Krýsuvík (volcanic system)
The volcanic system ofKrýsuvík(orKrísuvík,both pronounced[ˈkʰriːsʏˌviːk]inIcelandic,alsoTrölladyngja-KrýsuvíkorKrýsuvík-Trölladyngja[ˈtʰrœtlaˌtiɲca]volcanic system), is situated in the south–west ofIcelandon theReykjanespeninsula. It is located in the middle of Reykjanes and on the divergentplate boundaryof theMid-Atlantic Ridgewhich traverses Iceland. It was named after theKrýsuvíkarea which is part of it and consists of a fissure system without acentral volcano.[1]However, there are some indications—namely, the discovery bygeophysicalmethods of what scientists interpret as a buriedcaldera,combined with thewell-known,vigoroushydrothermalsystem above it—that an embryonic centralmagma chambermay already exist or be actively developing.[2]
The volcanic system has a length of 55 km (34 mi), a width of around 13 km (8.1 mi), covers an area of 350 km2(140 sq mi), and its highest elevation is 393 m (1,289 ft).[1]It is one of 4 (or up to 7, depending on the source)volcanic systemssituated within theReykjanes Volcanic Belt.[3]The volcanic systems are arranged en echelon and at an angle that varies from 20 to 45° to the direction of the rift zone on the divergent plate boundary traversing Reykjanes.
General characteristics
[edit]The volcanic system of Krýsuvík has no central volcanic edifice, but rather afissure swarmthat is 50 km (31 mi) long,[4]is composed of a mixture of volcanic and tectonic fissures and faults, of which 30 km (19 mi) are volcanic fissures.[4]Recentgeophysicalwork on the system, employingmagnetotelluricresistivitysamplingandmodeling,indicates the presence of a buriedcalderawith possibly an embryonic centralmagma chamberbeneath the system. This suggests that it could eventually develop into a central volcano like the similar, but more matureHengillvolcanic system farther to the east on the peninsula.[2]There are no known submarine fissures of the system which nevertheless reaches from the south coast in direction south–west to north–east over the Reykjanes Peninsula. The northernmost fissures are thought to reachLake Rauðavatn[ˈrœyːðaˌvahtn̥]on the outskirts ofReykjavík.There are no ice-covered volcanoes connected to the Krýsuvík system, but LakeKleifarvatnlies within the system andgeothermal activityis found at the lake bottom.[4]
The Krýsuvík volcanic system has a tendency toeffusivebasaltic fissure eruptions; the last eruption took place in the 14th century.[5]TheFagradalsfjallfissure swarm that erupted in 2021 was initially considered potentially a branch or a secondary part of the Krýsuvík volcanic system, but it is now usually considered a separate volcanic system.[6]The eruption products of the Krýsuvík system consist exclusively ofbasalt.[4]
Eruptions
[edit]The volcanic system is centered on the divergent plate boundary on Reykjanes peninsula. It is easier there formagmato reach the surface, because of the multitude of tectonic and volcanic faults and fissures in such regions. There have been at least 10 volcanic episodes within the volcanic system in the last 8,000 years. These episodes each comprised many single eruptions and were most probably connected torifting.[4]
SomeHoloceneeruptions have been dated specifically, especially the eruption that producedBúrfellshraun(ca. 5290 BP).[5]Since the time ofsettlement in Iceland,which is thought to have been in the 9th century, more eruptions have taken place within the system, all of them in theMiddle Ages.[5]
TheKrýsuvík fireswere a period of volcanic activity which started in the middle of the 12th century, probably in 1151 and written sources indicate that they ended in 1188. The activity ofPleistoceneshield volcanoessuch asÞráinskjöldur[ˈθrauːɪnˌscœltʏr̥]andHrútagjá[ˈr̥uːtaˌcauː],as well as oftuyaslikeFagradalsfjallwithin the volcanic system, are seen as separate from the fissure system, although the bigger volcanoes control parts of thetopography.[4]
The Krýsuvík system has a tendency tophreatic explosions,often within rifting episodes or during eruption series. The underground of Reykjanes peninsula is soaked with water as it has a high groundwater level as well as saline sea water in its cave systems. There is a prehistoricmaarcomplex around Grænavatn at Krýsuvík which has its origin in phreatic explosions connected to a period of effusive eruptions.[7]There an explosion connected to geothermal activity of an old borehole in 1999 atSeltún.[8][9]
Starting on 27 September 2021, an intense earthquake swarm began that was concentrated around the Keilir region with over 1000 earthquakes with a magnitude 4.2 event on 2 October. The earthquakes sparked concern that a second eruption could begin in the area but it was not known definitely what was causing the swarm.[10]During the overnight hours of 10 October 2021, a strong M3.2 earthquake occurred 2 km (1.2 mi) SSW of Keilier.[11]
List of lava fields
[edit]These are some lava fields which originated in eruptions of the Krýsuvík volcanic system since the end of the last glacial spell 13,000 years ago.
Búrfellshraun
[edit]Around 8,000 years ago, theBúrfellcrater nearHafnarfjörðurproduced a 18 km2(6.9 sq mi) lava field calledBúrfellshraun[ˈpurˌfɛlsˌr̥œyːn].[12]Today, a big part of midtown Hafnarfjörður is built onto and around Búrfellshraun.[12]The crater contains alava channelcalledBúrfellsgjá[ˈpurˌfɛlsˌcauː].
Óbrinnishólabruni
[edit]TheÓbrinnishólabruni[ˈouːˌprɪnːɪsˌhouːlaˌprʏːnɪ]lavas came 2,000 years ago from some craters near Bláfjallavegur[ˈplauːˌfjatlaˌvɛːɣʏr̥](Road 407) which have since been destroyed by quarrying. The name Óbrinnishólar[ˈouːˌprɪnːɪsˌhouːlar̥]means that there was no “fire” in them during further eruptions in the region in historical time.[12]Parts of Hafnarfjörður (midtown andVallahverfi[ˈvatlaˌkʰvɛrvɪ]) are located on top of this lava field.[12]
Kapelluhraun
[edit]The lavas ofKapelluhraun([ˈkʰaːpɛtlʏˌr̥œyːn],"chapel lava" ) from historical time (erupted around 1150)[12]have been given this name because of a medieval chapel whose ruins are still standing on them. A small statue ofSaint Barbarawas found at the place.[13]The Kapelluhraun lava field consists ofpāhoehoeandʻaʻālava which streamed from the highland down to the bay ofStraumsvíknear today'saluminium smelterand there into the sea.[12]The events were part of a ca. 30 years long unrest period in the late 12th century which is calledKrýsuvík Fires.This unrest period included repeated eruption series and rifting episodes and is recorded inFlateyjarbók.[12]
The eruption fissures had a length of 10 km (6.2 mi) and 6.5 km (4.0 mi) respectively, and the lava flows cover around 36 km2(14 sq mi).[12]Today it is agolf course[14]is situated in the middle of these lavas, seen when looking fromRoute 41between Straumsvík and Hafnarfjörður in direction ofFaxaflói.
Landforms
[edit]The Seltún[ˈsɛlˌtʰuːn]geothermal area is situated next to Krýsuvík in direction of lakeKleifarvatn(Route 42) and at the foot ofSveifluhálshyaloclastiteridge. It is a geothermal high temperature area,[8]hydrothermal alterationhas led to a multicolored environment. Heresolfataras,fumaroles,mudpotsandhot springsare formed; the soil is coloured bright yellow, red, and green caused byironoxidation,sulfurandcalciteprecipitation. The sulfur deposits were mined in 1722–1728 and in the 19th century. The German scientistRobert Bunsenvisited the site in 1845 and, based on research there, proposed a hypothesis on formation ofsulfuric acidin nature.[15]
Also found in the area are theÖgmundarhraun[ˈœɣˌmʏntar̥ˌr̥œyːn]lava field from the 12th century as well as somePleistocenesubglacial mounds and formations likeHelgafell,SveifluhálsandTrölladyngja.
Geothermal activity
[edit]Some active geothermal high temperature areas are to be found in the system, especially atSeltún.Since 2009 repeated uplift episodes with earthquake swarms occurred, probably connected toigneous intrusionsand hydrothermal changes.[16]
See also
[edit]- Brennisteinsfjöllvolcanic system
- Geology of Reykjanes Peninsula
- Volcanism of Iceland
External links
[edit]General information
[edit]- Krýsuvík at"Catalogue of Icelandic Volcanoes".icelandicvolcanos.is.Retrieved2021-03-22.
- "Global Volcanism Program | Krýsuvík-Trölladyngja".Smithsonian Institution | Global Volcanism Program.Retrieved2021-03-22.
Volcano monitoring
[edit]- Icelandic Met Office (IMO). Earthquake Monitoring. Reykjanes Peninsula
- IMO. Aviation Color CodeArchived2014-08-26 at theWayback Machine
- Geologist Páll Einarsson explains geology and volcanism of Reykjanes Peninsula as well as the 2020 earthquake series which partially takes place within this volcanic system.RÚV.20 October 2020. (in Icelandic)
Tourism
[edit]References
[edit]- ^abThorvaldur Thordarson, Ármann Höskuldsson:Postglacial volcanism in Iceland. Jökull No. 58(2008).Retrieved 20 August 2020.
- ^abHersir, Gylfi Páll; Árnason, Knútur; Vilhjálmsson, Arnar Már; Saemundsson, Kristján; Ágústsdóttir, Þorbjörg; Friðleifsson, Guðmundur Ómar (2020-02-01)."Krýsuvík high temperature geothermal area in SW Iceland: Geological setting and 3D inversion of magnetotelluric (MT) resistivity data".Journal of Volcanology and Geothermal Research.391(106500). Elsevier: 1–26.doi:10.1016/j.jvolgeores.2018.11.021.Retrieved2023-12-29.
- ^[1]Thorvaldur Thordarson and Ármann Höskuldsson:Postglacial volcanism in Iceland, Jökull no. 58,2008. Retrieved 2 August 2020. (System no. 2 on the maps and tables)
- ^abcdefEinarsson, Sigmundur (2019)."Catalogue of Icelandic Volcanoes:Krýsuvík-Trölladyngja Alternative name: Krísuvík".Retrieved2 August2020.
- ^abc"Krýsuvík".Global Volcanism Program.Smithsonian Institution.
- ^"Fagradalsfjall".Volcano Discovery.
- ^Thor Thordarson, Armann Hoskuldsson:Iceland. Classic geology of Europe 3.Harpenden 2002, p. 70
- ^ab"17. Seltún - High temperature area with solfataras | Iceland Geosurvey".en.isor.is.Retrieved22 March2021.
- ^"Borhola við Seltún spýtti úr sér"[A borehole by Seltún spat out].mbl.is(in Icelandic). 8 November 2010.Retrieved22 March2021.
- ^"Krísuvík volcano (Iceland): intense seismic activity, more than 1000 quakes".volcanodiscovery.com.Retrieved5 October2021.
- ^"Home-page - Icelandic Meteorological Office".Icelandic Meteorological office.Archived fromthe originalon 11 October 2021.Retrieved11 October2021.
- ^abcdefghJónasson, Daníel Páll (2012).Hraunflæði á höfuðborgarsvæðinu. Saga hraunflæðis á svæðinu á nútíma og kortlagning mögulegra farvega til byggða.(BS ritgerð). Leiðbeinandi Ármann Höskuldsson(PDF)(Thesis) (in Icelandic). Líf- og umhverfisvísindadeild Háskóli Íslands.Retrieved12 August2020.
- ^Íslandshandbókin. Náttúra, saga og sérkenni.Reykjavík 1989, p. 82
- ^"Golf club Keilir, Hafnarfjörður".Retrieved17 August2020.
- ^"Krýsuvík – Seltún geothermal area".Wondermondo. 14 July 2012.
- ^Gudjónsdóttir, SR; Ilyinskaya, E.; Hreinsdóttir, S.; Bergsson, B.; Pfeffer, M.A.; Michalczewska, K.; Aiuppa, A.; Óladóttir, A.A (2020)."Gas emissions and crustal deformation from the Krýsuvík high temperature geothermal system, Iceland".Journal of Volcanology and Geothermal Research.391:106350.doi:10.1016/j.jvolgeores.2018.04.007.hdl:10447/347068.ISSN0377-0273.