It may be possible to sniff out a soon-to-erupt volcano, according to Chinese scientists Chih-Chieh Su and Chih-An Huh. They have evidence that the air downwind of a volcano that?s ready to blow is laced with a distinctive radioactive gas.
The researchers measured high levels of radioactive polonium-210 in the air at Nankang in Taiwan several days and weeks before three eruptions of the Mayon volcano in the Philippines in June 1999 and early January and late February 2000.
The pair think that Mayon caused the polonium-210 surges north in Nankang. The prevailing winds were northward at these times, bringing air from the Philippines to Taiwan. High levels of polonium-210 have also been detected in volcanic emissions preceding other major volcanic eruptions, such as those of Mount St. Helens in Washington state in 1980 and El Chichon in Mexico in 1982.
Polonium-210 is formed by the radioactive decay of the gas radon-222, small amounts of which are dissolved in volcanic magma. Su and Huh think that volcanic emissions are responsible for much of the polonium that?s found in the atmosphere.
They suggest that the polonium-210 bubbles out of fresh magma, and leaks through cracks and pores in the rock until it escapes from a volcano. If they?re right, a pulse of polonium-210 could indicate that the chamber has been newly replenished with fresh magma, which can trigger an eruption.
In the atmosphere, polonium-210 is absorbed by tiny airborne dust particles that are flushed out of the air by rainfall. The researchers think that scientists should collect rainwater downstream of active volcanoes and analyze it to anticipate eruptions. With the worldwide increase in volcanic eruptions during the past few years, this technique could be invaluable.
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The ground near the long-dormant Three Sisters volcano in the central region of Oregon?s Cascade Mountains has risen approximately 4 inches in a 6 by 12 mile area since 1998, meaning that magma, underground lava, has flowed into the area, according to geologist Charles Wicks Jr. of the U.S. Geological Survey. ?It hasn?t erupted in about 1,500 years, so it?s a truly dormant volcano. Yet there?s something going on there,? says Wicks.
?Right now in the Cascades, the only volcano that we know is restless is Three Sisters, based on the deformation,? says fellow researcher Daniel Dzurisin of the USGS Cascade Volcano Observatory in Vancouver, Washington.
They say it?s far too early to tell if this swelling and movement of magma means a volcanic eruption is on the way. It might simply ?freeze out,? says Wicks, meaning the magma flow might simply stop.
The groundswell was observed by satellite radar images, which is a new technique. Dzurisin says, ?We now have a tool that allows us to see this kind of deformation around volcanoes, which we?ve suspected for a long time. But in the past we haven?t been able to observe it unless there was accompanying seismicity.? This refers to the earthquakes that occur when the magma breaks through the rocky crust prior to eruptions. Such quakes are often a warning of an impending eruption.
?As far as I know this type of observation hasn?t been made any other place. We don?t know if this type of uplift occurs fairly frequently at similar types of places around the world. This type of thing may be relatively common, but we don’t know,? says Stephen Malone, of the University of Washington. Geologists are installing seismometers in the area to monitor for earthquakes.
While the Three Sisters is only about 70 miles from Mt. St. Helens, which erupted in 1980, there is no direct physical connection between the two. The Cascades are volcanic because the Pacific tectonic plate slides under the North American plate and is melted by the heat of the Earth?s interior, producing magma that rises to the surface.
?Ultimately the goal is mitigate volcanic hazards, and the way we can do that is to understand the processes that lead up to eruptions better,? says Dzurisin. ?We hope that by being able to see ground deformation like this we might be able to extend the warnings that we might give.?
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