Broadly, any comparatively flat area of great extent and elevation; specif. an extensive land region considerably elevated (more than 150 to 300 m in altitude) above the adjacent country or above sea level; it is commonly limited on at least one side by an abrupt descent, has a flat or nearly smooth surface but is often dissected by deep valleys and surmounted by high hills or mountains, and has a large part of its total surface at or near the summit level. A plateau is usually higher and has more noticeable relief than a plain (it often represents an elevated plain), and it is usually higher and more extensive than a mesa; it may be tectonic, residual, or volcanic in origin.