Geograph - photograph every grid square

The part of White Nothe seen here was subject to massive historical landslides, where the Cretaceous Chalk and Greensand slid over the earlier, underlying layer of Jurassic Kimmeridge Clay.

Cretaceous Chalk and Greensand are permeable rock, so water filters through them until it reaches the Kimmeridge Clay, which is impermeable to water. In the past, when the permeable sediments became saturated and heavy, and water oozed between them and the impermeable Kimmeridge Clay, the soft clay crumbled from the weight, and the overlying Cretaceous rocks started to crack and slip down the slope of clay. The water acted as a lubricant between the layers, contributing to the landslide seen in the picture.