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I have designed a planet's landmasses and now am wondering where the tectonic plates would be. I understand this is backwards to the popular method of tectonics-first, but I wanted to design how the planet looked rather than hoping the long and tedious simulation method would result with my desire. Let me know if my question is too vague to be answered. Thanks!

The grid represents equirectangular 15° increments.

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Ylahris
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    It would help to know about mountain ranges. – futurebird Jun 26 '23 at 15:23
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    With the detail presented, no. We know that cratons (continental chunks) float on the basalt crust like soap bubbles in a bathtub. We can't tell what direction they're headed without knowing what the core-to-mantle currents look like. – Robert Rapplean Jun 26 '23 at 16:06
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    first congrats of having a map that actually looks like a natural one, we dont see many of those. – John Jun 26 '23 at 16:14
  • @John Thanks! I used GPlates. – Ylahris Jun 26 '23 at 17:42
  • To summerize the other answers - Determined is probably too strong of a word, but with knowledge of mountain ranges, coastlines - one could pretty reasonably infer where the plates where. – TheDemonLord Jun 26 '23 at 20:43
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    Did you review the other questions with the tag [tag:tectonics] for information about how to create a sensible tectonic map? I've answered two such questions with lists of general rules about tectonics: here and here. – JBH Jun 26 '23 at 20:57
  • The second image look suspiciously like a map of Europe... – Seggan Jun 27 '23 at 19:14

3 Answers3

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On the real Earth, the boundaries between tectonic plates can be:

  1. In the middle of an ocean, e.g., the Mid-Atlantic Ridge; or

  2. In the ocean near the coast of a continent, e.g., all along the western coasts of the Americas; or even

  3. In the middle of a continent, e.g., the East African Rift.

(1) is more common than (2), and (2) is more common than (3).

But really, geography worked just fine for thousands of years without any knowledge of tectonic plates. Just make up your geography, and let geologists bother to find the boundaries between tectonic plates.

Bonus:

Tectonic plates are not eternal.

  • Sometimes they split: for example the African plate is currently in the process of splitting into a main African plate and a new-ishly born Somali plate.

  • Sometimes they merge: for example the Ural mountains mark the former boundary between a European plate and an Asian plate, which are now solidly fused into a Eurasian plate.

  • Sometimes they vanish: for example, the tiny Juan de Fuca plate is all that remains of the once great Farallon plate, most of which has gone deep below the North-American plate and will never be seen again.

AlexP
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Well one thing we can do is point out you have a set of coastlines that match which would predict they are an ancient spreading center like the Atlantic. (in red)

You also have two areas that look like convergent boundary islands (in green) the southern one most likely a complex convergent boundary like Oceania.

Its not a complete map but it is a starting point.

enter image description here

The high distortion on polar continents will make it bit difficult, If your program can rotate your globe projection it would make it easier ith multiple projections.

John
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    I would also suggest that anywhere where there is a narrow gap of continental landmass, (such as the smaller ismus like form of the right most continent between the north and south or the left most continent from the Antarctic mass) might be a good place for either a continental or a continental convergence.).

    Also keep in mind that on earth like planets, poles are not always under continental land masses. Antartica (south pole) is an actual continent, but the Artic, (north pole) is a frozen artic ocean. The magnetic poles are also due to phenomena closer to the core than the crust.

     – hszmv Jun 26 '23 at 17:42
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Without knowing were mountain ranges are, all we can really go off is how fractured a coastline looks and where ocean islands are. Large island chains in the middle of the ocean for instance usually dont just happen without any tectonic activity nearby.

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This would be my guess. But i am not entirely happen with this. I am fairly confined the central island collection would look a bit like this. But idk what goes on in the northern hemisphere. Often times tectonics are not super intuative. As an example here is a map i simulated; enter image description here

And here are the Plates and mountain ranges; enter image description here

So as you can see, with simulated stuff it is just not super easy to get an accurate picture just by looking at the final continents. Especially fault lines going through continents are basically impossible to see without an elevation map.

ErikHall
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    A good example from Earth: without a map showing elevation, both surface and underwater, there's no particular reason why anyone would assume India was on its own plate and not part of the larger Asian one. Similarly, they'd have no idea the Australian plate is freaking huge, with the above-water portion only a small part of it. Without seeing the Chersky Range, there's be no reason to think the northeastern corner of Asia was on the North American plate, or by ignorance of the Rift Valley that Africa was coming apart. – Keith Morrison Jun 26 '23 at 22:49