ANU scientists discover a fifth layer in the earth’s core

The historic understanding of the earth’s inner core has been called into question by a group of scientists from the Australian National University after analysing earthquake data.

Seismologists from the university believe they have found evidence of a previously unknown layer inside Earth called the innermost inner core.

The layer, according to researchers, looks like a solid metallic ball, an article from ANU published on Wednesday said.

Findings uncovered by the researchers, published in Nature Communications, confirmed there are five layers to the earth’s core and not four like has been historically thought.

“The existence of an internal metallic ball within the inner core, the innermost inner core, was hypothesised about 20 years ago,” Dr Thanh-Son Phạm, from the ANU Research School of Earth Sciences, said.

“We now provide another line of evidence to prove the hypothesis.”

The researchers analysed seismic waves that travel directly through the Earth’s centre and “spit out” at the opposite side of the globe to where the earthquake was triggered, also known as the antipode.

The waves then travel back to the source of the quake in what the scientists have likened to a ping pong ball bouncing back and forth.

It has previously been thought that Earth’s structure comprised of just four distinct layers: the crust, the mantle, the outer core and the inner core.

But now, Professor Hrvoje Tkalčić, also from ANU, said new learnings about the earth’s inner core could reveal more about the planet’s past and evolution.

“This inner core is like a time capsule of Earth’s evolutionary history – it’s a fossilised 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,” he said.

One of the earthquakes scientists studied originated in Alaska where seismic waves triggered by the quake “bounced off” somewhere in the south Atlantic Ocean, before travelling back to Alaska.

They found the bouncing seismic waves repeatedly probed spots near the Earth’s centre from different angles.

By analysing the variation of travel times of seismic waves for different earthquakes, the scientists believe the crystallised structure within the inner core’s innermost region is likely different to the outer layer.

They say it might explain why the waves speed up or slow down depending on their angle of entry as they penetrate the innermost inner core.

According to the ANU team, the findings suggest there could have been a major global event at some point during Earth’s evolutionary timeline that led to a “significant” change in the crystal structure or texture of the Earth’s inner core.

“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,” Professor Tkalčić said.

The researchers analysed data from about 200 magnitude-6 and above earthquakes from the last decade.

Originally published as Scientists discover shocking new detail about Earth’s core

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