BASICS OF INTERNAL STRUCTURE OF EARTH

To understand geology first of all we have to understand the structure and composition of Earth itself as it is the key role playing for the further processes of understanding.

 EARTH STRUCTURE:

Internal structure of Earth resembles as a layered cake. 

Layered internal structure of Earth

The basic three lyers that are present in Erath are:

@  Crust

@  Mantle

@  Core

With the time as advancement of technology took place we were able to understand these layers in further detail.

DETAILED INTERNAL STRUCTURE OF EARTH

DETAILED EXPLANATION:

Now we will learn about the earth’s internal structure in detail:

A.    CRUST:

Crust is the top most layer of the planet earth, the layer that accommodates all the living beings on it. Now the crust is divided into two parts:

@  Oceanic crust

@  Continental crust

Oceanic crust:

Oceanic crust is the part of crust that is submerged under water that is oceans and seas. It’s thickness as compared to that of continental crust is very less that is just 7km.The density of the oceanic crust is more than continental crust i.e. 3.0gm/cm³. The type of material found in oceanic crust is basaltic which is underlain by gabbro. Basalt and gabbro they both are igneous rocks and as compared to metamorphic and sedimentary they have high density causing density of oceanic crust more than continental crust.

Continental crust:

Continental crust is the exposed part of the crust on which mostly human activities are taking place. This part of crust is less dense and has density of 2.7gm/cm³. The thickness of continental crust extends up to 30-50km. The reason of more thickness of continental crust as compared to that of oceanic is due to exposed portions of sedimentary and metamorphic rocks in the form of high rise mountains etc. in further discussions we will study about the processes going on the planet causing formation of different features of earth. The probable composition of continental crust is granite, other plutonic rocks, schist, gneiss (with sedimentary rock cover).

B.     MOHOROVICIC DISCONTINUTY:

Mohorovicic discontinuity is the boundary between the crust and the mantle.

C.     THE MANTLE:

Mantle is the 2^nd basic division of the earth’s internal structure. There are visible further divisions of mantle on the basis of difference of composition of mantle rock. The chemical composition of the mantle rocks is continuous throughout the mantle layer but the mineral formed and the physical changes in the minerals form further layers of the mantle. The layers formed are:

@  70-125 or 200 km- Asthenosphere:

According to some scientists after the Mohorovicic discontinuity the asthenosphere which is also known as low velocity zone is present which is extended from 70-125km or in different theories from 70-200km. the asthenosphere is considered to be formed by the partially molten rocks or we can say crystal and liquid slush. The upper layer of mantle and crust forming the tectonic plates of earth move over asthenosphere as it provides lubrication to their movement.

@  400-670km:

In the mantle there is prominent division at 400km and 670 km. the reason of the division is based upon the difference of minerals formed with the change of pressure and temperature while moving deep inside towards the center of the earth.

While at 670 km the prominent change is observed that separates upper mantle from the lower mantle and the difference between the two is based upon the chemical and physical change of the material.

D.    THE CORE:

Core is the 3^rd and last layer of the Earth. Its temperature is merely very high as compared to that of the mantle and the core. The core is basically divided in to two further layers on basis of their physical and chemical combination:

@  Outer core:

The outer core I the hot liquid layer composed largely of melted iron metal and the Earth’s magnetic field is also explained by this liquid art of the earth. As iron is a very good conductor and does possess high electric and magnetic properties. The density of outer core is less i.e. 10-12gm/cm³ as compared to that of the inner core.

@  Inner core:

Inner core is the solid layer which consists of iron-nickel alloy. Nickel metal has high density than iron so when iron and nickel combine together this tends to high density of inner core that is 12-13gm/cm³.