The inner core of the Earth no longer rotates as before. Today, new data from a study published in the journal confirm this hypothesis Nature by researchers from the University of Southern California and the Chinese Academy of Sciences who have demonstrated, in fact, how the internal nucleus is reversing its directionslowing down, compared to the surface of the planet.
How the nucleus moves
The movement of inner core of the Earth, a solid sphere of iron-nickel surrounded by the liquid outer core, has been at the center of scientific debate for decades now as it is one of the most mysterious and difficult places to reach and, therefore, to study in the entire Solar System. This is why scientists resort to seismic waves to create different models of the movement of the inner core. One of the most recent studies, for example, had come to the conclusion, after having analyzed the paths of seismic waves from the 1960s to today, that the nucleus was stopping to turn around. In particular, the hypothesis of researchers from Peking University published on Nature Geoscience, suggested that around 2009 the inner core had slowed down and that its rotation had stopped and started to reverse. A cyclical phenomenonaccording to the authors, which would occur every few decades and which could be connected to other periodic changes on the Earth’s surface.
Confirmation
The new study today provides evidence confirming that the inner core began decreasing in speed around 2010, moving more slowly than Earth’s surface. “When I first saw the seismograms suggesting this change, I was perplexed,” commented co-author John Vidale. “But when we found two dozen more observations reporting the same pattern, the result was unambiguous. Other scientists have recently supported similar and different models, but our latest study provides the most compelling resolution.”
A new model
The researchers of the new study, unlike previous ones, focused on multiple earthquakes, i.e. seismic events that occur in the same place producing identical seismograms. They then reviewed seismic data recorded around the South Sandwich Islands, an archipelago in the South Atlantic Ocean, from 121 multiple earthquakes that occurred between 1991 and 2023. From subsequent analyses, the researchers were able to observe that the slowdown of speed of the inner core was caused by the mixing of the outer core of liquid iron surrounding it, which generates the magnetic field terrestrial, as well as from the gravitational attractions coming from the dense regions of the coat rocky overlying.
The effects on the surface
The implications of this change in the motion of the inner core to the earth’s surface can only be conjectured. According to the authors, in fact, the backward movement of the internal nucleus could alter the duration of a day of fractions of a second. “It is very difficult to notice, on the order of a thousandth of a second, lost in the noise of the oceans and the atmosphere”, Vidale specified. The next step will be to analyze the trajectory of the inner core in even more detail to reveal exactly why it is moving. “The dance of the inner core may be even more lively than we know so far”concluded the expert.
