NCERT Class 7 Geography Chapter 2: Inside Our Earth YouTube Lecture Handouts
Get unlimited access to the best preparation resource for CBSE/Class-7 : get questions, notes, tests, video lectures and more- for all subjects of CBSE/Class-7.
Get video tutorial on: Examrace YouTube Channel
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
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
Rock Cycle and 3 Types of Rocks - Sedimentary, Igneous, and Metamorphic
Minerals
- Naturally occurring substances
- Have certain physical properties
- Definite chemical composition
- Fuels – Coal, Petroleum & Natural Gas
- Industries – Iron, Aluminum
- Medicines – Calcium, Phosphorus, Magnesium
✍ Manishika