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.

A new, detailed probe of Earth's heart reveals that the rotating inner core doesn't just change in rotation speed – it also appears to change in shape, with subtle variations appearing in the way acoustic waves propagate through the planetary center.

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.

Earth’s core is located below the middle layer called the mantle and the outer layer –or crust. It consists of two main parts–a liquid outer core and a more solid inner core. The outer layer is made of liquid iron-nickel and is responsible for producing Earth’s magnetic field.

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.

Earth’s inner core is changing shape, scientists have found.

Scientists at the University of Southern California have discovered the Earth's core is changing shape after analysing earthquake data.

A new study has found evidence that the Earth's inner core may have changed shape. Far from taking place over geological timescales, the changes appear to have taken place within the last two decades.