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Name: Mary Ellen
Status: student
Grade: 6-8
Location: NE
Country: USA
Date: N/A 

My earth science teacher has been telling us about continental drift and magnetic striping in ocean rocks due to magnetic reversals. She said that by the pattern, this is due to happen again, soon. Will the strip on my bus card still work? Will magnets that now attract, repel (and the other way around?

Mary Ellen,

Magnetic reversals are not predictable. There is no pattern to the reversals. There is no evidence that this will occur any time soon.

The last magnetic reversal occurred 730,000 years ago, so for the last 730,000 years the north end of the magnetic needle on your compass always pointed north. It takes about 1000 years for a reversal to occur, so, if you took a Rumpelstiltskin sleep, when you woke up, the north end of your compass needle would point south.

Earth’s magnetic field is much weaker than the magnets on your swipe cards and kitchen magnets, so, I would not worry about individual magnets or your bus card. The bus driver still knows which way to get home, even if the compass needle points backwards.

Leslie Kanat, Ph.D.
Professor of Geology
Department of Environmental Sciences

Hi Mary Ellen

The strip on your bus card will still work because the magnetic field is embedded in your bus card.

Individual magnets will also continue to attract and repel each other as before.

The only difference is that while magnets in compasses will still continue to point to the magnetic North Pole (not to be confused with the geographical North Pole), the magnetic North Pole will no longer be located near the geographic North Pole. In fact, today the magnetic North Pole drifts, is presently located near Ellesmere Island in Canada, and in 2009 was toward Russia at almost 40 miles (64 km) per year. Please click on this URL for more information:

So navigators have to make corrections to their magnetic North readings to discover the true direction of the geographic North pole so they can set a true course over the surface of the Earth.

You can find out more at:

and searching for "Magnetic North Pole" and the click the sites that are of interest to you.

Sincere regards,
Mike Stewart

In a magnetic field reversal, the magnet that changes is the earth itself. Other magnets will still behave and interact with each other as they always have. The laws of electricity and magnetism will not change at all. Only the specific features of the earth's magnetic field will be different.

Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming

The Earth's magnetic pole does wander, and on the geological time scale, it wanders fairly quickly. No one really knows what the impact will be if it wanders sufficiently to actually reverse. One concern is that the protection the Earth's magnetic field makes against high energy charged particles emitted by the Sun will disappear, leaving the surface vulnerable to those highly ionizing charged atomic fragments. However, it is unlikely that the reversal will influence your magnetic strip cards, nor will it cause a reversal of most magnets. Those magnetic fields are too strong to be affected by the Earth's magnetic field. An exception are magnetic compasses. Those are pivoted to respond to the weak magnetic of the Earth. Any reversals would also probably affect radio waves which are affected by the ionosphere surrounding the Earth, but exactly what the effect would be is difficult to predict.

Vince Calder

Mary Ellen,

The Earth has a magnetic field because substances within the molten outer core are moving in a particular direction or pattern. Imagine a figure 8 where the flow around the figure 8 is only one way. Because the flow of these substances are only going one way, there is also only one direction for the magnetism that is produced by this directional flow. This is theorized to be the main reason why we have a north and south pole. Suppose now that the flow, for whatever reason, starts to go in the opposite direction. This would result in the poles being reversed.

This means that the principles of magnetism do not change because of the pole reversal. The principles are still the same, its just that the source of the Earth magnetism, the direction of the flow of the molten outer core, has reversed. This also means that bar magnets, magnetic strips, etc. all still work - because the physics have not changed.

Greg (Roberto Gregorius)
Canisius College

Dear Mary Ellen:

A geomagnetic reversal changes only the Earth's magnetic field. North and South poles swap places, but all the other magnets will act the same.

The only thing we will notice is that all our compasses will point "south" instead of "north". We will still be bale to use our compasses, but will need to look at the other end of the arrow to go towards the Arctic or north.

As far as we can see from fossils and such, not much else happens during a reversal.

R. W. "Bob" Avakian
Arts and Sciences/CRC
Oklahoma State Univ. Inst. of Technology

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