The formation of a stump is a result of a series of erosional processes. These processes are hydraulic action and corrosion. The hydraulic action is the effect of build up pressure created by waves into the cracks by compressing air into them.
Corrosion, on the other hand, is the process of mechanical erosion of the surface of the earth which is caused by the transportation of materials across it by running water, glaciers, waves etc.
Well, to know about the formation of the stump, we must first look at the sequence of its formation as this would make it more clear to us. This is how it goes:
1: At first a large crack opens as a result of the hydraulic action which is also referred to as faults.
2: The large crack formed earlier which is the fault, turns into a cave because of the same reason. It also happens due to abrasion which is nothing but the process by which rocks wear off.
3: Gradually, the cave keeps on getting wider and deeper.
4: Next, a natural arch is formed when the cave breaks through the headland.
5: As the erosion continues, the arch collapses.
6: A tall rock stack is left behind after the arch collapses.
7: As time passes, the stack is eroded.
8: It is the erosion of the stack after which comes the formation of the stump.
The above was the series after which a stump is formed. To know the series is what gives the key to better understand and interpret the formation of a stump. This entire series takes a quite long time i.e. over thousands of years.
Throughout these thousands of years, the erosion occurs continuously due to the natural processes. Different shapes are formed over time thus, leading to the formation of the stump.