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I’m trying to create a planet with two small polar oceans with equatorial supercontinent in the middle. The land is in turn divided in two by high mountains that act as barrier and a source of water for rivers flowing into oceans.

How the world came to be: during its early youth planet rotated very quickly (few hours) which created substantial equatorial bulge. Continental plates were pushed toward equator creating multiple uplifting zones, oceanic floors between them were subducted, continental cores mashed together in a crazy jumble of high plateaus and mountain chains with lots and lots of volcanoes. Polar regions were left flat but crisscrossed with mid-oceanic ridges and hotspot archipelagos.

After that initial migration geological activity suddenly slowed down. The resulting uplifted regions were left frozen in place. The byproduct of this is CO2 depletion and very poor biosphere, but it's nothing that can’t be dealt with by terraformers, at least on human timescales.

Thanks to tides and a moon planetary rotation slowed a bit (the day is still 16 hrs. long). Centrifugal pressure weakened, atmosphere on the equator thinned a bit, water flowed toward poles, collecting in polar basins and flooding landmasses that didn’t move toward equator.

Result: polar oceans and equatorial supercontinent with mountains, glaciers and high plateaus in the middle. There are also gigantic valleys, which drain rain and melt water. Because equatorial bulge contributes to the elevation of the supercontinent above sea level, its more northern and southern parts consist of continental slopes and exposed basaltic oceanic floor.

Those ancient oceanic plains are now covered by sediments, and are flat. Very flat. They make a place where winds can blow around the whole world not encountering any obstacle. Coasts are muddy plains, where tides move tens of miles there and back again. Rivers the size of Nile, flowing toward oceans from the equatorial mountains fall from old continental slopes and escarpments in gigantic waterfalls and cataracts.

Does this scenario makes sense and is at least plausible?

(I’ve read this question: Climatic consequences of two Polar Oceans and a Circumspecting Landmass Definitely I’m using it for building climate but first I want to know how to make such configuration of land and water).

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    $\begingroup$ It strikes me that the shape of the planet might have needed to occur before liquid water was around much. Planet formation like this - then a slowing of rotation, then liquid water. Difficult to see how it might ultimately happen without a lot of contrived comets delivering ice. That being said, interesting question. $\endgroup$
    – Escaped dental patient.
    Feb 18, 2021 at 22:50
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    $\begingroup$ "Continental plates were pushed toward equator" - if continental plates formed before planet's spin-up, we need to explain how they stayed whole during the spin-up event. If continental planes formed after the spin-up event, I'm not sure they want to migrate to the equator after formation, because the entire planet is at hydrostatic equilibrium. $\endgroup$
    – Alexander
    Feb 18, 2021 at 23:09
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    $\begingroup$ Continents are not "pushed" towards the equator - that's not how it works. And this implies that your planet has lithospheric plates with continental and oceanic crusts, so what happened to plate tectonics? $\endgroup$
    – Gimelist
    Feb 19, 2021 at 1:53
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    $\begingroup$ This scenario requires that the planet start with active tectonics and a very high spin rate, followed by enough time for the tectonics to completely stagnate, before then initiating a drastic spin-down of the planet. This will require several billions of years. Yet, it must still have significant resources of water despite the absence of vulcanic sources to replenish it, and it must acquire a very large moon from somewhere to orbit close-in,to cause the de-spin. Individually everything works, but the timescale and ludicrous unlikeliness of the chain of events is a bit off-putting. $\endgroup$
    – PcMan
    Feb 19, 2021 at 10:06
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    $\begingroup$ The fast rotation would likely result in the complete opposite situation I think, with nearly all water on the planet concentrating near the equator due to a combination of centrifugal forces and the tidal pull from the star and the moon, if it exists. $\endgroup$
    – Darth Biomech
    Feb 19, 2021 at 13:52

1 Answer 1

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Short answer: planetogenesis do not work like this.

A fast rotation would change the overall planet shape, deviating from a purely spherical shape. This deformed shape ensures that gravity is directed downwards and not sideway, on all the surface of the planet. As a consequence, there will be no "push" towards the equator for continents or anything else.

Regarding geological activity, shutting it down requires a planet smaller than Earth to happen (considering you are on the same timeline than Earth's). Such cooldown will weaken or remove any magnetic field, making your surface exposed to cosmic rays. And the fact that the planet is smaller implies it may not have as much atmosphere.

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