C3.1 What were the origins of minerals in Britain that contributes to our economic wealth?
GEOLOGISTS are scientists who study rocks and the processes that formed them. They try to explain the past history of the Earth by modelling processes that can be observed today. We know that the Earth’s LITHOSPHERE (the crust and the upper part of the mantle) are divided into massive portions of rock called TECTONIC PLATES. These plates fit together like a jigsaw puzzle.
These plates have the ability to move due to CONVECTION CURRENTS that exist in the mantle. This movement means that parts of ancient continents that make up the Britain we know today have moved over the surface of the Earth.
Geologists can use MAGNETC CLUES in rock to track the very slow movement of the continents over the surface of the Earth. This movement is tracked by studying magnetic particles contained in some rocks such as certain types of lava and sediment that contain MAGNETITE. When lave has cooled, magnetite can become magnetised in the direction of the Earth’s magnetic field at that particular time – a similar process occurs with sediment.
Measuring the angle at which rocks are magnetised allows the latitude of the originally formed rock to be deduced. Comparing the predicted historical location and magnetic direction to the present location allows a map of continental movement to be developed.
The movement of continents has meant a wide range of rocks are found in Britain that has formed in different climates.
Over a million years, a number of NATURAL processes have led to the formation of valuable resources in Britain, such as COAL, LIMESTONE and SALT.
- Mountain formation
- Erosion
- Sedimentation
- Dissolving
- Evaporating
When plants have died and formed peat due to a lack of oxygen, the peat has been buried by sediment leading to a compression and heating. This eventually formed COAL.
Seawater that was inland millions of years ago created salt marshes. As water in these marshes EVAPORATED, deposits of ROCK SALT formed.
Today, geologists study sedimentary rocks to try to understand how they were formed and where the rocks came from. They look for clues buried in the rocks including:
- Fossils
- The presence of shell fragments
- Ripples from sea or riverbeds
- The shapes of water-borne grains compared to air-borne grains
Chemical industries grow up where resources are available locally. E.g. the chemical industry developed in the North-West of England because resources such as COAL, LIMESTONE and SALT were available locally. This meant that raw materials could be mined and used in one place, rather than having to be transported to a different part of the county. This made economic sense and provided jobs for local people.