Climates of Africa - "Low" and "High" Africa
In order to understand the distribution of natural vegetation, agriculture, wildlife, and domestic livestock in Africa, we must consider climate. Climate is shaped by the interaction of several interrelated factors; the most significant are altitude (topography) and rainfall. We start, of course, with the geology. Most of Africa has had no mountain-building event in about 570 million years—a long time, about twice the time since the Appalachians formed. As a result, the rocks we see at the surface are generally flat. This observation is important when we consider climate, which in Africa can be predicted primarily by distance from the equator. In the US, we worry about the Great Lakes, the Rockies, the Sierras and the Appalachians (to name a few features)—much of Africa has none of these complexities.
We customarily divide Africa into Low and High Africa, along a line running NE-SW across the country. To the north and west lie the Sahara desert, the Sahel (which means "shore" in Arabic and refers to the southern shore of the Sahara), and the major rain forests. To the south and east lie the East African Rift Valley and the uplifted portions of South Africa, with the Indian Ocean as their border. Remember: the Nile River depends on rain in both the Ethiopian Highlands (flood season) and the Equatorial Lakes (all year), so we'll explore rainfall in these areas as well as other parts of the continent.
