My world has giant geysers. The height of these geysers oscillates over a cycle of 3 or so days.

Things you need to know:
1. There is an unknown force in the core of the planet, which exerts pressure outwards that oscillates in cycles.
2. There is a layer of water beneath the crust.

All around the world, these geyser are synchronized, going off at the same time regardless of latitude, longitude, or orientation. This is caused by the fluctuating waves of pressure exerted upon the outer layers from the planet's core, forcing the water up and onto the surface. When the pressure eventually dwindles, the water then drains back down in a process known as flushing, after which they begin to increase in height again, restarting the cycle. At their maximum, they reach a height of 2551.7 ft (777.7 m).

This is not an Earth-like planet.

What I want to know:
1. Is anything in my model even possible? Please point out any flaws in it.
2. If nothing I said makes any sense at all, how can I plausibly explain giant geysers that fluctuate the way I've described. (I might have to scrap the idea that they are synchronized) This is the worldbuilding site, so any new ideas are greatly appreciated.
3. I'm willing to scrap the idea of fluctuating pressure from the core and even scrap the layer of water.

I just want to be able to explain the geysers and they must be periodic and consistent. Any other data I have provided can be scrapped, if necessary.

Telling me that it can't be a planet is not a solution to my issue.

I'm aware that the layer of water beneath the crust rules out any possible volcanic activity, which kind of messes up a lot of things about my world that I'm still trying to figure out. Any possible loopholes for this would be greatly appreciated. (maybe like giant vertical tunnels of rock that push lava through the water onto the surface)

  • 2
    $\begingroup$ Hi overlord, are these geysers synchronized across the planet as a whole? As in, they all go off at the exact same time no matter their longitude, latitude, or orientation? Tides would be an excellent option if they go off one "time zone" at a time. $\endgroup$
    – Dubukay
    Sep 19, 2019 at 18:30
  • $\begingroup$ @Dubukay Yes, they are synchronized across the planet as a whole, exactly as you have described. $\endgroup$
    – overlord
    Sep 19, 2019 at 18:38
  • 2
    $\begingroup$ @overlord If you want the planet's crust to be composed of rock, you cannot have a 'layer of water' beneath it. Rock is more dense than water. $\endgroup$ Sep 19, 2019 at 20:30
  • $\begingroup$ Tides can't possibly synchronize across the entire planet. The tides are highest on the sides directly-towards and directly-away from the tide-producing object (larger planet, star, etc.) and lowest 90 degrees away from those. You get two tides per day. Not possible for tides to do this. $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:38
  • $\begingroup$ @overlord Do me a quick estimate of the energy involved in one of these events. Then tell me where that energy could reasonably come from with a science-based tag. Just the moving of water you have specified is 7.6 million Joules per cubic meter, quite apart from any heating there may be. $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:42

6 Answers 6


Initial issues:

  1. To reach 777.7 m, assuming no air resistance, and a similar gravity to that of the earth, the water will need to move at a speed of 123.4 m/s this is just over 1/3 the speed of sound (275 mph). This is really fast, and would cause a lot of destruction (depending on the size of the geyser). If we factor in atmospheric resistance, you'll probably be close to the speed of sound, which is probably going to be limiting as the amount of energy needed to break the sound barrier is exponentially more.
  2. Water moving that fast would take rocks and things with it, this is called erosion and there would be substantial erosion of the hole that the water comes up through.
  3. If the hole becomes larger due to erosion, then the speed of the water going through it would be decreased. Speed=Flow/Area(cross section). Then your geyser isn't so high anymore.
  • $\begingroup$ I didn't know that. Interesting. $\endgroup$
    – overlord
    Sep 19, 2019 at 23:02
  • 1
    $\begingroup$ I find it odd that you've highlighted the sound barrier when that number is very dependent on earth like conditions. Otherwise, good answer. $\endgroup$
    – user458
    Sep 20, 2019 at 2:02
  • 2
    $\begingroup$ @fredsbend The reason why I mention the sound barrier is because it's a reasonable measure of at what speed atmospheric resistance starts to have a significant influence. While you're right that the speed of sound might be different on this planet than it is on earth, it's unlikely that it will be so vastly different as to change the result that approaching the speed of sound in that atmosphere is going to cause significant air resistance, as the speed of sound is going to be something of an artificial speed limit. $\endgroup$
    – Mathaddict
    Sep 20, 2019 at 15:22
  • $\begingroup$ As a point of comparison, Steamboat Geyser hits about 120 meters, and leaves a coating of mud on everything nearby when it erupts. Waimangu Geyser hit about half the desired height, and the eruptions were more akin to steam explosions than to what you see at Old Faithful. $\endgroup$
    – Mark
    Nov 7, 2019 at 23:22

Natural nuclear reactors.

It would have to be relatively early in the solar system's history, compared to Earth, because you'll need Uranium with a higher concentration of U235 to U238 compared to what Earth currently has... though it did have this concentration 1.7 billion years ago.

Your object will have to be very small for this to be a reasonable explanation; at most, a very large comet, several thousands of kilometers across, in order for these geyser outgassing events to be synchronized. The object would be best classified as a rubble pile, rather than a solid object, because it would need to be porous throughout.

How it works is, U235 decays fairly regularly and somewhat frequently, releasing a stray neutron. However, this is a Fast neutron, which is unlikely to be picked up by the nucleus of other Uranium in the area. Without the neutron being absorbed by another Uranium nucleus, there is no chain reaction.

However, water makes for a wonderful neutron moderator... It takes Fast neutrons and slows them down to Thermal neutrons. Thermal neutrons do get picked up by Uranium nuclei, which quickly split into radioactive iodine and release a few more Fast neutrons; as well as releasing quite a bit of heat.

The more water, the hotter the reactor gets, until the water turns to steam and sprays out as geysers onto the object's surface. Without water to moderate the reaction, the chain reaction stops, and the natural reactor cools, letting water condense once again.

  • $\begingroup$ Your best solution is that the planet is not a planet? $\endgroup$
    – overlord
    Sep 19, 2019 at 19:11
  • 3
    $\begingroup$ @overlord: For a natural explanation of a sub-surface event that happens across the entire object? Yes. $\endgroup$
    – Ghedipunk
    Sep 19, 2019 at 19:28
  • $\begingroup$ @overlord: The asteroid Vesta is the smallest thing that could have once been considered a planet. It has a solid core, which means there is no way for a single reservoir of water to heat/expand periodically that would reach both sides of the planetoid at the same time, even give-or-take several hours. Even an all-encompassing subsurface water ocean, like Europa, will not have geyser events at the same time on opposite sides of the object. The object needs to be porous to the core, which means it can't be a planet. $\endgroup$
    – Ghedipunk
    Sep 19, 2019 at 20:24
  • $\begingroup$ Except that natural reactors won't produce geysers, seeing as they formed in sandstone. If a reactor could produce a geyser it could not be stable enough to produce this. And won't sync up over the whole planet. And the Gabon reactors had a period round-about 7 to 10 hours of 1/2 hour on and the rest off. Even the different deposits at the same site had different periods due to different size and thickness and purity. $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:49
  • $\begingroup$ True, @puppetsock; the uranium deposits would not have formed "in place," and the formation would be more than just a little remarkable. Without active geology and hydrology (neither will happen on a rubble pile), the uranium won't form veins, so an object with such a natural reactor would have to have been ejected from a planet or protoplanet, which means a solid core, which means no single global water reservoir. With the reduced gravity, it would take water longer to seep back into the reactor, so the 3 to 7 hour periodicity of the Gabon reactors would be ramped up. $\endgroup$
    – Ghedipunk
    Sep 20, 2019 at 15:38

It is not a planet...

It is the egg of a swarm of gigantic water breathing life forms!

The egg is filled with water which was originally extremely oxygen rich. The atmosphere above the surface of the egg is even more oxygen rich.

As the fetuses mature, they consume the available oxygen from the water within the shell. Then, when those enclosed oxygen levels get dangerously low, the fetuses follow their instincts, pecking blow holes in the shell. Once the holes are ready, each fetus attaches itself to a hole and starts their second phase of development.

During this second phase, each creature puffs up like a blow fish, full of interior egg water, then it spits up out through the hole. The water thus freed from the egg's interior, absorbs oxygen from the atmosphere, then plummets back down into the hole where the creature is waiting to breath it.

This second phase of development last for thousands of years, with the creatures slowly growing and their associated geysers slowly growing in height as well.

When the geysers reach orbital heights and the water escapes, no longer plummeting back down for the creatures to use, the second phase of the creatures' development ends and hatching time has arrived. What the final adult creature looks like or how it functions in the post-hatching vacuum is a mystery. No intelligent civilization has ever lasted long enough to chronicle the entire gestation.

As for why these gigantic creatures synchronize their breathing... it's a family thing. After living together inside that egg for more than a million years, they've gotten very good at syncopation!

  • $\begingroup$ Quite brilliant! My original idea was actually that the synchronized pressure was caused by a giant creature living in the core. $\endgroup$
    – overlord
    Sep 20, 2019 at 13:32
  • $\begingroup$ Science based tag. Now do an estimate of the energy involved and tell me where that comes from. $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:35
  • $\begingroup$ Also, how do they sync up over the whole planet? And why do they sync up over the whole planet? $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:54
  • $\begingroup$ "Reaches orbital heights." Cough. That's something like 20 km/s minimum, not counting the fact that this is being squirted straight up and so will be very inefficient getting to orbit. That's 200 million Joules per kg. Recall what things look like when they go the other way. The critter will vaporize itself before it ever reaches anything like "orbital height." $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:58
  • $\begingroup$ Yep. I knew I was in trouble when, after writing this, I noticed the science-based tag. As for the missing energy, maybe a natural thorium breeder reactor at the core is induced to higher output by the pressure of the return of the synchronized falling water. The little beasts might be able to feed off of its' radiation directly, or just off of its' heat like any thermophile. The need for higher reactor output answers why they synchronize & as for how they handle planetwide synchronization, they don't. They just sync with their closest cousins which synch with their closest cousins, etc. $\endgroup$ Sep 20, 2019 at 23:07

Magnetic moon in an eccentric orbit.

  1. Your planet has a moon. It is magnetic.

  2. The moon has an eccentric orbit. It gets very close to its planet during the close part, skimming the atmosphere. It orbits its planet every 3 days.

  3. When the moon gets close, its magnetic field induces current in metallic regions of your planet.

  4. Metallic inclusions in the crust, close to the surface get hotter than those in the core, because those shallow regions are closer to the passing magnet moon. Your planet has several areas with metallic inclusions in the crust and surface, due to recent metallic meteor impacts.

  5. When these places get hot, the water in these places gets hot. Hot water can hold less dissolved gas. The gas comes out of solution as bubbles. If it gets hot enough there might be steam.

  6. A blast of gas which carries condensing steam and water droplets forms your geyser.

  7. The magnet moon has not been doing this for a long time. Each time it comes past it is slowed as its energy is transferred to the planet. Eventually it will hit the planet. It will become another one of the metallic inclusions in the crust.


The planet has an eccentric orbit around a gigantic microwave emitter

Many high-energy cosmic objects - the most notable being neutron stars and black holes - emit high levels of microwave radiation. Your planet orbits one of these (alternatively, a binary star where one of the pair is a neutron star or black hole) and has a highly eccentric (elliptical) orbit, drawing very close to the microwave source once a year.

When the planet draws close, the microwaves boil the water below the surface, causing high pressure and forcing the water out through geysers.

Of course, this planet will be very inhospitable to Earth life during this part of the year, as it will boil the water in their bodies, causing them to explode. Native life may be able to survive by going through a period of hibernation, drying out like a tardigrade and waking up again during the heavy rainfall that follows.


Oh that is easy if you are not looking for a planet. Possible with a planet too. Like Europa or Enceladus have an underground ocean with an ice crust. Then have another moon and the planet itself affect this moon with tidal forces. These tidal forces will most of the time cancel each other to have a diminished effect, however, when they are in sync to squeeze your moon, it will cause high tide for the underground ocean, which will break the ice and poor out of the resulting geyser.

If it has to be a planet, have it either a binary system or two large, probably captured, moons.

  • $\begingroup$ Tides don't sync like that. You get 2 high tides per rotation, and 2 low tides, distributed 90 degrees apart around the planet. $\endgroup$
    – puppetsock
    Sep 20, 2019 at 14:51
  • $\begingroup$ That is per acting body, so if you have two equalish pulls, you will have 4 high tides and 4 low tides that do not sync. But every now and then they will be in position so that high tides and low tides of different bodies will collide, causing larger tides. $\endgroup$ Sep 21, 2019 at 17:36

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