Something’s up with the Earth’s magnetic poles. Over the past few thousand years, Earth’s geomagnetic field has been getting weaker and weaker. If it decays enough, it could collapse altogether and flip the poles. North would become South and South would become North.
Looking at the geological history of Earth, magnetic field flips appear to occur every 200,000 to 300,000 years on average. Considering the last record of a total reversal was around 780,100 years. we are overdue for another. Some scientists, however, argue that a pole flip is not necessarily imminent.
Since the last pole flip, the events have been much shorter, with a temporary change 41,000 years ago that saw the poles reverse for 250 years before going back to the way they are today.
The reason why this phenomenon takes place is not clear.
The Earth’s magnetic field is generated by the rotation of its molten iron outer core. The core is gradually cooling, which creates movement in the outer core due to convection, like a boiling pot. However, unlike a boiling pot, this movement is a dynamo, where a magnetic field is generated thanks to moving charges like in an electromagnet. Only 1 percent of the magnetic field escapes our planet's interior and becomes observable on the surface.
The pole-reversal explanation with the most support has something to do with the turbulence that the molten iron encounters as it moves. This chaos is likely to play a role, but how exactly it happens is still a mystery.
The reversal of the magnetic poles may sound scary, but will it be dangerous? Well, not really (with some caveats). Pole flipping, or in technical terms the geomagnetic reversal, is fairly common throughout the history of our planet. Life has survived and thrived in spite of it happening. There is not going to be a mass extinction or another global catastrophe.
Evidence from the fossil record shows that living organisms didn’t suffer as a result of the poles switching around. There is also no suggestion that the flip led to more earthquakes, volcanic eruptions, or dramatic changes in the climate. Life and the planet will continue as we know it.
There is a question mark around modern-day technology, however. Our planet's magnetic field protects us against charged particles from the solar wind. This is particularly important during solar storms, where there is a higher-than-normal influx of energetic particles. These are again mostly harmless to us, but they might be devastating to our technology.
We don’t have much to go on to assess such a scenario. The best example might be the Carrington event, a powerful geomagnetic storm that happened in 1859. The storm was so powerful that aurorae were visible in the Northern Hemisphere all the way down to the Caribbean. Telegraph systems failed and, in some cases, gave operators electric shocks.
On the other hand, some telegraph operators were capable of operating the system without power. If such a storm were to happen today, the damages might be a lot more significant. The estimated cost of such damage would be in the trillions of dollars. However, damaging events such as these are more the exception than the rule.
The flipping of the magnetic poles doesn’t mean the Earth will not have a magnetic field anymore. Let's work this out with a compass. At the moment, your compass has a nice little red arrow pointing North. When a full geomagnetic reversal takes place, the arrow will point South.
But in between these two events, there is a chaotic period where multiple poles might form at once, confusing your compass and even the animals that use the magnetic field for navigation. This is a messy time and the strength of the field could be up to 20 percent lower than it currently is.
Also, the flip doesn’t happen overnight. The chaotic period during the reversal can last thousands of years or, at the very least, a few hundred years on some rare occasions. And sometimes, the magnetic field gets close to a reversal and then goes back.
An earlier version of this article was published in January 2019.