Caves arches stacks and stumps also form on the sides of headlands as a result of constant attack on the rocks of the headlands by destructive waves. Any points if weakness in the headlands rocks, such as faults or joints are attacked particularly by hydraulic action and abrasion. This is likely to lead to the opening up of a cave. If the cave is enlarged and extends back through to the other side of the headland, possibly meeting another cave, an arch is formed. Continued erosion by the sea widens the arch. As the sea undercuts the pillars of the arch. The roof is weakened and eventually collapses. This leaves a stack separated from the headland. Further erosion at the base of the stack may eventually cause it too to collapse. This will leave a small, flat portion of the original stack as a stump. It may only be visible at low tide. An excellent example of this is Old Harry rocks.
Geography iGCSE 