UNIVERSITY

OF NEVADA

RENO – University of Nevada, Reno seismologist John Louie and four other scientists have published new research suggesting southeastern Utah’s dramatic Upheaval Dome was created by a gigantic iron meteorite or icy comet that crashed to Earth as long as 90 million years ago.

Their article, "Seismic Reflection Study of Upheaval Dome, Canyonlands National Park, Utah," was published in the April 25 issue of the "Journal of Geophysical Research–Planets." Louie and article co-authors Z. Kanbur, S. Chavez-Perez, G. Plank and D. Morey explain that a 1995 geophysical survey across the circular dome indicates its severe upheaval was caused by an object that hit the area at about 25,000 miles per hour. The collision’s impact, the scientists say, blasted out a pit three miles in diameter that rapidly collapsed into a terraced crater with a central peak.

Upheaval Dome would be the largest impact structure that is easily identifiable in the western United States, Louie said. It is a popular scenic attraction within Canyonlands National Park.

"The first scientists who looked at Canyonlands 100 years ago thought it looked like other salt domes in the area," said Louie, who also teaches geophysics and geoscience classes at the university. "That’s certainly the simplest explanation. But what we’ve found is there’s no way to have salt involved in forming the dome. The impact blasted a hole that collapsed on itself and formed a central peak. Our surveys show the top of the salt layer underneath is flat right across the dome’s center and its flank."

Under a salt-formed dome hypothesis, the top of the underlying salt must deform to explain the upheaval. A vast deposit of salt accumulated more than a half-mile thick throughout the region 323 to 290 million years ago. In other areas near Canyonlands, the buoyant salt has broken through and uplifted the brittle overlying rocks, forming salt domes. But no salt appears within Upheaval Dome.

Former California Institute of Technology scientist and comet-tracker Eugene Shoemaker originated the impact hypothesis for the dome in 1983.

Louie was part of a 1995 scientific team that surveyed the area’s subsurface geology with seismic waves. Their seismic sections locate echoes from the top of the salt formation, much as how a medical sonogram locates organs in a patient. The National Aeronautics and Space Administration sponsored the research.

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