Caves of the Mendip Hills then rising up a fracture in the rock. Few caves on the Mendip Hills are more than deep or a few kilometres in length, (with some notable exceptions, such as Swildon's Hole which is over long), but a number are complex with several levels of passages which have been abandoned by the water, for example those around Cheddar. The catchment area of the Cheddar Yeo, which rises in Gough's Cave, measures . Dye marking shows that some of the water travels underground for up to , taking up to 14 days to reach Cheddar. When Banwell Bone Cave was discovered
Wookey Hole Caves system that is formed within the Dolomitic Conglomerate is characterised by shallow loops linking low bedding chambers, or tall narrow passages, known as 'rifts', developed by phreatic solutional enlargement of fractured rifts. The streamway in the inner part of the system formed within the limestone is characterised by deep phreatic loops reaching depths as much as , with the water flowing down-dip along bedding planes and rising up enlarged joints. In the far reaches of the cave the passages descend to below sea level. Witcombe suggests that the name "Wookey" is derived from the Celtic (Welsh) for 'cave', ""Ogo"" or