Unearthing Rock Glaciers: Hidden, Hydrological Landforms

Rock glaciers are distinctive, geomorphological landmasses composed of rock, ice, snow, mud, and water. Unlike exposed ice glaciers, the majority of ice and water is located within the rock glaciers’ underground permafrost. Above-ground characteristics of rock glaciers include unique tongue-shaped terminations, rock debris, and mountainous ridges.

Rock glaciers are frequently overshadowed by neighboring ice glaciers and overlooked due to their hidden nature. Although often forgotten, rock glaciers are common features in many mountain regions of the world and provide supplementary streamflow when water is needed most during dry, warm years.

Cross-section of a rock glacier which includes the above-ground layer, the permafrost core, and the hydrological system (Source: Schaffer et al.)

A Chilean-based scientific review team, from the Center for Advanced Studies in Arid Zones (CEAZA), published a study that evaluates the hydrological value of rock glaciers in the semiarid Andes (SA). Rock glaciers in the SA are rarely studied, so this group, led by scientist Nicole Schaffer, attempts to shed light on the region’s hidden landforms.

The SA is “a transition zone between the extremely arid region north of 25°S and the humid climate south of 40°S … over the twentieth century, total precipitation has declined and desertification has been recognized internationally as a critical problem,” states Schaffer et al.

Using published data sampling from the La Laguna Basin in Chile, the review team estimates glacial water contributions of the Llano de las Liebres, Las Tolas, Empalme, and Tapado Rock Glaciers using discharge measurements. Water discharge measurements collect the volume of moving water down a stream per unit of time.

Overall, rock glaciers in the semiarid Andes are believed to provide meaningful contributions to streamflows. The team’s findings indicate that the rock glaciers in the La Laguna Basin contribute between 9 to 20 percent of the total streamflow in the region.

How Will Rock Glaciers Respond to Warming Temperatures?

Through climate projections and historical evidence, the scientific community believes that rock glaciers will likely be less vulnerable to climate change.

North Cascades, Washington National Park (Source: Richard Droker, Flickr)

Due to the sheer size and high elevation of rock glaciers in the Chilean Andes, there will likely be delayed response times to climate change. As temperatures increase, smaller and lower elevation rock glaciers will likely thaw before substantial, high mountain rock glaciers.

U.S. Forest Service scientist Connie Millar studies both the historical and ongoing influences of climate change on rock glaciers in the western U.S. Millar’s research includes hydrological studies of rock glaciers in the Great Basin and ice glacier canyon mapping in the Sierra Nevada.

Millar said: “[Rock glaciers may] lag in response to climate change and maybe it’s more on scale of hundreds of years rather than thousands of years and it depends of course on where it is … and how quickly and how they respond to warming.”

North Cascades, Washington National Park (Source: Richard Droker, Flickr)

Alexander Brenning, scientist at Friedrich Schiller University Jena in Germany, also offers insight on the potential impacts of climate change.

Brenning shared: “Rock glaciers are complex systems that may react in various ways. The most worrying of all scenarios is the acceleration and even collapse of rock glaciers. Climatic warming may play a role in this scenario since it is expected to increase the availability of liquid water within the otherwise frozen rock glacier.”

Ultimately, rock glacial responses to climate change are highly variable and dependent on glacial size, elevation, and geographical location. To learn more about the climatic impacts, greater awareness of rock glaciers and further in-depth research is required.