Caves, arches and stacks

How did the original headland become eroded to the present coastal landscape?

A number of stages are involved:

• All rocks have lines of weakness; the sea and its waves use hydraulic action, abrasion and solution to erode along any lines of weakness.
• These lines of weakness get enlarged and develop into small sea caves.
• The caves are deepened and widened on both sides of the headland until eventually the sea cuts through the headland, forming an arch.
• The rock at the top of the arch becomes unsupported as the arch is enlarged, eventually collapsing to form a stack.
• The stack gets eroded until only a stump remains.
• Over time the stump will disappear.
• As the headland retreats under this erosion, the gently sloping land at the foot of the retreating cliff is called a wave-cut platform.