RELIEF
Africa consists of a vast plateau, high in the East but gradually sinking towards the west, its monotony relieved by great shallow basins and their river systems, by the deep incision of the rift valley, and by the often magnificent volcanoes, fault blocks and inselbergs.
The basis of this simple relief is a stable block of ancient crystalline rocks of Precambrian origin, rocks which sometimes rise to the surface in parts of the continent but are often marked by later sedimentaries and volcanic outpourings.
The rigid block has withstood the tremendous forces which elsewhere have formed the alps of europe and the Himalayas of India and fold ranges are confined to the edges of the block in the Atlas and Cape regions. But the plateau crust has not entirely escaped the effects of earth movements for vast warpings have formed huge shallow basins and great vertical movements have cracked the surface into giant fault lines
