Geography of Africa

Separated from Europe by the Mediterranean Sea and from much of Asia by the Red Sea, Africa is joined to Asia at its northeast extremity by the Isthmus of Suez (which is transected by the Suez Canal), 130 km (81 mi) wide. For geopolitical purposes, the Sinai Peninsula of Egypt – east of the Suez Canal – is often considered part of Africa. From the most northerly point, Ras ben Sakka in Tunisia, at 37°21′ N, to the most southerly point, Cape Agulhas in South Africa, 34°51′15″ S, is a distance approximately of 8,000 km (5,000 mi); from Cap-Vert, 17°31′13″W, the westernmost point, to Ras Hafun in the Somali Puntland region, in the Horn of Africa, 51°27′52″ E, the most easterly projection, is a distance (also approximately) of 7,400 km (4,600 mi).^[1]

The main structural lines of the continent show both the east-to-west direction characteristic, at least in the eastern hemisphere, of the more northern parts of the world, and the north-to-south direction seen in the southern peninsulas. Africa is thus mainly composed of two segments at right angles, the northern running from east to west, and the southern from north to south.^[1]

The average elevation of the continent approximates closely to 600 m (2,000 ft) above sea level, roughly near to the mean elevation of both North and South America, but considerably less than that of Asia, 950 m (3,120 ft). In contrast with other continents, it is marked by the comparatively small area of either very high or very low ground, lands under 180 m (590 ft) occupying an unusually small part of the surface; while not only are the highest elevations inferior to those of Asia or South America, but the area of land over 3,000 m (9,800 ft) is also quite insignificant, being represented almost entirely by individual peaks and mountain ranges. Moderately elevated tablelands are thus the characteristic feature of the continent, though the surface of these is broken by higher peaks and ridges. (So prevalent are these isolated peaks and ridges that a specialised term—Inselberg-Landschaft, island mountain landscape—has been adopted in Germany to describe this kind of country, thought to be in great part the result of wind action.)^[1]

As a general rule, the higher tablelands lie to the east and south, while a progressive diminution in altitude towards the west and north is observable. Apart from the lowlands and the Atlas Mountains, the continent may be divided into two regions of higher and lower plateaus, the dividing line (somewhat concave to the northwest) running from the middle of the Red Sea to about 6 degrees south on the west coast.^[1]

Africa can be divided into a number of geographic zones:

• The coastal plains—often fringed seawards by mangrove swamps—never stretching far from the coast, apart from the lower courses of streams. Recent alluvial flats are found chiefly in the delta of the more important rivers. Elsewhere, the coastal lowlands merely form the lowest steps of the system of terraces that constitutes the ascent to the inner plateaus.
• The Atlas range—orthographically distinct from the rest of the continent, being unconnected with and separated from the south by a depressed and desert area (the Sahara).^[1]

There are many plateaus in Africa.

The high southern and eastern plateaus, rarely falling below 600 m (2,000 ft), have a mean elevation of about 1,000 m (3,300 ft). The

Much of Africa is made up of plains of the pediplain and etchplain type often occurring as steps.^[2][3] The etchplains are commonly associated with laterite soil and inselbergs.^[2] Inselberg-dotted plains are common in Africa including Tanzania,^[4] the Anti-Atlas of Morocco,^[2] Namibia,^[5] and the interior of Angola.^[6] One of the most wideaspread plain is the African Surface, a composite etchplain occurring across much of the continent.^[7][2][8]

The area between the east and west coast highlands, which north of 17° N is mainly desert, is divided into separate basins by other bands of high ground, one of which runs nearly centrally through North Africa in a line corresponding roughly with the curved axis of the continent as a whole. The best marked of the basins so formed (the Congo Basin) occupies a circular area bisected by the equator, once probably the site of an inland sea.^[1]

Running along the south of desert is the plains region known as the Sahel.

The arid region, the

The mountains are an exception to Africa's general landscape. Geographers came up with the idea of "high Africa" and "low Africa" to help distinguish the difference in Geography; "high Africa" extending from Ethiopia down south to South Africa and the Cape of Good Hope while "low Africa" representing the plains of the rest of the continent.^[9] The following table gives the details of the chief mountains and ranges of the continent:^[1]

From the outer margin of the African plateaus, a large number of streams run to the sea with comparatively short courses, while the larger rivers flow for long distances on the interior highlands, before breaking through the outer ranges. The main drainage of the continent is to the north and west, or towards the basin of the Atlantic Ocean.^[1]

To the main African rivers belong: Nile (the longest river of Africa), Congo (river with the highest water discharge on the continent) and the Niger, which flows half of its length through the arid areas. The largest lakes are the following: Lake Victoria (Lake Ukerewe), Lake Chad, in the centre of the continent, Lake Tanganyika, lying between the Democratic Republic of Congo, Burundi, Tanzania and Zambia. There is also the considerably large Lake Malawi stretching along the eastern border of Malawi. There are also numerous water dams throughout the continent: Kariba on the river of Zambezi, Asuan in Egypt on the river of Nile, and Akosombo, the continent's biggest dam on the Volta River in Ghana (Fobil 2003). The high lake plateau of the African Great Lakes region contains the headwaters of both the Nile and the Congo.

The break-up of

The upper Nile receives its chief supplies from the mountainous region adjoining the Central African trough in the neighborhood of the equator. From there, streams pour eastward into Lake Victoria, the largest lake in Africa (covering over 26,000 square m.), and to the west and north into Lake Edward and Lake Albert. To the latter of these, the effluents of the other two lakes add their waters. Issuing from there, the Nile flows northward, and between the latitudes of 7 and 10 degrees north it traverses a vast marshy level, where its course is liable to being blocked by floating vegetation. After receiving the Bahr-el-Ghazal from the west and the Sobat, Blue Nile and Atbara from the Ethiopian Highlands (the chief gathering ground of the flood-water), it separates the great desert with its fertile watershed, and enters the Mediterranean at a vast delta.^[1]

The most remote head-stream of the Congo is the

West of Lake Chad is the basin of the Niger, the third major river of Africa. With its principal source in the far west, it reverses the direction of flow exhibited by the Nile and Congo,^[1] and ultimately flows into the Atlantic — a fact that eluded European geographers for many centuries. An important branch, however — the Benue — flows from the southeast.

These four river basins occupy the greater part of the lower plateaus of North and West Africa — the remainder consists of arid regions watered only by intermittent streams that do not reach the sea.^[1]

Of the remaining rivers of the Atlantic basin, the Orange, in the extreme south, brings the drainage from the Drakensberg on the opposite side of the continent, while the Kunene, Kwanza, Ogowe and Sanaga drain the west coastal highlands of the southern limb; the Volta, Komoe, Bandama, Gambia and Senegal the highlands of the western limb. North of the Senegal, for over 1,500 km (930 mi) of coast, the arid region reaches to the Atlantic. Farther north are the streams, with comparatively short courses, reaching the Atlantic and Mediterranean from the Atlas mountains.^[1]

Of the rivers flowing to the

North of the Congo basin, and separated from it by a broad undulation of the surface, is the basin of Lake Chad — a flat-shored, shallow lake filled principally by the Chari coming from the southeast.^[1]

The principal lakes of Africa are situated in the African Great Lakes plateau. The lakes found within the Great Rift Valley have steep sides and are very deep. This is the case with the two largest of the type, Tanganyika and Nyasa, the latter with depths of 800 m (2,600 ft).

Others, however, are shallow, and hardly reach the steep sides of the valleys in the dry season. Such are Lake Rukwa, in a subsidiary depression north of Nyasa, and Eiassi and Manyara in the system of the Great Rift Valley. Lakes of the broad type are of moderate depth, the deepest sounding in Lake Victoria being under 90 m (300 ft).^[1]

Besides the African Great Lakes, the principal lakes on the continent are: Lake Chad, in the northern inland watershed; Bangweulu and Mweru, traversed by the head-stream of the Congo; and Lake Mai-Ndombe and Ntomba (Mantumba), within the great bend of that river. All, except possibly Mweru, are more or less shallow, and Lake Chad appears to be drying up.^[1]

Divergent opinions have been held as to the mode of origin of the African Great Lakes, especially Tanganyika, which some geologists have considered to represent an old arm of the sea, dating from a time when the whole central Congo basin was under water; others holding that the lake water has accumulated in a depression caused by subsidence. The former view is based on the existence in the lake of organisms of a decidedly marine type. They include jellyfish, molluscs, prawns, crabs, etc.^[1]

With the exception of Madagascar, the African islands are small. Madagascar, with an area of 587,041 km² (226,658 sq mi), is, after Greenland, New Guinea and Borneo, the fourth largest island on the Earth. It lies in the Indian Ocean, off the southeast coast of the continent, from which it is separated by the deep Mozambique Channel, 400 km (250 mi) wide at its narrowest point. Madagascar in its general structure, as in flora and fauna, forms a connecting link between Africa and southern Asia. East of Madagascar are the small islands of Mauritius and Réunion.^[1] There are also islands in the Gulf of Guinea on which lies the Republic of São Tomé and Príncipe (islands of São Tomé and Príncipe). Part of the Republic of Equatorial Guinea is lying on the island of Bioko (with the capital Malabo and the town of Lubu) and the island of Annobón.^{[citation needed]} Socotra lies E.N.E. of Cape Guardafui. Off the north-west coast are the Canary and Cape Verde archipelagoes. which, like some small islands in the Gulf of Guinea, are of volcanic origin.^[1] The South Atlantic Islands of Saint Helena and Ascension are classed as Africa but are situated on the Mid-Atlantic Ridge halfway to South America.

Africa mean annual temperature

Africa mean annual precipitation

Lying almost entirely within the tropics, and equally to north and south of the equator, Africa does not show excessive variations of temperature.^[1][12]

Great heat is experienced in the lower plains and desert regions of North Africa, removed by the great width of the continent from the influence of the ocean, and here, too, the contrast between day and night, and between summer and winter, is greatest. (The rarity of the air and the great radiation during the night cause the temperature in the Sahara to fall occasionally to freezing point.) Farther south, the heat is to some extent modified by the moisture brought from the ocean, and by the greater elevation of a large part of the surface, especially in East Africa, where the range of temperature is wider than in the Congo basin or on the Guinea coast. In the extreme north and south the climate is a warm temperate one, the northern countries being on the whole hotter and drier than those in the southern zone; the south of the continent being narrower than the north, the influence of the surrounding ocean is more felt.^[1]

The most important climatic differences are due to variations in the amount of rainfall. The wide heated plains of the Sahara, and in a lesser degree the corresponding zone of the Kalahari in the south, have an exceedingly scanty rainfall, the winds which blow over them from the ocean losing part of their moisture as they pass over the outer highlands, and becoming constantly drier owing to the heating effects of the burning soil of the interior; while the scarcity of mountain ranges in the more central parts likewise tends to prevent condensation. In the inter-tropical zone of summer precipitation, the rainfall is greatest when the sun is vertical or soon after. It is therefore greatest of all near the equator, where the sun is twice vertical, and less in the direction of both tropics.^[1]

The rainfall zones are, however, somewhat deflected from a due west-to-east direction, the drier northern conditions extending southwards along the east coast, and those of the south northwards along the west. Within the equatorial zone certain areas, especially on the shores of the Gulf of Guinea and in the upper Nile basin, have an intensified rainfall, but this rarely approaches that of the rainiest regions of the world. The rainiest district in all Africa is a strip of coastland west of Mount Cameroon, where there is a mean annual rainfall of about 10,000 mm (394 in) as compared with a mean of 11,600 mm (457 in) at Cherrapunji, in Meghalaya, India.^[1]

The two distinct rainy seasons of the equatorial zone, where the sun is vertical at half-yearly intervals, become gradually merged into one in the direction of the tropics, where the sun is overhead but once. Snow falls on all the higher mountain ranges, and on the highest the climate is thoroughly Alpine.^[1]

The countries bordering the Sahara are much exposed to a very dry wind, full of fine particles of sand, blowing from the desert towards the sea. Known in Egypt as the khamsin, on the Mediterranean as the sirocco, it is called on the Guinea coast the harmattan. This wind is not invariably hot; its great dryness causes so much evaporation that cold is not infrequently the result. Similar dry winds blow from the Kalahari Desert in the south. On the eastern coast the monsoons of the Indian Ocean are regularly felt, and on the southeast hurricanes are occasionally experienced.^[1]

The

Yellow fever is a disease also transmitted by mosquitoes native to Africa. Unlike malaria, it cannot be contracted more than once. Like chicken pox, it is a disease that tends to be severe the later in life a person contracts the disease.^[12]

Sleeping sickness, or African trypanosomiasis, is a disease that usually affects animals, but has been known to be fatal to some humans as well. It is transmitted by the tsetse fly and is found almost exclusively in Sub-Saharan Africa.^[13] This disease has had a significant impact on African development not because of its deadly nature, like Malaria, but because it has prevented Africans from pursuing agriculture (as the sleeping sickness would kill their livestock).^[12]

• List of national parks in Africa
• Outline of Africa#Geography of Africa
• The Horn of Africa