Image: Earth from space -- wind-inspired design

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.

Provided by European Space Agency