We don't often think about Earth's magnetic poles except when we're navigating; we take it for granted that the Earth conveniently has two poles — one in the north and one in the south — and that our compasses point north.
But it turns out this arrangement was not always the case, according to new research out of the Carnegie Institution of Science. In fact, during a period between 500 million years ago and 1 billion years ago, something strange happened to Earth's magnetosphere. Multiple poles suddenly sprang up across the globe, causing the planet's magnetic field to go haywire. It very well could have caused life on Earth to be thrown into utter disarray.
"These findings could offer an explanation for the bizarre fluctuations in magnetic field direction seen in the geologic record around 600 to 700 million years ago," explained Peter Driscoll, the researcher who spearheaded the Carnegie study, which is published in the journal Geophysical Research Letters. "And there are widespread implications for such dramatic field changes."
What could have caused this sudden shift? It's generally understood that Earth's two-pole magnetic field comes from the rotation of the planet's liquid iron core around a smaller, solid core. But that inner core was not always solid. At some point in the planet's history, it must have transformed from a molten state into a solid one.
Driscoll believes this event may have been what happened between 0.5 and 1 billion years ago. As the inner core began to solidify, it wreaked havoc on the magnetic field. This period of chaos likely lasted until the inner core was completely solidified.
If true, the findings could dramatically alter how we study and understand Earth's geological history, particularly when it comes to how magnetic measurements are used to reconstruct continental motions and ancient climates. Since the magnetosphere is also responsible for shielding the planet from the sun's radiation, it may have had consequences for the evolution of life during this time too. A many-poled magnetic field likely would have offered much weaker protection.
More research will be needed to confirm Driscoll's theory, but these results nevertheless serve as a reminder of how much we take for granted the stability of Earth's systems. We're a tiny dot in a hostile cosmos, and the stability we enjoy today may not always be the case.