Earth’s inner core has an inner core of its own and its distinct properties may point to a dramatic event in the history of our planet, according to new research from the Australian National University.
The inner core of Earth has an inner core of its own, with crystals aligned in a different direction. Image credit: Lachina Publishing Services.
The Earth’s solid inner core remains one of the most enigmatic parts of our planet, despite numerous studies in the fields of seismology, geodynamics, mineral physics and materials science.
Making up only 1% of Earth’s total volume with a temperature of over 5,000 degrees Celsius, understanding the structure, current dynamics and evolution of the inner core is vital to understanding Earth’s thermal history.
In particular, this provides insights to the geodynamo, without which life would not exist as we know it today.
“Investigating the structure of the inner core can help us understand more about the Earth’s history and evolution,” said study’s lead author Dr. Joanne Stephenson, a researcher in the Research School of Earth Sciences at the Australian National University.
“Traditionally we’ve been taught the Earth has four main layers: the crust, the mantle, the outer core and the inner core.”
“The idea of another distinct layer was proposed a couple of decades ago, but the data has been very unclear.”
For the study, Dr. Stephenson and her colleagues from the Australian National University, Professor Hrvoje Tkalčić and Professor Malcolm Sambridge, used data from the International Seismological Centre (a database of seismic arrivals gathered from seismological institutions globally) in conjunction with the so-called ‘neighbourhood algorithm.’
“We got around this by using a very clever search algorithm to trawl through thousands of the models of the inner core,” Dr. Stephenson said.
“It’s very exciting — and might mean we have to re-write the textbooks!”
“While this new layer is difficult to observe, its distinct properties may point to an unknown, dramatic event in the Earth’s history,” she added.
“We found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth’s history.”
“The details of this big event are still a bit of a mystery, but we’ve added another piece of the puzzle when it comes to our knowledge of the Earth’s inner core.”
The findings were published in December 2020 in the Journal of Geophysical Research: Solid Earth.
J. Stephenson et al. Evidence for the Innermost Inner Core: Robust Parameter Search for Radially Varying Anisotropy Using the Neighborhood Algorithm. Journal of Geophysical Research: Solid Earth, published online December 7, 2020; doi: 10.1029/2020JB020545