Talk:Plate tectonics

Mars section

The discussion of plate tectonics on Mars is far from the consensus of the planetary science community...especially regarding plate tectonics having any relevance to young (Hesperian) features like Valles Marineris or the Tharsis Montes. Probably someone more interested in doing extensive editing of this article than me should read some of the relevant background on Mars tectonics (e.g., http://explanet.info/Chapter06.htm) and fix it up.

--just sayin' —Preceding unsigned comment added by 128.148.116.88 (talk) 22:33, 11 November 2009 (UTC)

You are correct. I will change the section. Awickert (talk) 16:58, 14 February 2010 (UTC)

Tracking the movement

Prompted by a query today at the Reference Desk: It would be great to have a short section that details the methods that have been used (past and present) for tracking plate movement. Comet Tuttle (talk) 00:21, 9 January 2010 (UTC)

What we really need is an article on plate reconstruction and probably one on magnetic stripe (geology) and apparent polar wander too. Certainly the methods used in plate reconstructions should be summarised here as well. The former has been on my 'to do' list for a while now, so you've inspired me to start building something. Don't hold your breath though. Mikenorton (talk) 20:07, 11 February 2010 (UTC)

I hope you didn't mind me stepping in, but I've created a stub on apparent polar wander. Unfortunately I've only got the one reference book that covers the subject (and sparsely at that) so any additions and amendments you can provide would be great. Lancevortex (talk) 00:08, 18 February 2010 (UTC)

Thanks, I don't mind anyone stepping in, better than waiting for me to get around to it. I'll take a look at it when I get a moment. Regarding magnetic stripes, there's a stub called magnetic anomaly that could probably be expanded to include more on the stripes for now. Mikenorton (talk) 07:11, 18 February 2010 (UTC)

Plate reconstruction article completed, just need to summarise it as a section in this article.Mikenorton (talk) 23:45, 22 February 2010 (UTC)

Section added to article. Mikenorton (talk) 00:17, 24 February 2010 (UTC)

Lack of Lyell - Uniformitarianism

This article contains no mention of early geologist Charles Lyell, who posited the possibility of continental drift as early as 1833 in his Principles of Geology<i\>. Why? (129.173.192.27 (talk) 00:53, 9 April 2010 (UTC))

Probably because nobody studied the book of Lyell in enough detail to cite the page where he talks about this. I'll see what I can do. But before stating that Lyell mentions continental drift, let's see what he actually said. —Preceding unsigned comment added by Jpvandijk (talkcontribs) 16:58, 30 August 2010 (UTC))

Charles Lyell defended uniformitarianism. Uniformitarianism blocked continental drift. Quote; Oreskes, Naomi. The rejection of continental drift: theory and method in American earth science, page 200: "Charles Schubert subscribed to a substantive uniformitarianism: the belief, expounded most famously by Charles Lyell, that the Earth today is more or less as it has always been". --Chris.urs-o (talk) 20:06, 30 August 2010 (UTC)

comment added by Jpvandijk (talkcontribs) 10:05, 31 August 2010 (UTC)): Oreskes, N. (1999); The Rejection of Continental Drift: Theory and Method in American Earth Science. Oxford University Press, 420 pp.

Very interesting the opinion expressed by Oreskes, and it stimulates surely some discussion. As promised, yesterday I checked all three volumes of Charles Lyell in the original form. In fact, he rejects any type of specific process that does anything else than impose vertical movements upon the Earth crust, to make sea where once land was and opposite (so its not really the Earth which has always been as it was, it are the Processes and Agents that have remained the same) infinitely and without any clearly defined regularity, which is the basis of his type of uniformitarianism. He doesn't speak at all about anything related to shifting continents. The only thing I noticed he talks a little bit about is the resemblance between the directions like N-S on the Globe of some volcanic chains as was used by his forerunners to expose other ideas, but he assigns this to merely accidental. The argument can be exposed more in detail elsewhere, on the page dedicated to Charles Lyell. I would say that in terms of Plate tectonics, he, therefore, doesn't play a role in development or early proposals of the concepts. We must, on the other hand, not forget that also Plate Tectonics is a sort of uniformitarianism if we suppose that the Processes related have been active always in the same way. So it's not the problem of uniformitarianism that "blocked" the acceptance of continental drift I would say. Anyway thats not the question here. comment added by Jpvandijk (talkcontribs) 10:05, 31 August 2010 (UTC))

Tectonic Plate movement

The below paragraph is quite weak:

Tectonic plates are able to move because of the relative density of oceanic lithosphere and the relative weakness of the asthenosphere. Dissipation of heat from the mantle is acknowledged to be the original source of energy driving plate tectonics. The current view, although it is still a matter of some debate, is that excess density of the oceanic lithosphere sinking in subduction zones is the most powerful source of plate motion. When it forms at mid-ocean ridges, the oceanic lithosphere is initially less dense than the underlying asthenosphere, but it becomes denser with age, as it conductively cools and thickens. The greater density of old lithosphere relative to the underlying asthenosphere allows it to sink into the deep mantle at subduction zones, providing most of the driving force for plate motions. The weakness of the asthenosphere allows the tectonic plates to move easily towards a subduction zone.[22] Although subduction is believed to be the strongest force driving plate motions, it cannot be the only force since there are plates such as the North American Plate which are moving, yet are nowhere being subducted. The same is true for the enormous Eurasian Plate. The sources of plate motion are a matter of intensive research and discussion among earth scientists.

Some objections:

1. Density is NOT the main issue; the issue is that the mantle is molten and the crust is solid.

2. If we look at the Mid-Ocean Ridge, we see that there is rising magma from the mantle. This pushes upward. So, it is CONVECTION that drives the movement.

3. "Sinking" is NOT the real issue here. We only see "subduction" zones where one plate goes under another. We don't see sinking, but instead a being forced downward.

So, the bottom line is, the above paragraph is a violation of common sense, and poorly sourced to boot. Ryoung122 10:27, 29 April 2010 (UTC)

This is not the whole story, if something gets more dense and sinks, something has to come up instead in a globus. --Chris.urs-o (talk) 10:32, 29 April 2010 (UTC)

That paragraph can be improved. However, #1 is wrong on both counts (mantle is solid, and its convection is density-driven) and #3 is partially right (the reason one goes up and the other goes down is density). For #2, it is true that "ridge push" is important. But this is because of the dynamics topography produced at ridges which creates a gravitational potential energy high there. When considering oceanic crust, it's not that mantle convection pushes it along. It is the upper boundary layer of the convection system.

So I see your point that convection must be mentioned, and I agree, but it might be worthwhile doing a little more reading about the topic before changing it. Awickert (talk) 16:53, 29 April 2010 (UTC)

Well, the ultimate driving force is the heat. If the subducted plate is not melted down, then the machine would stop. --Chris.urs-o (talk) 04:35, 30 April 2010 (UTC)

Yes and no. Heat drives convection. But the subducted plate is not melted (a small bit of it may be); it does change phase, however. Awickert (talk) 07:35, 30 April 2010 (UTC)

Use your imagination based on fluid dynamics and the fact that a fluid moving faster than the fractured surface crust will erode crust at the boundaries,this motion is ,of course,based on differential rotation http://www.youtube.com/watch?v=bKrbXPKz-Zw&feature=related. It is not heat moving the crust,it is rotation,heat only allows the fluid to exist in a viscous state and no rotating celestial object with a fluid composition is exempt from differential rotationOriel36 (talk) 06:56, 6 October 2010 (UTC)

If you read the literature, you will see that it has been done. The crust at the surface is coupled to the mantle; in fact, it is its upper thermal boundary layer. This coupling is not perfect, and there is shear due to convection (yes, there is plenty of evidence for thermal convection, you can look at measured parameters and construct a Rayleigh number if you like), but (other than potentially the core) the whole Earth has not been shown to undergo significant differential rotation. This is largely because of the extremely high effective viscosities of the materials involved and the lack of significant low-effective-viscosity regions that can decouple one section of the Earth from the other; I say "effective viscosity" because the mantle is a viscoelastic solid, and behaves as a pseudo-fluid (power-law creep) only at extremely slow rates. In any case, it is very different from the contact between a low-viscosity-high-density fluid (water) and a granular solid, in which the boundary shear stresses are high enough to easily dislodge the sand particles. Please cite some sources and offer some reason for why you think that something in particular should be included, because this is not a general forum for this topic. Awickert (talk) 08:24, 6 October 2010 (UTC)

Here is what you do,remove every article relating to differential rotation in rotating celestial objects so you can have your 'convection cell' mechanism which amounts to a heat driven stationary Earth concept.If you can show observational evidence of thermal convection in any rotating celestial object with an exposed viscous composition without differential rotation then you are free to remove what I wrote there but the evidence for differential rotation is not only stronger,it is observed and that is the difference between the mechanism with the strongest possibility in accounting for the Earth's surface features as opposed to a conjectured mechanism which is not observed in other rotating celestial objects with exposed fluid compositions. You are right,this is not a soapbox so don't push it even if you are comfortable with a mechanism that has no links to planetary shape or rotation while differential rotation does.Oriel36 (talk) 09:59, 6 October 2010 (UTC)

First, I won't do that, because differential rotation does exist. Second, you have only to read the scientific literature to find evidence of thermal convection in any high-Rayleigh-number body, rotating or no. I can offer suggestions if needed. But I have continued to present this, and you have ignored it, so I have little hope on this end. Third, your evidence is not stronger because you have given none and your hypotheses are in conflict with the entire published body of geodynamical literature. Fourth, the content I removed here had only to do with a misunderstanding of the Earth-Sun orbital geometry and not with the topic at hand. Until you come to grips with the fact that you are contradicting professional scientists, who just might know what they are talking about, or attempt to find WP:RS and make improvements to this article, you are not using this talk page for its proper purpose: namely, for discussing content to be added to the article. I understand that you feel strongly about this, but this is the way that things work here. Awickert (talk) 10:10, 6 October 2010 (UTC)

Giant impact hypothesis

I seem to recall hearing something about the possibility that the hypothesized Mars-sized planet that impacted the early Earth and created the Moon may have something to do with plate tectonics. I haven't had a chance to do any research into this, but the idea I read about or saw on some documentary is that the impact could have cracked the crust of the early Earth like an egg leading to the plates. Has this been discredited? Does anyone know of any research into this notion? Mego2005 (talk) 14:28, 18 May 2010 (UTC)

I've never heard anything about it, and I doubt it. The impact would have been more cataclysmic than to just fracture the upper layers. Plus, oceanic lithosphere is the upper part of mantle convection cells, and that seems to be what drives plate tectonics. Google Scholar is a good first step if you want to give it a search. Awickert (talk) 15:11, 18 May 2010 (UTC)

Giant impact hypothesis/ Theia (planet). It has something to do with the Earth's core and its magnetic field. --Chris.urs-o (talk) 09:28, 6 July 2010 (UTC)

I finally had some hazy recollection of where I heard about the impactor leading to plate tectonics -- it was in an article or documentary regarding the Rare Earth hypothesis. The Wiki article mentions it briefly: "The impact that formed the Moon may also have initiated plate tectonics..." but doesn't cite any reference about this particular point. Mego2005 (talk) 17:17, 22 July 2010 (UTC)

A more likely suggestion (as I naïvely see it) is that the crust before the impact was all continental; the impact punched an ocean-sized hole, allowing movement. —Tamfang (talk) 04:49, 30 July 2010 (UTC)

Grammar

"Plate tectonics (from the Late Latin tectonicus, from the Greek: τεκτονικός "pertaining to building") is a scientific theory which describes the large scale motions of Earth's lithosphere. It is vital for the existence of life on earth because of the role that it plays in the global cycle that maintains the balance of carbon between the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere".

Logically, the "It" which begins the second sentence refers to the noun "theory". Thus the paragraph is telling us that the theory is vital for the existence of life on earth, which seems unlikely. Intelligent Mr Toad (talk) 08:38, 3 June 2010 (UTC)

Removed the "vital for..." sentence. Unsourced and nothing appears in the article body to support its place in the lead. Vsmith (talk) 12:31, 3 June 2010 (UTC)

Development of the Theory

Is there a reference for the sentence "It was at this point that Wegener's theory became generally accepted by the scientific community", since it seems to be referring to the mid 1950's, which is at least ten years too early. Even one of the references (number 35) at the end of the paragraph indicates that the theory was only built upon after 1961:

"The result was the famous magnetic anomaly map (Mason and Raff, 1961; Raff and Mason, 1961) demonstrating the existence of bands of anomalously high and low magnetization having continuity over hundreds of miles-the fundamental building blocks of seafloor spreading and its successor plate tectonics."

It's not a major thing, but unless there is a reference, I think the sentence could just be deleted. Ersby (talk) 09:12, 18 August 2010 (UTC)

Agree and removed the sentence. "At this point..." seems quite out of place and as Ersby says, a decade too early. Vsmith (talk) 13:22, 18 August 2010 (UTC)

Possible flaws?

• Earth Rotation related Driving Forces
  • Quote: "Global reghmatic shear patterns". Is this a typo or is there a simpler word for this sentence?
• Mantle Convection related Driving Forces
  • Quote: "In that theory the mantle flows not in cells but in large scale channels, and the direction of the flow is strongly influenced by the Earth's rotation (see below)." Where is the see below?
• Ridge spreading, Subduction rediscovered, and Plate tectonics were born
  • Quote: "(the former published the same idea one year earlier in Nature; However, priority belongs to Hess, since he had already distributed an unpublished manuscript of his 1962 article by 1960)" Capital letters and brackets is this allowed? --Chris.urs-o (talk) 18:40, 6 September 2010 (UTC)

I removed the first thing in parentheses; that word seems to be all but unused. Its paragraph may be quite a bit of WP:OR as well. The second issue is in a sentence about something that is fringe and physically implausible, so I saved us the trouble and just deleted it. That whole section though ("Mantle Convection related Driving Forces") will need quite a bit of work; it will go on my to-do list. For the third, the "However" should not have been capitalized, but I just reworded. Awickert (talk) 07:13, 7 September 2010 (UTC)

Thx ;) You are quite a roadrunner (Geococcyx velox) :D --Chris.urs-o (talk) 07:17, 7 September 2010 (UTC)

A "lesser roadrunner"? Well, isn't that a backhanded compliment :). I finally took a paleontology course last Spring, but still don't know much about life, so thanks for the link. Awickert (talk) 07:22, 7 September 2010 (UTC)

Some comments:

• The surge tectonics theory is still much quoted. Its not physically unplausible, as it was tested against mantle tomography models and maybe its not to us to bother about physical plausibiliy, there are lots of models and mechanisms cited here that are seen by many as plausible and by others as unplausible. Jpvandijk (talk) 16:16, 7 September 2010 (UTC)
• Its actually strange there is not yet a Wikipedia page on the surge tectonics model, which was quite popular in a certain time span during the ninetees and certaintly not less important than the latest mantle plume models. We could say that it is just one of the variations of mantle flow and delamination modes. We should put back the references. Jpvandijk (talk) 16:16, 7 September 2010 (UTC)
• I will give some more information on the regmatic patterns. They are used a lot by Storetvedt, and also others revived them in their 21st century models. There is quite some literature on this subject refering to the first half of the nineteenth century, but this is out of the Plate Tectonic concepts page I would say. It is only cited to show the relationship between the observed kinematics and the later developed ideas. I will give some more information. Jpvandijk (talk) 16:16, 7 September 2010 (UTC)

Ok. Plate tectonics is at 75 kBytes, quite a lot I'd say. A page needs to be kept manageable in order to be able to achieve a good quality. Surge tectonics theory and Global reghmatic shear patterns might be out of scope of the broad view of this page. I liked that you showed the link between hotspot, mantle plume, plume tectonics and plate tectonics. We have geos on Wikipedia, they might help reach a consensus: User:Awickert, User:Vsmith, User:Mikenorton, User:Geologyguy, User:DanHobley. --Chris.urs-o (talk) 06:15, 8 September 2010 (UTC)

Thanks for all of the info, Jpvandijk! I will stay out of your way for the moment, as you clearly know more about the history of this than I do. I had never heard of surge tectonics (in spite of doing quite a bit of geodynamics), but that may just be my young-ness. Awickert (talk) 07:13, 8 September 2010 (UTC)

Thanks for the feed back, and actually the page plate tectonics is getting a little long, but its also quite an important issue in Earth Sciences, a sort of unifying theory everything is linked to nowadays. As many call it's "a paradigm". Well the link between all the items related to mantle dynamics is actually one of the main issues nowadays amongst us geoscientists, and the request to create some order is therefore justified. I'll try to do something here, so that also some of the background information can be transported to other pages more dedicated to the arguments.Jpvandijk (talk) 10:21, 8 September 2010 (UTC)

Gravity- and Mantle-related driving forces

In response to a message from Chris, I took a look at the driving forces section. I don't know how exactly "convection" and "gravity" related forces should be separated, since it is gravity+density-driven convection, so they are all one in the same in my mind. The one possible exception is ridge push, which is a matter of gravitational potential energy, but the elevation of the ridges is derived from the density structure of and motion within the mantle.

For at least one or two of the "citation needed" tags in the gravity section, I could easily find a ref... but perhaps we should think of a better way to organize this before I try to go ahead (at a snail's pace, as always).

Thoughts on how to structure the sections would be appreciated! Awickert (talk) 07:30, 27 October 2010 (UTC)

• Segev (2002) seems to speak of upwelling, continental volcanic floods & flood basalts, updoming, rifts 120° apart as a common view.
• Segev, A (2002). "Flood basalts, continental breakup and the dispersal of Gondwana: evidence for periodic migration of upwelling mantle flows (plumes)" (PDF). EGU Stephan Mueller Special Publication Series. 2: 171–191. Retrieved 5 August 2010.
  • Segev, A (30 October 2000). "Synchronous magmatic cycles during the fragmentation of Gondwana: radiometric ages from the Levant and other provinces". Tectonophysics. 325 (3–4): 257–277. doi:10.1016/S0040-1951(00)00122-0. The common geodynamic evolution of Gondwana igneous provinces was extension of the continental lithosphere, thinning, uplifting, breakup, massive igneous activity, spreading and drifting
• Georg Stadler, Michael Gurnis, Carsten Burstedde, Lucas C. Wilcox, Laura Alisic, Omar Ghattas (27 August 2010). "The Dynamics of Plate Tectonics and Mantle Flow: From Local to Global Scales". Science. 329 (5995): 1033–1038. doi:10.1126/science.1191223.{{cite journal}}: CS1 maint: multiple names: authors list (link)
• Philip Kearey, Keith A. Klepeis, Frederik J. Vine (2009). Global tectonics (3 ed.). Wiley-Blackwell. p. 482. ISBN 978-1-4051-0777-8.{{cite book}}: CS1 maint: multiple names: authors list (link)
• --Chris.urs-o (talk) 01:55, 28 October 2010 (UTC)

I read the Stadler et al. one a couple of weeks ago; it would be a good and newer perspective to glue the section(s) together. Email me if you want a PDF. Awickert (talk) 02:34, 28 October 2010 (UTC)

Trying to get a copy of Kearey (2009), Chapter 12: The mechanism of plate tectonics. --Chris.urs-o (talk) 03:16, 28 October 2010 (UTC)

Most of that chapter is available in preview on google books for ISBN 1405107774 if that helps. Alternatively there are full-text versions available through EBSCOHost, ebrary, etc. Or you can probably get it from your local university library. LeadSongDog come howl! 04:06, 28 October 2010 (UTC)

Missing two pages on google books, might be the important ones ;) --Chris.urs-o (talk) 04:31, 28 October 2010 (UTC)

• Other possible sources

• The generation of plate tectonics from mantle convection, Bercovici 2003 [1]
• Great earthquakes and slab pull: interaction between seismic coupling and plate-slab coupling, Conrad et al. 2004 [2]
• On the relationships between slab dip, back-arc stress, upper plate absolute motion, and crustal nature in subduction zones, Lallemand et al. 2005 [3]
• Testing hypotheses on plate-driving mechanisms with global lithosphere models including topography, thermal structure and faults Bird 1998 [4]
• Slab pull and the seismotectonics of subducting lithospere, Spence 1987 [5]

I don't think that all of the story is in place yet, although slab-pull as the dominant force seems to be generally agreed as does plate edge forces over basal traction. Mikenorton (talk) 15:10, 28 October 2010 (UTC)

Yup & thx, slab pull, back arc basin and "ridge-push" seems common view to me. Email me if you want a PDF of Kearey (2009), Chapter 12: The mechanism of plate tectonics. --Chris.urs-o (talk) 15:47, 28 October 2010 (UTC)

Unreadable

Whoever is responsible for inserting attribution after attribution makes this less an article than an exercise in listening to somebody who wants other to know he has done his homework. For goodness sake, put the citations where they belong because these things have got out of hand Oriel36 (talk) 04:49, 28 October 2010 (UTC)

I know, we r all volunteers here, some did a lot of work, some will improve it. --Chris.urs-o (talk) 15:43, 28 October 2010 (UTC)

What I see is a lot of groping going on,maybe this mechanism,maybe that mechanism while morphing more and more towards the highest probability of internal fluid dynamics and rotation.This is a fact - no celestial body with a fluid composition is exempt from an uneven rotational gradient between equator and polar latitudes,it is not an opinion,it is not a hunch,it is observed in every single rotating celestial object with an exposed viscous composition. so if you wish to exempt the Earth's fluid interior to discuss thermal convection alone then you may miss out on the lag/advance mechanism indicative of rotational shear bands and especially the relationship with the crustal characteristics of the MAR.If you want to propose thermal convection then do so but it will be entirely different than a rotational mechanism that joins planetary spherical deviation with crustal motion and evolution.The precedence is set by the difference between geocentric astronomy and that of planetary dynamics as it must be either definitely one or the other and there is no room for mixing both Oriel36 (talk) 16:24, 28 October 2010 (UTC)