Explain the formation of a stump

A stump is formed through a series of erosional processes. This are corrasion (the effects of material suspended in the water being thrown against the headland), and hydraulic action (the effect of the build-up of pressure, as waves compress air in to cracks). Through these processes a fissure will form in a headland, and over time this will widen and deepen in to a crack. This this then continue to be eroded until a cave is formed. Through the erosional processes this cave will eventually be eroded right through, leaving a three-sided landform known as an arch. An example of this is Durdle Door. Over time, the roof of this arch will become unsupported and will collapse, leaving a stack which is unconnected from the headland. An example of this is Old Harry. Over time this stack will be eroded in to a stump, which will eventually disappear completely.