New Delhi: Amid a magnitude 5.8 earthquake jolting Delhi as well as nearby areas on Tuesday with the epicentre in Nepal, a report recently published in the Nature Geoscience magazine says the earth's inner core stopped spinning sometime in the last decade and might have even reversed its spin.
The study, conducted by researchers Yi Yang and Xiaodong Song from Peking University in Beijing, China, suggested, using global data, that the inner core has halted its spin relative to the mantle - the layer outside the core. The paper can prove to be crucial to figure out the part played by the inner core to control Earth's magnetic field - and in turn affecting rotation, and the subsequent length of a day.
The earth's layers can be divided into three portions: The crust (outermost layer), mantle, and core (divided between inner and outer core). Discovered by scientists for the first time in 1936 during a study of seismic waves from earthquakes, the difference in speed of the waves' travel time revealed that the inner core was solid, and mostly made of iron.
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The outer core, on the other hand, is a shell made of liquid iron and covers the inner core. The planet's magnetic field is controlled through motions that are put into place as the outer core's liquid comes into contact with the surface of the inner core, and is subsequently crystallized. The outer core "decouples the solid inner core from the rest of the planet, so that it can swing at its own pace", the Nature report said. It also noted that starting in the 1960s, scientists reported a change in travel time of seismic waves, which indicated that the inner core rotated faster than the mantle - a phenomenon largely referred to 'super-rotation'.
At present, however, scientists from Peking University point out that the inner core has 'halted its spin relative to the mantle'. "They studied earthquakes mostly from between 1995 and 2021, and found that the inner core’s super-rotation had stopped around 2009," it says, noting that the change had been observed from various points on Earth.
On the contrary, the data hints at the core moving back towards subrotation. "We compared this recent pattern to the Alaskan seismic records of South Sandwich Islands doublets going back to 1964 and it seems to be associated with a gradual turning-back of the inner core as a part of an approximately seven-decade oscillation, with another turning point in the early 1970s" the scientists also noted in the paper. The next turning point, in line with this, is expected to be around 2040.
