TOPOGRAPHY. The typical expression of Afri can topography is that of a plateau that rises here and there by successive terraces to increas ing elevations up to and beyond 4000 feet, which altitude is the general level of the highland re gion that covers a large part of the southern and eastern portion of the continent. The edges of the continental mass are as a rule somewhat more elevated than is the interior, and the pla teau rims approach close to the sea. Only along the eastern part of the Mediterranean shore and along that part of the Atlantic seaboard between Cape Jnby, near the Canaries. and Freetown. can there be said to exist a coastal plain that extends for any considerable distance toward the interior. Swampy districts of limited extent are found along the upper Guinea shore and on the east coast about the mouths of the Zambezi River, and a lowland borders the south side of the Somali Peninsula. The mean elevation of Africa, obtained by a reduction of all irregulari ties of the surface, has been estimated to be about 2101) feet, which is about equal to that of South America and somewhat less than that of North America. while it is greatly exceeded by the mean elevation of the Enrasiati• continent.
The topography of the interior presents over large areas a marked of expression, though different. regions exhibit distinctive fea tures. The general plateau character of the surface is broken in the interior of the continent by four areas of depression which in the south and north are occupied by basins of internal drainage. In the southern highland is the Ka , lahari -NgamiDesert (altitude 2250-3000 feet) : the central plateau falls toward its middle to form the Congo Basin (altitude 600-1600 feet) ; in the central Sudan the Lake Chad (altitude 900 feet) and Bodele (altitude 500 feet) depres sions receive the drainage of a great interior region that has no outlet to the sea: and in the northwestern Sahara several inclosed basins lie at altitudes of from 400 to 600 feet above the ocean.
Africa is divided topographically into the fol lowing regions: (1) the elevated Southeastern Highlands. (2) the Sahara and Sudan plateau of lower level that covers the entire central and most of the northern part of the continent. and (3) the narrow, comparatively small area of the Atlas Mountains on the extreme northwest coast. On the whole, the general slope of the surface is from the southeast to the northwest.
The highest portions of the continent, called the Southeastern Highland-.. lie near the eastern coast and in the lower end of the southern limb. They are limited on the north by an irregular line that may be drawn from Loanda on the west coast, at the mouth of the River Kuanza, east ward to Ankoro on the Tipper Congo. thence northward to Darmna, and through Lado and Kassala to Suakin on the Red Sea. Northward
from Suakin the eastern highland is continued as a narrow ridge of lower elevation along the western shore of the Tied Sea almost to Cairo. This great highland region may be topographical ly considered to form the backbone of the conti nent, though it. is scarcely that in a sense, for the rocks of which it is composed lie generally horizontal, and the differences of topog raphy are the result of long continued erosion and denudation rather than of mountain-making forces. This highland has an elevation of over 4000 feet, and above this height rise numerous isolated and grouped peaks to altitudes of 10,000 feet and over. The majority of these high peaks are remnants of a dissected plateau of still high er level, while others are volcanic mountains that rest upon the tableland and rise above it to still greater heights of from 12,000 to 20,000 feet. The central depression of the Kalahari Desert and Ngami Basin in the southern part of the highland. and the deep valleys cut by the rivers that drain this interior basin, serve to divide this southern region into four well-marked isolated plateaus. The most southerly plateau occupies the Cape, Natal. Orange River, and Transvaal colonies, and their seaward edges, known as the Roggeveld, Schnee. Zwarte, and Drakenberg mountains. rise in single peaks of 9000 to 11.000 feet. North of the Transvaal. between the Limpopo and the Zambezi valleys, is the less extensive plateau of _Matabeleland. with an average level of -1500 feet and a single peak (Ma.shona Mountain. 7300 feet). near its eastern edge. On the western side of the conti nent, between the Kalahari-Ng,aini Basin and the Atlantic coast is the plateau of German West Africa. covering Damara and Great Namaqua land. This plateau rises to somewhat lesser sin gle heights than does the plateau of British South Africa: Kara (6500 feet), Awas (6530 feet) , and Omatoka (8700 feet). Northward of all these. and extending from west to east through Angola and British Central Africa to the vicinity of lakes Nyassa and Tanganyika, where it joins the great eastern hig,hland, is a broad plateau 750 miles wide from north to south and 1500 mile, from west to east, with a general elevation of 3000 to 0000 feet. This forms the divide between the Ngami and Zambezi basins on the south and the Congo waters on the north, and has its highest points on the west end in the plateau of Bihe (Lovili Mountains, 7800 feet), and at the eastern end in the plateau mountain of Chitane (050(1 feet) near Nyassa Lake. Toward the south it slopes gradually to the Ngand anal Zambezi basins, and toward the north it falls more abruptly to the Congo region. Neat' time eastern end are two lakes, .Mocro or 0000 feet 1. and Bangweolo (3700 feet), that drain into the Upper Comm Liver.