Talk:Plate tectonics

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

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)

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)

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)

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

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)

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)

Grammar issue

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

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)

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)

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)

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_self-referential_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)

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)

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)

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)

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

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)

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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)

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)

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

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)

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

Awesome article

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

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)

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)

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)

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)

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

"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)

Expansion request - end-to-end mapping

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)

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)

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).

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)

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)

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)

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)