4 minute read
Caving Phil Hendy
The search for further Mendip caves
CAVERS are often asked how many caves have yet to be discovered. Of course, we do not know. But our knowledge of Mendip and its geology gives us a fair idea of where we might find a new cave. The standard model gives us a stream sinking underground somewhere high on the hill and the water emerging lower down. Water-tracing experiments have proved most of the connections between sink and resurgence.
Possibly the first was the legal case of Hodgkinson of Wookey Hole Paper Mill versus Nicholas Ennor of St. Cuthbert’s Lead Works in 1863, when it was proved that pollution of the mill’s water was caused by discharges from the lead works via St. Cuthbert’s Swallet.
Cheddar Risings are fed by swallets on the south slope of Black Down, such as Manor Farm Swallet, Charterhouse Cave, G.B. Cave and Longwood Swallet. Although Swildon’s Hole was originally thought to flow to Cheddar, based on the westerly direction of the upper passages, it was later proved that this, and the other Priddy swallets feed Wookey Hole.
The longest water trace to Wookey comes from Wigmore Swallet at Red Quar. The water flows around the north side of North Hill, so was not captured by the Wookey drainage, as would have been expected. The Burrington swallets have been tested to Langford and Rickford Risings; some swallets feed both.
On eastern Mendip, St. Dunstan’s Well and Ashwick Grove Risings are major resurgences, fed by swallets along the north side of Beacon Hill.
Many of the swallets and the major resurgences are known caves, which have been, and are being, explored, with attempts to extend them. The dream would be to effect a passable route between them and a lot of effort has been put into trying to do just that.
Apart from extending known caves, cavers are on the look-out for anywhere on the surface that might lead to a route into the unknown central section of these stream passages. So far, no through trip is possible, although there are several good leads, all of which will require long-term digging.
An obvious starting point might be a depression, which could indicate either an abandoned sinkhole, or a collapsed cavern, with the subsidence gradually working its way to the surface. A good example of the former is Templeton Pot, while nearby the Cowshed Dig appears to be a collapsed rift in conglomerate.
A few years ago, digging in Reservoir Hole in Cheddar Gorge, led to the discovery of the vast Frozen Deep. At the bottom of this chamber, diggers found an active stream which is probably part of the main drainage or Master Cave between Black Down and Cheddar. Sadly, divers have found it to be too tight to explore, either up or downstream.
From time to time we examine the excellent geological maps produced by the British Geological Survey. Rock types and fault lines are shown, which can help in identifying likely digging spots, but apart from sparse data from mines, quarries and boreholes, the shown geology mainly relates to what is on the surface and we know that the rock strata largely dip towards the sides of the Hill and that faults are rarely vertical. So these maps must be interpreted very carefully.
So what other methods are available to the digger seeking to join up these known caves? We are all familiar with the use of “geofizz” as used by Time Team and other TV archaeologists. Various types of ground-penetrating energy have been used to try to locate caves, but with varying success. In 1938 Prof. Leo Palmer claimed to have located a large chamber near the Great Chamber in Lamb Leer, but attempts to dig into it have proved fruitless.
A more recent survey with modern equipment located Great Chamber, but not Palmer’s Chamber. We have used groundpenetrating radio for many years, mainly
With PHILIP HENDY for communication with the underground during rescues. It can also allow us to plot the course of caves on the surface. A few years ago we did this above Wigmore Hole at Red Quar and as a result diggers were able to locate and dig into the further reaches of the cave from a surface depression. This allowed non-divers to bypass the sumps and reach the end of the cave. We can, of course, hope for a winning throw of the dice from Lady Luck. Tractors have been known to cause the surface to collapse above a previously unknown void. Templeton Pot was found in this way, as was Star Shaft, a Cornish mineshaft. Quarrying can reveal caves, but they are, by the nature of their location, usually doomed to destruction. We are fortunate that most of the caves in Fairy Cave Quarry have been preserved. Apart from being beautifully decorated, they form a mid-section of the drainage between Beacon Hill and St. Dunstan’s Well. Mendip mining ceased many years ago, but this activity sometimes broke into caves. Lamb Leer Cavern is the most famous example of this, but mining led to the discovery of Banwell Bone and Stalactite Caves, while ochre miners discovered caves on Axbridge Hill. Dowsers claim to have located caves and there is some justifying evidence although with little in the way of end results. Just occasionally, nature helps us, as heavy rain or snowfall can cause the sudden opening of a hitherto unsuspected cave opening. Although we do not know how many Mendip caves have yet to be found, the search for them, and the elusive through routes from sink to resurgence seem as remote as ever. We will never find every last cave on Mendip, but we are certainly having a lot of fun trying.
