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    Paleomagnetists Create Controversy So They Can Solve It
    By Hank Campbell | October 2nd 2009 02:19 PM | 6 comments | Print | E-mail | Track Comments
    About Hank

    I'm the founder of Science 2.0® and co-author of "Science Left Behind".

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    Did you even know there was a discipline called paleomagnetics?   Probably not.(1)   It isn't easy to find a category on this site to put it in, that's for sure.

    But a discipline it is and it even has its own controversies, as all science must; namely, the nature of Earth's magnetic field 1.1 billion years ago.

    The Earth's magnetic field in two sentences:   it wraps around the globe and helps shield us from cosmic rays - lest we all burst into flame or turn into orange rock and say things like, "It's clobberin' time!"  

    fantastic four cosmic rays magnetic core
    If you don't have superpowers or look like a Jack Kirby drawing, blame Earth's magnetic field. ©  Marvel Comics and/or Disney, depending on when you read this article.

    The magnetic field is a result of the planet's iron core, the spinning of the Earth and differences in temperature between the inner core's outer layers and the lower mantle.

    Some paleomagnetists believe that the Earth's magnetic field was unstable in the past but a group at Princeton says that, in ancient times, the Earth's magnetic field was structured like the two-pole model of today, suggesting that the methods geoscientists use to reconstruct the geography of early land masses on the globe are accurate.

    In other words, the controversy is that there is now no controversy.

    By examining t the 1.1 billion-year-old volcanic rocks on the north shore of Lake Superior, they say they have found that Earth's ancient magnetic field was a geocentric axial dipole -  that's a large bar magnet centered in the core and aligned with the Earth's spin axis.

    So what's the rumpus?   Earlier studies of those same rocks led researchers to believe that the magnetic field of ancient Earth had four or even eight poles, which meant that modern models of the supercontinents that relied on that paleomagnetic data and its axial dipole assumption were wrong. 

    Nope, says the new report in Nature Geoscience, those other researchers were just confused by the migration of the continent toward the equator in the past. 

    Why does it matter?   If we don't know how continents moved in the past and how they massed to form supercontinents, we can't accurately model ocean currents, global average temperatures and wind patterns - which means models of ancient climate would be a lot less made up than they are right now.

    You may not have heard of paleomagnetics before but how they deduced this was interesting.   They studied the lava flows near previously mentioned Lake Superior, obtained magnetic measurements and used magnetic minerals within the rocks to record the orientation of the geomagnetic field at the time the rocks erupted onto the Earth's surface.  

    Clever, right?  Using the layers, they were able to track how the Earth's magnetic poles have flipped over the eons, when the North Magnetic Pole became the South Magnetic Pole and so on. They studied three of these reversals that occurred over a few million years.

    According to recent hypotheses, a supercontinent known as Rodinia (a Russian word meaning “homeland”) existed between 1 billion and 800 million years ago.  As it broke up, and the climate cooled 700 million years ago, it is believed the the rapid evolution of primitive life began.

    rodinia
    Artist’s conception of the supercontinent Rodinia circa 750 million years ago.  What will be North America lies in the center of the surrounding lands. Original painting by Tomo Narashima.

    You've probably heard of the  Pangaea supercontinent which came together about 300 million years ago and scientists learned about Rodinia in much the same fashion - detective work  comparing rocks with similar geological features that are now widely dispersed.

    That means the science of ancient geology can be a lot more ... scientific.

    NOTES:  

    (1) Princeton had a paranormal research group for 40 years also.  They cover all the bases.

    Comments

    Florian
    Actually, there are confusions from palaeomagnetic measurments leading to bad reconstructions. But it results from a flawed initial model of Earth's evolution derived from bad assumptions.
    Hank
    Sure, that's the controversy.   If there were 8 poles or 4 or whatever it makes a huge difference in understanding ancient geology and therefore ancient climate.   And climate studies are where the money is.
    Christina Znidarsic
    I've actually done paleomag work on long sediment cores from my thesis lake.  University of Akron has a paleomag lab and Dr. John Peck and I spent a fun day analyzing my sediment and trying to determine where the flops were.  It didn't work so well on my stuff because I had highly organic samples and we were getting very weak signals on most of it, like within the range of error.  It was still awesome; I have a good time doing anything you can't have a pacemaker or wear a watch near.

    Off their website:

    "A particular strength of the department is Terrestrial Records of environmental Change (TREC). TREC research covers such diverse but related topics as hydrogeology, paleoclimate reconstruction, climate change, glacial geology, modern siliciclastic and carbonate sedimentology, geomorphology and aqueous geochemistry. The Department recently acquired instrumentation for measuring environmental magnetism of Quaternary sediments and is pursuing funding for additional equipment to further augment this research. The Department is also developing a new area of leadership in earth science education and research."
    Your topic can go into category Earth Science (Geology) if no on else wants it.

    We should bear in mind that if there was no controversy, the research budget would be cut, and grants would be scarce.

    So the will always be a controversy.

    In Earth science it is always easy to get a controversy, especially when we are talking about the core layers, far away, out of sight, red hot, and squeezed hard in every direction.

    From my 10 semesters of geology, I do remember some small parts about reversal of magnetic field.

    The story goes that the core is solid, but nearly hot enough to melt, and almost as hot as the Curie temperature. For the beginners, above the Curie temperature a solid cannot be a permanent magnetic.

    Occasionally ( in geologic terms ) the core over heats from heavy radioactive elements that slowly sink down to the solid layers from the more fluid layers above.

    When the Curie temperature is reached the core starts to lose its permanent magnetism. That’s part of the story.

    The other part of the story is that the Earth is always passing through other magnetic fields from the Sun and major planets, mainly Jupiter and Saturn.

    So a new rock that is forming on earth will always have several components of it’s residual magnetism, and in many cases the Earth field will dominate all of the others, but not always. When the Earth field is weakened by a temperature cycle, the rock might express the polarity of the Sun and other planets.

    Now the polarity of the Sun changes with the sun spot cycles in a way that could be claimed to be linked to the locations of Jupiter and Saturn in the sky --- if you need a controversy to float your budget.

    Now for the big research grant controversy.

    It could be ( and really is ) argued that the reversal of polarity in the Earth field depends on the magnetic polarity of the Sun while the Earth core is cooling below the Curie point.

    The budget process would not be impressed with all of this, except for the fact that it has been quiet a long time since the last polarity reversal occurred in Earth rocks.

    So there is a chance we could witness a reversal of magnetic poles, and the environmental effects of our world without a magnetic field for a while.

    If it happens we will have a difficult choice to make about how to name the South Pole of a magnet.

    Text book publishers would have a good year.

    As usual, not everyone agrees.

    Hello Scientific,

    I am sending a news release regarding Earth's magnetic field that you can use on your blog. Please consider using it. You can find images on my website.

    Dennis

    CRAM SCHOOL

    FOR IMMEDIATE RELEASE

    Contact: Dennis Brooks
    Phone: 1-808-566-0654
    Email: dennisbroo@gmail.com

    Earth’s Magnetic Field Is Produced By An External Dynamo System, Not An Internal Dynamo.

    Researcher finds that Earth’s magnetic field is not produced by an internal dynamo. Nor is it produced by ocean current. The dynamo is outside the Planet! New findings by independent researcher, Dennis Brooks, show that Earth’s magnetic field and the planet itself are components of a complex dynamo system, which surrounds the planet. The planet and its magnetic field are part of the dynamo.

    According to this new theory, no internal dynamo or ocean current helps in producing or maintaining the magnetic field because other planets with magnetic fields do not have ocean currents or iron cores.

    Image by NASA

    Each planet does not have a unique way of producing its magnetic field. The magnetic field of each planet is produced by a planetary dynamo system and its ring current.

    For many years researchers thought that a similar dynamo system was within the planet and that this internal dynamo generated the magnetic field. However, we know now that it is too hot inside the planet to produce and maintain a magnetic field there.

    The planetary dynamo system is composed of a magnetosphere, the planet, the magnetic field, radiation belts, ring current, and charged particles from the solar wind. The planet is the central component of the system and its rotation plays an important part in operating the dynamo and generating ring current. The magnetic field is generated by the system’s ring current, which is made up of charged particles. The magnetic field captures even more charged particles and brings them into the dynamo system as fuel. Everything works together.

    Earth’s inner and outer core simply cannot provide the fuel a dynamo system needs. If earth’s dynamo had to depend on energy from the planet for fuel, the entire planet would have been completely consumed many years ago.

    To learn more about Earth’s magnetic field, Visit
    http://sites.google.com/site/earthsmagneticfield/

    ###

    Re: A couple of earlier comments

    "Dennis Brooks" and "Amateur Astronomer" are separated from scientific consensus here.

    The earth's core is waaay hotter than the Curie point of any ferromagnetic mineral (3500-7000 degrees C vs. up to 680 degrees C). The earth's magnetic field is not the product of stationary ferromagnetism, but rather of convecting charged particles. (See Wikipedia or other source for how moving charges produce a magnetic field.) The convection is driven by transfer of heat, both residual from the formation of the earth and in production via atomic decay. Rather than taking "too much energy," the magnetic field is a byproduct of the earth trying to get rid of "excess" energy.

    No one really knows why the earth's magnetic field switches polarity, but
    these guys
    intend to shed some light on the problem.

    Also, even when the earth's dipole magnetic field is in the process of switching, core convection still produces a much greater magnetic signal than the sun, though not in predictable places. And at any rate, most rocks (with the exception of lavas) take longer to record a signal than the magnetic field takes to switch (about 6k-10k years, if you're keeping score), so they'll just show one or the other polarity. I know of one example where a researcher analyzed a lava that showed an "east pole," but it's definitely not common.