Ancient Polar Wander?

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Ancient Polar Wander?

Postby Beagle » Wed Apr 09, 2008 2:16 pm

http://news.nationalgeographic.com/news/2008/04/080407-plate-tectonics.html

A new study lends weight to the controversial theory that Earth became massively imbalanced in the distant past, sending its tectonic plates on a mad dash to even things out.

Bernhard Steinberger and Trond Torsvik, of the Geological Survey of Norway, analyzed rock samples dating back 320 million years to hunt for clues in Earth's magnetic field about the history of plate motions.



Did Charles Hapgood have a point after all? :?:
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Postby spacecase0 » Thu Apr 10, 2008 10:03 am

I thought that the pole shift theory had lots of evidence.
such as green plants frozen in antarctica, and ancient people knowing what antarctica looked like under the ice.

I like this new study,

now that they know how much it took for this to happen once,
I wonder if anyone has calculated what it would take in the way of ice buildup at the poles for this to happen again ?
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Postby Forum Monk » Thu Apr 10, 2008 1:34 pm

spacecase0 wrote:now that they know how much it took for this to happen once,


No, they don't know it happened it once - it is just a theory.


spacecase0 wrote:I wonder if anyone has calculated what it would take in the way of ice buildup at the poles for this to happen again ?


If it did happen as theorized, it had nothing to do with ice buildup. True polar wander does not change the axial tilt of the earth, it is practically indistinguishable from plate tectonics except for the driving mechanism. You can not measure its progress with a calendar, it takes millions of years.
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Postby spacecase0 » Thu Apr 10, 2008 2:10 pm

No, they don't know it happened it once - it is just a theory.


your are right, and I knew that, I need to think about my phrasing more carefully,

I know that the ice had nothing to do with what they calculated,
I was more meaning I wonder if the ice buildup would change the weight of a land mass to cause it to be a new driving source for them moving, and would that return antartica to an ice free zone in the future, or would it keep it trapped because of the extra weight, or would there be no effect at all,

looks like the ocean is about 4000 meters deep on average, the arctic being about 1038 meters, that the land over the water is about 170 meters average, the average depth of the ice on antartica is about 2100 meters,
that seems like it is a significant percentage of the weight of that land mass is ice.
it just seems like all the ice in the ice age and the ice that is on antartica now may be causing a new movement.

and I wonder if someone has done the calculations to see if it could cause the continents to drift differently in an ice age than they are doing right now according to that theory.
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Postby Forum Monk » Thu Apr 10, 2008 2:57 pm

You would be correct were it not for the fact that under that 4000m of water (less at the poles) is many more 1000s of meters of earth material (crust, mantle, etc.). As a result water only makes up about 0.02 percent of the earth's total mass. Also bear in mind, ice is less massive than water.

Over all the amount and weight of water on the earth is relatively insignificant. However, if a significant amount of mantle were to shift over a short period of time, as in the upwheling of a massive volcano, it is possible, theoretically to change the balance of mass distribution enough to cause TPW as inertial forces tend to "push" or "pull" the imbalance back into equalibrium.
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Postby Digit » Sat Apr 12, 2008 5:06 am

According to theory the Earth's plates are moved by the upwellings from below. If this occurs beneath a land mass that mass can be driven apart. From that the most logical deductuion would seem to be that these upwellings can change their locations.
Currently the Atlantic is becoming wider due to this activity, suppose this ceased and started elsewhere? Would this be a one off or would it be the result, or the cause, of such activity elswhere also changing its location?
Do we have any evidence to suggest that these locations are fixed or alternatively that they move?
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Postby Rokcet Scientist » Sat Apr 12, 2008 6:15 am

Forum Monk wrote:You would be correct were it not for the fact that under that 4000m of water (less at the poles) is many more 1000s of meters of earth material (crust, mantle, etc.).


An average of 35 kilometers (35,000 meters)
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Postby Pippin » Fri Apr 18, 2008 9:58 am

Digit wrote:According to theory the Earth's plates are moved by the upwellings from below. If this occurs beneath a land mass that mass can be driven apart. From that the most logical deductuion would seem to be that these upwellings can change their locations.
Currently the Atlantic is becoming wider due to this activity, suppose this ceased and started elsewhere? Would this be a one off or would it be the result, or the cause, of such activity elswhere also changing its location?
Do we have any evidence to suggest that these locations are fixed or alternatively that they move?


Another theorised force to help this process is the pull of the plate going down into the mantle. This process to shift sometime. The water between norway and brittain is one such rift that started, but stopped again.

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