Cryovolcano

A cryovolcano (sometimes informally referred to as an ice volcano) is a type of volcano that erupts gases and volatile material such as liquid water, ammonia, and hydrocarbons. The erupted material is collectively referred to as cryolava; it originates from a reservoir of subsurface cryomagma. Cryovolcanic eruptions can take many forms, such as fissure and curtain eruptions, effusive cryolava flows, and large-scale resurfacing, and can vary greatly in output volumes. Immediately after an eruption, cryolava quickly freezes, constructing geological features and altering the surface. Although rare in the inner Solar System, past and recent cryovolcanism is common on planetary objects in the outer Solar System, especially on the icy moons of the giant planets and potentially amongst the dwarf planets as well. As such, cryovolcanism is important to the geological histories of these worlds, constructing landforms or even resurfacing entire regions. Despite this, only a few eruptions have ever been observed in the Solar System. The sporadic nature of direct observations means that the true number of extant cryovolcanoes is contentious. Like volcanism on the terrestrial planets, cryovolcanism is driven by escaping internal heat from within a celestial object, often supplied by extensive tidal heating in the case of the moons of the giant planets. However, isolated dwarf planets are capable of retaining enough internal heat from formation and radioactive decay to drive cryovolcanism on their own, an observation which has been supported by both in situ observations by spacecraft and distant observations by telescopes.