Magnetism and Palaeomagnetism

Magnetism arises from the motion and quantum spin of electrons in materials, producing fields that can be mapped by their intensity and direction. The Earth itself behaves as a giant magnet, whose dipolar field deflects solar wind plasma and shields the atmosphere from erosion by charged particles. Variations in field intensity, secular drift of the magnetic poles and occasional polarity reversals testify to the dynamo action in the liquid outer core, driven by thermal and compositional convection. Palaeomagnetism exploits the capacity of iron-bearing minerals in igneous and sedimentary rocks to record the ambient field as they cool below their Curie temperatures or settle through water. By sampling remanent magnetisation and isolating primary magnetic components, researchers reconstruct apparent polar wander paths and virtual geomagnetic poles, charting continental motions, testing geodynamic models and establishing timescales for field reversals and excursions. This archive has underpinned the theory of seafloor spreading and plate tectonics, provided global reference frames for palaeogeography and offered high-resolution markers for correlating climatic and oceanographic events.

Research from Nature Portfolio

New high-resolution sections of Lower Cambrian strata have revealed exceptionally rapid geomagnetic reversals and intervals of ultralow dipole strength, consistent with a nascent inner core too small to stabilise the geodynamo. These results constrain the timing of inner-core nucleation and support models in which early earth field behaviour was dominated by non-axial components and high reversal frequency. In parallel, finely laminated lake sediments from central Japan yield subcentennial records of twin Laschamp excursions. Varve-counted chronologies and modelling of sediment-magnetisation filtering show that even low-resolution marine and volcanic archives capture the key features of these rapid directional swings, confirming widespread intermittent dominance of non-axial dipolar sources during excursions.

Magnetism and Palaeomagnetism publication trend

The graph below shows the total number of articles in magnetism and palaeomagnetism across all publications each year (not limited to Nature Index journals).

Technical terms

Palaeomagnetism: Study of natural remanent magnetisation in rocks and sediments to recover past geomagnetic field directions and strengths.

Virtual geomagnetic pole (VGP): The inferred position of the geomagnetic pole at the time a rock acquired its remanent magnetisation, calculated from palaeomagnetic directions.

Apparent polar wander path (APWP): The trajectory of successive palaeomagnetic poles relative to a fixed continent, reflecting continental motion through time.

Geomagnetic excursion: A short-lived, large-amplitude deviation of field direction and intensity that does not culminate in a full polarity reversal.

Curie temperature: The critical temperature below which a magnetic mineral acquires permanent remanent magnetisation and above which it becomes paramagnetic.

References

1. Late Cambrian geomagnetic instability after the onset of inner core nucleation. Nature Communications (2023).
2. Intermittent non-axial dipolar-field dominance of twin Laschamp excursions. Communications Earth & Environment (2022).
3. The role of megacontinents in the supercontinent cycle. Geology (2020).
4. Archean geodynamics: Ephemeral supercontinents or long-lived supercratons. Geology (2021).
5. Paleomagnetic insights into the Cambrian biogeographic conundrum: Did the North China craton link Laurentia and East Gondwana?. Geology (2020).