Dust storm off West Africa
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Dust storm off West Africa

March 20, 2006

A massive cloud of dust from the Sahara sweeps into the Atlantic Ocean in this image acquired on March 8, 2006.

The Canary Islands (a part of Spain), are visible at the top right of the image and the Cape Verde Islands are located on the left; the coasts of Morocco, Western Sahara (currently under the control of Morocco), Mauritania, Senegal, Gambia, Guinea-Bissau, and Guinea (from top to bottom) are also depicted.

High winds carry sand from the erg, or sand dune deserts of West Africa may "fertilize" the oceans and even the Amazon rain forest by carrying and depositing minerals over great distances.

Dust storms are a natural phenomenon; however, they are sometimes exacerbated by agriculture practices that contribute to soil erosion- a process called desertification. Projects are currently underway to remedy this problem by creating barriers to block to movement of sand and planting vegetation to keep sand in place.

Also visible in the image (upper left corner) are interesting cloud formations. Clouds reflect all visible wavelengths of sunlight, which often makes appear white. However, clouds sometimes appear gray or even black, as they do here. This is caused by the process of accumulation, where droplets within the cloud merge with others, forming larger droplets.

The space between droplets then becomes larger, allowing more light to be absorbed within the cloud, making it appear darker to the naked eye. The clouds visible in this image demonstrate a fractal pattern. Although clouds look very irregular in shape, they exhibit "self-similarity", meaning that their structure looks similar when viewing it very close or very far away.

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