NCERT Class 7 Geography Chapter 2: Inside Our Earth YouTube Lecture Handouts
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Onion Peel: Demonstrating Earthีs Interior
Crust
- Continental - Silica & Aluminum (SIAL) โ 35 km
- Oceanic โ Silica & Magnesium (SIMA) โ 5 km
- B/w upper & lower crust โ Conrad Discontinuity
- B/w crust & mantle โ Moho Discontinuity
- Jigsaw puzzle
- Thinnest Layer
Mantle
- About 2900 km thick
- 85 % by volume
- 64 % by mass
- Made of iron but mainly silicates
- Asthenosphere โ Upper mantle โ Convection currents
- Viscous, weak and ductile
- Just below lithosphere
- Main source of Magma
- B/w Upper & lower mantle โ Repetti Discontinuity
- B/w Mantle & Core โ Guttenberg Discontinuity
Core
- Radius of about 3500 km
- Made of Iron & Nickel (NIFE)
- High temperature & pressure
- 15 % of earthีs volume
- 32.5 % of earthีs mass
- B/w Outer & Inner Core โ Lehmann Discontinuity
- Outer Core โ Liquid (Slow Moving โ Produces Earthีs Magnetic Field)
- Pressure, Density increases towards center
Rocks
- Earthีs 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 โ Cools inside, Slowly cools, Forms Large grains - Granite
- Extrusive โ Comes on Surface โ Basalt (Deccan Plateau) โ Fine Grained
Sedimentary Rocks
- Rocks roll, crack & hit to break
- Sediments are transported
- Then compressed & hardened
- Sandstone โ made from sand
- Red Fort โ red sandstone
- Include fossils
Metamorphic Rocks
- Igneous & Metamorphic change under heat & pressure
- Clay Slate
- Limestone Marble
- Taj Mahal โ White Marble
Rock Cycle โ Transformation
Minerals
- Naturally occurring substances
- Have certain physical properties
- Definite chemical composition
- Fuels โ Coal, Petroleum & Natural Gas
- Industries โ Iron, Aluminum
- Medicines โ Calcium, Phosphorus, Magnesium
โ Manishika