Earth's Structure & Dynamics

Earth's Layers

• Crust: Thin outer layer of the Earth.
  • Composes a small fraction of Earth's mass.
  • Analogous to the thin skin of a peach.
• Mantle: Semi-liquid layer beneath the crust.
  • Composed of molten magma.
  • Divided into the upper mantle and lower mantle.
  • Together with the crust, forms the lithosphere.
• Core: Central part of the Earth.
  • Outer Core: Composed of molten iron and nickel.
  • Inner Core: Solid ball of iron; hottest part of Earth, similar temperature to the Sun's surface.

Plate Tectonics

• The Earth's lithosphere is segmented into tectonic plates.
  • Plates fit together like a jigsaw puzzle.
  • Include 7 large key plates and several smaller ones.

Historical Context

• Pangaea: Supercontinent that existed 335 million years ago.
  • Continents were once connected, evidence from fossil distribution.

Plate Movements

• Driven by convection currents in the mantle.
• Types of Plate Margins:
  • Constructive (Divergent) Margin:
    • Plates move apart.
    • Magma fills gaps, forms new features (e.g., Mid-Atlantic Ridge).
  • Destructive (Convergent) Margin:
    • Plates move towards each other.
    • One plate may subduct or push upward, forming mountains and trenches (e.g., Himalayas).
    • Often cause earthquakes.
  • Conservative (Transform) Margin:
    • Plates slide past each other.
    • Movement can cause earthquakes (e.g., San Andreas Fault).

Earth's Dynamic Nature

• Constant movement due to convection currents.
• Responsible for tectonic hazards:
  • Volcanic eruptions
  • Earthquakes
  • Tsunamis

Key Takeaways

• The Earth's structure is complex with multiple layers each contributing to its dynamic nature.
• Tectonic activity is central to shaping the Earth's surface and causing natural disasters.