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Sahara

Sahara (səhâr´ə) [Arab.,=desert], world's largest desert, c.3,500,000 sq mi (9,065,000 sq km), N Africa; the western part of a great arid zone that continues into SW Asia. Extending more than 3,000 mi (4,830 km), from the Atlantic Ocean to the Red Sea, the Sahara is bounded on the N by the Atlas Mts., steppelands, and the Mediterranean Sea; it stretches south c.1,200 mi (1,930 km) to the Sahel, a steppe in W and central Africa that forms its southern border. The desert includes most of Western Sahara, Mauritania, Algeria, Niger, Libya, and Egypt; the southern portions of Morocco and Tunisia; and the northern portions of Senegal, Mali, Chad, and Sudan. The E Sahara is usually divided into three regions—the Libyan Desert, which extends west from the Nile valley through W Egypt and E Libya; the Arabian Desert, or Eastern Desert, which lies between the Nile valley and the Red Sea in Egypt; and the Nubian Desert, which is in NE Sudan.

Regions of sand dunes (erg) occupy only about 15% of the Sahara; "stone deserts," consisting of plateaus of denuded rock (hammada) or areas of coarse gravel (reg), cover about 70% of the region; mountains, oases, and transition zones account for the remainder. Sparse vegetation is found in most parts of the Sahara, with the exception of the sand dune regions. High mountain massifs rise in the central regions; they are the Ahagger (Hoggar) in S Algeria, which rises to more than 9,000 ft (2,740 m); the Tibesti Massif in N Chad, which rises to more than 11,000 ft (3,350 m); and the Aïr Mountains (Azbine) in N Niger, which rise to more than 6,000 ft (1,830 m). The mountains are deeply dissected and were in the past infamous for the shelter they provided to marauders preying on desert traffic. From west to east the four principal land routes across the desert are from Colomb-Bechar to Dakar; from Colomb-Bechar to Gao and Timbuktu by way of Reganne; from Touggourt to Agadez and Kano by way of In-Salah; and from Tripoli to Ghat.

Climate

The Sahara has one of the harshest climates in the world. Located in the trade winds belt, the region is subject to winds that are frequently strong and that blow constantly from the northeast between a subtropical high-pressure cell and an equatorial low-pressure cell. As air moves downward from the high-pressure into the low-pressure cell, it becomes warmer and drier. The desiccating and dust-laden winds are sometimes felt north and south of the desert, where they are variously known as sirocco, khamsin, simoom, and harmattan. The northern slopes of the Atlas Mts. intercept most of the moisture from winds blowing inshore from the Mediterranean Sea.

Border zones on the north and south, where the desert merges with the steppe, receive about 10 in. (25 cm) of rain a year with some seasonal regularity, but over most of the region rainfall is sparser, with an average annual total of less than 5 in. (12.7 cm); rainfall is usually torrential when it occurs after long dry periods that sometimes last for years. The region's low relative humidity rarely exceeds 30% and is often in the 4% to 5% range.

Daytime temperatures are high, averaging 86°F (30°C) and often over 100°F (37.5°C). Heat loss is rapid at night, and the diurnal range can be as great as 70°F (38°C). Freezing temperatures are not uncommon at night from December to February.

Water and Other Resources

The Nile and Niger rivers, both fed by rains outside the desert, are the only permanent rivers in the region. Water is present at or just below the surface gravel in wadis (intermittent streams) that radiate from the mountain massifs, in scattered oases where the water table comes to the surface, and at greater depths in huge underground aquifers. The aquifers are believed to be filled with water dating from the Pleistocene epoch, when the Sahara was much wetter than it is today and had very large lakes. The more than 20 lakes (called chotts in the north) and areas of salt flats and boggy salt marshes are also considered relics from this pluvial period.

Important discoveries of minerals, oil, and gas have been made in the Sahara. There are huge oil and gas deposits in Algeria and Libya, but in most cases, inaccessibility has delayed exploitation. In searching for oil reserves, underground deposits of water also have been found. Extensive iron ore deposits are worked in the Fort Gouraud area of Mauritania. Salt is still mined, as in the past, at Taoudenni, Mali, and at Bilma, Niger, and is transported, as in the days of the great medieval kingdoms of W Africa, by camel caravans across the desert.

People

Two thirds of the Sahara's estimated 2 million inhabitants (excluding those in the Nile valley) are concentrated in oases where date palms, fruits, vegetables, grains, and other crops are produced under irrigation. Nomads, with herds of sheep and goats and with camels for transportation, predominate in drier areas and continue to use oases (including modern oases created by the drilling of wells), as in centuries past, for water, trade, and provisioning stops. The principal ethnic groups of the Sahara are the Tuareg (of Berber origin), who dominate the mountains of the central Sahara; the peoples of mixed Berber and Arab origin in W Sahara; and the Tibu (Tébu), who dominate the Tibesti Massif.

History

The Sahara has undergone a series of wet periods, the most recent occurring c.5,000–10,000 years ago; it was not until c.3000 BC that the Sahara transformed into its present arid state. There is dispute as to whether the desertification of the region has continued into historic time. Those who support this theory contend that increasing aridity is the reason for the recorded advance of desert conditions into areas under cultivation in Roman times in the north and more recently (since the late 1960s) in the south. Opponents of this view explain such changes as being the result of alterations in land-use practices and neglect of water-supply and irrigation systems.

The camel was introduced probably in the 1st cent. AD and facilitated occupation by nomads (first the Berbers, later the Arabs), who lived in interdependence with the oasis dwellers, providing protection against enemies in exchange for supplies of food and water. A profitable trans-Saharan trade in gold and slaves from W Africa, salt from the desert, and cloth and other products from the cities on the Mediterranean coast was carried on by the nomads. The first European explorers to travel in the Sahara were Friedrich Horneman in 1805 and Mungo Park in 1806. Some areas of the Sahara remain virtually unexplored, although a network of air and automobile routes now crosses the desert and links the major oases and mining areas.

Bibliography

See C. Kruger et al., Sahara (tr. 1969); M. Williams and H. Faure, ed., The Sahara and the Nile: Quarternary Environments and Prehistoric Occupation in Northern Africa (1980); J. Cloudsley-Thompson, ed., Key Environments: Sahara Desert (1984); E. Gautier, Sahara (1987).

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Sahara

SAHARA

world's largest desert.

The Sahara (in Arabic, desert) encompasses an area of 3.32 million square miles (8.6 million sq km), stretching across eleven countries and Western Sahara, and covering nearly the entire northern region of Africa from the Atlantic Ocean to the Red Sea hills. Parts of the Sahara reach all the way north to the Mediterranean; to the south, it extends nearly 1,500 miles (2,400 km). The two countries with the highest percentage of desert are Libya (99 percent) and Egypt (98 percent). Fifteen percent of the Sahara consists of sand "seas"; the rest is a mixture of hammada (barren rocky plateaus), coarse gravel, two mountain chains in the central regions (with the highest point being 11,204 feet [3,417 m] at the peak of Emi Koussi in Chad), low lands, depressions (the lowest point being 436 feet [133 m] below sea level at the Qattara depression in western Egypt), oases, and transition zones.

The Nile and Niger are its only two permanent rivers. Transition zones receive between 5 and 10 inches (12.7 and 25.4 cm) of rain per year; most of the rest receives fewer than 5 inches (12.7 cm). Large portions of the area receive no rainfall for years at a time. Its climate is among the most inhospitablethe highest evaporation rates, highest temperatures, and lowest humidity (a life-threatening 2.5 percent) have all been registered there. Extreme wind velocities and massive drops in nighttime temperatures, sometimes to subfreezing level, are also a regular feature of the Sahara.

Desertification has slowly encroached upon previous transition zones, such as the sahel belt of vegetation covering fossil sand dunes that separate the Sahara from Equatorial Africa; some also occurs in Arab North African countries. The reasons for the Sahara's continuing expansion range from climatic changes to some direct human influence, such as overgrazing by sheep herds and wood gathering for fuel. The most important minerals found in the Sahara include petroleum and natural gas fields, uranium, phosphates, iron ore, and a long list of other metals.

The four main ethnic groups of the Sahara are all predominantly Berber in origin: the Arabo-Berbers in the north; the Moors (Maures), a mixture of Arab, Berber, and black African groups in the southwestern regions (encompassing parts of present-day Mauritania, Mali, and Western Sahara); the distinctive Twaregs, the most numerous of the four, of the south-central area; and the Tibu of the Tibesti area of Chad, who are also of Berber and black African mixture. Apart from livestock grazing, the old traditional economy included a profitable trade in gold and slaves from West Africa, salt from the desert, and cloth and other products from the Mediterranean coast. The camel, probably introduced in the second century b.c.e., was the backbone of trans-Saharan trade.


Before the prolonged droughts of the 1970s and 1980s, best estimates of the Sahara's population were approximately 2 million persons; about two-thirds were concentrated in oases; the rest engaged in seasonal movements and some were purely nomadic. In Arab North Africa, sedentarization had become almost complete, owing to the erosion of the pastoral economic base. Both "push" and "pull" factors were at work: desertification, which reduced livestock herds; displacement stemming from anti-colonial struggles; the exploitation of oil and gas fields, which provided employment; and the extension of governmental authority, resulting in increased enclosure of land for farming, as well as expanded health and education services.


Historically, the Sahara was a large barrier to aspiring conquerorsEgyptians, Romans, Carthaginians, and Arabs. Islam spread steadily, however, in part from the activities of Muslim traders and scholars. Explorers from Britain and France began to penetrate the Sahara in the early part of the nineteenth century. French conquests began in 1830. Political boundaries in the Sahara were defined only in the late nineteenth and the twentieth centuries. Much was left imprecise by the French, who ruled over most of the region, resulting in a number of border disputes after decolonization, including those between Morocco and Algeria over the Tindouf area, and Libya and Chad with regard to the Aozou strip.

see also aozou strip; berber; deserts; tindouf; twareg; western sahara.

bruce maddy-weitzman

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Sahara

Sahara World's largest desert, with an area of c.9,065,000sq km (3,500,000sq mi), covering nearly a third of Africa's total land area. It consists of Algeria, Niger, Libya, Egypt, and Mauritania, the s parts of Morocco and Tunisia, and the n parts of Senegal, Mali, Chad, and Sudan. It extends c.4800km (3000mi) w to e from the Atlantic Ocean to the Red Sea, and stretches c.1900km (1200mi) n to s from the Atlas Mountains to the Sahel. The annual rainfall is usually less than 10cm (4in) and there is very little natural vegetation. Two-thirds of the Sahara is stony desert, and the topography ranges from the Tibesti Massif (n Chad) at 3350m (11,000ft) to the Qattara Depression (Egypt) at 133m (436ft) below sea level. The numerous natural and man-made oases act as vital centres for water, crop farming and transport, and the Sahara's two million inhabitants are concentrated around them. The two main ethnic groups are the Tuareg and the Tibu. Nomads continue to herd sheep and goats. Four land routes have been constructed across the desert but transportation is still primarily by camel and horse. Mineral deposits include salt, iron ore, phosphates, oil, and gas.

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Sahara

Sahara a vast desert in North Africa, extending from the Atlantic in the west to the Red Sea in the east, and from the Mediterranean and the Atlas Mountains in the north to the Sahel in the south, the largest desert in the world. Often used figuratively.

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Sahara

Saharajarrah, para, Tara •abracadabra, Aldabra •Alhambra • Vanbrugh •Cassandra, Sandra •Aphra, Biafra •Niagara, pellagra, Viagra •bhangra, Ingres •Capra • Cleopatra •mantra, tantra, yantra •Basra •Asmara, Bukhara, carbonara, Carrara, cascara, Connemara, Damara, Ferrara, Gemara, Guadalajara, Guevara, Honiara, Lara, marinara, mascara, Nara, Sahara, Samara, samsara, samskara, shikara, Tamara, tiara, Varah, Zara •candelabra, macabre, sabra •Alexandra • Agra • fiacre •Chartres, Montmartre, Sartre, Sinatra, Sumatra •Shastra • Maharashtra • Le Havre •gurdwara •Berra, error, Ferrer, sierra, terror •zebra • ephedra • Porto Alegre •belles-lettres, Petra, raison d'être, tetra •Electra, plectra, spectra •Clytemnestra • extra •chèvre, Sèvres •Ezra

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