Canyon

A canyon (from Spanish: cañón; archaic British English spelling: cañon),[1] gorge or chasm, 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.

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.

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.

The cliffs form because harder rock strata that are resistant to erosion and weathering remain exposed on the valley walls.

The wind and water from the river combine to erode and cut away less resistant materials such as shales.

Box canyons were frequently used in the western United States as convenient corrals, with their entrances fenced.

[8] Others consider the Kali Gandaki Gorge in 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.

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),[9] is one of the world's largest canyons.

[11] In August 2013, the discovery of Greenland's Grand Canyon was reported, based on the analysis of data from Operation IceBridge.

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.