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salt glacier
A salt glacier is a rare flow of salt (typically halite) that is created when a rising diapir in a salt dome breaches the surface. The buried salt layer is less dense than the surrounding rock which is why it acts buoyantly, the pressure from the surround rock forcing the salt dome upward to a position of equilibrium or release into a surface flow.〔(【引用サイトリンク】 title=Salt Glaciers )〕 Gravity causes the salt to slowly move downslope, like ice glaciers, into adjacent valleys. If on flat ground, the weight of the salt itself will cause lateral spreading. Most of the flow occurs during the winter, when the salt is wet, as salt strength is critically dependent on its water content. The naturally dry conditions that are typical for salt glaciers, like those in Iran, help to preserve the flow rather than wash it away by precipitation. The combination of these conditions (salt presence, diapir movement, surface breaching, and arid climate) are what make finding salt glaciers so rare. However, in areas like the Persian Gulf, the conditions result in tongue-shaped salt glacier bodies that can extend for kilometers, with repeating bow-shaped ridges separated by crevasse-like gullies and with steep sides and fronts. Clays may be brought up with the salt, turning it dark.
The salt glaciers of the Zagros Mountains in Iran〔(【引用サイトリンク】 title=Iran's Salt Glaciers )〕〔Talbot, C.J. and Rogers, E.A. 1980. "Seasonal movements in a salt glacier in Iran". ''Science'', 208, 395-397.〕 are halite while the salt glacier of Lüneburg Kalkberg, Germany is composed of gypsum and carbonate minerals.
Ancient flows have been preserved in various rock records by sedimentation. Late Triassic salt glaciers repeatedly flowed onto a basin in Germany and were buried with sediment to create a series of preserved glaciers. Miocene glaciers flowed into sheets in the northern Gulf of Mexico and were similarly preserved by overriding sediment.〔(【引用サイトリンク】 title=Salt Glaciers )〕
==See also==
* Salt surface structures
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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