Презентация по теме "США" (10 класс)

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  National Park
  Grand Canyon National Park is one of the United States' oldest national parks and is located in Arizona. Within the park lies the Grand Canyon, a gorge of the Colorado River, considered to be one of the major natural wonders of the world. The park covers 1,902 mi2 (4927 km2) of unincorporated area in Coconino County and Mohave County.
  

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  Most visitors to the park come to the South Rim, arriving on Arizona State Route 64. The Highway enters the park through the South Entrance, near Tusayan, Arizona, and heads eastward, leaving the park through the East Entrance.
  

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  All park accommodations are operated by the Xanterra corporation. Park headquarters are at Grand Canyon Village, a short distance from the South Entrance, being also the center of the most popular viewpoints.
  

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  Some thirty miles of the South Rim are accessible by road. A much smaller venue for tourists is found on the North Rim, accessed by Arizona State Route 67. There is no road connection between the two within Arizona except via the Navajo Bridge, near Page, Arizona, entailing a five-hour drive. Otherwise, the two rims of the Canyon are connected via Las Vegas, Nevada, and the Hoover Dam.
  

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  The rest of the Grand Canyon is extremely rugged and remote, although many places are accessible by pack trail and backcountry roads.
  The area around the Grand Canyon became a national monument on January 11, 1908, and was designated national park on February 26, 1919.
  

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  The creation of the park was an early success of the environmental conservation movement; its National Park status may have helped thwart proposals to dam the Colorado River within its boundaries. (Lack of this fame may have enabled Glen Canyon Dam to be built upriver, flooding Glen Canyon and creating Lake Powell.) In 1979, UNESCO declared it as a World Heritage Site.
  

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  The Grand Canyon itself, including its extensive system of tributary canyons, is valued for the combination of large size, depth, and the exposed layering of colorful rocks dating back to Precambrian times. It was created through the incision of the Colorado River and its tributaries after the Colorado Plateau was uplifted and the Colorado River system developed along its present path.
  

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  Grand Canyon
  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.
  

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  Geography
  The Grand Canyon is a massive rift in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata, and is also one of the six distinct physiographic sections of the Colorado Plateau province. It is not the deepest canyon in the world (Kali Gandaki Gorge in Nepal is far deeper), nor the widest (Capertee Valley in Australia is about 1 km wider and longer than Grand Canyon); however, the Grand Canyon is known for its visually overwhelming size and its intricate and colorful landscape.
  

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  Geologically it is significant because of the thick sequence of ancient rocks that are beautifully preserved and exposed in the walls of the canyon. These rock layers record much of the early geologic history of the North American continent.
  

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  Temperatures on the North Rim are generally lower than the South Rim because of the greater elevation (averaging 8,000 ft/2,438 m above sea level).Heavy rains are common on both rims during the summer months. Access to the North Rim via the primary route leading to the canyon is limited during the winter season due to road closures. Views from the North Rim tend to give a better impression of the expanse of the canyon than those from the South Rim.
  

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  Geology
  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 the journal Science in 2008, 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.
  

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  The result of all this erosion is one of the most complete geologic columns on the planet.
  
  The major geologic exposures in the 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. Interestingly, there is a gap of about one billion years between the stratum that is about 500 million years old and the lower level, which is about 1.5 billion years old. That indicates a period of erosion between two periods of deposition.