..Subduction
zones - Uggh!
(...or plate tectonics' wooden half-a-leg)
..Subduction
zones - Uggh!
(...or plate tectonics' wooden half-a-leg)
| Empirically,
subduction does not exist because:-
1. Only half the the world's continental margins qualify, these being essentially the Pacific margins; i.e., all of the ocean floors are supposed to go down only half of the continental margins. Which implies descent at subduction zones is at twice the rate of ascent at spreading ridges. 2. The entire Eastern Pacific is a zone of overriding related to Atlantic opening, not of subduction (and yes there is a difference) (which leaves the Western Pacific only - i.e., effectively a quarter ammedable to supposed subduction. 3. In the Western Pacific the transform faults do not reach to the Asian margin (the ridges have moved away from the landmass), i.e., there are effectively no continental margins that would qualify as subduction zones. 4. The spreading ridges
are extending along their length as well as across them, which means that
by the time an earlier ridge element gets to the subduction zone the ocean
floors have grown substantially along their length. If subduction
is at the 'current' rate then the earlier ridge element is being consumed
faster than when it was created. But the zone itself must remain
the same size - otherwise if the subduction zone increases in length commensurate
with the spreading ridge, then the Earth would be getting bigger.
Unless the Ocean floors are shgrinking in the middle.
Logically subduction cannot occur because according even to the supposed dynamics of convection subduction could never begin in the first place, since in order for the Earth to maintain a constant size ocean floor creation must be matched by its destruction, ..i.e., if destruction balances creation, then the ocean floors would never open. |
"Subduction zone". It should be said at the outset that there is no quarrel with the word "zone" (Benioff). It's the 'subduction' we take issue with here. In a zone of relative 'plate-under' (subduction) v. 'plate-over' (overriding), plate tectonics arbitrarily chooses the former - for no other reason than it suits it, despite the clear alternative; it is "convenient".
'SUBDUCTION' ("sub" meaning down, or below; "duct" meaning carried), ...A code word for " the process whereby slabs of crust, piggiebacked on thermally driven, isotopically generated, convecting mantle cells are driven to their doom (like the Titanic) on the downwelling cycle of a cell" (picture). The process is the opposite of RIDGE (or plate) ACCRETION, which happens at the opposite, upwelling part of the cell. The pairing of upwelling (convective rise) and 'downwelling' (subduction) is imagined by platies to be similar to a pot of soup being heated from below, where floaties on the top are carried along on the top of the cell and either dragged down again or banked up against the side of the pot, which, in plate-speak, is analogous to a continental buttress. As a geological model it's really more befitting the days of the early part of last century, when geology was more about gentlemen on field trips rumpling tablecloths during pub lunches to simulate folding as continents drifted, than it is of the rocket- science present.Important point anyhow:- Subduction is an essential conceptual ingredient of plate tectonics but (concepts aside) empirically it seems only to apply to the Pacific margins. For the other ocean ridges it either doesn't exist (Atlantic and Antarctic margins) or it's arguable (part - Indian and Southern Oceans). Moreover, the Eastern Pacific is a zone of 'override', not subduction (and yes there is a difference - see again Encyclopedia quote ). In other words there is at least as much continental margin around the globe without a subduction zone ('passive') as there is with one ('active'). Both conceptually and empirically therefore, and on it's most substantial support, plate tectonics has only half a leg to stand on, even from the outset. On this ground alone it is hardly credible it should be given such unquestioning credence by anyone, let alone institutions as august as the USGS. Its inclusion in school curricula without the alternative of expansion is silly at best, and at worst akin to creationism being taught without evolution. I guess the logic is that it is more important to teach basic belief, rather than ability of critical thought.
In plate tectonics the Pacific is an upwelling convecting cell, whose axis is marked by the accretion zone of the East Pacific Rise. This convecting cell drives the oceanic crust away from its centre and subducts it under the continental periphery - Assumption: the Earth should remain a constant size). In Expansion the Pacific is an uprising mantle diapir which is collapsing at its margins and being overridden by the crust - Inference: the Earth is expanding.
Frozen as a snapshot in time there's not a great deal of kinetic difference between the two. The only real conceptual dynamic difference lies in the repetition or otherwise of the process:- multiple and rapid convective overturn in the case of plate tectonics as cells change their number and orientation (evidently at the drop of a hat - the boiling pot analogue), and once-only, slow rise in the case of diapiric uplift. And, ...and, ..and, ...(wait for it...) the assumption that there has to be (in plate tectonics) oceans as big as the current ones, that get swallowed at the same time as the current ones get created. The fact that this leaves huge question marks about how (and where) subduction is supposed to start in the first place is completely ignored in plate tectonics, ...or seen as a challenge to answer. That it might be irrelevant pales against the opportunity for 'more researech' that the contemplation offers.
| Even more important
point:- But the most important physical, empirical, actual, and
factual difference lies in the way that expansion/ rotation takes into
account the aspect of global torsion, where plate tectonics simply just
doesn't deal with it at all. Transform faults are given only a supporting
role in connecting primary zones of accretion and subduction as correlates
of convective overturn. Not only torsion doesn't figure on
plate
maps but neither (hardly) do transforms, and yet the gravity maps show
them clearly as every bit as important as the ridges. Expansion
on the other hand sees torsion as a primary feature of crustal divergence
(adjustment), and the transforms as its correlative expression on the ocean
floors. Consequently transforms are all-important as the expression
of global torsions on newly created crust.
How can one model (plate tectonics) see torsion as relatively unimportant and the other (expansion) see it as all-important? The answer is it's a 'mis-match of scale' problem - a question of perspective. In ignoring the importance of torsion, plate tectonics has just simply screwed things up, got things in wrong slots. In respect of ocean floors it invokes three dynamic parameters - accretion, transforms, and subduction - of which the second is given limited importance and the third is unproven - and assumes the Earth was a constant radius. Expansion invokes only two parameters - ridge accretion and transforms - sees the two as scale equivalents, and is led then to ask the question - "Is the Earth expanding?" Note the logical difference:-
|
| In other words, plate tectonics starts with an assumption of constant Earth-size, radio-active decay giving convection cells in the mantle, and fits the data around it. Earth expansion starts with the data of just transforms and ridges and how these relate to deformation in the crust, and directly observes a space - time pattern in them. Which is different from the space-time pattern assumed by plate tectonics. |
It's difficult to believe that the global rotational (torsional) element of Earth structure is not taken into account in plate tectonics, but it's true ....So, ...that half-a-leg mentioned above is not even a good one - it's more of a crutch - hardly a support at all really for all that's been built on it. So long as the supporters of plate tectonics fail to acknowledge the wooden half-a-leg they're standing on, and don't take into account alternatives which account for the torsions in such a way as to explain the conundrum of active v. passive margins without ad-hoc jiggery pokery of convection and subduction, continental reconstruction will remain compromised.In a single integrated picture, expansion and torsion provide the basis for continental reconstruction back to the Mesozoic and beyond - probably even to the early Proterozoic. This reconstruction points to a primeordial Earth no bigger than that covered by the sum of the present-day Archean shields (including that covered by later sediments), and possibly (when extension within the continents prior to ocean floor creation are taken into account) one substantially smaller. From earliest geological times the picture suggested is one of expansion - of inexorable, continuing and directed deformation - simple, elegant sobriety as befits our mother Earth, compared to the cock-eyed, flung-about, clunky, ad-hoc, disparate nonsense of Clever Dick loony-tunes Platespeak.