Inspired by A.C.A.C's comment, how can the metabolism of an animal that is harnessing the heat from magma or lava be explained?

I'm thinking of conventional "eating lava or magma", but it could be an unconventional method by absorbing the heat by skin. I'm also thinking whether this method can be used by birds or not. Oh, and don't worry, you can assume the needed parts in contact with the lava/magma are inherently made of fire and heat resistant parts. I read that magma can be as cool as 600 degree Celsius.

For reference you might want to read this question What traits would a species need to survive in magma?, but I still prefer carbon-based lifeform.

The animals won't have to "swim" and live in the magma. They just need to primarily get their energy from the magma/lava.

This question graduated from the Sandbox.

  • 2
    $\begingroup$ Just to note, on a world where ice is a mineral and volcanos erupt water, we would be seen as being made of magma. I recall a scene in Forward’s Camalot 30K where the viewpoint character meets the human visitors, how they were too hot to approach even with their suits, and the visible faces and air in the helmits glowed brightly. $\endgroup$
    – JDługosz
    Oct 14, 2017 at 2:31

4 Answers 4


Your lavabird could smelt.

Smelting is turning metal ore (usually a metal oxide) to the base metal. It must be hot and there must be carbon to carry away the oxygen from the metal oxide as CO2, leaving the base metal.

I could imagine these birds are full of iron ore or rust. They eat coal or wood or dung or some other carbon. Then they bake in the magma. The carbon leaves as the oxide and the iron is converted to the metal.

On leaving the magma the bird gradually oxidizes the metallic iron with inhaled oxygen, the way we oxidize dietary carbon. This oxidation is captured chemically for energy production. Iron oxidation is a well known energy source for bacteria and some bacteria can even get energy by oxidizing metallic iron. These lava birds could work that chemistry or perhaps have bacteria symbionts on board to do it for them.

The neat thing here is that we lose the carbon as CO2 but the bird keeps the rust inside of it. Once its supply of metallic iron is depleted it can eat some sort of carbon, go back to the magma, and regenerate the iron from the oxide. It is a way to capture the heat energy of magma in a chemical transformation that can be run backwards, slowly, to provide energy for life processes.

  • $\begingroup$ This could work though, you would need a high pressure oxygen rich environment (humans couldn't survive). You would need the pressure so the bird could actually fly and unrealistic levels of oxygen to oxidize the iron fast enough to provide meaningful energy. The bird would also need big lungs to survive the toxic atmosphere of the volcano $\endgroup$
    – anon
    Sep 25, 2017 at 21:43
  • $\begingroup$ Why do you think iron oxidation requires unrealistic levels of oxygen? Look at above links for bacteria that get energy that way. You can find these bacteria growing in springs. They look rusty. As re birds in volcanoes we are suspending disbelief for that aspect. $\endgroup$
    – Willk
    Sep 25, 2017 at 23:25
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    $\begingroup$ This looks promising. Now I'm left with how a bird can fly with a storage of pure iron in its belly. $\endgroup$
    – Vylix
    Sep 26, 2017 at 1:44
  • $\begingroup$ Neat solution, though I wouldn't want to run into a bird capable of not melting at forge temperatures... $\endgroup$
    – Joe Bloggs
    Sep 26, 2017 at 8:17

The yeti crab farms the bacteria that Ash mentions. This crab sits at hydrothermal vents (deep sea pressure prevents heat from lysing cells). The crab waves its pincers in the hot vent flow, which is over 100C. The pincers have many hairs, on which grow bacteria that Ash mentions (or similar.) The bacteria grow, and the crab eats the bacteria - basically having grown pincer-licking-good food for itself. I recall learning that this occurs at hydrothermal vents but online information does not state that explicitly. Anyway, the principle is generally sound and may be useful for your design. Here is a nice link showing the hairy pincers and waving behavior.

here is another video link.

A perhaps better video with narration.


How any lifeform works is by consuming energy, storing it, and releasing it.

plants take in sunlight convert it to sugar and break that down during respiration.

Animals eat plants convert the sugars and proteins into fat which they later burn during respiration.

How they use this energy and the efficiency to which they use it is purely based on their unique traits.

Chemically, sugars and fats are mechanically the same in the sense they are long for the most part; hydrocarbon chains, that can be easily reacted with oxygen to produce thermal energy.

This doesn't necessarily work for a magma eater as any hydrocarbon chain generally combusts long before that temperature is reached.

However, the principal still applies, absorb an external energy source, convert it into stable semi-reactive compounds which can react with a readily accessible external element (like air) to create energy.

  • $\begingroup$ Minor point: Plants don't turn sunlight directly into sugars, they use it to turn other chemicals (notably CO2 and water) into sugars that respiration then breaks down to retrieve the energy. It's a small thing, but may be important if there's no suitable similar chemical reaction this creature can exploit. Technicality, I know. :-) $\endgroup$
    – Joe Bloggs
    Sep 25, 2017 at 19:49
  • $\begingroup$ you forgot the nitrates from the soil too, I know though I didn't want to get too involved in the whole chemistry of this. A lot of people want to go deep into the science of what should be very small details to the point where it becomes "get textbooks". I'm trying to simplify as best as I can. $\endgroup$
    – anon
    Sep 25, 2017 at 19:54
  • $\begingroup$ Hah! Simplification was why I left all the extra chemicals out. Just wanted to make it clear that it's not a magical 'mass from nothing' reaction. $\endgroup$
    – Joe Bloggs
    Sep 25, 2017 at 20:15

Oops completely misread the question, non-chemical energy pathways for an animal living in close contact with a magmatic system or erupted lava. Okay first things first lava is easier, it's in contact with the carbon, water, oxygen, and nitrogen rich space we call the atmosphere, these elements are available in magma but they're harder to get at because they're dissolved or chemically bound into rock minerals. Also an external atmosphere makes thermal regulation easier too, that's going to be important. For sourcing the energy I'd start with the thermocouple, they use a "sandwich" of metal foils to create electron flow when in a thermal gradient. We use them mainly to measure temperature but they can be used on a larger scale to produce electrical currents from concentrated heat sources. In this situation thermal regulation is very important because the animals' core is going to have to be cooler than the outside environment or the thermal gradient disappears and the thermocouple stops generating energy.

In practice the animal will have a finely layered metallic skin of sorts that simultaneously generates free electrons for metabolic processes and protects them from a lot of direct heat transfer from the external environment. In normal, read carbon-based, systems free electrons are rare, we use ions that "swap" electrons instead. The actual chemical reactions for the creature I propose would be similar to those we see in carbon-based lifeforms, using the same basic structures of proteins and carbohydrates (but not the same carbohydrates and proteins because they aren't thermal stable at these temperatures) but instead of using direct ion exchanges they'd utilise a lot more direct elemental oxidation to source raw chemicals for protein synthesis and ionic reduction to source chemical elements for the thermocouple skin and other structural elements.

Effectively they're using electricity and adsorbed chemical building blocks to create energy storage structures (carbohydrates) and cellular structural members (proteins), technically they're not animals, they're really weird plants, primary producers, not consumers.

Couple of note on environment issues; if you are using the low temperature Carbonatite magma/lava systems then atmospheric material is less important to the life-systems chemistry due to the relative abundance of those elements in the magmatic material. If you use a traditional skeletal chemistry in non-Carbonatite systems Calcium is going to be a bottleneck element limiting populations as it's relatively unavailable.

Right hopefully that's clear-ish, drop me a comment if you want to know more about some element of what I've laid out.


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