A few make the distinction that canyons are usually found in arid (dry) regions characterized by plateaus, which are relatively level, large expanses of land that rise some 1,500 feet (457 meters) or more above their surroundings and have at least one steep side. The walls of some canyons are V-shaped and ragged; the walls of others are steeper and almost smooth.
Some canyons have been carved through sandstone and limestone and other types of sedimentary rock (rock formed by the accumulation and compression of sediment, which may consist of rock fragments, remains of microscopic organisms, and minerals).
If the rock forming their walls is hard and somewhat resistant to erosion, those walls may be high and steep.
If their walls are made of rock that is softer and more vulnerable to erosion, those walls are likely to be less steep, V-shaped, and prone to landslides and slumps (a slump is the downward movement of blocks of material on a curved surface).
Some canyons are dry; others are filled with rushing rivers.When it runs over the canyon, it descends in a wall of water that blasts through the canyon, eroding the walls and floor.As quickly as the water appears, it disappears, leaving the canyon dry and slightly changed until the next flood.Although perhaps much more slowly, canyons created millions of years ago continue to be shaped in the present day. A canyon may be defined as a narrow, deep, rocky, and steep-walled valley carved by a swift-moving river.Its depth may be considerably greater than its width.