New World (Help with Tectonics?)

[davoush]

Hello all,

I have decided that my previous WIP was an exercise in better understanding tectonics, climates, etc. (Thanks to Pixie, Azelor and all those who helped - your assistance was very much appreciated! ) In the end, I didn't like the configuration of landmasses (too similar to earth), and also I was not getting enough of the desired climate zones (as this world is a setting for other things, I had particular goals in mind). With that said, I have decided to try another world, but this time bearing in mind my goals while still aiming for some realism/plausibility.

I have sketched a rough map of landmasses with tectonics plates. I realise this is a very very messy sketch, but I would be very grateful if anybody could tell me whether there are any big mistakes I'm missing as I don't want to start drawing in more detail only to find I have to revise large portions of land? These are only the large main plates, I think adding in minor plates is less of an issue if the main plates are moving in the right directions.

Also, I originally drew a landmass on the large oceanic plate, but I was wondering if this is realistic? I wanted it to be an Australia type, old, flat continent, but that would be the equivalent of having it on the Pacific Plate? Would it more likely be on its own plate?

Many thanks!

(Edit: See latest post for map)

[davoush]

In addition, I also have a quick question regarding axial tilt and climate regions. This world has a smaller axial tilt of around 17.5-18 degrees. I realise this means a smaller band of tropics (spanning to 18 degrees N&S). But what about the subtropics? On earth, they are about half the size of the tropics either side (0-23 tropics, 23-35 subtropics). Would this mean the subtropics with a lower axial tilt would also be lower, (0-18 for tropical region, 18-27 for subtropics), or would they be more spread out? Any ideas about the implications would be appreciated.

I imagine that perhaps the transition from desert > temperate would be less severe, maybe with large bands of mediterranean like climate which receive quite a lot of sun and not much seasonal variation?

[Charerg]

In addition, I also have a quick question regarding axial tilt and climate regions. This world has a smaller axial tilt of around 17.5-18 degrees. I realise this means a smaller band of tropics (spanning to 18 degrees N&S). But what about the subtropics? On earth, they are about half the size of the tropics either side (0-23 tropics, 23-35 subtropics). Would this mean the subtropics with a lower axial tilt would also be lower, (0-18 for tropical region, 18-27 for subtropics), or would they be more spread out? Any ideas about the implications would be appreciated.

I imagine that perhaps the transition from desert > temperate would be less severe, maybe with large bands of mediterranean like climate which receive quite a lot of sun and not much seasonal variation?

Smaller axial tilt would mean less severe seasonal variation. So basically most climates that experience a seasonally variable climate would decrease in area. High latitude summers would be colder, resulting in tundra and ice cap climates expanding. Around the equator, the ITCZ would fluctuate less seasonally, meaning that the areas covered by savannah climates would generally decrease in terms of area (as you surmised). Deserts would be more expansive as a result of this.

In general, the transitions between the major climate zones would be more abrupt, because seasonal variability is what causes the "transitional climates" in between them. So, I'd say that in general mediterranean climates would decrease in terms of area.

[davoush]

Smaller axial tilt would mean less severe seasonal variation. So basically most climates that experience a seasonally variable climate would decrease in area. High latitude summers would be colder, resulting in tundra and ice cap climates expanding. Around the equator, the ITCZ would fluctuate less seasonally, meaning that the areas covered by savannah climates would generally decrease in terms of area (as you surmised). Deserts would be more expansive as a result of this.

In general, the transitions between the major climate zones would be more abrupt, because seasonal variability is what causes the "transitional climates" in between them. So, I'd say that in general mediterranean climates would decrease in terms of area.

Thanks - as informative as always! In that case, I may have to make the axial tilt slightly greater as I wanted a 'green Arabia' type setting and to avoid the huge deserts which plagued my previous map. I think I read somewhere that Arabia being green coincided with higher axial tilt? Maybe it will be tilted 27 degrees instead.

Would a greater axial tilt mean large deserts are less likely to form?

[Azélor]

Thanks - as informative as always! In that case, I may have to make the axial tilt slightly greater as I wanted a 'green Arabia' type setting and to avoid the huge deserts which plagued my previous map. I think I read somewhere that Arabia being green coincided with higher axial tilt? Maybe it will be tilted 27 degrees instead.

Would a greater axial tilt mean large deserts are less likely to form?

Sounds right but there are many other things influencing climates such as the atmospheric composition and speed of rotation of the planet.

I think the tilt was 24 when Sahara was savanna.

[Charerg]

Sounds right but there are many other things influencing climates such as the atmospheric composition and speed of rotation of the planet.

I think the tilt was 24 when Sahara was savanna.

Yeah the axial tilt was at maximum (24.5°) 8700 BCE, though it's worth noting that the planet was warmer on average back then too (the Holocene climatic optimum). And as you noted there's other factors too that have an effect.

Tbh, I'm not certain how well the Saharan green period is understood, or how extensively it became green. From what I understand, a lot of the evidence comes from the Saharan highland regions, and the climate there might have been different from that of the open ergs. Though the southern Sahara especially did receive a lot more rain, as attested by the "Lake Mega-Chad" that existed back then. I suspect the desert didn't disappear entirely though.

[davoush]

I've produced a cleaned-up version of my initial sketch with what I think are the main tectonic plates and their movement.

The main plates I am unsure about are: Plate 5 - I wanted this to be an Australasian type plate with lots of minor plates around it, and lots of islands, etc. I'm not sure if this is achievable given the surrounding plates? I also have no major orogeny on land - this will probably happen to plates 1 & 2 at some point, but I would like to have at least one huge orogeny zone.
I also have not indicated any rifts as I wasn't able to identify where they would be most likely to occur (if any?)

Many thanks for any criticism or comments!

(See latest post for map)

[Deoridhe]

Depending on exactly how it's moving relative to place 7, plate 4 could have an orogeny zone where it's being moved between 7 and 9 - I think at least. There could be similar if some of the plates were twisting as well as moving forward.

[davoush]

Thank you both - I have worked out some other details for the setting of this world, which I won't go into detail (yet), but the world is in generally a few degrees hotter than current earth and will have a slightly greater axial tilt, assume everything else is pretty similar to earth. Hopefully this gives a result similar to the Holocene climatic optimum.

Updated the tectonics a bit. I *think* it mostly looks plausible. Mostly concerned about plate 5 and surrounding plates. I really want that bunch of islands there. I would also like there to be some connecting island chain or corridor so that human dispersal can occur without too much difficulty.

This has been far easier to work out than my previous map so thanks to everyone who helped me further my understanding.

(See latest post for map)

[Azélor]

Tbh, I'm not certain how well the Saharan green period is understood, or how extensively it became green. From what I understand, a lot of the evidence comes from the Saharan highland regions, and the climate there might have been different from that of the open ergs. Though the southern Sahara especially did receive a lot more rain, as attested by the "Lake Mega-Chad" that existed back then. I suspect the desert didn't disappear entirely though.

Yes and maybe humans played a role in the desertification. As you say, this is poorly understood.