PhysOrg | ESA | 19 Nov 2010
http://www.esa.int/esa-mmg/mmg.pl?b=b&t ... t=1&size=bThe pastel colours and soft, flowing shapes in this Envisat radar image of the Tanezrouft Basin in the Algerian Sahara contradict the harshness of the terrain that has led to it being commonly referred to as the 'Land of Terror'.
Stone and pebbles make up most of the Sahara surface in Northern Africa. Erosion – first by water, now by wind – has created this landscape of hills, basins, steep canyon walls, stone plateaus and multi-storey sand dunes.
The concentric loop patterns of the sedimentary rock are exposed by wind erosion, much like the grain of wood after sanding.
Radar images reveal surface roughness – the rougher the surface, the brighter it appears. Hence, darker areas represent softer rock with a sandy or small-stoned surface.
Many steep canyon walls rising 250–500 m tower above the surrounding arid terrain. In this image, very low cliffs and faults appear bright.
This image was created by combining three Envisat radar passes (23 March 2009, 1 June 2009 and 14 September 2009) over the same area. The colours result from changes in the surface between acquisitions.
Credit: ESA/Envisat
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