The temperature in the earth’s interior is so high that it can even melt any tool used for drilling.
This fact restricts deep drilling, thus causing hindrance to direct observation of the materials of the earth’s interior.
The huge size of the earth and increasing temperature with depth has set a limit to direct observation of the earth’s interior.
STRUCTURE OF THE EARTH’S INTERIOR
The innermost layer surrounding the earth’s centre is called core, which is about 3500 kms in radius.
Core is the densest layer of the earth with its density range from 9.5 to 14.5 and sometimes even higher.
It is composed mainly of the iron and nickel thus commonly known as Nife. (Nickel+Ferrum).
Core consists of two sub-layers.
The inner one is solid and the outer one is semi-liquid.
The layer surrounding the core is known as mantle, a rock shell about 2900 kms thick and is composed of basic silicates.
Major constituent elements of mantle are magnesium and silicon, hence, this layer is termed as Sima (Silica+Magnesium).
The density of this layer varies from 3.3 to 5.7.
Mantle is surrounded by the outermost layer of the earth, known as lithosphere and its density varies from 2.70 to 2.95.
Major constituent elements of lithosphere are silica (Si) and aluminium (Al), thus this layer is termed as Sial (Silica+Aluminium).
The outermost part of the lithosphere is known as crust, normally about 8 to 40 kms thick.
Core, mantle and crust are the three main concentric layers of the earth’s interior.
Core is the innermost layer and has the highest density. It is made up mainly of nickel and iron.
Mantle is the layer lying between the core and lithosphere. Its major constituents are silicon and magnesium.
Crust is the outermost layer of the earth and is mainly composed of silicon and aluminium.