Continental Drift and Plate Tectonics

Introduction

• Earth's continents resemble a puzzle.
• Hypothesis: continents could fit together like puzzle pieces (e.g., South America and Africa).

Continental Drift Hypothesis

• Proposed by Alfred Wegener.
• Earth's land was once a supercontinent, Pangea, which drifted into seven continents.
• Initially met with skepticism.

Evidence Supporting Continental Drift

• Fossils of the same species found on different continents.
• Matching mountain ranges and rock formations in different locations (e.g., Europe and North America).

Limitations of Wegener's Theory

• Lacked explanation for the movement of continents.

Theory of Plate Tectonics

• Developed by studying earthquakes.
• Earthquakes occur along specific lines, revealing tectonic plates.
• Earth's crust is composed of about 20 tectonic plates.
• Movement driven by heat currents from Earth's core.

Relation between Continental Drift and Plate Tectonics

• Plate tectonics provide the mechanism for continental drift.
• Plates move; continents drift as a result.

Types of Plate Boundaries

Divergent Boundaries

• Plates move apart.
• Can cause earthquakes and volcanic activity.
• New crust forms as magma rises.
• Example: Iceland's divergent boundary.

Convergent Boundaries

• Plates collide.
• Denser plate subducts beneath the lighter one.
• Causes earthquakes and forms mountains or trenches.
• Example: Deep ocean trenches and high mountain ranges.

Transform Boundaries

• Plates slide past each other.
• Frequent earthquakes but no crust destruction/formation.
• Example: San Andreas Fault, California.

Future of Continents

• Continents continue to move.
• Possible future supercontinent formation in ~100 million years.

Conclusion

• Continental drift hypothesis supported by fossil and geological evidence.
• Plate tectonics explains Earth's crust divisions and movement.
• Three plate boundary types: divergent, convergent, and transform.

Next Steps

• Explore games and activities to deepen understanding.
• Prepare for next lesson on plate tectonics impact on Earth's shape.