Canyon

A canyon (Spanish: cañón; archaic British English spelling: cañon)[1] or gorge is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales.[2] Rivers have a natural tendency to cut through underlying surfaces, eventually wearing away rock layers as sediments are removed downstream. A river bed will gradually reach a baseline elevation, which is the same elevation as the body of water into which the river drains. The processes of weathering and erosion will form canyons when the river's headwaters and estuary are at significantly different elevations,[3] particularly through regions where softer rock layers are intermingled with harder layers more resistant to weathering.

"Gorge" and "Cañon" redirect here. For other uses, see Canyon (disambiguation), Gorge (disambiguation), and Canon (disambiguation).
The Grand Canyon, Arizona, at the confluence of the Colorado River and Little Colorado River

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

Steep-sided valleys in the seabed of the continental slope are referred to as submarine canyons. Unlike canyons on land, submarine canyons are thought to be formed by turbidity currents and landslides.

Etymology
Sumidero Canyon, Mexico

The word canyon is Spanish in origin (cañón,[4] pronounced [kaˈjɲon]), with the same meaning. The word canyon is generally used in North America, while the words gorge and ravine (French in origin) are used in Europe and Oceania, though gorge and ravine are also used in some parts of North America. In the United States, place names generally use canyon in the southwest (due to their proximity to Spanish-speaking Mexico) and gorge in the northeast (which is closer to French Canada), with the rest of the country graduating between these two according to geography. In Canada, a gorge is usually narrow while a ravine is more open and often wooded. The military-derived word defile is occasionally used in the United Kingdom.

Formation

Most canyons were formed by a process of long-time erosion from a plateau or table-land 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 than in wet areas because physical weathering has a more localized 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 serve 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, in a process known as frost wedging.[5] Canyon walls are often formed of resistant sandstones or granite.

Snake River Canyon, Idaho

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. In the United States, 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. As limestone is soluble to a certain extent, cave systems form in the rock. When a cave system collapses, a canyon is left, as in the Mendip Hills in Somerset and Yorkshire Dales in Yorkshire, England.

Box canyon

A box canyon is a small canyon that is generally shorter and narrower than a river canyon, with steep walls on three sides, allowing access and egress only through the mouth of the canyon. Box canyons were frequently used in the western United States as convenient corrals, with their entrances fenced.[6]

Largest canyons

The definition of "largest canyon" is imprecise, because a canyon can be large by its depth, its length, or the total area of the canyon system. Also, the inaccessibility of the major canyons in the Himalaya contributes to them 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).

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 metres (18,000 ft). It is slightly longer than the Grand Canyon in the United States.[7] Others consider the Kali Gandaki Gorge in midwest Nepal to be the deepest canyon, with a 6,400 metres (21,000 ft) difference between the level of the river and the peaks surrounding it.

Vying for the deepest canyon in the Americas is the Cotahuasi Canyon and Colca Canyon, in southern Peru. Both have been measured at over 3,500 metres (11,500 ft) deep.

The Grand Canyon of northern Arizona in the United States, with an average depth of 1,600 metres (5,200 ft) and a volume of 4.17 trillion cubic metres (147 trillion cubic feet),[8] is one of the world's largest canyons. It was among the 28 finalists of the New7Wonders of Nature worldwide poll. (Some referred to it as one of the seven natural wonders of the world.)[9]

The largest canyon in Africa is the Fish River Canyon in Namibia.[10]

In August 2013, the discovery of Greenland's Grand Canyon was reported, based on the analysis of data from Operation IceBridge. It is located under an ice sheet. At 750 kilometres (470 mi) long, it is believed to be the longest canyon in the world.[11]

The Capertee Valley in Australia is commonly reported as being the second largest (in terms of width) canyon in the world.[12][13]

Panoramic view of the Capertee Valley in Australia, the second largest (in terms of width) of any canyon in the world

Cultural significance

Some canyons have notable cultural significance. Evidence of early humanoids has been discovered in Africa's Olduvai Gorge. In the southwestern United States, canyons are important archeologically because of the many cliff-dwellings built in such areas, largely by the ancient Pueblo people who were their first inhabitants.

Notable examples
For a complete list, see List of canyons.

The following list contains only the most notable canyons of the world, arranged by continent and then country.

Africa
Fish River Canyon, Namibia
Oribi Gorge, South Africa

Namibia

South Africa

Tanzania

Americas

Argentina

Brazil
Itaimbezinho Canyon, Brazil

Canada

Colombia

Mexico

Peru

United States
Green River overlook, Canyonlands National Park, Utah

Asia
One of the Three Gorges of the Yangtze river, China
The gorge of the Kabul River in Afghanistan

China

India

Taiwan

Others
Cheddar Gorge, England
Le cirque de la Madeleine, Gorges de l'Ardèche, France

Europe

United Kingdom

France

Spain
  • Tagus River Gorge, Guadalajara Province
  • Gallo River Gorge, Guadalajara Province
  • Guadalope River Gorge, Teruel Province
  • Lobos River Gorge, Soria Province

Ukraine
Buky Canyon, Ukraine

Others
Joffre Gorge, Karijini National Park, Australia

Oceania

Australia

New Zealand

Canyons on other planetary bodies

Venus has many craters and canyons on its surface. The troughs on the planet are part of a system of canyons that is more than 6 400  km long.

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See also

 Environment portal

References
  1. "canon". archaic spelling of canyon
  2. Society, National Geographic (20 May 2011). "canyon". National Geographic Society.
  3. Ward Cameron. "Understanding Canyon Formation".
  4. Chisholm, Hugh, ed. (1911). "Canyon" . Encyclopædia Britannica (11th ed.). Cambridge University Press.
  5. "The Geology of the Grand Canyon". Retrieved 2015-10-01.
  6. "box canyon". Encarta World English Dictionary. 2009. Archived from the original on 2009-12-17. Retrieved 2009-08-04.
  7. "China Virtual Museums: Canyon". Kepu.net.
  8. "Park Statistics". National Park Service. USA.
  9. Truong, Alice (1 July 2011). "Everything About the Grand Canyon". Discovery Communications. Retrieved 5 February 2012.
  10. Cohen, Callan; Spottiswoode, Claire & Rossouw, Jonathan (2006). Southern African Birdfinder. p. 210. ISBN 978-1-86872-725-4.
  11. "Grand Canyon of Greenland Discovered under Ice". news.discovery.com. 2017-05-10.
  12. Fitzsimons, David (14 December 2015). "Capertee Valley: Australia's own Grand Canyon". Daily Telegraph. Retrieved March 28, 2016.
  13. Kruszelnicki, Dr. Karl S. (22 May 2012). "Grand Canyon is not so grand › Dr Karl's Great Moments In Science". ABC Science. Retrieved March 28, 2016.
  14. Valerio Poggiali, Marco Mastrogiuseppe, Alexander G. Hayes, Roberto Seu, Samuel P. D. Birch, Ralph Lorenz, Cyril Grima, Jason D. Hofgartner, "Liquid-filled Canyons on Titan", 9 August 2016, http://onlinelibrary.wiley.com/doi/10.1002/2016GL069679/abstract

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