The most difficult dunes riddles

White Sands, having 442 total square kilometers of dune fields, is the world's largest surface deposit of gypsum. Unlike other desert sands, it is cool to the touch, due to the high rate of evaporation of surface moisture and the fact that the sands reflect, rather than absorb, the sun's rays.

The Great Kobuk Sand Dune is located 65 km behind Arctic circle. Summer temperature may reach as high as 29°C! The 30 meters high dune is one of Alaska curiosities. There are 3 sets of dunes in the Kobuk Valley national park - Great Kobuk, Little Kobuk and Hunt River Dune that together cover 40 square km, and comprise the largest active Arctic dune field in North America.

The Dune of Pilat is located in France, 60 km from Bordeaux and is the tallest sand dune in Europe. It is around 500 m wide from east to west and 2.7 km in length from north to south. The dune is a famous tourist destination with more than one million visitors per year.