Scientists Discover Hidden Ice Reservoir Buried Inside Utah Rock Glacier

Hikers climbing toward Mount Timpanogos in Utah have walked past it for generations: a lumpy pile of rubble sitting in a bowl-shaped basin below the peak. Locals often mistake the patches of snow around it for a glacier, but the real story is buried underneath. Scientists have now mapped just how much ice is hiding beneath the debris: a block big enough to fill roughly 600 Olympic-sized swimming pools, sitting quietly under the rubble and creeping slowly downhill.

Geologists call this kind of landform a rock glacier, a glacier hiding in disguise. A thick blanket of loose rock and rubble covers the ice underneath, insulating it from the sun and heat in a way that lets it survive in places where a regular glacier could never last. That insulating layer of rock is exactly why scientists have struggled for decades to figure out how much ice these things actually hold. A research team from the University of Utah and the Utah Geological Survey decided to find out using a clever trick: measuring tiny variations in gravity across the landform to map what’s hiding below the surface. Their findings appear in the Journal of Geophysical Research: Earth Surface.

What they found at Timpanogos Rock Glacier was hard to ignore. The ice-rich core beneath the rocks stretches 30 to 45 meters thick (about 100 to 150 feet) down the center of the landform, deepening to as much as 55 meters near its lower end. Altogether, the researchers estimate the rock glacier holds about 1.55 million cubic meters of ice. That single, mid-size rock pile in a Utah mountain basin holds a real water reserve, one that’s been mistaken for scenery for a century.

How Scientists Mapped a Rock Glacier’s Ice Without Digging

Rock glaciers are hard to study because the usual tools scientists use to see inside ice, like radar, get scrambled by all the loose rock mixed throughout. So the team tried something different: a highly sensitive gravity meter, a device that can detect tiny changes in the pull of gravity from one spot to the next.

Ice is less dense than solid rock, so a patch of ground sitting on top of a thick ice body will register a slightly weaker gravitational pull than a patch sitting on solid bedrock. Between August and October of 2024, researchers walked across Timpanogos Rock Glacier and its surroundings, taking 232 separate gravity readings roughly 25 meters apart, wherever the terrain allowed the instrument to be set up and leveled. They also collected rock samples from the surface debris to measure its density, and used GPS to pin down the exact elevation of every reading with centimeter-level precision.

Turning those raw numbers into a 3D picture of what’s underground took some serious number crunching. The team built a computer model that started with a rough guess about the shape and density of the material below, then tested thousands of variations against the actual gravity readings until it found the one that fit best. Instead of spitting out one rigid answer, the process produced a range of likely models, along with a sense of how confident the scientists could be in each one.

Researchers ran three versions of this model: one that assumed a single layer of ice with the same density throughout, one that let the density shift along the length of the rock glacier, and one that split the underground structure into two layers, rock debris on top of ice underneath. All three versions agreed on the big picture: a bowl-shaped bed of rock beneath the ice, deepest near the lower end of the rock glacier where the ice has been building up the longest.

Checking the Math With Surface Movement

To make sure the gravity-based estimates held up, the team cross-checked their results against something completely different: how fast the rock glacier’s surface was moving. Using GPS equipment placed at 30 points across the landform in 2023 and again in 2024, researchers measured the ground creeping downhill at speeds ranging from about 8 to 20 centimeters per year.

That movement matters because ice deforms and flows under its own weight, and the rate of that flow depends partly on how thick the ice is. Plugging the measured surface speeds into standard equations for how ice flows produced thickness estimates that lined up well with what the gravity survey had already found, giving the researchers added confidence that their underground map was accurate.

Their best estimate came from the two-layer model, which found that the rock glacier’s ice core makes up about 83% of the material in that layer, with rock debris filling in the rest. Averaged across the whole landform, including a debris layer on top that measured a few meters thick, the entire structure held an ice fraction of 72% and stood about 18.8 meters thick on average.

What Rock Glaciers Worldwide Could Mean for Water Supplies

Once the team had a reliable ice-volume number for one rock glacier, they combined it with published data from ten other rock glaciers studied elsewhere in the world, from the Alps to the Andes to other sites in the American West. Pulling that data together, they built a new mathematical relationship linking a rock glacier’s surface area to how much ice it likely contains.

That relationship let the researchers scale their findings up to whole regions. They estimate the rock glaciers of the Wasatch Mountain Range hold a water volume equivalent to about 80 million tons. Statewide in Utah, that figure rises to nearly 1 billion tons. Across the western United States, the estimate climbs to almost 12 billion tons, and globally, the team calculates that the world’s intact rock glaciers may hold a water volume equivalent of about 48 billion tons.

Why This Hidden Water Source Matters

Rock glaciers do more than sit there looking like rubble piles. They act as slow-release water stores in mountain environments, capable of sustaining stream flow late in the melt season after regular snowpack is gone. Even so, scientists still have big questions about how much of that buried ice melts each year and how much of it reaches streams downstream. As warming temperatures cause traditional glaciers to shrink and disappear, especially in dry mountain regions, rock glaciers are expected to become an increasingly important source of stored water. They also create cool, stable microclimates that shelter cold-loving species, including the American pika, along with plants and small creatures that depend on chilly refuges as the climate warms.

There’s a flip side, too. When rock glaciers absorb more water and face warmer temperatures, they can become unstable. More liquid water inside these landforms has been linked to faster movement and, in rarer cases, outright collapse. One rock glacier in the French Alps lost between 250,000 and 500,000 cubic meters of material that slid 500 meters downslope over just a few days. Understanding what’s inside these landforms, how much ice, how much rock, and how it’s all arranged, is a meaningful step toward predicting which ones might destabilize and threaten mountain communities downstream.

Scientists behind this study say their estimate for Timpanogos Rock Glacier probably falls short of the true ice volume. Persistent snow and steep terrain kept them from taking gravity readings in the upper part of the landform, the same area where a hole in the surface exposed bare ice underneath, a sign that section may hold even more ice than the model captured.

What matters about Timpanogos Rock Glacier goes beyond the swimming-pool math. That figure points to a substantial mountain water store that has been hard to measure precisely because most of its ice stays hidden beneath rubble. As conventional glaciers shrink, rock glaciers like this one could hold a growing share of the ice left in some mountain environments, shifting from an overlooked corner of the water story to a central part of it.

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