Any elevated area of relatively smooth land. Usually the term is used more specifically to denote an upland of subdued relief that on at least one side drops off abruptly to adjacent lower lands. In most instances the upland is cut by deep but widely separated valleys or canyons. Small plateaus that stand above their surroundings on all sides are often called tables, tablelands, or mesas. The abrupt edge of a plateau is an escarpment or, especially in the western United States, a rim. In the study of landform development the word plateau is commonly used to refer to any elevated area, especially one underlain by nearly horizontal rock strata, that once had a smooth surface at high level, even though that surface may since have been largely destroyed by valley cutting. An example is the now-hilly Appalachian Plateau of western Pennsylvania, West Virginia, and eastern Kentucky.