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Author Topic: you think, Subduction of tectonic plates uplifted Earth's mountain chains?  (Read 33140 times)

Offline dareo

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First, I am glade to expound in this forum...

You should know the answer to my question is absolutely not. Let me start, by saying...subduction of the Earth's tectonic plates do not forge the uplift of mountain chains over a course of millions years.

1. a simple or logical explanation for subduction's imprecision is the placements, or locations of Earth's mountain chains.

2. Earth's surface is a thin cooled solid, while Earth's voluminous mantle is liquid molten magma...in constant motion, as the earth rotates. 

3. We will have to ponder on the forces, which will push massive continental slabs, considering the plates only options.


Ok...lets take the opposite end of the colliding plate. If we observe the forces, which supposedly pushes the plates, or exudes the plates from inner Earth in a perfect divide (over millions of years) is this enough force to uplift a mountain chain?

But you might say...the ocean's great ridges are know illusion. And that is correct, yet...continental slabs are again, not pushed from the ocean's ridges. New surface exudes from the ridges, notwithstanding...they do not push continental plates, and certainly not, do they forge the uplift of great mountain chains, as say...Afghanistan. I read about orogeny and i cringe every-time i see it. Subducting slabs of lighter density, slowly diving into the more denser abyss of the mantle...and the result is great mountains chains throughout the Earth.

Prepare for the scrutiny "subduction" so desperately needs and deserves.
« Last Edit: 12/12/2011 23:59:13 by dharp »


 

Offline CliffordK

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Certainly when you look at the mountain chains, you will see a few different types of rock and soil.

The Cascade mountains, for example, have many volcanic mountains.

Further inland, the Rocky mountains consist of a lot of granite, which presumably was formed far below the surface, and somehow delivered up into the mountains where we see it today. 

In some places, one can find clear evidence of sedimentary rock that has apparently been raised in elevation from where it was originally deposited, or apparently flat sediment deposition is now found at an angle.

Your theory will have to explain these features.

One possible explanation is that one gets far more uplifting when continents collide.  For example, the mountains in Tibet may be due to the collision of continents.

Keep in mind that a small change on an annual basis becomes a big change when considered over thousands, or millions of years.
 

Offline dareo

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Cliffordk, I can't wait to explain to you the uplift of the Tibetan Plateau...it was not uplifted as so many believe. The continent of India ramming into the Asia continent uplifting the Himalayan Mountains...is another good speculation which makes me cringe. The current theories has to change.

Now, the vast Cascade mountains with all the volcanoes and volcanic activity, consisting of uplifted forms of sedimentary rock, granite and igneous solids, yes much of it was uplifted from deep beneath the surface, yet again...the uplift of this great mountain chain was not due to continental collisions over millions of years. Nor are the volcanoes and their histories of activity the results of continental collisions.

Throughout this vast world of ours, the largest mountain chains, regions and belts were not forged into existence from continents colliding. To collide, you would need a force of impact. To say, 'over millions of years' suggests a slow push of force. A liquid mantle may be contrary to such force...even over millions of years.

To everyone reading this article, drifting continental plates has never created mountain chains on planet Earth.

Cliffordk, to start...the Cascade Mountains were created from a cosmic impact. The Cascade Mountains are a very small segment of the greater impact. The Cascade Mountains is what I call... ancient crater upheaval. Yes, crater upheaval.
Ok, the big picture...the Rockies. The Rocky Mountains is apart of the actual crater. Yes, we are talking enormous.

From this impact, sediment from below the surface could be anywhere; including in the mountains.

Lets discuss even further Cliffordk.

« Last Edit: 13/12/2011 00:01:07 by dharp »
 

Offline CliffordK

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Certainly there is more to it that just density.

While the core of the earth is likely more dense than the crust....

Rocks are generally denser than water, so one would expect a uniform crust of rock covered with a mile or so deep ocean water, around the entire world.  Clearly this isn't the case with the continents. 

I have seen it pointed out that a mile or two of the outer layers of Earth's crust is pretty insignificant when considering the 7926 mile diameter Earth.

Anyway, I eagerly await your alternative explanation of why we find granite and metamorphic rock high up in some mountains.
 

Post by rosy click to view.

Offline rosy

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I've deleted this post and the reply to it, since they related to forum housekeeping and not relevant to the subject under discussion in the thread.
« Last Edit: 13/12/2011 10:53:51 by rosy »
 

Offline CliffordK

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Ok, I think we got off a bit on the wrong foot here.  Let's try to get back onto the topic.

I suppose the idea of continental plates that are difficult or impossible to observe is quite a bit to consider. 

However, it is an elegant solution that explains things like the Pacific Ring of Fire, Mid-Atlantic Ridge, various mountain chains often along the coastlines, continental drift, preponderance of earthquakes and faultlines in certain locations, and etc.  I assume with modern satellite imagery, we can actually monitor the movement of various continents with actual distances that they move on a daily or annual basis.

If the Pacific Ocean is getting smaller, then that mass has to go somewhere... 

Perhaps rather than "plates", the surface just buckles and tears at various fault lines with continental drift.  But, in a sense, that is what the plate theory is saying.

Anyway, you need to come up with a good alternative theory to explain continental movement, where the lost mass goes, uplifting, and etc before just saying the current theories are incorrect.
 

Offline Geezer

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Isn't it all about convection?
 

Offline dareo

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Alright Cliffordk, we will talk about, as you put it "the lost mass". I will discuss the fault lines, the tearing of the surface and even why modern satellite imagery cannot tell why or how the mountain chains formed. I have to go now, I will get back this forum. I want to explain the problems with the convection theory and go into a detailed examination about the Ring of Fire. But lets be clear about Earth's mountain belts and chains.   
 

Offline dareo

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No Geezer, it is not all about convection. In fact, the convected energy from the mantle had absolutely nothing to do with the movements of the continents. Earth's exterior is a massive shell of fractured rock. At the fissures, we can see the contours of the continents; outlining in a puzzle like fashion, how the continents fit together and were once one.

Earth before these enormous cracks, was a smaller planet. Earth rather suddenly expanded in magnitude. But the expanse did not occur, due to its current  mantle, slowly exuding and dividing the surface..."convecting" slabs beneath slabs. Again, Earth's surface is a much lighter density than the mantle. Energy from the mantle exhuming throughout the surface is not likely to push a continent in a certain direction, especially if the mantle is liquid in form. This is certainly not enough force to collide continents and create mountains such as the Himalayas or the Andes; or any great mountain belt or chain. 
 

Offline dareo

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Cliffordk, you made very important point about the 'loss of mass'. Quite frankly Cliffordk, there was no loss of mass, if you are referring to the slabs, which are pushed downward beneath another continent and theoretically uplifts the mountains over a course of millions of years. That mass is not loss, and nor is it slowly moving under another continent. These are great masses of surface instantly forced into position, which have remained for millions of years. There is movement because the whole surface was fractured, and the Earth rotates.

We must be careful, because again, the locations of these surface beneath surfaces may seem as a loss of surface mass into the Earth; when most of the  theoretical surface sliding beneath another surface, occurs in the ring of fire...around the Pacific realm. The great Atlantic Ocean's floor is not plagued to the shores of Europe, Africa and the Americas with great mass losses. The Mid-Atlantic Ridge according to current theories has created, and actively creating new ocean flooring.

So that takes us back to the Pacific's ring of fire. West of North and South America where we find massive mountain chains.
 

Offline dareo

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The 'Ring of Fire' is extremely significant when understanding the origins of Earth's greatest mountain chains. Along the ring of fire, consisting of the Pacific realm, the near masses above sea level are mountainous. These are some of the world's greatest mountain chains.

But lets review the mountains of the far-east, such as the Khingan, or the Kunlun Mountains of China. These enormous mountains are inland, and much further from the ring of fire. Yet, the ring of fire conveys the most substantial clue to their very vast existences. So I question, was it convection of the mantle moving surface plates to form these expansive mountains so profoundly inland? And, did this type of gradual force actually occur over the millions of years? 

Through the millions of years, these mountains have slowly leveled out, due to weathering and acclimatization. We can strongly assume that all of the mountains of China were much higher and more defined. But I say again, the enormity and spaciousness of these mountains were created in less than a day.
 

Offline CliffordK

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But I say again, the enormity and spaciousness of these mountains were created in less than a day.

Are you saying that these mountains came into existence in a single day, or a few days?  Are you talking about some extraordinary earthquake, say a 15 on the Richter scale?

Still the mass to push up a mountain range has to come from somewhere.
Narrowing of the ocean basins,
Subsiding of nearby land.
I suppose you could have some sort of a bubble of molten earth down below, but still the mass is coming from somewhere...  subsiding.

You would need some mechanism for localized pressure buildup, and pressure relief.  Also a mechanism to store and release energy as continents gradually move closer to each other.
 

Offline dareo

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I am saying the great mountains of inland China came into existence in less than a day. The settlement of the enclave may have taken months or years. Cliffordk, I am talking extraordinary, more extraordinary than you can imagine. If we could measure the magnitude of force, which raised the mountains of China on a Richter scale, it would probably be one trillion. That sir, is not exactly an earthquake; we might want to call it an earth-shock.

Much of the mountains mass is adjacent and profound earth surface. Chinese Archaeologists have discovered fossils of living organisms in the mountains. (plants, insects, even small marine vertebra)

The mass of exceptional energy to raise mountain chains did not initiate from the mantle, or from any ocean basin; but from the cosmos. Before this stupendous mass of energy, Earth did not have the mountains of China, or the Cascades, or the Rockies, or any of its major mountain belts and chains.

Again, this was not an effort of colliding or subducting continents.
 

Offline dareo

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I would like to clarify the movements of continents.

Earth expanded in magnitude suddenly and very swiftly. Earth increased in volume approximately 1½ times its primal size. The swell of Earth's additional content, fractured the hardened shell surface to massive plates drifting to their own acquiescence; atop of a heavily disturbed mantle.

Its has been millions of years, since the expeditious occurrence. Earth has long since reached its peak of enlargement, thus the cracked surface throughout Earth reflects tectonic plates or drifting continents. But there is still movement of the continents, due to the dense liquefaction of the mantle, the fissures of the divided surface, and the rotation of Earth.
 

Offline Ophiolite

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I focus on two problems with your speculation:

First an error of fact:
Quote from: dareo
Earth's surface is a thin cooled solid, while Earth's voluminous mantle is liquid molten magma
The Earth's mantle is not molten. Small percentages (+/-15%) of very small portions of it display partial melting, but the mantle as a whole is solid. If you have contrary evidence to this then please provide it.


Then a conflict with evidence:
The mass of exceptional energy to raise mountain chains did not initiate from the mantle, or from any ocean basin; but from the cosmos. Before this stupendous mass of energy, Earth did not have the mountains of China, or the Cascades, or the Rockies, or any of its major mountain belts and chains.
Dating of current and ancient mountain belts demonstrates that their ages range from current to billions of years old. You assert that a single event, of limited duration generated these mountains. The evidence clearly contradicts this and thus invalidates your speculation.
 

Offline CliffordK

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If we could measure the magnitude of force, which raised the mountains of China on a Richter scale, it would probably be one trillion. That sir, is not exactly an earthquake; we might want to call it an earth-shock.

Earth?
What Earth?
Where?

Keep in mind that the Richter Scale is a logarithmic scale.
http://en.wikipedia.org/wiki/Richter_magnitude_scale#Examples

According to Wikipedia, a 12.55 Richter scale quake would be created by the Asteroid Impact creating the Chicxulub crater, and wiping out the Dinosaurs 65 Million Years ago.  A Starquake on a neutron star might be in the 30's.

In the Trillions?  Perhaps a stellar collision between two large stars with Earth caught in the middle, or perhaps a large star being ripped apart by a Black Hole.

Earth expanded in magnitude suddenly and very swiftly. Earth increased in volume approximately 1½ times its primal size. The swell of Earth's additional content, fractured the hardened shell surface to massive plates drifting to their own acquiescence; atop of a heavily disturbed mantle.

You need to expound more on the forces that created an initial compact Earth, and later expansion.

Thermal Expansion?  Why?  Why not cooling?
Acretion of meteorite material?  The Late Heavy Bombardment has left some remaining craters on the moon, but it was about 4 billion years ago, and little evidence of it remains on the surface of the planet.

I agree that the Appalachian and Rocky Mountains, both on the North American Continent appear to have very different ages.  There are many theories that the Appalachian mountains have gone through several phases of uplifting and erosion.  Although, it is odd that it doesn't seem to be a continuous process.

Most of the impact craters have a circular profile.  Many mountain chains are much more linear.  That would seem to indicate some kind of a sliding force, and a crustal shift, rather than being caused by, say waves from the impact.
 

Offline JimBob

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All I have seen so far to Dario's post are speculative assertion without any facts - such as the behavior of P,S and Raleigh waves -confirm or do not confirm his assertions. This is more akin to reading "Alice In Wonderland" than science in this way. Ther is no science contained in "Alice in Wonderland"

Dareo, if so much energy was put into the earth to do all you say it did, the earth would have been melted and nothing but a glass aphere would remain. Do the thermodynamics of the problem - it is obvious.
 

Offline dareo

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Gentlemen, you have proposed many questions. Most are good, but i will not comment on some responses. Ophiolite, we know the mantle is dense molten rock. There is plenty of evidence about the mantle. Yet, there is no evidence anywhere, which can prove...Earth's mountain chains are billions of years old. For even if, they were 'billions' of years old; the theory of subduction beneath the continents uplifting the mountain chains, has suddenly become more speculative. 
 

Offline dareo

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Cliffordk, i can't debate the accuracy of the amount of energy by the Woodson-Anderson seismograph, however the force was about 9 times larger than the energy impacting Earth, resulting in the Chixculub Crater. And yes, many mountain chains are linear, yet i am referring to an impact probably 90 times greater than the Chixculub Crater.

A crater of such magnitude and its effects would seem linear, depending on the perspective. From my vista, the major mountain chains of Earth are massive mounds of surface upheaval; forged into Earth from the powerful shock. There are some factors, which are keys that explain linear mountains  ie., size of object, shape, sphere of Earth, its angle, and very importantly Earth's rotation. We need to converse on the differences of the mountain chains, as to which and why some are more linear; and why they reside in a particular locale.

Again, I think we will find; subduction of the continents were not the cause for the creation of mountain chains.

 

Offline Ophiolite

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I only just noticed this reply.
Ophiolite, we know the mantle is dense molten rock.   
No, we most certainly do not. There is zero doubt that the mantle is solid. This is why it can transmit P-waves. If it were molten P-waves would not be transmitted by it. On this point you are simply 100% incorrect. As I noted previously, there are some portions of the mantle where partial melting has occured. There are pockets of molten material, perhaps constituting as much as 15% of the bulk of the rock, but the rock - overall - remains solid.

Since this is an elementary piece of knowledge about Earth structure I have to question your competence to have any meaningful thoughts about Earth history.

There is plenty of evidence about the mantle.
Yes there is and this evidence clearly indicates that the mantle is largely solid. If you wish to maintain otherwise it is your responsibility to provide that contrary evidence.

Yet, there is no evidence anywhere, which can prove...Earth's mountain chains are billions of years old.
Don't twist my words please. I stated that Earth's mountain chains were up to billions of years old. If you are challenging this observation then I presume you are denying the validity of isotope dating techniques. Is this the case?

For even if, they were 'billions' of years old; the theory of subduction beneath the continents uplifting the mountain chains, has suddenly become more speculative. 
Why would this make subduction more speculative? There is no apparent logic in your statement.
 

Offline dareo

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"Yes there is and this evidence clearly indicates that the mantle is largely solid. If you wish to maintain otherwise it is your responsibility to provide that contrary evidence."

If the mantle is 'largely solid', tell me please...how solid continental plates move across a largely solid planet to form mountain belts? Surely, you are not saying, solid rock moves like liquid? And do we agree, that continents move? ...(diverting, subducting, uplifting) mostly solid rock?

The isotopic dating techniques are excellent indicators for the age of material, however; isotope dating does not say anything about the timely uplift of Earth's greatest mountain chains..such as the Himalayas, or the Andes.

 

Offline Ophiolite

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Surely, you are not saying, solid rock moves like liquid?
That is exactly what I am saying. This concept is no longer in dispute.

Holmes demonstrated over seventy years ago that thermal convection in the solid mantle was a wholly plausible and practical mechanism.
Holmes, A. Radioactivity and Earthmovements, XVII.Trans.Geol.Soc.Glasgow, Vol.XVIII–PartIII, 1928–3118, 559–606. 1931.
Holmes, A. The thermal history of the Earth. J.Wash.Acad.Sci. 23, 169–95 1933.

If the mantle is 'largely solid', tell me please...how solid continental plates move across a largely solid planet to form mountain belts?
Much of the movement of the continents, or more precisely the plates, is via slippage along fault planes. However, movement at a microscopic level can occur by a variety of mechanisms, facilitated by high temperatures.
For example: Gordon,R.B. Diffusion creep in the Earth’s mantle. J.Geophys.Res.70, 2413–8 1965

Abstract:By the process of diffusion creep polycrystalline materials can deform at slow strain rates with Newtonian viscosity. Creep mechanisms involving dislocations can result in more rapid, non-Newtonian flow, but the diffusion creep rate sets an upper limit to the resistance to nonhydrostatic stresses. It is shown that under the conditions of temperature and pressure expected in the earth's mantle, diffusion creep in close-packed oxide structures leads to a viscosity of the same magnitude as that determined from observations of crustal uplift after unloading. The results also show that it is reasonable to assume Newtonian viscosity in calculations of large-scale flow processes in the mantle.

Quote
The isotopic dating techniques are excellent indicators for the age of material, however; isotope dating does not say anything about the timely uplift of Earth's greatest mountain chains..such as the Himalayas, or the Andes.
I am perplexed as to why you would say this. Here is one example of of where dating of one phase of the Himalyan orogeny is achieved with such tenchiques. One could easily find a dozen, a score a hundred or more similar papers. How did you come by such a mistaken idea that this was not possible?

de Sigoyer, J. , et al  Dating the Indian continental subduction and collisional thickening in the northwest Himalaya: Multichronology of the Tso Morari eclogites Geology v. 28 no. 6 p. 487-490 2000


Abstract:
Multichronometric studies of the low-temperature eclogitic Tso Morari unit (Ladakh, India) place timing constraints on the early evolution of the northwest Himalayan belt. Several isotopic systems have been used to date the eclogitization and the exhumation of the Tso Morari unit: Lu-Hf, Sm-Nd, Rb-Sr, and Ar-Ar. A ca. 55 Ma age for the eclogitization has been obtained by Lu-Hf on garnet, omphacite, and whole rock from mafic eclogite and by Sm-Nd on garnet, glaucophane, and whole rock from high-pressure metapelites. These results agree with a previously reported U-Pb age on allanite, and together these ages constrain the subduction of the Indian continental margin at the Paleocene-Eocene boundary. During exhumation, the Tso Morari rocks underwent thermal relaxation at about 9 ± 3 kbar, characterized by partial recrystallization under amphibolite facies conditions ca. 47 Ma, as dated by Sm-Nd on garnet, calcic amphibole, and whole rock from metabasalt, Rb-Sr on phengite, apatite, and whole rock, and Ar-Ar on medium-Si phengite from metapelites. Ar-Ar analyses of biotite and low-Si muscovite from metapelites, which recrystallized at <5 kbar toward the end of the exhumation, show that the Tso Morari unit was at upper crustal levels ca. 30 Ma. These results indicate variable exhumation rates for the Tso Morari unit, beginning with rapid exhumation while the Indian margin subduction was still active, and later proceeding at a slower pace during the crustal thickening associated with the Himalayan collision.

 

Offline dareo

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I only just noticed this reply.
Ophiolite, we know the mantle is dense molten rock.   
No, we most certainly do not. There is zero doubt that the mantle is solid. This is why it can transmit P-waves. If it were molten P-waves would not be transmitted by it. On this point you are simply 100% incorrect. As I noted previously, there are some portions of the mantle where partial melting has occured. There are pockets of molten material, perhaps constituting as much as 15% of the bulk of the rock, but the rock - overall - remains solid.

Since this is an elementary piece of knowledge about Earth structure I have to question your competence to have any meaningful thoughts about Earth history.

There is plenty of evidence about the mantle.
Yes there is and this evidence clearly indicates that the mantle is largely solid. If you wish to maintain otherwise it is your responsibility to provide that contrary evidence.


My good man, lets understand seismic waves. There are two types of seismic waves:

1. P-waves
2. S-waves

P-waves can travel through solids and liquids.
S-waves travel only through solids.

From the measurements of both waves, we know Earth's interior is largely liquid.
I am sorry, this is even more "elementary". Notwithstanding, it has nothing to do with the uplift of mountain chains, or the force or forces by which these great mountain formed.
 

Offline Ophiolite

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Dareo, you are absolutely correct that I completely reversed my intended statement on P and S waves. P waves do indeed travel comfortably through mantle and core, through liquid and solid (and gases for that matter). It is S-waves that will not travel through fluids. Please excuse the confusion I may have caused.

That said, it is because of these properties that we know absolutely that the mantle, which constitutes the bulk of the Earth in volumetric terms, is predominantly solid. I have no idea how you have come up with the wholly incorrect notion that: "From the measurements of both waves, we know Earth's interior is largely liquid." That is simply wrong.


Consult any elementary textbook of geophysics, or structural geology and you will see that the mantle is basically solid. Over long time intervals it flows. I've already given you a reference to this and you have responded, not with contrary evidence, but with bombast. Please provide even a single citation in support of your erroneous contention. In particular please explain why the mantle readily transmits S-waves if it is, as you appear to claim, largely liquid.

Once you have dealt with that, do you have any intention of responding to my other points that seemingly undermine your hypothesis? In particular on what basis do you dispute the clear evidence for the varied ages of Earth's mountain chains?



 

Offline dareo

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Well, you make so many interesting points, I must deal with them one at a time. Confusion, as you put it; seems... your way of conversing.

 I researched the mantle again, as to being a liquid. I think you are correct. Many studies, depending where you look... provide the mantle as 'mostly solid' with areas of magma.

Now to one of your interesting points; you mentioned, "solid rock moves like a liquid."

Surely, you are not saying, solid rock moves like liquid?
That is exactly what I am saying. This concept is no longer in dispute.

Holmes demonstrated over seventy years ago that thermal convection in the solid mantle was a wholly plausible and practical mechanism.
Holmes, A. Radioactivity and Earthmovements, XVII.Trans.Geol.Soc.Glasgow, Vol.XVIII–PartIII, 1928–3118, 559–606. 1931.
Holmes, A. The thermal history of the Earth. J.Wash.Acad.Sci. 23, 169–95 1933.

If the mantle is 'largely solid', tell me please...how solid continental plates move across a largely solid planet to form mountain belts?
Much of the movement of the continents, or more precisely the plates, is via slippage along fault planes. However, movement at a microscopic level can occur by a variety of mechanisms, facilitated by high temperatures.
For example: Gordon,R.B. Diffusion creep in the Earth’s mantle. J.Geophys.Res.70, 2413–8 1965

Abstract:By the process of diffusion creep polycrystalline materials can deform at slow strain rates with Newtonian viscosity. Creep mechanisms involving dislocations can result in more rapid, non-Newtonian flow, but the diffusion creep rate sets an upper limit to the resistance to nonhydrostatic stresses. It is shown that under the conditions of temperature and pressure expected in the earth's mantle, diffusion creep in close-packed oxide structures leads to a viscosity of the same magnitude as that determined from observations of crustal uplift after unloading. The results also show that it is reasonable to assume Newtonian viscosity in calculations of large-scale flow processes in the mantle.

Quote
The isotopic dating techniques are excellent indicators for the age of material, however; isotope dating does not say anything about the timely uplift of Earth's greatest mountain chains..such as the Himalayas, or the Andes.
I am perplexed as to why you would say this. Here is one example of of where dating of one phase of the Himalyan orogeny is achieved with such tenchiques. One could easily find a dozen, a score a hundred or more similar papers. How did you come by such a mistaken idea that this was not possible?

de Sigoyer, J. , et al  Dating the Indian continental subduction and collisional thickening in the northwest Himalaya: Multichronology of the Tso Morari eclogites Geology v. 28 no. 6 p. 487-490 2000


Abstract:
Multichronometric studies of the low-temperature eclogitic Tso Morari unit (Ladakh, India) place timing constraints on the early evolution of the northwest Himalayan belt. Several isotopic systems have been used to date the eclogitization and the exhumation of the Tso Morari unit: Lu-Hf, Sm-Nd, Rb-Sr, and Ar-Ar. A ca. 55 Ma age for the eclogitization has been obtained by Lu-Hf on garnet, omphacite, and whole rock from mafic eclogite and by Sm-Nd on garnet, glaucophane, and whole rock from high-pressure metapelites. These results agree with a previously reported U-Pb age on allanite, and together these ages constrain the subduction of the Indian continental margin at the Paleocene-Eocene boundary. During exhumation, the Tso Morari rocks underwent thermal relaxation at about 9 ± 3 kbar, characterized by partial recrystallization under amphibolite facies conditions ca. 47 Ma, as dated by Sm-Nd on garnet, calcic amphibole, and whole rock from metabasalt, Rb-Sr on phengite, apatite, and whole rock, and Ar-Ar on medium-Si phengite from metapelites. Ar-Ar analyses of biotite and low-Si muscovite from metapelites, which recrystallized at <5 kbar toward the end of the exhumation, show that the Tso Morari unit was at upper crustal levels ca. 30 Ma. These results indicate variable exhumation rates for the Tso Morari unit, beginning with rapid exhumation while the Indian margin subduction was still active, and later proceeding at a slower pace during the crustal thickening associated with the Himalayan collision.



The moment you use the term 'viscosity' you are referring to a liquid. Therefore, by thermal convection process of diffusion creep poly-crystalline, materials can deform at slow strain rates with Newtonian viscosity? That Ophiolite is again interesting. Slow strain rates with Newtonian viscosity? Newtonian... what are we talking millions of years at a slow rate. Would the slow strain rate have enough force to slowly forge the orogeny of say... the Andes Mountains?

And if so, please tell me...why this particular part of the world? Does the diffusion deform the rock in a specific direction?  ..and please, no need to insult...
 

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