Thousands of years ago, the Blue John Cavern was carved by ancient glacial melt waters that flowed through the Castleton, Derbyshire, England area forming the underground cave system. The geology of the area, while somewhat simple, is very interesting.
The Blue John Cavern is located in the Peak District in England near the town of Castleton, Derbyshire. The area of the cavern is formed within limestone strata that deposited in deep ocean waters millions of years ago. Layers of shale and some gritstone, a type of coarse sandstone common in this area, covered the limestone.
Over time, the layers buckled from folding and faulting. The cavern itself formed when glacial melt waters flowed through the area forming the valleys and seeping into a crack in the limestone strata and dissolving portions of the limestone. As the melt waters dissolved the limestone, underground rivers formed which washed out corridors and large underground rooms which became the network of the Blue John Cavern.