CRYOVOLCANISM ON TRITON

Unlike the hot molten lava that we are familiar with here on Earth, the volcanoes of Triton give forth to eruptions of extremely frigid gas and ice spewing from Triton's frozen core. A cryovolcano is an icy volcano that emit plumes of very cold methane, ammonia and/or water. This volcanic activity is a result of melted ices that are caused by tidal friction or another source of heat. Triton's volcanic activity were the first cryovolcanoes discovered in our solar system when the Voyager 2 flew by the moon in 1989, but possible evidence of cryovolcanoes have also been observed on Europa, Miranda, Enceladus, Titan and, most recently, Pluto.

Reference:
http://adsabs.harvard.edu/full/1990LPI....21..599K
http://www2.lowell.edu/workshops/aug2011/workshop_abstracts/prockter.pdf

Image credit: NASA