The diagrams show the process of headland erosion, starting with the rock eroding and finishing with the retreating of the headland.
First, the headland is typically a strong cliff that extends into the sea. In the first stage, the rock has a weak area at its base. When the water reaches this base, it becomes weak and starts to erode, causing the formation of a small cave. If this exposure to the water level continues, the cave will increase in size and gain a structure of an arch. During this process, if a high tide of the waves reaches its roof, it will cause erosion and form a small single rock that stands alone in the sea, known as a stack. The stack, on the other hand, if continues to be exposed to water, will be reduced to a tiny rock, called a stump. During this period, other stacks are formed.
To sum up, the headland erosion process is complex, involving several steps.