Grand Canyon
Encyclopedia : G : GR : GRA : Grand Canyon
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- For other Grand Canyons see Grand Canyon (disambiguation).
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 0.25 to 15 miles (0.4 to 24 kilometers) and attains a depth of more than a mile (1,600 m). Nearly two billion 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 first recorded sighting of the Grand Canyon by a European was in 1540, García López de Cárdenas from Spain.[[Citing sources citation needed]] The first scientific expedition to the canyon was led by U.S. Major John Wesley Powell in the late 1860s. Powell referred to the sedimentary rock units exposed in the canyon as "leaves in a great story book." Long before that, the area was inhabited by Native Americans who built settlements within the canyon walls.
Geography
The Grand Canyon is a very deep - in places over a mile deep - 277 mile (446 km) long cut in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata. The canyon appears on many versions of the Seven Natural Wonders of the World list, although none of these lists is by any means authoritative. 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.
Uplift associated with plate tectonics-caused mountain building events later moved these sediments thousands of feet upward and created the Colorado Plateau. 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 Plateau 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 meters 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 from the South Rim.
Geology
- Main article: Geology of the Grand Canyon area
The major geologic exposures in Grand Canyon range in age from the 2 billion 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 Permian Coconino Sandstone which was laid down as sand dunes in a desert and several parts of the Supai Group.
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 (during the Laramide Orogeny). 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 (see the elevation summary of the Colorado River for present conditions).
The Colorado River basin (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.
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 completely obstructed the river. These volcanic rocks are the youngest in the canyon.
Human history
Main article: History of the Grand Canyon areaThe
- 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 windo
The Modern
Other cultures
- The Cohonina
- The Sinagua
- The Pai (The People)
- The Hualapai (The People of the Pine Trees)
- The Havasupai (The People of the blue-green water)
- The Paiutes (The Water People)
- The Dineh (The People)
European discovery and settlement
The Spanish Explorers
Other cultures
- The Cohonina
- The Sinagua
- The Pai (The People)
- The Hualapai (The People of the Pine Trees)
- The Havasupai (The People of the blue-green water)
- The Paiutes (The Water People)
- The Dineh (The People)
European discovery and settlement
The Spanish Explorers
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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.[[Citing sources citation needed]] 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 two hundred years.
- Fathers Francisco Atanasio Dominguez and Silvestre Velez de Escalante were two Spanish Priests who, with a group of Spanish soldiers, explored southern Utah and traveled along the North Rim of the Canyon in Glen and Marble Canyons in search of a route from Santa Fe to California in 1776.[[Citing sources citation needed]]
American Exploration
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 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.[[Citing sources citation needed]]
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.[[Citing sources citation needed]] 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
- Miners
- *"Captain" John Hance
- *William W. Bass
- *Louis Boucher "The Hermit"
- *Seth Tanner
- *Charles Spencer
- *D. W. "James" Mooney
- Lees Ferry
- *John Doyle Lee
- *Emma Lee (17th of John Lee's 19 wives)
- *J. S. Emmett
- *Charles Spencer
- Phantom Ranch
- *David Rust
- *Mary Colter
- Grand Canyon Village
- *Ralph Cameron
- Federal protection
Recent history
On the morning of June 30, 1956, a TWA Lockheed Super Constellation and a United Airlines Douglas DC-7 departed Los Angeles International Airport within three minutes of one another on eastbound transcontinental flights. Approximately 90 minutes later, the two propeller-driven airliners collided above the canyon while both were flying in unmonitored airspace.
The wreckage of both planes fell into the eastern portion of the canyon, on Temple and Chuar buttes, near the confluence of the Colorado and Little Colorado rivers. The disaster killed all 128 passengers and crew members aboard both planes.
This accident lead to the institution of high-altitude flightways and positive control by en route ground controllers.
Activities
Aside from casual sightseeing from the South Rim (averaging 7000 feet/2134 m above sea level), whitewater rafting and hiking are especially popular.[[Citing sources citation needed]] 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 frequent warning signs posted along rim trails.The National Park Service provides wheelchairs for temporary day use by park visitors. No rental fee is charged.
See also
References
- Grand Canyon: A Visitor's Companion, George Wuerthner (Stackpole Books, 1998)
- Grand Canyon: Today and All Its Yesterdays, Joseph Wood Krutch (1957)
- How the Canyon Became Grand, Stephen J. Pyne (Penguin, 1998)
- An introduction to Grand Canyon Geology, by L. Greer Price (Grand Canyon Association, 1999, ISSN 0-938216-68-6)
- Along the Rim, by Michael F. Anderson (Grand Canyon Association, 2001, ISSN 0-938216-75-9)
- Life in Stone, by Christa Sadler (Grand Canyon Association, 2006, ISSN 0-938216-81-3)
External links
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