Fissure vent
Afissure vent,also known as avolcanic fissure,eruption fissureor simply a fissure, is a linearvolcanic ventthrough whichlavaerupts, usually without anyexplosive activity.The vent is often a few metres wide and may be many kilometres long. Fissure vents can cause largeflood basaltswhich run first inlava channelsand later inlava tubes.After some time, the eruption tends to become focused at one or morespatter cones.Small fissure vents may not be easily discernible from the air, but the crater rows (seeLaki) or the canyons (seeEldgjá) built up by some of them are.
Thedikesthat feed fissures reach the surface from depths of a few kilometers and connect them to deepermagma reservoirs,often under volcanic centers. Fissures are usually found in or alongriftsandrift zones,such asIcelandand theEast African Rift.Fissure vents are often part of the structure ofshield volcanoes.[1][2]
Iceland[edit]
In Iceland, volcanic vents, which can be long fissures, often open parallel to the rift zones where theEurasianand theNorth Americanlithosphericplatesare diverging, a system which is part of theMid-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 thecentral volcanoes,composite volcanoes,often withcalderas,which have been formed during thousands of years, and eruptions with one or more magma reservoirs underneath controlling their respective fissure system.[4]
TheLakifissures, part of theGrímsvötnvolcanic system, produced one of the biggesteffusive eruptionson earth in historical times, in the form of a flood basalt of 12–14 km3of lava in 1783.[5]During theEldgjáeruption A.D. 934–40, another very big effusive fissure eruption in the volcanic system ofKatlain 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 theBárðarbungavolcanic system.[7]
Hawaii[edit]
The radial fissure vents ofHawaiian volcanoesalso produce "curtains of fire" aslava fountainserupting along a portion of a fissure. These vents build up low ramparts ofbasalticspatter on both sides of the fissure. More isolated lava fountains along the fissure produce crater rows of small spatter andcinder cones.The fragments that form aspatter coneare 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[edit]
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References[edit]
- ^"V. Camp, Dept. of Geologic Sciences, Univ. of San Diego: How volcanoes work. Eruption types. Fissure eruptions".Archived fromthe originalon 2018-02-28.Retrieved2014-09-24.
- ^"Geology glossary".volcanodiscovery.RetrievedSeptember 25,2001.
- ^Einarsson, Páll (2008)."Plate boundaries, rifts and transforms in Iceland"(PDF).Jökull.58(12): 35–58.doi:10.33799/jokull2008.58.035.S2CID55021384.Archived fromthe original(PDF)on 2017-11-18.Retrieved2014-09-24.
- ^Thordarson, Thorvaldur; Höskuldsson, Ármann (2008)."Postglacial volcanism in Iceland"(PDF).Jökull.58(198): e228.doi:10.33799/jokull2008.58.197.S2CID53446884.
- ^"Institute of Earth Sciences, University of Iceland: Grímsvötn. Received 9/24, 2014".Archived fromthe originalon 2018-05-14.Retrieved2014-09-24.
- ^Institute of Earth Sciences, University of Iceland: Katla. Received 9/24, 2014.
- ^"Institute of Earth Sciences, University of Iceland: Bardarbunga 2014".Archived fromthe originalon 2021-04-15.Retrieved2014-09-24.
- ^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.S2CID129864863.
External links[edit]
Media related toFissure ventsat Wikimedia Commons- Detailed list and KML files for Fissure Vents
- Volcanolive Page on Fissure Vents
