It is finer than beach sand and runs out of your hand faster. Up on the edge the wind takes it straight away, a thin banner drifting sideways, settling again a few metres on. Seen from outside, this looks like a landscape with no history at all, a heap of sand in the sun. Few landscapes have more of it.
The route the sand takes: river, sea, wind
Almost all the sand in the younger, moving dunes comes from a single river, the Orange on the border with South Africa. Its catchment covers around one million square kilometres, a good part of that in the Kalahari. Whatever weathers away out there ends up in the water and gets carried west.
The mouth of the Orange lies some 250 kilometres south of the Namib Sand Sea. From there the ocean takes over. Longshore drift pushes the material north year after year, and not just in shallow water: sediment movement has been observed 125 metres down.
Off the coast sits the cold Benguela Current, and it is the reason all that water produces almost no rain. The moisture stays in low, thick banks of cloud and arrives as fog instead of rainfall. Dry air, plenty of wind, hardly any plant cover to hold anything in place. Surf throws the sand ashore, the wind picks it up and carries it inland, and there it piles into the dunes you climb today.
- Age of the desert
- 55 to 80 million yearssources differ
- Active sand sea
- around 5 to 6 million yearsthe moving dunes
- Main source of sand
- Orange River, 250 km southcatchment 1 million km²
- Tsauchab
- 150 km longnever reaches the Atlantic
- World Heritage
- since 2013around 3.08 million hectares
Why the sand is red
The grains themselves have no colour. They are quartz, the same as on any beach, wrapped in a coating of iron oxide so thin you never see it as a layer, mostly hematite. It forms as iron bearing rock fragments in the sand weather away. What you look at is not red sand but a film of rust.
Nearly every account adds that the older a grain gets, the redder it turns, and that the dunes far inland are darker than the ones near the coast for that reason. It sounds plausible enough. Proving it is another matter: the claim sits in popular science secondary sources, and we found no study with measurements behind it. Take it as a rule of thumb, not as a fact.
How old the desert is, and why the numbers disagree
German Wikipedia gives a flat figure of about 80 million years and calls the Namib the oldest desert on earth. The English article is more careful: arid to semi arid conditions have lasted roughly 55 to 80 million years, which makes the Namib possibly the oldest desert in the world. The range is the more honest answer. Nobody can name the day a desert begins.
The age of the desert and the age of the sand in front of you are two separate things. Under the moving dunes sits an older, partly cemented system, the Tsondab Sandstone Formation. Its age is given as at least 18 to 19 million years, while other sources date the deposition to 15 to 18 million years. Precise it is not.
That formation is the remnant of a fossil sand desert some 200 metres thick which covered large parts of Namibia around 20 million years ago. The loose sand sea lies on top of it. At five to six million years it is comparatively young. For Dune 45 the sand is dated explicitly to five million years. Two systems, then, one inside the other, and UNESCO names exactly that as what sets the area apart.
Barchans, linear dunes, star dunes
The shape a dune takes depends above all on how many directions the wind comes from.
- Crescent dunes, or barchans, stand closest to the coast, where wind blows from one dominant direction. Two horns point forward, and the whole thing migrates north.
- Linear dunes take over further inland. Where two wind directions alternate, they run as long parallel ridges across the plain.
- Star dunes need three or more wind directions. Several arms radiate from one summit, they are the tallest dune type, some exceed 300 metres, and they count as particularly stable.
The famous dunes at Sossusvlei are star dunes, and for Dune 45 that is documented outright. Wind never pushes them along in one direction; it builds them upward from several sides. Which is why Dune 45 has sat at kilometre 45 of the road for decades and not a stretch further on.
How fast the migrating barchans move is not settled. English Wikipedia mentions up to 1,000 metres a year in some areas, while GeoExpro puts it at more than 60 metres a year under strong one directional wind with a limited sand supply. Between the two lies a factor of more than ten. Neither source spells out which dunes its figure applies to, so no single number stands here.
The Tsauchab, a river that hardly ever arrives
The Tsauchab rises on the southern side of the Naukluft mountains and runs for 150 kilometres. After 80 kilometres it cuts through Sesriem Canyon, up to 30 metres deep into cemented ground. Then it heads for the sand sea. Arriving is the rare part.
It is an ephemeral river, carrying water only after rain and then seeping away or evaporating in the sand long before it sees the coast. From the point where it ends, the Atlantic is still 52 kilometres away in a straight line. The reason lies in the catchment: only 60 percent of its area gets more than 100 millimetres of rain in an average year.
As a rule of thumb, the river reaches the pan at Sossusvlei about once in ten years and turns the cracked clay into a lake. Documented years include 1997, 2000 and 2006, along with February 2011, when flooding cut Sossusvlei off from the outside world, and March 2022. How long the water then stays is where the sources part company. Sossusvlei.com writes that after four weeks it is all over, German Wikipedia mentions up to 18 months after strong floods. For 1997 a full year of standing water is on record.
How a vlei forms
Vlei is Afrikaans for a shallow hollow that holds water from time to time. Sossusvlei translates roughly as dead-end marsh, since sossus comes from Nama and stands for no return. Hard to name a place better than that.
When the Tsauchab reaches the sand sea, the sand slows it down. The water spreads out flat, stands, evaporates and drops its load: fine clay, silt and dissolved lime. Layer on layer, that becomes the hard pale floor which cracks into plates as it dries. And because those deposits push the river aside over time, Deadvlei was cut off from the main course at some point.
Below the surface lies a thick crust of calcrete. That crust is why nothing grows on the pan any more, because even deep roots no longer reach the groundwater through it. Where green camel thorn trees still stand along the edge, water under the sand is still within reach. The dead trees in Deadvlei are upright centuries later for one plain reason: it is too dry for them to rot.
World Heritage since 2013
The Namib Sand Sea went onto the UNESCO World Heritage list in 2013, decided at the 37th session of the committee. Sources disagree on the exact date, giving either 20 or 21 June 2013. The property covers around 3,077,700 hectares, a good 31,000 square kilometres, plus a buffer zone of roughly 9,000 square kilometres.
It is inscribed under all four natural criteria, vii to x. Part of the case was the pairing of two dune systems, the older partly cemented one and the younger active one above it. Those four criteria cover scenery, earth history, ecological processes and biodiversity.
What you will recognise on the ground
- Star dune or barchan? Count the ridges. One summit with several arms running off it is a star dune, a single arc with two horns pointing forward is a barchan. Which dune at Sossusvlei is which shows up best from above.
- The pale plates in Deadvlei and Sossusvlei are clay and lime, not a salt crust and not mud from yesterday. The Tsauchab left them there, a little more with every flood.
- The dry bed beside the road on the last stretch is the Tsauchab itself. Green camel thorns growing in it mean the roots still find water under the sand.
- In Sesriem Canyon you look at the ground all of this sits on: cemented sediment that the same river has cut up to 30 metres into.
Our tipAsk at the Sesriem gate when the Tsauchab last made it through to the pan. After heavy rain in February or March the water sometimes stands for weeks, and Sossusvlei then looks nothing like the photos you saw before you came.
Frequently asked questions about the Namib
Why is the sand at Sossusvlei red?
The sand at Sossusvlei is quartz wrapped in a coating of iron oxide, mostly hematite, thin enough that you never see it as a layer. The coating forms as iron bearing rock fragments in the sand weather away. The common rule that older grains turn redder comes from popular science sources and is not backed by any study we could find.
How old are the dunes of the Namib?
The Namib is considered possibly the oldest desert in the world: English Wikipedia gives 55 to 80 million years of arid to semi arid conditions, German Wikipedia a flat figure of about 80 million years. The loose sand sea on top, meaning the dunes people climb at Sossusvlei, is far younger at roughly five to six million years.
Where does the sand of the Namib come from?
The sand of the Namib Sand Sea comes mainly from the Orange River, whose mouth lies around 250 kilometres to the south. Longshore drift carries the material north, the surf throws it ashore, and wind moves it inland from there.
How often is there water in the pan at Sossusvlei?
As a rule of thumb the Tsauchab reaches the pan at Sossusvlei about once in ten years. Documented years include 1997, 2000, 2006, February 2011 and March 2022. How long the water stays is given very differently by the sources, from four weeks up to 18 months.
Why do the big dunes at Sossusvlei not migrate?
The big dunes at Sossusvlei are star dunes. Wind from three or more directions builds them upward instead of pushing them in one direction, which is why they count as particularly stable. Crescent dunes nearer the coast form under one dominant wind direction and migrate north.