LYCOS RETRIEVER 
Io: Lavas
built 659 days ago
The structure of Io's volcanoes are ... puzzling scientists, as the planet seems to break many of the rules by which volcanism is understood. Most interesting are the appearance of volcanic calderas on Io's mountain tops. Calderas are the pit-like scars of shallow lava eruptions. Unlike most volcanoes which build mountains, a caldera forms when a wide area of land collapses after being undercut by a wide pool of magma.
Source:
Understanding the balance between sulfur and silicate (basaltic) volcanism is important for scientists who are trying to understand how Io's interior is heated. Sulfur has a lower melting point so it doesn't need as much energy to make lava. The basaltic flows require much more internal heat.
Source:
The tidal heating produced by Io's forced orbital eccentricity has led the moon to become one of the most volcanically active worlds in the solar system, with hundreds of volcanic centers and extensive lava flows. During a major eruption, lava flows tens or even hundreds of kilometers long can be produced, consisting mostly of basalt silicate lavas with either mafic or ultramafic (magnesium-rich) compositions. As a by-product of this activity, sulfur, sulfur dioxide gas and silicate pyroclastic material (like ash) are blown up to 500 km (310 mi) into space, producing large, umbrella-shaped plumes, painting the surrounding terrain in red, black, and white, and providing material for Io's patchy atmosphere and Jupiter's extensive magnetosphere.
Source:
"One of the most interesting questions about Io is: do all Io's volcanoes erupt such hot lavas, or are most volcanoes similar to basaltic volcanoes on Earth?" asked Rosaly Lopes-Gautier, of JPL.
Source:
MORE ABOUT
Lavas