Earth's Magnetic Field Weakening

[Raven]

I was watching a NOVA episode that talked about how there are clear signs that Earth's Magnetic Field is weakening at a fairly rapid rate -- a found it very interesting. According to the scientists interviewed, it's undeniably weakening but no one has an explanation. At its current rate of dissipation, the Earth's magnetic field will be absent in a thousand years.

One theory, however, suggests that the Earth is preparing to shift poles (north becomes south and south becomes north). In the past this has happened fairly frequently (approximately once every 200,000 years). The thing is, it hasn't happened in the past 780,000 years and seems we are a bit overdue.

Any opinions on whether you believe the Earth's magnetic field may be getting ready to flip?

 

[chemical]

i read about that somewhere else. it is due to swap in the next couple of 1000's of years (i think), and it would be interesting to see a compass point the other way!

 

[Phobos]

All the talk I hear about it from scientists pertains to a flip. I have not heard predictions (from scientists) about it disappearing altogether.

 

[chroot]

Originally posted by Phobos
All the talk I hear about it from scientists pertains to a flip. I have not heard predictions (from scientists) about it disappearing altogether.

A flip has to involve a disappearance of the field first. The field dissipates to zero, and then rebuilds. When the field comes back, it can come back either in the same polarity as before, or with opposite polarity.

- Warren

 

[ranyart]

There is evidence that the Earths magnetic field undergoes regular reversals, "Flips".

Good link with projected data:http://www.psc.edu/science/Glatzmaier/glatzmaier.html

 

[Raven]

Originally posted by chroot
A flip has to involve a disappearance of the field first. The field dissipates to zero, and then rebuilds. When the field comes back, it can come back either in the same polarity as before, or with opposite polarity.

- Warren

I'm no expert of course, but according to the NOVA documentary on this subject, the scientists do not expect a complete disappearance of the magnetic field if it intends to flip. They only predict a drop of strenght to as low as 10-20% of what it is today. That in itself seems scary enough. Also they predict this drop to occur during the next 1000 years, but they do not have any idea when the actually flip will occur.

The Earth could remain in the 10-20% strength level for another 1000 years which has occurred in the past. It is also said that during this time the magnectic field will not have a designated north or south pole. In fact a compass would be completely useless since polarities of north and south will appear in various parts of the earth. The danger of having a magnetic field so low in strenght is that the solar winds will be able to penetrate the Earth's atmosphere with greater intensity and greater radiation. The good thing about it will be that aurora lights will be seen almost all over the world.

 

[Kerrie]

isn't there a point in the hudson bay that used to be where the north pole once was?

 

[Nommos Prime (Dogon)]

Look to Mars for Evidence of Magnetic Field Reversals

Mars' magnetic field recently reactivated (according to Viking data). This was confirmed by more recent observations from later US probes.
Comets/asteroids and massive solar storms have the ability to strip away or reverse planetary magnetic fields. The Russians and James McCanney have done some good work on this subject.

 

[LURCH]

There is also a thread about this in the "Earth" Sciences Forum (in "Other Sciences"). Polar inversions are a natural behavior of dynamos, so it is suspected that the Earth's magnetic field is created by a large dynamo in the core.

I have also heard it suggested that polar inversion accounts for the starnge alignment (or missalignment) of neptune's magnetic poles. We may actually be observing them in mid-flip. This of course is not the only proposed explanation, and makes no account for the alignment of the axial poles.

 

[Raven]

Originally posted by Kerrie
isn't there a point in the hudson bay that used to be where the north pole once was?

I am not familiar with that. I have heard, however, that there are areas near the north and south pole today in which a compass would be confused and spin or point in the wrong direction (not north). Some of this has to do with the difference between True North and Magnetic North. But scientists have also discovered anomalies in the southern area of the Earth in which north magnetic polarities occur and areas in the north where south magnetic polarities occur. It is suggested that as the Earth's magnetic field weakens, more of these anomalies will occur until the final polar shift completes.

Originally posted by Nommos Prime
Mars' magnetic field recently reactivated (according to Viking data). This was confirmed by more recent observations from later US probes.
Comets/asteroids and massive solar storms have the ability to strip away or reverse planetary magnetic fields. The Russians and James McCanney have done some good work on this subject.

Wow. I find really fascinating. I would like to hear more about it and will probably research it on my own. Any sites that you know of that shares this info?

 

[Nommos Prime (Dogon)]

The Martian Magnetic Spectre

Woops, posted the same stuff twice, and can't work out how to delete it.

 

[Nommos Prime (Dogon)]

The Martian Magnetic Spectre

All my Viking data is unfortunately in paper form, and I can’t locate it on the Internet yet (not surprising). But I’ll start from NASA’s latest admission, in August 1997. Here goes;

From the “Martian Magnetic Field Missions”;
http://denali.gsfc.nasa.gov/terr_mag/mars_missions.html

Here’s the Press Release from NASA (woops, better bury this one someone thought!);
http://www.qadas.com/qadas/nasa/nasa-hm/1004.html

Because then they claimed they were “localised”;
http://mgs-mager.gsfc.nasa.gov/press/release_1999-56_field.html

It then became “crustal”, rather than of “dynamo” origin;
http://solid_earth.ou.edu/readings/mars_mag_field.html

http://mgs-mager.gsfc.nasa.gov/publications/grl_28_connerney/images/grl_28_connerney_cover_black.jpg

The next bits from;
http://isaac.exploratorium.edu/~pauld/activities/magnetism/magnetismofplanets.html

“Mars does not have a strong dipole magnetic field and so does not have auroras circling its poles. However at one time it had a strong magnetic field which was recorded in molten volcanic rocks creating stripes like those due to continental drift on earth.
Red and Blue stripes on Mars record an ancient Martian magnetic field which changed its polarity.”

Here’s a nice little paper called “Paleomagnetic Pole Positions And Reversals Of Mars” by J. Arkani-Hamed.
http://www.lpi.usra.edu/meetings/lpsc2001/pdf/1478.pdf

Martian Magnetic Anomalies;
http://www.geophys.washington.edu/People/Students/eharnett/mars/mars.html

http://www.planetary.org/html/news/articlearchive/headlines/1997/headln-091897.html
Here’s the NASA stuff (even they concur – although its mostly typical pseudo-scientific “double-speak”);
http://denali.gsfc.nasa.gov/terr_mag/onldoc.html

Here’s a nice quote from NASA, in the below website;
“Second, the Martian magnetic field may have reversed direction less frequently, which would have given more time for anyone field direction to imprint itself in the steadily moving crust, resulting in wider bands.”
http://science.nasa.gov/newhome/headlines/ast29apr99_1.htm

and an oldie from ’78;
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978opm..conf...84R

That’s the saga from 97.

Other froot-loops like myself and some Russians have been doing some fringe work on the reactivation of Mars’ magnetic field. I don’t have a website, and I’m sure how many of you understand the Russian way of things (eg. they refer to space as the “vacuum medium”). For an idea on how comets/asteroids effect magnetic fields, have a suss at McCanney’s site;
http://www.jmccanneyscience.com/

If anybody wants a summary of the Viking data, drop me a line.

 

[russ_watters]

Originally posted by Kerrie
isn't there a point in the hudson bay that used to be where the north pole once was?

Probably. It moves pretty fast. http://www.geolab.nrcan.gc.ca/geomag/northpole_e.shtml

 

[CrazyEYe]

Video

This Video might be interesting because I saw the Nova video also and this is from it (I watched it in school)

http://www.pbs.org/wgbh/nova/magnetic/reversals.html

it's on the left side click on the picture (sorry if this is spam I don't think it is.)

this talk about the entire world changing poles is making my stomach weird fealing lol.

i'm hoping I get to live after the Magnetic poles switch that will be so cool.(i'm 15 so I'm not sure :S)

 

[ZaUS22]

I read that by studying lava samples it was determined the Earth’s magnetic field has reversed about 18,000 times in 20 million years--I wonder what will happen to us if it were to occur in our lifetime

 

[Chronos]

The last flip occurred about 780,000 years ago. I doubt we are in any immediate peril. See http://news.nationalgeographic.com/news/2004/09/0927_040927_field_flip.html

 

[Vanadium 50]

I read that by studying lava samples it was determined the Earth’s magnetic field has reversed about 18,000 times in 20 million years

Where did you read that? This sounds very, very high. That's every 1100 years.

 

[jixon]

Not to worry; the super volcano under Yellowstone will blow, removing the need to worry about compasses not working or excess RADiation from the Sun.

 

[Saul]

Yes the Earth's geomagnetic field is weakening. Why it is weaken, why it weakened in the past, and will it continue to weaken is not known.

The following comments are on based a presentation by Gubbins where he discussed geomagnetic observations that currently have no explanation in some detail. (i.e. He explained why current mechanisms could not explain what is observed.)

It has been found that the geomagnetic field intensity drops in magnitude by a factor of 5 to 10 from current levels for approximately 20% of the time. The abrupt drops in the geomagnetic field intensity are called geomagnetic excursions (failed field reversals). The geomagnetic excursions correlate with abrupt changes on the planet surface. One theory hypotheses that the abrupt changes on the surface of the planet Earth causes the abrupt changes to the geomagnetic field.

http://www.ipgp.fr/~dormy/Publications/MD03.pdf

Asymmetric behavior of magnetic dip poles

The north magnetic dip pole velocity has more than doubled in the last 30 years. This observation, together with the decrease in the Earth’s magnetic dipole intensity over the last century has raised the concern of a possible approaching polarity reversal. We show that this rapid variation is in fact to be expected, and will not affect the dipolar field as a whole, but only the north magnetic pole. We demonstrate how this rapid displacement of the north magnetic pole is made possible by the horizontal field morphology. This rapid variation of north magnetic pole position does not imply any important modification of the core processes associated with field generation. The north magnetic pole position being very sensitive to small as well as rapid variations of the field, we show that it can very effectively be used as a passive tracer (or indicator) of field variations. Indeed, its velocity over the last century very accurately indicates the geomagnetic impulses (or jerks) that were so far observed only in observatory data.

http://eprints.whiterose.ac.uk/416/1/gubbinsd4.pdf

Is the geodynamo process intrinsically unstable?Recent palaeomagnetic studies suggest that excursions of the geomagnetic field, during which the intensity drops suddenly by a factor of 5 to 10 and the local direction changes dramatically, are more common than previously expected. The `normal' state of the geomagnetic field, dominated by an axial dipole, seems to be interrupted every 30 to 100 kyr; it may not therefore be as stable as we thought.

Recent studies suggest that the Earth's magnetic field has fallen dramatically in magnitude and changed direction repeatedly since the last reversal 700 kyr ago (Langereis et al. 1997; Lund et al. 1998). These important results paint a rather different picture of the long-term behaviour of the field from the conventional one of a steady dipole reversing at random intervals: instead, the field appears to spend up to 20 per cent of its time in a weak, non-dipole state (Lund et al. 1998). One of us (Gubbins 1999) has suggested that this is evidence of a rapid natural timescale (500 yr) in the outer core, and that the magnetic field is usually prevented from reversing completely by the longer diffusion time of the inner core (2-5 kyr). This raises a number of important but difficult questions for geodynamo theory. How can the geomagnetic field change so rapidly and dramatically? Can slight variations of the geomagnetic field affect the dynamics of core convection significantly? If so, is the geodynamo process intrinsically unstable?

 

[Saul]

The following are more papers by authors that are trying to understand what causes the geomagnetic excursions. As the geomagnetic excursions correlate with abrupt climate change one theory is the increase in the ice sheet mass changes the planet's inertia which in turn cause the geomagnetic excursion. That is an interesting hypothesis. The geomagnetic excursion also correlate with the end of the interglacial periods. There must be some event that abruptly causes the planet to cool again and again. A side affect of that forcing event is it causes a geomagnetic excursion.

http://www.ias.ac.in/currsci/apr252003/1105.pdf

The effect of changes in the Earth’s moment of inertia during glaciation on geomagnetic polarity excursions and reversals: implications for Quaternary chronology

Geomagnetic polarity reversals and excursions in the Quaternary correlate well with interglacial-to-glacial transitions and glacial maxima. It is suggested that this relationship results from interactions between the Earth’s mantle and core that accompany decreases in the Earth’s moment of inertia during ice accumulation, which weaken the geomagnetic field in order to try to counter the decrease in differential rotation between the mantle and inner core that is being forced. In the Late pleistocene, geomagnetic excursions directly correlate with brief phases of rapid ice growth that accompany falls in global sea-level, notably during the Younger Dryas stage, Dansgaard–Oeschger interstadials 5 and 10 that precede the rapid melting events during Heinrich events H3 and H4, and during the transitions between oxygen isotope stages 5c-5b, and 5e-5d. It is proposed that similarrelationships between instabilities in climate and the geomagnetic field also typefied the Middle Pleistocene. As a result of the transfer of some of the mass of the oceans into polar ice sheets, the climate instabilities that initiate these rapid ice accumulations redistribute angular momentum and rotational kinetic energy between the Earth’s mantle and inner core. These changes weaken the Earth’s magnetic field, facilitating geomagnetic excursions and also causing enhanced production of cosmogenic nuclides, including 14C. The subsequent phases of rapid ice melting, Heinrich events, reverse this effect: strengthening the field. This explanation, of forcing of geomagnetic excursions by climate instabilities, provides a natural explanation for why, during the Middle-Late Pleistocene, excursions have been numerous but none has developed into a polarity reversal: the characteristic duration of the climate instabilities is too short. River terrace aggradation, in Europe at least, is also likely to be concentrated during Heinrich events. The most important of these can now be dated throughout the Middle and Late Pleistocene, as they are expected to lag the geomagnetic excursions by no more than ~ 2 ka. Timings of these fluvial aggradations could also be constrained by observation of in situ production spikes of cosmogenic nuclides such as 10Be, which would allow direct correlation with the geomagnetic excursions.

http://www.springerlink.com/content/k6x20160542j846q/

Paleomagnetic excursions recorded in the Yanchi Playa in middle hexi corridor, NW China since the last interglacial

Paleomagnetic determinations on lithological profiles of two paralleled long drilling cores covering the past 130 kyr B.P., GT40 and GT60, from the Yanchi Playa in the arid Northwestern China, indicate that a series of pronounced paleomagnetic excursions have been documented. By correlating our results with published regional and worldwide reports, 4 excursion events out of 10 apparent reversal signals (labeled from GT-1 to GT-10) were identified as excursion events coeval with the Mono Lake Event (28.4 kyr–25.8 kyr), Laschamp Event (43.3 kyr–40.5 kyr), Gaotai Event (82.8 kyr–72.4 kyr) and the Blake Event (127.4 kyr–113.3 kyr), respectively. GT-9 correlates with the above-mentioned Gaotai Event, GT-7 and GT-6 correspond to two stages of the Laschamp Event and GT-5 to the Mono Lake Event. It is noteworthy that the so-called Gaotai Event has not been reported as a pronounced paleomagnetic excursion in the Northwestern China. Every magnetic excursion event corresponds to paleointensity minima, anteceding those established abrupt paleoclimatic change events, such as the Younger Drays and the Heinrich Events (H1–H6). Here, we tentatively propose that these geomagnetic excursions/reversals can be viewed as precursors to climate abruptness. During the transitional stages when the earth’s magnetic field shifted between a temporal normal and a negative period, the earth’s magnetic paleointensity fell correspondingly to a pair of minima. Although more precise chronology and more convincing rock magnetic parameter determinations are essentially required for further interpretation of their intricate coupling mechanism, these results may have revealed, to some extent, that the earth’s incessantly changing magnetic field exerts an strong influence on the onset of saw-tooth shaped abrupt climate oscillations through certain feedback chains in arid Central Asia or even North Hemispheric high latitude regions.

 

[Philosophaie]

The sun flips polarity about every 11 years. Its cycle changes the amount of solar activity from little to a peak around reversal time. The next sun reversal will occur in 2012.

 

[Saul]

The sun flips polarity about every 11 years. Its cycle changes the amount of solar activity from little to a peak around reversal time. The next sun reversal will occur in 2012.

The mechanisms that drive the solar magnetic cycle are quite different than what creates and changes the Earth's geomagnetic field. Current hypothesized mechanisms cannot explain all observations for either body.

Theoretical Limitation of the Geomagnetic Field Mechanism
For the geomagnetic field the recent finding of very fast field intensity and direction changes is approaching the physical limit of the liquid core mechanism's capability to physically cause. As the Earth's mantel is conductive, any core change in the field intensity or direction is dampened by an opposing field that is created in the mantel. The same issue of a counter acting field resisting a field intensity or direction change occurs in the liquid core.

Due to the issue of counter acting opposing field generation, a fast geomagnetic field change must theoretically be created by a change in flow at the top of the liquid core of the planet.

Because there is no direct measurement of what is happening in the liquid core it was and is assumed the past and current geomagnetic field changes that are observed were and are due to liquid core changes. There is no physical explanation as to what could cause the rapid changes in the Earth's core.

Recently it has been found that in the recent past there have been what is called archeomagnetic jerks (different than geomagnetic jerks) where the geomagnetic field changes in direction/orientation by 10% to 15%. (The geomagnetic field no longer aligns with the planet's rotational axis.) There have been 10 archeomagnetic jerks found in the last 5000 years with a periodicity of roughly 500 years. What is causing the archeomagnetic jerks is not known.

http://www.nature.com/ngeo/journal/v1/n6/abs/ngeo203.html

Rapidly changing flows in the Earth's core
A large part of the Earth's magnetic field is generated by fluid motion in the molten outer core1. As a result of continuous satellite measurements since 1999, the core magnetic field and its recent variations can now be described with a high resolution in space and time2. These data have recently been used to investigate small-scale core flow3, 4, but no advantage has yet been taken of the improved temporal resolution, partly because the filtering effect of the electrically conducting mantle was assumed to mask short-period magnetic variations5. Here we show that changes in the magnetic field occurring over only a few months, indicative of fluid flow at the top of the core, can in fact be resolved. Using nine years of magnetic field data obtained by satellites as well as Earth-based observatories, we determine the temporal changes in the core magnetic field and flow in the core. We find that the core flow is spatially localized and involves rapid variations over a few months, with surprisingly large local accelerations. Our results suggest that short-term fluctuations of the core magnetic field are robust features of rapid core dynamics and should be considered in the development of future numerical models of the geodynamo.

 

[Philosophaie]

The sun flips its magnetic field every 11 years. This is a common event although the solar flare activity heightens.

http://solarscience.msfc.nasa.gov/predict.shtml

 

[d3x0r]

Or it's simply that we're measuring the flux and not the force of the field, and moving ever so slightly away from the sun is decompressing (making less dense) the magnetic field we experience in a flux sort of way.

 

[Vanadium 50]

That didn't make any sense. Are you sure you wrote what you intended to write?

 

[DaveC426913]

That didn't make any sense. Are you sure you wrote what you intended to write?

He's sure. He wrote the same thing in another thread, which has been locked. Find posts by d3x0r and you'll see what he's been up to.

 

[shredder666]

Just wondering, did magnetic pole reversals ever coincide with mass extinctions?

 

[rover2012]

The last flip occurred about 780,000 years ago. I doubt we are in any immediate peril. See http://news.nationalgeographic.com/news/2004/09/0927_040927_field_flip.html

why not.

 

[rover2012]

what do you think happens during a magnetic poler reversal?

 

[DaveC426913]

why not.

Because, geologically, they happen all the time. I don't think there are any extinction events correlated with pole reversals. Sure, it'll prolly require us to rejig our communications, which will cause people to change careers, but in the larger scheme, not so much.

 

[davenn]

The sun flips polarity about every 11 years. Its cycle changes the amount of solar activity from little to a peak around reversal time. The next sun reversal will occur in 2012.

Not quite right :) ... you are getting a bit confused, The 11 (approx) year cycle always changes polarity at solar minimum which we have just had and are slowly clawing our way out of. Solar max is at 2012-2013 approx

The sun flips its magnetic field every 11 years. This is a common event although the solar flare activity heightens.
http://solarscience.msfc.nasa.gov/predict.shtml

Also not quite right... You need to remember that there are 2 magnetic cycles happening in the sun.
1) ... the reversal of the sunspot magnetic fields 11 years and
2) the reversal of the actual solar magnetic field which is 22 yrs.

That article you cited is referring to the sunspot cycle ( ~ 11 yrs) I say ~ 11 yrs because it isn't a constant length of time. This last cycle transition from cyc23 to cyc24 produced one of the longest minimum period for a 100+ years

cheers
Dave

 

[davenn]

Originally Posted by ZaUS22
I read that by studying lava samples it was determined the Earth’s magnetic field has reversed about 18,000 times in 20 million years.

Where did you read that? This sounds very, very high. That's every 1100 years.

Agreed, Vanadium, in my Geology studies at uni, I would suggest more likely 8times in 20 million yrs.
Looking through the records the flipping is very random in the time periods between flips.

It was the early work on continental drift and seafloor spreading that lead researchers to tow magnetometers behind ships

Dave

just reading through my notes... Cox and Dalrymple who pioneered magnetic flip studies (on land) with their initial work on lava deposits in the Owens Valley, California. They were, after a few years (by 1966), able to confirm 9 reversals in the last 4 million years
It was Vine and Matthews of Cambridge Uni (England) that finally deciphered that the data was showing and were able to conclusively prove seafloor spreading

 

[rbluesky]

I am not a scientist, so please forgive my clumsiness with the following :

Is it true that the Earth has a "hole" in its magnetic field near Brazil?

Is it true that there has been a rapid increase in the amount of nutrenos in the Earth's atmosphere?

Is it true that the Earth's magnetic field is not only weakening at an increasing rate but also "true North " has shifted 60 miles in the past year?

IF ALL of these statements are true then, well, doesn't this fall into the Mayans end of days ?

"... at last I have the answer! But what was the question?"

Thank-you for reading this!
I am forever amazed at the wonders of the universe.
Rita

 

[qraal]

I am not a scientist, so please forgive my clumsiness with the following :

Is it true that the Earth has a "hole" in its magnetic field near Brazil?

The South Atlantic Anomaly could be called a hole.

Is it true that there has been a rapid increase in the amount of nutrenos in the Earth's atmosphere?

No. Did you get that from "2012" the movie? Total rubbish.

Is it true that the Earth's magnetic field is not only weakening at an increasing rate but also "true North " has shifted 60 miles in the past year?

The magnetic pole shifts around quite a bit, but "True North" is the direction of Earth's rotational axis, which most definitely hasn't moved. You'd know about it if it had.

IF ALL of these statements are true then, well, doesn't this fall into the Mayans end of days ?

"... at last I have the answer! But what was the question?"

Thank-you for reading this!
I am forever amazed at the wonders of the universe.
Rita

The "Mayan End of Days" has nothing to do with the end of the world. It's just when the Mayan calendar resets. Start of a new epoch, in one time-keeping system. It corresponds to nothing magical or catastrophic, aside from the perfervid imaginings of bored/gullible non-Mayans. The Maya are still around and resent the misuse of their calendar.

 

[cmb]

YU55 - I have gone to the trouble of calling your bluff here, so please do explain your hypotherflappery with respect to the following data:

http://i1177.photobucket.com/albums/x345/chris20055/ice_sheets_versus_geomag.jpg

Please do explain the correlations, for my education...

 

[cmb]

I'll take your graphic as correct. I don't know where that data comes from, I don't claim to know much about mag field reversals.

So plotting it against the ice sheet graphic... I still don't see the correlation you are implying:

http://i1177.photobucket.com/albums/x345/chris20055/ice_sheets_recent_geomag.jpg

 

[Evo]

There hasn't been a reversal for ~780,000 years.

Thread locked pending moderation and moved to Earth sciences.

Also thanks to Andre, the Gothenberg "flip has indeed been debunked, it was a bad sample. It also doesn't coincide with any extinction.

The Gothenburg "Flip"
In the case of the Gothenburg "flip," which Hancock (1995) misidentified as a "magnetic reversal, FOG again provided a poorly researched analysis. The still unproved Gothenburg "flip," if real, was a rapid and brief change of magnetic field that occurred about 12,350 BP. It was not a real magnetic reversal. The last true magnetic reversal occurred 730,000 years in the change from the reverse polarity of the Matuyama Magnetic Epoch to the normal polarity of the Brunhes Magnetic Epoch. The Gothenburg "flip," as proposed by Morner (1971) and reported by Anonymous (1972), is more properly called a "magnetic excursion" because the Earth magnetic field did not reverse itself permanently but briefly changed without complete reversal over the period of a few years. For this event to represent Earth crustal displacement, the Earth's crust at about 12,350 BP would have to shift 180 degrees one direction and shift another 180 degrees back to its exact original position within the space of a few years. The timing of the Gothenburg "flip" fails to match any proposed Earth shift by either Hapgood (1970) or Flem-Ath (1997) in either timing or amount of predicted shift. Also, the validity of the Gothenburg excursion has been challenged by a number of studies which repeated have failed to detect its presence in a number of paleomagnetic records that cover 12,350 BP. At this time there is considerable question that the Gothenburg excursion even occurred and, in fact, the result of soft sediment deformation (Jacob 1994:103-107).

continued...

http://www.intersurf.com/~chalcedony/FOG10b.html

See existing thread https://www.physicsforums.com/showthread.php?t=525126