Rock Glaciers in Utah

Scott Hotaling,1,2 Kendall Becker,1,2 and Matthew Morriss3

1 Department of Watershed Sciences, Utah State University (USU)

2 USU Climate Resiliency Extension

3 Utah Geological Survey

Utah’s primary water supply winter snowpack is in decline due to climate warming coupled with more precipitation falling as rain instead of snow. As snowpack dwindles, other sources of cold stream water, such as rock glaciers, will become more important. Rock glaciers contain significant volumes of internal ice covered by debris. This internal ice provides cold meltwater to mountain streams, sustaining flows in summer and supporting biodiversity. Rock glaciers are common in Utah’s mountains and are projected to be more stable under climate change than Utah’s snowpack. Thus, rock glaciers are likely to persist in their current form even as snowpack volumes continue to decrease. Because rock glaciers may provide a critical, climate-resilient water source for Utah, more research is needed to quantify their relevance for present and future water availability and ecosystems.

What Are Rock Glaciers?

Rock glaciers are large masses of talus and debris that “flow” downhill due to the deformation of substantial internal ice. Rock glaciers accumulate new ice in their higher elevation portions, typically when rockfall covers seasonal snowpack and insulates it. Rock glaciers can also accumulate new ice when rain or meltwater percolate into their interior and freeze. The internal ice of rock glaciers flows downhill through a mix of internal deformation and basal sliding, forming distinctive lobes (Figures 1 and 2). Pressure from the weight of the ice and debris paired with warmer conditions at the lower-elevation “toe” of the rock glacier causes internal ice to melt, which feeds streams and lakes (Figure 1, right). If the cycles of ice addition and loss are equal, the rock glacier is stable (i.e., not growing or receding). But any alterations to the balance, such as more melt than accumulation, drive directional change. At present, surface ice glaciers in the western United States are in the midst of a long-term trend of melt exceeding accumulation, causing them to broadly recede. Rock glaciers, in contrast, appear to be near a state of equilibrium, though more data are needed to confirm their slow rates of change.

Figure 1. A rock glacier outlined in red in the Gad Valley area of Little Cottonwood Canyon, UT. The “toe” of the rock glacier is the lower-elevation, rounded part in the bottom left of the image (left). A stream emanating from the terminus of the Gad Valley rock glacier (right).

Photo credits: (left) Adam Hiscock and (right) Matthew Morriss, both from Utah Geological Survey.

Why Do Rock Glaciers Matter?

Rock glaciers are important to Utah for four reasons: (1) Rock glaciers in the western United States may hold frozen water equivalent to our largest human-constructed reservoirs; (2) Rock glaciers release cold water in summer when it is most critical for agriculture and ecosystems; (3) Due to their insulating debris cover, rock glaciers are more resilient to climate change than other snow and ice features; and (4) Rock-glacier-fed lakes and streams are cold year-round (often less than about 3 °C) and may support habitat refugia for a host of coldwater species, including Utah’s state fish, the Bonneville cutthroat trout.

To date, more than 10,000 rock glaciers have been mapped in the western United States, with 834 in Utah (Johnson et al., 2021). Utah’s rock glaciers are concentrated in the Uinta and Wasatch Mountains (Figure 3).

3. Rock glaciers in Utah identified from satellite imagery. In addition to the Uinta Mountains, the popular Brighton and Snowbird ski areas, which both have rock glaciers in or near their boundaries, are labeled. Data source: Johnson et al. (2021).

Figure 2. The Timpanogos rock glacier near Provo, UT (left), with a glimpse of its internal ice (right). Photo credit: Matthew Morriss, Utah Geological Survey.

Figure

Rock Glaciers, a Potential Climate-Resilient Water Source

Rock glaciers may help mitigate an escalating water availability crisis in the western United States and Utah

As climate warming melts surface ice glaciers and reduces annual snowpack, rock glaciers may help mitigate an escalating water availability crisis in the western United States and Utah. As the second driest state in the nation, Utah gets about 95% of its annual water supply from mountain snowpack, which is in steady decline. Since 1979, Utah’s peak snow water equivalent a normalized measure of the total water in the snowpack has declined by 16.3%. And if the historic winter of 2022–2023 is excluded, the decline nearly doubles to 26.8%. Recent projections indicate that Utah’s mountains may be largely snow-free by 2080 (Siirila-Woodburn et al., 2021), making Utah more likely to run out of freshwater reserves during longer, hotter summers.

This change in Utah’s water supply is occurring in parallel with a population explosion. Since 1979, Utah’s population has more than doubled. Thus, there is a widening gap between available water resources and the needs of Utah’s human population, agricultural industry, and ecosystems. Meltwater from rock glaciers in summer may be crucial for meeting Utah’s late-season water demands. Moreover, many of these rock glaciers drain into the Upper Colorado River Basin, a key water resource for five states.

Ecological Value of Cold Water

In addition to our need for water in general, there is a specific need for cold water that flows from melting snowpack, high mountain aquifers, surface glaciers, and rock glaciers. Coldwater flows underpin fisheries and nongame species by providing the necessary thermal conditions for their survival. Many of Utah’s most important species including the Bonneville cutthroat trout require cold, year-round streamflows, which may increasingly come from sustainable rock glacier melt zones as opposed to nonexistent snowpack and surface ice glaciers (Idaho Department of Fish and Game, 2022). However, despite desirable coldwater contributions to mountain streamflows, rock glaciers could pose a risk to water quality as their internal ice melts.

Potential Risks to Water Quality

Rock glacier outflows are commonly rich in ions (e.g., nitrates, magnesium) and heavy metals at levels that exceed safe drinking water limits (Brighenti et al., 2021). These inputs can have detrimental effects on downstream ecosystems and biodiversity. For instance, high nitrate concentrations can enhance algal production and thereby increase the potential for harmful algal blooms. Elevated metal concentrations from rock glacier meltwater have also been linked to deformities in species that live in high mountain lakes (Ilyashuk et al., 2014). For Utah, monitoring rock glacier outflows is needed to assess the risk, if any, that melting rock glaciers may pose to water quality.

Research Advances

Recently, the study of rock glaciers in Utah has accelerated with promising results. In 2018, researchers mapped the distribution of rock glaciers in the Uintas (Munroe, 2018), then identified 205 rock glaciers that contain large-scale ice and used cutting-edge radar technology to track rock glacier movement, an indicator of active ice accumulation and melt (Brencher et al., 2021). In 2022, rock glacier meltwater was estimated to supply about 25% of the total flow in two high mountain streams of the Uintas (Munroe & Handwerger, 2023).

Guiding Questions for Future Research

As climate change proceeds, any water source in arid regions will become increasingly important, and cold water will become especially scarce. If rock glaciers can provide sources of cold water in Utah, they stand to greatly bolster the region’s climate resiliency. However, before this can be assessed, five questions must be answered:

1. How much water is locked up in Utah’s rock glaciers?

2. Is the volume of internal ice in rock glaciers changing?

3. How much do rock glaciers contribute to summer streamflows?

4. How important are rock glaciers to species that depend on cold water (e.g., Bonneville cutthroat trout)?

5. How will rock glacier meltwater influence water quality?

Acknowledgments

This publication was supported by the “Secure Water Future” project funded by an Agriculture and Food Research Initiative Competitive Grant (#2021-69012-35916) from the USDA National Institute of Food and Agriculture. This fact sheet was improved based on feedback from participants in USU Extension’s Climate Adaptation Intern Program

For correspondence: Scott Hotaling, scott.hotaling@usu.edu.

Sources

Brencher, G., Handwerger, A. L., & Munroe, J. S. (2021). InSAR-based characterization of rock glacier movement in the Uinta Mountains, Utah, USA. The Cryosphere, 15(10), 4823–4844.

Brighenti, S., Hotaling, S., Finn, D. S., Fountain, A. G., Hayashi, M., Herbst, D., Saros, J. E., Tronstad, L. M., & Millar, C. I. (2021). Rock glaciers and related cold rocky landforms: Overlooked climate refugia for mountain biodiversity. Global Change Biology, 27(8), 1504–1517.

Johnson, G., Chang, H., & Fountain, A. (2021). Active rock glaciers of the contiguous United States: geographic information system inventory and spatial distribution patterns. Earth System Science Data, 13(8), 3979–3994.

Idaho Department of Fish and Game. (2022). Management plan for the conservation of Bonneville cutthroat trout in Idaho https://idfg.idaho.gov/sites/default/files/planboncutthroat22.pdf

Ilyashuk, B. P., Ilyashuk, E. A., Psenner, R., Tessadri, R., & Koinig, K. A. (2014). Rock glacier outflows may adversely affect lakes: lessons from the past and present of two neighboring water bodies in a crystallinerock watershed. Environmental Science & Technology, 48(11), 6192–6200.

Munroe, J. S. (2018). Distribution, evidence for internal ice, and possible hydrologic significance of rock glaciers in the Uinta Mountains, Utah, USA. Quaternary Research, 90(1), 50–65.

Munroe, J. S., & Handwerger, A. L. (2023). Contribution of rock glacier discharge to late summer and fall streamflow in the Uinta Mountains, Utah, USA. Hydrology and Earth System Sciences, 27(2), 543–557. Siirila-Woodburn, E. R., Rhoades, A. M., Hatchett, B. J., Huning, L. S., Szinai, J., Tague, C., Nico, P. S., Feldman, D. R., Jones, A. D., Collins, W. D., & Kaatz, L. (2021). A low-to-no snow future and its impacts on water resources in the western United States. Nature Reviews Earth & Environment, 2(11), 800–819.

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June 2024

Utah State University Extension

Suggested citation:

Hotaling, S., Becker, K., & Morriss, M. (2024). Rock glaciers in Utah [Fact sheet]. Utah State University Extension.