‘ A recent estimate of the coastline of England and wales is 2750 miles and it is very rare to find the same kind of coastal scenery for more than 10 to 15 miles together’ J.A. Sheers, The Coastline of England and Wales, 1969
This coastlines is made of different rock types, some hard, some soft. Once upon a time it was straight.
This coastline consists of parallel bands of hard and soft rock which were perpendicular to the sea. As a result of differential erosion, the bands of soft rock are eroded much more quickly than the bands of resistant rock to form bays and headlands . The headland is eroded back as a result of wave refraction. Caves , arches , stacks and stumps will form which will eventually be eroded away. The bays will advance as deposition will take place at their heads to form Beaches . Eventually, the coastline will become straight again and the whole process of differential erosion will start again and result in an irregular coastline.
As waves enter the shallow waters of the headland, the influence of the shallow waters causes the wave fronts to bent and get refracted. Due to the wave refraction, wave energy is more concentrated towards headlands and dissipated towards bays. Differential rates of erosion along a coast with alternate bands of hard and soft rocks results in an irregular coastline - Headland and Bay. Marine processes - hydraulic action and corrosion erode along lines of weakness (e.g. joints, faults and bedding planes).
The top portion of the sea caves becomes an arch, linking the tip of the headland with the mainland. Continuous erosion causes back-to-back caves to extend backward until the sea caves meet and a natural tunnel is formed. When the arch collapses, the sea ward pillar is left standing and becomes a stack. Continual wave erosion eventually reduces the stack into a stump.
Destructive waves at an exposed coast erode a steep coastal slope through processes like hydraulic action and abrasion . The waves erode along lines of weakness in the rock face to form a notch. Continued erosion enlarges the notch and causes its roof to collapse, and a cliff is formed. Further undercutting at the base of the cliff results in an overhanging cliff which eventually collapses. As the steep cliff retreats landwards, a flat terrace at the foot of the cliff is exposed - wave-cut platform. The eroded materials which are transported away may be deposited in the sea to form an offshore terrace.