Tug of sun, moon could be driving plate motions on ‘imbalanced’ Earth, suggest researchers

Posted: January 22, 2022 by oldbrew in Geology, Gravity, moon, research, solar system dynamics
Tags: ,

Credit: reference.com

Plate tectonics has always been good for a science controversy or two. This one throws some solar-planetary spice into the mix, putting a focus on the Earth-Moon barycentre.
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A study led by geophysicist Anne M. Hofmeister in Arts & Sciences at Washington University in St. Louis proposes that imbalanced forces and torques in the Earth-moon-sun system drive circulation of the whole mantle, says Phys.org.

The new analysis provides an alternative to the hypothesis that the movement of tectonic plates is related to convection currents in the Earth’s mantle.

Convection involves buoyant rise of heated fluids, which Hofmeister and her colleagues argue does not apply to solid rocks.

They argue that force, not heat, moves large objects.

The new research is published in a special paper of the Geological Society of America, as part of a forthcoming collection assembled in honor of geologist Warren B. Hamilton.

Earth’s internal workings are popularly modeled as dissipating heat generated by internal radioactivity and from leftover energy created during collisions when our planet formed.

But even mantle convection proponents recognize that that amount of internal heat-energy is insufficient to drive large-scale tectonics. And there are other problems with using convection to explain observed plate motions.

Instead, Earth’s plates might be shifting because the sun exerts such a strong gravitational pull on the moon that it has caused the moon’s orbit around Earth to become elongated.

Over time, the position of the barycenter—the center of mass between the orbiting bodies of the Earth and the moon—has moved closer to Earth’s surface and now oscillates 600 km per month relative to the geocenter, Hofmeister said. This sets up internal stresses, as the Earth continues to spin.

“Because the oscillating barycenter lies ~4600 km from the geocenter, Earth’s tangential orbital acceleration and solar pull are imbalanced except at the barycenter,” Hofmeister said. “The planet’s warm, thick and strong interior layers can withstand these stresses, but its thin, cold, brittle lithosphere responds by fracturing.”

Daily spin flattens the Earth from a perfect spherical shape, which contributes to this brittle failure of the lithosphere. These two independent stresses create the mosaic of plates observed in the outer shell, the authors suggest.

The variety of plate motions comes from the changes in size and direction of the imbalanced gravitational forces with time. But how to test this alternative?

Full article here.
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ABSTRACT
Lateral accelerations require lateral forces. We propose that force imbalances in the unique Earth-Moon-Sun system cause large-scale, cooperative tectonic motions. The solar gravitational pull on the Moon, being 2.2× terrestrial pull, causes lunar drift, orbital elongation, and an ~1000 km radial monthly excursion of the Earth-Moon barycenter inside Earth’s mantle. Earth’s spin superimposes an approximately longitudinal 24 h circuit of the barycenter. Because the oscillating barycenter lies 3500–5500 km from the geocenter, Earth’s tangential orbital acceleration and solar pull are imbalanced. Near-surface motions are enabled by a weak low-velocity zone underlying the cold, brittle lithosphere: The thermal states of both layers result from leakage of Earth’s internal radiogenic heat to space. Concomitantly, stress induced by spin cracks the lithosphere in a classic X-pattern, creating mid-ocean ridges and plate segments. The inertial response of our high-spin planet with its low-velocity zone is ~10 cm yr–1 westward drift of the entire lithosphere, which largely dictates plate motions. The thermal profile causes sinking plates to thin and disappear by depths of ~200–660 km, depending on angle and speed. Cyclical stresses are effective agents of failure, thereby adding asymmetry to plate motions. A comparison of rocky planets shows that the presence and longevity of volcanism and tectonism depend on the particular combination of moon size, moon orbital orientation, proximity to the Sun, and rates of body spin and cooling. Earth is the only rocky planet with all the factors needed for plate tectonics.
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Study here [select ‘Chapter PDF’]

Comments
  1. […] Tug of sun, moon could be driving plate motions on ‘imbalanced’ Earth, suggest rese… […]

  2. Jim says:

    Interesting. Scummy on a warm interior, versus cold interior, by decomposition radiation and magnetic flux. In other words, could we create a warm mars? Or a cold Venus. According to the article, what is needed is a strong magnetic field, off center, and a few strong necular weapons underground to stimulate the development of a warm mars. That said, no one will be able to live there because of radiation from bombs, not heat. It’s more interesting to drop ice cubes on Venus. And see what happens.

  3. jb says:

    Where do they come up with the 2.2x gravitational force of the sun over earth’s?
    The sun’s gravitational force is 4.1645e20 (ms^-2m^2), falling off at the rate of 1/r^2, becomes at the earth’s radial distance of 1.4957e11 meters to .01859 (ms^-2m^2).
    The gravitational force of the earth is 1.25e15 ms^-2m^2, falling off at the moon, at a radial distance of 3.4844e8 meters becomes .01 (ms^-2m^2). This ratio is significantly less than 2.2x.

    I’m a neophyte at celestial mechanics. I’m sure I’ve overlooked something here. But somehow I don’t quite accept that Anne M. Hofmeister has got this down either. Especially the part about tectonic influence, especially regarding the inter-relational affects of the sun’s planetary barycenter, the E-M barycenter, and the resultant S-E-M vectored barycenter, with that complex differential driving plate movement. Something similar should also be present within the moon, more than just quakes.

  4. oldmanK says:

    Patrick Geryl says: January 22, 2022 at 3:51 pm

    From link (interesting)
    Quote “The full alignments will be published after the earthquake has happened. The theory is quite
    complicated, and a lot of the crucial alignments change every 15 minutes.”

    Just 15 minutes, and probably no warning. In an earlier thread I would have guessed ‘abrupt’ as Plato put it; “in a day and a night”.

  5. Paul Vaughan says:

    headline: “Tug of sun, moon could be driving plate motions on ‘imbalanced’ Earth”

    That’s what I said ….and modelers of “global average surface temperature” misinterpret, misunderstand, and misrepresent spatiotemporally, materially, & biologically biased sampling.
    (…thus ending up – for example – interpreting spatial bias as temporal signal).

    Unbelievable oversight: So many fixate on gravitational tides and totally ignore thermal tides.

  6. Paul Vaughan says:

    Frankly I think 99.9% of climate commentators misinterpret “thermal tide” every time they read it.
    If they read this note I’m confident 99.9% will simply continue misinterpreting. Weather ignorance or deception: dark hydrological instinct either way.

  7. Bloke down the pub says:

    ‘Convection involves buoyant rise of heated fluids, which Hofmeister and her colleagues argue does not apply to solid rocks.’
    Depends on your definition of solid. Glass is solid but over centuries a pane will gradually slump to the bottom.
    The idea of Sun/Moon gravitational pull on techtonic plates though may give a possible reason for why, over geologic history, the Earth’s plates have frequently clumped together to form single mega-continents.

  8. Phil Salmon says:

    Convection involves buoyant rise of heated fluids, which Hofmeister and her colleagues argue does not apply to solid rocks.’

    Are they seriously suggesting that the earth is solid to the core?

    Patches of scum on the surface of a convecting liquid will move horizontally in a manner very similar to the way earth’s continents have (speeds are different though). There’s no need to invoke an external horizontal force.

    At first earth’s continents huddled together without moving much because the liquid magma churning underneath was too mobile (runny), not viscous enough. Thus the “boring billion” from 0.8 – 1.8 BYa. Then the magma cooled and stiffened enough (increased viscosity) so that it could tug at the continents and pull down the subducting margins. Then the tectonic dance of continents kicked off. And soon after that multicellular life started.

  9. pochas94 says:

    Another example of differential rotation is the sun…

  10. Gamecock says:

    I’m with you, jb. I thought the barycenter was a calculated position, not a physical one.

    It certainly seems logical that as the moon and sun induce tides in the seas, they would also affect floating tectonic plates. However, plate movement is no faster than hair growth speed. I would expect plate movement driven by tidal forces to have greater movement.

    I’m okay with the force(s) moving tectonic plates being theoretical.

  11. oldbrew says:

    The exact barycentre of a system of moving masses is tricky, even assuming the total mass of the system is constant. But it’s not the centre of the Sun, mainly due to Jupiter.

    https://spaceplace.nasa.gov/barycenter/en/

  12. […] Tug of sun, moon could be driving plate motions on ‘imbalanced’ Earth, suggest researchers […]

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