Magnetic Pole Shift

[jeheron]

What are the consiquences of a magnetic pole shift?

[MolecularMan14]

think of something that we use that utilizes magnetics, and you might have your answer.

[5614]

compasses will all go backwards for a start.

 

but i dont think that it will happen for a long time, so not much for you to worry about. infact i think that the sun will swallow us before it happens, so nothing for man (or woman!) to worry about... unless we move to another planet, which means we wont be on earth so we dont need to worry about earth's magnet pole change!

[J'Dona]

Actually it happens quite often, on average about once every 700,000 years, and they say that we are now overdue for the next one since it's been 780,000 years since, though the gap varies a lot. But if you look at the past excinction record, there doesn't seem to be any correlation with the magnetic pole shift in the past and it, so I don't imagine it has a huge effect on animal life on Earth. As for mechincal devices, some things like compasses would obviously be messed up and some especially sensitive pieces of scientific equipment might be affected, though by the time it happens technology would have advanced to such a point that it won't be much of an issue.

 

The time taken for reversal can take up to several thousand years, however, during which time the field strength is 25% to 10% normal levels (though solar wind can set up a temporary one I hear) so there would be a point during which compasses would be pretty slow to turn, if they even had a solid direction to turn in. I'd have thought that this would affect birds and animals who make migrations by following the magnetic field, though they seemed to have managed all right in the past.

[Jordan14]

The magnetic pole shift has actually started happening, an analysis by I think a Norwegian has shown that the pole is moving at quite a rate. I'll try and find some links.

[Jordan14]

http://archives.cnn.com/2002/TECH/space/03/20/north.pole/

 

And here's a graphic picture

 

http://www.cnn.com/interactive/tech/0203/north.pole/popup.north.pole1.gif

[J'Dona]

Here's a map of the change over time too. It's moving pretty quickly:

 

 

Sorry, posted just as you updated.

[swansont]

Since we probably don't have data much past what is shown in the map, it's probably premature to conclude that this is part of a pole shift. That, plus the fact that the pole is actually moving north in the map.

 

Further, from what I've read, the overall field drops by 10-25%, not to that value (I think I referenced this in the other thread on the topic). Do you have links that claim otherwise?

[J'Dona]

The 10% to 25% figure I gave was from: http://www.geolab.nrcan.gc.ca/geomag/reversals_e.shtml

Double-checking that, it does seem that they are saying it would drop to that level, though that's the only link I've seen so far with that figure.

 

The image I linked to was from this page: http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm

It mentions that the magnetic field strength has decreased by 10% since the 19th century, which might be the figure you were thinking about or just something else.

 

Incidentally, following links on that page about the map comes up with this: http://www.geolab.nrcan.gc.ca/geomag/long_mvt_nmp2_e.shtml

It shows the pole moving both North and South with no real order, and one of the links on the way to it shows a projected course passing through and hitting Northern Russia in about 2050. It seems like normal fluctuations to me, like you say, as opposed to something to do with a pole reversal.

[Ophiolite]

J'Dona you have offended one of the few sensibilities I have. I apologise in advance for shouting and ask that you not take my following outburst in anway personally. Especially as I generally enjoy your posts and find them informative. OK. Ready.

IF A *****NG MAP DOES NOT HAVE A ****NG SCALE IT IS NOT A MAP IT IS A PIECE OF WORTHLESS GARBAGE.

 

Thanks you for your attention, normal service will now be resumed.

 

Edit: And I know that there isn't a scale on the site you lifted it from. I've already sent an e-mail to the site editor. If you had your fingers rapped for missing scales of maps, you would feel passionate about it too.

[J'Dona]

Uh, okay. I know exactly where you're coming from, but I'll still take that a little personally just because I'm Canadian, and so I happened to know already with a little pride about how large the given area was (about half the size of Europe). It's not obvious but one of the links on the page with the map also leads to a page that states how far it has moved in some 200 years or so, and approximately how far it moves per year, which gives a little idea as to the scale.

 

Of course the site that made the mistake was itself Canadian, which saddens me.

[Ophiolite]

And after I had calmed down I noticed there were lines of latitude and longditude, which therfeore implicitly gave the scale.

 

The original (Canadian) site is also interesting. What I can't find is anything giving a reasoned review of the change in thinking i.e. a decade ago reversals were thought to be a disaster waiting to happen, now they will just be an inconvenience unless you are a pigeon or a whale.

[coquina]

I believe you have been writing about 2 separate events. Polar Wandering occurs more or less continually as the location of the magnetic north pole moves as the result of convection currents in the mantle.

 

On the other hand - Polar Reversal is the swapping of the magnetic north and south poles. This has happened many times over the course of geologic time. Evidence of it can be seen in "magnetic striping". It is particularly obvious on either side of the Mid Atlantic Ridge. As molten lava emerges, the magnetic particles in it align themselves with the current position of the magnetic north pole. New lava continuously forms in the center and splits the newly hardened lava into twin sections, one on either side of the ridge.

 

There are "twin sets" of stripes of regular polarity and reversed polarity that are progressively older. Here's a link to a section of "This Dynamic Earth" by the USGS, which tells about it: http://pubs.usgs.gov/publications/text/developing.html

 

From the indications of the striping - polar reversals are relatively sudden.

 

Would a pole shift affect anything that uses man-made electricity? What about electric motors and electromagnets? Are they entirely independent of earth's magnetism?

[SCOOTER93]

Reversal of the earth's magnetic field would have no effect on electric motors. The only serious effect that I can think of is that for a short period of time the field would be zero. THEN, we would have no shielding from solar wind or gamma rays. (Actually, gamma "rays" are high energy protons). This would expose all of us to an additional load of radioactive

 

Scooter93

[swansont]

Reversal of the earth's magnetic field would have no effect on electric motors. The only serious effect that I can think of is that for a short period of time the field would be zero. THEN' date=' we would have no shielding from solar wind or gamma rays. (Actually, gamma "rays" are high energy protons). This would expose all of us to an additional load of radioactive

[/quote']

 

How exactly do you think the magnetic field protects us from gammas?

[swansont]

The 10% to 25% figure I gave was from: http://www.geolab.nrcan.gc.ca/geomag/reversals_e.shtml

Double-checking that' date=' it does seem that they are saying it would drop [i']to[/i] that level, though that's the only link I've seen so far with that figure.

 

Thanks. I was misremembering what I had read. I just ran across another citation that listed ~20% as the field minimum.

[Martin]

Sandi, that makes it a lot clearer.

dont say "shift" say either wandering or reversal.

 

maybe different mechanisms and far different time scale

 

And during reversal the field would presumably get much weaker for a brief time.

 

I believe you have been writing about 2 separate events. Polar Wandering occurs more or less continually as the location of the magnetic north pole moves as the result of convection currents in the mantle.

 

On the other hand - Polar Reversal is the swapping of the magnetic north and south poles. This has happened many times over the course of geologic time. Evidence of it can be seen in "magnetic striping". It is particularly obvious on either side of the Mid Atlantic Ridge. As molten lava emerges' date=' the magnetic particles in it align themselves with the current position of the magnetic north pole. New lava continuously forms in the center and splits the newly hardened lava into twin sections, one on either side of the ridge.

 

There are "twin sets" of stripes of regular polarity and reversed polarity that are progressively older. Here's a link to a section of "This Dynamic Earth" by the USGS, which tells about it: http://pubs.usgs.gov/publications/text/developing.html

 

From the indications of the striping - polar reversals are relatively sudden.

...[/quote']

 

A friend of ours is a geologist who back in 1960s was going all over the world finding this "striping" in the rock that showed how the NS had reversed to be SN, and back again, repeatedly

 

I've seen those maps of the midatlantic ridge that show fossil magnetism layers graphically. Remember something like that anyway.

 

to me, wandering is not so interesting. I can see how changing convection currents could cause it. Any conductor traps magnetic field lines in it and if the conductor is mooshed around or flows then the field flows mooshes accordingly.

 

the business of reversal, tho, is real interesting

wish someone could give simple explanation of how reversal happens

[jeheron]

How exactly do you think the magnetic field protects us from gammas?

 

 

 

 

The magnetic field does not protect the earth from solar flares. It simply

guides the ions of the solar wind to the polar regions, where their

energetic collisions with the upper atmosphere produce the luminous plasma

known as the Northern and Southern Lights (Aurora Borealis and Aurora

Australis). It is the earth's atmosphere that actually prevents the solar

wind from reaching the surface, and that is independent of the magnetic

field.

 

 

written by:

Richard E. Barrans Jr.

CHM/200/M019

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

 

 

found at:

http://www.newton.dep.anl.gov/askasci/env99/env034.htm