Discordant coastline

A discordant coastline occurs where bands of different rock types run perpendicular to the coast.

[1] The differing resistance to erosion leads to the formation of headlands and bays.

A hard rock type such as granite is resistant to erosion and creates a promontory whilst a softer rock type such as the clays of Bagshot Beds is easily eroded creating a bay.

The Portland limestone is resistant to erosion; then to the north there is a bay at Swanage where the rock type is a softer greensand.

North of Swanage, the chalk outcrop creates the headland which includes Old Harry Rocks.