In geology, extensive land formation. The top is flat or sloping; the elevation, from a few hundred to several thousand metres. A plateau is larger than a mesa or butte. Plateaux are often riven by erosion into deep canyons. Major plateaux in North America are the Columbia and Colorado plateaux."Plateau," Microsoft® Encarta® Online Encyclopedia 2001http://encarta.msn.co.uk © 1997-2001 Microsoft Corporation. All rights reserved.