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The Grand Canyon

Overlook over the Colorado River in the Grand ...
Overlook over the Colorado River in the Grand Canyon along the Escalante Route. 
The Grand Canyon (Hopi: Ongtupqa; Yavapai: Wi:kaʼi:la) is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is contained within and managed by Grand Canyon National Park, the Hualapai Tribal Nation, and the Havasupai Tribe. 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. It is considered one of the Seven Natural Wonders of the World.[1]
 
The Grand Canyon is 277 miles (446 km) long, up to 18 miles (29 km) wide and attains a depth of over a mile (6,000 feet or 1,800 metres).[2] Nearly two billion years of the Earth's geological history has been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted.[3] While the specific geologic processes and timing that formed the Grand Canyon are the subject of debate by geologists,[4] recent evidence suggests the Colorado River established its course through the canyon at least 17 million years ago.[5][6] Since that time, the Colorado River continued to erode and form the canyon to its present-day configuration.[7]
For thousands of years, the area has been continuously 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.[8] The first European known to have viewed the Grand Canyon was García López de Cárdenas from Spain, who arrived in 1540.[9]
Federal protection
 
U.S. President Theodore Roosevelt visited the Grand Canyon in 1903. An avid outdoorsman and staunch conservationist, he established the Grand Canyon Game Preserve on November 28, 1906. Livestock grazing was reduced, but predators such as mountain lions, eagles, and wolves were eradicated. Roosevelt added adjacent national forest lands and redesignated the preserve a U.S. National Monument on January 11, 1908. Opponents such as land and mining claim holders blocked efforts to reclassify the monument as a U.S. National Park for 11 years. Grand Canyon National Park was finally established as the 17th U.S. National Park by an Act of Congress signed into law by President Woodrow Wilson on February 26, 1919.[18]
 
The federal government administrators who manage park resources face many challenges. These include issues related to the recent reintroduction into the wild of the highly endangered California condor, air tour overflight noise levels, water rights disputes with various tribal reservations that border the park, and forest fire management. The Grand Canyon National Park superintendent is Steve Martin. Martin was named superintendent on February 5, 2007, to replace retiring superintendent Joe Alston. Martin was previously the National Park Service Deputy Director and superintendent of several other national parks, including Denali and Grand Teton.[29] Federal officials started a flood in the Grand Canyon in hopes of restoring its ecosystem on March 5, 2008. The canyon's ecosystem was permanently changed after the construction of the Glen Canyon Dam in 1963.[30]
 
Between 2003 and 2011, 2,215 mining claims have been requested that are adjacent to the Canyon, including claims for uranium mines. Mining has been suspended since 2009, when U.S. Interior Secretary Ken Salazar temporarily withdrew 1 million acres (4,000 km2) from the permitting process, pending assessment of the environmental impact of mining. Critics of the mines are concerned that, once mined, the uranium will leach into the water of the Colorado River and contaminate the water supply for up to 18 million peoplePlants
There are approximately 1,737 known species of vascular plants, 167 species of fungi, 64 species of moss and 195 species of lichen found in Grand Canyon National Park.[50] This variety is largely due to the 8,000 foot elevation change from the Colorado River up to the highest point on the North Rim.[50] Grand Canyon boasts a dozen endemic plants (known only within the Park's boundaries) while only ten percent of the Park's flora is exotic.[50] Sixty-three plants found here have been given special status by the U.S. Fish and Wildlife Service.[50]
 
The Mojave Desert influences the western sections of the canyon, Sonoran Desert vegetation covers the eastern sections, and ponderosa and pinyon pine forests grow on both rims.[51]
Natural seeps and springs percolating out of the canyon walls are home to 11% of all the plant species found in the Grand Canyon.[51] The Canyon itself can act as a connection between the east and the west by providing corridors of appropriate habitat along its length.[51] The canyon can also be a genetic barrier to some species, like the Tassel-eared squirrel.[51]
 
The aspect, or direction a slope faces, also plays a major role in adding diversity to the Grand Canyon. North-facing slopes receive about one-third the normal amount of sunlight, so plants growing there are similar to plants found at higher elevations, or in more northern latitudes.[51] The south-facing slopes receive the full amount of sunlight and are covered in vegetation typical of the Sonoran Desert.[51]

Animals

Of the 34 mammal species found along the Colorado River corridor, 18 are rodents and eight are bats.[52]

Life zones and communities

The Park contains several major ecosystems.[10] Its great biological diversity can be attributed to the presence of five of the seven life zones and three of the four desert types in North America.[10] The five life zones represented are the Lower Sonoran, Upper Sonoran, Transition, Canadian, and Hudsonian.[10] This is equivalent to traveling from Mexico to Canada. Differences in elevation and the resulting variations in climate are the major factors that form the various life zones and communities in and around the canyon. Grand Canyon National Park contains 129 vegetation communities, and the composition and distribution of plant species is influenced by climate, geomorphology and geology.[50].[31]
 
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