#Subduction & Ocean Basin
35 messages in this thread
I really don't get the plunging of the Oceanic basin Crust down under the
continent in the Subduction Process.
The continents and the ocean crust (plates?) are floating on the asthenosphere
that is (Plastics?) or molten liquids .
What forces could be exerted on the ocean basins that could cause them to
bend…. and then be pushed down into the material they are floating on ……
ridge-push? How?
convection currents? A whisper of a force, No Way
slab-pull? solids don't compress into significantly denser
materials.
"(Plate Subduction) aye no sink so
but ….if there were some force that could do that….
1.The crust would melt. The lighter liquids would rise up and build at the
surface. There would be huge active linear volcanoes rising _hundreds of miles
high_ along these zones if this had been happening for millions of years.
2. Another very big problem is the inside of the curved mid ocean ridges. Look
at the half circle bowl where the East Pacific Rise and the Axial Ridge curve
around Australia.
The Transform faults along this rise roughly all point inward to the deep
trenches of Japan and the Philippines. This is a focus point for the proposed
movement.
A few inches a year isn't much but in 100 million years the crust would
concentrate towards the center raising Australia and the whole Western Pacific
Basin at least a couple hundred miles high. <g>
Kamron
Another problem is the ocean basin crust as it started to curve down would
begin opening up huge cracks in the basin floor.
The mildest curve downward would be in the western pacific..
Even if the ocean basin crust is only 5 miles thick
there would be a 5 mile gap in the curve area…
The ocean basin is probably more like at least 150 miles thick thats a 100
miles of gap in the downward curving area.
IF the crust is rigid enough to crack in the such straight lines near the
ridges where it is …
(not yet completely cooled)
then in the thicker denser cooler areas it would crack also.
The subduction zone concept is not all that its cracked up to be.
The tilt of the pacific towards the deep trenches and the intense earthquakes
that occur there can be explained in a better way than subduction.
All the ocean basins were formed at the same time.
They are very recent in age.
They slightly shift periodically due mostly to the sun and moon gravitational
forces.
Kamron
The mid Atlantic ridge is the force that pushes the lithospheric plates. The
plate boundry is called a spreading plate boundry. The land spreads apart and
new magma rises and cools to make a new ocean basin. So slowly over millions
of years the Atlantic ocean will get larger and the Pacific ocean will get
smaller because of the plate boundries you were talking about, the converging
plate boundries. There are large volcanoes, and earthquakes were the
converging plate boundries are located. The Pacific Rim of Fire is a big
example of what is happeneng.Does this explian it a little better?
Megan:>
Hi, Kamron–
>> What forces could be exerted on the ocean basins that could cause them to
bend…. and then be pushed down into the material they are floating on …
There are forces enough to move the continents – whether it is pull or push,
those same forces require _something_ to happen when plates meet. They might
just crumple up as with the Himalayas for a time, but something has to give.
>> slab-pull? solids don't compress into significantly denser materials.
I have referred you to the Scientific American article that mentions such
transitions have actually been observed in olivine. How can you deny actual
observed occurrences that explain what we see in the world so well? Why do
deep quakes follow postulated plate boundaries so well if there is no such
compression and no forces to drive/pull the plates down?
The crust does indeed melt during subduction to some extent, hence the
volcanoes of the Pacific Ring of Fire. But mostly it does not – those deep
quakes are telling us so. The pressures are too great to allow such easy
melting at great depths.
Try 5-10 kilometers for the thickness of the oceanic crust. I do not have my
references handy, being on the road again, but I am quite confident it is
nothing like hundreds of miles.
The cracking you speak of may indeed occur near the subduction zones, though I
expect something to fill in the cracks generally and make them harder to spot.
I will be interested to hear if anyone knows of such cracks (or how they might
be avoided).
–Doug
HO HO HO!!! Merry Christmas Doug
>> Scientific American article that mentions such transitions have actually
been observed in olivine. <<
I remember glancing at the SA article but wasn't that interested at the
time……..I'll read the article in SA.
I am not denying that the material would get denser a bit if it was forced
down. But why would it go down? Its lighter material so it takes a lot of force
to push it down. If the Continental mass is overriding it, which could happen
if you could get it moving. It would be like an ice breaker. There would be a
pile of it out front.
Why would it go down?
The trenches are not proof it is going down
and earthquakes are coming from deep because the crust goes deep.
>> There are forces enough to move the continents <<
What forces?
On a plate wide front …what force is in play capable of pushing the mass
down. There is no evidence of it cracking where it curves down. It is
rigid…. so it can't bend.
The thinner the crust is the worse the problem gets for pushing the crust
down. The rise pushing along the thread of crust kid of like pushing a stray
into wood …tough to do if you do it slow.
The crust material is lighter than the material it is on isn't it? It would
go down. It would buckle and pile up.
As far as pulling down… what would pull it down? It would sure get slippery
once it started melting… the puller would lose grip.
Why would it go down?
What is the state of the different levels.
I see the plates as _rigid_ lithosphere.
Asthenosphere as a plastic liquid…
Mesosphere ?
>> The crust does indeed melt during subduction to some extent, hence the
volcanoes of the Pacific Ring of Fire. <<
Why would the melted crust not follow the seam it made.
instead it bores a new hole through the lithosphere and pops out as a volcano
away from the site of penetration. Why?
Even then the volcanoes aren't putting out near enough to vent the melting
crust. They are not all even near subduction zones.
Kamron (Merry Christmas from a Scientific Christian)
Hi Kamron — i usually don't jump into this kind of discussion and probably
shouldn't this time either, but here goes anyhow. It seems to me that you are
extrapolating from your observations of how things work here on the surface of
the planet. If you expect to convince folks that your ideas have merit, you
need to quantitate and model based on the physical properties of materials
and the environment below the crust. That is what the people who do plate
tectonic theory do. Until you make a better model than they have, you are
doing what many scientists call arm waving. Lots of luck. >—->howard
Hey Howard!
Pardon my "arm waving" …. but
I just so happen to have a rough model that to me explains all the
observations with less problems….
Here from a previous post….
Try an alternative view for a moment….
To do this you need to get an ocean basin map that shows the faults and rises
and follow this sequence…
Assume for a moment the Earth is totally covered with a continental geological
crust without deep ocean basins only shallow seas…no separate continents…
no large faults just rolling hills from the original cooling of the crust
1a A star pulls off the crust(my favorite) or
1ba very large meteor plunges into the earth(an almost direct hit) and gets
through but almost comes to a stop but not quite…. it exits where the pacific
is now…..
and the incoming mass carries with it 2/3 of old earths crust……..
becomes the moon with the large metallic mascons in the earth side.
The the remaining crust breaks into the continents..
and they all flow towards the hole were the crust was removed.
North and south america split off from Europe and Africa.
Antarctica slid down to the S pole.
The hot plastic magma flowed outward from under each continent piece. When
these planet wide flows met roughly in the middle of the continent masses the
hot masses mounded up. The western pacific flowed the farest to meet the
americas. The firming front of the flows already becoming more rigid
adjusted back and forth in sections acording to the momentum and mass of the
flow in that area creating the clean shears only in the central colliding area.
Further back from what became the elevated rise the more plastic basin hardened
with out the transform faults.
All the features we see in the ocean basin crust are satisfied with this
theory.
While I have problems with the Subduction of the basins in the current
theories.
While that is a very brief description of a model it works for me better than
others for the time being. I'll flip to anouther theory if it works better.
Kamron
Open the map and visualise the event… look how all the features make sense
this way….
Hi Kamron — Sorry, but I don't see any equations in your model. When did the
collision or near collision occur? When did the hole fill in? Today the
mid-ocean rises are far from continents and the flow of new crust is toward
the continents. How do you account for this? Why are the rises still active
after the hole filled? How do you account for symmetrical magnetic anomalies
around the spreading center? Why is there subduction? It still seems to me
that your ideas need quantitation and modeling. >—->howard
Hey Howard
Equations? I'd need to hire someone for that.<g>
>> When did the collision or near collision occur?<<
At the end of the Cretaceous period.
>> When did the hole fill in?<<
The new ocean basins were formed in a few days…and all the plates became
locked into their present locations giver or take a few miles.
>> Today the mid-ocean rises are far from continents and the flow of new
crust is toward the continents. How do you account for this?<<
The new ocean basin material flowed out from under the remaining crust meeting
in the middle of the space between the continents. The force of the collision
caused the symmetrical rise and its craggy features. The pressure on the newly
hardened rise material caused the transform faults and their slipped condition.
>> Why are the rises still active after the hole filled? <<
The rise area is very irregular and fractured as it came together creating
voids and cracks that magma seeps upward in meeting sea water.
>> How do you account for symmetrical magnetic anomalies around the spreading
center? <<
The magnetic center of the earth has some of its material removed during the
catastrophe and moved very erratically being unbalanced causing regular
reversal of the apparent fields during those few days until it regained a
balanced condition.
>>Why is there subduction?<<
I don't think subduction is occuring….the crust is floating on heavier
liquids and I see no force in play that could push or pull the lighter material
downward.
>> It still seems to me that your ideas need quantitation and modeling. <<
This is just entertainment….I have no need to prove this concept…I just
enjoy trying to work it all out.
Merry Christmas
Kamron
Kamron,
Well, a few points.
First, we know that plates are being subducted and that the subducted plates
plunge into the asthenosphere at a near 45 degree angle. This is fact.
How do we know this? Seismological sounding. This gets into some pretty
complex geophysics but to greatly simplify things the sounding is like a
radar. A good book on geophysics could give you all the details.
Now that we know what *is* happening, we can take a stab at why. First you
gotta think in geologic time. These motions are very slow. Given enough
time and pressure, what we perceive as solid objects will undergo plastic
deformation. Kinda like silly putty. Or window glass. Ever notice an
really old window and how the glass is thicker at the bottom? With the time
and pressures involved these "rigid" plates deform. The average time
for a cooled subducted plate to be assimilated into the mantle is about
12 million years.
What is the driving force? The jury is still out, but it is commonly
believed to be convection. Seismology tells us the asthenosphere is
partially molten (perhaps about 3 – 5 percent) and is capable of plastic
flow. It is believed that large convection cells exist under the plates and
we're pushed along like a raft in a current.
The shapes of the plates has a lot to do with geometry. The movement of
these plates over the earth cannot be appreciated on a flat map. The earth
is spherical and this adds a new twist to understanding the movements of the
lithospheric plates.
In summary: The oceanic plates are relatively thin and dense and easily
subducted. Continental plates are thicker and very buoyant. Convection
drives it all.
What you really need is a good college textbook on geology. All this stuff
is explained in a good text with bibliographies for more info.
Mike
Hi Mike
>> First, we know that plates are being subducted and that the subducted
plates plunge into the asthenosphere at a near 45 degree angle. This is fact.
<<
How can you claim this as fact?
I understand that by seeing the different arrivals of groups of waves that
the different layers can be "seen". This is not enough to take it as fact that
the plate subducts.
Could it be that subduction is so necessary to explain the new ocean basins
that we are interpreting the data in a convenient way?
It seams odd that the plates being lighter and relatively thin that they would
go down …..seams as though they would break up in sections and pile up at the
surface like what happens to ice when broken by an icebreaker.
>> The average time for a cooled subducted plate to be assimilated into the
mantle is about 12 million years. <<
Why would the lighter material be assimilated into the heavier material?
>> With the time and pressures involved these "rigid" plates deform. <<
Ok but lets look at the facts…. Where the plate is being fabricated in the
rise the plate demonstrates brittleness in that it has regular fractures across
the ridge, transform and shift faults. In fact it is the most regularly
fractured area on earth.
Here the crust is newer and should be easy to deform…but it has rugged
craggy features with tremendous faulting. Why wouldn't it show huge cracks
where it turns to go down. Even millions of years couldn't cause it to bend
without cracking.
The appearance of the ocean basin crust looks more like material flowed out
from under the continents and met at the rise. The forces at play during
contact of the fronts caused the shift faults.
When looking at the relative motions of the plates it appears like wide
expanses of plates are moving in a focusing manner into a much smaller area
without any wrinkling of the plate at all.
I am not balking at accepting the standard explanation for the sake of being
iconoclastic…. I just need more proof to accept subduction.
Do you know of any source of graphic data on the subduction proving soundings?
Kamron
+ >> First, we know that plates are being subducted and that the subducted
+ plates plunge into the asthenosphere at a near 45 degree angle. This is
+ fact.<<
+
+ How can you claim this as fact?
+ I understand that by seeing the different arrivals of groups of waves that
+ the different layers can be "seen". This is not enough to take it as fact that
+ the plate subducts.
There is more to it than that. This is getting beyond me, but as I
understand it, secondary waves are generated at the boundaries of density
changes. It's not just the timing of the waves but the number and types of
waves that enable geophyicist to determine the structure of unseen volumes.
+
+ Could it be that subduction is so necessary to explain the new ocean basins
+ that we are interpreting the data in a convenient way?
+
No. What would be the point?
+ It seams odd that the plates being lighter and relatively thin that they
+ would go down …..seams as though they would break up in sections and pile up
+ at the surface like what happens to ice when broken by an icebreaker.
+
Doesn't seem odd at all. If you put one ice cube on top of another in a
container of water the one on the bottom will sink (if it's movement is
constrained in the horizontal direction) below the surface of the water.
Same thing with the mafic rock of the crust.
+ >> The average time for a cooled subducted plate to be assimilated into the
+ mantle is about 12 million years. <<
+
+ Why would the lighter material be assimilated into the heavier material?
+
+ >> With the time and pressures involved these "rigid" plates deform. <<
+
+ Ok but lets look at the facts…. Where the plate is being fabricated in the
+ rise the plate demonstrates brittleness in that it has regular fractures
+ across the ridge, transform and shift faults. In fact it is the most regularly
+ fractured area on earth.
+ Here the crust is newer and should be easy to deform…but it has rugged
+ craggy features with tremendous faulting. Why wouldn't it show huge cracks
+ where it turns to go down. Even millions of years couldn't cause it to bend
+ without cracking.
You have tremendous faulting where plates subduct too. As the people of
Alaska if they have ever noticed any side effects of the subducting plates
(like earthquakes). Faulting and deformation are the trademarks of
tectonics. Transform faults in the oceanic ridges are necessary for these
large plates to move over a spherical surface. "Rugged and craggy" features
are characteristic of the upwelling magma that produces the plates. You
need to think large scale; both time and size.
And rock does flow like plastic given millions of years. Most any
metamorphic rock will show you this. Whole mountains have their lithology
upside down and overturned. You can see layers of rock that make complete
180 degree bends over themselves. Take a look at Shelton's "Geology
Illustrated" for examples of this.
+
+ The appearance of the ocean basin crust looks more like material flowed out
+ from under the continents and met at the rise. The forces at play during
+ contact of the fronts caused the shift faults.
+
The motion of the plates have been measured. New material is added at the
oceanic ridges. Two points, each on opposite sides of the ridge, are now
further apart from each other than in the past. Rates of movement of up to
18.3 centimeters per year have been measured between the Pacific and Nazca
plates.
+ When looking at the relative motions of the plates it appears like wide
+ expanses of plates are moving in a focusing manner into a much smaller area
+ without any wrinkling of the plate at all.
+
I'm looking at a plate map right now and don't see that at all.
+ I am not balking at accepting the standard explanation for the sake of being
+ iconoclastic…. I just need more proof to accept subduction.
+ Do you know of any source of graphic data on the subduction proving
+ soundings?
+
+ Kamron
Yes, you are balking. There is tons of evidence that plate tectonics is
real. There is no widespead conspiracy to force everyone to believe
tectonics exist. Why would there be?
Most any library should have many geology books with more info. Here are a
few at random:
_Earth_, Press & Siever
_Petrology_Igneous,_Sedimentary,_and_Metamorphic_, Ehlers & Blatt
_Elementary Seismology_, Richter
_Introduction_to_Geophysical_Prospecting_, Dobrin & Savit
_Exploration_Geophysics_of_the_Shallow_Subsurface_, Burger
_Geology_Illustrated_, Shelton
You can also GO USENET here on CompuServe and check out sci.geo.geology.
Take a look at GO ENCYCLOPEDIA as well.
Mike
>> determine the structure of unseen volumes. <<
There is no clear picture of what lies hundreds of miles below the surface. We
know that rock density increases from the surface of the earth to its center.
Seismic wave speeds and directions change abruptly at certain depths. Because
shear waves do not travel through the outer core we believe the outer core is
liquid.
Your stacked ice cubes won't hold water. The densities of the floating crust
and the liquid below is much different to start with. Then you could only push
it down if you could guide it. You can't push it down from the side. If it is
deformable it would buckle. It would seek at times if not all the time to run
up the beach and slide on up rather than force its way downward.
To help visualise the situation here think of a line of barges say 500 miles
long. There is no way to push them down. How would it get started?
And besides why wouldn't the melting crust leak back up the penetration seam?
Why would it bore threw the continent in a new place?
<<You have tremendous faulting where plates subduct too.>>
Yes but parallel with the motion instead of perpendicular with the motion as
the bending would require.
>> And rock does flow like plastic given millions of years. Most any
metamorphic rock will show you this. Whole mountains have their lithology
upside down and overturned. You can see layers of rock that make complete
180 degree bends over themselves. Take a look at Shelton's "Geology
Illustrated" for examples of this. <<
All this can better be explained with a much simpler single grand catastrophe
than with millions of years. Millions of years cannot explain things that go
against observed facts.
>> I'm looking at a plate map right now and don't see that at all. <<
referring to the focusing of motion….and other improbabilities
How about the convergent boundary at the north side of the Indo-australian
plate, The pacific plate has a convergent boundary in three compass directions.
How about the lower part of the african plate is divergent zones all moving
into a focal point in South Africa… yet the crust is actually getting
smoother as it moves from the rise to the continent.
>> There is tons of evidence that plate tectonics is real. <<
I don't pretend to have seen much of the evidence. All the books out are
pushing the theory and its got more bugs than my garden.
There are some very basic problems, the more I look at it the worse it gets.
>> Transform faults in the oceanic ridges are necessary for these large plates
to move over a spherical surface. <<
Not true. These faults again are perpendicular to the direction they would
occur to move over the curve.
The transform faults and shift faults could only exist just in the rise if the
formation occurred rapidly and recently.
These faults are the same as would result from flows of molten magma in rapid
motion meeting rapid motion and there being variations in the mass and momentum
along different lengths.
Look at the Heezen Fracture visualising the flows of magma. The distension of
the crust forming Australia & New Zealand and the other Islands dissipated and
slowed the flow below the fracture, above the fracture there was more speed and
momentum thus the rise shifted towards
South America. Look at the flow marks through the gap between antarctica and
south america from the rapid pacific flow.
The rise area was firming and cracked up while the slower cooling latter flows
cooled without cracks.
Let yourself go with a mental video and it clears up like a Stereolusion
….clearly popping into view.
Kamron
You regularly dodge the "simpler" aspects of your grand catastrophic
inter-planetary collision. You can't imagine plate movement, but you can
imagine Venus changing orbit?
HEy John
>> You regularly dodge the "simpler" aspects of your grand catastrophic
inter-planetary collision. <<
I am looking for interaction here and dogging is not my style.
Do you have a specific example?
>> You can't imagine plate movement, but you can imagine Venus changing orbit?
<<
I'm not sure what you mean here.
I agree there are plates and while I can imagine them moving they are
gridlocked and have very little motion only adjustments to the gravitational
effects of the Sun and Moon.
Venus being retrograde in rotation has obviously undergone trauma from some
type of collision or flyby. Don't you agree?
Kamron
Kamron,
You're still not getting it. There is more to seimology than S and P
waves. At any abrubt density or phase change you'll get a discontinuity and
the generation of second-order waves. This is one method gas and oil people
use to map underwater sedimentary structures in their quest for oil and gas.
If you really want to understand this you'll just have to read on the
references from my last post.
I just don't get what you're trying to say about the ice and barges.
And yes, melting crust does leak back up from subduction. That is where
granite comes from. You need to read a intro-geology text.
Bore threw the continent? I have no idea what you're talking about here
either.
Yes, the transform faults are indeed parallel with the motion of the plates.
You're still thinking of a 2D map. Once again, a good geology text should
illustrate why these transform faults exist.
You can explain all metamorphism and structurally geology with a *single*
catastropic event??? I'm beginning to see…..
I think your problem is that you think the earth is flat…like the map
you're looking at. Flat maps contain distortions. If you could visualize
the motions of the plates over the spherical surface of the earth your
problems with tectonics would go away. However, I don't think you really
want to believe anything except what you see as the truth.
I have given you all the info I'm going to. It's clear you're just not
willing to do the research necessary to debate this topic effectivly.
All you need to do is read some of the books I've referenced in my last post.
Mike
Settle down Mike
The only problem I have is subduction. I have too much experience working with
materials to bite off on the subduction concept. It doesn't mean it isn't
happening and it won't be the end of your world if it isn't. Healthy
questioning is what I am up to.
You still haven't explained how the convection currents have enough effect on
the plate to force it into doing something that it would not normally do.
Pushing won't work especially over the curved surface of the earth.
>> Bore threw the continent? I have no idea what you're talking about here
either. <<
Yes… thats the explanation of volcanic activity away from the "subduction
zone" the melting crust dissolves the lithosphere and arrives at the surface.
I am considering the plate activity as a whole and unless you can explain the
force that is pulling or pushing the oceanic crust downward
just say so…. its easy…. .
Convection forces cannot pull something floating down very far or for long.
When you read the text how did you solve the apparent problem?
Kamron
// >> Bore threw the continent? I have no idea what you're talking about here
either. <<
Yes… thats the explanation of volcanic activity away from the "subduction
zone" the melting crust dissolves the lithosphere and arrives at the surface.
//
Ahh…I see. The friction and pressure from one plate sliding under the other
produces a felsic magma. This magma is less dense then the surrounding
country rock and slowly "pushes" it's way to the surface…kinda like a lava
lamp.
Now, your next question will be why is this magma so much less dense than
the plate that is being subducted (which sinks)? Well, it's not much lighter.
The time for this magma to rise to the surface and form granitic plutons or
what-have-you is measured in millions of years. Also, there is some complex
geochemistry going on as well. The under-riding oceanic plate is, well, to
put it simply, waterlogged. The role of this presence of water, not to mention
the pressure, is very important in the compostion of these magmatic melts.
The chemistry is way beyond me. Now you need a good text on geochemistry
or Petrology.<grin>
// Convection forces cannot pull something floating down very far or for long.
When you read the text how did you solve the apparent problem?//
I don't see a problem. Let's look at it another way. The oceanic plates are
about
70 km thick. When two of these plates collide something has to happen. The
most logical thing is for one plate to override the other. So due when end up
with
70 km high mountains as one plate rises above the sea and flops down on top of
the other? No. Why? Weight. The mantle won't support that much weight in
a given area. Thus one is forced under the other as the "engine" that pushes
these plates around doesn't stop. As the bottom of a plate gets more than
about
100 – 150 km down it starts to melt from the greater heat at that depth.
How that?
Let me know if you have other questions. I'm frustrated as these medium
makes it kinda hard to present data of this type in a clear, logical manner.
It would help if I was a better teacher, too.
Mike
Mike
>> The friction and pressure from one plate sliding under the other produces a
felsic magma. This magma is less dense then the surrounding country rock and
slowly "pushes" it's way to the surface<<
I can see that it could rise straight up once it got started but it seams some
of it would go back up the seam of the subducted crust …and there isn't any
at all around the deepest trenches where the subduction is thought to be
occuring.
>>Now, your next question will be why is this magma so much less dense than
the plate that is being subducted (which sinks)?<<
No problem with that. The liquid form would be lighter than the solid.
Making it likely that some trace would leak back up the seam.
If the crust is floating on a liquid (which I agree with) and the pressure of
magma at the rise is sufficient to cause leaks….then the pressure in the deep
trenches were subduction is said to occur would much higher…the subducting
crust would open up a path for the magma and it should be squirting out all
along that zone. But there is no evidence of magma flows along the trenches
that I know of….
>> the "engine" that pushes these plates around <<
This is very tough for me also …I see no forces in play that could translate
into plate subduction. No pushing or pulling force. Convection doesn't have
enough grip to force the subduction especially where there is no breaking of
the surface. How do you see the engine?
Kamron
Hi, Kamron–
}} >> Bore threw the continent? I have no idea what you're talking about here
either. <<
}} Yes… thats the explanation of volcanic activity away from the "subduction
zone" the melting crust dissolves the lithosphere and arrives at the surface
If an ice sheet is pushed or pulled underwater at roughly a 45 degree angle,
bubbles trapped in the ice when freed by melting might rise straight up instead
of angling to follow the "weakness" made by ice penetrating water.
I am fuzzy on whether magma bubbles would be mostly generated so deep that they
would establish their rising direction in the realm of plasticity.
–Doug
<<If an ice sheet is pushed or pulled underwater at roughly a 45 degree angle,
bubbles trapped in the ice when freed by melting might rise straight up instead
of angling to follow the "weakness" made by ice penetrating water.>>
My understanding is that in the case of a denser oceanic crust subducting under
the edge of a less dense continental crust and the subsequent flow of magma to
the surface, we should remember that at the boundary, both plates are in
compression. As the edge of the continental crust is turned up as the oceanic
crust turns down, at some distance back from the boundary the lower portion of
the the continental crust goes into tension and bending, and cracks. The magma
takes the easy route and follows the cracks to the surface; it would be
contrary to the laws of physics for it to fight its way back through the zone
of compression to vent at the actual "edge" of the subduction zone.
Hi, Kamron–
>> Could it be that subduction is so necessary to explain the new ocean basins
that we are interpreting the data in a convenient way?
A lot of geologists had to be dragged kicking and screaming into the plate
tectonic consensus by the facts – I am sure they had to do a lot of looking for
other fits to the facts, including other explanations for young (to a
geologist) sea floors, but each "fit" attempt dissolved when subjected to
examination and test. If these had not been tried pretty thoroughly, too many
holdouts would remain.
It is not impossible the seismic readings do not mean what we think, but until
stronger evidence shows up, it is not wise to bet against them. What else
could they represent?
>> Why would the lighter material be assimilated into the heavier material?
Because they are roughly the same elements in roughly the same ratios. Put
basalt under high pressure and temperature, and the atoms will be rearranged to
match the mantle rock (from which the basalt originally came) at whatever depth
it has reached. Ice will be assimilated by water, or vice versa, whichever way
the temperature dictates. This takes a while, so if the basalt keeps sinking,
it may get a little deeper than the mantle it is matching, but sooner or later
the currents will stir them up together until their origins are lost.
Your line of barges might be sunk by a line of lighter barges, if the lines are
pushed together hard enough and there are big enough waves (or beveled bows)
enough to allow the lighter ones to start an edge atop the heavier ones. If our
"sonar" (seismic mapping) showed barges underwater in expected positions near
other appropriately moving barges, it would be reasonable to assume that this
happened, and that there was some driving force even without certainty of its
exact nature, especially with several plausible candidates vying for attention.
–Doug
>> A lot of geologists had to be dragged kicking and screaming into the plate
tectonic consensus by the facts too many holdouts would remain.<<
While I risk nothing discussing my views….It takes a lot of guts to buck
status quo if you are part of the Scientific establishment….and if the
evidence discovered steps on the established toes it would be a risk that only
fools would take.
>>It is not impossible the seismic readings do not mean what we think, but
until stronger evidence shows up, it is not wise to bet against them. What
else could they represent? <<
I guess I need to look at this evidence and see what else they could
represent. Would you know of a source of graphic data showing the structures
that appear as subducted crust?
Doug you have consistently and patiently discussed a wide variety of my
iconoclastic views with genuine interest and I really appreciate the exchanges.
Kamron
Hi, Kamron–
Regarding your answer to Mike in this thread, the mantle is not liquid, it is
plastic. I think even the thin asthenosphere between lithosphere and mantle is
only partially liquid if any. "Plastic" means it is a solid in a state where
crystalline bonds can break and reattach in new places in patterns that let the
material flow sort of like a liquid, but _much_ more slowly. It is like the
difference between independently rolling balls (the liquid), and a centipede
which remains bonded to the surface unlike the balls, yet still manages to
move.
This offers an answer to your remarks about how the convection currents can
push/pull the crust – I suspect the subducted lithosphere and the convecting
mantle are bonded together, even if the bonds are shifting from time to time.
They are likely coupled much more strongly than a liquid can be coupled to a
solid.
It also offers the answer to your problem with material melted out of the
subducted plate rising straight up instead of following the "weakness" where
the subducted lithosphere meets the mantle – I suspect there is no such
weakness as far as a faster-moving liquid is concerned, that the lithosphere is
already bonded with the mantle into a continuous solid. It is critical to ask
whether the magma starts rising in the realm of plasticity, because that is
where I expect this bonding would form, more or less.
–Doug
Hi, Kamron–
Sea floor basalt is less dense than mantle material, but it is more dense than
general continental rock. If a flat-topped iceberg meets a flat-bottomed boat,
and they are moving too fast to simply stop, the boat is likely to push up on
top of it, since it rides higher in the water – this will push the iceberg
underwater, and if there is also a downward current in the water, it may get
caught and be pulled still deeper (well, maybe not, but that is because the
density difference is likely greater than that between seafloor and mantle) and
"try" to drag down anything attached behind it. Unlike the iceberg, subducted
mantle may later become denser yet still remain "attached", able to drag
further seafloor behind it.
I gather geologists are still arguing about subduction-pull versus
spreading-push as the more important force moving the plates. If it is push
from spreading, that is the irresistible force that cannot easily be
"satisfied" by mere crumpling at the collision sites, which can only absorb a
limited amount of crust. Something has to dive.
Even if the force is "none of the above", the evidence for plate tectonic
motions is strong enough to declare that it must exist, whatever it is.
–Doug
Doug
>> I gather geologists are still arguing about subduction-pull versus
spreading-push as the more important force moving the plates. If it is push
from spreading, that is the irresistible force that cannot easily be
"satisfied" by mere crumpling at the collision sites, which can only absorb a
limited amount of crust. Something has to dive.<<
Considering the push aspect..
If the force is push…. it would be much like a hydraulic type of effect…
pressure building between two sides to push them apart…this to me seams
impossible in that if the pressure was enough to transmit force along the
hundreds sometimes thousands of miles of crust to the front and force
subduction…. it would blow out at the rise spewing magma miles into the
air…seeking the path of least resistance. The thin crust at the rise offers
very little bearing for the force to be applied it would seek the the easy way
out. Blowing away a few miles of crust in an area that is already fractured and
leaking would be its natural route.
>> Even if the force is "none of the above", the evidence for plate tectonic
motions is strong enough to declare that it must exist, whatever it is. <<
I am not convinced that the evidence proves motion beyond adjustments in the
plate interfaces. The conclusion that the motion continues in a direction
ending up in subduction is a stretch.
Kamron
Hi, Kamron–
I am not sure that pressure between the plates is the only string in the bow
of the "push" theorists – perhaps the asthenosphere is less than frictionless
and allows some coupling between the convection in the mantle and the
lithospheric plate, perhaps mountain roots project into the mantle and give it
something to push against, and so on. I do not know which of these are part of
the canon.
The pressure between plates need not be of the sort that explodes as magma
fountains. Consider water freezing in cracks to split rocks; I'll grant magma
probably does not expand on freezing, but note that not all pressures are prone
to explosions, nor must they become ineffective if there is an escape open.
I'd be interested to hear exactly what mechanisms the "push" theorists have
worked out.
It is not a "stretch" to jump from moving plates to subduction. If I am
convinced by radio-dating, paleomagnetism, hot spot relative-motions, etc. that
the sea floor is moving, it is quite straightforward to ask where it goes when
it meets another plate or continent and decide the "sonar" image we see on
seismographs is the answer (bearing in mind no other answer offers anything
approaching this quality of evidence).
Nowadays, anything contradicting plate tectonics might indeed get ignored for a
while if it is not too spectacular; scientists are human. But alternate
theories, including some rather like yours, were present before plate tectonics
became the standard-bearer. When the youth of the ocean floor was detected,
simultaneous resurfacing must have been an obvious contender to plate
renewal/movement/destruction, and must have received plenty of attention. In
that conflicting state, only evidence, not stodgy following of establishment
theory (which if anything favored the resurfacing-everywhere theory), can cause
a new consensus to form among true scientists despite their human failings.
If a scientist now comes up with solid evidence (not just theories) leading
away from plate tectonics, that person will indeed face considerable risk to
his/her career by pressing the battle, but also considerable gains if proven
right. Many fields of science show frequent overturns of consensus theories,
thus I know any institutional inertia can be overcome sooner or later.
–Doug
Doug
>> The pressure between plates need not be of the sort that explodes as
magma fountains.<<
The very nature of upwelling or moving up should dissipate any power the
magma would have unless the pressure was contained…it could offer no
power to push.
>>I'd be interested to hear exactly what mechanisms the "push" theorists
have worked out.<<
I would also…anyone listening?
>>It is not a "stretch" to jump from moving plates to subduction. If I
am convinced by radio-dating, paleomagnetism, hot spot relative-motions,
etc. that the sea floor is moving,<<
By moving I was not suggesting that it goes anywhere, the motions are
adjustments. The earthquakes occur very frequently when the
gravitational effects of the sun and moon are certain relationships. I
view part of the process as conjunctions of tides below the continents
in the liquid layers below the plates.
I am still digesting the plastic state you described.
Increasing the viscosity would enable a good enough "hold" to do the work
necessary to subduct.
Even if this condition existed below the plates…
and there was a wide area laminar flow the fragile crust would show more
evidence of deformation around the subduction areas.
For instance …look at the interface between the Pacific and Indo-Australian
plates around the Fiji Basin. You have the P plate going under the IA where
the Tonga trench is running North and South.
The IA plate is going under the P plate at the bottom of New Guinea and the
Coral Sea side of Melanesia.
The P plate supposedly is subducting under the Fiji Basin comming at it from
two sides. Here we have both plates subducting under each other at the same
place in the same location with out any fractures or pile ups or any
distortions in the fragile crust.
With all these motions in mind look at how the North Western Pacific area from
the Aleutian Trench Arc around and including the trenches on each side of the
Philippine Plate you have motions in many angles both away from certain points
and moving towards certain points and the crust shows no distortions warping
and bending and melding with very little character deviation aside from
seamounts in chains.
Why would the crust be fractured when created and smooth where it is denser,
thicker and colder. How could the crust stay so level going threw all those
perturbations….as it spreads away from itself …
and.. converges in on itself?
There is no material and certainly not magma that is more fragile when hot
than cold.
If the process that causes subduction is able to move new ocean basin under
the continents at a rate faster than continents build on top of it how did the
continental crust form initially? What preserved it when it was a thin sheet
like a present ocean basin.
The Rises are the most consistent appearing and composed structure on the
entire earth. It is also very balanced in its fracture system on each flank of
a given section of rise. The trans rise fractures are very parallel to each
other and very perpendicular to the symmetrical profile of the rise. They all
had a very similar creation process.
This Rise formation process included the greatest and fastest shifts on the
surface of the earth. These shifted plate fractures are very straight very long
and again very parallel with only small angles of change.
The plates _both_ shifted….. without a trace of the adjustment farther back
from the rise in either direction. How can this be possible?
If the process that causes the rise is a somewhat permanent Convection
Current….. arranged in a linear formation for millions of years…. why did
the convection current upwelling areas shift with the rise when the shift
fault movement occurred?
Kamron
Hi, Kamron–
>>The very nature of upwelling or moving up should dissipate any power the
magma would have unless the pressure was contained…it could offer no
power to push.
Since you have already claimed this, and I have offered a counterexample, this
is "proof by assertion". Have you any evidence? You could say the same about
water, but it would not be true as evidenced by my freezing example. I suspect
you are correct in this statement, but do not take it as a given.
>> Even if this condition existed below the plates… and there was a wide area
laminar flow the fragile crust would show more evidence of deformation around
the subduction areas.
More evidence than ocean trenches and volcanoes with a strong tendency to be
"downstream" of the trenches? I think this depends on how frictionless is the
connection between lithospheric plates and mantle at the asthenosphere; that is
why I had to specifically specify mountain roots to give the convection
currents something to "grab". Until someone can spend time making measurements
down there, this seems to be another adjustable parameter that neither confirms
nor denies the theory.
I am not equipped to discuss your geographic details while traveling; perhaps I
will have something to say when I get home to my references, in a bit over a
week (best guess).
>> The plates _both_ shifted….. without a trace of the adjustment farther
back from the rise in either direction. How can this be possible?
Most if not all faults come to an end, and the same question applies to all
those ends. It seems no better explained by your theory than by plate
tectonics.
>> why did the convection current upwelling areas shift with the rise when the
shift fault movement occurred?
We already discussed that, why are you repeating it? Perhaps the rise was
forced to move by a change in the current position rather than vice versa, or
perhaps the current is wider and the rise is atop the unmoved current as much
in the new position as the old.
–Doug
–Doug
Doug
Well I am starting to repeat myself and here I go again
Summary of my big problems with subduction
1. The ocean basin plates are very rigid evidenced by the fractures and
craggyness where they are being formed and the fact that they are hardened
magma and granitic scum. The Tectonic plate theory calls for plates to be
spreading, warping bending and converging. There is little evidence that this
is happening. The ocean floors aside from the rises, seamounts, and continents
are relatively smooth and show none of the bulging , cracking, waving,
splitting, piling up, ect that would be evident if all the motions in the
plates were taking place.
2. The shifting of the rise sections demonstrates that the source of the rise
is connected to the rise..moves with the rise and not formed from a massive
convection current system that dwarfs the continents and the puny ocean basins.
3. If the rise is caused by a convection current system how is it that a rise
is linear in a north and south alignment…what would cause a consistent linear
heat source on the interior of a sphere?
4. The floor has evidence of motion and swirls and streaks in the ocean basin
floor…why would these features remain visible when the rise features
disappear?
5. There should be a major pressure differential between the deep trench area
and the higher rise area causing massive magma flows at the trench areas.
6.The continents would need to change shapes and sizes as they shrink and
distend to accomidate the motions necessary to account for what appears by
Plate Tectonics.
BTW
The convection system would work much better if visualised just opposite in
flow. The flow comes up the sides of the continents and flows towards the
middle area between them. Where the flow meets and goes downward it would
naturally be between the continents. There is a backflow up the space between
the downward laminar flows and this is what is heating and reprocessing the
basin floor…..NAAAAAA.
The basin core magnetics may be the best place to start..know where we can get
our hands on any?
Know anybody at Woods Hole Ma.? they have core material there I believe.
Super New Year to Ya Doug!!
Kamron
Hi, Kamron–
>> 1. The ocean floors aside from the rises, seamounts, and continents are
relatively smooth and show none of the bulging , cracking, waving, splitting,
piling up, ect that would be evident if all the motions in the plates were
taking place.
I need to study on that one.
>> 2. The shifting of the rise sections demonstrates that the source of the
rise is connected to the rise..moves with the rise and not formed from a
massive convection current system that dwarfs the continents and the puny ocean
basins.
There is no need or evidence to suppose the convection follows rise movements.
You have offered no reason to suppose it could not be the other way around,
that the rise is moving because the convection is moving (or is in both places
equally).
>> 3. If the rise is caused by a convection current system how is it that a
rise is linear in a north and south alignment…what would cause a consistent
linear heat source on the interior of a sphere?
You have offered no reason why linear heat sources are needed to get planar
convections (and thus linear ridges). Since examples of non-linear sources
producing such flows are abundant, what is the problem?
>> 4. The floor has evidence of motion and swirls and streaks in the ocean
basin floor…why would these features remain visible when the rise features
disappear?
Interesting question – maybe when I get back to my references I will find an
answer.
>> 5. There should be a major pressure differential between the deep trench
area and the higher rise area causing massive magma flows at the trench areas.
Given that the ridges and trenches are so far apart, why would it have to be
released at the trenches? And why can it not be absorbed by deep processes?
>> 6.The continents would need to change shapes and sizes as they shrink and
distend to accomidate the motions necessary to account for what appears by
Plate Tectonics.
We see a continent changing shape in the Himalayas, which I believe have been
measured to be still rising as the collision of India with Asia continues to
push them up. Changes due to collisions and splittings are important to
supercontinent cycle theory. Continents are constantly growing as island arcs
accrete to them. Do they need to change shapes beyond this to accomodate plate
tectonics? Do shape-shifting continents force any predictions that contradict
observation? A theory can be weird and counterintuitive (consider quantum
mechanics), but only the facts really matter – nature is not concerned with
whether it is understandable to us.
>> The basin core magnetics may be the best place to start..know where we can
get our hands on any? Know anybody at Woods Hole Ma.? they have core material
there I believe.
I do not know where to look.
You told Jon certain solar system phenomena "can only be explained by flybys"
or words to that effect. If that is so then it looks like they cannot be
explained, period. The flybys would produce results like the flyby of Comet
Shoemaker-Levy and Jupiter – the comet was tossed into an orbit so wild that it
lasted only one time around before hitting Jupiter. There were indeed moons
formed (well not moons, since they had their own independent orbits so they did
not arrive all at once), and crust ripped off (well, it was more like being
taken apart rather than skinned), but in the end, just – SPLAT!
HNY! –Doug
Doug,
>> >> 1. The ocean floors aside from the rises, seamounts, and continents are
relatively smooth and show none of the bulging , cracking, waving, splitting,
piling up, ect that would be evident if all the motions in the plates were
taking place. <<
I need to study on that one. <<
Maybe I can save you a bit of time. I'm sitting here looking at a relief map
of the ocean floors, almost certainly done from satellite radar scans combined
with penetrating sonar scans. It shows that the vast majority of ocean floor
consists of continental rises, slopes, shelves, plateaus, ridges, fracture
zones, and submerged mountain ranges. "Abyssal plains" cover a very small
fraction of the total ocean floor, certainly no more than 10% and probably
around 5% or so.
A lot of this relief is *only* visible from satellite scans or penetrating
sonar scans. Over much of the sea, the features are buried beneath tens or
hundreds of meters of accumulated sediments.
Jon W.
>>There is no need or evidence to suppose the convection follows rise
movements. You have offered no reason to suppose it could not be the other way
around, that the rise is moving because the convection is moving (or is in both
places equally).<<
The rise is the most organized and consistant feature on the earth. It has the
same basic features all along its 50,000 mile length, an up lifted region that
has parallel and perpendicular fractures. It is more or less balanced between
the continent masses that it lies between. ( To see this fragmented continent
stragglers need to be estimated back against the main mass before the
measurements. the northern Pacific basin where I maintain departure occurred is
the only nonconforming basin.)Therefore the entire rise must have been created
by the same source in a similar way that underwent very similar chaotic
stresses to distort what was originally aligned. If the rise has been a
continuous creation over millions of years the shifted sections would have
blended centers…that is the rise initially would have shifted parallel
centers like we see now…but in time weather the building mechanism was huge
or focused these shifted parallel sections would end up looking like S curves
as new Rise was being created. The deep shifted transform faults and the rise
would have blended. This proves that the shifting all occurred recently and all
at once.
>>You have offered no reason why linear heat sources are needed to get planar
connections (and thus linear ridges). Since examples of non-linear sources
producing such flows are abundant, what is the problem?<<
On the earth linear convection on the surface of the earth is due to heat
absorption along a linear maximum, if the earth didn't rotate there would be a
less linear convection system and would organize into increasingly larger
cells. All convection is source dependant and for an uprising to occur there
must be a heat source. It will not organize into a linear upwelling unless
there is a linear source. The down cycle is more linear at times and is
confined by the down cycles of its neighbor cells and other restrictions. There
has been no explanation of how this interior linear source could function.
There is also another problem in that the rise is balanced even though the
speed of the flow on each side would be a factor of the size of the downward
cycle of the cell and when the up and down cycles are plotted there is a big
difference. The African and south american cells are much smaller than the
asian cell. The source of the up welling is the same but the materials that
move from the source through their cycle back down and then up again would have
different speeds. The rise should be forming and moving much slower on the
asian side of the rise than on the other sides. but it is balanced.
>>Given that the ridges and trenches are so far apart, why would it have to be
released at the trenches? And why can it not be absorbed by deep processes?<<
Pressures would all seek a balance. The flow that is said to occur towards the
trenches would increase the pressures if anything yet there is no leaking at
the subduction area.
Another problem… There are a few areas where the rise has three legs…
south of india, east of South America. These areas on one hand should have an
increased upwelling and increased building….the formation of new continent on
a three axis system should create an area that has the evidence of the
trilateral accretion of crust… that is there should be an increase of
material where the two sides of the rise are building towards each other, the
galopogos Islands for one may show this but instead of volcanic islands I would
expect to see a folding of the crust here.
Another observation… if you look at the area south of the Indian there are
linear features that flow southward towards Antarctica. It is easy to see the
flow of that continent away from the african and indian masses. The flow
patterns are carved into the basin. If the separation of the masses was caused
by the Rise why would these linear flow like patterns be evident in the basin?
Another problem…. There are pieces of Continental crust( this is crust with
a geological table as opposed to volcanic Islands.) all around the existing
continents. If the rise divided the masses and built up between them then why
are these pieces separated from the main mass. This has occurred all over the
planet. If the basin was formed in the rises and pushes the land masses apart
why have the rises formed around these masses as a rule.
Kamron
Hi Kamron & Doug & All
Keep it up! Your continuing conversations on Subducton & Ocean Basin
dialogue is interesting & informative.
Rod
Hey Rod!
It is very interesting…..and thanks for the encouragement
it is sometimes very lonely taking an opposing view…
Doug is such a great communicator and indulgent!
Chime in anytime you have an opinion!
Kamron