The Sossusvlei is a circular shaped hard-surfaced depression surrounded by dunes. It is a clay pan that holds rain water, forming a lake. Due to the high clay content, the clay pan retains water for quite some time. Sossusvlei is also known as the ‘Vlei’ the Afrikaans word for pan or marsh. It is the place where the dunes come together, which causes the Tsauchab River to stop its course, though it usually does not flow as far as the Vlei. If there is an unusually large amount of rainfall turns the dry Vlei into a lake flanked by high dunes. The dunes are now considered to be part of the Sossusvlei.
The sand that forms the dunes is thought to originate from the Orange River, carried over to the western coast of Africa and then deposited into the Atlantic Ocean. The currents of the ocean moved the material north and then redeposited it back on land. This constant re-deposition allowed the dunes to begin forming on the coast and then get shifted further inland by the winds. The sand that is deposited on the windward side is at a shallower angle than that deposited on the leeward side; the sand moves up the slope of the shallower side, eroding it in the process, and then accumulates on the steeper leeward side (http://bit.ly/14CSxcD). Sand dunes ‘move’ in the same direction of the wind, though the patterns on the dunes vary according to the direction and speed of the wind. The dunes of Sossusvlei have taken a million years to form.
The red colour of the sand dunes of Sossusvlei is due to the presence of iron oxides in the sand combined with garnet particles. The colour shades vary according to the age of the dunes; the older the dune, the brighter the colour. The dunes can appear to be different shades of red at different times during the day; the area is well photographed by professionals and amateurs alike. The best time to view Sossusvlei is close to sunrise and sunset as the colours are strong and constantly changing.
Though water is scarce in the region, to several species Sossusvlei is home. The toktokkie beetle is one such example, one of over 200 species of tenebrionid living in the Namib Desert. The beetles communicate between sexes under the surface of the sand by tapping their abdomens on the ground. The shovel-snouted lizard is another sub-sand survivor; it has the ability to store water in its body. Other creatures obtain water by drinking droplets of the desert's periodic fog or lick the drops of water that trickle down rocks and plants. Grant's golden mole burrows a channel in the sand, which allows it to accumulate moisture. The mole spends almost its entire life under the sand and as a result of this evolutionary adaptation, has no need for eyes.
Image: Olivier Peyre, http://www.flickr.com/