Geomagnetism and the rate of Sea-floor Spreading

Gengar says that convection currents that motivate plate tectonics have something to do with magnetic fields? I don't get that from any posts except yours. I am taking issue with the fact that you are conflating the mechanism of plate tectonics with the mechanism that creates magnetic fields. I know of no one who would say that the energy expended by a convection current would provide energy for continuation of the current ad infinitum. This is silly. Convection currents are a mechanism for transferring heat. When the heat is gone, the current stops. You are confused again. I say that the website is pretty funny. That may be the problem. So, when you provide a website, you don't expect us to look at it? It was one of several that you have given us to support your argument. It's rather non-sensical. If it was not on topic, why did you present it? I know what you mean.So, any site that says something like "Heat produced by radiogenic decay is insufficient in itself and contradicts the second law of thermodynamics:- "That which gravity has drawn together, let no thermal upstart set asunder". ", is nothing that you would recommend or comment on?This message has been edited by edge, 01-21-2005 22:17 AM

I don't think HH has ever realized that there is a separation between the plate tectonic driving currents and the magnetic field ones. For this reason he thinks that post 128 is saying that the currents are suppying the magnetic field.He is right in that Genger says that that some currents supply the magnetic field. It seems he also doesn't believe that this is possible but, of course, has no idea why it wouldn't be. Then he mixes the mantle currents with the core currents.With this confusion he probably appears right in what he is saying.I think he has gotten very muddled about what is what. Perhaps HH can clarify just what he does think and why?

First of all, you err in saying that anything 'proves' plate tectonics. What we say is that the evidence overwhelmingly supports plate tectonics. Now, in a debate, it may be said that plate tectonics is proven, but that is in the scientific sense that it has not been refuted, etc. etc. I see that you still do not get the point. Let me try to rephrase the question that you have ignored: Why should it be necessary to have third decimal place type precision when all we are measuring is direction of field? If core is continuous, or otherwise oriented, and a reversal of field occurs, do we really need to know within micro arc-seconds what the orientation is? I cannot see why for the purposes of this discussion.Furthermore, how do you explain such a reversal? Yes, let's... Ooops, there you go with 'proof' again. Are you sure that you have an understanding of science and scientists? Do you really think that geologists and geochronologists haven't thought of this? You really do have little respect for the profession. But if we look only at reversals, what is the beef? It either reverses or doesn't regardless of magnitude. Of course not. However, that is why we recognize several different variables of magnetic drift. Are you saying that entire tectonic plates have been rotated 180 degrees over a core distance of a few feet or inches? Talk about plate tectonics! Please document. I agree that there can be secondary imposef fields, but the primary TRM or SRM is usually the strongest. Again, these variablilities can be inferred from other types of data, such as mineralogy, metamorphic textures, and radiometric ages. If I were to measure the TRM of a metamorphic rock, I would not assume that it was the original depositional location that I was calculating. And the mechanism for this is what? And where does that occur in nature? Do you have any examples of measured effects? Any references to this? And just how would those storms affect the seafloor? I suppose this is possible. But I seriously doubt that a pattern would emerge. How many lightning strikes do you think there are on the sea floor? Yes, this occurs when a slowly cooling (volcanic) rock experiences a reversal of the imposed field. No big secret here. This is how reversals have been timed. Good Lord! You call this a credible reference? All of your high rhetoric about scientific precision and you use Pathlights as a supporting document. And you were complaining about my reference to a 'funny' website in an earlier post? This one is not funny, it's pathetic. Heck, some times I have a hard time measuring my carpets! What is the big deal here? Should we give up on a task because it is difficult? I'm beginning to see where you are coming from. So, you have just described some of the issues with paleomagnetic studies. Doesn't this give you a clue that we are aware of the problems and take careful measures to limit them? The point is that there are explanations for the deviations. Now, what is the explanation for the overall patterns that emerge? You will notice, for instance that there were no reversals in this study. Do you think they might have been detected if present? Sure, some reasons were not obvious or resolvable, so the kept the results. By the way, I'm sure that many paleomag studies are not from the type of terrain represented by stratovolcanos. Why not address some form sedimentary terranes? Or batholithic terrains with good radiometric control? No, because the stripes were originally found by towed magnetometers over the sea floor. As such they averaged the various rocks beneath the floor, probably recording mostly the rather structurally undisturbed parts of the subfloor. Not really. You have cited a single case which happens to have been in a known structurally complex area. The results are exactly what I would have expected. We would love to hear about them. But actually, no. This was really a pretty good way to do it. Believe it or not, geophysicists actually thought about these things before you came along. The ends they go to in order to correct for known issues are not casual. Yes, we have noticed this. It takes a lot of training and structural geology to be able to do this. That is one reason we don't let YECs do this on their own. If it is so terribly inexact, why then do we see the patterns that we do see? This is where you fall down. There are patterns. Shall we just ignore them because the subject is too hard, or we don't know everything so we actually know nothing? Then you might like to participate in another thread on radiometric dating, for instance. By the way, this is another funny site. I'm beginning to see your problem on this board. You do not critically analyze anything that is of YEC origin. Your standards for non-YEC data are considerably more stringent. Why not apply the same standards to Pathlights, for instance? Please elaborate. What values have been used and what is the problem with them. I think you have evaded this question before by blustering that 'viscosities were ignored' and eventually had to back down on that statement. The Astronomical Society? Weren't you the guy who was complaining that I couldn't stay on topic? And this has what to do with geology? You're right, let's just ignore the data. Good, then show us what fundamentals were ignored. YOu were already wrong on viscosities... You keep making this assertion but never back it up with evidence. Please do so or be prepared to no be taken seriously. Ooops, there you go with 'proof' again! Your true colors as a YEC are showing through. You have not refuted the methods or the results or the precision necessary to interpret reversals. You simply go of on tangents about 'how difficult it is' to measure magnetic fields as thought we don't know this.

Actually they do some of this kind of work. For example, right after

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Even with modern supercomputers, models cannot be run with the correct values for several key parameters, which are currently wrong by many orders of magnitude.

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They say:

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Dispite this drawback, comparisons with both geomagnetic and paleomagnetic data show that the models generate Earth-like magentic fields in most important respects, so we hope that they capture the essence of geodymamo action.

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It think that is would be appropriate to point out that it is a particular bad and dishonest habit of too many creationists to lift only part of a quote out-of-context to allow for a twisting of the meaning.

Hey Percy,I get the exact same thing Joe does occasionally. I learned quickly that the server error message was bogus - the post I tried to make was actually posted. I just have to crawl back through EvC's front door (just like starting a new session), and my message is nicely posted (singly). Hitting "back" then resubmit gets the double post.

The clue to understanding this is in the more technical name for these features - marine magnetic anomalies. They are measured as deviations from a global reference field: the remanent magnetisation of the crust is being superimposed on Earth's present day field, leading to local variations in the magnetic intensity.Normal polarity stripes are have a magnetisation which points in the same direction as the present day field and therefore add to the measured intensity, resulting in a positive anomaly.Reversed polarity stripes have a magnetisation which points in the opposite direction, and subtract from the measured intensity, leading to a negative anomaly.A simple variation in intensity would not produce the negative anomalies. Also, we have the directly measured and dated reversal stratigraphy from sediment cores: the ages of normal and reversed polarity intervals correlate nicely with the ages of the positive and negative stripes, determined from radiometric dating of the crust itself. I'm not sure why, in standard oceanic crust you have around 2km of basaltic lavas and dykes which will be packed with magnetic minerals like magnetite. That said, it is still not entirely clear exactly where the magnetic anomalies are sourced - mainly because we have yet to drill completely through the crust. We're getting there though.

After Joe's message I was unclear about whether the error is an EvC Forum error message page or a server error page. If I understand what you're saying, you seem sure it's a server error, which makes sense to me. If you simply click on the refresh or reload button it should take you to the right place.Is it also true for you that this only happens when you're at EvC Forum?The next time this happens, can you or Joe cut-n-paste the exact text and post it? I can take this evidence to our webhosting company. Thanks!--Percy

I think this is the missing data that HH is referring to. He believes that basalt underlying the sea floor has not been drilled to verify it as the source of the magnetic anomalies. It sounds like you're confirming this.Even if true, HH still has to provide an adequate alternative explanation for magnetic sea floor striping. His explanations so far have been contradictory. At one point he says the striping is imaginary and is just misinterpreted random fluctuations, at another he says the striping is real and is caused by sea floor bending at mid-oceanic ridges. Since this latter position has magnetic reversals being a local effect at mid-oceanic ridges, it fails to explain simultaneous reversals throughout the world.Here's a picture from the aforementioned Earth Story of what HH has to explain. This is a representation of the magnetization of the northwestern US off the coast of Washington and Oregon. The coastline is indicated with a thin black line:
Click for larger imageThis picture refutes the possiblity of random fluctuations - the stripes are very evident and could not be random. HH has yet to suggest a workable alternative to current theory.--Percy Correct spelling. --PercyThis message has been edited by Percy, 01-22-2005 10:27 AM

Right - only at EvC. I'll be happy to forward the error message next time it happens.

I don't know. However, I do know that many volcanic areas on land have been studied and their paleomagnetic signatures corelate with the sea floor studies. I remember stumbling across a great web site on this topic once, but I can't find it now. However, see (for example) Geochronology of the central Colorado volcanic field and LITHOLOGIC, AGE GROUP, MAGNETOPOLARITY, AND GEOCHEMICAL MAPS OF THE
SPRINGERVILLE VOLCANIC FIELD, EAST-CENTRAL ARIZONA.

Sadly for HH, where drilling has reached sea floor basement, the rocks invariably have a normal polarity in the positive stripes and a reversed polarity in the negative. What we're not yet sure of is how much of the crust is contributing to the overall anomaly. The net magnetization of the upper portions we've sampled does not seem to be large enough to produce the anomaly we see, implying that the lower crust is also involved.From an Ocean Drilling Program report: So, whilst there are some unanswered questions about these anomalies, their existence is not in doubt. As your rather cool picture clearly demonstrates!

A really good book on magnetic polarity stratigraphy is "Magnetic Stratigraphy" by my colleagues at Florida Neil Opdyke and Jim Channell. Neil is a member of the National Academy of Sciences and the winner of numerous awards from the Geophysics community, Jim is a fellow in the American Geophysical Union. The book outlines the evidence and the assembly of the magnetostratigraphic time scale. I've linked to the Amazon website below: http://www.amazon.com/exec/obidos/tg/detail/...
{Shortened display form of URL, to restore page width to normal - Adminnemooseus}CheersJoe MeertThis message has been edited by Joe Meert, 01-22-2005 11:31 AMThis message has been edited by Adminnemooseus, 01-22-2005 11:46 AM

Thanks Percy. Are you referring to the Hydroplate Hippie as maybe having a prior history at other sites?
That is interesting but I can assure you that I am a rookie at this stuff!!! Out of curiosity, who and what other site is suspected? I may want to meet them!In all seriousness, you are providing an excellent forum and I appreciate it! Only by sharing knowledge and understanding through discussion will we sharpen our insights. These exchanges have increased my focus and raised more questions for me.

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In all seriousness, you are providing an excellent forum and I appreciate it! Only by sharing knowledge and understanding through discussion will we sharpen our insights. These exchanges have increased my focus and raised more questions for me.

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--That is always good to hear, HH -Chris

Hello Gengar! No apologies necessary! This is a complex topic and can be difficult. Not sure what you mean by talking at cross-purposes but I am trying to keep it at a professional level. I find your posts to be the most professional and informative. I concur with Percy. Thorough post and informative. If the values of viscosity, thermal expansion, thermal diffusivity, etc, were actually known with a high confidence level, then there would be no issue here. I agree that the force of gravity would be lower just above the inner core (should be roughly similar to that of the moon). There appears to be some innovative work in recent years but the debate over actual parameter values and orders of magnitude will likely continue for some time. So I think the best we can do here is to - agree to disagree and - move on. Gengar,
On what basis do you know that the mantle convects? We may have to agree to disagree here as well for the same reasons - inability to either model the mechanism with reasonably expected parameters and inability to verify empirically. Computer models have the same problems with mantle convection using best estimates of the critical values for the Rayleigh number — they don’t work.The Lamont-Doherty Earth Observatory (LDEO) is a leading research institution where more than 200 research scientists seek fundamental knowledge about the origin, evolution and future of the natural world. Although they have not yet discounted mantle flow... they are acknowledging some of the problems with current textbook plate tectonics geology. I like the way you approach technical issues Gengar! This is the essence of knowledge and understanding through discussion. This might be possible if the Earth interior were a perfect superconductor, but it isn’t. The reason a geodynamo could not possibly power the geomagnetic field is the speed at which electrical current flows and dissipates into heat (this is why I stressed the relative speeds of proposed convection currents and electrical currents in the previous post).Let me make a loose analogy with a lightning strike to ground — it is not a perfect analogy since the atmosphere is a different type of conducting medium - but the concept is similar.Consider a voltage potential increasing in a cloud (it could be either positive or negative with respect to ground). At the threshold where the voltage is so high that it ionizes a conductive path to ground — lightning (electrical current) flows and creates huge electromagnetic fields, waxing all AM radio broadcasts.The electrical current continues to flow until the voltage potential is essentially the same between the cloud and the ground. At that point the current flow stops and the electromagnet field immediately collapses to zero.Let’s assume the lightning strike occurs in a hurricane with high wind speed and a certain volume of air moves a certain distance through the electromagnetic field during the lightning strike (the adjacent air may even ionize and create a branch of current flow with it’s own electromagnetic field).The problem is the voltage differential is quickly equalized and all the current is dissipated to heat — almost as fast as the flash of a camera.There will be some residual ionized air molecules after the strike which we smell as ozone. But there is no voltage potential difference remaining in the atmosphere to sustain a large current flow. The electromagnetic field will completely disappear until another large voltage is built and creates another current path.Earth’s core is different from the atmosphere in that it does not have to wait for the medium to ionize to conduct electrical current flow — electrical current will flow quite easily in liquid iron (with impurities).
And electrical current flows so fast that it is like taking a snapshot of the proposed convection currents — they are essentially static in motion during the instant of electrical current dissipation into heat.
In microseconds, all the voltage potential differences in the core would be equalized and the current flow would stop — collapsing the electromagnetic field to zero. This analogy does not address the additional problems:- why the electrical current direction of flow (and associated electromagnetic field) would be significantly affected by proposed convection currents at all — the electrical current will flow through all iron in the inner and outer core. Thus, even assuming convection currents are actually occurring, they still cannot reasonably be expected to cause conditions resulting in a flipped geomagnetic field.- how a large electromagnetic seed field would originate and what mechanism could possibly build (and more importantly - sustain) very large potential differences (voltages) in a conductive core medium.There is no plausible mechanism (that I know of) within the context of physical law that such a large voltage potential, electrical current, and electromagnetic field could be generated and/or sustained over time. This is why I say with very high confidence that a geodynamo is not sustaining the geomagnetic field and has not contributed to a geomagnetic field reversal. By extension, I can say with high confidence that a field reversal has not occurred on Earth due to a self-sustaining dynamo. And I firmly believe Hess’ geopoetry analysis has incorrectly interpreted magnetic seafloor measurements as geomagnetic field reversal striping.Data that seems to indicate a geomagnetic reversal must have alternative explanations (just as Ptolemy’s data did).I would be surprised if no one within the geophysical community has raised these fundamental issues in scientific forums concerning geomagnetism relating to a proposed geodynamo! It seems fairly fundamental.The solid inner core (with permanent magnet properties) is logically the primary generator of the geomagnetic field as it spins at a faster rotation speed and on a different axis from the crust. The Hydroplate theory explains logically how that configuration could occur. Not trying to nitpick here Gengar, but I believe realistic values would also be required to validate the mechanism as well. The critical values should at least include viscosity, thermal conductivity, thermal expansion, and electrical conductivity. And as you might notice through your searches, many in the scientific community differ with some of the values used in your Rayleigh calculation by orders of magnitude.Concerning the second point - trying to produce a model field with behavior that matches observations - this can be done with an infinite array of model parameters and model designs. But it is has minimal value without respecting physical laws and using realistic parameters. We can design a model to produce any results we desire. I don’t think anyone would use such a model in industrial or military design applications. I agree it is pretty cool. Unfortunately, without meaningful parameters and physical laws built into the model - it is similar to the special effects in movies like the Terminator — little basis in reality. I don't mean that to sound sarcastic... Gengar, I have the highest regard your work. Your knowledge and experience is important in this exchange. I am not questioning whether you have correctly observed samples with opposite magnetic polarity. As you know, many factors can cause or affect remanent sample magnetism. Without any plausible physical mechanism for geomagnetic pole reversals, I don’t think we can state as fact - with confidence - that pole reversals have occurred. There are many examples in scientific history where observations lead to an incorrect conclusion. Neither Gengar!!!You should not be insulted - because I am not questioning your competence in measuring sample remanent magnetism. It is the conclusion that pole reversals occur without understanding any plausible root cause of such a reversal that I cannot support.You should not be amused at any grand conspiracy suspicions from me either! I learned long ago that a secret conspiracy generally does not work if more than one person is involved! (Big Grin) Copy that!!! Thanks Gengar, no offense taken at all! You have been the most professional and persuasive contributor in this exchange. Maybe it is because we are both new in this forum and haven’t been tainted by sniper debate garbage (from both sides). It would be easy for me to get emotionally involved (pissed off) when folks start getting Michael Moore sideways with personal attacks and character assassination in this forum.I have to edit out my petty thoughts before replying to some posts — but still screw up now and then.I much prefer respecting people and the old Dragnet (TV series) approach — Just the facts Ma’am. Perhaps that is why I prefer work in the scientific arena rather than the political.Please let me know if you have any questions or concerns with this response concerning pole reversals. We may have to agree to disagree whether a lack of known physical mechanisms is a "show-stopper" for a given conclusion for root cause of an observation. Let's keep working through it if you don't mind...Gengar - If you ever get to the states, please let me know. Would really enjoy buying you a beer (or two, or three)!Hydroplate Hippie