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Fusion or fission within the Earth?

  1. Dec 22, 2009 #1
    I have been searching online for any credible information about fusion or fission occurring and contributing significantly to the Earth internal temperature. Can anyone explain this to me further?

    So far I have heard several media sources discussing how fusion within the Earth is a contributing factor to global warming. I had always believed that pressure was the primary cause of heat within the Earth.

    The http://en.wikipedia.org/wiki/Structure_of_the_Earth" [Broken] mentions nothing of fusion or fission occurring within the Earth.
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 22, 2009 #2
    This is crackpot territory (fusion). There have been cases made for fission heat, most likely, the decay of 40K to 40Ar/40Ca but basically everything is speculation.
     
  4. Dec 22, 2009 #3

    Integral

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    It is my understanding that radioactive decay contributes to the internal energy of our planet. Radioactive decay does not imply that either a sustained fussion or fission reaction is occuring.
     
  5. Dec 22, 2009 #4
    Ok, that makes more sense. I figured it was a crackpot statement, but I had heard about it enough to warrant making sure.
     
  6. Dec 22, 2009 #5

    Astronuc

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    One would not find any 'credible' source that would cite fission or fusion occuring in the earth, and certainly it's not causing global warming. The conditions in the earth are not favorable for pp-fusion, nor dd fusion. Any tritium would have decayed to He-3 (so no dt fusion, besides the conditions not favorable), and He-3 is pretty rare on earth.

    As far as we know the core is Fe or Fe-Ni, so not favorable for fission which would require the right amount of U-235. If there was ongoing fission, we'd be seeing lots of neutrinos from within the earth.

    One could ask if there is more geothermal energy/lava flows now than say 4 or 5 or 10 decades ago.
     
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  7. Dec 22, 2009 #6

    Xnn

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    Not so!

    While not a source of global warming, there is credible evidence of a natural fission reactor occuring in Africa approximately 1.7 billion years ago.

    Here is the fact sheet from the DOE:

    http://www.ocrwm.doe.gov/factsheets/doeymp0010.shtml [Broken]
     
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  8. Dec 22, 2009 #7

    Integral

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    yes, xnn, there was very likely an ancient natural reaction running for a period of time, however being located on the surface, did not contribute energy to heat the earths core. That was the original question.
     
  9. Dec 22, 2009 #8

    Astronuc

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    1.7 billion years ago is not within the last few decades or centuries - now is it? We're talking about present times - not millions of or a billion years ago. :rolleyes:

    The hottest part of the earth is the core, with some heat coming up through the crust in areas of volcanic activity, e.g. subduction zones. But we see no evidence of fission, and certainly not fusion.
     
    Last edited by a moderator: May 4, 2017
  10. Dec 24, 2009 #9

    LURCH

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    I believe that most of the statements one reads about "fission" in the core as a heat source are actually referring to radioactive decay. The term is not entirely inaccurate, as this is a process of atomic nuclei splitting and giving off energy as a by-product. However, the word "fission" normally refers to a sustained chain reaction.
     
  11. Dec 24, 2009 #10
    If earth is a reactor than fission reaction fuels the energy on earth .
    Refer to this abstract
    www(dot)pnas(dot)org/content/98/20/11085(dot)full
     
  12. Dec 24, 2009 #11
    I wonder if there has been any work done in this area since the paper was written? It was submitted in 2001.

    It would be interesting to see if there was any way to create a time line of significant fission periods and maybe see if they correlate with major and minor extinction events.
     
  13. Dec 24, 2009 #12

    Xnn

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    http://www.pnas.org/content/98/20/11085.full

    Interesting paper...

    In summary, if the inner core is formed of crystallized Nickel Silicide instead of Iron, then it would be stable. Over time Uranium, Thorium and other actinides due to their mass would tend to concentrate along the boundary of the inner core where they could reach a critical mass. Such a reactor could be producing about 10% of the heat within the earth and would vary over time as the actinides were gradually scavenged from the outer core and mantel. This variation over time might explain reversals of the earths geomagnetic field.

    The reactor would need to be a breeder to have lasted as long as it has and to have only slightly dropped in power over 4.5 billion years. The ratio of 3He/4He found in deep-mantle magma sources (Hawaiian volcanic lavas) are in excess of the current atmospheric ratio by a large factor, and are consistent with those from a Deep-Earth Reactor.

    More work is needed to obtain fission yield data for Neon to see if it is consistent with the above assumptions.
     
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