Tuonela Planitia is an elongated plain and probable cryolava lake on Neptune's moon Triton. Located in Triton's northern hemisphere within Monad Regio, it overlies part of Triton's unusual cantaloupe terrain. As with neighboring Ruach Planitia and the other walled plains on Triton, Tuonela Planitia is among the youngest features on Triton's surface.
Voyager 2 image of Tuonela Planitia across the upper half, with Ruach Planitia below. Several "islands" occupy Tuonela Planitia's interior, with Kasu Patera at the upper right
A cryovolcano 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.
Diagram of Enceladus's south polar plumes, an example of explosive cryovolcanism, and Enceladus's internal ocean
Enceladus's south polar plumes
Edifice of Wright Mons, a likely cryovolcano on Pluto. Coleman Mons can be seen just southwest of Wright Mons
Ruach Planitia and Tuonela Planitia, Triton
