7 Natural Wonders of the World

Grand Canyon
Arizona, United States
7 Natural Wonders of the World
Length of canyon-277 miles (446 km) long
Width of canyon- 4 to 18 miles (6.4 to 29 km)
Depth of canyon-over a mile (1.83 km) (6000 feet).[	The Grand Canyon [1]

 

Aside from casual sightseeing from the South Rim (averaging 7000 feet (2100 m) above sea level), whitewater rafting, hiking and running are especially popular. The floor of the valley is accessible by foot, muleback, or by boat or raft from upriver. Hiking down to the river and back up to the rim in one day is discouraged by park officials because of the distance, steep and rocky trails, change in elevation, and danger of heat exhaustion from the much higher temperatures at the bottom.

Eagle Rock at the Grand Canyon[2]

The Grand Canyon is a very colorful, steep-sided gorge, carved by the Colorado River, in the U.S. state of Arizona. It is contained largely within the Grand Canyon National Park, one of the first national parks in the United States. The canyon is about 277 miles (445 km) long, up to a mile (1.6km) deep, and from 0.25 - 15 miles (.4 - 24 km) wide.

Geologists estimate that formation of the canyon required at least 2 billion years considering that the layers exposed on the canyon walls and floor represent roughly two billion years of Earth history. Building up those hundreds of sedimentary layers required roughly 1.8 billion years, and 200 million years more were required for uplift and climate change to drain the seas then elevate them as the Colorado Plateau while the Colorado River simultaneously cut its channel. Most of the actual carving out of the canyon is thought to have occurred over the "brief" span of time between 2 and 1 million years ago.

The canyon appears on many versions of the Seven Natural Wonders of the World list and is one of the world's most popular tourist destinations. President Theodore Roosevelt, a major proponent of the Grand Canyon area, visited on numerous occasions to hunt mountain lions and enjoy the scenery.

Geography
The Grand Canyon is a deep cut in the Colorado Plateau that exposes uplifted Proterozoic and Paleozoic strata. The exposed strata are gradually revealed by the gentle incline beginning in the east at Lee's Ferry and continuing to Hance Rapid in the west. At the point where the Colorado River crosses the Grand Wash Fault (near Lake Mead), the Canyon ends.

Sedimentary layers exposed in the canyon walls range in age roughly from 200 million to 2 billion years and were formed primarily in warm shallow seas. 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 head-ward 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 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 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 than those from the South Rim.

Geology
The principal consensus among geologists is that the Colorado River basin (of which the Grand Canyon is a part) has developed in the past 40 million years and that the Grand Canyon itself is probably less than five to six million years old (with most of the down-cutting 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 major geologic exposures in Grand Canyon range in age from the two-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 5,000 to 10,000 feet 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).

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 (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.

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.

Canyon Exploration

The Spanish
Map of Grand Canyon area.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. Afterwards, no Europeans visited the canyon for over two hundred years until the search of a route from Santa Fe to California in 1776.

Native American inhabitation
The area was first inhabited by Native Americans who built settlements within the canyon walls. Among these, the earliest group identified to date have been classified as basketmakers and called the Anasazi tribe, which has been dated at about 500 B.C.E. Their successors in the canyon have been called the Pueblo people who are considered to be ancestors of the Hopi people. The Oraibi have occupied one of their dwelling sites, since 1150. The Cohonina also lived in the area. Large numbers of dated archaeological sites indicate that the Anasazi and the Cohonina flourished until about 1200 C.E. Something happened a hundred years after that, however, and common thought is that a drought forced inhabitants of both of these cultures to move away.

The Hopi people believe even today, that they emerged from the canyon and that their spirits rest there. The Paiute, Cerbat, and Navajo tribes also inhabited the area at different times. The Havasupai and Hualapai are descended from the Cerbat and still live in the immediate area. The Havasupai currently maintain 188,077 acres within the Canyon and rely on farming, grazing and tourism for their livelihood. Surrounded by cliffs, some portions of their reservation is only accessible by a narrow trail.

The European Americans
James Ohio Pattie, along with a group of European American trappers and mountain men, was probably the next European to reach the Grand Canyon in 1826, although there is little documentation to support this.

Jacob Hamblin (a Mormon missionary) was sent by Brigham Young in the 1850s 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.

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 European Americans to travel the Diamond Creek drainage and traveled eastwards along the South Rim.

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."