The climatic history of equatorial and sub-equatorial Africa is described through alternating pluvial and interpluvial phases. During pluvials, increased rainfall enlarged existing lakes, raised shorelines, and intensified the accumulation of alluvial deposits in wadis. These wetter conditions also altered the distribution of forests, savannahs, and other forms of vegetation across the continent.

Four principal African pluvials are named: Kageran, Kamasian, Kanjeran, and Gamblian. They were regarded as possible sub-equatorial equivalents of the four major glacial stages recognized in the northern hemisphere, although the excerpt emphasizes that this relationship had not been demonstrated. Two later subpluvial phases, Makalian and Nakuran, were recognized in the Holocene.

The contrast between pluvial and interpluvial conditions is visible in the landscape. Wetter intervals produced high lake sediments, beach lines, and expanded drainage, while drier intervals encouraged aeolian activity, the redistribution of wind-borne sands, and major shifts in vegetation. Former glacial features on volcanic peaks provide an additional indication that parts of equatorial Africa were substantially cooler during some episodes.