A dissected plateau is a plateau area that has been uplifted, then severely eroded so that the relief is sharp. Such an area may be referred to as mountainous, but dissected plateaus are distinguishable from orogenic mountain belts by the lack of folding, metamorphism, extensive faulting, or magmatic activity that accompanies orogeny. The Allegheny Plateau, the Cumberland Plateau, the Ozark Plateau, the Catskill Mountains, and the Blue Mountains are examples of dissected plateaus.
These older uplifts have been eroded by creeks and rivers to develop steep relief not immediately distinguishable from mountains. 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, or created, 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 glaciers, leaving the plateau into which erosion by water incises valleys. 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.