A tale of two theories
In a region defined by the orderly layers of sedimentary rock, Upheaval Dome is a chaotic anomaly. This circular structure, roughly 5 kilometers (3 miles) across, disrupts the flat-lying geology of Canyonlands National Park. At its center, older rock layers like the Permian Organ Rock Shale and White Rim Sandstone are violently pushed upwards, surrounded by a ring-like syncline, or a downward fold, of younger Jurassic rocks. For decades, geologists proposed two main explanations for this peculiar formation.
The first theory suggested Upheaval Dome was a "pinched-off" salt dome. Deep beneath southeastern Utah lies a thick layer of salt from the Paradox Formation, deposited during the Pennsylvanian period. This salt, being less dense than the overlying rock, can flow upwards over millions of years, creating a dome-like structure that deforms the surrounding rock layers. Proponents of this hypothesis argued that the original salt bubble and overlying rock had completely eroded away, leaving the structure seen today as the deeply eroded stem. This process would have taken up to 20 million years of moderate pressure.
Evidence for impact
The second theory proposed a more violent and sudden origin: the impact of a meteorite. This hypothesis suggests that an object about half a kilometer (one-third of a mile) in diameter struck the Earth here roughly 60 million years ago. The impact would have created a transient crater which quickly collapsed. During this collapse, the crater floor rebounded to form the central peak, thrusting up older rocks from deep below the surface.
For a long time, definitive evidence for either theory was missing due to extensive erosion that has removed the original crater floor and any potential meteorite fragments. The debate continued until German scientists Elmar Buchner and Thomas Kenkmann made an important discovery. In 2008, they published findings of shocked quartz in samples taken from the Jurassic Kayenta Formation within the dome. Shocked quartz has a microscopic structure with planar deformation features (PDFs) that can only be formed by the extreme, instantaneous pressures of a meteorite impact, estimated to be around 10 gigapascals in this case. This discovery, along with the presence of shatter cones, conical rock fractures also showing high-pressure events—provided evidence that Upheaval Dome is an eroded complex impact crater.