According to a study published on Monday in Nature Geoscience, the Earth’s core may be reversing direction on a regular cycle.
Unexpected new research that used seismic waves from earthquakes to explore the planet’s deepest regions suggests that the inner core of Earth has recently stopped spinning and may now be rotating in the opposite direction.
The astounding findings imply that Earth’s centre pauses and reverses course in a regular cycle lasting between 60 and 70 years. This finding may provide answers to long-standing questions about climate and geological events that occur on a similar timescale and have an impact on life on Earth.
There’s no need to worry about nuking the Earth’s core in order to stop the end of the world, despite the fact that this is essentially the narrative of the 2003 disaster movie The Core. Although the core’s rotation affects the environment on the planet’s surface, scientists believe that the core’s periodic spin switch is a normal aspect of its functioning and does not represent a threat to life as we know it.
A solid metal ball the size of the Moon makes up the inner core of Earth. Because it is encased in a liquid outer core, it can spin at a variety of speeds and directions in comparison to our planet, but scientists are unsure of the precise speed of its rotation or whether it varies over time.
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The centre of the planet, which is 3,000 miles beneath our feet, receives extreme heat on par with the Sun’s surface. Although it is obvious that the inner core is involved in many processes that make our planet habitable for life, such as the creation of Earth’s protective magnetic field, which prevents harmful radiation from reaching the surface, it is one of the least understood environments on our planet because of how remote and challenging it is to study.
At the SinoProbe Lab at the School of Earth and Space Sciences at Peking University, two researchers named Yi Yang and Xiaodong Song have now recorded “surprising observations that indicate the inner core has nearly ceased its rotation in the recent decade and may be experiencing a turning-back in a multidecadal oscillation, with another turning point in the early 1970s,” according to a study published on Monday in Nature Geoscience.
“There are two major forces acting on the inner core,” Yang and Song said in an email to Motherboard. “One is the electromagnetic force. The Earth’s magnetic field is generated by fluid motion in the outer core. The magnetic field acting on the metallic inner core is expected to drive the inner core to rotate by electromagnetic coupling. The other is gravity force. The mantle and inner core are both highly heterogeneous, so the gravity between their structures tends to drag the inner core to the position of gravitational equilibrium, so called gravitational coupling.”
“If the two forces are not balanced out, the inner core will accelerate or decelerate,” they added. “Both the magnetic field and the Earth’s rotation have a strong periodicity of 60-70 years. We believe that the proposed 70-year oscillation of the inner core is driven by the electromagnetic and gravitational forces.”
Song has been studying seismic waves that travel through this far-off region for decades in an effort to understand the inner core’s mysteries. He was a member of the group that discovered the inner core’s rotation in 1996 by detecting minute time (or “temporal”) variations in these earthquake-generated waves.
Since then, the cause of the temporal shifts has been a subject of discussion among geoscientists, with some believing that the wave patterns result from events near the boundary between the outer and inner core.
“Some researchers are still arguing that the temporal changes do not come from the inner-core rotation, but from localized deformation at the inner core boundary,” Yang and Song said. With their new study, the pair “tried to gather more data over a longer duration to test different models.”
In order to achieve this, the scientists examined seismic waves produced by earthquakes that took place since the 1960s and travelled through the inner core. According to the study, they specifically searched for “doublet” occurrences, which are repeated earthquakes with almost identical waveforms at similar receivers. Yang and Song were able to investigate the rotation of the inner core by examining the minute temporal variations between these doublets.
As it turned out, the temporal changes decreased to their lowest point around 2009, indicating that the inner core may have stopped rotating at this time, as seen by the seismic readings appearing to be more static at this time. The discovery of a similar turning point in the early 1970s, which suggested that the core stops and reverses rotation on a regular cycle, stunned the researchers even more.
“Our results further support the inner-core rotation, and more interestingly, reveal the multidecadal pattern of the rotation,” Yang and Song said to Motherboard.
The findings have significant implications for understanding the well-known world we live in on the surface of the Earth and provide a hitherto unseen view into the burning pit of our planet, an area that continues to defy explanation.
The study points out, for instance, that the Earth’s climate system also exhibits a multidecade cycle, with global mean temperatures and sea level rises appearing to oscillate every 60 to 70 years. The duration of the Earth’s day, which varies a little over time, also appears to be in harmony with the suggested cycle. The new study claims that this is why the new findings “may imply dynamic interactions between the deepest and shallowest layers of the solid Earth system.”
“We pointed the existence of similar periodicity of different observations, forming a resonating system,” Yang and Song told Motherboard. “The linkage, however, is less clear at the moment. The gravitational coupling between the inner core and the mantle may cause deformation at the Earth’s surface, which would affect the sea level. The changes of the sea level and the Earth’s rotation may affect the global atmospheric circulation and temperature. The resonance of different systems may also amplify the mutual interactions.”
It’s intriguing to consider that the revolving cycles of a strange metal ball at the centre of our world might shape some of the most common experiences we have, like the length of our days and the climatic patterns that determine our local weather. It will take fresh models and ongoing research into the mysterious centre region of Earth to unravel these nuances.
According to Yang and Song, the following steps involve “building quantitative models of the physical mechanisms on the multi-decadal oscillation system” and “monitoring how the rotation changes in the future.”
“We’d expect it to rotate westwards relative to the surface of the Earth in the coming years and decades,” the pair concluded. “Seismic waves are still the best way and thus continuous operation of high-quality seismic networks is crucial in this regard.”