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In Geology and Earth Science , a plateau, also called a '''tableland''', is an area of Highland , usually consisting of relatively flat open country if the uplift was recent in Geologic History . Plateaus (or plâteaux), like Mesa s and Butte s, are formed when land has been uplifted by Tectonic activity and then Eroded by Wind or Water . Flat-topped, sheer-sided plateaus, like the Tepui s of Guiana , are formed when a section of land is uplifted that is topped with a layer of particularly resistant rock, and underlain by softer rock. ''Plateau'' is also used to describe undersea geologic formations. Some undersea plateaus, like the Seychelles plateau, are fragments of continental crust that lie separate from continents; they are analogous to Continental Shelves , but without the continents. Some, like the Seychelles, have peaks that rise from the sea as islands; others rest entirely below the surface. Other undersea plateaus were formed by outpourings of Flood Basalts , and were never associated with continents; the vast Ontong Jaya Plateau of the western Pacific is an example of such. DISSECTED PLATEAUS A highly eroded plateau is called a Dissected Plateau . These older Uplift s have been eroded by Creeks and River s to develop steep relief not immediately distinguishable from Mountain s. Many areas of the Allegheny Plateau and the Cumberland Plateau , which are at the western edge of the Appalachian Mountains of eastern North America , are called "mountains" but are actually dissected plateaus. One can stand on a high "mountain" and note that all the other tops are at the same height, which represents the original Plain before uplift. A dissected plateau may also be formed, usually on a comparatively small scale, by the levelling of terrain by planing and deposition beneath an Ice Sheet or perhaps, an Ice Cap . Subsequently, during the same or a later Glacial , the margins of the Glacial Till plain are removed by Glacier s, leaving the plateau into which erosion by Water incises Valley s. Such a plateau may be level or gently sloping but may be distinguished by the till caps on its hills. Glacial till is still widely known in Britain by the older name of boulder clay. |
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