In geology and earth science, a plateau ( /pləˈtoʊ/ or /ˈplætoʊ/; plural plateaus or rarely plateaux), also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau. A volcanic plateau is a plateau produced by volcanic activity.
Plateaus can be formed by a number of processes, including, upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Magma rises from the mantle causing the ground to swell upward, in this way large, flat areas of rock are uplifted. Plateaus can also be built up by lava spreading outwards from cracks and weak areas in the crust, an example of such a plateau is the Columbia Plateau in the northwestern United States of America. Plateaus can also be formed due to the erosional processes of glaciers on mountain ranges, in this case the plateaus are left sitting between the mountain ranges. Water can also erode mountains and other landforms down into plateaus.
Plateaus are classified according to their surrounding environment, common categories are: intermontane, piedmont, and continental plateaus.