Chris Rowan is a geologist specialising in the dark arts of paleomagnetism, and getting people to pay him to travel to exotic destinations for fieldwork. Having drilled up New Zealand during his PhD, and South Africa in his first post-doc, he now works at the University of Edinburgh.
Anne Jefferson has a love of all things water-related and blends hydrology, geomorphology, geology, and climate change in her work. She has a Ph.D. from Oregon State University and is now an assistant professor at the University of North Carolina at Charlotte.Old geological theories don't die, they're just passed on to cranks - as the Expanding Earth Theory demonstrates. For those who have missed the recurring infestation of Expanding Earthers in the geoblogosphere (Eric, Bryan, Brian and most recently Julia have all been afflicted), and before I explain how the facts of the geological record conclusively falsify their model, I should acknowledge that it does actually incorporate a couple of valid ideas: that you can fit all the bits of continental crust on the Earth's surface, which are nowadays separated by sizeable ocean basins, back together into one coherent landmass; and that the ocean basins represent a different kind of later-forming crust that has formed between them and pushed them apart.
Indeed, back in the early 1900s, as a way of explaining the puzzling morphological and geological connections between the opposite sides of the Atlantic, the notion that the ocean basins had formed in the gaps left as the Earth increased its radius over time was arguably a more plausible explanation for "continental drift" than Alfred Wegener's conception of continents moving through the oceanic basins - or, at least, the physically implausible part was moved into the centre of the Earth, where it was less immediately obvious. To advocates of the Expanding Earth, then, the discovery of sea-floor spreading in the late 1950s and early 1960s probably looked like an exciting confirmation of their hypothesis- until geologists ruined the whole thing by showing that ocean trenches are subduction zones, where crust is recycled back into the mantle*. The creation of new crust at spreading ridges is therefore balanced out by its destruction at trenches, removing any need for the Earth to have got bigger - or break several fundamental laws of physics.
Suffice to say, the few remaining Expanding Earthers really, really don't like subduction, and spend most of their time trying to "prove" that it don't exist. In doing so, they conveniently ignore the fact that one of the basic predictions of the expanding earth model - that oceanic crust is only created, and never destroyed - is clearly contradicted by clear geological evidence for the presence, and closure, of older ocean basins.
One of the original strands of evidence that Alfred Wegener used to infer the prior existence of the supercontinent Pangaea was that plant and animal fossils from rocks of Late Paleozoic and Early Mesozoic age (approximately 200-400 million years ago) from now widely distributed continents were all remarkably similar. This shared biological history implies a geographical link that was lost following the opening of the Atlantic, leading to the extinction and evolution of different species on either side of the oceanic divide.
Having established the principle that similar plants and animals imply a geographical connection, and different plants and animals imply geographical separation, if you look at British rocks older than the ones used by Wegner and others to establish the Pangaea connection, you discover something rather interesting. The map below, courtesy of the BGS's nifty Make-A-Map application, shows the distribution of Cambrian (grey) and Ordovician (green) rocks, 550 to 450 million years old, in Britain and Ireland.
The fossils can be clearly divided into two distinctive groups, or assemblages: the trilobites, brachiopods, and other shallow marine animals to the south of the red dotted line (the reason for it being labelled the "Iapetus Suture" will be revealed below) are completely different from those found to the north of it.
It gets even more interesting when you look over the other side of the Atlantic. The USGS don't seem to have an on-line map-making app, they do have the rather beautiful "Time and Terrain" map, of which the image below is an excerpt. Cambrian and Ordovician rocks are purple.
Not only can you make a subdivision between two distinctive fossil assemblages, but it's the same subdivision - the rocks on the coast, east of the white dotted line, contain the same fossil groups as rocks of the same age in the southern British Isles - which is usually referred to as the "Avalonian" assemblage, after the Avalon Peninsula in Newfoundland. Palaeozoic rocks in the continental interior contain an entirely different, "Laurentian" assemblage, which consists of exactly the same fossil groups as are found in Palaeozoic rocks in Scotland.
It gets better. In the Cambrian and early Ordovician, the "Avalonian" fossil assemblage is closely linked to fossil groups found in similarly aged rocks in north-west Africa (now exposed in places like the Atlas Mountains in Morocco). Then, in the mid-late Ordovician (from around 460 million years ago), that link is broken, and Avalonian species form a unique assemblage that is only found in rocks from Newfoundland, Wales and the Lake District (and possibly some places in Belgium and Germany) - they are distinct from Africa and North American groups. Finally, in younger rocks, the fossil assemblages in all of these places start looking quite similar.
So what's going on? Well, reconstructions of Pangaea show that when you close up the Atlantic, Newfoundland and bits of Britain that contain the Avalonian fossils are juxtaposed against each other, and located on the same side of a particular geological feature - the Appalachian-Caledonian mountain belt (figure from McKerrow et al., 2000, J. Geol Soc. Lon. 157, 1149-1154).
Laurentian fossils are located on the far side of this mountain range, so it does seem to be related; however, it is a younger feature than the rocks it rises up between, having started forming about 350 million years ago. It can't have acted as a physical barrier preventing the mingling of Ordovician lifeforms, because it wasn't actually there yet.
The first to realise what the Avalonian rocks were telling us was J.Tuzo Wilson - possibly the smartest of the very smart bunch of people who formulated plate tectonics. He reasoned that observing distinct and unrelated forms of life in two different regions means exactly what it would mean in the present day - that those regions were geologically isolated from each other. Even if Scotland and Southern England are now right next door to each other, during the Cambrian and Ordovician, the "Avalonian" and "Laurentian" rocks were deposited on the opposite shores of a long-vanished ocean. Scotland and North America formed one coastline of the "Iapetus Ocean", and Africa, Newfoundland, and Southern Britain formed the other. The width of this ocean was sufficient to prevent the distinctive marine species inhabiting each of these shores from mixing. By the same reasoning, the bifurcation of Avalonian species from North African ones around 450 million years ago is a sign that a block of crust consisting of Newfoundland and southern Britain had rifted away from the larger African landmass, forming a distinct and isolated microcontinent which for obvious reasons is usually called Avalonia.
Eventually all of these fragments came together to form Pangaea, with the Appalachian and Caledonian mountains being formed by the continental collision that marked the final closure of the Iapetus and Rheic oceans (marked by the Iapetus Suture on the UK geology map above). Finally, a hundred million years or so later, something triggered another continental break-up. The rifting that went on to form the Atlantic ocean occurred along a similar trend to the Iapetus Suture, possibly because it was a zone of pre-existing weakness, but it wasn't exact - some bits of the Laurentian shoreline got stranded on the wrong side, and vice versa.
This inexact breakage provides the clues necessary for Wilson's great insight - that the geological record doesn't just show Pangaea breaking up into smaller fragments, it shows that Pangaea was itself amalagamated from smaller, pre-existing continental fragments - by the closure of ocean basins. By subduction, or at least a process that is destroying oceanic crust. This has no place on an expanding earth. It is falsified. It is an ex theory. It is pushing up the paradigms.
The geological record goes further; the picture is a little more fuzzy the further back in time you look, but the fragments that came together to form Pangaea seem to have themselves been the scattered remnants of an even earlier supercontinent (mostly referred to as Rodinia), which was itself welded together from older fragments. Earth's geological history seems to have consisted of several cycles of supercontinent formation and break-up - also known as Wilson Cycles, in honour of the man who solved the Avalonian conundrum by proposing them.
Of course, Expanding Earthers and their intellectual kissing cousins, the Catastrophic Plate Tectonics crowd, completely ignore the evidence that clearly falsifies their pet "theories", which cannot explain the sequential opening and closing of ocean basins. But they are falsified nonetheless. And that, Virginia, is why we refer to them as cranks.
*although in reality, the first evidence for subduction zones dates from the 1930s.
Physical Science
Environment
Comments
Nice post. Showing the continents were separated before Pangaea is something that has been under-appreciated in this "debate". It seems a common misconception that when the earth formed we had Pangaea.
Posted by: Bryan | January 13, 2009 12:31 PM
Good work Chris - I think you succeeded where a worryingly large number of Part 1A demonstrators failed there, explaining the Caledonian orogeny! I particularly like your brief lurch into Monty Python.
Posted by: Julia | January 13, 2009 12:35 PM
Chris, how dare you bring actual data into this debate ... gasp! Methinks the 'EEdiots' (coined by Bryan over at Julia's blog) have a psychological aversion to data. Especially specific data -- they can only respond with misleading generalities and woefully untested assertions.
Posted by: BrianR | January 13, 2009 12:37 PM
Great article Chris. But, the pedant in me has to point out that Wadati's paper on deep earthquakes was 1928.
Posted by: hypocentre | January 13, 2009 12:48 PM
...and the pedant in me wants to quibble with your suture location on North America. Your boundary goes through my old house in Vermont, and I think the orange stuff on the map is the Laurentian basement in the Green Mountains.
I'm not sure about the terrane affinities of the rocks between your line and the coast, for the most part. (And I've worked in them!) I don't think you get definitely Avalonian rocks until near Boston/far downeast Maine/Nova Scotia. The stuff in New Hampshire is kind of arc-ish, and the metasediments in Maine are mostly a bit younger, Silurian maybe?
Of course, the rocks I've worked on are too gorgeously fried to have fossils of any affinity, so not particularly useful for that kind of terrane analysis.
(Also, I guess I need to sit down and write an ultra-high-pressure metamorphism post, as that's yet another piece of the subduction story that deserves more recognition.)
Posted by: Kim | January 13, 2009 1:48 PM
I'd never heard of this expanding earth stuff before. What did its proponents say caused density decreases over time? (I hope they weren't postulating nonconservation of mass!)
Posted by: D | January 13, 2009 3:03 PM
A very good exposition, Chris. I've seen many similar maps before, but never had them so nicely explained.
I'm strictly an amateur and am not very familiar with these EE folks, so maybe I'm missing something. If they claim that the earth was previously smaller and that the oceans are only expanding, do they have any explanation for where all of the current water content of these ever-expanding oceans was back in the days before the oceans expanded?
Posted by: chezjake | January 13, 2009 4:25 PM
chezjake ... in my experience, the EEdiots don't have explanations for very much of anything ... and I'll urge caution in approaching them with sincere questions because they typically do not engage in sincere discourse. But, that's just my experience, which is perhaps limited.
Posted by: BrianR | January 13, 2009 4:49 PM
They didn't (though some argue that density is constant, and we are gaining mass). I think it was BrianR, in one of his comments on his series of posts, who pointed out they don't like to be pinned down by providing such "trivial" statements.
And Eric got in quite a good row with an EEdiot about how EE doesn't provide a falsifiable hypothesis, but several of its claims are demonstrably false.
They mostly like to point out that land masses can fit together (and get pissy when someone explains why that is).
Posted by: Bryan | January 13, 2009 4:55 PM
sorry my last post was meant to D.
Posted by: Bryan | January 13, 2009 4:57 PM
Priceless.
--------------------
What about ophiolites as evidence against subduction denialism? Ocean crust on top of dry land...
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A decades-old EEdiotic suggestion for where all the water used to be is that there simply was no dry land before the Devonian, that the Earth had a complete hydrosphere. Problem is, there are terrestrial sediments all the way back... for example, there are raindrop imprints that are 1.4 billion years old...
Posted by: David Marjanović | January 13, 2009 7:00 PM
I am curious about one thing though -- where do the EEdiots get their "round-the-back fit" idea? I did see on attempt to fit Australia into South America the way South America fits into Africa, but it's also implied on one of the threads you linked to that the west coast of South America was drastically reshaped by the Andean orogeny and compression from the advance of the Nazca plate. So I'm assuming it's all just so much confirmation bias? Or is it an artifact of the Rodinia or Pannotia breakups?
Posted by: Brian X | January 13, 2009 8:02 PM
Wow. A lot of work went into this blog, hope you get to send it somewhere else too for wider circulation - I stumbled onto it during REALLY intense procrastination and web browsing.
To the Vermont citizen - the Taconic frontal thrust region cuts through the Champlain Valley. So you can think of the Green Mt.s as an amalgamation of Laurentian basement and arc terranes that got 'plucked' from the margin, some in the Mid-Ordovician, some in the Devonian (details of the timing are controversial, but the basic structure is not, basically speaking).
But the question at hand about the Expanding Earth hypothesis is a bit harder to address, and I'm not quite sure that the blog really does. I have only crossed one EEer who I felt was intelligent enough to really get into it with. He really put it in perspective for me that the basic premise isn't about the EEer's need to 'negatively test' every hypothesis that is thrown his way, but is rather to point out that a "theory" is a house of cards that falls down when you pull one out. In the EEer's case, the card to pull is "subduction". Now, I am a (geologist masquerading as a) geophysicist, so I accept geophysical models of subduction zones. But if I didn't, the whole tectonic paradigm might seem a bit thin. Each one of Wegner and deToit's hypotheses is indirect - from the facies correlations to the pmag that came later. WE accept them because we work through them and are led to inescapable conclusions. But an EEer won't go there, pointing out (perhaps correctly!) that each piece of the puzzle has a flaw.
To get a sense of EEers, you really have to see it as a near-luddite movement. Other theories they attack include the ether (the Michelson-Morley experiments), and 911 (particularly Building 7). The point is that these guys aren't creationists, they are valid philosophers. Intriguingly, while we should find their challenges more intellectually stimulating, if not enjoyable, than the much more dangerous creationists, we tend to react with even more intense - dare I say emotive - responses to EEers.... I wonder why.....
Posted by: Nick | January 13, 2009 10:14 PM
Nick ... I find your comment interesting. You must've interacted with far more reasonable people. Most of what I read isn't "valid philosophy" ... not by a long shot ... it's fringe science at best, but typically straight up pseudoscience (at its worst, it's dishonest and vile). Yes, most of them play the part of someone after the "truth" and prefer to discuss inherently speculative and opinion-based aspects associated w/ philosophy.
I'm not saying that discussing philosophy of how we conduct science should not be done ... but I find a much more honest and constructive discussion occurs when it is done with those who have actually conducted their own analysis. When those who I have read or even interacted with show me some real analysis (not cherry-picked, loosely-associated papers or hastily-written internet screeds, but actual science) I will listen more intently.
They need to address DATA from around the globe in a comprehensive and integrated fashion. They argue their model of how the Earth works is the best model ... but they can't piece together more than a few pieces of real data from a specific place on the Earth (note: cartoons of a growing Earth, regardless of the quality of art, doesn't count). I'm sick of hearing about 'dogma' and 'groupthink' from these guys ... they refuse to actually learn anything technical, they are lazy, they are dishonest ... they are EEdiots. But, maybe I simply need to talk to different people. :)
Posted by: BrianR | January 13, 2009 10:50 PM
Do EEdiots ever explain how the continents accomodate the change in curvature implicit in an expanding planet?
Posted by: Andreas Johansson | January 14, 2009 10:05 AM
I remember stumbling across an 'Expanding Earth' paper from the 1960s during my PhD research years ago.. I didn't realise people still tried to argue that stuff!!
Posted by: Andrew Dodds | January 14, 2009 11:35 AM
Brian - I agree that its not science, in the sense that EE is a hypothesis that fails critical tests, and supporters of the hypothesis won't acknowledge those failures. Where EE becomes a valid philoshophy though, is in its challenge of 'knowledge', or what it is 'to know' something. I agree that EEers are unwilling to really evaluate evidence for subduction, and can be intellectually lazy. But that doesn't mean that they aren't picking up on something real:
For example, a favorite sidebar of EEers is the existence of the Ether, and hence a problem with Einstein's special relativity. But today, there really is 'ether theory' in the form of the undetectable, but theoretically demonstrated, subatomic particle interactions.
At risk of indulging some crackpot who comes our way in this conversation, another example is 911. A "group think" motivated by the press and the government would like us to accept a very simple story with 'Osamma sends terrorists, terrorists strike, World Trade Center goes down, hero passengers sacrifice themselves to prevent third collision'. But it is clear that the CIA knew that the operatives were in the US well before 911 (read "the Looming Tower" by Lawrence Wright), and it is a mystery as to why Building 7 - bought and insured a month beforehand - collapsed when it was far from the crash site and debris. And while there is no reason to doubt the United 93 story, isn't it funny how few people really asked any hard questions about the 'accepted' course of events.
So, what about the Earth. Well, we do have problems. Jeffrey's had a point that the shear stresses for lateral motion of the plates and subduction should prevent plate tectonics from working. We have made progress on explaining this - indeed may have solved it - with better understanding of high P-T deformation of materials. But its not like its a slam dunk. Similarly, our best evidence of subduction (in my opinion) are patterns of seismicity and tomographic imaging. However, these are fraught with problems as well (slow slip, inherited mantle and crustal structure, etc...).
Now, your case in your blog is that the evidence is in the plate reconstructions. But EEers have a point that our oldest ocean crust is 180 Ma. To go before then your restoring facies relationships, slivers of rocks, hell, in the archean a few crystals of Zircon. If ever a field NEEDED iconoclasts throwing stink bombs at them, I'd say its Geology.
Which brings me back to my point that these guys are practicing a legitimate form of philosophy. Not science, but philosophy. Creationists in contrast are practicing religion and ideology - i.e. not even challenging our science on its own grounds, saying the whole thing is wrong because it conflicts with their faith. A good EEer doesn't challenge on the basis of their faith in EE, but does so as a cry against "group think" etc... Not to say it can't be exasperating, but it can probably help us more than hurt.
Nick
p.s. I didn't answer the Vermonter quite clearly: he is correct that Avalonia doesn't begin until Maine-RI. The white line while representing the tectonic boundary of pre-pz Laurentia, does not in fact delineate the westernmost extent of Avalonian fauna etc...
Posted by: Nick | January 14, 2009 11:42 AM
Nick says: "Which brings me back to my point that these guys are practicing a legitimate form of philosophy. Not science, but philosophy."
That's fine ... but, in my experience, they CLAIM to be practicing science. So, regardless of the legitimacy of their philosophical contributions, their lack of awareness that they are NOT doing science results in a dishonest endeavor from the start.
I would like to see examples of EE proponents that explicitly state that they are solely questioning knowledge from a philosophical perspective. That level of self-awareness is absent from what I've seen. You take about a "good EEer" ... is there an example?
Posted by: BrianR | January 14, 2009 12:54 PM
Let me answer all of your questions about the Physics of planet formation
(1) During a "Big bang" or large supernova event "fusion" joins small atoms into large nucleus elements (the lower half of the periodic table)
(2) this material is thrown into space and eventually collects in stable orbits forming the beginning of a series of new solar systems.
(3) Due to the fusion process, the planetary material is highly radioactive (made from the lower part of the periodic table) and as the core of each planet takes shape, fission becomes more active due to compression of radioactive material.
(4) As "fission products" are produced, "fission poisoning" slows the reactions and moderates the core materials' rate of radioactive decay.
(5) After billions of years, much of the radioactive fuel has "fissed" into smaller atoms, which include: 100% of the planet's water, atmosphere, and metallic ore deposits. The reaction leaves behind an iron core.
(6) And MOST IMPORTANTLY, an expansion effect is produced due to the fact that fission products occupy far more physical space than the original fuel. FISSION = EXPANSION.
(7) You owe your life to Uranium
(8) The Earth has not changed mass! It has only changed density!
(9) Continents can only be produced from expansion. No other natural force will do this (go buy some French bread and look at the crust - ha!)
We all want the truth.
Please make each communication a discussion not an attack on scientific theories.
Posted by: Expanding Earth is True | January 14, 2009 1:01 PM
Here we go.... Sorry, Brian, I think your on your own now. I would just try to look at the positive.
EEIT - I think comparing our depth of understanding of solar system and planetary accretion to our understanding of the actual planetary processes of the Earth is a bit of a fools errand. We have enough control on the tectonic history and internal structure, and composition of the Earth to independently show that it hasn't changed volume significantly since the end of the Archean. If anything, Harold Jeffrey's used to point out that there was a few % decrease in volume due to contraction.
That said, particle physics pretty clearly shows that a "Big Bang" - as envisioned - can only produce the first 4 radionuclides. Similarly, the distribution of the elements in the Earth show that the core drop occurred fairly rapidly at the beginning of the Hadean. After that, density changes due to radioactive decay are nil (since daughter products are not lost to space), and fission is volumetrically negligable. Again, the net effect is heat loss, which doesn't favor expansion, but rather contraction (which turns out to be negligable for different reasons).
OK, I'm outta here!
N
Posted by: Nick | January 14, 2009 1:33 PM
"Please make each communication a discussion not an attack on scientific theories."
Ah, the ol' false equivalency gambit ... as if every hypothesis (NOT theory, as you write) has value just because someone thought it up. It's like political correctness on steroids or, as Ken Miller puts it, intellectual welfare. If asking people to rigorously test their hypotheses and/or defend their results/conclusions is an "attack" then those people better get used to it.
Posted by: BrianR | January 14, 2009 1:44 PM
Nick says: "Sorry, Brian, I think your on your own now. I would just try to look at the positive."
Just because I'm the only one in this particular conversation does not mean I am on my own. I was simply asking for examples of the honest and sincere EEers ... i.e., the ones who are aware they are discussing solely philosophy and not doing science. I think others would want to know too. This might help tamper our overall negative take on the whole thing.
Posted by: BrianR | January 14, 2009 1:50 PM
Hey Brian - I just meant that a bonafide EEer had entered the discussion, so - having been there before - I was going to bow out. Good luck! (your already off to a better start than your colleagues Eric, Bryan, Brian, and Julia).
Posted by: Nick | January 14, 2009 2:00 PM
Nick ... I see what you mean.
Posted by: BrianR | January 14, 2009 2:25 PM
I suggest people ignore EEIT unless he actually bothers to make a comment relevant to the actual post.
Nick - I'm preparing a post to respond to your comments, but I have to say that in my opinion the philosophy you're describing neither (a) describes the EEers' approach to plate tectonic theory nor (b) is valid. It's certainly not predicated on a particularly accurate conception of the plate tectonic framework. I also don't think your discussion benefited at all from mixing in 9/11 nuttiness, which is a whole new level of insane reality denial - but I'm giving you the benefit of the doubt on that one.
Kim (and others) - as I understand it (and I'm a few years out-of-date with the relevant literature), it's true that the extent and boundaries of Avalonia are rather poorly constrained as you go south, but all down that coast you have continental fragments which started off on the Gondwana/N Africa margin, rifted off it and collided at various times with the Laurentian margin - the Gander Terrane underlies N Carolina, as I recall, and Florida represents yet another chunk. I simplified somewhat: but the point is, it's not Laurentian.
Hypocentre - I actually wasn't thinking about Wadati (mutters, goes back to add something else to his 'real history of plate tectonics' post) - do you know if he actually gave the earthquake belts he discovered a subduction-esque interpretation or not?
Posted by: Chris Rowan | January 14, 2009 3:54 PM
Chris - sorry, for some reason i thought you were Brian. And apologies for hijacking your blog site.
Anyway, since your preparing a post motivated by the conversation, let me just be clear that I am actually a working geologist and geophysicist, and have published in peer-reviewed literature on both neo- and paleozoic tectonics. My point isn't that I think EEers are "valid", but that entertaining a fringe group's perspective is important to do once in a while, and serves a valuable purpose. The reason I describe the ether debate, and 911 'nuttiness' is that it is a different product of the same intellectual brand that brings us EE. Its not that these debates are just silly on the face of it - there *are* problems in our understanding of all these things. Its just what you want to do to fill in the blanks that is at issue.
And I do relish the thought that dinosaurs were bigger because of changes in gravity over time - its like "Phantasm" where the caretaker shrinks his victims so they can be slave labor in an alternate universe with different gravity. Great stuff...
oh, btw, by the time you get down into NC and Fla your in peri-Gondwanan - Laurentian regions, and now south of "Avalonia". I don't know much about the relationship between Avalonian and Gondwanan fauna though...
Posted by: Nick | January 14, 2009 4:46 PM
As I relate in the post, Avalonia was also a peri-Gondwanan terrane (North Africa was part of Gondwana).
Posted by: Chris Rowan | January 14, 2009 4:53 PM
oh, and about hypocenters, Chris, I was thinking about this just now. I need to look, but I don't think anybody related the Benioff zone to subduction until the late 60's. Bird's papers on the Tonga - and later Isaacs - are probably the most direct. And Sykes (1967?) as well. What's interesting is to see who else might have suggested these things earlier. For example, in reality, Alan Coode wrote a paper on transform-ridge intersections before Tuzo...
Posted by: hayman | January 14, 2009 5:00 PM
"As I relate in the post, Avalonia was also a peri-Gondwanan terrane (North Africa was part of Gondwana)."
So you did. When I used to think about this, Avalon was proximal to Baltica (i.e. Caledonian). The crux always was how Avalon-Baltica related paleo-geographically to Gondwana since the Laurentian interaction of both geographically overlapped, but occurred at different times (Ordovician-Devonian, and Penn-Perm). I know that some folks are pushing Gondwandan interaction back a bit in time, but I don't know how to evaluate that claim... Seems you have some good ideas though.
Posted by: Nick | January 14, 2009 5:09 PM
Interesting topic. I wonder if it's a cyclical pattern of contraction and expansion (planetary oscillation), related to a periodic orbital rate. Basically the whole solar system (depending on the then-position within the Milky way galaxy) slowing/cooling/contracting and speeding up/warming/expanding alternatively over millions of years, might cause apparent earth expansion due to "cooking" and then cooling of geologic components (but not at the surface, which wouldn't have been "cooked"; in a spheroid, the center accumulates heat faster than the exterior, like microwaving a raw egg in a shell). If so, the same thing would have happened on Mars and Venus, but with different details due to different minerals/sizes/positions involved, but approximately the same timing of events.
Subduction, deep geothermal currents and gravity well describe the local processes involved but not the actual cause for tectonic displacements. I'd thought it was the solunar tides, per Wegener, but now I'd guess it relates to galactic cycles. maybe!
Posted by: DDeden | January 14, 2009 5:20 PM
DDeden - most folks think that extraterrestrial forcing is a dead end because it doesn't provide adequate force. Exceptions include moon-earth interactions (Bob Bostrom, a UW professor pushed this for a long time; it does, in fact, provide a moment, though not enough to really generate much heat) and Jupiter's moon Io where Jupiter's gravity drives volcanism. There are some weirder things that happen with Mars's geoid that may have happened on Earth, that are orbital in nature...
OK, I'm going now, really, you can tell I'm REALLY procrastinating!
Posted by: Nick | January 14, 2009 5:32 PM
Thanks Chris for an intersting post, although something I had read multiple times.
I wonder if anyone has put together a decent time-lapse of what the available data tell us about the last 3 billion years or so. That would be a cool demonstration. I made one from some static images to show the last 650 years of the NA continent, but 1) the quality is not that great, 2) it's not a long time (!), and 3) its just the north american continent (although you see stuff suturing to it then others rifting off).
http://www.facebook.com/v/1031875993632
Posted by: Divalent | January 14, 2009 6:53 PM
Actually, in the time lapse I posted a link to immediately above, you can see england and scotland. Another way to view it is to drag the slider on the bottom, so you can go forwards or backwards to any time you want. At the end you can see where great britan ends up, and then slide back in time to follow how it got there.
Posted by: Divalent | January 14, 2009 7:15 PM
It is indeed like a sphere egg rotating in a nuker, the sphere shape acting like a lens for electromagnetic energy to concentrate at the core while leaving the surface cool, especially the oceans which translate light to evaporation, so the deep ocean thermal vents are both thin shell cracks and thermally insulated (water absorbs heat slower than substrata). Mars and Venus lack our hydrosphere, so no tectonics, just slow release of heat outwards.
The seafloor is thin crust, cracking along the MidAtlantic ridge oozing out magma, the Rim of fire is at weak subduction joints of the crust doing the same. The antipode of the supercontinent is where the initial crack begins, which widens and builds a new mountain ridge of lava. So the conveyer belt concept is valid, but requires thick hydrosphere, sunlight and focusing lens of rotating sphere. Not sure about the degree of expansion/contraction overall, perhaps not significant.
Posted by: DDeden | January 14, 2009 7:27 PM
Nick - the (ex)-Vermonter is a she. :D
And Chris - yes, I was nit-picking (as any structural geologist who has worked in the Appalachians is likely to do - there was quite a to-do a few years ago about where the suture in Vermont actually is, for instance). But, yes, regardless of the exact restoration of the structures, there are rocks on the eastern edge of North America that ain't from around there, as the people Down East would put it.
Posted by: Kim | January 14, 2009 8:30 PM
sorry Kim, didn't mean to assume! I lost track of the thread of the conversation (no wonder!).
Enjoy...
Posted by: Nick | January 14, 2009 8:59 PM
Chris- remind us again how we know Avalon rifted away from Gondwana?
Posted by: Nick | January 14, 2009 9:36 PM
Nick - as well as the divergence of fossil groups in the late Ordovician between Avalonia and places like Morocco, there's also palaeomagnetic data which shows Avalonia starting at high latitudes (like Gondwana) rather than low (like Laurentia), but then moving equatorwards at a much faster rate than Gondwana did. In the Ordovician, Avalonian sequences initally contain mature, well-sorted quartzite formations, which resemble more distal versions of the ones which were deposited on the Gondwanan margins, and can be directly linked using provenance studies; this sedimentary linkage appears to have been cut off in the mid-Ordovician (my masters project was actually looking at when this happens, to try and better constrain the date of rifting. Plus, there's the Variscan orogony, which records the closure of an ocean basin between Avalonia and Gondwana around 350-300 million years ago (I think).
Stop tempting me to write yet another post! I have other things to do, you know!
Posted by: Chris Rowan | January 15, 2009 3:46 AM
You overestimate the amount of radioactive material in an early planet by lots of orders of magnitude!!! By far most of the matter that comes out of a supernova is hydrogen, helium, carbon, oxygen, silicon, iron, and the like.
TSIB. The difference between continental and oceanic crust is one of fractionation -- granite crystallizes out of the magma and swims on top.
Do you actually know anything about geology/geophysics?
After all, you don't even know that plate movements can be measured by satellites, and have been. That's where all those figures of cm per year come from.
Excuse me, this is a Gish gallop. How is anything within this quote, let alone after it, supposed to be possible?!?
Sure they do -- slab pull.
This is correct, but for a completely different reason: water drastically lowers the melting point of rocks.
Sunlight?
Can I trust my eyes? What do you mean?
Posted by: David Marjanovi?, OM | January 15, 2009 11:19 AM
Oops. I used the wrong signature for this blog.
Posted by: David Marjanović | January 15, 2009 11:29 AM
The small amount of the EE stuff in the literatue comes from Dennis McCarthy and is heavily biogeographical:
McCarthy, D. (2005) Biogeographical and geological evidence for a smaller, completely-enclosed Pacific Basin in the Late Cretaceous. Journal of Biogeography, 32, 2161-2177.
McCarthy, D. (2003) The trans-Pacific zipper effect: disjunct sister taxa and matching
geological outlines that link the Pacific margins. Journal of Biogeography, 30, 1545-1561.
According to a friend who regularly attends biogeography conferences, it's not a surprise to see this stuff get passed by biogeographers to be honest. Anyway, they were both roundly smacked down by Derek Briggs and Jason Ali is replies. I think McCarthy is still going, he has a book coming out from OUP entitled:
"Here There Be Dragons / How the distributions of plants and animals have revolutionized our views of life and Earth."
If anyone is interested, this is his website:
http://www.4threvolt.com/
Posted by: SteveF | January 15, 2009 12:44 PM
Oh and whilst I'm at it, there was an absolutely enormous paper in Earth Science Reviews arguing against the Vine and Matthews model (IIRC) a few years ago:
Keith, M. (2001) Evidence for a plate tectonics debate. Earth Science Reviews, 55, 235-336.
a typical quote:
It is shown that the generation of oceanic magnetic stripes, which led to the ingenious spreading hypothesis, is a result of narrowing of a formerly expanded ocean ridge volcanic system, and resultant sequential cooling of crust and upper mantle, and does not require ocean floor spreading.
Posted by: SteveF | January 15, 2009 12:48 PM
Chris - thanks for the note about the Gondwana-Avalon connection. I think there's some debate about Avalon's Gondwana-connection (in the early Cambrian), but I'm not really up on it. I've always 'preffered' reconstructions that place Baltica and Avalon to the northeast of the Laurentian margin, and Gondwana to the south; this makes the most sense for the Appalachian chain. Doing that makes reconstructing Rodinia a bit tough - but I'm not sure Rodinia is as much a "sure thing" as some would like.
Steve - thanks for the post about the Keith (2001) paper. My gut is that he is picking on many disparate points about ocean-ridge systems that we don't yet fully understand and stringing them together. And then instead of keeping current on how we are trying to explain each of those things, he's trying to throw the baby out with the bathwater. But he is pointing out some important unknowns about the 'rift-to-drift' process. I'll read it more carefully when I have some free time ;).
And no, I'm not going to start my own blog when folks like Chris have offered to do the work!
Posted by: Nick | January 15, 2009 2:45 PM
DM: "Gish Gallop, a long string of assertions are thrown out in an argument" I didn't assert, I wondered, and still do, if the solar system's position in orbit around the milky way relates to effects on tectonic activity on earth's surface, and if the 3 supercontinents (Pangea, Rodinia, Nuna?) formed at a certain point in this orbit. Perhaps not, I don't know.
"Slab-pull: Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at trenches" wiki That's a process, not a cause.
Briefly IMO: sun surface = earth core temp. because spheroid rotating in stable orbit accumulates heat (EMR) at center, hydrosphere blocks heat from quickly leaving (greenhouse effect, unlike Mars), seafloor is dense/brittle & two-way-mirror-like accepting external (solar) energy while reflecting internal heat inwardly, magma escapes crust at weak seams/joints. Eg. As the mid-Atlantic ridge expands laterally, N America is pushed westerly (conveyer belt) over the Pacific, subducting the denser seafloor.
Posted by: DDeden | January 15, 2009 3:02 PM
I wondered, and still do, if the solar system's position in orbit around the milky way relates to effects on tectonic activity on earth's surface
Unless gravity has suddenly ceased being governed by an inverse square law, I think we can safely dismiss the effects of the stars on terrestrial tectonics.
And your last paragraph is the very definition of the Gish Gallop. Long on sciency assertions, and very short on actual evidence.
Posted by: Chris Rowan | January 15, 2009 3:14 PM
And Nick - as far as I know only one person, Ed Landing, seriously disputes Avalonia being attached to Gondwana in the Cambrian and early Ordovician. And even he may have changed his mind when the results of the zircon provenance studies started coming in. Either way, he was wrong ;-)
And there's always room for more geology blogs - I'm not sure we have a marine geophysicist...
Posted by: Chris Rowan | January 15, 2009 3:18 PM
CR: Perhaps, again, I don't know. I felt it worthy to consider, especially if supercontinents have a cyclical periodicity, like forming every x00 million years or so. Last paragraph (Briefly IMO...) is explanatory using some evidence, and conjecture based on logical inference. I hope to find out what is incorrect about it, if anything.
Posted by: DDeden | January 15, 2009 5:26 PM
That's more or less true, but it's a coincidence.
Bullshit. Really... just... simply... bullshit. None of this is anywhere near correct.
The Earth generates heat internally by radioactive decay. (Not just the core -- continental crust produces more heat than oceanic crust.)
Here you happen to touch on what was a genuine controversy a few decades ago, but that's over: slab pull, not ridge push. The Pacific seafloor dives at its eastern margin, and the Americas get sucked in and thus move to the west.
Could be halfway correct for the last few hundred million years, but that seems to be a coincidence, as should become very clear if you study the movements of the continents in any detail (just from published maps).
-------------------------------------
Look, if you don't know anything about a topic, you are not qualified to have any opinion about it. That's what I've been trying to explain to you over at Tet Zoo for years now.
Instead, you simply throw anything you can imagine up against the wall and hope that something might stick! And then you are surprised when we get annoyed?
That's the big difference between science and philosophy: there are problems out there that can't be solved by sitting on your ass and just merely thinking about them.
If you get an idea, test it first before you make it public. For example, if it springs up in your flowery imagination that plate tectonics might have anything to do with the rotation of the galaxy, ask yourself "how could that ever work", and if you can't find an answer, drop the idea.
Always ask yourself: "If I were wrong, how would I know?" -- that's the uttermost basic question of science.
What is so hard to understand about all this?
Posted by: David Marjanović | January 16, 2009 1:01 PM
None of today's EErs can hold a candle to Warren Carey. None of them know anything about geology; I daresay none of them have ever read Carey's 1958 book, and none of them understand how much extension is intimately involved in plate tectonics. Carey didn't understand that either because he didn't live long enough, nor did he live long enough to accept the GPS evidence. The current generation of EErs has no excuse for its ignorance. Fortunately they don't have a political movement like the creationists do, just the ability to spam.
Posted by: Andrew | January 16, 2009 10:29 PM
I know from personal experience that the mass of the earth has increased significantly in my lifetime resulting in an increase in gravity. I have noticed that standard size objects such as 18 litre water have become heavier every year. This must be due to an expanding earth - right ;)
Posted by: Militant Agnostic | January 16, 2009 10:44 PM
DM: What is so hard to understand about all this?
"coincidence"? Oh, ok. nvm.
Posted by: DDeden | January 16, 2009 11:36 PM
Coincidence is the null hypothesis. If you can't show that the null hypothesis is wrong, all you can do as a scientist is pack up and go home.
Posted by: David Marjanović | January 19, 2009 12:31 PM
Since you are a paleomagnetism specialist, you need to read http://www.jamesmaxlow.com. The paleomagnetic pole positions show strong evidence for earth expansion.
You are looking at the cells of the unicorn and don't see the big picture. Expansion is a fact laid out by the seafloor ages. There is no reason for the process of expansion in the Atlantic to be different from the Pacific. Suduction is not proven, and the outline of the pacific expansion ridge could not be the same shape as South American without expansion. Expansion is a fact.
Posted by: David de Hilster | January 23, 2009 8:49 PM
The paleomagnetic pole positions show strong evidence for earth expansion.
Actually, they quite clearly show differential movements of different continents relative to the Earth's spin axis. Whilst this result is, at best, somewhat neutral to the question of Earth expansion, More relevantly and rather inconveniently, palaeomagnetic data also shows the closure of ocean basins - you know, the subject of this post? That your comment fails to actually address in any respect? "strong evidence" consists of more than your say-so, or that of the website you link to.
Consider this notice that any new comments - from anyone - which do not clearly engage with the material in my post will be summarily deleted.
Posted by: Chris Rowan | January 24, 2009 2:11 PM
"Catastrophic Plate Tectonics" does not even pertain together with once thought plausible, yet refuted, even if fringe from its conception, scientific theories.
Posted by: Soares | August 24, 2009 3:10 PM
Hi Nick,
Great post and really interesting. As a geology graduate I am really fascinated by this debate, I do not really understand why there is so much animosity towards EEr's. I mean is it really pseudo science?
It seems really well constructed.
As far as I am aware though EE do not deny subduction, merely point out that compared to expansion rifts, the areas identified as destructive subduction zones - about 15 000 km in the pacific is far too small compared to the 80 000 km of mid ocean ridges, and additional 20 000 km of other expansion rifts, such as the African rift and Madrid fault to name but two.
All other arguments aside what is the explanation for this?
Posted by: Andy | February 3, 2010 5:12 PM
Hi Chris,
This article does not present information that disproves expanding earth at all.
The paleomagnetic data for the Iapetus suture indicates a shear along the axial zone of of the Appalachians, along the line of the suture, where by the british isles south of the Iapetus suture were located adjacent to North Carolina - then sheared 30 degrees counter clockwise, bringing North West Africa opposite North Carolina.
This is a much more conservative explanation of the paleo biological data - and is confirmed by the paleo-magnetic data.
Some of the data even suggests that this shearing continued for 100 million years, leading to a substantial displacement.
Unfortunately this interpretation is compatible with Expanding Earth - so we will just have to live with it for the moment.
ref: Dr W.A. Morris
Posted by: Andy | February 13, 2010 5:45 PM
Palaeomagnetic data cannot indicate anything of the sort. They tell you about latitudinal displacements, not the tectonic set-up that caused those displacements. And, in this case, that latitudinal displacement was more than 40 degrees (a bit more than between N Carolina and S Britain, especially if the Atlantic was not in the way) and occurred at a different time for the Avalonian fragments than it did for Africa. Besides, an active shear zone that would have to stretch, at minimum, a quarter of the way around the planet does not fit my definition of "conservative".
And that's before we get onto the fact that North Carolina also doesn't correlate to the Laurentian sequences that are now next door to it in the Paleozoic.
Posted by: Chris Rowan | February 14, 2010 4:21 AM
There is a strong relationship indicated by the phylogenetic analysis of the fossil record of Baltic and Pennsylvania faunas.
The paleomagnetic data tells us the latitude of the rock and direction of the pole. The pole displacement indicated by the difference between Africa and European rocks and North American plate rather than being in keeping with a subducted Iapetus ocean - suggest a displacement of about 30 degrees along the Appalachian-Caledonian axis.
That means simply that the paleomagnetic data, although it cannot tell us londitude, it can tell us the direction of movement. If the Iapeatus ocean had subducted the polar data would indicate a pole displacement in the transverse, which it does not.
Posted by: Andy | February 16, 2010 6:10 AM
Andy -you need to do some reading on Euler poles and how plate motions are expressed on a spherical surface. Purely longitudinal translation is exceedingly rare, and is anyhow no more diagnostic of convergence any more than a change in declination implies shear. Since it seems that you're quoting this argument from somewhere rather than interpreting the data yourself, you might consider that lecturing a palaeomagnetist on the interpretation of palaeomagnetic data is not the most sensible thing you can be doing with your time.
Note also that my original post did not actually mention the palaeomagnetic data; focussing on the distinct fossil assemblages and their divergence and mingling over time. This is more than enough to falsify the scenario you present.
And now - since this post is more than a year old - comments will be closed.
Posted by: Chris Rowan | February 16, 2010 3:59 PM