"Solfatara" redirects here. For the volcanic crater in Italy, see
Solfatara (volcano).
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.
Description
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
Italiansolfo, "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
Kilaueacaldera, 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
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:
Sicily, which had a near-monopoly on sulfur prior to development of the
Frasch process for mining sulfur from salt domes.[24]
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]
Occurrences
Fumaroles are found around the world in areas of volcanic activity. A few notable examples include:
Campi Flegrei, Italy, known since ancient times and regarded as the entrance to
Hell,[27] which is now closely monitored because of the hazard it poses to nearby urbanization.[28]
^
abcdeMacdonald, 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.
ISBN0824808320.
^
abAllaby, Michael (2013). A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press.
ISBN9780199653065.
^
abcdPhilpotts, Anthony R.; Ague, Jay J. (2009). Principles of igneous and metamorphic petrology (2nd ed.). Cambridge, UK: Cambridge University Press. p. 70.
ISBN9780521880060.
^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.
ISBN9780922152766. Retrieved 6 June 2015. fumarole field[:] A group of cool fumaroles.
^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.
^"Fumaroles". Volcanic Features and Landforms. National Park Service. Retrieved 1 March 2022.
^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.
ISBN978-3-319-22679-8.
^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.
S2CID55877335.
^"Fumaroles". Manaaki Whenua Landcare Research. Retrieved 1 March 2022.
^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.