Lecture Notes on Continental Drift and Plate Tectonics

Overview

• The lecture explores the concept of continents fitting together like puzzle pieces and the theory of continental drift proposed by Alfred Wegener.

Key Concepts

Pangea

• Early 20th-century scientist Alfred Wegener hypothesized that all continents were once part of a supercontinent called Pangea.
• Suggested that Pangea broke apart, leading to the formation of the continents as we know them today.
• Evidence supporting Wegener's theory:
  • Fossils of similar plants and animals found on different continents.
  • Matching age and type of rock layers across oceans.
• Despite evidence, Wegener's ideas were not widely accepted during his lifetime.

Seafloor Spreading

• In the 1950s, scientists mapped the Mid-Atlantic Ridge, discovering:
  • The ridge is a 10,000-mile mountain range on the ocean floor.
  • The seafloor gets older as you move away from the ridge.
• Harry Hess proposed the idea of seafloor spreading:
  • New seafloor forms at the ridge and spreads outward.
  • Indicates movement of Earth's surface.

Earth's Interior

• The Earth is composed of three main layers:
  • Core: Extremely hot, nearly as hot as the sun's surface.
  • Mantle: Middle section, experiences immense pressure.
  • Lithosphere: Rigid layer of solid rock, cracked into tectonic plates.
• Plates are moved by convection currents in the mantle, which is driven by heat from the core.

Plate Tectonics

• Plate tectonics is the theory explaining the movement of Earth's plates:
  • This movement causes geological changes on Earth's surface.
  • Plates collide, pull apart, and slide past each other, leading to:
    • Earthquakes: Most prominent along plate boundaries.
      • Convergent boundaries: Plates collide.
      • Divergent boundaries: Plates pull apart.
      • Transform boundaries: Plates slide past each other.
    • Volcanic Activity: Common at divergent boundaries and subduction zones.

Geological Features and Processes

• Plate tectonics contributes to the rock cycle:
  • Subduction zones: Dense ocean plates are pushed below lighter continental plates, leading to magma formation and volcanic eruptions.
  • Mountain Ranges: Formed when two continental plates converge, causing land to buckle and rise (e.g., the Himalayas).

Conclusion

• Wegener's theory has evolved into the widely accepted theory of plate tectonics, which unifies various geological processes and features.
• The understanding of tectonic movements has advanced significantly over the past century.