Earth’s inner core, a hot mass located in the very center of our planet, is spinning at about 0.05-0.1 degrees per year , according to a new analysis of earthquake seismic data by scientists at the University of Illinois in Urbana-Champaign and published in the journal Earth and Planetary Science Letters.
The truth is that geologists do not fully understand how the Earth’s magnetic field generator works but suspect that it is closely related to dynamic processes near the boundary area between the inner core and the outer core.
The new study based on seismic data and new data processing methods has revealed that the Earth’s inner core is spinning, a finding that could provide detailed information about the processes that control the planet’s magnetic field. In fact, scientists claim that it is “the best evidence so far” of the processes that control the Earth’s magnetic field.
The experts discovered, after reviewing seismic data from a wide variety of geographic locations and repeated earthquakes, called doublets – which occur in the same place over time – that some of the seismic waves generated by the earthquake penetrate through the iron body. below the limit of the inner core and vary with the passage of time, something that would not happen if the inner core were stationary.
“In 1996, our group detected for the first time a small but systematic change in the seismic waves passing through the inner core, which we interpret as evidence of the differential rotation of the inner core relative to the Earth’s surface,” explains Xiaodong Song, a co-author of the study.
“Importantly, we are seeing these refracted waves change before the reflected waves bounce off the inner core boundary, implying that the changes come from within the inner core,” Song clarifies.
What makes this analysis different from others?
According to Yi Yang, a graduate student and author of the study, “What makes our analysis different is our precise method of determining exactly when changes in seismic signals occur and arrive at various seismic stations around the world. We use a wave seismic that did not reach the inner core as a reference wave in our calculations, which eliminates a lot of ambiguity ”.
The basis of this great debate lies in the fact that previous studies analyzed a relatively small group of somewhat ambiguous data generated from a technique that relies heavily on the exact time of the clock.
The most striking fact of the study is that the rotation speed of the Earth’s core is less than one degree every million years , that is, that it grows very slowly over time while the material located in the outer core solidifies in the surface.
“This painstaking time-of-arrival analysis, extensive collection of top-quality data, and careful statistical analysis by Yang are what empower this study. This work confirms that the temporal changes come mainly, if not all, from the body of the inner nucleus, and now the idea that changes in the surface of the inner nucleus are the only source of the signal changes can be discarded ”.
Referencia: Yi Yang & Xiaodong Song. 2020. Origin of temporal changes of inner-core seismic waves. Earth and Planetary Science Letters 541: 116267; doi: 10.1016/j.epsl.2020.116267
