A fumarole ( lat.-it.; plural: fumaroles ) is a volcanic exhalation (ie the vapor leak) in the field of active volcanic areas, from the steam and volcanic gases escape to some extent.

Fumaroles occur when there is little in the deep water. By the absence of pressure, the water is fully converted to steam prior to its discharge. Fumaroles are classified by temperature and type of gases that emerge from them. The temperatures of the gases can be between 200 ° C and 800 ° C.. While most fumaroles excrete pure water vapor, but often occur from other volcanic gases, which partly deposited at the exit point. Oxidation and thermophilic ( heat-loving ) bacteria, this creates the characteristic of fumaroles colorful coloring. Exhalations, which are rich in sulfur compounds such as hydrogen sulfide, solfataras be called; Carbon dioxide exhalations hot mofettes. In the area of lying in depressions mofettes the carbon dioxide can accumulate because it is heavier than air, and so in animals and humans lead to death by asphyxiation.

Due to changes fumaroles can view volcanic activity. If their temperature increases or the composition of the effluent gas changes drastically, this may be a sign of a new volcanic eruption. Thus, the temperatures of the fumaroles rose on the island of Vulcano, which is quiet for over 100 years, 1986-1993 from 300 ° C to over 700 ° C at what caused great concern. Only after the temperatures dropped again, the all-clear was given.

As a rule, fumaroles, as well as the other exhalations, post-volcanic phenomena; Thus, their existence indicates decaying volcanism.