NCERT Solutions for Class 8 Social Science Geography Chapter 3

Minerals:
A naturally occurring substance that has a definite chemical composition is a mineral. Minerals are not evenly distributed over space. Some minerals are found in areas which are not easily accessible such as the Arctic Ocean bed and Antarctica. Minerals are formed in different types of geological environments, under varying conditions. They can be identified on the basis of their physical properties such as colour, density, hardness and chemical property such as solubility. They are created by natural processes without any human interference.

The process of taking out minerals from rocks buried under the earth’s surface is called mining. Minerals that lie at shallow depths are taken out by removing the surface layer; this is known as open-cast mining.

Deep bores, called shafts, have to be made to reach mineral deposits that lie at great depths. This is called shaft mining.

Petroleum and natural gas occur far below the earth’s surface. Deep wells are bored to take them out, this is called drilling.

Minerals that lie near the surface are simply dug out, by the process known as quarrying.

Salt, aluminum and iron.

Minerals rich in a particular element that can be extracted profitably is known as ores. Minerals occur in different types of rocks. Generally, metallic minerals are found in igneous and metamorphic rock formations that form large plateaus. While others occur in sedimentary rocks.

Russia, Norway, UK and the Netherlands are the regions in the world rich in natural gas. In India Jaisalmer, Krishna Godavari delta, Tripura and some areas off shore in Mumbai are rich in natural gas.

The sources of energy according to area are as follows: (a). Rural Areas: The biogas is one of the best sources of energy as per its availability and cost. (b). Coastal Areas: Hydel and tidal energy. (c). Arid Regions: Wind and solar energy as per speed of air and availability of sunlight.

The way to save energy at home are as follows: Switch on the appliances (bulb, fans, AC, etc.) only on requirement. Using led bulbs and tube which provides more light consuming less energy. Use efficient cooking or heating devices. Prevent leakage of electricity to save energy. Switching off all electrical objects in an empty rooms.

(b) Karnataka

(c) Chile

Building a dam faces a lot of environmental issues given below: It creates an imbalance in the Earth’s equilibrium leading earthquake threats. Large area of vegetation submerged under the water. Vegetation under the water decay under anaerobic condition realising greenhouse gases. Flood threats loom large. A huge population become displaced.

Coal is used as main source of energy in most of the industries that is why the most industries are concentrated around coal mines saving the cost of transportation of coal.

The crude form of petroleum is thick and black. It is sent to refineries which process the crude oil and produce a variety of products like diesel, petrol, kerosene, wax, plastics and lubricants. Petroleum and its derivatives are called Black Gold as they are very valuable.

Quarrying can become a major environmental concern because it may destroy the humus of soil which is much required for the growth of plants. It produces a lot of noise pollution due to use of explosives in order to break the huge chunks of rocks. During this process a lot of dust is also generated which causes air pollution.