Cambridge Underground 1977 pp 16-27


Introduction and Previous Exploration

Black Keld is the larger of the two main risings for the caves of East Wharfedale and is situated at NGR SD 974.710 about one mile to the south of the village of Kettlewell. To the casual observer it consists simply of a pool at the foot of a steep bank and small scar face from which a sizeable stream emerges. In normal weather conditions the flow is between 0.075 cubic metres per second and 0.150 cubic metres per second (1000 to 2000 gallons per minute), but this can easily double after heavy rain.

The catchment area of this resurgence is enormous. To the north, the stream sinking at Fog Cave and finally disappearing at Rain Pot is the limit of the watershed whilst to the south the dividing line between Black Keld and the Linton Low Mill rising is uncertain. The syphon passage of Mossdale Caverns and the stream sink at Gill House Pot are the southernmost feeds which have been definitely proved to flow to Black Keld. The destination of the water which disappears at Stream End Cave in Mossdale is uncertain. A similar uncertainty exists for the water sinking at Black Edge Pot and also for that at How Gill Nick where 5lbs of flourescein failed to appear anywhere in detectable concentrations! A small stream sinking below the old smelter at Grassington Moor has been positively shown to resurge at Low Mill so the dividing line must be somewhere between Gill House and the track from Yrnbury up to the old lead mines.

Already the Black Keld system is one of the country's major systems, which is all the more remarkable when it is noted that the main caves associated with the system are all formed entirely in the Yoredale Limestones. The present limits of exploration are some 600 feet above the resurgence and consist of boulder chokes or perched sumps which have so far proved to be impenetrable. Over 12 miles of passage have so far been explored and without doubt much more remains to be discovered.

At the entrance to the Black Keld resurgence there are no passages accessible to the non-diver, but in the pool, below a small thorn bush at the centre of the scar face, a slope down over boulders through a smallish opening allows divers to enter a large submerged bedding passage. Above water level there are several impenetrable beddings from which glooping sounds emerge when divers enter the resurgence. The first explorations at Black Keld took place on 1st and 2nd October 1949 when the divers were Davies, Davis and Thompson of the Derbyshire section of the CDG, together with Balcomb and Coase. They set out at the invitation of J. 0. Myers and the Northern Pennine Club, to ascertain whether it would be worth digging at the resurgence to gain access to dry caves. Their findings are reported in references (1) which are identical and include a sketch survey. The events have proved this to be a much simplified picture but it nevertheless represents a remarkable achievement considering the equipment available then to cave divers. Their conclusion that digging into dry cave passage from the resurgence would be impossible has, to date, stood the test of time.

Basically their findings consisted of 110 feet of underwater passage to an airbell, from which an underwater continuation was followed for 50 feet to a submerged 'pot' 17 feet deep. The floor of the pot was found to be 28 feet below the local water table. Here a tight slot with a strong current emerging was found to lead on downwards but it was quite clearly out of the question to attempt this using oxygen (the depth limit for re-breather apparatus is 30 to 35 feet due to the danger of oxygen poisoning). At the airbell a bedding plane was noticed but they don't seem to have explored it, quite possibly because getting out of the water here is rather difficult due to the depth and the sharp undercut.

Diving was resumed at Black Keld on 3rd August 1970, nearly 21 years after the initial exploratilns, when M. J. Wooding reported (2) that he had passed the slot at the bottom of the flooded pot found by Davies but had unfortunately lost the way shortly beyond due to poor visibility. On 5th May 1974 Alf Latham and Geoff Yeadon (3) failed to find the flooded pot but did locate an area of 'interleaved flakes' in which sense of direction and visibility were lost. Two dives were reported by L. Radcliffe in October 1973 and on 4th August 1974 (4). On the first of these he discovered a six foot 'submerged hole' with a bedding at the bottom in which a current was felt, but unfortunately he was unable to find this again on his second dive. It could be that the submerged hole and Davies' flooded pot are one and the same.

The Cambridge Explorations

The explorations described in this article began on 5th July 1975 (5) when Rob Shackleton made his debut dive into the resurgence. This was intended as a recce dive so the existing line was followed to an airbell, presumably the one found by Davies, which was subseqently named Lake I for reference sake. From here a line was found to continue to the left for 50 feet to a point at which it was tied off in the floor. A line reel was attached here and a search of the surrounding area revealed no way on to the right hand side and a confusion of fallen boulders straight ahead. On the way back the bedding plane leading off the airbell recorded, but not entered, by Davies was noticed. Compass bearings taken at that point indicated that it did not head back towards the entrance as had been thought but led off almost due north.

On the basis of the findings of the initial dive it was decided to scrap the idea of following the right hand wall and to try the left hand wall instead. On 3rd August 1975 (5) 160 feet of heavy Ulstron line was laid along the left hand wall to a point at which the solid wall gave way to a complicated area of fallen boulders very similar to the one entered from the right on the first dive. The heavy line was belayed off and a reel of 550 feet of light exploratory line was attached. Keeping as far to the left as possible the area of boulders was entered and 200 feet of line was reeled out through a series of squeezes, flooded pots, and ascents amongst the chaos of boulder obstacles. The compass bearing followed was 100 degrees although a subsequent survey has shown that the diver must have wandered quite significantly from this direction. At the furthest point the bearing of 100 degrees was lost as no way on could be found to the left, and so the line was tied off.

The next dive, on 9th August 1975 (5) proved to be quite a significant one. An opening on the left in the boulders about 20 feet from the end of the line laid on the previous dive, provided access via a couple of awkward sections to a large silt floored bedding at 30 feet depth. Unfortunately the way on along 100 degrees closed down to nothing after only a further 150 feet with no negotiable way on to either side at the end point. Disappointing though this was, the boulder area had at last been penetrated after some two and a half hours of underwater searching. On 10th August 1975 (5) a second attempt was made to find a way on in the flooded bedding plane but no route could be found along the left hand wall.

During the next week the weather broke and there was a heavy storm on Thursday 14th August continuing on the Friday. The effects were dramatic. By Saturday 16th the resurgence had risen by several feet and it had begun to disgorge vast quantities of heavily silted water making a dive impossible. By 23rd August the water level had subsided somewhat allowing a dive (5) to check the lines through the boulder area and to see whether there would be any hope of trying to push on in the reduced visibility. The lines were found to be still in position but the conditions were too poor to consider trying to explore further. On 24th August (5) it was decided to try a search of the roof above the line in the final bedding beyond the boulders to see if any airspace could be found. The area above the first 50 feet of line beyond the boulders was searched but no way upwards was found and due to the very poor visibility conditions the dive had to be abandoned. The following day RJS, discouraged by the poor visibility on the main route decided to go to the 1949 airbell to have a look at the dry outlets. The bedding plane recorded by Davies was entered after an ungainly struggle to get out of the deep water. This proved to be most surprising and very interesting as over 100 feet of pleasant hands and knees crawling passage was explored to a pool at a cross joint from which two ways on were noted. The first was a low bedding to the left and the second a flat out crawl in mud and water to the right hand side. The latter was explored for 50 feet before the diver decided to turn back without having pushed it to a definite conclusion.

The resurgence was next visited on 12th October (6). The visibility was still poor but it was decided that conditions had improved significantly enough to allow a search at the farthest reaches of the bedding plane beyond the boulder area. Both the northern and southern limits of the bedding plane were examined but no way on could be found. It was becoming apparent that horizontal progress in the far bedding would not be easy to come by and so on October 18th (6) the search of the roof above the bedding was resumed. It was decided to repeat the area searched on 24th August because of the appalling conditions under which that work had been done. This proved to be a wise decision as about 40 feet beyond the end of the boulder area a shaft in the roof, which must have been missed on the previous search, was discovered. Ascending 15 feet a small airbell was reached and a duck was found to lead off this into a large lake chamber some 30 feet long, 20 feet wide and 15 feet high with a small patch of 'dry land' in the centre. To the south of the chamber a scramble onto a shelf above water level was found to lead to a series of small overflow passages with low bedding planes leading on. At this point the explorer returned to the lake, eager to push on below the water level. Hopes for easy progress were soon dashed, however, when the diver reached a second boulder area after only 30 feet of underwater passage. Unsure as to whether the correct route onwards had been chosen, a suitable place to tie off was found and a retreat to base was made. The lake was named Lake II.

Returning the next day a more careful search of all the submerged beddings around Lake II was made (6) but the second boulder area was found to be even more complicated and tortuous than the first, and no further progress could be made under the prevailing water conditions.

The visibility in the resurgence remained very poor for several months during the winter of 1975-76 and it was not until 24th April 1976 (7) that RJS was able to return to the site to check the lines and attempt to push on beyond Lake II. The line through the duck into Lake II had frayed and broken but all the other lines although wearing thin in places seemed to be intact. Beyond Lake II 30 feet of new line was laid into the boulder area and a squeeze over a boulder was passed to yield only 10 feet more fumbling progress to a second squeeze which could not be passed with twin 40's. Unsure even as to whether he could reverse the first squeeze without dekitting, the diver decided to tie off and devote his energies to getting back safely. On 12th June (8), using a single 40 beyond Lake II, RJS passed the second squeeze but unfortunately found a complete boulder choke only a few feet beyond it. Several rather ridiculous possibilities were looked at all of which would have necessitated hand held kit. One consolation was the fact that the boulders seemed reasonably stable but the diver decided that it would be unwise to push his luck any further.

During the following few months significant new discoveries were made in Birk's Wood Cave at Buckden, and in the Ribblehead Area, which meant that Black Keld, of necessity, was forced into the background. One important consequence of the discoveries at Birks Wood Cave, however, was that Julian Griffiths was talked into doing some support diving. This he took to very rapidly, and, since there remained a few odds and ends of dry passage to sort out at Lake I in Black Keld, it seemed to be a good idea to combine some diving training with the necessary 'filling in' work. This was started on 11th July 1976 (8) when the crawl partially explored by RJS on 25th August 1975 was forced by JTG to a stal blockage 240 feet from Lake I. The passage was surveyed to grade III on the way out. Due to other commitments further progress had to wait until 14th November (9) when RJS hammered a way past the blockage, and together with JTG explored a further 350 feet of passage to a low bedding plane. The next weekend (9) this was followed up by the discovery of a bedding plane leading onwards above and to the right of the previous limit. This led to 140 feet of passage finally linking to the low bedding planes found by RJS at Lake II on 18th October 1975. These discoveries were surveyed on 12th December 1976 and were found to be 100 feet in length with some 100 feet of extra inlets and grovels none of which revealed any further significant discoveries. On 16th January 1977 JTG managed to link the 'low bedding to the left' noticed by RJS on 25th August 1975, with the beddings beyond the former stal blockage thus providing a second overland route to Lake II. RJS in the meanwhile laid a new heavy line through the underwater route to Lake II removing most of the confusing maze of thin exploratory lines in the process.

Details of the Extensions

(i)The Underwater Passages:

Passages below the water surface in Black Keld can only be described in broad terms as the visibility is never good enough for the diver to gain much more than vague impressions of the passage character. Therefore the line layout is described in some detail and only general comments are made as to the type of passage and grade of the route.

From the entrance, a thick Ulstron line leads into the submerged passage down a boulder slope through a smallish opening beneath the little scar face. At the bottom of the slope the line is belayed back and a blue line leads off from the Ulstron. This is the short route to Lake I and is an easy dive of 110 feet along the right hand wall passing a belay point at 50 feet. The Ulstron continues close to the left hand wall from the first belay point past a belay point on the left after 100 feet to a tie off in the left hand wall above a short drop in floor level forming a shallow flooded 'pot'. From this point two lines lead off. The red line (Crossover Line) leads back to Lake I after 60 feet of easy finning, whilst the blue line leading on is the through route to Lake II. The whole of the Crossover/Ulstron/Lake I triangle is in a large silt floored bedding type passage some 10 feet high in which diving is easy if a little murky. The Lake II line is an altogether more serious proposition. Beyond the Ulstron tie-off point lies some 200 feet of line passing through a chaos of fallen boulders, flooded 'pots', and bedding planes, to reach a second silt floored bedding passage similar to the one immediately inside the entrance. Lake II is reached via an ascent in a flooded shaft at the start of this bedding reaching a small airbell from which a duck leads forward to the main lake chamber. Much of the submerged area around and below the second lake remains to be adequately examined.

75 dpi survey - 11k gif

(ii) The 'Dry' Passages

The dry passages are best entered via Lake I where a scramble out of deep water gives access to the start of a hands and knees crawl in a passage some 10 feet wide and 3 feet high. This easy going continues for about 100 feet to a waist deep pool at a strong cross joint where two ways lead off. To the left is a low bedding plane but the more obvious way is a flat out crawl to the right. This continues for 100 feet through a series of revolting low muddy pools to a sharp turn to the left and low thrutch into a further muddy pool, with a squeeze halfway along it. A bend to the right and a second squeeze gives access to a small chamber with two upper passages both of which close down. At floor level a continuation of the flat out crawl leads over gours to an area of pools with very low airspace, best negotiated with one's nose in the roof. After 50 feet of wallowing a roof tube can be entered and a short crawl leads forward to a sudden enlargement at Stretch Cavern. To the right a section of stooped walking leads to a drop down to the left into a static sump of small dimensions. To the left walking passage leads to a descent over boulders back to the level of the pools again, whilst at roof level above the descent a small bedding gives access via an extremely tight squeeze to a small chamber and connection with Lake II. At the foot of the descent a tight duck gives access to a large and confusing bedding plane. Several routes to the left lead back towards the low bedding at the cross joint, some becoming too low, but at least one can be forced by the persistent explorer. The main route is to the right to a pool at a cross joint. From here a route to the right leads to a thrutch up into a higher bedding plane and a series of small chambers connected by low sandy crawls. The connection back to Stretch Cavern lies via a small tube to the right but the main way turns left and enlarges to emerge near roof level in the large chamber at Lake II. In all there are some 800 feet of dry passage.

Some Speculations on the Hydrology

Over most of the catchment area of Black Keld the limestone bench dips gently to the south east and so it is not greatly surprising that the passages explored from moor level trend directly away from the rising. The entrance to Langcliffe Pot is about one and a half miles from Black Keld and the main stream sump, Poseidon Sump, is some two and a quarter miles distant. Syphon Passage of Mossdale Caverns is over two and a half miles south east of the resurgence and is perched some 700 feet above it.

Theories conflict over the type of route which the water follows between the present limits of exploration at both ends of the system. The ideas behind the theories fall into main categories, which effectively demark the theories into two groups. For reference the two groups will be called the 'bedding control' theories, and the 'fault control' theories. Since the rock dips away from the resurgence the passages leading down to it cannot follow the normal type of development seen in such places as West Kingsdale or Leck Fell for instance. In these areas the active streamways, with four exceptions, meander steadily down dip flowing on or just above bands of impermeable shale or downcutting slowly through beds of harder limestone. Pitches are generally formed where the streams penetrate these obstacles to reach softer strata where they plunge rapidly to the next obstruction to their downward path. Streamways of this type in Eastern Wharfedale must therefore follow the dip and flow away from Black Keld. All the theories must account for the fact that the water somehow manages to flow up dip from the known feeders to the rising. In essence the 'bedding control' theories use this argument - as soon as the feeder streams hit the main limestones their development becomes largely vertical with only short lengths of classic stream passage between the pitches. The bottom of the caves would be reached at a deep sump at or just above the resurgence level which would probably be at the most remote point in the system from the rising. The lynch pin of the theories is that the flow to the resurgence is phreatic and thus doesn't mind flowing up dip. The rule for phreatic flow is that the water takes the path of least resistance and ignores other considerations. The configuration of the sumped passages could take the form of deep flooded pots followed by passages flowing up along the bedding to near water surface level before penetrating to lower beddings at subsequent flooded pots. Flow of this nature has been discovered recently at Wookey, but the dip at wookey is much greater than in East Wharfedale so Black Keld might not reach quite such a large underwater depth. A dip of 2.5 degrees drops one foot in 23 feet and so it would take a 690 foot sump to reach surface level from a depth of 30 feet.

The 'fault control' theories, on the other hand, suggest that the flow back up dip to the resurgence occurs along faults, large joints or lines of weakness, which have the same effect as the phreatic zone in the 'bedding control' theories in that the flow direction ceases to be controlled by the dip. The cave beyond Syphon Passage in Mossdale could drop down a few pitches and eventually hit a fault or series of faults which would take the flow back towards Black Keld until a sump is met, the proximity of which to the rising is roughly in proportion to the optimism of the theorist!!

In support of the 'fault control' theories is the existance of plenty of nice faults going in the right direction and in the right places to carry the flow. The Dowber Gill Passage of Dow Cave provides a good example of the fault control required to the north, and further examples are not too far away at Birks Fell Cave and Birks Wood Cave at Buckden. None of these examples are strictly speaking the same, as the water does not flow up dip although the dip can by no means be said to control the flow. In Langcliffe Pot, and to some extent in Mossdale, one is struck by the linearity of the passages indicating strong jointing in ther area. This is most significant below the Dirt Pot Grit band in Langcliffe as the Hardraw Limestone is at this point continuously bedded with the Great Scar Limestones although the cave most probably does not penetrate below the bottom of the Hardraw.

In favour of the 'bedding control' theories is the fact that the resurgence level rises within two days of floods on the moor above whilst the famous dye test carried out by J.O. Myers showed the water sinking in Syphon Passage of Mossdale Caverns to take eighteen days to reach Black Keld. The reason for this support of the theory is that a flood pulse is transmitted very quickly (in fact at the speed of sound) through a single long phreatic zone (which can be thought of as a U tube with its arms very far apart), whereas the flood pulse wave has physically to flow along active streamways which takes much longer, depending on the depth of water. Taking these facts into account it could thus be argued that the evidence provided by the dye test shows the flood pulse to take only two days to reach the phreatic zone and then sixteen more to get through the phreatic zone to the rising. This argument can be seen to strongly favour theories postulating a long phreatic zone.

Pursuing this line of reasoning a little further however, it becomes apparent that the above conclusion might not necessarily be correct because it must be noted that the feeders Rigg Pot and Rain Pot are much closer to Black Keld than is Syphon Passage. It is thus more likely that these feeders will cause a rise in resurgence level well before the Mossdale water could. A telling point to note here is that very shortly after the resurgence level rises during flood it begins to discharge very muddy water indicating that the actual flood water from somewhere quite close is beginning to emerge. However, there seems to be no observational evidence for more than one flood pulse coming through, which might be expected if the Mossdale Water reaches the phreas later than the flood pulses from closer sources. It must be remembered that Mossdale provides nearly half the water seen at Black Keld.

Several lines of reasoning can be made to account for the fact that muddy water emerges from the rising shortly after floods, without necessarily invoking the presence of water from closer feeders than Mossdale. From the above mentioned dye test it would be expected that the Mossdale mud might take eighteen days to reach the rising as did the flourescein. It may seem to be a contradiction but this might not be true. The increase in flow velocities in the phreatic zone caused by the flood pulse at Mossdale might actually re-entrain deposits of mud from sections of passage much nearer the resurgence. This is not impossible, but it must be remembered that deposition and re-entrainment of particles in a flow involves a considerable velocity hysteresis. In other words if the flow velocity falls to say 1cm per second, particles of a certain size will be deposited from the flow, but the flow might only pick them up again if its velocity rises to say 10cm per second. Experiments show that this effect becomes more significant the smaller the particles so that for exceedingly small particles of mud we may be talking of a hysteresis factor of 100. In normal flow conditions the large particles are deposited first and so only the small particles are carried very far into the phreatic zone. When it is noted that we are talking of a postulated zone which must be at least 3 miles long and most likely a good deal longer it can be seen that the particles available close to the rising for re-entrainment by the Mossdale Stream flood pulse are going to be very small. Can we have floods in which the increase in flow is a factor of 100 times? At Mossdale this might well be a possibility, so although the re-entrainment explanation is unlikely on fluid mechanic ground, it is not out of the question.

A second possible argument to explain the fact that the flood waters at Black Keld become muddy within two days of heavy rain involves the existence of overflow passages above the long gently dipping sumps. In high water conditions the submerged passages are unable to cope with the increased flow and so mud-ladened water cascades quickly through the higher level routes, effectively short circuiting the long phreatic route. This, as with the re-entrainment explanation, is unlikely though not impossible. In Black Keld we have found over 700 feet of overflow passages in which there is evidence of quite frequent flooding. There is no reason why the overflow passages should not be a general feature of the postulated lengthy sumps, but there seems to be no evidence in the overflow passages so far discovered that the flow through them is substantially faster than that in the active phreas below. Further away from the resurgence, under the hillside, this finding may not turn out to be the general case, but one suspects that the overflow passages, if they exist, will suffer from the same problems of sluggish up dip flow as do the active levels.

It can be appreciated from this brief discussion that neither of the two basic schemes is definitely ruled out by the available evidence. However, with most situations in which for good reason a polarisation of opinion occurs, the truth is eventually found to consist of some mixture of the extreme views in greater or lesser proportion. It is quite probable therefore that a 'master cave' of sorts is there for the finding.

Rob Shackleton


1 CDG Report No. 2 1949
Cave Science No. 13 1950
2 CDG Newsletter 17 p 10
3 CDG Newsletter 32 p 13
4 CDG Newsletter 33 p l0
6 CDG Newsletter 38 pp 11-12
7 CDG Newsletter 40 p 15
8 CDG Newsletter 41 p 11
9 CDG Newsletter 42 p 11

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