While most of us take the ground under our feet for granted, written in our complex layers, like the pages of a book, is the history of the earth. Our story.
The research shows that there are chapters little known in this story, deep in the past of the earth. In fact, the inner nucleus of the earth seems to have another even more interior nucleus.
“Traditionally, we were taught that the earth has four main layers: the crust, the mantle, the external nucleus and the inner nucleus”, the geophysicist of the Australian University Joanne Stephenson explained in 2021.
Our knowledge of what is under the crust of the earth was mainly deducted from what the volcanoes have disclosed and what seismic waves have whispered.
According to these indirect observations, scientists calculated that the warm and burning inner nucleus, with temperatures exceeding 5,000 degrees Celsius (9,000 fahrenheit), represents only 1% of the total volume of the earth.
But a few years ago, Stephenson and his colleagues found evidence that the inner nucleus of the earth could actually have two distinct layers.
“It’s very exciting – and could mean that we have to rewrite manuals!” Stephenson explained at the time.
The team used a research algorithm to browse and match thousands of inner nucleus models with data observed in many decades on the duration of seismic waves to travel through Earth, collected by the international seismological center.
Differences in the seismic wave paths through the layers of the earth. (Stephenson et al.Journal of Geophysical Research: Solid Earth, 2021)
So what’s up there? The team examined certain inner core models anisotropy – How the differences in the composition of its equipment modify the properties of seismic waves – and found that some were more likely than others.
While some models suggest the material of the inner core channels The seismic waves more quickly parallel to the equator, others indicate that the mixture of materials allows faster waves more parallel to the axis of rotation of the earth. Even then, there are arguments on the exact degree of difference from certain angles.
The study here has not shown much variation with the depth in the inner nucleus, but it found that there was a change in slow direction at a 54 -degree angle, with the faster direction of the waves parallel to the axis.
“We have found evidence that can indicate a change in the iron structure, which perhaps suggests two distinct cooling events in the history of the earth”, Stephenson said.
“The details of this great event are still a little a mystery, but we have added another piece of the puzzle with regard to our knowledge of the inside of the earth.”
These results can explain why Some experimental evidence was incompatible with our current models of the structure of the earth.
The presence of a most interior layer has been suspected BeforeWith clues that the iron crystals that make up the internal nucleus have different structural alignments.
“We are limited by the distribution of earthquakes and global receivers, especially in polar antipodes”, ” The team writes In their article, explaining the missing data decreases the certainty of their conclusions.
But their conclusions align with other studies on anisotropy of the most internal inner nucleus.
Future research could fill some of these data gaps and allow scientists to corroborate or contradict their results, and hopefully, translate more stories written in this first layer of the history of the earth.
This research was published in the Journal of Geophysical Research.
A previous version of this article was published in March 2021.