Overview
This lecture discusses Alfred Wegener's theory of continental drift, highlighting the evidence Wegener used to support the idea that continents were once joined as a single landmass.
Theory of Continental Drift
- Alfred Wegener proposed that continents were once part of a single landmass that drifted apart over time.
- Continental drift explains how the Earth's continents move gradually, at a rate similar to fingernail growth.
- The theory is now widely accepted in the scientific community.
Evidence Supporting Continental Drift
Puzzle-Like Fit of Continents
- Continents, especially South America and Africa, appear to fit together like pieces of a puzzle.
Glacial Evidence
- Similar glacial grooves (scrapings) are found in Africa, South America, India, and Australia, indicating they were once joined.
Fossil Evidence
- Fossils of Mesosaurus, a freshwater reptile, exist in both southern Africa and eastern South America, suggesting these continents were connected.
- Fossils of Cynognathus, an extinct mammal-like reptile, are found in South Africa and South America.
- Fossils of Lystrosaurus, a reptile, are found in Antarctica, India, and South America.
- Fossils of Glossopteris, a seed-bearing plant, are found in Australia, South America, South Africa, India, and Antarctica, indicating a once-unified landmass.
Mountain Range Evidence
- Similar mountain ranges (e.g., Appalachian Mountains) appear across the Atlantic in Greenland, Ireland, Great Britain, and Norway, suggesting they were once joined.
Coal Deposits
- Coal, formed from tropical plants, is found in Antarctica, suggesting it was once closer to the equator with a warmer climate.
Key Terms & Definitions
- Continental Drift — The theory that Earth's continents have moved apart from a single large landmass over time.
- Mesosaurus — An extinct freshwater reptile whose fossils support the idea of connected continents.
- Glossopteris — A prehistoric seed-bearing plant whose fossils are found on several continents.
- Glacial Scraping — Grooves or marks left by glaciers, used as evidence of past continental positions.
Action Items / Next Steps
- Review the major evidence supporting continental drift for upcoming quizzes.
- Study the locations of key fossils and mountain ranges associated with continental drift theory.