Earthquakes often occur in volcanic regions and are caused there , both by tectonic faults and the movement of magma in volcanoes . Such earthquakes can serve as an early warning of volcanic eruptions , as during the 1980 eruption of Mount St. Helens . Earthquake swarms can serve as markers for the location of the flowing magma throughout the volcanoes . These swarms can be recorded by seismometers and tiltmeters ( a device that measures ground slope ) and used as sensors to predict imminent or upcoming eruptions
1980 eruption of Mount St. Helens
1980 eruption of Mount St. Helens
Earthquake