The Grand Canyon is a steep-sided gorge carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, one of the first national parks in the United States. 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.
A map of the Grand Canyon and surrounding areas, circa 1908.Longstanding scientific consensus has been that the canyon was created by the Colorado River over a six million year period. The canyon is 277 miles (446 km) long, ranges in width from 4 to 18 miles (6.4 to 29 km) and attains a depth of over a mile (1.83 km) (6000 feet). Nearly two billion years of the 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. The "canyon began in the west, followed by another that formed in the east. Eventually, the two broke through and met as a single majestic rent in the earth some six million years ago. The merger apparently occurred where the river today bends to the west, in the area known as the Kaibab Arch."
A View of Colarado River
Grand Canyon Winter: Covered in Snow
Before European immigration, the area was inhabited by Native Americans who built settlements within the canyon and its many caves. The Pueblo people considered the Grand Canyon ("Ongtupqa" in Hopi language) a holy site and made pilgrimages to it. The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.
Geology
View from Grandview Point
A map of the Grand Canyon and surrounding areas, circa 1908.Longstanding scientific consensus has been that the canyon was created by the Colorado River over a six million year period. The canyon is 277 miles (446 km) long, ranges in width from 4 to 18 miles (6.4 to 29 km) and attains a depth of over a mile (1.83 km) (6000 feet). Nearly two billion years of the 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. The "canyon began in the west, followed by another that formed in the east. Eventually, the two broke through and met as a single majestic rent in the earth some six million years ago. The merger apparently occurred where the river today bends to the west, in the area known as the Kaibab Arch."
A View of Colarado River
Grand Canyon Winter: Covered in Snow
Before European immigration, the area was inhabited by Native Americans who built settlements within the canyon and its many caves. The Pueblo people considered the Grand Canyon ("Ongtupqa" in Hopi language) a holy site and made pilgrimages to it. The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.
Geology
The principal consensus among geologists is that the Colorado River basin (of which the Grand Canyon is a part) has developed in the past 40 million years. A recent study places the origins of the canyon beginning some 17 million years ago. Previous estimates had placed the age of the canyon at 5 to 6 million years. The study, which was published in 2008 in the journal Science utilized uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon. There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus. The result of all this erosion is one of the most complete geologic columns on the planet.
There are a number of lava flows on the plateau that the canyon is cut into (yellow in Figure 1, above). These lava flows are Cenozoic in age, and some of them spill into the canyon. The walls of the canyon are mostly cut into horizontal rock layers of Paleozoic age (green in Figure 1, above). There is an angular unconformity at the bottom of the Paleozoic layers. An angular unconformity is the result of tilting and eroding of the lower layers before the upper ones are deposited. These tilted and eroded layers are Precambrian in age (blue in Figure 1, above).
The geological relationships of the various formations are quite clear. The lava flows which spill into the canyon must be younger than the canyon. The canyon must be younger than the rock layers that it cuts into. The sediments above the angular unconformity must be younger than the sediments below it.
There are a number of lava flows on the plateau that the canyon is cut into (yellow in Figure 1, above). These lava flows are Cenozoic in age, and some of them spill into the canyon. The walls of the canyon are mostly cut into horizontal rock layers of Paleozoic age (green in Figure 1, above). There is an angular unconformity at the bottom of the Paleozoic layers. An angular unconformity is the result of tilting and eroding of the lower layers before the upper ones are deposited. These tilted and eroded layers are Precambrian in age (blue in Figure 1, above).
The geological relationships of the various formations are quite clear. The lava flows which spill into the canyon must be younger than the canyon. The canyon must be younger than the rock layers that it cuts into. The sediments above the angular unconformity must be younger than the sediments below it.
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