A leisurely walk through limestone country

MALHAM TARN

This is a large freshwater lake (60 ha), probably the largest in Britain at this altitude (373 m), very shallow – generally 1.8-3 m deep - and famous for its trout since the twelfth century.

Malham Tarn

There are good geological reasons for its existence on a limestone upland. Underlying most of it is impermeable Silurian slaty rock, part of the Lower Palaeozoic basement. Figure 1 shows how this basement has been exposed by the wearing back of the overlying limestone from the line of the North Craven Fault.

Fig. 1 Geological section from Fountains Fell southwards

This is only partly the reason why the Tarn does not drain away into the ground. At the end of the glacial period it was twice its present size, stretching over what is now Tarn Moss and Great Close Mire and emptying vast torrents over Malham Cove and down Gordale. When the ice melted, the Tarn was dammed at its southern end by a moraine of sand and gravel. Fine sections can be seen in the gravel pits near Water Sinks Gate and by the roadside to the east.

Even so, the Tarn's size is maintained now only by an artificial raising of its level by 4 1.2 m - a sluice gate, slipway, and embankment were constructed in 1791 by Thomas Lister, later the first Lord Ribblesdale, who then owned the estate. Tarn House was rebuilt and extended in the second half of the nineteenth century by William Morrison to replace an earlier hunting lodge.

Brown trout Salmo trutta. Painting ©www.davidmillerart.co.uk

The tarn was granted to Fountains Abbey and its medieval monks by William de Percy in the 12th century, with all its fishing rights - the tarn still has a reputation for its excellent trout. it also harbours a varied population of water birds - curlews, mallards, and greater crested grebe among them - protected in a sanctuary on the western shore.

Great crested grebe and chick Podiceps cristatus. © RSPB

WATER SINKS AND WATLOWES

After passing over the North Craven Fault, the Tarn outflow sinks into a ruckle of boulders at Water Sinks reappearing at Aire Head Springs (SD 901622).

Water Sinks

In very wet periods the flow goes further down the dry valley and has been known to reach Comb Scar. The dry valley winds between limestone scars, taking on the aspect of a narrow gorge obviously scoured by running water. It emerges eventually as a dry waterfall at Comb Scar at the side of a larger dry valley, Watlowes, which leads to the lip of Malham Cove. This once carried the Tarn outflow.

The progressive lowering of the water table over the Craven limestone country since glacial times is due probably to the widening of fissures by solution and the washing out of boulder clay from the joints and bedding planes. The asymmetrical cross profile of Watlowes has been attributed to solifluction on the south-facing slopes with frost shattering producing steeper craggy slopes on the north-facing side. There are many traces of Iron Age fields and hutments in this area while the wall running down the centre of Watlowes is an ancient boundary separating the lands of two monastic foundations, Fountains Abbey to the west and Bolton Priory to the east (Figure 2).

Fig. 2 View of the Watlowes dry valley from near Comb Scar. This valley once carried the outflow from Malham Tarn to the top of Malham Cove

MALHAM COVE

The path following the dry valley of Watlowes leads to the top of Malham Cove where there is one of the finest and most extensive outcrops of limestone pavement in the region (Figure 3). Essentially, limestone pavement consists of bare, often water sculptured surfaces (clint) abundantly fissured with joints widened and deepened by solution (grykes). The two major directions of jointing in the limestone in this region are clearly displayed. Scientists from a number of disciplines - geologists, geomorphologists, botanists, and pedologists - have studied such pavements. There has been general agreement that the sculpturing of the blocks is the result of solution by acids associated with lichens, peat, and soil, and that it has occurred and is still occurring under a cover of soil or glacial drift.

Malham Cove is an immense limestone cliff 72 m high and 274 m wide (Figure 4). It marks the site of what must have been a splendid waterfall, the outflow from Malham Tarn when at the end of the last glacial period it was twice its present size. The last known flows over the cove were towards the end of the eighteenth century and beginning of the nineteenth century during exceptionally heavy rainfall.

An analysis of the wonderful panorama from the top of the cove is made in Figure 3. The cove is a fault line scarp (Middle Craven Fault). That is, it is not the original scarp formed by the fault movement but one standing back some 364 m from the line of the fault. It has been cut back to its present position by the flow of water over it, the broad gorge in front being left as a result.

Fig. 3 View of the Craven lowlands from the top of Malham Cove.

Peregrine falcons Falco peregrinus have long been a prominent feature of this landscape (the pub in Arncliffe, over in the next dale is called The Falcon).

Peregrine Falcon Falco peregrinus. © RSPB

The peregrine is a large and powerful falcon. It has long, broad, pointed wings and a relatively short tail. It is blue-grey above, with a blackish top of the head and an obvious black ‘moustache’ that contrasts with its white face. Its breast is finely spotted. It is swift and agile in flight, chasing prey. The strongholds of the breeding birds in the UK are the uplands of the north and west and rocky seacoasts. Peregrines have suffered persecution from gamekeepers and landowners, and been a target for egg collectors, but better legal protection and control of pesticides (which indirectly poisoned birds) have helped the population to recover slightly from a low in the 1960s. They now regularly nest on the cove and with luck we shall see them.

Fig. 4 Malham Cove, an immense limestone cliff marking the line of the Middle Craven Fault.

The cultural features of the landscape are also well worth noting. The village of Malham lies half hidden among the trees in the shallow dale. Former cultivation terraces (lynchets) of uncertain age are seen both contouring along the slopes and running directly down them. The remains of Celtic field walls lie near the valley bottom below the cove - the footpath to Malham crosses them.

At the foot of the cove a broad stream issues. Although the earlier waterfall involved the Tam outflow, the water issuing here has been proved by dyes to originate partly from the sinks in the vicinity of the old smelt mill chimney (SD 883659) – i.e. northwest of the cove in line with one of the directions of the main joints in the limestone. The Tarn outflow now disappearing at Water Sinks reissues at Aire Head Springs. Typically of limestone country, the topography gives no indication of the routes taken by the water underground.

MALHAM VILLAGE

The village of Malham lies in the uppermost reaches of a shallow dale running away southwards from the upland edge. Easily accessible from the urban areas of Yorkshire and Lancashire, it is one of the best known and popular villages in the dales. On a summer weekend or a public holiday its square and car park are uncomfortably crowded with cars and coaches.

Malham village

The traditional view is that Malham, along with other villages of the dales, was founded in the seventh and eighth centuries by the Angles. Common fields grew around the village nucleus with houses clustered around a green or square. More recent studies have shown that village sites in the dales are of greater antiquity and that the Angles often took over pre-existing sites. Celtic (Iron Age) field systems and down-slope cultivation terraces are preserved but only archaeology could prove that Malham is built on a pre-Roman site. On the other hand, the common field system traceable today and usually attributable to the Angles may be later - a mature system resulting from the division of land due to inheritance and increasing population.

Basically, the plan of the village is what it was in the seventeenth and eighteenth centuries when, following the dissolution of the monasteries, new freeholders replaced wooden buildings with stone buildings. In the late eighteenth century increased prosperity led to further alterations to some buildings and an `estate' architecture.

As at Ingleton, local industries grew up based on geological resources and provided work and additional prosperity in the seventeenth and eighteenth centuries. Copper and calamine (Smithsonite - zinc carbonate) were mined on Pikedaw. Lead was mined locally and smelted at the mill where a chimney still stands . Coal came from a remarkable location - the top of Fountains Fell at over 2,000ft (600m), where thin seams of coal occur in the Millstone Grit.

JANET'S FOSS

Leaving Malham we walk through flower rich meadows and along a delightful chalk stream. Keep an eye open for dippers foraging in the stream. Dippers Cinclus cinclus are short-tailed, plump birds with a low, whirring flight. When perched on a rock they habitually bob up and down and frequently cock their tail. they are remarkable in their method of feeding which involves walking into and under water in search of aquatic invertebrates.

Dipper Cinclus cinclus. ©RSPB

Soon we shall enter a small area of ancient woodland before reaching a waterfall known as Janet's Foss. Janet (or Jennet) was believed to be the queen of the local fairies who lived in a cave behind the waterfall.

Foss is the old Viking word for waterfall (also seen as Force) and is one of several words of Scandinavian origin in northern England used to describe a physical feature.

Janet's foss

The pool below the waterfall was once used to wash sheep before shearing in late june. Washing encourages the growth of new wool which lifts the fleece from the skin. The sheep were driven to the pool and the men washing them would be up to their chests in water. Sacking and strong drink kept out the cold.

A cave behind the fall exists because the rock face originally responsible for the waterfall has had a remarkable screen of tufa (a soft porous calcareous deposit) built over it by a process akin to the formation of stalactites and stalagmites.

Limestone is made of almost entirely soluble calcium carbonate. Its solubility is greatly increased by the presence of carbon dioxide (as in rain water) since a bicarbonate is formed of higher solubility than a normal salt. Thus:

CaCO3 + CO2 + H2O = Ca(HCO3)2

calcium carbonate + carbon dioxide + water = calcium bicarbonate.

When carbon dioxide is given off from the solution, as in broken, flowing water and spray over a waterfall, the carbonate is reformed and deposited as tufa.

Gordale Beck contains large quantities of dissolved carbonate and the waterfalls here and in Gordale have provided a site suitable for the accumulation of large amounts of tufa, often in an attractive banded form. At Janet's Foss the process appears to have been aided by the growth and decay of moss at the base of the fall.

On the east side of the stream is a small cave beneath a beautiful little fold in the limestone - it was once inhabited, supposedly, in the eighteenth century by miners from Pikedaw.

GORDALE

Some 2 miles east of Malham the line of scars marking the scarp of the Middle Craven Fault is broken by the narrow, deep rift of Gordale. From the road at the view of Gordale is of a triangular-shaped flat piece of land bordered by limestone cliffs (Figure 5). The Norse name `gore' or 'geir', an angular piece of land, is descriptive of this pasture. The path from the road leads towards the apex of the triangle and the view increases in impressiveness as the cliffs close in on either side.

Even so, the newcomer is unprepared for the view on turning the corner. Slightly overhanging walls of limestone rise sheer up for 45 m, barely 9 m apart at the base. The absence of sunlight, the cold wind funnelling out, and the constant drops of water from above add to the drama of the scene. It is no wonder that it has attracted many attempts at written and artistic description.

At the far end of this ravine, high up, Gordale Beck plunges through a hole and then divides into two waterfalls covered over with great masses of tufa. On the right, at ground level, the tufa is very beautifully banded.

This part of Gordale has been presumed to represent a collapsed system of underground caverns and passages. If so, the water probably went underground via Gordale Cave above the waterfalls and reappeared at the foot of Gordale Scar. Gordale formerly provided an escape route for the waters of a much larger Malham Tarn. The collapse perhaps occurred then and the rubble swept out of the gorge and built up into a coarse delta now forming the triangular piece of land at the entrance.

The hole through which the stream plunges is a relic of the collapsed Gordale Cave. Up to about 1730 it was blocked and the route of the stream is marked by an old tufa screen to the left of the hole. When the water broke through the cave this waterfall was left `dry'.

Fig. 5 Entrance to Gordale.

Climb up the tufa screen to the top of the left-hand waterfall and continue up a steep scree slope onto a narrow ridge. This is a useful observation point from which to look back down into the gorge. A minor fault, an offshoot of the Middle Craven Fault, which probably caused the cave to be formed in the first place, can be seen on the opposite side. It forms a fissure opened out in places to form minor caves; the displacement of the beds on either side is clear.

There is, at present, no right of way up Gordale Beck Valley. Therefore continue carefully up the west side of the valley to a viewpoint at about SD 914643. It is doubtful if there is any finer view of a limestone gorge in the country (Figure 6). For a mile, Gordale Beck occupies a deep trench incised into the 395 m plateau. Water may have been ponded up for a time as a lake in this valley; in the banks of the stream have been found masses of tufaceous deposits in which leaves and twigs have been preserved in exquisite detail.

Fig. 6 Gordale, a limestone gorge incised into a limestone plateau

MALHAM ROMAN CAMP

To the east, across Gordale Beck (stream) Mastiles lane passes through the centre of a 8 ha Roman marching camp.

Plan and satellite image of Roman camp

The earthwork remains of the temporary camp are clearly visible on teh ground and are situated on relatively dry rough grassland, on the W side of a fairly level saddle between High Stony Bank and Low Stony Bank, at about 385 m above OD. Although there are good views from the SW around to the W and N, it is not in a particularly strong defensive position. Overlooked by higher ground from the NE, and from the E where the crest of the saddle rises gently to about 400 m above OD, the site is also dominated by the elevated limestone pavement of Low Stony Bank, only about 140 m from the S edge of the camp. On the W the deep and narrow valley of the Gordale Beck offers some good natural protection, supplemented less effectively on the N by the shallow gully of an unnamed tributary.

The defences of the camp, which faces N, consist of a rampart with an outer ditch enclosing an area of nearly 8.1 ha. There are four gates, each with an internal clavicula. The remains are in relatively good condition; such damage as there has been to the defences has resulted from the traffic along the green track of Mastiles Lane which almost bisects the camp immediately N of the E to W wall.

Evidently there were problems with the original setting out of the camp which is not a perfect rectangle: the N side is 8 m shorter than the S, and the E side is 4 m longer than the W. The NE corner is a right angle but the E rampart veers outwards by up to 6m at the SE corner, the angle of which is thus slightly acute. The E end of the S side also curves inwards off the general line of this side. These misalignments are probably due to the gently undulating topography. The four corners of the camp are not all inter-visible, either from each other or from a central point.

LEAD SMELT MILL

Between Gordale Beck and the old smelt mill chimney, the North Craven Fault coincides with a low topographic feature. A line of water sinks is present and the water which sinks near the smelt mill reappears (augmented some twenty times from the other sources) at the foot of Malham Cove.

The smelt mill served local copper and lead mines in the eighteenth and nineteenth centuries. The stream was diverted (a grassed-over bank is visible) for washing the ore. Little remains of the mill except for foundations of the dam, washing floor, chimney and the flue from the smelting hearth. After zinc ores were discovered locally in the 1790s they were calcined for a time here. In the early nineteenth century great quantities of Calamine (zinc carbonate) were mined at sites still called Calamine Pits between Pikedaw Hill and Grizedales. Raw and calcined Calamine was stored at Malham and then taken by horse and cart to a wharf on the Leeds and Liverpool Canal at Gargrave. The Fountains Fell coalfield (at over 2,000ft (600m) high) was important at this time supplying fuel for domestic use and for the smelters.