Red dunes at the Sossuvlei are among the highest in the world
with a relative height of about 375 metres above the Tsauchab
river. The red colour on the Sossuvlai dunes is caused by iron
oxide which covers the sand grains as a thin coating.This 'rusting'
of iron implies that these
sand grains must have been exposed to atmospheric conditions
since their formation. It is believed that these sands blown
by east winds originated from the continental interior (Kalahari).