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I want a continent of waterfalls: a place on the scale of South America where the land is broken terraces from mountain heights to sea level. And I want massive waterfalls to be ubiquitous, like entire seas spilling over the edge of plateaus.

For ease of discussion, let’s say the high plateaus are at north of the continent with sea level at south.

I’ve worked out to my satisfaction the plate tectonics to get the land mass. My problem is the water cycle. Evaporation and rain is not capable of moving as much water as I want to cycle. I have concluded that I need a water pump.

My idea is massive under-ocean caves at the north end of the continent. The caves allow ocean water to flow over geothermal heat source, which produces massive geysers up to the mountain heights.

My hope is that this geyser system could pump large seas worth of water up for hundreds of thousands of years.

Is this set up viable? If so, is it feasible albeit improbable to form naturally? How long could this setup last?

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    $\begingroup$ Both geysers and waterfalls are short-lived on geological timescales. Geysers may not last for a thousand years, as the water deposits minerals in the spout, so they either block up or explode. The Zanclean flood where the Mediterranean seal filled would have looked like your scene, but that probably lasted a decade. $\endgroup$ Jan 29, 2023 at 10:01
  • $\begingroup$ @RichardKirk That's been my suspicion, I'm just hoping for an out of some sort. But if you write your comment out as an answer, I can upvote it and maybe mark it as an answer. $\endgroup$
    – SRM
    Jan 29, 2023 at 14:37
  • $\begingroup$ Water via rain is essentially salt free. Meanwhile water then its pumped via geothermal from the ocean would have lots of salt. this will cause issues with most plant growth. $\endgroup$ Jan 30, 2023 at 19:24
  • $\begingroup$ @GaultDrakkor I was ok with that side effect. I was prepared for some very different plant and animal biology if that was what it took to make the landscape work. Alas, consensus in answers is "nope." $\endgroup$
    – SRM
    Jan 30, 2023 at 23:03

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Unfortunately, this setup is not viable or feasible. It would not be possible for massive under-ocean caves to pump large seas worth of water to mountain heights through geysers for a sustained period of time. Additionally, the amount of energy required to pump such a large amount of water would likely far exceed the energy available from geothermal sources.

In terms of a natural occurrence, it is extremely unlikely for a water pump of this magnitude to form naturally. The forces required to create such a system are beyond what is typically seen in nature, and even if such a system were to form, it would likely not last for hundreds of thousands of years as it would be subject to various geological and climatic changes.

It is important to note that the water cycle in nature is a delicate balance and is dependent on many factors, including precipitation, evaporation, and transpiration. It is not possible to artificially pump large amounts of water in a sustainable manner, as it would likely disrupt the natural water cycle and have significant impacts on the surrounding environment.

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Short answer: Just use rainfall

A cave/cavern system is not feasible, as @tech show already pointed out.

However, I am surprised that you ruled out evaporation and rainfall. The discharge of the Amazon river is more than ten times higher than the discharge of the Mississippi river. This is entirely created by rainfall. If you would lift up the entire basin, you would get waterfalls up to the horizon (horizontally, not vertically) close to the coast. A few tens of meters should be enough to create impressive waterfalls and avoid altering the climate of the basin. If you are messing with the geology a bit, the amount of water would be even higher. However, I would keep it at a east-west orientation so the whole basin can be in the tropical climate zone. The natural formation of such a system might not be extremely likely, but certainly not impossible.

Edit: Take a look at the Iguazú falls, that visualizes the concept. At this point, the Iguazú river carries ~1% of the water that is carried by the Amazon river at its estuary.

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  • $\begingroup$ I've been through the math on evap/rain. Every way I looked at it, getting up to "seas worth of water" wasn't feasible that way without enough heat from the local star to push the planet out of the habitable zone. Thus my search for alternates. $\endgroup$
    – SRM
    Jan 30, 2023 at 23:00
  • $\begingroup$ @SRM How much water do you need? The Amazon river carries on average 200,000 m3/s and has a width up to 190 km. Standing at the shore, an observer would see no difference to the sea. I would estimate that the amount of water can easily be doubled when playing around with the geology a bit. $\endgroup$
    – Matthias
    Jan 31, 2023 at 6:47
  • $\begingroup$ Width of Amazon: 190 km. I'm looking for falls on the order of 5000 km. Literally terraced continents if I can pull it off. $\endgroup$
    – SRM
    Jan 31, 2023 at 13:23
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No, it is not feasible to pump geothermal water at the scale of multiple Mississippi rivers.

The flow rate of a river is determined by many factors, including the amount of precipitation, the slope of the land, and the size of the watershed.

Geothermal water, on the other hand, is heated by the Earth's interior and its flow rate is limited by the heat exchange at the surface and the permeability of the rock formations. Pumping geothermal water at the scale of a river would require a significantly larger heat source and more permeable rock formations than currently exist, making it unfeasible with current technology.

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Both geysers and waterfalls are short-lived on geological timescales. Geysers may not last for a thousand years, as the water deposits minerals in the spout, so they either block up or explode. Large waterfalls erode. The Zanclean flood where the Mediterranean sea filled would have looked like your scene, but that probably lasted a decade.

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