Before we can learn of the compositional layers and mechanical layers of the interiors of earth, we need to know some basic concept of the four spheres. As we may know the four spheres responsible for life on earth: lithosphere, atmosphere, hydrosphere and biosphere; and their interaction with each other is called Geosphere (Fig. 1.). Another sphere that isn’t included among the rest for its different property is Pedosphere. Pedosphere is basically the interaction between the lithosphere, atmosphere, hydrosphere and biosphere. We can even say pedosphere is the layer that lies below the biosphere and above the lithosphere and hydrosphere which is the soil. Not getting in depth with pedosphere, we shall now talk about …show more content…
1, Shows the four sphere.
Atmosphere: it is the air that surrounds us. The earth’s atmosphere contains maximum quantity of nitrogen, which is about 78 .08%, oxygen of 20.95%, argon of 0.93%, carbon dioxide of 0.038%, hydrogen, helium, and other "noble" gases are also present. These current compositions of gases is the result of biochemical modification, over billions years.
Earth’s atmosphere provides us with oxygen which we breathe, carbon dioxide which is used by plants for photosynthesis and also protects living organisms from harmful radiations from the sun, by creating a protective layer around the earth’s surface.
Hydrosphere: this includes all the water bodies found on the earth. For example: ponds, lakes, rivers, streams, oceans, seas etc. glaciers, icebergs, snow, clouds, rain is also a part of hydrosphere. Of all, only 2.5% of fresh water and about 97.5% of salt water covers the earth. About 75% of the earth’s surface is covered by oceans.
Lithosphere: it includes the outer surface of the earth i.e. the crust. Everything from high mountains to ground level is a part of lithosphere.
Biosphere: it includes all the living organism, all possible live on …show more content…
Based on the chemical compositions of the different layers, it has given rise to the terms: Crust, Mantle and core. Fig. 2, Shows the compositional layers of the earth: crust, mantle and core. (http://fastoutofthegate.com/Notes%20from%20the%20Geosphere)
Beginning with the outermost layer, called the crust. Crust is the thinnest layer of the other. It is about 8 to 40 kilometers in-depth. It is mostly made up of silicate. Because of its low density is floats above the denser mantle. Crust are found in two types:
1. Continental Crust.
It is the thickest in the mountainous regions. The thickness of continental crust ranges from 15km to 70km. It’s composed of volcanic lava and sediments forming andesite and granite.
2. Oceanic Crust.
It is the crust that lies beneath the oceans’ bed and is thin. The thickness of oceanic crust ranges from 5km to 10km. It is composed of maximum proportion of magnesium, basalt and gabbro.
Fig.3, shows the two types of earth’s crust: continental crust and oceanic