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.
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.
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 hold 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.
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.