<P> The high southern and eastern plateaus, rarely falling below 600 m (2,000 ft), have a mean elevation of about 1,000 m (3,300 ft). The South African Plateau, as far as about 12 ° S, is bounded east, west and south by bands of high ground which fall steeply to the coasts . On this account South Africa has a general resemblance to an inverted saucer . Due south, the plateau rim is formed by three parallel steps with level ground between them . The largest of these level areas, the Great Karoo, is a dry, barren region, and a large tract of the plateau proper is of a still more arid character and is known as the Kalahari Desert . </P> <P> The South African Plateau is connected towards East African plateau, with probably a slightly greater average elevation, and marked by some distinct features . It is formed by a widening out of the eastern axis of high ground, which becomes subdivided into a number of zones running north and south and consisting in turn of ranges, tablelands and depressions . The most striking feature is the existence of two great lines of depression, due largely to the subsidence of whole segments of the Earth's crust, the lowest parts of which are occupied by vast lakes . Towards the south the two lines converge and give place to one great valley (occupied by Lake Nyasa), the southern part of which is less distinctly due to rifting and subsidence than the rest of the system . </P> <P> Farther north the western hollow, known as the Albertine Rift, is occupied for more than half its length by water, forming the Great Lakes of Tanganyika, Kivu, Lake Edward and Lake Albert, the first - named over 400 miles (640 km) long and the longest freshwater lake in the world . Associated with these great valleys are a number of volcanic peaks, the greatest of which occur on a meridional line east of the eastern trough . The eastern branch of the East African Rift, contains much smaller lakes, many of them brackish and without outlet, the only one comparable to those of the western trough being Lake Turkana or Basso Norok . </P> <P> A short distance east of this rift - valley is Mount Kilimanjaro--with its two peaks Kibo and Mawenzi, the latter being 5,889 m (19,321 ft), and the culminating point of the whole continent--and Mount Kenya, which is 5,184 m (17,008 ft). Hardly less important is the Ruwenzori Range, over 5,060 m (16,600 ft), which lies east of the western trough . Other volcanic peaks rise from the floor of the valleys, some of the Kirunga (Mfumbiro) group, north of Lake Kivu, being still partially active . This could cause most of the cities and states to be flooded with lava and ash . </P>

How might topography and climate limit the population of the continent of africa