Tracking Magma on the Move

A network of seismometers on Hawaii's Kilauea volcano is producing an unprecedented picture of the plumbing beneath the mountain. Seismologists have developed a technique that reveals the subterranean sloshing of magma in practically real time, providing clues that could help predict eruptions.

To track magma moving beneath a volcano primed to erupt, geologists typically have to rely on indirect measures, such as shock waves from rock that's fractured as magma shifts the overlying volcano . These small earthquakes reveal that magma is on the move, but without much precision. So a team of seismologists led by Phillip Dawson of the U.S. Geological Survey in Menlo Park, California, developed a new technique that quickly locates moving magma on a map of the volcano's insides.

The team used a network of 10 broadband seismometers that can detect very low frequency vibrations. Standard seismometers are only sensitive to faster events such as rock fracturing. But the broadband sensors can detect the slow signals created by flowing magma. These signals reach each sensor at a slightly different time, and a computer uses these time differences to calculate the magma's location and direction of movement. The calculations take just a few minutes, allowing scientists to track the magma in near real time. After a brief pause in eruption activity at Kilauea in March, Dawson's team tracked the renewed magma movement, which revealed a maze of conduits, much more complex than expected. The results were published online 5 November in Geophysical Research Letters.

The team is also working on networks on Stromboli in Italy and Popocatépetl in Mexico, and they say similar networks could be deployed at other hazardous volcanoes, such as Mount St. Helens, to improve predictions of eruptions. But there is likely to be debate about how useful it will be for monitoring other volcanoes, says volcanologist Jackie Caplan-Auerbach of the USGS Alaska Volcano Observatory. "This is a huge step forward in terms of understanding the structure of volcanoes, but I think it's premature to suggest it's the next step for crisis management," she says. "I just don't know if that's what we need to tell whether a volcano is going to blow its top."

Related sites
Hawaiian Volcano Observatory
Alaska Volcano Observatory