1902 Encyclopedia > Africa > The Great African Plateau

Africa
(Part 4)



(B) AFRICA - GEOGRAPHY (cont'd)

(b) The Great African Plateau

To the south and east of the region just described Africa may be considered as one connected mass of elevated land, comprising the most extensive table-lands, as well as high mountain groups and chains.

The Eastern Edge of the Great African Plateau

The great mass of the African plateau land is to southward of the 10th parallel of N. latitude, but it is prolonged on the eastern side almost to the north coast of the continent by the wedge-shaped table-land of Abyssinia, the highest surface in Africa, and by the mountains which extend from it between the lower course of the Nile and the Red Sea. The terminal point of the high land in this direction may be said to be Jebel attaka, which rises immediately west of Suez to a height of 2640 feet. From this point to the southern extremity of the continent the eastern, and generally higher edge, of the great plateau runs in an almost unbroken line. Passing southwards along its margin, the most prominent heights before the table-land of Abyssinia is reached are Mounts Elba, 6900, and Soturba, 6000 feet in elevation, near the middle of the African coast of the red Sea. There may, however, be greater heights in the little known region of Nubia, which lies between these mountains and the Nile.

The eastern slope of the Abyssinian plateau begins immediately south of the port of Massowah, and is a uniform line of steep descent, unbroken by any river, falling abruptly from an average height of 7000 feet to the depressed plain which here skirts the coast of the Red Sea. This edge, which extends southward for at least 800 miles, forms the water-parting of the rivers which have furrowed deeply into the opposite slopes of the plateau, and appears to be higher than the general surface of the country; yet several lofty groups of mountains rising from the level of the high land attain a much greater elevation, and Mount Abba Jared, the highest known point, is estimated at 15,000 feet above the sea. Between the most southern part of Abyssinia which is known and the equator, where the edge of the plateau has again been partly explored, a long space of unknown country intervenes; but there is every reason to believe that the slope is continuous. Mount Kenia, 18,000 feet, and Kilima-njaro, 18715 feet, the highest points in all Africa, mark the eastern edge under the equator; further south on the inland route from Zanzibar to the Tanganyika, the edge is known as the Rubeho Mountains, with a height of 5700 feet at the pass by which they are crossed on the caravan route. Still further, the edge is again known where it forms a rampart, called the Njesa, walling in the Nyassa Lake. From this point Mount Zomba, 7000 feet high, near Lake Shirwa, Mount Milanje, 8000 feet, and Mount Clarendon, 6000 feet, carry it south to where the Zambeze river makes the first break in its uniform line. The narrows and rapids of Lupata, below the town of Tete, mark the point at which the river breaks through the plateau land to the coast slope beneath it. Passing the river, the eastern edge is again followed in the Mashona and matoppo Mountains (7200 feet) of Mosilikatse's kingdom, from which heights the chief tributaries of the Limpopo river flow. At the headwaters of that river the plateau edge forms the Hooge Veldt of the Transvaal Republic which joins with the Kathlamba or Drakenberg. The portion of the edge which bears this name is specially prominent: it runs southward in a huge wall of rocky crags which support the table-land behind for 500 miles, almost parallel with the coast, and at a distance of 150 miles from it, having Zulu Land, Natal, and Caffraria on the slopes of the spurs which it throws down to the coast. In the Transvaal republic, where the Drakenberg joins the Hooge Veldt, the edge attains a height of 8725 feet in the summit named after the explorer Mauch, but it is highest where it forms the interior limit of Natal, and where Cathkin Peak rises to 10,357 feet above the sea.

The Southern Edge of the Great African Plateau

As in Abyssinia, so here, this part of the eastern plateau edge is the great water-parting of the continent, and the streams which form the Orange river flow down its inward slope. There is no break in the continuance of the edge where it passes round from the Drakenberg to form the inmost and highest of the alternate ridges and terraces of the Cape Colony. It is now named in successive parts from east to west the Storm Berge, the Zuur Berg, Schnee Berge, Nieuwe-veld, and Rogge-veld, the last-named portion of the edge turning northward with the bend of the western coast. Its greatest height within the Cape Colony is in compass Berg, the summit of the Schnee Berge, 8500 feet above the sea.

The outer terraces of the Cape Colony, in which two chief ridges may be traced, lie closer together, and much nearer the coast; between these and the inmost or chief edge is the dry elevated region known as the Great Karroo. Their elevation is also very considerable, though they are broken through by lies of drainage sloping from the chief edge; the part of the middle ridge, which is named the Little Zwarte Berge, attains 7628 feet, and several points in both are upwards of 6000 feet above the sea. Table Mountain, a well-known and flat-topped mass of granite overhanging Cape Town, 3550 feet high, is the nucleus of the peninsula which extends south to form the cape of Good Hope, but is altogether separated from the mountain ridges of the colony.





The Western Edge of the Great African Plateau

The western edge of the great African plateau is generally lower than the eastern, since the whole slope of the continent is more or less from the great heights on its eastern side, towards the west, but it is also clearly traceable, and of great height throughout. Rounding the western side of the Cape colony, the three ridges above noticed run together, and decrease somewhat in elevation as the mouth of the Orange river is approached. Their elevation at the point of union in Little Namaqua Land is still very considerable; and here Mount Welcome attains 5130 feet, and Vogelklip, to north of it 4343 feet above the sea, beyond the Orange river in Namaqua and Damara Lands, the western edge continues in one or more terraces parallel to the coast. Mount Omatako, in the latter country, rises to 8800 feet. Northward, through Benguela and Angola, a more broken series of ridges and terraces mark the descent from the interior plateau, and the great Congo river breaks through to the coast-land at the place where it forms the cataracts of the narrow gorge of Yellala. Sierra Complida is the name given by the Portuguese to that part of the western edge which runs between the Congo and the rapids of the lower Ogowai river on the equator. On the plateau edge at the southern side of this river, Du Chaillu has made known a mountain of 12,000 feet in elevation; and the furthest point which has been reached on the Ogowai was in the vicinity of high mountains. Passing the Oggowai, and following the coast of the Bight of Biafra, the edge is now known as the Sierra do Crystal. The Camaroon mountains, at the head of the gulf, form a high peninsula of volcanic mountains, rising to 13,700 feet; but are isolated from the plateau lands, and belong rather to the remarkable line of volcanic heights which shows itself in the islands of Fernando Po, Prince's Island, St Thomas, and Annobon, stretching away into the ocean in the direction of St Helena. From the Sierra do Crystal the plateau edge inclines towards the lower course of the river Niger to a point above its delta, and below the confluence of the Benue, and turns abruptly to the east.

The heights which skirt the northern coast-land of the Gulf of Guinea, and which stretch as far as the head-waters of the Senegal and Gambia, and in inner slope of which the Niger also has its sources, may be considered as an extension from the great plateau. But they are of smaller general elevation; and that best known part of the ridge, which has the name of the Kong Mountains, is apparently not higher than from 2000 to 3000 feet.

The Northern Edge of the Great African Plateau

The northern edge of the great African plateau is almost unknown; but there are evidences that it runs eastward between the 4th and 8th parallels of N. latitude, to a point at which it is well known, and where the Nile falls over its slope, forming the succession of rapids above Gondokoro. The character of the upper Benue river is that of a mountain-born river; and Mounts Alantika, 10,000 feet high, and Mindif, 6000 feet, which rise to southward of Lake Chad, seem to be the outliers of the plateau edge in which the Benue has its sources. Beyond the Nile the margin of the plateau curves northward, to form the inner slope of the Abyssinian table-land.

Heights in the Interior of the Great African Plateau

The general elevation of the surface of the great African plateau, the limits of which have now been traced, may be taken at from 3000 to 4000 feet above the sea; but its surface presents very great undulations, from the depressions which are occupied by some of the great lakes, to the high mountains which rise above its average level. The most prominent of these interior masses yet known are the Blue Mountains, discovered by Baker, rising from the western shore o the Albert Lake to a height of perhaps 10,000 feet, and which are believed to extend southward to unite with the Balegga Mountains, made known by Livingstone in his journey of 1871, north-west of Lake Tanganyika; these again are believed to join with the mountains which rise midway between the Victoria, the Albert Nyanza, and the Tanganyika, dividing the drainage to these vast lakes, and rising here in Mount M'fumbiro to upwards of 10,000 feet. Another great central line of heights which also had an important part in directing the water-shed to the interior of South Africa, runs from the north of the Nyassa Lake, where it is named the Lobisa plateau, through the Muchinga Mountains, which separate the drainage of the Lualaba and its lakes from that of the Zambeza basin, westward to the heights in the far interior of Angolo, known as the Mossamba Mountains, and from which rivers flow in all directions.

The Plateau of Barbary

The plateau of Barbary, in the north of the continent, beyond the lower land of the Sahara, is a distinct and separate high land, stretching from Cape Bon, on the Mediterranean coast opposite Sicily, in a south-westerly direction to the Atlantic coast, through Tunis, Algeria, and Marocco. The eastern portion of it in Algeria and Tunis rises in a broad plateau from 2000 to 3000 feet in general height, with outer heights, enclosing an elevated steppe, at a distance of about 100 miles apart. On the west, where it enters Marocco, these outer ridges draw together and form the high ranges of the Atlas Mountains, rising to a much greater elevation, and attaining 11,400 feet in the summit named Mount Miltsin.





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