Located on the northern slope of the Mont-Blanc massif, the Mer de Glace is the largest glacier in France.
Almost 7 kilometres long and covering an area of about 40 km², it extends from an altitude of 3,900 metres to about 1,500 metres. Its thickness, once impressive, still reaches several hundred meters in places.
The Mer de Glace is a glacier in perpetual motion. Fed by the eternal snows of the surrounding peaks, it advances slowly, at an average speed of 70 meters per year at its center. However, like many Alpine glaciers, it is now suffering the effects of global warming, leading to a significant decline in its mass and extent.