Schoolchildren have long been taught that Earth’s composed of four main layers: the crust, the mantle, the outer core, and the inner core. But a new study suggests their textbooks may be incomplete.
Researchers from The Australian National University (ANU) discovered a mysterious new layer at the center of the planet: the “innermost inner core.”
They suspect it contains secrets about an unknown, dramatic event in the Earth’s history.
Geologists first proposed the idea of a fifth layer decades ago, but had previously struggled to detect it.
The new study unearthed further evidence by analyzing changes to seismic waves as they travel through our planet’s core.
The team used a search algorithm to compare thousands of models of the inner core with travel time data for seismic waves.
They found changes to the structure of iron around 650km from the center of the Earth — indicating the presence of an extra layer.
“We found evidence that may indicate a change in the structure of iron, which suggests perhaps two separate cooling events in Earth’s history,” said study author Joanne Stephenson in a statement.
The details of these events remain somewhat mysterious. But Stephenson believes further analysis could deepen our understanding of the Earth’s evolution:
It’s very exciting — and might mean we have to re-write the textbooks!
You can read the study paper in the Journal of Geophysical Research: Solid Earth.