The Grand Canyon is a steep-sided
canyon carved by the Colorado River in Arizona, United States. The Grand Canyon
is 277 miles (446 km) long, up to 18 miles (29 km) wide and attains a depth of
over a mile (6,093 feet or 1,857 meters).[5]
The canyon and adjacent rim are contained within Grand
Canyon National Park, the Kaibab National Forest, Grand Canyon–Parashant
National Monument, the Hualapai Indian Reservation, the Havasupai Indian
Reservation and the Navajo Nation. President Theodore Roosevelt was a major
proponent of preservation of the Grand Canyon area and visited it on numerous
occasions to hunt and enjoy the scenery.
Nearly two billion years of Earth's geological 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.[6]
While some aspects about the history of incision of the canyon are debated by
geologists,[7] several recent studies support the hypothesis that the Colorado
River established its course through the area about 5 to 6 million years
ago.[1][8][9] Since that time, the Colorado River has driven the down-cutting
of the tributaries and retreat of the cliffs, simultaneously deepening and
widening the canyon.
