A team of researchers from Peking University has just come to the disturbing conclusion that, by the year 2009, the rotation of Earth’s solid inner core has stopped and may be beginning to reverse. The finding, published in the latest issue of ‘Nature Geoscience’, makes scientists think that this inversion occurs periodically, around once every seven decades, and can cause changes in the intensity of the magnetic field and the length of days.
According to Yi Yang and Xiaodong Song, authors of the research, the fact that these changes can occur on such a short time scale suggests that they are common in the history of the planet, and therefore will help to better understand how what happens in the depths of the Earth affects its surface.
The internal core, solid and formed mainly by iron and nickel, is physically separated from the rest of the Earth mass by the external core, made of liquid iron, which allows it to maintain a rotation independent and different from that of the Earth itself.
The spin of the inner core, in fact, gets its momentum from the strong magnetic fields generated by the outer core and is balanced by the gravitational effects of the thick mantle layer just above it. For decades, geologists have debated the speed of this rotation, and also the possibility that it varies over time.
The journey of seismic waves
To reach these conclusions, Yang and Song studied the differences in the shape and travel time of seismic waves generated by nearly identical earthquakes, which since the 1960s have traversed the center of the Earth along similar paths. And they discovered that, around 2009, the paths that previously showed significant temporal variation, that is, those that seismic waves took different times to travel in each different earthquake, stopped changing, indicating a ‘slowdown’ in rotation. of the inner core, which stopped by compelo.
But not only that. In fact, the researchers think that this ‘stop’ may be associated with a reversal of the rotation of the inner nucleus. And that this type of reversals are not something exceptional, but that they occur in a cyclical way, around once every seven decades. According to the study, the previous turning point took place in the early 1970s. The authors explain that this variation is related to changes in geophysical observations at the Earth’s surface, such as the magnetic field and the length of days.
Yang and Song, therefore, conclude that the oscillation detected by them in the rotation of the inner core coincides with periodic changes in the Earth’s surface, which demonstrates the deep interaction that exists between the different layers of our planet.