Description of the East African plateau. South African plateau. Finished works on a similar topic
Subcontinent South Africa occupies the south of the African continent. In the north, the border with Central Africa passes along the watersheds of the river basin. Congo, in the northeast (c) - along a tectonic fault occupied by the river valley. Zambezi. The remaining borders are maritime. The subcontinent of South Africa includes two continental physiographic countries: the South African plateaus and plateaus, the Cape Mountains and the island of Madagascar, which shares some natural features with them.
The unity of the region is determined by the predominance within its borders of elevated relief, higher along the outskirts and somewhat lower in the central parts, as well as its position in the narrowed southern part of the continent, which, in combination with the relief features, causes a change in natural conditions from west to east rather than from north to south. This pattern is evident in all three physiographic countries of the subcontinent. The main environmental problems of the region are land degradation in conditions of dissected relief and irrational environmental management and desertification in arid regions.
South African plateaus and plateaus
The physiographic country occupies most of South Africa. The southern border (with the Cape Mountains) follows the foot of the Great Escarpment in the north of the Great Karoo Basin. The region contains South Africa, Namibia, Botswana, Lesotho, Swaziland and the southern parts of Angola, Zambia and Mozambique.
The outskirts of the region are elevated, and in the center there is a chain of basins - the Kalahari, Makarikari, Okavanga and Upper Zambezi. This structure is associated with the last stages of geological history: starting from the Mesozoic, the territory rose, and the outskirts rose at a faster rate than the central parts.
This is a high region. Even the bottoms of the basins lie at altitudes of 900-1000 meters, the outskirts are raised to 2000-2500 meters, and in some places above 3000 meters. On the ledges of the ancient crystalline foundation, plateaus with fragments of planation surfaces of different ages were formed. Within the vast Karoo syneclise, inversion relief is widespread: on a thick layer of sedimentary deposits (Karoo Formation - up to 7 km) a system of plateaus has been formed - Great, Middle, Low, Shrub Velds, Upper Karoo, etc. These plateaus and plateaus break off to narrow coastal lowlands and to the Great Karoo plateau, forming the so-called Great Escarpment. It is dissected by tectonic fractures and erosion. The highest part of the Great Escarpment is the Drakensberg Mountains, which in the south - in the Basuto Highlands - reach a height of more than 3000 m, the peak is Thabana Ntlenyana (3482 meters). The highlands are composed of sedimentary rocks overlain by basaltic lavas. From the edges of the plateaus and plateaus they descend in steps to the flat bottoms of the basins, where alluvial and ancient lacustrine deposits lie on the surface.
The climate of the region is tropical. The amount of precipitation varies from east to west.
The eastern regions are influenced by the trade wind flow from Indian Ocean, which, rising along the slopes of mountains and plateaus, gives abundant precipitation (1000-1500 mm per year). In winter, this flow weakens and is quite often replaced by winds coming from the continent, from the subtropical high pressure zone. The Indian trade wind descends into the basins, and the annual rainfall already on the velds decreases to 500-600 mm, and in the Upper Zambezi and Kalahari basins - to 300 mm or less. However, in the western Kalahari, in the intertropical convergence zone, a front is formed between tropical air masses arriving with different properties. from the Indian Ocean it is warm and humid, from the Atlantic it is colder, since it comes from high latitudes. On west coast The typical climate of the western coasts of the continents of the tropical zone is formed.
The South African plateaus and plateaus are drained by several large rivers - the Zambezi, Limpopo, Orange, and Okavango. All of them have an uneven flow regime with a summer maximum and rapids.
On the river The Zambezi is widely known as one of the most large waterfalls- Victoria. The rivers here fall from a height of 120 meters into a narrow tectonic fissure. The Okavango River and some other smaller rivers end in the central parts of the basins, losing themselves in swamps or sands.
The soil and vegetation cover changes from east to west according to changes in moisture conditions.
On the Mozambican lowland, eastern slopes and in the northern part of the region on the border with Central (Equatorial) Africa, evergreen seasonally moist tropical forests with an abundance of palm trees grow. On the slopes of the Great Escarpment above 800-1000 meters, bushes and meadows are common. The velds (which means “steppes” in Dutch) are occupied by xerophytic shrub formations (aloe, euphorbia, acacia) and mountain steppes with a predominance of thema. The Matabele Plateau is home to sparse deciduous forests on brown-red soils combined with savannas of predominantly anthropogenic origin. The northern part of the central basins is dominated by sparse savannah forests of brachystegia and isoberinia with dense undergrowth. Brown-red soils form under them. South of the river In the Zambezi, swamps and salt marshes form at the bottoms of the basins, usually occupying the place of dry lakes. South part The Kalahari consists of dry shrubby savannas (bush) and woodlands; the southwest of the region is a real desert with ridged sands and limestone outcrops. Usually the sands are anchored by succulent and thorny bushes. Large spaces are covered with creeping vines of wild watermelons. Lots of ephemera. The vegetation of the western marginal plateaus and plateaus, which descend in a steep dissected ledge (300-800 meters high) to the coastal Namib desert - a typical “cold” or “wet” desert, is even more arid in nature. The northern part of the Namib is a combination of gravelly and sandy areas with sparse vegetation of thorny bushes and succulents. Among them, sometimes there is a wonderful plant - Velvichia with two long (up to 2 meters) leathery leaves capable of absorbing moisture from the air. In the south the vegetation is denser.
The soils of the eastern and northern plateaus and plateaus of South Africa are fertile, the velds with their grassy vegetation are excellent pastures. The lands are intensively used. Continuous plowing and excessive grazing lead to increased linear and planar erosion and land degradation.
South Africa is rich in mineral resources. The Karoo Formation contains large reserves of coal, platform basement structures and ancient syneclises - deposits of a variety of ores and gold. Diamonds and garnets are mined in explosion tubes filled with kimberlite. There are also gold and diamonds in alluvial deposits. Large reserves of gold are contained in conglomerates formed from the alluvium of Paleozoic rivers. In the famous Witwatersrand deposit, gold and uranium ores are extracted from such deposits in deep mines (up to 1500 meters deep) under very difficult conditions.
The region was developed economically mainly by Dutch (Boer) and English settlers. Until recently, the indigenous black population in the Republic of South Africa was disenfranchised and mercilessly oppressed. Now the dark-skinned residents of the region (mainly Hottentots) have received political rights, but the consequences of racial discrimination complicate the situation in South Africa to this day.
A number of national parks and reserves have been created in the region to preserve unique fauna and landscapes. The Namib Desert, Etosha and Skeleton Coast (“Skeleton Coast”) in Namibia, Royal Natal in South Africa and some others have existed as protected areas since the beginning of the 20th century, and the Kruger Park and the Saint Lucia Faunal Reserve (South Africa) function as nature reserves since the 90s of the 19th century.
Cape Mountains
The physical-geographical country of the Cape Mountains occupies the extreme south of the African continent in the region of subtropical climate. It is smaller than others in area, but has very unique natural conditions. From the west, the region is washed by the waters of the Atlantic Ocean with the cold Benguela Current, and in the east and south by the waters of the Indian Ocean with the warm Mozambique Current, passing into Agulhas (Cape Agulhas). In the north, the border with the South African plateaus and plateaus runs along the foot of the Great Escarpment. The entire physical-geographical country is located within South Africa.
The Cape Mountains arose as a result of the rejuvenation of Hercynian fold structures. Ridges parallel to each other - anticlines, raised by neotectonic movements, are separated by intermountain valleys - synclines. Transverse gorges of tectonic and erosional origin divide the ridges into short segments. In the very south, low isolated massifs and ridges rise among the coastal plain.
The region is located in a subtropical climate, in the west - Mediterranean type with winter cyclonic precipitation.
From typical Mediterranean climate and North Africa, it is characterized by low summer temperatures, which is associated with the dominance in summer season air masses coming from the south. In the eastern Cape Mountains, precipitation is more evenly distributed across seasons.
In winter there are fewer of them here than in the west, since the westerly transport of air from temperate latitudes dominates, but in summer rains of orographic origin fall from air masses coming from the Indian Ocean, which also pass over the warm Mozambique Current. The climate in the east of the region is rather maritime with a uniform distribution of moisture and small temperature amplitudes. In the interior valleys the climate is arid with continental features.
Cape flora appearance reminiscent of the Mediterranean. Xerophytic shrubs on brown soils (fynbos) are similar to maquis in structure and ecological features, but are very different from it in species composition. Proteaceae, heathers, and legumes predominate, usually represented by endemic species.
There are many bulbous and rhizomatous brightly flowering herbs. Many of them are cultivated around the world as ornamental and indoor plants (gladioli, daffodils, hyacinths, amaryllis, cineraria, geraniums, etc.). On the slopes facing the oceans, small forests of pine and podocarpus have been preserved in some places. There are more forests in the east.
In the Cape region, subtropical crops are grown on all cultivable land: grapes, olives, figs, fruit trees and shrubs. Almost no natural vegetation has been preserved.
There are four national parks and three provincial reserves in the region, where rare plants and animals are protected. Some of them were created in the 30s. XX century
Madagascar
This peculiar physical-geographical country lies on one of the largest islands Earth (596 thousand km 2). Until now, its nature preserves the memory of the ancient past of the planet - the rarest species of plants and animals have been preserved there, and scientists are still discovering new species. The significant endemicity of flora and fauna is explained by the long-standing (since the Neogene) isolation of the island from the mainland. The Mozambique Strait is up to 400 km wide. Madagascar is a block that broke away from the African Platform at the end of the Paleozoic, inclined towards the strait. The island extends in the submeridional direction for 1600 km from 12° to 26° S. w. The nature of Madagascar has truly unique features.
On a small island compared to the mainland physiographic countries of South Africa, there is a significant diversity of surface structure.
The main tectonic structures of the Madagascar block are elongated, like the entire region, from north to south and successively replace each other. In the east, about 1/3 of the island's territory is occupied by the Madagascar (Malgassy) massif - an uplift within which a crystalline platform foundation comes to the surface. In the southern half, igneous rocks have undergone significant metamorphism. Gneisses with granite intrusions, quartzites, and marbles are common here. The second petrographic zone is graphite, the most widely represented and variegated in composition: graphites, mica schists, gneisses, etc. The third zone is found in small areas throughout the massif. These are sedimentary rocks of varying degrees of metamorphosis: granitoids, crystalline schists, ferruginous quartzites. The massif underwent significant fragmentation, accompanied by volcanic processes. Within its boundaries, the Central Highlands (High Plateau) with a height of 800-1800 meters was formed, divided by faults into separate massifs with flat-bottomed depressions and valleys between them. In the north rises the Tsaratanana basalt massif with highest point islands (2876 meters), there are other extinct ones. The process of fragmentation of the block was most active at the beginning of the Cenozoic. Earthquakes are still common, and there are many thermal springs. At the eastern foot of the High Plateau stretches a narrow (10-20 km) low-lying accumulative plain composed of marine sediments, including limestones with manifestations of tropical karst. From the west, within the side of the Mozambique tectonic trough, lower stratal plateaus (up to 800 meters) adjoin the Central Highlands. Along the western coast there are hilly lowlands.
Most of Madagascar is located in the tropical climatic zone with trade wind circulation. Only the northwest is under the influence of the equatorial monsoons. The climate on the plains is hot.
Average monthly temperatures range from 13-20°C in winter to 26-30°C in summer. The course of isotherms is generally submeridional. The climate on the High Plateau is cool (from 13°C to 20°C). Since the island is under the influence of the trade wind flow from the Indian Ocean almost the entire year, the annual rainfall decreases from east to west - from 2000-3000 mm to 500-600 mm and even 400 mm in the extreme southwest. The windward slopes of the highlands are most uniformly and abundantly moistened. More precipitation occurs in summer, and in the north-west in winter there is a well-defined dry season, which is typical for trade wind circulation.
Madagascar's climate and topography favor the development of a dense river network. The rivers of the eastern slopes are full-flowing, short, stormy, rapids, while the rivers of the western slopes are longer, but less watery. They carry a lot of solid material onto the plains, forming numerous sandbanks. The flat bottoms of intermountain valleys contain lakes and wetlands.
Vegetation is distributed depending on moisture conditions.
In the past, the windward eastern slopes of the mountains and the coastal lowlands were covered with evergreen forests, under which red-yellow ferralitic soils formed. Forests have survived only in isolated tracts. The High Plateau is dominated by secondary grass savannas with thorny bushes on mountain red and red-brown soils formed on ferralite weathering crust. Within the lava covers, dark red and black fertile soils are developed. On the western plains, under dry bushland, the soils are brown and red-brown. The most arid southwest is occupied by semi-desert and desert vegetation with candelabra-shaped milkweeds and thorny bushes. Mangroves are common on the low-lying west coast. The vegetation cover of the island has been greatly modified by humans.
The flora and fauna of Madagascar are unique.
Its forests share common species with Asian ones (some ferns, Asteraceae, legumes), but of the 6,765 species of angiosperms known here, 89% are endemic. Since the Miocene, the island has been completely isolated from the neighboring land. The most famous endemics of Madagascar: Ravenala - “travelers tree” from bananas (another species of this genus lives in South America), angrekum orchid with flowers up to 25 cm in diameter, royal piitsiana - “flame of the forest” with fiery red flowers, etc. No less unique animal world. Madagascar is sometimes called Lemuria. Indeed, only here many species of lemur primates live: indri with big eyes and a five-fingered paw, cat, brown, dwarf and other lemurs. Only within Madagascar and the nearby Comoros Islands are representatives of about 20 species of the relict family of tenrecs (“bristle hedgehogs”) of insectivores preserved. Carnivores are represented by civets. There are many reptiles (50 species of chameleons alone) and birds, almost half of which are endemic. On the island a large number of insects, including colorful butterflies. Both in terms of flora and fauna, Madagascar is divided into separate subregions of the corresponding regions - they differ in such original features.
About 9 million people live on the island within the Malagasy Republic, the vast majority of whom are indigenous people, closer in anthropological type, language and culture to the peoples South-East Asia than to the population of Africa. 3/4 of the territory of Madagascar has a climate that is very favorable for human life and for agriculture. Good moisture in many areas of the island, plenty of heat, and the presence of fertile soils create excellent conditions for growing many valuable tropical crops. Significant areas are occupied by rice crops. Cattle breeding is also developed (the main livestock is zebu, but other breeds are also bred). There are no tsetse flies on the island, which is important for this industry.
The island is well endowed with other species natural resources: water, including hydropower in the east of the region, mineral (there are large deposits of mica, graphite, uranium, chromite, nickel, lead ores, gold, precious and semi precious stones and etc.). Madagascar ranks first in the world in terms of reserves of amethyst from soft lilac to deep purple shades. Amethyst druses are often found in rock dumps after ore mining. Forest resources have suffered greatly as a result of unsustainable management. Now only 10% of the island's area is occupied by forests. Forests containing reserves of valuable timber and other resources were destroyed.
Natural complexes are greatly changed by human activity. Many unique species of plants and animals have disappeared or are on the verge of extinction. The habitats of many of them have been destroyed. Some animals were simply exterminated by humans: large lemurs, giant turtles, flightless birds - apiornis, related to ostriches and moas, vurupatra, etc. Colorful butterflies are disappearing. To protect the remaining unique flora and fauna, a number of reserves were created (mainly in the 20s of the 20th century), there are 2 national parks, several reserves.
see also nature photographs of the South African plateau(with geographical and biological captions for photographs) from the section Natural landscapes of the world:
On the gentle slopes of the eastern plateaus, facing inland, there is still quite a lot of precipitation; treeless terrain with a dense cover of tall grasses prevails there (). This type of landscape is called the "veld" in South Africa.
As you move westward, the amount of precipitation decreases and the vegetation takes on an increasingly xerophytic appearance. It consists of various bulbous plants that turn green and bloom only during a short period of rain, low-growing prickly acacias, and numerous types of aloe. In the Kalahari there are completely barren rocky areas where plants do not form a continuous cover (). Wild watermelons are very characteristic of the Kalahari, the lashes of which cover large areas. Obviously, all known cultivated types of watermelons originate from here. When there is a great lack of moisture, watermelons with their water reserves save people and animals from thirst.
The vegetation of the Namib Desert is even poorer, where only isolated specimens of Welwitschia are found, anchored on the sands with powerful roots, and low-growing thorny bushes ().
The shores of drying lakes and swamps in the depressions of the Kalahari and the upper reaches of the Zambezi are covered with more moisture-loving vegetation (), which serves as a refuge for wild animals.
, Rwanda, Burundi, Tanzania, Zambia, Malawi). Heights 500–1500 m, mountains in the west Rwenzori (peak Margherita , 5109 m), massif Virunga . To the south are flat-topped mountains Mitumba (3305 m). On the NE. plateaus volcanic cones Elgon (4221 m), Kenya (5199 m), Meru (4566 m), Kilimanjaro (5895 m); in the center Crater Highlands with caldera Ngorongoro . A large uplift of the ancient African platform, broken by a system of faults called the East African Rift System. It is composed of ancient crystalline and young volcanic rocks. Characterized by high seismicity and modern volcanism. Deposits of coal, fluorite, polymetallic ores and rare metals; placers of precious stones, diamond-bearing kimberlite pipe Mwadui. The most large rivers Africa: , Nile , Congo Zambezi . A series of large lakes ( , Victoria, Edward , Tanganyika Rudolf and etc.); modern glaciers on the volcanoes of Kilimanjaro, Kenya and in the Rwenzori massif. The climate is equatorial and subequatorial, seasonally humid, hot. Savannah woodlands and shrubs predominate. In the mountains there are tropical rainforests, subalpine and alpine meadows. National parks Virunga, Serengeti
and a number of others. Explored by Europeans in the second half of the 19th century. (D.-H. Speke, R.-F. Burton, D.-O. Grant, D. Livingston, G.-M. Stanley, etc.). Dictionary of modern geographical names. . - Ekaterinburg: U-Factoria. 2006 .
Under the general editorship of academician. V. M. Kotlyakova
East African plateau in Kenya, Uganda, Rwanda, Burundi, Tanzania, Zambia, Malawi. Extent from north to south is approx. 1750 km, latitude. OK. 1400 km. Located between the Ethiopian Highlands and the north. edge of the lake Nyasa. In the west and south it is limited by mountains and depressions, in the east by the coastal plains of the Indian Ocean. Broken by a system of faults that make up part East African Rift . Most of the plateau is composed of crystalline and metamorphic rocks of the Precambrian; there are covers of Quaternary lavas and tuffs. Characterized by high seismicity and modern volcanism. Deposits of coal, polymetallic ores, precious and semi-precious stones, diamonds. High Plains from Wed. high from 500 to 1500 m, above which the remnant mountains rise. To the west are the Rwenzori Mountains with Peak Margherita (5109 m), Virunga with more than 400 small and 8. Of these, Nyamlagira (3058 m) and Nyiragongo (3470 m) are active. To the south are the flat-topped Mitumba Mountains (3305 m). On the north-east the cones of the extinct volcanoes Elgon (4221 m) and Kenya (5199 m), and in the center - the Crater Highlands with the giant Ngorongoro caldera (fauna and flora reserve). The largest volcanic massif with the active Meru volcano (4566 m) and the main peak of Africa - the extinct volcano Kilimanjaro (5895 m). A number of large and small lakes (Victoria, Edward, Tanganyika, Rudolf, etc.). Modern glaciers on the Kilimanjaro and Kenya volcanoes and in the Rwenzori massif. The climate is equatorial and subequatorial, seasonally humid, hot. Annual precipitation is up to 2000–3000 mm or more, and the deep valleys are dry. The largest rivers in Africa – the Nile, Congo, and Zambezi – originate on the plateau. Subequatorial forests, savanna woodlands and shrubs predominate. In the mountains there are subalpine and alpine meadows. National Virunga, Serengeti, and many smaller parks; numerous nature reserves.
Geography. Modern illustrated encyclopedia. - M.: Rosman. Edited by prof. A. P. Gorkina. 2006 .
See what the “East African Plateau” is in other dictionaries:
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Meridional system of faults in the earth's crust. Formed by tectonic movements in the Mesozoic and Cenozoic, accompanied by powerful outpouring of lavas. It has no equal on land both in length (over 6000 km) and in the amplitude of vertical movements... Geographical encyclopedia
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Africa. Physico-geographical sketch. Relief- In the mountains of Kabylia. Algeria. The creation of most modern forms of relief in Africa occurred in the Neogene and at the beginning of the Quaternary period, when differentiated tectonic movements formed the inland depressions and those separating them... ... Encyclopedic reference book "Africa"
The East African Plateau is located on both sides of the equator, between the Congo Basin in the west and the Indian Ocean in the east, Eastern Sudan, the Ethiopian Highlands, the Somali Peninsula in the north and the lower reaches of the Zambezi in the south and covers the area from 5° N. w. to 17° south w.
The plateau is a mobile, tectonically active part of the African Plate. The greatest rift system and the greatest heights of the continent are concentrated here. It is composed of Precambrian crystalline rocks, among which granites are widespread. The ancient foundation is covered in places by Paleozoic and Mesozoic, mainly continental sediments.
The plateau remained an elevated area for a long time. In the Cenozoic, enormous tectonic faults and rifts arose. They continue the grabens of the Red Sea and the Ethiopian Highlands and branch south of Lake Rudolf, forming the western, central and eastern fault systems. Rifts are expressed in relief as narrow depressions with steep stepped slopes; along their edges rise tall mountain ranges(Rwenzori massif, volcanoes Kilimanjaro, Kenya, Elgon, etc.). Volcanic activity along the faults has not ended to this day. Areas not affected by faults have the appearance of a typical peneplain with island mountains. The plateau also contains extensive basins (Lake Victoria).
Western fault system runs along the western edge of the plateau and includes deep grabens,
occupied by the Albert Nile River valley, lakes Albert (Mobutu-Sese-Seko), Edward, Kivu, Tanganyika. From Lake Tanganyika it stretches through the depression with the endorheic Lake Rukwa, the tectonic basin of Lake Nyasa, the Shire River valley and the lower reaches of the Zambezi. Fault tectonics is especially evident here. This is one of the most seismic zones of the continent and an arena of modern volcanism.
The grabens of Lakes Albert and Lake Edward are separated by the Rwenzori horst massif, the highest peak in Africa (5119 m) after Kilimanjaro (5895 m) and Kenya (5199 m). The massif is composed of gneisses, crystalline schists and intrusions of basic rocks, has glacial forms of Quaternary and modern glaciation (kars, cirques, trough valleys, terminal moraines), giving an alpine character to the relief of its peaks.
Located between the grabens of lakes Eduard and Kivu Virunga volcanic region(seven volcanoes). Here besides active volcanoes New volcanic cones are also formed. Ancient lavas cover the tectonic trough between the depressions of lakes Kivu and Tanganyika.
Underwater volcanic eruptions occur at the bottom of lakes Kivu and Nyasa
Adjacent to the northern segment of the western fault system from the east is Lake Plateau(Uganda plateau), located between lakes Edward, Albert, Victoria and the White Nile basin. The plateau has an undulating surface, is composed mainly of crystalline rocks and reaches a height of 1000 to 1500 m. The central part of the plateau is swampy
186 Africa. Regional overview
plain with Lake Kyoga. The plateau ends with stepped slopes towards the East Sudanese Basin, and in the east it joins the volcanic plateau of Kenya.
Central fault system serves as a continuation of the Ethiopian graben, running in a meridional direction from Lake Rudolf in the north to Lake Nyasa in the south, where it meets the western fault system.
In the northern part of the central faults, within the volcanic plateau of Kenya, the volcanic relief is especially pronounced. The extinct volcanoes Kilimanjaro, Kenya, Elgon and a group of giant craters rise along tectonic cracks, the edges of which are covered with basalts and tuffs. Among the group of giant craters stands out the Ngorongoro volcano with a huge caldera.
Between the western and central fault systems, on the one hand, and lakes Victoria and Nyasa, on the other, there is Unyamwezi plateau. It is composed of granites and is very swampy. To the east are the Nyasa and Masai plateaus. These are peneplains on a granite base, broken by faults and crowned with rounded crystalline outlier peaks.
Eastern fault system is represented predominantly by one-sided faults. They limit with ledges from the west a narrow coastal lowland, composed mainly of permeable Tertiary sandstones and limestones.
The climate of the East African Plateau is subequatorial, hot, variable-humid, with a clearly defined climatic zone on high mountain ranges. Only in the vicinity of Lake Victoria, on the Lake Plateau, does it approach the equatorial
rial both in terms of the amount and regime of precipitation, and in the even course of temperatures, which, however, due to the high altitude of the area, are 3-5 ° C lower than the average monthly temperatures of the equatorial strip in the Congo Basin.
Within the plateau, trade winds and equatorial monsoons dominate. During the winter months of the Northern Hemisphere, the northeast trade wind, without changing its direction, is drawn into a pressure depression over the Kalahari. Passing over the ocean from Southeast Asia to Africa, it is moistened and produces a small amount of precipitation, mainly orographic. In the summer of the Northern Hemisphere, the south trade wind (southeast wind) intensifies; crossing the equator, it takes on the character of a southwest monsoon. The main wet period is also associated with them; most precipitation falls on the windward slopes of the mountains.
High temperatures are observed only at low altitudes, especially along the Indian Ocean coast. In Dar es Salaam, for example, average temperature the warmest month (January) is +28 °C, the coldest month (August) is +23 °C. It becomes cooler with height, although the annual cycle remains uniform. In the mountains at an altitude of more than 2000 m, the temperature is below 0 ° C, snow falls above 3500 m, and on the highest massifs - Rwenzori, Kilimanjaro and Kenya - there are small glaciers.
The moisture content of different parts of the East African Plateau varies. Largest quantity High mountain ranges receive precipitation (up to 2000-3000 mm or more). From 1000 mm to 1500 mm of precipitation falls in the north-west and south-west of the country, as well as on the Indian coast
East African plateau 187
ocean south of 4° S. sh., where the mountainous meridional coast delays moist winds from the Indian Ocean. In the rest of the plateau, 750-1000 mm of precipitation falls per year, decreasing in the extreme northeast and in closed depressions to 500 mm or less. Kenya is the driest region of the plateau, with a long rainless period of 7 to 9 months.
For territories located between 5° N. w. and 5° S. sh., is characterized by an equatorial precipitation regime, with two rainy seasons (March-May and November-December), separated by two periods of relative decrease. To the south they merge into one rainy season (from October-November to March-April), followed by a dry period.
The East African Plateau occupies a watershed - a position between the basins of the Atlantic, Indian and Mediterranean Sea. In the north-west of the region, the Nile originates, the system of which includes lakes Victoria, Kyoga, Albert and Edward. Lakes Tanganyika and Kivu belong to the Congo river system; Lake Nyasa drains into the Zambezi. In the central part of the plateau are located closed lakes(Rudolph, Ruk-va, Baringo, etc.). In terms of size, depth, influence on flow and climate, the lakes of the plateau are comparable to the Great Lakes of North America.
Tectonic fragmentation of the plateau, diversity of relief and climatic conditions determine the diversity and variety of landscapes. Inland areas are dominated by typical savannas with fairly large tracts of open forests and shrubs that shed their leaves during the dry season. The vegetation consists of cereals, acacias, mimosas, baobabs, tama-
risks, milkweed, etc. Red-brown soils are developed under typical savannas and open forests on the plains, black tropical soils are developed in poorly drained relief depressions, and young brown tropical soils are found on basic volcanic rocks.
In the arid northeastern regions (Kenya plateau, north of 2°-3° N latitude), desert savannas and thickets of thorny shrubs of xerophytic acacias, leafless for most of the year, are developed on red-brown soils, sometimes turning into semi-desert. Similar and drier landscapes characterize deep depressions central system faults, where drainless lakes are half-filled with sand, covered with a crust of salts, and surrounded by salt marshes with halophytic vegetation.
The northern part of the coastal lowland off the coast of the Indian Ocean also has sparse, semi-desert vegetation. In the southern part of the lowlands, semi-deserts give way to savannas, red-brown soils give way to red ones; Mixed deciduous-evergreen forests appear along rivers and on the windward slopes of mountains. There are mangroves along the coast.
In heavily moist areas
widespread humid equatorial
forests on red-yellow soils and
mixed deciduous-evergreen-
new ones - on red soils. They are mostly cut down and replaced by secondary formations - wet tall grass savannas. Evergreen and mixed forests are found mainly in the west (Lacustrine Plateau), where they meet the hylaea of the Congo Basin, as well as on the windward moist slopes of the high mountain ranges.
188 Africa. Regional overview
Africa is the second largest continent after Eurasia. Area 29.2 million km2 (with islands 30.3 million km2, about 1/5 of the land area of the globe). Population 328 million people. (1967).
Main features of orography
The relief of A. is dominated by plains, plateaus and plateaus, lying at an altitude of 200-500 m above sea level (39% of the area) and 500-1000 m above sea level (28.1% of the area). Lowlands occupy only 9.8% of the area, mainly along the coastal margins. In terms of average altitude above sea level (750 m), Africa is second only to Antarctica and Eurasia.
Almost the entire A. to the north of the equator is occupied by the plains and plateaus of the Sahara and Sudan, among which in the center of the Sahara rise the Ahaggar and Tibesti highlands (Emi-Kusi, height 3415 m), in Sudan - the Darfur plateau (Marra, 3088 m). To the north-west The Atlas Mountains rise above the Saharan plains (the city of Toubkal, 4165 m), and the Etbay ridge stretches to the east along the Red Sea (the city of Oda, 2259 m). The plains of Sudan from the south are framed by the North Guinea Upland (Bintimani, 1948 m) and the Azande plateau; from the east, the Ethiopian Highlands rise above them (Ras Dashan, 4620 m). It drops steeply to the Afar depression, where the deepest depression of Afar is located (Lake Assal, 150 m). Behind the Azande plateau lies the Congo depression, bounded on the west by the South Guinea Upland, on the south by the Lunda-Katanga plateau, and on the east by the East African plateau, on which the most high peaks A. - Mount Kilimanjaro (5895 m), Mount Rwenzori (5109 m).
Southern Africa is occupied by the high Kalahari plains, framed from the west by the plateaus of Namaqualand, Damaraland, Kaoko, and from the east by the Drakensberg Mountains (Thabana-Ntlenyana, 3482 m). The mid-altitude Cape Mountains stretch along the southern edge of the mainland.
The predominance of leveled relief on the mainland is due to its platform structure. In the northwestern part of Africa, with a deep foundation and widespread development of the sedimentary cover, heights of less than 1000 m predominate (Low Africa); in the southwest of Africa, where the ancient foundation is raised and exposed in many places, the heights of St. 1000 m (High A.). The troughs and protrusions of the African Platform correspond to large depressions (Kalahari, Congo, Chad, etc.) and the uplifts separating and bordering them. The most elevated and fragmented eastern margin of Africa is within the activated section of the platform (Ethiopian Highlands, East African Plateau), where a complex system of East African faults extends.
In the elevated areas of Vysokaya A., the largest area is occupied by basement plains and basement block mountains, framing the depressions of the Vostochny grabens. A. (including Rwenzori) and Katanga. In Low Africa, basement ridges and massifs extend along the coast of the Gulf of Guinea and protrude into the Sahara (in the Lhaggar and Tibesti highlands, and the Etbai ridge). Lava plateaus and cones are widespread in the Ethiopian Highlands and East. A. (Kilimanjaro, Kenya, etc.), crown the peaks of Ahaggar and Tibesti, are found in Sudan (Marra), Cameroon (Cameroon Volcano, Adamawa Mountains), overlap the Drakensberg Mountains in Lesotho. Stratified denudation plains and plateaus occupy most of the area in Low Africa (Sahara, Sudan); in High A. they are confined to the sediments of the Karoo syneclise and make up the Drakensberg Mountains, the Veld plateau adjacent to them from the west and lying to the south of the river. Orange Top. Karoo. Accumulative plains are found mainly in Low Africa: in the middle reaches of the Niger, in the Chad and White Nile basins, and in the Congo basin; in High Africa they occupy the Kalahari depression. The folded block mountains include the Cape Mountains and the interior regions of the Atlas. The northern ridges of the Atlas are the only young folded mountains in Africa of Neogene-Paleogene age.
The relief of Africa is dominated by surfaces of the Neogene cycle of denudation and accumulation, dissected by the modern Congo cycle. Above them rise the remains of the predominant surfaces, worked out by more ancient cycles (up to the Gondwanan cycle).
Geological map
Geological structure and minerals.
Almost all of Africa, except for the Atlas Mountains in the north-west. and the Cape Mountains in the extreme south, is an ancient platform that also includes the Arabian Peninsula and about. Madagascar with Seychelles. The foundation of this African-Arabian platform, composed of Precambrian rocks, mostly folded and metamorphosed, appears in many regions of Africa - from the Anti-Atlas to the north-west. and Zap. Arabia in the north-east to the Transvaal in the south. The basement contains rocks of all age divisions of the Precambrian - from the Lower Archean (more than 3 billion years old) to the upper Proterozoic. The consolidation of most of Africa was completed by the middle of the Proterozoic (1.9-1.7 billion years ago); in the late Proterozoic, only peripheral (Mauritian-Senegalese, Arabian) and some internal (Ugarta-Atakor, Western Congo, Namaqualand-Kibar) geosynclinal systems developed, and by the beginning of the Paleozoic the entire area of the modern platform was already stabilized (according to the latest data, sediments shown on the geological map south of the Sahara as Cambrian, turned out to be Upper Proterozoic). In areas of early consolidation, deposits of the late, and in some places even early or middle Proterozoic (Transvaal, Zimbabwe and some others massifs) already belong to the platform cover. The rocks of the Early Precambrian basement are represented by various crystalline schists, gneisses, metamorphosed volcanic formations, over large areas replaced by granites. They are subject to deposits of iron ores of sedimentary-metamorphic origin, gold (in connection with granites), and chromites (in ultrabasic rocks). Large accumulations of gold and uranium ores are known in the coarse rocks of the base of the sedimentary cover in the south of Africa. Younger, weakly metamorphosed rocks of the Upper Proterozoic of intraplatform folded zones (Katanga, Zambia, Southwestern Africa, etc.) contain deposits of tin, tungsten (in granites or near them), copper, lead, zinc and uranium ores.
The Phanerozoic sedimentary cover is developed on top of the Precambrian basement mainly in the western and central parts of North Africa (Saharan plate), in large depressions of Equatorial and South Africa (Congo, Okavango, Kalahari, Karoo), in the Mozambique trough east coast and between the mainland and the island. Madagascar, as well as along the Atlantic coast from Mauritania to Angola. Marine Early and Middle Paleozoic folded sediments are distributed mainly in the region of the Sahara Plate, where they host large deposits of oil and gas (Algeria, Libya), as well as in the Atlas and Cape geosynclines. The formations of the Upper Paleozoic and Triassic are almost everywhere continental; in Equatorial and Southern Africa they begin with glacial deposits (upper Carboniferous - lower Permian) - witnesses of the cover glaciation of a significant part of the continent - and continue with Lower Permian coal-bearing deposits, with which the main coal resources of Africa are associated (South Africa, Southern Rhodesia, etc.). In Northern Africa, the Middle Carboniferous is carboniferous, above which red-colored continents and lagoonal sediments (in the Triassic with large strata of salts and gypsum) are common.
The beginning of the Jurassic included powerful volcanic eruptions and intrusions of basic (basaltic) magma, most common in Southern Africa, but also found in Western Northern Africa. During the Jurassic and Early Cretaceous, most of Africa experienced uplift; continental sediments accumulated in the internal depressions; At the end of the Jurassic - the beginning of the Cretaceous, the intrusion of alkaline granites and carbonatites with deposits of rare elements (niobium, tantalum, etc.) took place, as well as the formation of kimberlite pipes, which are associated with diamond deposits - primary and redeposited in younger sediments and placers (South Africa, Angola , Democratic Republic of the Congo, countries north coast Gulf of Guinea). The formation of the modern contours of the continent dates back to the same time (end of the Jurassic - beginning of the Cretaceous), associated with the subsidence of the bottom of the Indian and Atlantic Oceans and the formation of a system of perioceanic troughs containing significant deposits of oil and gas (Nigeria, Gabon, Angola, etc.). Madagascar separated from the continent at the end of the Paleozoic. At the same time, intensive subsidence of the modern coast of Tunisia and Libya occurred with the formation of oil deposits in Cretaceous and Eocene deposits. In the middle and end of the Cretaceous, a significant transgression engulfed the Sahara Plate: sea straits arose that connected the Mediterranean Sea with the Gulf of Guinea and existed until the middle of the Eocene.
From the end of the Eocene to the beginning of the Oligocene, Africa (mainly the eastern and southern regions) experienced intense uplift, accompanied by the formation of mountainous terrain, the emergence of the East African fault zone and graben-rifts of the Red Sea, Gulf of Aden, Ethiopia, lakes Rudolph, Albert, Rukwa, Tanganyika, Nyasa, etc. An outbreak of volcanic activity dates back to the same time, continuing in certain areas in the modern era (Kenya, Kilimanjaro, volcanoes of the Virungi region). Uplifts and volcanic activity also appeared in the Ahaggar and Tibesti highlands in the Sahara, Cameroon (Cameroon volcano) and in some areas of the Atlantic coast (Cape Verde).
At the end of the Miocene, the folded structure of the Atlas Mountains arose; in the Pliocene it central part fell along faults into the Alboran depression of the Mediterranean Sea.
A. has large reserves of iron ores (total reserves are estimated at approximately 16-23 billion tons), manganese ores (about 400 million tons), chromites (500-700 million tons), bauxites (3.3 billion tons), copper (reliable and probable reserves of about 48 million tons), cobalt (0.5 million tons), phosphorites (26 billion tons), tin, antimony, lithium, uranium, asbestos, gold (A. provides about 80% of the total production of capitalist and developing countries), platinum and platinum group metals (about 60% of production), diamonds (98% of production). After World War II, large reserves of oil (total reserves are estimated at 5.6 billion tons) and natural gas were discovered in Algeria (mainly in Algeria, Libya, and Nigeria).
Tectonic map
