Research shows that there are unknown chapters in the history of the interior of the Earth’s past. In fact, the Earth’s inner core appears to have another inner core within it.
“Traditionally, we have been taught that the Earth is composed of four main layers: the Earth’s crust, the core (outer and inner mantle), and the core,” said Joan Stephenson, a geophysicist at the Australian National University.
Our knowledge of what lies beneath the earth’s crust is largely based on what volcanoes reveal and what seismic waves whisper.
Through these indirect observations, scientists have determined that the superheated inner core, with temperatures exceeding 5,000 degrees Celsius (9,000 Fahrenheit), makes up only 1% of the Earth’s total volume.
But a few years ago, researchers found evidence that the Earth’s inner core may actually have two separate layers.
“It’s very exciting – and it could mean we’ll have to rewrite textbooks!” Stephenson explained.
The team used the algorithm to search through thousands of inner core models and compared it to decades of observational data on how long seismic waves travel through the Earth, collected by the International Seismological Center.
So what’s down there? The team looked at some models of inner core anisotropy — how differences in its material composition change the properties of seismic waves — and found that some are more likely than others.
While some models suggest that material in the inner core directs faster seismic waves parallel to the equator, others suggest that the mixture of materials provides faster waves more parallel to the Earth’s axis of rotation. However, there are arguments about the exact degree of divergence at certain angles.
The study here did not show significant changes with depth in the inner core, but found a slow change in direction up to an angle of 54 degrees with faster wave direction parallel to the axis.
“We found evidence that could point to a change in the structure of iron, pointing perhaps to two separate cooling events in Earth’s history,” Stephenson said. “The details of this major event are still a little unclear, but we’ve added another piece of data.” a mystery when it comes to our knowledge of the Earth’s inner core.”
These new discoveries may explain why some of the experimental evidence is inconsistent with our current models of the Earth’s structure.
A deeper layer has previously been suggested, with hints that the iron crystals that make up the inner core have a different structural alignment.
“We are limited by the distribution of global earthquakes and receivers, especially in the antipolar one,” the team wrote in their paper, explaining that missing data reduces the validity of their conclusions.
But their findings are consistent with other studies of anisotropy in the innermost inner core.
Future research may fill in some of these data gaps, allow scientists to confirm or refute their findings, and hopefully translate more of the stories written at this early stage in Earth’s history.
The study is published in the journal Geophysical Research.
Source: Science Alert