1. Carboniferous Limestone
Lithosphere
Carboniferous Limestone

2. Carboniferous limestone
Is entirely made up of calcium carbonate.
Is pervious – water is able to pass through it by means of joints and bedding planes.
It is physically strong but dissolves slowly in rainwater.
Joints and bedding planes are gradually enlarged by underground water into wide channels and gaping chambers
It absorbs all surface drainage.

3. How was it formed?
In the carboniferous period shallow tropical seas covered the area. Corals and remains of sea creatures were deposited.
Over 60 million years these were compressed into limestone as other sediments were overlain.

4. And…. Crustal movements then upfolded the entire area.
As the younger sedimentary have been eroded, the limestone was exposed, forming high rugged uplands reaching over 600 metres

5. Joints and Bedding Planes
The bedding planes are the old sea beds.
The joints formed as the limestone dried out or as pressure was released.

6. Limestone Pavements
Grykes
Clints
The Limestone Pavement

7. Formation of surface features
The process of solution has been a major importance in shaping the limestone scenery.
The rate that limestone dissolves depends on the amount of carbon dioxide present in the water acting upon it.
Glaciers scraped away vegetation to expose bare rock which allows the rock to be weathered by solution
CaCo3 + Co2 + H2O = Ca(HCO3)2
Insoluble carbonic acid soluble

8. Formation of Limestone pavement
Limestone Pavements are bare limestone rock surfaces composed of slabs of rock (clints), separated by variable-width vertical cracks (grikes). These grikes have developed by weathering and enhanced solution along joints. Composed principally of calcite, limestone is vulnerable to chemical weathering by water (solution) and dissolves easily. In the Yorkshire Dales, exposure of very extensive pavements may be partly an example of the stripping of soil by moving ice during the last glaciation period more than 10,000 years ago.

9. Sink Hole
Surface and rain water do not flow far on exposed limestone, but infiltrate rapidly into the rock and soil. Where a joint or intersection of joints has been greatly weathered or dissolved water can pass down through the limestone . A stream travelling over an impermeable rock will very quickly disappear when it has to travel over limestone. These sinkholes can be many metres deep leading down to a series of subsurface features
Sink Hole

10. Shake Hole
A shakehole is a depression in the limestone landscape. In some limestone areas there is a covering of boulder clay about two or three metres thick. Shakeholes are formed where surface water washes the boulder clay down into cracks or fissures in the limestone under the boulder clay. They are usually found in groups. Cavers have to dig the boulder clay out to see if there is a pothole of any size underneath
Shake Hole

11. Drainage features Resurgence
When a stream disappears it travels underground through a complex series of caves and eventually works its way down to a level of impermeable rock or until it reaches the top of the water table. The stream travels along the surface of the impermeable rock until it reaches the surface as a spring. Where limestone lies on top of impermeable rock along a valley there can be several springs formed along the intersection of the two rocks. This is a spring line
Resurgence

12. Dry Valleys Watlowes Dry Valley
During the last ice age the limestone was frozen to great depths. When the ice melted it carved out valleys over the frozen rock. When the limestone thawed out the surface water was able to infiltrate down through the rocks and the dry valleys were left with no surface water.
Watlowes Dry Valley

13. Surface features resulting from underground drainage
During the meltwater phase of the last ice age, underground streams eroded vast caverns as huge volumes of water travelled through the limestone. Sometimes the roofs of these caverns can collapse exposing the "underground stream" in a very steep sided gorge.
Gordale Scar – a steep
Sided gorge

14. Underground Features

15. Formation of underground features
Heavy rain quickly infiltrates down. The caverns and passages can infill with water.
Where solution is more active underground caves form. Corrosion widens the cave until parts of the roof fall in.
Joints and bedding planes are enlarged by solution.
Stream flow erodes the passages by solution and the abrasive stream action.

16. Stalagmites, stalactites and pillars
In a process known as gas diffusion, water saturated with dissolved Calcium Carbonate enters a cave through joints in the roof. As it does so, it loses some CO2 and, helped by evaporation, this causes some Calcite (the pure form of the mineral) to precipitate out - forming a variety of underground dripstone features.

17. Stalactites and Stalagmites
Stalactites grow from the roof of the cave at a rate of about one inch every 5oo years. They are very pointed, due to the way in which the water drips from the end of the features.
Stalagmites are more rounded.The calcite ‘spreads’ more as the water drop drips from the ceiling to the floor.
Limestone pillars result from stalactites and stalagmites joining together.

18. Slopes
Scree slopes form in upland limestone areas. Here there is minimum surface drainage and little breakdown of bedrock to form soil so vegetation cover tends to be thin or absent. In winter this allows frost shattering to produces SCREE at the foot of steep cliffs.