Grand Canyon

The Grand Canyon is a famous canyon in Arizona, formed by the Colorado River. It is a UNESCO World Heritage Site,^[1] and a National Park of the United States. It is also one of the Seven Natural Wonders of the World.

The Grand Canyon is 277 miles (446 km) long, up to 18 miles (29 km) wide and is over a mile (1.83 km) (6000 feet) deep in places.^[2] Nearly two billion years past of the Earth's geological history have been exposed as the Colorado River and its tributaries (smaller rivers) cut their channels through layer after layer of rock.^[3]

Evidence suggests the Colorado River established its course through the canyon at least 17 million years ago.^[4][5][6] Since that time, the Colorado River continued to erode and form the canyon to the point we see it at today.

"Local erosion in the western Grand Canyon began about 17 million years ago, but a through-flowing Colorado River to the Pacific Ocean did not exist until about 5.4 million years ago... most of the downward cutting has been concentrated in the last 2.5 million years".^[7]

1. ↑ UNESCO, "Grand Canyon National Park"; retrieved 2012-4-18
2. ↑ Kiver, E.P.; Harris, D.V. (1999). Geology of US Parklands. Wiley. p. 902.
3. ↑ Geologic formations of the Grand Canyon National Park Service. Retrieved 2009-11-17
4. ↑ Ranney, Wayne (2005). Carving Grand Canyon: evidence, theories, and mystery. Grand Canyon Association. ISBN 978-0-938216-82-7.
5. ↑ "Grand Canyon still grand but older". New York Times. 2008-03-07.
6. ↑ Polyak, Victor; Hill, Carol; Asmerom, Yemane (2008-03-07). "Age and evolution of the Grand Canyon revealed by U-Pb dating of water table-type speleothems" (PDF). Science. 319 (5868): 1377–1380. Bibcode:2008Sci...319.1377P. doi:10.1126/science.1151248. PMID 18323451. S2CID 206509716.
7. ↑ Butler, Bill. "Evolution of the Colorado River and its tributaries including the origin and formation of the Grand Canyon. Geologic history of the Grand Canyon". Retrieved 2010-10-22.