NCERT Class 7 Geography Chapter 2: Inside our Earth (Examrace - Dr. Manishika) | English | CBSE

Dr. Manishika Jain explains the NCERT Class 7 Geography Chapter 2: Inside our Earth

Onion Peel: Demonstrating Earth’s Interior
Crust
Continental - Silica & Aluminum (SIAL) – 35 km
Oceanic – Silica & Magnesium (SIMA) – 5 km
B/w upper & lower crust – Conrad Discontinuity
B/w crust & mantle – Moho Discontinuity
Jigsaw puzzle
Thinnest Layer

Onion Peel: Demonstrating Earth’s Interior @0:13
Crust @1:17
Mantle @3:59
Core @5:59
Rocks @:35
Igneous Rocks @8:16
Intrusive @8:48
Extrusive @9:08
Sedimentary Rocks @9:52
Metamorphic Rocks @11:00
Rock Cycle – Transformation @11:58
Minerals @13:22
#Fuels #Sandstone #Molten #Sedimentary #Viscous #Silicates #Continental #Thinnest #Crust #Demonstrating #Manishika #Examrace

Mantle
About 2900 km thick
85% by volume
64% by mass
Made of iron but mainly silicates
Asthenosphere – Upper mantle – Convection currents
Viscous, weak and ductile
Just below lithosphere
Main source of Magma
B/w Upper & lower mantle – Repetti Discontinuity
B/w Mantle & Core – Guttenberg Discontinuity
Core
Radius of about 3500 km
Made of Iron & Nickel (NIFE)
High temperature & pressure
15% of earth’s volume
32.5% of earth’s mass
B/w Outer & Inner Core – Lehmann Discontinuity
Outer Core – Liquid (Slow Moving – Produces Earth’s Magnetic Field)
Pressure, Density increases towards center

Rocks
Earth’s Crust
Natural mass of matter that makes the crust
Differ in Size, Color & Texture
3 Types of Rocks
Igneous
Sedimentary
Metamorphic
Igneous Rocks
Molten Magma Cools & Solidifies
Also known as Primary Rocks
Two Types
Intrusive – Cools inside, Slowly cools, Forms Large grains - Granite
Extrusive – Comes on Surface – Basalt (Deccan Plateau) – Fine Grained

Sedimentary Rocks
Rocks roll, crack & hit to break
Sediments are transported
Then compressed & hardened
Sandstone – made from sand
Red Fort – red sandstone
Include fossils
Metamorphic Rocks
Igneous & Metamorphic change under heat & pressure
Clay → Slate
Limestone → Marble
Taj Mahal – White Marble
Rock Cycle – Transformation
Minerals
Naturally occurring substances
Have certain physical properties
Definite chemical composition
Fuels – Coal, Petroleum & Natural Gas
Industries – Iron, Aluminum
Medicines – Calcium, Phosphorus, Magnesium

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