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Continents Adrift (Geophysics)
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admin
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This thread is the precursor to The Great Prime Mover Treasure Hunt.
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Mick Harper
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In: London
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Before I make a complete fool of myself I want to make sure I've got this Continental Drift business right. As I understand it, a continent can only do one of three things:
1. It can swan around the briny minding its own business.
2. It can can split into two continents, whereupon the two halves swan around the briny minding their own businesses.
3. It can bash into another continent, whereupon the two joined up bits form one continent and that one swans around the briny minding its own business.
Is that a fair summation? Please advise.
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Ra


In: Finland
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No! They cannot "swan around minding their own business" since they are still connected. One's swanning affects all and every continent, one way or another. In any case you're confusing Plates with Continents. It's the plates that do all the moving.
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Mick Harper
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I appreciate that, according to the blessed tenets of Plate Tectonics, all things are connected via the substructure, Ra, but actually it's not me that is confusing continents and plates, this is built in to the theory itself. As you know it began as Continental Drift and latterly became Plate Tectonics. Applied Epistemology always takes a close interest when two...um...slightly different things get quietly conjoined, especially when it's a paradigm question. But whatever is going on "down below" I am in this thread going to be dealing strictly with the outward manifestation of the business -- the continental landmasses.

Now, is it or is it not true that a given continent can only be in a state of a) being alone surrounded by ocean or b) in the process of splitting from another continent or c) colliding with another continent?
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Oakey Dokey



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Yes, continents (the light, thick spongy type of crust) either move away from each other or together or generally do little (Australia for example). Most movement occurs in the oceanic crust not in continental crust. Where's this leading to?
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DPCrisp


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It's self-evidently true that continents will wander lonely as a cloud until they bash into another continent since the earth is finite and there is, so far as I know, no mechanism for continents avoiding one another. And as there are continents (plural) in the first place, I suppose it is also a reasonable supposition that continents split. I agree with Oakey, where the hell is this going?
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Mick Harper
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I won't say at this stage where we are going to but I can say where we are coming from. Applied Epistemology deconstructs academic subjects down to their paradigm theories and is always on the lookout for various swindles. One is called "Having Your Cake And Eating It" which is to say that the paradigm is split in half so that professional practitioners can skip from one to another to avoid anomalies and other difficulties thrown up by the evidence. Those of you have read The History of Britain Revealed will be familiar with an example of The Cake Trick -- the splitting of the past into History and Pre-History so that anomalies can be shovelled into the Pre-History bit (and blamed on Pre-Historians) while History proper insists that Pre-History is subject to whatever paradigms Historians currently require.

In the Earth Sciences, there is a similar split between Geologists and Geographers (the line is roughly drawn at the surface of the earth) and their basic paradigms have also been split between what's going on below the surface and what's going on above. In the case of their currently favoured Prime Mover Theory, Plate Tectonics is the bit you can't see (below the surface), while Continental Drift is the bit you can see (above the surface). And as Ra and others have pointed out, you can shift seamlessly between one and the other in order to explain just about everything.

But Applied Epistemology points out that Having Your Cake And Eating It can also mean having Twin Hostages To Fortune, and seeks to exploit that. You'll soon see what I mean. So let's move on to the next question. We have established that at any one time a continent may be in one of three different aspects a) all alone set in a silver sea b) bashing into another continent or c) splitting into two continents. How do you tell the difference between b) and c)?
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Oakey Dokey



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Simplistically we associate ' joining' continents with mountain building, 'sitting' continents with flat stable landscapes and 'moving away' continents with volcano formation.
Examples of which are
1. joining - India
2. sitting - Australia
3. moving apart - Atlantic ridge (Americas and Africa)
But there are many (land masses) that don't fit into this neat scenario, Antarctica for one.
Pretty simple
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Mick Harper
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Simple indeed, Oakey, but given that we only have a coupla handfuls of landmasses to play with, and they are to be distributed among three different categories, your qualification that

there are many (land masses) that don't fit into this neat scenario

is somewhat alarming.
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Keimpe


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You measure the starting position of each continent accurate to an inch and then keep a continuous record for a few years and then you'll know whether they are splitting or joining.
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Mick Harper
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Compelling, Keimpe, but not compelling enough. It might be fair enough measuring the distance between points on very discrete continents, say New York and London, but how do you tell within an inch or two when such messy things as continent boundaries are in close conjunction? You can see this kind of thing every time some dude from KNPG-TV stands by some newly-formed rut in a Pasadena highway saying, "Plate tectonics in action, you can see the Pacific plate pulling away from the California plate." So you can there but a coupla feet don't make a whole continental boundary.

However, I'm glad you raised this point because it's an illustration of the good old Applied Epistmological nostrum -- "the careful ignoral". Many of you will remember, in the early days of geostationary satellite measurement, that people actually were claiming that New York and London had separated by a further centimetre or so since the previous year. The reason I remember it was because I was putting together a hatchet job on Continental Drift at the time and felt thoroughly depressed because whatever I said would be instantly swept away by the "fact" that the process had actually been measured and recorded.

So naturally I kept my eyes and ears out for further mentions. And they were not forthcoming. Now this is extremely significant because the Holy Grail of the Earth Sciences is actually to come up with a definitive map of the tectonic plates (the ones you see only look like maps, they are in fact models constructed from tectonic features). Over the last few decades, with earth measurement both accurate down to an inch and cheap enough to do wholesale, it has become theoretically possible to make such a map. All you would have to do is to measure the annual change in distance between (let's say) a thousand points distributed over the earth's surface and this will reveal every moving plate.

But it ain't been done. Draw your own conclusions.
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DPCrisp


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The conclusion I'd draw is they prolly haven't got that kind of money but there there are plenty of ways of telling splitting from bashing, just by looking. For instance sea-floor spreading, like the mid-Atlantic ridge is a sign of the European Plate splitting from the North American one, and the Himalayan massif is a sign of the Indian Plate colliding with the Asian one.
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Mick Harper
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I have carefully (you might argue unfairly) distinguished between plates and continents. You might be perfectly correct about the mid-Atlantic ridge, Dan, but it's a long way from any continent. Is there any way of telling that Europe is a splitting continent other than pointing to something happening a thousand miles away and merely claiming that Europe is perched on a plate that is splitting? Your other example does qualify. You say that the Himalayan massif is there because one continental landmass (India) has collided with another continental landmass (Asia) and hence we can see two colliding continents. Fair enough except for all the other mountain ranges on earth. Are you saying that the Andes are evidence that something just bashed into the west coast of South America? Are you saying that the Great Dividing Range is evidence that Australia is a "colliding" continent?
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Keimpe


In: Leeuwarden, Frisia
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Dunno about anyone else but I'm inclined to trust Mick (or humour him, I can't quite tell) and just accept where he is going for the sake of argument. It might get this show on the road. All right, Mick, since it's what you want to hear, nobody can tell the difference between "splitting" and "colliding" continents. Now what?
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Mick Harper
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Thanks for the charity, Keimps, but as it happens I don't need it. I don't care if you can or you can't tell them apart because (it's an old Applied Epistemology trick) I'm going to add them together into a single category (it's called "Removing a mirror" -- from the smoke-and-mirrors). In other words any continent that isn't swanning about in the briny minding its own business goes into a single category..

Giving us two categories of continents:
1) discrete ones, the ones swanning about the briny (hereinafter called O-continents, which you can remember because they are entire and complete unto themselves, very gnostic) and
2) non-discrete ones (hereinafter called X-continents because they are two things that are either joining or splitting).
Unless there are any strenuous objections I now intend to play noughts-and-crosses with the world.
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