The caves of the Mendip Hills are formed by the particular geology of the

Mendip Hills The Mendip Hills (commonly called the Mendips) is a range of limestone hills to the south of Bristol and Bath in Somerset, England. Running from Weston-super-Mare and the Bristol Channel in the west to the Frome valley in the east, the hills ...

: large areas of limestone worn away by water makes it a national centre for

caving Caving – also known as spelunking in the United States and Canada and potholing in the United Kingdom and Ireland – is the recreational pastime of exploring wild cave systems (as distinguished from show caves). In contrast, speleology i ...

. The hills conceal the largest underground river system in Britain.

Geology

The hills consist of

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is t ...

s of Carboniferous Limestone lying over

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

Old Red Sandstone The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...

, 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", (also known locally as a "slocker"), 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 (or parts of caves) are left dry. Goughscave

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 A sump is a low space that collects often undesirable liquids such as water or chemicals. A sump can also be an infiltration basin used to manage surface runoff water and recharge underground aquifers. Sump can also refer to an area in a cave ...

" as the cave reaches and descends below the prevailing

water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...

. The passages below the water table (which may be accessible by cave diving) often have a loop formation caused by the water flowing down a

bedding plane In geology, a bed is a layer of sediment, sedimentary rock, or pyroclastic material "bounded above and below by more or less well-defined bedding surfaces".Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005. ''Glossary of Geology'' ...

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, (with some notable exceptions, such as

Swildon's Hole Swildon's Hole is an extensive cave in Priddy, Somerset. At in length, it is the longest cave on the Mendip Hills. It has been found to be connected to Priddy Green Sink and forms part of the Priddy Caves Site of Special Scientific Interest (SSS ...

which is over long), 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 The Cheddar Yeo is a small river in Somerset, England. Beneath the limestone of the Mendip Hills it forms the largest underground river system in Britain. After emerging into Cheddar Gorge it flows through the village of Cheddar, where it has be ...

, 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 Burrington Combe is a Carboniferous Limestone gorge near the village of Burrington, on the north side of the Mendip Hills Area of Outstanding Natural Beauty, in North Somerset, England. "Combe" or "coombe" is a word of Celtic origin found i ...

. 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 The Mesolithic ( Greek: μέσος, ''mesos'' 'middle' + λίθος, ''lithos'' 'stone') or Middle Stone Age is the Old World archaeological period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic is often used synonymo ...

Neolithic The Neolithic period, or New Stone Age, is an Old World archaeological period and the final division of the Stone Age. It saw the Neolithic Revolution, a wide-ranging set of developments that appear to have arisen independently in several pa ...

Bronze Age The Bronze Age is a historic period, lasting approximately from 3300 BC to 1200 BC, characterized by the use of bronze, the presence of writing in some areas, and other early features of urban civilization. The Bronze Age is the second pri ...

Iron Age The Iron Age is the final epoch of the three-age division of the prehistory and protohistory of humanity. It was preceded by the Stone Age ( Paleolithic, Mesolithic, Neolithic) and the Bronze Age ( Chalcolithic). The concept has been mostly ...

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 Ochre ( ; , ), or ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also the name of the colours produced ...

miners in 1757. Many caves in the Mendip area were photographed by caver Harry Savory early in the 20th century using huge

cameras A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

, 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 Herbert Ernest Balch (4 November 1869 – 27 May 1958) MA FSA was an English archaeologist, naturalist, caver and geologist who explored the caves of the Mendip Hills and pioneered many of the techniques used by modern cavers. Born in Wells, h ...

. The caves are recorded in the Mendip Cave Registry and Archive.

Access

The caves which are easily accessible to the public are at

Cheddar Gorge Cheddar Gorge is a limestone gorge in the Mendip Hills, near the village of Cheddar, Somerset, England. The gorge is the site of the Cheddar show caves, where Britain's oldest complete human skeleton, Cheddar Man, estimated to be 9,000 years ...

and

Wookey Hole Wookey Hole is a village in Somerset, England. It is the location of the Wookey Hole show caves. Location Wookey Hole is located in the civil parish of St Cuthbert Out, in Mendip District. It is one mile north-west of the city of Wells, and l ...

, but the vast majority of the caves require specialist equipment and knowledge. Many of the caves are gated and operate leader systems in an attempt to reduce the damage caused when the caves are visited. Local caving groups organise trips and continue to discover new caverns. Some estimates put the number of cavers active on the Mendip Hills over a busy weekend at more than 500.Irwin & Knibbs, ''Mendip Underground: A Cavers Guide''

Cave diving

Attempts made in the Mendip Hills to traverse from one cave to another through the underground rivers led to the development of

cave diving Cave-diving is underwater diving in water-filled caves. It may be done as an extreme sport, a way of exploring flooded caves for scientific investigation, or for the search for and recovery of divers or, as in the 2018 Thai cave rescue, other ...

; the first cave dive attempt in Britain took place at

in 1934. The first successful cave dive in Britain was achieved the following year at Wookey Hole Caves, where the last sump is currently the deepest in Britain at .

Sites of special scientific interest

The cave complexes at St. Dunstan's Well Catchment, Thrupe Lane Swallet, Lamb Leer and Priddy Caves have been identified as

geological Site of Special Scientific Interest A Site of Special Scientific Interest (SSSI) in Great Britain or an Area of Special Scientific Interest (ASSI) in the Isle of Man and Northern Ireland is a conservation designation denoting a protected area in the United Kingdom and Is ...

. There are also caves within the

Cheddar Complex The Cheddar Complex is a biological Site of Special Scientific Interest near Cheddar around the Cheddar Gorge and north east to Charterhouse in the Mendip Hills, Somerset, England, notified in 1952. The very large area includes 4 SSSIs fo ...

SSSI.

List of caves

A selection of the better known caves are listed below

References

Bibliography

* * *

External links

Mendip Cave Registry and Archive

Council of Southern Caving Clubs

* ttp://www.cerberusspeleo.org.uk Cerberus Spelaeological Society {{Mendip Hills

Caves, Mendip