North Pole, South Pole

I just finished reading a fascinating book by Gillian Turner titled "North Pole, South Pole.

It’s about how little we really know about the magnetic field of our Earth. And how important it is to us all.


The Cretaceous–Paleogene (K–Pg) mass extinction event happened 66 million years ago. The popular theory, up until very recently, was that it was a nuclear winter caused by a giant asteroid impacting Earth in the Gulf of Mexico near the Yucatan peninsula. The theory surmised the resulting ash and dust cloud surrounded the Earth, shutting off the sun’s warming effect to the extent that it extinguished many of the living organisms on Earth, including the great dinosaurs.

But with recent revelations that the earth has undergone periods of magnetic pole reversals throughout it’s existence, another extinction theory is surfacing. space radiation, aka cosmic rays could be the culprit for the demise of the dinosaurs.

Many paleomagnetists now believe that when the north and south poles swap places, the earth’s magnetic field temporarily shuts down in the process. When that magnetic field is not active, the earth is subject to the full effects and forces of space radiation. That radiation has a detrimental effect on living DNA and destroys much of it.

The theory is based on recent evidence that the earth’s magnetic field is powered by the convective heat exchanges of the molten layers between it’s core and mantle. The asteroid is believed to have penetrated the mantle and interfered with the dynamo action that powers the earth’s magnetic field causing an electrical polarity reversal which resulted in the magnetic pole flip-flop.

I always loved the question: if you’re at the (magnetic) North Pole, which way will the compass needle point?!?

and another concept – the “North Pole” of a magnet/compass is labelled “N”, and if opposite polarities attract, then the Earth’s North Pole is actually magnetically, a South Pole. Fun stuff.

This link takes a bit of the scariness factor away from a pole flip and provides some other useful information. Click on the link to in interactive map that shows how changes have occurred during the time period from 1500 up until 2024.

Tracking Changes in Earth’s Magnetic Poles | News | National Centers for Environmental Information (NCEI).

Interesting. Sounds like a book I would enjoy, so I just ordered it thru my library. The book has been around long enough (pub. in 2010), so there must be some opinions about the idea that magnetic reversals can cause mass extinctions:

Alas, there is more work to do. :slight_smile:

Here’s a recommendation for you, it even includes magnetic reversals! The work of mapmaker Marie Tharp at Columbia University in the '50s and '60s is why we finally started believing Wegner’s continental drift theory.

The end of the compass needle labeled north would tilt downward and swing randomly in a circle depending on exactly where you stood relative to the absolute axis of the magnetic north pole.

The site you linked redirects to a NOAA web site. The explanation there indicates that, due to the very long span of geologic time and the fact that a pole reversal hasn’t taken place in a very long (in life-on-earth terms,) that: “Scientists have determined that, in the short-term, there is no real change to Earth’s environment and no threat to life due to a pole flip.” And, for all practical purposes we have nothing to worry about.

But more recent studies and computer models indicate that there’s not a predictable pattern as to when they might occur. But… even if we could accurately predict a polarity reversal, there’s absolutely nothing within human capabilities that could be done. And the reversal process itself could easily take hundreds or thousands of years… :slightly_smiling_face:

This is one reason we need good science!!!

The more pieces we cut out of the pie, the bigger it gets!.. :nerd_face:

@H200h You explained it better than most Geophysicists!

It is a good read. Most of the book is about the work of some 40 scientists, naturalists, mathematicians and even an ancient Greek philosopher who have contributed to our understanding of Earth’s magnetism. The author only devotes 5 paragraphs in her epilogue to the idea (first published in 1985) that a magnetic reversal could have caused the end-Cretaceous mass extinction, and says only time will tell if enough observations [evidence] will support the hypothesis. Geophysics is a challenging field to work in, since so much of what is studied is intangible.

Actually, the theory is, that it’s the absence of the earth’s magnetic field that causes the organic die-off. The pole reversal occurs very slowly in human terms, maybe hundreds or thousands of years. During that time there is likely an absence of the normal protection brought about with a magnetic field of either polarity.

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Agreed. But I and 4 other geologists I’ve talked to about this still believe the K-T extinction was caused by climate change due to the asteroid impact and/or flood basalts in India, not an influx of cosmic rays due to weakened magnetic field during a reversal. I know you like the ‘theory’ of magnetic reversals causing extinctions, but more work needs to be done to convince enough scientists to believe it.

Reminds me of an old joke:
What’s 2+2?
Mathematician: 4
Geologist: between 3 and 5
Geophysicist: what would you like it to be?

I agree all possibilities are strictly theory regarding the K-T event. But my bias is probably driven by my background in electric motors and generators. As you are undoubtedly aware, the earth’s magnetic field exists because of the dynamo action of the non-solid layers between the solid inner core and the inner layers of earth’s solid outer crust. It works because of convective movements within those boundaries.

When that convective activity is interrupted by something like a large asteroid penetrating that non-solid moving mass that is generating electricity and the resulting magnetic field around the earth, it’s like shutting down a gigantic power plant. It’ll take a while for it to shut down and… a while to get it up and running again. Maybe a couple of thousand years or so. It’s not like turning a switch off and on again. We know that most complex life on earth would not survive or be able to reproduce if exposed to that cosmic radiation that our earth’s magnetic field shields us from.

On the other hand, logic tells me that while a nuclear winter would radically change things on the surface of the earth, it’s a fact that the sun’s radiant energy is absorbed by dark matter and reflected by matter that is lighter in color. If the asteroid landed in an area covered by ocean water a lot of water would be turned into water vapor and we all know that water vapor is a greenhouse gas and would contribute, not detract, from global temps. And the solid particles created by the impact would all likely contribute to the heating of the atmosphere. And all of that disruptive activity would probably not last more than twenty or fifty years.

Of the two scenarios, I think the loss of the protective magnetic field a more likely cause for the demise of the dinosaurs…