Why are the dunes red?
Iron oxide gives the dunes their colour. The more iron oxide in the sand, the redder the dunes are.
What causes the different shapes of the dunes?
The prevailing wind of the desert, the south-western, shapes the dunes at Sossusvlei into pointed multi-crested stars. There are also linear and hummock dunes in other parts of the Namib Desert formed by different wind regimes. Besides sculpting the dunes into distinctive shapes, wind keeps the sand loose. This allows reptiles, beetles and small mammals the chance to dive into the sand and escape from predators.
What is the maximum degree angle of a slipface?
Wind continuously reshapes the dunes. It forces the grains of sand on the flat windward slope upwards to the crest of the dune. Here they fall down in the wind shade. The leeward slope is therefore always considerably steeper than the windward side but never more than a maximum of a 32 degree angle.
What stops the dunes from taking over the entire desert?
Wind and water, coming from the occasional flooding of the Tsauchab River, keep the encroaching movements of the dunes in check.
How old is the Namib?
This is an age-old and hotly debated question. The answer dates back to between the breaking up of the super-continent, Gondwanaland, some 130 million years ago and 80 million years ago.
Source: Sossusvlei information sheet, Republic of Namibia, Ministry of Environment and Tourism
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