I'm not sure this is true, but happy to be proven wrong: if there was a geothermal source, say, hundreds of miles from anywhere, the transmission losses might m

I'm not sure this is true, but happy to be proven wrong: if there was a geothermal source, say, hundreds of miles from anywhere, the transmission losses might make it uneconomic to exploit, but it would be usable for proof-of-work or a similar project. (Not arguing for or against this application, and it may be that this is too rare a phenomenon to matter; just quibbling over the fungibility.)