Red Crag
The cliffs themselves are a Site of Special Scientific Interest (SSSI), the base of which is London Clay (54 million years old) which is overlaid with a 2-million-year-old sandy deposit of Red Crag. This sandy deposit contains many fossils including bivalve and gastropod shells, sharks' teeth and whale bones. The clay base is considered one of the best sites for pyritised fossils (mainly wood) and for bird bones (which are very rare).