When the magnetic field around the Earth grows stronger, oxygen levels rise. That is the surprising finding of a new study looking at more than half a billion years of planetary history.
Researchers can track the rise and fall in oxygen levels by studying charcoal left over from ancient wildfires. The more oxygen, the larger the fires. And they can gauge changes in the geomagnetic field by studying rocks formed by ancient volcanic eruptions. Magnetic crystals found in cooling lava align with the geomagnetic field, offering some indication of its strength.
The new study combined these data, revealing a powerful link between oxygen levels and the strength of the geomagnetic field. Over the last 540 million years, the strength of the magnetic field has trended up, and so has the level of oxygen, making the planet more hospitable to life. The findings were published in Science Advances.
“We don’t really have a good explanation for it,” coauthor Benjamin Mills, of the University of Leeds, told Nature, though he offered a few ideas.
As the tectonic plates have shifted, over hundreds of millions of years, their movements have, at times, unleashed essential nutrients, such as zinc and phosphorus, into the ocean, fueling massive algal blooms. Those blooms produced huge volumes of oxygen. It may be the case, scientists propose, that the same currents driving the movement of the tectonic plates may also be affecting the Earth’s iron core, the source of its magnetic field.
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