Unlike conventional glaciers, rock glaciers appear as piles of rock that obscure large masses of unaccounted-for ice. Rock glaciers are common in the Wasatch and Uinta ranges, even appearing on the Colorado Plateau in the La Sal Mountains near Moab.
Now, University of Utah geologists are bringing one of Utah’s largest rock glaciers, located under the towering, iconic summit of Mount Timpanogos near Salt Lake City and Provo, into sharp focus. Two new studies document how Timpanogos Rock Glacier formed and how much ice it contains. By measuring minute differences in gravitational pull between rock and ice, the team created a novel technique to image the 3D ice body within a large rock glacier.
Timpanogos Rock Glacier stores enough frozen water to fill 600 Olympic swimming pools or 1.5 million cubic meters. That is also equivalent to the volume of the largest pyramid at Giza in Egypt, according to Bronson Cvijanovich, a former graduate student in the Department of Geology & Geophysics.
“Timpanogos Rock Glacier is surprisingly ice rich. It is 83% ice and 17% loose rock, said Cvijanovich, the lead author of one of two studies overseen by geophysics professor Michael Thorne and glaciology professor Leif Anderson.
The ice hiding under our feet
“There’s a lot of ice that’s hidden in Utah’s mountains,” Anderson said. “When we are high in the mountains and walking across loose rocks or rubble, you don’t realize there could be 120 feet of ice buried beneath your feet.”
Timpanogos Rock Glacier was selected for study because of its easy access from a trailhead and long history of what was known as “Timpanogos Glacier,” really a rock glacier the whole time. Still, it’s a five-mile hike in with an elevation gain of 3,500 feet.
Cvijanovich led field campaigns to Timpanogos Rock Glacier hauling sensitive instruments, including a state-of-the-art gravimeter, to the ice buried above Emerald Lake in the fall of 2024. Over the course of six forays, Cvijanovich took gravity readings at 232 spots, separated by 25 meters (~80 feet) in a grid atop the rock glacier. In 2026, Cvijanovich completed his master’s degree at the U and now works as a field gravimetry technician for a Utah geothermal company.
The gravimeter measures density differences between rock and ice, enabling scientists to calculate the 3D shape of the buried ice body. “There is a large contrast in mass density between the rock that makes up Mount Timpanogos and the much lower density ice that is in the rock glacier adjacent to it,” Thorne said. “When we measure the gravitational acceleration over the rock glacier, we see a larger decrease in that gravitational acceleration as we make measurements over areas with thicker ice.”
Once the gravity observations were collected, they still needed to be corrected for differences in gravity due to the position of the sun and the moon, the location’s terrain, latitude, and elevation. After these corrections, the research really broke new ground. The team developed a novel method for imaging the internal ice of the rock glacier in 3D using Bayesian statistics. “We spent months of computation time doing the imaging with our new techniques,” Thorne said.