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The African continent covers an area of 12 million square miles, about one-fifth of the total land surface of the earth. It is three times the size of Europe and half as large again as North America but being naturally very compact, it has a much shorter coastline. Together with Asia and Europe, Africa makes up the great landmass known as The Old World.
However, it differs fundamentally in many respects from its neighbors and is often classed with South America and Australasia as one of the three southern continents. Certainly it resembles them in the relative tardiness of its economic development, and is similar in build, consisting mainly of a huge plateau which rises quite sharply from narrow coastlands. Africa, however, lacks the great mountain barriers that are responsible for the sudden and marked climatic and vegetable contrasts in both South America and Australasia.
The immensity of Africa is shown by its north-south and west-east extents. It stretches about 5,000 miles from Cap Blanc in Tunisia to Cape Agulhas in South Africa and 4,600 miles from Cape Verde in western Africa to Ras Hafun in Somalia. It is the only continent to be crossed by the equator and both the Tropics of Cancer and Capricorn. More than three-fourths of its area lies within the tropics, although, because of its shape, two-thirds of the continent lies north of the equator.
Bordered by the Atlantic and Indian Oceans and by the Mediterranean and Red Seas, the continent has few large gulfs and inlets apart from the Gulf of Guinea in the west, the Gulf of Aden in the east and the Gulf of Tripoli in the north. It has comparatively few islands, but Madagascar, separated from the mainland by the Mozambique Channel, is the fifth largest island in the world.
The African Plateau
The African Plateau in which some very ancient and hard crystalline rocks are exposed, is dominated by granites and highly metamorphosed schists and gneisses. These rocks have withstood erosion for millions of years and are responsible for the generally regular and uniform surface features over extensive areas.
Nearly everywhere the plateaus rise sharply from the usually narrow and sometimes almost absent coastal plains. In general the plateaus of southern Africa, sometimes called High Africa, are considerably higher and more continuous than those in Low Africa in the north and west. In the south there is a particularly steep edge to the plateau in the Drakensberg of South Africa which overlooks the narrow coastal plain along the Indian Ocean. North of the Congo Basin the plateau is lower and much more broken up. In West Africa the higher parts are widely separated from one another with the Fouta Djallon on Plateau in the westernmost part, the Jos Plateau in central Nigeria and the Adamawa and the Cameroon Mountains in the east. In the Sahara the highest parts are the Air Plateau and the mountains of Hoggar and Tibesti.
There are, however, important exceptions to the general uniformity of the physical features. At the extreme northern and southern ends of the continent are high folded mountain ranges. In the north the Atlas Mountains, rising in places to 13,000 feet are associated with the great mountain system of Eurasia that includes the Alps, Pyrenees, Caucasus and Himalayas. In the south there are the lower yet very prominent Cape Ranges (over 5,000 feet) to the east of Cape Town.
The Rift Valley
The Rift Valley of East Africa is the continent's grandest and most spectacular physical feature. It lies between parallel faults along a line of crustal weakness, and leaves a tremendous gash of relatively low land running from Syria and the Jordan valley in the Middle East, through the Red Sea, to the Shire river, a tributary of the Zambezi, in southern Africa. A series of mostly extinct volcanoes are found along the edges of the valley and many lakes have formed in the lower parts of the depression. They are generally steep-sided and deep. Lake Tanganyika, 4,700 feet deep, is the second deepest lake in the world.
The Rift Valley and its branches can be traced out by its lakes. Lake Abaya in Ethiopia is succeeded southward in Kenya by Turkana and Naivasha and in Tanzania by Natron and Manyara with Eyasi in a branch rift. Across central Tanzania the rift is a less conspicuous feature until the shores of Lake Malawi, formerly Nyasa, are reached. Beyond the lake it continues down the Shire valley almost to Beira on the coast of the Indian Ocean. From the northern end of Lake Malawi a great arm extends northwestward and west, marked by a succession of lakes.
Lake Victoria, the greatest of Africa's lakes, covers an area as large as Scotland, having a coastline of 4,000 miles. It is quite different from other rift valley lakes. It has formed in a depression on the surface of the plateau and is fairly shallow, with a maximum depth of (270 feet) .
The volcanic peaks near the East African Rift Valley are among the continent's highest mountains. They include the most famous of all, Kilimanjaro (19,340 feet).
In the Virunga, or Mfumbiro, Mountains on the Uganda-Zaire border there is still occasional volcanic activity. By contrast the mountains of the great Ruwenzori range, also between Uganda and the Congo Basin, extending from Lake Edward to Lake Albert, owe their height to the hardness of their constituent rocks.
Coastal Lowlands, areas less than 1,000 feet above sea level, are uncommon in Africa. Most are associated with the lower sections of river basins and, particularly within the tropics, have caused many problems of settlement and development through poor drainage, the hot and humid climate, the impenetrable nature of the vegetation and the generally unhealthy conditions.
Rivers are numerous and are often very long with extensive basins. Many of the largest enter the sea through deltas. The tracing of their courses and the discovery of their sources lured many 18th- and 19th century European explorers.
The longest river, the Nile, which flows for more than 4,000 miles, kept the secret of its headwaters in East Africa for many centuries. It rises in areas with equatorial rainfall and has important tributaries like the Blue Nile and the Atbarah which originate in the highlands of Ethiopia. There are large seasonal fluctuations, but the flow of the river continues throughout the year, even though it receives no tributary in its long passage across the desert and loses much water through intense evaporation.
The Congo, or Zaire, though shorter than the Nile (2,900 miles) drains a much larger area. Its basin is the largest in the world apart from that of the Amazon in South America. In contrast to the Nile, its flow varies relatively little with the seasons, since it has tributaries from both north and south of the equator and receives considerable rainfall in every month of the year in some part of its basin.
The Congo is unique among the large African rivers in reaching the Atlantic Ocean through an estuary, but navigation upstream is prevented by the falls and rapids of the Crystal Mountains above Matadi.
The River Niger in West Africa, 2,600 miles long, rises on the Sierra Leone-Guinea border and flows in an enormous arc in an easterly and then southerly direction before reaching the Gulf of Guinea through a vast delta in southern Nigeria. Its flow varies considerably with the seasons. Upstream it is navigable as far as Jebba, some 400 miles, and its left bank tributary, the Benue, is used by shipping for another 600 miles during the rainy season.
Rapids and falls impede navigation up many African rivers. The most magnificent and famous, the Victoria Falls, restricting movement up the Zambezi river, are widely regarded as one of the seven wonders of the world. They were first seen by the missionary-explorer David Livingstone in 1885. With a height of 354 feet, they are more than twice as tall as North America's Niagara Falls, and in recent years have become an important tourist attraction.
The Orange River, the longest river in South Africa (1,300 miles), resembles the Nile in flowing through desert and semi-desert regions in its middle and lower courses. Thus, although its major tributary, the Vaal, rises in the well-watered areas of the Drakensberg, so much water is taken off for irrigation and lost through evaporation that at times there is almost no flow in its lower reaches.
Climatic conditions are dominated by the sun's movements. It is overhead at the equator in March and September, at the Tropic of Cancer in June, and at the Tropic of Capricorn in December. In June nearly the whole of northern Africa experiences temperatures that may average 80°F with an average maximum as high as 100°F in parts of the Sahara.
Night temperatures here are much lower because the desert rapidly loses heat by radiation as a result of the almost cloudless skies.
The temperature in areas on either side of the equator is never exceptionally high, even when the sun is overhead, because rain falls in nearly every month and there is considerable cloud cover.