Africa, second-largest of the Earth’s seven continents, with adjacent islands, covering about 30,330,000 sq km (11,699,000 sq mi), or about 22 per cent of the world’s total land area. In the mid 1990s more than 12 per cent of the world’s population lived in Africa.

Straddling the equator, Africa stretches 8,050 km (4,970 mi) from its northernmost point, Cape Blanc (Ra’s al Abyad;) in Tunisia, to its southernmost tip, Cape Agulhas in South Africa. The maximum width of the continent, measured from the tip of Cape Vert in Senegal, in the west, to Cape Xaafuun (Ras Hafun) in Somalia, in the east, is about 7,560 km (4,700 mi). The highest point on the continent is the perpetually snowcapped Mount Kilimanjaro (5,895 m/19,340 ft) in Tanzania; the lowest is Lake ‘Asal (153 m/502 ft below sea level) in Djibouti. Africa has a regular coastline characterized by few indentations. Its total length is about 30,490 km (18,950 mi), which in proportion to its area is less than that of any other continent.

The main islands associated with Africa, which have a combined area of some 621,600 sq km (240,000 sq mi), are Madagascar, Zanzibar, Pemba, Mauritius, Réunion, the Seychelles, and the Comoro Islands in the Indian Ocean; São Tomé, Príncipe, and Bioko in the Gulf of Guinea; St Helena, Ascension, and the Bijagós Archipelago in the Atlantic; and the Cape Verde Islands, the Canary Islands, and the Madeira Islands in the North Atlantic. Although considered geographically part of Africa, St Helena, Ascension, the Bijagós Archipelago, the Canary Islands, and the Madeira Islands have few, if any, economic, political, or cultural links with the continent. Their ties are rather with western Europe: St Helena and Ascension are dependencies of the United Kingdom; the Canary and Madeira islands are an integral part of metropolitan Spain and Portugal respectively.

II THE NATURAL ENVIRONMENT

The African continent comprises a vast, rolling plateau; just 10 per cent of its land area lies at less than 500 ft above sea level, compared with 54 per cent of Europe and 25 per cent of North America. Only in the extreme south and north have great folded mountain ranges been built up. Elsewhere in the continent differences in elevation have been caused either by the faulting which produced the Rift Valley, or by the creation of the enormous river basins—notably those of the Congo, the Niger, the Nile, the Volta, and the Zambezi—which are a more prominent feature of the geography of Africa than that of any other continent. At its margins the plateau gives way, via steep escarpments, to the narrow coastal plain that surrounds the continent. All the great rivers of Africa, except the Niger-Benue and Zambezi-Shire systems, plunge in falls or rapids over the escarpments, making effective navigation inland from the sea impossible.

A Geological History

The African continental plateau is a vast shield of ancient, hard rock, dating from the Precambrian and related in age and history to South America’s Brazilian Highlands. The shield extends south from the Atlas Mountains to the Cape of Good Hope. To the east, it includes the Arabian Peninsula and Madagascar, which were split off from Africa during the Tertiary Period (see Plate Tectonics). Within these ancient rocks some of the earliest traces of life on Earth—fossil micro-organisms 3.2 billion years old—have been found. Geologically, the folded Atlas Mountains of north-west Africa are part of Europe, having been created by the same forces that produced the Alpine mountain ranges of southern and central Europe.

The tectonic forces that split Africa and South America apart during the breakup of the supercontinent Gondwanaland, over 150 million years ago (see Jurassic Period), have continued into more recent times, creating the Rift Valley during the Tertiary Period and triggering eruptions of the East African volcanic cones, Mount Kenya and Mount Kilimanjaro.

B Physiographic Regions

Africa may be divided into three major regions: the Northern Plateau, the Central and Southern Plateau, and the Eastern Highlands. In general, elevations increase across the continent from north-west to south-east, the average being about 560 m (1,900 ft). The coastal plains, with the exception of the Mediterranean and the Guinea coasts, are generally narrow.

The outstanding feature of the Northern Plateau is the Sahara, the great desert that occupies more than one-quarter of Africa. At the fringes of the Northern Plateau are several mountainous regions. To the north-west lie the Atlas Mountains, a chain of rugged peaks linked by high plateaux, extending from Morocco into Tunisia. Other prominent uplands are the Fouta Djallon, in the south-west, and the Adamawa Plateau and the Cameroon mountain range, in the south. The Lake Chad basin is situated in the approximate centre of the Northern Plateau.

The Central and Southern Plateau is considerably higher than the Northern Plateau, averaging more than 900 m (3,000 ft) in height. It includes west-central and southern Africa, and contains several major depressions, notably the Congo River basin and the Kalahari. South of this plateau is the folded chain of the Drakensberg of South Africa, which runs some 1,100 km (700 mi) along the south-eastern coast of the continent. In the extreme south is the Karoo, an arid plateau covering about 259,000 sq km (100,000 sq mi).

The Eastern Highlands, the highest part of the continent, lie near the eastern coast, extending from the Red Sea south to the Zambezi along the fault line of the Rift Valley. The region has an average elevation of more than 1,500 m (5,000 ft), and in the Ethiopian Plateau it rises in stages to about 3,000 m (10,000 ft). Ras Dashan (4,620 m/15,157 ft) in northern Ethiopia is the highest point of the plateau. South of the Ethiopian Plateau are a number of towering volcanic peaks, including Mount Kilimanjaro, Mount Kenya, and Mount Elgon. The most distinctive feature of the Eastern Highlands is the Rift Valley, the vast geologic fault system that begins in Anatolia, in eastern Turkey, stretches through the Jordan Valley and the Dead Sea, and then follows down the length of the Red Sea to Lake Turkana (formerly Lake Rudolph). At the southern end of Lake Turkana, the rift divides around Lake Victoria, but joins again at the head of Lake Malawi (Lake Nyasa), from where it runs down the Shire and Zambezi rivers, and finally out to sea. Altogether the Rift Valley extends around almost one-fifth of the Earth, and contains some of its deepest lakes. West of the Rift Valley is the Ruwenzori Range, which rises up to 5,119 m (16,795 ft) above sea level. The topography of the island of Madagascar features a rugged central highland extending in a generally north-south direction near the eastern coast.

Except for a few incursions from the sea, Africa has been a land area since Precambrian times. Its soils have therefore developed locally, chiefly by weathering. A few areas have alluvial soils laid down by rivers or ocean currents. African soils, for the most part, have irregular drainage and no definite water tables. Being typical tropical soils, most are relatively infertile, lacking humus and subject to mineral leaching from heavy rainfall and high temperatures. Desert soils (aridisols and entisols), which have the least organic content, cover large areas. The most fertile soils include the mollisols, also known as chernozems and black soils, of eastern Africa, and the alfisols, or podzolic soils, of parts of western and southern Africa.

C Drainage and Water Resources

Africa contains some of the world’s greatest rivers. In all, six major networks drain Africa. With the exception of those draining into the Lake Chad basin, and those surrounding the Kalahari, all have outlets to the sea. The River Nile drains north-eastern Africa, and, at 6,650 km (4,132 mi), is the longest river in the world. It is formed from the Blue Nile, which originates at Lake Tana in Ethiopia, and the White Nile, which originates at Lake Victoria. The two converge at Khartoum in Sudan, from where the Nile flows west and north before emptying into the Mediterranean Sea. The River Congo, some 4,670 km (2,900 mi) long, drains much of central Africa. It originates in Zambia, in southern Africa, and flows north, west, and south to empty into the Atlantic Ocean in the Democratic Republic of the Congo. The third longest African river, the Niger in west Africa, is about 4,180 km (2,600 mi) long; its upper portions are navigable only during rainy seasons. The Niger rises in the highlands of the Fouta Djallon and flows north and east before turning south to empty into the Gulf of Guinea. The River Zambezi, about 3,540 km (2,200 mi) long, originates from tributaries that begin in Zambia and Angola, and converge in Zambia; it then flows south and east to empty into the Indian Ocean in Mozambique. The Zambezi is cut by numerous rapids, the most spectacular being the Victoria Falls. Draining southern Africa are the Limpopo and Orange rivers. The Orange River, with its tributary, the River Vaal, has a length of about 2,100 km (1,300 mi). It rises in the Drakensberg and flows west to the Atlantic. Lake Chad, a shallow freshwater lake with an average depth of only about 1.2 m (4 ft), drains nearby rivers and constitutes the largest inland drainage system on the continent.

The Rift Valley contains a series of great lakes. This equatorial lake system includes lakes Turkana, Albert, Tanganyika, and Malawi. Lake Victoria, the largest lake in Africa and the third-largest in the world, is, however, not part of this system; it occupies a shallow depression in the Eastern Highlands. The River Limpopo originates in South Africa and runs 1,610 km (1,000 mi), east and south to drain into the Indian Ocean in southern Mozambique.

Achieving effective control of water supplies is a major problem in Africa. Vast areas suffer low rainfall; still larger areas receive only irregular rainfall and must store water as insurance against drought or poor rains. Other areas have an over-abundance of water: there are great swamps, like the Sudd of southern Sudan, and large areas suffer from periodic flooding. Since the 1950s many dams and reservoirs have been built to channel water for irrigation and for hydroelectric power. The continent’s numerous rivers and their abrupt descent over the coastal escarpments have led to estimates that Africa has approximately 40 per cent of total world hydroelectric power potential.

D Climate

The climate of Africa is the most generally uniform of any of the continents. This results from the position of the continent in the Tropical Zone, the impact of cool ocean currents, and the general absence within the continental plateau of mountain chains serving as climatic barriers.

Seven main African climatic zones can be distinguished. The central portion of the continent and the eastern coast of Madagascar have a tropical rainforest climate. Here the average annual temperature is about 26.7° C (80° F), and the average annual rainfall is about 1,780 mm (70 in). The climate of the Guinea coast resembles the equatorial climate, except that rainfall is concentrated in one season; no months, however, are rainless.

To the north and south the rainforest climate is supplanted by a tropical savannah climate zone that encompasses about one-fifth of Africa. Here the climate is characterized by a wet season during the summer months and a dry season during the winter months. Total annual rainfall varies from 550 mm (20 in) to more than 1,550 mm (60 in). Away from the equator, to the north and south, the savannah climate zone grades into the drier steppe climate zone. Average annual rainfall varies between 250 and 500 mm (10 and 20 in) and is concentrated in one season.

Africa has a proportionately larger area in arid, or desert, climate zones than any continent except Australia. Each of these areas—the Sahara in the north, the Horn of Africa in the east, and the Kalahari and Namib deserts in the south-west—has less than 250 mm (10 in) of rainfall annually. In the Sahara, daily and seasonal extremes of temperatures are great; the average July temperature is more than 32.2° C (90° F); during the cold season the night-time temperature often drops below freezing.

Mediterranean climate zones are found in the extreme north-west of Africa and in the extreme south-west. These regions are characterized by mild, wet winters and warm, dry summers. In the highlands of eastern Africa, particularly in Kenya and Uganda, rainfall is well distributed throughout the year, and temperatures are equable. The climate on the high plateau of southern Africa is temperate.

E Vegetation

African vegetation can be classified according to rainfall and climate zones. The tropical rainforest zone, where the average annual rainfall is more than 1,270 mm (50 in), has a dense surface covering of shrubs, ferns, and mosses, above which tower evergreens, oil palms, and numerous species of tropical hardwood trees. A mountain forest zone, with average annual rainfall only slightly less than in the tropical rainforest, is found in the high mountains of Cameroon, Angola, eastern Africa, and parts of Ethiopia. Here a ground covering of shrubs gives way to oil palms, hardwood trees, and primitive conifers. A savannah woodland zone, with annual rainfall of 890 to 1,400 mm (35 to 55 in), covers vast areas with a layer of grass and fire-resistant shrubs, above which are found deciduous and leguminous fire-resistant trees. A savannah grassland zone, with annual rainfall of about 500 to 890 mm (20 to 35 in), is covered by low grasses and shrubs, and scattered, small deciduous trees. The thornbush zone, a steppe vegetation, with an annual rainfall of about 300 to 510 mm (12 to 20 in), has a thinner grass covering and a scattering of succulent or semisucculent trees. The subdesert scrub zone, with an annual rainfall of 130 to 300 mm (5 to 12 in), has a covering of grasses and scattered low shrubs. The zone of desert vegetation, found in areas with an annual rainfall of less than 130 mm (5 in), has sparse vegetation or none at all.

F Animal Life

Africa has two distinct faunal zones: the North and North-western zone, including the Sahara; and the Ethiopian zone, including all of sub-Saharan Africa. The North and North-western zone is characterized by animals similar to those of Eurasia. Sheep, goats, horses, and camels (introduced by the Romans) are common. Barbary sheep, African red deer, and two types of ibex are native to the north African coast. Desert foxes are found in the Sahara, along with hares, gazelles, and the jerboa, a small leaping rodent. The Ethiopian zone is famous for its great variety of distinctive animals and birds, although many of these are now under threat of extinction from loss of habitat and poaching. The woodland and grassland areas are the traditional habitats of numerous species of antelope and deer, of zebra, giraffe, buffalo, the African elephant, rhinoceros, and the baboon and various monkeys. Carnivores, or meat-eating animals, include the lion, leopard, cheetah, hyena, jackal, and mongoose. The hippopotamus is found in the rivers, emerging at night to graze. The gorilla, the largest ape in the world, inhabits the rainforests of equatorial Africa, as do monkeys, flying squirrels, bats, and lemurs. However, many of these species, notably the elephant, rhinoceros, leopard, lion, and gorilla, are now found only in specially delineated game reserves.

Most bird life belongs to Old World groups. The guinea fowl is a leading game bird. Water birds, notably pelicans, goliath herons, flamingos, storks, and egrets, congregate in great numbers. The ibis is common in the Nile region, and the ostrich is found in eastern and southern Africa. Reptiles are also mainly of Old World origin and include lizards, crocodiles, and tortoises. A variety of venomous snakes, including the mamba, are encountered throughout the Ethiopian zone. Among the constricting snakes, pythons are found mainly in western Africa. Boa constrictors are indigenous only to Madagascar, which has a large number of unique species. Freshwater fish abound, with more than 2,000 known species. The continent has a variety of highly destructive insects, notably mosquitoes, driver ants, termites, locusts, and tsetse flies. The tsetse transmit sleeping sickness to humans and animals.

G Mineral Resources

Africa is very rich in mineral resources, possessing almost all types of the known minerals of the world, many of which are found in significant quantities, although the geographic distribution is uneven. Fossil fuels are abundant, including major deposits of coal, oil, and natural gas. Africa has some of the world’s largest reserves of gold, diamonds, copper, bauxite, manganese, nickel, platinum, cobalt, radium, germanium, lithium, titanium, and phosphates. Other important mineral resources include iron ore, chromium, tin, zinc, lead, thorium, zirconium, vanadium, antimony, and beryllium. Also found in exploitable quantities are clays, mica, sulphur, salt, natron, graphite, limestone, and gypsum.