West Africa is part of the great ancient African plateau which was formed in pre- Cambrian times over 3,000 million years ago. The rocks are therefore among the oldest in the world.
West Africa is generally lower than Southern and eastern Africa. It can be broadly divided into three relief regions - coastal lowlands, interior plateau surface and the highlands
The coastal lowlands are generally below 200 meters above sea level. They are broadest on the coasts of Mauritania, Senegal and Nigeria.
The interior plateau. Thus is the most extensive relief feature in West Africa. The interior plateau has an average height of 600 meters, ranging from 300 to 900m. In several places rivers have cut into the plateau thereby splitting it up into discontinuous blocks.
Most of the plateau is made up of ancient rocks of granite; Genesis and schist. The plateau is therefore part of the stable basement complex if Africa. The landscape is one of monotonous gentle slopes with some impressive residual hills known as inselbergs. They are often small and only a few hundred meters high. They are possibly formed from relatively hard, or resistant rock which stood out against weathering processes.
The highlands stand out on the general plateau surface. They are the Guinea highlands the highest point of which is called fouta jallon highlands, the Jos plateau which rises high above the general plateau.
The major rivers of west Africa are Niger, Senegal, Gambia and Volta. Apart from these major rivers there are several coastal rivers which are shorter and flow more swiftly. Among them are Rivers Ogun, Oshun, Sassandra, Mano and Cross River.
The river Niger is the longest (4,180 KM). It has two deltas - one, a coastal delta in Nigeria, the other, an inland delta in Mali. It's major tributary is the River Benue.