Earth’s Inner Core is Slowing Down

A recent study published in the Journal Nature suggests that Earth’s inner core began slowing its rotation in 2010, potentially altering the length of a day by fractions of a second.

Earth’s Inner Core is Slowing Down: Latest Study

• Research Conduction: Researchers from the University of Southern California analyzed seismic data and nuclear tests and provided “unambiguous evidence” of this slowdown, sparking debate on core dynamics and Earth’s rotation.
• Data Used for Latest Study: The researchers looked at seismic data recorded from 121 repeating earthquakes – multiple quakes occurring in the same location – between 1991 and 2023 in the South Sandwich Islands, a remote archipelago in the South Atlantic Ocean. 
  • • The islands are prone to violent earthquakes.
  • Data from twin Soviet nuclear tests between 1971 and 1974, along with multiple French and American nuclear tests from other studies of the inner core, were also included in the analysis.
• Crucial Finding: It is considered that the inner core is reversing and backtracking relative to the surface, because of rotating slower than the mantle for the first time in about 40 years.
• Reason for Slowing Down: They observed a slowdown starting around 2010, possibly influenced by the surrounding liquid outer core’s movements generating Earth’s magnetic field or gravitational forces and the gravitational pulls from dense regions in the overlying rocky mantle.

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Implications of Earth’s Inner Core is Slowing Down

• Impact on Length of the Day: It could change the length of one day on the Earth by fractions of a second.
• Influence on Geological Processes: The inner core’s rotation is crucial in generating Earth’s magnetic field, which shields the planet from harmful solar radiation and influences geological processes.
  • Therefore, any changes in the inner core’s rotational speed could potentially impact Earth’s magnetic properties, possibly affecting geomagnetic events and natural conditions on the planet’s surface.
  • So far there is little to indicate that what the inner core does has much effect on surface dwellers.
• A New Avenue: The study not only resolves a long-standing scientific debate but also opens up new avenues for understanding the intricate dynamics of our planet’s interior, with potential implications for Earth’s magnetic field and rotational patterns.

Layers of the Earth

• Four Main Layers: 
  • The solid inner core, composed of iron and nickel
  • The liquid outer core, which generates the magnetic field
  • The viscous mantle, with convection currents driving plate tectonics
  • The thin, solid crust, where life exists and geological activity occurs

About Earth Inner Core

• Position: The inner core of Earth, a solid iron-nickel sphere surrounded by the liquid outer core, is roughly the size of the moon and lies over 4,500 kilometers beneath our feet. 
• Observation: While it cannot be directly observed, researchers can study its behavior by analysing seismic waves generated by earthquakes and nuclear tests.
• Rotation: The inner core rotates, relative to the Earth’s surface, back and forth, like a swing.
  • One cycle of the swing is about seven decades.
• Variations Observed in Rotation:
  • In Early 1970s: The inner core started rotating slightly faster than the rest of the planet.
  • Around 2009: The inner core had been slowing down before coming in sync with Earth’s rotation.
  • Afterwards: There has been a “negative trend” since, meaning the inner core is now rotating slower than the surface.
    • The researchers predicted the next change would occur in the mid-2040s.
    • Researchers said this rotation timeline roughly lines up with changes in what is called the “length of day”— small variations in the exact time it takes Earth to rotate on its axis.

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