Researchers discover massive hidden ice reservoir beneath Utah's Mount Timpanogos

From a distance it looks like nothing more than a sprawling pile of rocks high in Utah’s Wasatch Range. But beneath the rubble of Mount Timpanogos is a spectacular hidden reservoir: ice enough to hold some 1.55 million cubic meters of water, which is about 600 Olympic-sized swimming pools.

Now, researchers at the University of Utah have mapped this invisible ice using an unusual approach: measuring tiny variations in gravity across the rocky landscape, the university website reports.

It’s the Timpanogos Rock Glacier, one of hundreds of rock glaciers in Utah. Unlike normal glaciers, which are large masses of exposed ice and snow, rock glaciers are covered by a thick mantle of loose rock. That rocky exterior is difficult to study, but below it there may be vast amounts of frozen water, the news report states.

Timpanogos Rock Glacier is estimated to be around 83% ice and 17% loose rock and is particularly ice-rich. At its deepest point, the ice is buried about 150 feet beneath the surface. According to glaciologist Leif Anderson, “There’s a lot of ice hiding in Utah’s mountains.” Hikers walking over what seems to be normal rubble may be blissfully unaware that dozens of meters of ice could be underneath.

In fall 2024, University of Utah geologist Bronson Cvijanovich led fieldwork at the glacier to get a better sense of what was beneath the surface. The team made six trips to the site, carrying sensitive scientific equipment up a tough trail. The site is accessible from a trailhead, but it’s a five-mile hike and climb of some 3,500 feet to reach the rock glacier.

The researchers used a sophisticated gravimeter to take readings at 232 locations about 25 meters apart. It measures small variations in gravitational acceleration resulting from density differences. Areas with thicker buried ice have a slightly weaker pull from gravity, because rock is much denser than ice.

Scientists corrected the measurements for elevation, latitude, terrain, and gravitational effects from the Sun and Moon. They then used Bayesian statistical modeling to generate a three-dimensional picture of the ice under the rocks. It gave an unprecedented view of the interior of Timpanogos Rock Glacier.

The researchers also explored yet another equally interesting question: how does a rock glacier develop ice when its surface is covered with rocks? The answer seems to be a combination of snowfall and rockfall.

Rock glaciers often occur beneath steep mountain slopes and cirques where rocks frequently break loose. Large rocks falling on areas of persistent snow can bury and protect the snow from melting. This process adds ice to the rock glacier over time.

Researchers found that years with heavy snowfall, cool summers and substantial rockfalls can contribute to ice accumulation. More than 70 patches of debris-covered snow still exist at Timpanogos, scientists have found.

They used Bayesian statistical modeling to generate a three-dimensional picture of the ice under the rocks. It gave an unprecedented view of the interior of Timpanogos Rock Glacier.

The discovery could have implications far beyond Mount Timpanogos. Utah has 836 known rock glaciers, but researchers believe there are about 50,000 rock glaciers worldwide. The authors estimate that the world's rock glaciers contain about 48 gigatons of water by using a correlation between the surface area of a rock glacier and its buried ice volume.

Rock glaciers in Utah may contain about one gigaton of water, or about 815,000 acre-feet. Scientists note that not all rock glaciers are necessarily gaining ice today. Some have already lost their frozen hearts. But Timpanogos Rock Glacier seems to still be active, adding ice.

Such hidden ice reserves could be especially significant to a warm, dry state like Utah. A thick layer of rock helps shield the ice below from heat and sun, potentially allowing rock glaciers to keep water around longer than exposed ice.

The research also alters scientists’ view of these formations. Some rock glaciers are not just relics of ancient glacial history but are dynamic systems interacting with today's climate. So what looks from above like a normal field of rocks could be concealing a large reserve of frozen water—and new scientific tools are finally allowing scientists to see what is underneath.