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Adissected plateau is aplateau area that has been severely eroded, and the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable fromorogenic mountain belts by the lack offolding,metamorphism, extensivefaulting, ormagmatic activity accompanyingorogeny.
A dissected plateau may also be formed, usually on a comparatively small scale, by the levelling of terrain by planing and deposition beneath anice sheet or perhaps anice cap.[citation needed]
Subsequently, during the same or a laterglacial period, the margins of theglacial till plain are removed byglaciers, leaving the plateau into which erosion bywater incisesvalleys. 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 inBritain by the older name of boulder clay.[citation needed]
Dissectedvolcanic plateaus include thePajarito Plateau inNew Mexico, on the skirt of the enormousValles Caldera.[1] Isolated portions of this plateau are known asmesas, and long, connected portions are known aspotreros.
TheAllegheny Plateau,[2] theCumberland Plateau,[3] theOzark Plateau,[4] and theCatskill Mountains[5] in the United States, theBlue Mountains andHornsby Plateau inAustralia, and theDeccan Plateau inIndia are examples of dissected plateaus formed after regional uplift.[citation needed]
These olderuplifts have been eroded bycreeks andrivers to develop steep relief not immediately distinguishable frommountains.[citation needed]
Many areas of the Allegheny Plateau and the Cumberland Plateau, at the western edge of theAppalachian Mountains of easternNorth America, are called "mountains" but are actually dissected plateaus. One can stand on the top of one of these high "mountains" and note that all the other tops are nearly the same height, representing the original elevation profile of theplain before uplift and thereafter the subsequent weather erosion.[citation needed]