People have been taught for decades that our planet Earth is made up of four layers – the crust, the mantle, the outer core, and the inner core. This assumption has been widely accepted in scientific circles. But now, a study from Australian National University has revealed evidence of a fifth layer – a giant metal ball named the “innermost inner core.”
Whilst this has come as a surprise to many, this was not the case for some scientists. “The existence of an internal metallic ball within the inner core, the innermost inner core, was hypothesized about 20 years ago, and we now provide another line of evidence to prove the hypothesis,” explained Dr. Thanh-Son Phạm from ANU’s Research School of Earth Sciences.
The experts were able to come to their conclusion by studying the seismic activity produced during 200 earthquakes and tremors across the last decade. In particular, they studied how fast the seismic waves passed through the inner core of the earth.
These waves travel directly through the Earth’s center and come out at the opposite side of the earthquake’s trigger point (also known as the antipode), before finally returning to the point of the earthquake.
“By developing a technique to boost the signals recorded by densely populated seismograph networks, we observed, for the first time, seismic waves that bounce back-and-forth up to five times along the Earth’s diameter. Previous studies have documented only a single antipodal bounce,” explained Dr. Pham.
Not only will this technological advancement help us to better understand our planet in its current state, but it also shows great potential for helping researchers learn more about the past and future of Earth.
According to study co-author Professor Hrvoje Tkalčić, the findings are exciting because they provide a new way to probe the Earth’s inner core and its centermost region.
“This inner core is like a time capsule of Earth’s evolutionary history,” said Professor Tkalčić. “It’s a fossilized record that serves as a gateway into the events of our planet’s past. Events that happened on Earth hundreds of millions to billions of years ago.”
Specifically, some researchers are curious about what the makeup of the innermost inner core could teach us about a major global event that has not been studied. The seismic wave analysis has led to the conclusion that the innermost inner core has a crystalline alloy structure that is very different from the outer sections, essentially presenting scientists with a whole new chapter of planetary evolution to investigate.
“There are still many unanswered questions about the Earth’s innermost inner core, which could hold the secrets to piecing together the mystery of our planet’s formation,” said Professor Tkalčić.
The study is published in the journal Nature Communications.
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