RiverApe, I am sorry you feel I am 'having a go at you'. In my first post I supported your view that an expanding Earth had been a perfectly valid, mainstream hypothesis. I did express puzzlement as to why you felt Venus's surface was 'concealed' and my reasons for this were expanded in my next post. I am simply trying to understand why you feel we can't 'see' its surface, when I know we can.Laika, Hipparchia: I think you two should settle the dispute between you before you have another go at me!
River Ape, I have difficulty believing that such a misinterpretation is anything but deliberate but, just in case, I will confirm what Hipparchia has clarified above. Earth and Venus are similar in size, mass and (presumably) composition. They are decidedly different in that Earth bears the scars of ongoing (local!) crustal expansion, while Venus apparently does not.River Ape said:Laika, Hipparchia: I think you two should settle the dispute between you before you have another go at me!
I am flattered. Thank you.Hipparchia said:In fact I've read through all her posts and she seems to make lots of sense.
Yet these are not insignificant similarities. Based on these similarities we can do more than speculate about the composition: we can infer that it is similar to Earth's. This is supported by Venus's flood-basalt-like surface features. I admit that there are major differences between Earth and Venus - this was, in fact, my whole point in comparing these planets! One has supposedly grown six-fold in the last 200 million years (and is still expanding furiously), while the other planet, similar in size and mass, has been unchanged for about 500 million years.Earth and Venus are similar in size and mass -- and in practically nothing else! We can only speculate about the composition of Venus, but that planet's lack of a magnetic field suggests some major differences from Earth.
I would also be reluctant to talk about clear evidence of subduction zones if the position I had adopted required their nonexistence. Perhaps, if you are determined not be drawn on this subject, you could provide a link to such a debate.I have been reluctant through lack of time to repeat the debates over subduction which (as I have indicated) can be found elsewhere, and which must to a large extent come down to analysis of individual sites.
Again, this seems to me like willful misrepresentation. As you have clearly studied geology at least casually, you must know that not all subduction zones are signified by deep ocean trenches. Also, in many instances crustal shortening is accommodated at continental-continental plate margins by folding and thrusting. If you have trouble with the model, try looking at actual plate motion and at an actual subducting slab.A model which asserts continuous formation of new oceanic crust at Earth's mid-ocean-ridges and eventual removal of oceanic crust in deep ocean trenches suffers from the major weakness that there are far more sites of new oceanic crust generation than trenches to equally dispose of oceanic crust.
I have said before that I am not a physicist; such quantitative investigation is beyond me. However, I am interested to know the reasoning behind your(?) estimates. What value do you assign to the "energy available from all the proposed motivating mechanisms combined", and just how many orders of magnitude smaller is it than the value necessary to overcome the friction you talk about?The mechanical resistance to tractional transit of oceanic crust across an ocean basin is orders of magnitude greater than the energy available from all the proposed motivating mechanisms combined. If you can produce any satisfactory explanation of the power source please do so.
Sure, but just find me -- somewhere -- an explanation of the driving mechanism that seems vaguely plausible!Laika said:I have said before that I am not a physicist; such quantitative investigation is beyond me.
You could start here. Or, if you regard Wikipedia as insufficiently academic, you could try Science (I went on Google Scholar and this is the first paper I found). I look forward to finding out why you consider plate tectonics so implausible.Sure, but just find me -- somewhere -- an explanation of the driving mechanism that seems vaguely plausible!
Although I am interested in learning what it is specifically about conventional plate tectonics that you disagree with, I would also like to point out that in previous posts we apparently agreed that the causal mechanism for supposed global expansion could be left unspecified. Therefore, it seems a little inconsistent to me that you consider your speculative musings about dark matter and neutrinos as a satisfactory underpinning for the expansion theory, yet denounce as implausible the relatively robust geophysical framework behind conventional plate tectonics.I look forward to finding out why you consider plate tectonics so implausible.
I do not think there can be much debate about neutrinos. These particles began as speculation; they were later discovered to exist; they were quite recently discovered (to the general satisfaction of the scientific community) to have a miniscule mass. They are generated by the sun (as a by-product of fusion) among other sources. A tiny fraction of the squillions which at every moment course through the planet are intercepted. Their mass is added, internally, to the planet, causing an outward pressure -- a near-unstoppable force. (Incidentally, this must happen also to Venus.) Thus, however small a contribution is made to the expansion of the Earth by neutrinos, I think it is established that internal growth takes place -- which many people find hard to imagine. I am happy to accept the term "musings" for my hypothesis that other forms of dark(ish) matter may also be intercepted.. . . speculative musings about dark matter and neutrinos . . .
River Ape, I am genuinely puzzled by some of the statements you are making. It seems apparent from your posts that you are both well read and intelligent. (That is not meant to be in any way patronising, but is a real observation.) Despite that you post these strange statements that just don't match up to reality. Compare Earth and Venus with any other two planets in the solar system and ask which is it closest to. There is no competition - Earth and Venus are twins.Earth and Venus are similar in size and mass -- and in practically nothing else! We can only speculate about the composition of Venus, but that planet's lack of a magnetic field suggests some major differences from Earth.
It isn't just the ocean floor that is taking the dive, but the mantle below the ocean floor. As to evidence, we have lots:I really did not discover in the Wipipedia article a satisfactory causative mechanism able to force thin ocean floors only 10 km thick to dive beneath thick continental shields 25-40 km thick without leaving behind some physical evidence.
I just don't think we are going to agree over this. I expect the value of real estate to remain much higher on Earth.Earth and Venus are twins.
River Ape, I did not dismiss the existence of neutrinos as speculation (as I think you know very well), but the mechanism my which they contribute to planetary expansion. I have learned that when a neutrino interacts with matter, it can either transfer its momentum to the impactee, causing EM radiation to be emitted, or it can cause a neutron to become a proton and an electron. The Earth is composed largely of iron and iron/magnesium silicates. If iron gains a proton, it will presumably become a light (stable?) isotope of cobalt. Is this the process you envisage? Gradual transmutation of Earth's elements by neutrino interaction? By my admittedly elementary calculations, the combined mass of the proton + electron is actually lower than that of a neutron, but I'm on shaky ground. Please explain.I do not think there can be much debate about neutrinos. These particles began as speculation; they were later discovered to exist; they were quite recently discovered (to the general satisfaction of the scientific community) to have a miniscule mass. They are generated by the sun (as a by-product of fusion) among other sources. A tiny fraction of the squillions which at every moment course through the planet are intercepted. Their mass is added, internally, to the planet, causing an outward pressure -- a near-unstoppable force. (Incidentally, this must happen also to Venus.)
If it is established, I imagine you can supply a reference or two. Perhaps you can do this in the same post in which you provide your calculations showing that the "mechanical resistance to tractional transit of oceanic crust across an ocean basin is orders of magnitude greater than the energy available from all the proposed motivating mechanisms combined", and in which you also demonstrate matthyaouw's and my naivete regarding the Moon's recession from the Earth.Thus, however small a contribution is made to the expansion of the Earth by neutrinos, I think it is established that internal growth takes place -- which many people find hard to imagine.
I concede that expansion might be expressed differently on the surfaces of different bodies. But I will point out again the differences and similarities between Europa, Ganymede and Callisto. All similar in same size and make-up, but decidedly different in surface age and morphology.Given that the Earth is swelling, one can readily imagine that an outward force would create fractures and that internal material would spill out along the surface lines of those fractures, rearraging the surface features of the planet over a long period of time. (On other planets/moons, depending on structure and composition, such fracturing might not occur in the same way.)
This adds nothing. You've merely restated your position. We know that you think it's "inherently more plausible", but that's not important. Incidentally, another subject of ongoing discussion and research is the nature of gravitation - I assume you don't doubt the existence of gravity simply because the theory has not yet been nailed.On the face of it (though you cannot always trust faces), it is inherently more plausible that an unstoppable outward pressure would force apart trillion of tons of rock than that the surface features would slither around driven by forces which are best described as "still very active subjects of on-going discussion and research in the geophysical community" (to quote Wikipedia).
I will reiterate for emphasis what Hipparchia has already said very eloquently above. I apologise if you already got the message.I really did not discover in the Wipipedia article a satisfactory causative mechanism able to force thin ocean floors only 10 km thick to dive beneath thick continental shields 25-40 km thick without leaving behind some physical evidence.
You have described accretionary prisms. I mentioned them in a previous post, and they do exist.How about the problem of unconsolidated sediments covering the floor of the Pacific to very varying depths -- but let's say an average of ten meters. Massive amounts of sediments should be piled up against continental shores, or in the deep ocean trenches off the eastern coasts of Asia and Australia, the western coasts of North and South America, or in the Aleutian Trench. The sediments just aren't there; the ocean trenches are relatively free of sediments and there are no mountains of soft sediments piled up against any Pacific shore, nor indicative remnants.
The ocean lithosphere thickens as it moves away from the rift. This is because the upper mantle cools by conduction and by water circulating through cracks. Eventually, enough cooler (denser) mantle material will have been underplated to compensate for the more buoyant, slightly more felsic crust above, and the lithosphere as a unit will have become denser than the mantle immediately beneath. This is when a slight disturbance can initiate subduction, and is the reason that oceanic crust tends to have a maximum age. However, not all oceanic crust is recycled; in some tectonic environments oceanic crust can be obducted onto the continent, where it is preserved. These are ophiolites (I think that matthyaouw already mentioned them), and have been studied extensively.Also, please explain to me why none of the ocean floors date back to more than 200mya. Why would every last bit of ocean floor get subducted someplace or other before it got any older? Coincidence?
GPS measurements are not the only method of geodesy. Look up, for example, very long baseline interferometry.BTW, I think you are a little too trusting of the data said to be deduced from global positioning satellites. It is some time since I read anything on this, but I seem to remember that the data relating to the Pacific was notably contentious. (There might be something on this on the bautforum site referred to in a previous post.)
I did not respond to your previous post about dinosaurs for two reasons:I notice that no one has so far offered to explain how creatures up to fifteen times the size of an African elephant lived upon the surface of the Earth in past times -- unless gravity was much less strong.
On the contrary, I think that expertise in biology (and possibly structural engineering) is very much necessary to make such a confident assertion.One does not need to be a biologist to see that the elephant represents something approaching the "maximum design stretch" for quadrupeds. I have read the books that seek to explain the dynamics of dinosaur motion under present Earth gravity (they are in my personal library). They do indeed explain that a 100-ton beast might exist today, provided it stood still. I cannot entirely overturn their mathematics -- but they rely on Nature not having built in the engineering "margins" and "tolerances" that she does today, and I will not wear that idea. I don't think that is something that would change.
I'll answer the one you repeated, but could you go back an address my points about the evidence for plate tectonics - and include by all means the points Laika raised.How about the other questions I raised?
The shapes are complex, but the basic principle is simple: ocean crust can get absorbed, continental crust doesn't. I have no dificult imagining all the floor beign absorbed. Equally I would not be surprised to find that a small portion of older floor is to be found in a poorly explored region of the oceans - under arctic ice for example.If the oceans have been around for a few billion years, why would every bit of ocean floor dating back above c.200mya just happen to have disappeared? We are dealing with a pretty complex and irregular set of shapes here. Wouldn't you expect a patch of old ocean to survive tucked away in some odd corner?