WIP: unnamed Earh-like planet

[groovey]

Hello again.

I've fixed Pixie's first two suggestions, at least I hope so (let me know if boundary btw nº2 and 3 has to be even more close to the west).

About the third point, so instead of nº6 getting subducted into nº7 and 5, it's the opposite, both nº 7 and nº5 are subducted into nº6, is that right?

I'm not sure I understand what you mean about the curvature of the boundaries though, is it that nº6 has to have concave boundaries instead of convex, since it's the one "eating" the other two plates?


Anyway, while I get that clarified, I worked on the boundaries and decided to use a very simplified version of the style Akubra used, without those little straight lines vertical to the boundaries, which of course make a tectonic map more realistic, but also more time consuming to make. I will add little triangles to indicate subduction on the next session, which leads me to the question I haven't been able to answer myself:

- From what I've read and what I see in Earth's tectonic maps, in convergent boundaries not 100% of the times subduction happens. At least in maps I've seen blue lines (convergent), but without subduction triangles (which are placed in other blue areas in the same map). Is that appreciation correct? If so, what determines when subduction does occur and when not?

So here's what I got now (some boundaries around nº6, 7 and 5 are still black until I fix point nº3 Pixie pointed out in a previous post). It looks pretty 'meh' really, visually, not pretty at all to put in a book, but well, if it manages to convey the information it'll do.



(Sigh) I feel like I'm missing something very important, because right now the tectonic map is predominantly divergent, which I guess is plausible (Earth itself looks that way to me, would you say so?) but still... and I haven't been able to identify any transformation boundary (there are cases when one side of the boundary moves laterally, but the other is convergent or divergent, so together they don't create a transformation boundary), which seems very, very suspicious to me. So what is it that I'm missing?

Edit: um, just realized most transformation boundaries are in fact those little vertical lines that break up the boundaries, but not all transformation boundaries are vertical lines, are they? I'm thinking of my fab transformation boundary: the San Andreas Fault. So is it that I just don't have any of those, or I have but I don't see them?


Thanks a lot Akubra! It's weird how much I love the word "groovy", especially since it's such an American thing (and from the 60's/70's), so I love that you brought it up.

[Pixie]

Hi, sorry for bluntness and hurry, I am pretty busy this week. Still, like yourselves, I am enjoying watching all our efforts moving more or less simultaneously.

On your questions, groovey:
- yes, concave instead of convex.
- some maps of Earth's plates have different representations for subduction (oceanic plates sinking) and obduction (two continental plates, neither sinks, they bend and rise) - the one Akubra referred to the other way is such a case. Careful when comparing maps, I don't think there's an established color code.
- I don't see any huge transform fault in your map, but at least part of the 4/3 boundary should be transform.

- You do have one huge ring of fire, by the way. About half around plate 5 and all the northern side of plate 6 are a very long subduction region, lots of small islands and volcanic mountain ranges should pop up in there. The islands between 8 and 9 will also be volcanic.

[groovey]

No need to apologize for being brief. I feel bad enough for needing your help so much, specially when you have your own project going on. Plus, you managed to solve my doubts, so thank you once again.

Awesome, I have a ring of fire. I mean, I suspected a little that I had the potential to have one, specially after watching one documentary on Earth's ring of fire, but I guess I kind of delayed checking my map for one in case I didn't, because I would have been very disappointed.

Well, I'm off to work a bit more on the map.

[groovey]

Another little update, thankfully advancing forward a little.



I edited just a bit of boundary btw nº11 and 12, and nº11 and 10 and moved the boundary btw 12 and 1 a bit to be more centred. I also edited a bit my original volcanic islands btw 8 and 9 so they actually stay on the right side...

Apart from that the major change is on the south-east part. I made nº6 concave and broke nº7 in two plates, that is, nº16 broke off nº7, so 16 is moving away from 7 and getting subducted by 15 and 6 (on the side). Does that make sense? I can make changes easily enough if really needed.

I added subduction zones on convergent boundaries when I thought they were mandatory, and I left a few convergent segments without subduction where I though wouldn't be mandatory, if only to have a bit of diversity, or when it was continental/continental. I guess the tectonic map is a bit bland visually with so many divergent boundaries.

I also added volcanic subduction island chains, and also a volcanic island btw nº 1 and 14 not created by subduction but mirroring Iceland's creation, but I don't know if it's actually plausible where I've placed it. Would it have to happen in the mid oceanic ridge btw 1 and 12 instead?

What about the subduction island chains? Too many islands? Not enough?

Then I have an issue with a non volcanic island I've awkwardly placed on plate nº7. The issue is I'd kind of need it there so that the Empire on plate nº1 has a similar advantage than that of south of nº3 to get to the islands chain in the south, by shortening the purely ocean travel time (I'm aware other factors influence travel time and routes).

The problem is: how did that isolated island end up there? My reasoning is that it was chopped off (by a rift of course) the south-east of plate nº1, where there's that big "bay", and swirled down, but I don't think it makes any sense at all with the current plates configuration; so could I get away with saying that the chopped bit ended up in 7 in a previous tectonic configuration, or it doesn't make sense anyway?


I'd appreciate any opinions and see if I can settle all this and move one to get the basic terrain and hot spots outline ready, that is: roughly indicating volcanic areas (seismic hot spots would be nice too, but since I don't have many transformation boundaries I guess it won't be as heavy as in Earth), current mountain ranges being created, and also old ones.

I have to say, after all, I'm glad I got the map back to the working table for the second time to re-do the tectonic map. It was very frustrating and I wasn't sure that I'd be able to pull it off, to be honest (at one point I felt completely lost), and yes I've spent quite a bit of time doing it, but I feel like it has paid off, so I'm really happy for that, even if any of you think I've yet things to polish on the tectonics (don't hesitate to tell me if you do).

EDIT: just noticed that the little volcanic island on the north of the east side of plate 5 (big oceanic one) is on the wrong side of the boundary, I'll fix that for the next update.

Game time: can anybody spot the two islands I ruthlessly plagiarized from good ol' Earth?

[Akubra]

Really nice map groovey! I love the big island arc in the southeast and the one between plates 8 and 9. Very realistic!

I must say that I am a bit confused about plate 16. If it moves away from 7 that would mean it moves in a roughly southwestern direction, right? As far as I can see 6 is moving northwards. So how can you have a subduction zone between 16 and 6? Unless I'm missing something I'd say it would be a transform fault, no?

I can't see anything wrong with the island between 1 and 14. To me, the number of islands you drew near subduction zones seem plausible. On Earth there are also subduction zones with few islands and others with many (cfr. Indonesia).

Another explanation for the island on plate 7 could be that it is a "failed continent", lying on a large continental shelf that is mainly under sea level.

I'm very glad it works out well for you! There's a lot of work involved, but if you're happy with the result (and you've got every reason to be!) all that work certainly pays off in the end. Excellent job!

Oh, and yes, I've recognized the two islands. Not sure if I can mention them here, let me do it in a cryptical way: 2 and 3. No, these numbers have nothing to do with the plate numbering, but with a way of numbering here on Earth, even in two different ways... Hope that wasn't too cryptic!

Cheers - Akubra

[Pixie]

groovey, I'm sorry - I misled you about the curvature on plate 6. You had it right from the start (the curvature, but the placement of the islands is right as it is now).

The island-arcs have a nice density of islands but.. they don't look like arcs in most cases - see the aleutians or the kuril islands for text-book examples.

Overall, however, you've got a terrible amount of divergent boundaries. I'm not totally convinced by that, that much oceanic crust has to be consumed somewhere.

[groovey]

Thanks for your comments, you were both right with your points, nº16 did need a different general direction coherent with nº7, and there was more crust created by divergency than it was destroyed by convergency, and equilibrium between those two processes is a key factor, so I tried to fix those two things.



Did I though? Do I still need more subduction zones? It's hard for me to tell visually and today I'm in a bit of a hurry and I don't think I'll have time to work on the map anymore, but I can rearrange things a bit more if necessary to create more convergent boundaries.

For example, I could divide plate nº11 in two on the west of the continent, creating yet another oceanic smaller plate which could create more subduction segments, either with nº5 and nº15, or even with nº11 and the other two mentioned if it's moving towards nº11 and rotating south-east anti clock-wise.

Do nº16 and 7 make more sense now?

Pixie, do I need to change the curvature of nº6 then? I have a copy saved of that shape, so I can easily put it back, but if the current shape is also "correct", I'd keep it. Does it mean then that the side "eating" another plate is usually convex, or it was only a particular observation for plate nº6?

EDIT: Pixie, I think you kind of answered to this in ascanius's thread: "[...] you have to consider the same reasoning when placing the subduction between the two oceanic plates that are converging. The one that is "sinking" should be disappearing, hence, should be narrower". So basically yes, as a good rule of thumb, since the side of the plate getting subducted should be shrinking, it would have the concave shape when the boundary is curvy, would that be right?

I'm not sure I understand very well about the islands, even after looking at map pictures of many of them. You mean that instead of following so much the outline of the boundary, they should be more linearly arched?

[Pixie]

Hi groovey, today I have little present for you - something I scribbled in 30 mins. It's three drawn "tips". Since you have adopted me as the "grandfather" of your project and since I want to see you done with this bit and moving on, here's some ideas:


This is the same sort of issue we were discussing with ascanius map - the age of the oceanic crust and where to place the divergent rise of new rocks in relation to limits of the ocean. If it subducts on one side and not on the other, the two sides can't be of equal width.



I think I pretty covered what I mean with the text boxes. Alternatively to this suggestion, you can have a larger chunk of land, which would have been part of the main continent long ago. This would add, potentially another continent (which could be quite thin), with a long string of volcanic mountains on one side and a passive (lowland) margin on the other, so I suspect it goes against your planned story plot.


Lastly, I hope this image ends with our mess about which curvature to draw between two plates in subduction areas. I haven't been doing the best job with words on this, so maybe a drawing settles it once and for all. And, as for your question, yes, I mean that subduction areas should be more linearly arched that what you have on a number of places.

I need to say though, all this is refinement of your already good-and-running model. Overall plates distribution and movement is fine as it is.

[groovey]

Very nice present Pixie, and great timing! Only days away from my birthday. Thank you, sincerely, and it means even more knowing you're a busy person and that you are working hard on your own project.

Yesterday's boundaries btw nº8 and 9:


Curvature changed:


So, apart from dividing in two plate nº11 as I mentioned, I've done a lot of polishing that may not even be very noticeable, basically boundaries' shapes, so they were more rounded, and I also changed some boundaries Euler's pole to get more subduction segment (this is especially true for nº 5 on the east and btw nº1 and 3, which now give me another very welcomed orogeny zone in the south). I hope it paid off and I didn't mess everything instead.

I also tried to apply Pixie's suggestions as best as I could.

I know that the boundary btw nº9 and 8 should be curved the other way around, but I don't have it in me to do it today, because I'm exhausted, so hopefully I'll be able to change it on the next session, and hopefully without messing the already existing dynamic there. EDIT: changed it and posted the updated map in this very post. I reckon visually it looked better before, but well, I guess now it's more correct, isn't it?

How is the map looking now? Better, or did I mess it up even more?

Also, don't I still have too much red going on?

[groovey]

Forgot about my little game! Akubra, I have no idea of what you mean by those cryptic numbers, I tried to do some searches about it, but found nothing conclusive. What's the mystery about those numbers all about? What are they?

The fun thing about those two islands I stole from Eath is that after doing so, I completely forgot about it, so when I checked Google Earth days later looking for islands chains in the west pacific, I stumbled upon them and was a bit shocked at first and was like: "wow that looks a lot like one of my big islands!", until I remembered what I did... and felt a bit silly.