Magnetic field reversal

[Obo]

Anyone have any thoughts on what the consequences of the Earth's magnetic field reversing would be?

[PaulYukochan]

Yes. I read that this happens once in a while.

[wildwood]

...in fact, I seem to remember reading that this happened more than once. Wil post more tonight if there is no other explanation.

[xyzzyplugh]

I suggest that navigation for all living things would be affected and that they would adjust within a matter of days. Also that humans would merely rename north as south and vice versa. Or do you think it would be more impinging than this?

[sft42]

It has happened more than once and can be traced through magnetic mineral deposits in layers of rocks. The actual effects on life would be negligable but on modern life ie computers navigation etc. then who knows????

[wildwood]

Sorry Paul, I didn't read your answer properly. You did in fact correctly state that it happens once in a while.

[Obo]

It happens more than once in a while, over the last 60 million years it has happened on average every 250,000 years, but the last one was 1 million years ago so we appear to be long overdue one. The reason I asked is that I read in the papers that scientists believe that the magnetic field at the poles is weakening and it has been suggested that this is the build up to a magnetic field reversal, so was wondering what the consequences of this would be.

[wildwood]

I haven't found where I read about the magnetic field reversals and it is quite possible that a new reversal is in progress. I vaguely remember that it had something to do with the Earth's core rotating slightly faster then the mantle so upsetting all the iron ore in the lower mantle. As this is the main cause of mountains and earth fissures I presume the actual reversal would be a long way off yet. The actual reversal of the field would not be anywhere as dramatic as the consequences of the cause.

[xyzzyplugh]

do we expect this as a gradual change? or in fact an 'instant' flip?

[wildwood]

Have done a lot of reading on the Net today about magnetic field reversals because the subject fascinates me. Now I am more confused than ever :-)
It appears that even the expert are not exactly sure what happens. I did find a question/answered similar to Obo's - at least one that I can mostly understand. If interested go to http://image.gsfc.nasa.gov/poetry/ask/q279.html

[Obo]

Wildwood... Thank you for posting the link, but I'm not sure what you are refering to about the main cause of mountains and fissures.... the Earth's magnetic field is caused by eddies and currents in the molten outer core of the Earth. These are continuously fluctuating and the magnetic poles of the Earth are always "wandering". Mountains and "fissures" in the Earth's surface are caused by plate tectonics thought to be driven by convection in the solid mantle (models differ as to whether this convection takes place in the upper, lower or entire mantle. Hotspots, which can cause volcanic activity, mountain ranges and rupturing of the Earth's surface may be caused by abnomalies at the mantle/core boundary, but again this is just one theory put forward for their cause.

[DavidUK]

There's a good article on this on the Observer website. Go to http://www.observer.co.uk/science and select the link "Sun's rays to roast Earth...". This says that human's greatest risk from pole reversal would come from intense solar radiation bursts.

[wildwood]

Obo, I am not very good at explaining complicated matters, especially when I don't understand them fully. I meant that many mountains and fissures (canyons) contain some very irregular gaps in the layers of mineral deposits. It is not unreasonable therefore to presume that, at the odd times, part of their formation took a big jump which I presume to have been caused by tremendously active tectonic plate movement. Could this not have been caused by the 'occasional' fluctuation of geothermal activity that is (at least partly) responsible for the field reversals? Is it possible (this is only from memory) that increased activity is temporary lowering the viscocity of the layers between the core and the mantle, so allowing the earth's core to turn slightly ahead of the crust and causing unusually active iron ore which may flip the poles? On more than one occasion I found reference (on the Net) to the Van Allen Belt also being instrumental in magnetic fields on earth. I still believe that when it comes, the magnetic field reversal would be instant, because as far as I can understand the rotation of the planet is what keeps the field poles close to true north/south. To wrench the poles to the other direction would take some pretty violent activity. As I said before, the more I read about it, the more confused I become, I'll probably have to do some backpeddaling on my thoughts :-).

[xyzzyplugh]

here is a great article on pole reversal http://www.observer.co.uk/international/story/0,69
03,837058,00.html