As usual Dave an amusing take on the situation. I agree though I’ll be more cautious in future about taking on homework tasks unless it is a multiple choice-might get more response from the audience !!

Thanks Bal, another mystery solved,those rocks are eye catching. But you’ve asked the audience and phoned a friend so you’ll need to think carefully before taking on another question !!

Ok clearly no geologists out there but fortunately I have a friend who has come up with the answer. It is solution weathering . It would have been a circular hole at a weakness in a joint and then one slab of rock has slipped leaving the semi circle. The pattern caused by the water travelling down the hole I a spiral motion -bit like water going down the plug hole. The type of weathering has another name which relates to a pigs anatomy -I am told -but couldn’t possibly write that name on here.