Formed from the accumulation of sand washed ashore by sea waves in the amount equivalent to 130,000 km2 of beaches. The sand dried by the wind and the sun, blown off by strong winds inland, creates high sand dunes (from 30 to 40 m high), among which the forty-meter Łącka Dune is the highest. For centuries they have been moved east and south-east at a speed of 1.2–1.6 m a year. The force of a wandering dune is enormous, as it threatens vegetation and covers everything that is on its path. Its power depends on the wind strength, height of the slope, dune face and topography. Wandering sands form a beautiful desert landscape, unique in Europe, often called the Polish Sahara.