Introduction
In 1912, German meteorologist Alfred Wegener proposed the Continental Drift Theory, postulating that all landmasses initially formed a single supercontinent called Pangaea surrounded by a mega-ocean named Panthalassa. Wegener suggested that Pangaea began splitting approximately 200 million years ago, supporting his radical proposition with extensive multi-disciplinary empirical evidence across multiple continents.
Evidence Put Forward by Wegener
- Geomorphological Matching (Jigsaw Fit): The shorelines of Africa and South America facing each other display a remarkable and unmistakable fit, especially when evaluated at the continental shelf margin (later corroborated mathematically by Edward Bullard in 1964).
- Geological Rocks and Placer Deposits: Radiometric dating confirms that belts of ancient rock dating back 2,000 million years along the Brazilian coast match those found in Western Africa. Additionally, rich placer deposits of gold occur along the Ghana coast without any local source rock, directly matching the gold-bearing veins located in Brazil.
- Paleoclimatic Evidence (Tillite Deposits): Extensive sedimentary deposits formed by glaciers (tillites) dating to the Permo-Carboniferous period are found across peninsular India, Africa, the Falkland Islands, Madagascar, Antarctica, and Australia. This points to a shared geological history under a southern polar glaciated climate.
- Paleontological Evidence (Fossil Distribution): Identical fossil remains of the freshwater reptile Mesosaurus and the extinct seed fern Glossopteris are preserved in rocks across separated Southern Hemisphere landmasses, precluding the possibility of separate evolution across wide oceanic divides.
Critical Examination and Limitations
- Inadequate Driving Mechanism: Wegener attributed continental movement to tidal forces from the Sun and Moon, as well as the 'pole-fleeing force' caused by Earth's rotation. Physical calculations proved these forces to be utterly inadequate to displace vast continental masses.
- Misconceptions Regarding Ocean Crust: Wegener hypothesized that the lighter continental granitic blocks (Sial) ploughed directly through the denser oceanic basaltic crust (Sima), an assumption that ignored basic mechanical friction and crustal rigidity.
- Temporal Inconsistencies: Wegener failed to convincingly account for why the continental breakup commenced specifically in the Mesozoic era after remaining intact for preceding geological eons.
Conclusion
Although Wegener was unable to identify the correct driving mechanism—later discovered as mantle convection currents—his compilation of geological, paleontological, and paleoclimatic evidence dismantled fixist paradigms and provided the indispensable foundation for modern Plate Tectonics Theory.