https://www.nature.com/articles/d41586-023-00167-1 Skip to main content Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Advertisement Advertisement Nature * View all journals * Search * Log in * Explore content * About the journal * Publish with us * Subscribe * Sign up for alerts * RSS feed 1. nature 2. news 3. article * NEWS * 23 January 2023 Has Earth's inner core stopped its strange spin? Earthquake data hint that the inner core stopped rotating faster than the rest of the planet in 2009, but not all researchers agree. * Alexandra Witze 1. Alexandra Witze View author publications You can also search for this author in PubMed Google Scholar * Twitter * Facebook * Email You have full access to this article via your institution. Download PDF Earth's core, illustration. Earth's inner core is made mostly of solid iron, and can rotate separately from the outer parts of the planet.Credit: Johan Swanepoel /SPL Thousands of kilometres beneath your feet, Earth's interior might be doing something very weird. Many scientists think that the inner core spins faster than the rest of the planet -- but sometime in the past decade, according to a study, it apparently stopped doing so. [d41586-023] Mars's core has been measured -- and it's surprisingly large "We were quite surprised," say Yi Yang and Xiaodong Song, seismologists at Peking University in Beijing who reported the findings today in Nature Geoscience^1. The results could help to shine light on the many mysteries of the deep Earth, including what part the inner core plays in maintaining the planet's magnetic field and in affecting the speed of the whole planet's rotation -- and thus the length of a day. But they are just the latest instalment in a long-running effort to explain the inner core's unusual rotation, and might not be the final word on the matter. "I keep thinking we're on the verge of figuring this out," says John Vidale, a seismologist at the University of Southern California in Los Angeles. "But I'm not sure." Mysteries of the deep Researchers discovered the inner core in 1936, after studying how seismic waves from earthquakes travel through the planet. Changes in the speed of the waves revealed that the planet's core, which is about 7,000 kilometres wide, consists of a solid centre, made mostly of iron, inside a shell of liquid iron and other elements. As iron from the outer core crystallizes on the surface of the inner core, it changes the density of the outer liquid, driving churning motions that maintain Earth's magnetic field. Ebeko Volcano, Paramushir Island, Kuril Islands, Russia. Researchers have learnt about the inner core's rotation by studying earthquakes that originated in the same region, such as the Kuril Islands (shown here), over decades.Credit: Getty The liquid outer core essentially decouples the 2,400-kilometre-wide inner core from the rest of the planet, so the inner core can spin at its own pace. In 1996, Song and another researcher reported^2 studying earthquakes that originated in the same region over three decades, and whose energy was detected by the same monitoring station thousands of kilometres away. Since the 1960s, the scientists said, the travel time of seismic waves emanating from those earthquakes had changed, indicating that the inner core rotates faster than the planet's mantle, the layer just beyond the outer core. Later studies refined estimates of the rate of that 'super-rotation', to conclude that the inner core rotates faster than the mantle by about one-tenth of a degree per year. But not everyone agrees. Other work has suggested that super-rotation happens mostly in distinct periods, such as in the early 2000s, rather than being a continuous, steady phenomenon^3. Some scientists even argue that super-rotation does not exist, and that the differences in earthquake travel times are instead caused by physical changes on the surface of the inner core^4. Last June, Vidale and Wei Wang, an Earth scientist also at the University of Southern California, threw another spanner into the works. Using data on seismic waves generated by US nuclear test blasts in 1969 and 1971, they reported that between those years, Earth's inner core had 'subrotated', or rotated more slowly than the mantle^5. Only after 1971, they say, did it speed up and begin to super-rotate. A rotational shift Now, Yang and Song say that the inner core has halted its spin relative to the mantle. They studied earthquakes mostly from between 1995 and 2021, and found that the inner core's super-rotation had stopped around 2009. They observed the change at various points around the globe, which the researchers say confirms it is a true planet-wide phenomenon related to core rotation, and not just a local change on the inner core's surface. Earth's magnetic field is acting up and geologists don't know why The data hint that the inner core might even be in the process of shifting back towards subrotation. If so, something is probably happening to the magnetic and gravitational forces that drive the inner core's rotation. Such changes might link the inner core to broader geophysical phenomena such as increases or decreases in the length of a day on Earth. Still, many questions remain, such as how to reconcile the slow pace of the changes that Yang and Song report with some of the faster changes reported by others. The only way out of the morass is to wait for more earthquakes to happen. A "long history of continuous recording of seismic data is critical for monitoring the motion of the heart of the planet", say Yang and Song. "We just have to wait," Vidale adds. doi: https://doi.org/10.1038/d41586-023-00167-1 References 1. Yang, Y. & Song, X. Nature Geosci. https://doi.org/10.1038/ s41561-022-01112-z (2023). Article Google Scholar 2. Song, X. & Richards, P. G. Nature 382, 221-224 (1996). Article Google Scholar 3. Pang, G. & Koper, K. D. Earth Planet. Sci. Lett. 584, 117504 (2022). Article Google Scholar 4. Yao, J., Tian, D., Sun, L. & Wen, L. J. Geophys. Res. Solid Earth 124, 6720-6736 (2019). Article Google Scholar 5. Wang, W. & Vidale, J. E. Sci. Adv. 8, eabm9916 (2022). Article PubMed Google Scholar Download references Related Articles * [d41586-023] Mars's core has been measured -- and it's surprisingly large * [d41586-023] 'Marsquakes' reveal red planet's hidden geology * Earth's magnetic field is acting up and geologists don't know why * Earth's core lightens up Subjects * Geophysics * Seismology * Planetary science Latest on: Geophysics Anomalous thermal transport under high pressure in boron arsenide Anomalous thermal transport under high pressure in boron arsenide Article 23 NOV 22 Extensive inland thinning and speed-up of Northeast Greenland Ice Stream Extensive inland thinning and speed-up of Northeast Greenland Ice Stream Article 09 NOV 22 Calcium dissolution in bridgmanite in the Earth's deep mantle Calcium dissolution in bridgmanite in the Earth's deep mantle Article 19 OCT 22 Seismology NASA spacecraft records epic 'marsquakes' as it prepares to die NASA spacecraft records epic 'marsquakes' as it prepares to die News 27 OCT 22 What do Nord Stream methane leaks mean for climate change? What do Nord Stream methane leaks mean for climate change? News 30 SEP 22 Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar Layered subsurface in Utopia Basin of Mars revealed by Zhurong rover radar Article 26 SEP 22 Planetary science Unconventional tracers show that spring waters on Mount Fuji run deep Unconventional tracers show that spring waters on Mount Fuji run deep News & Views 19 JAN 23 Grain shape effects in bed load sediment transport Grain shape effects in bed load sediment transport Article 11 JAN 23 Demon goddess moon takes control of a planet Demon goddess moon takes control of a planet Research Highlight 10 JAN 23 Nature Careers Jobs * Postdoctoral Associate Baylor College of Medicine (BCM) Houston, TX, United States * Physician-Scientists and Basic Scientists in Cancer Biology Assistant Professor-Yale Cancer Center Yale Cancer Center New Haven, United States * Associate Director, Biological and Environmental Research Program U.S. Department of Energy (DOE) germantown, MD, United States * E-2350 RESEARCHER IN TELECOMMUNICATION - IoT AND xG COMMUNICATION NETWORKS FOR ENVIRONMENTAL APP. Luxembourg Institute of Science and Technology (LIST) Esch-Sur-Alzette, Luxembourg You have full access to this article via your institution. Download PDF Related Articles * [d41586-023] Mars's core has been measured -- and it's surprisingly large * [d41586-023] 'Marsquakes' reveal red planet's hidden geology * Earth's magnetic field is acting up and geologists don't know why * Earth's core lightens up Subjects * Geophysics * Seismology * Planetary science Advertisement Sign up to Nature Briefing An essential round-up of science news, opinion and analysis, delivered to your inbox every weekday. Email address [ ] [ ] Yes! Sign me up to receive the daily Nature Briefing email. I agree my information will be processed in accordance with the Nature and Springer Nature Limited Privacy Policy. Sign up * Close Nature Briefing Sign up for the Nature Briefing newsletter -- what matters in science, free to your inbox daily. Email address [ ] Sign up [ ] I agree my information will be processed in accordance with the Nature and Springer Nature Limited Privacy Policy. Close Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing Explore content * Research articles * News * Opinion * Research Analysis * Careers * Books & Culture * Podcasts * Videos * Current issue * Browse issues * Collections * Subjects * Follow us on Facebook * Follow us on Twitter * Subscribe * Sign up for alerts * RSS feed About the journal * Journal Staff * About the Editors * Journal Information * Our publishing models * Editorial Values Statement * Journal Metrics * Awards * Contact * Editorial policies * History of Nature * Send a news tip Publish with us * For Authors * For Referees * Language editing services * Submit manuscript Search Search articles by subject, keyword or author [ ] Show results from [All journals] Search Advanced search Quick links * Explore articles by subject * Find a job * Guide to authors * Editorial policies Nature (Nature) ISSN 1476-4687 (online) ISSN 0028-0836 (print) nature.com sitemap About Nature Portfolio * About us * Press releases * Press office * Contact us Discover content * Journals A-Z * Articles by subject * Nano * Protocol Exchange * Nature Index Publishing policies * Nature portfolio policies * Open access Author & Researcher services * Reprints & permissions * Research data * Language editing * Scientific editing * Nature Masterclasses * Nature Research Academies * Research Solutions Libraries & institutions * Librarian service & tools * Librarian portal * Open research * Recommend to library Advertising & partnerships * Advertising * Partnerships & Services * Media kits * Branded content Career development * Nature Careers * Nature Conferences * Nature events Regional websites * Nature Africa * Nature China * Nature India * Nature Italy * Nature Japan * Nature Korea * Nature Middle East * Privacy Policy * Use of cookies * Manage cookies/Do not sell my data * Legal notice * Accessibility statement * Terms & Conditions * California Privacy Statement Springer Nature (c) 2023 Springer Nature Limited