Earth's magnetic field could reverse itself in just four years...and maybe it once didS

The North and South magnetic poles swap places every 300,000 years, in a process that takes as much as 5,000 years. But evidence from an ancient lava flow suggests the poles were once moving 53 degrees per year.

We're currently overdue for a pole reversal, and a particularly rapid shift could cause chaos for birds' migration patterns and human navigational instruments. One reassuring thing is that, in general, pole shifts are very, very gradual, and a 5,000 year flip would be disruptive but not catastrophic for Earth with a little sensible planning.

However, we've found bits and pieces of evidence that suggests the Earth's magnetic field can move way, way more quickly. In 1995, an ancient lava flow in Oregon held a magnetic pattern that suggested the poles had once been moving six degrees a day, which is about 10,000 times faster than normal and quick enough to completely reverse the Earth's magnetic field in just about one month. A lot of scientists dismissed that as utterly implausible, certain there had to be some error.

Now another instance of accelerated reversal has been discovered in a preserved lava flow in Nevada. The rocks there indicate Earth's field moved 53 degrees in a year. If that rate was constant, then the poles would have reversed in well under four years. It's not quite the blazing fast speed of the original find, but it's still much, much faster than we ever would have expected.

Researcher Scott Bogue of Los Angeles's Occidental College says that's definitely a possibility, but he also considered the alternative that the overall movement of the poles was much slower, with a rapid acceleration for a year in the middle of a much longer, drawn out process. Either way, if such rapid shifts are possible, even likely, then we had better be ready for some minor chaos when the next reversal finally gets underway.

[Geophysical Research Letters via New Scientist]