Africa
From Encyclopædia
Africa is the second-largest continent after
Asia. It is separated from
Asia by the
Suez Canal, the Gulf of
Suez, and the Red Sea, and from
Europe by the Straits of
Gibraltar and Mediterranean Sea. It is bounded by the
Atlantic Ocean on the west and the Indian Ocean on the east. Offshore islands considered part of Africa include, in the Indian Ocean, MADAGASCAR,
Mauritius, REUNION, ZANZIBAR,
Pemba, the
Seychelles and the COMOROS. In the North
Atlantic Ocean are the CANARY ISLANDS, CAPE VERDE ISLANDS, and MADEIRA ISLANDS; in the South Atlantic are
Ascension Island and
saint HELENA; and in the Gulf of Guinea (See
Gulf of Guinea) are Annobon, BIOKO, and SAO TOME and PRINCIPE.The earliest known protohuman fossils have been found in Africa, primarily in Kenya and Tanzania. The continent was also the home of one of the
world's oldest
civilizations, that of ancient
Egypt. Egyptian influence spread south up the Nile into present
Sudan by the 1st millennium BC, at the same time as the Phoenicians were founding Carthage and other
city states along the Mediterranean coast north of the
Atlas Mountains.
North Africa came under European influence during the period of Roman rule (1st century BC-7th century AD). Beginning in the 7th century, Arab culture and the Muslim faith spread across the
Sahara following trade routes between the north coast and towns along the
Sahara's southern border region. There a
number of powerful African kingdoms, including Ghana, Mali,
Kanem-Bornu, and SONGHAI, flourished during the
middle ages. Further south in the rainforests the kingdoms of ASHANTI,
Benin, KONGO, Oyo, and Dahomey emerged after the 14th century and lasted until the colonial partition of Africa. East
Central Africa was occupied by the kingdoms of Ankole, Buganda, Bunyoro, Luba, and
Lunda.The modern European colonization of Africa was begun by the Portuguese, who established trading stations on the coasts in the 15th and 16th centuries, but the interior of what Europeans called "the Dark Continent" was not explored or colonized until the 19th century. By the early 20th century nearly all of Africa had been subjected to European rule. Since
world War II, 48
nations have gained their
Independence, but the colonial experience left Africa with arbitrarily defined boundaries, a diversity of political systems and problems, and economies dependent upon the industrial
world. (The Republic of South Africa, though independent, is controlled by descendants of European settlers; its black African majority is not represented in the government.) Africa's peoples remain divided by
race,
language, religion, and politics in a complex cultural
mosaic. In 1990, Africa contained about 12% of the
world's population and was the second most populous continent after
Asia.LAND AND RESOURCESAfrica has a
number of outstanding natural features that have influenced its history and development. The northern coastal area is separated from the rest of the continent by the
Sahara, the largest
desert in the
world. The coastlines are remarkably straight with a few large bays, estuaries, and protected indentations that can serve as harbors. Most major rivers have waterfalls and rapids close to the coast, which hindered colonial penetration and still limit
navigation. In Subsaharan Africa a narrow coastal plain, often swampy along the Gulf of Guinea, arid from Angola south to
Cape Town, and swampy, forested, or arid northward along the east coast to the Red Sea, is backed by steep
escarpments and mountain ranges that form the edge of the African high
plateau.Africa lacks a major mountain system like the Andes of South
America or the Himalayas of
Asia. Several small ranges, however, break the monotony of the flat to gently rolling
plateaus that constitute the bulk of Africa. The
Atlas Mountains of northwest Africa extend from east to west across Tunisia, Algeria, and Morocco, reaching their highest elevation, 4,166 m (13,668 ft), at Mount Toubkal, Morocco. The DRAKENSBERG, rising above 3,000 m (10,000 ft), extends through eastern South Africa and Lesotho. The high
plateau of Africa stretches from
Ethiopia southwest to Angola and
Namibia and includes the Ethiopian Massif, the East African
plateau, the RUWENZORI (Mountains of the
Moon), the Munchinga Mountains of Zambia, and the Bihe of Angola. Rising above this
plateau are Mount
Kilimanjaro (5,895 m/19,340 ft), a semiactive volcano and Africa's highest peak, Mount Kenya (5,199 m/17,058 ft), and Mount Elgon (4,321 m/14,178 ft), also of volcanic origin. The
Sahara is interrupted by the
Tibesti Massif and Ahaggar and Air mountains. The
Cameroon Mountains, a volcanic chain extending northeast through
Cameroon, are the highest mountains in western Africa. The Futa Jallon of Guinea and Liberia contains the headwaters of the NIGER (Djouf) RIVER and the
Senegal River,
West Africa's largest. Between these
Highland zones are a series of shallow sedimentary basins usually associated with rivers. They include the basins of the Niger,
Chad, and Sudd rivers on the southern margins of the
Sahara, the CONGO (
Zaire) RIVER of
Central equatorial Africa, and the KALAHARI
desert in southern Africa.One of Africa's most distinct topographical features is the GREAT RIFT VALLEY. This is a giant trough that cuts into the high
plateaus and extends from the Dead Sea in the Middle East southward to Mozambique and Swaziland, a distance of almost 8,000 km (5,500 mi). The northern section is filled b? the Red Sea between Africa and Arabia. The
Central section cuts through
Ethiopia and divides near Lake Rudolf, or Turkana (see RUDOLF, LAKE), into two branches: the western rift arcs through
Uganda to Lake NYASA (Lake Malawi), and is occupied by Lakes Albert, Edward, Kivu, and Tanganyika (see
ALBERT, LAKE;
EDWARD, LAKE;
KIVU, LAKE;
TANGANYIKA, LAKE); the eastern rift cuts through Kenya and Tanzania and joins the western rift near Lake Nyasa. In places the rift-valley walls rise more than 3,200 m (10,500 ft) above the flat and sometimes drowned valley floor. (See also EAST AFRICAN RIFT SYSTEM.)GeologyAfrica is a massive crystalline platform of ancient granites, schists, and gneisses, the oldest of which are more than 3.2 billion years old. They contain rich and varied minerals including
Copper,
zinc,
lead, gold,
uranium, diamonds, and many rare
metals. Present-day Africa was once part of the supercontinent known as GONDWANALAND, which also included
Australia, Antarctica, South
America, Madagascar, and the Indian subcontinent. During the Late Jurassic and Early
Cretaceous Periods these land masses drifted apart, but compared with the other continents, Africa remained relatively stable. South
America was separated from Africa about 80 million years ago when the floor of the
Atlantic Ocean was opened up by seafloor spreading. Arabia
Split off approximately 20 million years ago.As Gondwanaland fractured and drifted, Africa acquired its scarp-dominated coastline, interior seas that occupied shallow depressions emptied, and rivers carved steep gorges and formed new courses. Volcanic outpourings covered vast areas of east and southern Africa. As the
Cretaceous Period came to an end, the
sedimentary rocks of northwestern Africa were severely folded and uplifted in a series of orogenic phases to form the
Atlas Mountains, which geologically are part of
Europe's alpine system. Epicontinental seas extended across
North Africa linking the present Mediterranean with the Gulf of Guinea, which in their wake left extensive deposits of
limestone and sandstone. Gigantic meridian
fractures occurred in the African shield producing the Great Rift Valley. As tensional forces wrenched the land apart, some land blocks sank while others rose and tilted, allowing volcanic materials to break the surface. Mount
Kilimanjaro and Mount
Cameroon were formed this way.During Gondwana's last 100 million years of existence, southern Africa was covered by the Dwyka ice field, which scoured the crystalline surface and deposited tillites hundreds of meters thick. Following the glacial age, southern Africa became progressively drier, and a lengthy period of sedimentary accumulation began in the Kalahari and Karroo basins. These sediments in turn were covered by outpourings of basalt as much as 7,600 m (25,000 ft) thick.ClimateThe climates of Africa are predominantly tropical. Limited areas of subtropical and temperate climates are found only at the northern and southern extremities and in the high altitudes of
Ethiopia and East Africa. The cold
ocean currents that parallel the western
Sahara (Canaries Current) and
Namibia (
Benguela Current) modify the temperatures of the adjoining coastal lowlands. The absence of lengthy high mountains and other weather divides permits a free circulation of tropical air over the continent so that changes in climate occur very gradually. Rainfall is heaviest along the coast of the Gulf of Guinea, in the equatorial lowlands facing the Atlantic, in scattered mountain locations, and in eastern Madagascar. There the
average annual rainfall exceeds 2,032 mm (80 in). Africa's wettest place is in western
Cameroon (10,160 mm/400 in). Rainfall decreases polward from the equator to the
Sahara, Kalahari, and NAMIB
deserts, regions that generally receive less than 150 mm (6 in) of rain in the
average year. Rainfall rather than temperature is the most variable element of climate effecting distribution of
soils, vegetation, and populations. There is increasing
evidence that much of Africa is becoming progressively drier.
