SOUTH AFRICA, UNION OF. South Africa, geographi cally, is held to be that part of the Continent south of the middle course of the Zambezi, but for convenience the term is usually considered to be identical with the expression Union of South Africa. The total area is 473,089 sq.m. The Union is divided into four provinces, which consist of the Cape Province, or Cape Col ony, covering 276,966 sq.m.; Natal (including Zululand), sq.m. ; the Orange Free State, 50,389 sq.m. ; and the Transvaal, 110,450 sq. miles. Along its northern borders lie Portuguese East Africa, Rhodesia, Bechuanaland and South-West Africa, the latter being mandated territory of the Union. Basutoland, 11,716 sq.m., which is entirely surrounded by the Union, and Swaziland, lying between Natal, the Transvaal and Portuguese East Africa, are not included in the Union. The shores are washed by the Atlantic, and the Indian oceans, the conventional division between the two being the line of longitude, E.
South Africa as a whole is an elevated region, over 4o% of its area being more than 4,000 ft. above sea-level. The area below 1,500 ft. is practically confined to a coastal strip and to part of the Limpopo valley. The whole region is part of a remarkably stable land block, which has known no serious en croachment of the sea since Devonian times, with the exception of some transgression in the Cretaceous Period in the south, and along the coasts of Natal and Zululand. Since the Triassic Period it has probably been exposed to sub-aerial conditions. In Cre taceous and post-Cretaceous times it appears to have been greatly uplifted. The gradients of most of the rivers are steep between the great escarpment and the coast, and marine de posits, believed to be of Miocene and Pliocene Age, are known to occur up to 1,300 feet above the present sea-level. In conse quence, perhaps, of this movement the coast line is remarkably uniform, and there is a striking absence of good natural harbours. A subsequent, but smaller, depression of the land led to the sub mergence of the coastward ends of the valleys, and produced a series of estuaries, such as those of the Umkomaas, Umzimkulu, Keurbooms and Knysna. The value of these estuaries for ship ping has been almost destroyed by the silting action of the rivers, and by the formation of barriers of deposition across their mouths. The smaller ones have in many cases been converted in flat areas of alluvium or marsh.
On broad, topographical lines the country can be divided into an interior plateau, which includes much of the elevated country, and which is bounded by the great escarpment, and the region between the escarpment and the sea.
Much of the interior plateau is formed of Karroo rocks, which are horizontal, or gently inclined. This portion consists of great, undulating plains, broken by flat-topped, steep-sided hills, which are due to the resistance of certain beds of sandstone or sills of dolerite. Good examples of such hills may be seen in the Plat berg, near Harrismith, and in numerous hills along the Basuto land border. In the regions to the west and north-west, older rocks outcrop to form more irregular hills, e.g., Magaliesberg, and
many small ranges in Griqualand West and Namaqualand. The dolomites of the Transvaal system occur over a considerable ex tent of country about Pretoria, Rustenberg, Marico and Lichten burg. They are an important water-bearing series, and here may be found numbers of springs, and the sources of rivers. Be tween the Asbestos-Kuruman hills and the Campbell Rand es carpment, on the western side of the Dry Harts valley, is a lime stone area, forming part of the Kaap Plateau, an area of under ground drainage. The highest points in South Africa generally occur about the margins of the interior plateau.
For about 1,400 m. the Great Escarpment can be traced through the Union, bounding the interior plateau, and running more or less parallel with the coast. Different sections are known by various names, such as the Drakenberg in the Transvaal, the Draken berg or Kahlamba in Natal, and the Transkei and the Stormberg in the north-east of the Cape province, and then, proceeding westward, as the Sneeuwberg, Nieuweveld, Roggeveld, Bokke veld and Kamiesberg. Under less well known names it can be traced along the western side of South Africa to beyond the Kunene. For about 1,200 miles its structure is well known, and it can be shown, that it is a feature due to denudation. The degree of boldness of the escarpment is related to the resistance of the rocks which take part in its formation. In the northern and southern portions of the Transvaal section the scarp has been eroded in granite, but in the central part of this section Black Reef Quartzites and dolomites come in, and the height and boldness of the Drakenberg increase with the thickness of these beds. The peak of Iron Crown, near Haenertsburg, reaches 6,964 ft., and Mount Anderson, east of Lydenburg, 7,484 feet. Toward Natal stratified Karroo rocks enter into the escarpment, higher and higher beds appearing as it is followed toward the south. The escarpment attains its greatest development between Basuto land and Natal, where it is formed entirely of Upper Karroo beds. The upper part of the Kahlamba consists of about 4,000 ft. of lavas, underlain by the Cave Sandstone and other beds of the Stormberg series. Several peaks exceed i 0,00o f t., as, for example, Giants' Castle, Mont aux Sources, Cathkin Peak, etc. The Kah lamba does not rise in a simple wall. Many ridges reach out from it towards the east, and bear witness of its former more easterly situation. In this section is to be found some of the finest moun tain scenery in South Africa. It is a region of deep, picturesque valleys, which lead up at their heads to great walls of rock, whose tops are weathered and riven into pinnacles and turrets, like some cyclopean castellation. The lavas persist for about 28o m., and then disappear from the face of the escarpment in the Storm berg, and are replaced towards the west by successively lower and lower beds, until, in the Van Rhynsdorp district, Nama, and even older, rocks enter into its composition. The height diminishes after the volcanics have gone. From the Sneeuwberg to the Roggeveld the altitude is generally less than 3,500 feet.