Headlands and Bays

Headlands are resistant outcrops of rock sticking out into the sea, whilst bays are indents in the coastline between two headlands. Headlands form along discordant coastlines in which bands of soft and hard rock outcrop at right angles to the coastline. Due to the presence of soft and hard rock, differential erosion occurs, with the soft, less resistant rock (e.g. shale), eroding quicker than the hard, resistant rock (e.g. chalk)

Where the erosion of the soft rock is rapid, bays are formed. Where there is more resistant rock, erosion is slower and the hard rock is left sticking out into the sea as a headland which shelters the adjacent bays from further erosion

The exposed headland now becomes vulnerable to the force of destructive waves .Caves, arches, stacks and stumps will form which will eventually be eroded away.

Over time the coastline will become straight again and the whole process of differential erosion will resume again to result in an irregular coastline.

The Southwest has many examples of Headlands and Bays.The coast around Lulworth Cove demonstrates every stage in the development of bays and headlands and how that development is controlled by the underlying geology.

Along this section of coast the rocks have been tilted into a near vertical position. The oldest rocks, the Portland Limestone, provide a barrier to the sea but behind it are progressively softer rocks, Purbeck Limestone, Lower Greensand, Walden Clay and Upper Greensand. The youngest rocks are the Chalk, which, although soft, is massive in thickness.