6
$\begingroup$

This is a community-wiki question

Worldbuilding Stack Exchange regularly hosts questions asking either how to establish plate tectonics based on an existing planetary map or to judge the suitability of a user's pre-designed tectonics. Consequently, the same basic question has been asked over and over leading to a considerable amount of highly redundant information on this Stack that is no longer easily accessed.

The community-wiki answer, below, exists to bring together the knowledge of so many questions and is intended to be a canonical answer helping worldbuilders to create sensible plate tectonics for their worlds.

Questions asking about plate tectonics that do not indicate that the OP has visited this page should be invited to close their question and look here before asking again. OPs who do not find sufficient information here to solve their problem are asked to clearly explain why this page did not solve the problem. Thank you.

The Rules

  1. There will be only one answer to this question. Please edit that answer with your improvements. All other answers will be deleted.

  2. Please review the contents of the answer before adding your insight to keep duplicated information to a minimum. There's nothing wrong with correcting or adding to what someone else has already written.

  3. If you feel an instruction is intrinsically wrong, please consider carefully what it's trying to convey before you choose to delete it and replace it. If you are not prepared to replace such a rule with something better, please consider leaving it alone until you are ready to do so.

  4. Where possible, the quality of this answer will be improved if you either link back to the Stack Exchange answer you obtained the information from, or link to an outside source that substantiates the idea. This will be a work in process as much of the information in former questions was not provided under the condition and so no citations were included. That doesn't diminish the value of this question, it would simply be improved by the links.

  5. Finally, while it's possible for the answer to become a thousand-page definitive treatise on the subject, that's not the point of worldbuilding. The goal here is to provide practical guidance to solve a practical problem. let's try to stay focused on that.

This question is linked to the site's List of Worldbuilding Resources.

If you have questions about the intent or operation of this question, please post a comment. Once your question has been answered, please delete your comment. Thanks.

$\endgroup$
0

1 Answer 1

5
$\begingroup$
  • Always start with a chart of Earth's plates before you. We know they work! Use them as a guide. JBH, JBH

  • Tectonic plates always have low spots and high spots. Though not mandatory, the low spots are usually water basins or edge oceans and the high spots are often plateaus and mountains. [JBH (https://worldbuilding.stackexchange.com/a/246679/40609)

  • Most oceans are on a tectonic plate. They are also the largest. I would recommend finding the coasts that look like they could find into a different coast on an adjacent continent. Martamo

  • Plates should never meet at a “t”. A “t” is a four-way meeting of tectonic plates. Martamo

  • Plates move and rotate. When they move away from one another, they create chasms (e.g., the Mariana Trench). When they collide they create mountains (e.g., the Himalayan Mountains). JBH, GaultDrakkor

  • Volcanoes frequently happen along plate boundaries (e.g., islands and mountains). This is especially true when the plate is rotating rather than moving. JBH

  • Plates (fault lines) rarely cross in the middle of landmasses. It isn't that they can't, it's that water erosion usually eats away at the sides of the land masses, leaving seas between the two land masses with a plate division along the sea. Thus, a plate bisecting a continent (incredibly rare) would have been two plates pushing together for a very long time, resulting in a substantial mountain range bisecting the continent. JBH, GaultDrakkor

  • Though hard to imagine, it is believed the U.S. Rocky Mountains (forming the U.S. Continental Divide) were caused by the shockwaves of two plates colliding. In other words, mountains don't form only because of two plates pushing against one another. Mountains (or, generically, "high spots") also form due to meteor strikes or, perceptually, from water erosion (e.g., draining Lake Bonneville) or wind erosion (U.S. southwestern bluffs) due to low-density rock being blown away from high-density rock. You can also have sink holes due to the type of rock (e.g., limestone). In short, you need to realize that you'll have high spots (mountains) and low spots (lakes...) in locations other than plate boundaries. JBH

  • Your average plate will have ocean encompassing a landmass. JBH

  • In the majority of cases, touching landmasses will touch lightly or with small stretches of land (e.g., an isthmus). Note that an isthmus can form due to soil buildup around the two plate boundaries having little or nothing to do with the plate boundaries. I.E., ocean currents deposit sediment that reinforces the currents' behavior until an isthmus forms. JBH

  • Polar caps help identify how much water is available. In a warm year there's less cap and more water, meaning greater separation between land masses. In a cold year there's more cap, less water, and more connectivity between the land masses. JBH

  • If your map is only showing coast lines, it doesn't show us topography, which is really what we need to identify plates. You can identify tectonic plates and derive mountains from them, or set your mountain ranges to identify plates. In the end, your goal is a topological map. JBH

  • Fault lines run parallel to ridge lines, not perpendicular to them. JBH

  • Fault lines frequently run parallel with a series of deep-water points rather than bisecting them. JBH

  • Islands frequently pop up along fault lines. JBH

  • A tectonic plate frequently encompasses a body of water and some coastline, or a large landmass with some coastline. Not both (Something is causing the subsidence of the ocean or "supersidence" of the land mass). As an example, if you look at the Earth's South American Plate, you'll see that the fault lines run along the major mountain range along South America's western coast, and the trench lines in the middle of the Atlantic Ocean. It encompasses all of South America — but not all of the Atlantic Ocean to the next continent. JBH

  • Boundaries should be mostly made of many joined roughly 120 degree 3 way junctions, right angle T, or large smooth arcs of subduction island arcs (Aleutian islands, Java), and if you have an island arc it should be on a subduction zone Image examples island arcs John

  • Tectonics plate are usually made of continental AND oceanic crust or just oceanic crust, because forming oceanic crust is part of how plates move, it is always present. Even the Arabian plate has small slivers of oceanic crust. John

  • tectonics plate boundaries are defined by what kind of crust is interacting and how, there are 6 basic ways and it may be worth looking at them, in short any combination can form convergent boundaries, and give you drastically different geography based on which. Divergent boundaries are always the same on both sides (both oceanic or both continental. [John]

$\endgroup$
4
  • 3
    $\begingroup$ I don’t believe that the bullet mentioning the Marianas trench is correct. Plates pulling apart form a series of ridges as new material rises from below. I believe the Marianas trench is in a subduction zone, where the pacific plate dives under an Asian plate. If I can confirm this later I will edit… $\endgroup$ Jun 27, 2023 at 14:26
  • $\begingroup$ @MichaelHall --- Were you able to confirm? $\endgroup$
    – elemtilas
    Oct 4, 2023 at 0:51
  • $\begingroup$ @elemtilas. I haven't had time to research, but very confident. Look up "Mid-Atlantic Ridge". $\endgroup$ Oct 4, 2023 at 2:56
  • $\begingroup$ plates should not meat at a t they should meet at 3 way junctions made of roughly 120 degree angles. 4-way junctions are very rare. Also yes the Marianas trench is a subduction zone, chasms form when continental crust separates not oceanic crust. $\endgroup$
    – John
    Oct 4, 2023 at 20:00

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .