There's the magnetohydrodynamic effect, which can be used for propulsion[1], guess the reverse should generate electricity? edit: Hunch correct[2]. Off course

There's the magnetohydrodynamic effect, which can be used for propulsion[1], guess the reverse should generate electricity? edit: Hunch correct[2]. Off course requires magnetic field, and while naturally magnetized rocks exist AFAIK, not sure how strong they are. [1]: https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive https://en.wikipedia.org/wiki/Magnetohydrodynamic_drive [2]: https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator