Scientists Detect Hidden Structure In Earth’s Core

Earth’s Complex History Beneath Our Feet

While many of us take the ground beneath our feet for granted, it holds Earth’s complex history within its layers, like pages of a book. Research suggests there are lesser-known chapters in that history, buried deep in Earth’s past. In fact, Earth’s inner core seems to have another, even more internal core within it.

Traditionally, we have learned that Earth has four main layers: the crust, the mantle, the outer core, and the inner core, explained geophysicist Joanne Stephenson from the Australian National University in 2021.

Our understanding of what lies beneath Earth’s crust comes largely from what volcanoes reveal and what seismic waves suggest. Based on these indirect observations, scientists have estimated that the extremely hot inner core, with temperatures exceeding 5,000 degrees Celsius (9,000 Fahrenheit), accounts for only 1% of Earth’s total volume

A Two-Layered Inner Core?

However, a few years ago, Stephenson and her colleagues found evidence that Earth’s inner core may actually consist of two distinct layers.

This is very exciting and could mean we have to rewrite the textbooks! Stephenson said at the time.

So, what’s down there? The team examined models of inner core anisotropy—how variations in its material affect the properties of seismic waves—and found that some models were more likely than others.

While some suggest that the inner core’s material channels seismic waves faster along the equator, others indicate that the mix of materials allows for faster waves along Earth’s rotational axis. Even then, there is debate over the exact degree of difference at certain angles.

The study did not show much variation with depth in the inner core, but it did find a shift in the slower direction at a 54-degree angle, with the faster direction of waves aligned with the axis.

Iron’s Role and Earth’s Cooling History

“We found evidence that may indicate a change in iron’s structure, suggesting perhaps two separate cooling events in Earth’s history,” Stephenson explained.

The details of this major event are still somewhat mysterious, but we’ve added another piece to the puzzle when it comes to our understanding of Earth’s inner core.

These findings might explain why some experimental evidence has been inconsistent with our current models of Earth’s structure.

The presence of an innermost layer has been suspected before, with hints that the iron crystals making up the inner core have different structural alignments.

“We are limited by the distribution of global earthquakes and receivers, especially at polar antipodes,” the team wrote in their paper, explaining that the lack of data decreases the certainty of their conclusions.

Still, their conclusions align with other studies on the anisotropy of the innermost core.

Future Research and Discoveries

Future research may fill in some of these data gaps, allowing scientists to confirm or refute their findings and hopefully uncover more stories written in this early layer of Earth’s history.

Read the original article: Science Alert

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