Picture: USGS/NASA/Landsat / Rex Features
"What look like pale yellow paint streaks slashing through a mosaic of mottled colours are ridges of wind-blown sand that make up Erg Iguidi, an area of ever-shifting sand dunes extending from Algeria into Mauritania in northwestern Africa. Erg Iguidi is one of several Saharan ergs, or sand seas, where individual dunes often surpass 500 metres - nearly a third of a mile - in both width and height."









