Science Fact of the Week 54 - The Grand Canyon
The Grand Canyon is a large gorge on the surface of the Earth which was created by the flow of the Colorado River, and is one of the natural wonders of the world. The canyon is close to 1 mile (1.6 km) deep, from 4 to 18 mi (6.4-29 km) wide and an impressive 217 mi (349 km) long. 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 geological 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 today. The exposed geological strata, layer upon layer, rising over a mile above the river, represent one of the most complete records of geological history that can be seen anywhere in the world.
The nearly 40 major sedimentary rock layers exposed in the Grand Canyon range in age from about 200 million to nearly 2 billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores in western North America. Both marine and terrestrial sediments are represented, including fossilized sand dunes from an extinct desert. Currently, the Grand Canyon is home to approximately 80 species of mammals, 250 species of birds, 25 types of reptiles and five species of amphibians. Plant life on the canyon is rare, as there is little soil, but varies from subtropical at the base to subarctic near the rims. The floor of the Grand Canyon contains fossil footprints of over 20 species of reptiles and amphibians, yet no fossilised reptile bones or teeth have ever been uncovered.
The Grand Canyon was set aside by the U.S. government in 1908 as a national monument and is now set inside the Grand Canyon National Park.