The sands of the Kalahari

The Kalahari is not a true desert, because it gets too much rain to qualify.

It is however a thirst-land because it has no surface water.

It's a large geological basin filled with deep sand into which all rainfall disappears rapidly.

It's the reddish brown area that occupies the western half of Southern Africa in satellite photographs.

Anciently it was much larger as is indicated by the fossil dunes that extend far northward into Angola and even Central Africa.

The pictures, like this one in yesterdays post, were taken at its southern extent. They are small and stunted compared to the dunes as you travel further north.

The dunes in the central dune fields are well developed, straight and vegetated with hardy thorn trees and bushes.

Zooming out they are some of the longest dunes in the world.

They are oriented perpendicular to the prevailing wind and there are literally hundreds of them intersected only by roads and the occasional dry riverbed.

The bright spots are deflation pans where salt and calcium deposits build up over millennia.

At their northern extent the ancient dunes have been covered by forests.

Here they are silent reminders of a time when the climate was much drier and the desert covered virtually all of the western side of southern and central Africa.

This drier period corresponds to ice age maximums in the northern hemisphere.

In the center of southern Africa, the rivers of the Angolan Highlands drain into the Okavongo swamp and disappear never to make it to the sea.

but even in this unusual paradise of green the fossil dunes are evident beneath the savanna grasslands.

Satellite images cropped from Google Earth.