current models of the earth’s magnetic field only cover a few years, and are updated at roughly five-year intervals.
At some locations, alignment between magnetic north and geographic north is very unlikely at any time, based on predictions.
The locations of the magnetic poles are constantly changingMost compasses point towards earth’s north magnetic pole, which is usually in a different place to the north geographic pole. The locations of the magnetic poles are constantly changing.
Earth’s magnetic poles exist because of its magnetic field, which is produced by electric currents in the liquid part of its core. This magnetic field is defined by intensity and two angles, inclination and declination.
The relationship between geographic location and declination is something people using magnetic compasses have to consider. Declination is the reason a compass reading for north in one location is different to a
reading for north in another, especially if there is considerable distance between both locations.
Bushwalkers have to be mindful of declination. In Perth, declination is currently close to 0° but in eastern Australia it can be up to 12°. This difference can be significant. If a bush walker following a magnetic compass disregards the local value of declination, they may walk in the wrong direction.
The polarity of earth’s magnetic poles has also changed over time and has undergone pole reversals. This was significant as we learnt more about plate tectonics in the 1960s, because it linked the idea of seafloor spreading from mid-ocean ridges to magnetic pole reversals.
Geographic northGeographic north, perhaps the more straightforward of the two, is the direction that points straight at the North Pole from any location on earth.