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==Iceland== |
==Iceland== |
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In Iceland, volcanic vents, which can be long fissures, often open parallel to the rift zones where the [[Eurasian Plate|Eurasian]] and the [[North American Plate]] [[lithosphere|lithospheric]] [[plate tectonics|plates]] are diverging, a system which is part of the [[Mid-Atlantic Ridge]].<ref>{{cite journal |url=http://jardvis.hi.is/sites/jardvis.hi.is/files/Pdf_skjol/Jokull58_pdf/jokull58-einarsson.pdf |first1=Páll |last1=Einarsson |title=Plate boundaries, rifts and transforms in Iceland |journal=Jökull |volume=58 |issue=12 |year=2008 |pages=35–58 }}</ref> Renewed eruptions generally occur from new parallel fractures offset by a few hundred to thousands of metres from the earlier fissures. This distribution of vents and sometimes voluminous eruptions of fluid basaltic lava usually builds up a thick lava plateau, rather than a single volcanic edifice. But there are also the [[central volcano]]es, [[composite volcano]]es, often with [[caldera]]s, which have been formed during thousands of years, and eruptions with one or more magma reservoirs underneath controlling their respective fissure system.<ref>{{cite journal |url=http://www.geo.mtu.edu/~raman/papers2/Thordarson%20and%20Hoskuldsson%202008%20Postglacial%20volcanism.pdf |first1=Thorvaldur |last1=Thordarson |first2=Ármann |last2=Höskuldsson |title=Postglacial volcanism in Iceland |journal=Jökull |volume=58 |issue=198 |year=2008 |pages=e228 }}</ref> |
In Iceland, volcanic vents, which can be long fissures, often open parallel to the rift zones where the [[Eurasian Plate|Eurasian]] and the [[North American Plate]] [[lithosphere|lithospheric]] [[plate tectonics|plates]] are diverging, a system which is part of the [[Mid-Atlantic Ridge]].<ref>{{cite journal |url=http://jardvis.hi.is/sites/jardvis.hi.is/files/Pdf_skjol/Jokull58_pdf/jokull58-einarsson.pdf |first1=Páll |last1=Einarsson |title=Plate boundaries, rifts and transforms in Iceland |journal=Jökull |volume=58 |issue=12 |year=2008 |pages=35–58 |doi=10.33799/jokull2008.58.035 |s2cid=55021384 }}</ref> Renewed eruptions generally occur from new parallel fractures offset by a few hundred to thousands of metres from the earlier fissures. This distribution of vents and sometimes voluminous eruptions of fluid basaltic lava usually builds up a thick lava plateau, rather than a single volcanic edifice. But there are also the [[central volcano]]es, [[composite volcano]]es, often with [[caldera]]s, which have been formed during thousands of years, and eruptions with one or more magma reservoirs underneath controlling their respective fissure system.<ref>{{cite journal |url=http://www.geo.mtu.edu/~raman/papers2/Thordarson%20and%20Hoskuldsson%202008%20Postglacial%20volcanism.pdf |first1=Thorvaldur |last1=Thordarson |first2=Ármann |last2=Höskuldsson |title=Postglacial volcanism in Iceland |journal=Jökull |volume=58 |issue=198 |year=2008 |pages=e228 |doi=10.33799/jokull2008.58.197 |s2cid=53446884 }}</ref> |
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The [[Laki]] fissures, part of the [[Grímsvötn]] volcanic system, produced one of the biggest [[effusive eruption]]s on earth in historical times, in the form of a flood basalt of 12–14 km<sup>3</sup> of lava in 1783.<ref>[http://earthice.hi.is/grimsvotn_volcano Institute of Earth Sciences, University of Iceland: Grímsvötn. Received 9/24, 2014.]</ref> During the [[Eldgjá]] eruption A.D. 934–40, another very big effusive fissure eruption in the volcanic system of [[Katla volcano|Katla]] in South Iceland, ~{{convert|18|km3|cumi|abbr=on}} of lava were released.<ref>[http://earthice.hi.is/katla_volcano Institute of Earth Sciences, University of Iceland: Katla. Received 9/24, 2014.]</ref> In September 2014, a fissure eruption was ongoing on the site of the 18th century lava field Holuhraun. The eruption is part of an eruption series in the [[Bárðarbunga]] volcanic system.<ref>[http://earthice.hi.is/bardarbunga_2014 Institute of Earth Sciences, University of Iceland: Bardarbunga 2014]</ref> |
The [[Laki]] fissures, part of the [[Grímsvötn]] volcanic system, produced one of the biggest [[effusive eruption]]s on earth in historical times, in the form of a flood basalt of 12–14 km<sup>3</sup> of lava in 1783.<ref>[http://earthice.hi.is/grimsvotn_volcano Institute of Earth Sciences, University of Iceland: Grímsvötn. Received 9/24, 2014.]</ref> During the [[Eldgjá]] eruption A.D. 934–40, another very big effusive fissure eruption in the volcanic system of [[Katla volcano|Katla]] in South Iceland, ~{{convert|18|km3|cumi|abbr=on}} of lava were released.<ref>[http://earthice.hi.is/katla_volcano Institute of Earth Sciences, University of Iceland: Katla. Received 9/24, 2014.]</ref> In September 2014, a fissure eruption was ongoing on the site of the 18th century lava field Holuhraun. The eruption is part of an eruption series in the [[Bárðarbunga]] volcanic system.<ref>[http://earthice.hi.is/bardarbunga_2014 Institute of Earth Sciences, University of Iceland: Bardarbunga 2014]</ref> |
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Revision as of 05:20, 8 June 2023
A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilometres long. Fissure vents can cause large flood basalts which run first in lava channels and later in lava tubes. After some time, the eruption tends to become focused at one or more spatter cones. Small fissure vents may not be easily discernible from the air, but the crater rows (see Laki) or the canyons (see Eldgjá) built up by some of them are.
The dikes that feed fissures reach the surface from depths of a few kilometers and connect them to deeper magma reservoirs, often under volcanic centers. Fissures are usually found in or along rifts and rift zones, such as Iceland and the East African Rift. Fissure vents are often part of the structure of shield volcanoes.[1][2]
Iceland
In Iceland, volcanic vents, which can be long fissures, often open parallel to the rift zones where the Eurasian and the North American Plate lithospheric plates are diverging, a system which is part of the Mid-Atlantic Ridge.[3] Renewed eruptions generally occur from new parallel fractures offset by a few hundred to thousands of metres from the earlier fissures. This distribution of vents and sometimes voluminous eruptions of fluid basaltic lava usually builds up a thick lava plateau, rather than a single volcanic edifice. But there are also the central volcanoes, composite volcanoes, often with calderas, which have been formed during thousands of years, and eruptions with one or more magma reservoirs underneath controlling their respective fissure system.[4]
The Laki fissures, part of the Grímsvötn volcanic system, produced one of the biggest effusive eruptions on earth in historical times, in the form of a flood basalt of 12–14 km3 of lava in 1783.[5] During the Eldgjá eruption A.D. 934–40, another very big effusive fissure eruption in the volcanic system of Katla in South Iceland, ~18 km3 (4.3 cu mi) of lava were released.[6] In September 2014, a fissure eruption was ongoing on the site of the 18th century lava field Holuhraun. The eruption is part of an eruption series in the Bárðarbunga volcanic system.[7]
Hawaii
The radial fissure vents of Hawaiian volcanoes also produce "curtains of fire" as lava fountains erupting along a portion of a fissure. These vents build up low ramparts of basaltic spatter on both sides of the fissure. More isolated lava fountains along the fissure produce crater rows of small spatter and cinder cones. The fragments that form a spatter cone are hot and plastic enough to weld together, while the fragments that form a cinder cone remain separate because of their lower temperature.
List of fissure vents
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Hydrothermal vents
Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspots.[9] The dispersal of hydrothermal fluids throughout the global ocean at active vent sites creates hydrothermal plumes. Hydrothermal deposits are rocks and mineral ore deposits formed by the action of hydrothermal vents.
Hydrothermal vents exist because the Earth is both geologically active and has large amounts of water on its surface and within its crust. Under the sea, they may form features called black smokers or white smokers, which deliver a wide range of elements to the world's oceans, thus contributing to global marine biogeochemistry. Relative to the majority of the deep sea, the areas around hydrothermal vents are biologically more productive, often hosting complex communities fueled by the chemicals dissolved in the vent fluids. Chemosynthetic bacteria and archaea found around hydrothermal vents form the base of the food chain, supporting diverse organisms including giant tube worms, clams, limpets, and shrimp. Active hydrothermal vents are thought to exist on Jupiter's moon Europa and Saturn's moon Enceladus,[10][11] and it is speculated that ancient hydrothermal vents once existed on Mars.[9][12]
Hydrothermal vents have been hypothesized to have been a significant factor to starting abiogenesis and the survival of primitive life. The conditions of these vents have been shown to support the synthesis of molecules important to life. Some evidence suggests that certain vents such as alkaline hydrothermal vents or those containing supercritical CO2 are more conducive to the formation of these organic molecules. However, the origin of life is a widely debated topic, and there are many conflicting viewpoints.References
- ^ "V. Camp, Dept. of Geologic Sciences, Univ. of San Diego: How volcanoes work. Eruption types. Fissure eruptions". Archived from the original on 2018-02-28. Retrieved 2014-09-24.
- ^ "Geology glossary". www.volcanodiscovery.com. Retrieved September 25, 2001.
- ^ Einarsson, Páll (2008). "Plate boundaries, rifts and transforms in Iceland" (PDF). Jökull. 58 (12): 35–58. doi:10.33799/jokull2008.58.035. S2CID 55021384.
- ^ Thordarson, Thorvaldur; Höskuldsson, Ármann (2008). "Postglacial volcanism in Iceland" (PDF). Jökull. 58 (198): e228. doi:10.33799/jokull2008.58.197. S2CID 53446884.
- ^ Institute of Earth Sciences, University of Iceland: Grímsvötn. Received 9/24, 2014.
- ^ Institute of Earth Sciences, University of Iceland: Katla. Received 9/24, 2014.
- ^ Institute of Earth Sciences, University of Iceland: Bardarbunga 2014
- ^ Kerr, A. C; Khan, M; McDonald, I (2010). "Eruption of basaltic magma at Tor Zawar, Balochistan, Pakistan on 27 January 2010: Geochemical and petrological constraints on petrogenesis". Mineralogical Magazine. 74 (6): 1027–36. Bibcode:2010MinM...74.1027K. doi:10.1180/minmag.2010.074.6.1027. S2CID 129864863.
- ^ a b Colín-García, María (2016). "Hydrothermal vents and prebiotic chemistry: a review". Boletín de la Sociedad Geológica Mexicana. 68 (3): 599–620. doi:10.18268/BSGM2016v68n3a13.
- ^ Chang, Kenneth (13 April 2017). "Conditions for Life Detected on Saturn Moon Enceladus". New York Times. Retrieved 14 April 2017.
- ^ "Spacecraft Data Suggest Saturn Moon's Ocean May Harbor Hydrothermal Activity". NASA. 11 March 2015. Archived from the original on 13 March 2015. Retrieved 12 March 2015.
- ^ Paine, M. (15 May 2001). "Mars Explorers to Benefit from Australian Research". Space.com. Archived from the original on 21 February 2006.
External links
Media related to Fissure vents at Wikimedia Commons- Detailed list and KML files for Fissure Vents
- Volcanolive.com Page on Fissure Vents
