The Great Sand Dune of Pyrrha in France is the tallest sand dune in Europe and took 4,000 years to form. Not only is it a stunning natural landmark, it is a living, ever-changing landscape carved by wind and time.

The great dune of Pyrrha towers over France's Atlantic coast, migrating inland every year as breezes push the sand up its gentle seaward slopes and down its steep forested slopes. Ancient soil layers reveal the story of climate change, while efforts to stabilize the dunes with forests have left their mark. Just inland, fire-scarred pine forests and the diverse wetlands of Arcachon Bay frame this ever-changing coastal landscape.

Gradually formed by climate change and constant winds, the Great Dune of Pyrrha rises more than 100 meters (330 feet) above France's Atlantic coast. It is located southwest of Bordeaux and is the highest sand dune in Europe.

Stretching for about 2.7 kilometers (1.7 miles) along the coast and 0.5 kilometers (0.3 miles) inland, this massive sand dune is a feature of the coastal landscape. On July 8, 2024, the Land Imager (OLI) on NASA's Landsat 8 satellite captured its spectacular appearance.

Wind migration and dune movement

Although the dunes look like frozen formations, they are always moving. Driven by wind, it moves 4 to 5 meters (13 to 16 feet) inland each year. Onshore breezes push the sand up the gentle seaward slopes of the dunes, where it collects near the tops. From there, the sand often cascades down the steeper inland side, with slopes that can slope up to 29 degrees.

Fluctuating environmental conditions over thousands of years shaped the dunes into what they are today. Scientists believe the sand accumulated during cooler, drier periods. Forests grow in several warmer, wetter areas, which help stabilize loose material and allow dunes to grow taller. Layers of ancient soil are scattered throughout the sandy material, helping scientists decipher its history. Traces of these dark layers often appear on the slopes of dunes.

The Great Dune of Pyrrha is a massive wind-eroded sand dune on the French coast that grows and moves every year. Its history is written in the subsoil, affected by climate change and forest growth.

Forests, fires and ecosystem impacts

Forests inland from the sandy coastline include coastal pines, introduced in the early 19th century to stabilize dunes, and English oaks, which can live up to 1,000 years. In July 2022, a wildfire burned more than 6,000 hectares (23 square miles) of this forest, although the burned area is not visible in this 2024 photo.

Arcachon Bay: a coastal habitat hotspot

The dunes are located near the entrance to Arcachon Bay, the estuary of a long sandy beach on France's southwest coast. A series of channels and sandbars at the entrance to the bay, including the vast Altyn Bay, are the product of a dynamic tidal environment. In the semi-enclosed lagoon, the salt marshes provide habitat for a variety of flora and fauna, and the aptly named Bird Island (Îleaux Oiseaux) is home to 150 species of birds year-round.

The NASA Earth Observatory image was taken by Wanmei Liang, using Landsat data from the U.S. Geological Survey.

Compiled from /ScitechDaily