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Geography of Africa

2007 Schools Wikipedia Selection. Related subjects: African Geography

   Africa is a continent comprised of 61 political territories (including
   53 countries), representing the largest of the three great southward
   projections from the main mass of Earth's surface. It includes, within
   its remarkably regular outline, an area of 30,368,609 km² (11,725,385
   mi²), including adjacent islands.

   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 (80
   miles) 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, in 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 miles); from Cape Verde,
   17°33′22″ W, the westernmost point, to Ras Hafun in Somalia, 51°27′52″
   E, the most easterly projection, is a distance (also approximately) of
   7,400 km (4,600 miles). The length of coast-line is 26,000 km (16,100
   miles) and the absence of deep indentations of the shore is shown by
   the fact that Europe, which covers only 10,400,000 km² (4,010,000
   square miles), has a coastline of 32,000 km (19,800 miles).

   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 composed of two segments at
   right angles, the northern running from east to west, the southern from
   north to south, the subordinate lines corresponding in the main to
   these two directions.

Main Geographical Features

   Enlarge

   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
   (3,117 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 (600 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 (10,000 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] 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 mountain range,
   the continent may be divided into two regions of higher and lower
   plateaus, the dividing line (somewhat concave to the north-west)
   running from the middle of the Red Sea to about 6 deg. S. 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 — orographically 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

   Topography of Africa
   Enlarge
   Topography of Africa

   The high southern and eastern plateaus, rarely falling below 600 m
   (2000 ft), and having a mean elevation of about 1000 m (3500 ft). The
   South African plateau as far as about 12° S, 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 the north-east with the
   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 depression, known as the Great Rift Valley is
   occupied for more than half its length by water, forming the Great
   Lakes lakes of Tanganyika, Kivu, Lake Edward and Lake Albert, the
   first-named over 400 miles (600 km) 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 depression, known as the East
   African trough or rift-valley, 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.

   At no great distance east of this rift-valley are Mount Kilimanjaro -
   with its two peaks Kibo and Mawenzi, the latter being 5889 m (19,321
   ft), and the culminating point of the whole continent - and Mount
   Kenya, which is 5184 m (17,007 ft). Hardly less important is the
   Ruwenzori Range, over 5060 m (16,600 ft), 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.

   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 1500 m (5000 ft), while the summits reach heights
   of 4600 m to 4900 m (15,000 to 16,000 ft). 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 2000 m (7000 ft). 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 1800 m to 2400 m (6000 to 8000 ft)
   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 4075 m (13,370 ft), while Clarence Peak, in
   Fernando Po, the first of the line of islands, rises to over 2700 m
   (9000 ft). 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

   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 desert in the world, covering
   9,000,000 km² (3,500,000 square miles) — extends from the Atlantic to
   the Red Sea. Though generally of slight elevation it contains mountain
   ranges with peaks rising to 2400 m (8000 ft) 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
   delta of the Nile. That river (see below) pierces the desert without
   modifying its character. The Atlas range, the north-westerly part of
   the continent, between its seaward and landward heights encloses
   elevated steppes in places 160 km (100 miles) broad. From the inner
   slopes of the plateau numerous wadis take a direction towards the
   Sahara. The greater part of that now desert region is, indeed, furrowed
   by old water-channels.

   The following table gives the approximate altitudes of the chief
   mountains and lakes of the continent:

                Mountain                ft    m
   Mount Rungwe (Nyasa)               10,400 3170
   Drakensberg                        10,700 3261
   Lereko or Sattima (Aberdare Range) 13,214 4028
   Cameroon                           13,370 4075
   Elgon                              14,152 4314
   Karisimbi (Mfumbiro)               14,683 4475
   Meru                               14,955 4558
   Taggharat (Atlas)                  15,000 4572
   Simens, Ethiopia                   15,160 4621
   Ruwenzori                          16,619 5065
   Kenya                              17,007 5184
   Kilimanjaro                        19,321 5889

                                                    Lake     ft   m
                                                 Chad       850  259
                                                 Mai-Ndombe 1100 335
                                                 Rudolf     1250 381
                                                 Nyasa      1645 501
                                                 Albert     2028 618
                                                 Tanganyika 2624 800
                                                 Ngami      2950 899
                                                 Mweru      3000 914
                                                 Edward     3004 916
                                                 Bangweulu  3700 1128
                                                 Victoria   3720 1134
                                                 Abaya      4200 1280
                                                 Kivu       4829 1472
                                                 Tsana      5690 1734
                                                 Naivasha   6135 1870

National Parks and Game Reserves

     * List of National Parks in Africa

The Hydrographic Systems

   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.

   The high lake plateau of East Africa contains the headwaters of both
   the Nile and the Congo: the former the longest, and the latter the
   largest river of the continent.

   The upper Nile receives its chief supplies from the mountainous region
   adjoining the Central African trough in the neighbourhood of the
   equator. From there, streams pour eastward into Lake Victoria, the
   largest African lake (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
   N. 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.

   The most remote head-stream of the Congo is the Chambezi, which flows
   southwest into the marshy Lake Bangweulu. From this lake issues the
   Congo, known in its upper course by various names. Flowing first south,
   it afterwards turns north through Lake Mweru and descends to the
   forest-clad basin of west equatorial Africa. Traversing this in a
   majestic northward curve, and receiving vast supplies of water from
   many great tributaries, it finally turns southwest and cuts a way to
   the Atlantic Ocean through the western highlands.

   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 Shad coming from the southeast.

   West of this 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, 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 consisting of arid regions
   watered only by intermittent streams that do not reach the sea.

   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 1000 miles (1600 km) 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.

   Of the rivers flowing to the Indian Ocean, the only one draining any
   large part of the interior plateaus is the Zambezi, whose western
   branches rise in the western coastal highlands. The main stream has its
   rise in 11°21′3″ S 24°22′ E, at an elevation of 5000 ft. It flows to
   the west and south for a considerable distance before turning eastward.
   All the largest tributaries, including the Shire, the outflow of Lake
   Nyasa, flow down the southern slopes of the band of high ground
   stretching across the continent from 10 deg. to 12 deg. S. In the
   southwest, the Zambezi system interlaces with that of the Taukhe (or
   Tioghe), from which it at times receives surplus water. The rest of the
   water of the Taukhe, known in its middle course as the Okavango, is
   lost in a system of swamps and saltpans that was formerly centred in
   Lake Ngami, now dried up.

   Farther south, the Limpopo drains a portion of the interior plateau,
   but breaks through the bounding highlands on the side of the continent
   nearest its source. The Rovuma, Rufiji, Tana, Jubba and Webi Shebeli
   principally drain the outer slopes of the East African highlands, the
   last of these losing itself in the sands in proximity to the sea.
   Another large stream, the Hawash, rising in the Ethiopian mountains, is
   lost in a saline depression near the Gulf of Aden.

   Lastly, between the basins of the Atlantic and Indian Oceans, there is
   an area of inland drainage along the centre of the East African
   plateau, directed chiefly into the lakes in the great rift valley. The
   largest river is the Omo, which, fed by the rains of the Ethiopian
   highlands, carries down a large body of water into Lake Rudolf. The
   rivers of Africa are generally obstructed either by bars at their
   mouths, or by cataracts at no great distance upstream. But when these
   obstacles have been overcome, the rivers and lakes afford a vast
   network of navigable waters.

   The calculation of the areas of African drainage systems, made by Dr A.
   Bludau (Petermanns Mitteilungen, 43, 1897, pp. 184-186) yields the
   following general results:
                                 mi²     Mm²
   Basin of the Atlantic      4,070,000 10.541
   Basin of the Mediterranean 1,680,000 4.351
   Basin of the Indian Ocean  2,086,000 5.403
   Inland drainage area       3,452,000 8.941

   The areas of individual river basins are:
                                              mi²     Mm²
   Congo, length over 3000 mi (4800 km)    1,425,000 3.691
   Nile, length fully 4000 mi (6500 km)    1,082,000 2.802
   Niger, length about 2600 mi (4200 km)   808,000   2.093
   Zambezi, length about 2000 mi (3200 km) 513,500   1.330
   Lake Chad                               394,000   1.020
   Orange, length about 1300 mi (2100 km)  370,505   0.9596
   Orange (actual drainage area)           172,500   0.447

   The area of the Congo basin is greater than that of any other river
   except the Amazon, while the African inland drainage area is greater
   than that of any continent but Asia, where the corresponding area is
   4,000,000 square miles (10 Mm²).

   The principal African lakes have been mentioned in the description of
   the East African plateau, but some of the phenomena connected with them
   may be spoken of more particularly here. As a rule, the lakes found
   within the great rift-valleys 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 430 fathoms (790 m).

   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
   eastern rift-valley. Lakes of the broad type are of moderate depth, the
   deepest sounding in Lake Victoria being under 50 fathoms (90 m).

   Besides the East African lakes, the principal 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.

   Divergent opinions have been held as to the mode of origin of the East
   African 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.

Islands

   With one exception - Madagascar - the African islands are small.
   Madagascar, with an area of 229,820 square miles (595,230 km²), is,
   after Greenland, New Guinea and Borneo, the fourth largest island on
   the Earth. It lies off the S.E. coast of the continent, from which it
   is separated by the deep Mozambique channel, 250 miles (400 km) 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.
   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.

Climate and health

   Vegetation in February and August
   Enlarge
   Vegetation in February and August

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

   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.

   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.

   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 390 in (9.91 m) as compared with a mean of 458 in (11.63 m) at
   Cherrapunji, in Meghalaya, India.

   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.

   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.

Extreme points

   This is a list of the extreme points of Africa, the points that are
   farther north, south, east or west than any other location on the
   continent.

   Africa
     * Northernmost Point — Ras ben Sakka, Tunisia
     * Southernmost Point — Cape Agulhas, South Africa (34°51'15"S) ¹
     * Westernmost Point — Santo Antão, Cape Verde Islands (25°25'W)
     * Easternmost Point — Rodrigues, Mauritius (63°30'E)
     * African pole of inaccessibility is close to the border of Central
       African Republic, Sudan and Congo, near the town Obo.

   Africa (mainland)
     * Northernmost Point — Ra's al Abyad ( Cape Blanc), Tunisia
     * Southernmost Point — Cape Agulhas, South Africa ( 34°51′15″S,
       17°33′22″E)
     * Westernmost Point — Pointe des Almadies, Cap Vert Peninsula,
       Senegal (17°33'22"W)
     * Easternmost Point — Ras Hafun (Raas Xaafuun), Somalia (51°27'52"E)

     * ¹ If the Prince Edward Islands are included in Africa, then Marion
       Island is the southernmost point at 46°54'S.

   This article incorporates text from the Encyclopædia Britannica
   Eleventh Edition, a publication now in the public domain.

   Retrieved from " http://en.wikipedia.org/wiki/Geography_of_Africa"
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