Caves of the Mendip Hills Caves of the Mendip Hills The caves of the Mendip Hills are formed by the particular geology of the Mendip Hills: large areas of limestone worn away by water makes it a national centre for caving. The hills conceal the largest underground river system in Britain. The hills consist of anticlines of Carboniferous Limestone lying over Devonian Old Red Sandstone, with the sandstone exposed on the summits. When a surface stream running off the sandstone reaches the limestone it sinks below ground through a "swallet", (also known locally as a "slocker"), continuing on its way down towards sea level by
Wookey Hole Caves SSSI designation, which would restrict what farmers and other landowners were allowed to do, would cover the entire catchment area. This was opposed as being too restrictive and difficult to enforce. It was argued that agricultural uses of fields which were not directly in contact with cave entrances would have little detrimental effect on the caves themselves. There was also debate about which caves and cave features should be considered "important". The final settlement resulted in a smaller area being designated and many agricultural practices being removed from the list of proscribed "Potentially Damaging Operations". The entrance weir and sluice