Asked by: Melanie Garder, London
Buildings don’t actually sink into the sand, they are covered as it’s blown sideways by the wind. Without any plants to hold the sand in place, it is blown into horseshoe-shaped dunes, called barchans. Each grain gets blown from the bottom of the dune up to the crest and then tumbles down the steeper slope on the leeward side. This means that the barchan as a whole gradually creeps downwind at about 15m per year.
In Tunisia, the set of Anakin Skywalker’s home, used for Star Wars Episode 1, is currently being engulfed. In another five or six years it will be completely covered.