|WikiProject Geology||(Rated Start-class, High-importance)|
|WikiProject Mountains||(Rated Start-class, High-importance)|
- 1 Untitled
- 2 Missing article
- 3 "...coupled with study of flora and fauna"
- 4 List of orogenies
- 5 Mountain formation
- 6 Proposed merge of Mountain building into Orogeny
- 7 Vocabulary
- 8 Physiography
- 9 Mountain formation
- 10 Revisions needed
- 11 Recent edits on meaning of orogeny
- 12 Some sourced statements about orogeny and its usages
- 13 Mountain building on continents
- 14 A better section header?
This seems to be a rather poorly written intro to a list of orogenies. Maybe some sort of merge with Continental collision which is much more informative and better written would be in order. Maybe not all of the orogenies listed are true continental collisions - for example the Andean Orogeny, but most are. Rename this as List of orogenies and then rename Continental collision as Orogeny? Any thoughts on the idea? Vsmith 03:35, 18 September 2005 (UTC)
I agree that the whole article is just a preface to a list. I don't think that it should be merged with continental collision because the bulk of orogenic activity is linked to plain old subduction. The fact is, this list is incomplete, ad the over-representation of continental collisions reflects the whole geology of continental crust; it's much more likely to preserve collisional sutures than fragile fold belts created in suprasubduction environments.
I'll get round to this one soon. I even have a whole book devoted to orogeny, with the whole historical perspective from the "Jaws of a Vice" theory, to cooling earth theory, etc, right up to plate tectonics. Rolinator 14:29, 28 December 2005 (UTC)
In case anyone is interested in tackling it, I thought I'd mention Hudsonian Orogeny is listed on Wikipedia:WikiProject_Missing_encyclopedic_articles/Hot/H5. Thanks! :) jengod 07:27, 31 December 2005 (UTC)
"...coupled with study of flora and fauna"
List of orogenies
The list of orogenies is in danger of taking over this article IMO. I propose that a new list article be started, leaving this one to actually describe what orogenies are about. Mikenorton (talk) 22:05, 12 November 2009 (UTC)
- Good idea, split off List of orogenies to another article, crediting the version of this one you copied. Graeme Bartlett (talk) 11:51, 13 November 2009 (UTC)
The introductory definition of this article (Orogeny (Greek for "mountain generating") refers to natural mountain building) as having something to do with mountain formation is entirely lost sight of in this article, and no reference to another article where this is discussed carefully is given. In fact, this article gives the impression that mountain formation is irrelevant: "An orogen is different from a mountain range in that an orogen may be almost completely eroded away, and only recognizable by studying (old) rocks that bear traces of orogenesis."
All this is unfortunate as mountain formation is far more of general interest than suggested by orogeny, a technical term probably known to no-one but a specialist. Brews ohare (talk) 19:34, 24 January 2010 (UTC)
After further perusal, I concluded that Orogeny was not really so much about specific mountain building as about processes leading to long arcuate tracts of rock. So I removed the initial figures I'd added and put in a lead drawing a distinction from mountain building per se. Brews ohare (talk) 00:09, 25 January 2010 (UTC)
- Commented at Wikipedia_talk:WikiProject_Geology#Mountain_formation. Vsmith (talk) 04:16, 25 January 2010 (UTC)
Proposed merge of Mountain building into Orogeny
Of course, I put up Mountain building as a new page, so I'm not inclined to merge it with Orogeny. I feel that "mountain building" is a rather narrow topic, referring to some rather specific eventualities, and of interets to a popular audience.
"Orogeny" is a much broader and more ambitious topic, of interest to a more technical audience, as seen in any discussion of any particular orogeny, say the Caledonian Orogeny. Orogeny is tied to epic phenomena of a wide variety of kinds, and mountain building is part of that, but not the major focus. The major focus of orogeny is the connection of observations of many geographic features to particular large-scale events like plate collisions and subductions, delaminations, and erosion and uplift, all connected to minutiae of geology and used to assemble all kinds of evidence to support the hypothetical events in the orogenic cycle associated with the orogen. Mountain building plays a part, but that is not the point of it all, which is assembly of the big event picture. Brews ohare (talk) 20:29, 25 January 2010 (UTC)
- Let's continue the discussion in a central place at Wikipedia_talk:WikiProject_Geology#Mountain_formation. Thanks! —hike395 (talk) 04:53, 26 January 2010 (UTC)
This article somehow has to distinguish between a number of terms: orogenesis, orogeny, orogen, orogenic cycle. How does usage of orogens and orogenies differ, for example? Is orogeny only about plate tectonics, or is it about the detailed consequences like magmatization and delamination as well? Or are these latter just geological clues to help identify a tectonic scenario? It would be one way to do this to include a discussion of a particular orogen (at a fairly distant perspective) and point out how the vocabulary is used, and where mountain building fits into the orogenic cycle, and just which events in the cycle are considered to constitute orogeny, and which are not. I've made a stab at this, but it could be done better. Brews ohare (talk) 16:30, 26 January 2010 (UTC)
This section is in bad shape. It is too brief, too narrow , and makes some unsupportable claims. Brews ohare (talk) 16:59, 26 January 2010 (UTC) I've tinkered with this section and added a figure, but more is needed. Brews ohare (talk) 19:34, 26 January 2010 (UTC)
Ollier and Pain argue forcefully that orogenesis has little to do with mountain formation. Mikenorton appears to agree. Maybe someone who knows a bit more geology can take a look at this article and determine whether it is accurate by today's standards? Brews ohare (talk) 19:31, 1 February 2010 (UTC)
- Er... read the second rather devastating review here Real weird geology in here... seems rather telling. Don't think that book makes it by today's standards. Yes, rugged mountain landscapes are the result of intense erosion of tectonically uplifted and currently uplifting mountain masses -- but as the reviewer states: The latest developments (and by latest I mean some solid four decades of research) in structural geology and global tectonics are dismissed as a scientific fad, while the authors focus instead on exogenous processes as the main producers of mountain landscapes. So let's not lean too heavily on that geomorphologists view. What mileage (professional citations) has that book received in the decade since publication? Vsmith (talk) 21:00, 1 February 2010 (UTC)
I was disturbed by that review as well. However, Ollier and Pain make very good use of quotes from many sources on the usage of the term Orogeny, so I'd accept their definition, which seems to me to fit very well with what one finds under specific Orogenies. Their ideas about mountain formation may go further than Mikenorton, who seems to feel that rock folding is a side trip in mountain formation. I backed off from these authors on this topic. Brews ohare (talk) 21:40, 1 February 2010 (UTC) A google search of Ollier shows him to be an actively publishing author in the technical literature on geomorphology, although not universally agreed with. Brews ohare (talk) 21:58, 1 February 2010 (UTC)
The notions of the role of orogeny in mountain building has undergone recent transformation, with growing doubt as to its underlying significance. I've added some discussion to make that point, with a number of sources. In addition, the accounting of mechanisms involved in continental collisions and subductions appears to be in flux, and the attention of a versed geographer is sorely needed. Brews ohare (talk) 17:39, 2 February 2010 (UTC)
Recent edits on meaning of orogeny
The changes made appear salutary. However, it strikes me that deleting the discussion of the drift in meaning of orogenesis away from its etymological meaning, and replacing that discussion by stating the original meaning and then saying: mountain building occurs by many processes unrelated to orogeny, is not really clarifying matters. If orogney is only one basis for mountain building, then why say it is about mountain building? It isn't. It's about some processes that occur in association with mountain building and is neither co-extensive with nor a sub-topic of mountain building. Brews ohare (talk) 22:30, 4 February 2010 (UTC)
- I read over the lede twice now and I don't see how it's confusing: it states that it is deformation related to plate collisions, it mentions the etymology, and then it mentions other ways that mountains can be formed. I'm making some edits that will hopefully streamline this. If things don't improve in your opinion, please continue this conversation. (Is it that you think the clarification shouldn't be in the lede? If so, I'd agree and be happy to move it elsewhere - I was just trying to address concerns quickly in my edits this morning). Awickert (talk) 00:56, 5 February 2010 (UTC)
I posted the following on Awickert's talk page:
- I put a quote in the "Relation to Mountain Formation" section from Jackson and Bates. It is quoted by Ollier & Pain. You may have noticed in earlier discussion that there are a half-dozen or so references that seem to treat orogeny as including stuff not related to mountain building and excluding stuff that is. So it seems reasonable to me to include some heads up on that score. Brews ohare (talk) 14:45, 5 February 2010 (UTC) Here is a recent discussion. Brews ohare (talk) 14:52, 5 February 2010 (UTC)
- Actually, I have a minute right now, so I'll respond here to keep it in the public. While that paragraph may come from what is a WP:RS, what it says is completely wrong. There is direct evidence for past topographic highs in terms of the sedimentary basins that form in association with orogenesis. This is confirmed by basic geology and provenance studies, including detrital zircon (U-Pb dating) work. Further, the fact that high-grade metamorphic rocks are exposed on the surface is evidence that there has been a ton of erosion, which can't happen without a lot of uplift. The fact that they say that mountain formation is postorogenic is physically absurd; uplift won't happen after deformation stops. In short, I have absolutely no clue why that was written in the glossary of geology, and I'd like to find original reference myself, because it's completely idiotic. Send me an email and I will send you peer-reviewed papers by experts in the field on collisional tectonics and orogenesis.
- I'm going to leave it there for the moment because it is cited and all, but I strongly protest! Awickert (talk) 15:59, 5 February 2010 (UTC)
Hi Awickert: The sentence you object to: mountain formation is postorogenic is not key to the point about the scope of the word orogenic. The main point is that orogenesis is neither inclusive of all mountain building (as is pointed out already in the article), nor is it limited to only a subset of those processes contributing directly to mountain building; it includes processes only incidental to mountain building. That is, the term's connection to its etymology oro + genesis is distant, and its etymological meaning is not particularly illuminating to a reader trying to understand its usage, e.g. as in Caledonian Orogeny.
So my view is that something helpful along these lines should be stated; it needn't include the above statement about postorogeny. For example, it could be the earlier sentences:
- According to Ollier and Pain,(check this link), who provide much documentation for their view, “orogeny is now used to refer to the folding of rocks in fold belts. It does not mean mountain building, despite its etymology.” Rather, it refers to the processes by which rock structures within the mountain chains or fold belts are created.
How does that look? Brews ohare (talk) 17:42, 5 February 2010 (UTC) Maybe a shopping list of what orogeny does and does not include is better?? Brews ohare (talk) 17:48, 5 February 2010 (UTC) I deleted the offending sentence and left the rest of the quote. Brews ohare (talk) 17:58, 5 February 2010 (UTC)
To add to all this: Davis and Reynolds, Structural Geology of Rocks and Regions, page 8 say: “Mountain systems are a physiographic expression of orogenic belts, but the presence of mountains is not integral to our view of an orogen. ...And of the presently forming orogens, the structurally interesting parts may not lie in the mountains, but ...10 - 700 km below the Earth's surface. In this perspective, mountains, if they exist at all, are just the roofline of an orogen.” Brews ohare (talk) 18:26, 5 February 2010 (UTC)
- I am in agreement with Davis and Reynolds. As to this and the other stuff... let me pull up a bunch of sources and try to explain why I say what I say when I have time. I'd rather not do it as a quick hack job right now, but instead do it with sources and the whole deal. Awickert (talk) 18:36, 5 February 2010 (UTC)
That sounds very helpful. I read Davis and Reynolds as focusing upon an orogen as a particular ensemble of plate interactions occurring at a particular time, making it a theoretical concept that can be supported by various rock structures and other evidence; thus, they are a step removed from Ollier and Pain, who want to focus upon a collection of geological artifacts as an orogen, and do not focus upon possibly conjectural ideas of their origins. (That is understandable for them, because they want to provide a model for the origins of artifacts somewhat different from the usual convergence of plates, it seems, and so they want to stress the facts to be explained, not the theory behind the facts.) It would appear that orogen is a classic case of multiple usages, and they have to be identified and distinguished, eh? Brews ohare (talk) 18:53, 5 February 2010 (UTC)
In this connection, here and here is a piece of possibly fringe science (as in Expanding Earth) trying to explain an orogen without plate collisions using magma upwelling instead. It's pretty helpful if we want to compare different theories like these two if we have some idea of what exactly has to be explained, and what is ancillary, eh? Otherwise, how is success to be measured? Brews ohare (talk) 19:23, 5 February 2010 (UTC)
- As to your second paragraph: Scalera can't get himself published in any reputable journal due to some fundamental inconsistencies between what he writes and the state of knowledge and data, so we can ignore that. I'm compiling sources to answer your other questions. Awickert (talk) 00:50, 6 February 2010 (UTC)
- So I will start with a criticism of the quote from Ollier and Pain, with whom I have more general issues than the "postorogenic part". Phrase by phrase that I disagree with:
- Only much later was it realized that the two processes [deformation and the creation of topography] were mostly not closely related, either in origin or in time. Very wrong. Deformation causes topography, and the generation of topography is synchronous with deformation. I will email you a copy of Dahlen and Suppe (1988), which shows that this is the case - send me a message so I have your address and can attach a PDF. They tackle the large-scale deformation of sedimentary rocks via folding and thrusting during orogenesis.
- ...fold-belt mountainous areas...: "fold-belt" isn't used professionally (AFAIK) to refer to a collisional mountain-building event. A minor thing though.
- Only in the very youngest, late Cenozoic mountains is there any evident causal relation between rock structure and surface landscape. and the following sentence: If I were British, I would call this "utter twaddle". As I mentioned above, there is no way for many of the exposed structures to get to the surface without large amounts of rock uplift and erosion. And as a matter of fact, the trajectory of different units of rock through an orogen is in part determined by patterns of surface erosion. To keep it simple and send you one paper, you'll find this in and at the end of the paper by Dahlen and Suppe (1988).
- Awickert (talk) 01:12, 6 February 2010 (UTC)
- Oooh, boy, I just saw this in the Amazon.com product description: This book is a ground breaking and highly illustrated study challenging existing plate tectonics theory. Now that lights off about 3 different alarms in my head, and indicates to me that it is likely an unreliable vanity publication. That, and the fact that the parts I've read completely misrepresent plate tectonics; to say anything else would be a problem with WP:BLP :). I'll find you a list of standard geological textbooks, and I'm happy to provide peer-reviewed publications for your perusal. But if you want to learn about real geology, consider that book off-limits. Awickert (talk) 01:27, 6 February 2010 (UTC)
- Indeed, I've also uncovered this gem: Mountain building and orogeny on an expanding Earth, Cliff Ollier, Bollettino della Società Geologica Italiana, 2005 . Quite simply fringe. We don't need to include his views in the article. Maybe in the expanding earth article? Vsmith (talk) 01:50, 6 February 2010 (UTC)
Pardon me guys, but you're picking the low-hanging fruit here. I agree that any connection to the Expanding Earth hypothesis is out of mainstream, but that doesn't mean these guys are entirely out to lunch. They just like some novelty, which in no way impacts the present discussion. And in particular, none of this fringe activity has any bearing upon the basic questions about the multiple meanings of orogeny, which are laid out above and which you are ignoring in the fun games of batting about fringe science.
- The purpose of the Ollier and Pain book is to provide a non plate tectonic explanation for things, largely by ignoring work since the 50's and 60's. Since that is the overriding purpose, I think that other sources are needed. Starting anew without reference to them would be good, as I'm not sure what the remaining issues are beyond their definition. Awickert (talk) 03:56, 6 February 2010 (UTC)
Here is a new header to break up this discussion:
Some sourced statements about orogeny and its usages
There is the long quote from Davis and Reynolds, Structural Geology of Rocks and Regions, page 8 above, which says in part: the presence of mountains is not integral to our view of an orogen. ... In this perspective, mountains, if they exist at all, are just the roofline of an orogen.
In my mind, these authors are distancing orogeny from mountains. Mountains are there, but they are incidental.
Then there is the quote from PB King (apparently a stellar authority) in this account, and on the legend of the Tectonic Map of North America, “orogeny” is therefore used for the processes by which the rock structures within the mountain chains or fold belts are created.
This statement appears to require the presence of mountains, but orogeny refers to aspects of events surrounding the formation of rock structures in these mountains, not to the formation of the mountains per se. This statement is very close to the one by Jackson & Bates: By present geological usage, orogeny is the process by which structures within fold-belt mountainous areas were formed, including thrusting, folding, and faulting in the outer and higher layers, and plastic folding, metamorphism, and plutonism in the inner and deeper layers.
This statement refers to rock-forming processes in mountainous areas, (and way, way beneath them) not to mountain building per se, and goes on to point out that: the deformation of rocks within the mountains, and the creation of the mountainous topography ... were mostly not closely related, either in origin or in time.
So I have a spectrum of opinion ranging from a reference almost to plate tectonics itself onward to what is instead a catalog of possible processes that form rock structures. All statements distance orogeny from mountain building per se.
I also find myself in my own reading that the usage of orogeny in the long detailed descriptions of specific orogens like Caledonian orogeny, Antler orogeny & so forth agree with the above statements as to subject better than than they agree with the etymology of orogen.
So, IMO there is a clear line of thought and sources that differs from what you two (Awickert & Vsmith) find to be common usage, indicating perhaps that multiple usages abound and should be clearly discussed and differentiated, eh? Brews ohare (talk) 07:09, 6 February 2010 (UTC)
- I actually don't find these to be in conflict with each other or with my views. Davis and Reynolds study the roots of old orogenies, from which information of them can be derived; this is a major occupation of structural geologists. King says that mountains are formed during orogenies; this is also true. Jackson and Bates talk about the processes that go on within an orogen. I feel like I'm starting to sound like a broken record when I say that during orogenesis, the crust is shortened laterally and thickened vertically and topographic highs (mountains) are formed. Does that help? Awickert (talk) 07:22, 6 February 2010 (UTC)
- The article by Dahlen and Suppe suggested above really nails the connection between an active orogeny and current mountain range development in the Taiwan orogen/central mountain range. The full reference is: Dahlen, F. A., and Suppe, J., 1988, Mechanics, growth, and erosion of mountain belts, in Clark, S.P., Burchfiel, B.C., and Suppe, J., eds., Processes in Continental Lithospheric Deformation: Geological Society of America Special Paper 218, p. 161–178. You really should read it either via good library access or take Awickert up on his offer above. It beautifully ties plate tectonics, orogeny, mountain building and erosion together. Vsmith (talk) 15:23, 6 February 2010 (UTC)
Gentlemen: As I understand you both, you agree with the above statements. These statements are similar to each other in stressing a wide range of forces. But they are not what is suggested by the etymology of oros + genesis, the focus of the WP article.
I see contrast with the etymology in: “the presence of mountains is not integral to our view of an orogen”; “mountains, if they exist at all, are just the roofline of an orogen”; “the deformation of rocks within the mountains, and the creation of the mountainous topography ... were mostly not closely related, either in origin or in time.” “"orogeny" is ... the processes by which the rock structures within the mountain chains or fold belts are created.”
I find the article inadequate in conveying these points of difference. At the moment, the article defines orogeny by: orogeny is the primary mechanism by which mountains are built on continents; even if orogeny is related to this mechanism, the above statements are trumpet clear that orogeny is not co-extensive with or defined by the association with mountain building.
I can produce additional sources along the same vein, but that would appear to be a useless enterprise as the statements provided are (i) very clear and unambiguous, and (ii) impeccably sourced. However, it seems we do not read these statements the same way, which baffles me. Brews ohare (talk) 15:53, 6 February 2010 (UTC)
- Your quote from Davis and Reynolds is good. The mountains above the orogen are just the transient surface expression of the orogen that formed them. The geologist is more focused on the rock structures than on the geomorphic surface features. But, those surface features would not be there without the causative mechanism. Also, there is a connection between the erosion rates of those "surface expressions" and the driving tectonic mechanisms as discussed in the paper on the Taiwan orogeny/mountains mentioned just above. So, yes we read them differently. Vsmith (talk) 16:51, 6 February 2010 (UTC)
Vsmith: You say exactly what I say: The geologist is more focused on the rock structures than on the geomorphic surface features. But, those surface features would not be there without the causative mechanism. The conclusion is that orogeny is not to be equated with "the transient surface expression of the orogen that formed them". That is, today's meaning of orogeny is not oros + genesis. Do we agree? If so, the article doesn't agree with us. Brews ohare (talk) 16:55, 6 February 2010 (UTC)
- You're going to have to accept that high topography is built during orogenesis. I've tried to explain this above via uplift and erosion as the only way to expose the deep rocks of an orogenic belt that we see at the surface, but I must not be clear enough.
- You're right: there's more to it that just building mountains; if this (its etymology) is the point of confusion, then we can write to explain that.
- Davis and Reynolds are probably talking about mapping past orogenies, since it is a structural geology textbook. At this point, there may not be present-day mountains, though there certainly were in the past. Hence mountains are "not integral" (D&R get their information from the rocks, whether or not the topography exists), and Davis & Reynolds use present tense ("exist") with respect to the presence of mountains; they certainly existed, but they may not still be there.
- I spoke too soon above and missed the second statement by Jackson and Bates. They are wrong are wrong when they say there is no genetic link between deformation and topography; this is certainly not the first time that the Glossary of Geology has been wrong. I wonder what the most recent edition (as opposed to that from over a decade ago) would say.
- Orogeny is the primary mechanism of continental mountain building. It is not just related. I think I've said this several times, so you can either trust me or keep going through sources, some of which are correct and some of which are not. This is the way it goes with geological terminology; the experts have it right, but lots of non-experts screw it up, and the non-experts are often the ones that write the more freely-available sources. Trust Davis and Reynolds; they mapped much of the Western US. Awickert (talk) 16:58, 6 February 2010 (UTC)
- Since I edit-conflicted, I'll reply to your more recent post: orogeny forms the surface features, and there is a connection between erosion of the surface features and spatial distribution of rock uplift (resulting in geological structures), so the presence of a topographic high (whether or not it exists today) is integral to the definition. Awickert (talk) 17:00, 6 February 2010 (UTC)
- Item two in your list (the connection with etymology) is the problem to be fixed in the article. Maybe nothing else really needs to be settled. However, my reading of Davis and Reynolds is that they focus upon tectonics, and evidence for various tectonic events, and divorce themselves verbatim from mountains. Brews ohare (talk) 17:21, 6 February 2010 (UTC)
- It appears that there is a long tradition in connecting orogeny with tectonics. See Stille's biography and this quote: “As a matter of fact, orogeny in the tectonic sense [my emphasis] generally fails as an explanation for the existence of the topographically great mountains of the earth, such as the Alps of Europe or the Cordilleras of North America. These mountains exist – or still exist – as a result of post-orogenic en bloc movements, for the most part still going on, and belonging to the category of epeirogenic processes. Thus arises the terminological contradiction, that the mountains as we see them today owe their origin not to what is called orogeny, but to an entirely different type of movement that is to be strongly contrasted with the orogenic process.” (Stille, H. Bull. Am. Assoc. Petrol. Geol. 20 849-880 (1936) Brews ohare (talk) 17:34, 6 February 2010 (UTC)
- OK - I'll add this clarification to my mental to-do list then. I think that Davis and Reynolds distance themselves from mountains as part of saying "Look. Metamorphic rocks are formed deep below the mountain, and most faulting and folding occurs at depth. Even after the mountain erodes away, these features will still be present and we can map them to understand what happened."
- The quote is from 1936, which is pre-plate-tectonics. Orogenesis had a different mechanism then, because there wasn't the concept of two plates continually grinding into each other to form long-lived mountain belts. Awickert (talk) 17:42, 6 February 2010 (UTC)
- Most mountainous topography is initially caused by orogenic processes, but from then on is continually modified by an erosion + isostatic adjustment cycle that leads to progressively deeper parts of the mountain belt (or orogen if you prefer) reaching the surface. This process goes on during the orogenic event and persists after it, so we do see 'vertical tectonics' throughout the orogenic cycle, but without the crustal thickening caused by the collision it would never have started. Mikenorton (talk) 18:24, 6 February 2010 (UTC)
- In addition to what Mike says about vertical tectonics, I will add on that during an active orogeny, erosion is balanced by both isostatic adjustment and increased rock uplift in order to maintain a critical taper. The post-orogenic isostatic uplift can restore only some of the elevation lost due to erosion.
Mountain building on continents
A better section header?
Using "History" as a title to one section in this article appears to be unintentionally confusing. "History" could refer to the history of how man understood this process (which is obviously the intent), or to the geologic history of orogeny (e.g., "The earliest known creation of mountains through Orogeny was ... The next incident was in the XXX period when the so-&-so mountains were created, &c.) Perhaps this section should be renamed to something along the lines of "History of man's understanding"? -- llywrch (talk) 20:58, 5 April 2010 (UTC)