Earth’S Inner Core is Older Than Previously Determined (Download PDF)

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Earth՚s Inner Core is Older Than Previously Determined

  • The estimate of the age of Earth՚s solid inner core has been revised by researchers.
  • They have revised it from 565 million years to 1 - 1.3 billion years.
  • Over the years, estimates for core age have fluctuated.
Earth Structure


  • Last year a paper had reported age of inner core to be 565 million years that is quite young compared to the age of our 4.5 billion years old planet.
  • The research to re-determine the age of core has given out some other interesting attributes like
    • The process of heat convection of the iron core
    • The energy sources that power geodynamo that sustains magnetic field
  • Earth՚s inner core is solid and is made of iron.
  • The temperature of inner core is 6000 degree Celsius.
  • The outer core is also iron but is liquid due to comparatively low pressure.
  • Convection current is created by the rise of lighter elements through the liquid iron of the outer core at different temperatures.
  • The convection current thus created resembles a dynamo.
  • The process is like cream swirling in a mug of coffee.
  • The liquid metal circulation creates electric current which turns Earth into a giant electromagnet.
  • This process results in generation of Earth՚s magnetic field.
  • The process is called geodynamo and is fed by convection.
  • The age of the inner core has been calculated by the effectiveness of iron to transfer heat, known as thermal conductivity.
  • However, there was a paradox with the previously determined younger estimates of the inner core.
  • To sustain the geodynamo for billions of years before the inner core would be formed, the core would have had to reach unrealistically high temperatures.
  • The high amount of conductivity of the iron core was impossible because it would have little energy to convection.
  • It also only supported the existence of geodynamo for about a billion year, while other studies have shown that the process has existed for at least 3.4 billion years.
  • The recent research looked at the paradox and found a solution by keeping the temperature of the core within realistic parameters.
  • The research suggests that geodynamo was sustained by two different energy sources and mechanisms-
    • Thermal convection – the buoyancy is due to temperature fluctuations
    • Compositional convection – buoyancy produced by light material released at the inner core boundary
  • At the time the inner core started to grow, the geodynamo got powered by a new source of energy.

- Published/Last Modified on: December 30, 2020

Environment/Ecology, Down-to-Earth

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