Limestone

Rural land resources are the product of the interaction of a wide range of physical factors modified by human activity. The resultant rural landscapes present a variety of physical, economic and social opportunities and challenges.

Limestone pavements and swallow holes

The Pennines is the backbone of Northern England, running from Northumberland in the north to Derbyshire in the south. It’s also one of the areas in the United Kingdom where upland limestone scenery is found. In the North Pennines this type of scenery is found in the Yorkshire Dales, and in the South Pennines the Peak District is well known. Both these areas are National Parks because of their beautiful scenery, range of wildlife and local history. The examples we’re using in this bite are from the Yorkshire Dales National Park.

If carboniferous limestone is capped by impermeable rock, surface streams can run on to limestone. However, this water disappears from the surface, either by seeping through joints in the limestone or as streams disappearing down through swallow holes. It is the action of water which is responsible for many of the distinctive features of upland limestone scenery.

When you study upland limestone scenery remember you should describe and explain both surface and underground features. Surface features include limestone pavements, dry valleys, gorges and scars. Underground features include caverns, potholes, stalactites and stalagmites.

Limestone pavement

Limestone pavement, near Malham

Carboniferous limestone is made of blocks of rock. The clear horizontal lines are called planes and the vertical cracks are called joints. The rock is permeable which means water can pass through the lines of weakness – the bedding planes and joints.

Rainwater is a weak carbonic acid which reacts with the limestone as it passes through the rock. It dissolves the stone, enlarging joints and bedding planes. On the surface the chemical weathering widens and deepens cracks to form grykes. This leaves exposed blocks of limestone called clints and the resulting pattern of blocky rock is called a limestone pavement.

Clints and grykes

Chemical weathering of limestone pavement

The chemical weathering is shown by the formula:

CaCO3 + H2CO3→Ca(HCO3)2

(limestone + carbonic acid →calcium hydrogen carbonate solution)

Shakeholes and potholes

Occasionally, hollows are created on the surface of limestone. They form where drift material falls into joints which have been enlarged and widened by chemical solution. The hollows are called dolines or shakeholes.

The shakehole is then eroded by streams and a vertical hole known as a potholeor swallow hole is formed. These holes can, in turn, be enlarged by heavy rainfall or glacial meltwater. Gaping Gill, in the Yorkshire Dales, is an example of an enlarged swallow hole.

Scars and gorges

Limestone cliff and scree slope

Scar and scree, Yorkshire Dales

Scars

Scars are exposed cliffs of limestone. They were created during the last ice age, when huge sheets of ice scraped away the soil-covered spurs in many valleys in the Yorkshire Dales.

The exposed surface is affected by freeze-thaw action on the well-jointed limestone. Water enters the cracks, and if it freezes, expands. As the water expands, so do the cracks.

Repeated freezes and thaws eventually break off rock, and at the bottom of the scar cliff a talus or scree slope is formed. A dramatic example of scar landscape can be found at Twistleton Scar, in the Yorkshire Dales.

Gorges

There are two theories about the formation of gorges in limestone landscapes. The first is that the gorges were formed by large caverns whose roofs eventually collapsed. The other is that gorges were formed by powerful rivers of glacial meltwater flowing through valleys or caverns, eroding the stone as they pass and producing deep, steep-sided valleys.

A well-known example of a gorge in the Yorkshire Dales National Park is the Trow Gill gorge, near Clapham.

Underground features

Cave

Cave, Slovenia

Large caverns can form underground in carboniferous limestone landscapes. They form when chemical solution is more active. They can be enlarged by erosion from rocks and stones carried by underground streams and waterfalls.

Inside the cave are a number of distinctive features, which have formed over hundreds of years. They are all the result of water permeating the rock and dissolving the limestone.

Stalactities, straw stalactities, stalagmites and pillar

Dripstone features

  • As drips appear from joints in the roof, carbon dioxide is lost from the lime-rich solution leaving calcite (calcium carbonate). The calcite builds up to form a stalactite hanging from the roof, like an icicle.
  • As drips land on the floor again carbon dioxide leaves and calcite deposits form a stalagmite. Because they build up this way, stalagmites are more rounded in appearance.
  • Rock pillars form where stalactites and stalagmites meet.
  • Straw stalactites are hollow and often appear like curtains hanging from the roof.

Social and economic opportunities

Most upland areas in the UK, including those which are National Parks, provide a range of social and economic opportunities for people. Some of these include farming, forestry, military training, recreation, water supply, mining and quarrying, as shown in the diagram below.

Mining and quarrying, water supply, farming, recreation, military training, and forestry

Socio-economic opportunities in upland areas

The relative importance of these land uses will vary, depending on the nature of the rocks and the physical landscape. Military training, for example, is more likely to occur in areas of moorland with few people. Water supply will be more important in a glaciated upland, such as Snowdonia, than in a limestone area such as the Yorkshire Dales.

Three land uses which are particularly important in the Yorkshire Dales are farming, mining and quarrying, and recreation. We’ll look at each in turn.

Farming

Farming in the Yorkshire Dales is characterised by:

  • sheep grazing on the uplands
  • cattle fed from hay meadows in the valley floors
  • a landscape of dry stone walls and stone barns

However, the traditional system is under threat, due to falling meat prices and increased competition from more intensive units both in this country and abroad. Within a National Park, it is important to maintain the traditional system and landscape.

Various methods are used:

  • EU price support for farmers rearing cattle and sheep
  • UK government grants to farmers who farm in a traditional way
  • payments for repair and conservation of barns and walls
  • help with farm diversification, so that farmers can get income from other sources

Mining and quarrying

Mining and quarrying will take place in a National Park if the rocks are in sufficient demand. In the Yorkshire Dales, around 4.5 million tonnes of rock are quarried each year. The main rocks quarried are carboniferous limestone and gritstone.

Most of the rock is used in the construction industry – half as roadstone and a further quarter as aggregate. The quarries have a substantial impact on the environment and their operation is opposed by many people.

Recreation

Visitors have been coming to the Yorkshire Dales since the 18th century, when writers and artists sought out the dramatic landscapes. The growth of the rail network in the 19th century brought increased numbers, but the most dramatic growth came in the late 20th century as a result of the rise in car ownership. More than 90% of today’s visitors come by car.

People visit the Yorkshire Dales to:

  • admire the distinctive scenery and landscape, such as Malham Cove and Goredale Scar and the waterfalls at Aysgarth and Ingleton
  • walk and climb
  • visit limestone caves – for example, the White Scar Caves
  • go potholing
  • enjoy peace and quiet
  • visit specific built attractions, like castles and museums

What opportunities for local people do these visitors provide? A recent survey identified the following numbers of tourism-generated jobs.

Tourism generated jobs

   
Serviced and self catering accommodation 852
Cafes, pubs and bars 506
Food and specialist shops 289
Garages 80
Parking 37
Visitor attractions 32

Be aware, though, that tourists also have a substantial impact on the environment and some people oppose their presence.

Environmental issues and conflicts

The upland limestone landscapes of Britain provide a range of opportunities for human activities, but these activities sometimes conflict with each other, and with the environment.

Quarrying

Quarrying is an important activity in the Yorkshire Dales, because:

  • limestone has a variety of uses – aggregate for the construction industry, flux for the steel industry, building stone, agricultural lime
  • millstone grit is used for various surfacing applications – roads, footpaths, airport runways
  • the quarrying industry employs seven per cent of the working population of the Dales and contributes £6 million a year to the local economy

Some people object to quarrying in the Dales because:

  • limestone and the grits are non-renewable resources
  • most of the stone (85 per cent) is transported by heavy goods vehicles on roads which are often busy with tourist and other local traffic
  • quarries produce noise and dust, and can pollute water supplies
  • quarries can leave a scarred landscape when they are finally abandoned

One of the tasks of the National Park Authority is to ensure that quarrying operations are as environmentally acceptable as possible. They do this by:

  • encouraging screening of the quarry, for example through a programme of tree-planting at Ingleton quarry
  • promoting rail transport by, for example, upgrading the rail facilities at Swinden Quarry near Skipton
  • ensuring restoration is carried out appropriately, often with nature conservation in mind

Tourism

Tourism is hugely important to the economy of the Dales. It is estimated that more than 1,000 jobs depend on tourism; in providing accommodation, in catering and in shops, for example. Tourists spend around £100 million in and around the National Park.

Tourists do create tensions, however – sometimes upsetting local residents and sometimes damaging the environment. These tensions are found in many parts of the Dales, but especially in ‘honeypots’, like the village of Malham, where:

  • tourist traffic creates congestion in the village, and impedes local people carrying out their everyday activities
  • the demand for car parking exceeds the number of spaces provided, resulting in parking on grass verges
  • footpaths have been eroded, particularly in the areas around Malham Cove and Gordale Scar
  • litter detracts from the appearance of the area and can harm livestock and wildlife
  • tourists sometimes wander over cultivated land, worry sheep and damage walls
  • house prices in the village increase, partly because of incomers wishing to live in the village, and partly because there’s a demand for second homes
  • young people are forced to move away because of the increase in house prices
  • the limestone pavements suffer from wear and tear, and from the removal of stone

The National Park Authority attempts to ease these tensions by:

  • removing litter bins, in the hope that visitors will take litter home
  • surfacing busy paths and building steps up the side of Malham Cove, to prevent further erosion
  • promoting the use of public transport such as Postbus passenger services and a Dales Bike Bus, which can carry 24 bikes
  • introducing legislation and a warden service to protect limestone pavements
  • publishing a Dales Visitor Guide which advises visitors on environmentally positive behaviour

 

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