Scientists say the Earth's core is changing - what does this mean?

New research shows that the inner core of planet Earth has changed shape in the last two decades. Scientists have learnt that the inner core is not shaped like a ball as we used to think but has deformed edges of about 100m or more in height in places.

The Earth’s core is more than 4,000 miles from the planet's surface and, so far, no scientists have been able to reach it.

The core is the heart of the planet as it produces a magnetic field that protects life from burning up in the Sun's radiation. The inner core spins separately from the liquid outer core and from the rest of the planet. Without this motion, Earth would die and become more like barren Mars which lost its magnetic field billions of years ago.

This was all part of the research led by scientists John Vidale, Wei Wang, Ruoyan Wang, Guanning Pang and Keith Koper. It was published in the scientific journal Nature Geoscience.

Initially, Vidale and his team set out to determine why the inner core may have decelerated to a pace slower than Earth's rotation before accelerating again in 2010. Vidale, an earth scientist at the University of Southern California, found further evidence supporting the theory that the inner core indeed slowed down around that time.

According to their research, the scientists learnt that the Earth's inner core changes its rotation speed and shape over time. By studying seismic waves from repeated earthquakes, they found that the core rotated faster than the rest of the Earth for some time but then slowed down in recent decades.

The change in shape could be happening where the edge of the solid inner core touches the extremely hot, liquid metal outer core.

They analysed earthquake data from 1991 to 2023 using seismic stations in North America and the South Sandwich Islands. They found differences in how the waves behaved between 2004 and 2008, suggesting that changes were happening near the surface of the inner core rather than deeper inside.

This research helps settle a long-standing debate: the inner core’s changes come from both rotation and shifts near its boundary. These shifts might be caused by the movement of the surrounding mantle or forces from the liquid outer core affecting the inner core's shape.