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Yellowstone Supervolcano Swelling Mysteriously

Larry O'Hanlon, Discovery News

The rising heat from that blob, plus the upward flow of some molten materials, are the most likely explanation for the swelling surface, as detected by a network of Global Positioning System stations in the park.

Smith said he hopes that a recent gravity survey -- conducted on a shoestring budget -- will help them sort out exactly what is moving, and where, underground. Gravity measurements allow geologist to detect how masses change underground by the tiny changes in gravity at any given spot on the surface.

And even though there is no mountain of magma about to erupt, the study of Yellowstone is central to understanding caldera-type "supervolcanoes" worldwide, said geologist David Hill of the U.S. Geological Survey in Menlo Park, Calif. Hill's job is to monitor California's version of Yellowstone -- the Long Valley Caldera east of Yosemite National Park.

"Any time we see one of these unrest episodes we learn about the processes that drive it," said Hill. For instance, calderas have been known to rise nearly several feet without erupting, he said. "That's a lot more uplift than we see before eruption on central vent volcanoes," he said, referring to the deadly blasts from single-maw volcanoes like Vesuvius, Pinatubo or St. Helen.

Calderas, by comparison, cover a lot more ground than central-vent volcanoes and have many vents from which they could pour ash and lava, said Hill. As a result, even a relatively small eruption from a caldera is much harder to predict and plan for because it's hard to know where in the caldera the magma will burst out.

Related Links:

Larry O'Hanlon's blog: Earth Impacts

What's Under a Supervolcano