How is Coal Formed

Coal is a black or brownish black fossil fuel, that was formed millions of years ago deep within the Earth's layers. It is a readily combustible fossil fuel, that is formed from dead plant matter of the Carboniferous Period. It is primarily carbon. However, it may also contain other elements like sulfur, hydrogen, oxygen and nitrogen in varying amounts. Coal is the source that meets most of the electricity requirements of the world. But coal takes million of years to form and we have accessed large reserves of this fossil fuel already. This has send us into a scurry for finding alternative energy sources. But how is coal formed? Let us understand the phenomenon in the succeeding lines.

Formation of Coal
Coal was formed 300 million years ago when most of the Earth's surface was covered with swamps. Terrestrial plants, mainly tall trees of swampy forests like lycopods, the giant ferns, horsetails, and club mosses died and fell in these swamps or shallow bodies of water, that were a common feature of the terrain. Due to climatic changes and catastrophic events, large amounts of forests sank into these swamps. These layers got covered with large quantities of mud and sand. As a result, the lower layers of vegetation got compressed to form a soggy, sponge like material called peat. The event of dead vegetation accumulating in the swamps and getting covered with sand and mud kept taking place as a cycle. This explains the alternating layers of coal and clay or sandstone (compacted sand) in the substratum. As the dead vegetation got buried in wet and acidic conditions, they also got cut off from direct supply of air. Hence, the decomposition process got slowed down and what resulted was peat, the first stage of coal formation. With more layers of soil and vegetable matter accumulating over peat, oxygen, hydrogen and water was squeezed out of it. With increase in pressure and further compacting between layers of sediments, peat changed into bituminous, subbituminous coal and finally to coal. In each step, the newly formed material is more rich in carbon than material in the previous stage. This is the story of how coal was formed in Earth.

The process of coal formation is an extremely slow process. The best form of coal with 90 to 95% carbon belongs to the Carboniferous Period, that dates back to 360 to 250 millions of years ago. However, coal was also formed in the subsequent ages like the Permian Period and the Secondary Period that spanned over 290 to 65 million years ago. Coals from certain areas formed during the Tertiary Period (65 million years ago to 2.6 million years ago) are also of excellent quality. This is due to the fact that the peat was brought into early maturity by heat generated due to collision of tectonic plates.

Where is Coal Found
Coal is found in seams (veins or coal beds) that may lie within less than 200 feet of the Earth, to those that are buried more than 1000 feet below the layers of soil. These coal beds are accessed through mining. If the coal deposits are shallow, then they are accessed through surface mining. The deeper coal beds that lie more than 1000 feet deep, are excavated using the process of deep mining or underground mining. However, this coal that is mined, needs to be processed which involves removing dirt, rocks, ash, sulfur and other contaminants. Removing these impurities increases the heating value of coal.

As far as the leading producers of coal are concerned, China tops the list. However, it is the United States of America that has the largest coal reserves. United States is followed by Russia, China and India in coal reserves. However, notable coal producing countries in the world are Australia, South Africa, USA, Russia, India and China.

So, that was the story of how is coal formed from ancient flora, that covered the Earth millions of years ago. Although, coal meets most of our energy requirements, burning coal releases more amount of pollutants than any other form of fossil fuel. This, coupled with the fact that we may soon run out of the reserves of coal, is making us consider other forms of fuel that could take the place of coal.