Cryovolcanoes, also known as ice volcanoes, are a type of volcano that erupts volatiles such as water, ammonia, or methane, in an extremely cold environment that is at or below their freezing point. The process of their formation is known as cryovolcanism.
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).
How do cryovolcanoes form?
Cryovolcanoes form when heat from the interior of a celestial body melts ice beneath its surface. The melted ice then rises to the surface and erupts. The heat that powers cryovolcanism can come from a variety of sources, including tidal heating, radioactive decay, and impacts from other celestial bodies.
What do cryovolcanoes erupt?
Cryovolcanoes erupt a variety of volatiles, including water, ammonia, and methane. These volatiles can form plumes that can reach into the atmosphere of the celestial body. In some cases, the volatiles can even escape into space.
A geyser, but it gives you an idea of how a cryovolcano looks like!
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.