Tuesday, September 14, 2010
Reversal of Earth's magnetic poles underway?
Geomagnetic field flip-flops in a flash
Scientists unearth more evidence of superfast changes in Earth's magnetic polarity
ScienceNews: Just north of a truck stop along Interstate 80 in Battle Mountain's Nev., lies evidence that the Earth's magnetic field once went haywire. Magnetic minerals in 15-million-year-old rocks appear to preserve a moment when the magnetic north pole was rapidly on its way to becoming the south pole, and vice versa. Such 'geomagnetic field reversals' occur every couple hundred thousand years, normally taking about 4,000 years to make the change.
The Nevada rocks suggest that this particular switch happened at a remarkably fast clip. Anyone carrying a compass would have seen its measurements skew by about a degree a week -- a flash in geologic time. A paper describing the discovery is slated to appear in Geophysical Research Letters...
Researchers aren't sure why the geomagnetic field reverses itself. Many think it must have something to do with what creates the field in the first place -- convective motions of liquid iron in the planet's spinning outer core... The last stable reversal occurred 780,000 year ago. Some geologists argue the Earth is overdue for a reversal and might even be entering one now, as the geomagnetic field has been getting weaker over the past 150 years or more.
But apocalyptic SyFy channel movies to the contrary, nobody should worry about waking up one morning to geomagnetic havoc, says [lead authors Scott] Bogue. 'To geologists a polarity reversal is a nearly instantaneous thing that changes a global feature of the Earth -- it's really a spectacular phenomenon... But if you were alive when it was happening, it probably wouldn't be that big a deal.'
Image source here.