IAS Gyan

Daily News Analysis


27th February, 2023 Science and Technology

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  • Seismologists at The Australian National University believe they’ve documented evidence of a distinct fifth layer lurking underneath it — the “innermost inner core”.

Earlier Assumptions

  • For the longest time since Danish scientist Inge Lehmann used seismic waves to discover Earth’s inner core in 1936, our rocky spheroidal planet was thought to have four layers: the crust, the mantle, the outer core, and the inner core.
  • Earth’s inner core — which is about 70% the size of the Moon with a diameter of 2,440 km — was previously thought to be the hottest and densest of all four concentric layers. Its interaction with the 6,970 km-wide molten outer core drives convection currents — heat released from solidification— to create and maintain Earth’s magnetic field.
  • Temperatures that far deep ought to be extreme, making this steaming cauldron of iron and nickel currently inaccessible.

New Findings

  • New findings published in Nature Communications confirm the existence of a distinct fifth layer — a solid ball measuring 650 km across.
  • This "innermost inner core" is an iron-nickel alloy ball.
  • The scientists found the 'hidden' core by studying seismic waves that traveled back and forth across the Earth's entire diameter up to five times.
  • The earthquake waves probed places near the center at angles that suggested a different crystalline structure inside the innermost layer. Effectively, the alloy is skewing the travel times for the waves as they pass through.


  • The findings create room for further research — which could lay bare the mystery of how a major global event caused a significant change in its composition.
  • This inner core is like a time capsule of Earth's evolutionary history — it's a fossilized record that serves as a gateway into the events of our planet's past [and hides information related to the] events that happened on Earth hundreds of millions to billions of years ago.


Q) Earth's core is responsible for the generation of Earth's magnetic field and it contains information regarding the earliest history of accretion of the planet. Comment.