Remember? .. what we said about when you get a log-jam in the natural flow of things? .. and everything gets clogged up? .. and a breakout happening further back upstream so that the flow can find a better course to continue on, and leave the stagnation behind? (link) Well, .since we are into profanity, scatology and bad puns when it comes to plate tectonics, .. and in the name (believe it or not) of trying to clean things up, I want to have another go at floating a certain geological word past everybody, .. firstly because it is so delightfully risible, causing (as it frequently does) everything from a polite grin to an uproariously coarse cackle of unrestrained guffaws that helps to earn the Earth sciences the reputation of a romance that you can't take seriously, and secondly because i.m.h.o. it rates as *THE* most important structure in geology, such is the simultaneously holistic, scale-invariant simplicity/complexity that the structure offers as a key to understanding geology at all scales.
And the word is? ..
Boudinage. Or, as it is increasingly known by its larger-than-life expression - lithospheric boudinage.
Boudinage is ...
"....a rare geological phenomenon. There is no mention of this type of deformation in any works in English, so far as the writer is aware, nor does it seem to have had consideration from any but thegeologists of Belgium... There seems to be nothing in the arts or in nature which can be compared in mechanical origin to boudinages, which makes them the more interesting and the more worthy of study." (Quirke, T. 1923. Boudinage, an unusual structural phenomenon. Bulletin of the Geological Society of America, v.34, pp 659-650
Quirke was wrong. The structure was described nearly a century earlier by MacCulloch, J. 1816, A
geological description of Glen Tilt. Geological Society of London Transactions, v.3, p.259-337.]
It is nearly a century since Quirke eulogised its importance, and I would agree with him. Completely. The way I see it, the dearth of attention paid to it in the interim decades is the reason Plate Tectonics has gained such a foothold. Anyone cognisant of its holistic qualities of boudinage cannot help but be awed by its (quirky) explanatory power when it comes to understanding crustal deformation, particularly when it comes to relating domains of extension to compression on all scales ( link )
A 'boudin'(French word) is a sausage, defined (once-upon-a-time), not as your end-to-end links-type British sort piled in a heap, but the bigger continental salami sort that you often see "side-by-side on a butcher's slab or hanging up in the window (though the way the sausages are packaged these days for the supermarket there's not a lot of difference.
The arrangement is a bit like the hand with the fingers firmed up for a karate chop (sort of like a layer of rock. The closed gaps /'breaks') between the fingers are like fractures. If you cut the fingers off (as a butcher might), and and put some mince around them and squeeze them flat on the table, the fingers separate, with the mince squeezing into the gaps between them, but keep their orientation relative to each other. That's the sort of separation that happens when a layer is compressed by gravity. If the fingers are extended (sideways) then the mince is mobilised relatively passively into the gap. With the compression being gravitational force, and the fingers free to spread then the separation is like what happens when a sequence of rocks that is riddled with fractures is 'spread'.
It happens at all scales, from micron-scale muds to the scale of the lithosphere, and at all levels in the crust. Given that two-thirds of the Earth's surface is ocean floor (/mantle emplacement,compensating for spreading), boudinage (as abyssal hills) provides a good analogy by which to understand this emplacement as well as what's happening in the overlying continental crust. However, geologists in the dining car of the gravytrain of free lunch would far rather have this simplicity (first coined by Lohest, Fourmarier and others more than a century ago as just "sausages") dressed up as something like "non-homogeneousl lithospheric stretching structures". Which is what you do when you don't much care to be labelled 'Johnnies-come-lately' - first you change the language, then you label it as 'new' (and hope nobody notices).
Boudinage combines brittle and ductile structres on all scales applies from unconsolidated sediments on continental shelves to the highest temperature regimes in the crust. It provides the most comprehensive framework there is by which to understand geological structure.
"Boudinage is a result of compression and consequent elongation which, in large complexes must yield truly large-scale plastic transfer of rock matter; this is of obvious significance for large-scale tectonics." (Hans Ramberg, 1955. Natural and experimental boudinage and pinch-and-swell structures, Journal of Geology, p.513.)
"Boudinage occurs on all scales." (Dennis, J.G., 1972.. Structural Geology, Ronald Press, New York, 532pp.) (Student text book.)
And indeed Lohest interpreted the uplift of the Batogne region of Belgium as due to large-scale boudinage, an interpretation that was later (1980) applied to the metamorphic core complexes of the Basin and Range province of North America.
If all roads lead to Rome (Earth expansion) then the shortcut is lithospheric boudinage. But going by the bullshit that is building up under the rubric of Plate Tectonics, it will certainly be interesting to witness what happens when there is a breakout and the *importance* of it for understanding the larger-scale framework for global tectonics (as well as physics) hits the fan.
Why the delay (of half a century at least)? Because Plate Tectonics got in the way, and however much that paradigm is wrong it serves a purpose - which is that of 'scientists' (not of science), who, when the game isrumbled, just shrug their shoulder and say, well, being wrong is how science moves forward. But do you see any of them accenting the negatives with a pinch of Popper? Never. To a man (and woman) they will only publish in the name of consensus ('coz that way, you get the money).
Simple. And understandable. And it must be said, necessary. But scientists will only take cognisance of the 'facts' (in context) when they are forced to. Theories, on the other hand offer much better return on investment.
From go. ..
.. to woh :-Fig.1. Asymmetrical boudinage in ferruginous muds. Specimen is about 5cm across
Fig.2. H. Fossen modelling lithospheric boudinage, citing Gartrell, 1997, .. also modelling. Crustal thickness is between 20-40 km - an order of magnitude more when the lithosphere is referenced. [ Note the *asymmetry of boudinage structure chosen for the illustration.]
"Scale invariance" - the most important phenomenon encountered by astrophysicists exploring the universe and by (some) geologists noticing the crustal structure on Earth. )
".. One generation passeth away, and another generation cometh: but the earth abideth for ever. The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose. The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits. All the rivers run into the sea; yet the sea is not full: unto the place from whence the rivers come, thither they return again. The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun. Is there any thing whereof it may be said, See, this is new? it hath been already of old time, which was before us. There is no remembrance of former things; neither shall there be any remembrance of things that are to come with those that shall come after." (Ecclesiastes : "All is vanity, .. a chase after wind.")
And more than wind it certainly will be, when that bag breaks. ... ... You know, I get the feeling it already has, which is why everybody is keeping their head down on this topic. The calm before the clamouring storm? Nope. It will all creep in the back door as the train clatters over the points at walking speed, to save everybody falling off - as the above figure is doing. There are no marks for making a noise when it comes to the memes of change that everybody discovers they already know, .. nor for drawing their dormancy to attention - like mountains are erosional features, and that there is a belt of them going all around the Earth's Pangaean equatorial zone, and that it split around the middle to let the mantle out, and that subduction is really overriding, and that rollback is silly, .. etc., etc. ..and that the Earth is getting bigger (because of all that obvious ocean floor, the ridges, the transform faults, the mountains etc etc.)
It is absolutely amazing, is it not, .. that given the magnetic and gravity detail of the ocean floors available today there isn't a structural map of it coming out of any of our institutions. Anybody got any idea why the only one we do have is that multi-hued rainbow map-of-ages? What's that? There really *is* a pot of gold at the end of it? (Oh, .. right, .. I see ee.)
Joke? I don't think so. I think that is *precisely* the reason. Nobody's game to upset it. They're all working out how to cannibalise the new stuff from satellites and gross regional compilations into the old, so that nothing of the old ideas changes, .. very quickly at any rate. First you have to milk the golden eggs for what they're worth, *before* they lose their attraction, even if it is becoming much tarnished. From the consensus veiwpoint there is nothing acceptable-to-purpose to put in its place. When it comes to resurrecting old stuff as redolent and on the nose as Earth expansion, .. well, .. that is very risky business.
It will have to be done though, before geology makes sense again though. The bubble needs to burst. The boil needs lanced. Breakout needs to happen to clear the stagnation.
"Mash with your sausages, sir?"
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