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Actual linkage between tectonic-mantle motions and lunar recession speeds?
Is there an overarching link between the fact that, on the one hand: (1)
plate tectonic motions range typically between a few mm/year to about 100 mm/year, & (2) mantle convection speeds average roughly around "..20 mm/yr.." (wikipedia entry)...and on the other hand: (3) the Moon, due to tidal effects, is "..spiraling away from Earth at a rate of 3.8 cm/yr [or about 38 mm/yr...me] per year (wikipedia entry) ? Ie: Can these very similar values all have a common origin--perhaps in the mutual spin and tidal interactions of the Earth-Moon-Sun system? The usual driver for mantle (and plate) motion is said to be due to the heat flow and the local geochemistry of the Earth's interior, and of course the decay of several radionuclides. Ie: Is this similarity between (1, 2) and (3) merely a quirky coincidence? Or, over billions of years, have all three processes achieved some mutual energetics 'partitioning' balance? [[Mod. note -- It's a coincidence. -- jt]] |
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Actual linkage between tectonic-mantle motions and lunar recession speeds?
In article ,
stargene writes: Is there an overarching link between the fact that, on the one hand: (1) plate tectonic motions range typically between a few mm/year to about 100 mm/year, & (2) mantle convection speeds average roughly around "..20 mm/yr.." (wikipedia entry)...and on the other hand: (3) the Moon, due to tidal effects, is "..spiraling away from Earth at a rate of 3.8 cm/yr [or about 38 mm/yr...me] per year (wikipedia entry) ? Ie: Can these very similar values all have a common origin--perhaps in the mutual spin and tidal interactions of the Earth-Moon-Sun system? The usual driver for mantle (and plate) motion is said to be due to the heat flow and the local geochemistry of the Earth's interior, and of course the decay of several radionuclides. Ie: Is this similarity between (1, 2) and (3) merely a quirky coincidence? Or, over billions of years, have all three processes achieved some mutual energetics 'partitioning' balance? [[Mod. note -- It's a coincidence. -- jt]] I agree with jt here. In cosmology, some people make much of apparently unrelated quantities, for example the age of the universe and the Hubble time (which means that, essentially, the decelerating and accelerating phases cancel---more interestingly, they do so only now), or the energy density due to matter and the cosmological constant. Coincidence or something deeper? Essentially, this means that two quantities are roughly equal, or that their ratio is a very small (or, if the other way around, very large) number. Other people claim that it is extremely small (or large) dimensionless numbers which need explanation, not the other way around (cue "naturalness"). (I tend to think that an equality needs an explanation; if two things are unrelated, chances are that their ratio will be a small (or large) number.) The literature here is confusing, to say the least. The angular size of the Sun and the Moon---which allows the corona to be seen during a total solar eclipse---is also such an equality, but for some reason most don't see it as significant (and, as noted above, the Moon is receding from the Earth, so this equality holds only now). What determines whether such an equality (or near equality) is "interesting"? The brightest stars, planets, and meteors are all about 0 mag. As far as I know, this is just a coincidence. (At other locations in the universe, this would not hold.) As Yogi Berra said, one can find a lot of things by looking. ------------------------------------------------------------------------------- Well, the trouble with coincidences is that sometimes they tell you something and sometimes they don't. ---Mike Turner |
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Actual linkage between tectonic-mantle motions and lunar
Ie: Can these very similar values all have a common origin--perhaps in the
mutual spin and tidal interactions of the Earth-Moon-Sun system? The usual driver for mantle (and plate) motion is said to be due to the heat flow and the local geochemistry of the Earth's interior, and of course the decay of several radionuclides. Ie: Is this similarity between (1, 2) and (3) merely a quirky coincidence? Or, over billions of years, have all three processes achieved some mutual energetics 'partitioning' balance? [[Mod. note -- It's a coincidence. -- jt]] Earth core heating can be stated as an effect of Sun/Earth/Moon gravity tidal effects. This effect is seen in comet core heating as it passes near the sun. The core of the comet heats before the surface does. So if tidal heating is real, the moon certainly be said to effect the Earth core heating. And core heating then could be said possibly altering mantle state. Star to star tidal heating would then be seen as a dark matter effect. Begging the question of observing dark matter in this solar system. |
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Actual linkage between tectonic-mantle motions and lunar
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Actual linkage between tectonic-mantle motions and lunar
On Friday, August 17, 2018 at 12:14:11 AM UTC-7, stargene wrote:
Is there an overarching link between the fact that, on the one ..... Okay, I can understand how the closeness between mantle/plate motion and lunar recession motion can be a coincidence. Nothing suggests otherwise apparently. It does seem to me that a check might be to compare their respective motion rates in the deep geophysical past--Say, over two billion years or so--One would somehow need to detect fossil plate-motion speeds, probably using proxies. Additionally, could one reliably constrain lunar recession speeds over the same intervals? Ie: If it then appeared that the two different motions were close over the Earth's age, it might suggest a coupling. But again, a plausible coupling mechanism would be needed, to consider linkage to be not merely circumstantial. I don't know if current geophysical techniques would reasonably support such a search. [[Mod. note -- Alas, I don't think we have experimental data giving either of those rates at any time other than "now". So any estimates for gigayears in the past are going to be heavily dependent on theoretical models of the underlying dynamics. There are then two possibilities: * If you think the the models are basically ok, then it's obvious that the plate-tectonic and lunar-orbit-evolution rates are independent. * If you don't think the models are basically ok, then you probably shouldn't trust their estimates of either rates in the distant past. -- jt]] |
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Actual linkage between tectonic-mantle motions and lunar
On 2018-08-20, Phillip Helbig (undress to reply)
wrote: In article , writes: Earth core heating can be stated as an effect of Sun/Earth/Moon gravity tidal effects. That certainly plays a role. However, the Earth is heated by radioactivity to a significant extent as well. The text by W Hubbard on Planetary Interiors notes that the Earth has an unusually large dissipation coefficient for tidal dissipation and suggests a lot of it is in the surface or near surface layers. Tidal motion of the oceans (main sloshing period about 40 hours, compared to the 24 hr rotation... IIRC originally noted by Laplace) seems to have a big effect. The discussion suggested that not a lot of the tidal effects in the Earth have to do with the core. Quesiton about the radioactive heating: is it more Potassium 40 in the deep core anyway (I thought the heavy U or Th stuff was closer to the surface, maybe outer mantle)? -- ciao, Bruce |
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Actual linkage between tectonic-mantle motions and lunar
In article , "Richard D.
Saam" writes: Lord Kelvin(1824 - 1907) did not have the radioactivity concept available to him (he did not believe Marie Curie's 1867- 1934 radioactivity) and thermodynamically predicted the earth's age at 20-200 million years (off by factor of thousands). Even 20 million to 4 billion is a factor of only 200. Yes, he was very wrong, but not by a factor of thousands. In his famous estimate of the age of the Earth, he did include the caveat "unless another source of energy is found", as, indeed, it was. |
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