We’ve all been taught the same thing in school: the earth is made up of four layers – the crust, the mantle, the inner core, and the outer core. We’ve known this all along, and we probably haven’t given it much thought the moment we left school.
In reality, the ground beneath us tells of tales before man walked the earth. It’s filled with stories of history and of how the world came to be. We may have studied the earth for years, but so much has yet to be discovered. We’ve only scratched the layer of our home’s history.
In the study published in the Journal of Geophysical Research, researchers have actually found new evidence for further stories deep within the earth’s core. This could give us a better glimpse on the window to our past. While we assumed that the layer ended with the inner core, it seems as if our planet has another even deeper core within.
“Traditionally we’ve been taught the Earth has four main layers: the crust, the mantle, the outer core and the inner core,” says Australian National University geophysicist Joanne Stephenson.
What we know about what’s found beneath Earth’s crust is from what came out of volcanoes. The seismic waves we’ve observed have given us clues, but these weren’t firm enough to form a solid conclusion. Scientists base what they know from indirect observations. They know that the inner core exudes immense heat. Temperatures go beyond 5,000 degrees Celsius (or 9,000 Fahrenheit), and the core only makes up one percent of earth’s overall volume.
Now, Stephenson and his colleagues have stumbled upon new evidence that the earth’s inner core may actually have two perceptible layers. Stephenson adds, “It’s very exciting – and might mean we have to re-write the textbooks!”
How did the team find such clues? They made use of a search algorithm to fish out information and match a variety of the inner core models. They used observed data that was collected across the decades. They studies how long seismic waves take to travel up the surface with the data gathered by the International Seismological Centre.
So, what exactly is down there? Stephenson and her troop looked into models of the inner core’s anisotropy. They studied how the differences in the make-up of the materials found beneath can change the properties of seismic waves. They found that found changes some were more likely to happen than the rest.
There were several models available, some of which assume that the material found of the inner core channels seismic waves faster parallel to the equator. Then, there are models that hypothesize that the different blend of materials allows the waves to travel faster more parallel to the rotational axis. There are still valid arguments to be answered from both ends because no one can really tell the exact degree of difference at specific angles.
This study never really showed much differences with depth in the inner core. However, they did discover that there was a change in the slow direction to a 54-degree angle, and with the faster direction of waves running parallel to the earth’s axis.
Stephenson further explains, “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 Earths’ inner core.”
The team’s uncovered facts could actually explain why some experimental evidence has been inconsistent when these are being compared with the most current models of planet’s physical structure. There is an innermost layer, and many have believed this to be true for quite some time. There are hints that iron crystals which make up the inner core have unlike structural alignments.
With the discoveries they have gathered and made, the team behind wrote a paper that implicitly stated, “We are limited by the distribution of global earthquakes and receivers, especially at polar antipodes.” They stated how the missing data decreases the certainty of their final interpretation. However, what they found was that their conclusions complemented with other recent studies on the anisotropy of the innermost inner core.
For now, they are all trying to come up with new methods that may answer questions and fill in the gaps. It is with hope that their efforts will either support or go against the findings. Whatever the case may be, history could be rewritten should they successfully manage to gather more solid data.
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