15
   

The Earths Magnetic Poles will reverse .

 
 
rosborne979
 
  1  
Reply Fri 27 Aug, 2010 07:34 pm
@HexHammer,
HexHammer wrote:
Pole shifts has occured plenty of times through prehistoric time, nothing new.

Hunter gatherers didn't have satellites, power grids and Airline passengers at 30k feet to worry about. Something new.
HexHammer
 
  1  
Reply Fri 27 Aug, 2010 07:43 pm
@rosborne979,
rosborne979 wrote:

HexHammer wrote:
Pole shifts has occured plenty of times through prehistoric time, nothing new.

Hunter gatherers didn't have satellites, power grids and Airline passengers at 30k feet to worry about. Something new.
Back before GPS wasn't for the general public, or was scrambled it sure would pose a problem with a pole shift, but now with very extensive GPS usage, it has become less of a problem. GPS rely on star positioning, not magnetic poles.
Besides, poles will wander and are inaccurate.
0 Replies
 
georgeob1
 
  1  
Reply Fri 27 Aug, 2010 09:37 pm
@farmerman,
farmerman wrote:

We are not really certain of the mwechanism involved in such reversals. As it turns out , 2 of the big 5 extinction events were also correlated to a polar reversal at the same (geologic) instant. That has led to the theory that polar reversals are associated with deep welling of magma and new vulcanism (These are possibloe events that trigger the poles to wander more quickly than our present speed of 50Km /yr).
Magma upqwelling releases a competing pole and e lose our dipole for a period of time. (It may be that because magma upwelling can break outr on the surface, this apparent association of magama and polar reversals may only be an artifact, not a cause and effect.

So, with 2 of the big 5 extinctions associated with polar reversals (as qwell as incresed vulcanism), the die outs may not really be related anyway.

HOWEVER, sea creatures , like radiolarians ARE very susceptibloe to polar changes and, instead of dying out, they merely evolve into a form that reflcts the change of the poles. (Most radiolarians have thee tint shells with unique twists and patterns)

We use radiolarians as key indicators for oil exploration


Well farmer is the damn geologist here, but my understanding is that there are several hundred polar reversals recorded in the geological record, primarily indicated by the preserved polarity of formerly liquid basaltic rock on both sides of upwelling sones between plates in the pacific/Indian ocean and other areas.

From the perspective of fluid mechanics and electrodynamics earth's nagnetic field is the result of quasi stable circulating convection currents of molten iron carrying heat from earth's fissioning core to the outer mantle. Like most convection currents, even those involving slow moving viscous fluids (low Reynold's numbers), these flows exhibit chaos in their detailed variations but a quasi stability in their gross characteristics. Volcanism resulting from a thinning or fault in the mantle or just the slowly varying flow patterns of the molten magma can significally alter the local strength and orientation of the earth's magnetic field. The reversals are not well understood, but known to have occurred, and certainly result from fairly rapid changes in the circulating magma currents. My understanding is they take place over a span of centuries, but farmerman can probably offer more accurate info on this.

During a long interregnum with a highly weakened magnetic field the incidence of high energy penetrating solar ratiation on the earth's surface will be increased by a factor of at least ten (not nearly enough for mass deaths, but lethal over time), and, without the deflecting effect of the magnetic field, the earth's atmosphere will be slowly stripped away. Based on the available geological evidence, none of the previous reversals has gone slowly enough to significantly reduce the atmosphere. There have been a lot more magnetic reversals than mass extinctions in the earth's geological record.
farmerman
 
  1  
Reply Tue 31 Aug, 2010 08:21 pm
@georgeob1,
MAjor polar reversals have been given names by which we can detect them in magma and sedimentary rocks. (Remember that, because the plates are always moving, we have to conduct what are called palinspastic analyses wherein we correct the paleomagnetics with tectonics.
You are correct that there were many mag reversals but we actually measure the time operiods (in chrons) during which the normal or reversed magnetics prevail. Thus the sediments or cooling magma along ocean ridges record these chrons like stripes in a barcode line on a soda bottle.
Chron data gives each geological timespan in a system series or stage, a unique name and alphanumeric title(eg C3n[4n]) describes the time period of stratigraphy in the earliest Pliocene period. It conforms to a specific stratigraphic range of time/sediment.

The chron methiod is mostly important for cultural and paleo anthropological analyses where some geologist is called in on a archeo site to describe the geology. Usually, in the past, one could only describe a uniquely local geologic sequence. But with chron numbers, we can identify the actual time stratigraphic sequence that is unique to that time peweriod worldwide. It applies to sediments, marine sediments, magmas and metamorphics.
I use it in mineral resource evaluations where I may need to (for example), identify a really good deposit of cement rock that is low Magnesium. I can go do a lot of drilling, or I can, do an initial field survey and seek out rocks of a specific chron where, in a regional basin, shows that the limestones contain high Calcium and low magnesium. Saves some time in initial exploration.

The thing that concerns me is that, during the time period that the dipole dissapears and the mag field decays to almost zero, there is a period of time that, maybe less than a few hundred years, could be an environmental nightmare to folks who live in, say Denver or Santiago.
georgeob1
 
  1  
Reply Tue 31 Aug, 2010 09:20 pm
@farmerman,
I have seen some of these charts for the polar reversals in the record of sea floor spreading. My vague impression is that the reccord shows something over a hundred such reversals. Is that about right? You are correct about the increase in radiation intensity during periods of low strength in the earth's magnetic field. It is interesting to note that there have been many more polar reversals than mass extinctions. I don't know how the geologic time scale for these polar reversals fits with what is known about the evolution of life forms, but that might lead to some interesting conclusions.
farmerman
 
  1  
Reply Wed 1 Sep, 2010 03:07 am
@georgeob1,
Remember, only 2 of the five big mass extinctions are bounded by a pole reversal. Obviously something else is in play.
There are actually about 125 reversals in the Tertiary alone. the "chrons" asystem records the interval of either normal or reversed polar conditions from a worldwide basis.
The reversals in the Mesozoic are only recordeable from a few sites and from the PAleozoic, fewer still. Reson is that with tectonic activities it is difficult to ID these old intervals.

parados
 
  1  
Reply Thu 2 Sep, 2010 05:37 pm
@farmerman,
Quote:
Remember, only 2 of the five big mass extinctions are bounded by a pole reversal. Obviously something else is in play.
There are actually about 125 reversals in the Tertiary alone.

I don't know.... Coincidence might be what is in play.
farmerman
 
  1  
Reply Thu 2 Sep, 2010 05:39 pm
@parados,
Thats the point.

parados
 
  1  
Reply Thu 2 Sep, 2010 06:47 pm
@farmerman,
farmerman wrote:

Thats the point.



Ouch!!!

Why did you sharpen it so much?
0 Replies
 
Eorl
 
  1  
Reply Thu 2 Sep, 2010 07:23 pm
I there any evidence that meteor impacts can be aligned with polar reversals? The impacts could slow or accelerate the rotation of the crust against the core. Also explains extinction concurrency (and non-concurrency depending on angle of impact)
roger
 
  1  
Reply Thu 2 Sep, 2010 08:07 pm
@Eorl,
My off hand quess it that if they were large enough to have effect, that would explain any extinctions related to pole reversals.

Just a guess, remember.
Eorl
 
  1  
Reply Thu 2 Sep, 2010 10:06 pm
@roger,
Yeah same here. It was actually thinking about large impacts that got me theorizing about the cause of the magnetic field in the first place, ie. crust/core differential.
0 Replies
 
High Seas
 
  1  
Reply Thu 2 Sep, 2010 10:24 pm
@farmerman,
farmerman wrote:
...
The reversals in the Mesozoic are only recordeable from a few sites and from the PAleozoic, fewer still. Reson is that with tectonic activities it is difficult to ID these old intervals.

But the more recent timeline isn't in doubt? http://www.pbs.org/wgbh/nova/magnetic/timeline.html
http://www.pbs.org/wgbh/nova/magnetic/images/timeline.gif
farmerman
 
  1  
Reply Fri 3 Sep, 2010 04:34 am
@High Seas,
weve actually given names to normal and reversed sequences in the Tertiary and Quaternary. In oil exploration, the old chestnut of "drill to the Eocene" is assisted by worldwide correlation of "Chron sequences" defined by paleomags.
0 Replies
 
farmerman
 
  3  
Reply Sun 16 Jan, 2011 08:06 am
Is the predicted reversal closer than we think?
Several lines of evidence point to this.

1"P" wave deflections in specific seismic areas (Ring of fire along the Asiatic side) indicate a aslight change in viscosity within the mantke core ouple,

2Increasing vulcanism in several tectonic margins. (As of 1/14/11 there were about 21 recently active volcanoes and about 10 others that were alrady erupting,-This includes Etna which only began erupting in the last week).

3The N pole is wandering at an increased rate of speed (About 75 km/yr)

4The dipole strength is decreasing and several other dipoles have shown up in the mid PAcific.

As a result, several USAIrports have recently shut down specific runways to "Repaint" their cardinal directions on the ends.

It takes several centuries for the poles to reach full reversal and then a time period of reversed polarity exists (like the Cretaceous). Will our gizmos get cooked in the sky? Will our atmosphere bestripped away like old paint? Will we deplete our worlds supply of Zinc sun screen?

May we live in interesting times.

JTT
 
  1  
Reply Sun 16 Jan, 2011 11:32 am
@farmerman,
Quote:
Will our atmosphere bestripped away like old paint?


If that happens will we have to use aqualungs, Farmer?
0 Replies
 
tsarstepan
 
  1  
Reply Sun 16 Jan, 2011 11:36 am
@farmerman,
I recently heard a week or two ago about the Florida airport that had to change it's runway plan around:
Magnetic North Pole Switch Has Airport Scrambling
by STEVE NEWBORN
http://www.npr.org/2011/01/07/132743598/switch-in-magnetic-north-pole-has-airport-scrambling
littlek
 
  1  
Reply Sun 16 Jan, 2011 11:41 am
@tsarstepan,
More from NPR:
http://www.npr.org/2011/01/14/132934010/following-a-wandering-north-pole
tsarstepan
 
  1  
Reply Sun 16 Jan, 2011 11:52 am
@littlek,
If the North Pole travels to Siberia then the RUSKIES WIN! Crying or Very sad
(Listening to Sir Ira Flatow right now)
0 Replies
 
georgeob1
 
  1  
Reply Sun 16 Jan, 2011 02:04 pm
@tsarstepan,
Airport runways are labelled with the magnetic heading of their orientation - to the nearest 10 degrees. In fact many airport runways are oriented 3 or 4 degrees left or right of their named direction, just as a matter of routine rounding to the nearest 10 degree increment. All that is required is a two or three degree shiuft in local variation (not an unusual occurrence) to require an adjustment in the runway label.

Such adjustments occur every year in several places. What is unusual in this case is that some news reporter made a big deal out of it.
 

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