Grey dune

Grey dune in Baleal, Peniche, Portugal

Grey dunes are fixed, stable sand dunes that are covered by a continuous layer of herbaceous vegetation. These dunes are typically located 50–100 meters from the ocean shore and are found on the landward side of foredunes (also known as yellow dunes). Grey dunes are named for their characteristic grey color which is a result of the ground cover of lichen combined with a top soil layer of humus.