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Topic: Testy Explains the Layers Which Include the Tonto Group (Read 9189 times) previous topic - next topic

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  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1100
Hey here's a question: if cratons are just stuck together out of lots of random old bits, which seems to be the case, why are they so stable?
Cratons are usually the center bits (i.e. the canadian shield) > 2.5Gya...
Yes, I do realise this. :p

...while everything else is glued, glommed and cemented into it.  But there's just not much left that's "original", but's broken apart and cemented together a few times over earth's history tends to mix stuff up.
That, too. :grin:

Ok, this is a good example. The Canadian section of the Laurentian craton is composite. Very much composite, as I've just found out by looking at the detailed cross sections.

That Superior "well-defined craton" just under the "Laurentia" label makes it sound like a "big lump of rock", but in fact it's built up of all sorts of random bits and pieces, including bits of ancient ocean floor sliding under other Archaean crust, and including Archaean sediments scraped off said ocean floor and piled up between the base of the eroded orogeny, that was at one side of said ocean floor, and the large block of other Archaean crust that it collided with. It just happened a long time ago, and it's been stable ever since.



So this is a case where we have old bits of an orogeny (labelled "Wawa"), with relict ocean floor attached, just "glommed on" to the Wabigoon/Winnipeg lump, which itself is just "glommed on" to the North Caribou lump which, being a superterrane itself, is just a whole lot of old lumps "glommed on" to each other. And, between the North Caribou and the Winnipeg is another whole lot of Archaean sediment that got trapped between the two.

In other words, the whole thing is just a random clusterfuck of whatever was lying around at the time, including large volumes of loose sediment. Yet, despite this, it's all listed under "Laurentia" and it's all called a craton and it has been stable for around 2.5 billion years.

This is the bit that intrigues me. Why is the thing so stable, if it's apparently just as much of a mess as the bits that aren't?


Stability is a misnomer, they tilt and move but they DO float higher compared to oceanic plates...
Yup. IIRC it's partly due to them trapping heat under the thicker crust there. Expands the rock and makes it more buoyant. This was mentioned in the recent Zealandia paper as part of the reason why it sank when the crust was thinned.[1] And the floating higher is also due to the extra thickness of course (basic Archimedes stuff).

And of course I realise that cratons move around the planet, and tilt and bend when sediment piles up on their edges, but the thing is they still tend to behave like one big solid lump over billions of years. That's what I mean by "stability". They are "building blocks" that just keep getting rearranged, without getting fragmented.

...plus IIRC the continental plates, made up of sedimentary profiles, tend to buckle and roil at impact while the oceanic plates are a bit more structurally sound.  The combination is why you see subduction more often than buckling, suture or orogeny at the plate boundaries between land and ocean plates.
I suppose more structurally sound makes sense given that ocean floor is usually igneous, although on the other hand it is also usually thinner.

That "Wawa" bit of ocean floor is an odd case. It obviously thought about subducting, but then decided it didn't want to.


A few things that spring to mind. I may be quite wrong on some of these, so be warned. :P
1) Cratons typically have very deep lithospheric roots. This is the reason they tend to "float" higher.
2) This may be entirely due to their age. Archean time had much higher heat flow, leading to much thicker crust formation. Melting of mantle material and subsequent fractionation from mafic -> felsic mineralisation occurs due to heat and pressure. Release the pressure and melt occurs, increase the temperature, and melt occurs. https://en.wikipedia.org/wiki/Archean_subduction
3) Their age is why they seem so much more stable than most other continental crust. Anything weak in their structure would have been recycled during the normal ebb and flow of tectonics. What we have left after x-billion years are the bits that are stronger than everything else. They don't generally rift apart, as they have very thick lithospheric roots. They can't subduct. All they can do is erode down over time.
Just looked it up. The term they use is "thermal relaxation".
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1101
Spoiler (click to show/hide)
A few things that spring to mind. I may be quite wrong on some of these, so be warned. :P
1) Cratons typically have very deep lithospheric roots. This is the reason they tend to "float" higher.
2) This may be entirely due to their age. Archean time had much higher heat flow, leading to much thicker crust formation. Melting of mantle material and subsequent fractionation from mafic -> felsic mineralisation occurs due to heat and pressure. Release the pressure and melt occurs, increase the temperature, and melt occurs. https://en.wikipedia.org/wiki/Archean_subduction
Takign a look now... :)

3) Their age is why they seem so much more stable than most other continental crust. Anything weak in their structure would have been recycled during the normal ebb and flow of tectonics. What we have left after x-billion years are the bits that are stronger than everything else. They don't generally rift apart, as they have very thick lithospheric roots. They can't subduct. All they can do is erode down over time.
Yup, I get that anything that survives, even if it is totally random, will appear to be more durable simply due to the result of a random process. But that doesn't appear to be what's going on here. They have had plenty of opportunities to get munched. They really are stronger, and the lithospheric mantle appears to have a lot to do with it.
Truth is out of style

Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1102
Hmm ... my buddy Derek Ager ... who I've quoted before ...

Quote
British geologist Derek Ager in his book The Nature of the Stratigraphical Record4 marvelled at the way sedimentary rocks layers persisted for thousands of kilometres across continents. Like a blanket, they are relatively thin compared with the area they cover. https://creation.com/continent-wide-sedimentary-strata

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1103
Yes. And?
Truth is out of style

Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1104
Marveled did he? We'll, then, that's definitely solid evidence.
Love is like a magic penny
 if you hold it tight you won't have any
if you give it away you'll have so many
they'll be rolling all over the floor

Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1105
Hmm ... my buddy Derek Ager ... who I've quoted before ...

Quote
British geologist Derek Ager in his book The Nature of the Stratigraphical Record4 marvelled at the way sedimentary rocks layers persisted for thousands of kilometres across continents. Like a blanket, they are relatively thin compared with the area they cover. https://creation.com/continent-wide-sedimentary-strata

You can't even explain the distribution of sediment in your own state you dumbass.   ::)

  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1106
Hmm ... my buddy Derek Ager ... who I've quoted before ...

Quote
British geologist Derek Ager in his book The Nature of the Stratigraphical Record4 marvelled at the way sedimentary rocks layers persisted for thousands of kilometres across continents. Like a blanket, they are relatively thin compared with the area they cover. https://creation.com/continent-wide-sedimentary-strata

This Derek Ager?
Quote
"For a century and a half the geological world has been dominated, one might even say brain-washed, by the gradualistic uniformitarianism of Charles Lyell.  Any suggestion of 'catastrophic' events has been rejected as old-fashioned, unscientific and even laughable.  This is partly due to the extremism of some of Cuvier's followers, though not of Cuvier himself.

On that side too were the obviously untenable views of bible-oriented fanatics, obsessed with myths such as Noah's flood, and of classicists thinking of Nemesis.  That is why I think it necessary to include the following 'disclaimer': in view of the misuse that my words have been put to in the past, I wish to say that nothing in this book should be taken out of context and thought in any way to support the views of the 'creationists' (who I refuse to call 'scientific')." [Ager's emphasis]

He's a buddy of yours, is he? I guess that makes sense, given your recent efforts to debunk the fludde.
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1107
Yes, that one.
Truth is out of style

  • Zombies!
  • These violent delights have violent ends.
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1108
Hmm ... my buddy Derek Ager ... who I've quoted before ...
Spoiler (click to show/hide)
Is he a real buddy, or is he one of those 'investors', or young strong men that's clamoring to shit in buckets with you, Dave?
I mean, Ager is real, but do you hang out?  Talk about old times?
I really should call your department head and tell him or her how badly you are behaving while posing as a credentialed professional scientist.

  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1109
He's someone Dave likes to quotemine. :D
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • VoxRat
  • wtactualf
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1110
Hmm ... my buddy Derek Ager ... who I've quoted before ...
Did someone mention Derek Ager?

Quote
in view of the misuse that my words have been put to in the past, I wish to say that nothing in this book should be taken out of context and thought in any way to support the views of the 'creationists' (who I refuse to call 'scientific')."
"I understand Donald Trump better than many people because I really am a lot like him." - Dave Hawkins

  • Zombies!
  • These violent delights have violent ends.
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1111
 :ohdear: Dave, do you have any buddies who know you? :ohdear:
I really should call your department head and tell him or her how badly you are behaving while posing as a credentialed professional scientist.

  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1112
He's someone Dave likes to quotemine. :D
Speaking of quote mining, Dave seems to have stopped using quotes from various sources these days (as well as the quote function on this site). I wonder why?
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • Zombies!
  • These violent delights have violent ends.
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1113
He's someone Dave likes to quotemine. :D
Speaking of quote mining, Dave seems to have stopped using quotes from various sources these days (as well as the quote function on this site). I wonder why?
I visited his website, and he is flogging a collection of quotemines there.  A book. 
The website is a collection of sad, wrong, and broken links."Their words against them" or something.  Pretty embarrassing.
I really should call your department head and tell him or her how badly you are behaving while posing as a credentialed professional scientist.

  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1114
Just tries to hide his dishonesty from us then. Of course, the fact that he's not using quote mines here now, suggests that maybe he's figured out why they're dishonest. However, he still uses them elsewhere, where criticism is not so forthright. Hmmm.
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • Zombies!
  • These violent delights have violent ends.
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1115

Quote
This quote and many others are now available RIGHT HERE at my blog. The book pictured above is a wonderful resource for showing the inadequacy of the Theory of Evolution available from www.icr.org. I have used many of the quotes contained there and the CD-ROM is very easy to use. I have always wished there was a later volume (it was first published in 1997), but there is none. So I have begun compiling my own quotes and I now am making them available here free of charge. I own (or have online instant access to) many of the scientific papers from which these quotes come and I am very strict about dishonest quote mining.

Just tries to hide his dishonesty from us then. Of course, the fact that he's not using quote mines here now, suggests that maybe he's figured out why they're dishonest. However, he still uses them elsewhere, where criticism is not so forthright. Hmmm.
I really should call your department head and tell him or her how badly you are behaving while posing as a credentialed professional scientist.

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1116
Ok, just going through this a bit more, because it's far more interesting than silly creo stuff...

A few things that spring to mind. I may be quite wrong on some of these, so be warned. :P

1) Cratons typically have very deep lithospheric roots. This is the reason they tend to "float" higher.
Wiki says the thick lithosphere (ie: the mantle bit, not the crust bit) under cratons is actually colder than the norm, despite being less dense. Which indicates the elements that it's composed of must, on average, necessarily be lighter elements than are found in non-cratonic lithosphere. Which ties in with...

2) This may be entirely due to their age. Archean time had much higher heat flow, leading to much thicker crust formation. Melting of mantle material and subsequent fractionation from mafic -> felsic mineralisation occurs due to heat and pressure. Release the pressure and melt occurs, increase the temperature, and melt occurs. https://en.wikipedia.org/wiki/Archean_subduction
If it's more heavily/thoroughly melted then it makes sense that heavier elements and compounds would tend to turn on, tune in and drop out, much in the same way that iron headed for the core of the planet in the early days. So I can get why an Archaean lithosphere might tend to be lighter than a more modern one.

And if large depths of this stuff got stuck underneath budding cratons then, obviously, it would tend to make a good set of Floaties. The obvious question here is how did it get stuck? On the face of it, there's nothing to stop it spreading out and dissipating.

I can see how it could stay stuck in later eras, because if the cratons are floatier and are tough as old boots then it would make sense that anything hitting one would subduct, which would tend to make a "fence" around the craton's lithosphere. But it's the accretion phase is currently looking a tad mysterious.
  • Last Edit: October 02, 2017, 07:16:54 PM by osmanthus
Truth is out of style

  • Martin.au
  • Thingyologist
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1117
Yep, he's a very strict practitioner of honest quote mining. He'll honestly seek out quotes devoid of context, and that don't represent what the author was saying.

Like an honest liar, who will honestly lie about everything. :D
"That which can be asserted with evidence can also be dismissed without evidence." (Dave Hawkins)

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1118

Quote
This quote and many others are now available RIGHT HERE at my blog. The book pictured above is a wonderful resource for showing the inadequacy of the Theory of Evolution available from www.icr.org. I have used many of the quotes contained there and the CD-ROM is very easy to use. I have always wished there was a later volume (it was first published in 1997), but there is none. So I have begun compiling my own quotes and I now am making them available here free of charge. I own (or have online instant access to) many of the scientific papers from which these quotes come and I am very strict about dishonest quote mining.
:rofl: Yes, he's very strict about dishonest quote mining. Wouldn't even consider using any other sort. A man of principle.
Truth is out of style

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1119
Hey this looks useful:

Craton formation: Internal structure inherited from closing of the early oceans

Quote from: Abstract
The closure of ancient oceans created a dynamic setting suitable for craton formation via the thickening of continental material over a mantle downwelling. This process subjected the thickening lithosphere to extensive deformation, forming internal structure that can be preserved over the lifetime of the craton. Recent seismic imaging of cratonic lithosphere has led to observations of anomalous features colloquially known as midlithospheric discontinuities. These discontinuities are attributed to a range of sources, including the lithosphere-asthenosphere boundary, melt accumulation, and phase transitions. However, the internal structure imaged within these cratons might be reflective of their formation. In particular, the orientation and nature of the variable depths of the midlithospheric discontinuities suggest a more complicated origin such as that which could be introduced during the formation and thickening phase of cratonic lithosphere. Here, we present geodynamic models demonstrating the internal structures produced during the formation of cratonic lithosphere as well as new seismological observations of midlithospheric discontinuities in the West African craton, together with reassessment of midlithospheric discontinuities observed in the North American, South African, Fennoscandia, and Australian cratons. We suggest that the midlithospheric discontinuities observed in these cratons could be remnants of deformation structures produced during the formation of the cratons after ancient oceans closed.
Any chance of a dastardly octohatter grabbing that one for the plebs? :parrot:
Truth is out of style

Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1120
Hey this looks useful:

Craton formation: Internal structure inherited from closing of the early oceans

Quote from: Abstract
The closure of ancient oceans created a dynamic setting suitable for craton formation via the thickening of continental material over a mantle downwelling. This process subjected the thickening lithosphere to extensive deformation, forming internal structure that can be preserved over the lifetime of the craton. Recent seismic imaging of cratonic lithosphere has led to observations of anomalous features colloquially known as midlithospheric discontinuities. These discontinuities are attributed to a range of sources, including the lithosphere-asthenosphere boundary, melt accumulation, and phase transitions. However, the internal structure imaged within these cratons might be reflective of their formation. In particular, the orientation and nature of the variable depths of the midlithospheric discontinuities suggest a more complicated origin such as that which could be introduced during the formation and thickening phase of cratonic lithosphere. Here, we present geodynamic models demonstrating the internal structures produced during the formation of cratonic lithosphere as well as new seismological observations of midlithospheric discontinuities in the West African craton, together with reassessment of midlithospheric discontinuities observed in the North American, South African, Fennoscandia, and Australian cratons. We suggest that the midlithospheric discontinuities observed in these cratons could be remnants of deformation structures produced during the formation of the cratons after ancient oceans closed.
Any chance of a dastardly octohatter grabbing that one for the plebs? :parrot:

It's available as an open source pdf here.

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1121
Cool. Thanks. :beer:
Truth is out of style

  • borealis
  • Administrator
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1122
Quote
We suggest that the midlithospheric discontinuities observed in these cratons could be remnants of deformation structures produced during the formation of the cratons after ancient oceans closed.

Or that's where the Old Ones are really imprisoned.

Or it's balrogs - "They dug too deep!"

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1123
 :deadthread:  :civility:  :hair:
Truth is out of style

  • osmanthus
  • Administrator
  • Fingerer of piglets
Re: Testy Explains the Layers Which Include the Tonto Group
Reply #1124
Have only done the pictures and the conclusions so far (will do the gnarly bitz later)[1] but some of the references look interesting too. Like:

Quote
Gray, R., and Pysklywec, R.N., 2010, Geodynamic models of Archean continental collision and the formation of mantle lithosphere keels: Geophysical Research Letters, v. 37, L19301, doi:10.1029/2010GL043965
And...

Quote
Lenardic, A., Moresi, L.-N., and Muhlhaus, H., 2003, Longevity and stability of cratonic lithosphere: Insights from numerical simulations of coupled mantle convection and continental tectonic: Journal of Geophysical Research, v. 108, no. B6, 2303, p. 1-15, doi:10.1029/2002JB001859.
Just as two quick examples.
totally not an AFDave law either
Truth is out of style