Probably the most famous coastal landform in Britain? Durdle Door natural arch.
Durdle Door is formed from a layer of Portland limestone standing almost vertically out in the sea. Normally layers of limestone would be horizontal. Only the most fundamental force in geology could have altered these rocks in this way – plate tectonics.
Here is all the geological detail from Ian West, Southampton University bhttp://www.southampton.ac.uk/~imw/durdle.htm