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Rock glacier
Rock glaciers are distinctive geomorphological landforms, consisting either of angular rock debris frozen in interstitial ice, or true glaciers overlain by a layer of talus. Rock glaciers may extend outward and downslope from talus cones, glaciers or terminal moraines of glaciers. There are two types of rock glaciers: periglacial glaciers, or talus-derived glaciers, and glacial rock glaciers, such as the Timpanogos Glacier in Utah, which are often found in the former places of glaciers. Possible Martian rock glacier features have been identified by the Mars Orbiter spacecraft.〔(W. Brian Whalley and Fethi Azizi, ''Rock glaciers and protalus landforms: Analogous forms and ice sources on Earth and Mars,'' Journal of Geophysical Research: Planets, Volume 108, Issue E4, April 2003 (abstract) )〕 A rock glacier, especially if its origin is unclear, can be considered as a discrete debris accumulation.
==Formation==
The two known factors that must be present in order to create rock glaciers are low ice velocity and permafrost. Most glacial rock glaciers are created by the recession of debris covered glaciers. Glacial rock glaciers are often found in cirque basins where rocky debris falls off the steep sides and accumulates on ice glaciers. As the glaciers shrink, their composition changes as they become increasingly covered with debris. Eventually, the glacial ice is replaced by ice cored rocks.〔Gürgen, Gürcan, et al. "Debris Covered Glaciers and Rock Glaciers," e-Journal of New World Sciences Academy (NWSA) 5.1 (2010): 32-45.〕 With the exception of ice-cored rock glaciers, rock glaciers are a periglacial process. This means that they are a nonglacial landform associated with cold climates, particularly with various aspects of frozen ground. Periglacial rock glaciers require permafrost instead of glacial ice in order to form. Instead, they are caused by continuous freezing occurring within a talus lobe.〔
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抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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