Earth’s Inner Core Dynamics

February 12, 2025

Recent studies reveal that Earth’s inner core is less stable than previously thought. Research published in the journal *Nature Geoscience* indicates that structural changes may be occurring within the inner core. These changes could affect its rotation and even influence the length of a day. The interactions between the inner and outer core are believed to be the driving force behind these developments.

Earth’s Internal Structure

Earth consists of several layers:

The outermost layer is the crust, where life exists.
Beneath this is the mantle, followed by the molten, iron-rich outer core.
At the centre lies the solid inner core.
The outer core has long been acknowledged for its turbulence, but its influence on the inner core was thought to operate over geological timescales.

Turbulence in the Outer Core

The outer core’s turbulent nature has been known for years. However, the recent findings suggest that this turbulence can disrupt the inner core’s stability on human timescales. The outer core’s disturbances are now observed to affect the inner core, challenging earlier assumptions.

Observations Through Seismic Waves

Researchers utilised seismic waves to examine the inner core’s structure. These waves, produced by earthquakes, travel through Earth’s layers and provide insights similar to CT scans in medicine. Sensitive instruments called seismometers capture these waves, producing seismograms that reveal the inner workings of the Earth.

Data from Repeating Earthquakes

The research focused on 121 repeating earthquakes recorded near Antarctica’s South Sandwich Islands between 1991 and 2024. The consistent location of these quakes allowed scientists to detect subtle changes in seismic wave behaviour. An anomaly in the seismic waveforms indicated unexpected properties, prompting further investigation.

Structural Changes in the Inner Core

The findings suggest that the near surface of the inner core is undergoing structural changes. This could be due to viscous deformation, where materials flow under stress. This phenomenon is akin to how honey flows when poured. The research implies that the inner core may not be as rigid as once believed.

Implications of the Research

Understanding the dynamic relationship between the inner and outer core can enhance our knowledge of Earth’s geophysical processes. It may also provide vital information about how these processes affect the planet’s rotation and the length of a day.

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