<P> Ionian lava lakes are depressions partially filled with molten lava covered by a thin solidified crust . These lava lakes are directly connected to a magma reservoir lying below . Observations of thermal emission at several Ionian lava lakes reveal glowing molten rock along the patera margin, caused by the lake's crust breaking up along the edge of the patera . Over time, because the solidified lava is denser than the still - molten magma below, this crust can founder, triggering an increase in thermal emission at the volcano . For some lava lakes, like the one at Pele, this occurs continuously, making Pele one of the brightest emitters of heat in the near - infrared spectrum on Io . At other sites, such as at Loki Patera, this can occur episodically . During an overturning episode at these more quiescent lava lakes, a wave of foundering crust spreads out across the patera at the rate of about 1 kilometre (0.6 mi) per day, with new crust forming behind it until the entire lake has been resurfaced . Another eruption would only begin once the new crust has cooled and thickened enough for it to no longer be buoyant over the molten lava . During an overturning episode, Loki can emit up to ten times more heat than when its crust is stable . </P> <P> Flow - dominated eruptions are long - lived events that build up extensive, compound lava flows . The extent of these flows makes them a major terrain type on Io . In this style of eruption, magma emerges onto the surface from vents on the floor of paterae, vents surrounding paterae, or from fissures on the plains, producing inflated, compound lava flows similar to those seen at Kīlauea in Hawaii . Images from the Galileo spacecraft revealed that many of Io's major flows, like those at Prometheus and Amirani, are produced by the build - up of small breakouts of lava on top of older flows . Flow - dominated eruptions differ from explosion - dominated eruptions by their longevity and their lower energy output per unit of time . Lava erupts at a generally steady rate, and flow - dominated eruptions can last for years or decades . </P> <P> Active flow fields more than 300 kilometres (190 mi) long have been observed on Io at Amirani and Masubi . A relatively inactive flow field named Lei - Kung Fluctus covers more than 125,000 square kilometres (48,000 sq mi), an area slightly larger than Nicaragua . The thickness of flow fields was not determined by Galileo, but the individual breakouts on their surface are likely to be 1 m (3 ft) thick . In many cases, active lava breakouts flow out onto the surface at locations tens to hundreds of kilometres from the source vent, with low amounts of thermal emission observed between it and the breakout . This suggests that lava flows through lava tubes from the source vent to the breakout . </P> <P> Although these eruptions generally have a steady eruption rate, larger outbreaks of lava have been observed at many flow - dominated eruption sites . For example, the leading edge of the Prometheus flow field moved 75 to 95 kilometres (47 to 59 mi) between observations by Voyager in 1979 and Galileo in 1996 . Although generally dwarfed by explosion - dominated eruptions, the average flow rate at these compound flow fields is much greater than what is observed at similar contemporary lava flows on Earth . Average surface coverage rates of 35--60 square metres (380--650 sq ft) per second were observed at Prometheus and Amirani during the Galileo mission, compared to 0.6 square metres (6.5 sq ft) per second at Kīlauea . </P>

Are the volcanoes of io efficient replacers of the surface of this moon