The find may help scientists better understand the formation of volcanic regions such as those in Iceland, Hawaii, and Yellowstone National Park.
(Read related story: "Supervolcano Raises Yellowstone, Fuels Geysers, Study Says" [March 1, 2006].)
One theory suggests that these areas are volcanic because hot spots deep within the Earth's interior melt the underlying rock like a giant blowtorch, producing large quantities of lava.
Wysession says that the presence of water may allow such hot spots to melt more rock, thereby creating more lava.
"If you add water [to the rock] you can get an increased amount of melting," he said.
"There's a consensus that not all hot spots are equal. Some are hot spots; some are wet spots."
Wysession and Lawrence report their findings in a study published by the American Geophysical Union.
A Look at Earth's Fate
The new study also reveals clues to Earth's long-term fate, says Norman Sleep, a geophysicist at Stanford University who was not involved in the project.
When the planet was young, steam came from the deep interior to the surface as volcanic gas and eventually produced today's oceans. But as Earth's interior ages and cools, it becomes easier for water to return below the surface.
"So, rather than degassing, now [Earth] may be losing water into the mantle," Sleep said.
This gradual suction of water back below the surface may be a good thing for Earth's geological stability, he notes.
Underground water acts as a kind of lubricant that allows plates in Earth's crust to keep shifting at their present rate, Sleep explains.
This helps keep the thickness and elevation of the continents relatively stable.
If things changed, he said, "we'd have Pike's Peak boat tours."
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