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Fumarole at Sol de Mañana, Bolivia

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. Fumaroles are characteristic of the late stages of volcanic activity, but fumarole activity can also precede a volcanic eruption and has been used for eruption prediction. 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. An area containing fumaroles is known as a fumarole field.

The predominant vapor emitted by fumaroles is steam, formed by the circulation of groundwater through heated rock. This is typically accompanied by volcanic gases given off by magma cooling deep below the surface. These volcanic gases include sulfur compounds, such as various sulfur oxides and hydrogen sulfide, and sometimes hydrogen chloride, hydrogen fluoride, and other gases. A fumarole that emits significant sulfur compounds is sometimes called a solfatara.

Fumarole activity can break down rock around the vent, while simultaneously depositing sulfur and other minerals. Valuable hydrothermal mineral deposits can form beneath fumaroles. However, active fumaroles can be a hazard due to their emission of hot, poisonous gases.


Sampling gases at a fumarole on Mount Baker in Washington, United States
Fumaroles at Vulcano, Sicily, Italy

A fumarole (or fumerole; from French fumerolle, a domed structure with lateral openings, built over a kitchen to permit the escape of smoke[2]) is an opening in a planet's crust which emits steam and gases, but no liquid or solid material.[3] The temperature of the gases leaving the vent ranges from about 100 to 1,000 °C (210 to 1,800 °F).[4] The steam forms when groundwater is superheated by hot rock, then flashes (boils due to depressurization) as it approaches the surface.[5]

In addition to steam, gases released by fumaroles include carbon dioxide, sulfur oxides, hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. These have their origin in magma cooling underground. Not all these gases are present in all fumaroles; for example, fumaroles of Kilauea in Hawaii, US, contain almost no hydrogen chloride or hydrogen fluoride.[3] The gases may also include traces of carbonyl sulfide, carbon disulfide, hydrogen, methane, or carbon monoxide.[6] A fumarole that emits sulfurous gases can be referred to as a solfatara (from old Italian solfo, "sulfur"[7][8]). Acid-sulfate hot springs can be formed by fumaroles when some of the steam condenses at the surface. Rising acidic vapors from below, such as CO2 and H2S, will then dissolve, creating steam-heated low-pH hot springs.[9]

Fumaroles are normally associated with the late stages of volcanic activity,[10] although they may also precede volcanic activity[4] and have been used to predict volcanic eruptions.[5] In particular, changes in the composition and temperature of fumarole gases may point to an imminent eruption.[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. Continued sulfur oxide emissions after an eruption is an indication that magma is continuing to rise towards the surface.[6]

Fumaroles may occur along tiny cracks, along long fissures, or in chaotic clusters or fields. They also occur on the surface of lava flows and pyroclastic flows.[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.[12] When they occur in freezing environments, fumaroles may cause fumarolic ice towers.

Fumaroles may persist for decades or centuries if located above a persistent heat source; or they may disappear within weeks to months if they occur atop a fresh volcanic deposit that quickly cools.[11] The Valley of Ten Thousand Smokes, for example, was formed during the 1912 eruption of Novarupta in Alaska. Initially, thousands of fumaroles occurred in the cooling ash from the eruption, but over time most of them have become extinct.[13] Persistent fumaroles are found at Sulfur Bank on the northern edge of the Kilauea caldera, but most fumaroles in Hawaii last no more than a few months.[3] There are still numerous active fumaroles at Yellowstone National Park, US,[14] some 70,000 years after the most recent eruption.[15]

Economic resources and hazards

Traditional sulfur mining at Kawah Ijen.

The acidic fumes from fumaroles can break down the rock around the vents, producing brightly colored alteration haloes.[5] At Sulfur Bank near Kilauea, mild alteration reduces the rock to gray to white opal and kaolinite with the original texture of the rock still discernible. Alteration begins along joints in the rock and works inwards until the entire joint block is altered. More extreme alteration (at lower pH) reduces the material to clay minerals and iron oxides to produce red to reddish-brown clay.[16] The same process can produce valuable hydrothermal ore deposits at depth.[5]

Fumaroles emitting sulfurous vapors form surface deposits of sulfur-rich minerals and of fumarole minerals. Sulfur crystals at Sulfur Banks near Kilauea can grow to 2 centimeters (0.8 in) in length, and considerable sulfur has been deposited at Sulfur Cone within Mauna Loa caldera.[3] Places in which these deposits have been mined include:

Sulfur mining in Indonesia is sometimes done for low pay, by hand, without respirators or other protective equipment.[17]

In April 2006 fumarole emissions killed three ski-patrol workers east of Chair 3 at Mammoth Mountain Ski Area in California. The workers were overpowered by an accumulation of toxic fumes (a mazuku) in a crevasse they had fallen into.[25][26]



Fumaroles are found around the world in areas of volcanic activity. A few notable examples include:

On Mars


The formation known as Home Plate at Gusev Crater on Mars, which was examined by the Mars Exploration Rover (MER) Spirit, is suspected to be the eroded remains of an ancient and extinct fumarole.[35]

See also



  1. ^ "fumerole – Definition and meaning". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 4 June 2023.
  2. ^ "fumarole". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  3. ^ a b c d e Macdonald, Gordon A.; Abbott, Agatin T.; Peterson, Frank L. (1983). Volcanoes in the sea : the geology of Hawaii (2nd ed.). Honolulu: University of Hawaii Press. pp. 53–55. ISBN 0824808320.
  4. ^ a b Allaby, Michael (2013). A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press. ISBN 9780199653065.
  5. ^ a b c d Philpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. p. 70. ISBN 9780521880060.
  6. ^ a b Schmincke, Hans-Ulrich (2004). Volcanism. Springer Science & Business Media. p. 47. ISBN 9783540436508.
  7. ^ "solfatara". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  8. ^ "Solfatara". Merriam-Webster.com Dictionary. Merriam-Webster. Retrieved 20 February 2020.
  9. ^ White, D.E.; Muffler, L.J.P.; Truesdell, A.H. (1971). "Vapor-dominated hydrothermal systems compared with hot-water systems". Economic Geology. 66 (1): 75–97. Bibcode:1971EcGeo..66...75W. doi:10.2113/gsecongeo.66.1.75.
  10. ^ Jackson, Julia A., ed. (1997). "fumarole". Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN 0922152349.
  11. ^ a b Public Domain This article incorporates public domain material from "Fumarole". USGS Photo Glossary. United States Geological Survey. Retrieved 6 February 2019.
  12. ^ Neuendorf, Klaus K. E. (2005). Jackson, Julia A.; Mehl, James P.; Neuendorf, Klaus K. E. (eds.). Glossary of Geology. Springer Science & Business Media. p. 257. ISBN 9780922152766. Retrieved 6 June 2015. fumarole field[:] A group of cool fumaroles.
  13. ^ Hildreth, W.; Fierstein, J. (2012). The Novarupta-Katmai eruption of 1912– largest eruption of the twentieth century; centennial perspectives. Reston: USGS Professional Paper 1791. p. 135.
  14. ^ "Fumaroles". Volcanic Features and Landforms. National Park Service. Retrieved 1 March 2022.
  15. ^ "Summary of Eruption History". Yellowstone Geology and History. U.S. Geological Survey. Retrieved 1 March 2022.
  16. ^ Macdonald, Abbott & Peterson 1983, p. 134.
  17. ^ a b "Kawah Ijen: Between potential & threat". The Jakarta Post. 19 December 2011.
  18. ^ Dukehart, Coburn (17 November 2015). "The Struggle and Strain of Mining "Devil's Gold"". National Geographic. Archived from the original on 9 April 2021. Retrieved 1 March 2022.
  19. ^ Pfeiffer, Tom (2006). "Welirang volcano photos". Volcano Discovery. Retrieved 1 March 2022.
  20. ^ Global Volcanism Program, National Museum of Natural History, Smithsonian Institution
  21. ^ Simpson, Mark P.; Bignall, Greg (January 2016). "Undeveloped high-enthalpy geothermal fields of the Taupo Volcanic Zone, New Zealand". Geothermics. 59: 325–346. Bibcode:2016Geoth..59..325S. doi:10.1016/j.geothermics.2015.08.006.
  22. ^ "Eruption on Whakaari White Island kills 10 people". nzhistory.govt.nz. Retrieved 26 October 2021.
  23. ^ "Disaster at White Island". New Zealand Geographic. Retrieved 26 October 2021.
  24. ^ Ferrara, Vincenzo (2016). "The Sulphur Mining Industry in Sicily". Essays on the History of Mechanical Engineering. History of Mechanism and Machine Science. Vol. 31. pp. 111–130. doi:10.1007/978-3-319-22680-4_8. ISBN 978-3-319-22679-8.
  25. ^ Hymon, Steve; Covarrubias, Amanda (9 April 2006). "How Routine Turned to Tragedy at Mammoth". Los Angeles Times. Retrieved 9 May 2011.
  26. ^ Cantrell, Lee; Young, Michael (March 2009). "Fatal Fall into a Volcanic Fumarole". Wilderness & Environmental Medicine. 20 (1): 77–79. doi:10.1580/08-WEME-CR-199.1. PMID 19364170. S2CID 207182190.
  27. ^ Carrabba, Paola (2010). "The Gate of Hades: The Phlegraean Fields". Natural Heritage from East to West. pp. 193–200. doi:10.1007/978-3-642-01577-9_24. ISBN 978-3-642-01576-2.
  28. ^ Troiano, A.; Isaia, R.; Tramparulo, F. D. A.; Di Giuseppe, M. G. (December 2021). "The Pisciarelli main fumarole mechanisms reconstructed by electrical resistivity and induced polarization imaging". Scientific Reports. 11 (1): 18639. Bibcode:2021NatSR..1118639T. doi:10.1038/s41598-021-97413-1. PMC 8452721. PMID 34545113.
  29. ^ Tamburello, G.; Hansteen, T. H.; Bredemeyer, S.; Aiuppa, A.; Tassi, F. (28 July 2014). "Gas emissions from five volcanoes in northern Chile and implications for the volatiles budget of the Central Volcanic Zone: Volatiles budget of the CVZ, Chile". Geophysical Research Letters. 41 (14): 4961–4969. doi:10.1002/2014GL060653. hdl:10447/99158. S2CID 55877335.
  30. ^ Paola, G. M. (June 1971). "Geology of the Corbetti Caldera area (Main Ethiopian Rift Valley)". Bulletin Volcanologique. 35 (2): 497–506. Bibcode:1971BVol...35..497D. doi:10.1007/BF02596970. S2CID 130428510.
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  32. ^ Symonds, R.B.; Mizutani, Y.; Briggs, Paul H. (1996). "Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan". Journal of Volcanology and Geothermal Research. 73 (3–4): 177–211. Bibcode:1996JVGR...73..177S. doi:10.1016/0377-0273(96)00029-7.
  33. ^ "Morne Trois Pitons National Park". UNESCO. 1997. Retrieved 28 July 2020.
  34. ^ "Hydrothermal Features". Yellowstone National Park. U.S. National Park Service. Retrieved 1 March 2022.
  35. ^ R.V.Morris, S.W.Squyres, et al. "The Hydrothermal System at Home Plate in Gusev Crater, Mars". Lunar & Planetary Science XXXIX(2008)