Plate Techtonics!

[Nyril]

Several years ago (more then one, less then ten thousand) the idea that the Earth was not the center of the Universe was high in the ranks of things we argued about. Neatly behind that would be the age of the Universe, age of the Earth, the Earth goes around the sun, Earth is flat, etc. In time, a number of these ideas were accepted by pretty much everyone. By that I mean that I doubt even YEC will argue the point that the Earth is the center of the Universe and in addition to being flat also has the sun and everything else revolve around it.

On that line of thinking, I'd like to ask what you think of plate tectonics in that regard. It isn't brought up much on these boards, but because it neatly explains how we get fossils and strata on opposite sides of the Ocean all neatly lined up (such as the shore between Africa and South America), I imagine there must be some controversy surrounding it.

So, plate tectonics, is it like the Earth being round, or closer to evolution in terms of the amount of public debate surrounding it?

[ST88]

Plate tectonics says that plates move because of mantle convection. Plates are supposed to have moved for large distances and in a fairly straight path. For example, we see the Americas moved west from the oceanic ridge and Europe/Africa moved east from the ridge. And if hotspot theory is correct, we further see that plates move in a fairly straight path (except for the bending).

So, these plates movements are not random. That is, they are not moving east for a few hundred years, then southwest for a thousand years, then north for a decade, then south for a few thousand years. They have moved in a singular direction for millions of years. Even looking at this animation shows that convection cycles must be in place for millions of years to move the continents apart. The continents are moving apart and not randomly wandering.

If convection cycles were random, we should see the plates also moving randomly. But, the evidence shows that the plates have not been moving randomly.

Why are we stuck on randomness? By the definition of physics, these things aren't random, through they may appear so. They are determined by the structure of the material and nature of the heating element. When Jose says it's a "chaotic" system, that doesn't mean the various elements shift around randomly like drunks in an English village -- they follow very specific rules about where they should go. It's just that it happens in such a way -- either very quickly or in such large quantities that we can't practicably follow them.

Assuming the movements of the plates aren't random, but are determined by specific forces of convection, what is the issue?

3) The mantle isn't molten (except in a small number of areas). In other words the mantle is usually solid. How do we know this? There are two types of seismic waves; P-waves (compressional waves) and S-waves (shear waves). P-waves travel through solids and liquids, S-waves only travel through liquids. S-waves travel through the mantle, therefore the mantle isn't liquid. The only region of the interior of the earth that is liquid is the outer core.

The point I'm trying to make? The mantle is hot, dense, generally solid, slow moving, really viscous rock.

Thank you for that clarification and that nifty example of evidence. I assume you mean S-waves only travel through solids. As I understand it, this is how we know the outer core is liquid, because S-waves can't pass through it.

[John S]

Thank you for that clarification and that nifty example of evidence. I assume you mean S-waves only travel through solids. As I understand it, this is how we know the outer core is liquid, because S-waves can't pass through it.

Yes, that's what I meant. Thanks for catching that.

[otseng]

Declination is a horizontal angle, so it'll be effected by rotation around a vertical axis (like a record spinning). If a rock forms with a declination of 60 degrees, and sometime after that is rotated 20 degrees counterclockwise, the measured declination would be 40 degrees.

The fact that the core samples are taken by rotating drills does shed some light on the problem. But, I still have some further questions on it. Does the drilling process somehow scramble the samples within a horizontal layer or does it simply rotate the entire layer? Using your record example, before the drill actually takes the sample, the declination information should be preserved. All the points on that record should point to the same direction. But, when it is sampled (and rotated), the data shows that it points to random directions, rather than simply the entire sample being rotated. Let me put it this way, suppose we have arrows drawn on the record prior to it being sampled. They should all point in the same direction. Let's suppose it's 0 degrees. Then the record is spun 90 degrees by the drilling process. All the arrows should point to 90 degrees also. But, in the core sample, they randomly point to all different angles.

The viscosity of the mantle is really high. The viscosity of the upper mantle is 10^19 to 10^21 Pascal seconds - for comparison the viscosity of water is 10^-3 PaS. That means that the mantle is at least 10^23 times more viscous than water. Something that viscous isn't going to move very quickly.

How fast would the mantle be moving?

The mantle isn't molten (except in a small number of areas). In other words the mantle is usually solid.

Like I said before, I'm learning a lot here in this thread. And all along I had been assuming that the mantle was a liquid!

Since the mantle is a solid, not a liquid, this raises some more questions. When plate tectonics refer to mantle convection, how can convection apply to a solid? As I understand solids, it does not "flow" as we understand liquids. If the mantle is a solid, and the plates are solids (obviously), then what causes the distinction between the mantle being moved by convection (heat) and the plates being moved by physical pressure?

Using a technique called siesmic tomography it's possible to figure out where areas that are slower than average (hotter) (shown in red on most tomographic images) and faster than average (colder) (shown in blue) in the mantle.

I can understand it showing temperature differences, but how does temperature differences show movement? In particular when we are talking about solids?

Why are we stuck on randomness? By the definition of physics, these things aren't random, through they may appear so. They are determined by the structure of the material and nature of the heating element. When Jose says it's a "chaotic" system, that doesn't mean the various elements shift around randomly like drunks in an English village -- they follow very specific rules about where they should go. It's just that it happens in such a way -- either very quickly or in such large quantities that we can't practicably follow them.

What are the definition of physics that are being applied to make it not appear random? What are the rules that determine the nonrandom behavior of mantle convection cycles?

[Jose]

Thanks for more great images, John!

Just for laughs, I amused myself just now by asking how long it might take to "stir" the mantle, if by analogy with boiling water, there was simple convection--if viscosity happened by accident to relate more or less linearly with speed of flow. It wouldn't be linear, of course, so this is an extremely goofy calculation. Even so, with a difference in viscosity of some 23 orders of magnitude, it comes out in the range of 10 e10 years. I'm probably off by a wee bit, but the point is that really slow movement can still be chaotic, even if it takes a hundred million years (a mere 10 e5) for a convection cell to go "bloop" and change direction.

I also spent some time in our geology library the other day. Among other things, one of the books on tectonics that I browsed through listed at least a dozen forces that may contribute in one way or another to plate movement.

Given the complexity of the system, it shouldn't be a surprise that plates change direction from time to time. Given the viscosity of the mantle, it shouldn't be a surprise that they do so slowly. We have an unfortunate vantage point from which to watch, each of our lives being geologically instantaneous, as it were.

[ST88]

Why are we stuck on randomness? By the definition of physics, these things aren't random, through they may appear so. They are determined by the structure of the material and nature of the heating element. When Jose says it's a "chaotic" system, that doesn't mean the various elements shift around randomly like drunks in an English village -- they follow very specific rules about where they should go. It's just that it happens in such a way -- either very quickly or in such large quantities that we can't practicably follow them.

What are the definition of physics that are being applied to make it not appear random? What are the rules that determine the nonrandom behavior of mantle convection cycles?

As I understand it, an object will behave according to its intrinsic properties and the forces that are applied to it. If true, then actual randomness is not possible, because everything is just behaving as it oughta and reacting to everything else. Chaos theory (or Complexity, I forget which) says, among other things, that systems appear random because it is impossible to know all variables in any given situation. I think plate movement is covered by this. Judging by the graphics presented in this thread, I would guess that mantle convection is governed by the the initial state of the Earth upon its creation, the movement of the core, the amount of material being sucked down into the mantle (and the type of material), and the material makeup of the mantle. Since materials behave according to their own intrinsic properties and according to the forces that act upon them, we would expect this material to behave in a manner that would be predictable if we knew what the heck was really going on down there.

[otseng]

Since this thread seems to be subducting due to lack of activity, I thought I would offer my closing arguments now before this thread gets too buried. Of course, this post could stimulate more discussion on the topic, but at least this post would serve as a synopsis of my posts so far of my critique of plate tectonics.

My first argument against plate tectonics is the lack of evidence of folding or faulting in the geologic record.

First, let's look at one typical illustration of how supposedly the plates moved - Color coded continents.

That is a lot of geological movement over a period 620 million years. Entire continents have moved over a vast amount of distance. One would expect that geological changes of such magnitude would have evidence of it in the rock record through folds or faults or any other evidence of rock movement. That is, one would expect that each layer in which the plates have moved would exhibit some evidence of earth movement. However, rather than this being the rule, it is by far the exception. Stratas are all generally parallel to each other with little to no evidence of any faults or folds between each successive layer.

If entire continents have been moving over a period of over 600 million years up to now, why are sedimentary layers for each time period parallel to each other with little evidence of any faulting or folding?

http://www.debatingchristianity.com/for ... 0082#20082

Also, I argued that evidence for folding/faulting in "old" stratas should at least be on the order of 600:1 as compared to "modern" stratas.

The evidence that I requested were photos that would conform to the following diagrams:





Since photos could not be presented, various explanation were offered to explain the absence of such evidence. One explanation is that top layers conformed to the bottom layers. Another explanation is that new faults would happen at the exact same spot as old faults. However, such explanations lacked any evidence or rationale to support them.

One would also expect this diagram to be quite common:


And again, nobody has been able to present very many photos to illustrate my diagrams.

Another argument that plate tectonics has problems is that the ridges do not extend all the way to the continents. No satisfactory answer has been given to address this.

I argued that if magma was coming out of the ridges, it should come out radially and not form straight lines. Yet, all the ridges have quite distinct lines.

The areas on earth where rock collisions are occurring would be at the subduction zones. I argued that sediment residue from these areas should be evident from the rocks colliding with one another. It was conveniently answered that it gets all subducted away.

Subduction is also explained by the "heavier" continental plate going under the "lighter" oceanic plate. Yet, there is also supposedly subduction going on at the Himalayas (which is obviously not under water).

We also looked at the GPS map of continental movement and do notice that the continents are moving. However, the vectors of the movement do not correlate with the plate tectonics theory.

Based on the GPS data, I come to the conclusion that it does not correlate to ridge growth based on the following:

As you stated, the "North America is rotating about a point somewhere near the Yucutan Peninsula". This movement would indicate that it did not move due west from the mid-Atlantic ridge.

South America is generally moving north from GPS data. So, this is in contrast to it having moved due west.

Europe and Africa are moving northeast. Yet the coast of Europe/Africa matches the mid-Atlantic ridge only if it moved due east.

Also, I have pointed out that the velocities of the continental movement does not match the rate of growth of the ridges in several places.

http://www.debatingchristianity.com/for ... 0549#20549

I argued that "the continent moved due west from the ridge to its current position. Then at its current position, it moves differently as depicted by the GPS measurements. But, the problem with plate tectonics is that it doesn't explain why this change occurred. Why would it move due west to its current position, then "abruptly" change?" And no satisfactory answer was given for this question.

I also asked what causes the plates to move. It has been answered that molten rock moves by convection in the mantle and moves the plates.

It is necessary to picture more than just the rocks themselves. They are floating on the earth's mantle, essentially a magma pool. It's liquid (from the heat of compression and radioactive decay). The continents are the light elements forming a "scum" on this liquid gloop. It's a pretty thick liquid, so it doesn't move very fast, and things don't happen on the time scale that they do in, say, a saucepan in which we might be making a consumme--but the principles are similar. So, the densities of different rock strata are not the issue, but the average density of the whole conglomerate of layers, relative to the density of the mantle.

http://www.debatingchristianity.com/for ... 0303#20303

Convection in the atmosphere causes clouds to move. Cool air sinks, displacing warmer air, causing a convection pattern. The same applies to the asthenosphere. Cooler molten rock (nearer the surface) sinks, displacing the molten rock which had been warming nearer the core. That warmer molten rock rises, then becomes relatively cool as it nears the surface. The resulting convection currents carry the lithospheric plates with them, like a conveyor belt.

http://www.debatingchristianity.com/for ... 0333#20333

But, it turns out that the mantle is not a liquid, but a solid.

The mantle isn't molten (except in a small number of areas). In other words the mantle is usually solid.

http://www.debatingchristianity.com/for ... 1732#21732

So, there is then no mechanism left for the plates to move large distances required by plate tectonics since the mantle is a solid.

We also explored some core analysis and looked at the magnetic data in the samples. I brought up the fact that declination information demonstrates totally random magnetic bearings. And so far, no answer has been given to account for this.

Then by only using the inclination data, it is inferred that magnetic polarity reversals have occurred many times over the history of the earth. And nobody has been able to explain how this can happen. One computer model has been presented to illustrate the dynamo theory, but even that is inconclusive.

Also I brought up some questions if the earth's magnetic field has indeed reversed itself in the past.

Where is the energy coming from to increase the magnetic field? Why is it oscillating? Has the magnetic field intensity ever been zero? Would not magnetic polarity reversals screw up migratory animals? How can they adapt to such changes?

http://www.debatingchristianity.com/for ... 0986#20986

I have also offered this request, "I guess what I'm waiting for is a coherent model to explain what has been presented so far in regards to the continental movement (GPS measurements), ridge growth, ridge lines, and the shape of the continents." But, so far, this has remained unanswered.

I have also asked "if anyone can produce a diagram showing how mantle convections are operating on a global scale. All the diagrams I've seen are a cross-sectional illustration just to give the concept. But I have not seen a global top-view model to illustrate the convection cycles relative to all the convergent and divergent boundaries." And again, nothing has been produced.

In this thread, we have probably only scratched the surface of the theory of plate tectonics. And there is most likely more we can discuss and learn. But, based on the discussions so far, plate tectonics seems to me full of inconsistencies and lacking in support.

In conclusion, can the theory of plate tectonics be "Pure fact, just like the Earth goes around the Sun"? Or can it be "Almost nailed down, think gravity (we know it happens, but not everything about it)"? I would submit it hardly approaches these two. A more accurate description would be, "Unstable, this will be gone as soon as we figure out what's really happening".

[Jose]

Since this thread seems to be subducting due to lack of activity, I thought I would offer my closing arguments now before this thread gets too buried. Of course, this post could stimulate more discussion on the topic, but at least this post would serve as a synopsis of my posts so far of my critique of plate tectonics.

The thread does seem to be subducting, doesn't it? I'll give it a tickle here...

My first argument against plate tectonics is the lack of evidence of folding or faulting in the geologic record.

I don't understand what you are saying here. There's lots of folding and faulting. But, since we've been showing each other the same pictures to make our opposite points, it seems that there must be something different about how we see the data, and what we infer from it.

First, let's look at one typical illustration of how supposedly the plates moved - Color coded continents.

That is a lot of geological movement over a period 620 million years. Entire continents have moved over a vast amount of distance. One would expect that geological changes of such magnitude would have evidence of it in the rock record through folds or faults or any other evidence of rock movement. That is, one would expect that each layer in which the plates have moved would exhibit some evidence of earth movement. However, rather than this being the rule, it is by far the exception. Stratas are all generally parallel to each other with little to no evidence of any faults or folds between each successive layer.

If entire continents have been moving over a period of over 600 million years up to now, why are sedimentary layers for each time period parallel to each other with little evidence of any faulting or folding?

http://www.debatingchristianity.com/for ... 0082#20082

Well, this quote misrepresents the findings. If we go back a few pages, we can look at the sonograms that show us lots of folding and faulting in the subduction zones. If we actually look at the world, we find that it is very hard not to find evidence of earth movement--especially in California. There are faults all over the place. BUT, of course, most of the activity is on the edges of the plates--so it's kinda sneaky to say that you don't see lots of folding and faulting, and then point to the centers of the plates. This is picking-and-choosing the data you like from the total data set. I'm not suggesting that you have done this, but rather that the Flood Geologists who have summarized the arguments do so. It's hard for any of us, not being experts, to dig up the raw data and analyze it, so we pay attention to people who can do so...or who claim to be able to do so.

How do geologists come up with those maps of where the continents were at different times in the past? It's from looking at all of the data from folding and faulting, from magnetic reversal data, from rock types and fossil assemblages, etc. To state that there's no evidence of movement is to ignore the data.

For the layers being parallel, we have all agreed (I thought) that no matter what model we use for sediment deposition under the force of gravity, strata should be parallel. When they are folded and tilted, they tend to be folded and tilted in large blocks, with the layers folding and tilting in parallel. This is what we see, and it is what we expect no matter what model we follow.

Perhaps the expectation that strata should not be parallel is from the image of strata tilting or folding, and then having new strata deposited on them. In general, we don't expect this (again, by either model), because strata are generally deposited through water, and tilted/folded after uplift above sea level. Look at the map of sea floor sediment thickness...those sediments are the ones that are now forming rock strata horizontally, and that are likely to be uplifted and folded/faulted in the future.

Also, I argued that evidence for folding/faulting in "old" stratas should at least be on the order of 600:1 as compared to "modern" stratas.

You'll have to remind me why this should be the case. We expect folding/faulting on the edges of continental plates, and much less in their centers, which is what we see. There are folds and faults in precambrian rock in places where it should be, and there are "recent" rocks that show little folding/faulting, exactly as predicted by tectonics. We can also look at old vs new mountain ranges--the Appalachians vs the Sierras--and we see that the older ones are much more convoluted.

The evidence that I requested were photos that would conform to the following diagrams:





Since photos could not be presented, various explanation were offered to explain the absence of such evidence. One explanation is that top layers conformed to the bottom layers. Another explanation is that new faults would happen at the exact same spot as old faults. However, such explanations lacked any evidence or rationale to support them.

I think this is a bit of an oversimplification. There are many photos of faults with slips covering many strata, as in your second figure above. There are also photos of erosional surfaces that have been filled in (your first figure), such as the nonconformity in the Grand Canyon. These things really do exist (even if the most illustrative examples are not easy to find on the web).

One reason that examples are not shown everywhere is that science gives points for being the first to describe something. After that principle has been fully demonstrated, no one gets points for showing more examples. It's really hard to publish things that merely confirm what's already in the literature. So, additional examples will typically be listed in geological field trip road logs ("stop at mile 12.4 and note the XXX in the roadcut on your left").

One would also expect this diagram to be quite common:


And again, nobody has been able to present very many photos to illustrate my diagrams.

Again, the photo of the Grand Canyon shows exactly this. As it turns out, this and your first figure above are really the same thing, just with thicker or thinner strata filling in the eroded bits. So, photos were presented.

But consider what it would require to create such depositional features. First, the lower strata must be deposited (typically offshore). Next, the strata must lurk there long enough to be compacted into rock, and then they must be uplifted to allow erosion. After a period of erosion, these strata must again be submerged below sea level so that additional sediment can settle on them. (Or, volcanic ash can settle on them, creating terrestrial deposits like the Morrison).

Places where this sort of thing is evident are places where creationists complain that "part of the geological column is missing." They use this as evidence that geologists are making up the idea that there even is a geological column. (They don't mention the dozen or so places where the entire column does exist, such as western North Dakota). These are the unconformities we hear about--like the Great Unconformity in the Grand Canyon. This is exactly what you've asked to see--folded and faulted old rocks, with new layers deposited on top.

Another argument that plate tectonics has problems is that the ridges do not extend all the way to the continents. No satisfactory answer has been given to address this.

The last paper I looked up on this in the geology library indicated that the big bulge in the ridge itself (ie, what makes it a "ridge" rather than just a fissure) is from the heat itself. Think of a thermometer, in which the liquid expands with temperature. Rock does the same thing. So, Where it's hottest at the fissure, it's expanded the most. As it spreads farther from the heat, it shrinks. I'm not sure this is adequate, but it's what they said. I also imagine that there's some collapse of the cracks and fissures through which the water swirls, to create the black smokers and such. Is there also erosion? Probably.

Still, the particular shape of the ridge is not reason to discount the fact that magma spills from it, and causes the spreading of the ocean floor, and that the continents move away from these spreading centers.

I argued that if magma was coming out of the ridges, it should come out radially and not form straight lines. Yet, all the ridges have quite distinct lines.

Again, we addressed this. You can have spokes radiating out from a point source, but from a linear source, the spokes must radiate perpendicularly.

The areas on earth where rock collisions are occurring would be at the subduction zones. I argued that sediment residue from these areas should be evident from the rocks colliding with one another. It was conveniently answered that it gets all subducted away.

That's partly because it does get subducted away. However, those sonograms I mentioned above were images of sediment in the subduction zones. Your expectation is met, but with the complexity that much of the seafloor is subducted, and provides the magma to create volcanoes. This is one of the amazing things about plate tectonics--it not only explains the movements of the continents, but also the origins of the volcanoes around, say, the Ring of Fire. If we take away subduction and say it doesn't exist, then we have to cobble together some other explanation for the Ring of Fire (and, of course, the remarkable coincidence of earthquakes and plate boundaries...or non-plate non-boundaries, if plates don't exist).

This raises an important point: in order to demonstrate that a particular scientific model is incorrect, it is necessary to address the features of that model. In this case, the model states that the sediment in the trenches gets subducted as the ocean floor is subducted. Therefore, it is not an argument against the model to say that an expectation at variance with the model is not met. Rather, one must show that expectations based on the model are not met.

This is the fundamental criticism with ID. It pretends to prove that evolution is impossible, but it chooses to criticize a fake model of evolution. It rules out that fake model quite well--but it does not address the real model at all.

Subduction is also explained by the "heavier" continental plate going under the "lighter" oceanic plate. [the other way to, really, but that's ok--JB] Yet, there is also supposedly subduction going on at the Himalayas (which is obviously not under water).

Well, if two continental plates collide, something has to happen. This creates folding and faulting. The Himalaya show folding and faulting. Needless to say, if two plates collide, there's no good reason to expect that neither one could ever ride up over the other. If one's more dense, fine. If they're similar, then there's still the possibility for one to go over the other--just as cars tend to slip over and under each other when tail-gating idiots drive too fast in the fog and end up in a pile-up.

We also looked at the GPS map of continental movement and do notice that the continents are moving. However, the vectors of the movement do not correlate with the plate tectonics theory.

Actually, they do correlate. We discussed the inherent awkwardness of creating a 2D projection of a 3D spherical surface, and of the convention of assigning Antarctica the role of being the point of reference against which the other vectors are measured. Furthermore, the vectors are of the surface rock, not necessarily of the subducted rock--which is something that became very clear to me in studying the vectors of the LA basin. It's clearly crumbling as Baja rips off. The vectors show it.

Based on the GPS data, I come to the conclusion that it does not correlate to ridge growth based on the following:

As you stated, the "North America is rotating about a point somewhere near the Yucutan Peninsula". This movement would indicate that it did not move due west from the mid-Atlantic ridge.

This logic is equivalent to saying that because I am sitting at my computer right now, I didn't take the dog for a walk this morning. Current movement does not necessarily match previous movement. Rather, current movement forces us to conclude that the continents move. If we must decide between plate tectonics and the Hydroplate Hypothesis for an explanation of their movement, then we must choose tectonics. The Hydroplate idea says that the force for movement was the opening of the fissures--so movement should have stopped, as there is no longer any force that could keep them moving.

South America is generally moving north from GPS data. So, this is in contrast to it having moved due west.

And last week I drove east on I40, in contrast to having previously driven west. Plate tectonics does not posit that continents may only move in one direction forever, and that directions may never change.

Europe and Africa are moving northeast. Yet the coast of Europe/Africa matches the mid-Atlantic ridge only if it moved due east.

This is partly a problem of a 2D representation of 3D data. Draw correct lines of longitude and latitude on the map, and it won't look like that. Furthermore, these continents need only move east/west with respect to each other to create what we observe; their direction relative to Antarctica is due to forces besides the mid-Atlantic ridge.

Also, I have pointed out that the velocities of the continental movement does not match the rate of growth of the ridges in several places.
http://www.debatingchristianity.com/for ... 0549#20549

According to C. Lithgow-Bertelloni at U Mich., the Mid Atlantic ridge is spreading with a rate of 1-5 cm/year. The variation probably depends on where (and probably when) you make the measurements. The 1.8cm/year that was measured at DUBO is within this range. Part of the imperfect match is the roundness of the earth, so that material that moves due-east of due-west has very different amounts of stuff to push out of the way if it is at the equator or near the poles. It it's also moving north at the same time, then there are additional complications to working out the expected rates. I would be wary of basing any conclusions on this comparison until you've plotted them on a spherical earth and made sure that you have worked out the relative vectors of the specific sites of comparison.

I argued that "the continent moved due west from the ridge to its current position. Then at its current position, it moves differently as depicted by the GPS measurements. But, the problem with plate tectonics is that it doesn't explain why this change occurred. Why would it move due west to its current position, then "abruptly" change?" And no satisfactory answer was given for this question.

Plate tectonics does explain why this change occurred, albeit in an unsatisfactory way: "the forces acting on the plate changed." (That's my phrasing, which is a lot like saying "it couldn't help it"). We would like to know what all of the forces are. We'd like to know why they changed. The data indicate that this did, indeed, happen. Geologists need more data to formulate adequate explanations of the mechanistic details.

I imagine that this type of thing is a problem for people who want answers that are Really Truly True, comparable to the certainty that religion claims to offer. It's certainly a difficulty for students. We have only the data we've collected so far. We interpret those data to the best of our ability. the interpretations give us direction for further investigation. Do we not know the mechanism in detail? That's right...so we know that we should investigate potential forces, and try to disentangle their relative contributions. But, before we can do that, we have to reconstruct the past movements so that we know what force changes to look for, and when they seem to have happened. We're left with a model that retains some uncertainty, but despite that, offers a remarkably good explanation of vast numbers of observations. If you want certainty you'll have to wait a while.

I also asked what causes the plates to move. It has been answered that molten rock moves by convection in the mantle and moves the plates.

It is necessary to picture more than just the rocks themselves. They are floating on the earth's mantle, essentially a magma pool. It's liquid (from the heat of compression and radioactive decay). The continents are the light elements forming a "scum" on this liquid gloop. It's a pretty thick liquid, so it doesn't move very fast, and things don't happen on the time scale that they do in, say, a saucepan in which we might be making a consumme--but the principles are similar. So, the densities of different rock strata are not the issue, but the average density of the whole conglomerate of layers, relative to the density of the mantle.

http://www.debatingchristianity.com/for ... 0303#20303

Convection in the atmosphere causes clouds to move. Cool air sinks, displacing warmer air, causing a convection pattern. The same applies to the asthenosphere. Cooler molten rock (nearer the surface) sinks, displacing the molten rock which had been warming nearer the core. That warmer molten rock rises, then becomes relatively cool as it nears the surface. The resulting convection currents carry the lithospheric plates with them, like a conveyor belt.

http://www.debatingchristianity.com/for ... 0333#20333

But, it turns out that the mantle is not a liquid, but a solid.

The mantle isn't molten (except in a small number of areas). In other words the mantle is usually solid.

http://www.debatingchristianity.com/for ... 1732#21732

So, there is then no mechanism left for the plates to move large distances required by plate tectonics since the mantle is a solid.

It isn't quite fair to dismiss the convection analogies as irrlelevant based on the fact that the viscosity of the mantle is much greater. The difference in viscosities merely affects the timescales. We already know that "solid" rock can move, from the folded strata that are so evident in many places on earth (and, as I noted, we've been showing each other). The fact that folded strata exist doesn't prove that they had to fold when still mud, or that solid rock can fold. Rather, it proves that there have been conditions on earth in which seemingly-solid rock can fold--and that those conditions are not those of the surface world in which we live. Both calculations and measurements indicate that heat and pressure deep within the earth are sufficient to produce these conditions. Thus, there is no reason to reject movement within the mantle based on common sense and common experience. Based on our understanding of the mantle, however, movement (albeit slow) is perfectly reasonable.

We also explored some core analysis and looked at the magnetic data in the samples. I brought up the fact that declination information demonstrates totally random magnetic bearings. And so far, no answer has been given to account for this.

Then by only using the inclination data, it is inferred that magnetic polarity reversals have occurred many times over the history of the earth. And nobody has been able to explain how this can happen. One computer model has been presented to illustrate the dynamo theory, but even that is inconclusive.

Also I brought up some questions if the earth's magnetic field has indeed reversed itself in the past.

Where is the energy coming from to increase the magnetic field? Why is it oscillating? Has the magnetic field intensity ever been zero? Would not magnetic polarity reversals screw up migratory animals? How can they adapt to such changes?

http://www.debatingchristianity.com/for ... 0986#20986

This is similar to several of your comments above. We don't know the detailed mechanism, so it seems implausible. As scientists, we work the other way around. What are the observations? What can account for these observations? What mechanism can we envision for this? Can we obtain data to confirm or reject that mechanism, and to stregthen our understanding? The fact is that magnetic variations exist in depostions of different ages. Deposits of a particular age show the same magnetic features. So, some kind of world-wide event occurred to change the magnetic properties of the earth's field. This inference is very hard to avoid. We're left with figuring out the mechanism. Again, there's uncertainty: "gosh, it looks like the magnetic field reverses from time to time...I wonder how?" If we're uncomfortable with such uncertainty, we tend not to become scientists. Scientists must live with uncertainty as a fact of life.

Certainly, there are bound to be implications of field reversals--such as the effects on migratory animals. However, that's irrelevant--the earth's field doesn't know about animals and doesn't care. If there were a deity in charge, and the deity cared about the animals, he would either not allow the field changes or he would help the animals through the field reversals. It's fine to posit the latter, but it's also fine to say "well, we just don't know of any data that suggest the field cares about the animals, so we'll have to conclude for now that the animals had to put up with it." I don't know of any data that correlate extinctions with magnetic field reversals, but I wouldn't be surprised if some species have been wiped out when this has happened. The ones that weren't wiped out are the ones with the adaptations that enabled them to survive.

I have also offered this request, "I guess what I'm waiting for is a coherent model to explain what has been presented so far in regards to the continental movement (GPS measurements), ridge growth, ridge lines, and the shape of the continents." But, so far, this has remained unanswered.

This will sound silly to you, but it seems to me that we have presented this model in all its glory: it's called plate tectonics. There are lots of data supporting it. There are some mechanistic details that remain to be worked out. Still, the fact that we don't know all of the mechanistic details does not make tectonic movements impossible.

I have also asked "if anyone can produce a diagram showing how mantle convections are operating on a global scale. All the diagrams I've seen are a cross-sectional illustration just to give the concept. But I have not seen a global top-view model to illustrate the convection cycles relative to all the convergent and divergent boundaries." And again, nothing has been produced.

It is true that nothing has been produced here. John had mentioned a figure in a book that he might scan for us, but we're still waiting. I suggest that the lack of such an illustration, particularly on the tectonics websites, reflects more of that uncertainty of which science is replete. It's hard to measure mantle movement. It's hard to get a good image of just what the mantle is really like, for that matter. Convection models make sense, and the typical approach is to illustrate the principle with the sorts of diagrams to which you refer. But, and accurate map of global mantle movements may be beyond us still.

As (I think) I mentioned earlier, there are a number of possible forces for plate movement that are contending for major and minor roles in the overall story of plate tectonics. This suggests to me that the mechanisms driving movement and direction (and change of direction) remain uncertain. The evidence for movement is clear enough, and the "footprints" of past movements are also clear enough. We pretty much have to accept movement as a fact of life. But as for mechanisms, there remains uncertainty.

In this thread, we have probably only scratched the surface of the theory of plate tectonics. And there is most likely more we can discuss and learn. But, based on the discussions so far, plate tectonics seems to me full of inconsistencies and lacking in support.

To which I reply, "pfffft!" or maybe "Balderdash!" The support is there, and the inconsistencies go away upon closer scrutiny (ie, looking below the surface). I think that enough is known to say that the parts that you find unsatisfying are primarily those for which there remains uncertainty as to mechanism. Uncertainty is tough. The ID folks deal with it by saying "if there's uncertainty, we'll conclude God did it." I deal with it by saying "I don't know...yet." I assume that people will keep studying it, and eventually come up with satisfactory explanations. But, like evolution, the "fuzzy bits" deal with details of the mechanism, and instances in which mechanisms in one region differ from the mechanisms in another region. They do not deal with the overall theory, which enjoys tremendous support, and which offers tremendous explanatory power.

In conclusion, can the theory of plate tectonics be "Pure fact, just like the Earth goes around the Sun"? Or can it be "Almost nailed down, think gravity (we know it happens, but not everything about it)"? I would submit it hardly approaches these two. A more accurate description would be, "Unstable, this will be gone as soon as we figure out what's really happening".

As you might surmise, I disagree. There is simply too much evidence, too much predictive value, too much explanatory power for it to be likely to disappear soon. On the other hand, it may well disappear from science classrooms as the Christian Taliban change the laws and force theology into the schools. Even so, insisting that scientific findings not be taught, whether tectonics or evolution, or that theistic explanations be taught in their place, will not make these things go away. The plates will still move, and life will continue to evolve.