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Grand Canyon Characteristics

 

Although many theories exist on the formation of the Grand Canyon, no one theory can be proved as the single most influential cause. However, it is most likely that the Grand Canyon be attributed to the coalescence of many processes such as vulcanism, erosion( by both wind and water/ice) and continental drift.. Yet most geologists do agree that The Colorado River and its course had a very profound impact on the formation of the Grand Canyon. Another huge factor in the creation of the Grand Canyon is its location, primarily in a desert region. Soil in the desert gets baked by the sun and becomes very dry and hard, thus making it hard to absorb water when it is prevalent and increasing its susceptibility to erosion.

The Grand Canyon, created by the Colorado River cutting a canal over millions of years, is about 277 miles (446 km) long, ranges in width from 0.25 to 18 miles (0.5 to 29 kilometers) and attains a depth of more than a mile (1,600 m). Almost two billion years of the Earth’s history has been exposed as the Colorado River and its tributaries cut through layer after layer of sediment while the Colorado Plateaus have uplifted.

The Colorado River basin (in which the Grand Canyon is situated) has developed in the past 40 million years and the Grand Canyon itself is probably less than five to six million years old (with most of the downcutting 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 enormous depth of the Grand Canyon and especially the height of its strata (most of which formed below sea level) was created by  5000 to 10,000 feet (1500 to 3000 m) of uplift of the Colorado Plateaus starting about 65 million years ago (during the Laramide Orogeny). This uplift steepened the stream gradient of the Colorado River and its tributaries, which thusly increased their speed and their ability to cut through rock. Also, wetter conditions during ice ages increased the amount of water in the Colorado River drainage system. The ancestral Colorado River responded by cutting its channel faster and deeper.

Then the base level and course of the Colorado River (or its ancestral equivalent) changed when about 5.3 million years ago 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. The Grand Canyon is also home to volcanic rocks A million years ago volcanic activity (mostly near the western canyon area) deposited ash and lava over the area which at times completely occluded the river. These volcanic rocks are the youngest in the canyon.

Grand Canyon rock layers

 

sources:

http://en.wikipedia.org/wiki/The_Grand_Canyon#Geology

http://www.kaibab.org/geology/gc_geol.htm