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A pediment is a very gently sloping (.5°-7°) inclined bedrock surface.〔Encyclopedia Britannica, Pediment, ()〕 It typically slopes down from the base of a steeper retreating desert cliff, or escarpment,〔Essentials of Geology, 3rd Edition, Stephen Marshak, p464, pG-15〕 but may continue to exist after the mountain has eroded away.〔 It is caused by erosion.〔 It develops when sheets of running water (laminar sheet flows) wash over it in intense rainfall events.〔〔 It may be thinly covered with fluvial gravel that has washed over it from the foot of mountains produced by cliff retreat erosion. It is typically a concave surface gently sloping away from mountainous desert areas.〔Easterbrook, Don J. (1999) ''Surface Processes and Landforms'', New Jersey, Prentice Hall〕 It is not to be confused with merged groups of alluvial fans (bajadas), which also may appear to gently slope from an escarpment, but are composed of material eroded from canyons, not bedrock.〔 Coalescence of pediments over a large area results in a pediplain. == Processes responsible for carving pediments == * Lateral planation or erosion by a stream 〔Johnson, Douglas (1932) ''Rock Planes of Arid Regions'', Geographical Review, Vol. 22, No. 4 (Oct., 1932), pp. 656–665〕 * Sheetwash or sheet erosion-
* Rillwash or rill erosion-
* Mountain-front retreating by weathering 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pediment (geology)」の詳細全文を読む スポンサード リンク
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