The earth holds many mysteries and one of the greatest is the solid iron core at its centre, lying deep beneath the surface of the earth. The inner core, an iron ball, is a mystery that may have recently stopped rotating, and then reversed direction, according to a recent study. Scientists believe that this change won’t have a significant impact on life on the surface. However, they would like to have a better understanding of the inner core’s activities.
Scientists can get hints of the inner core’s activities through powerful earthquakes and Cold War nuclear weapons tests, which have sent seismic waves reverberating through the centre of the Earth. These waves have revealed that the inner core is mostly composed of pure iron and nickel and that it may spin faster than the rest of the Earth. But the new study suggests that the inner core could experience changes in its rotation every few decades.
The researchers found that the paths of seismic waves did not change in the last decade, starting in 2009. This suggests that the inner core may have stopped spinning around that time. Data from two pairs of nuclear blasts hint at a similar pause around 1971, with the core spinning eastward afterwards. The researchers believe that the inner core may pause and reverse its spin about every 70 years.
The theory is that Earth’s magnetic field pulls the inner core and causes it to spin, while the gravitational field of the mantle creates a counterforce, dragging on the inner core. Every few decades, one force may win out over the other, changing the spin of the great iron ball. However, another explanation is that the surface of the inner core is changing over time, rather than the whole iron ball spinning.
The new study may shed further light on the inner core and its interactions with Earth’s other layers, but it could be a long time before the full picture is pieced together. Until then, scientists will continue to listen to seismic waves that travel through the iron core, which they themselves can never reach. The inner core remains one of the greatest mysteries of the earth, but scientists remain optimistic that someday, the pieces will fall into place.
