Wharfedale and Littondale
The landscape of Wharfedale and Littondale is a combination of the result of physical influences and the influence of people. The principal physical influences have been the nature of the underlying rocks, the influence of the Ice Age and the resultant thin, immature soils reflected in the nature of vegetation and agricultural practices found in the dale.
The characteristic broad shape of the dale and overall smooth form has resulted from the various periods of glaciation, the last of which reached its peak 20,000 years ago during which time both the dales and fells were covered in ice. As the climate became warmer, about 15,000 years ago, the melting of the valley glacier resulted in the formation a number of retreat moraines, such as those across the valley at Skirfare Bridge, Mill Scar Lash and Drebley, each of which may have resulted in the temporary formation of a glacial lake in the valley contributing to the very flat valley floor in parts of the dale. Lakes also formed, overflowed and cut channels high in the side valleys creating the complex features still visible above Storiths. At Conistone, a meltwater channel created a waterfall which retreated back into the hillside creating Dib Scar and below it the limestone gorge Conistone Dib, both now dry features as the water flows underground.
Since the end of the Ice Age the action of the River Wharfe and its tributaries has created waterfalls, cut gorges, created river cliffs and deposited patches of sand and shingle on riversides.
The geology of the dale is complex, but essentially comprises layers of rocks, mainly types of limestone, which have been exposed through the effects of glaciation, natural weathering, hydrological effects and the effects of the Mid Craven and North Craven faultlines and localised upthrusting of rocks such as the Skyreholme folds.
The two main types of limestone are the Great Scar Limestone, a pure limestone about 180m thick, and the overlying rock which comprises a series of 4 or 5 thin bands of limestone intermixed with thin shales and occasional sandstones, known as Yoredales. Both types of rock exert characteristic influences over the landscape, the first, a lighter coloured almost white rock, outcropping to form dramatic cliffs such as those at Kilnsey Crag (a spur of land truncated by the effects of glaciation) and, less prominently, at Grass Wood. The Yoredales, slightly darker in appearance, exert the greatest influence, outcropping for miles along the section of Upper Wharfedale north of Kettlewell, along each side of Littondale and along Langstrothdale, creating a very characteristic stepped or terraced appearance.
In addition to the cliffs and scars which are a prominent feature of the valley, Upper Wharfedale exhibits many other features associated with classic limestone scenery which occur less frequently or are on a smaller scale and thereby add both variety and detail to the overall unity of the landscape. These include gorges, as at Conistone, dry valleys, shakeholes, sinkholes, swallowholes and springs, together with caves and areas of limestone pavement, such as those above Conistone. In addition to above ground landscape, an underground landscape of passages, caves, pools and streams, waterfalls, stalactites and stalagmites has developed as a result of dissolution by water percolating through limestone. This extensive underground scenery is best represented at caves such as Dow Cave, Kettlewell and Boreham Cave, Littondale.
Boulders, carried by the ice, have been left strewn about hillsides and in the valley bottom and are often of a different rock type to that underlying (hence known as erratics). Pieces of non-local stone carried by the ice can often be found within drystone walls.
Further complexity is added by the Skyreholme Folds, an anticline that has thrust limestone to the surface visible as a darker limestone at Loup Scar and Trollers Gill, and the mineral veins which have resulted in the past development of orefields at Grassington Moor, Greenhow Hill, Appletreewick and the fells above Conistone and Buckden.
Along the Mid and North Craven Faultlines which cross the dale in an east to west direction between Grassington and Burnsall, the underlying rock changes abruptly from mostly limestones to the north to thick layers of shales to the south and this is reflected in the complex undulating topography and vegetation changes that occur across the faultline. Lying near the faultline on its southern side is a line of green dome shaped hills known as reef knolls (eg the two Kail Hills, Stebden and Elbolton). The knolls comprise conical mounds of pure limestone which 330 million years ago formed part of a seabed reef and were eventually buried in mud, which has since eroded leaving the knolls exposed as features within the valley floor and on the valley sides. These features represent the national classic example of their type and are of great importance to the study of Lower Carboniferous carbonate environments and are essential for the understanding of reef communities and their paleoecology, having great potential for future research.
The underlying geology of Mid Wharfedale comprises mainly sandstones and shales of the Millstone grit series, which extend over the majority of the valley floor and on moor tops at Barden Fell and Barden Moor. The rock is a course yellow brown sandstone which is seen outcropping as rock stacks on the moor tops, for example at Simons Seat. Bowland Shales can be seen outcropping by the river at Bolton Abbey and near Bolton Bridge. Complexity is added by the Skipton anticline that has thrust underlying limestone to the surface, visible above and below the Cavendish Pavilion, upstream of Bolton Abbey.
Soils that have developed on the upper valley sides in this area are peaty and acid, and fairly infertile, supporting a limited range of plant species including heather, cotton grass, bilberry and bracken and plantations of coniferous trees. On the valley floor and lower valley sides soils formed by the effects of fluvial and glacial deposition are richer and support grazing by cattle and sheep and have allowed the development of mixed broadleaved woodland.
