Talk:Plate tectonics

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Reviewed version: June 11, 2008

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Overview: Needs a good copyedit. Britannica's entry "contained an error in its opening paragraph", "too long for most people's needs", and "reminded me of one of my worst lectures at university". Encarta "clearly written by an expert" and "the only one to display enthusiasm for the subject". Please examine the findings.

Contents

[edit] Non-boundary faults

Bearing in mind that I am not a geologist, I thought it was the case that faults exist within plates as well as between them. Is this not true? yes I am thinking of the "fault" that produced the New Madrid earthquake as an example of an intra-continental fault. -- Egern

  • I confess to not being a geologist either, but I believe that non-boundary faults are sometimes caused by material welling up from the mantle at "hotspots", which if I recall correctly are thinner/weakened areas in the middle of plates. -- April
    • The plate boundaries are not simply equal to faults as previously stated. Rift valleys have been called faults, it simply means a break in rock. We sort of get trapped in words and legacy. Back when plate tectonics was heresy (I remember the arguments in our organization!) a trench or rift might more easily been seen as "just a fault" as its unique activity and even function was not recognized. Conventional faults don't "do" anything. They just slip and jar. Transform faults are such passive beasts, even ones like San Andreas. Rifts (divergence) and trenches (convergence) function. Rifts add new surface. If it weren't for the trenches this old globe would perhaps be like an expanding balloon. It hasn't gotten significantly larger considering all that spreading. Remember Harry Hess' "recycle" comment. Convergence boundaries consume what divergences produced so long ago. They deserve not just being "faults."
    • And, yes, faults occur well away from any current plate boundary with origins thought to be other than direct plate boundary action. That New Madrid earthquake fault is an interesting thing. There was some thinking, if I recall correctly, that it could be what might be termed a "fossil" plate boundary and it lies quite deep.
***The faults associated with Spain and Portugal that run generally N-S are associated with the opening of the North Atlantic. When the plates here started to diverge several zones of weakness would open up. Rifting (probably due to less resistive forces) was favoured to the West of Portugal; if it was to the east - Portugal would now be next to Florida (idealised of course!). Large faults are generally associated with plate techtonic processes; however slip/creep; slumping; sliding of sedimentary rock layers can also produce faults; as can excessive over burden finding weakness in rock joints. MeanStreets "...Chorizo..." 11:09, 18 April 2007 (UTC)
    • In my view this section either needs much more work or much simplification. If it is to stand alone it needs more work. On the other hand there is a great deal of excellent and authoritative material already on the Internet; for example, the U.S. Geological Survey's excellent on line publication This Dynamic Earth provides more than is ever likely to be found here. Perhaps a brief descriptive definition and reference to several such publications would be better. -- 209.249.180.153

[edit] List of major plates

Does this, perhaps, need a list of the major tectonic plates? Memory is failing me here; I can recall the Pacific and North Atlantic oceanic plates, and the North American, South American, and African plates, but after that I get sketchy as to what's a plate and what isn't. -- April

Well, there are 10 plates: Pacific, North American, Cocos, Nazca, South American, African, Eurasian, Indian, Australian, and Antarctic plates.

These are the major plates and some minor plates. There are also the Philippine Sea, Caribben, Juan de Fuca, and Arabian plates (minor plates) --Zyzzy2

I think it only necessary to mention the 10 largest and possibly the 4 minor plates. However, this list isn't exhaustive. There are perhaps even more than this. MeanStreets "...Chorizo..." 11:11, 18 April 2007 (UTC)

[edit] Model or Theory

Plate tectonics is a model rather than merely a theory is it not? (How fortunate the Bible had nothing to say in the subject.) Wetman 19:16, 22 Nov 2003 (UTC)

If this helps, the definition of "theoy" is,"a well tested idea which explains observations". Plate tectonics expains Wagner's idea of " continental drift"

Also, it explains the movement, subduction, and creation of earths crust.Andrew the science guy 00:23, 16 February 2007 (UTC)

Geologists perhaps don't think of fundamentals as much as they should, but 'plate tectonics' is a theory. It makes enough verifiable predictions (though the experiments are long over) to qualify as one. Most important is its function of explaining (a word I still don't quite understand). A model is a simplification, an object containing just enough properties to substitute for a more complex object: the poor manequin in the automotive crash tests, thermodynamic mixing equations that interpolate. Distringuishing models from theories can be difficult, as with van der Waals equation, but plate tectonics is clearly a theory. I noticed a distinction drawn between plate tectonics, sea-floor spreading, & continental 'drift', one which I never drew. Plate tectonics is a collection of well-fitting ideas, some of which I find better tested & more convincing than others. (Yes, I believe in logical induction.) Geologist 21:07, 7 November 2007 (UTC)

[edit] Opposition to the theory?

I was under the impression that there is some fairly vocal opposition to this theory. It is just a hunch, I heard years ago, but I remember it enough to raise the question. Anyone else familiar with that? If so, it should be covered in the article. - Taxman 21:27, Nov 19, 2004 (UTC)

  • Well, it was certainly controversial when it came out, but very few mainsteam geologists are opposed to it today. The main opposition (if it could be called "main") is the expanding earth theory, promoted for a long time by S. Warren Carey, an Australian geologist. When he started in 1956, plate tectonics wasn't yet developed. The big problem is, by what mechanism does the Earth expand? It's definitely a fringe view today.Gwimpey 01:12, Nov 20, 2004 (UTC)

No, there is unanimous agreement that this is an accepted theor, like the theory of gravity zyzzy2

  • It may be an accepted theory, but that doesn't mean it's 100% correct. Einstein's original theory of relativity included the famous "gravitational constant" to keep the universe the same size. Plate tectonics has the same problem. Everyone agrees that there are plates, and that the Atlantic seafloor is growing. But "plate tectonics theory" also includes Pangaea, Gondwanaland, and the primordial super-ocean to fit the fossil evidence, and the Expanding Earth theory fits the fossil evidence better than this. Thus, when we talk about plate tectonics, are we talking about magma-floating plates or are we talking about Gondwanaland? Because the two ideas are so conflated that it's hard to tell them apart. And the Gondwanaland side of the theory is extremely flawed, even to the most casual observer. -broodlinger 24.184.67.122 07:57, 29 January 2007 (UTC)
Flawed in what way? And I understand that the fossil evidence - as well as the geological evidence - fits quite nicely when you look at the stata of South America, Africa, India, Australia and Antarctica. We have a great deal of evidence here and geologists now fully accept it. Darkmind1970 11:28, 30 January 2007 (UTC)
I think the Gondwana theory is one of the more concrete parts of the theory. After all, the Gondwana part of the theory is well supported by physical evidence (mainly fossil, geological and evolutionary evidence) while the existence of Pangea and a super-ocean is slightly more theoretical (although there is still some small amounts of physical evidence, but not much because it was just so long ago). Still there is some opposition to the Gondwana and indeed the entire 'plate tectonics' theory. It is interesting though the lack of publicity the opposing opinions get compared to other unproven (or perhaps unprovable) observed theory's such as Evolution and Global Warming; I bet all three theories have about equal ratios of supporting / detracting experts (probably in the region of >99% - <1%) yet we are always hearing about detractors to Evolution and Global Warming. Although we probably shouldn't be too vocal about the minuscule amount of opposition or we'll have half of America believing the expanding earth principle instead (despite its complete lack of evidence and rejection by well over 99% of experts). Canderra 17:31, 2 February 2007 (UTC)
Pangaea is essentially as well documented as Gondwana - the evidence is perhaps slightly less obvious than the long-recognized continuity of fossils, paleoenvironments, and strata of Gondwana, but it is nonetheless clear-cut and virtually uniformly accepted by geoscientists, as Darkmind1970 and Canderra suggest for Gondwana. The extent and variety of the evidence for Pangaea, Gondwana, and Panthalassa is overwhelming. Cheers Geologyguy 17:43, 2 February 2007 (UTC)
This is a link describing the alternate theory : http://www.maniacworld.com/Conspiracy-of-Science.html Peoplez1k 12:31, 4 May 2007 (UTC)
Broodlinger wrote It may be an accepted theory, but that doesn't mean it's 100% correct. Indeed, none is. (Classical thermodynamics, in fact, makes physicists uncomfortable because it works too well.) The really nasty fight was between the geosynclinal theory (which drew upon vertical tectonics toward its end) and sea-floor spreading. It's my recollection that supporters the former became mute & switched sides when a paper was published that mapped the orientations of magnetic domains on an ocean floor. There have been recent objections, but from people who distort the 'rules of science'. Geologist 21:32, 7 November 2007 (UTC)
I'm not a fan of the pangea theory. People thought the world was flat once. there is no rule written that any planet has to stay exactly the same size. also, i find that the earth fits together really well as a smaller planet, when australia connects with the americas. And personally i've never seen a continent going underground, so i can't say anything about that. yet i do hear of continents growing. i'm not saying that you shouldn't believe in anything in case you're wrong, just that i'm more open with this issue, and a growing planet isn't illogical, since there're cycles with everything; nothing stays the same forever. - 6th June 2008 -Leigh
I'm not old enough either to have seen a continent going underground. If you look at List of tectonic plates#Ancient plates you find several examples of land which was added to a continent instead of being subducted. I think our most visible subduction event is the Farallon Plate, both its subducted traces and what remains of it on the surface; but that was an oceanic plate and not a subducted continent. You're right that parts of the continents fit together if you remove the intervening ocean floor, and that is part of the basis of inferring past continents such as Pangaea. If you look at the origin and destruction of oceanic crust you see how the pieces fit, or rather flow, together. There is also evidence of at least one ocean just after the Earth formed, so the different characteristics of continents and ocean floors may have existed during the lifetime of the planet. I'm not aware of an article which mentions how the first continental crust formed, but it is also likely that is not known; I have seen mention of the oldest rocks but that's different from crustal formation. -- SEWilco (talk) 19:17, 6 June 2008 (UTC)
Thank you for your reply - on this subject i'm open to hear all sides. For me this is a very interesting topic since i saw some different opinions on subductions. i think questioning subjects that we've learnt in high school is healthy, since schools are an instution with a syllabus. for me, i think time will tell with this subject. just because there is subduction doesn't mean the rate of growth/destruction of the plates needs to be exactly the same. from the other perspectives i've seen, they show the same Pangaea continent - the only difference is that there is no super ocean, and that all sides of the continent are connected; there is no ocean plate. but this can only happen on an earth which is obviously smaller. as i said, i might just have to wait and see what happens, i'm open to the subduction theory but i just think it's too cut-and-fit, and seems to have been found by someone who wanted to find such a neat answer. thanks for your time - 7th June 2008 - Leigh —Preceding unsigned comment added by 202.173.135.119 (talk) 02:52, 7 June 2008 (UTC)
What sources show the perfectly fitted continents? -- SEWilco (talk) 03:26, 7 June 2008 (UTC)
The one above. althought i don't agree with some of the things the narrator says, the image of all of the continents together (all sides touching) does seem to fit, which is the main point to lead me to question the subduction theory or the rate of subduction. - 7th June 2008 - Leigh —Preceding unsigned comment added by 202.173.135.119 (talk) 05:23, 7 June 2008 (UTC)

[edit] Andes

Could anyone who is geologicaly inclined please have a look at Andes. There is currently a warning saying that the section on geology is pre-plate tectonics, so could anyone who knows about such things please have a squiz. The bellman 11:04, 2004 Nov 26 (UTC)

Will do zyzzy2

[edit] Ocean get bigger?

I think that the ocean in fact does not get bigger because of plate tectonics. If the magme spreads the plates apart and creates more oceanic crust, then the oceanic plates will just go below other plates and the ocean will get new crust and lose old crust. I do think, however, that the land masses will get bigger from the rifts on the land and the land plates will go over all the oceanic crusted plates. -Zach

I am sorry for putting this under the wrong category- it should be under Opposition To The Theory. Anyway, if I am wrong on my previous theory, would somebody please respond at Talk:Seafloor_spreading discussion? Thank you. -Zach

Depends. You can have some oceans getting bigger, and some where oceanic crust, as you describe, plunges below some continental crust. See, for instance, the formation of the Himalaya: the Indian peninsula came from the south, the sea between India and Asia gradually disappeared, and they collided fully. David.Monniaux 10:27, 30 Mar 2005 (UTC)

[edit] Invitation

Work is currently in progress on a page entitled Views of Creationists and mainstream scientists compared. Also currently being worked upon is Wikipedia: NPOV (Comparison of views in science) giving guidelines for this type of page. It is meant to be a set of guidelines for NPOV in this setting. People knowledgable in many areas of science and the philosophy of science are greatly needed here. And all are needed to ensure the guidelines correctly represent NPOV in this setting.  :) Barnaby dawson 21:42, 29 Dec 2004 (UTC)

[edit] Grammar issue

Just out of curiosity, shouldn't it be "Types of Plate Boudaries"? Sasquatch 21:38, 31 Dec 2004 (UTC)

[edit] Geological paradigm shift

This section is very good, but needs a rework to be more encylopeadic. At present it reads a little too much like an essay or a speech. In particular the use of the personal pro-noun, "we". Is it possible that someone could rework this section. --Fermion 01:29, 21 Jun 2005 (UTC)

I agree, this section still needs some reworking even two years later, and there is one additional omission in the historical section I would like to note. Can anyone add to the history of the theory of plate tectonics any information as to when exactly convection within the mantle was suggested as a driving force behind plate motion? Convection is mentioned earlier in the article, but the history only mentions continental drift, seafloor spreading, and subduction, and then moves straight to the conclusion without mentioning who proposed the forces behind it. See Continental Drift --68.186.255.28 (talk) 08:32, 21 December 2007 (UTC)

[edit] Convergent Plate Boundaries

'As organic material from the ocean bottom is transformed and heated by friction a liquid magma with a great amount of dissolved gasses will be created.'

I'm fairly certain this section is misleading - the heating due to friction within a subduction zone is negligible. However, as the subducting plate warms due to its descent into the asthenosphere, volatiles within the plate will be driven off (eg. water from amphibolites in the oceanic crust) - it is this water that causes melting in the mantle of the overriding plate, since the water depresses the melting point. --J chaloner 7 July 2005 18:13 (UTC)

I agree. Change it. Vsmith 8 July 2005 02:39 (UTC)

[edit] Tectonics ?

I don't understand, why is tectonics redirected here. Tectonics is a branch of geology as well as petrology or sedimentology, but plate tectonics is a scientific theory. Siim 09:45, 4 August 2005 (UTC)

Tectonics did exist as a short article until last Feb. when the redirect was created. I feel the article should be re-instated and expanded to include its relation to structural geology and discuss the development of the field through the plate tectonics revolution. Plate tectonics seems to be treated as a field of study at times, rather than the unifying theory that it is. It appears the redirect was made without any discussion on the talk page. Vsmith 03:43, 5 August 2005 (UTC)
Old discussion, but I'll add my support anyway. I wanted to link to tectonics from the Astronomy page (as a geologic process on other planets), but I really don't want to imply PLATE tectonics.--Will.i.am 00:56, 19 July 2006 (UTC)
Good - just revived and modified the old tectonics article. Needs more work though. Cheers, Vsmith 03:07, 19 July 2006 (UTC)

[edit] POV Section

I just marked the section "Geological Paradigm Shift" as POV - this is not about the section's content, but about the highly POV, unencyclopedic tone of the section's language. I don't know enough about plate tectonics and its history to try to fix it (I'd probably insert lots of inaccuracies and wrong statements when trying to rephrase everything in a neutral way), but i think somebody should have a close look at this section. -- Ferkelparade π 12:28, 30 September 2005 (UTC)

In this case one can either learn about the history of plate tectonics or the history of paradigm shift. Plate tectonics is often given as an example of a paradigm shift, as it is widely recognized there was a shifting in POV due to the acceptance of the concept of tectonic movement. I removed the POV mark. (SEWilco 14:44, 30 September 2005 (UTC))
No one is disputing that plate tectonics constituted a paradigm shift. Rather, I think the issue is about the tone of the section. I commented on this earlier (see section geological paradigm shift on this page). The section is not encylopedic in tone. For example
Mysteries were no longer mysteries. Forests of complex and obtuse answers were swept away. Why were there striking parallels in the geology of parts of Africa and South America?
or
We have inherited some of the old terminology, but the underlying concept is as radical and simple as "The Earth moves" was in astronomy.
The first reads more like a feature article in a magazine, the second uses the first person "we". Neither is encyclopedic. I concur that the section needs a rework. Again the issue is not POV but tone. -Fermion 00:01, 2 October 2005 (UTC)

Tone ... Well this isn't grandpa's old encyclopedia or are we supposed to emulate the 1911 style? It is pretty good prose, and has been around since January 2003 [1] when it was added by an anon and has been essentially unchanged. I say don't mess with good informative writing just because it's not encyclopedic, whatever that means. Vsmith 03:20, 2 October 2005 (UTC)

I certainly agree that it is good prose. However, it doesn't fit with the overall tone of the article. It changes style, it has a different feel. Either this section needs a re-write or the article needs a re-write to match the tone of this section. The argument that it has been essentially unchanged is not compelling, we can always be better.
I also appeal to the principles in the five pillars which indicates we are aiming for the best. Traditionally the best writing for encyclopedias has been neutral third person. The section under discussion is not neutral third person. See also Wikipedia:Manual_of_Style#Avoid_first-person_pronouns that discourages first person. -Fermion 06:21, 2 October 2005 (UTC)
Hmm... As I see it, the use of We here is not really a first person - rather it is all inclusive. If we replace We have... with Geology has... or Science has... that would solve the perceived first person problem, but also severely weaken the point and mess up the good prose.
Tradition be damned - Wikipedia is re-inventing encyclopedia. We should not be aiming to copy EB style just for the sake of tradition. The best is being re-invented. Use the traditional good style when appropriate, but don't be bound by it - good style can transcend tradition.
Geeesh, what a bunch of blather that was :-) Vsmith 15:28, 2 October 2005 (UTC)
Re-reading Wikipedia:Manual_of_Style#Avoid_first-person_pronouns one finds an explicit acceptance of using ``we`` in a history context like this to connote the whole modern world.LeadSongDog (talk) 14:29, 21 December 2007 (UTC)

[edit] Continent-continent convergence

The bit on continent-continent convergence seems a little lame. Since I'm new to wikipedia, I'm reluctant to edit the page itself, but it seems still an open issue scientifically whether extrusion happens (e.g. Tapponier and Molnar) or underthrusting or delamination, etc. is still an open question, especially with respect to the India-Eurasion collision. I don't know anything about the validity of these models at this link: http://www.geo.arizona.edu/~ozacar/models~1.htm but they seem to capture the uncertainty around the issue.

Peter Burkholder 20:00, 5 October 2005 (UTC)


[edit] Hotspots

There is an inaccuracy in the article. In this article written that hotspots is associated with divergent boundaries. But hotspots are independent of divergent/convergent boundaries and plates move above hotspots. Most known hotspot - Hawaii is center of Pacific Ocean plate. Iceland hotspot moves from West to East. It seems to me that hotspots must be described more completely in this article, because it conception plies important role in plate tectonics - it allow to determine absolute plates motions.Stepanovas 21:15, 19 November 2005 (UTC)

[edit] refs

I've removed some odd quotes in the ref section. Also don't think we need the footnote style for a general ref like the Thompson & Turk college text. If a specific part came from this text then a simple and easy to follow Harvard style ref would be preferable. Open to suggestions here, but see Harvard style as most common in science references. Do we need to tie each section in to a source? and if so which of the various gen refs was used for each. Seems the general refs support the whole and any specific (or controversial) points may need specific refs. Also de-linked individual years, decades and centuries. Vsmith 01:08, 1 January 2006 (UTC)

I added the detailed refs you mentioned. My reasoning was that such highly detailed referencing (citing even "obvious" points, providing the quotes that make the claims, etc.) would help make it possible to detect and correct even subtle vandalism without being knowledgable about the subject. I still do consider this to be a good and useful project, but I'd be happy to discuss it, of course. I did avoid referencing statements whose topics had articles, like lithosphere; I considered that they could be checked by looking at the more detailed articles (which would have detailed sources themselves, of course.) I have no opinion on the formatting, and I'm delighted to use whatever format is most common or preferred for this subject. Thanks for bringing this up! JesseW, the juggling janitor 20:55, 1 January 2006 (UTC)
I understand your reasoning, and yes, full verification is important. However, the addition of source quotes in the reference section would soon make the ref section quite lengthy and it is not the standard practice. The listing of a good reference, either general or specific is important, but, except maybe for controversial material, the quotes aren't needed. As for the immediate case, any number of college texts could be referenced for the article - should we cite and quote them all - could get real lengthy :-). Add content with sources, but we don't need to quote them all. Thanks, Vsmith 01:42, 2 January 2006 (UTC)
I agree that making the ref section too large is a Bad Thing. However, I also feel that quotes are helpful in full verification. A possible format that could solve the large ref section problem would be a Plate tectonics/References subpage, with a single line link to it in the main article. An example of this is at United States/References. As for citing all the different textbooks for "textbook facts", I see no need, but at the same time, no harm (except for the added length of the main article, solved by putting the content in a subpage). I was doing Thompson & Turk because I had it available. Thoughts, objections? JesseW, the juggling janitor 02:32, 2 January 2006 (UTC)
I see some articles do have a ref subpage [2], but don't see any that include quotes from each source. Seems this should be discussed at the above page or Wikipedia talk:Citing sources or maybe Wikipedia:Village pump as you seem to be introducing a new element here. This quotes reccommendation carried out Wiki-wide would add lots of bulk :-) that's why I suggest discussing it with a wider audience. Related note: college texts are good refs., but are not primary sources. Cheers, Vsmith 03:44, 2 January 2006 (UTC)
I have started the discussion you suggested, here. Thanks for pushing me to do that, it helped me clarify my ideas, and I'm sure the public input will be helpful also. On your related note, I certainly was aware that college texts are not primary sources; however, they are very good sources to demonstrate the widespread agreement on a specific points - if a standard textbook says it, it must not be either really new, or non-mainstream. For that purpose, they seem like about as good sources as you could get. JesseW, the juggling janitor 08:59, 4 January 2006 (UTC)

[edit] Origin of Tectonic Plates

I understand neither Mars nor Venus have tectonic plates. Do you think a small section or a pointer to another page as to why Earth alone has plates, and how the current system of plates developed could be appropriate?

John D. Croft 08:43, 28 January 2006 (UTC)Regards John

It's not that earth alone has tectonic plates, but that a planet has to be geologically active to have plates (at least plates that move).thx1138 11:18, 28 April 2006 (UTC)
And in fact, there is some legitimate debate as to whether or not Mars once had plate tectonics early in its history. Even on Earth it is not clear that plate tectonics was in effect during the Archean (some studies on diapirs and greenstone provinces suggest instead that vertical tectonics dominated). Aharlap

[edit] Vertical tectonics versus Plate tectonics

My edition is not 'original research' as every sentence and conception conveyed is sourced. The articles are scientific peer-reviewed; due to deletions in this and other articles I copy it to here for those who really want to make scientific research and not scientific politics. Regards --GalaazV 23:52, 14 February 2006 (UTC)

See main article Vertical tectonics.

Criticism of plate tectonics has increased in line with the growing number of observational anomalies. [3]

According to the orthodox model of plate tectonics, the earth's outer shell, or lithosphere, is divided into a number of large, rigid plates that move over a soft layer of the mantle known as the asthenosphere, and interact at their boundaries, where they converge, diverge, or slide past one another. Such interactions are believed to be responsible for most of the seismic and volcanic activity of the earth. Plates cause mountains to rise where they push together, and continents to fracture and oceans to form where they rift apart. The continents, sitting passively on the backs of the plates, drift with them, at the rate of a few centimeters a year. At the end of the Permian, some 250 million years ago, all the present continents are said to have been gathered together in a single supercontinent, Pangaea, consisting of two major landmasses: Laurasia in the north, and Gondwanaland in the south. Pangaea is widely believed to have started fragmenting in the early Jurassic -- though this is sometimes said to have begun earlier, in the Triassic, or even as late as the Cretaceous -- resulting in the configuration of oceans and continents observed today.

Geophysical data show that, far from the asthenosphere being a continuous layer, there are disconnected lenses (asthenolenses), which are observed only in regions of tectonic activation and high heat flow. Although surface-wave observations suggested that the asthenosphere was universally present beneath the oceans, detailed seismic studies show that here, too, there are only asthenospheric lenses. Seismic research has revealed complicated zoning and inhomogeneity in the upper mantle, and the alternation of layers with higher and lower velocities and layers of different quality. Individual low-velocity layers are bedded at different depths in different regions and do not compose a single layer. This renders the very concept of the lithosphere ambiguous, at least that of its base. Indeed, the definition of the lithosphere and asthenosphere has become increasingly blurred with time . Thus, the lithosphere has a highly complex and irregular structure. Far from being homogeneous, "plates" are actually "a megabreccia, a 'pudding' of inhomogeneities whose nature, size and properties vary widely". The crust and uppermost mantle are divided by faults into a mosaic of separate, jostling blocks of different shapes and sizes, generally a few hundred kilometers across, and of varying internal structure and strength. Pavlenkova concludes: "This means that the movement of lithospheric plates over long distances, as single rigid bodies, is hardly possible. Moreover, if we take into account the absence of the asthenosphere as a single continuous zone, then this movement seems utterly impossible." She states that this is further confirmed by the strong evidence that regional geological features, too, are connected with deep (more than 400 km) inhomogeneities and that these connections remain stable during long periods of geologic time; considerable movement between the lithosphere and asthenosphere would detach near-surface structures from their deep mantle roots.

Continental drift theory far from being a simple, elegant, all-embracing global theory, it is confronted with a multitude of observational anomalies, and has had to be patched up with a complex variety of ad-hoc modifications and auxiliary hypotheses. The existence of deep continental roots and the absence of a continuous, global asthenosphere to 'lubricate' plate motions, have rendered the classical model of plate movements untenable. There is no consensus on the thickness of the 'plates' and no certainty as to the forces responsible for their supposed movement. The hypotheses of large-scale continental drift, seafloor spreading and subduction, and the relative youth of the oceanic crust are contradicted by a considerable volume of data. Evidence for substantial vertical crustal movements and for significant amounts of submerged continental crust in the present-day oceans poses another major challenge to plate tectonics.

A major new hypothesis of geodynamics [4] is surge tectonics, which rejects both seafloor spreading and continental drift. Surge tectonics postulates that all the major features of the earth's surface, including rifts, foldbelts, metamorphic belts, and strike-slip zones, are underlain by shallow (less than 80 km) magma chambers and channels (known as 'surge channels'). Seismotomographic data suggest that surge channels form an interconnected worldwide network, which has been dubbed 'the earth's cardiovascular system'. Active surge channels are characterized by high heat flow and microearthquakes. Magma from the asthenosphere flows slowly through active channels at the rate of a few centimeters a year. This horizontal flow is demonstrated by two major surface features: linear, belt-parallel faults, fractures, and fissures; and the division of tectonic belts into fairly uniform segments. The same features characterize all lava flows and tunnels, and have also been observed on Mars, Venus, and several moons of the outer planets. Surge tectonics postulates that the main cause of geodynamics is lithosphere compression, generated by the cooling and contraction of the earth. As compression increases during a geotectonic cycle, it causes the magma to move through a channel in pulsed surges and eventually to rupture it, so that the contents of the channel surge bilaterally upward and outward to initiate tectogenesis. The asthenosphere (in regions where it is present) alternately contracts during periods of tectonic activity and expands during periods of tectonic quiescence. The earth's rotation, combined with differential lag between the more rigid lithosphere above and the more fluid asthenosphere below, causes the fluid or semifluid materials to move predominantly eastward.


References

  1. ^  Pratt, David Plate Tectonics: A Paradigm Under Threat first published in the Journal of Scientific Exploration, vol. 14, no. 3, pp. 307-352, 2000; idem, Problems with Plate Tectonics, first published in New Concepts in Global Tectonics Newsletter, no. 21, p. 10-24, December 2001; :idem, Plate Tectonics Subducted, published in the Journal of Scientific Exploration, vol. 19, no. 3, pp. 490-495, Fall 2005
  2. ^  Pratt, David Sunken Continents versus Continental Drift

The topic of opposition to plate tectonincs is most likely encyclopedic, but it is not appropriate to describe it in detail in an article on plate tectonics itself, and even more inappropriate to describe one particular alternative to it in such detail. That is the gist of my objection. --EMS | Talk 00:03, 15 February 2006 (UTC)

_______________

Dubious at best. Ref links are to compuserve userpage for one David Pratt. The ref Journal of Scientific Exploration appears to be a place to get your wild ideas and speculations published - peer reviewed by what peers? If it wasn't bunk it would be published in a real journal. The J of Sci Expl. publishes stuff on bigfoot and re-incarnation, unlikely bedfellows for a serious geophysics article. In other words nonsense! Now, there are unanswered questions and plenty of room for new research related to plate tectonics - it is a vibrant living science and new discoveries and controversies are there. If the controversies have validity, they will be published in true peer reviewed journals. I say begone with it - or write an article for it properly labeled as speculation and pseudoscience - along with the flat and/or hollow earthers. Vsmith 00:51, 15 February 2006 (UTC)

[edit] Motion - relative to ?

Removed the following:

It should be noted that the actual direction of movement of the plates which abut at a transform like the San Andreas Fault is often not the same as their relative motion. For instance, the North American Plate is actually moving southwestward, nearly perpendicular to the Pacific Plate while the Pacific Plate is actually moving slightly more westward than its relative northwest motion along the San Andreas Fault.

Motion is not absolute - actual direction of movement?? - must be relative to something? Vsmith 14:54, 1 April 2006 (UTC)

Removed again, but included NASA map in the article above. The JPL site does show the relative motions, but note the detailed map at the bottom of that page. It shows the area east of the San Andreas moving SSE at ~2 cm/yr while the area just to the west of the fault shows a S to SSE motion of ~0.25 cm/yr or less. The devil is in the details :-) Vsmith 02:08, 2 April 2006 (UTC)

The fact remains that the North American Plate is moving toward the SW, not the SSE. The discrepancy between the motion near the fault and the movement of the NA Plate needs to be noted. There are many things here that are a matter of ongoing research, for instance the role of Great Basin-centered rifting in the modifying of velocities along the San Andreas.

And the question remains: Motion relative to what? I agree the main JPL map does show a SW motion vector for the N. Am. plate, but the website doesn't give a reference point. The apparent rotation of the Antarctic plate around a point in the Indian Ocean to the SW of Kerguelen Island would indicate a stationary rotating pole there. However the site doesn't elaborate. The added paragraph (I'm leaving it there for now) needs further clarification on that point if it is to remain. I'm still not convinced that the detail is appropriate in this section. Vsmith 04:33, 2 April 2006 (UTC)

I assume---and perhaps wrongly---that GPS satellites use astronomical points of reference (star positions, etc.). The "contradictory" velocities you see at the bottom of the JPL page are relative velocities based on Santa Catalina Island ("CAT") Obviously, since this station is on the Pacific Plate, and moving NW, velocities to its east will appear to be southerly. Note something interesting and illustrative where the vectors point east and close to the San Andreas: they point ACROSS it, not along it. One way to derive the velocities locally is to add the vector of the North American Plate motion (sw), plus the posited spreading vectors in the Basin and Range (oriented wnw-ese), and you get a rough approximation of the relative motion along the San Andreas. Tmangray 23:15, 5 April 2006 (UTC)

Excuse the ambiguity above. Rephrasing: Note something interesting and illustrative where the vectors just east and close to the San Andreas point...etc. Tmangray 23:28, 5 April 2006 (UTC)

[edit] Plates motion: asthenosphere?

The article states about the asthenosphere:

"Below the lithosphere lies the asthenosphere which comprises the inner viscous part of the mantle."

"The lithosphere essentially "floats" on the asthenosphere. The lithosphere is broken up into what are called tectonic plates."

"The key principle of plate tectonics is that the lithosphere exists as separate and distinct tectonic plates, which float on the fluid-like (visco-elastic liquid) asthenosphere. The relative fluidity of the asthenosphere allows the tectonic plates to undergo motion in different directions."

How can tectonic plates float in an theoretical continuous asthenosphere zone that evidence from seismic-velocity, heat-flow, and gravity studies which has been building up for several decades, shows that ancient continental shields have very deep roots and that the low-velocity asthenosphere is very thin or absent beneath them?! There are several studies and available technical data in Geology showing the fallacy in the concept of huge continental drift movements over a continuous fluid-like zone called 'asthenosphere'! It is no surprise that secondary school books forget to metion this little detail and other crucial factors, but an encyclopedia should not compromise itself, transmiting fallacies, just in order to present a beautifull text along the 'official' line.
eg: "This means that the movement of lithospheric plates over long distances, as single rigid bodies, is hardly possible. Moreover, if we take into account the absence of the asthenosphere as a single continuous zone, then this movement seems utterly impossible." Pavlenkova, N. I. (1990). Crustal and upper mantle structure and plate tectonics. In Barto-Kyriakidis, 1990, vol. 1, pp. 73-86.
"We are surprised and concerned for the objectivity and honesty of science that such data can be overlooked or ignored. ... There is a vast need for future Ocean Drilling Program initiatives to drill below the base of the basaltic ocean floor crust to confirm the real composition of what is currently designated oceanic crust." Dickins, J. M., Choi, D. R., & Yeates, A. N. (1992). Past distribution of oceans and continents. In Chatterjee & Hotton, 1992, pp. 193-199

[edit] Neal Adams Science Project New Model of the Universe Two Guys in a Bar

Earth... and Mars... like all other planets, moons, suns, solar systems, galaxies and the universe is growing.

Neal Adams

--194.134.193.16 16:18, 13 April 2006 (UTC)Keiser Soza

Yeah, I watched clip 00 and 12, where Mr. Neal Adams explained on the grounds of continental plates fitting together perfectly on a small sphere, that the earth's core has been composed of water, which is forming the earth's oceans, while the diameter of the planet is increasing. Interestingly, the continental plates actually do fit together around the planet if the diameter is reduced. Care someone to elaborate this? ;D Teemu Ruskeepää 14:21, 1 June 2006 (UTC)


Funny, but bogus. I remember hearing a very convincing answer to the question, 'How do we know the Earth is not expanding?' which I unfortunately do not remember. I'll see if I can find it, though. Aharlap
Yeah, see if you can dig that up because as far as I'm concerned, Neal Adams' model is more predictive than plate tectonics. Not that I think PT is wrong per se, but I don't believe for an instant that there was a Pangaea on one side and a super-ocean on the other. There are numerous problems with the Pangaea model starting with the fact that it's completely arbitrary, and doesn't fit the fossil, or even geographical evidence, all that well. -broodlinger 24.184.67.122 08:06, 29 January 2007 (UTC)
Thanks. I wouldn't call that bogus though. Mr. Neal Adams seems to believe it and it's rude to call him a lier. Teemu Ruskeepää 13:38, 16 August 2006 (UTC)
You might try the following link: [5] (SEWilco 21:56, 16 August 2006 (UTC))
Another problem is that the modern continents did not begin with this shape. For example, Florida is new. Look at the images on Craton and you see hints of how various volcanic islands and other structures grew together to create the continents. There are smaller continents as you go further back in time, so the argument that the present continents fit on a smaller sphere is weakened. One has to claim the Earth was much smaller in a very short geologic time scale, and in my quick look I've seen some very awkward explanations for such growth. I'm not going to go through all the issues, as it is not hard to find discussion. I also remind searchers that you can take the above Neal Adams URL, do a Google search on it, and search for sites which reference that URL, as you may then find other sites discussing that specific info. (SEWilco 04:10, 17 August 2006 (UTC))
I think this question should be considered only as it is, to entertain the thought by trying to think who it actually could be true, not consentrate on creating serious counter-arguments. After all, Neil Adams names his title "two guys in a bar" Teemu Ruskeepää 12:37, 17 August 2006 (UTC)

[edit] The age of fragments

I saw in Wikipedia a couple of weeks ago a picture of the age of the parts of the contemporary plate arrangement. It had an explanation something like "on orange are shown the parts that have survived unchanged all the continental shifts". I found it while I was browsing pages relating to glaciology. Now I can't find it anywhere. Do you know where it is? Teemu Ruskeepää 07:20, 1 June 2006 (UTC)

I believe the term you're looking for is craton. Aharlap

[edit] Awesome article

--Anchoress 06:10, 8 June 2006 (UTC)

[edit] Merge suggestion

I've suggested to merge tectonic plate into this article. - Samsara (talk • contribs) 20:13, 10 July 2006 (UTC)

Good idea - there is little in the Tectonic plate article that is not here already; anything else should be. --Geologyguy 20:30, 10 July 2006 (UTC)
I think it's all merged in now except for the interwiki links (I think they have to die) and this passage about the Galilean moons:
As far as is known, the Earth is the only planet in the Solar System to possess active plate tectonics, although there are suggestions that different styles of plate tectonics were in operation on [...] some of the Galilean satellites in the past.
I'll set a redirect now, but one may want to consider some of the material for the introduction of this article, as it is very well-written and particularly easy to understand.
Samsara (talk • contribs) 20:58, 10 July 2006 (UTC)

I added from the Tectonic Plate article the lines about plate boundaries not coinciding with geographic continents, and under the section on other planets, a ref to the Galilean satellites. If you did this and I didn't see it, please revert. Thanks for doing the merge. --Geologyguy 21:28, 10 July 2006 (UTC)

[edit] Confusion of terms

The assertion that: "Plate tectonics ... is a theory of geology developed to explain the phenomenon of continental drift" is very misleading. Continental drift and plate tectonics are often confused theories (in my experience) which are competing. Plate tectonics is, I would say, simply a model of the Earth in which the outermost layer is divided into rigid regions (ie, plates) and in which deformation is localized along plate margins / boundaries. On the other hand, continental drift treats the regions of continental crust as rigid bodies which float like ice cubes amidst a deformable regions of ocean. I don't actually, unfortunately, what phenomenon it was developed to explain specifically. Now I just need to find some references... and then I'll take a go at improving this...

--Aharlap 02:30, 1 August 2006 (UTC)

Reworded a bit. Continental drift and plate tectonics were not competing theories rather plate tectonics encompasses and superceded the older continental drift ideas based on more abundant evidence collected during the 60s & 70s. Vsmith 13:26, 1 August 2006 (UTC)


That's much better! But I still think there should be a more explicit mention of the plates being defined as rigid regions of the Earth's lithosphere with deformation occuring at plate boundaries (in the several forms listed) early on and not just in key principles. That is, I think it should be mentioned in the first three paragraphs as it's fundamental to the theory's definition. --Aharlap 19:30, 1 August 2006 (UTC)

[edit] Universally accepted?

I don't think this is quite true as worded: "[Plate tectonics] has since been universally accepted by virtually all scientists" It is the reigning paradigm, but is certainly not universally accepted. I also do not see a need for use of the word 'virtually.' Virtual scientists? :) --Aharlap 19:34, 1 August 2006 (UTC)

Go see the talk page on Age of the Earth for the reasons why you wwon't find this phrase being changed anytime soon.Rolinator 08:28, 11 November 2006 (UTC)

[edit] Regarding 'Development' & 'History & Impact'

I'm not quite sure that these two sections need to be separate. I would suggest that they be merged as Development seems very short on this topic subject, and the theory's development is anyhow explained quite nicely in 'History & Impact.'

However, a graph of the terms "plate tectonics" and "continental drift" vs date in journals might illustrate its scientific development quite elegantly. Perhaps to be included in my suggested merged section. --Aharlap 19:38, 1 August 2006 (UTC)

[edit] Suggestions to: 'sources of plate motions'

Perhaps a more appropriate title is: 'Driving forces of plate motions.'

Also, a simple picture of a cross-section at a subduction zone with appropriate arrows and labels would go a long way to illustrating what the differences are in these competing forces. Aharlap

[edit] "Torques"

The article is becoming heavily laden with jargon that is undefined and unexplained, and therefore, not useful. One example is the appearance of the term "torque". The average reader is left baffled unless the term is explained. Torque is generally understood as having something to do with turning force. One can go to the link for torque, but this is of no help at all in making the connection with plate tectonics. What has "turning" have to do with the forces moving the plates? Tmangray 04:44, 29 August 2006 (UTC)

Why should torque not have something to do with plate tectonics? The Earth rotates, it is round, and we conceptualise layers of rock as being "plates". As they move across the spheroid, they 'twist' in relation to not only lines f latitude and longitude (which are artifices of mapping) but in relation to their original orientation within the Earth. This would, if you can visualise this, result in a torsional effect, hence some effect of twisting and turning n one of the three directions (or, correctly put, along a vector). Examples would include transpression, transtension, listric faults, nappes, etc. This is not to say that the use of jargon is great, or appropriate. It may need explaining. Rolinator 08:25, 11 November 2006 (UTC)

[edit] Expansion request - end-to-end mapping

 Please help improve this article or section by expanding it.
Further information might be found on the talk page or at requests for expansion. (January 2007)

I was reading History of Earth which mentions various continental configurations. I came here hoping to see a complete history of the shapes of the continents. It would be nice if that were either added here or spawned into a separate article. -- Beland 20:45, 4 September 2006 (UTC)

An interesting idea. Laurentia#Geological history of Laurentian craton in chronological order may give an idea of how complex this may be. Also see Commons:Category:Plate_tectonics. (SEWilco 05:48, 5 September 2006 (UTC))
Not only that, I was hoping for a computer simulation with a globe that can be rotated to see it from all sides, starting from the beginning of the Earth. A job for Google Earth?--Robert van der Hoff 05:46, 16 May 2007 (UTC)

[edit] Alternative theories

Would a short description of the alternativ theory to place tectonics, by professor Karsten Storetvedt, fit into the article? No matter if it is correct or not, good alternatives are always interesting. 193.217.194.200 23:17, 23 September 2006 (UTC)

If it is a good alternative, isn't there enough material for an article Global wrench tectonics? (SEWilco 02:09, 24 September 2006 (UTC))
Yes, it probably is, but I don't think I am the right person to write such an article. At least not for the moment. 193.217.195.13 03:35, 24 September 2006 (UTC)
Here is a link to an alternate theory, detailed video : http://www.maniacworld.com/Conspiracy-of-Science.html Peoplez1k 12:31, 4 May 2007 (UTC)

[edit] Vandalism

This page has been attacked quite a lot recently. Is it time for semi-protection? --Masamage 04:42, 30 November 2006 (UTC)

I would say so; it's increased quite a bit. Doc Tropics 04:52, 30 November 2006 (UTC)
End of the school term, I guess. Everyone's bitter. X) I'll go put in the request. --Masamage 04:57, 30 November 2006 (UTC)
LOL. Good move, thanks for taking care of it. Doc Tropics 05:03, 30 November 2006 (UTC)
I've removed the protection now. Zocky | picture popups 03:44, 10 December 2006 (UTC)

It has been innappropriately vandalized lately...GUEST

I noticed some more vandalism under "Divergent (constructive) boundaries" 21 February 2007 —The preceding unsigned comment was added by Hinek (talk • contribs) 13:54, 21 February 2007 (UTC).
I've put in for semi-pro again. the diff over the last 50 edits shows it's almost all vandalism and reversions. —Preceding unsigned comment added by LeadSongDog (talk • contribs) 03:09, 5 November 2007 (UTC)
It's been declined as not being vandalized often enough. LeadSongDog 04:47, 5 November 2007 (UTC)

[edit] Minik T. Rosing

Removed the following unsourced bit from the Floating continents section. Seems to be talking about something other than the historical development of continental drift.

The Danish professor in Geology Minik T. Rosing and some of his colleagues at Stanford University in California have suggested that the continents which consists of granite and other light materials, are floating over the basalt like foam on water, covering the basalt. There is an ongoing cyclus between the basalt and the magma, where the heavy basalt sinks into the hot earth, melts into lava and is pressed to the surface again through cracks in the basalt crust, while the continents float on top of the cyclus.
The theory says it is life itself that created the continents. When photosyntesis was "invented" by early organisms, the cyanobacteria produced massive amounts of oxygen. Basalt that was exposed to oxygen was broken down through an oxidizing process. When this weathered basalt sank down into the crust, some elements in the mass melted at just 650 degrees Celsius, while basalt normally melts at temperatures between 1100-1200 degrees Celsius. This melting mass was separated from the rest of the oxidized basalt and rose to the surface where an opening was found. Since it was a much lighter material, the granite ended up covering over the basalt crust, forming the continents. This made dry land, while the rest of the crust taking part in the basalt/magma cyclus made up the sea floor.

The info is from Minik T. Rosing's work on the Isua complex of Greenland and the theories of continental crust development during the Archaen. In that respect it is about the development of granites and the earliest continental crust - essential early developments for plate tectonics - as driven by early photosynthesis. But it seems out of place where it was. We do need a new section on the early development of plate tectonics - early as in Archaen tectonics and the birth of continental crust as an essential starting point. Most google hits are to article in journals for which I lack access, but the following are sources to support the info: http://environment.newscientist.com/article/mg18925444.200.html and http://news.bbc.co.uk/2/low/science/nature/3321819.stm . Vsmith 02:46, 26 January 2007 (UTC)

[edit] Lead image

I think that Plate tectonics map.gif would be more apt as a lead image of the article. The current one serves little purpose. — Ambuj Saxena (☎) 05:10, 21 February 2007 (UTC)

That image would be too hard to read at the 300-350px max width of a lead image. I agree that the current one is not a good lead, so I have moved the other map of plates to the top now. --Seattle Skier (See talk tierS) 00:02, 23 April 2007 (UTC)

[edit] Laser Ranging

I think the plate tectonics article could be strengthened by noting that in the 1970's relative motion between different plates was measured by laser ranging to a retroreflector package placed on the moon by on of the Apollo missions. Data was about 1 cm a year if I recall, consistent with geological data from other sources.

Retrospective article that I found is "Lunar Laser Ranging: A Continuing Legacy of the Apollo Program", Science 265, 482-490 (1994), J. O. Dickey, P. L. Bender, J. E. Faller, et al.

64.252.75.35 15:34, 30 March 2007 (UTC)

[edit] Bias on article

I'm disappointed to see this article makes no mention of Fred Vine who, with Matthews, created the Vine-Matthews hypothesis which postulated the theory of plate tectonics. See article Fred Vine for details. I don't think this page should be locked down until this omission is corrected - jonthegeologist

—The preceding unsigned comment was added by 82.32.99.164 (talk) 09:05, 9 April 2007 (UTC).

Feel free to add an appropriate link. The page will never be "locked down" if by that you mean "declared finished". It is often semi-protected to deter anonymous vandalism, but that will not affect you if you establish a username. Cheers Geologyguy 13:51, 9 April 2007 (UTC)
... or put your suggestion on the talk page. The page could be 'locked down' in any of the published versions. ☻ Fred|☝ discussion|✍ contributions 03:14, 18 June 2007 (UTC)

[edit] This article was reviewed by a leading expert in the field

In PCPro Magazine on 12th July 2007 Glen Burridge, Chief geophysicist, Geopetrol International, Monaco, evaluates this article and compares it to Britannica's and Encarta's. Lumos3 21:53, 13 July 2007 (UTC)

This is already noted in the template at the top and is covered by Wikipedia:External peer review/PCPRO154. violet/riga (t) 13:34, 27 July 2007 (UTC)

[edit] Metaphorical Uses Heading

I feel like this section should be removed. Besides not being very informative, the content is suited to a dictionary entry rather than an encyclopedia article. —Preceding unsigned comment added by 132.177.41.203 (talk) 02:45, 31 July 2007

[edit] Roberto Mantovani

Its remarkable to see that Roberto Mantovani construct the entire theory of Plate Tectonics When Wegener was only 9 Years old, and the wegener got the recognition for it !! Roberto Mantovani gave the theory of Continental drift to the world, and now Wegener is the father of it !!?? Furthermore is remarkable that there are no references to Mantovani in the WIKIPEDIA WEGENER Biography !? The truth is that Mantovani established the theory of plate tectonics in its entirety, Wegenr made a copy Of it and come out with the same identical theory ( in his own word Mantovanis work on Continental drift was remarkably similar !! ) And noe wegener takes the glory for it !! Indeed both man were erroneous when describing the Mechanism responsible for the drifting of continents, and took some 70 years after mantovanis Death with the development of Seismic, gravity and magnetic and computer science to be able to shape the science of continental drift. Wegener was not honest when he wrote the note as to Mantovanis work, for he never said that He took Mantovanis theory and became a prominent Follower. Weger embarked to offer a different view as to the Mechanisms responsable for Continental Drift. Wegener in changing montovani idea of thermal expansion Proposed a theory for far more incorrect, one of centrifugal force ………….“being the responsible factor for explaining continental drift“ !!!! But I would go further to prove the injustice toward Mantovanis recognition of his revolutionary work, by taking WIKIPEDIA historians to look at the Alfred Wegener page !! There is no clear reference to Roberto Mantovani when addressing The historical development of the so called ………… "WEGENER THEORY OF CONTINENTAL DRIFT” !!!! Is like looking into the history of the development of quantum mechanics and not mentioning Heisenberg !!?? …………..or……….. …….. Looking into the history page of Wolfang Pauli on WIKIPEDIA and not finding Reference to Heisenberg !!?? 86.136.16.132 22:39, 16 September 2007 (UTC)

I've added Roberto Mantovani to the list of scientists who suggested continental drift before Wegener. As he wasn't the first to do so, it's unclear why his contributions outweigh those of other scientists. If you're convinced that WP's doing him an injustice here (and his absence in my geology textbook suggests that WP would not be alone on this point), it might be an idea to flesh out his ideas over at his article, or to discuss them here. That Mantovani's explanation for continental drift centred on the now-discredited expanding Earth theory probably explains why he is overlooked today rather than the laziness/conspiracy of science historians. Cheers, --Plumbago 08:29, 17 September 2007 (UTC)

[edit] Tectonics on Mars

This paragraph leaves me in a puzzled state. I wonder what magnetic evidence there is for (a form of) plate tectonics on Mars? Could someone make this paragraph clearer? The quoted source does not provide any evidence for it at all. Or has somebody made a mistake? (plate tectonics is not the same as tectonic structures) Woodwalker 13:28, 14 October 2007 (UTC)

See ref 10 and the main article Geology of Mars#Crust and mantle. LeadSongDog 13:51, 14 October 2007 (UTC)

I have a problem with that ref. In the article it links to the term "plate tectonics" is not used even once. Instead, it tells me about a tectonic structure (a graben), that is not necessarily indicative for plate tectonics. In fact I know a lot of graben structures that were not formed by plate tectonics.

I also wonder how measurements of the magnetic field (or hypotheses about the field in the past) can tell us anything about the style of tectonics on Mars. It goes unexplained in both articles. Woodwalker 18:37, 14 October 2007 (UTC)

As indicated at the link from LeadSongDog, the presence of alternating bands of high and low (perhaps positive and negative polarity) can be interpreted as reflecting fluctuations in the magnetic field. This may (not certain, but may) indicate that a dynamo similar to that of earth was at one time present on Mars. That, in turn, can suggest plate tectonics similar to earth. It is by no means certain, but is suggestive. Cheers Geologyguy 22:58, 14 October 2007 (UTC)

I think I misunderstood LeadSongDog then. Are we talking about this article? It does not tell us about magnetic polarities, it only mentions "unexplained linear features".

Or do you mean the article that goes with this abstract? It says the Martian magnetic field reversed at least once. That would still be insufficient to create a thing similar to the "magnetic striping" of the Earth's oceanic crust. Woodwalker 22:00, 15 October 2007 (UTC)

My humble apologies, I should have pointed you to Geology of Mars#Magnetic field and internal structure

and the refs thereto, particularly ref 9. LeadSongDog 06:28, 16 October 2007 (UTC)

This explains it. So the ref was wrong. I googled the names of the researchers and they claim indeed that the magnetic patterns on Mars were formed by some form of plate tectonics:

The most straightforward interpretation of the magnetic lineations in the Mars highland crust is that they formed early in the planet’s evolutionary history (early to mid Noachian) by plate tectonics and sea floor spreading, analogous to terrestrial oceanic crust. (Connerey e.a. 1999)

For us the three most interesting articles of the team are:

  1. Connerney, J.E.P.; Acuña, M.H.; Wasilewski, P.J.; Ness, N.F.; Rème, H.; Mazelle, C.; Vignes, D.; Lin, R.P.; Mitchell, D.L. & Cloutier, P.A.; 1999: Magnetic Lineations in the Ancient Crust of Mars, Science 284, p. 794-798.
  2. Connerney, J.E.P.; Acuna, M.H.; Wasilewski, P.J.; Kletetschka, G.; Ness, N.F.; Reme, H.; Lin, R.P. & Mitchell, D.L.; 2001: The Global Magnetic Field of Mars and Implications for Crustal Evolution, Geophysical Research Letters 28, p. 4015-4018.
  3. Connerney, J.E.P.; Acuña, M.H.; Ness, N.F.; Kletetschka, G.; Mitchell, D.L.; Lin, R.P. & Rème, H.; 2005: Tectonic implications of Mars crustal magnetism, Proceedings of the National Academy of Sciences 102, p. 14970-14975.

I suggest we use these three refs instead of the NASA-articles, in both articles. The current ref in this article doesn't cover the content anyway. If someone is interested, I can send the full-texts of articles 1 & 3 if you have an email address at wikipedia. Woodwalker 17:35, 16 October 2007 (UTC)

[edit] Cessation of plate tectonics

There should be a section about the future when plate tectonic movement ceases on the Earth in roughly a billion years from now. JAF1970 05:01, 11 November 2007 (UTC)

Never heard of it. Where did you read/hear this theory? Woodwalker 14:32, 16 November 2007 (UTC)

[edit] November 2007 edits

Hello, adding my two cents here to the recent changes. I'm not sure why there seems to be a problem with North America, or any other plate, "not subducting". The leading edge (the edge away from the spreading center where new crust is being generated, in the Atlantic) of North America is mostly continental crust which cannot be subducted. You could say the same for most of the continental-dominant plates: the S. Am., Africa, Eurasia, and Australian plates are also "not being subducted". This is certainly not a problem - it follows from the theory. Some plates subduct, some override, and a dynamic balance is more or less maintained. Big changes to the pattern develop where continent-continent collisions occur and neither plate can subduct, as in the India-Eurasia collision. Cheers Geologyguy 15:40, 11 November 2007 (UTC)

The problem arises when the claim is made that only subduction causes plate motion. Since the North American Plate moves, and it isn't subducting anywhere, then logically it cannot be in motion because of subduction. That leaves friction acting horizontally, or ridge-push. I see little good evidence for ridge-push, so that really only leaves friction. I do believe that the evidence shows that subduction is probably a larger force than friction, explaining why the slowest-moving plates are the ones that have little or no subduction acting on them. Tmangray 00:27, 14 November 2007 (UTC)
And while we're at it, perhaps someone might explain why only friction and gravity are mentioned as originating forces for plate motion. What happened to the expansive force of heat which creates the "hill" at ocean ridges which allows gravity to act secondarily? Tmangray 00:41, 14 November 2007 (UTC)
WP:OR requires us to not edit based on what we figure out. We might make mistakes, such as not taking into account forces such as the Farallon plate sinking underneath North America. We can report what researchers have figured out, or what they know is unknown. (SEWilco 01:41, 14 November 2007 (UTC))
That a misreading of the policy. The policy allows and even encourages the statement of undisputed facts. It is undisputed that the North American Plate moves. It is also undisputed that it is subducting nowhere. This is important information when the assertion is made that only subduction moves plates. Tmangray 01:45, 14 November 2007 (UTC)
So don't say "only". "Driving force", "primary force", "main cause"? It also doesn't matter much that not every bit of sea floor as subducted and that not all pieces of continents are light materials. (SEWilco 01:58, 14 November 2007 (UTC))
I agree that any statement or implication that only subduction is at work should be revised. This is why I made the edits. The best way to illustrate that is to refer to plates that aren't subducting yet are moving, which is evident in two maps provided in the article. In those instances, subduction isn't a major factor, it isn't even a factor at all, and the most important force(s) must be something else. Or put another way in accordance with policy, to add in undisputed facts which make the point. Tmangray 02:15, 14 November 2007 (UTC)
Subduction may still be the major factor causing motion, even if the subduction is taking place on the other side of the planet. In the case of North America, obvious forces are the widening of the Atlantic and subduction on the west side of the Pacific. Those forces are probably pushing and pulling the NA plate through adjoining plates, but I'd have to go find sources before I can say that in the article. (SEWilco 16:02, 14 November 2007 (UTC))
Good luck. It seems unlikely. For one, the only "pushing" possible in the case of North America would be from the Mid Atlantic Rift, not another plate, and the consensus of opinion and evidence is that ridge-push may not even exist, as extension, not compression is seen at the ridges. And I have never encountered any theory or hypothesis about a pulling force exerted by any plate on another. I can't even conceive how that would be possible physically. Tmangray (talk) 01:56, 17 November 2007 (UTC)
Actually, on the global scale, I've seen mention that it's the subduction which drives the entire system due to pulling crust down, increasing the volume of melt, and possibly creating currents which flow upward along ridges. So what is happening under the crust may also be important in the motion of the crust. The Farallon Plate, in addition to contributing to western NA hot springs, may also be indicating an easterly flow of material under NA. (SEWilco (talk) 02:47, 17 November 2007 (UTC))
There is no subduction acting on the North American Plate with respect to horizontal motion. What is going on under North America is interesting, but that would be entirely the force of friction acting horizontally. Subduction is a downward force at a subduction zone, where a plate is consumed and pulled in by the force of gravity. That is the current consensus of plate tectonics. Our own speculations beyond that makes for an interesting discussion, but probably not what this discussion page is for. Tmangray (talk) 03:20, 17 November 2007 (UTC)
Well, I think I've seen it stated someplace that subduction is driving most plate motion on a global scale, whatever an individual plate is doing. If that isn't already sourced in the article it should be. (SEWilco (talk) 04:05, 17 November 2007 (UTC))
I fact-tagged "Plate motion is driven by the weight of cold, dense plates sinking into the mantle at trenches". The source might be in the existing references someplace. (SEWilco (talk) 04:11, 17 November 2007 (UTC))
Some researchers think so. Others think friction with the asthenosphere is more important. And then we also have "ridge push", the force on a plate driven by the gravitational gradient from ridge to trench. Woodwalker (talk) 08:16, 17 November 2007 (UTC)
That's not ridge-push, that's the other one, the dead-weight toward subduction. Ridge-push as I understand it has to do with expansive force exerted against the edge of the plates at a ridge, which would be reflected in compression at the ridges. But the opposite is found---extension. That doesn't mean that expansive force isn't important, since it creates, as you say, the gradient for subduction "pull". Tmangray (talk) 21:50, 18 November 2007 (UTC)
Ridge push is, as i learned it, the slope-parallel force on the oceanic plate (in which the slope is the gravitational potential gradient from the shallower ridge to the deeper trench). Ridge push makes the plate slide down the slope. Slab pull is the force that comes from the weight of the heavy eclogitized slab in the mantle. It pulls the plate towards the trench (and into the subduction zone). Woodwalker (talk) 13:45, 20 November 2007 (UTC)
I need to brush up on my tectonic terminology. I believe you are right. My notion of ridge-push comes from the memory of some distant lecture wherein the idea that ridges are forced open by the magma forming new plate material was dismissed. In my mind, this became "ridge-push". If I understand it correctly now, ridge-push refers to the gravitational force created by the elevation of the ridge, while slab-pull refers to the gravitational force acting on densified crust. A quick google shows that there is apparently quite a debate still raging about these various hypothesized forces. I guess we might say the jury is out pending further research. Tmangray (talk) 05:35, 21 November 2007 (UTC)
That seems to me a good summary of the current geophysical debate. There are a number of schools and they don't aggree yet what the dominant force is. Currently my feeling is that the slabpullers have the upper hand, but the debate is far from over. Woodwalker (talk) 16:05, 23 November 2007 (UTC)
The slabpullers may have the upper hand, but they also have the huge problem of those plates, like North America, that move yet are headed toward no trench. And then there's the IndoAustralian Plate, moving at breakneck speed---but not a trench in sight, just the Himalayas. Tmangray (talk) 17:02, 23 November 2007 (UTC)
Indo-Australian Plate says there is subduction next to it. Is there a map showing subduction zones? Plate motions? (SEWilco (talk) 02:41, 24 November 2007 (UTC))
Here's a tectonic map of the Australian plate, there is also one of the Indian plate. Not yet translated from French though.(World map like this, in English, is on this article's main page) Woodwalker (talk) 11:53, 24 November 2007 (UTC)
Here's a tectonic map of the Australian plate, there is also one of the Indian plate. Not yet translated from French though.(World map like this, in English, is on this article's main page) Woodwalker (talk) 11:53, 24 November 2007 (UTC)

The Indo-Australian plate, specifically the oceanic crust of the east Indian Ocean, is subducting beneath Eurasia from Burma, through the Sumatra-Java Trench, all the way (almost) to New Guinea. There is probably some subduction of the Australian portion in the Solomon Sea, beneath either a microplate or a part of the Pacific Plate. It's quite a mess in there, though. More likely is subduction of the NE corner of the Australian Plate (Coral Sea area) beneath what is sometimes called the Fiji Plate, a likely broken part of the leading edge of the Pacific Plate. That one is an oceanic-oceanic interaction along the New Hebrides Trench. Cheers Geologyguy (talk) 03:58, 24 November 2007 (UTC)

Yes ,there are parts of the IndoAust Plate which are subducting, but not in the direction of motion that is creating the Himalyas. Not only that, the motion toward the subduction zones EAST of the Indian Ocean is greater on the far side of the plate, the Australian side, according to the map in the article. Yes, motion is oblique into most of the trenches, but that is taken up by the oblique crustal deformation in SE Asia. The motion toward the Himalyas is essentially perpendicular to the range, driving north toward no trench at all. Since there are no volcanics in Tibet (are there?) it can't even be argued that there is a hidden subduction zone. And then, we're still left with the fact that North America is moving toward no subduction zone anywhere. Tmangray (talk) 17:04, 24 November 2007 (UTC)
Well, personally I really don't see a problem, but what I think is pretty irrelevant. To return to what we should be discussing, as I look at the article it seems to me to be relatively even-handed in its approach to what causes plate motions and the ongoing research and questions about it. Are there things in the article that any editors participating here have serious problems with? Cheers Geologyguy (talk) 17:37, 24 November 2007 (UTC)
For new readers: Continents are less dense (lighter) than ocean floor rock. They've grown as they accumulated such material (see craton). Continents have been pushed around the surface of the planet for quite a long time. Oceanic plates have been subducted continually, so the floor of all the oceans is quite young (less than 200 million years, I think). It is thought that much of the motion of the continents is due to oceanic plates pushing them around. (SEWilco 15:42, 12 November 2007 (UTC))
That's the general theory yes. However recent research shows continental crust (especially the lower parts of it) can indeed subduct to large depths when some (uncommon) circumstances occur. But I regard that as the exception to the rule. Woodwalker 18:19, 13 November 2007 (UTC)

[edit] ratio calcium / magnesium

At the BBC In our Times by Melvyn Bragg it's indicated that the ratio calcium / magnesium is affected by this phenomenon. 216.86.113.233 (talk) 03:31, 25 January 2008 (UTC)

[edit] English geologist Arthur Holmes

I'm no patriot, and that's probably the point. I'm an Englishman and therefore a British man, and I rarely hear about "Scottish" geologists. But people get pretty patriotic about this crap. Therefore, unless Scotland or Wales or Northern Ireland declare independence, Arthur Holmes should be noted as "British", unless he personally requested otherwise. I'm just trying to avoid silly patriotic arguments :-)

I just want to clarify that - I'm not saying that great Scottish geologists don't exist, in fact, I'm sure that many do, but both the English and the Scots are tired of the fact that great Englishmen are quoted as "English" whilst great Scots are quoted as "British". It's an annoying fact of British media.

[edit] Citations

I've been over all the cites to standardize them to a common format. There are still a few exceptions, but the bulk are done. Much of the article text still fails to call out the sources used. This is a major reason the article was recently demoted to B class. Dig in, folks!LeadSongDog (talk) 04:41, 5 March 2008 (UTC)

[edit] Picture

I believe that the article's first picture is someone's idea of a joke. It's a 10th century ceramic plate from Iran with the inscription "the tectonic plates of the world were mapped in the second half of the 20th century". —Preceding unsigned comment added by 74.15.136.109 (talk) 01:34, 8 April 2008 (UTC)

[edit] Cocos Plate?

I'm not sure if this is right, but isn't The Cocos plate also one of the minor ones? It is not listed in this article

Vicky 2012 (talk) 13:22, 26 April 2008 (UTC)

Thanks, I added it - it is actually listed as a "major" plate at List of tectonic plates, but major and minor are rather subjective and will vary. Cheers Geologyguy (talk) 13:47, 26 April 2008 (UTC)