Science and Technology

Earthquakes show it: Earth’s inner core may no longer be spinning

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Inside the Earth, there is a solid inner core surrounded by a liquid core. (archive photo)

© dpa / Yomitsat

A Chinese study has shown that the Earth’s inner core appears to have stopped spinning. It should soon start changing its direction of rotation.

BEIJING – Scientists doing research on the ground sometimes don’t find it easy. To study the Earth’s interior, for example, they have to use seismic waves that move through the different layers of the Earth during an earthquake.

From these observations, we know that there is a solid core surrounded by a liquid outer core. Earth’s magnetic field is generated in this liquid core, which protects the planet from space radiation, for example.

The Earth’s inner core can move independently of the Earth’s rotation because it is surrounded by a liquid core. Thanks to decades of probing the Earth’s interior using seismic waves, researchers hypothesize that the Earth’s inner core vibrates — sometimes spinning one way, then the other. The study now appears in the journal NatureGeoscience He published that the movement of the inner core of the Earth has apparently stopped.

A Surprising Discovery: The Earth’s Core Has Apparently Stopped Spinning

Seismologist Jon Vidal, who was not involved in the study, agrees that the fact that Earth’s core has apparently stopped spinning is a surprising finding. opposite the gate inverse “The interesting thing for me,” he explains, “is that we see all the complexities here on Earth.”

Vidale continues: “Things seem to be changing more there than we see on the surface. So there may be some interesting things that we don’t yet understand about the limits of the inner core.”

Chinese researchers Yi Yang and Xiaodun Song of Peking University took seismic data from the 1990s and 2000s for their study. She was interested in so-called double earthquakes – pairs of earthquakes of approximately the same magnitude in the same place at different times.

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The researchers compared these pairs and found that in earthquakes between 1995 and 2008, seismic waves differed significantly from each other – between 2009 and 2020, however, there was a high degree of agreement in the earthquake pairs. The researchers concluded that the Earth’s inner core appears to have stopped moving around 2009.

The Earth’s inner core appears to change direction every 30 years

After looking at seismic data from the 1960s and 1970s, the two researchers found that the Earth’s core appears to oscillate over a 70-year period, changing direction about every 30 years. The researchers’ thesis: the inner core rotated in one direction, pausing and reversing until the early 1970s. It seems that this phenomenon is happening again: the Earth’s core stops and turns in the other direction.

The internal structure of the Earth is complex. There is a solid inner core and thus a liquid core. This is surrounded by the Earth’s mantle.

© Imago

According to researcher Song, the Earth’s inner core has been rotating eastward since the early 1970s – faster than Earth. Around 2009, this rotation paused and is now reversing. “If the oscillation model is correct, we expect the inner core to rotate more slowly than the surface by the mid-2040s,” Song explains in an email. inverse.

The two researchers also found that days on Earth shorten by 0.01 milliseconds when Earth’s inner core rotates in a westerly direction. On the other hand, if you move to the east — the direction in which Earth also rotates — the day becomes 0.12 milliseconds longer, according to the researchers in their study. In fact, research has found that the Earth is spinning faster. (tab)

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