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Science Frontiers ONLINE No. 90: Nov-Dec 1993 |
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Dune Circles Of Sossusvlei
The Dead Pan of Sossusvlei lies in the Namibian Desert some 50 kilometers from the Atlantic Ocean. It is a 5-hour drive from Windhoek, the capital of Namibia. Geologically, this feature is a clay pan in the flood plain of the Tsauchah River, which flows on the average only once in a decade. Towering above the clay pan are sand dunes that reach 350 meters elevation above the river bed. They are veritable mountains of sand and the tallest dunes in the world. The potential anomaly at Sossusvlei is not the size of the dunes but rather the mysterious circles of grass that grow upon them. All we have to go on is a photograph showing a dozen or so of the circles situated at some unspecified distance from the photographer. Somewhat irregular in shape, the circles seem to be on the order of 100 meters in diameter. No grass at all grows within the rings of thick grass, but outside grow sparse, evenly distributed grass clumps. The writer of the Sossusvlei article labels the circles "unusual phenomena." (Pupkewitz, Tony; "Sossusvlei," Optima, 36:136, 1988. Cr. P.A. Hill. Optima is a South African publication.)
Comment. Are these circles akin to the "fairy rings" found in moister climates? Perhaps also pertinent are the clones of creosote bushes which grow outwards in expanding circles, as mentioned in a fascinating recent article on giant aspen clones, which may be a million years old! (Grant, Michael C.; "The Trembling Giant," Discover, 14:82, October 1993.)