Scientists say the central region of Yellowstone National Park is rising. The area is dubbed the Yellowstone caldera and has been moving upward since 2004 at a rate of up to three inches a year.

"Our best evidence is that the crustal magma chamber is filling with molten rock," said Robert B. Smith, a professor of geophysics at the University of Utah, in a statement. "But we have no idea how long this process goes on before there either is an eruption or the inflow of molten rock stops and the caldera deflates again."

The good news is that there is no evidence of an imminent volcanic eruption, Smith says. That's great news for the Park, because the volcano at Yellowstone's center produced massive eruptions 2 million, 1.3 million and 642,000 years ago, all larger than the 1980 eruption of Mount St. Helens.

The research, which shows a threefold increase in the speed the Yellowstone caldera is rising each year, appeared in today's Science. The paper by Smith and his colleagues attempts to explain the phenomenon using a combination of the composition of the caldera and computer modeling. At the center of his theory is that there is a large magma plume that comes near the surface through a weak point in the continental plate.

"It's really kind of a sponge, where you have interlaced open spaces with magma and solid rock between. Only 10 percent [of the chambers are] actually made up of molten rock," Smith said.

The volcano underneath Yellowstone National Park is watched 24/7 by the Yellowstone Volcano Observatory, which is jointly administered by the University of Utah, the U.S. Geological Survey, and Yellowstone National Park.

Yellowstone National Park is the United States' first national park. It spreads across 2,219,789 acres in Wyoming, Montana and Idaho. Yellowstone is the centerpiece of the Greater Yellowstone Ecosystem, believed to be the largest remaining, nearly-intact ecosystem in the Earth's northern temperate zone. Hundreds of species of mammals, birds, fish and reptiles have been documented here, including several that are either endangered or threatened.