◆Research findings by an international research group led by Professor Yuji Yamamoto of Marine Core Research Institute（MaCRI） have been published in the scientific journal *Communications Earth & Environment*
Release Date:
Using Earth's magnetic field from 40 million years ago
New Discovery of an “Unprecedented Long-Term Reversal”
Professor Yuji Yamamoto of Marine Core Research Institute（MaCRI）, Dr. Slah Boulila of the French National Centre for Scientific Research (CNRS) and Sorbonne University,an international research team led by Associate Professor Futoshi Takahashi Graduate School and Associate Professor C. Peter Lippert of the University of Utah, analyzed paleomagnetic records preserved in deep-sea sediments dating back approximately 40 million years with high precision and identified two magnetic field reversals that occurred during that period.The analysis revealed that these reversals unfolded over approximately 18,000 and 70,000 years, respectively, significantly exceeding the previously held understanding that “reversals are completed in about 10,000 years.” Furthermore, numerical models simulating the processes that generate the magnetic field within the Earth’s interior have shown that the duration of reversals can vary widely; thus, these findings provide crucial evidence supporting the existence of inherent diversity in the timescales of magnetic field reversals.
During reversal periods, the magnetic field weakens, reducing the Earth’s surface defense against high-energy particles arriving from the Sun. Therefore, if “prolonged reversals” such as those revealed in this study occurred, the Earth’s environment and ecosystems at that time may have been exposed to the effects of intense radiation over a much longer period.
These research findings were published in the online edition of the scientific journal *Communications Earth & Environment* on January 20, 2026.
[Paper Information]
Journal: Communications Earth & Environment
URL:
Paper Title: Extraordinarily long duration of Eocene geomagnetic polarity reversals
DOI: 10.1038/s43247-026-03205-8
Authors: Yuji Yamamoto ( Marine Core Research Institute（MaCRI） ), Slah Boulila (French National Center for Scientific Research, Sorbonne University), Futoshi Takahashi (Faculty of Science, Kyushu University), C. Peter Lippert (University of Utah, USA)