It is not unusual for the Earth’s core to experience changes in its rotational speed and shape over time. However, recent research has revealed some unexpected developments.
Scientists have been debating the reasons behind peculiar alterations in seismic waves caused by earthquakes. One side argues that changes in the rotational speed affect the travel time of the waves, while the other side suggests that alterations in the shape of the inner core are responsible. A new study published in Natural Earth Science by Chinese and US scientists indicates that it could be a combination of both factors.
The study reveals that in 2010, the Earth’s inner core started to rotate faster than other planets, potentially impacting seismic waves with changes near the surface of the core. These waves, similar to X-rays, provide insights into the planet’s interior. The findings are expected to provide more information about the core’s properties and structure.
“These findings present observable changes that offer a clearer understanding of how the inner core evolves over a few years. There could be more surprises in store,” said Professor John Emilio Vidale, the lead author of the study, to BBC Science Focus.
The Earth’s core is almost as hot as the sun’s surface and is located approximately 6,500 km (4,000 miles) below the Earth’s surface, with pressure exceeding that of the deepest ocean depths. Due to these extreme conditions, direct exploration of the core is not feasible.
Scientists rely on seismic waves generated by earthquakes to study the core. By analyzing how these waves travel through different layers of the Earth, including the core, scientists can gain a better understanding of its structure and movement.
In this recent research, the team focused on seismic waves from 121 repeat earthquake pairs in the South Sandwich Islands between 1991 and 2023. By examining changes in the arrival times and waveforms of these signals over decades, the team identified minor shifts in core movement.
These findings revealed interesting trends in the Earth’s inner core. It rotated faster than the mantle and crust for decades before slowing down around 2010. However, some earthquakes showed no significant time shifts, indicating occasional pauses or reversals in rotations.
The study also made secondary findings, suggesting that factors other than rotation might be affecting the inner core. The team believes that viscous transformations near the inner core’s boundary could be influencing its behavior.
While this behavior may appear unstable, further data is needed to confirm its normality and deepen our understanding of how the Earth’s core functions.
According to Vidale, the simplest explanation is that the movement of the outer core initiates rotations in the inner core, readjusting its position over decades. However, the exact mechanisms behind these adjustments remain uncertain.
“The inner core’s movements may not follow a harmonious pattern, as they seem to align with the outer core’s movements,” he explained.
While this study presents intriguing insights into the Earth’s core behavior, it could pave the way for more discoveries in the future. Vidale suggests that further analysis may reveal more about the core’s activity and its potential impact on Earth’s magnetic field and other phenomena.
This could help researchers understand unpredictable occurrences that may affect satellite operations and compass readings, although they may not have a direct impact on daily life.
About our experts
John Vidale is a professor of Earth Sciences and Dean at the University of Southern California. His research focuses on earthquakes, the Earth’s structure, volcanoes, and seismic hazards. Vidale has held various roles in earthquake research institutions and warning systems, contributing significantly to our understanding of seismic events.
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Source: www.sciencefocus.com
