The changing lingo of plate tectonics
( 'Subduction' is changing to 'overriding')
The changing lingo of plate tectonics
( 'Subduction' is changing to 'overriding')
Wherein the NEW PLATESPEAK of subduction is highlighted
| NASA
"This leads us to the second type of plate boundary, which is called a convergent boundary or subduction zone. These are plate margins where one plate is overriding another, thereby forcing the other into the mantle beneath it. These boundaries are in the form of trench and island arc systems. All the old oceanic crust is going into these systems as new crust is formed at the spreading centers. Convergent boundaries also explain why crust older than the Cretaceous cannot be found in any ocean basin-- it has already been destroyed by the process of subduction." USGS
(hedging bets)
Compare with the old definitions where one plate is being pushed under the other |
Straight from the horse's mouth (USGS/ NASA) - papal encyclicals for distribution to other edu.'s and schools) - where 'subduction' is now, either explicitly or implicitly, 'overriding'. It didn't used to be like this. Subduction used to be subduction, "carrying down", ...not "riding over", as it is now becoming. ( Interesting, is it not, that of all the sites on the web with definitions of subduction, it just happens to be the USGS and NASA who have changed theirs to overriding, in line with the current drama that plate tectonics is now in the Pages of Life Support It will happen, don't worry. The others are just slow to update their definitions, which they probably got in the first place from those prime sites in prime PT-time.But anyway, what's the difference (between subduction and overriding)? There is none. At least, that's what you're supposed to think, for the time being - till the next piece of lingo-change is put in place, which is the importance of the Earth's rotation. This is the way that clandestine, conspiratorial, 'black-hand-gang' change happens. It happens in the language used, not in the geological facts, but in the spin put on the words by which meaning is conveyed to the reader. 'Black-hand-gang'? Nah, ..Platies don't have the nouce to plot or plan anything. They are being forced into this lingo-change by the exigencies of the science itself. And by the manipulations of Pteros who do: someone has to physically change the writing on the page, and why would they, unless they recognise the benefits of emphasis. If you're wondering why it happens to be nasa and the usgs and the pair who put plate tectonics on life support who are doing this, ... 'leading the way', .. you could ask yourself if it might have anything to do with these pages being up on the web for the last four years (as of 2004) promulgating what is obvious to anyone with half an eye and half a brain, that the Earth has got bigger by the extent of the ocean floors and that subduction is nonsense, and that there is a responsibility on these institutions to acknowledge some aspects of this given the obviousness of it and the Garden Path they've been leading all these poor schoolchildren up for decades, ..aided and abetted by universities. And that all the people who learned it all off by heart are now teaching others by heart, and knocking on the head all sensible questions put to them. They should be more circumspect and keep everybody appraised of the options in order to encourage thinking and discussion and to prevent the theology of monolithism taking hold, instead of doing their utmost to promote it - as they have been.
But anyhow, ..it's true, there is no difference (between subduction and overriding), ..if you are in relative movement mode that is, but if you are channelling REAL DEAL in mantle dynamics and plate kinetics the difference between subduction and overriding is profound:-
- Subduction:- Cycling mantle. Continental Crust is stopped. Mantle is thrust under crust
- Overriding:- No cycling mantle. Mantle is stopped. Crust rides over mantle. No Plate Tectonics.
Splitting hairs? Not at all. The difference is Very Important. The first bullet point is mantle convection. The second is decoupling of the Earth's differentiated shells, with the crust lagging westwards, just as (it is now known) the mantle lags westwards relative to the spinning core, so the crust lags westwards relative to the mantle. Subduction is proof of convection (not the other way round). Overriding (when taken in the context of the integrated picture of transforms and ridges on this site) points in the direction of a control by the change in the Earth's rotation over time.The conceptual difference (between 'plate pushing under' and 'plate riding over' ) also highlights the point that so-called 'subduction zones', i.e., overriding zones, have nothing whatsoever to do with the dynamics of spreading ridges. That is, they are not necessary corollaries of each other. So we have two distinct dynamic sets:- 1. mantle accretion at the ridges (that we can see), which is Earth expansion, ...and 2. overriding due to the Earth's rotation, which expresses the torsional adjustment.
And that's it. That's all.
Conclusion:- Subduction is an unnecessary figment, and convection, whether it exists or not, is not a necessary player in the Earth's deformation. And that is the direction the change in Plate Tectonics is headed. Towards no Plate Tectonics at all.