According to two Chinese scientists, the Earth’s inner core has slowed its rotation; maybe he even changed the direction of rotation.
The research duo concludes this from the analysis of earthquake waves. However, the study also triggers critical reactions in the professional world.
Does the interior of the earth rotate differently?
Beneath the earth’s crust, the blue planet consists of liquid rock called magma. But deep down, the earth is solid again. This «inner core», consisting mainly of iron and nickel, has a diameter of 2440 kilometers.
The rotational behavior of the planetary interior is currently a matter of scientific debate. According to some experts, the inner core rotates relative to the Earth’s mantle and crust.
Two of those experts now claim that the relative rotation stopped around 2009. At least that’s what a new study says, which can be read in the journal “Nature Geoscience”.
Earthquake waves provide the evidence
Yi Yang and Xiaodong Song from Peking University examined earthquake waves for their study. Some of these waves pass through the Earth’s inner core, which affects their propagation paths.
The researchers were able to identify characteristic changes in the past: if two earthquakes occurred in the same place but at a certain time interval, the earthquake waves each spread slightly differently.
These changes indicated that the Earth’s inner core was rotating in the meantime. In previous studies, rotation before the year 2000 was estimated to change angles by 0.1 degrees per year.
Is the relative rotation constantly changing?
For the measurements since 2009, however, Yi Yang and Xiaodong Song have not observed any change in wave propagation. They take this as an indication that the relative rotation of the Earth’s inner core has come to a standstill.
In addition, the researchers speculate, based on previous measurements of earthquake waves, that the rotation of the inner core fluctuates periodically, with a period of about 70 years.
The motion of the inner core of the Earth is commonly understood to be related to the rest of the planet in two ways. One of them is the interaction with the Earth’s mantle, which occurs due to the mutual gravitational forces. The other is the electromagnetic interaction with the outer, liquid core of the earth. So it’s possible that there is a relative rotation of the inner core that can change over time.
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