Although most eruptions on Io take the form of explosive plumes or effusive lava flows, there are other phenomena too. A rare close fly-by by Galileo in November 1999 detected a fire fountain eruption occurring along a 20 km length of volcanic fissure on a caldera floor.

Text adapted from 'Teach Yourself Volcanoes' (2001, Hodder & Stoughton) and 'Teach Yourself Planets' (2000, Hodder & Stoughton), both by David A. Rothery of the Open University Department of Earth Sciences. All images courtesy of NASA.