2012: Magnetic Pole Reversal Happens All The (Geologic) Time

[OKIsItJustMe]

http://www.nasa.gov/topics/earth/features/2012-poleReversal.html

2012: Magnetic Pole Reversal Happens All The (Geologic) Time

11.30.11

Scientists understand that Earth's magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years ago, and facing what we call north with a magnetic compass in your hand, the needle would point to 'south.' This is because a magnetic compass is calibrated based on Earth's poles. The N-S markings of a compass would be 180 degrees wrong if the polarity of today's magnetic field were reversed. Many doomsday theorists have tried to take this natural geological occurrence and suggest it could lead to Earth's destruction. But would there be any dramatic effects? The answer, from the geologic and fossil records we have from hundreds of past magnetic polarity reversals, seems to be 'no.'

Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. Magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. Scientists estimate reversals have happened at least hundreds of times over the past three billion years. And while reversals have happened more frequently in "recent" years, when dinosaurs walked Earth a reversal was more likely to happen only about every one million years.

…

Another doomsday hypothesis about a geomagnetic flip plays up fears about incoming solar activity. This suggestion mistakenly assumes that a pole reversal would momentarily leave Earth without the magnetic field that protects us from solar flares and coronal mass ejections from the sun. But, while Earth's magnetic field can indeed weaken and strengthen over time, there is no indication that it has ever disappeared completely. A weaker field would certainly lead to a small increase in solar radiation on Earth – as well as a beautiful display of aurora at lower latitudes -- but nothing deadly. Moreover, even with a weakened magnetic field, Earth's thick atmosphere also offers protection against the sun's incoming particles.

The science shows that magnetic pole reversal is – in terms of geologic time scales – a common occurrence that happens gradually over millennia. While the conditions that cause polarity reversals are not entirely predictable – the north pole's movement could subtly change direction, for instance – there is nothing in the millions of years of geologic record to suggest that any of the 2012 doomsday scenarios connected to a pole reversal should be taken seriously. A reversal might, however, be good business for magnetic compass manufacturers.

[BlueToTheBone]

1. Does this mean

that one day next year, we'll wake up and north will be south?

[BadgerKid]

2. I doubt it.

Current theory for why Earth has a magnetic field in the first place is based on the dynamo effect. If it's correct, then it's a matter of asking how long does it take for changes in Earth's internal electrically conductive fluid not only to occur, but for those changes to affect Earth's magnetic field.

http://en.wikipedia.org/wiki/Dynamo_effect

[OKIsItJustMe]

3. No

http://www.nasa.gov/topics/earth/features/2012-poleReversal.html
“… A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. …”

[Odin2005]

4. No, generally it takes a few thousand years.

What happens is that first the field weakens, then the magnetic poles disintegrate into several scattered positive and negative zones, and then the scattered zones coalesce into a new pole.

[Fumesucker]

5. The N magnetic pole has been heading lickety split for Siberia lately..

[MarkCharles]

6. What your diagram describes, of course, you are aware, is the

wobbling of the planet upon it's axis, like a top as it spins, which is a normal occurrence, not related to pole-switches.

[Fumesucker]

7. No, that's the migration of the N magnetic pole..

Not precession of the spin axis, that's about a 26,000 year cycle.

And nutation has about a 19 year cycle.

The N magnetic pole migration may or may not be related to magnetic pole reversal.

[AtheistCrusader]

8. No, it is not. The pole is indeed in motion.

http://www.npr.org/2011/01/14/132934010/following-a-wandering-north-pole

The earth is not wobbling no 40 miles per year.

[muriel_volestrangler]

9. You could also call that 'headed for the geographical north pole'

The line doesn't go quite through it, but it's got a lot closer in the past 100 years.

[Fumesucker]

10. Perhaps, but I'll be surprised if it stops at the rotation axis..

If anything the rate of migration seems to be increasing, it looks like in another decade or so the magnetic pole will be on the other side of the rotation axis from where it was a hundred years ago.

[YankeyMCC]

11. Oh boy watch out

Santa's going to start asking people to help him and the elves move. I can just see him standing there holding the naughty list in hand "Oh by the way can you lend a hand...have any boxes....say that's a nice big truck you have..."