A canyon (occasionally spelled cañon) or gorge is a deep ravine between cliffs often carved from the landscape by a river. Rivers have a natural tendency to reach a baseline elevation, which is the same elevation as the body of water it will eventually drain into. This forms a canyon. Most canyons were formed by a process of long-time erosion from a plateau level. The cliffs form because harder rock strata that are resistant to erosion and weathering remain exposed on the valley walls. The word canyon is Spanish in origin (cañón, pronounced: [kaˈɲon]). The word canyon is generally used in the United States, while the word gorge is more common in Europe and Oceania, though gorge and ravine are also used in some parts of the United States and Canada. The military derived word defile is occasionally used in the United Kingdom.[source]