1902 Encyclopedia > Africa > African Volcanoes. African Geology. African Rocks and Minerals.

(Part 5)


(d) African Volcanoes. African Geology.

The African continent, as far as it has yet been explored, seems to be the portion of the globe least disturbed by volcanic action. The known active volcanoes in the continent are those of the Camaroon Mountains, on the coast of the gulf of Guinea in the west, and the Artali volcano in the depressed region of the salt desert which lies between the Abyssinian plateau and the Red Sea. This latter volcano is probably a part of the system with which the volcanic island of Jebel Tur, in the Red Sea, near the same latitude, is connected. One other active volcano only is known by report, - the Njemsi volcano, in the country between Mount Kenia and the Victoria Lake. Shocks of earthquake appear to be almost unknown in any part of the continent. It has been pointed out by the late Sir Roderick Murchison that the older rocks which are known to circle round the continent, unquestionably included an interior marshy or lacustrine country, and that the present centre zone of waters, whether lakes, rivers, or marches, extending from Lake Chad to Lake Ngami, are but the great modern residual phenomena of those of a Mesozoic age. The surface of the South African continent has not been diversified in recent times by the outpouring of lava streams, or broken up by the efforts of subterranean heat to escape. Nor has it been subjected to those great oscillations by which the surfaces of many other countries have been so placed under the waters of the ocean as to have been strewed over with erratic blocks and marine exuviae. The interior of South Africa may therefore be viewed as a country of very ancient conservative terrestrial character. Knowledge of the special geology of Africa is yet confined to the few parts of the continent in which Europeans have permanently settled. In this respect the southern region of the Cape Colony and Natal have advanced furthest, and their geological features have been mapped out with some accuracy. Elsewhere in the continent, excepting in Algeria and Angola, light has only been thrown along the line followed by the few explorers who have given attention to this subject.

African Minerals and Metals

Among the minerals of Africa, salt is wifely distributed, though in some districts wholly wanting. Thus in the Abyssinian high land the salt, which is brought up in small blocks from the depressed salt plain on the Red Sea coast beneath, is so valued as to be used as a money currency; and in the native kingdoms of South Central Africa, the salt districts are royal possessions strictly guarded. Metals seem nowhere very abundant. Gold is perhaps the most generally distributed. The gold-fields of the Transvaal Republic and of the country which extends thence to the Zambeze, are numerous; but no yield has as yet been discovered of sufficient quantity to overcome the difficulties of working, and of transport to the distant sea-ports, to which no navigable rivers lead from this region. Copper is known to exist in large quantities in the mountains of native kingdoms of the centre of South Africa; and one of the objects of Dr Livingstone's present journey is to visit the famed copper country of Katanga south-west of the Tanganyika Lake. The diamond-fields in the districts of the Vaal and Orange rivers north of the Cape Colony are now steadily worked, and give good returns.

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