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Originally posted by twitchy
Byrd I'm not saying ice is magnetic, neither was Noone. A magnetic shift does indeed occur periodically, that is generally well known, but the drifting that you are referring to is not the same concept as shifting, your talking about declination.
This would explain residual magnetisim in oddball areas like bermuda or Kimberley in South Africa .
Scientists aren't too awfully keen to explain these areas of localized magnetic anamolies, I have seen explinations ranging from ore deposits to topography, and have even seen frequently 'deposited' fulgurites as possible causes and even natural gas hydrates...
As far as the spinning ball experiment, if that spinning ball gradually added mass to one or both of it's 'poles' over a period of time, eventually point of greatest mass will shift to the point of greatest spin, I promise.
Ah byrd you should know me better than that by now.. Of course I have sources :-)
In a paper published in the July 25th issue of Science, the Caltech group reports that this evolutionary burst coincides with another apparently unique event in earth history--a 90-degree change in the direction of Earth's spin axis relative to the continents. Dr. Joseph Kirschvink, a geologist at Caltech and lead author of the study, speculates that a major reorganization of tectonic plates during latest Precambrian time changed the balance of mass within the Earth, triggering the reorientation. Thus, the regions that were previously at the north and south poles were relocated to the equator, and two antipodal points near the equator became the new poles.
Originally posted by Byrd
Erm, magentism is a force. There's no such thing as "residual magentism." That's like "residual light" when you turn the light off inside a cave.
Ain't no such thing.
If you didn't know electric/magnetic fields and radiation can be detected from much farther distance than they can cause bigger "force".
Originally posted by Johannmon
Actually this is only true if you are close enough to the source of the field. Is the earth’s Magnetic field strong enough to generate torque at its source (the outer core)? Well lets consider this. The most powerful magnetic fields we are capable of producing are through EMP devices. These fields Extend maybe 10’s of miles from their source. Yet similar fields have been shown to be able to produce HP and torque capable of the propulsion of a several thousand ton aircraft carrier. Now you try to say that a magnetic field which is measurable from 10,000 miles away from its source does not have sufficient power to produce torque? I will concede that the magnetic field does not have the power to produce torque at the surface of the Earth but as noted earlier the potential energy of a field increases exponentially with proximity to the source of the field. I am certain that if you got anywhere near the source of the Earths magnetic field your storage media would be wiped clean in an instant, not to mention that they would be incinerated. Lol.
if magnetic field is strong enough to affect ferromagnetic materials enough to cause torque it will always destroy all magnetic medias anyway!
Originally posted by Johannmon
First we have no absolute data as to the depths of the different sublayers of our earth nor do we have absolute temperature reading below 20 KM. We have never drilled to a depth that even approaches the mantle so all the information we have is a best guess. That being as it may the temperature that is most agreed upon for the approximate threshold between the mantle and the crust is only 100 degrees C above the Curie point of iron. Further it is widely accepted that the mantle is made up of a much richer combination of heavy ferrous metals than is found in the upper crust.
It is reasonable to assume then that within the portion of the crust that is bordering the mantle there should be found higher concentrations of ferrous metals that could retain a magnetic charge since their curie point has not been reached. In fact I find it most fascinating that the point where the Curie temperature of Iron is crossed is so near to the estimated border between the crust and the mantle. This would seem to indicate that perhaps the magnetization that this theory requires could take place as the mantle cools and becomes part of the crust.
Now in the interest of being balanced, my research into this theory has come across an alternative to the dynamo theory of magnetic field generation that if proven correct would disprove the theory of catastrophic polar flips entirely. This alternative theory seems to explain some of the major anomolies in the Earth's field quite well. If you are interested it is a good read.
Field theory
en.wikipedia.org...
Taken as a whole, the Earth's composition by mass is:
iron: 34.6 %
oxygen: 29.5 %
silicon: 15.2 %
magnesium: 12.7 %
nickel: 2.4 %
sulfur: 1.9 %
titanium: 0.05 %
other elements: 3.65 %
Originally posted by E_T
Now when thinking it... if considerable part of mantle is iron it would be two-edged sword...
When we want to protect some device from magnetic fields (and interference caused by those) it's "wrapped" inside metal which causes lines of magnetic field to travel in that metal instead of going through device. But it also works to other way, it prevents that device from sending magnetic field to other devices around it so wrapping metal around earth's magnetic field would suppress/make density of it much weaker outside this "shell".
I checked little that theory, basically it's "conversion" of original theory, power source for matter flow is just now heat instead of earth's rotation.
But I don't have more time now so I'll check more later.
Originally posted by Johannmon
Originally posted by Byrd
Erm, magentism is a force. There's no such thing as "residual magentism." That's like "residual light" when you turn the light off inside a cave.
Ain't no such thing.
residual magnetism is that force that is retained in a material that is magnetised after the forece that intially magnetised it is removed. It is present in most ferrous minerals that are magnetised. What do you think a permanent magnet is? pure force? Come on surely you are not so caught up in your definitions that you cannot apply common sense to them.
Originally posted by Johannmon
It is reasonable to assume then that within the portion of the crust that is bordering the mantle there should be found higher concentrations of ferrous metals that could retain a magnetic charge since their curie point has not been reached.
One other thing that so many who have posted have failed to realize and so I will try once again to explain it is that We are not dealing with standard magnetic orientation here. The poles create a very different magnetic orientation than is found say in the mid atlantic ridge. The difference is that the orientation of the poles is perpendicular to curve of the crust,
Originally posted by Johannmon
\Just so I understand, are you suggesting that the mantle, if it proves iron rich could act as a magnetic shield of sorts lessening the measurable intensity of the Earths magnetic field? IF so then the iron rich mantle would seem to be a triple edged sword. In that the measurements we use for the Earth's magnetic field at the surface would be scewed to the weaken the actual intensity of the field towards the core.
Well... that's something I have real experience.
Originally posted by Johannmon
I also wonder what effect if any the proximity of the crust to such a cold portion of the earth has on mantle cooling. The distances between the surface and the mantle being as large as they are the effect may be minimal but if there was a portion of the crust where we saw significant mantle cooling one would expect it in the polar regions where surface temps drop as low as -100 degrees and input radiation from the sun is nonexistant for 3-6 months of the year.
Originally posted by Byrd
If this was the case, then once their magnetic properties were laid down, the earth's pole wouldn't switch or even wander. You can set a magnet down, and put another underneath that and move it around... and the lines of force from THAT one won't override the one on top of it.
Originally posted by Byrd
That's not "residual" -- that's plain old magnetism. You've aligned the atoms within the element and they generate the magnetic force. There's nothing "left over" about it.
Originally posted by Byrd
here it's actually iron oxide (rust) which is not magnetizeable