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Mahesh

12/08/22 01:00 AM IST

Giant meteorite impacts could be responsible for Continents formation

In News 
  • Earth’s continents were formed by massive meteorite impacts that were prevalent during the first billion years of our planet’s four and a half billion-year history, according to a new study.
About the study 
  •  The researchers looked for evidence in zircon crystals embedded in rocks from the Pilbara Craton in Western Australia. This craton is the remnant of an ancient crust that began forming more than three billion years ago.
  • A craton is an old and stable part of the continental lithosphere, which consists of Earth’s two topmost layers, the crust and the uppermost mantle.
  • Studying the composition of oxygen isotopes in these zircon crystals revealed a ‘top-down’ process starting with the melting of rocks near the surface and progressing deeper, consistent with the geological effect of giant meteorite impacts.
  • Zircons are formed by the crystallisation of magma or are found in metamorphic rocks. They act as tiny time capsules, recording the period of geologic activity. Newer zircon adds to the original crystal as time progresses.
Significance 
  • Understanding the formation and evolution of continents is important, as it is the key to reserves of metals such as lithium, tin and nickel.
  • Most of Earth’s biomass and most humans live on these landmasses, so understanding how continents form and evolve is crucial.
Theory of plate Tectonics 
  • Alfred Wegener in his paper in 1912 hypothesized that all of the modern-day continents had previously been clumped together in a supercontinent he called Pangaea.
  • Over 200 million years, the continents had drifted apart. This was called continental drift theory.
  • But it was widely ridiculed as a mere hypothesis.
  • It was only in the 1960s, when technologies had developed that the validity of his theory was proved and further enhanced by McKenzie and Parker, through their theory of plate tectonics.
Source- Down to Earth 

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