Dunes

The Witsand System as it is today, is situated approximately 1200m above sea level, and comprises a combination of linear and parabolic dunes which vary between 20m and 30m in height. The dunes run a length of 9km in a NE - SW direction and are up to 5km in width.

 

Roaring Sand

The Roaring Sand or Brulsand is probably the most well known feature of the Witsand Nature Reserve, and one of the main attractions visitors hope to experience. In order to emit their characteristic sound, which may vary from a hum to a roar, the sand needs to be warm, dry and clean. This effect is the result of the intense friction build-up as the fine, even grains of sand are scoured together expelling the air trapped between them. Fulgurites are shafts of fused silica varying in shape and size, which are created by lightning strikes into the sand. Because of the high water table, and the elevation of the dune system, lightning frequently strikes in the dunes, and visitors are cautioned to keep out of the dunes during thunderstorms, which occur most often during summer afternoons. Many visitors to Witsand are intrigued by the apparent separation of the different coloured sands. However, this is quite easy to understand when one considers that the varying sand colours indicate the amount of leaching to which the sand has been exposed. This process would leave the white sand (virtually free from oxide deposits and therefore lighter than the other sand) on the surface, while the darker sand below the surface is occasionally exposed by wind.

 

Upper Pleistocene Period

Ferricrete outcrops occurring in the yellow sandy areas indicate that climatic conditions during the Upper Pleistocene period (ca 20000 to 45000 BC) differed radically from modern conditions, and that the iron (ferric) oxide was leached from the typically red Kalahari sand in wet, "bottomland" conditions.

Aeolian Sand

The Witsand System consists primarily of aeolian (windborne) sand. This extremely light and fine Kalahari sand was blown into the quartzite formation that underlies the dune system and holds vast quantities of spring, run-off and rainwater. Here in time, the oxides are leached from the sand, providing the many different colours and nuances, which give these dunes their particular beauty. Water: It is estimated that between 20 and 30% of the basin volume is now filled with water (both surface and ground water). The heavy clay and fine silts allow very little evaporation to occur and act as a sponge retaining the bulk of the water. It is estimated that the quartzite basin holds no less than 1211 million cubic metres of water at any particular time. The water is pure throughout the system, and is known to contain fewer solids than rainwater! The system is presently in balance. The annual rains replenish the amount of water utilised and lost to evaporation.

 

 

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