Utah's mountains have a hidden glacier that looks just like a pile of rocks from outside but actually contains frozen water as huge as Egypt's Great Pyramid inside

Utah's mountains are hiding a huge body of ice beneath what looks like a pile of loose rocks. Scientists studying the Timpanogos Rock Glacier found an ice-rich core that is 83% ice and contains about 1.55 million cubic metres of ice, roughly the volume of Egypt's Great Pyramid.

The discovery came after researchers used hundreds of gravity measurements to reconstruct the glacier's hidden interior in three dimensions. Their findings reveal how much frozen water can remain concealed beneath rocky mountain surfaces and offer a new way to estimate ice stored in similar formations worldwide.

A glacier hiding beneath a rocky surface

Unlike conventional glaciers, rock glaciers do not necessarily look like glaciers from the surface. The Timpanogos Rock Glacier is covered by loose rocks and debris, concealing the ice underneath.


The researchers describe rock glaciers as “bodies of ice buried by loose rock” that move slowly downhill in mountain environments.

The Timpanogos formation sits below Mount Timpanogos in Utah's Wasatch Mountain Range. It is about 800 metres long and between 100 and 200 metres wide.

The researchers' modelling found an ice volume of 1.55 million cubic metres, with an average thickness of 18.8 metres. Their two-layer model estimated that the entire rock glacier contains 72% ice and 28% debris by volume, while the buried ice-rich core itself is 83% ice and 17% debris.

University of Utah researcher Bronson Cvijanovich, the study's lead author, described the glacier as “surprisingly ice rich.”

Frozen water almost equal to the Great Pyramid

The amount of ice hidden beneath the rocks is what makes the discovery particularly striking.

The researchers estimate that the glacier contains about 1.55 million cubic metres of ice, equivalent to roughly 600 Olympic-sized swimming pools. The University of Utah also notes that this volume is comparable to the volume of the largest pyramid at Giza in Egypt.

That means a rocky-looking formation beneath a popular Utah mountain contains a quantity of frozen water comparable in volume to one of the world's most recognisable ancient structures.

Scientists used gravity to see beneath the rocks

The researchers could not simply look at the surface to determine how much ice was underneath it.

Instead, they collected 232 relative gravity measurements between August and October 2024. The measurement points were roughly 25 metres apart across the rock glacier.

A gravimeter can detect tiny variations in gravitational acceleration caused by differences in density. Rock is substantially denser than ice, so thicker sections of buried ice produce measurable changes.

The researchers then used a 3D Bayesian inversion technique to turn those measurements into a model of the hidden ice.

The paper says the method allowed them to image the glacier's internal structure and estimate its thickness and composition. The model found an ice-rich layer that reaches roughly 30 to 45 metres in thickness, with some areas deeper.

The University of Utah compared the approach to a CT scanner, explaining that the researchers effectively created a virtual map of what lies beneath the rocky surface.

The mountains may be burying snow to create the glacier

The researchers also investigated how the unusual formation gets its ice.

Their findings suggest that rockfalls from the steep mountain walls can bury persistent snow. Over time, the debris protects the snow and allows it to become incorporated into the rock glacier.

Leif Anderson, a glaciology professor involved in the research, explained: “The mountains themselves are eroding and burying the snow, and that's why the rock glaciers exist.”

The researchers' companion study found that years with heavy snowfall, cooler summers and larger rockfalls can contribute to ice addition.

This also means the Timpanogos Rock Glacier is not simply an ancient remnant left behind by the last Ice Age.

It is still adding ice today

One of the more surprising findings is that the Timpanogos Rock Glacier appears to remain active.

Anderson said the formation is “still adding ice today.” The research indicates that Utah's rock glaciers formed during the thousands of years after Ice Age glaciers disappeared, rather than simply preserving ice left over from that period.

The paper also notes that rock glaciers can act as important stores of ice in mountain environments. Their thick debris cover protects the ice and makes these formations difficult to quantify using surface observations alone.

Utah may have much more hidden ice

Timpanogos is just one of 836 rock glaciers identified in Utah.

Using measurements from Timpanogos and data from 10 other rock glaciers, the researchers developed a relationship between a rock glacier's surface area and its ice volume. They then used that relationship to estimate the amount of ice stored in other formations.

Their estimate suggests Utah's rock glaciers could collectively contain about 1 gigaton of water, equivalent to roughly 815,000 acre-feet.

The researchers extended the calculation globally and estimated that the world's intact rock glaciers could hold about 48.03 gigatonnes of water.

Cvijanovich described rock glaciers as “climate-resilient water storage sites” because their rocky covering protects and hides the ice.

The researchers acknowledge that the estimates still carry uncertainty and say more three-dimensional geophysical studies are needed. But the Timpanogos study demonstrates that gravity measurements can reveal what is hidden beneath rocky terrain without having to excavate the glacier.