According to NASA the magnetic pole reversal is a continuous event that takes hundreds of thousands of years to complete.
Sailors have been aware of this since the discovery of the loadstone. It you look at a marine chart, a map of an area of the sea, you will notice off to the side a large, round thing consisting of two concentric circles called a compass rose, which has two Norths. These two concentric circles describe, in degrees from 0 to 360, a compass in relation to the landmarks on the chart. However, each circle, or compass, is a few degrees different from the other.
That is because one of the Norths are what is called True North, or geodetic north. In other words, if you follow that direction you will ultimately arrive at the True geodetic north pole that you see on globes.
The other North is Magnetic North, which points toward the magnetic north pole. If you follow this line, you will end up miles to the left or right of your destination. But, this is where your magnetic compass will lead you, if you do not make an adjustment.
The difference is called deviation and the compass rose allows navigators to adjust their compasses accordingly.
Magnetic North is slowly drifting all the time, so every few years you must buy new charts in order to make the new adjustments and not get lost at sea. This is the magnetic drift—the poles “flipping”—and it has been going on since the beginning of time. It is nothing new, it doesn’t portend catastrophe, nor is it anything to worry about.
We live on a pretty good planet.