In a question I saw on here a while back, somebody said that the development of a sapient, technologically progressing species requires fire, and thus such a phenomenon could not occur under water.

However, geothermal vents can become quite hot, and so could it be possible for an underwater species to use that for purposes that would normally require a fire, such as cooking meat and melting metal and such?

If such conditions are not possible on earth, could a situation allow this on other planets? And what would be the effects of the required changes?

Thank you!


They key thing determining what you can do with a geothermal vent is how hot it gets. The hottest subsea vents on Earth measure around 410 °C at the surface; you might be able to get a bit hotter though clever plumbing or isolating the water supply.

Now, what can you do with 400-500° water?

  • Cooking. Virtually all cooking takes place at lower temperatures, so there's no problem here. (In fact, Fishing Cone Geyser in Yellowstone was used for cooking fresh-caught fish).
  • Casting metal. Out of the classic metals, tin, zinc, and lead all have melting points below 500°C. The actual process would be a bit tricky, as you need to isolate the metal and the mold from water to prevent overly-quick cooling; if you're using a shallow vent, you also need to worry about steam explosions.

What you can't do:

  • Smelt the metal in the first place. Tin, zinc, and lead all are smelted by heating the appropriate oxide to temperatures in excess of 1000°C in the presence of a reducing agent.

Just to widen the scope a bit, in regards to "the development of a sapient, technologically progressing species requires fire, and thus such a phenomenon could not occur under water.", that statement shows a distinct lack of imagination and critical thought. perhaps not a "technologically progressing species" in the same way WE progress, but just a moments thought can give many alternatives. for example, where we progressed thru fire and metallurgy, the hypothetical aquatics may progress thru biological manipulation and electricity. for example, suppose some genius noticed that the shocks give off by an electric eel analogue are transmitted thru a certain species of seaweed analogue, and had the idea of trapping a electric eel and constructing a barrier of said conductive seaweed, where he could connect the eel to the barrier and induce it to give off a shock to ward away a predator. is this not considered "technologically progressing" ? it could lead to genetic manipulation via breeding both eels and seaweed, and looking for other such things like finding and improving a biological source of stronger materials, perhaps based on calcium, silicon, etc to make weapons and devices from. Our own science is just beginning to explore making materials from, for example, inducing bacteria and other "living" organisms to grow them how we want them.


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