what type of sediments are the white cliffs of dover made of
White Cliffs of Dover The White Cliffs of Dover are cliffs that form part of the English coastline facing the Strait of Dover and France. The cliffs are part of the North Downs formation. The cliff face, which reaches up to 350 feet (110Â m), owes its striking appearance to its composition of chalk accented by streaks of black flint. The cliffs stretch along the coastline for eight miles (13 km), spreading east and west from the town of Dover in Kent, and part of them were purchased by the National Trust in 2016.[1] They are part of the Dover to Kingsdown Cliffs Site of Special Scientific Interest[2] and Special Area of Conservation[3]
Chalk Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores. Flint (a type of chert) is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint).