and angles has allowed us to locate stations in a coordinate system that offers a three-dimensional view of ground deformation in the crater.
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