Coastal Erosion: Sea arch and stack

Wave action is concentrated along the line of weakness that occurs across the headland. Line of weakness is enlarged to form sea caves on both sides of the headland.

Wave erosion continues to take place in the sea caves and over time, the two sea caves connect, forming a sea arch.

When the tip of the sea arch is further eroded, the rock is weakened and eventually collapses. A small mass of rock, called a stack, is formed