Series: Types of Glaciers

Rock Glaciers

A rock glacier on Sourdough Peak (Wrangell-St Elias National Park, AK)
A rock glacier flows down from Sourdough Peak in the heart of Wrangell-St. Elias National Park (Alaska).

NPS Photo

Rock glaciers may not look like glaciers at all at first sight: That is because they are often mantled with a thick layer of rock and debris. This rock and debris shields them from ablation (melting), which means they can persist in areas where meltrates might be too high to sustain large alpine glaciers. For this reason, they can be found in many parks with high mountains in the contiguous United States.

What the actual flowing ice in a rock glacier looks like and how these glaciers form in the first place is subject to debate. Some scientists think that the ice is likely very similar to that of other glaciers and the main difference between them is that rock glaciers are covered in rocks at the surface. Others think they probably have high concentrations of rocks throughout and that the ice just binds these rocks together, creating a mass that can flow downslope like a glacier. Either way, rock glaciers are flowing masses, and they form distinct lobes that look much like other kinds of glaciers.

Find Your Park: Which Parks Have Rock Glaciers?

To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.