Earth's Structure and Dynamics

Overview of Earth's Layers

• Crust: The outermost layer, thin compared to the whole planet.
• Mantle: Located beneath the crust, semi-liquid layer of molten magma.
  • Upper Mantle: Together with crust, forms the lithosphere.
  • Lower Mantle: Below the upper mantle.
• Core: Divided into outer and inner core.
  • Outer Core: Molten iron and nickel due to high temperatures.
  • Inner Core: Solid ball of iron, hottest part of Earth, remains solid due to strong gravity.

Earth's Changing Surface

• Earth's surface is constantly changing.
• Tectonic Plates: Earth's lithosphere divided into various plates fitting together like a jigsaw puzzle.
  • Types of Plates: Seven large key plates and several smaller ones.
• Pangaea: All continents once formed a single supercontinent 335 million years ago.
• Plate Tectonics: Process of movement of tectonic plates, also known as continental drift.
• Fossil Evidence: Fossils found on separate continents indicate past connectivity.

Movement of Tectonic Plates

• Convection Currents: Slow circular movements in the mantle due to heat and pressure drive plate movement.

Types of Plate Margins

1. Constructive (Divergent) Plate Margin:

   • Plates move away from each other.
   • Formation of new geological features (e.g., volcanoes).
   • Example: Mid-Atlantic Ridge.

2. Destructive (Convergent) Plate Margin:

   • Plates move towards each other.
   • One plate may go under another or push upwards, forming mountains and trenches.
   • Example: Himalayas, including Mount Everest.

3. Conservative (Transform) Plate Margin:

   • Plates slide past each other.
   • Often causes earthquakes.
   • Example: San Andreas Fault.

Conclusion

• Earth is dynamic with plates in constant motion due to convection currents.
• Movements lead to geological hazards such as volcanic eruptions, earthquakes, and tsunamis.