Table of Contents

25 Amazing Points of Structure of Earth

Interior Structure of Earth

The Earth is made up of rocks with different compositions. Three concentric layers of rocks are found beneath the sedimentary rocks of the continents-

(a) Upper layer:

It is made of acidic rocks like granite and gneiss, which is called Sial (SIAI).

25 Amazing Points of Structure of Earth

(b) Middle layer:

This layer is made up of basic rocks like basalt and gabbro. This is known as Sima.

It is mainly dominated by heavy metals like nickel and iron. These rocks exist because of the Earth’s magnetism.

The structure of the Earth is three-layered and it is made up of three concentric rocky layers called crust, mantle and core.

25 Amazing Points of Structure of Earth

The structure of the Earth is three-layered and it is made up of three concentric rocky layers called crust, mantle and core.

1. Crust: This is the uppermost and thinnest layer of the Earth, whose average thickness is 33 km. In continental parts its thickness is about 40 km, whereas in oceanic parts it is only 5 to 10 km thick. A thin and disintegrated layer of stratified rocks is found in the uppermost part of the earth’s crust, below which is a layer of crumbly rocks like granite. Instead of granite, layers of basalt rocks are found in ocean basins. The earth’s crust is divided into two parts-

(a) Upper layer: Where mainly granite rocks are found, through which fishes have been formed. Elements like silica and aluminum predominate in this layer, hence it is also called SiAl-Silica + Aluminium. Its average density is 2.7.

(b) Lower layer: An uninterrupted layer of basalt rocks is found in it, through which the ocean surface has been formed. It mainly consists of silica (Si) and magnesium (Ma). Hence it is called limit. Its average density is 3.0.

25 Amazing Points of Structure of Earth

2.Mantle: The mantle extends from the Moho discontinuity to a depth of about 2900 km. 83% of the Earth’s total volume and about 68% of its mass is occupied by the mantle. The density of the upper part of the mantle is 3-3.5 and the density of the lower part is 4.5-5.5. Thus, it is made up of hard rocks with high density and heavy minerals like magnesium and iron predominate in it.

The crust and the uppermost part of the mantle together form the lithosphere. It is mainly made of brittle rocks and extends to a depth of 100 km. Below this, there is a plastic and relatively molten part of the asthenosphere to a depth of 200 km.

25 Amazing Points of Structure of Earth

3.Core: This is the innermost part of the Earth. And it is called Borysphere. It is mainly made of nickel (Ni) and iron (Fe), it is called NiFe.

(a) The part up to a depth of 2900 to 5150 km is in liquid state.

(b) The part at depth from 5150 to 6371 km is in solid state. Due to high pressure in this part, gases have converted into solid state.

25 Amazing Points of Structure of Earth

>The maximum temperature of the core is 5500°C and density is 13.

> Generally every 32 m with depth when moving from the earth’s crust to the underground. But the temperature increases at the rate of 1°C. However, the rate of increase in temperature decreases with depth. The reason for increase in temperature underground is pressure and disintegration of radioactive substances.