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The earth's magnetic field is constantly changing. In the past, variation from year to year has been not so great so as to make estimates of location unreliable from place to place worldwide, and such practices as land surveying and navigation at sea have been able to use updated maps for currently reliable data. In recent years, however, the magnetic poles (called dip poles) of the earth have been moving more quickly such that services and trades that rely on currently updated locations of the dip poles have had to obtain more frequent assessment and updates.
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Observed north dip poles during 1831 - 2007 are yellow squares.
Modeled pole locations from 1590 to 2020 are circles progressing from blue to yellow.
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[Obviously, the locations for 2020, 2019, 2018 and 2017 are estimates. This present data is current as of 2015.]
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Magnetic poles are defined in different ways. They are commonly understood as positions on the Earth's surface where the geomagnetic field is vertical (i.e., perpendicular) to the ellipsoid. These north and south positions, called dip poles, do not need to be (and are not currently) antipodal. In principle the dip poles can be found by conducting a magnetic survey to determine where the field is vertical. Other definitions of geomagnetic poles depend on the way the poles are computed from a geomagnetic model. In practice the geomagnetic field is vertical on oval-shaped loci traced on a daily basis, with considerable variation from one day to the next.
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It has been long understood that dip poles migrate over time. In 1831, James Clark Ross located the north dip pole position in northern Canada. Natural Resources Canada (NRCan) tracked the North Magnetic Pole, which is slowly drifting across the Canadian Arctic, by periodically carrying out magnetic surveys to reestablish the Pole's location from 1948 to 1994. An international collaboration, led by a French fundraising association, Poly-Arctique, and involving NRCan, Institut de Physique du Globe de Paris and Bureau de Recherche Geologique et Miniere, added two locations of the North Magnetic Pole in 2001 and 2007. The most recent survey determined that the Pole is moving approximately north-northwest at 55 km per year.
Modeled pole locations for magnetic north from 1831 to 2020 [1831.000 - 2020.000 -- these are not observed north pole locations]:
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222.596 85.370 2011.000 217.521 85.676 2012.000 211.982 85.933 2013.000 206.059 86.138 2014.000
199.975 86.289 2015.000 193.710 86.395 2016.000
187.413 86.455 2017.000 181.245 86.471 2018.000 175.346 86.448 2019.000 169.818 86.391 2020.000
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[The
years' data for 2015 and 2017 are in bold - degrees longitude west, degrees latitude north, year.]
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The cause of the earth's magnetic field is not actually known, but there are theories proposed that would explain it. It is thought that some large quantity of ferrous material in the earth's core is moving to produce this field, but how much iron, where exactly it's located and how fast it's moving are all unknowns and up for speculation. One thing scientists can agree on is that wherever this iron is precisely, it exists at a temperature of over 1,000 degrees Fahrenheit, or perhaps even 2,000, which would mean it would be molten at atmospheric pressure, however, since it is expected to have an ambient pressure of hundreds of atmospheres, the liquidity/solidity or whatever state it is in cannot be certain. In any event, since the magnetic poles of the earth are observed to in fact be moving, we can reasonably presume that the ferrous or iron mass deep within the earth must not only be moving so as to generate this field but must be moving in a variable manner, that is, moving differently today than it has moved in previous centuries.
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Since it is essentially unknown what forces are acting on the iron inside the earth, we cannot know for sure what kinds of changes the magnetic field will undergo in the future. We can presume to expect it to move in a somewhat predictable manner, but as you can see from the image above, in the years 1732 (George Washington's birthday and the square root of 3), 1859, 1890 and 1900 the north dip pole changed direction of drift quite abruptly and without apparent or observable cause as far as we know (the birth of Washington or the square root of 3 can't explain a pole shift), therefore a similar change could likewise occur in our present age and we have no way of predicting it or even of anticipating when or whether it will occur.
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