Earth’s inner core found to be 1-1.5bn years old

8 Oct 2015

The mystery over the potential age of Earth’s inner core may have been solved, after new data has revealed that it might have formed as early as 1-1.5 billion years ago.

Trying to determine the actual age of Earth’s inner core – the hot, molten iron core at the centre of our planet – has somewhat perplexed researchers until now, with the best estimates putting its age somewhere between 500 million and 2bn years old.

The inner core currently exists in a state of liquid, molten iron, 3,000km beneath the surface of the planet. The planet’s magnetic field is created as this molten iron reacts to the cooler outer core, causing convection.

But now, in a new study published in Nature by a team from the University of Liverpool, an exhaustive search through magnetic data from ancient igneous rocks has shown the Pluto-sized region within Earth experienced a massive surge in magnetic activity 1-1.5bn years ago.

This, the researchers say, would indicate the first example of solid iron being formed in the centre of the Earth, caused by the freezing of liquid iron at its surface.

1bn years of magnetic activity left

During this period of freezing, convection received a strong power boost, with light, non-metallic elements remaining molten in the outer core and exhibiting buoyancy relative to the overlying liquid.

These new findings shed new light on the inner workings of our planet and the rate at which it is cooling.

“The results suggest that the Earth’s core is cooling down less quickly than previously thought, which has implications for the whole of Earth sciences,” said Dr Andy Biggin, lead researcher on the study. “It also suggests an average growth rate of the solid inner core of approximately 1mm per year, which affects our understanding of the Earth’s magnetic field.”

Going by their calculations, this should keep the Earth’s magnetic field active for at least another 1bn years.

“This contrasts sharply with Mars which had a strong magnetic field early in its history, which then appears to have died after half a billion years,” Dr Biggin said.

Earth’s inner core image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic