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Paleomagnetism

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Mikebits

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Geologist claim that when minerals are forming rock, the metals in the rock polarize to the poles of the planet, as the mineral is solidifying, thus sealing the magnetic properties of the rock forever in time. Is it not possible that the rocks magnetic properties could not be influenced over time by external forces and the magnetic properties may not be as they were when the rock solidified?

Your thoughts...
 

dknguyen

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Wouldn't something like that require the material to be liquified again, and then cooled in the presence of some other widespread magnetic field that is stronger than the earth's? I suppose that could happen if the rock were liquified near a large deposit of some other magnetic mineral that was aligned at a different point in time.
 
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Torben

Well-Known Member
Geologist claim that when minerals are forming rock, the metals in the rock polarize to the poles of the planet, as the mineral is solidifying, thus sealing the magnetic properties of the rock forever in time. Is it not possible that the rocks magnetic properties could not be influenced over time by external forces and the magnetic properties may not be as they were when the rock solidified?

Your thoughts...
Ramblings of a man who is stumbling off to bed soon:

I think it's entirely possible. However, I would think that geologically speaking, the solidification of the mineral would be pretty quick and that the planet would provide the dominant magnetic force at the time. Perhaps later something happens which might have a changing effect on the mineral, but unless it was very strong perhaps only a fraction of the total mass of the mineral would be permanently affected. And then if the destabilizing field were removed, the dominant effect on the altered parts of the mineral mass would be the planet and the rest of the surrounding polarized mass.

So in short (sorry, feeling long-winded again) sure, perhaps it's affected. But perhaps enough remains unaffected to allow us to make some decent guesses which might be later tested.


Cheers,

Torben
 

ericgibbs

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Geologist claim that when minerals are forming rock, the metals in the rock polarize to the poles of the planet, as the mineral is solidifying, thus sealing the magnetic properties of the rock forever in time. Is it not possible that the rocks magnetic properties could not be influenced over time by external forces and the magnetic properties may not be as they were when the rock solidified?

Your thoughts...
hi Mike,
If you study the charts of the geomagnetic bands, either side of the mid Atlantic ridge [ sea floor spreading] you will see that either side is a mirror image of the other.

If the re-magnetising worked in the manner you suggested, it would have a global effect order to effect such a large area, so all the worlds rocks [ land and marine] would show the same pattern.
 
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