Are pyrenees currently growing?

Discussion in 'Earth Science' started by elchapero, Jun 10, 2011.

  1. elchapero Registered Member

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    Hello, I'm studying geology, and is a question that I cannot answer:

    1) Are pyrenees currently growing? What's the growing rythm? (in mm)

    I don't know the answer. Do you know it ?
     
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  3. chimpkin C'mon, get happy! Registered Senior Member

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    http://en.wikipedia.org/wiki/Geology_of_the_Pyrenees

    From skimming the Wikipedia page, only the Western end of the chain is still undergoing compression, therefore that alone might be growing. The rest seems to be stable.

    If you live there, or in Europe, your local libraries would have better references than I would be able to access physically at mine, or that would be accessible online.

    I can tell you a few things about Texas's geology, including granite upthrusts and the mountains we have that used to be islands, along with our local faultline, somewhere, under several hundred feet of mud. We have earth jiggles.
     
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  5. elchapero Registered Member

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    I don't have info, in any library, I don't found anything, my only solution is this forum .
     
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  7. James R Just this guy, you know? Staff Member

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    Yes. The African plate and the Iberian plate are colliding, causing the Pyrenees to grow.

    I can't tell what you're asking. mm is a measure of distance.

    Do you want to know the growth rate? That might be in units such as mm/year.

    The problem is that different mountain peaks will change heights at slightly different rates depending on local upthrusting forces.

    I assume in your geology courses you have studied plate tectonics. Is that correct? What did you learn about the Pyrenees?
     
  8. florian Debunking machine Registered Senior Member

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    I don't think so. If Africa and Iberia were colliding, that would close the strait of Gibraltar.
     
  9. elchapero Registered Member

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    Eurasian and African plates stopped 20 million years ago, I think.
     
  10. chimpkin C'mon, get happy! Registered Senior Member

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    I know the Himalayans and the mountains of Afghanistan are getting taller, by something like (and do not quote me!) 5 mm a year. They are very friable too-one of the reasons fighting in them is A REALLY BAD IDEA and I didn't think we should have stayed...but I digress.
     
  11. florian Debunking machine Registered Senior Member

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    Eurasia and Africa have been parting for more than 30 millions years, leading to the formation of the Algero-Provençal Basin.
     
  12. Trippy ALEA IACTA EST Staff Member

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    Only, the information that we have suggests that this is precisely what is happening, there is even some information about that suggests that the Mediterranean basin has been closed off, and dried out to somme degree, multiple times. The current projection is that the mediterranean will continue to close, resulting in the closure of the mediterranean sea, and it's eventual replacement with a mountain range (the answer to the OP is yes, there is an active orogen occuring there at the moment).

    The mediterranean sea now looks much like the area we call currently call the Himalayas did around 30 million years ago.

    The Algero-Provençal Basin is a marginal sea, it's back arc spreading, the same thing probably happened between the indoaustralian and eurasian plates 30 million years ago.

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  13. florian Debunking machine Registered Senior Member

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    The western basin is far from closing. May be that a geodynamic map of the region will help:

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    The whole dynamic of the basin is driven by large mantle flows, which reaches the surface, and finally form new oceanic crust (after rifting). Once the head of the diapir reaches the surface, it spreads outward, away from the uplift center. Outward spreading induces overthusting, and thus the formation of thrust belts at the periphery of the spreading diapir, at the front and in the direction of the flow.
    The first diapiric event occurred around -30 Ma and induced the opening of the western basin, with Corsica and Sardinia parting from the mainland. Then a second episode happened around -16 Ma. The last event corresponds to the opening of the Tyrrhenean Sea. According to each event, spreading moved progressively to east.
    So no, the western basin will certainly not close. It is actually quiet at this time, compared to the eastern basin where an active mantle flow (anatolia) is running toward the coast of Lybia. There you can expect the formation of a thrust belt, but nowhere else in the two basins.

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    The Carpathian arc is another illustration of these spreading mantle flows, the Alps as well with a specific westward progression and counterclockwise rotation.
    And yes, similar events occurred in the actual tibetan plateau which is still active and flows eastward. The himalaya thrust belt is just the southern margin of this flow.
     
  14. Trippy ALEA IACTA EST Staff Member

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    The only problem with that is that the map contradicts you, rather than supporting you - it clearly shows Europe and Africa rotating towards each other, with Europe rotating clockwise (well Spain/Iberia anyway), and Africa rotating counter clockwise, with the bulk of (mainland) Italy rotating counter clockwise, except for Calabria which is rotating clockwise, up towards Campania, along with Sicily. Sardinia & Corsica are being rotated Counter clockwise, again, towards Campania. The net result of all of which is Italy being folded up and out of the way, closing the Adriatic sea, with italy effectively accreeting on to mainland Europe, and Sicili, Sardinia, and Corsica accreting onto Italy, while Africa continues to move northwards at a rate of about 5mm/year, and Europe continues to fold on itself. Although it's not shown on your map, it seems reaonsble to surmise the eventual closure of the gulf of Gascogne.

    Well, certainly there is rifting occuring, but it's not in the mediterranean.

    Only thrust belts are typically associated with destructive margins, not constructive margins.

    Here's a question for you, why do (for example) Vesuvius and Etna have more in common with the Japanese or Andean volcanics, than with Icelandic volcanics - in otherwords, why are the volcanics of Etna and Vesuvius typical of a convergent margin, than a divergent margin?


    All the available evidence suggests otherwise.

    There is still, however, activity, activity that is consistent with the idea of the western basin closing.

    Actually, it has already formed.
     
  15. florian Debunking machine Registered Senior Member

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    The rotations symbol shown in the the figure do not indicate that Europe is rotating clockwise and Africa is rotating counterclokwise. In plate tectonics, for the last 30 My, Africa is thought to move NNE and rotate *clockwise* hence the opening of the western basin and the proposed push on anatolia.
    Second these symbols indicate the lateral rotations associated to the arcs migration (the arrows represent the path). It is quite evident for the Carpathian arc and Hellenic arc: the rotations are opposite in the western and eastern Aegean Sea, and in the southern and northern pannonian basin.

    The bay of Biscay opened between -110 and -80 Ma and did not evolved since that period.


    The initial opening of the western basin at -30 Ma was associated to rifting along languedoc. This rift was part of the west european rift system (including the Rhone Valley, Bresse, Rhine valley…).



    You confuse constructive margins (MOR) and mobile thrust belts resulting from lateral spreading of a diapir.

    Because the margins of the spreading diapir overthrust older lithosphere which evidently leads to arc volcanism.

    There is some overthrusting activity around the Tyrrhenian sea and some deep sismicity under the strait of Sicily, but nothing suggesting that the western basin is closing. On the contrary, it shows that the Tyrrhenian Sea grows in surface.

    Yes, but that's nothing compared to the belt that will form when the front will reach Africa. Ready to go skiing in Libya?
     
  16. Trippy ALEA IACTA EST Staff Member

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    Only, that's not what the mainstream reconstructions suggest:

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    (Both images courtosey of USGS).
    Notice that both reconstructions require the counter clockwise rotation of Africa, and the clockwise rotation of europe to acheive their modern configurations.

    Do you suppose, then, that the arcs are capable of rotating, without the rotation of the blocks or plates they rest upon? Or the blocks or plates around them?

    And? I didn't suggest otherwise, did I? I offered one possible hypothesis of what might happen in the future.

    Once again... And? I didn't suggest otherwise, did I? I only stated that the current, active, rifting is occuring elsewhere. The most I have done is suggest that it is a marginal sea formed by back arc spreading. What you're proposing is one of the two main kinds of models developed to account for the genesis of the western mediterranean basin, what I have proposed is the other. My personal opinion on the matter, based on the reading that I have done is that a pure abortive rifting process is unable to account for all of the available evidence, and that at best if rifting has been involved, then the history must be a hybrid.

    Nonsense.

    I'm beginning to wonder if a Diapir is what you seem to think it is. You are talking about a magmatic Diapir - IE Plutons (Dikes, Sills, Batholiths and the like).

    Only according to Roca, the Valencia Trough, Gulf of Lions, and Liguro-Provençal basin have been in a compressive regime for at least the last 5 million years, which appears to be in the wrong direction, and of the wrong timing to be as a result of the back arc spreading in the Tyrrenhian sea - and Tondi et al published an analysis of the 1968 Belice seismic sequence that bears a striking resemblance to a WBZ (the best explanation for the opening of the Tyrrhenian sea AFAIK appears to be a combination of slab pull, trench retreat, and gravitational collapse all relating to the advance of the African plate).

    I don't recall suggesting that it was in its final state, only that it already existed.
     
  17. florian Debunking machine Registered Senior Member

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    You're absolutely right. I really meant counterclockwise. So we begin with Africa squeezed against southern europe with spain packed against the british island, and a slow counterclockwise rotation of Africa leading to 1) the opening of the Bay of Biscay, 2) the opening of the algero-provençal basin 3) the current opening of the Tyrrhenian sea. => so the western mediterranean basin is not closing anytime soon, on the contrary, it is expanding though the Tyrrhenian sea.


    I suppose nothing. These are mantle flows driving the tectonic of the whole region and the arc/trench mark the front of these mantle flows. So these flows can make turns, rotate while they are progressing in the middle of a static region of the lithosphere. The concept of plates is not adapted to described what's going on in the mediterranean region.

    You clearly wrote that the Bay of Biscay will close. This is false.


    OK, but did I say that rifting was happening currently in the algero-provençal basin? I don't think so. I just say that rifting did occur before the opening of the bassin circa -30 My. Now for information, there is currently rifting in the Tyrrhenian sea and aegean sea, (gulf of Corinth).


    Not at all, you made a confusion between MOR and back-arc spreading induced by mantle diapiric flows. The diapiric flow is at the cause of both back-arc spreading and the Benioff zone (which materialize the place where it overthrust older water-rich lithosphere.


    Certainly not. I'm talking about mantle diapiric flow, which dimensions are in the order of many hundred kms, not magmatic diapir.



    No, you do not understand. The opening of the Tyrrhenian sea (and earlier basins) is a consequence of diapiric mantle flows which provoke a roll-back of the older lithosphere they encounter on their path. See this paper by Lavecchia and Creati for example "A mantle plume head trapped in the transition zone beneath the Mediterranean: a new idea"

    Here is a figure to help you understand the general principle:

    http://nachon.free.fr/flowtectonic/flow-rollback.jpg
     
    Last edited by a moderator: Jun 17, 2011
  18. Trippy ALEA IACTA EST Staff Member

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    Yes, I am, on all counts, including the closure of the western basin.

    Your assertion to the contrary is contradicted by the available evidence, which indicates shortening in the North-south direction.

    You've avoided the question.

    Wrong, again.

    Here's what I said:
    I suggest it as a future possibility, not a current certainty.

    No, the context of the discussion was the current movement, and the causes of it. What is currently happening, not what has happened.

    There has been episodic extension, not the same thing as rifting. What has happened there is an example of back arc spreading, nothing more.

    Nonsense, you're the one that keeps calling it rifting. I'm very clear they are different things, and have been trying to explain as much to you.

    According to your toy model, maybe.

    Some how I thought you would say that.

    Actually, I do understand. Better than you, apparently.

    Yes, I've seen that image on other fora you've posted it on.
     
  19. florian Debunking machine Registered Senior Member

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    False. The western basin is still expanding (Tyrrhenian sea).


    False. There is no North-South shortening. there is only spreding diapir towrd east (for the Tyrrhenian sea)


    False. I explained in details what's going on and why there is convergence on the margin of a diapir, including a figure describing it in 3 dimensions.



    There are no evidence that it is a future possibility at all. That would be different if Africa was rotating clockwise. Fact is that It is not.

    I exposed the whole history of the basin to demonstrate that it is expanding for 30 my and continue to to so. You're denying it.

    You're wrong. What is happening in the gulf of Corinth is rifting. There are plenty of paper discussing this rift. Google "Corinth rift".

    You can't understand what is back-arc spreading as long as you ignore the driving force: mantle flows. and you ignore it.


    False. See above Corinth's rift.


    This is not a "toy model" this is a very modern model that is gaining ground in the literature (see for example Facenna and Becker (2010) Nature 465, p602).


    No you prove that you failed to understand this concept at many level.


    But still do not understand it, and will certainly never do as I can judge from your behaviour.
     
  20. Trippy ALEA IACTA EST Staff Member

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    Baloney, you just can't wrap your mind around the fact that extension and shortening are not mutually exclusive.

    Again, you're wrong here is well, and let us, for a moment, assume that the paper you linked to is correct, it hypothesizes the existence of a plume, not the same thing as a Diapir, so you're still wrong.

    Let's assume the diapir exists, for a moment. You're own diagram predicts that the shortening should be east-west, but the observed shortening is North-South, so your theory fails.

    Look, I know you're a native Francophone, and English isn't your first language, so I'm trying to cut you a little bit of lee-way here.

    But the simple fact of the matter is that I didn't even claim that there was evidence to support it's closure. I speculated that it might occur at some point in the future, that you read more into it than that is your problem, not mine.

    I'm denying nothing. In fact I have EXPLICITLY aknowledged that extension has occured in the past. You keep setting up strawmen, arguing against things that I'm not claiming.

    This is a red herring - the Gulf of Corinth is in the Eastern Mediterranean, which we've both agreed is closing. - and, it seems, that the the Corinth Rift has causes other than back arc spreading, so I'm not sure what your point is here in bringing it up.

    This is an adhominem argument, as well as simply being wrong.

    The Corinth Rift disproves nothing I have said.

    Yours is a toy model, and is not the same thing as what is discussed in the literature.

    Ad hominem, and you're sounding increasingly like a troll.

    I do understand it, and I understand its consequences, and have pointed some of them out to you, but you, apparently, do not understand why (for example) the observed motion of the Ohkotsk plate relative to its subduction zone with the pacific plate is fatal to your toy model.

    Addendum: And, in one of lifes.... I want to use the word 'Ironies' but Irony doesn't seem quite appropriate, Becker and Facenna also support the idea that the Mediterranean (including the western mediterranean) is closing. And yes, the talk about global mantle flow, however, that's not what I was calling a toy model, and they explicitly assert that (for example) the flow that's driving the back arc spreading that's causing the extension in the Tyrrhenian Sea, is itself being driven by the subduction of the African plate under the European plate, which is the same thing that I have been saying.
     
    Last edited: Jun 18, 2011
  21. florian Debunking machine Registered Senior Member

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    When mantle spreads in the middle of static lithosphere you call that "shortening". Non sense.


    A mantle plume is not the same thing as a mantle diapir? It is the same thing.


    Jeeez, there is no shortening! there is SPREADING! and spreading translates into EXTENSION at the surface of the diapir and OVERTHRUSTING along its margins. Why is it so difficult to understand for you.


    Your claim that it might happen in the future is baseless, because the general trend is that Africa is parting from europe letting room for extruding and spreading mantle diapirs. You could claim as well that pink unicorns will appear in the future.


    Oh yes you're denying that there is current expansion of the western basin, calling shortening what is actually the margins of a spreading mantle diapir.


    No red herring at all, the crust of the Tyrrhenian sea has been thinning and rifting because it is in expansion. And the cause of the Corinth rift is the anatolian mantle flow running to the south-west.

    This is a fact that you can't understand that the geodynamic of the mediterranean sea is driven by spreading mantle flows without any shortening, and not by sinking slabs as it is believed in the plate tectonics paradigm.


    Oh no, not the Okhotsk plate moving parallel to the subduction zone again...
    I explained you at length that it would be true only if an absolute reference frame exists. That's not true, and it is more appropriate to choose a referential frame that is clearly showing the convergence, either Okhotsk or Pacific. You're hopeless.
     
  22. Trippy ALEA IACTA EST Staff Member

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    Strawman hypothesis, this isn't what I said.
    What I said was the shortening - the north south compression observed in all parts of the mediterranean basin, are not mutually exclusive with the extension in an east west direction - it wouldn't even be exclusive with some extension occuring in a north south direction, because the extension is being driven by the subduction.

    No, it is not. A Plume is not a Diapir.

    Because you are WRONG, and the literature you cited to support your argument ALSO says you are wrong.

    It's called speculation. I've never claimed it to be anything other than speculation - in part based on several observations.

    And no, Africa is not parting from Europe, they are colliding.

    I can't work out if this is a red herring, or poisoning the well, it fits the characteristics of both.

    The simple dismissal is to point out that there is at least evidence supporting the idea that the bay of biscay might close, by observing the difference in motion between the Iberian plate and the rest of Europe, and hypothesizing that it might occur as the collision with Africa continues.

    Ummm. No.
    I have explicitly stated, several times, that there are back arc extensional tectonics occuring in the Western Mediterranean basin that have resulted in East-West crustal extension.

    Total red herring.

    Wrong,at this point the Geodynamic appears to be being driven subduction of the African plate, the ongoing collision between the African and Eurasian plate, vigorous local convection, which is also being driven by the subduction, which may or may not be being complicated by the anatolia flow.

    Arguably, absolute reference frames do exist, for example, we could measure motion relative to hotspots, or the fixed and distance stars, or even the source of the CMB.

    The point is that your theory makes wrong predictions, and requires a specific reference frame to be assumed by validity, where as the current theory of subduction does not, it is valid in all reference frames.
     
  23. florian Debunking machine Registered Senior Member

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    Here again, You associate compression to shortening (whatever the direction), whereas compression is associated to spreading. It is a fundamental difference on which I'm afraid we will never agree. You're much like a Phlogiston advocate facing evidence of the existence of oxygen.

    I have the feeling that you oppose to whatever I say by principle. I use the term diapir as defined by Carey 50 years ago in the framework of expansion tectonics. Diapir is derived from greek diapeirein (to pierce through) and it does fit very well the observations: a mantle diapir is a mantle upwelling piercing through the lithosphere, and spreading laterally away from the uplift center as more mantle material upwells.


    Non sense. When the top of a diapir overshoots the point of isostatic equilibrium because more mantle mateiral is pushing from below, at some point, it must spread laterally due to gravity and this leads to COMPRESSION. This is EXPECTED. I wonder how you reach the conclusion that something expected is wrong. Or do you really believe that the mantle will continue to rise forever straight to the sky?


    What observations make you believe that the Bay of Biscay will close? Compression around the western basin due to diapir spreading? It does not make any sense. Your specualtion is baseless.

    You confuse the prediction of plate tectonics and facts. The facts support a very long history of expansion, that is currently happening mostly in the Tyrrhenian sea.

    let's see how much contradiction you can support: Do you claim that there is not a North-South expansion component in the past and current expansion of the western basin? And don't forget to look again at this figure:

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    So, still no North-South component of expansion?

    Yep, this is clearly the point of disagreement. I let you think about this figure:

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    Does it ring a bell or do you persist in your irrational belief in subduction driven tectonics?

    We know this is a strawman.
     

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