Generally, it is believed that part of Sun, which has been detached form the Sun after the collision; is Earth. At the time of its origin, it was in the form of a fireball. This fireball started to cool down slowly. Many elements of the Earth got transformed into liquid and further into solid form. During this process, the elements which got transformed into solid are known as the lithosphere. The elements which got transformed into liquid are known as the hydrosphere. The elements which got transformed into gases are known as the atmosphere. Above all. the living world which developed due to land, water and air came to be known as the Biosphere. In this way, the four spheres came into existence on.
Hydrosphere
The Hydrosphere is the liquid component of the Earth. It includes the oceans, seas, lakes, ponds, rivers and streams. On the surface of the Earth, the area of water is more than that of land. Hydrosphere covers 71% of the Earth’s surface. A water body in the hydrosphere that carries a huge amount of water is known as the ocean. These oceans are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Arctic Ocean. All these oceans are connected with each other. The water bodies close to the land are known as seas, bays, straits, gulfs, etc. The oceans on the earth are huge and deep. Valleys with depth of 10 to 11 kms are located at their bottom. The ocean bed has similar features like that of the surface of the Earth. It has high mountains, plateaus, vast plains, valleys, etc.
Oceans contain 97% of the total amount of water on the earth. Approximately 1/3 of remaining water is trapped in ice-caps and glaciers (at Poles, Himalayas and other mountains). Some water is accumulated in the lakes and some flows in the rivers and some is stored in the interior of Earth as ground water. The amount of potable (fit for drinking) water is less. Fresh water is precious. This Fresh water is required by living beings for their existence. The moisture for rain, which is the main source of freshwater, comes from the oceans only.
Valuable chemicals, minerals, salt, fishes, etc. are found in the seas. As we have living organisms on the land, in the same way, the seas and oceans have aquatic life inside them. The tremendous force of waves, tides and currents of oceans are potential sources for generating electricity. Besides, these oceans are also useful as waterways.
Biosphere
The part of the lithosphere, hydrosphere and atmosphere where the living world exists is known as the biosphere. Biosphere is one of the most important spheres on Earth. Earth is the only planet in the solar system having a biosphere. Biosphere includes vegetation, animals, insects and human beings. We obtain food and many other necessary things from the biosphere. We cannot live without vegetation and animals. Biosphere is the base of our existence and living. It is divided into two parts: (1) Non-living and (2) Living. Lithosphere, Hydrosphere and Atmosphere form the non-living part while plants, animals and microorganisms are included in the living world.
Lithosphere
The sphere on which we live is known as the lithosphere. ‘Litho’ means rock and ‘sphere’ means layer. The upper layer of the Earth is made of soil and solid materials like rock. Approximately 29% of the surface of the Earth is covered with lithosphere. This layer is almost 64 km to 100 km thick. The thickness of the lithosphere is not the same everywhere on the earth. Similarly, their interior and exterior do not have identical physical features. It is mostly made up of substances like soil and rocks.
Landforms like mountains, plateaus, plains and valleys are seen on the lithosphere. The temperature increases as we move towards the center of the Earth. The molten rocks in the interior of the Earth are known as Magma. There are many gases present in the interior of the Earth which rise up with pressure and heat. But the pressure of rocks on the surface of the Earth is equally strong. Thus, balance between the two is maintained. So, the crust of the Earth does not break. When the balance between the two is not maintained the crust breaks and a volcano erupts.
Atmosphere
The sphere of air that wraps the Earth from all sides is called Atmosphere. It extends approximately upto 1600 km from the surface of Earth. It cannot be seen clearly with the naked eye like Lithosphere and Hydrosphere. Atmosphere is composed of various gases, water vapour, dust particles, smoke, salt, micro organisms etc. Atmosphere is colourless, odourless and transparent. Solid, liquid and gaseous elements are included in the Atmosphere. It contains approximately 78% nitrogen, 21% oxygen and 1% other gases.
When we go higher from the surface of the Earth, the amount of the most of the gases in the atmosphere decreases. Carbon dioxide gas is heavy so it is found more in the lower layer of the air.
Ozone gas comprises a very small proportion in the air. This gas absorbs the ultraviolet rays from the Sun and protects the Earth from excessive heat from the Sun. This gas is more in proportion in the morning in the open ground and in the air near the sea.
Gases like oxygen and nitrogen and keeps the living creatures on the Earth alive. Nitrogen reduces the intensity of oxygen. Water is the most important component in the atmosphere. Due to heat, the water in the form of vapour evaporates and mixes with air which is known as moisture. The process of cooling of vapour is called condensation. Various forms of moisture like dew, fog, clouds and precipitation are due to condensation. The effect of atmosphere is seen on human beings in every aspect of life such as in their food habits, clothing, habitat, colour, economic activities, etc.
Many dust particles are seen in the atmosphere. Spreads of Sundays are visible due to these particles. It is due to dust particles that it does not suddenly turn dark after the sunset and it does not suddenly turn bright after the sunrise. The sunrays are reflected back with the help of these dust particles on the surface of the Earth and we receive the light of the Sun. We are able to listen to the sounds due to the presence of atmosphere.
How human activities affect the spheres?
Human beings knowingly and unknowingly undertake many activities for their development. Human action causes an imbalance in the different spheres. Due to this, the balance of various spheres is threatened. Underground nuclear testing, too much drilling for mineral oil and excessive drilling of tube wells affects the lithosphere and causes an imbalance. The dumping of waste from villages and cities along with industrial waste into the water bodies pollute them. The Polar caps have started melting due to increasing heat. The oil spills from ships and disposal of industrial and chemical waste into the water causes the destruction of marine life which is highly dangerous for the hydrosphere. Harmful gases emitted by the industries, workshops, power stations and vehicles pollute air. The areas with the higher frequency of vehicles show increased rates of carbon monoxide in the air. The amount of CO2 in the air increases due to the cutting of trees. Heat on the Earth increases due to increase in CO2 in air. In this way, Human activities affect the Biosphere.
The nurturing links of nature are endangered due to the exploitation of the environment which endangers the Biosphere.
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