Geography-Lisophere-Limestone

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Explain the formation of a lime stone pavement?
- A limestone pavement is a large, flat outcrop of bare limestone lying horizontally on hillslopes or summits
- it is formed when soil was stripped by glacial erosion which exposes the bare limestone to chemical weathering
- Carbonation and solution chemically erode the exposed limeston and deepen and widen the joints in the rock(grikes)
- Grikes are further deepened by frost action and plant roots
- The higher limestone blocks are called clints.
Explain the formation of Stalactites, Stalagmites and pillars.
- Found in cave systems where the underground water is rich in calcium carbonate(CaCO₃)
- CaCO₃ rich water percolates downwards through joints in the limestone.
- As it reaches the open cave, some water evaporates and the CaCO₃ is redeposited as Calcite
- Stalagmites are rounded mounds of calcite which build up on the floor of the cave as the water drips splash on the ground
- Stalagtites are calcite 'icicles' hanging from the roof of a cave formed as water drips downwards.
- Where Stalactites and Stalagmites meet a calcite pillar forms
Explain the formation of a swallow hole
- A swallow hole is a very large joint where a stream disappears into the underground drainage system (intermitted)
- They are found at the boundry of impermiable rock -eg Shale and the permeable limestone
- The river flows on the surface across the impermiable rock but when it reaches the limestone the water reacts with the CaCO₃ and carbonation and solution enlarge the joint so much that the river flows into the limestone.
- Often an underground waterfall forms at a swallow hole- eg Gaping Ghyll
- The stream flows underground along the bedding planes and down joints until it meets impermeable rock again.it is forces to reapear at the surface at a resurgance point
Explain the formation of a gorge
- A gorge is a valley in limestone with near vertical cliffs. it is sometimes ocupied by a river.
- it is thought to be formed from a roof collapse of an underground cavern
- most likely to happen during meltwater surges at the end of the ice age which would have enlarged the underground cavern and de-stabalised it
- Meltwater exploited the weak line of a major joint causing collapse of the cavern roof
- may also have been formed due to rapid downcutting by a former river when the water table was higher

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Smyth159

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Geography-Lisophere-Limestone

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Geography-Lisophere-Limestone

Updated

4/5/2011, 4:37:14 PM

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