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Why Earth's mantle is solid



 
 
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  #1  
Old September 4th 08, 10:53 PM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Default Why Earth's mantle is solid

Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.

This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up, except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.

Freezing from the bottom up is a much faster process than freezing
from the top down, as the heat flux from below continues to decrease
(yes, there is convection, but the effective viscosity is much higher
in a solid than a liquid), and therefore should go to completion.

Andrew Usher
  #2  
Old September 4th 08, 11:51 PM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Uncle Al
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Default Why Earth's mantle is solid

Andrew Usher wrote:

Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.


Bull****. Silicon, bismuth, clathrates... have denser liquids than
solids. Ditto silicate melts vs. zeolites. Metal-organic
frameworks. It's a trivial thing to do given crystal structure.

This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up,


Since it can only cool from the top down you might want to rethink
that. Hawaii is frozen at the top and liquid at the base.

except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.

Freezing from the bottom up is a much faster process than freezing
from the top down, as the heat flux from below continues to decrease
(yes, there is convection, but the effective viscosity is much higher
in a solid than a liquid), and therefore should go to completion.


So sad.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
  #3  
Old September 5th 08, 01:13 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Posts: 586
Default Why Earth's mantle is solid

On Sep 4, 4:51 pm, Uncle Al wrote:
Andrew Usher wrote:

Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.


Bull****. Silicon, bismuth, clathrates... have denser liquids than
solids. Ditto silicate melts vs. zeolites. Metal-organic
frameworks. It's a trivial thing to do given crystal structure.


Silicon and bismuth are the semi-metals I was thinking of, along with
Ge, Sb, As, graphite. I consider clathrates a type of water ice.
Zeolites
are not equilibrium phases and can't coexist with a melt.

Saying it's 'trivial' is pointless; of course it's a function of
crystal
structure.

This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up,


Since it can only cool from the top down you might want to rethink
that.


So? Convection is faster than heat loss in a liquid.

Hawaii is frozen at the top and liquid at the base.


Hawaii, like all volcanoes, has liquid under it but that's only
possible locally as the magma is less dense than the surrounding
rock. This is simply hydrostatic equilibrium.

except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.


Freezing from the bottom up is a much faster process than freezing
from the top down, as the heat flux from below continues to decrease
(yes, there is convection, but the effective viscosity is much higher
in a solid than a liquid), and therefore should go to completion.


So sad.


I don't think you're really this stupid.

Andrew Usher
  #4  
Old September 5th 08, 07:08 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Yousuf Khan
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Posts: 594
Default Why Earth's mantle is solid

Andrew Usher wrote:
Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.

This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up, except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.


Is the crust really all that different material from the mantle? In the
early days, I just thought the crust was just cooled mantle material.
How do they really know what the mantle is made of?

Anyways, what's the liquid (i.e. magma) that exists below the crust made
of? Is it liquefied crust, or liquefied mantle? If it's liquefied crust,
then isn't that another example of a liquid existing below its solid phase?

Yousuf Khan
  #5  
Old September 5th 08, 11:13 PM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Posts: 586
Default Why Earth's mantle is solid

On Sep 5, 12:08 am, Yousuf Khan wrote:
Andrew Usher wrote:
Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.


This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up, except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.


Is the crust really all that different material from the mantle? In the
early days, I just thought the crust was just cooled mantle material.
How do they really know what the mantle is made of?


The crust is differentiated from the mantle, oceanic crust less so
than continental. We know the composition of the mantle, I think,
largely from astronomical abundances.

Anyways, what's the liquid (i.e. magma) that exists below the crust made
of? Is it liquefied crust, or liquefied mantle? If it's liquefied crust,
then isn't that another example of a liquid existing below its solid phase?


Magma is formed by partial melting of either mantle or crust. Yes, it
is
less dense than surrounding rock, which is why it moves upward.

Andrew Usher
  #6  
Old September 6th 08, 12:37 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
[email protected]
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Posts: 134
Default Why Earth's mantle is solid

On Sep 5, 6:13*pm, Andrew Usher wrote:
On Sep 5, 12:08 am, Yousuf Khan wrote:

Andrew Usher wrote:
Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure..


This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up, except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.


Is the crust really all that different material from the mantle? In the
early days, I just thought the crust was just cooled mantle material.
How do they really know what the mantle is made of?


The crust is differentiated from the mantle, oceanic crust less so
than continental. We know the composition of the mantle, I think,
largely from astronomical abundances.

Anyways, what's the liquid (i.e. magma) that exists below the crust made
of? Is it liquefied crust, or liquefied mantle? If it's liquefied crust,
then isn't that another example of a liquid existing below its solid phase?


Magma is formed by partial melting of either mantle or crust. Yes, it
is
less dense than surrounding rock, which is why it moves upward.

Andrew Usher


My guess is that you have no idea of what the mantle is. Am I close to
being correct?

My second guess is that you've never completed a college course in
geology, or even own a textbook on the subject.

Am I close again?

Seriously, the dyanics of the earth's interior are likely much more
complex than a layman might assume.

Just for the record, the mantle is an interface point upon which the
less denser continental masses float. The interior of the earth is
generally considered to be a totally molten mass of mixed heavy
metals, starting with iron and going through uranium and possibly even
heavier elements.

Physicist and geologist tend to disagree on the reason why the core of
the earth remains liquid, or ever if it is liquid. Actually, finding
out exatly what is going on in the earth's interior remain today
unknown.

Harry C,
  #7  
Old September 6th 08, 04:45 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Number Eleven - GPEMC!
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Posts: 22
Default Why Earth's mantle is solid

"Andrew Usher" wrote in message
...
On Sep 4, 4:51 pm, Uncle Al wrote:
Andrew Usher wrote:

Every solid save water ice and a few semi-metals is denser than the
liquid of the same composition, and the same temperature and pressure.


Bull****. Silicon, bismuth, clathrates... have denser liquids than
solids. Ditto silicate melts vs. zeolites. Metal-organic
frameworks. It's a trivial thing to do given crystal structure.


Silicon and bismuth are the semi-metals I was thinking of, along with
Ge, Sb, As, graphite. I consider clathrates a type of water ice.
Zeolites
are not equilibrium phases and can't coexist with a melt.

Saying it's 'trivial' is pointless; of course it's a function of
crystal
structure.

This means that a liquid other than water will not exist beneath a
solid of the same composition in a planet. A magma ocean therefore can
only freeze from the bottom up,


Since it can only cool from the top down you might want to rethink
that.


So? Convection is faster than heat loss in a liquid.

Hawaii is frozen at the top and liquid at the base.


Hawaii, like all volcanoes, has liquid under it but that's only
possible locally as the magma is less dense than the surrounding
rock. This is simply hydrostatic equilibrium.

except for the granitic crust which,
owing to its composition, is lighter than the liquid mantle. The
amount of granitic crust which could exsolve is pretty high, if the
mean composition is that of albite perhaps 20% of the mantle in the
extreme - but this would not be reached until far below the solidus.


Freezing from the bottom up is a much faster process than freezing
from the top down, as the heat flux from below continues to decrease
(yes, there is convection, but the effective viscosity is much higher
in a solid than a liquid), and therefore should go to completion.


So sad.


I don't think you're really this stupid.

Andrew Usher


The "I don't think you're really this stupid" statement is an example of a
conditional variation on argumentum ad homenim. Statistically, I don't need
to see the rest of the thesis to be fairly certain that the author of that
statement has insufficient supporting facts - so if I'm pressed for time and
I catch you making a false argument, I'll just assume you're in error and
move on. Here's why:

The verity of a conclusion may well be independent of the supporting
argument's fallaciousness, but nearly all of the times when people resort to
fallacy, they generally only do so when there is a glaring lack of
supporting evidence. Do a bit of reading (actually, quite a bit of reading!)
and you too will discover that the fallacy is only very rarely used in
association with an otherwise genuinely valid thesis.

Try again...

--
Timothy Casey GPEMC! Conditions apply. See www.fieldcraft.biz/GPEMC
Essays: http://timothycasey.info; http://speed-reading-comprehension.com
Softwa http://fieldcraft.biz; Scientific IQ Test, Web Menus, Security.
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  #8  
Old September 6th 08, 06:16 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Posts: 586
Default Why Earth's mantle is solid

On Sep 5, 9:45 pm, "Number Eleven - GPEMC!"
wrote:

Freezing from the bottom up is a much faster process than freezing
from the top down, as the heat flux from below continues to decrease
(yes, there is convection, but the effective viscosity is much higher
in a solid than a liquid), and therefore should go to completion.


So sad.


I don't think you're really this stupid.


Andrew Usher


The "I don't think you're really this stupid" statement is an example of a
conditional variation on argumentum ad homenim.


What do you think his 'So sad' was?

Andrew Usher
  #9  
Old September 6th 08, 06:17 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Posts: 586
Default Why Earth's mantle is solid

On Sep 5, 5:37 pm, " wrote:

Physicist and geologist tend to disagree on the reason why the core of
the earth remains liquid, or ever if it is liquid. Actually, finding
out exatly what is going on in the earth's interior remain today
unknown.


The Earth's interior is far from unknown. Learn something
before posting.

Andrew Usher
  #10  
Old September 6th 08, 07:10 AM posted to sci.astro,sci.chem,sci.physics,sci.geo.geology
Andrew Usher
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Posts: 586
Default Why Earth's mantle is solid

On Sep 6, 12:02 am, Sam Wormley wrote:

How about that liquid outer core of iron and sulfur that can not
support shear waves.


I was obviously referring to the mantle only.

And that "plastic" Asthenosphere
http://en.wikipedia.org/wiki/Asthenosphere

"The upper part of the asthenosphere is believed to be the zone
upon which the great rigid and brittle lithospheric plates of
the Earth's crust move about. Due to the temperature and pressure
conditions in the asthenosphere, rock becomes ductile, moving at
rates of deformation measured in cm/yr over lineal distances
eventually measuring thousands of kilometers. In this way, it
flows like a convection current, radiating heat outward from the
Earth's interior. Above the asthenosphere, at the same rate of
deformation, rock behaves elastically and, being brittle, can
break, causing faults. The rigid lithosphere is thought to "float"
or move about on the slowly flowing asthenosphere, creating the
movement of crustal plates described by Plate tectonics theory".


This doesn't contradict anything I said. The asthenosphere is
still essentially solid.

Andrew Usher
 




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