In reply to pepperpot:
Do you mean shake hole rather than sink hole? I can't see any sink holes on the OS 1:25k maps around Malham. There are plenty of shake holes, though: these are depressions or pits in the ground, caused by underground collapses, whereas pot holes are open shafts. There is also the occasional swallow hole, which is where a stream disappears underground. Does that help?