Essay: Physical Geology

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Wind, Dust, And Deserts

Deserts represent a third of the landscape on Earth, and are created as a result of the lack of water (Planet Earth 2006, film documentary). Every desert has one thing in common; the intense daytime sun. In Australia, the most arid continent on Earth, and in the daytime temperatures rise five degrees per hour, and by noon, is a threat to any surface life (Planet Earth). The Gobi Desert is one of the most interesting, because it is a constantly frozen desert. One would think that the presence of snow would equate to moisture, but the Gobi air is so cold that the snow never melts (Planet Earth). With the intensity of the sun during the day, the snow literally evaporates, and no moisture is absorbed into the sand dunes (Planet Earth). One of the reasons for the Gobi's lack of water is the Himalayas, to the south. The massive mountain range, which prevents rain clouds from moving over the Gobi (Planet Earth). As a result, the south side of the Himalayas, where the water from rain spills over the mountainside, is a lush and green area (Planet Earth).

The Sahara Desert in North Africa is the largest desert in the world. There are constant winds blowing across the Sahara, which have eroded what were once a continuous rock formation, leaving in its stead broken sections of sharp rock formations scattered across the region (Planet Earth). Over time, with the constant blowing winds and the sand being blown against the rock formations, they, too, will erode into sand (Planet Earth). The Colorado Plateau, in the Southwestern United States, is geologically comparable to the Sahara (Baars 2000, p. 143). On the Plateau, the change from an environment where there was once water to one without water was an abrupt change (p. 143). Evidence of the transformation is seen in the sandstone formations (p. 143), which, like the Sahara, are eroding, although the erosion is perhaps not as remarkable as that in the Sahara, indicating only that the Colorado Plateau is a relatively new desert in terms of the eons of the planet's evolution.

"The sandstone formations represent the desert accumulations of this interval of time. The lower of the great windblown deposits is the Wingate Sandstone, which is nearly everywhere a reddish cliff-forming formation that directly overlies the Chinle Formation. The sandstone is usually cross-stratified with the expected steeply dipping individual beds in variably shaped bundles that typify windblown deposits. In a few localities the small-scale, low angle cross-bedding of stream deposits can be differentiated from the normal texture of the formation. Thus, conditions varied, at least seasonally, within the great southwest desert of the Early Jurassic time (p. 143)."

The deserts of the American Southwest are not completely dry, and for that reason we find cacti, which, during the yearly monsoonal rain season, absorb the water. In the Sahara, we find no such water or plant life, and the rainfall is sporadic, not enough to give life to vegetation. The Sahara gives rise to massive windstorms, with dust rising 500 meters high, and reducing visibility for days at a time (Planet Earth). Satellite imaging of the Sahara show river patterns, where thousands of years ago, the Sahara could have been green, and could have supported an agrarian society (Druy 2001, p. 179).

One of the most arid deserts on earth is Chile's Atacama Desert, where it rains once every 50 years (Planet Earth). There are cacti and animal life, which get their water from the cacti (Planet Earth). The moisture that forms on the cacti is as a result of a cold ocean current, which creates a fog over the Atacama at its ocean perimeter (Planet Earth). The fog and cold air form dew on the cacti (Planet Earth). Otherwise, the Atacama is a dry, arid, and hostile environment. The soil conditions of the Atacama Desert are extremely low in organic carbon and nitrogen levels (Maier, Pepper, and Gerba 2009, p. 128). Like the Gobi, the Atacama is the product of a high mountain range, the Andes, which block the moisture from reaching the Atacama (Bowman 1915, p. 85).

Egypt's White Desert is a marked with strange looking rocks, that are white, and are being constantly assaulted by sandy winds blowing against them and eroding them. The erosion of what were clearly once massive rock formations,… [END OF PREVIEW]

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