Cheddar Complex the Pleistocene period. Cheddar Caves contain both active and fossil systems. The active cave system is one of the most heavily studied karst systems in Britain with reference to the conduit and diffuse flow characteristics of its hydrology. Charterhouse Caves include four major swallet caves that provide an indisputable record of Pleistocene landform development in the Mendips and surrounding area. Sun Hole Cave provides a varied fauna radiocarbon-dated to the end of the Late Devensian Cold Stage. Several types of limestone including Clifton Down Limestone, Cheddar Limestone and Cheddar Oolite are visible in the Gorge and surrounding areas with pale
Wookey Hole Caves is of what is described in the guide book as "magnificent" river passage, high and wide, which finishes at a cascade falling from a long lake. There are also more than of high level passages above the river. The way on continues underwater for some reaching a depth of before surfacing in the 25th chamber – called the Lake of Gloom because of its thick mud deposits. The sump at the end of this has been dived for to a maximum depth of before gravel chokes prevented further progress. The end is located about northeast of the entrance. Wookey Hole