Introduction to The Sahara Desert

Sahara, the vast desert of northern Africa, and the world's largest arid region. It occupies much of the broad northern half of Africa and covers some 3,500,000 square miles (9,000,000 km2), an area only slightly less than that of the United States.

The northern boundaries of the Sahara are the Atlas Mountains and, in Egypt and parts of Libya, the Mediterranean Sea. From there the desert stretches 1,200 miles (1,900 km) southward to about 17° north of the Equator.

From the Red Sea on the east to the Atlantic Ocean on the west the Sahara stretches more than 3,500 miles (5,600 km)—farther than from New York to Los Angeles.

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Physical Geography

Considered as a whole, the Sahara is a rather low plateau with an uplifted center that has several mountainous areas. Elevations over much of the Sahara average only 1,000 to 1,500 feet (300 to 450 m) above sea level; in the central mountains a few peaks reach 10,000 to 11,000 feet (3,000 to 3,350 m). Except for the Nile and the Niger, which flow along the desert margins, there are no permanent rivers. There are numerous wadis, desert watercourses that contain water for only a short time after heavy rains.

The most familiar of the Sahara's features is the erg, an area of dunes and drifting sand. Although widely distributed, ergs occupy scarcely more than a tenth of the Sahara's total area. Less well known than ergs, but covering much more of the surface, are regs,stony plains from which all sand and other fine materials have been removed by the wind. Large areas of exposed bedrock that have been worn smooth by the wind are known as hammadas.

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Regions

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Dominating the central Sahara are the mountainous areas of the Ahaggar, in southern Algeria, and the Tibesti, which lies mainly in northern Chad. These rugged and barren highlands of volcanic origin have been eroded by wind and water into many strangely shaped peaks. The extinct volcano of Emi Koussi, in the Tibesti, reaching 11,204 feet (3,415 m), is the Sahara's highest point; Tahat, in the Ahaggar, rises to 9,573 feet (2,918 m). Southward lie two mountainous extensions of the Ahaggar, the Air and the Adrar des Iforas. The Air descends abruptly eastward to the flat, sandy plains of the Tenere in northern Niger.

The western Sahara is a low, gently sloping region of dunes and gravel plains interspersed with a few low hammadas and ranges of low hills. Its largest areas are the Tanezrouft, a featureless reg that is one of the most desolate and arid parts of the Sahara; the El Djouf desert; Erg Chech; and Erg Iguidi. Only a small portion of the western Sahara lies more than 1,000 feet (300 m) above sea level, and large parts of the far west are below 500 feet (150 m).

In the northern Sahara are the huge sand wastes of the Great Eastern and Great Western ergs. Near the base of the eastern Atlas Mountains, salt flats and intermittent salt lakes known as chottsoccupy basins that dip below sea level at points.

Most of the eastern Sahara is occupied by the Libyan Desert, a 500,000-square-mile (1,300,000-km2) region of dunes and rock outcrops. Along its northeastern margin, in Egypt, is the Qattara Depression, which descends 436 feet (133 m) below sea level— second lowest point on the continent.

Climate

Extreme dryness is one of the Sahara's chief characteristics Except in a few of the higher mountainous areas, the average annual rainfall nowhere exceeds 5 inches (130 mm). Most areas receive much less, and the annual total is highly variable Some areas may have no rain for several years and then receive 5 inches or more m one brief downpour. The chief cause of the Sahara's dryness is the northeast trade winds, which blow toward the Equator all year As the air moves southward it becomes warmer (which increases its water-holding capacity) and quickly absorbs any available moisture. Under these conditions, precipitation is rare.

Daytime temperatures, especially in summer, are among the hottest in the world. Highs of more than 100° F. (38° C.) are common. Azizia, Libya, holds the world record high temperature of 136.4° F. (58° C.). Because the air is so dry and has so few clouds, the temperature drops quickly after sunset. Differences of as much as 50° F. (28° C.) between day and night occur regularly, and overnight freezes are common during winter.

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Plants and Animals

Except in oases, where water is relatively abundant, vegetation in the Sahara is quite sparse and widely scattered. Only a few areas, however, such as the Tanezrouft and parts of the Libyan Desert, have no plant life of any kind. Most of the plants found in the Sahara, particularly the small flowering types, have very shallow roots and depend on an occasional rainfall for moisture. They complete their growing cycle in a short time after a rain, producing seeds that lie dormant until the next rain, often after a lapse of several years.

Some plants, especially those in oases or near wadis, have long roots that reach subsurface water. Such plants include date palms, tamarisks, and other trees, as well as most kinds of desert shrubs.

Most of the Sahara's animal life is concentrated along the northern and southern fringes of the desert and in oases. Antelopes and gazelles are the largest animals of the Sahara. There are also hares, foxes, lizards, a few species of snakes, and numerous kinds of insects.

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Economic Development

With few exceptions, human activities in the Sahara are totally dependent on the availability of water. Only in oases, where water is at or near the surface, can humans make a permanent home. Oases are scattered throughout much of the Sahara; many are situated along wadis and in the highlands, where rainfall is somewhat greater than in the rest of the desert. Some consist of small groves of palm trees, while others are large areas suitable for cultivation. Most of the Sahara's people live in oases and are engaged in agriculture. Dates, figs, and other fruits are the leading commercial crops. Wheat, barley, and a variety of vegetables are raised for local use. Crops are grown mainly by irrigation.

There are also many nomads who spend part of the year in the desert and the remainder either in the mountains or in an oasis. They live chiefly by herding sheep, goats, and camels, and by trading between oases and the cities on the desert fringe. Their number has been greatly reduced since the 1960's because of increasing aridity in and along the margins of the desert.

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Minerals

The Sahara is developing as a major source of oil, gas, and metal ores. The petroleum fields of Algeria, Libya, and Tunisia, linked by pipeline to several Mediterranean ports, are important producers of oil and gas. Iron ore, manganese, and copper are the chief metals mined in the Sahara. Phosphate is exported in large amounts from Morocco.

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Transportation

Many of the problems of extracting the Sahara's resources lie in the difficulty of the terrain itself and the expense of building and maintaining adequate transport routes. No railway penetrates more than a short distance into the desert, and only a few roads make the crossing from north to south. Trucks and buses are being used increasingly for long-distance hauling, although the traditional camel caravans are still used. Many goods and passengers are transported by air, and a number of the larger oases have scheduled air service.

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The People

Most of the inhabitants of the Sahara are Arab, Berber, black, or a combination thereof. Generally, the northern Sahara has a greater share of Caucasoid peoples (represented by the Arabs and Berbers); increasing numbers of Negroid peoples occur to the south. Virtually all Saharans are of the Islamic faith.

The Tuareg, nomads of Berber origin, are one of the most populous and widespread of the groups who live in the desert. They are centered in the Air and Ahaggar highlands and range across most of the central and western Sahara in their travels. The Moors, an Arab-Berber mixture living principally in the western Sahara, are another large group. In the Tibesti area are the Toubou, a largely nomadic people. They are predominantly Negroid in appearance and are thought by some authorities to be descended from the Sahara's earliest inhabitants.

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