Earth’s inner core may be slowing its rotation and preparing to change spin directions compared to the rest of the planet.
This appears to be part of a 60-year cycle in which the core periodically accelerates up and calms down.
Earth’s Inner Core Movement
A swirling layer of molten iron and nickel lies beneath Earth’s mantle, with a compact inner core of iron maintained solid by immense pressure near the planet’s core.
The movement of the inner core relative to the mantle and surface has been debated for decades, and seismic observations are now assisting researchers in better understanding it.
Yi Yang and Xiaodong Song of Peking University in China, together with their colleagues, studied seismic waves from nearly identical earthquakes that occurred in the planet’s core over the last 60 years or more.
If the Earth’s solid core were completely spherical and had the same structure all the way through, we would expect each pair of waves to look the same no matter when they passed through. Because it isn’t, we may utilize the variations between the waves to measure the changes deep beneath the ground.
Before around 2009, the researchers discovered that the planet’s core appeared to rotate slightly faster than the mantle and the surface, implying that if you could stand on the surface and gaze down to the core, you would see it steadily moving forward.
However, this rotation began to slow down after 2009. If you could gaze down at the core right now, their measurements show that it isn’t spinning at all because it rotates at the same pace as the surface.
The last turning point in the rotation of the inner core, according to Yang and Song’s data, was in the early 1970s, therefore the spin rate appears to be oscillating periodically.
So yet, there is little evidence that what the inner core accomplishes has a significant impact on surface inhabitants. However, the researchers stated that they believed physical links existed between all of Earth’s layers, from the inner core to the surface.
Last year, Vidale presented studies indicating that the inner core oscillates faster, changing direction every six years or so. Seismic waves from two nuclear explosions in the late 1960s and early 1970s were used in his research.
That timeframe is approximately the point when Monday’s research reveals the inner core last shifted direction — which Vidale called “sort of a coincidence”.
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Geophysicists Have Split Theory
Another possibility, according to Vidale, is that the inner core only moved significantly between 2001 and 2013 and remained stationary thereafter.
Hrvoje Tkalcic, an Australian National University geophysicist, has published data indicating that the inner core’s cycle occurs every 20 to 30 years, rather than the 70 years predicted in the current study.
“These mathematical models are most likely all incorrect because they explain the observed data but are not required by the data,” Tkalcic said.
“Therefore, the geophysical community will be divided about this finding and the topic will remain controversial.”