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Today the Earth's magnetic field is moving a little bit. But is there going to be a point where the field suddenly radically changes direction? If so what is the cause of that? If not, then is the field changing all the time gradually?

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  • $\begingroup$ I edited a "geomagnetism" tag to your question. Click it and you will find a bunch of questions and answers that should give you an answer. $\endgroup$ – Gimelist Feb 2 '16 at 12:09
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    $\begingroup$ While there's still some unknowns, the quick answer to your question is no. The Magnetic field is not thought to suddenly "flip", it's a more gradual process and in the process it's thought to twist and tangle, not suddenly "flip", the process can take a century or more. At the same time, and generally speaking, it does go through periods of change (100-1000 years or so) and longer periods of relative stability (80,000-800,000 years or so). $\endgroup$ – userLTK Feb 3 '16 at 3:41
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    $\begingroup$ @userLTK -- why not make this into a regular answer to the question? $\endgroup$ – Wolfgang Bangerth Feb 3 '16 at 15:23
  • $\begingroup$ @WolfgangBangerth I thought about that, but felt a regular answer should be a bit longer and better backed up and would require some more research on my part. A comment was more the level I was comfortable with. $\endgroup$ – userLTK Feb 4 '16 at 2:28
  • $\begingroup$ But when it is always graduyally going than the results of the directions of magnetic pools of small metal particles burried in the earth shows all directions at the same level? $\endgroup$ – Marijn Feb 4 '16 at 8:33
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The magnetic north pole (and presumably the south pole) currently moves around 40km/year, although within a year it loops around, may travel much further than that forwards and backwards. Here is a map of the movement from the past century and a half (source) :

Movement of the pole over the last 170 years

However, during a magnetic reversal, the pole may move up to 10 times faster than that, over a period of less than 100 years. Here's a map showing the relative movements (the numbers are thousands of years ago (kya)) (source)

Magnetic field reversal 786kya]

The reason for reversals aren't very well understood (according to the previous link), and I'm in no way an expert in the field, but just for some fun speculation, I would wonder whether reversals might be related to this phenomenon. Obviously a liquid outer core is going to operate differently from a screwdriver, but the two systems both appear to be exhibiting a bistable rotation while floating in space.

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Having worked on this problem myself in my master's thesis, see our paper in geophysical journal international(GJI) at http://ceas.iisc.ernet.in/~bsreeni/gji14.pdf the likely timeframe of this event is about 1000 years as per our calculations.

For us humans this is definitely not instantaneous but for the timeframes relevant to earth's history, this is a very short amount of time. So, don't lose your sleep over it, it won't happen in your lifetime.

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Magnetic field exist because of the hot liquid in the external core of Earth moves, that movement of charged particles produces the magnetism. Therefore, the magnetic field can't change at once, it only can change slowly with variations of these inner flows.

I "suppose" that earthquakes might produce small changes in the magnetic field, because seismic waves travel through the Earth core and mantle.

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