Six leather ropes in a sea of sand

The Sesriem Canyon is one of the most visited geological sites in Namibia.

From Namibia: Fascination of Geology by Nicole Grünert

The Sesriem Canyon owes its name to the first settlers who had to connect six lengths of leather rope (in Afrikaans: ses rieme) to scoop water out of the canyon. Its geological history began in the middle Tertiary about 30 million years ago. At that time a true desert climate prevailed as in the present Namib Desert.

Large parts of the country were covered by up to 200m thick desert sands, which later solidified into the Tsondab Sanstone Formation. Then a climatic change occurred, and wetter (semi-arid) conditions commenced.

Numerous rivers were formed which rose in the area of the Great Escarpment further to the east and unlike today often reached the Atlantic Ocean.

The Tsauchab River was one of these. The Tsauchab transported large amounts of erosion debris and dissolved carbonates from the nearby Naukluft and Zaris Mountains and deposited these gravels on the desert sands of the Tsondab Sandstone Formation. The debris is about 50m thick and fans the foot of the Great Escarpment.

The carbonate transported in the river water was precipitated and this lead to a cementation of the deposited sand and boulder forming conglomerates.

The actual formation of the Sesriem Canyon was initiated by a drop in sea level about 2 million years ago. This drop was connected to the commencement of ice ages in the Northern Hemisphere.

Large amounts of seawater were absorbed as ice in the newly formed glaciers, which caused a worldwide drop of the sea-level. This led to an increase of the gradient to the ocean and thus to an increase in the erosional forces of the rivers, which resulted in the Tsauchab cutting into its own, previously deposited conglomeratic sediments.

The erosion processes, which formed the small canyon (about 30m deep and 3km long) still show this effect, when water flows at high speed through the gorge in good rainy seasons. The recent return to full arid conditions makes further shaping of the canyon take place progressively slower.

During a walk through the Sesriem Canyon you can read its geological history from the steep canyon walls. A distinct change from fine sandy layers to mighty boulder beds is obvious. This sequence in the sediments reflects the different water load capacity of the Tsauchab River during the single sedimentation phases.

Coarse boulders point to strong flowing water with large transportation power and thus high rainfall. Fine grained sand deposits are an indication of weaker flowing water due to lower rainfall. By means of such outcrops, the geologist can reconstruct the climate history of the whole region.

The Sesriem Canyon is one of the stop overs on Endorphin Expeditions’ natural history overland tour of Southern Africa. Book now for next year’s trip to avoid disappointment.

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