The cliffs of the Côte d'Albâtre (Alabaster Coast) consist of alternating beds of black flint and white chalk formed in the Upper Cretaceous (between 100 and 65 million years ago). Fairly rare planetwide, the local chalk crumbles under the action of a dual erosion. Rainwater flows from the plateau of the summits while the base, whose limestone is slowly diluting, leaves screes of flint that the sea transforms into round pebbles. These two phenomena lead to a retreat of the shorelines and sometimes larger landslides.