<P> Both in the east and west of the continent the bordering highlands are continued as strips of plateau parallel to the coast, the Ethiopian mountains being continued northwards along the Red Sea coast by a series of ridges reaching in places a height of 2,000 m (6,600 ft). In the west the zone of high land is broader but somewhat lower . The most mountainous districts lie inland from the head of the Gulf of Guinea (Adamawa, etc .), where heights of 1,800 to 2,400 m (5,900 to 7,900 ft) are reached . Exactly at the head of the gulf the great peak of the Cameroon, on a line of volcanic action continued by the islands to the south - west, has a height of 4,075 m (13,369 ft), while Clarence Peak, in Fernando Po, the first of the line of islands, rises to over 2,700 m (8,900 ft). Towards the extreme west the Futa Jallon highlands form an important diverging point of rivers, but beyond this, as far as the Atlas chain, the elevated rim of the continent is almost wanting . </P> <P> Much is Africa is made up of plains of the pediplain and etchplain type often occurring as steps . The etchplains aare commonly associated with laterite soil and inselbergs . </P> <P> The area between the east and west coast highlands, which north of 17 ° N is mainly desert, is divided into separate basins by other bands of high ground, one of which runs nearly centrally through North Africa in a line corresponding roughly with the curved axis of the continent as a whole . The best marked of the basins so formed (the Congo basin) occupies a circular area bisected by the equator, once probably the site of an inland sea . </P> <P> Running along the south of desert is the plains region known as the Sahel . </P>

What geographic feature separates north africa from the rest of africa