Africa is a continent comprising 63 political territories, representing the largest of the great southward projections from the main mass of Earth's surface. Within its regular outline, it comprises an area of , including adjacent islands. Its highest mountain is Kilimanjaro; its largest lake is Lake Victoria.
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), 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 ; 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 .
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.
Main features
The average elevation of the continent approximates closely to above sea level, roughly near to the mean elevation of both North and South America, but considerably less than that of Asia, . In contrast with other continents, it is marked by the comparatively small area of either very high or very low ground, lands under occupying an unusually small part of the surface; while not only are the highest elevations lower to those of Asia or South America, but the area of land over is also rather limited, 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.)
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.
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).
Plateau region
There are many plateaus in Africa.
The high southern and eastern plateaus, rarely falling below , have a mean elevation of about . The South African plateau, as far as about 12° S, is bounded east, west and south by bands of high ground which fall steeply to the coasts. On this account South Africa has a general resemblance to an inverted saucer. Due south, the plateau rim is formed by three parallel steps with level ground between them. The largest of these level areas, the Great Karoo, is a dry, barren region, and a large tract of the plateau proper is of a still more arid character and is known as the Kalahari Desert.
The South African plateau is connected towards East African plateau, with probably a slightly greater average elevation, and marked by some distinct features. It is formed by a widening out of the eastern axis of high ground, which becomes subdivided into a number of zones running north and south and consisting in turn of ranges, tablelands and depressions. The most striking feature is the existence of two great lines of depression, due largely to the subsidence of whole segments of the Earth's crust, the lowest parts of which are occupied by vast lakes. Towards the south the two lines converge and give place to one great valley (occupied by Lake Nyasa), the southern part of which is less distinctly due to rifting and subsidence than the rest of the system.
Farther north the western hollow, known as the Albertine Rift, is occupied for more than half its length by water, forming the Great Lakes of Tanganyika, Kivu, Lake Edward and Lake Albert, the first-named over long and the longest freshwater lake in the world. Associated with these great valleys are a number of volcanic peaks, the greatest of which occur on a meridional line east of the eastern trough. The eastern branch of the East African Rift, contains much smaller lakes, many of them brackish and without outlet, the only one comparable to those of the western trough being Lake Turkana or Basso Norok.
A short distance east of this rift valley is Mount Kilimanjaro – with its two peaks Kibo and Mawenzi, the latter being , and the culminating point of the whole continent – and Mount Kenya, which is . Hardly less important is the Ruwenzori Range, over , which lies east of the western trough. Other volcanic peaks rise from the floor of the valleys, some of the Kirunga (Mfumbiro) group, north of Lake Kivu, being still partially active. This could cause most of the cities and states to be flooded with lava and ash.
The third division of the higher region of Africa is formed by the Ethiopian Highlands, a rugged mass of mountains forming the largest continuous area of its altitude in the whole continent, little of its surface falling below , while the summits reach heights of 4400 m to 4550 m. This block of country lies just west of the line of the great East African Trough, the northern continuation of which passes along its eastern escarpment as it runs up to join the Red Sea. There is, however, in the centre a circular basin occupied by Lake Tsana.
Both in the east and west of the continent the bordering highlands are continued as strips of plateau parallel to the coast, the Ethiopian mountains being continued northwards along the Red Sea coast by a series of ridges reaching in places a height of . In the west the zone of high land is broader but somewhat lower. The most mountainous districts lie inland from the head of the Gulf of Guinea (Adamawa, etc.), where heights of are reached. Exactly at the head of the gulf the great peak of the Cameroon, on a line of volcanic action continued by the islands to the south-west, has a height of , while Clarence Peak, in Fernando Po, the first of the line of islands, rises to over . Towards the extreme west the Futa Jallon highlands form an important diverging point of rivers, but beyond this, as far as the Atlas chain, the elevated rim of the continent is almost wanting.
Plains Much of Africa consists of plains of the pediplain and etchplain type often occurring as steps. The etchplains are commonly associated with laterite soil and inselbergs. Inselberg-dotted plains are common in Africa including Tanzania,Sundborg, Å., & Rapp, A. (1986). Erosion and sedimentation by water: problems and prospects. Ambio, 215-225. the Anti-Atlas of Morocco, Namibia, and the interior of Angola. One of the most widespread plains is the African Surface, a composite etchplain occurring across much of the continent.
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.
Running along the south of desert is the plains region known as the Sahel.
The arid region, the Sahara — the largest hot desert in the world, covering — extends from the Atlantic to the Red Sea. Though generally of slight elevation, it contains mountain ranges with peaks rising to Bordered N.W. by the Atlas range, to the northeast a rocky plateau separates it from the Mediterranean; this plateau gives place at the extreme east to the Nile Delta. That river (see below) pierces the desert without modifying its character. The Atlas range, the northwesterly region of the Maghreb, between its seaward and landward heights encloses elevated steppes in places broad. From the inner slopes of the plateau numerous wadis take a direction toward the Sahara. The greater part of that now desert region is, indeed, furrowed by old water-channels.
Mountains
Mountains are exceptions to the continent's general landscapes. 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. The following table gives the details of the chief mountains and ranges of the continent:
+ Mountain Range Country Height (m) Height (ft) Prominence (m) Isolation (km) Kilimanjaro Eastern Rift volcanoes Tanzania 5895 19,340 5885 5510 Mount Kenya Eastern Rift volcanoes Kenya 5199 17,058 3825 323 Mount Stanley Rwenzori Mtns Uganda/DRC 5109 16,762 3951 830 Mount Meru Eastern Rift volcanoes Tanzania 4566 14,980 3170 70 Ras Dashen Semien Mountains Ethiopia 4533 14,872 3997 1483 Mount Karisimbi Virunga Mountains Rwanda/DRC 4507 14,787 3312 207 Mount Elgon Eastern Rift volcanoes Uganda 4321 14,178 2458 339 Toubkal Atlas Mountains Morocco 4167 13,671 3755 2078 Mount Cameroon Cameroon line Cameroon 4095 13,435 3901 2338 Mount Satima Aberdare range Kenya 4001 13,120 2081 77 Mount Teide Canary Islands Spain 3718 12,198 3715 893 Thabana Ntlenyana Drakensberg Lesotho 3482 11,422 2390 3003 Emi Koussi Tibesti Mountains Chad 3445 11,302 2934 2001 Emba mossino Emba Soira Eritrea 3038 9,849 2319 1272
Rivers
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.
To the main African rivers belong: the 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, and Lake Tanganyika (which lies 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, Aswan in Egypt, 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 Gondwana in Late Cretaceous and Cenozoic times led to a major reorganization of the river courses of various large African rivers including the Congo, Niger, Nile, Orange, Limpopo, and Zambezi rivers.
Flowing to the Mediterranean Sea