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A geomagnetic reversal is overdue or imminent

Status: Contested Verdict: Overdue: depends on how you average. Imminent: no measured sign yet

The claim: Earth's magnetic field is overdue for a polarity reversal, and the current weakening shows that one is about to happen.

Why this label: The 'overdue' part depends on the statistics used. ESA notes that by the average rate (roughly every 250,000 years) we are 'long overdue', but USGS and the paleomagnetic literature describe reversals as irregular, with gaps from about 10,000 years to 50 million years or more. On the 'imminent' part, the agencies and the main peer-reviewed analysis find no sign that a reversal has begun, while noting that one could only be recognized well after it had started.

Background

In a geomagnetic reversal, the magnetic north and south poles swap. This has happened many times. NASA counts 183 reversals in the last 83 million years. The last full reversal, the Matuyama-Brunhes, completed about 773,000 years ago according to the most detailed recent dating (Singer et al. 2019), often rounded to 780,000. Shorter 'excursions', where the field weakens sharply and briefly swings before recovering, are more frequent. The best known, the Laschamp excursion, occurred about 41,000 years ago. This entry concerns the magnetic field only. It is a different topic from physical movement of the crust or the rotation axis; see Crustal displacement and ECDO.

Evidence and arguments for

  • ESA notes that by the average rate at which reversals have happened (roughly every 250,000 years), Earth is 'long overdue'. [1]
  • The field has weakened for nearly two centuries, and a growing low-intensity region (the South Atlantic Anomaly) is the kind of feature some researchers have suggested could precede a reversal or excursion. [2][5]
  • Reversals take time. Singer et al. date the last one as a process of at least 22,000 years, starting with field weakening about 795,000 years ago, so a slow decline is not by itself inconsistent with an early stage. [4]

Evidence and arguments against

  • USGS answers 'Are we about to have a magnetic reversal?' with 'Almost certainly not', noting the current decrease is not a dramatic departure from normal and the field may strengthen again. [3]
  • Brown et al. (2018) modelled the field 30,000-50,000 years ago and found South-Atlantic-Anomaly-like structures at about 49,000 and 46,000 years ago that recovered without an excursion or reversal. The two real excursions in that window looked different from today's field. [2]
  • In the Swarm data, the lead author of the 2025 study is quoted (by AGU's Eos) as seeing no sign of an impending reversal, and as describing the present changes as more likely decade-to-century fluctuations. [6]
  • USGS describes reversals as random with no apparent periodicity, with gaps from about 10,000 years to 50 million years or more, which makes 'overdue' a statistical description rather than a prediction. [8]

Open questions & what would change the label

Nobody can currently predict when the next reversal or excursion will start; USGS notes it would probably be recognized only when it was well underway. What would change the status: a sustained, global collapse of the dipole with field structures resembling those reconstructed for past excursions.

Sources

  1. ESA, 20 May 2020: Swarm probes weakening of Earth's magnetic field. https://www.esa.int/Applications/Observing_the_Earth/FutureEO/Swarm/Swarm_probes_weakening_of_Earth_s_magnetic_field data
  2. Brown, M. et al. (2018). Earth's magnetic field is probably not reversing. PNAS. doi:10.1073/pnas.1722110115 critic/test
  3. USGS FAQ: Are we about to have a magnetic reversal? https://www.usgs.gov/faqs/are-we-about-have-a-magnetic-reversal critic/test
  4. Singer, B. S. et al. (2019). Synchronizing volcanic, sedimentary, and ice core records of Earth's last magnetic polarity reversal. Science Advances. doi:10.1126/sciadv.aaw4621 data
  5. Finlay, C. C. et al. (2025). Core field changes from eleven years of Swarm satellite observations. Physics of the Earth and Planetary Interiors. doi:10.1016/j.pepi.2025.107447 data
  6. Eos (AGU), 2025: A Weak Spot in Earth's Magnetic Field Is Going from Bad to Worse (news report quoting C. Finlay). https://eos.org/articles/a-weak-spot-in-earths-magnetic-field-is-going-from-bad-to-worse background
  7. NASA Science (2021): Flip Flop: Why Variations in Earth's Magnetic Field Aren't Causing Today's Climate Change. https://science.nasa.gov/science-research/earth-science/flip-flop-why-variations-in-earths-magnetic-field-arent-causing-todays-climate-change/ background
  8. USGS FAQ: Is it true that Earth's magnetic field occasionally reverses its polarity? https://www.usgs.gov/faqs/it-true-earths-magnetic-field-occasionally-reverses-its-polarity background

More in this section: Geomagnetic Field & Pole Shift, including the current status of the geomagnetic field.

Interest signal: Wikipedia 'Geomagnetic reversal' averaged 11,762 views/month (Oct 2025-Sep 2026). Sources were checked against Crossref/publisher pages on 2026-10-22. Labels describe the claim, not the people who hold it. Disclaimer.