Source of Earth's Interior Heat

Discussion in 'Earth Science' started by Facial, Mar 23, 2018.

  1. Facial Valued Senior Member

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    The two most prominent explanations are:

    1. Heat left over from the planet's initial formation. Planetary accretion generates a tremendous temperature far higher than silicate melting temperatures. When considering the measured geothermal gradient, accounting for convection is able to push the estimate for earth's age up to 3 billion years using the same initial temperature (~3900K) as Kelvin did for his erroneous calculation. We now know accretion can generate initial temperatures of up to 10000K, although a fraction of this is lost into space.

    Further reading:
    https://www.scientificamerican.com/article/why-is-the-earths-core-so/
    https://websites.pmc.ucsc.edu/~rcoe/eart206/England_Kelvin-Perry_AmSci07.pdf

    2. Heat generated by the decay of radioactive elements. Estimates amount to at least 20 terawatts according to a study with neutrinos. Confidence from these 'geoneutrinos' derives from analysis of their velocity spectra. The fraction of power output is about half that of the total heat flux currently leaving the deep earth.

    So which one is more important? I think the radiogenic studies compare the total volumetric heat production to that merely leaving earth's deep interior, not its total heat content. Thus I am left with the impression that primordial heating is the dominant source. Just asking because I've been confused about this issue for a long time.
     
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  3. DaveC426913 Valued Senior Member

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    Last I heard, the heat left over from formation is nowhere near sufficient to keep a body heated from so long. I thought they'd debunked that hypothesis.
     
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  5. exchemist Valued Senior Member

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    I'm not sure anybody knows which of the two makes the bigger contribution. Certainly the Wiki article suggests the estimates of each source of heat cover a wide range, and the two ranges are comparable in magnitude.
     
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  7. Write4U Valued Senior Member

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    Doesn't the earth itself generate heat?

    Being that most of the earth's mass (gravity) surrounds the inner core is it not true that compression causes heat?

    Being that the earth's outer core is fluid, and the earth's mantle is in constant movement over the outer core, is it not true this movement causes heat?
     
  8. exchemist Valued Senior Member

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    No. The act of compressing something raises the temperature: work is done on the system being compressed and this is converted to heat, resulting in a rise in temperature. However something that is merely in a static compressed state has no work being done on it. It is in an equilibrium state , in which the compressive force is balanced by the force of resistance from the material that has been compressed.

    In the ancient past, as the Earth was forming, then yes, the reduction in radius as it was compressed by its own gravity did lead to internal heating. However, so far as I am aware, the Earth is not thought to be being further compressed today, so that process has stopped and we are just left with the heat left over from that original compression process.

    Regarding the internal motions of the rocks of the Earth, it is the interior heat that creates a temperature gradient, which leads to convective motion of the rocks, not the other way round.

    There is some tidal heating due to the moon, but from what I read, its contribution is not significant.
     
    Last edited: Mar 31, 2018
  9. RainbowSingularity Valued Senior Member

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    1,090
    for arguement sake...
    if the core was a spinning molten core, would it gain energy from earth rotation and orbit around the sun ? kinda like a giant ellectrical motor winding with the megnetic fields and rotational spin... ?
    just a passing thought
     
  10. exchemist Valued Senior Member

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    I don't think so.
     
  11. RainbowSingularity Valued Senior Member

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    1,090
    i am trying to visualise a newtons cradle of spinning orbital force vectors.
    plus squeezing from the sun & planetary alignment.

    we already know our solar system is quite rare having only 1 sun...etc...

    im kinda picturing a YoYo which is also in orbit around a big magnet...

    refering to a different thread RE dark energy... RE accelerating expansion... etc...
    all we are missing is the ability to see the giant space alien pulling the string of ther giant YoYo(euphemistically)
     
  12. DaveC426913 Valued Senior Member

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    The sun, by many, many orders of magnitude is the most gravitationally influential mass in our solar system. (excepting Earth's and Pluto's own moons.)
    The other bodies in the system barely disturb their orbits, let alone squish them.


    If the sun's pull were strong enough to distort a planet so much as to liquify its core, then Mercury - the closest planet to it - would certainly have a liquid core. Which it does not.
     
  13. RainbowSingularity Valued Senior Member

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    1,090
    a body in motion etc etc... ?
    escape velocity
    liquification terminal energy point requirement...
    flashpoints...
    gasious metals etc etc....
    im pondering if the combined effect maintains the required force/energy to maintain the inertia which maintains the potential "molten" thingey.
     
  14. DaveC426913 Valued Senior Member

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    You have merely apply these to our system's planets and see if any apply. I think you'll find that every one of those factors has an exception.
     
  15. exchemist Valued Senior Member

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    What's with the word salad, suddenly? What is meant by "liquification terminal energy point requirement"? And what does "flashpoint", (which is concept related to combustion, have to do with any of this?
     
  16. RainbowSingularity Valued Senior Member

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    1,090
    yesss, well... there you have it... im not a physicist specialising in Supramolecular chemistry with a panchent for radiant energy puzzles & Hydrology.
    a degree in math might come in handy, though i am at quite a loss.


    i am not feeling very dynamic in my fluid cognition presently.
    im hoping its just a phase.


    This i can do
    This i wont do

    pick 1
     
  17. Michael 345 Looking for Bali in Nov Valued Senior Member

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    ? another nebel?

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  18. exchemist Valued Senior Member

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    Not quite. I don't think numerology is his thing. This seems to be just throwing out random sciency-sounding terms, perhaps in the hope that someone will pick one of them up. Oh well, maybe someone with more patience than I can have a go at dealing with it. Dave seems to be less easily annoyed than I am, for example.......

    To be charitable it may be that he thinks this is the way to talk to scientists, a bit like that Flanders and Swann dialogue about how you talk to a scientist: "Ah, H2SO4 professor! Don't synthesise anything I wouldn't synthesise. Oh, and the reciprocal of π to your good wife."

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    Last edited: Apr 2, 2018
  19. Michael 345 Looking for Bali in Nov Valued Senior Member

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    Take out the word salad - the remaining mayonnaise has no flavour

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  20. DaveC426913 Valued Senior Member

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    I thought we'd agreed that rainsing is a sock of a banned member.
     

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