Highly Realistic Tectonic Map Project

[Peter Toth]

Hello fellow cartographers,

I’ve been crafting this conworld over the past month or so, aiming for utmost accuracy with regards to plate tectonics; after I’ve successfully accomplished that phase, I'll be moving on to the next level—rendering mountains and other surface geological features. Before I move on to those other juicy details, however, I am hoping to get a critique from some of you accomplished and experienced fantasy cartographers (is Pixie still looking through this sub-forum?).

In particular, I’d like to know if my tectonics look plausible, especially some of my island chains. If you view the animation, you'll notice that the middle continent that spins counterclockwise somewhat "blocks" the development of the island chain to the west, at least until the last several million years. Figuring that the north has had more time to accumulate continental crust, I've slimmed down the souhtern part, which I reason formed later. Likewise, I've done the same to another island chain at around -90 longitude. Are these subduction zones plausible from a technical viewpoint? Is there anything I've overlooked? Please let me know.

By the way, the time frame from supercontinent-breakup-phase to "now" is 107.57 million years. Although Pangea officially broke up about 175 million years ago, I'm justifying my shorter time interval by positing that my conworld is somewhat younger than the Earth.

And lastly, the figures on the second tectonic map represent absolute plate motions in degrees per million years.

As always, this "atlas" style may not be everyone's forte, but I appreciate your viewing.

Peter

Basic Map.png

Tectonic Map.png

https://www.facebook.com/peter.toth....type=3&theater

[Naima]

HAve you tested with Gplates? Also I notice there is a lot of land and few water, Water has a big influence over tectonic movements , the lesser the water the lesser the movements and so the possibilities of mountain ranges etc.

In the ductile creep regime, the viscosity of wet rocks is weaker than the viscosity of dry rocks by several orders of magnitude. In the brittle regime, the most substantial effect is probably serpentinization which can reduce the friction coefficient by a factor of 2 or more. The difference between the strength of a wet lithosphere and that of a dry lithosphere seems to be big enough to control the very existence of plate tectonics. Because of dehydration due to partial melting the oceanic lithosphere is expected to be essentially dry above some critical depth, around 60-80 km. This would make the lithosphere strong enough to prevent plate motion. Percolation of water from the surface can be the main mechanism supplying water to the upper parts of the lithosphere. This implies that liquid water can be crucial for maintaining plate tectonics. On the other hand, the surface temperature is above the freezing point because of the greenhouse gases such as carbon dioxide. A simple model shows that if the blackbody temperature of the Earth is slightly below the freezing point of water, the feedback between plate tectonics, volcanism, and water and carbon cycles can result in an equilibrium state in which the surface temperature is established within the stability field of liquid water.

[Charerg]

The land/water ratio is probably about the same as on Earth, at a quick glance, so I don't think that's an issue. Interesting read about the interplay between water and tectonic movements. However, I'm not sure how relevant that is to the issue of how much of the actual surface is under sea level, since even the rocks forming the continents typically contain some water. Though I would definitely be interested in reading more on the subject if you have some suggestions.

[Peter Toth]

Hello,

Thank you for your responses. I hope the land/water ratio permits earthlike tectonics on my planet. By the way, I did include a GPlates animation of the tectonic evolution of this conworld, although due to its inconspicuous location, many might have missed it.

Here it is again: https://www.facebook.com/peter.toth....type=3&theater

I hope this helps decide whether my island chain locations are realistic.

Thanks,

Peter

[Charerg]

So, feedback regarding the tectonics and island chain locations in specific... first of all let me apologise for this being a bit "late to the party" but tectonics is a fairly complicated subject and often providing useful feedback can be a bit daunting in itself, since there are a lot of things that need to be explained.

But let me start off with the definition of "realistic". Because this can be a bit subjective term. If you want to go really hardcore, there are a number of things that could be improved, like using GPlates to track the formation of oceanic crust, to alter the movement speeds of the plates depending on the forces acting on them, etc. The program does have a lot more utility beyond the basic functionality of creating continent outlines and moving them across the globe (in case you're not aware, there is a GPlates tutorial I wrote that explains most stuff). It all depends where you want to draw the line (as in "how realistic do you want to go" because all this involves extra work).

For example, looking at the animation, your movements would likely not work out if creation of oceanic crust at mid-oceanic ridges was included. Also most continents seem to move at more-or-less similar speed regardless of the forces acting on them (are they subducted/subducting, is there a major collision and so forth).

Regarding the island chains themselves, it all depends on whether it makes sense for the plate boundaries to be located where they are. At least some of those seem to be a bit arbitrarily located in the middle of the ocean, without a good reason for that as far I can see. Typically in a scenario where a plate is converging with another (likely being subducted in this case) you'd expect the boundary to be located at the "edge of the landmass" since the subducting plate normally won't have a leading edge of oceanic crust.

I'll try to post some more practical examples later on (maybe during the weekend), but I hope this was at least somewhat helpful.

Cheers, and keep up the good work!

[Naima]

Totally agree with what Chareg wrote.