Researchers studying decades of earthquake data say they have found the first evidence that, in addition to spinning backward, Earth’s inner core in changing shape.

At the center of our planet is a very hot rotating ball of mostly iron and nickel (sorry Journey to the Center of the Earth fans). Scientists infer features of this innermost geographic layer—like the fact that it’s divided into a liquid outer core and a solid inner core—by analyzing how it distorts seismic waves caused by earthquakes.

Scientists of course cannot cut into Earth and directly observe its insides. Instead, their knowledge is inferred from the vibrations generated by earthquakes that pass through the planet. The speed and the direction of the seismic vibrations change depending on the density and the elasticity of the rocks.

The inner core of Earth may have changed shape in the past 20 years, according to a group of scientists. The inner core is usually thought to be shaped like a ball, but its edges may actually have deformed by 100m or more in height in places, according to Prof John Vidale who led the research.

Recent research suggests Earth's inner core, primarily composed of iron and nickel, may not be entirely solid. Scientists observed shape alterations at the inner core's outer boundary, potentially due to outer core turbulence.

Scientists found that the inner core’s structure changes as it rotates. It deforms at its border, potentially accumulating more material in some areas and less in others — almost like creating hills and valleys.

The surface of the Earth's inner core may be changing, as shown by a new study by USC scientists that detected structural changes near the planet's center, published in Nature Geoscience.