Io

Io is the first large moon of Jupiter and is the most geologically active body in the solar system. Its close proximity to Jupiter and tidal forces from the giant and its three other giant moons push and pull the moon apart internally. This causes Io to turn itself inside out and fuels its many active volcanos. Due to this constant volcanic activity the surface of Io is quite young, continually being reshaped with not a crater to be found.