Alfred Wegener ('continental drift' in 1915) is a geologist, and not a meteorologist

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“A wing generates ‘lift’ due to the faster air over the upper surface creating a ‘vacuum’ which lifts the airfoil”
“How does an airplane fly upside down then”
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I even recall reading that in a book for adults. Yes, there is lower air pressure above the wing than below.

So, how does a plane fly upside down? Maybe not as well and only using previous air speed! I don't know for sure. Excellent question. :)
 
. . . This is not really a convection cell, as the rising plume is not connected to the spreading centre . . .
Okay, even if slab pull is a stronger force than ridge push, it still means there's some force behind the ridge push at mid-ocean ridges. Which to my untutored eye, looks a lot like convection.
 
Okay, even if slab pull is a stronger force than ridge push, it still means there's some force behind the ridge push at mid-ocean ridges. Which to my untutored eye, looks a lot like convection.
Its not the upwelling of material itself that pushes the plate away from the ridge, but rather the plate sliding down the upwelled ridge in the mantle. The mantle itself has upwelled becasue it has been uncompressed by the fracture in the plate caused by the slab pull forces. There is no plume underneath the upwelling in the mantle that is carrying material from deeper in the mantle to the surface.

Simply put the upwelling occurs because the crust fractures and the mantle is uncovered. For convection to be the cause it would have to be the other way around, with the mantle actively breaking though the crust to force it apart. That is not an impossible scenairo, and it has occured several times on Earth beore, but it is rather... apocalyptic. The most signficant example was the Deccan Traps, during the Cretacous, and is thought to have played a part in the K-T extinction event.

It happens much more frequently on Venus, where the lack of water has prevented tectonic movment, and instead the crust is periodically resurfaced by titanic flood eruptions.
 
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I even recall reading that in a book for adults. Yes, there is lower air pressure above the wing than below.

So, how does a plane fly upside down? Maybe not as well and only using previous air speed! I don't know for sure. Excellent question. :)

Actually, despite the obvious 'airfoil' shape a wing still generate lift 'upside-down' just not as well. If you watch them usually you'll note a bit of a higher 'AoA' (Angle of Attack) to the aircraft when flying upside down near the ground to enhance this lift...

Now on the subduction zones I am aware that it has been suggested that we could 'recycle' (read: get rid of, not really recycle) nuclear waste by drilling into the subduction plate and putting the waste. But that diagram would seem to argue that unless the waste is really deep in the layer it might 'precipitate' out too soon?

Randy
 
. . . For convection to be the cause it would have to be the other way around, with the mantle actively breaking though the crust to force it apart. . .
I’m open to the idea that convection merely is the “conventional wisdom,” even repeated in textbooks.

All the same, I’d like to see a reference or two.
 
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Now on the subduction zones I am aware that it has been suggested that we could 'recycle' (read: get rid of, not really recycle) nuclear waste by drilling into the subduction plate and putting the waste. But that diagram would seem to argue that unless the waste is really deep in the layer it might 'precipitate' out too soon?
Some of it might come through as volcanic lava in (?) 20,000 years or so, just guessing at time frame.

Of course we humans are so right-now oriented, not even sure that would work well in fiction.
 
Yes, thank you, I see per this website by Columbia University:

‘ . . . variation in gravity produced by upwelling and downwelling regions, indicates that there are multiple convection cells beneath the Pacific plate. The combined effect would not be one that would drive the motion of the plate - some cells would help, some would hinder. . . ’

‘ . . . However, mantle flow may be important locally with respect to the motion of continents with deep keels (thickened lithosphere, especially in old orogenic belts), but not for oceanic lithosphere.’
Instead, the driving force for oceanic plates is . . .
 
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driving_forces.gif


. . . just plain old gravity!
 
It happens much more frequently on Venus, where the lack of water has prevented tectonic movment, and instead the crust is periodically resurfaced by titanic flood eruptions.
So when someone says continental drift is caused by convection, I can retort with 'only on Venus' and be correct?
 
So when someone says continental drift is caused by convection, I can retort with 'only on Venus' and be correct?

Well no. Venus has no tectonic plate movement , and thus no continental drift, as it has no water, which is vital for lubricating subduction. Instead it is thought that periodically massive plume build up under the Venusian crust, putting so much pressure on it that the plume breaks through and floods the surface with titanic amounts of lava. Successive events are thought to eventually resurface the entirety of the planet.

There are presumably mechanisms by which parts of the crust are forced down into the mantle to balance this. Perhaps a sort of fragmentary subduction lubricated by the lava itself. However not being able to take field trip to Venus an take some core samples, we don't really know.

Venus is interesting because its geomechanics work on almost entirely different processes to our own.
 
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And how early did geologists, and heck even historians and journalists, talk about the Pacific’s “Ring of Fire”?

This is the simple observation that a lot of the world’s earthquakes and volcanoes seem to occur in lands next to the Pacific Ocean.
 
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