(ORDO NEWS) — In 2009, the inner core of our planet stopped and has been spinning in the opposite direction ever since.
New work by Chinese geologists has shown that its rotation can change approximately every 35 years.
The central part of our planet is divided into two parts: a liquid outer core, the movements of which create a global magnetic field, and a solid inner core.
Its diameter is about 2500 kilometers – about a thousand kilometers less than that of the moon. This is a hot sphere of iron and nickel that rotates as a whole inside the outer core.
It is believed that, pushed by the same magnetic field, it is slightly ahead of the rotation of the earth’s crust. However, there are more exotic hypotheses about the movement of the inner core.
In particular, it has been noted that some features of the propagation of seismic waves change cyclically with a period of several decades.
This may be due to oscillations in the rotation of the inner core, which from time to time stops and spins in the opposite direction. New evidence for this hypothesis was found by geologists from Peking University.
Both Yi Yang and Xiaodong Song analyzed archival seismic data up to the 1960s.
Scientists were interested in recording signals from “double earthquakes” – doublets that propagate from a common epicenter and are characterized by almost identical wave oscillations.
Due to the small time difference, they usually pass through different regions of the inner core, which indicates its rotation.
However, as Yang and Song found, around 2009, these differences almost disappeared, which scientists attribute to a temporary stop of the inner core.
Then they appeared again, but now their characteristics can be associated with a set of speed in the opposite direction.
Similar changes were found in data dating back to the early 1970s, so geologists concluded that the inner core changes rotation approximately every 35 years.
These cycles do not have a big impact on what is happening on the surface of the planet.
Nevertheless, due to electromagnetic and gravitational forces, the inner core should influence the Earth‘s magnetosphere and its rotation.
Yang and Song indicate that changes in the direction of its rotation may be associated with weak climate and temperature cycles lasting 60-70 years.
However, the features of the propagation of seismic waves through the center of the Earth can also be associated with other effects – for example, with fluctuations in the boundary layer that separates the outer core from the inner one, or simply with an uneven speed of its rotation, without changing direction.
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