- A new study suggests that Earth’s inner core may have stopped and reversed its spin.
- Earthquakes and nuclear explosions can send seismic waves through the mysterious solid iron core.
- These waves indicate that the core changed direction in the 1970s and that another reversal may occur today.
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While on Earth’s surface, we only see about 0.5% of the planet. Beneath the crust, mantle of hot rocks, and molten outer core hides one of our planet’s greatest mysteries: its solid iron core.
According to a new study, the ball of iron—Earth’s inner core—recently stopped spinning and changed direction for no apparent reason.
It may sound apocalyptic, but don’t worry. Scientists don’t think it will significantly change life on the surface except to surprise.
“It’s probably benign, but we don’t want things we don’t understand deep in the earth,” he said. Washington Post John Vidale, a geophysicist at the University of Southern California.
The research was published Monday in the journal Nature geology suggests that Earth’s solid inner core may undergo changes in its rotation every several decades.
Earthquake and nuclear explosion point to change in 2009
Scientists can’t directly observe Earth’s inner core, but they can glean signs of its activity from earthquakes and Cold War nuclear tests, which caused seismic waves to resonate through Earth’s center.
These deep seismic waves have shown that the core is composed mostly of solid, pure iron and nickel, and that it may be rotating slightly faster than the rest of the Earth.
If the inner core is inert, rotating in line with the planet’s outer layers, similar waves would have to travel similar paths through it. But over time, the speed of those waves changes, indicating that the nucleus itself is changing. Rotation is one of the main explanations for these seismic anomalies.
But the new study debunks this theory. Analyze seismic waves from the 1960s to the present. Researchers discovered a peculiarity as far back as 2009: over the past decade, similar seismic wave trajectories haven’t changed. This suggests that the inner core may have stopped rotating at this time.
Data from two pairs of nuclear explosions point to a similar pause around 1971, with the core rotating eastward, leading researchers to believe the inner core may stop its spin every 70 years or so. is and can be reversed.
The theory is that Earth’s magnetic field pulls on the inner core and spins it, while the gravitational field of the mantle pulls the inner core along, creating a counterforce. Every few decades, one force might triumph over the other, changing the spin of the great iron ball.
The inner core is a great mystery, and we may never solve it
Interpreting these features in the seismic record is difficult and involves speculation, as little is known about the inner core.
Another explanation is that the surface of the inner core is changing over time, rather than the entire iron sphere rotating. Lianxing Wen, a seismologist at Stony Brook University, propounded this theory in a 2006 paper and maintains it today. as said Washington PostWhich would explain the break in 1971 and 2009.
“This study points to a misinterpretation of seismic signals caused by episodic changes of the surface of Earth’s inner core,” Wen said. Post,
The new study may help shed more light on the mysterious nature of the inner core and how it interacts with Earth’s other layers. However, it may be decades before scientists piece together the full picture, if ever.
“It is quite possible that we will never understand it,” Vidale pointed out. new York Times,
However, “I am optimistic. Someday the pieces will fit together.
Until then, Vidale and his colleagues will continue to listen for seismic waves, which travel from one side of the planet to the other directly through the iron core, which researchers themselves would never be able to reach.