We get many substances from nature. They satisfy a variety of our daily needs. Soil, stones, minerals, air, water, plants and animals on the earth are all various kinds of natural resources.
Natural resources in the earth’s crust
The earth’s lithosphere is made up of land and the hard crust beneath it. The lithosphere is not homogeneous but is made up of many types of rocks. Resources in the earth’s crust include minerals, ores, mineral oil and other fuels, rocks, water, elements, etc.
Minerals and ores
Mineral wealth has an important place among natural resources. Minerals are formed by various processes taking place in the environment. The rocks on the earth are mainly made of minerals. These minerals can be obtained by mining.
Only a few metals like, for example, gold, silver, copper, platinum and bismuth occur in the free state in nature. A majority of the metals occur in the form of compounds. Minerals that contain a high proportion of metal are called ores. It is economical to obtain metals from ores. The properties of minerals become clear from their characteristic colour, lustre, hardness, shape (length), cleavage or fracture and streak.
Some important minerals and ores
- Iron ore : Iron occurring in the impure state is called iron ore. Iron ore is used to make a variety of articles from pins to heavy machinery. For example, farming implements, rails of railway tracks, etc. The four main ores of iron are magnetite, haematite, limonite and siderite.
- Manganese : Manganese occurs in the form of its carbonate, silicate and oxide. Compounds of manganese are used in the preparation of medicines and for giving a pink tinge to glass. Manganese is also used in electrical appliances.
- Bauxite : Bauxite is the most important ore of aluminium. It contains 55% aluminium. Bauxite consists mainly of aluminium oxide. Aluminium is a very good conductor of electricity and heat. Its density is low. Therefore, it is used mainly in aeroplanes, transport vehicles and to make electric wires.
- Copper : Copper is found in the impure state in the vicinity of iron and other minerals. Copper is a very good conductor of electricity. Therefore, it is used to make electric wires as well as in radios, telephones, vehicles, and for making kitchen utensils and statues.
- Mica : Mica is a bad conductor of electricity. Its value depends on the thickness of its layers. Mica has many uses such as in ayurvedic medicines, dyes, electric machines and equipment, wireless communication equipment, etc. How did the various ages of the prehistoric period get their names on the basis of the use of metals ?
Various substances are used in day-to-day life for generating energy. These substances are called fuels. Fuels are found in the solid, liquid or gaseous state.
Millions of years ago, forests got buried underground as a result of certain natural events. Layers of soil kept getting deposited over them. The very high pressure from above and the heat from the earth’s interior, slowly transformed the buried plants into fuel. Coal was thus formed from the remains of those plants. That is why coal is said to be a fossil fuel.
Coal is found in mines. Peat, lignite (brown coal), bituminous coal and anthracite are the various types of coal. Anthracite is the coal of the highest grade.
Coal is, in a way, a storehouse of carbon. It is burnt to obtain heat energy. Coal is used as fuel. It is used as a fuel in thermal power plants as well as to run boilers and railway engines. Coal is also used as a fuel for cooking and for baking bricks in kilns on a large scale. The gaseous fuels, producer gas and water gas, are obtained from coal. Coal, as an energy resource, contributes greatly to industrial development.
The demand for fuels has increased greatly due to the rapidly growing population but the reserves of fossil fuel are limited. It is becoming difficult to meet the increased demand. The likelihood of these reserves getting exhausted is known as the energy crisis. As the reserves of fossil fuels, namely, mineral oil and coal are limited and the demand is increasing, alternative fuels are coming into use. Hydrogen, biofuels, methanol or wood alcohol, ethanol or green alcohol are some of the alternative fuels.
An extensive area of land covered by a variety of plants is called a forest. A forest is a natural habitat of plants, animals and microbes. About 30% of the total land of the world is covered by forests. Forests perform certain specific protective and productive functions.
We have learnt that oceans occupy a greater part of the earth’s surface than land does. Energy can be obtained on a large scale from oceans. Sea waves at high and low tide and ocean currents are being used for generation of power. Last year, we have learnt something about this in Geography. There are reserves of a variety of natural resources in seawater, at the bottom of the sea and beneath the seabed, too. These resources available from seas and oceans are called marine resources.
Mineral and bio-resources from oceans
Scientists believe that billions of tons of minerals are to be found dissolved in ocean water. There are very large reserves of tin, chromium, phosphates, copper, zinc, iron, lead, manganese, sulphur, uranium, etc. in the ocean and seabeds. We get many types of gems, conches, shells and pearls from the sea. Real pearls are even costlier than gold. There are large scale reserves of mineral oil and natural gas at the bottom of sea. We avail of these by drilling oil and gas wells.