Shaped by past climatic changes and the power of the wind, La Grande Dune du Pilat stands more than 100 meters (330 feet) above the Atlantic Ocean. This slowly shifting sand dune, southwest of Bordeaux in France, is the tallest in Europe.
The behemoth dune extends approximately 2.7 kilometers (1.7 miles) along the coast and about 0.5 kilometers (0.3 miles) inland. The OLI (Operational Land Imager) on Landsat 8 captured this image of its bright expanse on July 8, 2024.
While La Grande Dune du Pilat might appear static, the feature is actually on the move. Windblown sand drives the dune’s steady migration 4 to 5 meters (13 to 16 feet) inland each year, experts say. Onshore winds carry sand up the dune’s gently sloping seaward side, where it builds up near the dune crest. There, the sand is prone to avalanching down the landward slopes, which can be as steep as 29 degrees.
Fluctuations in environmental conditions over thousands of years made the dune what it is today. Scientists think that sand accumulated during periods of cooler, drier conditions. Forests developed in several warmer and wetter stretches, which helped stabilize loose material and enabled the dune to grow higher. The sandy mass is interspersed with several layers of paleosols, or ancient soils, that have helped scientists decode its history. Traces of these dark layers often surface on the dune’s slopes.
The forest inland of the sandy coastline contains maritime pines, introduced at the turn of the 19th century to try to stabilize the dune, as well as English oaks, which can live up to 1,000 years. In July 2022, a wildfire burned through more than 6,000 hectares (23 square miles) of this forest, although the burned area is not apparent in this 2024 image.
The dune is situated near the entrance to Bassin d’Arcachon (Arcachon Bay), an estuary interrupting a long sandy stretch of beach along France’s southwest coast. The series of channels and sandbanks at the mouth of the bay, including the expansive Banc d’Arguin, are the product of a dynamic tidal environment. Within the semi-enclosed lagoon, salt marshes provide habitat for diverse plant and animal life, and the appropriately named Île aux Oiseaux—Bird Island—is utilized by 150 avian species throughout the year.
NASA Earth Observatory images by Wanmei Liang, using Landsat data from the U.S. Geological Survey. Story by Lindsey Doermann.
