Sossusvlei is where a river gives up. The Tsauchab comes down out of the mountains of Namibia, meets the sand and stops, sixty kilometres short of the Atlantic. Rust-red dunes over 300 metres tall wall the pan in, and climbing one is what you came for. Big Daddy is the one with the view, up a knife-edge spine of soft sand that gives way under every step: slow, sinking work. From the top the sand sea rolls away on every side of you. Coming off is the fast part: you run down the face with the sand sliding out from under you. Dune 45, named for its distance from the gate, is the easy climb, and its ridge fills before sunrise. The colour runs with the hour, pale gold at midday and a few minutes of blood-red at dusk. It also runs with age: the iron in the grains keeps oxidising as they sit, so the oldest dunes are the reddest.
None of that sand was made here. It was ground off the interior of southern Africa and washed down to the Atlantic, mostly by the Orange River. The cold Benguela Current dragged it north along the coast, and surf and southerly wind drove it back inland into these dunes. In rare wet years the Tsauchab gets through and floods the pan into a shallow mirror ringed by dunes, once a decade or so, and several times lately. From a balloon two hundred metres up, the grass flats beside the dune sea turn out to be pocked with bare circles four to ten metres wide, each ringed by taller grass. Nobody has explained them, and on the ground you walk straight through one without noticing. Almost no rain falls on any of this, and it is still alive, because the water arrives from the sea. Fog comes off the cold Atlantic at night and drifts far inland over the dunes. At first light the beetles climb to a crest, tip head-down into it, and let the mist gather on their backs and run down to their mouths.