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Stalagmites and Stalactites in Gough's cave
The Caves of the Mendip Hills are formed by the
particular geology of the Mendip Hills, with 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.[1]
Geology
The hills consist of anticlines of Carboniferous Limestone lying over Devonian Old Red
Sandstone. When a surface stream running down one of the
impermeable Sandstone peaks reaches the layer of 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, finding a more direct route, some
caves (or parts of caves) are left dry.[2]
There is 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 (which may be accessible by cave diving) often have a loop
formation caused by the water flowing down a bedding plane and then rising up a fracture
in the rock.[2]
Few caves on the Mendip Hills are more than 150 metres (492 ft) deep or a few
kilometers in length,[3] (with
some notable exceptions, such as Swildon's Hole which is over 9 kilometres (6 mi) long[4]), but a
number are complex with several levels of passages which have been
abandoned by the water, for example those around Cheddar.[5]
The catchment area of the Cheddar Yeo, which rises in Gough's
Cave, measures 54 km2 (20.8 sq mi). Dye
marking shows that some of the water travels underground for up to
10 miles (16 km), 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.[6]
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.[7][8]
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.[9][10]
A number of Mendip caves were found by miners, for example the
Banwell Caves which were opened by ochre miners in 1757.[6]
Access
The caves which are easily accessible to the public are at Cheddar Gorge and
Wookey Hole, 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.[11] 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 over 500.[12]
Cave
Diving
Attempts to move from one cave to another through the
underground rivers led to the development of cave diving, with Swildon's Hole
being the site of the first cave dive attempt in Britain, in 1934
and the first successful cave dive in Britain, being achieved the
following year at Wookey
Hole where the last sump is currently the deepest sump in
Britain at 76 m
(249 ft).
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. There are also caves within the Cheddar Complex
SSSI.
List of
caves
A selection of the better known caves are listed below
References
Bibliography
- Barrington, Nicholas; Stanton,
William (1977). Mendip: The Complete Caves and a View of the
Hills. Cheddar Valley P. ISBN
0950145920.
- Irwin, David John; Knibbs Anthony
J. (1999). Mendip Underground: A Cavers Guide. Bat
Products. ISBN
0953610306.
External
links
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