New World (Help with Tectonics?)

[davoush]

Thank you both!

@Pixie: I’ve been messing around on GPlates for a while, so hopefully I’ll be able to present something soon (within my limited capabilities).

@Charerg: Thanks! Your GPlates tutorial has been extremely helpful.

Random question:
Can an oceanic plate subduct entirely under another oceanic plate? I.e. it disappears before it suducts under continental crust?

[Charerg]

Thank you both!

@Pixie: I’ve been messing around on GPlates for a while, so hopefully I’ll be able to present something soon (within my limited capabilities).

@Charerg: Thanks! Your GPlates tutorial has been extremely helpful.

Random question:
Can an oceanic plate subduct entirely under another oceanic plate? I.e. it disappears before it suducts under continental crust?

Well, to answer that you have to consider how that oceanic plate came to exist in the first place. I don't see why an oceanic plate couldn't subduct entirely under another, so I guess it's possible. Oceanic crust being subducted under oceanic crust is a relatively rare phenomenon though.

[davoush]

Thanks - is there a specific reason, or it is just because it's far more likely to subduct under continental crust because of the relative densities etc?

Anyway, I managed to produce a kind of draft GIF (which looks quite cool!) from GPlates. A brief explanation to go along with it:

For clarity, I am calling the Pink, Orange and Green supercontinent in the West 'West-C'. The Eastern Pink & Yellow continent is 'East-C', and the other lone continent is 'Purple'.

Pink, Orange and Green form one supercontinent circa 200Mya (Lets call it West-C). The Eastern half of West-C starts to get pulled towards an ocean being subducted under the northern half of the Eastern Super Continent (East-C), causing a huge rift in West-C. The green plate of West-C is still travelling with it at this time. The Purple continent was likely once attached to East-C, but it is already rifted by 200Mya. I imagine Purple Continent will have the most unique flora and fauna.

By circa 150Mya, the rift is widening and southern West-C is moving south-west-ish, indicating a subduction zone around there. Purple is also moving towards the space created by the rift, indicating a new subduction zone. I assume this means some relatively new oceanic crust is being subducted - is this at all plausible? (I did have flow lines, but they look really ugly, with some lines appearing on the other side of the continent? Perhaps it's because the rift shapes aren't that linear?.

By circa 100Mya, the northern parts of West-C and East-C have collided, signalling the closing of the old ocean which was being subducted. Maybe a few final parts of this subduction is still active along the bay between Pink-Yellow-Green.

The collision slows down northern West-C and East-C. The rift breaking apart West-C is also now very mature. The south-polar ocean starts subducting more rapidly, pulling southern West-C towards it. This also causes the green part of West-C to rift and move south rapidly. Will the collision of WC & EC, The southern half of East-C also gets pulled towards this subduction, rifting as well (it was already slightly rifting).

By 50Mya, this motion continues in the same way as the subduction of the polar ocean continues. The continental collision is now likely becoming inactive. This means it is quite a lot older than the Himalayas - so I don't now how tall the mountains would be there?

By present day, the old polar ocean is now mostly closed, perhaps only with a narrow active subduction along the southern coasts.

I am mostly unsure about:

The northern polar ocean - not much seems to be happening there, but it can't have just stayed in place without moving? The other plates seem to basically be rotation around it, so maybe just a big plate surrounding by transform boundaries?

Thanks for everyone's expertise and encouragement!

(Edit: Made GIF clearer)

[Charerg]

Thanks - is there a specific reason, or it is just because it's far more likely to subduct under continental crust because of the relative densities etc?

As far as I know it's due to the relative densities. While oceanic crust (usually older in age) can subduct under other oceanic crust (typically younger), continental crust never subducts under oceanic crust of any kind (or indeed gets subducted at all, even in continent-to-continent collisions continental crust doesn't really subduct).

I am mostly unsure about:

The northern polar ocean - not much seems to be happening there, but it can't have just stayed in place without moving? The other plates seem to basically be rotation around it, so maybe just a big plate surrounding by transform boundaries?

Thanks for everyone's expertise and encouragement!

The fact that it's just been oceanic crust for 200 Mya isn't a problem, the same is true of the Pacific after all. Though that doesn't necessarily mean that nothing has happened. In fact, it would be far more likely for the polar plate to be more-or-less surrounded by subduction boundaries (think the Pacific ring of fire) than transform boundaries. I don't think there even exist any large plates surrounded by transform boundaries, that's just a really unlikely configuration (especially for an oceanic plate). Altervatively it could be split between some of the neighbouring plates (for example, the oceanic crust could be largely part of the same plate as the purple continent).

Oh, and very nice model of the continental movements, btw! I might suggest also creating some flowlines between the continents drifting apart, that makes it easier to figure out everything since you can see where the spreading ridges are located.