Is it possible for a planet's surface to be wetlands, such that…

  1. There are no great land masses (continents).

  2. There would still be two polar caps, and I am considering a greater width of equator such that more temperate lands further north and south than we see on Earth.

  3. I am including canals for boat traffic similar to the narrow boats on the rivers in England or the canals of Venice.

  4. Finally, I am considering a solid core to provide the magnetic field needed for gravity.

My goal is to shadow earth's wetlands in many ways across an entire planet.

  • $\begingroup$ A solid core is not required for gravity, a liquid one will do just as well. I'm assuming you want a molten core to create a geomagnetic field. $\endgroup$
    – o.m.
    Commented Feb 1, 2017 at 6:06
  • $\begingroup$ Travel tip of the day: Dagobah $\endgroup$ Commented Feb 1, 2017 at 6:11
  • $\begingroup$ Welcome to Worldbuilding, Maryann, thanks for your interesting question. Several years ago i designed a planet something like this for a friend and fellow writer. I will need to some digging to find it and then edit it to meet your needs. Will get back to you. $\endgroup$
    – a4android
    Commented Feb 1, 2017 at 6:14
  • $\begingroup$ Thanks for the tip on the molten core. This is my first world and I am trying to keep to things I can understand. So not going to mess with gravity on this one. $\endgroup$
    – Maryann
    Commented Feb 1, 2017 at 6:15
  • 1
    $\begingroup$ You might want to reconsider the absence of plate tectonics: there is a planet in Solar system that has no plate tectonics, and the result is not good: "Whereas Earth's crust is in continuous motion, Venus is thought to be unable to sustain such a process. Without plate tectonics to dissipate heat from its mantle, Venus instead undergoes a cyclical process in which mantle temperatures rise until they reach a critical level that weakens the crust. Then, over a period of about 100 million years, subduction occurs on an enormous scale, completely recycling the crust" $\endgroup$
    – user61244
    Commented Feb 1, 2017 at 13:39

3 Answers 3


Assume an earthlike planet with less mass than Earth. The planet is super-habitable. It has shallow oceans, was geologically active but is now geologically inactive, the main continents are east-west and there are no north-south continental land masses like Africa and the Americas.

The planet stopped being geologically active approximately two million years ago. Vulcanism ceased, i.e., no volcanoes. Continental drift stopped. Mountain building was halted. A planet with shallow ocean will have warm seas which pump enormous volumes of water vapour into the atmosphere leading to high rainfall globally. The mountain ranges have been ground down to effectively nothing soil erosion and water activity over the last two million years. Much of the shallow oceans has filled with silt and run-off soil. Water levels have risen to cover large areas of the mostly flattened continental land masses.

Marshes and swamps are now the dominant land form. There will be areas where the free oceans still exist. It seems worthwhile to leave some vestiges of the planet's earlier environment. This adds to its plausibility. And it adds to the author's plausibility: I, the author, know one-environment planet aren't too likely. Note: there are some exceptions, but we don't need to worry about them.

Because the planet is, was or has been super-habitable, there will be vast reserves of material to drive the food chain (this could be more difficult than this glibly suggestion; but it can simply be assumed it is so) though this may be mainly detritus feeding, which is much like swamp or marshland ecology anyway.

This means there should be a rich flora and fauna on the planet which as it changes into Planet Marshlands adaptive changes and evolutionary pressures will adapt them to this environment.

The above model is based on the super-habitable planet and is well worth your while to do some further research into to help build your planet. The Wikipedia entry linked above is a good starting point.

There is a certain amount of pure hand-waving in this model for marshlands-only (well, almost) planet There is another putative model for a swamp environment planet, but that involves a super-Earth type of planet with high gravity and a rigid crust which suppresses mountain building, vulcanism, and continental drift.

In this case, the high gravity would be the killer. No natural Earth humans could move around such a planet without lots of advanced technology. While this logically makes sense, it's the death knock for plausible fiction.

  • $\begingroup$ I think super-earth planets become flatter not because vulcanism is suppressed but because erosion wears the mountains down faster. Still, the high gravity is a problem for land-dwelling species. $\endgroup$
    – papidave
    Commented Aug 19, 2017 at 21:40
  • $\begingroup$ @papidave I think it's a combination of the two. Perhaps I didn't make it clear the time scale for erosion was meant to be fast and certainly on high-gravity planets erosion would be a more powerful force. Vulcanism does tend to make more mountains and if it's shutdown then soil erosion can obliterate them more efficiently. It was the combination that aimed at producing the intended result. Soil erosion is often underappreciated in shaping landscapes. Your comment is appreciated. Thanks. $\endgroup$
    – a4android
    Commented Aug 20, 2017 at 2:34
  • $\begingroup$ Two million years is nothing on the timescale of mountain building. It's roughly the age of some of the recent volcanic activity in the Sierra Nevada, for instance. $\endgroup$
    – jamesqf
    Commented Aug 20, 2017 at 17:57
  • $\begingroup$ @jamesqf Precisely why my scenario shutdown mountain building and allowed for accelerated erosion. $\endgroup$
    – a4android
    Commented Aug 21, 2017 at 0:54
  • $\begingroup$ @a4android: But you'd have to shut down mountain building more like 200 million years ago, not 2 million. And without significant vertical relief, how do you get accelerated erosion? On Earth, the mountains create their own accelerated erosion through orographic rainfall patterns. As the relief wears down, erosion slows... $\endgroup$
    – jamesqf
    Commented Aug 22, 2017 at 4:39


On Earth continents are piled up by plate tectonics and worn down by erosion. Rock is ground down to sand and rivers carry mud into the ocean.

An all-wetland planet would have to stop the rising of new mountains, but then all land mass will erode into the ocean trenches. There would be a brief period when only wetlands are left, but that won't last.

  • $\begingroup$ Won’t last? With no oceans, where would subsequent erosion go? If the eroded level ground is just soggy, it can’t get lower or fill in. $\endgroup$
    – JDługosz
    Commented Feb 1, 2017 at 7:22

Yes it is possible to have such a planet. As long as you do not have anything which hinders something in science, it is usually very possible.

Furthermore, there are planets known as Ocean Planets which do not have any land surface at all. To further add to the concept, Earth, in its early days, had several dozens of very small protocontinents instead of the large continents we have today. This would also have looked more or less like the world you have enquired about.


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