NCERT Class 7 Geography Chapter 2: Inside our Earth YouTube Lecture Handouts

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Onion Peel: Demonstrating Earth’S Interior

https://www.YouTube.com/watch?v=eJ5e7fhRP1M

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

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

-Manishika