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Rock glaciers are distinctive geomorphological that consist either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of Scree, or something in between. Rock glaciers are normally found at high latitudes and/or elevations, and may extend outward and downslope from talus cones, or of glaciers. The early textbook 'Characteristics of Existing Glaciers' refers to the varied, sometimes confusing, names given to these features; 'stone rivers', 'rock flows', 'rock streams' and 'rock glaciers', and includes a map and two photographs of 'rock streams' from the Silverton area of Colorado from the US Geological Surveyors Ernest Howe and W Cross . About the same time, Stephen Capps was surveying in the Wrangell Mountains, Alaska and reported similar landforms in the McCarthy area . Although a variety of names seemed to have be used in the USGS at this time, it is 'rock glacier' that is now generally used.
There are two models of rock glacier formation and flow: permafrost rock glaciers (sometimes termed talus-derived rock glaciers), and glacial rock glaciers, such as the Timpanogos Glacier 40.3847,-111.6415 in Utah, which may be found where glaciers once existed. A rock glacier has formed with rock debris covering a small glacier on Mt. St. Helens 46.2074,-122.1838.JGabrielli, S, Spagnolo, M., De Sienna, L. (2020):Journal of Maps 16, 585-594. Possible Mars rock glacier features have been identified by the Mars Reconnaissance Orbiter spacecraft. A rock glacier, especially if its origin is unclear, can be considered as a discrete debris accumulation. Rock avalanches can be misidentified as rock glaciers, or may evolve into them.Jarman D, Wilson P, Harrison, S. (2013): Are there any relict rock glaciers in Britain? Journal of Quaternary Science 28, 131-143.
With the exception of ice-cored rock glaciers, rock glaciers are a periglacial/permafrost process. This means that they are a nonglacial landform associated with cold climates, particularly with various aspects of frozen ground. Permafrost rock glaciers require permafrost-derved ice instead of glacial ice in order to form. Instead, they are caused by continuous freezing occurring within a talus lobe. Permafrost rock glaciers can form from the alternation of rock debris incoming with autumn firn or avalanche snow.
Nearby cliffs are in many cases a requirement for the formation of rock glaciers, and as such many rock glaciers form in U-shaped valley. Rock masses of rock glaciers have been found to make up different rock types depending on the local geology. These rock types include andesite, basalt, granite, porphyry, quartzite, and sandstone.
Ordinary glaciers can override rock glaciers, acquiring some of its material and properties. More usually, rock glaciers originate from weathered rock debris progressively covering an existing glacier. Typically in the European Alps, this is post Little Ice Age
Some rock glaciers can reach lengths of and can have terminal embankments high. Blocks on the surface can be up to in diameter. Flow features on the surface of rock glaciers may develop from:
According to recent studies, rock glaciers positively influence the streams around them.
Subject to climate variation, rock glaciers in proximity tend to have a highly synchronous movement pattern over a short time scale; over long term, however, the relationship between rock glacier velocity and climate difference may not be as pronounced, due to the influences of topographic factors and lack of ice or debris budget within the glacier body.
Movement
Rock glaciers move downslope by deformation of the ice contained within them, causing their surface to resemble those of glaciers. Rock glaciers may flow or creep at a very slow rate, in part dependent on the thickness of ice present. Surface velocities are generally less than 2m/a, although this depends where measurements have been taken on the length of the rock glacier .
Their growth and formation is subject to some debate, with three main theories :
(1996). 9783540607427, Springer. ISBN 9783540607427;
Human use
Rock glaciers in the Chilean Andes help supply the water for much of Chile, including the capital of Santiago. Mining operations in the high mountains have led to the degradation and destruction of more than two rock glaciers. Several copper mines dump their waste rock onto rock glaciers, which results in faster melting and higher velocity movement of these rock glaciers. The dumping of waste rock on the rock glaciers may lead to their destabilization. In 2004, protesting irrigation farmers and environmentalists changed rules so new mining projects can no longer damage or alter rock glaciers in Chile.*
Parts of the only road into Denali National Park and Preserve in Alaska are built on a 'rock glacier' known as "Pretty Rocks". In late summer 2021 the road had to be closed due to accelerating rockslides in that area, sometimes sliding up to in a single day, apparently due to climate change. Pretty Rocks Landslide, National Park Service. Retrieved 2025-10-06. Although the National Park Service has called this landslide a 'rock glacier', location 63.5360,-149.8174, it has none of the basic characteristics of rock glaciers, such as large area and high altitude as seen in the mountains of Alaska, where the rock glacier on Sourdough Peak is a good example. In Colorado, the large landslide, Slumgullion Earthflow has a plan-form more typical of a rock glacier but it does not flow from a glacial cirque .
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