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Grand Canyon

From Academic Kids

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Grand Cañon at the foot of the Toroweap - looking east, by William Henry Holmes

The Grand Canyon is a colorful, steep-sided gorge, carved by the Colorado River, in northern Arizona. The canyon is one of the seven natural wonders of the world and is largely contained in the Grand Canyon National Park — one of the first national parks in the United States. President Theodore Roosevelt was a major proponent of the Grand Canyon area, visiting on numerous occasions to hunt mountain lions and enjoy the breathtaking scenery.

The canyon, created by the Colorado River cutting a channel over millions of years, is about 277 miles (446 km) long, ranges in width from 4 to 18 miles (6 to 29 kilometers) and attains a depth of more than a mile (1,600 m). Nearly 2000 million years of the Earth's history has been exposed as the Colorado River and its tributaries cut through layer after layer of sediment as the Colorado Plateaus have uplifted.

The Grand Canyon was first seen 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 in the canyon walls.

Grand Canyon from Moran Point
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Grand Canyon from Moran Point


Looking down Bright Angel Trail to the Grand Canyon.
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Looking down Bright Angel Trail to the Grand Canyon.
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Sunset seen from South Rim
Contents

Geography

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 Phantom Ranch. At the point where the river crosses the Grand Wash Fault (near Lake Mead) the Canyon ends.

Uplift associated with plate tectonics-caused mountain building events later moved these sediments thousands of feet upward and created the Colorado Plateaus. The higher elevation has also resulted in greater precipitation in the Colorado River drainage area, but not enough to change the Grand Canyon area from being semi-arid. Landslides and other mass wasting events then caused headward erosion and stream capture - all of which tend to increase the depth and width of canyons in arid environments.

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. The fact that the Colorado River flows closer to the South Rim is also explained by this asymmetrical uplift. Almost all runoff from the plateau behind the North Rim (which also gets more rain and snow) flows toward the Grand Canyon, while much of the runoff on the plateau behind the South Rim flows away from the canyon (following the general tilt). The result is much greater erosion and thus faster widening of the canyon and its tributary canyons north of the Colorado River.

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. Views from the North Rim tend to give a better impression of the expanse of the canyon rather than the views down which characterize the South Rim.

The Havasupai Indian Reservation is in a large tributary canyon on the south side of the Colorado River; it is administered by the Havasupai Indian Tribe.

Geology

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The Grand Canyon as seen from Earth orbit. Photo courtesy NASA.
Main article: Geology of the Grand Canyon area

The major sedimentary rock units exposed in the 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. Most 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. The major exception being the Cococino Sandstone which was laid down as sand dunes in a desert.

The great depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) can be attributed to 5000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateaus starting about 65 million years ago (which occurred in a series of uplift events rather than a continuous rise). This uplift has steepened the stream gradient of the Colorado River and its tributaries, which in turn has increased their speed and thus their ability to cut through rock.

The Colorado River drainage (of which the Grand Canyon is a part) has developed in the past 40 million years and the Grand Canyon itself is probably less than five to six million years old (with most of the downcutting occurring in the last two million years). The result of all this erosion is one of the most complete geologic columns on the planet. The river is still actively cutting deeper and is thus exposing older and older rock.

Wetter conditions during ice ages also increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper.

Then the base level and course of the Colorado River (or its ancestral equivalent) changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level (its lowest point). This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. The terraced walls of the canyon were created by differential erosion.

A million years ago volcanic activity (mostly near the western canyon area) deposited ash and lava over the area which at times even dammed the Colorado. These are the youngest rocks in the park.

With its current stream gradient, the Colorado River should cut another 1200 to 2000 feet (370 to 600 meters) into the rock of the canyon before reaching its base level.

Human history

Main article: History of the Grand Canyon area

Native American cultures

The Desert Culture

Little is known about the people who lived in western North America between 9,000 and 3,000 years ago. The earliest signs of human life in the Grand Canyon, radiocarbon dated to older than 3,000 years, belong to them - tiny willow twig representations of animals, a few of which were pierced with tiny twig spears. The desert culture were hunters and gatherers and made baskets and sandals, and hunted with stone-tipped spears. The first Europeans to find evidence of their activities were the 1934 Frazier, Eddy and Hatch expedition.

Large Kiva at Tusayan site
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Large Kiva at Tusayan site

The Ancestral Puebloans (The Ancient Ones, or Anasazi)

  • The Basketmakers
  • The Pueblo Anasazi
  • Ancient Puebloan Occupation of the Grand Canyon
    • Nankoweap Canyon
    • The Unkar Delta
    • The Bright Angel Site
  • Ancient Pueblo peoples leave the Canyon
    • Beamer's Cabin
      • The Beamers back window

The Modern Hopi (see also Pueblo people)

Other Cultures

European discovery and settlement

The Spanish Explorers

In September 1540, under orders from the conquistador Francisco Vasquez de Coronado to search for the fabled Seven Cities of Cibola, Captain Garcia Lopez de Cardenas, along with Hopi guides and a small group of Spanish soldiers, traveled to the South Rim of the Grand Canyon between Desert View and Moran Point. Pablo de Melgrossa, Juan Galeras and a third soldier descended some one third of the way into the Canyon until they were forced to return because of lack of water. It is speculated that their Hopi guides must have been reluctant to lead them to the river, since they must have known routes to the canyon floor. No Europeans visited the canyon for over 200 years.

American Exploration

The United States government made the Grand Canyon a national park in 1919.
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The United States government made the Grand Canyon a national park in 1919.

James Ohio Pattie, with a group of American trappers and mountain men were probably the next Europeans to reach the Canyon in 1826, although there is little in terms of documentation to support this.

Jacob Hamblin (a Mormon missionary) was sent by Brigham Young in the 1850's to locate easy river crossing sites in the Canyon. Building good relations with local Native Americans and white settlers, he discovered Lee's Ferry in 1858 and Pierce Ferry (later operated by, and named for, Harrison Pierce) - the only two sites suitable for ferry operation.

George Johnson led an expedition by stern wheeler steam boat that reached Black Canyon in 1857.

Also in 1857, the U.S. War Department asked Lieutenant Joseph Ives to lead an expedition to assess the feasibility of an up-river navigation from the Gulf of California. Also in a stern wheeler steamboat "Explorer", after two months and 350 miles of difficult navigation, his party reached Black Canyon some two months after George Johnson. The "Explorer" struck a rock and was abandoned. Ives led his party east into the Canyon - they were the first Europeans to travel the Diamond Creek drainage and traveled eastwards along the South Rim.

James White (this links to a disambiguation page that does not contain a link to this James White yet!)

  • The John Wesley Powell River Expeditions
  • The Brown-Stanton River Expedition
  • Other expeditions

Settlement on the rim

El Tovar Hotel
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El Tovar Hotel

Activities

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Aside from casual sightseeing from the South Rim (averaging 7000 feet/2134 m above sea level), whitewater rafting and hiking are especially popular. The floor of the valley is accessible by hiking, muleback, or by boat or raft from upriver. Hiking down to the river and back up to the rim in one day is highly discouraged by park officials, due to the distance, effort required, and danger of heat exhaustion from the much higher temperatures at the bottom. Even hiking along the rim must be done with care in spots, and there are frequently warning signs posted along rim trails.

Commercially organized rafting trips, using 35-foot, 15 person "baloney boats" equipped with outboard engines, make the trip from Lee's Ferry to Diamond Creek in about six days. 18-foot rafts and dories powered only with oars and paddles take over two weeks to complete the journey. Sightseers are also carried over the canyon by helicopter.

In 1963, author and backpacker Colin Fletcher became the first man to walk the length of Grand Canyon National Park entirely within the rim of the canyon, as chronicled in his bestselling memoir The Man Who Walked Through Time.

Colorado River system
Dams and aqueducts (see US Bureau of Reclamation)
Shadow Mountain Dam | Granby Dam | Glen Canyon Dam | Hoover Dam | Davis Dam | Parker Dam | Palo Verde Diversion Dam | Imperial Dam | Laguna Dam | Morelos Dam | Colorado River Aqueduct | San Diego Aqueduct | Central Arizona Project Aqueduct | All-American Canal | Coachella Canal | Redwall Dam
Natural features
Colorado River | Rocky Mountains | Colorado River Basin | Grand Lake | Sonoran desert | Mojave desert | Imperial Valley | Colorado Plateau | Grand Canyon | Glen Canyon | Marble Canyon | Paria Canyon | Gulf of California/Sea of Cortez | Salton Sea
Tributaries
Dirty Devil River | Dolores River | Escalante River | Gila River | Green River | Gunnison River | Kanab River | Little Colorado River | Paria River | San Juan River | Virgin River
Major reservoirs
Fontenelle Reservoir | Flaming Gorge Reservoir | Taylor Park Reservoir | | Navajo Reservoir | Lake Powell | Lake Mead | Lake Havasu
Dependent states
Arizona | California | Colorado | Nevada | New Mexico | Utah (See: Colorado River Compact)
Designated areas
Glen Canyon National Recreation Area | Lake Mead National Recreation Area


See also

External links

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da:Grand Canyon de:Grand-Canyon-Nationalpark es:Gran Can fr:Parc national du Grand Canyon id:Grand Canyon ja:グランド・キャニオン nl:Grand Canyon pl:Wielki Kanion zh:科羅拉多大峽谷

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