Deformation monitoring at Medine Lake volcano
When magma moves into a volcanic system, and closer to the surface of the earth, the area surrounding the volcano may move upward and outward. At Lassen Volcanic Center, this swelling is measured using the Global Positioning System (GPS).
Continuously recording GPS instruments are the most used type of volcanic deformation-monitoring equipment in the world. 24 satellites, orbiting the Earth twice each day, transmit their position in orbit to receivers on the surface of the Earth. The receivers record vertical and horizontal position, and by comparing these measurements through time, it is possible to determine the amount of movement for a specific location on the surface of the earth.
There are currently 3 GPS receivers that make up continuous deformation monitoring network at Medicine Lake volcano. The instruments were installed between 2005 and 2006. Ground surveys by USGS scientists show that the center of the volcano is slowly subsiding, due to motions on through-going regional faults and weakening of the rocks by high heat flow.