The Sahara Desert is the world's largest desert area. The word Sahara comes from the Arabic word sahra', meaning desert. It extends from the Africa's Atlantic Ocean side to the Red Sea and consists of the countries of Morocco, Algeria, Tunisia, Libya, Egypt, Mauritania, Mali, Niger, Chad, and Sudan. It is about 5,200 miles long. Overall, the Sahara Desert covers 3,500,000 square miles. The geography of the desert is varied. In the west, the Sahara is rocky with varied elevation. It does contain underground rivers, which sometime penetrate the surface, resulting in oases. The central region of the Sahara has more elevation than the other areas, with peaks such as Emi Koussi and Tahat. Even though the area lacks rainfall, these peaks are snowcapped during the winter. The Eastern part of the Sahara, the Libyan Desert, is dry with very few oases.
The Sahara's landscape features include shallow basins, large oasis depressions, gravel-covered plains, plateaus, and mountains, sand sheets, dunes and sand seas. Sand sheets and dunes cover over 25 percent of the Sahara's surface. The most common types of dunes include tied dunes, blowout dunes, and transverse dunes. Within the Sahara are several pyramidal dunes that reach over 500 feet in height while others reach over 1,000 feet. Researchers have for many years tried to figure out how these dunes were formed, but the case remains unsolved.
The boundaries, however, are not clearly defined and have been shifting for millennia. The Sahara was once a fertile area; millet was cultivated there over 8000 years ago. About 10,000 years ago, the Sahara was used as land for grazing in which elephants, giraffes and other animals thrived. It is estimated that in 4,000 B.C., the climate began to get drier. The fertile landscape dried up and the desert widened, creating the form that appears today. As conditions gradually became drier, however, and desertification set in, farmers abandoned their land and the...
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