It seems to be quite well established that the Earth’s magnetic field reverses polarity about every 100,000 years, and that the last one was about 100,000 years ago. That means that “soon” – in geologic terms – we’re due for another magnetic reversal.
Are there any peer-reviewed theories on when this will happen, how it will occur, and how long it will take? Will we go to bed some night and wake up to find that our compasses point south and Santa and his reindeer are resident at the South Pole, while the penguins live on the northernmost coasts? Or will there be a significant period when magnetic compasses are useless, with no definite magnetic field? Will this affect magnetospheric shielding from cosmic rays and Solar radiation?
No one really knows what to expect. The reversals have not been exactly regular anyway.
What about the Yellowstone volcano? Some of those blasts have been huge. It’s erupted catastrophically three times, with about 700,000 years between, and it’s been over 600,000 years. We’re due for that too.
Actually, the last polarity reversal occurred 780,000 years ago. To see what the reversal pattern has been like over the past 180 million years or so, have a look at this time scale. The black and white bands indicate intervals of normal and reversed polarity, respectively, with the current magnetic field orientation considered normal. We only know the record of polarity changes with a high degree of confidence & continuity back to the Middle Jurassic because the full record of polarity changes is best preserved in ocean-floor basalts, and the oldest sea floor is about 180 million years old (sea-floor basalts older than that have been subducted and recycled into the Earth’s mantle). That’s not to say that polarity reversals haven’t been observed in older rocks; we just don’t have a continuous record of the changes anymore.
The pattern of magnetic field reversal seems to be one of the few earth system processes that is completely and utterly random, so there is in fact no way to know when the next reversal will take place.
From the geological record, it appears that polarity reversals may take anywhere from 3,000 to 10,000 years to complete. It’s not entirely clear what happens during the reversal interval, but it’s thought that the higher order components of the Earth’s magnetic field become more prominent. (About 90% of the current field can be approximated as a dipole field; think of a giant bar magnet roughly aligned with Earth’s rotational axis. High-order, non-dipole components have other geometries, e.g., quadrupole, octupole, and so on.) So, during a polarity change, your trusty compass would become useless, and animals that rely upon the magnetic field for orientation/migration would probably be pretty confused.
Some of the more, ah, entertaining futurists would have us believe that mass extinctions would occur, terrible geological calamities would take place, etc. Happily, there is no correlation between polarity changes and such events. Neither is there any indication that electrical or electronic equipment would stop functioning.
Whenever the next magnetic pole reversal occurs, polar bears will not be moving to the south geographic pole and penguins will not be moving to the north geographic pole.
They will still complain their TV reception is lousy and I doubt a magenetic pole reversal will change that, too.
You’re probably aware of this but the reversals have been captured in extruded magnetic rock along both sides of the Mid-Atlantic Ridge as well. They document many fluctuations over the millennia as evidenced by parallel bands of basalt whose magnetic orientations periodically flip. Since they were extruded to either side, they form a mirror image of each other and their width roughly is an indicator of the length of time between reversals.
I tried to draw a crappy little diagram but couldn’t enlarge the bands so here’s a link instead… Shazam
The center of the ridge represents today and further extrusions in the future will continue to push the mirroring sides away from each other at roughly similar rates.
I believe the earth is shielded from radiation by the atmosphere and the magnetosphere acts mostly to redirect charged particles toward the magnetic poles.
Nope, imo. I strongly doubt the shift would happen overnight.
Could be, but I doubt it will be within our lifetimes. Here is an interesting link on the movement of the magnetic North Pole:
“The North Magnetic Pole is slowly drifting across the Canadian Arctic. The Geological Survey of Canada keeps track of this motion by periodically carrying out magnetic surveys to redetermine the Pole’s location. The most recent survey, completed in May, 2001, determined an updated position for the Pole and established that it is moving approximately northwest at 40 km per year.” http://www.geolab.nrcan.gc.ca/geomag/northpole_e.shtml
3. Since this topic is real big in the New Age movement, I expect nothing at all to happen. There are some people who are predicting the End Of The World As We Know It due to an impending pole shift. 2012 seems to be a good year to choose for that, if you want to sell a lot of books but not be on the hook for being accurate until 9 or 10 years have passed.
HTH
Duckster, in case my tongue-in-cheek humor escaped you, what I was suggesting was that after a reversal, the south magnetic pole would be in the Canadian Arctic and the north one near the coast of Antarctia, not that the critters found near each pole would migrate!
