Why are the dunes of the Sossusvlei red?

Red dunes of the Namib Sand Sea.
Star dune in Namib Sand Sea

The incredible story of the red dunes of the Namib Sand Sea and Sossusvlei starts about 3000 km away in the highlands of Lesotho as the Senqunyane River, the Caledon River and as the Vaal River which rises in Chrissiesmeer near Breyten in Mpumalanga, South Africa.

Not to bore you with a long explanation of how the geological events that shaped this area, here is a short, very short, version of events.

The area was once part of an enormous inland lake on the vast supercontinent of Gondwanaland (Africa, Australia, New Zealand, South America and Antarctica). When Gondwanaland cracked and our current continents started to drift apart, the volcanic action (not the explosive kind) resulted in thick lava rivers that flowed and cooled several times, each time laying down the basalt rock that forms the basis of the current Drakensberg and Maloti ranges.

How good was that, condensing the period from the beginning of time to about 160 million years ago (about 500 million years) into one paragraph?

The Orange River near its source in Lesotho
The Orange River starts life as the Senqunyane River (Little Orange) in Lesotho

Fred’s Journey

It is here that the journey of our grain of sand, let’s call him Fred, begins. The continuous erosion of these mountain ranges by wind and water, sees the Senqunyane, Caledon, Vaal and Orange rivers carry Fred, more sand, mud and sediment to the mouth of the Orange River some 2200 km away. Before the many dams on the river were built, the Orange River was second only to the Yellow River in China in the concentration of sediment it carried.

Orange River mouth.

On reaching the Atlantic Ocean, Fred, his sand cousins, mud and gravel have no time for sun-bathing, but are caught up in the powerful ocean currents. Most of the mud moves north and west, out into the Atlantic Ocean, but much of the sand and gravel, including Fred, stays within the breaker zone and moves along the shore due to strong longshore currents. These currents are caused by the pressure of the fierce southerly winds. Fred and his cousins are spat out of the ocean onto the beaches in southern Namibia, the area as Diamond Area No. 2. It is also here that rich deposits of alluvial diamonds were placed by the same process as well as the area south of Luderitz known as the Sperrgebiet.

Barchanoid dunes along the southern Namibian coast
South Namibian coast and begining of the Namib Sand Sea

The southerly and southwesterly tradewinds of this area, pick Fred up and blow him eastwards where Fred becomes part of the Namib Sand Sea. (we will return to Fred a little later, but let him rest from his 2800 km journey for a while).

Where is the Namib Sand Sea?

Namib Sand Sea

The Namib Sand Sea, approximately 34000 km² in area, stretches almost 600 km along the south coast of Namibia, from Luderitz in the south to the Kuiseb River in the north and about 150km inland to the base of the Great Escarpment. The western side of the Sand Sea was formed by sand blown from the Atlantic Ocean (Fred), while the eastern side is formed from sand blown westwards from the interior.

The Namib Sand Sea is dominated by high linear dunes (see image 1), near the coast, however,  there are mainly barchanoid dunes (see image 2) and in the east (Sossusvlei area) there are a mixture of linear and enormous star dunes. (see image 3). The star dunes are the oldest type of dune in the sand sea and also the biggest.

Sossusvlei

Where is the Sossusvlei?

Lets talk Sossusvlei, as this is the main tourist attraction in this part of the world. The dunes in this area are given numbers. The highest dune is Dune 7 at 383m but Big Daddy and Big Mama are only slightly lower. These are examples of the highest fixed dunes in the world. Star dunes are formed by winds blowing from all directions resulting in a dune with several arms. Because the winds blow from all directions, the dunes hardly move at all, hence the term fixed dunes. This is in contrast to the linear dunes that move along with the prevailing winds.

So why are the dunes red, Fred?

Getting back to Fred. Fred and his cousins are sand particles that are low in iron oxide and have a slight grey/yellow colour. They have been blown all the way to the eastern part of the sand sea where their next door neighbours are sand particles blown from the interior that are high in iron oxide, which form a pink- red coating to the dunes. You could say that the neighbours have been rusting over many, many centuries. This causes the dunes in the eastern part of the sand sea to have the characteristic red colour, but there are patches to be seen, where Fred and his cousins have not mixed with their neighbours, that are grey/white/yellow. These patches are quite clear in amongst the red dunes. As you move towards the coast, the red dunes become less prominent and the sand sea changes from pink-red to dusky yellow/orange right until you get to the coast where they are lighter still.

The Sossusvlei is a pan at the end of the Tsauchab River that is blocked from emptying out into the Atlantic Ocean by the sand sea. The Tsauchab River only flows when heavy rains are experienced in its catchment area and as this is semi-desert, this is not often. The rest of the time it is dry and the pan empty. Adjacent to the Sossusvlei pan is the 4×4 parking lot for both the pan and Big Daddy Dune. Big Daddy is a fantastic dune to climb as the view from above is awesome. You can clearly see the star shapes of the surrounding dunes and way below, the harsh white salt that characterizes Dead Vlei and its petrified trees.

View of Dead Vlei from on top of Big Daddy

I was personally disappointed with the Sossusvlei pan itself,  but have come to realise that when people talk about the beautiful Sossusvlei, they are referring to the range of dunes, starting from Dune 1 and ending with Big Daddy. The most photographed dune is Dune 7 as it is much smaller than Big Daddy, but fits into a standard camera lens better.

Driving from the gate into the Namiba Naukluft Park, near Sesriem Canyon, is about 60 km on a good tar road to the normal 2×4 vehicle car park. From there, if you do not have a 4×4 vehicle, you can pay for a shuttle to take you the remaining 4 km to the Sossusvlei, Big Daddy and Dead Vlei.

Here lies Fred

So ends Fred’s journey here in the red dunes of the Sossusvlei, where he will most probably remain as part of a fixed dune until the world is no longer. Goodbye Fred, you exist in one of the most unusually beautiful parts of our planet.

Added Bonus:

Note on the Great Escarpment:

The Great Escarpment is a major topographical feature in Africa. The high central plateau slopes downwards to the oceans the surround southern Africa and it is where the slope becomes steep that is referred to as the Great Escarpment. It comprises the Muchinga Escarpment in Zambia, the escarpment between Zimbabwe and Mozambique, the Drakensberg, Maloti and othert mountains of South Africa and extends through Namibia into Angola.

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