Model Answer
0 min readIntroduction
Alfred Wegener’s theory of Continental Drift, proposed in the early 20th century, initially faced significant opposition. However, several lines of evidence gradually accumulated to support his hypothesis. Among the most compelling was the evidence of widespread Palaeozoic glaciation. During the late Palaeozoic Era (approximately 360 to 250 million years ago), extensive ice sheets covered parts of Gondwana – the ancient supercontinent. The distribution of glacial deposits from this period provided crucial clues that aligned with Wegener’s idea of continents having once been joined together. This evidence, initially observed in India, South Africa, Australia, and South America, played a pivotal role in the eventual acceptance of plate tectonics.
Palaeozoic Glaciation: Evidence and Distribution
The Palaeozoic Era witnessed multiple glacial periods, the most significant being the Karoo Ice Age (late Carboniferous to early Permian). Evidence of this glaciation is found in the form of:
- Tillites: These are consolidated glacial sediments, characterized by poorly sorted rock fragments and a matrix of clay.
- Striations: Scratches and grooves on bedrock surfaces caused by glaciers dragging rocks across them.
- Erratics: Large boulders transported by glaciers and deposited far from their source.
- Coal Deposits: Formed from the remains of lush vegetation that grew in warmer climates following glacial retreat.
Continental Drift and Glacial Evidence
The remarkable aspect of these glacial deposits is their distribution. They are found on continents that are now widely separated, but when assembled into the supercontinent of Gondwana, the glacial features form a continuous pattern.
- India: Extensive tillite deposits are found in the Talchir Formation of Gondwana sediments in the Damodar Valley and other parts of eastern and central India.
- South Africa: The Dwyka Group in South Africa contains thick sequences of tillites, providing strong evidence of glaciation.
- Australia: Similar tillite deposits are found in the Permian sequences of Australia, particularly in the Bowen Basin.
- South America: Glacial deposits are present in Argentina and Brazil, aligning with the glacial pattern observed in Africa, India, and Australia.
Wegener’s Explanation and Significance
Wegener argued that these widespread glacial deposits could only be explained if the continents were once joined together in a polar region. He proposed that the centre of the ice sheet was located over Gondwana, and the glacial flow radiated outwards towards the present-day coastlines of these continents. This explanation provided a compelling link between the observed geological features and his theory of Continental Drift.
Comparison of Glacial Deposits Across Continents
| Continent | Formation/Location | Key Features |
|---|---|---|
| India | Talchir Formation, Gondwana Basin | Tillites, striated bedrock |
| South Africa | Dwyka Group | Thick tillite sequences, glacial erratics |
| Australia | Bowen Basin | Permian tillites, glacial striations |
| South America | Argentina & Brazil | Glacial deposits, evidence of ice flow |
While initially met with skepticism, the evidence from Palaeozoic glaciation, combined with other lines of evidence like matching fossil distributions and geological structures, gradually led to the acceptance of Wegener’s ideas. The development of plate tectonics in the 1960s provided the mechanism to explain how continents could drift over time, solidifying the understanding of Earth’s dynamic processes.
Conclusion
The Palaeozoic glacial evidence provided a crucial piece of the puzzle in supporting the theory of Continental Drift. The remarkable correlation of glacial deposits across continents now separated by vast oceans strongly suggested that these landmasses were once connected. While Wegener lacked a convincing mechanism for continental movement, his observations, particularly those related to glaciation, laid the foundation for the revolutionary theory of plate tectonics, fundamentally changing our understanding of Earth’s geological history and processes.
Answer Length
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