Dust Storm off Egypt
A large, swirling mass of dust, visible on the top left portion of the image, is blowing from the Sahara into the Mediterranean Sea. The country on the left is Libya, while the Nile Delta of Egypt is clearly recognizable on the right side of the image. Dust storms occur when very strong winds carry sand from the erg, or sand dune deserts, of the Sahara. They are a naturally occurring phenomenon and may â€œfertilizeâ€ the oceans and even the Amazon rain forest by carrying and depositing minerals over great distances. However, dust storms are often 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 by planting vegetation to keep sand in place.
The Sahara, which means â€œdesertâ€ in Arabic, is the world's second largest desert (after Antarctica) spanning 9 million square kilometers (3.5 million square miles). The Sahara is of course very hot and dry, with a mean annual temperature of about 30 degrees Celsius (86 degrees Fahrenheit) and mean annual rainfall of 25 millimeters (less than an inch). But what makes this environmental one of the harshest on the planet is its variability: temperature can fluctuate by as many as 38 degrees Celsius (100 degrees Fahrenheit) in a single day; the region can also receive no rain for years at a time, only to be deluged with a single, large rainfall event.