WIP: unnamed Earh-like planet

[Pixie]

Haven't started yet, so don't worry.

But I am about to take your map and have a good look at that plate 5, on a stereographic projection centered on it - I suspect it might be surprising.... I'll post back in 30 mins or so.

...
...
(EDIT) 45 mins later...

(EDIT 2) a couple of hours later.... scrap everything I had posted here before, it was wrong, my bad, will redo it asap
I just deleted it

[Pixie]

So, I have done it correctly now, I hope. The problem with the original analysis was that I was considering only the euler pole you marked and not its symmetrical pole (for computing the rotation of the part of the plate on the other hemisphere - but never mind the geometry issues, you've got plenty on your plate)

So, here's my take:

I think the movement is pretty easy to visualize, those sequences of little circles give a general idea of direction and speed. I can explain my workflow on a different thread if people are interested.


As you can see, your work is pretty consistent, congrats. One boundary of plate 5 needs change - it's northern boundary, where it looks to be transform, but it will depend on the polar plate.
The only place where it definitely doesn't fit, in my opinion, is with plate 22. As plate 5 spreads away, so should plate 22 in the opposite direction. Hence, 22 is pushed towards the continent to the east. You could also look at plate 17 again...

Finally, the northeastern tip of plate 5 with plate 12... I can't really make see how that corner is working. Crust being formed on the the NW boundaries, but plate 12 moving westward... hmm you may me better off extending the north pole plate into that area.

So, overall, the devil is in the details as you know. The large plates look alright, but the microplates between them still need some ironing out.

[Akubra]

Ah, I was working on a reply offline, but Pixie beat me

Anyway, I'm going to post it here as is. Here's what I see:

North Pole:
- 14/5 = convergent (divergent on your map)
- 14/4 = convergent (ok)
- 14/18 = convergent (ok)
- 14/1 = transform (convergent on your map)
- 14/12 = divergent (ok)

South Pole
- 15/6 = divergent (ok)
- 15/16 = divergent (ok)
- 15/10 = convergent (ok)
- 15/19 = convergent (ok)
- 15/17 = convergent (ok)
- 15/5 = convergent, but changing into transform towards the western part (divergent on your map)

Additional question:
15/10 and 15/19 are both divergent but 15 goes over 10, but under 19. I now know it is because of the curvature, but is that possible? It seems like 15 is ripping in two at the tripoint 15/10/19. This also happens with 14, going under 18, but over 4. One of my plates (Yirral) has the same thing happening to it, and I was wondering if it's ok. Looking at the Earth's tectonic map I see two places where something similar is happening, but with one crucial difference: there is a short transform fault in between. (The two places are the Western Aleutians and on both sides of New Zealand's South Island - see this map)

Cheers - Akubra

[groovey]

Oh my, Pixie! That's an amazing view of plate 5 and surroundings, I can see much clearer what you mean. Thanks a lot for taking the time to do that for me, I really appreciated. And I agree 100% about those damned details, they're a pain in the ass, but necessary to fix.

Thanks you too Akubra for such a clear answer on the poles and the plates they touch. I see what you mean with the last issue. I'm not sure at all about it. At one point when doing one of my first tectonic maps I wondered about it, if the triangles/circles had to point always in the same direction through the whole plate, and ultimately what I got as a rule checking for a while that map you linked was: when a plate has a subduction boundary with more than one plate, with each plate the direction can be the same or the other way around, depending, I reasoned, of relative speed and which side of the oceanic + oceanic boundary happened to be heavier or lighter, factors which would allow me a bit of freedom with it.

But to be honest, I basically made that up on my own and I guess there's more than that to have in mind. So I'd like to know too. To make it easier I might just change the circles to point to the same direction, but it'd be nice to know what the rules are for that. Edit: checking again the map... yep, it looks as I'm going to have to change the direction of some circles for sure...

Anyway, thanks again guys, you gave me plenty to work on tomorrow.

Edit: trying to fins any lead to an answer about the direction of the triangles doubt we have, I have found nothing conclusive really, just this particular non specific mention to our problem in the wiki article(Theory on origin): "A model of the initiation of subduction, based on analytic and analogue modeling, presumes that the difference of density between two adjacent lithospheric slabs is sufficient to lead to the initiation of subduction", and so, one could simplify that to justify the subduction symbols to point opposing directions along the same convergent boundary, but sadly doesn't address our specific question. I'm going to try and find a better answer.

[groovey]

Ok, so here we go again!



"Major" changes:

WEST:

- Plates 13/12 got the boundary fixed to make sense with nº5, and nº13 got a new Euler pole.

- Plate 5: corrected the western boundary to be 100% divergent.

- old Plate 22: got a major overhaul since it didn't fit once I cut nº5's section with 11. That area is a bit awkward because you can see the square like shape resulting from cutting that bit from nº5, so it looks a bit off to me, but I can live with it as long as the micro-plates it contains (24-27) work fine.

- Plate 17: boundaries fixed and new Euler pole position.

- new Plate 22: created to fix boundary btw nº17 and 11 so it's not convergent + divergent.


EAST:

- old plate 24 is gone because nº4 got a new Euler pole so the micro-plate wasn't needed there.

- Plate 4 also got an opposite curvature with nº14.

- Plate 18 also got a new Euler pole and a bit more of surface so its curvature matches nº4's.

- Plate 10 now has an outward curvature with 15.


I think that's all.

Well, now plate 5's boundary with 14 is a transform one, and so it's most of it on 5 with 15, except for a little bit on the west where the little bump is, which in stereographic projection, if I try to visualize the rotation, looks convergent.






So, how's it looking? Anything to fix?

[Pixie]

As always, positives and negatives.. Not sure about the mess left after breaking up plate 22, but the corrections on the NE corner make that area more plausible. The south pole is perfect, don't touch it again, the north pole not so much, it should move towards plates 1 and 18 (away from 12).

A major issue you still have in some places is the location of divergent boundaries very close to continental borders... that's hard to explain when the other side of that boundary is a long stretch of oceanic crust.

[Akubra]

I don't have much time right now, but I think I agree with Pixie about the poles. South Pole's ok, but I have trouble seeing the reason for a transform boundary between 14/5. 14 is now moving towards 5, so it should be a convergent boundary. If you change the direction of 14 and make it move towards 1 and 18 (as Pixie suggests) then I have no problem with the transform boundary.

Cheers - Akubra

[Cuin]

Sorry if I repeat any previous points (long thread!)

Have you considered any plate to be inert? The African plate nearly remains in place while other plates move away from it. If plate 14 was inert then a transform boundary between 14 and 5 would be fine. However, such a stable plate would probably have to be centered on a large stable craton, which doesn't appear to fit for plate 14.

My other impression is that the large number of plates (nearly double the number of plates on Earth) over-complicate your map. Sometimes less is more.

Divergent margins can be close to subduction zones even if the width of the ocean is asymmetrical about the spreading center. On Earth, the Juan de Fuca and Cocos plates are actually the same plate (Farallon Plate). A divergent margin between the Pacific and Farallon plates was subducted underneath the N.A. plate. This was how the San Andreas transform began.

Another detail is that divergent boundaries do not form in straight lines. They are staggered by abundant transform faults. This comes down to some physics that I haven't really looked into, but there is a maximum length of divergent boundary that is stable before it becomes segmented. Here is a picture. At a global scale this feature is visible, so if you're going for realism I would add a stepwise nature to your divergent boundaries.

Back to an earlier post, I don't see why plate boundaries are necessarily independent of N-S magnetic poles. That is actually a very neat question. Earth's dynamo is caused by movement in the outer core, which very well could be tied to convection of the mantle and thus plate margins.

Anyhow, I really like your project! Keep it up.

[groovey]

@Pixie, interesting, I had assumed (big mistake when it comes to science in general) that in oceanic/continental boundary it wasn't necessary to watch out for that like with continental/continental, but it does.

Just curious, since I noticed on the boundaries' map I kept a bit of boundary 5/15 on the west convergent, but in the South pole projection I had it all in yellow, when you guys say the south pole is ok as it is, how do you mean, 100% transform or with the little convergent zone?

Hello Cuin, thanks for dropping by. Long and I guess very repetitious thread indeed for newcomers just looking for results, can't blame them. I hadn't considered an inert plate at all, I didn't even know/remember about that trait of the African one. I wouldn't have minded 14 being inert if it meant simplifying things, but there must be some specific rules or conditions for a plate to be inert, wouldn't it? I guess you can't just say, this plate is inert so it doesn't rotate or move, or can you?

I agree I might have gone a bit overhead with the number of plates. My original idea was to have about 12-14, but then one need lead to a certain situation, which required new plate divisions and micro-plates... and well. Plus when I had just about a dozen of them the model looked too simple, like a facebook game (no offense, I've played some in the past for a bit) compared to a robust PC game. Look at ascanius, Akubra or Pixie's projects, they have about the same volume of plates and their models look amazing. Of course, they have a level of understanding and execution I don't have, so they make it work and look realistic while I probably just make it look crowded and unnecessarily over-complicated. I guess that my point is you might be right in my case, but having 20-30 plates can work if you've got the skills, so it's not always a negative thing. EDIT: I'm not sure anymore why I'm "arguing", since you never say having more than a dozen plates over-complicates maps in general, just mine in particular, to which I'm actually bound to agree since I can't pull it off too well.

Lastly, unfortunately, I abandoned any aspiration for visual realism a while ago, as it's too much for me to handle. I know divergent boundaries are not continuous, but to be honest I opted not to do them because (please read in 100% casual informative tone, because it might sound defensive, but it's not meant to):

1. Takes more work and time, that's why I use circles instead of triangles.

2. They don't really add much more information to my purposes, the boundary is mainly divergent.

3. My tectonic map is not really meant to add to my still empty gallery, it's 100% for information and terrain purposes to myself, so I've accepted it'll look ugly and rough, but as long as it fulfills its purpose I'm ok with that.

Thanks again for sharing your thoughts.

[Pixie]

Hey groovey.

As promised, I took your map to have an "fresh" look. I kept as close as possible to what you had been doing, but in some places, to reduce micro-plates, I changed the movement of larger plates or moved land masses. The following is a rough map using your color codes. I think every place is plausible as it is, but you guys tell me what you think.


This is a poor-resolution-version. Send me a personal message so we can transfer the actual work files.

Also, this was the first time I used the program g.plates and wow, I am convinced! Forget the stereographic projections, the layer rotations, etc.. It took me an hour or so to learn how to define the shape of a plate , how to set an absolute euler pole for it and to see it rotating. Then I also noticed it can draw "small circles" and that makes it absolutely easy for figuring out the path of every point.
It was so easy that I am now using it to review my stuff as well...