Grand Canyon
Tours of the Grand Canyon are available daily by bus or air from Las Vegas.
The Grand Canyon was carved by the Colorado River, in northern Arizona, USA. The canyon usually appears Seven Natural Wonders of the World lists. Mosty of the canyon is contained within the Grand Canyon National Park — one of the first national parks in the United States.
The first recorded sighting of the Grand Canyon was by a European in 1540, García López de Cárdenas from Spain. The first scientific expedition to the canyon was led by U.S. Major John Wesely Powell in the late 1870s. Powell referred to the sedimentary rock units exposed in the canyon as "leaves in a great story book." However, long before that, the area was inhabited by Native Americans who built settlements within the canyon walls.
The Grand Canyon is a very deep - in places even a mile deep - 277 mile (446 km) long cut in the Colorado Plateaus that exposes uplifted Proteozoic and Paleozoic strata. The exposed strata are gradually revealed by the gentle incline beginning at Lee's Ferry and continuing to Hance Rapid. At the point where the river crosses the Grand Wash Fault (near Lake Mead) the Canyon ends.
The uplift of the Colorado Plateaus is uneven, resulting in the North Rim of the Grand Canyon being over a thousand feet (about 300 meters) higher than the South Rim.
Temperatures on the North Rim are generally lower than the South Rim because of the greater elevation (8000 feet/2438 m above sea level). Heavy snowfall is common during the winter months.
The details of the canyon's formation are still highly controversial. Geologists continue to debate ideas about the formation of Grand Canyon. According to Geologist Wayne Ranney: "To date, geologists have been unable to determine the canyon's precise age and what specific processes were at work in carving it". There is no authoritative theory on the formation of Grand Canyon.
The major geologic exposures in Grand Canyon range in age from the 2000 million year old Vishnu Schist at the bottom of the Inner Gorge to the 230 million year old Kaibab Limestone on the Rim. Many of the formations were deposited in warm shallow seas, near-shore environments (such as beaches), and swamps as the seashore repeatedly advanced and retreated over the edge of a proto-North America. Major exceptions include the Cococino Sandstone which was laid down as sand dunes in a desert and several parts of the Supai formation.
