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A Weakening Magnetic Field and Mass Extinctions

A new study has suggested that the unexpected reversal of Earth’s magnetic poles approximately 41,000 - 42,000 years ago may have drastically decreased the magnetic field’s strength, thus precipitating a number of environmental crises on Earth.

New, accurate carbon dating procedures obtained data from ancient tree fossils through which scientists were able to observe correlations between shifts in climate patterns, large mammal extinctions, and changes in human behavior and the Laschamps excursion. The Laschamps excursion was a brief reversal of Earth’s magnetic field that occurred during the Last Glacial Period. The field was reversed for approximately 400 years and this reduced its strength by 75%.

Earth’s protective magnetic field protects the planet from an outpour of charged particles streaming from the sun. During a reversal, the field can diminish in strength and researchers have suggested that this decrease in strength could be connected to mass extinction events. However, it has been difficult to procure conclusive evidence for these suggestions because according to evolutionary biologist Alan Cooper, “the general belief had been that geomagnetic changes had no impact on climate or anything else”. This belief has been supported by a lack of precise dates for the length of the reversal event to correlate with environmental, magnetic rock, and ice core records.

Currently, the Australian Research Council is funding research to observe New Zealand’s kauri tree, one of the oldest trees in the world. Carbon dating has revealed that the tree was alive during the Laschamps excursion (41,000-42,000 years ago). Cooper and his team acquired cross-sections from four ancient trees retrieved from a swamp at Ng­āwhā Springs in New Zealand. These cross-sections were analyzed for carbon-14 which is a radioactive form of carbon. A giant log dating to approximately 14,000 years ago showed a 1,700 year-long carbon-14 record which unveiled significant changes in carbon-14 before and during the Laschamps excursion. These changes have been attributed to the fact that increasing incoming cosmic rays, which would have been seen with the weakened magnetic field, would have produced more carbon-14. This increase in carbon-14 would have then been absorbed into the tree’s tissues.

Cooper and his colleagues simulated how a weakened magnetic field would have impacted weather patterns and computer analysis suggested that the rise in charged particles entering the atmosph