Model Answer
0 min readIntroduction
The theory of ‘continental drift’ proposes that Earth’s continents were once joined together in a single landmass, called Pangaea, and have gradually drifted apart over millions of years. First proposed by Alfred Wegener in 1912, this revolutionary idea initially faced resistance due to the lack of a plausible mechanism. However, subsequent discoveries in the field of plate tectonics provided the necessary explanation, solidifying continental drift as a cornerstone of modern geology. Understanding this theory is crucial for comprehending the distribution of landforms, earthquakes, and volcanic activity across the globe.
Evidence Supporting Continental Drift
The evidence supporting the theory of continental drift can be broadly categorized into geological, paleontological, and geophysical evidence.
1. Geological Evidence
- Jigsaw Puzzle Fit: The most striking evidence is the apparent fit of the continents, particularly South America and Africa. Their coastlines seem to match like pieces of a jigsaw puzzle.
- Rock Formations & Mountain Ranges: Matching rock formations and mountain ranges are found on different continents. For example, the Appalachian Mountains in North America are geologically similar to the Caledonian Mountains in Scotland and Norway.
- Glacial Deposits: Evidence of past glaciation, such as glacial striations and till deposits, are found in regions that are now located in warm climates (e.g., India, Africa, Australia), suggesting they were once closer to the poles.
2. Paleontological Evidence
- Fossil Distribution: Identical fossils of plants and animals have been discovered on widely separated continents. Mesosaurus, a freshwater reptile, fossils are found only in South America and Africa. Similarly, fossils of Glossopteris, an extinct seed fern, are found in South America, Africa, India, Australia, and Antarctica.
- Land Reptile Distribution: The distribution of fossils of land reptiles like Lystrosaurus, found in South Africa, India, and Antarctica, supports the idea of these continents being connected.
3. Geophysical Evidence
- Paleomagnetism: Studies of the Earth’s ancient magnetic field preserved in rocks (paleomagnetism) show that continents have moved relative to the magnetic poles over time. The apparent polar wander paths for different continents only coincide if the continents were once joined.
- Seafloor Spreading: While discovered *after* Wegener’s initial proposal, the discovery of seafloor spreading, a key component of plate tectonics, provided the mechanism for continental drift. Mid-ocean ridges are sites where new oceanic crust is created, pushing continents apart.
Wegener lacked a convincing explanation for *how* continents moved. The acceptance of Harry Hess’s theory of seafloor spreading and the development of plate tectonics in the 1960s provided the missing mechanism – convection currents in the mantle driving the movement of lithospheric plates.
Conclusion
The theory of continental drift, initially met with skepticism, is now a fundamental principle in geology. The compelling evidence from geological formations, fossil distribution, and geophysical studies, coupled with the understanding of plate tectonics, has established the dynamic nature of Earth’s continents. This understanding is vital for comprehending various geological phenomena and predicting future changes in Earth’s landscape.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.