High Quality Content by WIKIPEDIA articles! In geology and earth science, a plateau, 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 magma, excretion of lava, and erosion by water and glaciers. Magma rises from the mantle causing the ground to swell upward, in this way large, flat pieces of rock are uplifted.