North to South

There are some truths on which one should always be able to rely.  For example, the sky is blue, the Chicago Bears will lose to the Green Bay Packers, the Pope is Catholic, and that north is north.  When using a compass, the arrow will point to magnetic north, which is not the same as the North Pole.  Some world maps show both the North Pole and magnetic north, but magnetic north is fluid.  The location of magnetic north is dependent upon the inner workings in the center of the earth.  Scientists now think that the earth is nearing a time when the poles will reverse.

Magnetic pole influence

A NASA article notes that over the past 20 million years, the earth has settled in a pattern of pole reversal of every 200,000—300,000 years.  The last known pole reversal was 781,000 years ago, so in geologic time frame, we are due for another pole reversal.  If the poles reverse, my compass will no longer point north, but instead will point south.  If you were to take your compass and hop in Doc Brown’s DeLorean, and go back in time 800,000 years, you would find the compass pointing south.  If you went back 500,000 years ago it would be located in the north, similar to what is today.    The magnetic field, however, is important to more than our compass.

Cross section of the earth

The earth’s magnetic field is due to the big ball of iron that is located at the core of the earth, and that core is surrounded by a layer of molten metal. Changes in core temperature and the rotation of the earth swirl this liquid, molten metal and create the magnetic  field.   As the core’s temperature changes the boiling in one part of the outer core slows down and releases fewer charged particles.  This weakens the magnetic field.  The European Space Agency (ESA), has been tracking magnetic field and other data from its Swarm satellite.  The magnetic field produced by this activity rises up to 370,000 miles above surface of the earth.  This protects us against solar and cosmic radiation.  ESA reports that large weak spots in the magnetic field have popped up over the Western Hemisphere.  A weakened magnetic field could lead to higher cancer rates as solar and cosmic rays penetrate the atmosphere and reach earth.  Perhaps we in the Western Hemisphere need to be more careful outside, but this is particularly true if you are a red head.   

Map showing alteration in magnetic field, blue it is being reduced
red indicates where field is increasing

NASA reports that magnetic north has moved northerly by more than 600 miles since the early 19^th century.  (Magnetic north was never aligned, at least in modern times, with the North Pole.)  Explorers of that era precisely located magnetic north.  However, it is now reported that the movement of magnetic north  is about twice the rate than it was about 100 years earlier.  Physics.org notes that evidence would appear to indicate that the magnetic field slowly fades out before reappearing with the poles reversed.  So the weakening in the Western part of the globe has some scientists wondering if we are in the midst of an upcoming pole reversal.  However, the magnetic field over the Indian subcontinent has been strengthening. 

This image indicates the movement of magnetic north

What is interesting is how scientists were able to find evidence of pole reversals.  It is not like it was written down nearly 800,000 years ago in a cave in France, or a rift valley in Africa the last time it happened.  They know this from studying rock layers.  As you recall from early science there are three types of rocks, igneous, metamorphic and sedimentary.  Igneous rocks are formed by the flow of lava and lava contains metal oxide particles.  These metal oxide particles when cooled will essentially be frozen in the direction of the prevailing magnetic field.  By studying past lava flows, hopefully hot upset by earthquake activity, scientists know the historic position of magnetic north.  Rocks of the ocean floor and in Italy have been studied, and to date they point to 170 magnetic pole reversals during the last 100 million years. 

Volcanic spring which contains metal oxide particles

Are they occurring more frequently?  If the last one occurred 781,000 years ago, it would seem not likely since the average spacing is about 588,000 years between reversals over the 100 million year time period.  If you wish to really get back in time, it is also thought that there have been more flips between 500 million and 1.5 billion years ago, than 1.5 to 2.9 billion years ago.   Why is this occurring?  One explanation is that the inner core is slowly growing as the outer core cools and solidifies.  They theorize that as this occurs the pole flips would occur more frequently.  The idea is just like a bigger prostate restricts the urinary tract leading to less output, so too does a larger core become an obstruction to currents in the fluid outer core, leading to a less stable magnetic field.  A less stable magnetic field apparently leads to more pole reversals.

Standard field compass

Fortunately, the historical record does not seem to support any doomsday scenarios where mass destruction of life on earth was affected by a pole reversal.   Geo-physicists have studied oxygen isotopes in the rock to believe that the pole reversal does not affect the rotation of the earth.   However, modern society was long in the distant future when the last reversal occurred, and the population of the earth has become dependent upon electricity, and it is possible that communication systems and power grids would be most at risk.  Then again, these systems, as we were told, were not to have survived intact in Y2k. (To me Y2k was conceived by some IT people as a IT full employment act.)  So, if this is to occur, over what course of time does the reversal occur?  One article, in Scientific American, quotes the manager of the ESA Swarm project as saying “Such a flip is not instantaneous, but would take many hundred (sic) if not a few thousand years.”  However, Paul Renne, a professor at the University of California at Berkley in earth and planetary science, says in Techtimes.com, that their study of rocks and data indicated that at least the last one “had to have happened very quickly, probably in less than 100 years.” 

The movement of magnetic north should not disrupt
the delivery of goods on Christmas

So perhaps in my grandchildren, or even children’s life time, they will see magnetic north become south.  Perhaps their cell phone may not work for a while, and they may be more susceptible to cancer due to the weakening magnetic field.  The poles should still be the poles, the sky will still be blue, and contrary to what some in the US church hierarchy may think, the Pope will still be Catholic.  While we can always hang on to some certainties, I would not want to be the person out for a backpacking trip and have my compass is giving me the wrong bearing.   

Images from Google Images