Rock glaciers look very different from conventional glaciers. Instead of exposed ice, they resemble sprawling fields of loose rock, while potentially concealing large quantities of ice below the surface. These formations are widespread across Utah’s Wasatch and Uinta ranges and can also be found on the Colorado Plateau in the La Sal Mountains near Moab.
University of Utah geologists have now taken a detailed look inside one of the state’s largest examples, the Timpanogos Rock Glacier beneath the prominent summit of Mount Timpanogos near Salt Lake City and Provo. Two new studies examine how the glacier formed and reveal how much ice is buried inside it. By detecting extremely small differences in the gravitational pull of rock and ice, the researchers developed a new way to create a 3D image of the hidden ice within a large rock glacier.
The results show that Timpanogos Rock Glacier contains about 1.5 million cubic meters of frozen water, enough to fill roughly 600 Olympic swimming pools. Bronson Cvijanovich, a former graduate student in the Department of Geology & Geophysics, noted that this is also about the same volume as the largest pyramid at Giza in Egypt.
“Timpanogos Rock Glacier is surprisingly ice rich. It is 83% ice and 17% loose rock,” said Cvijanovich, lead author of one of the two studies overseen by geophysics professor Michael Thorne and glaciology professor Leif Anderson.
Hidden Ice Beneath Mount Timpanogos
“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.”
During the fall of 2024, Cvijanovich led a series of field trips to Timpanogos Rock Glacier, carrying sensitive equipment to the buried ice above Emerald Lake. Among the instruments was a state-of-the-art gravimeter. Across six trips, he collected gravity measurements at 232 locations arranged in a grid across the glacier, with each point separated by 25 meters (~80 feet).
A gravimeter can detect differences in density, allowing researchers to distinguish the denser surrounding rock from the much lighter buried ice. Those measurements can then be used to estimate the shape and thickness of the hidden glacier.
“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 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.”
Building a 3D View With Gravity
Collecting the gravity data was only the first step. The researchers also had to account for subtle changes caused by the positions of the sun and the moon, as well as differences in terrain, latitude, and elevation.
After making those corrections, the team developed a new method for reconstructing the glacier’s internal ice in three dimensions using Bayesian statistics. “We spent months of computation time doing the imaging with our new techniques,” Thorne said.
Satellite images can show the surface footprint of a rock glacier, but they provide much less information about its depth, internal structure, and total amount of buried ice. Measuring those features requires instruments capable of revealing what lies beneath the rubble, similar to how a CT scanner can reveal bones and tissues inside the human body.
How Utah’s Rock Glaciers Form
Rock glaciers commonly develop beneath steep mountain valleys or cirques where falling debris regularly collects. In the Wasatch Mountains, that falling material appears to play a key role in protecting snow from melting.
“In the Wasatch, the mountains themselves are eroding and burying the snow, and that’s why the rock glaciers exist,” Anderson noted.
The researchers developed a new mathematical model describing how these glaciers grow. Their results suggest that rockfalls repeatedly cover persistent snow in the upper sections of rock glaciers, adding mass and helping preserve the snow beneath layers of debris.
The second study also indicates that Utah’s rock glaciers are not leftover features from the Ice Age (which reached its peak 21,000 to 18,000 years ago). Instead, they are reservoirs of frozen water that developed during the thousands of years after the major Ice Age glaciers disappeared.
A Potentially Huge Mountain Water Reserve
Timpanogos Rock Glacier is one of 836 rock glaciers identified across Utah through satellite imagery. Using the detailed measurements from Timpanogos, the researchers established a relationship between a rock glacier’s surface area and the volume of ice stored underneath it.
They then applied that relationship more broadly. Their calculations suggest that the roughly 50,000 known rock glaciers around the world could collectively contain about 48 gigatons of water. Equal to 1 billion metric tons, a gigaton is the equivalent of a cubic kilometer of water, enough to fill 400,000 Olympic swimming pools.
Within Utah alone, rock glaciers may contain about 1 gigaton of water, or approximately 815,000 acre-feet, according to the researchers.
Two Studies Examine Utah’s Hidden Ice
The research titled “The internal ice content of Timpanogos Rock Glacier, Utah, USA from 3-D Bayesian inversion of gravity data,” was published Aug. 26 in the Journal of Geophysical Research.
The earlier paper, “Mass Addition to Timpanogos Rock Glacier: Debris‐ Covered Snow and the Importance of Interannual Variability in Headwall Erosion and Climate,” appeared in Geophysical Research Letters on April 2, 2026. Isaiah Davies, an undergraduate at Stanford University and visiting summer researcher at the University of Utah in 2023, was the lead author.
The research was supported by the U.S. Geological Survey, National Science Foundation, University of Utah’s Wilkes Center for Climate Science & Policy, the U’s Office of Undergraduate Research, and the Summer Program for Undergraduate Research.