Stretching across northern Africa from the Atlantic Ocean in the west to the Red Sea in the east, the Sahara is the world's largest desert. It forms a natural barrier between two very different geographic and cultural regions: NORTH AFRICA, with its Arab-influenced Mediterranean culture; and sub-Saharan Africa, where indigenous African culture is dominant. Yet for centuries people have crossed this dangerous expanse along trade routes, supplying goods to the towns and kingdoms on the Sahara's borders and linking Africa's northern and southern communities. Today the desert supports a population of about 2.5 million people.
About a fifth of the Sahara is covered with sand seas, called ergs. In some places the strong Saharan winds shape the sand into rows of towering dunes. Elsewhere the desert consists mostly of plains covered with gravel or barren rock. Within the Sahara lie two mountain ranges, the Ahaggar in ALGERIA and the Tibesti in CHAD. The highest point in the desert is Emi Koussi, an 11,204-foot peak in Chad. The lowest point, 4,356 feet below sea level, is in Egypt's Qattara depression, one of several Saharan basins.
Two rivers flow all year through the Sahara: the NILE in the eastern desert and the NIGER in the southwest. After the desert's rare rainfalls, smaller streams and rivers appear briefly before drying up and disappearing. The driest parts of the Sahara receive no more than 4 to 6 inches of rain each year. The SAHEL, the zone of transition between the true desert and the rest of Africa to the south, receives up to 24 inches of rain. Occasional springs or pools dot the desert, giving rise to oases, islands of green vegetation amid arid surroundings.
The Sahara was not always as dry as it is now. Before about 3000 B.C., the area experienced cycles of heavier rainfall in which a wide variety of plant and animal life flourished. Prehistoric humans occupied the region during these periods, leaving ROCK ART that shows images of a greener, wetter time when even water-loving hippopotamuses lived in the Sahara.
Arab invaders gained control of northern Africa in the A.D. 600s. In the centuries that followed, camel caravans carried gold, slaves, spices, leather, and ostrich feathers from sub-Saharan Africa north across the Sahara and exchanged these goods for weapons, horses, textiles, and paper from the Mediterranean coast. The Saharan people benefited from the trade, providing marketplaces in the oases and collecting tolls and protection money from foreign traders. Cities such as TIMBUKTU (in what is now northern MALI) became thriving centers of commerce.
During the Middle Ages, several kingdoms rose on the fringes of the Sahara. States in the area that is now GHANA and NIGERIA extended their influence into the desert region, but their dominance over the western Sahara ended in 1591, when the sultan of MOROCCO conquered Timbuktu. Saharan groups such as the TUAREG then took control of the region.
Around 1850 Europeans began colonizing Algeria and other parts of the Sahara region. Most of the desert came under French control. When North Africa regained independence in the 1960s, the colonial divisions made by the French became national boundaries. However, the border between Libya and Chad remained in dispute until 1994.
People and Economy
Most of the people who live in the Sahara occupy the oases and the highlands on the desert fringes. Arabic-speaking peoples, including the Bedouin of Libya and the Chaamba of Algeria, live in the northern Sahara. On the northern and western edges of the desert are many groups of BERBERS. The largest Berber-speaking group within the Sahara is the Tuareg, who number between 500,000 and 1 million people. The Berbers and Tuareg have cultural and religious ties to Islamic, Arab-speaking northern Africa. To the east, in NIGER and northern Chad, live the Teda or Tubu peoples, whose languages and cultures are closely linked to those of sub-Saharan African groups.
Livestock herding and trade are the main economic activities of the Sahara. Desert dwellers raise camels, goats, and sheep, and in some oases they also grow gardens and date palms. The principal trade good is salt, either mined or obtained from evaporated water. Since ancient times, Saharans have traded salt for grain and other goods from the agricultural regions south of the desert. The Tuareg salt trade continues today, unlike most of the long-distance trade that once crisscrossed the Sahara. The major economic event of the 1900s in the Sahara was the discovery of mineral resources, particularly oil, phosphate, iron, uranium, and bauxite, the source of aluminum.
Jenne and the Saharan Borderlands. In ancient times, many cities and states flourished in the southern and southwestern borderlands of the Sahara. Before the 1970s historians believed that Arabs and Berbers from North Africa sparked the formation of these states by introducing long-distance trade to the region in the A.D. 800s or 900s.
Recent archaeological evidence, however, reveals a different history. Excavations show that large, highly organized towns existed before the Arabs arrived and before major trade began across the Sahara. Jenne (or Jenne-jeno) in Mali is one of the best studied of these sites. Human settlement at Jenne dates from the 200s or 100s B.C. The city reached its height between A.D. 500 and 1000, with a population of at least 10,000. Its citizens exported copper, pottery, and agricultural goods through a local trade network that covered much of the middle course of the Niger River.
Two features show that Jenne was a purely African creation, different from ancient cities built by Arabs and Europeans. First, there is no evidence of a ruling class. Jenne does not have the rich burial sites or monumental public architecture that indicate the presence of nobles or powerful rulers. Second, Jenne was not a dense urban settlement enclosed by a city wall. It was a central town with satellite communities clustered around it. Ruins at other ancient sites in the Niger region suggest that this clustered organization was typical of the African civilizations that arose there. These societies later merged with or developed into the states that joined in the cross-Saharan trade established by Arabs. (See also Climate, Deserts and Drought, Ecosystems.)