There's also evidence of it, recorded in iron-rich lava in areas like the Transatlantic Ridge. The thing to be concerned about isn't the flip itself, so much a

There's also evidence of it, recorded in iron-rich lava in areas like the Transatlantic Ridge. The thing to be concerned about isn't the flip itself, so much as that the fluctuations could lead to a period where the magnetic field isn't strong enough to deflect the solar wind. While it (most likely) wouldn't be permanent, it would be a pretty unpleasant period. :)