Utah's Hidden Ice: Scientists Discover 1 Billion Tons Beneath Rock Glaciers

High in Utah's mountains, beneath loose rock and rubble that crunches underfoot, lies something most hikers will never see: a billion tons of ice. Not the gleaming white glaciers of postcards, but something far more hidden—rock glaciers, strange hybrid landforms where massive sheets of ice lie entombed under a dense armor of stone and boulders. A new study published in the Journal of Geophysical Research: Earth Surface has found a way to measure what was previously invisible, and the numbers are staggering.

Rock glaciers exist worldwide. More than 51,000 have been documented globally, with over 10,000 in the United States alone. They are common enough that scientists have long known they exist, yet common enough that most people have never heard of them. The challenge has always been the same: how do you measure ice you cannot see? Conventional ground-penetrating radar, the tool that works well for ordinary glaciers, fails here. The rocky debris mixed throughout the ice scatters radio waves and destroys image quality, leaving the ice's true volume a mystery.

Leif Anderson, a glaciologist at the University of Utah, and his team found another way. Instead of trying to see through the rock, they measured gravity. A gravimeter detects the subtle differences in gravitational pull created by objects of different densities buried underground. Ice is far less dense than the rock that makes up a mountain. When researchers took 232 measurements across Timpanogos Glacier at the base of Mount Timpanogos, the gravimeter revealed where the ice was thickest by showing where gravitational acceleration decreased most noticeably. Michael Thorne, a geophysicist on the team, explained the principle simply: the contrast in mass density between mountain rock and glacier ice creates a measurable gravitational signature.

Using those measurements, the researchers built a three-dimensional model of the glacier's internal structure through Bayesian statistics and computational modeling. What they found was striking. Timpanogos Glacier is roughly 83 percent ice and 17 percent rocky debris by volume. The ice averages 18.8 meters thick—about 62 feet—across the entire formation. In total, the glacier contains approximately 1.5 million cubic meters of ice, a volume equivalent to the Great Pyramid of Giza or roughly 600 Olympic swimming pools. In weight, that translates to about 1.4 million tons of ice hidden beneath the rocky surface.

But Timpanogos Glacier is just one formation. Using their findings as a template, the researchers developed a method to estimate ice volume in rock glaciers based on surface area measurements alone. They applied this approach to Utah's 836 documented rock glaciers and arrived at a figure that reframes how we think about water storage in the American West: approximately one billion tons of ice across the entire state. The western United States holds nearly 12 billion tons. Globally, rock glaciers contain about 48 billion tons of ice—a vast reservoir of frozen water that has been hiding in plain sight.

The discovery matters because rock glaciers are not stable. As climate change warms the mountains, these formations can destabilize and shift, potentially releasing water downstream or creating hazards for infrastructure built in their shadow. Understanding how much ice they contain, where it is located, and how it is structured becomes essential for predicting water availability, managing ecological impacts, and preparing for potential dangers. The researchers note that as conventional glaciers respond to warming and transition into debris-covered forms and eventually rock glaciers, the need to measure and model these features will only grow more urgent. For the first time, scientists have a reliable tool to do it.