SALT LAKE CITY -- A 17-year U.S. study shows the power of the huge volcanic hotspot beneath Yellowstone National Park is much greater than thought.

The $2.3 million, 1987-2004 University of Utah study revealed the approximately 300-mile-wide underground plume of molten rock known as the Yellowstone hotspot exerts itself forcefully even when not triggering eruptions and earthquakes.

"The Yellowstone hotspot has had a much bigger effect over a larger area with more energy than ever expected," said University of Utah geophysics Professor Robert Smith, who led the study.

"We're seeing large-scale deformation of the Earth's crust in the western United States because of the effects of the Yellowstone hotspot," added Christine Puskas, a geophysics doctoral student and the study's first author.

The research -- conducted by Smith, Puskas, postdoctoral fellow Wu-Lung Chang and former Utah researcher Chuck Meertens -- focused on the Yellowstone caldera, a gigantic volcanic crater formed by a catastrophic eruption 642,000 years ago that was 1,000 times bigger than the 1980 eruption of Mount St. Helens.

The research is to appear in the March 2 issue of the Journal of Geophysical Research -- Solid Earth.