Real Science Radio: Plate Tectonics. Not.

[Stripe]

If you want to point out something in particular from your show that you think is good evidence, I would be happy to go over it with you, although I won't have internet this weekend so keep that in mind.

I think all 16 points are pretty good. Take your pick.

 

[gcthomas]

I think all 16 points are pretty good. Take your pick.

One by one...

1. A subducting plate would experience too much resistance in diving down through just the top of the mantle. The blunt front end alone would stop movement. Also, the unspecified force needed to overcome these resistances would (if a pushing force) crush the plate or (if a pulling force) pull the plate apart.

The mantle is semi-fluid and can sustain convection currents, and the presence of water lowers the melting point. With the low speeds, the mechanical strength of the plates is sufficient.

 

[gcthomas]

2. Sediments, volcanoes, and plateaus have not been scraped off “subducting” plates in trenches.

3. Sedimentary layers in trenches are undisturbed. These layers would be mangled if plates subducted.

See here at Wikipedia, Accretionary Wedge page.

"Accretionary wedges and accreted terranes are not equivalent to tectonic plates, but rather are associated with tectonic plates and accrete as a result of tectonic collision. Materials incorporated in accretionary wedges include:
Ocean-floor basalts – typically seamounts scraped off the subducting plate, [etc]"

 

[gcthomas]

4. No known forces are available to break the crust into plates and separate those plates from their bases.

Except for mantle convection and asteroid impacts, no. None at all.

 

[gcthomas]

5. One plate cannot even begin its dive under an adjacent plate that is 30–60 miles thick, because, as Figure 93 on page 169 shows, long cliffs would be 30–60 miles high—an impossible condition.32

The Marianas Trench is ~11 km deep. Then there is the sediment filling up much of the rest. The long cliffs exist, rendered less vertical by erosion of the edges. The passage suggests that high cliffs will collapse: this would just produce the profile of the continental plate margins we actually see.

 

[Stripe]

The mantle is semi-fluid and can sustain convection currents

No, it can't. And even if it could, there's nowhere near enough energy to drag the crust of the Earth into the far denser mantle.

With the low speeds, the mechanical strength of the plates is sufficient.

Time is not a factor. Rock will shatter or break upon the application of enough force regardless of how quickly that force is applied.

 

[gcthomas]

6. Subduction cannot occur along an arc. Subduction is geometrically possible only along a straight line. (The arc-and-cusp pattern of ocean trenches shows subsidence, not subduction.)

That is only true for materials that cannot deform plastically. Even steel can be folded along curved lines - just look at your car body.

 

[gcthomas]

7. Most volcanoes are on the wrong side of trenches if subducting plates produce volcanoes.

There is more than one subduction region in the western Pacific (look up the Fiji Plate) so the will, obviously, volcanoes that are on the correct side for one zone and the wrong side for the unrelated subduction zone.

 

[gcthomas]

8. Below trenches are mass deficiencies, not mass excesses as subduction would produce.

The gravity anomaly is measured 'above' the trench, and is largely due to the depression of the plate by the downward forces of the continental plate on top of it. As the mass is pushed down, it produces the reduced gravity as measured above the sea.

 

[gcthomas]

9. Beneath trenches, earthquakes sometimes occur across a much broader region than the width of a plate.

Is this a problem or important?

 

[gcthomas]

10. Seismic tomography has not shown unambiguous subducted plates in even two dimensions. If plates subducted, seismic tomography could convincingly and dramatically show them in three dimensions.

Try here for research that shows such convincing data: http://eri-ndc.eri.u-tokyo.ac.jp/jp/ohrc/ken1/global/slab/stagnant/index.html

 

[gcthomas]

No, it can't. And even if it could, there's nowhere near enough energy to drag the crust of the Earth into the far denser mantle.

As the basalt descends gravity is enough to pull the slab down further. Do you have an energy calculation to hand to illustrate your claim? I predict you will ignore this question.

Time is not a factor. Rock will shatter or break upon the application of enough force regardless of how quickly that force is applied.

Strain rate is a major factor in material behaviour, and I have already shown how rocks become more plastic (deformable) when under extreme pressures.

 

[Daedalean's_Sun]

I think all 16 points are pretty good. Take your pick.

Stretched Oceanic Ridges. The topography along oceanic ridges is best explained by stretching the ocean floors in two perpendicular directions. How could that happen? HP: [Hydroplate Theory suggests] As the Atlantic floor and Mid-Oceanic Ridge rose, they stretched in all directions, for the same reason an expanding balloon stretches in all directions. PT: Plate tectonics describes this stretching as seafloor spreading—movement of the ocean floor away from the ridge.

Here is a topographic render of the Atlantic Ocean basin:

Does it look more like expansion-driven stretching? The wrinkle-like ridges being highly concentrated around these oceanic ridges is consistent with seafloor spreading. However one would not think that stretching would result in "wrinkling" at these ridges.


Here is the "wrinkling" effect explained by Plate Tectonics:

Spoiler

It's the build-up of escaped magma.

Also we see from experiments that the seafloor closer to the ridges consistently return back a younger age for the seabed, which is exactly what we would expect if Seafloor spreading were true.

Here are two other effects explained by Seafloor spreading:


Magnetic reversal strips along Oceanic ridges

The Zig-zag Transform Faults:

Discovery, prediction and cause of transform faults


SUMMARY: Seafloor spreading effectively explains the "wrinkling" of the oceanic plate, age measurements of the seafloor, Magnetic reversal strips found along ridges, and the Zig-zagging of transform Faults that we see from the topographic render.

 

[Stripe]

As the basalt descends gravity is enough to pull the slab down further.

Well, that's not a convection current, is it?

Do you have an energy calculation to hand to illustrate your claim?

Nope, a physical property of rock within the Earth called the crossover depth.

Strain rate is a major factor in material behaviour, and I have already shown how rocks become more plastic (deformable) when under extreme pressures.

Irrelevant. Whatever the environment, the same amount of energy is always required to break a rock regardless of how long it takes to apply that energy.

 

[gcthomas]

Well, that's not a convection current, is it?

Er, no of course. The convection is in the mantle and there is friction between that and the plate. A big driver is gravity acting on the descending plate.

Nope, a physical property of rock within the Earth called the crossover depth.

According to http://www.creationscience.com/onlinebook/Trenches3.html#wp12281668 (crossover depth is a term used exclusively by creationists) the term is applied to circulating 'magma' or melted rock. The descending slab is solid, so your comment is irrelevant.

Irrelevant. Whatever the environment, the same amount of energy is always required to break a rock regardless of how long it takes to apply that energy.

Do you know what strain rate is? Try this paper:

Effect Of Strain Rate On A Set Of Fractures
Authors H. Wu and D.D. Polllard, Stanford University

INTRODUCTION
In general, the fracture toughness of brittle materials increases with decreasing loading (strain) rate [ 1 ]. That is why a low rate produces fewer and shorter fractures. Some mechanical properties of a rock such as Young's modulus and compressive strength depend strongly on strain rate, thus fracture propagation in the rock is affected [2]. Laboratory experiments of rock samples show that elastic moduli, as well as fracture parameters, are functions of strain rate [3, 4, 5]. Natural fractures indicate the significant influence of strain rate [6]. In brittle rocks fracture growth can occur at velocities ranging over many orders of magnitude due to the change of strain rate and this results in different fracture patterns and geometries.

 

[Daedalean's_Sun]

Let's not forget Slab Pull, and Ridge Push either.

 

[Stripe]

Er, no of course. The convection is in the mantle and there is friction between that and the plate. A big driver is gravity acting on the descending plate.

We were talking about convection. Try to stay on topic. :up:

According to http://www.creationscience.com/onlinebook/Trenches3.html#wp12281668 (crossover depth is a term used exclusively by creationists) the term is applied to circulating 'magma' or melted rock. The descending slab is solid, so your comment is irrelevant.

1. We were talking about convection currents, which is why I brought it up.
2. Who cares who invented and uses the term.

Do you know what strain rate is? Try this paper:

Does it change the amount of energy required before a rock will fracture or, as I read it, just the pattern of fracturing?

 

[gcthomas]

We were talking about convection. Try to stay on topic. :up:


1. We were talking about convection currents, which is why I brought it up.
2. Who cares who invented and uses the term.

Does it change the amount of energy required before a rock will fracture or, as I read it, just the pattern of fracturing?

Lies again. Oh dear. YOU changed the discussion from one where we were talking about the ability of rocks to fold without fracturing, to an irrelevant one about fracture energies (which are measured using a very hi strain rate to force a fracture: take a small sample of rock, hold at both ends and strike with a sharp edge in the middle, see how much energy is used to make the fracture)

Crossover depth: either use the term correctly or don't use it at all. Simple.

Pattern of fractures? Yes, the fractures become very small, or nonexistent, which allows the bulk of the rock to deform plastically. As I said, the deformation of rock is strain rate dependant, even though you denied it out of hand.

You are out of your depth, and you crack me up! (geddit?)

 

[Stripe]

Lies again. Oh dear. YOU changed the discussion from one where we were talking about the ability of rocks to fold without fracturing, to an irrelevant one about fracture energies (which are measured using a very hi strain rate to force a fracture: take a small sample of rock, hold at both ends and strike with a sharp edge in the middle, see how much energy is used to make the fracture)

:dizzy:

Crossover depth: either use the term correctly or don't use it at all. Simple.

:AMR:

Pattern of fractures? Yes, the fractures become very small, or nonexistent, which allows the bulk of the rock to deform plastically. As I said, the deformation of rock is strain rate dependant, even though you denied it out of hand.

Non-existant? I don't think your link says anything like that. Where are you getting this?

And I didn't say anything about the deformation of the rock. I spoke of the fracture of the rock. A material will break upon reaching a certain threshold of strain regardless of the rate at which the strain is applied.

Your link does say:

In general, the fracture toughness of brittle materials increases with decreasing loading (strain) rate. That is why a low rate produces fewer and shorter fractures.​

First of all, fracture toughness refers to a material that is already fractured.

I doubt any part of the study investigates what's happening where no fracture is found.

It goes on that:

Some mechanical properties of a rock such as Young's modulus and compressive strength depend strongly on strain rate, thus fracture propagation in the rock is affected.​

Young's modulus and compressive strength are only applicable before the material breaks. The strain rate might allow for different patterns of fracture because the elastic deformation is affected, but this paper seems to say nothing necessarily against what I said.

Laboratory experiments of rock samples show that elastic moduli, as well as fracture parameters, are functions of strain rate. Natural fractures indicate the significant influence of strain rate. In brittle rocks fracture growth can occur at velocities ranging over many orders of magnitude due to the change of strain rate and this results in different fracture patterns and geometries.​

I don't deny that rock can deform plasticly and that might be rate dependent. But the point at which they fracture is not.

You are out of your depth, and you crack me up! (geddit?)

:blabla:

Evolutionists love to declare victory. Just have the discussion!

 

[gcthomas]

I don't deny that rock can deform plasticly and that might be rate dependent. But the point at which they fracture is not.

The point? Do you mean the strain or the stress? Plastic deformation of the rock allows it to bend without cracking (it flows) which REDUCES the stress. The tensile stress is not the limiting factor here, but the strain (level of deformation). Plastic flow depends on both the pressure (due to depth) and the strain rate (think 'silly putty').