Location 7 Kalahari Desert

Location 7

Kalahari Desert

The Kalahari Desert is in the Southern part of Africa. It is mainly sand sheet sand longitudinal dunes. It termed a sub tropical desert the same as the Sahara in the North. It is mostly flat and has windblown sand and also in the north sand deposited by the river.

The rainfall in the desert is 660 mm per year in the North, 400-450mm per year in the East and less than 200mm per year in the south west. There are lakes and rivers in the Kalahari but they are dry for 95% of the time.

The main characteristic of the Kalahari is the nature of the soil. It is fine sand, uniform grain size, but the colour varies from red in the drier parts and grey in the areas that have a higher rainfall.

Sand dunes in the Kalahari desert

This is a dune form the Kalahari desert. The red soil indicates that it is a dry region.

Image provided kindly by Jez Simpson

There are also relict ergs in the Kalahari desert. These are inactive dunes stabilized by vegetation in the desert. The Kalahari desert is mainly covered in these relict ergs, which are formed in response to climate change. The dunes that are found in this desert are the lunette dunes.

Fossilised dunes and stabilised sand seas and ergs are covered in vegetation in the Kalahari.
Wind is from the Northeast and the northwest in the winter and the spring. In the summer there are secondary winds which blow from the west and the south west. (Lancaster 1987).
There is evidence whithin the desert that there have been episodic periods of Aeolian and fluvial dominance. The Aeolian periods are from the Quaternary.
The Kalahari sands stretch a long way and are relict evidence of periods of high wind velocities and the wind orientation is different from that of today.
Dune expansion occurred in the Cenozoic cooling. Uplift of the Tibetan Plateau and the polar cap build up, and this had a big effect had a big effect on the Kalahari sand seas and ergs.
Uplift of the Tibetan Plateau created an east jet stream providing dry subsiding air combined with progressive build up of polar ice caps in the polar regions during the late Cenozoic.
This established a steeper pressure gradient over South Africa and this increased the wind velocity.
Radiometric dating suggests that there were possible periods of aridity and dune activity or reactivation for the south, which coincides with the last glacial maximum.
The Temperature in South Africa was 5°C colder than it is today, this increased wind velocity up to 177% greater than today, which caused reactivation of the sand seas in the west and the south parts of the Kalahari. (Lancaster, 1987).
The high moisture in the north and the east Kalahari means that dune reactivation is not possible.
Linear dunes are orientated parallel to the wind direction. In the north the dunes are Pliocene in age and they are orientated to the east. In the north east the dunes indicate northeasterly wind direction.
In the South west, late Pleistocene the primary wind direction is from the north west.
Today dune activity occurs in the south west of the desert because the influence of the precipitation in the north ceases the Aeolian activity.