Star dunes from space Dunes tend to accumulate in shapes dictated by the prevailing winds. Long line
Star dunes from space Dunes tend to accumulate in shapes dictated by the prevailing winds. Long lines of transverse dunes or crescent shaped barchans form where there is only one main direction. These radial dunes form when winds blow from several directions at once, and grow upwards rather than sideways. They dominate the Sahara’s Grand Erg Oriental, and occur at the edge of sand seas elsewhere in Terra’s deserts, especially where they meet hills or mountains. Paleo dunes with distinctive bedding features in redbeds (sandstones formed from desert sands where the grains are covered in a patina of iron oxide) give us information on prevailing wind directions in deep time. The image was taken by NASA’s TERRA satellite. Loz Image credit: NASAhttp://earthobservatory.nasa.gov/IOTD/view.php?id=81996 -- source link
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