The Caves And Pot-Holes Of Yorkshire

By S.W. Cuttriss

Among the many interesting features of England’s greatest county, the numerous caves and allied physical phenomena contained within its boundaries form by no means the least important of its characteristics. In no other part of Great Britain, except the adjoining county of Derbyshire, which partakes of the same geological formation, is the rock structure so favourable to their formation.

Within the last few years the sport of cave-hunting, as distinguished from the strictly scientific work of exploration, has received a large addition to its votaries, but while the former may appeal more strongly to the majority of our readers, the opportunity thus afforded for increasing the sum of our knowledge of this feature of Nature’s handiwork should not be lost. The study of the formation, characteristics, and relations the caves bear to the topography of the country is one well worthy of close attention, and it is here proposed to briefly outline a few general conclusions resulting from work already accomplished.

The excavations caused by the action of the sea on the chalk cliffs of Flamborough, though interesting as examples of the mechanical erosion of rocks by water, form a class distinct from the caves of the interior, and may here be neglected. The Oolitic Limestones lying to the north of the Vale of Pickering contain a few small caves and underground watercourses, but so far as is at present known they are of no great interest if we except the Kirkdale Cave, made famous by the investigations of Dr. Buckland in the early part of the present century, and which gave occasion to the publication of his “Reliquia Diluvianae.” ^[1] It is in the hills to the west of the great central plain, where the Carboniferous Limestones and mountainous character of the country make it particularly suited to the formation of caverns and underground watercourses, that the largest number and finest examples are found.

The base of the hills forming the Pennine Chain – the backbone of England – is composed of the Silurian slates and grits, the oldest rocks in Yorkshire. Upon them has been deposited a mass of limestone, the Carboniferous, Mountain, or Scar Limestone, as it is variously called. This limestone consists of a hard, compact series of calcareous beds, mostly of a light grey or bluish colour. On Gragreth, Whernside, Ingleborough, and Pen-y-Ghent it attains a thickness of about 500 feet from the base to the exposed surface, where the pot-holes are situated. Above this are a series of shales, limestones, and sandstones, collectively named by Professor Phillips the “Yoredales,” from the valley of that name, where they attain their greatest development. On the top of the Yoredales lies the Millstone Grit, which merely forms a cap on the mountains named. The direction of the dip of the rocks is towards the north-east, the effect being to bury the limestones far below the surface in the neighbourhood of the central plain, but in the west the valleys have penetrated the entire series, exposing the foundation rocks in several places. On Leck Fells the Carboniferous Limestone has been cut off by a geological fault, known as the Dent Fault, running in a direction north and south. ^[2] The southern extension of the limestone is bounded by the Craven Faults, which run in an easterly direction from Ingleton. So far, therefore, the limestone area is clearly defined, but towards the north and east it becomes gradually obscured by the overlying strata. It will serve our present purpose, however, to make an arbitrary boundary extending from the Leck Fells, round the Kingsdale Valley, up Chapel-le-dale to the head of Ribblesdale, then down the east side of that valley, skirting Cam Fell and Pen-y-ghent, and across to Malham, where it meets the Mid Craven Fault.

The whole of the limestone area in which the caves are found may be divided into three distinct sections, each having their own characteristics:-

I.-The Yoredales, including the rocks of that formation.

ll.-The Southern Carboniferous or Craven Section, including the Carboniferous Limestone lying between the North and Mid Craven Faults.

lll.-The Main Carboniferous Limestone Section, comprising the remainder of the out-crop included within the imaginary boundary defined.

The reason why caves and underground watercourses are formed in limestone may be stated in a few words. The essential constituent of the rock is carbonate of lime, with which is associated in mechanical admixture more or less of earthy impurities. The carbonate is capable of being dissolved slightly in water charged with carbonic acid gas. As rain is precipitated from the clouds it absorbs a small amount of this gas from the atmosphere, and gathers still more from decomposing vegetation in the ground. Finding its way into the cracks and fissures of the rock, the water carries off a portion as bicarbonate of lime. The cracks may at first be very minute, but particle by particle the rock is eaten away, a definite line of drainage is created, and ultimately an extensive system of underground watercourses and reservoirs formed. The mechanical effect of the running water, assisted by sand and stones carried with it, adds its erosive action to the chemical solution, and the channels more rapidly increase in size. In process of time the passages and caverns may become too large to be self-supporting, the roof falls in, and a rugged gorge is formed which atmospheric agencies ultimately convert into an open valley. 

As the water oozes out upon the roof or sides of the subterranean cavities evaporation takes place, and solid carbonate of lime is deposited on the exposed surface. Inequalities in the roof lead the trickling water to definite points, where it drops off; the calcareous deposits at these places gradually increase in size and stalactites are formed, often of exquisite beauty and delicacy of form. Some are in the shape of long, thin tubes, full of water, which break off with the slightest touch. Others form solid, tapering masses like petrified icicles, hanging in clusters from the roof; or they may take the shape of beautiful folded curtains. When pure they are semi-transparent, like the finest porcelain, and give a clear metallic ring when gently struck. Usually the deeper the cavern from the surface, the purer the stalactites. Where the drops of water touch the floor further deposits take place, which grow upwards as stalagmites. These often exhibit inequalities of thickness and scattered rising bosses, owing to the more frequent dripping at some places than at others. Sometimes both stalactite and stalagmite unite, forming a solid pillar. Again, the walls and floor may be entirely coated with a smooth, calcareous deposit, having the appearance of ice. The rate of deposition is very irregular. It grows here, stops growing there; is laid on thickly in one place favourable for its rapid precipitation, while it takes ages to form a thin film in an adjoining chamber. After a stream has flowed along a passage for some time it may find a lower level, the old course is deserted and a new one formed. In these dry passages the deposition of lime is more rapid, ^[3] and it is in the darkness and solitude of such lonely recesses the explorer usually finds most of beauty, a charm intensified by the novelty and weirdness of his surroundings.

As a general explanation of the formation of caves, solution of the limestone by water charged with carbonic acid gas is indisputable, but that alone hardly seems sufficient to account for the huge caverns frequently met with. Here local influences must have been at work, not only determining the situation, but actually performing part of the work of production. What those influences were is not an easy matter to determine, and must always remain largely a matter of conjecture.

I.-Caves of the Yoredales.

Turning to a consideration of the caves themselves, and following the classification already defined, the first to be noticed are those found in the limestones of the Yoredale formation. Towards the west the strata are comparatively thin, being intercalated with beds of shale and sandstone, which, being unaffected by water, prevent the formation of high passages and caverns in the limestone. Being small and encumbered with accumulations of fallen rock and dirt, they do not offer much sport to the cave-hunter, nor do they materially affect the general drainage of the ground. Travelling eastwards the limestones increase in thickness and hardness, and contain many caves of considerable dimensions and extent, notably in Upper Nidderdale and Wharfedale, with their tributary valleys. Several of these have been found to contain remains of species of animals long since extinct in this country, also relics of early man, and this district can be recommended as likely to yield still further discoveries of a similar nature to the painstaking investigator.

II.-Caves of the Southern Carboniferous or Craven Section.

Although geologically all the rocks named which lie above the Silurians are included in the Carboniferous Period, it is convenient for our purpose to give the distinctive title of Carboniferous Limestone only to the great mass of rock forming the basement bed underlying the Yoredales.

The district included in this section is that lying between the North and Mid Craven Faults. From Ingleton the main line of fault runs through Clapham

and Austwick to Settle, forming the bold escarpment of the Giggleswick Scars. Thence it continues in a due easterly direction by the Attermire Scars, through Malham and across Wharfedale to Nidderdale. North of this main line of dislocation is another fault, close to the one just named at Austwick, and continuing eastward in a fairly straight line, about 11/4 miles separating the two at Malham. The area enclosed is in the form of a long triangular strip, 10 miles from west to east, and 21/2 miles from north to south at Settle, its broadest part. Lithologically the limestone is the same as that north of the fault, yet the caves contained in the two areas are entirely distinct. Briefly, the characteristics of those in this section are the absence of running water and the choking up of the entrances to the caves with clay, &c., together with rock debris from the overhanging cliffs. The scars principally face the south and west, and the direction of the rock drainage above the Attermire and Langcliffe Scars is towards the northeast, being in the direction of the dip of the strata. During the Glacial Epoch the country was overridden by ice, which flowed down the Ribble valley, and there is strong evidence that this was the principal agent at work in closing the mouths of the numerous caves in the faces of the scars. From a sporting point of view these caves are disappointing, but as a field for the study of cave deposits the district is superior to the Yoredales. The well-known Victoria Cave has yielded a store of archaeological remains unequalled by any in the country, and there are many other caves still awaiting careful examination.

The absence of running water in these caves is accounted for by the present configuration of the ground. When they were in process of formation the limestone in all probability lay partially covered by the Yoredale strata draining towards the south and west; the caves would then form the drainage channels. At the present day none of this higher ground remains, the limestone being quite exposed on the surface, or bearing only a thin covering of drift, and the drainage now follows the dip of the rock. A further marked characteristic of this section is the entire absence of pot-holes. A pot-hole differs from a cave, in the usual acceptation of the word, in the fact of its being a more or less vertical pit or chasm, down which a stream of water plunges, often to an enormous depth. ^[4] Bearing in mind that here the limestone does not receive drainage from higher ground, the one agent necessary to the formation of pot-holes is absent, viz., a more or less perennial stream. The rain and surface moisture at once sinks underground, without collecting in surface streams. For this reason pot-holes need never be expected where limestone now forms the highest ground.

III.-Caves of the Main Carboniferous Limestone Section.

As a field for studying the action of water on limestone, and the effect of the resulting underground watercourses on the general drainage of the district, this section is by far the most interesting. The area includes the whole of the Carboniferous Limestone outcrop contained within a boundary roughly determined by the Leck Fells, Kingsdale, Chapel-le-dale, and Ribblesdale, its southern extension being limited by the North Craven Fault.

The contrast between the caves of this and the previous division, as already mentioned, is very marked. In the former there is not a known accessible cave which has a stream flowing through it, and they are all more or less choked with drift and other deposits. In this section the reverse is the case; the writer is not aware of a single example which is not at present an active drainage channel. ^[5] Some have dry passages, resulting from the water finding a lower level, but all in some part of their ramifications have water flowing through them. Another distinction is the abundance of pot-holes present. Here no hard and fast line can be drawn between the two classes of phenomena of caves and pot-holes. The latter frequently have caverns and passages at the bottom, while the former occasionally include pot-holes in some part of their course. The caves may be divided into two classes – Caves of Engulfment and Caves of Debouchure. In the Leck Fell and Kingsdale districts they are almost entirely of the first-named variety, while in Chapel-le-dale and Ribblesdale the principal ones are Caves of Debouchure.

Caves of Engulfment – those which receive water are usually low and encumbered with loose stones, entrance being only possible in many cases by creeping. The passage generally increases in height to 20 feet or more, but rarely exceeds six feet in width. When they expand sufficiently to be dignified by the title of a chamber or cavern, either a present or past waterfall is always associated with them. They usually terminate, so far as it is possible to explore them, in one of three ways. Either a deep pool with smooth vertical walls converging to a fissure perhaps only a few inches wide, or, if the passage is in the direction of the dip of the rock, it will broaden out and the flat roof descend to the surface of the water, or close to the stones choking the channel, or thirdly by terminating abruptly in the side of a pot-hole. When a passage becomes blocked by the lowering of the roof and accumulation of stones, the channel is passing from one bed of rock to a lower, and when an opening can be cleared sufficiently large to squeeze through, the obstruction will be found to continue only for a short distance, after which the passage will gradually open out again. These obstructions usually occur near the top of the limestone, where the beds are thinner. Great care is necessary in exploring Caves of Engulfment, owing to the possibility of a sudden rush of water, and the danger of falling down holes which cannot always be clearly detected by the dim light of a candle, especially when the rock is a black limestone.

Caves of Debouchure far exceed the others in number. In Ribblesdale, more particularly, the entrance is generally at the base of a limestone scar or at the upper end of a narrow gorge. It is generally commodious, with a broad flat roof forming the underside of one bed of limestone, a thin parting of softer material separating this from the underlying rock in which the water channel is cut. Some little distance in, a cascade or waterfall will generally have to be negotiated, at the top of which the passage is usually found to be a simple water-worn channel, gradually shallowing and broadening until it becomes too low to permit of further progress. Almost invariably is it the case that where a waterfall occurs, an old channel exists, which may afford a ready means of passing the difficulty.

In channels at or near the top of a bed of rock the limestone is worn into long, thin, vertical ribs, the edges of which are almost as sharp as knives. When the passages are cut through a series of thin strata, such as exist at the top of the main mass of Carboniferous Limestone, these stand out in horizontal slabs with keen edges similar to the vertical ribs.

Although the caves afford varied work for the explorer, far greater interest is attached to the pot-holes which abound in the district. These offer considerable sport to the climber who seeks to penetrate their depths, a sport accentuated by the element of mystery and awe surrounding them. Many attain depths of 300 feet and more, and it is here that the pluck and endurance of the explorer is called into full exercise, especially when the difficulties are increased by falling water.

Pot-holes are always found at or near the top of the Carboniferous Limestone, at an elevation of between 1,100 and 1,300 feet above sea level, and only in such localities where there is higher ground above to give birth to the streams which have been the active agents in their formation. The appearance of these chasms on the surface varies considerably, the size of the opening being no criterion of their depth. Gable Pot on the Leck Fells is 450 feet in circumference, being the largest in area of any in the country, yet its extreme depth does not exceed 115 feet. In contrast to this is Long Kin West, on the south side of Ingleborough, a narrow fissure at the top, which though it may be easily stepped across, attains the great depth of 325 feet. The bottoms of the chasms are usually covered with fallen rocks and water-worn stones, between which the water sinks out of sight, or forms a pool. Sometimes they open out into large chambers, with one or more passages extending for some distance, but these eventually become blocked with stones or water, or become too narrow to squeeze through. In the chasms themselves there is necessarily an absence of stalactites and other concretions, owing to the continually falling water uncharged with lime, but in protected fissures and passages there will often be found an abundance of these rock decorations.

The question is frequently asked whether there is no danger to be feared from the presence of foul air in these chasms. Experience in caves and pot-holes, which are absolutely dry as well as wet, leads to the belief there is no danger to be apprehended from that cause in limestone formations. Sometimes the carcass of a sheep or other animal, in a more or less advanced state of decomposition, will be found, the presence of which becomes unpleasantly evident, but this may be considered rather an inconvenience than a danger.

Local reports of the depth of pot-holes and length of caves should never be trusted, and unless there is strong evidence that particular care has been taken in making measurements, the figures given in even comparatively recent publications should be accepted with reserve. It is practically impossible to correctly estimate distances or depths when exploring these places owing to the novelty or difficulties of the situation, which magnify distances enormously. Many instances could be given where there is an astonishing discrepancy between published figures and actual facts as proved by later measurements.

The sport of cave-hunting and pot-holing, apart from its scientific interest, has fascinations and charms peculiar to itself. Though possibly not apparent to the uninitiated, its pleasures are none the less real, and the explorer often becomes fascinated by his weird surroundings when peering into the recesses of these secret chambers of Dame Nature, where she carves the rocks into fantastic shapes, and clothes them with drapery and ornaments of delicate and beautiful form. Like the kindred sport of mountaineering, the mere fact of facing and overcoming difficulties strengthens the nerves and develops a spirit of self-reliance and resourcefulness which react in the battle of everyday life. 

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