Earth’s Inner Core Rotation May Have Paused, Study Suggests

Beneath the surface of our planet, where continents and oceans shift, lies a solid sphere of iron and nickel at the Earth’s heart. Recent research indicates that the rotation of this inner core, though imperceptible to those on the surface, may have undergone a significant change in recent decades, potentially slowing down, pausing and even reversing direction.

How Scientists Reached the Conclusion

Researchers at Peking University in China arrived at this conclusion through the analysis of seismic data collected between 1990 and 2021. By examining records of earthquakes around the world, they observed the behavior of seismic waves as they traveled through the Earth’s interior. Comparing variations in the propagation time of these waves over three decades, seismologists identified changes in the movement of the planet’s deepest region.

The results suggest that until 2009, the inner core rotated slightly faster than the Earth’s surface. After this period, the movement began to slow, with data indicating a possible temporary pause in rotation. This analysis is possible because seismic waves subtly change speed as they pass through different internal layers of the planet. [Scientific American]

The Phenomenon Isn’t New

The researchers also found evidence suggesting this isn’t the first time such a reversal has occurred. Data analysis indicates a similar change in the inner core’s movement may have taken place in the 1970s. [Inverse] Based on this historical comparison, scientists propose the phenomenon follows an approximate 70-year cycle, reinforcing the idea that the inner core undergoes periodic oscillations relative to the Earth’s surface.

What Explains the Change in Earth’s Rotation?

The inner core is a solid sphere primarily composed of iron and nickel, surrounded by the liquid outer core, which is responsible for generating Earth’s magnetic field. Several factors can influence the movement of this deep region, including gravitational interactions between the Earth’s core and mantle, forces generated by the magnetic field, and differences in density and temperature within the inner layers. [Science News] A study published in the journal Nature Geoscience suggests slight variations in this balance can cause oscillations in the nucleus’s rotation over decades.

Could These Changes Affect the Planet?

Although the phenomenon occurs thousands of kilometers underground, experts believe it could have indirect effects on the planet’s surface. Previous research suggests changes in the rotation of the nucleus may be linked to small variations in the length of days on Earth, measured in milliseconds. Scientists point to potential impacts on natural processes, such as subtle changes in Earth’s magnetic field, influences on seismic activity, changes in the dynamics of tectonic plates, and variations in long-term geological processes.

Impacts for Humans

Despite the scale of the phenomenon, experts emphasize that direct effects on the population are extremely subtle and do not pose an immediate risk. The primary scientific interest lies in understanding how the Earth’s interior functions and how these changes might affect natural systems over decades or centuries. The magnetic field, for example, is crucial for protecting the planet from solar radiation and influences modern technologies like navigation and communication systems.

Researchers continue to analyze seismic records and geophysical data to better understand the dynamics of the planet’s interior, including the exact duration of the core’s rotation cycles, the relationship between the core and the magnetic field, and potential connections to climate and geological changes.