How is coal formed?

6 Answers
How is coal formed?

Most fossil fuels are made from decayed plants, coal is mainly made up of carbon with differing amounts of other constituents like hydrogen, sulfer, nitrogen and oxygen.

Coal started life as layers of plants and leaves and other vegetation that collected at the bottom of a pool of water. These over a long period of time eventually became massive peat bogs in which the acidic water halted the decay of the plant matter and pressure from layers of sediment and mud created chemical changes which transformed it into the sold mass of coal.

There are different standards of coal.

It starts with the poorer grades of coal such as Lignite and Sub-bitumous coal, jet is a form of lignite and was polished and often used in making jewellery, particularly mourning items due to its somber colouring.

Bitumous coal comes next and is mainly used in power stations and for making Coke.

Anthracite is the highest quality coal and is used for residential purposes as it creates the greatest heat per tonne.

Graphite comes after this but is seldom used as a fuel but more commonly as lead for pencils and ground as a lubricant.

Oil and gas are formed in a very similar way, from layers of organic matter, the only difference is that both oil and gas were heated during the transformation. Gas is found at a deeper level than oil as the heat and the pressure increased.

Another fuel made from organic matter is peat or turf which is used in Ireland as one of the principle fuel sources. it is made of the same organic matter as coal but it is earlier in the process of transformation. It fires power stations for electricity and is also cut by individuals for their home fuel supply. The European Union has recently issued a directive to say that all Irelands peat bogs have to be preserved for the future and no more cutting is allowed.


There are two theories on this. Although it is accepted and proven that Carbon (animal and plant matter) turns to coal and oil.

There are now two camps, which are Biotic (traditional theory and assumption, that comes from accepted research) and Abiotic (A modern theory, that comes from extensive study, data and new research).

The Biotic Theory is that only plant and animal material that has decayed, contribute to coal's formation or that this material in concert with the Earth's natural processes, is the catalyst for all Coal (and Oil).

The there is the Abiotic camp. The Abiotic theory, recognizes that carbon from plants and animals help to form coal and oil; But, says that it is a natural process in and of it's self. Abiotic states that even without the added carbon from plants and animals; the Earth produces enough of it's own Carbon, that there would be Coal and Oil anyway.

This is basest explanation of the two competing theories. Of course there's much more to it than that, but in short, these are the opinions.

Having studied this, I can say that the Abiotic theory is definately gaining ground, due to samples, surveys, chronological, geologic and geographical comparisons.

That's a quick overview on what helps to make Coal.

As far as how it it is formed, here is a quick and basic answer.

The intense pressures within the Earth not only compacts Carbon, elements and minerals together; but the pressure and heat also cause a change in chemical composition.

Til, in the end, after much pressure, heat and gradual change, we find coal in place of the basic recipe.


Coal is called a fossil fuel because it was formed from the remains of vegetation that grew as long as 400 million years ago. It is often referred to as "buried sunshine," because the plants which formed coal captured energy from the sun through photosynthesis to create the compounds that make up plant tissues. The most important element in the plant material is carbon, which gives coal most of its energy.
Most of our coal was formed about 300 million years ago, when much of the earth was covered by steamy swamps. As plants and trees died, their remains sank to the bottom of the swampy areas, accumulating layer upon layer and eventually forming a soggy, dense material called peat.


The formation of coal is a process of hundreds of thousands of years. Coal is formed by the action of extremee temperature and pressure under the earth's surface on dead remains of plants and animals. The only element that is left in abundance from the biomass of the plants and animals is Carbon. Under the extreme temperature and pressure inside the earth's crust, the carbon-carbon bonds are so modified, that they form coal. Thus, coal is nothing but carbon, although traces of other elements are also found in it like sulfur. These also come from the remains of plants and animals.

Thank you for the question.


Coal is a fossil fuel, formed when the forest trees and vegetation got buried under the earth. Due to heavy pressure and heat, these trees and plants became coal.
Coal is highly rich in carbon and are classified in three groups, lignite coal, bituminous coal and anthracite coal.


Coal is a natural dark brown to black graphitelike material used as a fuel, formed from fossilized plants and consisting of amorphous carbon with various organic and some inorganic compounds.