—fumarolic /fyooh'meuh rol"ik/, adj./fyooh"meuh rohl'/, n.a hole in or near a volcano, from which vapor rises.[1805-15; < F fumerolle < LL fumariolum, dim. of L fumarium smoke chamber, equiv. to fum(us) smoke + -arium -ARIUM; see -OLE1]
* * *Vent from which volcanic vapours issue.Fumaroles, like geysers, are caused by hot springs, which disperse groundwater from the upper parts of the Earth's crust after it has been heated by magma. As magma begins to solidify, the gases in it, mostly water vapour, become concentrated by the pressure of the remaining liquid. When the pressure becomes high enough, the liquid is forced into cracks in the surrounding rock. A fumarole forms if a crack extends to the surface.
* * *▪ geologyvent in the Earth's surface from which steam and volcanic gases are emitted. The major source of the water vapour emitted by fumaroles is groundwater heated by bodies of magma lying relatively close to the surface. Carbon dioxide, sulfur dioxide, and hydrogen sulfide are usually emitted directly from the magma. Fumaroles are often present on active volcanoes (volcano) during periods of relative quiet between eruptions.Fumaroles are closely related to hot springs (hot spring) and geysers (geyser). In areas where the water table rises near the surface, fumaroles can become hot springs. A fumarole rich in sulfur gases is called a solfatara; a fumarole rich in carbon dioxide is called a mofette.
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