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.
Geology
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",, continuing on its way down towards sea level by enlarging existing cracks in the rock to form caves, and reappearing at the base of the limestone outcrop. As the water changes route within the hill some caves are left dry.There is a characteristic type of Mendip cave, in which there is an initially steep descent, and then a more level stretch ending in a "sump" as the cave reaches and descends below the prevailing water table. The passages below the water table often have a loop formation caused by the water flowing down a bedding plane and then rising up a fracture in the rock. Few caves on the Mendip Hills are more than deep or a few kilometres in length,, 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.
History
When Banwell Bone Cave was discovered in 1824, it was found to contain a great many animal bones which have been dated as about 80,000 years old.The earliest scientifically dated human cemetery in Britain was found at Aveline's Hole, in Burrington Combe. The human bone fragments it contained, from about 21 different individuals, are thought to be between roughly 10,200 and 10,400 years old.
Archaeological evidence including pottery, flints, hearths, coins, burials and metalwork from the Mesolithic, Neolithic, Bronze Age, Iron Age and Roman eras have been found in many of the caves.
A number of Mendip caves were found by miners, for example the Banwell Caves which were opened by ochre miners in 1757.
Many caves in the Mendip area were photographed by caver Harry Savory early in the 20th century using huge cameras, glass plates and flash powder. His work has been described as "...of a quality to shame virtually all modern cave photographers". The 1990 book A Man Deep in Mendip: The Caving Diaries of Harry Savory, 1910-1921 provides a diary made by Harry Savory, explained and extended by his son John.
A number of important cave excavations and explorations were undertaken, from the 1920s onwards, by pioneer caver Herbert E. Balch. The caves are recorded in the Mendip Cave Registry and Archive.