Geophysicist John Vidale observed something remarkable while studying the movement of seismic waves through Earth’s interior.
At the planet’s very center, a solid sphere composed of iron and nickel, surrounded by molten rock, appears to be slowing down relative to Earth’s overall rotation. This inner core has decelerated to the extent that it is effectively reversing its direction.
This discovery, made by Vidale and his colleague Wei Wang from the Chinese Academy of Sciences, was recently published in the journal Nature. It provides the most compelling evidence to date that the inner core seems to operate independently from the rest of the planet.
“It might be cycling back and forth, but it could also be on a random walk,” Vidale explained. “It went one way for a while, and now it’s heading back the other way. Who knows what it’s going to do next?”
According to Vidale, these fluctuations occurring 3,000 miles beneath the Earth’s surface are unlikely to have any noticeable impact on life above—at least for the time being.
“There appears to be no effect on people based on our observations,” said Vidale, Dean’s Professor of Earth Sciences at USC Dornsife College of Letters, Arts and Sciences. “Our research is fundamentally aimed at understanding the planet’s evolution. Another critical aspect we aim to explore is the forces driving the movement of the inner core.”
Vidale noted that scientists first suspected the inner core was moving in the 1990s. However, it has taken years to gather concrete evidence to support this theory due to the significant challenges involved in studying a mass located deep within the Earth, surrounded by a searing sea of liquid iron with temperatures ranging from 8,000 to 10,000 degrees Fahrenheit.
Instead, Vidale, who served as the director of the Southern California Earthquake Center at USC from 2017 to 2018, investigated the Earth’s interior by analyzing seismic waves from earthquakes near the southern tip of South America. These waves traveled through the Earth’s core and were recorded by 400 seismometers located in Alaska and Northern Canada—the same type of sensors used to detect ground vibrations during nuclear tests.
Vidale compared these refined readings to historical earthquake data to identify patterns and determine that the Earth’s core rotation has been slowing since 2010. Before this period, the core’s rotation had been accelerating.
According to Vidale, these findings contribute to the ongoing intrigue surrounding the Earth’s core, a region that remains largely enigmatic. Over the years, literature and folklore have filled the knowledge gap with a variety of imaginative concepts.
“I may not be a philosopher, but we’ve all had our share of nightmares about what lies beneath the Earth’s surface,” Vidale remarked. “A mere couple of centuries ago, people believed the planet was hollow and inhabited. It’s quite an exotic notion—exotic like Jupiter, yet just beneath our feet.”
In Jules Verne’s 1864 science-fiction classic “Journey to the Center of the Earth,” a German professor, his nephew, and their guide venture into the Earth through an Icelandic volcano. Along their journey, they discover vast caverns, a subterranean ocean, living dinosaurs, strange sea creatures, and even a prehistoric giant herding mastodons, ultimately emerging through a volcano off the coast of Sicily.
The 2003 disaster film “The Core” envisions a scenario where the Earth’s core stops rotating, leading to the deterioration of the planet’s magnetic field. This fictional catastrophe results in a violent lightning storm that devastates Rome and “invisible microwaves” that melt the Golden Gate Bridge. In response, a team of elite scientists embarks on a mission to drill through the Earth’s layers and restart the core using a nuclear bomb.
In reality, however, no human could endure the extreme heat and crushing pressure at such depths, even if a vehicle capable of reaching the core existed, according to expert Vidale. While it is true that the outer core generates electrical currents that maintain Earth’s magnetic field, Vidale explains that any shifts in the Texas-sized inner core are far too small to cause significant effects.
Though the true nature of Earth’s interior may not be as dramatic as depicted in novels and Hollywood films, it remains a captivating subject for scientists like Vidale, whose role is to replace speculation with scientific facts.
Recent findings increasingly indicate that the inner core is influenced by the surrounding layers of the Earth in various ways.
“The mechanics involve the outer core circulating and generating a magnetic field, which essentially tugs the inner core back and forth,” explained Vidale.
Adding to the complex dynamics is the lower mantle, which exerts its own unique magnetic influence due to its mixture of solid and less-dense materials, Vidale noted.
“We tend to think that the outer core agitates the inner core, while the mantle attempts to keep it aligned—perhaps this interaction is why the inner core oscillates,” he said.
These latest insights into the inner core have sparked intense debates among leading Earth scientists and led to a range of competing theories with varying degrees of credibility, Vidale added. Some researchers argue that the core does not rotate at all, while others believe that surface forces, such as earthquakes, temporarily affect its rotation.
During a phone conversation, Vidale reads a review from an Australian scientist who has expressed significant skepticism towards Vidale’s recent findings. The Australian claims that the analysis could result in “the erosion of seismology as a credible branch of science and the destruction of seismologists as credible researchers.”
“I think he’s just frustrated—he knows he’s lost,” Vidale remarked, lightly teasing his colleague.
“It’s exciting because the Earth’s core is quite large, it’s moving in measurable ways, and it remains a mystery,” Vidale continued. “We’re making progress, discovering new phenomena, engaging in debates with international peers, and striving to gather more data. Our paper has managed to convince most of the scientific community.”
This story originally appeared in the Los Angeles Times.
