The liquid iron outer core of the Earth is in constant motion due to convecting heat and the rotation of the planet. This causes the magnetic field to move and shift around. Roughly every million years the magnetic field flips entirely about 4 or 5 times, so that the north and south poles swap places. The last one took place about 780,000 years ago during the Stone Age.
We see evidence for this in the new crust that is created between tectonic plates as they move apart. The mid-ocean ridge in the floor of the Atlantic Ocean shows many field reversals, with magnetic patterns in the hardened lava showing the history of the Earth’s magnetic field.
There seems to be a reduction in the magnetic field at present, suggesting that a reversal may take place in the next couple of thousand years. A reversal happens gradually and so would go largely unnoticed. There is no scientific consensus as to the effects that would be experienced. With the weaker magnetic field providing less protection to Earth, it is possible that the effects of the solar wind may be stronger. This might cause holes in the Earth’s ozone layer and increase the rates of skin cancer. However, the atmosphere would still provide considerable protection and so it is also possible that these effects may be minimal.
Some animals, such as pigeons, bees and whales, are thought to use the Earth’s magnetic field for navigation. It is therefore theoretically possible that they may become disorientated at this time. However, the slowness of the reversal may also mean that individuals are able to adapt.
- Catherine Bell
We see evidence for this in the new crust that is created between tectonic plates as they move apart. The mid-ocean ridge in the floor of the Atlantic Ocean shows many field reversals, with magnetic patterns in the hardened lava showing the history of the Earth’s magnetic field.
There seems to be a reduction in the magnetic field at present, suggesting that a reversal may take place in the next couple of thousand years. A reversal happens gradually and so would go largely unnoticed. There is no scientific consensus as to the effects that would be experienced. With the weaker magnetic field providing less protection to Earth, it is possible that the effects of the solar wind may be stronger. This might cause holes in the Earth’s ozone layer and increase the rates of skin cancer. However, the atmosphere would still provide considerable protection and so it is also possible that these effects may be minimal.
Some animals, such as pigeons, bees and whales, are thought to use the Earth’s magnetic field for navigation. It is therefore theoretically possible that they may become disorientated at this time. However, the slowness of the reversal may also mean that individuals are able to adapt.
- Catherine Bell
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