NASA Earth Observatory (2018, July 5) Between the Ripples of the Namib Sand Seaf.NASA Earth Observatory (2020, January 2) Where the Dunes End.NASA Earth Observatory (2020, January 13) Sandscapes of the Namib Desert.Developments in Sedimentology, 38, 261–289. (1983) Controls of Dune Morphology in the Namib Sand Sea. The Geography Teachers Association of NSW & ACT Inc.(2018) Fluvial-aeolian sedimentary facies, Sossusvlei, Namib Desert. Journal of Quaternary Science, 21, 347–362. (2006) Characteristics and OSL minimum ages of relict fluvial deposits near Sossus Vlei, Tsauchab River, Namibia, and a regional climate record for the last 30 ka. NASA image by Alan Holmes/ NASA’s Ocean Color Web, using data from SeaHawk/HawkEye. This moisture results in relatively abundant and diverse vegetation, particularly on the rocky hills or mountains (inselbergs) that rise above the desert. Fog is the primary source of water for the Namib Sand Sea, which is the only coastal desert in the world to contain large dune fields influenced by fog.
Still, life has found a unique way to survive even without much rain. In the 2020 view above, the riverbed and clay pans are dry. Water tends to flow in the Tsauchab and pool up in Sossusvlei every few years or so, generally after a rare heavy rainstorm.
Like most rivers and streams in the region, the Tsauchab is ephemeral. The Tsauchab originates in the Naukluft Mountains, then cuts across the sand sea before coming to an end at Sossusvlei, a salt and clay pan about 40 kilometers (25 miles) from the sand sea’s eastern flank. Other large dunes-including the sand sea’s tallest, a 325-meter (1,065-foot) dune nicknamed Big Daddy-line the bed of the Tsauchab River. Composed of 5-million-year-old sands, Dune 45 towers 80 meters (260 feet) over the desert floor on the eastern flank of the sand sea. Dune 45, visible in the detailed image above and the photograph below, is an example of a star dune. Farther inland, linear dunes dominate, interrupted in places by patches of star dunes shaped by wind blowing from all directions. Crescent (barchan) dunes appear closest to the shore and are shaped by onshore winds. Sculpted by winds, the dunes are visible throughout the sand sea. Strong prevailing winds out of the south also can pick up sand and deliver it to the sand sea. The Orange River carries sandy sediment into the Atlantic Ocean, and then northward flowing currents move it along the coast and deposit it along the shore. Most of the sand originated from erosion processes that occur to the south of this image, near the Orange River valley. The sand sea and its dunes are visible in this image, acquired on January 20, 2020, with the HawkEye sensor on the SeaHawk CubeSat. Many of the highest dunes are found within the Namib Sand Sea, a section of the desert that spans 34,000 square kilometers (13,000 square miles) of coastal Namibia. It also gives rise to some of the planet’s tallest dunes. The Namib Desert in southwestern Africa is considered the oldest desert on Earth.
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