Utah
Not all the weird and wonderfully strange rock formations in Utah’s canyon country have consensus on their geological beginnings. One such enigma is Upheaval Dome, in the northern section of Canyonlands National Park. It could be an oddly eroded salt dome—or it could be a meteor impact crater. And the overhead perspective of this rounded, roughly circular curiosity offers few clues to its origin, revealing elements of both a crater and an upswell.
Located in the high-elevation Island in the Sky district of Canyonlands National Park, Upheaval Dome features colorful concentric rings that stand out in a sea of carved sandstone. In the center, the rocks are shaped into a convex dome, or anticline, while the sides sweep into a downwarp called a syncline, with the whole structure measuring an impressive three miles across. What could have caused these unusual folds in the rock?
There are two competing theories regarding Upheaval Dome’s creation. The first is the salt dome theory. Much of Canyonlands National Park and southeastern Utah is underlain by a thick layer of salt, formed during the Cretaceous Period, when this region was inundated by shallow seas. Under pressure, salt deposits can behave strangely, flowing like slow-moving water or glacial ice. Salt is less dense than sandstone and over time, it can rise through the layers, deforming the overlying rock into a dome at the surface.
The oldest rocks are exposed in the center of Upheaval Dome, with the youngest rocks at the sides, a structure that could support the salt dome theory of formation.
Enigmatic Upheaval Dome lies east of the Green River in the northern unit of Canyonlands National Park.
Two competing theories of how Upheaval Dome formed could both produce similar structures on the surface.
But while the salt dome theory is a perfectly reasonable explanation for how such an odd formation could develop here, some geologists think that more exotic forces created the concentric rings—Upheaval Dome could also be the highly eroded crater left by a meteor impact.
Based on the age of the layers in the dome and the pattern of erosion, geologists estimate that a meteorite about 1000 feet in diameter may have hit the site between 100 million and 60 million years ago. This impact could have created an unstable crater in the relatively soft rock that may have partially collapsed in on itself. When violent impacts occur, the rocks at the center of the impact zone sometimes rebound into a dome shape because of the rapid expansion of superheated rocks.
Most of the scientific studies that have been conducted at the dome in recent years seem to support the meteor impact theory, including seismic refraction and detailed mapping of the rock layers. In 2008, a team found samples of shocked quartz near the dome, suggesting that the rocks had been subjected to the kind of extreme conditions created only by a large impact.
You could view Upheaval Dome on a scenic flight out of Moab, Utah. Look for concentric rings in a sea of canyon-carved sandstone.
