Radiation evidence in Volcanic lava

Discussion in 'Free Thoughts' started by river, Jan 10, 2018.

  1. Janus58 Valued Senior Member

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    The total estimated wattage produced by radioactive decay in the Earth is 2e13 watts. That's the equivalent of
    The whole problem here is that you are assuming that in order to maintain the 2e13 watt generated by radioactive decay, that the interior of the Earth must be more radioactive than the crust of the Earth is on average. This is not the case.

    For instance, it is estimated that the crust contain ~2 parts per million of Uranium. If we were to assume that this held for the entirety of the Earth, this gives us ~ 1.2e19 kg of Uranium for the Earth. At roughly 2.5e24 uranium atoms per kg, this gives us 3e43 uranium atoms in the Earth total. Given the half-life of U-238, the most abundant isotope of 4.468e9 years, We get a decay rate of ~4.9e-10/sec. At this decay rate, and starting with 3e43 uranium atoms, in one second, ~1.5e26 atoms will have decayed.
    Upon decaying, each atom releases ~6.9e-13 joules of energy, so this equates to 1e14 joules/sec or 1e14 watts. This is 5 times the 2e13 watts needed. In essence what this means that the interior of the Earth, if anything is on average less radioactive than the crust. Of course this is just a rough estimate, but is close enough in degrees of magnitude to show that lava expelled by volcanoes does not need to be more radioactive than surface rock in order to get the estimated heat output from radioactive decay within the Earth.
     
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  3. exchemist Valued Senior Member

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    Yes indeed. However these plumes are not what lava is made of - or not in any simple way. The plumes are convection currents in the mantle that lead to a higher than normal temperature in the rocks in the upper mantle and lower crust, at these so-called "hot spots". This can lead to "zones of partial melting", within which the temperature is high enough, in relation to the prevailing pressure from the weight of rock above, for some of the lower melting points minerals to liquefy, producing a magma. https://en.wikipedia.org/wiki/Partial_melting. Melting reduces their density and so the magma tends to rise through any weak spots or cracks and, as the pressure drops further as it rises, dissolved gases may be released, further reducing the density and providing a pressurised medium for penetrating and expanding cracks. Eventually this may break through to the surface and the magma becomes lava.

    As it is partial melting, there is a fractionation process, whereby certain minerals are selectively melted out and rise up. So the composition of any lava erupted at the surface will not accurately reflect the composition of the rocks from which it is derived. As my earlier post indicates, radioactive minerals are often largely left behind and are found more in granite than in most lavas.

    Footnote: But it looks to me as if Janus's contribution is the real point here. I must admit I did not know that. Very interesting.

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  5. river

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    But lava should be radioactive to some extent .
     
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  7. Janus58 Valued Senior Member

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    No more so than anything else. The total geo-radioactivity of the Earth is the equivalent of four U-238 atoms decaying per second, per kg of the Earth. Naturally occurring carbon, contains enough C-14 for there to be ~1700 atoms decaying in every kilogram per second. I would hardly call naturally occurring carbon as being "radioactive", and it is many more times so than you would expect lava to be, even if all the geo-radioactivity were constrained to the mantle.
    There simply is no reason to expect lava to be exceptional in terms of radioactivity.
     
  8. Gawdzilla Sama Valued Senior Member

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    Besides, we'd have to allow for radiation loss due to Pellucidar's proximity to the outer surface of the Earth.
     
  9. iceaura Valued Senior Member

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    And no reason to measure and check while the stuff is still hot enough to melt rock.
     
  10. river

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    Fiction
     
  11. river

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    Does the lava have radioactivity in the first place , is the question .


    Why not ?
     
  12. Gawdzilla Sama Valued Senior Member

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    Are you sure you get the Internet?
     
  13. river

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    Does lava have radioactive material in it , hot or cooled ?

    I have looked this up from the start of the OP . And nowhere is there any evidence that this has been done , nowhere .

    And if it had been, I'm sure you bunch would have mentioned the website that did by now.
     
    Last edited: Jan 20, 2018
  14. Gawdzilla Sama Valued Senior Member

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    Madame Curie got everybody into checking everything for signs of radioactive materials. Lava was probably checked off well before July 4, 1934.
     
  15. river

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    Probably does not count as a fact .

    So until you can prove that lava has signs of radioactive materials , in any time period , your just spouting non-sense .
     
  16. Gawdzilla Sama Valued Senior Member

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    Poor boy, can't read a book.
     
  17. river

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    What book ?
     
  18. Gawdzilla Sama Valued Senior Member

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    Callahan's Crosstime Saloon.
     
  19. river

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    Which is about ?
     
  20. Gawdzilla Sama Valued Senior Member

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    ~198 pages.
     
  21. river

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    Subject of the book
     
  22. Gawdzilla Sama Valued Senior Member

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    Science.
     
  23. river

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    Science of what exactly ?
     

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