Coal and Petroleum - Exhaustible Natural Resources

There are so many materials catering to our various needs on a daily basis. We drink water, eat food, breathe air, go to school etc. All these things are available to us, but are all free of cost and readily accessible without fear of being depleted one day?

No. Not everything is readily available to us. For instance, sunlight, air etc are resources which we find in abundance and it won’t be depleted any time soon. Hence, these resources are called as Inexhaustible natural resources.

Other resources are created in very limited quantities and it takes a very long time for such resources to be replenished. Such resources are known as exhaustible natural resources. Ex: coal, petroleum, minerals, natural gas etc. Let us briefly understand few of these resources.

Coal and Petroleum

Coal and petroleum are formed as a result of degradation of ancient plant life which lived millions of years ago. These dead plant matter started to pile up, eventually forming a substance called peat. Over time, heat and pressure from geological processes transformed these materials into coal. Since these are formed from essentially fossils, they are also known as fossil fuels.

How Is Coal Formed?

Formation of coal dates back to millions of years ago, when the earth was covered only with vast moist forests, having huge trees, shrubs, ferns etc. These plants underwent their life cycle and withered away eventually falling back to the ground, most of which were swamps. New plants replaced them, they underwent a life cycle and the whole process continued repeatedly over the years as a result of which the earth bed started accumulating all these dead plants.

This gave rise to a very thick layer of dead decomposed matter packing down plant matter washing away all the decayed matter. Physical and chemical changes took place as a result of heat and temperature extracting out all oxygen leaving the plant layers with carbon-rich content, thus resulting in the formation of coal over a period of time.

Types Of Coal

Coal is a readily combustible rock containing more than 50% by weight of carbon.

Coal formed can be of three types depending on the amount of oxygen, carbon and hydrogen they contain, they are:

  • Lignite
  • Bituminous
  • Anthracite


Petroleum is a fossil fuel that naturally occurs in the liquid form created by the decomposition of organic matter beneath the surface of the earth millions of years ago. These fossil fuels are then refined into usable substances such as petrol, kerosene etc. It is formed by the combination of hydrocarbons and other substances, mainly sulphur. When first collected in its natural form, it is termed as crude oil. This substance is generally characterized by a brownish- black colour. Although, it can also differ between red to pale yellow or even colourless. Its thickness (viscosity) varies from nearly solid tar-like consistency to low viscosity, almost like water.

Refining petroleum thus obtained yields many useful products. Let’s have a look at it.

Products of Petroleum

Petroleum products are obtained as a result of refining crude oil in oil refineries. There are numerous products that are created from petroleum and its by-products. A study reveals that by-products of petroleum alone provides scope to obtain 6000+ new products, to name a few, fertilizer, perfume, flooring, insecticides, soaps, vitamins, petroleum jelly etc.

Few of the products obtained from petroleum are:

  • Gasoline
  • Diesel oil
  • Kerosene
  • Tar
  • Heavy fuel oil
  • Petroleum coke
  • Lubricants
  • Special Naphthas
  • Paraffin wax
  • Aviation Gasoline

Uses of Petroleum

Petroleum is one of the most important and widely used fuels in today’s time. Some of its advantages are:

  • These are transportation fuels, i.e, via air, water or land.
  • Diesel is used to power turbines for the production of electricity in large scale industries.
  • Oil is used to produce electricity at homes and shops
  • Oils help lubricate different types of high-end machines used in different industries, hospitals etc.
  • Kerosene is used for domestic purposes at home
  • Used by chemical industries to produce plastic, dyes, paints, synthetic rubber, pesticides, perfumes etc.

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Practise This Question

Identify the following labeled parts of pituitary gland.