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INSIDE OUR EARTH FULL CHAPTER | NCERT Class 7 Geography Chapter 2 | हमारी पृथ्वी के अंदर in hindi

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Topics Covered: Interior of the Earth key facts
Layers of the Earth & subparts: Crust, Mantle & Core
How tectonic plates moves..?
How Earths magnetic field formed..?
Rocks & Minerals
Types of Rocks: Igneous(intrusive & Extrusive), Sedimentary (Clastic, Chemical & Organic) & Metamorphic
Rocks Cycle

Key Facts of our earth: The deepest mine in the world, is in South Africa. It is about 4 km. deep.
In search for oil engineers have dug a hole about 6 km. deep.
To reach to the centre of the earth (which is not possible!) you will have to dig a hole 6000 km. deep on the ocean floor.
We know the Earth's interior by studying seismic waves from earthquakes, which act like a form of natural "X-ray" to reveal the planet's structure

INTERIOR OF THE EARTH: The crust : The uppermost layer over the earth’s surface is called the crust.
It is the thinnest of all the layers.
It is about 35 km on the continental masses and only 5 km on the ocean floors.
The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (si-silica and al-alumina).
The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium)

2. Mantle: Just beneath the crust is the mantle which extends up to a depth of 2900 km. below the crust.
The thickest layer, located beneath the crust. It is a semi-solid, viscous layer of molten rock that is constantly in motion. The upper part of the mantle, the asthenosphere, is particularly weak and ductile. 

3. Core: The innermost layer is the core with a radius of about 3500 km.
It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous i.e. iron).
The central core has very high temperature and pressure.
The movement of this metallic fluid is responsible for creating the Earth's magnetic field. 
The deepest, hottest, and most dense layer. It is a solid sphere of iron and nickel, kept in a solid state despite its extreme temperature due to immense pressure. 

ROCKS AND MINERALS: There are three major types of rocks:
Igneous rocks(आग्नेय चट्टानें),
Sedimentary rocks(अवसादी चट्टानें)
Metamorphic rocks(कायांतरित चट्टानें)

Igneous Rocks आग्नेय चट्टानें : When the molten magma cools, it becomes solid. Rocks thus formed are called igneous rocks.
They are also called primary rocks.
There are two types of igneous rocks: intrusive rocks and extrusive rocks.

Intrusive igneous rocksअंतर्वेधी आग्नेय चट्टानें: Sometimes the molten magma cools down deep inside the earth’s crust. Solid rocks so formed are called intrusive igneous rocks.
Since they cool down slowly they form large grains.
Granite is an example of such a rock.
Grinding stones used to prepare paste/powder of spices and grains are made of granite.
Extrusive igneous rocksबहिर्वेधी आग्नेय चट्टानें: Lava is actually fiery red molten magma coming out from the interior of the earth on its surface. When this molten lava comes on the earth’s surface, it rapidly cools down and becomes solid. Rocks formed in such a way on the crust are called extrusive igneous rocks.
They have a very fine grained structure.
For example, basalt.
The Deccan plateau is made up of basalt rocks.

Sedimentary rocks अवसादी चट्टानें: Rocks roll down, crack, and hit each other and are broken down into small fragments. These smaller particles are called sediments.
These sediments are transported and deposited by wind, water, etc. These loose sediments are compressed and hardened to form layers of rocks. These types of rocks are called sedimentary rocks.
बलुआ पत्थर (Sandstone), शेल (Shale), चूना पत्थर (Limestone), कांग्लोमरेट (Conglomerate), कोयला (Coal). 
These rocks may also contain fossils of plants, animals and other microorganisms that once lived on them.

Metamorphic rocks कायांतरित चट्टानें: Igneous and sedimentary rocks can change into metamorphic rocks under great heat and pressure.
For example, clay changes into slate and limestone into marble.

कायांतरित चट्टानों के उदाहरण: संगमरमर (Marble): 
चूना पत्थर(lime stone) के कायांतरण से बनता है। 
स्लेट (Slate): 
शेल (shale) जैसे अवसादी चट्टानों के रूपांतरण से बनती है। 
क्वार्टजाइट (Quartzite): 
बलुआ पत्थर(sand stone) के कायांतरण से बनता है। 
शिस्ट (Gneiss): 
ग्रेनाइट जैसी आग्नेय चट्टानों से बन सकती है। 

Rock Cycle