A
fumarole (ultimately from the
Latin fumus," smoke") is an opening in a planet's
crust, often in the neighborhood of
volcanoes, which emits
steam and
gases such as
carbon dioxide,
sulfur dioxide,
hydrogen chloride, and
hydrogen sulfide. The steam forms when superheated water vaporizes as its pressure drops when it emerges from the ground. The name
solfatara, from the
Italian solfo, sulfur (via the
Sicilian language, compare
Solfatara (volcano)), is given to fumaroles that emit
sulfurous gases.