Home >> Science & Nature >> Nature

How Do Earthquakes Cause Volcanoes to Erupt?

In December 2008, University of Oxford scientists announced the existence of new evidence indicating that large earthquakes can induce activity at nearby volcanoes. Their conclusions, based upon an examination of records in southern Chile, indicated that four times as many volcanic eruptions take place during a one-year period after powerful earthquake events than during noneventful years. Prior to the release of the Oxford findings, scientists could not establish a link between ordinary earthquakes and volcanic activities.

Origins
- Common earthquakes and volcanic eruptions generally occur independently of one another and are induced by somewhat different phenomena. The theory of plate tectonics explains how and why the majority of earthquakes take place. Volcanoes serve as relief valves that reduce subterranean pressure through the release of molten rock called magma. Earthquakes can either accompany volcanic eruptions or indicate that such activity is imminent. They are not necessarily related to tectonic tremors however.
Plate Tectonics
- The Earth's outer crust consists of a series of continental and oceanic plates which are constantly in motion. Deep inside the crust, temperature variations bring about a type of rock convection that places stress upon the overlying plates, thereby inducing movement. Over time, the stresses derived from this movement deform brittle portions of the plates along their edges, resulting in the storage of huge amounts of energy. When the energy buildup supersedes the strength of the plate's fragile outer perimeters, earthquakes result.
Volcanic Eruptions
- Volcanic activity results from several unique subterranean occurrences. Spreading plate margin eruptions generally take place under the ocean when plates move away from one another and magma rises from deep below the ocean floor to fill in the gaps caused by plate or seafloor separation. Subducting plate margins are events during which one plate is pushed under another, thereby creating violent eruptions of lava. Intraplate volcanoes form above deep mantle plumes when a tectonic plate, which previously blocked the magma's access to the surface, moves away.
Connecting the Two
- The Oxford findings suggest that seismic waves radiating from earthquake epicenters may induce volcanic eruptions by shaking the molten lava that lies beneath volcanoes. The report further speculates that the amount of time required for pressure buildup and the subsequent flow of magma toward the surface following the original agitation might account for the time lag between the original earthquake and the resulting volcanic activity. After a large earthquake, the volcanoes most likely affected by its seismic activity generally lie within a 311-mile radius from the quake's epicenter. Such earth tremors can affect both active and inactive volcanoes.

Nature