The Grand Canyon is a steep-sided gorge carved by the Colorado River in the U.S. state of Arizona, and parts of Nevada. It is largely contained within the Grand Canyon National Park — one of the first national parks in the United States.
Longstanding scientific consensus has been that the canyon was created by the Colorado River over a period of six million years, but research released in 2008 suggests a much longer 17 million year time span.
Nearly two billion years of the Earth's history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. The canyon started from the west, then another formed from the east, and the two broke through and met as a single majestic rent in the earth some six million years ago.
The Grand Canyon is unmatched throughout the world for the vistas it offers to visitors on the rim. It is not the deepest canyon in the world — Cotahuasi Canyon (11598 feet or 3535 m) and Colca Canyon (10499 feet or 3200 m), both in Arequipa, Peru, and Hell's Canyon (7,993 feet or2436 m) on the Oregon-Idaho border, are all deeper — but Grand Canyon is known for its overwhelming size and its intricate and colorful landscape.
Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.
Aside from casual sightseeing from the South Rim (a portion of the Grand Canyon (averaging 7000 feet or 2100 metres above sea level), whitewater rafting, hiking and running are also popular.
