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)
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). 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), 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.
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