Earth’s Magnetic Flips May Have Triggered Mass Extinctions

By Robin Wylie | June 10, 2014 8:00 am

Postosuchus, which went extinct in the Triassic-Jurassic event, is seen here attacking a silesaur. Credit Victor Leshyk/NPS

At several times in Earth’s history, mass extinctions have come close to wiping life out altogether. The reasons for these catastrophes are still unclear – they’ve been blamed on everything from asteroid impacts to cosmic ray blasts. But a new study has found that our planet itself could have a surprising hand in these disasters.

Research recently published in Earth and Planetary Science Letters suggests that reversals of the Earth’s magnetic field may have sparked mass extinctions in the past by stripping oxygen from the atmosphere.

Field Flips

607968main_geomagnetic-field-orig_fullThe Earth’s natural magnetic field, generated in the liquid outer core, spontaneously changes direction every 500,000 years or so. Known as geomagnetic reversals, these processes cause the field’s north and south poles to swap places.

Normally, the Earth’s magnetic field acts like a shield around the atmosphere, protecting it from the damaging effects of the solar wind (the supersonic stream of charged particles emitted by the sun​). During a geomagnetic reversal, however, the field weakens dramatically, exposing the atmosphere to the full force of the solar wind – and causing oxygen ions to be stripped off into space.

This much was already known. But in the recent study, a team led by Yong Wei of the Chinese Academy of Sciences set out to discover if the oxygen lost during geomagnetic reversals could bring about mass extinctions.

It had long been known that mass extinctions are often accompanied by both an increase in the rate of geomagnetic reversals and a decrease in atmospheric oxygen levels (one of the potential drivers of mass extinctions). The researchers’ goal was to determine if geomagnetic reversals could actually have caused such oxygen loss – and therefore potentially have caused mass extinctions, too.

Oxygen Depletion

Wei and colleagues focused on the “Triassic-Jurassic” mass extinction of 200m years ago, in which up to 84% of all species on Earth perished. Independent studies had already shown that, during this extinction, the geomagnetic reversal rate doubled, and the amount of atmospheric oxygen simultaneously dropped by 9 percent. This oxygen drop is one of the possible reasons for the extinction.

Using a computer model, Wei and his team concluded that geomagetic reversals stripped at least 218 trillion tons of oxygen from the Earth’s atmosphere during the Triassic-Jurassic extinction – or 4.5 percent of the total amount. This indicates that at least half of the 9 percent oxygen drop that occurred during the extinction could have been caused by geomagnetic reversals alone – more than enough, the study’s authors say, to have played a major role in the die-off.

This theory may explain even deadlier mass extinctions. Study coauthor Markus Fraenz of the Max Planck Institute for Solar System Research said that the oxygen loss caused by geomagnetic reversals could also have caused the end-Permian mass extinction (also known as the “Great Dying”), in which up to 97% of all species were wiped out.

Perhaps then, alongside the meteoric collisions, supernovae explosions and volcanic eruptions – which have variously been proposed to explain mass extinctions – it’s time to add another suspect. The invisible fluctuations of a physical field might not be as cinematic, but their consequences throughout history may have been just as dire.

MORE ABOUT: paleontology
  • Huh?!?

    Not sure how this theory matches up with 1) Other mass extinctions, and 2) the many pole-reversals throughout geologic time.

    Also, my understanding was that the pole reversal was more frequent than every 500,000 years…

    • Robin Wylie

      Thanks for your comment. Addressing your points in reverse order:

      1) The average time between field reversals is about 450,000 years (which I rounded up for the article). However the exact inter-reversal time varies significantly; as Uncle Al says, the last one occurred 780,000 years ago.

      2) There have indeed been many field reversals throughout geological time. It is not the reversals per se which are proposed to cause (only some) mass extinctions, but rather periods when reversals begin to increase in frequency.

      Hope this clarifies things : )

      • crazybaldhead

        I’ve read (years ago) of the potential/evidence of a flip ats close as a 27, 500 year spacing. How frequent are you saying , in relation their “increase in frequency”?

        • Robin Wylie

          Do you remember where you heard that? I’m not positive, but that seems unlikely. As far as I’m aware, at the end of the Triassic-Jurassic mass extinction the field was reversing once every 200,000 years on average.

          • Heimdall222

            “…reversing once every 200,000 years….”

            That was God flipping the Celestial light switch.

            Apparently, His saying ‘Let there be light’ didn’t have a result at first, so He tried the Celestial switch several times.

            And finally, and there was light….

      • Emkay

        How do we know that a reversal happened 780K years ago? and ‘do compasses point North even when they are, say, in Tierra Del Fuego?

        • John Scanlon

          Some rocks preserve a record of the direction and magnitude of the earth’s magnetic field, and some rocks can be precisely dated based on radioactive decay of unstable isotopes in their minerals. Some sequences of rocks do both (e.g. ash or lava beds from long sequences of eruptions), and for events as recent as 780ka there are many records of the reversal around the world. Try googling ‘magnetostratigraphy’. Cheers

    • dscot

      I think that’s the ‘or so’ part. What is the definition of ‘or so’ in science terms anyway +/- 1000, 100,000, 250,000?

      • Dfargo

        Its very wide. Time is very approximate in respect to Earth’s geologic history. The going joke in Geology is always the phrase “give or take a few million years”. Which begs another question, how did Mr. Wei narrow the time window to believe the extinction events are parallel in time to the pole reversals?

  • Uncle Al

    The Brunhes–Matuyama most recent field reversal occurred 780,000 years ago. We are Officially within days of being ended.

    Human metabolism averages about 2 kcal/day or 2.2 × 10^16 J/year in summation. World energy consumption is about 6 ×10^20 joules/year. Ban oxidation to Save The Earth!. The very first faith-based engineering step is to lower human population by half to conserve oxygen. The Pol Pot business model is proven effective, even in developing economies. NSA metadata-locate everybody wearing glasses or contact lenses to Save The Earth!

    Yellowstone is going to blow, ending North America and pretty much everything downwind. Shouldn’t the whole of civilization, certainly the First World except China, be heavily taxed in anticipation of manufacturing a very large biodegradable, sugar-based sustainable, polymer cork?

    • Heimdall222

      “…the First World except China….”

      Why not tax China? After all, the weight of that immense number of Chinese is causing the earth to be squeezed in a relatively small area, such that Yellowstone will be forced to blow to relieve the pressure.

      “…a very large biodegradable, sugar-based sustainable, polymer cork….”

      So, in reference to Yellowstone, when we say ‘put a cork in it’….

      • Uncle Al

        Solving a serious problem unemploys those who demand absence of workable solutions for it. Advocacy demands presence of unworkable solutions, thereby self-employing. I am an advocate of advocacy. There is no worry so worrisome that studies (Bayesian studies!) of its studies must not be mandated.

        • Huhster

          Are you guys both actually insane or is this just a clown act for the comments section?

          • Heimdall222

            We’re both actually insane.

            Happy, though!

            Say, while you’re here, you got any thoughts about taxing China?

          • watcherofolde

            It’s plenty taxing, all right.

          • Uncle Al

            A psychopath is a sociopath with goals. A sociopath is a businessman in an unjust society. The just and proper solution is to make all society insane so that there is no goal to be gained by deviant behavior.

            The premise of the article is smartless. Deuterium/hydrogen ratio tells us about local atmospheric stripping re Venus and Mars. Fe(II)/Fe(III) ratio in well-ordered sedimentary rock tells us about atmospheric oxidation chemical activity over time re Uluru in Australia.

            Here’s a panic! Suppose a volume of spacetime only contained so many microprocessor cycles and no more? How can we know! All adventitious computation must be immediately shut down for National Security reasons. Yadda yadda publish or perish.

          • Dfargo

            People have no sense of humor anymore.

        • Huhster

          Are you guys both actually insane or is this just a clown act for the comments section?

        • Allen Barringer

          Marvellous logic. I cringe at your monument to resolve. Since we do not know which of several disasters will befall us first, we must prepare for advocacy by studying the situation through extensive modeling. For example, take clouds: do they cool us down or heat us up? Modeling clouds is good for at least a ten year postponement of important advocacy isn’t it? And then there is the advocacy itself: should it be planned for and directed at the underlying situation in Yellowstone, or the nature of the “cork” to put in it, or the nature of the modelling, or the political outfall of action at the U.N.? So many uncertainties; so little time! I suggest we go to the pub, compass in hand, wait there for the next magnetic reversal to become manifest, and then study its effects.

          Or not. Seriously, what else can we do but laugh a little about our helplessness to influence events of that magnitude?

          • Heimdall222

            “…your monument to resolve.”

            Have you got any suggestions as to how Al should resolve his monument?

            As we all know, monuments are deucedly difficult to resolve. Any and all suggestions are welcome!

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  • Brazilian werewolf

    When have it happened the last reversal of earth’s magnetic field ? Were there australopithecus or ancestors in that time ? Intersting paper. Many questions to me have appeared in my mind ….

  • Carole O’Brien

    By “frequent reversals”, do you mean that the fields flip back and forth? If so, how many and how often?

  • Landry Jeffrey

    Lizards are small……..less oxygen.

  • LucciBotto

    because gravity changes when poles flip. maybe not by much but maybe sometimes more than others. we are accustomed to 1 G…body will modify biologically and flora and fauna evolve to adapt.

    • bobgeezer

      Gravity changes?

      Did Newton know about that?

      • LucciBotto

        a lot newton didn’t know about…didn’t think he was in touch with Einstein…only way you could determine is water tables and that not possible.

        • bobgeezer

          So the statement that “gravity changes” is provable exactly how?

          • LucciBotto

            same way it is proven not to be variable

          • LucciBotto

            geez…why they call it the theory of gravity not the law of gravity

          • Hominid

            It’s very easy to precisely measure.

      • Hominid

        Since gravity is a function of both mass and distance from the center of the planet, and the Earth’s surface altitude is dynamic, relatively small, local changes in gravity occur commonly. For instance, the Fukushima earthquake produced a pronounced change in the gravitational force over a region of the western Pacific basin.

        • mbkeefer

          That require extremely sensitive instruments to detect.

          • Hominid


    • Plenum

      Pole reversal is simply that – a reversal of the Earth’s poles. There is no evidence for a change in the mass of the earth during pole reversals. Therefore, there is no change in the Earth’s gravity.

  • Dfargo

    There are a lot of problems with this theory. Lets start with the most
    basic. The fossil record does not agree. If you consider hard data like
    the fossil record, there have been vastly more pole reversals than
    there have been mass extinctions. We have ice cores that date back
    farther than the last pole reversal. An analysis of the gases over the
    periods in question would easily confirm or refute this theory. It is a
    fact that some oxygen gets lost in a pole reversal, but does his theory
    account for the production of new oxygen that we know happens or was it a
    static model? As a geologist, I am always open to new theory. When you
    deal with something as old as the Earth there are so many unknowns.
    But, this theory does not seem to hold water even with the most basic of arguments.

    • bobgeezer

      I’m not a professional geologist, but an avid amateur student. I’ve never seen any geologist claim that fossil data is “hard data”, especially that older than a few hundred thousand years. When did that conclusion come about and is it universally agreed among “professionals”??

      • Dfargo

        By hard data in this case, I literally meant physical. Perhaps i should of said actual data. You are correct that geologic time is relative. It is in fact broken up into rather broad periods. As mentioned up higher in the thread. This is yet another issue I see with the theory.

        • bobgeezer

          Sorry, I can’t accept “actual” any better than “hard”, as every fossil I have ever heard of is subject to the opinions of the discoverer and his peers . . with no scientific way to prove anything; not even it’s age, by many factors of 10 or more, thus subjecting the entire sequence to a lack of scientific credibility. The fossil record is certainly better than the lack of any information, but it is certainly not proof of anything in my view. Add to that the lack of fossil evidence of tissue-based or plant life, and it gets even more suspect.

          • Dfargo

            No sense of humor. You do not have to accept anything. Im talking about a physical record of plant and animal life. We will just have to disagree on whether this is physical or actual evidence in your eyes. Im not trying to throw big words at you, Im saying this record is real and tangible. The dating of these are very approximate and you make my point. How can Mr. Wei assign an extinction event to a polar reversal? Geologic time is relative. Take the K/T Boundary. We can say something is newer or older than this event based on its location relative to the K/T Boundary. Thats how we place rocks in the geologic record.

          • Dfargo

            And since we are talking about this relationship between the features of the rock. The primary clue to the polar reversal is the orientation of the iron in rock samples. This changes as the iron will orient to the existing direction of the poles. These rocks are the only ones that would “record” what Mr. Wei is looking for. These rocks are formed in volcanoes, like at the Mid Atlantic Ridge where the rock is fluid enough to allow the iron to orient itself based on its reaction to magnetic north/south. Fossils do not occur in igneous rocks. Fossils occur in sedimentary rocks. So Mr. Wei does not have a fossil record for rocks capable of recording the magnetic signature.

          • crazybaldhead

            **thinking, thinking**…very good point. Causation and correlation are pretty sticky subjects in a subjective and/or relative model/hypothesis/theory

          • Jodye Rudolph

            You need proof? Go take a look at the mid alantic ridge. See the zebra pattern? There is your proof. Each line represents a cycle of the magnetic pole reversal, last I checked anyway.

          • Hominid

            There are multiple ways to determine fossil age with better accuracy than “multiple factors of ten” (whatever that vague phrase might mean). Fossil records of plant life forms abound. You’re scientifically illiterate.

      • Hominid

        There are always error bars – that doesn’t invalidate the data – it just suggests caution. Are you suggesting that data should be ignored because of the resolution of the metric?

  • WildaBob

    its the birds! they were the only “dinosaurs” to survive the extinction, right? well maybe they survived because of the ability of their blood to absorb oxygen extremely efficiently.

  • Alan Lowey

    The Laschamps event was a full but brief reversal just 41,000 B.P. This has implications for the demise of the megafauna.

  • JimShea

    “Geologic time is relative”??? What does that mean.

    In geochronology there are two broad types of “dating”: relative and quantitative. Relative dates are determined by the “law” of superposition, by cross-cutting relationships, etc..
    Quantitative dates (which are numerical) are determined by radiometric and other methods.
    The relative dating methods gave us most of the geologic time scale by about 1840. Radiometric dating began shortly after the discovery of radioactivity (about 1900). It subsequently confirmed the geologic time as previously determined by relative dating.
    Modern quantitative dates are accurate to within at least 10%.
    See Brent Dalrymple’s book “The Age of the Earth”.

  • John Hanson

    The reason is simple: migrating animals walked, flew, swam, or slithered in the wrong direction. *poof*

  • Tony Borowiecki

    My apologies if this is a duplicate of an attempted send from 2 minutes ago // Is not the protection afforded by the earth’s magnetic field in deflecting and intercepting the sun’s more harmful rays and particles from reaching earth’s surface more important than its role in preserving the amount of oxygen in the atmosphere? After all, many species – humans included – can survive and thrive in altitudes which contain much less oxygen than is found at sea level for instance. Whereas a dramatic increase in the amounts of cosmic rays raining down on the surface would, I think, more readily cause deaths and genetic breakdowns on a more massive scale.

    • Dfargo

      I agree. The cosmic rays and additional radiation reaching the ground would easily be my biggest concern. Leaving that the fossil record does not agree with the extinction/reversal relationship out of it……………………………………………………………………Do realize that the lower limit for oxygen which is considered safe for humans is 19.5%. The normal O2 level if your not in upper elevations is going to be in the mid to upper 21% range. Around 21.9% near sea level. Further, leaving those that live at higher elevations out for our purposes here, this leaves the majority of humans with that 2.4% maximum tolerable range in O2 and Mr. Wei is claiming 4 to 9% variations during previous events in his study. Those numbers ARE big and potentially deadly to Humans. Obviously other animals might have different O2 requirements. Clearly we can lose O2 during a reversal but there is SO much more to consider. We do not know if his model was designed to include the natural production of O2. The fact is we really do not understand the actual O2 control system that well. We do not know why O2 is stabilized in the 21% area vs 30% or whatever. So how does this work in his theory? He is assuming A Lot.

      • mbkeefer

        Taking into account how humans do deal with altitude, it is quite obvious that we can survive very well at sea level with oxygen levels below 10%.

  • John Stojanowski

    A scientific paper ‘Plate tectonics may control geomagnetic reversal frequency’ by Petrelis, Besse and Valet (2011) indirectly supports my theory of mass extinction. This theory posits the offsetting of the Earth’s core elements from Earth-centricity in response to plate tectonics.

    The theory, the Gravity Theory of Mass Extinction, explains dinosaur gigantism, the primary cause of all mass extinctions (i.e., changes in surface gravity), geomagnetic reversals, secular variation and other things.

    The theory posits that when the inner core moves relative to the outer core, in response to tectonic plate movement, geomagnetic reversals are more likely to occur. It also posits that when the core elements rapidly move back toward Earth-centricity, mass extinctions occur primarily due to an increase in surface gravity on part of the Earth (e.g., on Pangea).This movement also initiates massive flood basalt volcanism which is associated with almost all mass extinctions.

    Therefore, there is a relationship between geomagnetic reversals and mass extinctions. However, it is not one of cause and effect.

    • Dfargo

      There is no evidence a reversal increases volcanism. Even if the flood basalt part is right, basalt is a product of oceanic plates. Consider Hawaii, hot spot volcanism in the middle of an ocean plate. It produces dark, iron rich rocks like basalt. Now look to the volcanoes on the continental crust. Silica rich, explosive volcanoes. Think granite. The explosive continental crust volcanoes are much much more likely to cause problems than flood basalts. I do not see the relationship. Would love to see some articles presenting this.

      Again, the primary point of this article is the oxygen loss. But the ice cores will record the mix of atmospheric gases which occurred over several reversals and could easily reinforce, or shoot Mr. Wei’s theory down in flames. The record is there and as an academic im sure he can gain access. Seems like an easy enough thing to investigate.

      • John Stojanowski


        No claim was made that geomagnetic reversals increase volcanism. Flood basalt volcanism appears to be associated with all mass extinctions, as noted by Vincent Courtillot. If the volcanism occurred over about 200 mya and occurred on the ocean floor rather than on a land mass we wouldn’t be able to confirm that because the ocean floor would have been subducted.

        Since this type of volcanism initiates at the core-mantle boundary, it can occur on either oceanic or continental plates, as it did with the Siberian Traps.

        The explosive type of volcanism (e.g., the pyroclastic type) are of short duration (of days, weeks) compared to flood basalt volcanism (up to millions of years), therefore their impact is relatively small.

        Flood basalt volcanism (such as the Siberian Traps, Deccan Traps, CAMP, etc.) were massive compared to the current Hawaiian flood basalt volcanism. The theory I referenced explains why these massive eruptions can only occur when a supercontinent or supercontinents (such as Gondwana and Laurasia) exist.

        Getting back to Wei’s theory concerning oxygen levels, he will first have to show that there is a direct relationship between reversals and oxygen level change and he will have to do that for periods when there was no ice to record oxygen levels. I hope there is a followup article on his research.

        • Dfargo

          I did not say any claims were made. It was a genuine request for links to this info. I have simply never seen an significant extinction event that fell parallel to a flood basalt deposit. I do not pretend to be a paleontologist. I would love to see the data supporting the claim.

          • John Stojanowski

            I’ve been trying to reply to your request for data but my responses have been deleted.
            If you google “mass extinction” and “flood basalt volcanism” and then select “images” you will find charts that confirm the coincidence of the two.

  • Joe Blow

    We just don’t know enough, and this article completely fails to mention any interaction. For instance:
    A large meteor strike could trigger large lava flows, which might alter oxygen levels.
    A mass extinction would include plant life, which would lower oxygen levels.
    Carbon sequestration and water levels are both influenced by plant and animal life, effecting tectonic activity, which in turn effects the Earth’s magnetic field.
    Large meteor strikes often occur around the same time as increased volcanism, which effects the atmosphere obviously, but whose lava flows might effect the magnetosphere.
    So, a “chicken and egg” question is reported as “magnetic field may be the cause instead of x”, when in fact, there may be several interacting phenomena at the same time.

  • speakertoanimals

    Very weak science. To begin with, there is only ONE geomagnetic reversal anywhere near (in time) to the Triassic-Jurassic extinction. so, there’s no possible evidence that the RATE of reversals anywhere close to this is even known, much less was higher. And think of the timescales: typical times between reversals are a bit under half a million years (with wide variance), MUCH too long, even for ONE, to be associated with an extinction event. It’s not credible that the earth could lose even 5% of it’s oxygen during the few thousand years during a reversal (maximum time) when the magnetic field is lower (but not gone, maybe 20% of the average field strength).

    More than likely the authors have confused cause and effect: some extinction events seem to be associated with vastly increased volcanic activity, which itself may be indicative of geophysical processes that themselves CAUSE the magnetic reversals. It’s the effects of the volcanic activity that likely cause the changes in the composition of the earth’s atmosphere NOT solar stripping.

    Discover needs to do a much better job of vetting very controversial publications!

  • Roman Justme

    Wonder what would happen if a massive star goes supernova and the Gamma ray jets at the stars poles were directed toward earth. This gamma ray burst is traveling at the speed of light, with the energy billions of times what our sun puts out in a year, This would ionizes our atmosphere, destroy / kill all animals, only deep sea animals would be somewhat protected. There is evidence this caused the extinction 200 million years ago. Not the reversal of the earths magnet field. The field does not diminish and reappear in the opposite direction. The earths Iron core continues to rotate it doesn’t stop. What I believe happens is the the magnetic field destabilizes and becomes erratic, having multiple poles around the earth, like a magnet in a motor can have multiple poles.

  • mark dames

    Has anyone computer modeled the over-lap of polar reversals and periodic solar mass ejections? With the protection of the magnetic field temporarily interrupted by a polar reversal wouldn’t life on this planet be threatened by an unfortunately timed solar mass ejection?

  • Eric Schramm

    What if the magnetic reversals cause global warming? Case:
    1 The core produces both the magnetic field AND magma
    2 magma runs in-between the crust and mantle

    3 This could – just might – act like oil in an internal combustion engine.

    Without as much magma, you get crust and magma rub together and cause friction heat.
    4 Warm water rises, it doesn’t sink.
    5 The cold jet stream under the ocean is shutting down.

    If the bottom of the ocean floor is rubbing against the mantle, that would create friction heat, warming the floor AND the ocean water.

    6 The spots that have shown to be the most weak to friction heat already have volcanoes under them. They just ran out of heat.
    7 The icebergs are vanishing, but the air on the mountains where they are melting is still sub zero F.
    8 ALL the mountains whose icebergs have vanished – are dormant volcanoes.

    If the magma under the crust USED to be a mile thick but is now a half-mile, you now have less space for the same amount of crust. The compression should cause friction heat and that would provide the heat to restart those volcanoes. The icecaps are melting because the crust under the mountains is getting hotter.

    The south pole is melting – you DO know that there are 200 registered volcanoes on that continent, right?

    The North pole is melting – it is above a hot spot of crust.

    The fossils of five-year old saltwater clams have been found 200 miles inland where Tennessee would eventually be – just below the KT boundary. This would need a century of drought for ocean water to climb that far inland.
    Thousands of dinosaur bones have been found just a centimeter below the KT boundary. Not even one IN the boundary. Not a smallest one. They had to have died out BEFORE the boundary for there not to be any skeletons IN it.

    Does that all follow?



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