Is there an established distinction between a geyser and a cryovolcano in the context of cold solar-system bodies such as the moons of Jupiter and Saturn, or Kuiper belt objects (e.g. Pluto)?

Both can lead to spreading of new water across the surface, and both can result in plumes of water vapor above the surface. Do they have distinctly different mechanisms?

Or is it unclear or in a state of flux, a bit like the diagram in @zephyr's answer to Do astronomers generally agree that the distinction between comets and asteroids is not so clear?

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    $\begingroup$ Isn't there a physical distinction in how a geysir works and what triggers a volcanic eruption? $\endgroup$ Jan 13 at 8:14
  • $\begingroup$ @planetmaker if when you think "volcanic eruption" and "geyser" you think of those things on Earth, ya, they're very different. However in the context of how the expressions "cryovolcano" and "geyser" are used by planetary scientists "in the context of cold solar-system bodies such as the moons of Jupiter and Saturn, or Kuiper belt objects (e.g. Pluto)" as I've asked about here, the situation may be quite different, whether we think it should be or not. $\endgroup$
    – uhoh
    Jan 13 at 9:14
  • $\begingroup$ I want to believe that the people doing planetology are sufficiently knowledgable in (geo)physics to make a reasonable distinction. As far as I remember I've not heard the use of "geysir" referred to anything else than those on Earth. I'm very much looking forward to answers, possibly from people who might actually study the volcanism on the icy moons in the outer solar system. $\endgroup$ Jan 13 at 9:22
  • $\begingroup$ @planetmaker see the numerous Astronomy SE questions (and their answers) linked in my two comments below this answer to Can a cryovolcanic eruption be as powerful as a normal volcanic eruption? It's not about being sufficiently knowledgable, it's about cross-disciplinary terminology heterogeneity. Feel free to add additional answers wherever you see fit! $\endgroup$
    – uhoh
    Jan 13 at 10:58

1 Answer 1


An educated guess: on Earth, the working fluid in a "geyser" is water, which remains a fluid more or less permanently after each eruption. This means that geyser eruptions are not associated with buildup of new geological material around the geyser (apart from the much slower process of dissolved minerals accumulating as the water evaporates).

Contrariwise, on Earth, the working fluid in a "volcano" is molten rock, which solidifies after reaching the surface. Each new eruption permanently deposits new solid material in the vicinity of the volcano.

If I were writing definitions, I would define a "cryovolcano" as a geological vent system where the working fluid is water, but where the environment is cold enough that the ejecta from eruptions accumulates in a permanent mountain of ice around the vent.

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    $\begingroup$ This sounds very plausible. It might be a good idea to try to track down some supporting information as well. An example each of the usage of "geyser" and "volcano" on another solar system body in a technical setting perhaps. $\endgroup$
    – uhoh
    Feb 6, 2019 at 0:17

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