CNN Indonesia
Friday, 17 Feb 2023 16:22 WIB
Jakarta, CNN Indonesia —
Scientists detect the deepest secrets in Earth’s corenamely a hidden structure or layer that is thought to have an effect on earthquake.
“Traditionally we have been taught that the Earth has four main layers: crust, mantle, outer core and inner core,” explained Joanne Stephenson, an Australian National University geophysicist in 2021, quoted from ScienceAlert.
Human knowledge of what lies beneath the Earth’s crust is largely deduced from what volcanoes have uncovered and what seismic waves indicate, aka earthquakes.
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From these indirect observations, scientists found that the extremely hot inner core with temperatures exceeding 5,000 degrees Celsius makes up only 1 percent of Earth’s total volume.
Several years ago, Stephenson and colleagues found evidence that Earth’s inner core actually has two distinct layers.
“This is very exciting – and might mean we have to rewrite our textbooks!” Stephenson said.
Stephenson and his team used search algorithms to sift through and match thousands of deep core models with decades of observed data about how long it takes seismic waves to travel through the Earth’s layers.
These data are data collected by the International Seismological Center.
The team looked at several models of anisotropy (the different qualities or properties of matter when measured in different axes, as opposed to isotropy) of the inner core.
One is about how differences in material composition change the nature of seismic waves.
From these observations, they found that some materials are more likely to change the behavior of seismic waves than others.
Some models suggest material seismic waves in the inner core align more quickly with the equator, while others suggest a mixture of materials allows waves to align more quickly with Earth’s axis of rotation.
Studies published in Journal of Geophysical Research it does not show much variation in depth in the inner core.
However, the team found there was a shift in seismic waves that slowed to an angle of 54 degrees, with the direction of the faster waves traveling parallel to the axis.
“We found evidence that might point to changes in the structure of iron, which points to the possibility of two separate cooling events in Earth’s history,” said Stephenson.
“The details of this major event are still a bit of a mystery, but we have added another piece of the puzzle to our knowledge of Earth’s inner core.”
The new findings may explain why some experimental evidence is inconsistent with our current models of Earth structure.
The presence of Earth’s innermost layers has been suspected before, with clues that the iron crystals that make up the innermost core have different structural alignments.
“We are limited by the global distribution of earthquakes and their recipients, especially at the polar antipodes (diametrically opposite points on Earth),” the team wrote in a paper.
(lom/arh)
