Collins New Naturalist Library

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To tell the spirit of the scene.

EDMUND BLUNDEN: Dovedale

THE SCENERY of the Peak District is a treasury of features, some new, some old. Relics of the far-distant past are closely linked with others of more recent origin; some beautiful, others rugged, weird, mystifying. It is the outcome of a long process of sculpturing which was produced by slow incessant change. Throughout all these ages, however, the rocks have remained unchanged in quality and arrangement and have exerted a constant though passive influence upon the landscape. A brief consideration of the nature of that influence will provide a useful background against which to watch the development of the scenery as it exists today.

There are three main types of rocks in the district—limestone, grit and shale. Volcanic tuffs and intrusive dolerite play a minor but interesting part.

ROCKS AND SCENERY

Limestone is a hard, almost impervious stone. Consequently very little rain-water penetrates into its substance. This fact shields it from the shattering action of frost. On the other hand, it is slightly soluble in natural water. Just as a cube of sugar becomes rounded as it dissolves in tea, so the contours of the limestone surface tend to develop smooth curving outlines.

Even the purest limestone contains small quantities of dust and other earthy materials. This is left behind on the surface of the rock and accumulates to form soil. On slopes the soil is usually too shallow to give firm foothold for trees, except for the ash, but it is covered by a carpet of grass and flowers which provides valuable pasturage. The more level ground on the platforms and along valley bottoms has a covering of much deeper soil. Here trees and bushes may flourish except where the altitude is such as to expose them to the influences of strong winds.

The debris shed by the vegetation becomes mixed with the soil. There it rots and produces weak humic acids which are taken into the water percolating down through the soil and thus intensify its solvent action upon the limestone.

Limestone, like other rocks, is arranged in layers or strata, each of which is broken into more or less cubical blocks by the presence of two sets of cracks known as joints and bedding planes. Descending water finds its way down even the finest of the joints and along the closest bedding planes, and by dissolving the stone on either side widens these into open fissures. Eventually these become so spacious that most of the rain-water abandons the streams upon the surface and flows away along these newly formed underground channels. Below a certain depth all cracks and fissures are permanently filled with water. That depth is spoken of as the water-table and thus becomes the surface along which these underground streams flow.

Sometimes a surface valley is deep enough for its floor to lie along or even slightly below the water-table. In these circumstances a surface stream or river is maintained which is remarkably constant in its flow and rarely swells into flood in wet seasons or shrinks and disappears in times of drought. The Dove is a good example of this type of river.

Grit, on the other hand, is practically insoluble in water. It is, however, so porous that rain-water is quickly absorbed and, soaking inwards away from the surface, leaves this dry. The water, however, fills all the pores and cracks in the deeper layer, which then become saturated. The dry superficial parts of the grit are consequently less liable to destruction by frost action and therefore retain their angular forms and sharp edges. Some grits contain grains of felspar, a mineral which is gradually rotted by natural water. In these cases the rock disintegrates more rapidly.

Shale is more finely porous than grit. Water therefore percolates into it more slowly and is retained in its surface films. There its prolonged presence softens the rock and favours the pulverising action of frost. In areas where shale is the dominant rock, vertical erosion by streams and valley-widening proceed more rapidly. In these areas landslips occur on the steeper slopes and under the overwhelming pressure of superincumbent rocks the shaley sides of the valleys may even begin to bulge. Examples of such features may be seen around Edale and other vales.

The limestone, which is the oldest rock in this district, underlies all the others and occurs as a great mass at least 1,500 feet thick. In its uppermost portions thin layers of shale appear. Passing upwards these thicken and the intervening bands of limestone become thinner and eventually disappear. The succeeding 1,000 feet of shales are called the Edale Shales.

Thin beds of grit begin to appear in the upper levels of the shales which are referred to as the Grit Shales. Passing upwards through the rock series the grit layers become more massive. Of these there are five, of which the Kinderscout Grit may be specifically mentioned, for in the north of the district around Black Hill and Bleaklow it attains a thickness of as much as 600 feet. All these grits, however, have a lenticular form and tend to become thinner towards the south where the surface features they form are much less prominent than in the north.

Turning now to the arrangement of the rocks it will be recalled that they have all been folded, a fact which has a marked influence upon the features of the landscape. The folds are of the two general types—upfolds or anticlines and downfolds or synclines. The sides of each fold are its limbs and these link the crest of the former with the trough of the latter. The rock layers are horizontal or nearly so at these two points but are more or less steeply dipping in the limbs.

Erosive or denuding agencies naturally attack the upfolds to begin with and in doing so strip away the younger rocks first and the older ones in turn until in the centre of the crest the limestone is brought to view as in the Derbyshire upland. Northwards from the upland, earlier stages in this stripping process are exemplified in succession. In the moorland area much of the grit cover still remains. On the other hand, on the downfolds the youngest rocks survive longest in the centre of the trough, hence the presence of Coal Measures in the lower Goyt valley. Along the zones of country occupied by the outcropping limbs of the folds the rocks dip down from the surface and the edges of the strata produce such scarp-like features called “edges,” as Axe Edge, Froggatt Edge, Baslow Edge and Black Edge (Fig. 4, see here (#ulink_0db0e8a3-a156-5892-a5af-24b2c659a86e)).

TIME AND SCENERY

The Peak District is but a minute portion of the earth’s crust. This latter is often spoken of as “terra firma” as though it were quite rigid. But it is rigid only in the sense that a block of wood is rigid. Anyone who has jumped off a diving-board knows, however, that when the block is so long that it becomes a plank it is springy and flexible. The rock layers which make up the Peak District are similarly flexible. Deep down in the earth beneath them lies a plastic foundation which during long periods of time has crept slowly from one region to another and the crust of rocks which rests upon it has risen and fallen accordingly. In the middle and again in late Pliocene times movements of this kind took place in the Peak District and resulted in a general uplift of the region. Each uplift probably took place in a series of stages but, for the sake of brevity with clarity, only the total results will be considered for the two occasions.

With each total uplift of the Peak District its level above the sea was increased. Consequently all the agencies which had almost gone to sleep were aroused into activity once more; water flowed more rapidly; vertical and later on horizontal erosion were renewed. Thus it came about during the remaining 15 million years of Pliocene, Pleistocene and recent times, that rain and rivers, frost and glaciers gave to the district those magical touches of beauty which make it so attractive to its many visitors.

The process of carving the surface was by no means haphazard. On the contrary, as the result of successive uplifts there was a majestic rhythm about its progress which inscribed its score everywhere. For those who learn to read that score the appreciation and enjoyment of the scenery are greatly enhanced. How was that score written? That is the next problem to be explored.

The key agents in carving inland scenery have always been the rivers and streams. Those of the Peak District are all tributaries of large rivers—the Mersey, Trent and Don—which in turn pour their waters into the sea. This last phrase, though trite, leads straight to the central influence that ultimately controls the whole activity of running water, for both flow and erosive activity cease at sea-level. This last term, however, lacks precision for both land and sea rise and sink independently of one another. Strictly speaking, therefore, the controlling influence is the relative level of these two and this is called the base level. Throughout its course a river flows and works only so long as its bed is above base level.

The character of the work done by the river changes at different portions of its course. In its upper reaches the bed is steep and water flows rapidly. Like a man running swiftly, it follows almost a straight course and overcomes all obstacles that lie across its path. Downstream, as the slope of the bed becomes more gentle the rate of flow declines and the water is more easily diverted. Henceforth the river meanders from side to side.

Upstream the more rapid flow gives to the water greater power for rolling boulders and stones along, and these by their continual passage wear grooves and channels across even the hardest rocks. This wearing of the river bed is described as vertical erosion. Downstream this power is lost. Nevertheless as the river meanders along it impinges against the outside bank of each bend. In times of flood, when the water is carrying a load of sand and gravel, it undercuts and wears the bank away. It is then said to be eroding horizontally.

Upstream again, the valley sides come down to the margin of the water and the valley is V-shaped in cross-section. Downstream, on the other hand, as the river meanders it also erodes the lower fringes of the valley sides and thus the valley bottom is widened into a flat which increases in width as it approaches the sea. This broad flat with its cloak of gravel, silt and mud constitutes the alluvial plain.

While all these changes are going on frost and rain are busy working upon the valley side. The one pulverises the rocks and converts them into soil. The other washes away the surface of the soil and discharges it into the stream. At the same time the rain soaks into the soil and causes this to swell. In dry weather the water evaporates and the soil shrinks. This alternate wetting and drying, swelling and shrinking causes the soil to wriggle slowly downhill and ultimately to fall into the stream. This process is known as soil creep. Long after the river ceases to erode vertically these processes continue, the valley sides recede from the stream and the valley increases in width. There is, however, a limit to all these activities; they cannot be carried on below the level of the alluvial plain which serves as their local base level. As the steeper convex sides of the valley recede from the river they leave behind them a gently sloping apron of deep fertile soil which in these days is occupied by prosperous farms and villages.

Meanwhile the plateau-like high ground between the valleys diminishes in height and extent and becomes reduced to a gentle rise of ground. In this way hilly and even mountainous country is levelled down almost to a plain, a “peneplain” (pene=almost), and is characterised by a gently undulating surface with broad open valleys and low spreading rises. This late stage in the development of landscape was attained in the Peak District in or about early Pliocene times. The level of the land relatively to the sea was about 1,200 feet lower than it is now. It remained near this level for so long a time that the work of denuding agencies was carried almost to complete fruition even in the uppermost and far inland portions of the drainage system in the region.

The open breezy highlands of the Peak District are remnants of the peneplain then produced. The features described above are best exemplified in the limestone uplands where the rock is almost uniform in quality. An excellent viewpoint from which to see them in profile is from the summit of Thorpe Cloud. In the moorland areas in the north the alternating grits and shales have produced a rugged surface (Plate 1, see here (#ulink_8af04216-c3c4-5b3e-b040-573ad6dc4a29)). Upstanding peaks were absent, but even in those far-off days the plateaux and ridges rose above the general level of that ancient peneplain. Ancient indeed, for it dates back to early Pliocene times, when for several million years land and sea remained relatively stable with only small oscillations of level. The denuding processes continued their work without serious interruption until it was accomplished. At that time the Peak District did not rise above the surrounding country as it does now, for its surface was only a small part of an extensive peneplain that sloped away gently towards the far distant sea, the sea whose nearly constant level had for so long a time exerted a controlling influence that was felt along the whole length of every river and stream and across the breadth of the whole countryside.

Fig. 5. Surface relief of the Peak National Park (#ulink_8174dd1d-7b81-5bac-9d14-5b9193a72e8e)

BEYOND THE DALES

For many tourists the word Derbyshire spells “dales.” It is the dales they love to explore. It is up the dales they hike. When eventually they emerge into the upland, as for instance out of Lathkill Dale they lose interest for “there is nothing to see,” nothing but stone walls and tame pastures. Nevertheless, for a full appreciation of the more exciting vistas within the dales the story of these uplands must be told.

The sequence of events detailed in the last section is known as a cycle of erosion. Whenever the level of the land rises or that of the sea sinks, the current “cycle” is interrupted or even ended. A general movement of this kind took place about the middle of the Pliocene period. The whole landscape was uplifted about 300 feet and remained at the new level for a long time. The rivers were rejuvenated and recommenced excavating their channels, first of all in their lower reaches. The point near which the steep new bed joins up with the gently sloping old one is commonly called the knick point. Below this the newly formed valley was at first a narrow gorge and ran like a trench along the floor of the broad, open, ancient valley of the former cycle. Above the knick point that valley remained unchanged. The river continued excavating its channel and the knick point receded upstream along nearly the whole length of the former valley.

Meanwhile the sides of the gorge were worn by weathering agencies into steep and then gentle slopes. The gorge was thus slowly converted into a wide valley lying within the limits of the old one. Along its margin where the steeper side of the new valley merged into the floor of the old one there was a “break of slope,” essentially a greatly elongated extension of the knick point. Had this widening process been carried on to its utmost limit all traces of the older landscape would have been destroyed. Fortunately this cycle of erosion was interrupted in late Pliocene times and consequently relics of the earlier landscape survive in the loftiest portions of this upland.

The late Pliocene uplift raised the general level another 200 feet and all the weathering machinery was set going once more. Through out the Pleistocene and later times, river channels were worn deeply once more and thus the dales as now seen came into being as the youngest features in the Derbyshire scenery.

That, then, in rapidly drawn outline is the general story of this limestone scenery in the Peak District. Further details must now be considered and these vary from dale to dale mainly in association with the size of the streams.

The Lathkill, though only a small stream, provides a pocket edition of the whole story. In the centre of its basin lies Monyash surrounded by a broad open valley formed mainly in mid-Pliocene times. The high ground enclosing this basin bears the last traces of the early Pliocene peneplanation. Downstream from Monyash the floor of the valley is gashed by the dale, the excavation of which was begun in late Pliocene times and continued until now.

The survival of so many traces of the early phases in the development of the landscape is largely due to the fact that it lies wholly within the limestone region. Apart from the Lathkill there are no surface streams. Had such streams been present they would have inscribed an intricate pattern of new valleys and in doing so would have removed still further and larger portions of the ancient surface. The rain, however, instead of flowing off along the surface descended down cracks and joints in the rock and dissolved out underground channels along which it journeyed to the newly forming dale. Thus many of the dales are now dry at the surface, Gratton Dale being a good example (Plate VIIb, see here (#litres_trial_promo)).

It must not be supposed that the relics of the more ancient landscape have survived the passage of ages without undergoing change. On the contrary the whole of the limestone area is like a marble statue which has been exposed to the weather for a long time. Every fall of rain which has washed its surface has dissolved away some of the marble and gradually destroyed the finer details of the carving. But the major features of the face, chin, nose and eyes can still be recognised as such. So though the limestone of this upland has been washed by rain for 5, 10 or 15 million years, the major features originally carved upon its surface can still be recognised.

The water which disappears underground is by no means idle. It finishes its downward journey when it reaches the water-table, that is to say the surface below which all cracks and joints are already filled with water. This surface differs from that of a lake in that it is not flat and horizontal but has a general slope roughly parallel to that of the surface of the countryside above it. The water newly arrived from above now flows along this watery surface, dissolving the limestone away on either side of the crack which forms its path. The level of the water-table rises and falls according as the season is wet or dry and consequently the crack is widened into a tunnel or cave within the limits of that rise and fall. Such a cave may be seen soon after entering the dale from its upper end. In a rainy season the water-table rises above the floor of the dale and the stream is then seen issuing from the cave as a surface stream. In times of drought the water-table sinks and the stream, finding that its underground channel is enough, disappears from the surface and continues its course below ground. With this alternating rise and fall of the water the roof of the underground channel is being gradually dissolved away and ultimately collapses and thus a new and romantic addition is introduced into the floor of the dale. This type of deepening has been going on in all the dales since late Pliocene times.

The limestone varies in quality from place to place throughout the uplands. Sometimes it is rich in fossils which are slightly less soluble than the rock itself. This is particularly the case where coral or shelly reefs existed on the floor of the Carboniferous sea. At such places the rock is less rapidly dissolved than is the surrounding limestone and so it stands up as a more or less prominent hill known as a reef knoll. Thorpe Cloud, Bunster, Wetton and Gratton Hills are examples of such knolls.

One important result accruing from the solvent action of rainwater upon the limestone is that the insoluble residue remains on the surface and accumulates to form soil. This is particularly the case where the surface is almost level, for then rain-wash and soil creep have only slight effect. The soil is then said to be stationary. Where the surface has a marked slope these two factors come into action more vigorously and the soil is transported downhill. On such slopes the soil covering is thin but in the adjoining valley it is deep. These differences from place to place exert an important influence upon the agriculture of the upland.

The wet surfaces over which the escaping water flows become moss-grown. The moss, however, takes up the carbon dioxide from this water with the result that it can no longer hold much lime in solution. The latter is therefore deposited and, covering the moss, forms a spongy-looking rock called tufa. This is often used for rockeries and sometimes for building as in the case of Tufa Cottage in the Via Gellia. In some springs the water rises from great depth and as it does so the pressure upon it diminishes rapidly. Once more much of the lime held in solution is set free and covers any objects, such as toys and birds’ nests that are put into it, with a hard coating lime. As they have the appearance of having been changed to stone such springs are spoken of as petrifying wells.

In caves the water dropping from the roof or flowing down the sides also parts with its lime. In so doing it deposits this either as icicle-shaped pendants from the roof or as pinnacles rising from the floor. These features are known as stalactites and stalagmites respectively. Sheets of lime may also be laid over the walls or hang like curtains from ridges on the ceiling. When such a cave is judiciously illuminated it becomes a beautiful scene and a profitable centre of attraction.

WITHIN THE DALES

The rambler approaching Dovedale and the uplands along the Belper-Ashbourne road begins to catch visions of the promised land when he passes beyond Hulland. He looks across a succession of level-topped hills with an altitude of six or seven hundred feet. These level tops are relics of a mid-Pliocene peneplained platform. Away in the distance beyond them the uplands appear as a lofty rampart, bounding this platform on the north, and extending to the Weaver Hills.

In the centre of the rampart is Thorpe Cloud, rising like a bastion at the entry to Dovedale. Making that his first objective, he scrambles to the top and, looking northwards, finds himself on a level with the upper or early Pliocene platform and sees it as a gently undulating landscape having all the general characteristics of a peneplain (Plate VIIa, see here (#litres_trial_promo)).

In striking contrast to that is the deep steep-sided dale looking like a cleft in that ancient landscape. Closer inspection of the cleft reveals a feature that is easily overlooked. The precipitous sides of the cleft do not rise to the level of the upland itself for their rims spread out like a shallow funnel about 200 feet deep. The sides of this funnel curve upwards from the lips of the gorge to the level of the upland platform. The funnel is in fact the profile or cross-section of a moderately broad valley in the floor of which the gorge has been carved. This floor extends southwards into the 600-700-foot platform already noticed between Hulland and Ashbourne. The sight of this valley takes the thoughts back to middle Pliocene times when the Dove flowed along this floor and debouched on to the plain of which this platform is a survival.

Leaving his eyrie, the rambler descends and sets out to explore the dale (Plate 2a, see here (#ulink_8fc9d959-31b9-5bd3-a90f-47c235ce3a5f)). At first his path lies alongside the stream. Presently it rises steeply and takes him up to the Lover’s Leap, the name given to a spur which projects towards the gorge. Standing upon the tip of the spur he looks down into the gorge and his eyes come to rest on the wooded slopes of the opposite side. Here and there amongst the greenery may be seen grey pinnacles of limestone known as the Twelve Apostles. How these came to be there will emerge later. For the present it must suffice to say that they are the degraded remnants of another spur that once projected from the other side, the counterpart of the Lover’s Leap.

Turning back from viewing the Twelve Apostles, it is seen that the flat surface of the Leap slopes upwards like a valley side and merges into the upper plain. Looking up the dale similar spurs may be seen farther on. Each of these shows the same traces of the old valley features, for all these spurs are also relics of the mid-Pliocene valley. The observer is standing where at that far distant date the Dove actually flowed.

Leaving the Lover’s Leap behind, the explorer descends past the successive levels through which the river excavated on its way down to its present bed. Once more the path lies alongside the stream through smooth grassy flats unimpeded by boulders. On either side are the rocky cliffs criss-crossed by vertical cracks or joints and horizontal or gently dipping bedding planes. In winter some of these become filled with water from melting snow. When this freezes it expands and the ice, acting like a quarryman’s wedge, gradually prises lumps of rock from the face of the cliff which fall and form a blocky scree at the base (Plate VIa, see here (#litres_trial_promo)).

Here and there other narrow spurs once projected into the dale, but these have been partly or wholly destroyed. Frost working at both sides of the spur has worked its way in along major joints or fractures and cut it up into isolated columns such as that of the Ilam Rock (Plate III, see here (#ulink_5375b2f9-a0d8-5315-a557-ffd8f4edbd29)). Rain falling upon such a column dissolves the corners and edges and eventually reduces it to the shape of a pinnacle such as those already seen from the Lover’s Leap.

Another feature of the dale that is easily overlooked is the fact that it follows a winding course. One result of this is that the vistas are usually not long but are closed in by a succession of rocky pictures often of great beauty. As each bend of the gorge is passed there come into view new cliffs, fresh and fantastic shapes or even a cave, such as Dove Hole and Reynard’s Cave. These last are a reminder that the excavating of the dale has not been entirely due to the direct deepening of the river channel. Disappearing streams like those of the Lathkill and the Manifold have played their part by dissolving underground passage-ways beneath the floor of the dale which became open to the air and the sunshine, in the way already described for Lathkill Dale, and henceforth became part of the main dale. The two caves just mentioned were formed by tributary streams which, however, were drained dry when the Dove itself deepened its channel below their level.

The winding of the dale is reminiscent of the meanders of a river flowing along an alluvial plain. When such a river is rejuvenated the knick point, followed by the deepened channel, travels upstream along the meandering course round bend after bend. Such was the history of the Dove when, with the mid-Pliocene uplift, it became rejuvenated and incised its new valley into the early Pliocene peneplain, and at a later date excavated the dale in the floor of that valley.

At last the explorer comes to the end of the dale and finds that it opens out into a normal valley. From this point up to its source on Axe Edge it does not flow over limestone but over shale with some grits. As already seen these shales yield much more readily than does limestone to the destructive influence of rain and frost. When therefore this uppermost section of the river came under the influence of the latest rejuvenation, the sides of the deepening channel were more rapidly worn back and a wide valley formed.

THE MOORLANDS

The striking change of scenery met with along the upper reaches of the Dove is a reminder that the limestone uplands form only part of the Peak District; the other part is made up of grits and shales. The change reflects the still greater contrast between the uplands and the moors. This gives to the district much of its attractiveness as is typified by the streams of visitors to the dales and the comparative trickle of energetic hikers who make the lofty, windswept moors their main objectives.

The rocks which form the moorlands completely encircle the uplands like the oval frame of a beautiful portrait. At the top of the frame, where the grits have their maximum thickness, the moulding stands out in bold relief. Along the sides this declines and at the bottom it almost disappears for the grits become much thinner as they pass southwards round the limestone. On the south such features as they produce still remain largely hidden under ancient covering of Triassic sands and marls.

In the uplands the limestone is almost uniform in character, but in the moorlands extremes meet and resistant grits lie in close juxtaposition with the much more easily weathered shales. This is illustrated in The Peak itself which is capped with a mighty slab of grit, several hundred feet thick, resting on a pedestal of shale. The slab forms a plateau bounded by steep rugged cliffs. The pedestal is flanked by slopes whose surface is roughened by landslips or broken by steps caused by the presence of occasional thin beds of grit.

The rock of the plateau is so porous that rain-water soaks into it rapidly and, percolating downwards, saturates the lower layers. This great slab of grit therefore functions as an underground reservoir having an impervious floor but is without retaining walls around its margins where, at the junction of the two kinds of rock, the water leaks slowly away and is lost. Within the grit the water flows freely through the fissures but elsewhere its flow is hindered as it seeps slowly through the fine pores of the rock. Unlike the water-table of an ordinary open-air reservoir, the surface of which is perfectly flat, that in the grit is heaped up in the centre and slopes thence in all directions.

Wherever a valley has been developed on the plateau deep enough for its floor to reach the water-table, water escapes and forms a stream flowing along the valley bottom. Elsewhere the plateau is dry and streamless.

At the base of the cliffs bounding the plateau water leaks away perpetually and, soaking into the adjoining shale, softens it to such an extent that it yields to the pressure of the overlying rock and is slowly squeezed out. The cliff, with its foundation thus weakened, eventually collapses and tumbles its fragments down the slopes. It is in this way that the slabs of rock which cap the highest grounds in the district have been and are being worn away gradually, so that large plateaux in time become small ones, e.g. Brown Hill and Stanton Moor, and small ones become conical peaks or pikes such as Win Hill near Hope and Oaker Hill near Matlock.

Where a crack or fissure running through the rock emerges at the cliff-face a copious spring of water gushes forth. At such a point the destructive action just described takes place more rapidly and leads to the formation of a notch, a gully or even a “clough,” the floor of which is cumbered with fallen blocks of grit (Plate IV, see here (#ulink_af784047-a0de-5f0f-a97d-ee13bea8bb09)). All these features may be seen well developed round the margins of any grit plateau or along a grit edge.

Turn now to the pedestal which supports the rock. This consists mainly of shale with occasional thin grits. Each of these as it crops out to the surface acts as a protective covering for the shale below; but the shale above it is weathered into a concave slope. This merges downwards on to the flat upper surface of the grit which is exposed as a narrow platform.

The vicinity of Matlock Bank yields an excellent and easily accessible example of these types of topography. Standing in Salters Lane and looking across the valley, the step-like features produced by the sub-divisions of the Kinderscout Grit are well seen. They are indeed emphasised by the plan of the town in which main roads run parallel to one another along each shelf and are flanked by buildings which have developed along the ledges.

On the skyline above all this are Matlock and Farley Moors, which owe their presence to a small plateau formed by the Chatsworth or Belper Grit. This layer, however, does not lie quite flat but is bent into a broad shallow downfold having a slight southwards tilt. Rainwater falling on this seeps through the rock to the centre of the fold, where it accumulates as a valuable underground reservoir from which the Matlock Urban District draws its main water supply.

The vegetation cover of the plateau shows an interesting zonation of plants from those which flourish on very dry situations near the scarp margin where the ground level is high above the water-table, to those which favour the boggy conditions near the centre where the ground has dipped down to the level of the water-table.

On the southern margin of the fold the water from the reservoir spills out as a copious stream, the Bentley Brook. This flows for a short distance through a rock-strewn clough whose rugged sides suddenly diverge and pass into two long curving scarps which enclose a broad shallow valley excavated out of the underlying shale down on to the upper surface of another grit layer. This is a good example of a type of hanging valley which is frequently met elsewhere in the moorlands. After flowing for about a mile the stream plunges over the lip of the grit and sets out on a tempestuous journey down the steep valley side east of Matlock, cascading through Lumsdale in a succession of cloughs and ultimately joining the Derwent river.

Similar combinations of topographical features are met with repeatedly throughout the moorlands especially in its northern section. Here, as already seen, the underlying form of the region is based upon a dome-like arrangement of the rocks. Owing to the asymmetry of the anticline its crest lies nearer to the west side, a fact which accounts for the asymmetric position of the dominating features situated along the line from Kinderscout to the extreme northern end of the Peak District, where the influence of the Derbyshire dome ceases to be felt. There the moorlands have a minimum width of only about two miles as contrasted with twelve or more miles in the latitude of The Peak. Along the crest the higher members of the Millstone Grit series have been removed and the lower ones which are more massive dominate the scene. In association with the dip of the rocks away from the crest, the summit level declines most rapidly towards the west. Towards the north-east and east, owing to the low angle of dip, the grits and shales give rise to more widely spaced scarps and broader vales than those on the west.

Thus the general form and arrangement of the major features of the moorlands are controlled by the arrangement of the rocks. But these alone would have led to nothing more than a vast expanse of desolate and even repulsive moors. The area has, however, been redeemed from such a fate by the carving activities of running water. Everywhere are to be found streams fed from the inexhaustible reservoirs of the grits. These set out from the crest on their journey to the lowlands, carving for themselves narrow, often deep gorges through the massive grits. By joining forces they become larger streams. With their power increased and aided by associated agencies they excavate an endless variety of cloughs ranging from mere notches down the faces of steep scarps to narrow, wild and impressive valleys such as that of the Crowden Great Brook which opens on to the north side of Longendale. A swift torrent flowing down the western slope of Kinderscout starts as the Kinder Downfall, which is the only considerable waterfall in The Peak (Plate V, see here (#litres_trial_promo)) Two rivers, the Etherow and the Derwent, are the centres towards which many of these streams converge. The spacious valleys of these rivers have steep sides with the usual step-like grit features at successive levels crowned by magnificent scarps. In each case the left side rises more abruptly, forming a continuous feature of great grandeur only slightly broken by notchlike cloughs. On the right side the valley sides are less abrupt and are deeply dissected by larger valley-like cloughs.

In the northern outskirts of the drainage basin of the Derwent much of the Kinderscout Grit has been removed and has left the underlying shales with minor grits exposed over extensive areas. These are occupied by moors and mosses lying some 500 feet lower than The Peak. They also are redeemed from monotony by the presence of attractive tributary valleys, spacious but steep-sided.

East of the Derwent the outcrops of the Kinderscout Grit continue south as the East Moors. These are defined on the west by a series of prominent scarps (Derwent, Stanage, Froggatt and other Edges) overlooking the main valley. They dip at a steeper angle than that already seen in the north but carry a similar series of dip slopes and scarps. Here, however, the continuity of the latter is interrupted by the transverse folds already mentioned. They give rise to structural and surface features like those described above in detail for Matlock Moor.

In the West Moors, between Buxton and Macclesfield, the geological structure of the district reaches its maximum of complexity in sharp north-to-south folds crossed by minor ones trending west to east, thus producing an area of intermingling types of scenery like those already described but on a smaller scale, surrounding or enclosing in their synclinal hollows patches of lowland types due to the presence of pockets of Coal Measures and even of Triassic rocks.

One more element in the make-up of the district remains to be mentioned. The Edale Shales which lie between the limestone and the grit have a maximum thickness of some 1,000 feet. Under normal circumstances it should crop out as a relatively broad zone between the limestone uplands and the moorlands. Owing to cross-folding and faulting, especially in the west, the zone is broken into a number of separate patches which give origin to the gracious landscapes of Darley Dale, Edale, overlooked by Mam Tor (Plate VIb, see here (#litres_trial_promo)), and Hope Dale. The more extensive patches lie outside the area to the south and south-west.

THE WORLD UNDERGROUND

Reference has already been made see here (#ulink_db329224-d24e-5d91-aa42-ec496e5ff054) to the formation of caves as a common feature of the limestone area of The Peak. The exploration of these caves under proper auspices is a challenging form of recreation for the physically fit, exciting but rigorous, while many of them are of special scientific and archaeological interest. Some of the larger and more spectacular examples are exploited commercially, like the famous Blue John Cavern (strictly the Blue John Mine), the Peak and Speedwell Caves and the Treak Cliff Caverns (Plate 2b, see here (#ulink_8fc9d959-31b9-5bd3-a90f-47c235ce3a5f)), all in the Castleton district, and are an unfailing attraction for the general sightseer, though they are not quite so impressive as those of Cheddar.

While the processes by which caves are formed are not disputed, opinions differ as to the conditions necessary for the processes themselves to operate. As already explained, caves mainly owe their origin to water action, either as a solvent in the limestone or as an agent for the transporting of rock material by which the beds of underground streams are scoured. The relative importance of each of these forms of water action doubtless varies with local conditions. Authorities hold different views, however, as to where, in regard to the underground water, the cave-forming processes take place. Some maintain that caves originate and develop above the water-table within what is termed the “vadose” zone, i.e. the zone between the surface and the level of saturation, within which water moves downwards by gravity. This view implies that water percolating downwards from the surface will dissolve almost all the calcium carbonate it can hold before it reaches the water-table. Others have shown that many caves must have originated below the water-table in the “phreatic” or water-logged zone. Regarding this issue much depends on such factors as the extent to which solutional activity may continue below the water-table and the nature of water movement resulting from pressure exerted in the phreatic zone. It is likely that each of the theories is applicable to certain caves. In many cases, since there is ample evidence in the Peak District, as elsewhere, of past changes in the level of the water-table, it is reasonable to favour a compromise involving the application of both theories.

Although the phenomenon of limestone caves has been widely studied in many parts of the world, there is scope for much further investigation. For this the Peak District presents an obvious field. As Dr. G. T. Warwick has pointed out, the need is for a careful examination of particular caves, including the basic work of surveying them, without which detailed study cannot be advanced. In this connection the recent work of Dr. Trevor Ford on the Treak Cliff Caverns is to be welcomed not only for its intrinsic value but as pointing the way for further investigations.

Caves are seldom found in the Millstone Grit and when they do occur they generally take the form of narrow fissures resulting from the displacement of large blocks of rock. The Kinderlow Cavern on the western edge of Kinderscout is of this type, where a large but narrow block of gritstone has slipped from the main mass, yet still leans upon it, so forming a roof. The Kittycross Cave in Bradwell Dale, though primarily a limestone cave, is partly developed in decomposed toadstone.

In the limestone area it is important to distinguish between natural caves on the one hand and the underground passages and chambers resulting from lead-mining operations on the other, although the latter have often been the means of revealing some of the deepest and most impressive of the natural caves. A good example is the Bottomless Pit in the Speedwell Mine at Castleton which is due to the solution of lime-bearing minerals, mostly calcite, surrounding the ore body. Again, in the Blue John Mine and the Treak Cliff Mine the search for lead resulted in the discovery of extensive natural chambers. In fact many of the more intricate caverns now exploited as show-places owe their accessibility to former mine workings.

Fig. 6. Distribution of the principal caves in the Peak District. (Based on G. T. Warwick) (#ulink_d08ca058-c042-56b0-87ea-88722be58d55)

In the Peak District the distribution of caves is by no means haphazard. The majority tend to occur around the margin of the limestone in the neighbourhood of streams which flow on to that rock from the higher gritstone areas around it (Fig. 6, see here (#ulink_14a78743-46af-5f3c-8376-9de256d801b9)). Such streams, on encountering the limestone, have developed considerable underground drainage, the more so since much of the limestone, especially along the northern and western margins, is of the reef type (see here (#ulink_b505daa3-0087-546b-a563-b58f75afad06)), which is relatively pure and highly soluble. Under such conditions there is a marked concentration of caves in particular districts. Of these the Castleton, Bradwell, and Eyam-Middleton districts in the north, the Dove-Manifold area in the south-west and the Matlock-Wirks-worth district in the south-east are the chief. In the interior of the limestone area caves occur along some of the valleys such as the Wye and the Lathkill.

Most of the caves, except some in the Castleton group, are situated on the valley slopes or near the present stream level. High-level caves like the Harborough Cave near Brassington, at over 1,000 feet, are seldom found though they are of interest in indicating that ages have elapsed since the water-table stood at such an altitude and they must therefore be of great antiquity. Eldon Hole and Nettle Pot on opposite flanks of Eldon Hill are the only Derbyshire pot-holes, i.e. caves with a vertical pitch, like Gaping Gill in Yorkshire. Eldon Hole is 120 feet long and about 20 feet wide; it reaches to a depth of over 180 feet where it opens into two distinct caverns. Many of the Peak District caves have yielded significant palaeontological and archaeological remains. Thus, from a fissure in the old Victory Quarry north of Buxton, remains of Pliocene mammalian species, including the sabre-tooth tiger, mastodon and southern elephant were brought to light at the beginning of the present century and rank among the few instances of Pliocene cave-finds in Europe. Numerous relics of primitive Man dating as far back as the Bronze Age and even earlier have been found in such places as the Harborough Cave, Thor’s Cave, Thor’s Fissure and Beeston Tor (St. Bertram’s) Cave. None of these, however, is of such outstanding importance as regards evidence of prehistoric conditions as the famous series of caves in the Magnesian Limestone at Creswell in east Derbyshire well beyond the boundary of the National Park. It is their detailed features, including calcite curtains of varying hue, cavities lined with fluorspar, diverse forms of stalactites and stalagmites and the subterranean streams which give to the caves their popular appeal. The Peak Cavern has been famous for centuries. It is referred to as a “marvel of England” in Henry of Huntingdon’s Historia Anglorum, which was written in the twelfth century. Just as generations ago the Cavern earned a reputation among travellers as one of the wonders of The Peak, so today thousands of people each year are attracted to this and other caves which are exploited as commercial ventures. The caves in this category at present open to the public are the Blue John Mine, the Peak Cavern, the Speedwell Cavern and the Treak Cliff Caverns, all in the neighbourhood of Castleton, the Bagshawe Cavern near Bradwell, Poole’s Cavern at Buxton, the Cumberland, Masson and Rutland Caverns at Matlock Bath, and the Fern Cave and Roman Cave at High Tor, Matlock.