it stretches, and can be located by the spring lines around the chalk ridges and escarpments. The water that sits between these two beds is responsible for the many landslips that have occurred throughout the county's history. Around Compton Valence, it lies on the Fuller's earth, whereas between Ringstead and White Nothe, it covers the Kimmeridge Clay and the Portland and Purbeck strata. Because geologists are certain all the formations from the Lias to the Kimmeridge Clay were deposited over the whole of the county, the Gault clay reveals the scale of uplift and erosion that must have taken place before Dorset was flooded. The overlying Gault is revealed in the spring lines around the chalk ridges and escarpments. This water is also responsible for the many landslips throughout Dorset's history from the prehistoric to modern times. Above the Gault is the Upper Greensand, which varies from the golden sands that crown the West Dorset heights, such as Pilsdon Pen and Golden Cap, to the rubbly sandstones found in the centre of the county. The fossiliferous, green sandstone found around Shaftesbury contains many ammonites, which when compared to other deposits, indicates condensed deposition during different periods at different locations, and detailed analysis reveals that basement structures were still active at this time. Chalk Group The sea levels remained more or less unchanged until the end of the Cretaceous period, and despite Dorset having moved even further north to 40°, the climate had reverted to a tropical one. During the Late Cretaceous epoch, the sea deposited an enormous amount of chalk across the county, perhaps as much as 300 m more than currently remaining. The first chalk deposits contained sands and grits thought to have originated in Cornubia. This gritty chalk was deposited across central Dorset, and can clearly be seen in the sides of Eggardon Hill. As the water deepened, plankton, coccoliths, and foraminifera became the main source for the calcareous soup, which would later form the Dorset chalk. The chalk forms a narrow strip inland between Studland and Worbarrow Bay, when it reaches the coast once more. A much wider strip continues westward along the coast until it meets the wide swathe of chalk that cuts north-west across the county and forms the south-east point of the Hampshire Basin. Generally, the Dorset chalk is too soft to be used as a building stone except along the Ridgeway, where faulting