How Coal Formed

The coal mined in many parts of the world today formed around 250 to 350 million years ago. This period is known as the Carboniferous and Permian periods. Large reptiles lived on Earth at that time; the age of the dinosaurs had not yet begun.

It was very hot and humid, and there were vast swamp forests where ferns and the ancestors of our trees grew. When the trees and other plants died, they settled in the swampy ground. From time to time, they were covered by other layers of sediment.

This process was repeated over a very long period, and new layers of dead plant material kept forming. The weight of the layers created great pressure.

First, peat formed. Over time, it was compressed and drained. The proportion of carbon steadily increased. Peat first became lignite and eventually hard coal.

The key conditions for coal to form were that the plant remains were sealed off from the air, and exposed to high pressure and high temperatures. The layers that turned into coal are called coal seams.

Coal can be turned into coke. To do this, coal is heated to high temperatures in an airtight chamber. This removes the gases, water and sulphur trapped inside. What remains is coke. This fuel produces high temperatures and only small amounts of smoke or soot. It was once used mainly in blast furnaces to produce iron and steel.

Burning peat, lignite or hard coal releases carbon dioxide, also known as CO2. This gas builds up in the Earth’s atmosphere and contributes to climate change.

Find out:

How long ago did coal form?
What is this geological era called?
How was coal formed?
What formed first from the dead plant material?
What happened next?
What was needed for coal to form?
What fuel can coal be converted into?
What was coke used for in the past?
Which gas is released when peat, coal and coke are burned?
What does this gas contribute to?