STRUCTURE OF THE EARTH 

CORE IDEA

Earth has a layered internal structure with different composition and physical properties → explains earthquakes, volcanoes, plate tectonics

1. COMPOSITIONAL LAYERS

2. CRUST

• Outermost, supports life
• Continental (thick, less dense)
• Oceanic (thin, more dense)

👉 Key: Continental ≠ Oceanic

3. MANTLE

• Largest layer (~84%)
• Semi-solid, plastic

👉 Drives plate movement

4. CORE

• Outer core → liquid
• Inner core → solid

👉 Generates magnetic field

5. PHYSICAL LAYERS (IMPORTANT)

6. SEISMIC EVIDENCE

👉 S-wave absence → liquid outer core

7. UPSC TRAPS

• Lithosphere = crust + upper mantle
• Asthenosphere ≠ liquid (plastic)
• Oceanic crust more dense
• Inner core solid despite heat
• Core = NIFE

8. 5-SECOND REVISION

👉 SIAL → SIMA → NIFE
👉 Crust → Mantle → Core

MAINS LINE

“Earth’s layered structure, inferred mainly from seismic waves, explains its internal dynamics and surface processes.”