the precambrian is by far the most interesting time in earths history - this was a great (if rambling) story and I am going to checkout your other content. Thanks!
I have been wondering about this for ~ 20+ years. Nice summation of evidence and logic. I try sometimes to teach students that geology is full of unsettled controversies / debates and that they may have a role in said debates.
@@professorsasha9100 People keep telling me it's not a theory. What is it? ua-cam.com/video/Othb0xsvZb4/v-deo.htmlsi=lvpMvi9U-kxaBtca Samuel Warren Carey is one of the creators of the plate tectonics theory/hypotheses. He changed his mind. How does Pangea spread apart and the ocean on the other side stay the same size? Not Possible unless the Earth grew. Read S W Carey's book: The Expanding Earth: Developments in Geotectonics 10. I dare you to read 1 book on Expanding Earth. Then you will see the Earth Grows and we can really see what's going on. (T-Rex lived in lower gravity)
Thank you. The rotation of plates around poles really caught my attention. It seems absolutely obvious once you said it, because all the reconstructions of Pangea splitting show different plates rotating away from each other, and/or pieces moving on curving paths like India wheeling around to slam into Asia. And it makes sense: how else are you going to move on a sphere? But then I'm confused about features that look like straight lines. Not transform faults so much - I see they're accommodating a rip on a curved surface - but the Hawaiian island and Emperor seamounts, which not only are a straight line (I think?) across the Pacific but changed angle as if the plate changed direction slightly when the San Andreas choked on a mid ocean ridge and shifted from subduction to transform . Also I'm curious what rotating plates anchor on as they rotate, if anything, or are they just turning on eddies, so to speak? Going to part II to see what more you may have said on this - and everything! m I wish my geology teacher grandfather were still alive to see all this. My mom remembers when he sat down with her to discuss the theory of plate tectonics/continental drift when it was gaining traction, but was by no means scientific consensus, in the 50s. They talked over the new evidence just coming out which hadn't yet made its way into textbooks. ( This would've been before the 1964 Alaska earthquake provided seismic and sea level change evidence for subduction.)
Working a lot in the Great Basin, I can't believe that rifting is entirely a passive phenomenon. It appears that North America overrode the East Pacific Rise and it jacked up the western 1/3 of the US thousands of feet into the air and caused a broad zone of rifting. The Wilson "Cycle" seems to me to be more of a random thing. There hasn't been a continent-continent collision on the west coast since the continental margin formed when Rodinia broke up. (Other than the accretion of terranes smaller than a continent.) I've only heard "ophiolite" pronounced OH-fee-oh-lite before.
The basin and range is sort of a unique situation. I fall into the camp that it will eventually be a successful rift because of the perfect storm there. What do you think?
@@stevenbaumann8692 Who knows? We won't be around to see it. :-). Maybe the plate tectonics machine will get tired of trying to push N. America up and over the E. Pacific Rise and a subduction zone will develop on the east coast.
Hi just found you via GEO-GIRL's colab video with you. Interesting perspective from a structural geologist on these processes and the important ever evolving arguments over geological narratives. So you talked about how most mantle upwelling zones are shallow but what are your thoughts regarding the apparent depth of the seismic tomographic low sheer velocity zone features beneath the East Pacific Rise which linearly follow the overlying ridge structure of the fast spreading ridge? Noting there is some evidence based on igneous petrology of Siletzia to link the Yellowstone hotspot prior to collision with North America of having been ridge aligned or adjacent is this possibly a remnant process of earlier stages of Earth's tectonics? The seismic tomographic work from Sigloch and others is quite fascinating and building up a picture where plate recycling is a generally quite deep process with subducted slabs undergoing chemical/crystalline transformations on their way down to the core mantle boundary which can as in the case of mount Paektu fueled by deep hydrous upwelling from the stagnant Pacific slab which appears to be undergoing recrystallization at or around the mantle Transition zone. I also can't help but wonder is other intraplate volcanism phenomenon like Lamproite and Kimberlite pipes might be driven by subduction recycling given the positions of underlying slabs in the mantle for more recent such volcanic pipes with regards to both Africa and North America. Also there was a paper I came across earlier this year which disgust evidence that suggests that the deep mantle hot spots appear to move towards mid ocean ridges which does suggests something intermediate between the two regimes. At the very least both the East Pacific Rise and to a lesser extent the Mid Atlantic Ridge appear to have some deeper upwelling structure going on with evidence for multiple plume signatures along their extents. There is also the curious case of the Galapagos hotspot which during its major flood basalt eruptive phase in the late Cretaceous ~90 Ma appears to have produced Komatiite lavas a type of lava otherwise generally found deep in Earth's geological past at or around the Archean, which seems to be a pretty strong sign of evidence that pre plate tectonic processes are still occurring. Its these unresolved questions which are particularly interesting like you I suspect there was no one this is when plate tectonics began moments rather a more gradual transition which my still be in progress.
We know we can generate magma in the shallow mantle. It's a lot easier than under deep and dry conditions. What I meant by shallow was above 700 km depth. There are basically two schools of thought on mantle plumes. They generate near the core or they generate above 700 km depth. It's likely not that simple. Something needs to initiate continental rifting. What that exactly is, I don't know. It's quite possible there are unknown mechanisms. I personally don't think plates make it to near the core. The only thing I have to go on that is honestly, intuition. There's no reason for a plate to remain cool and intact down to the core. The felsic minerals melt under cooler temperatures. The plates are mostly mafic but they are basaltic instead ultramafic. Plus near the core densities are big enough to stop the subduction. If there were deep plumes of magma, S-waves wouldn't go thru them and they do. Now it's possible that the plumes start out as solid deep in the mantle and only melt when the pressure is low enough. Since the mantle is a solid. Plus we have a room problem. As for Yellowstone we have a complex situation. We have a subducting rift, a hot spot, and extension in the Basin and Range. What goes on below 700 km I am unsure about.
@@stevenbaumann8692 I wouldn't have thought the plates would remain intact to those depths but it's kind of hard to interpret the seismic tomography fast sheer velocity zones as anything but slabs sinking since they can be traced through seismic tomographic cross sections back towards the trench where the subducted down into the lower mantle. Though it does appear to be more complicated than just sinking as the material doesn't remain unchanged along its descent as they appear to change shape and density along their journey. from what I've read it is thought to be related to remineralization under the increasing pressures and temperatures which effectively allows for further differentiation of the former slab material as incompatible elements are forced out of the former slab. Because the net effect of this remineralization is a denser crystal structure with the remaining slab material still being somewhat cooler than the adjacent mantle at those depths there really isn't anything which can stop gravity from continuing to pull the former slab down deeper. It's possible the system could reach equilibrium before the core mantle boundary but even then it is likely to stall out within the lower mantle. T hat at least seems to be the general picture reality is almost certainly more complicated as not all the subducting slabs are behaving the same way but either way it appears to be a gravity driven downwelling convective structure. There was a paper earlier this year which showed that the plumes derived from the African Large Low Sheer Velocity Province has the chemical fingerprint of formerly subducted crust piling up at the core mantle boundary. It is theorized some of that LLSVP might be derived from Theia with the added slab material piled up on the African LLSVP contributing to the difference in relative height to the Pacific LLSVP. I don't know about that but at the very least there seems to be a fairly strong connection linking these deeper plumes with LLSVP like discontinuities floating at or near the boundary between the liquid outer core and the lower mantle. Notably Plumes appear to propagate up from the edges of these provinces at the core mantle boundary The picture of whatever is going on beneath North America is likely connected to this as there is a relatively small, relative to the two big supercontinent sized LLSVP structures, LLSVP structure which in turn is directly connected to the still sinking slab wall curtains underneath North America. Going off the work of Robert Hildebrand and Karin Sigloch and others this minor LLSVP appears to likely be a slab graveyard which had built up beneath the series of fixed long lived oceanic volcanic archipelagos which had been out in the Panthalassa ocean prior to North America plowing through them between the Jurassic through early Paleogene. Thus in this context the subduction and rifting are both likely directly linked on the timescale of the Wilson cycle with North America having gotten in the way. My guess is that North America is going to fully break apart especially if the hot upwelling beneath Adirondack uplift dome turns out to be a rising mantle plume from this minor LLSVP which might end up driving North America to break up into three major pieces, The Colorado plateau Basin Range Baja + California block, the Eastern US and Mexico block and the Canadian Pacific Northwest Aleutian crustal blocks. Also while it is still somewhat speculative I recently learned that the appearance of Yellowstone Hotspot magmatic signatures within the cascades over the last 5 million years is confined to a relatively narrow band roughly aligned with the Snake river plain. The origin of this is still controversial though it has been noted that the underlying subducted Juan de Fuca slab appears to be thinning beneath this zone. This raises some interesting questions about the nature and origin of the notched deviation in the underlying ridge like buoyant mantle region south which appears to look like it may have been pinched south along a SW-NE trend roughly consistent with North America's trajectory and the offshore notch zone known as the Gouda ridge. Can a continent pulling on a Subduction zone possibly have carried a portion of the EPR discontinuity along with it only for the path to be in the process of restoring its original configuration? If so this also raises an interesting prospect of this southern section of the Cascades ending up to the southwest of the East Pacific Rise even as the EPR successfully rifts the continent apart. This were it to occur might give a similar outcome to what was seen with Zealandia becoming a largely submarine continental platform and subduction archipelago. This is of course all speculation, resting on the general model picture for the staged and delayed onset of the Basin and Range province as a consequence since there are many competing tectonic forces and the dynamics involved are effectively a chaotic multivariate system of partial differential equations but it is curious to think about. Perhaps one day will will finally have enough data and understanding of the underlying geophysics to know for sure but for now its just speculation albeit informed speculation.
I know that subduction is really important for strictly defining plate Techtonics, but I think some of the events from the order of billions of years, that allowed for large chunks to stay afloat are pretty important. I’m no geologist, I’d say enthusiast. I’m thinking there was some sorting process that allowed the separation of lighter elements from the heavier ones, making the chemistry that lead to granitic rocks, and with those floating chunks, they were able to grow. That said I enjoyed your presentation. You have a nice way of presenting that makes this stuff accessible to us regular folk. Cheers
This is gonna be good, been sitting in my watch list for a while now since it came out. As an aspiring geophysicist this is right up my alley :) (hopefully my love for being a "field person" prevents some of the academic ignorance you mentioned from setting in!)
Steve another question if I may please... transition from hot dry mafic crust with thick wet atmosphere to dryer atmosphere and oceanic crust... I assume an intense hot acid rain out period until the surface cooled enough that rain didn't evaporate instantly. I read initial ocean temp of 200 degrees isn't unrealistic. So under these intense chemical weathering conditions with predominantly olivine reacting at the crust ocean interface .... would boundaries between Hadean oceanic crust units have had water penetrate down to create phylosilicates between the crustal units and thus lubricate their motion, potentially aiding onset of plate tectonics? Also would highly fractured Hadean oceanic crust that had deeply penetrative Serpentinitisation - hence corresponding density reduction, volume and temperature increase ... essentially a deeply silicified slightly buoyant section of oceanic crust.... could that become the nucleus of a first plate..... given its physical properties make it less likely to subduct and also a higher propensity for capturing felsic partial melts that are migrating upwards ... similarly given the buoyant nature of 1 area there would be a natural propensity for other buoyant crustal units to "float" towards each other as this arrangement lowers total entropy within the felsic/mafic crust arrangement across earth's surface. For analogy drips of thick oil with strong surface tension and a density of say 0.9 ... the drips on water will seemingly randomly move about until they contact and join.... making a bigger blob of oil with different displacement properties that creates positive feedback... this could aid in dragging the most buoyant crust together. ... similarly higher density sections of crust would naturally fall towards other dense areas that are slightly depressing the lithosphere compared to where the hydrated buoyant bits are. I assume processes that reduce entropy fastest are those that dominate. I've watched flour gold floating on the surface tension in a gold pan. Each spec of gold depresses the water surface tenssion and over time these deformed surface zones coalesce and become deeper with steeper sides. Eventually so much flour gold has slid down the water surface into a seeming singularly that the water surface tension can no longer support the mass of hydrophobic gold particles.... the sides of the surface tension hole Eventually touch and all the gold sinks back to the bottom of the pan.... aka drip-duction Does all that resonate somewhere near what could have happened?
Sorry I wasn’t there for the premier. I had other obligations and no WiFi. I tried but it didn’t work. I was able to get on twitter but that’s about it.
I have no clue how the crust formed. I don’t think anyone really does. We can tell you there’s no large voids. Shear waves (from earthquakes) pass right through it. Shear waves don’t move through liquids and gases.
@@stevenbaumann8692 how can the crust be all the same?... the more pressure the closer the molecules are?... i would think the crust has a graduating type of elasticity?...
@@jonerlandson1956 maybe I’m not understanding your statement. The crust isn’t all compositionally the same. But the lithosphere and crust behave mechanically as a ridged body. Composition only comes into play I. The fact the continents don’t get subducted. Just because things are compositionally different doesn’t mean they have to mechanically behave differently. The composition and structure isn’t different enough for them to behave that differently. Plus the forces involved in plate tectonics are far greater than any local internal variations. Plate tectonics can literally move mountains.
I probably should have chose better words. Like greater surface area greater cooling. I also may have misspoke. If that is the case, thanks for pointing it out
Thanks for the question. It doesn't. Gondwana came far later. Long after plate tectonics was in operation. About 2 billion years later. If you're talking about the cratons that would eventually come together to make up Gondwana, those were mostly formed during the Archean.
@@stevenbaumann8692 thanks for such a quick response .... i live on the Balingup terrane on the far western edge of the Yilgarn Craton very near near 3.2 Ga quartzite and BIF. .... the quartzite has geochron at 3.2 inherited zircon and the BIF is only 200m away from quartzite. Serpentinite is only few hundred m from both.... possible PGE mineralisation in layered ultramafic that was deformed by TTG dated at 2.6Ga so ultramafic older than 2.6 Does this situation sound like obduction prior to 2.6 Ga granitoid crationisation?
It's all good! I live to respond to insightful comments like yours! I see you're in Australia! It sounds like it could be. I don't know ow enough about it to say. I don't want to lead you down any wrong paths. But now my rusty wheels are starting to spin
@@stevenbaumann8692 thanks Steve... I love being stimulated by smart people making quality information content! Yes I'm in Australia but one of the least studied areas... It's good farm land and in late 1800s gov said if you want to mine gold go to Kalgoorlie .... Otherwise the only permitted digging was for fence posts . people even had land confiscated because they found a few nuggets and wouldn't stop prospecting... Food production was so critical for early Western Australia that the Premier of the state banned people looking for gold in the SW also the mines Department recording info about gold discoveries... ... It's exciting when you find old workings and even more so when the Geo says he has only seen rocks like that at Uni... Komatiite vs picrite vs olivine cumulate vs metamorphic olivine either way they are super cool 😎
Unfortunately most of this stuff wrong. Satellites can see the Earth is growing. Age of the ocean floor data revealed after the plate tectonic theory, proves plate tectonics wrong. The Earth grows and has grown 2-3 times its original size, mostly in about 200 million years ago. It's the Expanding Earth theory and its whats happening. Not convection currents or plate pull moving plates. There is a tiny bit of subduction, but to tell me all ancient ocean floor over 200 mya have been subducted is a mathematical impossibility. Some ancient ocean floor should remain, and it does not. And where did most of the continental granite plates go? Are you saying 30 mile thick continental plate was subducted? I don't think so. No "Slab Pull" pulled the continents under each other. If Pangea was half the globe, then it opened up, the Pacific ocean should be much smaller. The Pacific is STILL about half the Earth. Only possible on an Expanding Earth. Come on people, it's obvious.
Don't come here not watchthe video. This is about the tectonics of earth before plate tectonics. Not about plate tectonics. I have videos on that to. I'm pretty sure I've forgotten more about it that you think you know, which your comment shows you lack even the basics. Let alone Euler poles, angular velocity, mantle mechanics, or any other words I know you don't understand. Earth is not growing. That's BS. And if you knew the basics of plate tectonics you would know felsic lithosphere doesn't get recycled. It's why we have 3.8 Ga continental crust and only 0.3 Ga ocean crust. We have prepangea supercontinents. We can reconstruct them based on the paleomagnetism of Precambrian LIP. Like Rodinia and Nuna.
What if the old Precambrian crust was derived from elsewhere and was a large type 2 interference refold structure formed by 2.5 byo and 1.3 byo impact events? Maybe the large structure was subdivided into crescent moon shaped structures with an open end and a closed end and connected similar to how we know Africa and South America were connected. It appears that North America has rotated about the Canadian impact giving away to the counterclockwise dial gauge at the Hudson Bay, the Great Lakes counterclockwise propagating rotational feature, and the drag fold at Like Superior that ends at a front. If this is the case, I have a model that matches geologic literature on many levels and solves many mysteries, except matching on the "big picture" scale, which is also admittedly strange. It may also suggest that there has been Earth expansion and that this is associated with the LLSVP zones and plate boundaries. At this present time, there may not be expansion as the system of structures is actually in a more stabilizing phase as opposed to the previous phase say 45 mya.
the precambrian is by far the most interesting time in earths history - this was a great (if rambling) story and I am going to checkout your other content. Thanks!
Thank you! I agree! The Precambrian is the place to be
Good video. Great way to spend a Saturday night studying geology
I have been wondering about this for ~ 20+ years. Nice summation of evidence and logic. I try sometimes to teach students that geology is full of unsettled controversies / debates and that they may have a role in said debates.
Yeah it’s great to find this
You need to teach the Expanding Earth Theory. The new evidence points towards a growing Earth.
@@bobrainy5324 It's not a theory and there is a body of evidence that supports other hypotheses / theories
@@professorsasha9100 People keep telling me it's not a theory. What is it?
ua-cam.com/video/Othb0xsvZb4/v-deo.htmlsi=lvpMvi9U-kxaBtca
Samuel Warren Carey is one of the creators of the plate tectonics theory/hypotheses. He changed his mind. How does Pangea spread apart and the ocean on the other side stay the same size? Not Possible unless the Earth grew.
Read S W Carey's book: The Expanding Earth: Developments in Geotectonics 10. I dare you to read 1 book on Expanding Earth. Then you will see the Earth Grows and we can really see what's going on. (T-Rex lived in lower gravity)
15:45 I suspect the oceans may play a roll as well. Or is the water only there because oceanic crust is so thin?
Reminder set my friend.
I hope you enjoyed it!
I learned a lot from this video! Thanks, and I look forward to the next one!
Thanks for watching. It will hopefully be out in a week or so.
Very nice summary. Thanks also for editing it to keep things on track. Really good job! 😊
Thank you. The rotation of plates around poles really caught my attention. It seems absolutely obvious once you said it, because all the reconstructions of Pangea splitting show different plates rotating away from each other, and/or pieces moving on curving paths like India wheeling around to slam into Asia. And it makes sense: how else are you going to move on a sphere?
But then I'm confused about features that look like straight lines. Not transform faults so much - I see they're accommodating a rip on a curved surface - but the Hawaiian island and Emperor seamounts, which not only are a straight line (I think?) across the Pacific but changed angle as if the plate changed direction slightly when the San Andreas choked on a mid ocean ridge and shifted from subduction to transform .
Also I'm curious what rotating plates anchor on as they rotate, if anything, or are they just turning on eddies, so to speak?
Going to part II to see what more you may have said on this - and everything!
m
I wish my geology teacher grandfather were still alive to see all this. My mom remembers when he sat down with her to discuss the theory of plate tectonics/continental drift when it was gaining traction, but was by no means scientific consensus, in the 50s. They talked over the new evidence just coming out which hadn't yet made its way into textbooks.
( This would've been before the 1964 Alaska earthquake provided seismic and sea level change evidence for subduction.)
Working a lot in the Great Basin, I can't believe that rifting is entirely a passive phenomenon. It appears that North America overrode the East Pacific Rise and it jacked up the western 1/3 of the US thousands of feet into the air and caused a broad zone of rifting. The Wilson "Cycle" seems to me to be more of a random thing. There hasn't been a continent-continent collision on the west coast since the continental margin formed when Rodinia broke up. (Other than the accretion of terranes smaller than a continent.)
I've only heard "ophiolite" pronounced OH-fee-oh-lite before.
The basin and range is sort of a unique situation. I fall into the camp that it will eventually be a successful rift because of the perfect storm there. What do you think?
@@stevenbaumann8692 Who knows? We won't be around to see it. :-). Maybe the plate tectonics machine will get tired of trying to push N. America up and over the E. Pacific Rise and a subduction zone will develop on the east coast.
Hi just found you via GEO-GIRL's colab video with you. Interesting perspective from a structural geologist on these processes and the important ever evolving arguments over geological narratives.
So you talked about how most mantle upwelling zones are shallow but what are your thoughts regarding the apparent depth of the seismic tomographic low sheer velocity zone features beneath the East Pacific Rise which linearly follow the overlying ridge structure of the fast spreading ridge? Noting there is some evidence based on igneous petrology of Siletzia to link the Yellowstone hotspot prior to collision with North America of having been ridge aligned or adjacent is this possibly a remnant process of earlier stages of Earth's tectonics? The seismic tomographic work from Sigloch and others is quite fascinating and building up a picture where plate recycling is a generally quite deep process with subducted slabs undergoing chemical/crystalline transformations on their way down to the core mantle boundary which can as in the case of mount Paektu fueled by deep hydrous upwelling from the stagnant Pacific slab which appears to be undergoing recrystallization at or around the mantle Transition zone. I also can't help but wonder is other intraplate volcanism phenomenon like Lamproite and Kimberlite pipes might be driven by subduction recycling given the positions of underlying slabs in the mantle for more recent such volcanic pipes with regards to both Africa and North America.
Also there was a paper I came across earlier this year which disgust evidence that suggests that the deep mantle hot spots appear to move towards mid ocean ridges which does suggests something intermediate between the two regimes. At the very least both the East Pacific Rise and to a lesser extent the Mid Atlantic Ridge appear to have some deeper upwelling structure going on with evidence for multiple plume signatures along their extents.
There is also the curious case of the Galapagos hotspot which during its major flood basalt eruptive phase in the late Cretaceous ~90 Ma appears to have produced Komatiite lavas a type of lava otherwise generally found deep in Earth's geological past at or around the Archean, which seems to be a pretty strong sign of evidence that pre plate tectonic processes are still occurring.
Its these unresolved questions which are particularly interesting like you I suspect there was no one this is when plate tectonics began moments rather a more gradual transition which my still be in progress.
We know we can generate magma in the shallow mantle. It's a lot easier than under deep and dry conditions. What I meant by shallow was above 700 km depth.
There are basically two schools of thought on mantle plumes. They generate near the core or they generate above 700 km depth. It's likely not that simple.
Something needs to initiate continental rifting. What that exactly is, I don't know. It's quite possible there are unknown mechanisms.
I personally don't think plates make it to near the core. The only thing I have to go on that is honestly, intuition. There's no reason for a plate to remain cool and intact down to the core. The felsic minerals melt under cooler temperatures. The plates are mostly mafic but they are basaltic instead ultramafic. Plus near the core densities are big enough to stop the subduction. If there were deep plumes of magma, S-waves wouldn't go thru them and they do. Now it's possible that the plumes start out as solid deep in the mantle and only melt when the pressure is low enough. Since the mantle is a solid. Plus we have a room problem.
As for Yellowstone we have a complex situation. We have a subducting rift, a hot spot, and extension in the Basin and Range.
What goes on below 700 km I am unsure about.
@@stevenbaumann8692 I wouldn't have thought the plates would remain intact to those depths but it's kind of hard to interpret the seismic tomography fast sheer velocity zones as anything but slabs sinking since they can be traced through seismic tomographic cross sections back towards the trench where the subducted down into the lower mantle. Though it does appear to be more complicated than just sinking as the material doesn't remain unchanged along its descent as they appear to change shape and density along their journey. from what I've read it is thought to be related to remineralization under the increasing pressures and temperatures which effectively allows for further differentiation of the former slab material as incompatible elements are forced out of the former slab. Because the net effect of this remineralization is a denser crystal structure with the remaining slab material still being somewhat cooler than the adjacent mantle at those depths there really isn't anything which can stop gravity from continuing to pull the former slab down deeper. It's possible the system could reach equilibrium before the core mantle boundary but even then it is likely to stall out within the lower mantle.
T hat at least seems to be the general picture reality is almost certainly more complicated as not all the subducting slabs are behaving the same way but either way it appears to be a gravity driven downwelling convective structure.
There was a paper earlier this year which showed that the plumes derived from the African Large Low Sheer Velocity Province has the chemical fingerprint of formerly subducted crust piling up at the core mantle boundary. It is theorized some of that LLSVP might be derived from Theia with the added slab material piled up on the African LLSVP contributing to the difference in relative height to the Pacific LLSVP. I don't know about that but at the very least there seems to be a fairly strong connection linking these deeper plumes with LLSVP like discontinuities floating at or near the boundary between the liquid outer core and the lower mantle. Notably Plumes appear to propagate up from the edges of these provinces at the core mantle boundary
The picture of whatever is going on beneath North America is likely connected to this as there is a relatively small, relative to the two big supercontinent sized LLSVP structures, LLSVP structure which in turn is directly connected to the still sinking slab wall curtains underneath North America.
Going off the work of Robert Hildebrand and Karin Sigloch and others this minor LLSVP appears to likely be a slab graveyard which had built up beneath the series of fixed long lived oceanic volcanic archipelagos which had been out in the Panthalassa ocean prior to North America plowing through them between the Jurassic through early Paleogene.
Thus in this context the subduction and rifting are both likely directly linked on the timescale of the Wilson cycle with North America having gotten in the way. My guess is that North America is going to fully break apart especially if the hot upwelling beneath Adirondack uplift dome turns out to be a rising mantle plume from this minor LLSVP which might end up driving North America to break up into three major pieces, The Colorado plateau Basin Range Baja + California block, the Eastern US and Mexico block and the Canadian Pacific Northwest Aleutian crustal blocks.
Also while it is still somewhat speculative I recently learned that the appearance of Yellowstone Hotspot magmatic signatures within the cascades over the last 5 million years is confined to a relatively narrow band roughly aligned with the Snake river plain. The origin of this is still controversial though it has been noted that the underlying subducted Juan de Fuca slab appears to be thinning beneath this zone.
This raises some interesting questions about the nature and origin of the notched deviation in the underlying ridge like buoyant mantle region south which appears to look like it may have been pinched south along a SW-NE trend roughly consistent with North America's trajectory and the offshore notch zone known as the Gouda ridge. Can a continent pulling on a Subduction zone possibly have carried a portion of the EPR discontinuity along with it only for the path to be in the process of restoring its original configuration? If so this also raises an interesting prospect of this southern section of the Cascades ending up to the southwest of the East Pacific Rise even as the EPR successfully rifts the continent apart. This were it to occur might give a similar outcome to what was seen with Zealandia becoming a largely submarine continental platform and subduction archipelago.
This is of course all speculation, resting on the general model picture for the staged and delayed onset of the Basin and Range province as a consequence since there are many competing tectonic forces and the dynamics involved are effectively a chaotic multivariate system of partial differential equations but it is curious to think about. Perhaps one day will will finally have enough data and understanding of the underlying geophysics to know for sure but for now its just speculation albeit informed speculation.
I know that subduction is really important for strictly defining plate Techtonics, but I think some of the events from the order of billions of years, that allowed for large chunks to stay afloat are pretty important. I’m no geologist, I’d say enthusiast. I’m thinking there was some sorting process that allowed the separation of lighter elements from the heavier ones, making the chemistry that lead to granitic rocks, and with those floating chunks, they were able to grow. That said I enjoyed your presentation. You have a nice way of presenting that makes this stuff accessible to us regular folk. Cheers
I am so glad you take an interest. Normal people enjoying my presentations is why I do this! And your assessment is not a bad one.
Excellent. Looking forward to part 2.
It’s recorded. I just need to get around to editing it
@@stevenbaumann8692 I hear that! 😂😂😂 the struggle is real!
This is gonna be good, been sitting in my watch list for a while now since it came out. As an aspiring geophysicist this is right up my alley :)
(hopefully my love for being a "field person" prevents some of the academic ignorance you mentioned from setting in!)
Do you know if an asteroid hit Earth and cracked the crust into pieces?
@@theamericanjoeshow Nah, any impact powerful enough to do that would have liquified the surface, rather than cracked it.
IM HERE CAUSE OF GEOGIRL & you. Educate me sir!!!!!!
Boring?!? Hella nope. Although I’m gonna need breaks to digest.
Omg 17 minutes in was hilarious. No plus or minus arguments. No no no. 😂
Haha good luck telling stromatolites apart. My goodness you are hilarious.
The debate feedback tangent was great
29 minutes the don’t care vibe ❤
this is great, thanks!
Steve another question if I may please... transition from hot dry mafic crust with thick wet atmosphere to dryer atmosphere and oceanic crust... I assume an intense hot acid rain out period until the surface cooled enough that rain didn't evaporate instantly. I read initial ocean temp of 200 degrees isn't unrealistic.
So under these intense chemical weathering conditions with predominantly olivine reacting at the crust ocean interface .... would boundaries between Hadean oceanic crust units have had water penetrate down to create phylosilicates between the crustal units and thus lubricate their motion, potentially aiding onset of plate tectonics?
Also would highly fractured Hadean oceanic crust that had deeply penetrative Serpentinitisation - hence corresponding density reduction, volume and temperature increase ... essentially a deeply silicified slightly buoyant section of oceanic crust.... could that become the nucleus of a first plate..... given its physical properties make it less likely to subduct and also a higher propensity for capturing felsic partial melts that are migrating upwards ... similarly given the buoyant nature of 1 area there would be a natural propensity for other buoyant crustal units to "float" towards each other as this arrangement lowers total entropy within the felsic/mafic crust arrangement across earth's surface. For analogy drips of thick oil with strong surface tension and a density of say 0.9 ... the drips on water will seemingly randomly move about until they contact and join.... making a bigger blob of oil with different displacement properties that creates positive feedback... this could aid in dragging the most buoyant crust together. ... similarly higher density sections of crust would naturally fall towards other dense areas that are slightly depressing the lithosphere compared to where the hydrated buoyant bits are.
I assume processes that reduce entropy fastest are those that dominate.
I've watched flour gold floating on the surface tension in a gold pan. Each spec of gold depresses the water surface tenssion and over time these deformed surface zones coalesce and become deeper with steeper sides. Eventually so much flour gold has slid down the water surface into a seeming singularly that the water surface tension can no longer support the mass of hydrophobic gold particles.... the sides of the surface tension hole Eventually touch and all the gold sinks back to the bottom of the pan.... aka drip-duction
Does all that resonate somewhere near what could have happened?
Sorry I wasn’t there for the premier. I had other obligations and no WiFi. I tried but it didn’t work. I was able to get on twitter but that’s about it.
Neat bit on the snowball earth theory
how did the crust form... and... is there void space in the mantle?...
I have no clue how the crust formed. I don’t think anyone really does. We can tell you there’s no large voids. Shear waves (from earthquakes) pass right through it. Shear waves don’t move through liquids and gases.
@@stevenbaumann8692
how can the crust be all the same?... the more pressure the closer the molecules are?... i would think the crust has a graduating type of elasticity?...
@@stevenbaumann8692
if the crust was molten at one time... then it cooled and shrank... outside probably faster than the inside?...
@@jonerlandson1956 it probably was molten at once. But it couldn’t have been for long. The oceans could have formed as early as 4 billion years ago.
@@jonerlandson1956 maybe I’m not understanding your statement. The crust isn’t all compositionally the same. But the lithosphere and crust behave mechanically as a ridged body. Composition only comes into play I. The fact the continents don’t get subducted. Just because things are compositionally different doesn’t mean they have to mechanically behave differently. The composition and structure isn’t different enough for them to behave that differently. Plus the forces involved in plate tectonics are far greater than any local internal variations. Plate tectonics can literally move mountains.
„… I know it can be boring.”
Bull….t. It’s fascinating!
“greater mass, greater cooling” pardon me? Isn’t it the other way around.
I probably should have chose better words. Like greater surface area greater cooling. I also may have misspoke. If that is the case, thanks for pointing it out
yes! the present is not necessarily the key to the past
Where is Gondwana fitting into this
Thanks for the question. It doesn't. Gondwana came far later. Long after plate tectonics was in operation. About 2 billion years later.
If you're talking about the cratons that would eventually come together to make up Gondwana, those were mostly formed during the Archean.
@@stevenbaumann8692 thanks for such a quick response .... i live on the Balingup terrane on the far western edge of the Yilgarn Craton very near near 3.2 Ga quartzite and BIF. .... the quartzite has geochron at 3.2 inherited zircon and the BIF is only 200m away from quartzite. Serpentinite is only few hundred m from both.... possible PGE mineralisation in layered ultramafic that was deformed by TTG dated at 2.6Ga so ultramafic older than 2.6
Does this situation sound like obduction prior to 2.6 Ga granitoid crationisation?
It's all good! I live to respond to insightful comments like yours! I see you're in Australia!
It sounds like it could be. I don't know ow enough about it to say. I don't want to lead you down any wrong paths.
But now my rusty wheels are starting to spin
@@stevenbaumann8692 thanks Steve... I love being stimulated by smart people making quality information content!
Yes I'm in Australia but one of the least studied areas...
It's good farm land and in late 1800s gov said if you want to mine gold go to Kalgoorlie .... Otherwise the only permitted digging was for fence posts . people even had land confiscated because they found a few nuggets and wouldn't stop prospecting... Food production was so critical for early Western Australia that the Premier of the state banned people looking for gold in the SW also the mines Department recording info about gold discoveries... ... It's exciting when you find old workings and even more so when the Geo says he has only seen rocks like that at Uni... Komatiite vs picrite vs olivine cumulate vs metamorphic olivine either way they are super cool 😎
I'm not buying the slab-pull mechanism. Rocks have very little strength in tension.
Is it possible that an asteroid hit Earth and cracked the crust into plates?
The answer to that, might make a good video.
When, whenever scientists tell us😅
👍🥰
Unfortunately most of this stuff wrong. Satellites can see the Earth is growing. Age of the ocean floor data revealed after the plate tectonic theory, proves plate tectonics wrong. The Earth grows and has grown 2-3 times its original size, mostly in about 200 million years ago. It's the Expanding Earth theory and its whats happening. Not convection currents or plate pull moving plates. There is a tiny bit of subduction, but to tell me all ancient ocean floor over 200 mya have been subducted is a mathematical impossibility. Some ancient ocean floor should remain, and it does not. And where did most of the continental granite plates go? Are you saying 30 mile thick continental plate was subducted? I don't think so. No "Slab Pull" pulled the continents under each other. If Pangea was half the globe, then it opened up, the Pacific ocean should be much smaller. The Pacific is STILL about half the Earth. Only possible on an Expanding Earth. Come on people, it's obvious.
Don't come here not watchthe video. This is about the tectonics of earth before plate tectonics. Not about plate tectonics. I have videos on that to. I'm pretty sure I've forgotten more about it that you think you know, which your comment shows you lack even the basics. Let alone Euler poles, angular velocity, mantle mechanics, or any other words I know you don't understand.
Earth is not growing. That's BS. And if you knew the basics of plate tectonics you would know felsic lithosphere doesn't get recycled. It's why we have 3.8 Ga continental crust and only 0.3 Ga ocean crust.
We have prepangea supercontinents. We can reconstruct them based on the paleomagnetism of Precambrian LIP. Like Rodinia and Nuna.
What if the old Precambrian crust was derived from elsewhere and was a large type 2 interference refold structure formed by 2.5 byo and 1.3 byo impact events? Maybe the large structure was subdivided into crescent moon shaped structures with an open end and a closed end and connected similar to how we know Africa and South America were connected. It appears that North America has rotated about the Canadian impact giving away to the counterclockwise dial gauge at the Hudson Bay, the Great Lakes counterclockwise propagating rotational feature, and the drag fold at Like Superior that ends at a front. If this is the case, I have a model that matches geologic literature on many levels and solves many mysteries, except matching on the "big picture" scale, which is also admittedly strange. It may also suggest that there has been Earth expansion and that this is associated with the LLSVP zones and plate boundaries. At this present time, there may not be expansion as the system of structures is actually in a more stabilizing phase as opposed to the previous phase say 45 mya.