The diagram illustrates how the headland erodes sequentially. Overall, there are four sequences, starting from the erosion of weaker rock, cave arching, water beating the stack roof and subsequently the headline retreats, resulting in a new formation of stack and stump.
At the beginning, the rock cliff stood by the coastal line before the tidal current swept the weaker scope of it. Periodically, the eroded part of the rock then turns into a small hollow and afterwards it transforms into a bigger curve as the waves hit it regularly. Furthermore, the result of the deformed rock evolves progressively into a much larger cave in the shape of an arch. One of many examples of this natural event is Durdle Door, a limestone arch in Dorset, England.
This does not stop there because after the rock has transformed into the stone arch it creates a way for more waves. At high tide, the waves sometimes reach the roof of the stack and it beats against it consistently with some force. After a period of time, the power of these waves loosen and wear away the stacked rock, causing it to crack and collapse. The collapsed roof creates a huge space between both rock pillars and causes the headland to retreat. In addition, it will leave a big stack of rock and stump, creating a new area on the coastline.