Q.Bring about the basic difference between the drift theory and Plate tectonics.
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Start your 14-day free trial to unlock the full solution →The drift theory says continents plow through the oceanic crust on their own, while plate tectonics says the Earth’s surface is broken into rigid plates that move together, carrying continents as passengers.
The drift theory, most famously associated with Alfred Wegener in the early twentieth century, was a bold and beautiful idea that the continents had once been joined in a single supercontinent and had since drifted apart. Wegener’s evidence was compelling: the jigsaw fit of South America and Africa, matching fossil plants and animals across oceans, and glacial striations that lined up only if the continents were once connected. But his mechanism was the weak link. He proposed that continents, made of lighter rock, plowed through the heavier oceanic crust like ships through ice, driven by tidal forces or the Earth’s rotation. Geologists rightly objected — there was no force strong enough to push a continent through solid rock, and the physics simply did not work. The idea was brilliant on observation but failed on explanation.
Plate tectonics, which emerged in the 1960s, kept Wegener’s continental drift as a consequence but completely rewrote the mechanism. Instead of continents moving independently, the theory says the Earth’s outer shell — the lithosphere — is broken into about a dozen large rigid plates that float on the hotter, softer asthenosphere below. These plates move as a whole, carrying both continents and ocean floors with them. The continents are not plowing through the ocean; they are riding on plates that also include the ocean floor. When plates collide, separate, or slide past each other, we get mountain building, earthquakes, and volcanic activity. The driving force is not the continents themselves but the slow convection currents in the mantle, along with gravity pulling the dense, cold edges of plates downward at subduction zones. …
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