Tonguelike body of coarse rock fragments, found above the timberline on mountains, that moves slowly down a valley. The rock material usually has fallen from the valley walls and may contain large boulders; it resembles the material left at the end (terminus) of a true glacier. A rock glacier may be 100 ft (30 m) deep and nearly a mile (1.5 km) long.
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Rock glaciers are distinctive geomorphological landforms of blocky detritus which may extend outward and downslope from talus cones or from glaciers or the terminal moraines of glaciers. Their growth and formation is subject to some debate, with three main theories in prominence:
Rock glaciers may move or creep at a very slow rate in part dependent on the amount of ice present.