Wikipedia:Today's featured article/November 10, 2008

Volcanism on Io,a moon ofJupiter,produceslavaflows,volcanicpits, and plumes ofsulfurandsulfur dioxidehundreds of kilometres high. This volcanic activity was discovered in 1979 byVoyager 1imaging scientists.Observations ofIoby passing spacecraft and Earth-based astronomers have revealed more than 150 active volcanoes. Io's volcanism makes the satellite one of only four known volcanically active worlds in the solar system. First predicted shortly before theVoyager 1flyby, the heat source for Io's volcanism comes fromtidal heatingproduced by Io's forcedorbital eccentricity.Io's volcanism has led to the formation of hundreds of volcanic centres and extensive lava formations, making the moon the most volcanically active body in the solar system. Three different types of volcanic eruptions have been identified, differing in duration, intensity,lava effusionrate, and whether the eruption occurs within a volcanic pit. Lava flows on Io, tens or hundreds of kilometres long, have primarilybasalticcomposition, similar to lavas seen on Earth atshield volcanoessuch asKīlaueainHawaii.As a result of the presence of significant quantities of sulfurous materials in Io's crust and on its surface, during some eruptions, sulfur, sulfur dioxide gas, andpyroclastic materialare blown up to 500 kilometres (310 mi) into space, producing large, umbrella-shaped volcanic plumes. (more...)

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