fumaroles

A fumarole is a vent in a volcanic or hydrothermal area from which steam and volcanic gases escape into the atmosphere. Fumaroles occur on crater floors, within lava tubes, along fissures, and in geothermal fields associated with active or recently active volcanoes. They are one of several surface manifestations of subsurface heat and magmatic gas activity.

The gases released by fumaroles typically include water vapor as the dominant component, along with carbon dioxide, sulfur dioxide, hydrogen sulfide, hydrogen chloride, and other trace gases. The temperature of fumarolic emission can range from just above ambient to several hundred degrees Celsius, and the plumes may be clear or colored by mineral aerosols and sulfur deposits. When gases cool and react with the surrounding air, they can deposit sulfur crystals or other minerals around the vent, forming distinctive sulfur rims, mounds, or terraces.

Fumaroles form when groundwater is heated by hot rock or magma and becomes superheated enough to flash into steam, escaping through a conduit to the surface. They are diagnostic of geothermal and volcanic systems and provide important information about magma chemistry and degassing processes. Changes in fumarole activity, gas composition, or temperature can signal shifts in volcanic behavior and are monitored by scientists as indicators of unrest.

Hazards associated with fumaroles include toxic and suffocating gases, extreme heat, and unstable ground near vents. Visitors to active geothermal or volcanic areas are advised to respect warning signs and stay on designated paths.