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 -

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  • 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

Image of Earthquakes Shadow Zones For Geography

Image of Earthquakes Shadow Zones for Geography

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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

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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 13g/cm3, NIFE


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  • 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

Image of Intrusive Volcanic Landforms For Geography

Image of Intrusive Volcanic Landforms for Geography

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