Wookey Hole Caves then passes through major cave systems such as Swildon's Hole, Eastwater Cavern and St Cuthbert's Swallet, around Priddy, but 95% is water that has percolated directly into the limestone. The southern slopes of the Mendip Hills largely follow the flanks of an anticline, a fold in the rock that is convex upwards and has its oldest beds at its core. On the Mendips the crest of the anticline is truncated by erosion, forming a plateau. The rock strata here dip 10–15 degrees to the southwest. The outer slopes are mainly of Carboniferous Limestone, with Devonian age Old Red Sandstone exposed
Wookey Hole Caves resurgences. In particular, the passages in the 20th chamber are interpreted as a former Vauclusian spring, the waters of which once surfaced in the Ebbor Gorge. It is uncertain whether that was the original rising or whether it formed when the main rising at Wookey was blocked. The current resurgence is located close to the base of the Dolomitic Conglomerate at the head of a short gorge formed by headward erosion with subsequent cavern collapse. The morphology of the passages is determined by the rock strata in which they are formed. The streamway in the outer part of the cave