Factors Behind Frequency and Magnitude of Volcanic Eruptions Revealed

Scientists have shed new light on volcanic activity. They found the factors behind determining the frequency and magnitude of volcanic phenomena, which could help predict and better understand eruptions in the future.

Volcanic eruptions may be frequent, but their size is notoriously hard to predict. For example, the Stromboli volcano in Italy ejects magma every ten minutes and would take two days to fill an Olympic swimming pool. Yet the last super-eruption of a volcano, which occurred over 70,000 years ago, spewed enough magma to fill a billion swimming pools. Needless to say, it's crucial to better understand how volcanoes function.

In order to find that out, the scientists used numerical modeling and statistical techniques to identify the circumstances that control the frequency of volcanic activity and the amount of magma that will be released. In all, the researchers carried out over 1.2 million simulations to establish the conditions in which volcanic eruptions of different sizes occur.

So what did they find? Different size eruptions have different causes. For example, small, frequent eruptions are known to be triggered by a process called magma replenishment, which stresses the walls around a magma chamber to a breaking point. Larger, less frequent eruptions, though, are caused by magma buoyancy, which is driven by the slow accumulation of low-density magma beneath a volcano.

"Some volcanoes ooze modest quantities of magma at regular intervals, whereas others blow their tops in infrequent super-eruptions," said Jon Blundy, one of the researchers, in a news release. "Understanding what controls these different types of behavior is a fundamental geological question. Our work shows that this behavior results from interplay between the rate at which magma is supplied to the shallow crust underneath a volcano and the strength of the curst itself. Very large eruptions require just the right (or wrong!) combination of magma supply and crustal strength."

The findings are published in the journal Nature Geoscience.