You may be surprised by how little we actually know about the inner workings of the Earth. While we have a good grasp of how the Earth’s surface moves to create mountains and trigger earthquakes, the deeper we delve, the more mysterious it becomes.
One highly debated topic for years has been the movement of the Earth’s inner core. Does it move forward, backward, left, right? The truth is, nobody really knows. However, recent research published in Nature suggests that the core is receding relative to the surface, potentially putting an end to the long-standing debate.
This study confirms a controversial paper from the previous year by researchers at Peking University, as detailed in Nature Chemistry.
The inner core of the Earth is a solid, crystallized sphere of iron, approximately the size of the Moon, situated around 5,000 km beneath us in a liquid metal sea known as the outer core comprised of iron, nickel, and other metals.
“The inner core is a solid entity that floats within the outer core, lacking any anchorage,” explained Professor John Vidal, co-author of the study, a researcher at the University of Southern California (USC), in an interview with BBC Science Focus.
According to a press release from USC, the study presents “unequivocal evidence” that the movement of the inner core slowed around 2010 and is now lagging behind the surface movement. This new motion pattern makes the core appear to move backward compared to the surface, akin to how a slowing car seems to move in reverse to a steady-speed driver.
If the findings are accurate, this marks the initial detection of a slowdown in 40 years and supports the notion that the core’s velocity fluctuates in a 70-year cycle.
The research team utilized seismometers in Canada and Alaska to analyze repeated earthquakes, focusing on 121 events in the South Sandwich Islands between 1991 and 2023, along with data from past nuclear tests conducted by the Soviets.
By examining matching seismic waveforms from various time periods, the team sought to determine if the inner core rotates independently from the rest of the Earth. Discrepancies in wave patterns indicated changes in the core’s rotation, with some signals aligning pre and post-shift, implying a realignment of the core.
Bidart, one of the researchers, expressed initial confusion upon seeing seismic records suggesting a change but became convinced upon discovering more consistent observations. The slowdown in the inner core’s movement, unseen for decades, aligns with their latest findings, offering a plausible resolution to the ongoing debate.
Despite uncertainties regarding surface impacts, Bidale acknowledged a slight potential change in the length of a day, barely perceptible amid the Earth’s bustling activity of oceanic and atmospheric movements.
Future research aims to gather additional waveform data from diverse global locations and pathways. Vidar highlighted a wait-and-see approach, anticipating unusual core movements around 2001 and further exploration to elucidate these occurrences.
About our experts
John Vidale Dr. Schneider currently chairs the Department of Geosciences at the University of Southern California. His research covers earthquakes, Earth structure, volcanoes, and seismic hazards. At USC since 2017, Dr. Schneider previously directed the Southern California Earthquake Center and contributed to earthquake-related committees and working groups.
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Source: www.sciencefocus.com
