Lecture Notes: Wegener's Theory of Continental Drift

Introduction

• Observation: Continents appear to fit together like puzzle pieces.
• Most noticeable along the eastern coast of South America and the western coast of Africa.
• Alfred Wegener, a German meteorologist, developed the theory of continental drift.

Wegener’s Theory of Continental Drift

• Hypothesis: Continents are moving; once formed a supercontinent called Pangaea.
• Pangaea means "all Earth" in Greek.
• Wegener needed evidence to support his theory.

Evidence Supporting Continental Drift

1. Apparent Fit of Continents

• Coastlines of continents look like they fit together (e.g., South America and Africa).

2. Fossil Correlation

• Study of ancient fossils and their locations.
• Mesosaurus fossil distribution: Found only in southern South America and Africa.
  • Mesosaurus was a freshwater reptile, unable to cross oceans.
• Similar fossil distributions for other species like Cynognathus, Glossopteris, and Lystrosaurus.
• Fossil evidence makes sense when continents are reassembled.

3. Rock and Mountain Correlation

• Similar rock types and ages found in different continents.
• Example: Rocks in northeastern US match those in the UK and Scandinavia.
• Conclusion: These rocks were formed together before continents drifted apart.

4. Paleo Climate Data

• Study of past climates using geological evidence.
• Glacial striations found in now-equatorial regions like the Amazon and Central Africa.
• Coal deposits found in cold regions (e.g., Northern Asia, Antarctica) imply past tropical climates.
• These findings suggest continents were once in different climatic zones.

Challenges and Legacy

• Wegener could not explain the mechanism driving continental drift.
• His theory was initially rejected.
• Wegener died in 1930 on an expedition in Greenland.
• Modern geology owes much to Wegener’s pioneering work on continental drift.

Conclusion

• Wegener's evidence for continental drift laid the groundwork for understanding Earth's geology.
• His tragic story highlights the struggles of scientific innovation before its time.

These notes summarize the key points discussed about Alfred Wegener's theory of continental drift and the evidence he gathered to support his hypothesis.