Magnetic Reversal and Magnetic Strips
Name: Mary Ellen
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?
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
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.
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.
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)
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
R. W. "Bob" Avakian
Arts and Sciences/CRC
Oklahoma State Univ. Inst. of Technology
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Update: June 2012