Is it known what determines the rate with which plate tectonics occur?

When investigating the rate of the move of the Hawaii hotspot, from information provided here on Stack Exchange Earth Science, I cannot find a determination of cause for the rate, that does not point back to plate tectonics as the reason for the rate, but I am unable to determine if there is a known cause for the rate of plate tectonics.

Is it:

1. Random?

2. Natural sphere dynamics and nothing else?

3. The angles between the milky way, the "great attractor", the CMB, and earth's place between the three?

4. Other geological processes of which I am unaware??

Speaking to the possibility of it being #3, as far as I can determine, the sun seems to orbit around the Milky Way with a similar periodicity as many geological functions I am aware of on Earth. And the formation then spread of Pangea and recollection into Pangea Ultima if correctly predicted, would seem to further bolster this thought. And the rate of orbit around the Milky Way would seem to approximate (or match) the rate of the hotspots movement, which other than "driven by plate tectonics" would seem to be a global mystery.

So "little help over here"?

ADDED Oct 12, an excerpt from an article provided by Omen. Please ignore the part about evolutionary pressure.

The amount of radioactive material in the Core was certainly greater in the distant past. That greater amount proportionally created greater heat amounts which had to get to the Earth's surface to be able to be radiated away. One result of this was certainly that the materials of the Core and Mantle were hotter than today, and therefore more fluid. That situation was enhanced by the remaining presence of a substantial amount of heat remaining from the original formation of the Earth. Finally, convection cell flow rates are driven by the amount of heat that is present, so that also would make the Core convective cells and the Mantle convective cells much more active and much more dynamically unstable than today.

The result of all this was more heat driving convective cells in materials which were more fluid. This necessarily caused more rapid movements of those materials. This would have created substantially greater geomagnetic field strengths in the distant past. It would also have caused far more rapid lateral flow velocities in the Mantle convection cell tops.

Depending on the 'grip' (or static / dynamic coefficient of friction) between Mantle and Crust, this could enable very rapid tectonic plate movements in the distant past. When that caused substantial north-south movement in the continental plates, strong evolutionary pressure would suddenly exist.

Sorry for the delay, I waited a little to compose my words correctly, and to see if any alternate theories were strongly supported, to explain the 200+ million year rate of movement of the Emperor chain.

To the best of my ability to understand the answers so far, the "RATE" of churn" within the mantle, and resulting heaving and swirling of plate movement are derivatives of:

• the amount of heat within the earth,
• primordial,
• gravity pressure,
• tidal friction),
• combined with
• the gravitational tugs of the Sun and Moon on Earth,
• the resulting "jitter" within the earth caused by the Milankovitch cycles
• and the physical dynamics, properties and characteristics of
• heat generation rates,
• and transfer rates through varied mediums,
• sphere dynamics,
• the patterns within the movements caused by existing physical geographical patterns
• plus the random interaction between the Earth and various celestial bodies that have happened into our path over time, creating such geological features as the gulf of Mexico, the pool of nickel under Sudbury, etc. .

And therefor the shape of mountains and valleys, continent and ice cap are existential in nature. Random compared to other regards, such as other universal interaction to the Milky Way, or the shape and position and relative density of the various parts of the superclusters Laniakea and Perseus.

This is I believe accepted as the depth to which the situation has been considered? Or it has been considered further with less information and been decided non-consequential, perhaps (ie declining influence of gravitational force over distance)?

Some of the things within this frame-work of cumulative understandings, that I see as "unknown", "not clearly known", "potential factors", "assumptions", "theories" that are in contention", or "flat out Scooby Doo mysteries" are many and of significant value in consideration:

• the nature of the insides of an atom (now believed filled with Quanta energy field, the ratio of this energy to the mass energy of the sub components of the atom are massive),
• the nature of the insides of space (now believed "filled" with Dark Matter and Dark Energy equalling 95-96 percent of existence, squishing the 4% we see, know, and understand, into a pretty small corner.
• the nature of the "shape" of gravity, sought by IBEX, being re-sought by the Planck mission
• the nature of the "shape" of the Universe, (we have only in the past decade "perceived documented and published" details of the super-clusters existence. It is built on current understanding which include above noted lack of understanding.
• the nature of the origins of the Universe (the existence of the superclusters pretty much rule out the "viability of the truth of the Big Bang Theory (R.I.P.)
• the cause of the Milankovitch cycles ranges, parameters, timing, (causes I think)??
• the rate of disassembly of Pangea and recreation into the predicted PangeaUltima.

And so it is recognition of these conditions combined that begged me to ask the question...Is it known what determines the RATE with which plate tectonics occur?

The true underlying cause of the timing.

And as far as I can tell the best answer is circumstantial existence combined with the Sun and the moon.

Creating "It Is, What It Is."

I'll post this as an answer but I hope it get's down voted.

And some latitude to explore hypothetically will be granted. :-)

• +1 on your question - there is a lot more to plate tectonics than the standard theories, including some evidence suggesting lunar and rotational forces (as I added to my answer) – user889 Oct 12 '14 at 7:30
• and +1 on your find, and previous article. great stuff. My apologies for slow absorption. the first article you linked was pretty long, and no pictures to help it along. :-) – Alistair Riddoch Oct 12 '14 at 7:57
• @Omen do you think I should change the question title to questioning the cause of the rate of changes to mantle tide directions, and related location of tidal node points? Or break that off into a new question? – Alistair Riddoch Oct 12 '14 at 8:03
• That would probably be best as a separate linked question, as that change would render my answer as off-topic – user889 Oct 12 '14 at 8:06
• this question arose from another question I had about the cause of the shape of the emporor hawaii chain. should I link this to that, or that to this? (is there an "etiquette", or common "practice")? – Alistair Riddoch Oct 12 '14 at 8:08

We have a reasonably good idea of what mechanisms cause varying rates of plate tectonic movement. First though, the overall mechanism is postulated and generally accepted as being due to mantle convection, as summarised in the diagram below:

Image source: USGS

Essentially, the mantle plume is heated by deeper processes, so it partly melts and rises towards the surface and drags the crust, cooling at the same time, and the cooler more dense material drops (A full description is on the link).

So, in answer to your question about the rate of tectonic movement, the factors that cause different rates, suggested on the webpage The Mechanism Causing Plate Tectonic Movements friction between the crust and mantle, and friction at collision zones play a major role, as illustrated below:

Image source

Specific mechanisms include (from the links above):

• the thickness and density of the overlying crust

• given that mountains have 'crustal roots' into the upper mantle (asthenosphere), they can act as obstacles for mantle flow

• The heat energy within the mantle plume itself, as sources of radiogenic heat (e.g. uranium decay) are unevenly distributed.

Edited to include a recent theory involving tidal affects of the moon on our rotation:

Can Earth's rotation and tidal despinning drive plate tectonics? (Riguzzi et al. 2009), who assert that the Earth's and the moon's rotation may play a pivotal role in plate movement, the evidence for this includes:

1) plates move along a westerly polarized flow that forms an angle relative to the equator close to the revolution plane of the Moon;

2) plate boundaries are asymmetric, being their geographic polarity the first order controlling parameter; unlike recent analysis, the slab dip is confirmed to be steeper along W-directed subduction zones;

3) the global seismicity depends on latitude and correlates with the decadal oscillations of the excess length of day (LOD);

4) the Earth's deceleration supplies energy to plate tectonics comparable to the computed budget dissipated by the deformation processes;

• Thanks Omen. Do you know if there are tidal influences on the mantle from the sun, the moon (and perhaps neighbouring planets?)?? In a similar nature to the tidal influences of the sun, moon, etc, on the oceans? – Alistair Riddoch Oct 12 '14 at 7:12
• You're welcome @AlistairRiddoch, I found a couple more references which I will edit into my answer. – user889 Oct 12 '14 at 7:17
• I have read what you put in the answer above, and tried reading through some of the article you linked. (it is pretty heavy for my brain, I have to stop and think a lot to visualize what I am reading). I am copying one excerpt into my question, for further address. As I come across other information I think is specifically relevant I will post it too. And thanks again. :-) – Alistair Riddoch Oct 12 '14 at 7:25
• @AlistairRiddoch I found a pretty convincing one about the moon's effects on plate tectonics, given that gravitational tidal effects of the moon are likely to have a greater influence than from other bodies in the solar system (potentially drowning out other influences). Let me know if there is anything else you would like me to find and add. – user889 Oct 12 '14 at 7:27
• lol. sorry. I am trying. for clarity from relation, do you know if earths spin rate is constant gradual decline, or oscillates? and whether there have been flow history pattern studies done on the ring of fire? I don't mind the looking, when i know something exists (i dont mind when I don't know either, but am more wiling to ask when that's the case). :-) – Alistair Riddoch Oct 12 '14 at 8:29

As the likely main causes for the rate of tectonic shifts have already been laid out, I just wanted to give a brief argument on why we can discard other sources (Planets, Galactic..) as sources for frictional energy in the Earth's interior.

Tidal forces originate in differential gravity forces (= 2 or more mechanically connected points of a body experiencing different gravitational forces).

Those forces scale as $\sim \frac{M_{central}}{R^3}$ (gravity decreases slower, as $\sim \frac{1}{R^2}!)$. Also we know that in certain Sun-Moon-alignments on Earth there happen certain events of very strong neap tides. So we can conclude, that Solar tidal forces can still play a role in the Earth's interior.

But when we now want to scale this to planets of the solar system, distant molecular clouds, stars, central black hole, great attractor or whatever you want, we loose very fast any contribution to those forces.

I don't get however, how you want the CMB to contribute to tidal forces?

OCTOBER 20, 2014

Q: Is it known what determines the rate with which plate tectonics occur?

A: It is existential, natural and random in nature caused by so many factors that we believe there is no opportunity for influence by celestial bodies outside our solar system, and we know enough about gravity, the atom, the universe, and the nature of existence to believe we have thoroughly investigated and believe our understandings/conclusions to be complete and finite. We "accept this as the whole truth and nothing but the truth"???

"I believe this to be succinct, to the point and accurate, but I don't like it" - AR Oct 20, 2014. Vote down if you don't like it and encourage some hypothetical wild speculation. :-)

• Seems like you want the answer to be that extraterrestrial objects can affect plate tectonics on Earth. They don't. You can stop your wishful thinking. – Gimelist Dec 16 '14 at 5:41
• Yes, and I am trying to figure out the best way of saying why and how. Perhaps to suggest, consider the perpetual and omnipresent nature of gravity, that while we circle the milky way, everything exterior to it, is relatively stationary in comparison. The continents seem to act in an oscillating pattern like two balloons tied in the middle, bouncing back and forth about every 250,000,000 years. So I wondered if some of the oddly moving hot spots could also relate. The universe is always there, but we move greatly relative to the milky way, relative to the universe. – Alistair Riddoch Dec 19 '14 at 22:59
• The gravitational pull of extraterrestrial objects is negligible relative to other sources. Even the gravitational pull exerted by high density objects in the Earth itself is higher. You are "trying to figure out the best way of saying why and how". You don't need that. There is physics. Physics will say that - and physics says it does not happen. – Gimelist Dec 20 '14 at 6:21
• But if every body of matter in the universe affects every other body of matter in the universe, and all matter is made of matter that previously existed, just getting constantly rearranged all the time, then isn't all of space "pre" configured, by the waves of energy/gravity/whatever that left, are leaving, and will leave, all objects, back forever, and until forever. Gravity is a two way street. you are not attracted "as much" to the side of the planet, or star, that is rotating towards you, as you are to the side of the planet or star, that is rotating away from you. Lots of factors. – Alistair Riddoch Jan 18 '15 at 0:45
• Is there an effect? Yes. Is it significant? No. Does it affect plate tectonics on Earth? Definitely no. – Gimelist Jan 18 '15 at 0:59