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FOUR SPHERE OF EARTH

The natural environment can be broadly divided into four spheres, i.e. Lithosphere, Atmosphere, Hydrosphere and Biosphere. Each of these is unique in its own way and supports others in sustaining life forms on our planet called the Mother Earth. Let us understand the importance of each sphere of the natural environment.

Lithosphere

The literal meaning of 'lithosphere' is the 'sphere of rocks'. The earth's solid layer is called lithosphere.The lithosphere is about 100 km in thickness. The uppermost part of the lithosphere is composed of rocks rich in silica and aluminium called sial. Below the sial layer, the rocks are mainly rich in silica and magnesium and are called sima, which is generally found below the bottom of the ocean basins

Thus, lithosphere is that part of the earth which provides us land over which we live. It provides soil for the plants and is also a source of all the mineral wealth)


Atmosphere

The literal meaning of 'atmosphere' is the 'sphere of air'. The atmosphere is composed of a mixture of gases which forms an envelope around the earth. It is a gaseous envelope extending about 1,600 km above the earth's surface. Of the total mass of the atmosphere, 99 per cent exist within 32 km of height from the earth's surface.

Among the four major elements of environment, atmosphere is the most dynamic in natu where changes occur not only from one season to another but also within a short period of time s a few hours. These sudden changes produce changes in atmospheric conditions which affect our both directly and indirectly.

Hydrosphere

Hydrosphere refers to the 'sphere of water' which is present in oceans, rivers, lakes and other water bodies on the earth's surface. The planet earth is often called the Water Planet or the Blue Planet because of abundance of water on its surface. The water bodies that include rivers, lakes, seas and oceans cover 71 per cent of the earth's surface.


The distribution of water is not uniform in both the Northern and the Southern Hemispheres. It is estimated that 43 per cent of the total area covered by water lies in the Northern Hemisphere whereas the remaining 57 per cent lies in the Southern Hemisphere. Oceans hold 96.5 per cent water on the earth. Rest of the water is available in the form of ice, water vapours, underground water, rivers and lakes.

Biosphere

 The word 'biosphere literally means the 'sphere of life'. Biosphere is the narrow zone of contact between all the other three spheres of environment where ail kinds of life exist.

Most of the living organisms like plants, animals and microbes present on the earth are found on or near the earth's surface of the land, water and air. Human beings are an important part of the biosphere. They are capable of changing it.



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