Earth’s inner core may have started spinning in another direction - what does it mean?
and live on Freeview channel 276
The earth’s inner core may have stopped spinning or started to spin in the opposite direction, according to scientists. The scientists’ research may help us understand how our planet’s inner core affects events such as the length of a day and navigation.
The research, recently published in the publication Nature Geoscience by scientists at Peking University in Beijing, looked at seismic activity and how it travels inside earth. When a big earthquake occurs, the seismic energy travels all the way down to the earth’s core and back up, and scientists have noticed that there has been “little change over the past decade”.
The earth’s core is separated from the rest of the planet by a liquid metal outer shell, and is rotating independently from the rest of the planet. So as seismic energy travels to the earth’s core via the same path, the energy would change as the core is rotating independently.
While analysing near-identical earthquakes that have passed through similar paths to the earth’s core since the 1960s, the research team noticed that since 2009, the change in travel time and waveform have decreased. The lack of change indicates that the core may have stopped spinning and might be starting to spin in a new direction.
“Here we analyse repeated seismic waves from the early 1990s and show that all of the paths that previously showed significant temporal changes have exhibited little change over the past decade,” the scientists, including Yi Yang and Xiaodong Song, write in the study.
The discovery might help scientists further understand the interaction between the earth’s three layers; the crust, which is the surface where we live, the mantle, a thick layer of rock that separates the crust from the inner centre, the core.
“This multidecadal periodicity coincides with changes in several other geophysical observations, especially the length of day and magnetic field. These observations provide evidence for dynamic interactions between the Earth’s layers, from the deepest interior to the surface,” the scientists add.
This is not the first time the core has stopped and changed direction, as the scientists noted this happened in the early 1970s. It can lead to effects for humans, for example in navigation and the length of a day.
For example, since discovering the earth’s magnetic fields, the north and south poles have been moving quite far. It has since 1832 moved about 1,400 miles from northern Canada towards Russia.
There is however still a lot of debate about the centre of our planet. Dr John Vidale, leading Geophysicist in Southern California and not involved in the study, said that looking at the earth’s core is like a doctor looking at the human body without a scanner as "our image of the inner Earth is still blurry."
"This is a very cautious study carried out by excellent scientists who used a lot of data," he said, adding that "none of the existing models really explains all the available data well”.
"Something’s happening and I think we’re gonna figure it out. But it may take a decade."