Fumarole

A fumarole (or fumerole)[1] is a vent in the surface of the Earth or another rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids.

Most fumaroles die down within a few days or weeks of the end of an eruption, but a few are persistent, lasting for decades or longer.

The predominant vapor emitted by fumaroles is steam, formed by the circulation of groundwater through heated rock.

[4] The steam forms when groundwater is superheated by hot rock, then flashes (boils due to depressurization) as it approaches the surface.

Rising acidic vapors from below, such as CO2 and H2S, will then dissolve, creating steam-heated low-pH hot springs.

[3] An increase in sulfur oxide emissions is a particularly robust indication that new magma is rising from the depths, and may be detectable months to years before the eruption.

[11] A fumarole field is an area of thermal springs and gas vents where shallow magma or hot igneous rocks release gases or interact with groundwater.

[15] The acidic fumes from fumaroles can break down the rock around the vents, producing brightly colored alteration haloes.

[17] In April 2006 fumarole emissions killed three ski-patrol workers east of Chair 3 at Mammoth Mountain Ski Area in California.