NEW DELHI: New research has confirmed that Earth’s inner core, a moon-sized chunk of solid iron and nickel located over 3,000 miles below the surface, has been spinning unusually slowly for the past 14 years. This slowdown could potentially lengthen Earth’s days, though any changes would likely be imperceptible to humans.
Inner core dynamics
As per a Live Science report, Earth’s inner core is surrounded by the outer core, a superhot layer of molten metals, and the mantle, a more solid sea of molten rock.While the entire planet rotates, the inner core can spin at a different speed than the mantle and crust due to the viscosity of the outer core.
For the past 40 years, since scientists began mapping Earth’s inner layers with detailed seismic activity records, the inner core has been rotating slightly faster than the mantle and crust. However, a new study published in the journal Nature on June 12 found that since 2010, the inner core has been slowing down and is now rotating more slowly than the planet’s outer layers.
Research findings
“When I first saw the seismograms that hinted at this change, I was stumped,” said John Vidale, a seismologist at the University of Southern California, Dornsife. “But when we found two dozen more observations signaling the same pattern, the result was inescapable.”
If the inner core’s rotation continues to decelerate, its gravitational pull could eventually cause the outer layers of Earth to spin more slowly, potentially altering the length of our days. However, any change would be on the order of thousandths of a second, which would be “very hard to notice,” according to Vidale. As a result, there would likely be no need to adjust clocks or calendars, especially if the change is temporary.
Historical context and future research
This is not the first time scientists have suggested that Earth’s inner core is slowing down, a phenomenon known as “backtracking.” This idea has been debated for around a decade but has been challenging to prove.
In the recent study, researchers analyzed data from more than 100 repeating earthquakes along a tectonic plate boundary in the South Sandwich Islands from 1991 to 2023. These seismic events allowed scientists to map the core’s position relative to the mantle, revealing changes in the inner core’s rotation rate over time.
The study provides the “most convincing” evidence so far that backtracking has been occurring, Vidale noted. It remains unclear why the inner core is backtracking, but possible causes include the churning of the liquid iron outer core or gravitational tugs from dense regions of the rocky mantle, the Live Science report said.
Longer data sets are needed to understand the frequency and long-term trends of these changes. The inner core remains one of Earth’s most mysterious layers, but new technologies are enabling researchers to learn more about its dynamics.
“The dance of the inner core might be even more lively than we know,” Vidale said.
The study authors will continue to analyze seismic data to further understand the inner core’s behavior and its implications for our planet.