New World (Help with Tectonics?)

[davoush]

An updated tectonics map.

The main part I am unhappy with is Plate 8. Red lines indicate orogeny/subduction. There are two massive orogenies happening between continental plates (1+5, 7+2).

I want all landmasses to at least be connected by island arcs in habitable regions. 2, 7 & 8 are quite isolated at the minute. I would also like to chart volcanic activity this time, and add in some hotspots. I also want some interesting and complicated tectonic areas - this looks quite simple right now.

IF there are any glaring errors or suggestion, please let me know. Thanks

UPDATE:

Worked on polar regions and changed a few things to make it interesting and give me islands where I want them. I don't really like just throwing in random plates to justify things, it seems more organic when it comes together well.

[davoush]

Phew, big update.

I begin thinking about how the world looked before this setup, and I think it has helped clarify some movements. Basically:

W1, W2, W3 formed one big supercontinent, located approximately over the ocean-spreading between W1&W2. W3 was part of the bottom of W2.

E1 and E2 were joined, located to the east of the W supercontinent.

B1 is an Australasia type old continent.


So what happened?:
A massive subduction of an old oceanic plate in the north caused W1 and E1 to start being pulled towards this subduction. There was then subduction in the south and the east, causing W3 to split from W1 and follow W2 to the south-east. E2 also began moving south and east.

O3 is the last remains of this big subduction, as it is currently subducting under W2.

W1 and E1 eventually collide. O1 shifts in movement, moving south and westward and the ocean starts to spread above W1. The big subducting O2 plate pulls part of B1 and W2 with it, giving a large rifting line.

E2, originally moving eastward towards the subduction is now shifting north towards the big continental and subduction areas. The minor plate of E2 was originally part of a rift and now also islands due to subduction.

Questions:
1) I am mostly unsure about where O1 comes from. Is it the remnant of the old oceanic plate which was subducting in the north of the supercontinents, with most of it being closed by W1 and E1? It is also mostly subducting under another oceanic plate (O2). Can this happen?

2) The motion of E2 seems strange - is my explanation adequate? I.e. was moving south and east, now shifting north due to subduction?

3) I'm not sure I like the explanation for W3. It could also just be an old continent not previously part of the supercontinent which is moving towards the subduction. Which seems more plausible?

(E2 and the minor plate also look suspiciously like Australia and Sunda...argh! I was trying to avoid Earth-like configurations...maybe I'll flip it once I've figured out the tectonics).

Thanks!

[Pixie]

Phew, big update.

I begin thinking about how the world looked before this setup, and I think it has helped clarify some movements.

And that's how tectonics is worked, everytime

Questions:
1) I am mostly unsure about where O1 comes from. Is it the remnant of the old oceanic plate which was subducting in the north of the supercontinents, with most of it being closed by W1 and E1? It is also mostly subducting under another oceanic plate (O2). Can this happen?

2) The motion of E2 seems strange - is my explanation adequate? I.e. was moving south and east, now shifting north due to subduction?

3) I'm not sure I like the explanation for W3. It could also just be an old continent not previously part of the supercontinent which is moving towards the subduction. Which seems more plausible?

(E2 and the minor plate also look suspiciously like Australia and Sunda...argh! I was trying to avoid Earth-like configurations...maybe I'll flip it once I've figured out the tectonics).

Thanks!

My take on your questions...
1) O1 is your Pacific plate - it doesn't come from anywhere, it has just been there for a while, continuously formed (and subducted somewhere, but I'll get to that in a minute)

2) E2 has hardly moved, if you think about it - it's not being subducted, just slightly pushed away from the ridge between itself and E1. E2, however, creates a problem for O3, the southern polar ocean, because O3 seems to be subducting under E2 and moving away from it, and you know that that can't happen.

3) Your explanation for W3 sounds fine.

In general, you're on the right track but it doesn't seem that you're "there" yet. I would definitely recommend you get this on g.plates and have a look at it "some million years earlier". Charerg has a great tutorial about g.plates - have a look.

[Charerg]

Just popping in to say that it's coming along nicely. Especially the final update is a big improvement over the initial version. Keep up the good work ! I'll try and post some actually relevant feedback regarding the tectonics at some point.

[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.

[davoush]

Thanks Charerg.

I did have flow lines for two main rifts, but for some reason it is behaving oddly on another rift and not spreading properly?

[Charerg]

That's probably because one or the other (or both) of the continents have a non-zero present-day (0 Mya) rotation in the rotation file.