For the first time, scientists have watched magma move through a volcano before it erupts in fountains of ash and lava.
Using imaging methods similar to those employed in medical CT scans, researchers tracked the flow of magma in Italy's Mount Etna, which towers nearly 11,000 feet (3,350 meters) above the island of Sicily (map of Italy).
The scan, which detected areas rich in gases that produce explosive eruptions, may become a powerful tool for eruption prediction.
Scientists used 45 seismic stations positioned on the slopes of Etna to take measurements of the intermittently active volcano.
These seismic stations recorded more than 2,500 earthquakes during an 18-month interval that included one unusually violent eruption in 2002.
(Related story: "Etna Volcano Becoming Dangerous, Experts Warn" [February 6, 2003].)
The seismic waves from such earthquakes can be used to produce detailed three-dimensional images of a volcano's interior, seismologist Domenico Patanè of Italy's National Institute of Geophysics and Volcanology in Catania said in an email.
Patanè is lead author of a study that used the quake readings to make before-and-after maps during the 18-month period. The research will appear in tomorrow's issue of the journal Science.
3-D Image
The maps show the mountain's interior down to depths of three miles (five kilometers).
Such maps can be made, Patanè says, by comparing the speed with which seismic waves reach each of the stations. Different speeds mean waves are traveling through different types of rock.
This imaging technique had never before been applied to an erupting volcano.
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