Io 
Dust plume on Ioand
http://www.space.com/scienceastronomy/solarsystem/io_volcanoes_000504.html
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Io
Dust plume on Io |
Io is one of Jupiter's largest moons.
It is also the most volcanically active body in the solar system.
Because Io's orbit passes so close to Jupiter, the tremendous
tidal forces cause internal heating and tectonic movement that cause such
violent volcanic activity and to sustain it for a much longer time than Earth's
moon, who's volcanic activity has ceased. Io has a very thin atmosphere,
so the volcanic ash from the eruptions shoots high over Io, to heights of
up to 280 km. The plumes stay in near perfect arcs due to the lack
of wind, then fall back to the surface. The ash collects around the
vents in a circular pattern. Io's surface is covered almost entirely
of vast planes of pyroclastic debris, and lava flow planes from hundreds
of millions of years of volcanic activity. |
| Images taken from http://www.astronomy.com/content/static/AstroForKids/jupiter.asp and http://www.space.com/scienceastronomy/solarsystem/io_volcanoes_000504.html |