Question

Anyone tell me how stacks and stump are formed

Answer 1

Stacks are formed over time by wind and water, processes of coastal geomorphology. They are formed when part of a headland is eroded by hydraulic action, which is the force of the sea or water crashing against the rock.

Answer 2

When an arch collapses, it leaves the headland on one side and a stack on the other. The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.