The English Channel is a shallow sea (-564 ft / 172 m maximum) resting on a continental crust dating from the Pleistocene. Its renowned cliffs were created by breaking waves associated with a drop in sea level. They consist of a regular alternation of chalk layers, flint beds, and a succession of marls topped with more friable limestone. The ABMC (American Battle Monuments Commission) is carrying out reinforcement work on the Pointe du Hoc cliff in order to protect it from sea erosion.