Synchronizing volcanic, sedimentary, and ice core records of Earth's last magnetic polarity reversal.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31457087.
- Also identified by DOI 10.1126/sciadv.aaw4621 and PMC identifier 6685714.
- Licence recorded as CC BY-NC.
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Abstract
Reversal of Earth's magnetic field polarity every 10<sup>5</sup> to 10<sup>6</sup> years is among the most far-reaching, yet enigmatic, geophysical phenomena. The short duration of reversals make precise temporal records of past magnetic field behavior paramount to understanding the processes that produce them. We correlate new <sup>40</sup>Ar/<sup>39</sup>Ar dates from transitionally magnetized lava flows to astronomically dated sediment and ice records to map the evolution of Earth's last reversal. The final 180° polarity reversal at ~773 ka culminates a complex process beginning at ~795 ka with weakening of the field, succeeded by increased field intensity manifested in sediments and ice, and then by an excursion and weakening of intensity at ~784 ka that heralds a >10 ka period wherein sediments record highly variable directions. The 22 ka evolution of this reversal suggested by our findings is mirrored by a numerical geodynamo simulation that may capture much of the naturally observed reversal process.