[WIP] The Construction of Acean - Looking for advice on plate tectonics

[Feybrad]

Hello Cartographers,

I come to you with my project on the world tentatively named "Acean". I have been working various disparate parts of it's worldbuilding for a couple of years now, rather sporadically to be honest. During that work, I had created an elevation map and worked my way up there to a climate map (alongside some of the great tutorials on this guild). That process, though, showed me a couple of missteps I had made when creating the elevation map (most egregious of all - coastal island arcs that stretch in nearly random directions, around which I extended the continental shelf, forcing me to adjust sea currents, ultimately leading to tropical rainforests near the polar circle, which points toward a host of mistakes I had made during the whole ordeal). Thus, I decided to start over from only the shape of the continents and the bare plate tectonic map underneath.

But, looking at it, I am both hit by a spark of inspiration and a major conundrum. See, when I created that first elevation map, I did not pay much mind to older mountain ranges (and, in general, structures that may have existed previous to "current" tectonic developments). This is a mistake I wish to correct this time - yet I feel like my own understanding of the matter is awfully limited. I resolved to ask for advice in here (and use this opportunity to stop lurking and properly enter this community). And while doing that, perhaps have someone look over my very crude tectonic outline and tell me if I made some terrible mistakes. Thus, without further ado, I shall present the foundation on which I want to base my work on.

Shadowland.png Here we see the basic shapes of the landmasses I want to have on my world (land as black, oceans as white). While I am not married to the specific shapes, I aim to preserve the general composition if possible.

My Boundaries.png This is the tectonic outline. Red lines indicate the actual boundaries, yellow lines indicate the direction the move in: Toward the orange zones (somewhat indicative of subductions or collisions). In an earlier draft I had marked some plates as continental and oceanic, but most of my research indicated that there is no such thing as an "oceanic" and "continental" plate, only oceanic and continental crust on a plate.

Shadow over Boundaries.png For ease of viewing, here is a combination of those two maps.

My goal now is twofold:
1. Check if my current tectonic layout has any grave errors or implausibilities - and please, do not shy away from other criticism or ideas you may have, if you look at it.
2. Try to extrapolate from this, where older mountain ranges (and other structures) could have formed, basically, try and retrace the tectonic history of the planet. Or at least find a method by which to do so.

I will keep tinkering on these questions on my own, but I feel like, with such a wealth of more experienced mapmakers in the guild, I would be remiss not to ask for advice or help.

Thus, I thank you for taking your time to read this and, perhaps, help me out.

Jan

[Jean-Abdel]

First, you should add whether boundaries are transform or divergent, herer it's not very clear if a boundary is actually producing crust or not, and remember that ridges produce crust perpendicularly to it, at the same rate on each side so they are right in the middle of the oceans. Your coastmine looks a bit to shredded, even though the general shape is cool. You don't need that plate for your round shaped lake/inner sea, it looks very unnatural. The early-rift zone on the middle left is very weird, that coast should not have all these peninsulas in a rifting area, look at the red sea. Finally the very narrow straight at the top of the map don't look really feasible. There are other things I surrounded on this map

[Feybrad]

First of all, thank you so much for answering!
You have opened my eyes towards some rather embarassing flaws in my basic tectonic map, that I have hopefully now taken a first step toward correcting.

Paint my World.png
Again, in orange you can see boundaries the plate in question is moving towards. In green, conversely, you can see boundaries the plate in question is moving away from. Yellow(ish) are boundaries that plate is moving alongside.

Thus, orange/orange boundaries indicate a collision of plates. Green/green boundaries indicate a rift zone, where crust is created.

The narrow strait in the far north I tried to keep, atthe cost of using a copious amount of micro plates in that region.
The young rift at the equator (left side of the maP), with the many weird peninsulas, has been mostly corrected or reigned in a little bit.

That said, please keep the feedback coming, if you have the time - I hope you can see that I am very receptive of it!

[Naima]

Agree qith the above comments, and the round shaped lake/inner sea it just fit perfectly for a meteoric impact ... so you can add a mountainous island in center and the surrounding shores of the lake might have a mountain range encircling it, though according to how old is this the montains can even be just hills or be smoothed totally , consider though that the more new is the crater the more impact might have had in the recent history and climate of the world .

[Feybrad]

Thanks for the interest, Naima!

While I agree that a meteoric impact crater would be a really cool explanation for that particular sea, that "meteor" would have had to be the size of a major moon. However, this reminded me of something I should have clarified at the beginning - this map is supposed to show the whole world, from pole to pole. I have not had time today to make big updates, but here is a version of the map with the earth overlaid, for the comparison of sizes.

The World and Acean.png
As you can see, any meteor that would have caused a crater this big would have been roughly the size of the continental US - an impact with such an object would be a world-ending cataclysm, I fear.

That said, I still like the general idea, but I am not quite sure if it is feasible. How far back do you think would such an impact have to have happened, in order for both to be still visible on such a scale AND for life to exist in a vibrant and diverse form on the planet, if that is at all possible?

[Feybrad]

So, I have been thinking about how to properly reconstruct some tectonic history.

A while ago I had been trying to simply go backwards, but even discounting the somewhat glaring errors in my tectonic makeup (see the opening post of the thread), it was a rather tedious undertaking and yielded very incoherent results.
I needed to have an Idea of what was there before, so I could then pursue this tectonic history with, perhaps, a little more direction.

Of course, finding that point is hard. I have looked at basically "reversing" a lot of the more current movements and arrived at this following stage for a start.
Long Ago Version I.png
I must say, I don't like it very much. It feels somewhat lacking, without really being able to serve as that point of reference. That said, it will help me going forward.

Afterward, I created a second mock-up - again, extremely rough and broken down to basics, since I do not feel like I need any real deatil at that stage - that could more properly serve as a "waypoint" in my tectonic history.
Long Ago Version II.png
It is a super continent. In principle, I like this more than the first version, however, I have a nagging feeling that a super continent might be, what everyone does when pursuing these stages of work.

I will continue tweaking - I am looking to create a map with the plate boundaries for the super-continent stage next, and then use that to "break it apart" again by reconstructing the layout of the world before it was that super continent.

Please, tell me your thoughts on this, both the "results" (in very big quotations marks) and, more importantly, this "workflow" of mine.

[Feybrad]

So, shorter update today, since I was very busy with work the last days.

I updated the basic plate tectonic map to better reflect what boundaries lie where.
Red denotes confrontative boundaries.
Green denotes divergences.
Blue denotes subductions.
And the one yellow boundary is a transitional one. I fear I might have too little transitional boundaries here (mostly to the benefit of divergence zones).
Hand drawn triangles are the worst.png

What do you think?

[Jean-Abdel]

You usually don't have divergent directly sexy to convergent, there's always a little bit of transform between the two. Otherwise it looks ok, let's just say that it's geologically very active.

[Feybrad]

Thanks again for your Input! Divergence zones are very sexy indeed.

But your comment about the world being geologically very active got me thinking. While I am not opposed to the idea (I am quite attached to the general layout of the continents by this point), I always strive to stray on the earthlike side. And a driving factor behind me having so many plates under the continents is that I wanted a number of mountain ranges to be where they are, without a) knowing where to plausibly place "old" mountain ranges and b) honestly, thinking about "older" mountain ranges much at all. This led me to create a tectonic layout that featured quite a number of plates and led to a geologically very active world.

Thus, I pose, perhaps, a bigger plea to anyone who is interested. What follows is a map with the major and minor mountain ranges I want to have in the world , in decreasing height and importance. You can assume that continental boundaries are more important to me than those mountains, but if I can have my cake, I would like to eat it too.

Mountains of my Madness.png
Dark red denotes the most important and highest mountains.
Orange denotes other major mountain ranges.
Yellow shows mountains of median importance.
And green shows "nice-to-have" minor mountain ranges.

Take note that these ideas are still based on my "original" tectonic layout found in the opening post on this thread, and that they were formed without taking into account that some of them could be old mountains.

Thank you again for reading and helping me out.

[Jean-Abdel]

It wasn't supposed to be sexy but next