Canyon

For other uses, see Canyon (disambiguation).

"Gorge" redirects here. For the figure from Greek mythology, see Gorge (mythology). For the old English meaning, see throat.

Grand Canyon, Arizona

Sianok canyon in Bukittinggi, Indonesia

Kali Gandaki Gorge near Ghassa village, Nepal

Noravank Monastery complex and canyon in Armenia.

Aerial view of canyons in western United States.

The Pont d'Arc in the Ardèche gorges in France.

Sapadere Canyon, Antalya, Turkey.

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.^[1] 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. Canyons are much more common in arid areas than in wet areas because physical weathering has a greater effect in arid zones. The wind and water from the river combine to erode and cut away less resistant materials such as shales. The freezing and expansion of water also serves to help form canyons. Water seeps into cracks between the rocks and freezes, pushing the rocks apart and eventually causing large chunks to break off the canyon walls which are also known as frost wedging.^[2] Canyon walls are often formed of resistant sandstones or granite. Submarine canyons form underwater, generally at the mouths of rivers. 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 it is also used in some parts of the United States and Canada. The military derived word defile is occasionally used in the United Kingdom.

A famous example, and the largest gorge in the world,^[3] is the Grand Canyon in Arizona with an average depth of one mile and a volume of 4.17 trillion cubic metres.^[4] In the southwestern United States, canyons are important archeologically because of the many cliff-dwellings built there, largely by the earlier inhabitants, Ancient Pueblo Peoples. The second largest canyon, and the largest in Africa, is Fish River Canyon in Namibia.^[5]

The Yarlung Tsangpo Grand Canyon (or Tsangpo Canyon), along the Yarlung Tsangpo River in Tibet, is regarded by some as the deepest canyon in the world at 5,500 m (18,000 ft), and is slightly longer than Grand Canyon making it one of the world's largest.^[6] The Kali Gandaki Gorge in midwest Nepal is seen by others to be the deepest canyon, with a 6400 m (21,000 ft) difference between the level of the river and the peaks surrounding it.

Sometimes large rivers run through canyons as the result of gradual geological uplift. These are called entrenched rivers, because they are unable to easily alter their course. The Colorado River in the Southwest and the Snake River in the Northwest are two examples of tectonic uplift.

Canyons often form in areas of limestone rock. Limestone is to a certain extent soluble, so cave systems form in the rock. When these collapse a canyon is left, for example in the Mendip Hills in Somerset and Yorkshire Dales in Yorkshire, England.

A canyon may also refer to a rift between two mountain peaks such as those in ranges such as the Rocky Mountains, the Alps, the Himalayas or the Andes. Usually a river or stream and erosion carve out such splits between mountains. Examples of mountain type canyons are Provo Canyon in Utah or Yosemite National Park in California's Sierra Nevada. Canyons within mountains or gorges that only have an opening on one side are called box canyons. Slot canyons are very narrow canyons, often with smooth walls.

[edit] Largest canyons

View of Grand Canyon from Space Shuttle Challenger.

The definition of "largest canyon" is rather imprecise, as a canyon can be large by its depth, length, or the total area of the canyon system. Also the inaccessibility of the major canyons in the Himalaya contributes to their not being regarded as candidates for the biggest canyon. The definition of "deepest canyon" is similarly imprecise, especially if one includes mountain canyons as well as canyons cut through relatively flat plateaus (which have a somewhat well-defined rim elevation).