The Grand Canyon is a steep-sided canyon 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. The Grand Canyon is 277 miles (446 km) long, up to 18 miles (29 km) wide 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. While the specific geologic processes and timing that formed the Grand Canyon are the subject of debate by geologists, recent evidence suggests the Colorado River established its course through the canyon at least 17 million years ago. Since that time, the Colorado River continued to erode and form the canyon to the point we see it at today.
Grand Canyon National Park is one of the world's premier natural attractions, attracting about five million visitors per year. 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 two rims of the Canyon are connected via Las Vegas, Nevada, and the Hoover Dam. The rest of the Grand Canyon is extremely rugged and remote, although many places are accessible by pack trail and backcountry roads.
In 1979, UNESCO declared it as a World Heritage Site. 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.
Video of Grand Canyon Helicoptor Tour 2010 © Joe Mendonca
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 a holy site and made pilgrimages to it. The first European known to have viewed the Grand Canyon was Garc?a L?pez de C?rdenas from Spain, who arrived in 1540.
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. 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 5,000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateau, starting about 65 million years ago. 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. Weather conditions during the 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.
The base level and course of the Colorado River changed 5.3 million years ago when the Gulf of California opened and lowered the river's base level. This increased the rate of erosion and cut nearly all of the Grand Canyon's current depth by 1.2 million years ago. About one 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.
|Country||United States of America|
|Area||1,217,403.32 acres (4,926.6564 km²)|
|Established||February 26, 1919|