A few miles north of Bridlington, the chalk cliffs of Flamborough Head jut out into the North Sea. Chalk is the shells of minute coccolithophores, laid down on the bed of a warm clear sea 95-65 million years ago. Faults or joints in the rock provide the weak spot for the constant pounding by the waves to form a sea cave. When the cave is large enough a blow hole might form following a collapse in the roof. This will eventually erode after thousands of years into a sea arch. Time passes and the arch will collapse leaving a sea stack. The stack will finally succumb to the power of the sea and topple leaving a wave cut platform. High Stacks has caves, arches and stacks, all the stages in the erosion of the chalk cliffs. It is not quite an island, connected to the mainland by a narrow neck of chalk topped by glacial till.