Lecture on Earth's Structure and Plate Tectonics

Introduction

• Australia moves north by 7 cm each year, fastest moving continent.
• GPS systems updated frequently to keep pace.
• Fascinating animals and ecosystems, no active volcanoes on the continent.
• Most volcanoes located around the Pacific Ocean, known as the "Ring of Fire".

Structure of Earth

• Earth is heavier than surface rocks suggest.
• 1800s scientist used pendulum and gravity to measure Earth's mass.
• Earth consists of layers: Crust, Mantle, Outer Core (liquid), Inner Core (solid).

Earth's Layers

Crust

• Outermost layer; solid, brittle, varies in thickness (5-70 km).
• Comparable to a thin shell.

Mantle

• Below the crust; a plastic solid, moves slowly.
• 84% of Earth's volume.

Core

• Outer Core: Liquid, creates Earth's magnetic field.
• Inner Core: Solid, growing over time by crystallizing iron.

Seismic Waves

• Earthquakes used to study Earth's interior, similar to X-rays for bones.
• P waves travel through both solid and liquid, S waves do not travel through liquid.
• Presence of liquid outer core deduced from S wave absorption.

Earth's Magnetic Field

• Generated by spinning of liquid outer core.
• Protects from solar wind, preserves Earth's atmosphere.

Magnetic Pole Reversal

• Earth's magnetic poles switch places periodically.
• Cause and duration of reversals are not well understood.

Plate Tectonics

• Earth's crust is divided into tectonic plates (crust + upper mantle).
• Plates move due to mantle convection.
• Types of Plate Boundaries:
  • Convergent: Plates move towards each other, can form mountains or volcanoes.
  • Divergent: Plates move apart, create new crust.
  • Transform: Plates slide past each other, cause earthquakes.

Conclusion

• Study of tectonics crucial to understanding Earth's geology.
• Mantle and core dynamics important for Earth's magnetic field and plate motion.
• Exploration of tectonic activity helps explain formation of geological features like mountains and faults.

Additional Notes

• Continents move slowly, akin to fingernail growth speed.
• Australia’s rapid movement requires frequent GPS updates.
• Tectonic activity related to formation of natural features and phenomena, such as earthquakes and mountain ranges.
• Earth's magnetic field vital in shielding Earth from harmful solar radiation.