It is thought that the current hydrology is relatively recent, and that some 350,000 years ago Rumbling Hole was a major sink that took water into now-blocked passages at the north end of the shaft, through East Passage and West Passage in Death's Head Hole and the passages associated with Glasfurds Chamber in Gavel Pot, and hence to a resurgence in the Leck Beck valley some 100 meters above the current resurgence which is now covered with glacial till.