Erosion of coastal Chalk cliffs is slow. Chalk is relatively hard, and only becomes unstable when the sea has carved a cave into its base, destabilising the weight of cliff above. The sea then has to wash away the cliff fall before the process can start all over again. The milky coloured seawater found at the base of Chalk cliffs, particularly around fresh falls, is evidence of coastal cliff erosion in progress.
Seaton Hole (Fault)
At Seaton Hole the continuity of the cliffs is interrupted by a fault, which has lowered the cliffs to its west by around 60 meters to sea level, allowing the 90 million year old white cretaceous chalk to dominate the coastline. This unconformity has resulted in the best exposure of chalk to be found anywhere along the south coast of England.