The Kalahari Desert is not really a desert, but rather a large arid to semi-arid sandy area in southern Africa, covering much of Botswana and parts of Namibia and South Africa. Though it is semi-desert, it has huge tracts of excellent grazing after good rains and is rich in wildlife.
The Kalahari has existed as an inland desert since the Cretaceous period (65-135 million years ago). It has experienced both periods of greater humidity and more aridity, documented in fossil dune fields. It was during a period of greater rainfall that the Makgadikgadi Depression in northern Botswana was formed. The former lake at one point covered 23,000 square miles (60,000 square kilometers), about the same size as Lake Victoria today. The dry riverbeds that now only hold water when it rains are also from such periods.
Credit: New World Encyclopedia
Picture Credit: Google