Erg Chebbi

These aching, rolling dunes of sand are the largest in Morocco—strange, smooth mountains that defy any sense of scale, rising out of the flat region that surrounds them. The way the great, 50-metre high pile of sand just appears from nowhere is the bit that really defies understanding, but the way that the wind creates strange shapes in them is also a source of unanswerable questions.ong before the Andes soared skyward out of the Argentinean ground, the 670,000 sq km cold, frequently frost-covered Patagonian Desert of plains and basalt sheets was smothered in the dense rainforest. Much of this forest was swamped by lava and fossilised where it stood, which is why the Patagonian Desert now contains the world's best-preserved petrified trees.