Walk across the loose rubble high on Utah's Mount Timpanogos and you'd never guess what's buried beneath your boots: an ice body the size of the Great Pyramid of Giza, frozen solid and hidden from sight. University of Utah scientists just brought that hidden world into sharp focus, and what they found is startling — the pile of rocks is actually 83% ice.
For years, hikers and researchers knew these "rock glaciers" dotted the mountains near Salt Lake City and Provo, but nobody could see inside them. Unlike the familiar gleaming glaciers we picture, rock glaciers look like ordinary heaps of broken stone that hide enormous stores of ice underneath. They're common across Utah's Wasatch and Uinta ranges, and they even appear near Moab on the Colorado Plateau.
That's where the mystery lay. Ice is far less dense than the solid rock around it, so it pulls on gravity slightly less. By hauling a state-of-the-art instrument called a gravimeter up the mountain in fall 2024, geology student Bronson Cvijanovich and his team took precise gravity readings at 232 points spaced 25 meters apart, woven into a grid above the ice. Each reading had to be corrected for the pull of the sun and moon, the terrain, latitude, and elevation. Then the team spent months of computing time to turn those numbers into a 3D picture, the same way a CT scanner sees bone and tissue inside a human body.
The result, published in two new studies led by Cvijanovich with geophysics professor Michael Thorne and glaciology professor Leif Anderson, is remarkable. Timpanogos Rock Glacier alone holds about 1.5 million cubic meters of frozen water — enough to fill 600 Olympic swimming pools, or to equal the volume of the largest pyramid at Giza. "Timpanogos Rock Glacier is surprisingly ice-rich. It is 83% ice and 17% loose rock," Cvijanovich said.
This matters far beyond one mountain. Utah's rock glaciers turn out to be crucial hidden reservoirs of water. "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." The second study revealed these stores are not leftovers from the last Ice Age, which peaked roughly 21,000 to 18,000 years ago, but younger reserves that formed over thousands of years as moving rockfalls buried persistent snow.
Timpanogos Rock Glacier is just one of 836 rock glaciers documented across Utah. Now that scientists have a proven way to see inside them, the question is how much more hidden water the state's mountains are holding — and what it means for communities that rely on every drop.