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Earth’s core

9th July, 2024 Geography

Earth’s core

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Context: A new study has indicated that Earth's core is rotating at a different speed compared to the rest of the planet. Moreover, the rotation speed is slowing down continuously.


Core of the earth

  • Earth's core is the hottest part of the planet, equivalent to that of the Sun's surface.
  • It is the innermost layer surrounding the earth’s centre.
  • The core is separated from the mantle by Guttenberg’s Discontinuity.


  • It is composed mainly of iron (Fe) and nickel (Ni) and hence it is also called as
  • The core constitutes nearly 15% of earth’s volume and 32.5% of earth’s mass.
  • The core is the densest layer of the earth with its density ranges between 9.5-14.5g/cm3.

The inner core and the outer core

  • The Core consists of two sub-layers: the inner core and the outer core.
  • The inner core is in solid state and the outer core is in the liquid state (or semi-liquid).
  • The inner core is surrounded by a liquid metal outer core, which acts as a barrier with the rest of the Earth.
  • This barrier allows Earth's core, akin to a hot solid ball of metal, to spin independently and not necessarily align with the rest of the planet.
  • The discontinuity between the upper core and the lower core is called as Lehmann Discontinuity.
  • Danish seismologist Inge Lehmann discovered the planet's inner core in 1936.
  • Barysphere is sometimes used to refer the core of the earth or sometimes the whole interior.

Recent Findings

Earth's core slowing down

  • The inner core of the Earth's movements are slowing down and also is moving in reverse direction or backwards.
  • Scientists have been observing the core since 1936.
  • Scientists have used the method of the earthquake to identify the inner core moments, the P and S waves emerge during the earthquake.

  • The data of the seismic moment was first published in 1990, according to recent studies and reports of 2023 the core that used to spin faster than the Earth itself is now spinning slower.

Characteristics of P wave and S wave

Reason for backward moments of the inner core

  • The cause of these movements is that the solid contains iron and nickel whereas the outer core is
  • The Earth’s magnetic field influences the movement of the inner core, particularly in the active region where the inner and outer cores meet.


Studying the rotation of the inner core is crucial for a deeper understanding of our planet. It allows scientists to develop comprehensive dynamic models of the Earth's systems. Examining seismic waves can improve our understanding and management of earthquakes.


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Q. Consider the followings pairs

1.Conrad Discontinuity: between the Crust and Mantle.

2.Mohorovicic Discontinuity:between upper and lower Crust.

3.Gutenberg Discontinuity: between Mantle and Core.

4.Lehman Discontinuity: between Outer core and Inner core.

How many of the above pairs is/are correctly matched?

A.Only one

B.Only two

C.Only three

D.All four

Answer B


Conrad Discontinuity:  Transition zone between SIAL and SIMA layers of crust.

Mohorovicic Discontinuity:  Transition zone between the Crust and Mantle.

Repiti Discontinuity: Transition zone between Outer mantle and Inner mantle.

Gutenberg Discontinuity: Transition zone between Mantle and Core.

Lehman Discontinuity: Transition zone between Outer core and Inner core.