Principles of Plate Tectonics

Earth's Layers Overview

• Core, Mantle, and Crust: Primary compositional layers formed due to density separation.

Earth's Core

• Composition: Mostly iron.
• Inner Core:
  • Small, solid.
  • Exists due to high pressure despite high temperatures.
• Outer Core:
  • Larger, liquid.
  • Iron stable as liquid due to lower pressure.
• Together, the core layers are about half of Earth's radius.

Earth's Crust

• Thinness: Max 50 km thick, significantly thin compared to Earth's 6400 km radius.
• Types of Crust:
  • Oceanic Crust:
    • Denser, thinner, made of basalt.
    • Underlies ocean basins.
  • Continental Crust:
    • Thicker, less dense, similar composition to granite.
    • Creates continents due to buoyancy and thickness.

Mantle and Crust Interaction

• Asthenosphere:
  • Zone between 100-300 km depth.
  • Behaves like plastic solid, capable of flow.
  • Convective movements due to temperature and density differences.
• Lithosphere:
  • Upper mantle plus all crust above asthenosphere.
  • Broken into tectonic plates.
  • Contains both continental and oceanic crust.

Isostasy

• Concept: Sinking of lithosphere into asthenosphere, similar to icebergs.
• Density Variation:
  • Ocean crust denser, sinks lower.
  • Continental crust less dense, thicker, floats higher.

Moho Boundary

• Definition: Boundary between crust and mantle.
• Location: Middle of lithosphere.
• Seismic Studies:
  • Moho discovered using seismic waves.
  • Depth varies (3-5 km beneath oceans, up to 15 km under mountains).

Isostatic Adjustments

• Crust Adjustments:
  • Rises/sinks as weight is removed/added.
  • Processes include erosion, deposition, volcanic activity.

Conclusion

• Dynamic Surface: Earth's surface continuously adjusts due to various geological processes.
• For further details, additional resources or videos can be consulted.