What is the primary mechanism causing the intense internal heating on Jupiter's moon Io?

Answer

Tidal flexing from gravitational interactions

Io's geological intensity is driven by tidal flexing, the continuous squeezing and stretching caused by its resonance orbit with Europa and Ganymede, converting orbital energy directly into heat.

What is the primary mechanism causing the intense internal heating on Jupiter's moon Io?
GeologyPlanetary SciencemoonsVolcanismIo