The Earth’s inner core is a solid sphere made of iron and nickel, surrounded by the liquid outer core, which is made of molten metals. Together, they form one of the Earth’s three layers, with the other two being the mantle and the crust.
Since the core is not physically accessible so scientists study it by analyzing waves generated by earthquakes, known as seismograms. These waves provide data about the inner workings of the Earth.
John Vidale, a professor of Earth Sciences at the University of Southern California, noticed unusual patterns in seismograms. “When I first saw the seismograms that hinted at this change, I was stumped,” Vidale said. After finding more observations showing the same pattern, it became clear that the inner core had slowed down for the first time in decades.
The slowing of the inner core is a hot and surprising topic in the scientific community. Some studies suggest that the inner core rotates faster than the Earth’s surface. The spin of the inner core is influenced by the magnetic field in the outer core and gravitational effects within the mantle.
It is believed that the inner core is now reversing and moving slower than the mantle for the first time in about 40 years. Vidale stated, “Other scientists have recently argued for similar and different models, but our latest study provides the most convincing resolution.”
Another study earlier this year found that the melting of ice in Greenland and Antarctica due to climate change was also affecting Earth’s rotation. Duncan Agnew, a geophysicist, showed that while the Earth’s liquid core was slowing down, the Earth was rotating faster. This change has led to fewer ‘leap seconds’ being needed to adjust Coordinated Universal Time (UTC).
For the latest study, researchers analyzed seismic data from 121 repeating earthquakes in the South Sandwich Islands between 1991 and 2023. These islands, located in the South Atlantic Ocean, are prone to violent earthquakes. The study also included data from Soviet, French, and American nuclear tests conducted between 1971 and 1974.
This study provides significant information about the changes occurring within the Earth’s inner core. Understanding these changes is crucial as they can have less yet important effects on our planet’s rotation and timekeeping.
-Prisha Jaiswal