Main Rock Types in the UK (Edexcel GCSE Geography A)

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

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Formation of sedimentary 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

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

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Distribution of rock types in the UK

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