Formation of Coal
Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. It is the our most abundant fossil fuel in the world.
Coal is a nonrenewable energy source because it takes millions of years to create. Please have a look at our Time Line, where you will see that it took coal over 300 million years to form, while we humans are only 1.8 million years around and have been able to deplete the coal reserves already by a 30%.
The energy in coal comes from the energy stored by plants that lived hundreds of millions of years ago, when the earth was partly covered with swampy forests. For millions of years, a layer of dead plants at the bottom of the swamps was covered by layers of water and dirt, trapping the energy of the dead plants. The heat and pressure from the top layers helped the plant remains turn into what we today call coal.
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1 Lush vegetation grew in warm swampy areas that covered much of the world about 300 million years ago. The plants and trees absorbed the rays of the sun - used in photosynthesis - which was stored in the leaves and tissues.
2 As the vegetation died, it fell into the swamps. As the amount of material accumulated in the presence of the water, it began to form a spongy, brown material which we know as peat or peat moss.
3 Over time, geologic forces buried the peat bogs - sometimes hundreds of feet deep - where they were compacted by the pressure of the soil and rock on top of them.
4 Coal was gradually formed from the buried peat. The greater the pressure under which the coal was formed, the harder the coal that was produced.
