Implementing Underwater Civilizations

In order to work metals, you have to heat them up past a specific
temperature, which is usually quite high. You needn’t melt them
completely, but melting point is a good guide to the temperature needed
to work with them. Of course some metals don’t even need to be
considered for melting points, since they are never found free in
nature, and they would have to be found free in nature for the aquatic
species to work with them. These metals are the alkali and alkali earth
metals, plus aluminum, manganese and zinc. For these, especially the
alkalis, which explode on contact with water, use -and discovery-
underwater is almost impossible to imagine. Iron, Nickel, Tin, and Lead
are all very easy to work with, but underwater are likely to oxidize
quickly, or in the case of lead, pose a danger to the organism. On top
of that they’re only very rarely found free in nature, so we can
essentially count them out.

Metals commonly found in nature include Copper, a great candidate for
metalworking, Bismuth, Mercury, and Silver. Bismuth isn’t great to
work with because it’s quite soft, Mercury isn’t solid at the same
temperatures that water is liquid, plus it’s highly toxic, so it’s a
noncandidate. Platinum and gold are usually found free as well, but are
too soft to do a whole lot with. So our best candidate for metalworking
underwater would be copper or silver. Let’s see what temperatures we
would need to melt copper.

The melting point of copper is 1084.62°C, which, you might realize, is fairly hot.

One of the most common proposals on the forums is that metalworking
be carried out at undersea hot vents, volcanoes, black smokers, or
continental rifts. Assuming that these lie close enough to the surface
not to crush the organism under the pressure of water above, they seem
to everyone like a good candidate for a neptunian forge. I don’t use the
term everyone lightly: at Thrive we’ve had this suggested probably a
dozen or more times by many different members and fans, all of whom make
the mistake of thinking that we have no idea what we’re doing.

Unfortunately, we like science at Thrive, so we’ve done our homework
on the subject- here are a few suggested “forges” and their respective
temperatures- bearing in mind that copper’s melting point is 1084.62°C.

Black Smoker- Up to 464°C

Magma- Up to 1300°C

Komatiite Magma (Hottest type known)- up to around 1600°C

Aha, so there is magma hot enough to melt copper. Which is great if
that’s all you’re looking for. But I like to kill things dead.
Considering that this is going to take place underwater, the environment
immediately around the Komatiite Magma is going to be extremely hot as
well, since water is a great heat conductor and has a very high specific
heat, hot enough to severely injure or kill any large animal around it.
At temperatures of even 100°C, almost every organism
known, save some bacteria, is going to die. So even at lower
temperatures, it’s extremely dangerous to approach something so hot in
water, and that copper isn’t going to be easy to work with.