At the entrance to the Arcachon Basin, opposite the Banc d'Arguin stands the famous Dune du Pilat, a mountain of about 60 million cubes of sand. This little corner of desert between moors and ocean has been formed gradually for centuries by the accumulation of sand driven by wind and ocean currents.
Pilat takes its name from the Gascon "Pilot" which means "heap" or "mound". Current measurements: 2.7 km long, 500 m wide, 109.86 m high
The dune is mobile and «rolls» on itself. Under the effect of the wind, it moves irregularly between 1 to 5 m per year towards the forest.Its progression is inevitable and contributes to its remarkable character.
Its history can be reconstructed by alternating layers of sand and black layers that can be seen, especially in winter, on its western side of the ocean. These black layers are in fact ancient forest soils that scientists call "paleoclasts". The elements they contain (stumps of trees, pieces of ceramics, fragments of pottery...) allow to date them. In winter, strong winds cause sand grains to rise on the west face, releasing trunks of trees buried under the dune.