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Stopped and ready for reversal: Earth’s inner core is in the process of changing direction

Stopped and ready for reversal: Earth's inner core is in the process of changing direction 1
Photo: sciencealert.com

Few of us give much thought to the seething, swirling contents of the Earth until some sudden movement, earthquake or volcanic eruption brings us back to our senses.

Geologists, however, have a slightly better understanding of the dynamics of the Earth’s interiors and have just discovered that the Earth’s solid inner iron core, which normally spins inside a molten, nearly frictionless outer shell, appears to have slowed to a halt.

Before anyone panics and starts looking for a copy of a 20-year-old horror sci-fi movie predicting such an event in hopes of inspiring a decision, this is not the first record of such an event. This is not even the first in recent history.

“We show surprising observations indicating that the inner core has almost ceased its rotation in the last decade and may be experiencing a multi-decadal wobble reversal with another turning point in the early 1970s,” geophysicists Yi Yang and Xiaodong Song of Beijing. The University of Beijing writes in its published article.

We have known for only a  few decades that  the Earth’s inner core rotates relative to the mantle above it, as it was confirmed in 1996 by Song and fellow seismologist Paul Richards of Columbia University. Prior to their work, the idea that the Earth’s inner core rotates separately from the rest of the planet was an unproven theory, predicted by an unproven model of the Earth’s magnetic field.

Since then, scientists on Earth have been trying to figure out — from a distance of 5,100 kilometers (or 3,170 miles) — how fast or slow the inner core is spinning.

At first it was believed that the inner core makes a complete revolution every 400 years under the influence of electromagnetic torque and is balanced by gravitational attraction. But other scientists soon suggested that it rotated much more slowly,  taking 1,000 years or more to complete a revolution.

The speed of this rotation and whether it changes is still debated. However, the inner core continues its merry way, unaware of the heated debate at the top.

After weighing everything again, Song returned to the same method that he and Richards had used to conclude that the inner core was spinning. In 1996, the duo tracked seismic wave readings from repetitive earthquakes, called doublets, that passed through the inner core from the South Atlantic to Alaska between 1967 and 1995.

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If the inner core were not moving, the shock waves would have to follow the same path. But Song and Richards showed that between the 1960s and 1990s, seismic waves got a fraction of a second faster.

Now, in a new study with Yang, Song has revisited that old data, comparing it to more recent patterns of nearly identical seismic waves, which suggest the inner core has slowed to a halt and may even have changed.

They found that since about 2009, paths that previously exhibited significant temporal variation remained virtually unchanged as seismic waves passed through the core and exited the other side. Any difference in time has disappeared.

“This globally consistent pattern suggests that the rotation of the inner core has recently been suspended,” Yang and Song write.

It also seems that this recent shutdown of the inner core is due to a spin reversal, Yang and Song say, as the solid iron sphere slides the other way as part of a seventy-year wobble.

According to their calculations, a slight imbalance of electromagnetic and gravitational forces would be enough to slow and then reverse the rotation of the inner core, as observed.

That’s not all. The researchers note that the 70-year switch coincides with other periodic changes observed on the Earth’s surface in day length and magnetic field, which have a periodicity of six to seven decades. Decadal patterns in climate observations, global average temperature and sea level rise also seem to coincide in a strange way.

For Yang and Song, this frequent, slow, subtle wobble that oscillates back and forth every 60 to 70 years seems to indicate “a resonant system in different layers of the Earth” – as if the entire planet is humming along to the same humming tune. 

Since the Earth’s inner core is believed to be dynamically connected to its outer layers, connected to the outer core by electromagnetic coupling, and connected to the mantle by gravitational forces, the study can also help us understand how processes occurring deep inside our planet affect its surface. the thin crust on which we live, sitting on top of a seething interior.

“These observations provide evidence of a dynamic interaction between the layers of the Earth, from the deepest interior to the surface,” Yang and Song conclude.

What could be the main misconception

The assumption that both the shell and the yolk in the egg rotate strictly in the same direction does not take place in mechanical systems. If two adjacent media of different densities rotate, then there will be a difference in both the speed of rotation and the direction. Obviously, this difference is behind the migration of the magnetic poles, which is also quite correlated with the migration of swarms over hot spots.

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In other words, the crust rotates by itself, the core by itself, and we see the difference in rotations in the displacement of phenomena caused by the core of the planet. The core heats the mantle plumes, and therefore, when it rotates, hot spots move, it causes deviations of the compass needle, and therefore, when the core moves, the magnetic poles shift. According to rough calculations, the shift in speeds began around 2009, but no one can even say approximately how it will end. 

With a good option, we are in for a period of strong earthquakes. Although the mantle looks like egg white, it also looks like a gear, which has teeth along the inner edge. The same gear, but colder and harder, is the lithosphere. Now, if the core inside these gears is slowed down, it will inevitably catch with the teeth, which will make the mechanism shake and vibrate. Microbes living on the surface of this mechanism will rate shaking at nine or more on the Richter scale. 

And with a bad option, the teeth can break, which will cause a free uncontrolled rotation of the nucleus. It will rotate not like a gear, but like a bearing, with unknown consequences for us.

If we look at the mantle plumes of Yellowstone, the Hawaiian Islands and other similar, carefully observed volcanoes, we can clearly see that over the past 10 years, the arithmetic mean of earthquake coordinates has moved significantly. In this case, the movement is not chaotic, but in the same direction for each hemisphere. And since this cannot be in nature, the only explanation for the situation is the movement of the Earth’s core relative to the mantle, relative to the movement of plumes. 

 

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