The region of West Africa includes the southern portion of the bulge of the continent, which extends westward to the Atlantic Ocean. This region is bisected by the African Transition Zone, which borders the southern edge of the Sahara Desert. The main physical features include the Sahara Desert and the Niger River.
Central Africa covers a large physical area that can range from desert conditions to the north in Chad to tropical rain forests and mountains in the equatorial region of The Congo. The entire region is roughly the same size as the United States west of the Mississippi River.