The left and center were taken four months apart. None of the ionian volcanoes appear to be high stratocones such as are displayed as the majestic volcanic peaks observed in the Ring of Fire on Earth. Where some relief is evident, the Ionian volcanoes are more like terrestrial shield volcanoes, many with wide calderas. These compounds can account for Io's orange, yellow, and black colors that are typical of this element. Sulphur-rich lakes have been observed.
Sulphur dioxide makes up a tenuous atmosphere.
The tidal energies acting on Io induce heating, and the stretching causes it to wobble. Io has the highest degree of volcanic activity of any planetary body in the solar system. However, the Earth of about 800,000 years of age probably didn't have a sulphur-rich crust. Io also seems to have an ionosphere. A flux tube between Io and Jupiter allows a current of 10 million amps.