Africa is an enormous landmass that connects with Asia at the Isthmus of Suez and almost joins Europe at Gibraltar. Major bodies of water that border the continent are the Mediterranean Sea on the north, the Red Sea on the northeast, the Indian Ocean on the southeast, and the Atlantic Ocean on the west. Arms of the oceans include the Gulf of Aden, the Mozambique Channel, and the Gulf of Guinea.
Lying on the Equator (0° latitude) and the Prime Meridian (0° longitude), Africa is the only continent occupying part of all four hemispheres. It is also unique in that there are no deep indentations and few well-defined peninsulas. The coastline, which measures some 18,900 miles (30,400 km), is nearly everywhere regular. There are few islands. Madagascar is by far the largest island; the Canaries, consisting of 13 islands, are the largest group.Africa is the second largest continent. Only the continent of Asia is larger
Despite its great size, Africa does not have a great variety of physical features. Nearly the entire continent consists of vast plateaus the surfaces of which lie at varying elevations and are generally rolling to flat. Rarely are the plateau surfaces rough. The plateaus' edges, however, especially the eastern and the southern ones, are marked by sharp escarpments (mountainous walls) that descend to narrow plains along the coast. There are few broad coastal plains comparable to those of most other continents. Underlying the continent, and in many areas exposed, is an ancient block of stable crystalline rock.
Most of the wide northern part of Africa is covered by the vast stretches of gravel, rock, shifting sand, and dunes of the Sahara—the largest arid region on earth. Included in the Sahara are such smaller deserts as the Libyan and Nubian deserts in the east and the Great Eastern Erg, Great Western Erg, and Erg Iguidi in the west. Wind-scoured highlands jut above the surrounding surface in several areas. The most prominent are Tibesti and Ahaggar, in the central part of the Sahara. The land is also marked by widely separated depressions, deepest of which is Lake Assal's basin—512 feet (156 m) below sea level.
Along the southern margin of the Sahara are three immense basins: Djouf, through which runs the Niger River; Chad, containing Lake Chad; and Sudan, centered on the junction of the Blue and the White Nile rivers. Flanking all three basins are tablelands. Those inland from the Gulf of Guinea coast, such as the Fouta Djallon in Guinea and the Jos Plateau in Nigeria, have deeply eroded seaward slopes.
The Congo Basin, in central Africa, is almost surrounded by plateaus, the highest being the East African Plateau. The basin contains most of the broad Congo River valley, which narrows abruptly in the Crystal Mountains near the Atlantic coast.
East and south of the Sudan and the Congo basins are the highest plateaus on the continent. There are considerable expanses of almost level tableland in the interior, especially in Tanzania, Zambia, and South Africa. The interior's only large basin, the Kalahari, is in the southwest. Through the eastern part of the plateau region, from northern Ethiopia into Mozambique, runs the Great Rift Valley, a series of deep trenches caused by faulting, or fracturing, of the earth's surface. In several areas, steep sides of the valley appear as mountains, among which are the Ruwenzori Mountains in central Africa. Associated with the faulted valleys are numerous volcanoes, including Africa's two highest peaks—19,340-foot (5,895-m) Kilimanjaro in Tanzania and 17,058-foot (5,199-m) Mount Kenya in Kenya.
Along the east and southeast coast, high plateau edges form a series of escarpments. The loftiest of these, reaching 11,000 feet (3,350 m), is South Africa's Drakensberg. In the southwest, along part of the coast, lies the Namib Desert.
Rivers cut through all parts of the continent except the Sahara, where rains are extremely infrequent. Only the Nile—longest river in the world—survives the desert path to the sea. The well-watered equatorial regions are drained mainly by the Congo River, which carries more water than any river but the Amazon of South America. The chief river of western Africa is the Niger; the Orange, Zambezi, and Limpopo systems drain most of the south.
Many of the rivers have falls and cascades that limit navigation but provide great hydroelectric potential. Most important are Victoria Falls, on the Zambezi River, and Boyoma (formerly Stanley) Falls, a series of cataracts on the Congo River.
The principal lake region is in the Great Rift Valley, where several large, narrow lakes lie between steep valley walls. These include Lakes Albert, Tanganyika, and Nyasa (or Malawi). Lake Victoria, on the broad plateau between branches of the Great Rift Valley, is Africa's largest lake and the chief source of the White Nile. The only large natural lake outside eastern Africa is Lake Chad, on the southern edge of the Sahara. Its size varies, depending on seasonal rainfall.