The Peak District, Derbyshire

The landscape

The Peak District is situated at the southern end of the Pennine chain, not far from Buxton and Matlock. Looking down from above, the Carboniferous limestone of this region is almost surrounded by younger shales, sandstone and grit. This is because the Peak District is a dome-like anticline that has been eroded so that the oldest rocks in its core (the limestone) have been exposed. The impermeable shale is more easily eroded by the rivers (like the Derwent and the Dove) and so forms the lower ground.

The landscape contains a number of habitats. The alkaline soils on the limestone region supports woodlands of native tree species (e.g. ash, wych elm and hazel) and plants (e.g. Common Birdsfoot Trefoil and Horseshoe Vetch). Rare plants grow on the steep slopes of gorges and quarries, where grazing animals such as sheep and rabbits, cannot reach. However, the landscape has been modified by human activity in the form of mining, quarrying and agriculture.

Fluviokarst features include dry valleys, steep-sided gorges, scars and cave systems, containing stalactites and stalagmites.

Pressures on the Peak District

Like the Yorkshire Dales and the Mendip Hills, environmental pressure is related to human activity in three main ways:

Industry

Middlepeak Quarry, Wirksworth.

During the long geological history of the Peak District, mineralised fluids percolated through the limestones, leaving behind veins. These were mined for hundreds of years and mine workings can be seen in many places. Fluorspar was originally mined for iron smelting although now it has a number of other uses. One type of fluorspar unique to the Peak District National Park is banded purple and yellow or grey and is known as Blue John. Galena (or lead) is found in veins that may also contain silver. Lead was mined in long, straight trenches, as long ago as the Roman times, but reached a peak between 1750 and 1850. Even though mining stopped over 150 years ago, the tip heaps are so toxic from the lead they contain that very few plants (except sandwort and wild thyme) will grow on them.

Limestone has been quarried in the Peak District since Roman times. It has been used for building stone, for making mortar and cement, as a source of lime for agriculture, in lead smelting and as an aggregate for road making. Millions of tons of limestone are removed each year. There are significant environmental impacts caused by quarrying – noise, disturbance, scars on the landscape, air pollution, transport, etc. However there is a plus side because the old quarries act like the crags and support many different plants, including orchids.

Farming

Mick Low. Feature formed by P1 apron-reef limestones at the eastern end of the Castleton reef belt.

Agriculture has changed the landscape of the Peak District. The traditional permanent hay meadows and pastures of the limestone plateau are being replaced by seeded pastures. This "improvement" of the marginal land, which is then capable of more intensive farming, does not support such a large number of wild plant and animal species, and results in a much lower biodiversity.

Tourism

Peveril Castle and gorge, Castleton. Looking E.

More than 17 million people live within a 60 mile radius of The Peak District National Park, in the cities of Yorkshire, the Midlands and Greater Manchester. Many like to visit the Peak District, especially the 'honey-pot' sites such as the market town of Bakewell, Chatsworth House, Dovedale, the Goyt valley and the villages of Hartington and Castleton.

Tourism is an important part of the Peak District economy and provides jobs for hundreds of people (hotels, bed & breakfast, restaurants, camp sites, renting cottages, tourist attractions, etc) and many more jobs when other services are included like shops, petrol stations, etc.

However, tourism also brings with it problems. Congestion is an issue as about 20 million people visit the Peak District National Park each year. Popular honeypot areas are overcrowded, there are blocked roads, and overstretched local facilities, especially during the summer. Erosion takes place along the most popular pathways due to walkers and horse riding on unsurfaced bridleways. Wildlife is disturbed on the moorland by walkers, mountain bikers, etc and farmland, dry stone walls and hay pastures are damaged. Some tourists buy houses, but use them only as holiday homes, so that not only are house prices pushed up so that local people cannot afford them, but for much of the year the owners do not add to the local economy.

Karst of the Peak District

Glutton, near Longmor. Looking W.

The Carboniferous limestone region of the Peak District (called the White Peak to distinguish it from the sandstone and grit moors that make up the Dark Peak) extends about 40 km between Castleton and Brassington and up to 15km wide, between Buxton and Bakewell. The limestone plateau generally rises up to between 200 and 300m above sea level (but its highest point is Eldon Hill near Castleton). Thick limestones that originally formed in shallow water, make up most of the White Peak, but thin, impure, deeper water limestones and shallow reef limestones also occur.

Compared to the Yorkshire Dales, the Peak District is far less rugged as the area was not greatly glaciated (although there are tills that prove that ice once moved over the region). Limestone pavements are rare and generally old (they formed about half a million years ago during the Anglian glaciation). Scars occur along some of the deeper valleys, but they are generally harder beds of limestone and not due to glaciation as in Yorkshire. Dolines are present, and although there are few sinkholes, examples are found near Castleton, where streams rising on the sandstone areas disappear into the limestone.

White Peak differs from the Mendip Hills because the limestone does not dip steeply downwards. However there are many dendritic dry valley systems, gorges cut by streams in periglacial conditions and large cave systems. In some places tufa barriers have formed at springs.

A few rivers still flow across the surface of the limestone of the Peak District. In some places this is due to the valley having cut down to the water table and in other places it is due to a high water table where impermeable volcanic rocks occur.

Karst features in the Peak District

Dry valleys

Deep Dale. Right hand side of valley in Chee Tor Rock, faulted along valley floor against Woo Dale Limestones

During the last Ice Age, Southern England was an area where the ground was permanently frozen (permafrost), similar to the tundra areas of northern Russia and Canada today. Erosion resulted from the release of water from the glaciers and ice fields to the north. There are many 'fluviokarst' dry valleys in the Peak District, where the ancient rivers have cut V-shaped valleys (very different from the glacial U-shaped valleys of Yorkshire). Perhaps one of the best examples of dry valleys is at Lathkill Dale, between Monyash and Alport.

Lathkill Dale is a dendritic dry valley system deeply entrenched into the karst plateau in the central part of the White Peak region. Lathkill Head Cave and Critchlow Cave are a resurgences in wet weather, but in the lower end of the dale, water emerges from Pudding Springs and Bubble Springs forming a permanent stream and sheets of tufa have come out of solution and form low barriers across the stream.

Gorges

Winnats, Castleton. Looking ESE.

Winnats Pass is a deeply eroded gorge near Castleton. It is about 1 km long and its cliffs are up to 100m high. Although it was cut by water it is now dry and several caves are present in the sides of the gorge.

Some geologists believe that Winnats Pass has had a very long and spectacular history. It is though to have started out during the Carboniferous, about 340 million years ago, as a hollow in the reef. It was then uplifted above sea level by earth movements about 320 million years ago and eroded. More earth movement perhaps 315 million years ago dropped the gorge below sea level again, when it was filled with shale. Again it was raised above sea level, and during the ice ages, it was scoured by the action of melt water during periods of periglacial conditions. The scouring removed nearly all of the shale and the gorge was further deepened.

Dove Holes, Dove Dale. Looking E.

The River Dove is a river that cuts across the limestone in the southern part of the White Peak, cutting a deep gorge- Dove Dale. The river rises on the sandstones, grits and shale to the north of the karst area, but there is too much water to sink into the limestone, so it flows over its surface, eroding a deep, valley as it does so. It meanders across the limestone plateau due to the presence of hard reef knolls. Tributary valleys that were cut during periglacial times, join the River Dove, but these are all dry. Parts of the valley sides form cliffs and crags, in which there are small phreatic caves. Reynard's Cave, for example, which formed at a zone of weakness where numerous closely spaced joints cross the major set of joints, was later truncated to form a rock arch.

Another deep gorge that formed by melt water during periglacial conditions, is Miller's Dale.

Caves

There are a number of cave systems in the White Peak region. There are four show caves near Castleton (Peak Cavern, Speedwell Cavern, Treak Cliff Cavern and Blue John Caverns) and another near Buxton (Poole's Cavern). Many of the caverns are extremely old, forming before the last Ice Age. The water that formed the caverns near Castleton flowed off the sandstone hills to the north and sunk into the cave system (which exceeds 20 km of passages). A dozen sinkholes leading to the Castleton caves are found near Rushup Edge and Perryfoot, where there are vadose trenches cut into the floor of the phreatic passages, old abandoned phreatic tubes and water-filled sumps. Peak Cavern is an example where resurgence of the underground streams takes places. Caves at Treak Cliff Cavern are formed in massive reef limestone and shallow water limestone with large numbers of speleothems at least 125,000 years old. Old phreatic tubes formed by solution, can be seen in the Peak and Speedwell caverns. Blue John Cavern also has old phreatic passages, but several hundred million years ago, some were filled with the mineral fluorspar (Blue John) when mineralised fluids entered the caves.