Cryovolcano is the vast volcano.

A cryovolcano is a type of volcano that erupts volatiles such as water, ammonia or methane instead if molten rock and ash into an extremely cold environment that is at or below their freezing point. The process of formation is known as cryovolcanism. Earth simply is too warm for this type of formation to occur, even in the deepest reaches of Antarctica or Greenland, it wouldn't be possible. So, there are no cryovolcanoes on earth. Pluto, perched nearer the edge of the solar system, is home to a wholly different type of tectonic activity. In order for ice volcanoes to exist on Pluto, heat from the dwarf planet's interior would need to melt ices and push them to the surface, suggesting that Pluto has been geologically alive. Looking at an area southwest of Sputnik Planitia, researchers found a series of dome-like structures that could be explained by volcanic activity spewing material onto Pluto's surface. The unique nature of Pluto's cryovolcanoes likely results from a special combination of its thin atmosphere, extremely cold temperatures, low gravity, and unique composition. It remains uncertain how Pluto might still possess enough heat for cryovolcanoes to recently erupt on its surface.