By Richard I. Gibson
Much of the Transvaal or Cape Craton, in South Africa, is exposed at the earth’s surface. This is one reason that the oldest examples of earth rocks come from this area, and why South Africa is so rich in the kinds of dense elements that were concentrated in the early earth, like diamonds, platinum and palladium.
Map of some of Africa's cratons modified from U.S. Geological Survey.
Here is the podcast: