UPSC MainsGeneral Studies Paper IGeographyPractice question

Continental Drift Theory and Evidences

What do you understand by Continental Drift Theory (CDT)? Discuss the prominent evidences in support of it.

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How to approach

Begin by defining the Continental Drift Theory (CDT) proposed by Alfred Wegener, mentioning Pangaea and Panthalassa. Then, detail the primary empirical evidences supporting the theory across geological, fossil, and paleoclimatic lines. Conclude with a brief note on its mechanical limitations and its role as a precursor to Plate Tectonic Theory.

Model answer

326 words

Introduction

Proposed by German meteorologist Alfred Wegener in 1912, the Continental Drift Theory (CDT) postulates that all present-day continents were once united as a single supercontinent called Pangaea, enveloped by a vast mega-ocean named Panthalassa. Approximately 200 million years ago during the Mesozoic era, Pangaea began rifting into Laurasia in the north and Gondwanaland in the south, eventually drifting into their contemporary geographic positions.

Prominent Evidences in Support of Continental Drift

Wegener and later geologists marshaled diverse cross-continental empirical proofs to substantiate continental displacement:

  • Matching of Shorelines (Jig-Saw Fit): The complementary shorelines of continents across the Atlantic, particularly the eastern coast of South America and the western coast of Africa, show a remarkable fit. This correlation was quantitatively corroborated at the 500-fathom contour by Edward Bullard's computer simulation in 1964.
  • Rocks of Same Age Across Oceans: Radiometric dating confirms that a 2,000-million-year-old belt of ancient rocks extending along the Brazilian coastline matches an identical rock belt traversing West Africa, indicating contiguous formation prior to separation.
  • Paleontological (Fossil) Distribution: Identical fossil records appear across vast ocean expanses that modern organisms could not cross. Fossils of Mesosaurus, a small freshwater aquatic reptile, are exclusively preserved in the black shales of eastern Brazil and southwestern Africa. Similarly, the sub-polar fossil flora Glossopteris is uniformly distributed across India, Australia, Antarctica, Africa, and South America.
  • Placer Deposits: Rich alluvial gold placer deposits along the Ghana coast of West Africa lack local upstream gold-bearing quartz veins, which are instead situated across the Atlantic Ocean along the Brazilian plateau.
  • Tillite and Paleoclimatic Evidence: Glacial tillite deposits belonging to the Gondwana sequence in peninsular India have direct lithological equivalents in Madagascar, Africa, Australia, and Antarctica, proving these landmasses shared a common glacial epoch near the South Pole.

Conclusion

While Wegener was unable to identify a plausible driving mechanism—falsely invoking weak tidal friction and centrifugal 'pole-fleeing' forces—the observational strength of his empirical evidence dismantled the permanentist paradigm and laid the indispensable foundation for modern Plate Tectonics.

Key facts to remember

definition
Continental Drift Theory (CDT)

A geological theory formulated by Alfred Wegener in 1912 proposing that Earth's continents were once merged into a single landmass (Pangaea) and gradually drifted apart across oceanic basins over geological time.

definition
Tillite

A sedimentary rock formed through the compaction and induration of unsorted glacial till, serving as strong geological proof of past glaciations across joined continents.

example
Mesosaurus Fossil Discontinuity

Fossils of the freshwater reptile Mesosaurus are uniquely found in Early Permian rock formations in eastern South America and southern Africa, demonstrating that the two continents were joined since this species could not cross open saltwater oceans.

Frequently asked questions

Why was Alfred Wegener's Continental Drift Theory initially rejected?

Wegener's theory was widely rejected by the scientific community because the forces he proposed to drive the continents—tidal friction from the Moon and Sun, along with centrifugal pole-fleeing force—were mathematically inadequate to displace rigid continental crusts through ocean floors.