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A cryovolcano (colloquially known as an ice volcano) is a volcano that erupts volatiles such as water, ammonia or methane, instead of molten rock. Collectively referred to as cryomagma or ice-volcanic melt, these substances are usually liquids and form plumes, but can also be in vapour form. After eruption, cryomagma condenses to a solid form when exposed to the very low surrounding temperature. Cryovolcanoes form on icy moons, and possibly on other low-temperature astronomical objects (e.g., Kuiper belt objects).
The energy required to melt ices and produce cryovolcanoes usually comes from tidal friction. It has also been suggested that translucent deposits of frozen materials could create a sub-surface greenhouse effect that would accumulate the required heat.
Signs of past warming of the Kuiper belt object Quaoar have led scientists to speculate that it exhibited cryovolcanism in the past. Radioactive decay could provide the energy necessary for such activity, as cryovolcanoes can emit water mixed with ammonia, which would melt at 180 K (−95 °C) and create an extremely cold liquid that would flow out of the volcano.
Indirect evidence of cryovolcanic activity was later observed on several other icy moons of our Solar System, including Europa, Titan, Ganymede, and Miranda. Cassini has observed several features thought to be cryovolcanoes on Titan, notably Sotra Patera, a feature regarded as "the very best evidence, by far, for volcanic topography anywhere documented on an icy satellite". Cryovolcanism is one process hypothesized to be a significant source of the methane found in Titan's atmosphere.
In 2007, observations by the Gemini Observatory showing patches of ammonia hydrates and water crystals on the surface of Pluto's moon Charon suggested the presence of active cryovolcanoes/cryo-geysers.
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- Jewitt, D.C.; J. Luu (2004). "Crystalline water ice on the Kuiper belt object (50000) Quaoar". Nature 432 (7018): 731–3. Bibcode:2004Natur.432..731J. doi:10.1038/nature03111. PMID 15592406.. Reprint on Jewitt's site (pdf)
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- Triton - Triton at the eight Planets
- South Pole of Triton - Triton at SolarViews.com
- Enceladus' South Polar Stripes Spew "Warm" Water - News article at the Planetary Society
- Cryovolcanism on Charon and other Kuiper Belt Objects
- Ice Volcanoes of Lake Superior's South Shore
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- Herzog, Karen (February 6, 2011). "Ice volcanoes attract curious explorers to Lake Michigan shore: Experts warn to explore formations with caution". Journal Sentinel. Retrieved February 8, 2011.