Plate tectonics | Year 9 Physics (Cambridge) PDF Download

Introduction to Plate Tectonics

Plate tectonics is the scientific theory that Earth's lithosphere is divided into several large and small plates that float and move on the semi-fluid asthenosphere beneath them.

Evidence Supporting Plate Tectonics

• Fossil Similarities: Fossils of the same species found on continents now separated by oceans suggest they were once connected.
• Paleomagnetism: Magnetic minerals in rocks record the orientation of Earth's magnetic field at the time of their formation, showing past plate positions.
• Geological Fit: Matching coastlines of continents like South America and Africa provide evidence of their past proximity.

Types of Plate Boundaries

• Divergent Boundaries
  • Plates move apart from each other.
  • Example: Mid-Atlantic Ridge where new oceanic crust forms as plates diverge.
  • Resulting features: Mid-ocean ridges and rift valleys (e.g., East African Rift).
• Convergent Boundaries
  • Plates move towards each other.
  • Subtypes:
    • Oceanic-Continental: Oceanic plate subducts beneath continental plate.
    • Oceanic-Oceanic: One oceanic plate subducts beneath another.
    • Continental-Continental: Collision leads to mountain formation.
  • Example: Andes Mountains formed by the convergence of the Nazca Plate and South American Plate.
• Transform Boundaries:
  • Plates slide past each other horizontally.
  • Example: San Andreas Fault in California.
  • Resulting features: Earthquakes due to friction along faults.

Driving Forces of Plate Tectonics

Convection Currents: Heat-driven movements in the mantle cause plates to move.

• Hot mantle material rises at mid-ocean ridges, spreads horizontally, and sinks at subduction zones.

Impact of Plate Tectonics

• Volcanic Activity: Subduction zones and hot spots (e.g., Hawaii) lead to volcanic eruptions.
• Earthquakes: Transform boundaries and subduction zones generate seismic activity.
• Mountain Building: Collision of continental plates forms mountain ranges (e.g., Himalayas).

Measurement and Study of Plate Movement

• GPS Satellites: Track precise movements of Earth's surface points over time.
• Seismic Monitoring: Records earthquakes and their locations to understand plate interactions.

Conclusion

Plate tectonics is crucial for shaping Earth's surface and plays a significant role in geological processes such as volcanic eruptions, earthquakes, and mountain formation. Understanding these processes helps scientists predict geological hazards and study Earth's history and future changes.