Tuesday, April 4, 2017

How Plate Tectonics gets going ..

(Repost from indigo website archives, 2008)
Rubber numbers rule - ( you bet.)
  ....In which Team-Leader Rubbery Trolley-Dosser argues the case for Plate Tectonics via thermal modelling...

Having answered to his satisfaction the question, "What keeps fragments of the Earth's crust bouncing backwards and forwards off each other from one end of the planet to the other (like railcars in a shunting yard", and feeling hugged by a Size 0 Rubber Number, our intrepid convectioneer sets out to explore the contradictions and conundrums of subduction in a bid to answer what gets it all going in the first place, fully aware (but hoping nobody notices) he has explicitly chosen colours which, if everything goes belly-up, will identify him as a fifth-column expansionist.

 Maybe (not):-  Always game for a throw of the rubbery dice when it comes to numbers, our bold convectioneer is less confident when it comes to matters of the sophomoric mind: -
 "Maybe. Maybe not. I agree that how subduction gets going is an interesting problem. What keeps it going is a less interesting one. " | link1 | | link2 |

 Convecting substances:-  The predicament for Plate Tectonics is that despite the many geological conundrums it faces, support centres purely in the dynamics of convection.  Rather than confront those conundrums, ever more substances are examined in a drive to find the one which, through the kalaiedoscope of rubbernumber manipulation, may most closely match that of solid rock:-
Ketchup:-  "Really? Diffusion works different in ketchup?  Simple fact is one can find regimes where the properties of ketchup remain more or less uniform i.e, the phases don't separate. I was able to find them for corn syrup, silicon oil, all sorts of stuff."   | link |

Smart:- In a bold and ostentatious move to outsmart the argument for a Nobel Prize, our brave fifth columnist volunteers a moniker for Plate Tectonics as  "massive academic fraud",  thus sticking his paddle through the gunnels of his canoe and seriously compromising his chances of making it over the next wave.

 The next wave - a rubber number:- In a bid to redeem himself over his gaffe of academic fraud and casting to the wind grammar, syntax, spelling, and the fact that the ocean floors are riddled with more fractures than a truckload of slack, our bold convectioneer proceeds to demonstrate the parameterisations by which Plate Tectonics has attained celebrity - how seismic wave speed anomalies may be converted to temperature / pressure, "using equations of state determined from actual rocks" and thus converted to density enabling a further calculation be made to extract stiffness of the lithosphere, from which may then be calculated subduction rates and thus rates of mantle overturn - so proving that convection driven by subducting slabs is truly the dynamic agent for global tectonics.

 No subducting slab:- Exhilarated by the thrill of discovery that no subducting slab underlies the extinct northern Kamchatka volcanic arc and paddling himself with excitement, our bold convectioneer cites this absence as direct proof for catastrophic slab loss, proposing avalanches of subducting slabs into the mantle for good measure.  Commenting on findings in Nature by an international team of researchers, team leader Rubbery Trolley-Dosser said, "Now you see 'em, now you don't.  It's like fairies at the bottom of the garden, everyone knows they are invisible so the fact that you don't see them is overwhelming direct proof for their presence.  With future research we hope to be able to document more areas where slabs are not present, thus confirming our present findings of catastrophic slab loss into the mantle.  We are excited by the prospect that this could put a whole new perspective on the Atlantic and Indian Oceans, and open up an entirely new avenue for research." ?link>


 Oblivious to the fact that time is not a variable in the equations of state governing the rubbery stiffness of tomato sauce, our bold convectioneer, who has himself assumed the rubberyness of numbers, is excited to see direct evidence of plates transiting from the upper and lower mantle, 
"This process has been predicted by models before, but no one has been able to link these predictions with observations, as we now do for plate motions."
addresses the stiffness of collapsing buildings and discovers exciting parallels with the rubbery downward descent of cooling slabs into the rubbery mantle, even pulling along the ocean floors in its wake

(Trapdoors, ..mantle slabs, .. and avalanches..) ..and mantle wind.

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