ABSTRACT
This chapter discusses the form of a general outline of Africa as a whole and by special regions, from the point of view of physical features and basic ecology. Cooke began with a factual, geological outline of the whole continent stressing the importance of basins of sedimentation and, in Late Tertiary and Pleistocene times, of sediment traps formed by the Rift Valley system. Emphasis was laid on the fact that the effects of temperature and rainfall on vegetation can be considerably modified by basic geology, physical features, and the nature of the soil. Arambourg spoke on northern Africa. Moreau asked whether the Sahara had always been desert and was told that for most of the time it had. In the Western Sahara Paleozoic sandstones are found between Precambrian and Cambrian Basement rocks. There is evidence that the Nile shifted back and forth, and moist conditions may have occurred locally during the Pliocene.
