Dead Vlei is a white clay pan located near the more famous salt pan of Sossusvlei. Dead Vlei is surrounded by the highest sand dunes in the world, the highest reaching 300-400 meters. The clay pan was formed after rainfall, when the Tsauchab river flooded, creating temporary shallow pools where the abundance of water allowed camel thorn trees to grow. When the climate changed, drought hit the area, and sand dunes encroached on the pan, which blocked the river from the area. The trees died, as there no longer was enough water to survive. There are some species of plants remaining, such as salsola and clumps of !nara, adapted to surviving off of the morning mist and very rare rainfall. The remaining skeletons of the trees, which are believed to be about 900 years old, are now black because the intense sun has scorched them. Though not petrified, the wood does not decompose because it is so dry.