Acanyon(fromSpanish:cañón;archaicBritish Englishspelling:cañon),[1]gorgeorchasm,is a deep cleft betweenescarpmentsorcliffsresulting fromweatheringand theerosiveactivity of a river overgeologic time scales.[2]Rivers have a natural tendency to cut through underlying surfaces, eventually wearing away rock layers assedimentsare removed downstream. Ariver bedwill 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'sheadwatersandestuaryare at significantly different elevations,[3]particularly through regions where softer rock layers are intermingled with harder layers more resistant to weathering.
A canyon may also refer to a rift between two mountain peaks, such as those in ranges including theRocky Mountains,theAlps,theHimalayasor theAndes.Usually, a river or stream carves out such splits between mountains. Examples of mountain-type canyons areProvo Canyonin Utah orYosemite Valleyin California'sSierra Nevada.Canyons within mountains, or gorges that have an opening on only one side, are called box canyons.Slot canyonsare very narrow canyons that often have smooth walls.
The wordcanyonis Spanish in origin (cañón,[4]pronounced[kaˈɲon]), with the same meaning. The word canyon is generally used inNorth America,while the wordsgorgeandravine(French in origin) are used inEuropeandOceania,thoughgorgeandravineare also used in some parts of North America. In theUnited States,place names generally usecanyonin the southwest (due to their proximity toSpanish-speaking Mexico) andgorgein the northeast (which is closer toFrench Canada), with the rest of the country graduating between these two according to geography. InCanada,agorgeis usually narrow while aravineis more open and often wooded. The military-derived worddefileis occasionally used in theUnited Kingdom.
Most canyons were formed by a process of long-timeerosionfrom aplateauor table-land level. Thecliffsform because harderrock stratathat areresistantto 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 more localized effect in arid zones. The wind and water from the river combine to erode and cut away less resistant materials such asshales.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, in a process known as frost wedging.[5]Canyon walls are often formed of resistantsandstonesorgranite.
Canyons often form in areas oflimestonerock. As limestone is soluble to a certain extent,cavesystems form in the rock. When a cave system collapses, a canyon is left, as in theMendip HillsinSomersetandYorkshire DalesinYorkshire,England.
Abox canyonis 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 thewestern United Statesas convenient corrals, with their entrances fenced.[6]
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 theHimalayacontributes 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 flatplateaus(which have a somewhat well-defined rim elevation).
TheYarlung Tsangpo Grand Canyon(or Tsangpo Canyon), along theYarlung Tsangpo RiverinTibet,is regarded by some as the deepest canyon in the world at 5,500 metres (18,000 ft). It is slightly longer than theGrand Canyonin the United States.[7]Others consider theKali Gandaki Gorgein midwest Nepal to be the deepest canyon, with a 6,400-metre (21,000 ft) difference between the level of the river and the peaks surrounding it.
Vying for the deepest canyon in the Americas is theCotahuasi CanyonandColca Canyon,in southern Peru. Both have been measured at over 3,500 metres (11,500 ft) deep.
TheGrand Canyonof northernArizonain 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 theNew 7 Wonders of Natureworldwide poll. (Some referred to it as one of theseven natural wonders of the world.)[9]
In August 2013, the discovery ofGreenland'sGrand Canyonwas reported, based on the analysis of data fromOperation 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]
Despite not being quite as deep or long as the Grand Canyon, theCapertee Valleyin Australia is actually 1 km wider than the Grand Canyon, making it the widest canyon in the world.[12][13]
Panoramic view of theCapertee Valleyin Australia, the widest largest canyon in the world
Some canyons have notable cultural significance. Evidence ofarchaic humanshas been discovered in Africa'sOlduvai Gorge.In the southwestern United States, canyons are importantarcheologicallybecause of the manycliff-dwellingsbuilt in such areas, largely by theancient Pueblo peoplewho were their first inhabitants.
^Cohen, Callan; Spottiswoode, Claire & Rossouw, Jonathan (2006).Southern African Birdfinder.Penguin Random House South Africa. p. 210.ISBN978-1-86872-725-4.
Canyons and gorgestravel guide from Wikivoyage
Media related toCanyonsat Wikimedia Commons
