Rex Trulove
The magnetic north pole isn’t the same thing as the true north pole. The two are in different locations. The rotation of the earth is around an imaginary line that passes through the true north and south poles. However, the magnetic north pole is located at quite a distance from the true north pole and it is found in northern Canada, at present.
All of this is interesting, but a lot of people know this already. Many people also know that the north and south magnetic poles periodically flip, so the north magnetic pole ends up in the southern hemisphere and the south magnetic pole takes a position in the northern hemisphere.
Scientists can measure fairly accurately when the magnetic north and south poles have swapped places by studying the rocks on the ocean floor in the Atlantic. Along the ocean floor in the Atlantic, tectonic plates are pulling apart and this results in a rift where magma is continually welling up. As the magma becomes lava and solidifies, the iron in the rock becomes magnetized and like a compass, it points toward the magnetic north pole. By measuring the direction of magnetization, they know where the north magnetic pole was and the farther away from the rift the rock is, the longer ago it welled up. This means that science has a rough time frame to go by.
They don’t even need to go to the bottom of the ocean, in fact, since the rift passes through Iceland.
From this, they know that the poles swap places about ever 10,000 years or so. As it happens, we are overdue for another polar reversal. Incidentally, the sun also has a polar reversal and we’ve witnessed many of them. With the sun, they occur roughly every 11 years.
This isn’t even the most interesting part. You see, the magnetic north pole, which I mentioned is presently in Canada, isn’t static. That is, it is in constant motion. It moves about 20 feet every year. It also doesn’t move in a direct line. Instead, it sort of wanders around.
This has a practical meaning to sailors and others who use a magnetic compass. It means that compass readings aren’t very accurate unless you know exactly where the north magnetic pole actually is at any given time. Because of the current location, it also means that a compass in my location will point slightly east of the true north pole. For someone in New York City, the compass will point slightly west of the north pole. The farther north a person gets, the more noticeable this is, too.
As if it was really necessary, this shows that our planet is very dynamic and constantly changing, whether we are aware of it or not. It is interesting, isn’t it?
It’s funny because I use a compass sometimes and I would have thought they were always right.
For what the average person uses a compass for, they are close enough. They just don’t point due north and the magnetic pole does wander a bit.