Coal-bearing rocks in the Zambezi trough are of this same system. Over the western third of the country there are extensive and deep wind-deposited sands, a relic of periods when the climate was drier and desert conditions in southern Africa were more widespread than at present. The continental divide separating Atlantic from Indian Ocean drainage forms the frontier with DRC south of the Pedicle, then traverses the north-east of Zambia to the Tanzanian border. Rapids occur along most river courses so that the rivers are of little use for transportation. The country's larger lakes, including the man-made Lakes Kariba and Itezhitezhi, offer possibilities of water use as yet relatively little developed.
Temperatures are generally moderate.
The ancient rocks of the eastern two-thirds of the country have generally poor soils. Soils on the Kalahari Sands of the west are exceptionally infertile, while seasonal waterlogging of soils in basin and riverine flats makes them difficult to use. Savannah vegetation dominates, with miombo woodland extensive over the plateau, and mopane woodland in the lowlying areas. Small areas of dry evergreen forest occur in the north, while treeless grasslands characterize the flats of the river basins. There are no fewer than 73 different ethnic groups among Zambia's indigenous population.