New study details formation of Earth's inner core

Researchers say the Earth's inner core fueled magnetic field will likely remain strong for a long time.

By Brooks Hays
New study details formation of Earth's inner core
An artistic rendering shows Earth's inner and outer cores. Photo by NASA/JPL-Université Paris Diderot - Institut de Physique du Globe de Paris

LIVERPOOL, England, Oct. 8 (UPI) -- New analysis of ancient rock samples suggest Earth's inner core formed between 1 and 1.5 billion years ago.

Earth's inner core is a solid ball of iron. It's surrounded by an outer core of liquid iron and nickle. Earth didn't always have a solid inner core. Early Earth featured an entirely molten core.


Scientists have long disagreed on when the planet's solid inner core first formed, with estimates ranging from 0.5 to 2 billion years ago. Scientists at the University of Liverpool say their latest research shrinks the range.

In studying core samples from a variety of ancient igneous rocks, geoscientists at Liverpool say they've detected a significant increase in the Earth's magnetic field between 1 and 1.5 billion years ago.

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The research team published their new findings in the journal Nature Letters.

Earth's magnetic field is powered by the movements of the planet's liquid outer core. Scientists theorize the freezing out or solidification of rock from Earth's molten outer core into the inner core pushes impurities, volatiles and thermal energy into the liquid layer, encouraging the convection that drives the Earth's magnetic field.

Researchers believe the Earth's magnetic field, which strips away ozone in the upper atmosphere and protects the planet from harmful solar radiation, was and is key to the development of life on Earth. Understanding when and how Earth's core and magnetic field first developed can help scientists predict Earth's electromagnetic future.

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"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," lead study author Andy Biggin said in a press release. "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."

In addition to offering a more accurate birth date for Earth's inner core, the new analysis suggests Earth's core-fueled magnetic field will likely remain strong for a long time.

"The theoretical model which best fits our data indicates that the core is losing heat more slowly than at any point in the last 4.5 billion years and that this flow of energy should keep the Earth's magnetic field going for another billion years or more," Biggin said. "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."

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