Conventional wisdom at the time was that moons are small, inert bodies, so the discovery of lava lakes and sulfur jets on Io came as a shock. (discovermagazine.com)
On the mountain's summit the source of the light thrashes and boils: the largest and most active lava lake in the world. (sciencenews.org)
In 2010 the hot spots were dominated by two volcanic centers: Loki Patera, an extremely large active lava lake on Io, and Kanehekili Fluctus, an area of continuing pahoehoe lava flows. (keckobservatory.org)