A new study shows that the inner core changed shape in just a few decades, challenging previous assumptions and revealing hidden dynamics deep within Earth.

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.

The surface of Earth's inner core appears to be dynamic, changing shape as it rotates, earthquake waves reveal.

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.

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 planet’s inner core was previously thought of as a hard, solid sphere. But a new study has found that its edges are softer than realized and actually changing shape.