Geology The study of rocks

Geology of the British Isles

The British Isles is made up of many different types of rock.

These different rock types give us the wonderful range of scenery we enjoy.

How rocks are formed

Igneous RocksThese rocks are formed when magma / lava cools and hardens on the surface and in the crust.

Igneous rocks are very hard / resistant.

Granite is a good example.

Granite is used for buildings, roads, etc.

Intrusive feature / batholith

Igneous LandscapesDartmoor

Dartmoor in S.W. England is an upland area over 800m high. It can be wet windy and misty but also stunningly beautiful on clear days.

It is a National Park.

Sedimentary Rocks

Sedimentary Rocks

These rocks are formed under water in rivers lakes and oceans.

They build up in layers.

Examples include:

Sandstone, Limestone and Chalk.

Limestone SceneryMalham in Derbyshire

Limestone Caves

Limestone is alkaline and has a chemical reaction with rainwater which is slightly acid.

The rock dissolves and forms amazing features like underground caves.

Stalactites and stalagmites are special underground features.

Metamorphic RocksThese rocks are formed by changes in heat and pressure.

Clay can be changed into slate when superheated.

These rocks are very resistant.

Slate is a good example.

It is used for roofing.

Weathering and Erosion

All rocks are eventually broken down even the hardest like granite.

Rocks can be broken down by Weathering, Erosion or a combination of both.

Erosion by water

Erosion by Wind

Erosion by Ice

Biological Weathering

The roots systems of this tree are working their way into the cracks of the rocks.

They break open the cracks and weaken the rock.

Chemical Weathering

Pollution in the atmosphere from factories makes all rainwater slightly acidic.

CO2 + SO2

When this rain falls onto limestone it chemically

dissolves it creating spectacular underground

scenery.

Physical WeatheringFreeze Thaw Process

All rocks have small cracks in them called fissures.

Water collects in the cracks and when it is cold enough freezes. The ice expands opening up the crack.

More water fills the crack. Ice forms and expands opening the crack further.

The process is repeated until the rock breaks down.

This process happens in mountain regions where temperatures are low.

Mechanical Weathering

Temperature changes can cause the rock to expand / contract. The layers can break away and the rock breaks down.

This can happen in desert environments.

Rock weathering in Australia

Weathering SketchWeathering Sketch