NCERT Class 11 Geography Part 1 Chapter 3: Interior of the Earth YouTube Lecture Handouts
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NCERT Class 11 Geography Part 1 Chapter 3: Interior of the Earth
Only Indirect Evidences
- Exogenic + Endogenic forces = Shaping of landform
- Earth radius = 6730 km (centre can՚t be reached)
- Knowledge of interior based on estimate and inference (direct observation & analysis)
- Matter from mining (temp. , pressure & density )
- Meteors reaching earth
- Gravitation (more near poles) , magnetic field (magnetic material in crust) , and seismic activity
Direct Sources
- Deep mines (gold mines – 3 to 4 km)
- “Deep Ocean Drilling Project” and “Integrated Ocean Drilling Project”
- Deepest drill – Kola, Arctic Ocean 12 km deep
- Volcanic eruptions – magma
Earthquakes -
- Shaking of earth
- Natural event
- Release of energy from waves
- Along faults – break in crustal rocks, move in opposite direction
- Seismograph – record waves reaching surface
- Body waves – through body & interact with surface – are P & S waves
- Surface waves – move along surface
Earthquakes Shadow Zones
Types of Earthquakes
- Tectonic – Sliding of rocks
- Volcanic – near volcanoes
- Collapse – intense mining activity
- Explosion – explosion of chemical or nuclear device
- Reduced induced – in areas of large reservoir
Measurement of Earthquakes
- Richter Scale – magnitude (energy released during earthquake 0 - 10)
- Mercalli – intensity (visible damage 1 - 12)
Effects of Earthquakes
- Ground Shaking
- Differential ground settlement
- Land and mud slides
- Soil liquefaction
- Ground lurching
- Avalanches
- Ground displacement
- Floods from dam and levee failures
- Fires
- Structural collapse
- Falling objects
- Tsunami
Structure of Earth
- Crust: Outermost (oceanic is thinner 5 km & continental is 30 km) - mean density of oceanic crust is 2.7 g/cm3
- Mantle: from Moho till 2900 km; upper part is asthenosphere, higher density; lower mantle is solid
- Core: Outer is liquid & inner is solid. Density is 5 g⟋cm3 and at centre it is 13 g⟋cm3, NIFE
Volcanoes
- Gas, ash & lava escape to ground
- From asthenosphere – molten magma arises – lava
Types of Volcanoes
- Shield: Largest, Hawaiian, Basalt & fluid, not steep, low explosivity
- Composite: Eruption of cool & viscous lava, pyroclastic material and ashes, explosive eruption
- Caldera: most explosive, collapse themselves and form calderas
- Flood basalt province: Fluid lava to long distances (kms) , Deccan Trap covers Maharashtra Plateau
- Mid-Oceanic Ridge volcano: oceanic area, central fissure with frequent eruption
Intrusive Volcanic Landforms
- Volcanic: Cool at surface
- Plutonic: Cool in crust
- Batholith
- Laccolith
- Lapolith
- Phacolith
- Sill
- Sheet
- Dyke
✍ Manishika