maximus otter
Recovering policeman
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Researchers have found more evidence for a whole new chapter deep within Earth's past - Earth's inner core appears to have another even more inner core within it.
"Traditionally we've been taught the Earth has four main layers: the crust, the mantle, the outer core and the inner core," explained Australian National University geophysicist Joanne Stephenson.
Our knowledge of what lies beneath Earth's crust has been inferred mostly from what volcanoes have divulged and seismic waves have whispered.
Stephenson and colleagues have found more evidence Earth's inner core may have two distinct layers.
Differences in seismic wave paths through layers of Earth. (Stephenson et al., Journal of Geophysical Research: Solid Earth, 2021)
The team looked at some models of the inner core's anisotropy - how differences in the make-up of its material alters the properties of seismic waves - and found some were more likely than others.
This study failed to show much variation with depth in the inner core, but did find there was a change in the slow direction to a 54 degree angle, with the faster direction of waves running parallel to the axis.
"We found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth's history," Stephenson said.
These new findings may explain why some experimental evidence has been inconsistent with our current models of Earth's structure.
The presence of an innermost layer has been suspected for some time now, with hints that iron crystals which compose the inner core have different structural alignments.
https://www.sciencealert.com/earth-...hints-at-an-even-more-dramatic-planet-history
maximus otter
"Traditionally we've been taught the Earth has four main layers: the crust, the mantle, the outer core and the inner core," explained Australian National University geophysicist Joanne Stephenson.
Our knowledge of what lies beneath Earth's crust has been inferred mostly from what volcanoes have divulged and seismic waves have whispered.
Stephenson and colleagues have found more evidence Earth's inner core may have two distinct layers.
Differences in seismic wave paths through layers of Earth. (Stephenson et al., Journal of Geophysical Research: Solid Earth, 2021)
The team looked at some models of the inner core's anisotropy - how differences in the make-up of its material alters the properties of seismic waves - and found some were more likely than others.
This study failed to show much variation with depth in the inner core, but did find there was a change in the slow direction to a 54 degree angle, with the faster direction of waves running parallel to the axis.
"We found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth's history," Stephenson said.
These new findings may explain why some experimental evidence has been inconsistent with our current models of Earth's structure.
The presence of an innermost layer has been suspected for some time now, with hints that iron crystals which compose the inner core have different structural alignments.
https://www.sciencealert.com/earth-...hints-at-an-even-more-dramatic-planet-history
maximus otter
