The Sahara is one of the hottest places on Earth. Even though temperatures there may rise to 136 F (57.7 C), its dryness, not heat, that makes a place like the Sahara a desert. The frozen continent of Antarctica is so dry that some scientists consider it a desert, too.
By studying satellite photos, some scientists have come to believe that the Sahara regularly shrinks and grows. In the early 1980s, the Sahara's southern edge expanded into the Sahel, a dry band that separates the desert from the savanna. But by the mid-1980s this area was green and wet again.
Due to the massive size of the Sahara, Africa is split into 2 regions: that which lies above or forms part of the Sahara and the rest of Africa south of the Sahara. On the west, the Sahara is bordered by the Atlantic Ocean and on the east by the Red Sea, and to the north are the Atlas Mountains and Mediterranean Sea.
Many researchers have gone into the Sahara looking for clues as to how long ago humans began inhabiting the desert. According to archeologists, the Sahara was much more densely populated thousands of years ago when the desert's climate was not as harsh as it is today. Fossils, rock art, stone artifacts, bone harpoons, shells and many other items have been found in areas which today are considered too hot and dry to inhabit. This suggests that these areas were quite habitable thousands of years ago, but that the climate of the Sahara has since changed drastically. The artifacts found were located near remains of giraffe, elephant, buffalo, antelopes, rhinoceros, and warthog, as well as the remains of fish, crocodiles, hippopotamuses and other aquatic animals which suggests that thousands of years ago water was quite abundant in the Sahara.
The majority of the people living in the Sahara Desert are nomads, which means that these people continuously move from region to region in search of better living conditions. It is believed that the first nomadic peoples came to this region after domestic animals were introduced to the Sahara 7,000 years ago. Researchers believe that sheep and goats were introduced to the Sahara region by the Caspain culture of northern Africa.
Many of the Sahara's winds have special names:
Haboob is the Arabic name for a wild, sand-laden wind.
Khamsin, also Arabic, means "50 days." This wind sweeps across the desert from March through May, filling the air with sand.
The name of the desert wind Harmattan comes from a word in the West African language Twi that means "to tear your breath apart."
Sand dunes make up only about 15 % of the Sahara, but the desert is so huge (about 5.63 million sq km) that even a single dune may be enormous. The sand dune known as the Libyan Erg is as big as France.
About 70 % of the Sahara consists of rocky plains covered with stones and gravel. Shale and limestone plateaus or mountain ranges make up the rest. Before the Sahara became a desert, it was home to many savanna animals, including the giraffe. People began to paint and etch the Sahara's animals in desert rock about 12,000 years ago. Archaeologists estimate that the oldest remaining pictures date back to 6500 B.C.
By looking at paintings and etchings created thousands of years apart, we can see how life changed as the Sahara slowly became a desert.