The Stromboli Volcano in Italy has been erupting every five to 20 minutes for thousands of years. New research calls into a question a theory scientists have used to explain the frequent eruptions. (Credit: U.S. Geological Survey)

ScienceDaily (July 29, 2010) — Understanding the processes that cause volcanic eruptions can help scientists predict how often and how violently a volcano will erupt. Although scientists have a general idea of how these processes work — the melting of magma below the volcano causes liquid magma and gases to force their way to Earth's surface — eruptions happen so rarely, and often with little warning, that it can be difficult to study them in detail.

One volcano that volcanologists believe they understand fairly well is Italy's Stromboli, which has been erupting every five to 20 minutes for thousands of years, spewing fountains of ash and magma several meters into the sky. For several decades, scientists have pretty much used one theory to explain what is causing huge amounts of gas to erupt so frequently: swimming-pool-sized bubbles that travel through a few hundred meters of molten magma before popping at the surface.

But they may be wrong, according to new research by Jenny Suckale, a graduate student in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS), who has developed a sophisticated computer model to simulate Stromboli's magma flow. In a two-paper series published July 20 in The Journal of Geophysical Research, Suckale suggests that giant gas bubbles can't be driving the Stromboli eruptions because such bubbles aren't compatible with the basic laws of fluid dynamics, or the science of how fluids move. Instead of large bubbles that pop at the top of Stromboli's conduits — pipelike openings that connect the volcano's magma chamber to the Earth's surface — Suckale thinks that the eruptions are caused by a spongelike plug located within the conduit, similar to a cork in a champagne bottle, that fractures every few minutes as a result of pressure created by significantly smaller bubbles.

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