|Interior of Earth|
In this article we will be discussing the summary of NCERT class 7 Chapter 2 of Geography book which is ‘Inside our earth’. our earth is a dynamic planet. Changes happen inside and outside of our earth with time.
We know that our earth’s radius is about 6400 km and this 6400 km earth is divided into layers of different material and has different characteristics at every layer. This layer is spherical and concentric.
Interior of Earth
The uppermost layer is called as the crust. It is the thinnest layer of all three and is about 35 km on the continental surface and only about 5 km thick on ocean surface. This layer which is on continent, mainly consists silica and alumina and therefore called as sial (si of silica and al of alumina). The crust at ocean surface is mainly consist of silica and magnesium therefore it is called as sima (si of silica and ma of magnesium).
The layer just below the crust is called as mantle and it is further divided into three part – upper, middle and inner mantle. The depth of mantle is around 2900 km.
The inner most layer of earth is known as core and it has its radius of about 3500 km. core is also further divided into two-part outer core and inner core. It is mainly made up of nickel and ferrous that is iron and therefore called as nife.
Some facts about Interior of earth
- The deepest hole on the earth surface is of about 6 km in south Africa.
- The earth crust is only one present of the total volume of the earth, mantle consist of 84% and the core is 15 per cent.
- The exact radius of the earth is 6371 km.
- The core of the earth is in fluid state.
Rocks and Minerals
The earth’s crust is made up of different type of rocks. Rocks are any natural mass of mineral matter that makes up the earth’s crust. Rocks can have different color, size and texture. Majorly there are three type of rocks – igneous, sedimentary and metamorphic rocks.
Igneous rocks also called as primary rocks. These rocks formed during the cooling process of molten magma. There are two type of igneous rocks – Intrusive igneous rocks and extrusive igneous rocks.
When lava come outside through volcano on the earth’s crust it cools down rapidly and become solid, rocks formed in this way are called as extrusive igneous rocks. These type of rocks has very fine grained structure. For example, basalt (the Deccan plateau is made up of these type of rocks).
The other one intrusive igneous rocks are formed when the molten magma does not come out and cool down inside the earth’s crust. Because the process of cooling is slow they form large grain size for example, graphite.
When rocks roll down, crack and hit each other, they form small fragment and these small particles are called as sediment. These sediments transported by wind, water etc. and deposited somewhere. After deposition they go through process of compression and hardening and form layers of rocks which is known as sedimentary rocks for example, sandstone. These type of rocks may contain fossils of plants, animal and other microorganism.
When igneous or sedimentary rocks goes under great heat and pressure they can become metamorphic rocks for example, clay into slate and limestone become marble after great heat and pressure.
One type of rock change into another in a cyclic manner and therefore in is called as rock cycle. Molten magma changes into igneous rocks, igneous rocks break into sediments and become sedimentary rocks, sedimentary rocks and igneous rocks goes under pressure and heat and form metamorphic rocks and lastly metamorphic rocks goes under more heat and pressure melt down and become magma. You can understand this cycle through the below image.
I hope you like this article please share this with your friend and don’t go with any doubts, leave a comment below. This was the summary of NCERT class 7 Chapter 2 of Geography ‘Inside our Earth’.