Jupiter's moon named IO is almost same size as Earth's moon. It has rivers of molted rock and lakes of hot liquid sulfur. There are 1000 of mantle plumes in IO. Some erupting lava on IO is 500 degree celsius hotter than lava on Earth. IO can provide valuable data of earlier state of volcanoes in Earth. Temperatures can rise up to 1600 degree celsius. As the gravity of IO is very low compared to Earth the gases and rocks from volcanic explosion can rise up to 100 of miles into the sky. They can be seen from Earth with Hubble telescope. There are 300 erupting volcano at IO in any given moment.
The massive volcanic activity seen in IO is becuse of it's close distance from Jupiter. As it is very close to the Jupiter, it experiences tidal forces. It is the same tidal force we observe on ocean water because of the Moon. But instead of waves of water, IO experiences waves of lands because of huge tidal force generated by Jupitar. Tidal force of IO is so big because of the enormous mass of giant Jupiter, that the land bulges up 300ft and then goes back again. These tides create friction that heats the interior of IO and melts it. So the exterior of IO remain solid and interior becomes liquid and the result is numerous volcanoes. IO's largest volcano is 120 mile long and 4 times larger than Yellowstone super volcano in Earth.