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
Mendip Hills been known about since the establishment of the Mendip lead mining industry in Roman times. However, many have been discovered or explored only in the 20th century. Specialist equipment and knowledge is required to visit the vast majority of the caves, but Cheddar Gorge and Wookey Hole Caves are two show caves which are easily accessible to the public. The active Mendip Caving Group and other local caving organisations organise trips and continue to discover new caverns. The Hills conceal the largest underground river system in Britain; attempts to move from one cave to another through the underground rivers led