What exactly happens during a pole change?

Question

What exactly happens when there is pole change on earth? In my physics class last year I understood it as just the magnetic fields around the earth change, so that only the magnetic poles are changed and everything else stays the same. We really only talked about how it would affect things we use in every day life that use magnants (compasses for example). Then a couple weeks ago I was watching a doomsday 2012 show on the discovory channel and they described (with illustrations) that the world tilts. The more I try to describe what they said the more confused I get and think it does not make sense. But they say it tilts in a way that Canada would be on the equator and like Brazil would be one of the poles. But this would cause major devastation and many people have said there has not been major devastation during the last couple pole changes So did I misunderstand my physics teacher? or did the discovery channel s***w up? or are there theorys saying each one is correct? Google did not really seem to help.

Answer 1

You did not misunderstand your teacher.

Discovery and History and other channels have a horrible habit of misleading the public by misrepresenting science..

The magnetic poles move all the time.

There is a geologic record that shows it has happened many times in our past but not at regular intervals. Time between reversals can be 10000 yrs or a million years.

However - we know that the magnetic field does not collapse in the process - if it did, there would be major extinctions that correlate with the geologic record for pole reversals - there is no correlation.

The latest hypothesis is that the Earth's magnetic field gets chaotic, with lots of north and south poles - so we still have a magnetic field, but compasses will be useless. And then it straightens itself back out, but with north and south reverse.

This is actually similar to what the sun does - but the sun does it on a regular 11 year cycle.

As for when it will happen - those people that observe the magnetic field think it will go through its chaotic thing and reverse some time soon based on how it is currently behaving, but that is a hypothesis waiting for the event to occur to be tested, and the exact date certainly is not known.

Now for the rotational axis and its shift:

The axis of the earth does wobble on several known timescales. These wobbles are known as the Milankovic cycles.

See: http://en.wikipedia.org/wiki/Milankovic_...

Basically the axis of the earth’s rotation does not always point to Polaris (the Pole Star); and we are not always inclined at 23.5 deg. So the poles do move relative to the plane of the earth’s orbit around the sun, and relative to the stars – but the shifts are minor.

As for Canada ending up at the equator etc - it's not due to a shift in the Earth's axis - but plate tectonics and continental drift means that the surface of the earth moves. So place currently at the pole were once close to the poles and continue to move.

Like I said TV channels tends to take perfectly legitimate science that is well-founded and they mix up ideas and mess everything up, misleading their viewers...

Answer 2

You didn't misunderstand your physics teacher.  In physics you were discussing magnetic pole reversal, a phenomenon that we know has happened repeatedly in the past.  To quote the website DoomsDay Information Guide:

"On average, there is a (magnetic pole) reversal around every 400,000 years, but this varies a lot.” The geological record suggests that the last reversal was around 800,000 years ago."

From my knowledge of space physics, while it is possible for the actual rotational axis of Earth to change, to do so would require a huge impact between Earth and another planetoid.  No such impact is predicted (thank goodness) so my guess is that the Discovery channel got it wrong.  The producers of the show probably confused magnetic poles with the rotational poles.  It is necessary to take any science seen on TV and movies with a grain of salt.  I congratulate you for catching this TV shows mistake.  Good job!

Answer 3

The doomsday show you watched was a complete waste of your time, since they obviously didn't explain what they were talking about (probably because they didn't understand the science themselves).

There are 2 definitions for a "pole shift".

The 'pole shift theory' is the hypothesis that the axis of rotation of the Earth has not always been at its present-day locations or that the axis will not persist there; in other words, that its physical poles had been or will be shifted.    

It is now established that true polar wander has occurred at various times in the past, but at rates of 1 degree per million years or less.

So for the Earth's rotation to suddenly change in 4 years is completely ridiculous.

The Earth tilts by 23.5 degrees (in relation to its orbit) and it would take a huge mass in space to alter that in 4 years.  The Earth's axial tilt varies between 22.1 and 24.5 degrees, with a 41,000-year period.  Right now, the tilt is decreasing (in addition to this steady decrease, there are also much smaller short term variations of about 18.6 years).

But this tilt still has the Earth rotating around the same point - the tilt is the angle that axis makes to the Earth's orbit.

The second "pole shift" is actually called geomagnetic reversal - this is the periodic reversal of the earth's magnetic field (effectively switching the north and south magnetic poles).  Geomagnetic reversal has more acceptance in the scientific community than pole shift hypotheses.

At present, Earth's overall geomagnetic field is becoming weaker at a rate which would, if it continues, cause the field to temporarily collapse by around 3000 AD.

Magnetic reversals have occured in the past, but paleomagnetic data indicate that they take millions of years to develop (not 4 years as in the 2012 trash).

Discovery Channel was wrong (or at the very least misleading).