Main Rock Types in the UK (Edexcel GCSE Geography A)
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Sedimentary Rocks
Rock groups
There are three types of rock
Each rock type's characteristics depend on its formation
Sedimentary rock
Formed from sediments and the remains of plants and animals which have settled at the bottom of a lake or ocean
The layers of sediment are compacted together until they become solid rock
There are two main types of sedimentary rocks in the UK:
Limestone and chalk
Clay and shale
Limestone and chalk come from the tiny shells and skeletons of dead sea creatures
Limestone is harder than chalk, but both are less resistant to erosion (softer compared to granite)
Limestone and chalk are relatively strong and permeable
Clays and shales are made from mud and clay minerals. They are:
Softer than limestone and chalk
Impermeable
Found mostly in the UK's lowland areas of the south, southeast and central UK
Clay landscapes are typically wide, flat plains
Igneous Rocks
Igneous rock
Igneous rock forms when magma from the mantle cools and hardens
As it cools, crystals form in the rock
Igneous rocks are hard and more resistant to erosion, e.g. granite and basalt
Mostly found in the northern upland areas of the UK
Metamorphic Rocks
Metamorphic rock
When rock (igneous, sedimentary or older metamorphic rock) is put under pressure and heated (but not melted)
The original rock becomes a new type of rock
This new rock becomes harder and more compact e.g. shale becomes slate and with more pressure and heat, slate becomes schist
Found within the upland areas of the UK
Very strong and resistant to erosion or weathering
Upland & Lowland Landscapes
The impact of geology on landscape
Stronger, more resistant rocks tend to produce highland areas
Weaker rocks tend to form lowlands
Permeability is whether a rock allows water to pass through it
Water will pass through permeable rocks
But impermeable rocks won't let water through
The permeability of rocks determines how wet or dry the surface of a landscape is
Limestone is a permeable rock that tends to form dry upland areas with few streams and thin soils
Clay is impermeable and often produces wet lowland areas
Granite landscapes are usually boggy and badly drained, as granite is impermeable
Rock types and their relationship to the landscape
Rock Type | Hardness | Resistance to Erosion and Weathering | Permeability | Found Mainly | Landscape Feature |
---|---|---|---|---|---|
Igneous | Hard | Resistant | Impermeable | Upland | Granite landscapes are usually boggy and badly drained |
Metamorphic | Very hard | Very resistant | Impermeable | Upland | Badly drained and boggy |
Sedimentary | Hard to very soft | Less resistant | Permeable Clay is impermeable | Lowland | Limestone features are caves and karst Chalk landscapes tend to be dry valleys (Inland - gentle hills, Steep cliffs at the coast) Clay collapses easily when wet (slumping) and forms gentle, wide landscapes, which are frequently waterlogged |
UK Geology
The relationship between geology and landscape can be seen in a map of the UK
The upland areas of the area to the north-west of the Tees-Exe line are dominated by igneous and metamorphic rocks
The lowland areas of the south-eastern UK are dominated by sedimentary rocks
Awaiting Image
Landscape
A landscape is defined as:
The character of an area, resulting from the action and interaction of natural and human elements
A landscape's character will depend on its initial geology, which gives a landscape its relief, which in turn attracts human action and interaction, for example:
Slate, a type of resistant rock, is found in the mountains of North Wales and has attracted people to quarry for roofing material
Upland and lowland landscapes of the UK
Role of tectonic processes
Past tectonic activity has shaped the UK's landscape:
Plate movement has moved the UK from the tropics
In the tropics, it was partially submerged in warm, shallow water
This formed the limestones of the Peak District, parts of south Wales and south-west England
The chalks and clays of England are the youngest rocks in the UK
These formed in the swamps and shallow seas before the tectonic plates moved the UK to its present position
When tectonic plates collided 520 million years ago, it forced the rocks to fold and uplift
This created the mountain ranges of the uplands: Scottish Highlands, Snowdonia, and the Lake District
The pressure and heat created the slate, shale and schist of the uplands
The UK used to be much closer to a plate boundary than it is now, and volcanic activity formed the granite (igneous rock) of the upper landscape:
The Giant's Causeway in Northern Ireland is made of huge hexagonal columns of basalt
Tors in Dartmoor formed as the less resistant rock around the granite was weathered and eroded
Worked Example
UK landscapes are made up of different rock types.
Identify one example of an igneous rock
(1 mark)
| A. Chalk |
| B. Granite |
| C Sandstone |
| D. Schist |
Answer:
B: Granite
The alternative answers are incorrect because
A and C are sedimentary rocks formed from deposits on the seabed being compressed over time
D is a metamorphic rock formed by heat and pressure at a plate boundary
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