• The Earth's interior is structured in concentric layers with distinct physical and chemical properties.  
• These layers include the crust, mantle, outer core, and inner core.  
• Layers of the Earth 
  • Crust: 
    • Outermost layer; accounts for 0.5-1.0% of Earth's volume. 
    • Density: ~2.7 g/cm³; thickness: 5-30 km (oceanic) and 50-70 km (continental). 
    • Composition: 
    • Continental crust: Felsic rocks (granite), silica, and aluminum (sial). 
    • Oceanic crust: Mafic rocks (basalt), silica, and magnesium (sima). 
    • Temperature: Increases by ~30°C/km, reaching 200-400°C near the mantle boundary. 
    • Seismic Discontinuity: Moho (boundary with mantle). 
  • Mantle: 
    • Forms 83% of Earth's volume and 67% of its mass. 
    • Extends from 30 km to 2900 km depth. 
    • Density: 2.9–5.7 g/cm³; Temperature: 200°C to ~4000°C. 
    • Composition: Silicate rocks rich in iron and magnesium (OSM - Oxygen, Silicon, Magnesium). 
    • Convection currents drive tectonic plate movements. 
  • Asthenosphere: 
    • Upper mantle layer, 80-200 km deep. 
    • Highly viscous and ductile; facilitates tectonic plate movement. 
    • Main source of magma for volcanic activity. 
  • Outer Core: 
    • Liquid layer extending from 2900-5100 km depth. 
    • Composed of iron and nickel (nife); Density: 9.9–12.2 g/cm³. 
    • Temperature: 4400–6000°C. 
    • Responsible for Earth's magnetic field (dynamo theory). 
  • Inner Core: 
    • Solid core from 5100 km to Earth's center. 
    • Composed of 80% iron; Density: 12.6–13 g/cm³. 
    • Temperature: ~6000°C, comparable to the Sun's surface. 
    • Rotates slightly faster than Earth's surface. 
• Seismic Discontinuities 
  • Moho Discontinuity: Separates the crust and mantle. 
  • Gutenberg Discontinuity: Lies between the mantle and outer core. 
• The interior structure of Earth, with its dynamic processes, shapes its geological features and influences tectonic activities. 

Interior of Earth