How did Earth crack? New study may explain origins of plate tectonics on our planet.

Jul 26, 2020
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There may be two significant flaws in this new theory about the origins of the tectonic plates. The Continental crust only covers 30% of the Earth's surface and, unless you include the crust that is underneath the oceans which is regularly recycled into the mantle, has no features similar to the Continental crust and structurally is more similar to Oceanic crust. If that is not included, then the paucity of Continental crust must be explained.

My second issue is the statement that we know how the continental plates move. As far as I know, only mantle currents or mantle plumes are under consideration. Yet, neither of those mechanisms adequately explains the fissure that extends from the North to the South pole and separates Europe and Africa from the Americans.
 
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There may be two significant flaws in this new theory about the origins of the tectonic plates. The Continental crust only covers 30% of the Earth's surface and, unless you include the crust that is underneath the oceans which is regularly recycled into the mantle, has no features similar to the Continental crust and structurally is more similar to Oceanic crust. If that is not included, then the paucity of Continental crust must be explained.



My second issue is the statement that we know how the continental plates move. As far as I know, only mantle currents or mantle plumes are under consideration. Yet, neither of those mechanisms adequately explains the fissure that extends from the North to the South pole and separates Europe and Africa from the Americans.
The intention was to explain why plate tectonics got started, which they do (as in proposing one among many earlier such explanations). I agree that the extent of continental crust and specifically its history remains to be better explained!

Plate tectonics is mostly driven by subduction, meaning gravitational potential energy is responsible. How much of that mechanism builds from convection or from gravitational driven sorting and shrinkage in the mantle I don't know, that is why we have models covering the complexities, but it is AFAIK sourced by the heat flow out to space.

There is no "fissure" extending between the poles. If we look at a map of the current plates, we can notice two general properties and one that apply today.

1. Plate boundaries align the plates.
2. There are so called mid oceanic ridges between ocean crusts "in the middle" of large oceans, where oceanic crust is made by as oceanic plates separates - this is where plates are mostly made. There are also coastal stretches of volcanic arcs, where oceanic plates are subducted beneath continental plates - this is where plates are mostly destroyed.
3. Today the Antarctic continental plate covers the south pole and an Arctic oceanic plate the north pole - no polar plate boundaries.

https://en.wikipedia.org/wiki/Plate_tectonics :

[
 
Jun 1, 2020
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Are the cracks located along prior volcanic activity? If so, how does this model account for that? Wouldn't the advection reduce the volume beneath the crust causing more contraction than expansion?
 
I should add that the fit between the Americas and the Europe/Asian and African plates have long been noticed and was among the initial evidence for "continental drift" theory which later helped originate plate tectonic theory. The reason for the good fit is a recent and large continental separation, so geologists also see matching rock and fossils.

But the modern biogeographical evidence is also exciting. The New World monkeys as well as its crocodiles were able to transit from Africa to South America (originally, I think) while the ocean was open but narrower and had more volcanic islands. But aside from island hopping - which would have meant several trips - and the hardiness of crocodiles, even "pregnant" such, in salt water - I think floating "islands" are the best bet for both instances. I was reminded today it is a constant problem among local lakes as water is regulated and lift off tens of meters of floating islands that persist for at least a season (birds use them for nesting and some can be walked albeit very risky of course). Similar stuff happens around river outlets when the wet lands get flooded.
 
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Are the cracks located along prior volcanic activity? If so, how does this model account for that? Wouldn't the advection reduce the volume beneath the crust causing more contraction than expansion?
Good questions!

I haven't read the paper through, but I think either that or another article covering the paper discussed that both happens (so there likely is a competition here), but that their model can result in what they describe for some parts of the parameter space, I'm sure there is lots to criticize, I was waiting for the next series of papers where this model would be accepted or not. (Or sometimes people write a specific, immediate criticism.)
 
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Jun 1, 2020
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Thanks for your response.

There are a lot of ways to look at this, which makes it that much more of an interesting topic.

I'm no geologist, but I would guess that rock strata are more vulnerable to cracking under tension vs. compression, so contraction, if there was any, would make it easier to crack. But, on the other hand, contraction wouldn't paint much of a picture for initiating any subduction flows.

Another guess is that we have maps showing the varying depths of the mantle, so the thin regions might be the more vulnerable locations, which would affect any model, no doubt.
 
Jul 26, 2020
5
2
515
The intention was to explain why plate tectonics got started, which they do (as in proposing one among many earlier such explanations). I agree that the extent of continental crust and specifically its history remains to be better explained!

Plate tectonics is mostly driven by subduction, meaning gravitational potential energy is responsible. How much of that mechanism builds from convection or from gravitational driven sorting and shrinkage in the mantle I don't know, that is why we have models covering the complexities, but it is AFAIK sourced by the heat flow out to space.

There is no "fissure" extending between the poles. If we look at a map of the current plates, we can notice two general properties and one that apply today.

1. Plate boundaries align the plates.
2. There are so called mid oceanic ridges between ocean crusts "in the middle" of large oceans, where oceanic crust is made by as oceanic plates separates - this is where plates are mostly made. There are also coastal stretches of volcanic arcs, where oceanic plates are subducted beneath continental plates - this is where plates are mostly destroyed.
3. Today the Antarctic continental plate covers the south pole and an Arctic oceanic plate the north pole - no polar plate boundaries.

https://en.wikipedia.org/wiki/Plate_tectonics :

[
Describing the mid Atlantic ridge can get confusing. Yes it is a mountainous ridge. However, it is due to the separation of the continents and is also a fissure which opens into the mantle. Magma flowing from the mantle subsequently created the ridge.
 
Jul 26, 2020
5
2
515
The intention was to explain why plate tectonics got started, which they do (as in proposing one among many earlier such explanations). I agree that the extent of continental crust and specifically its history remains to be better explained!

Plate tectonics is mostly driven by subduction, meaning gravitational potential energy is responsible. How much of that mechanism builds from convection or from gravitational driven sorting and shrinkage in the mantle I don't know, that is why we have models covering the complexities, but it is AFAIK sourced by the heat flow out to space.

There is no "fissure" extending between the poles. If we look at a map of the current plates, we can notice two general properties and one that apply today.

1. Plate boundaries align the plates.
2. There are so called mid oceanic ridges between ocean crusts "in the middle" of large oceans, where oceanic crust is made by as oceanic plates separates - this is where plates are mostly made. There are also coastal stretches of volcanic arcs, where oceanic plates are subducted beneath continental plates - this is where plates are mostly destroyed.
3. Today the Antarctic continental plate covers the south pole and an Arctic oceanic plate the north pole - no polar plate boundaries.

https://en.wikipedia.org/wiki/Plate_tectonics :

[
"There is no "fissure" extending between the poles. "
The intention was to explain why plate tectonics got started, which they do (as in proposing one among many earlier such explanations). I agree that the extent of continental crust and specifically its history remains to be better explained!

Plate tectonics is mostly driven by subduction, meaning gravitational potential energy is responsible. How much of that mechanism builds from convection or from gravitational driven sorting and shrinkage in the mantle I don't know, that is why we have models covering the complexities, but it is AFAIK sourced by the heat flow out to space.

There is no "fissure" extending between the poles. If we look at a map of the current plates, we can notice two general properties and one that apply today.

1. Plate boundaries align the plates.
2. There are so called mid oceanic ridges between ocean crusts "in the middle" of large oceans, where oceanic crust is made by as oceanic plates separates - this is where plates are mostly made. There are also coastal stretches of volcanic arcs, where oceanic plates are subducted beneath continental plates - this is where plates are mostly destroyed.
3. Today the Antarctic continental plate covers the south pole and an Arctic oceanic plate the north pole - no polar plate boundaries.

https://en.wikipedia.org/wiki/Plate_tectonics :

[

"There is no "fissure" extending between the poles." This can be confusing. How can a fissure be a mountain ridge. As Torbjorn Larsson pointed out, the longitudinal ridge is the point where the continental plates separate, i.e. a fissure. Magma from the mantle rises through the fissure and creates the mountainous ridge which does extend almost the entire distance between the poles. My point is that this structure which defines the tectonic motion of the continents on either side of it, does not correspond either to the mantle current or mantle plume theories and, as one the most remarkable oceanic structures, does not have a good explanation.
 
Jul 26, 2020
5
2
515
"There is no "fissure" extending between the poles." This can be confusing. How can a fissure be a mountain ridge. As Torbjorn Larsson pointed out, the longitudinal ridge is the point where the continental plates separate, i.e. a fissure. Magma from the mantle rises through the fissure and creates the mountainous ridge which does extend almost the entire distance between the poles. My point is that this structure which defines the tectonic motion of the continents on either side of it, does not correspond either to the mantle current or mantle plume theories and, as one the most remarkable oceanic structures, does not have a good explanation.
 

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