Hundreds of volcanoes pockmark the surface of Io, the third largest of Jupiter’s 78 known moons, and the only body in our solar system other than Earth where widespread volcanism can be observed. The source of the moon’s inner heat is radically different than Earth’s, making the moon a unique system to investigate volcanism.
Source:
https://phys.org/news/2019-08-io-volcanic-tides.html