Continental Drift Theory – Essential Evidence

Continental Drift Theory Overview

• Proposes that today’s continents were once joined in a single supercontinent, Pangaea (Greek: “All Earth”).
• Formulated by Alfred Lothar Wegener (German geophysicist & meteorologist) in $1912$.

Alfred Wegener’s Observation

• Coastlines of South America and Africa appear to interlock.
• Initial visual fit inspired search for further evidence.

Key Evidence for Continental Drift

Geological Fit

• Matching coastlines: South America–Africa.
• Correlating rock formations:
  • Karoo System (South Africa) aligns with Santa Catarina System (Brazil).
• Glacial striations in now-warm regions indicate past shared glaciated landscape.

Paleoclimatic Evidence

• Coal beds discovered in Antarctica.
  • Coal forms from dense plant matter in warm, swampy climates over $\text{millions}$ of years.
  • Implies Antarctica once lay in a temperate zone.

Fossil Correlation

• Mesosaurus (aquatic reptile) – Early Permian $286\text{–}258\;\text{Ma}$
  • Fossils in Brazil & South Africa; fresh-water habitat precludes trans-oceanic migration.
• Cynognathus – Triassic $250\text{–}240\;\text{Ma}$
  • Found only in South America & Africa.
• Lystrosaurus – Triassic herbivore; fossils in Antarctica, India, South Africa.
• Glossopteris (seed fern)
  • Fossils in Australia, Antarctica, India, South Africa, South America.
  • Large, heavy seeds unlikely to cross oceans; suggests contiguous landmasses.

Core Conclusion

• Concordant geological structures, paleoclimate indicators, and widely distributed but identical fossils collectively support that present continents were formerly connected and have since drifted apart via plate motions.