Does the earth’s magnetic field change over time?

The reversal of the earth’s magnetic field happens every 100,000 years or so. The frequency is not constant. It is important because several processes we see everyday are linked to it. However, geomagnetic reversal is least likely to cause us any harm. Let’s discuss how often does the earth’s magnetic field change over time.

Why does the earth have a magnetic field?

The source of Earth’s magnetic field is the molten iron-nickel inside its core. It is generated due to the Dynamo Effect which generates an electric current in the molten metals, which gives rise to magnetic fields.

The magnetic field is different from the gravitational field. Every body in the universe has a gravitational field, no matter how small. The magnetic field depends on the composition of that body.

Earth’s magnetic field comes from dense molten metals in the earth’s core. Right now, the magnetic north pole is somewhere near 86.54 N 170.88 E, in the Arctic Ocean. As of 2020, it is moving east towards Siberia. While the geographic north pole is fixed at 90 N, 135 W.

For the purpose of simplicity, it is approximated that there is a bar of magnet inside the earth at an angle of 11 degrees to the geographical axis. 

Although the magnetic poles are a bit more complex than the fixed north and south poles of the supposed bar magnet.

The magnetic poles of the earth are never stationary but constantly moving at their own rates. Right now, the magnetic north pole is shifting towards Siberia. 

Has the earth’s magnetic field reversed in the past?

Yes. Ever since the earth came into existence, the magnetic poles have flipped over hundreds of times, scientists estimate. The latest complete reversal happened about 770,000 years ago. It took about 100 years for the magnetic poles to “settle”.

How often the reversal takes place has varied greatly. Over 72 million years ago, the rate of reversal has been 5 times per million years. There were 10 reversals per 4 million years over 52 million years ago. Over 42 million years ago, 17 reversals happened every 3 million years. Over 15 million years ago, 51 reversals occurred every 12 million years.

If no reversal occurs for a period of 10 million years, it’s called a superchron.

How did we find out that geomagnetic reversals exist?

Scientists first found out that geomagnetic reversal occurs after observing certain magnetic rocks that were stuck in a position opposite to they should have been.

What are some precursor signs of geomagnetic reversal?

Increased movement in magnetic poles may mean a geomagnetic reversal is about to happen. Although these poles are always on the move, their movements become more extreme and rapid when a geomagnetic reversal is about to take place.

When will the next magnetic flip happen?

It can’t be predicted. It may happen today or in 200,000 years. Till now, the rate of magnetic flips has remained inconsistent.

Does the earth's magnetic field change over time?
via flickr

What will happen when the magnetic field shifts?

As per the fossil fuel records, magnetic field reversal does not impact living beings. It will take almost a century for the poles to complete the shift. Meanwhile, the earth is left with almost zero magnetic field. Here are some things worth thinking about:

  1. Geomagnetic reversal can allow cosmic rays to enter the earth’s atmosphere. It is likely for these rays to cause mutations in living forms. It can also increase our chances of getting cancer. This is probably the worst part.
  2.  During the reversal period, the disturbed magnetic fields can cause aurora borealis to form anywhere on earth. 
  3. The magnetic compass will stop giving the correct direction.
  4. Some plants and animals that use the magnetic field to calibrate themselves will get confused.
  5. It may cause the resultant magnetic field to become weaker or stronger than it is now.

References:

  1. NASA: Pole Reversal Happens All The Time
  2. Science Alert: Earth’s Magnetic North Pole Keeps Moving Towards Siberia at a Mysteriously Fast Pace
  3. Phys.org: The complex history of Earth’s magnetic reversals
  4. ScienceMag: When the Compass Stopped Reversing Its Poles
  5. NASA: Archive of Dr. Magneto’s Questions and Answers

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