Cheddar Gorge & the Mendip caves

Cheddar Gorge cuts 137 metres into the southern edge of the Mendip Hills in Somerset, and the show caves in its walls produced the oldest complete human skeleton found in Britain. Cheddar Man, roughly 9,000 years old, was found in 1903, and older remains from the Upper Late Palaeolithic, 12,000 to 13,000 years back, have come out of the same complex.

The caves were cut by an underground river and hold the usual stalactites and stalagmites. The gorge above them is a Site of Special Scientific Interest, the Cheddar Complex.

The rock is Carboniferous Limestone: Black Rock slate, Burrington Oolite and Clifton Down Limestone, full of ooliths and fossil debris, sitting on Old Red Sandstone and Keuper dolomitic conglomerate. Sheared rock and cleaved shales record the Variscan orogeny, the continental collision that crumpled this part of Europe.

The gorge itself began forming about 1.2 million years ago, during the Pleistocene, when the Mendip limestone stood as a line of whaleback hills. In limestone country water normally vanishes underground rather than running across it, so gorges are not what you expect. The answer is ice: during the glacial periods permafrost plugged the caves with ice and frozen mud, which made the limestone impermeable. When that melted each summer the water had nowhere to go but over the surface, and it cut down through the softer rock instead of sinking into it.

The gorge has no river of its own today. The underground Cheddar Yeo emerges in the lower part of it, out of Gough's Cave.

It draws around 500,000 visitors a year. In a 2005 Radio Times poll after the programme Seven Natural Wonders, it was voted the second greatest natural wonder in Britain, behind only the Dan yr Ogof caves. Two show caves are open, the extensive Gough's Cave and the smaller Cox's Cave, each named after the man who found it, along with a clifftop walk around the rim.