1918 eruption of Katla

Volcanic event in Iceland March 2020 1918 eruption of Katla Katla 1918.jpg 280px Coloured in photo of Katla volcano erupting through Mýrdalsjökull ice cap in 1918 1918 10 12 y 1918 11 04 y Katla hydromagmatic basaltic eruptionLarsen 2010 Introduction Southern Region, Iceland 63 38 N 19 03 W dms inline,title type:event_region:IS 4 yes center 270 350 -18.8 63.64 8 [,] Approximate areas significantly affected by 1918 Katla eruption. Key: #f836fd Vents #f4e79a 10 cm tephra isopach #faf6c0 5 cm tephra isopach which is relevant due to fluoride content and damage to agriculture #9db2b3 First phase jökulhlaup #7d9d9d Combined first and second phase jökulhlaup. Jökulhlaup subsurface catchment at the time is not shown. #e3e1f7 Twenty-first century glacier surface catchmentsThe jökulhlaup subsurface catchment is defined by the southern caldera rim and this eruptions vents were just north of this (see Katla for caldera maps). Jökulhlaup flow was initially on the surface as well as subsurface to the 1918 glaciers before becoming solely subsurface.Larsen Janebo Guðmundsson 2021 p10-14 Some of the ice below the caldera rim is locked in until it melts so does not contribute to usual outlet glacier catchments. More detail is available by clicking to enlarge map that enables mouse-over. 3 farms abandoned, depopulation Between October and November 1918 a series of jökulhlaups, a type of glacial outburst flood, following an eruption of Katla in Iceland caused significant property damage and disruption in Iceland with local depopulation. Background Katla is an active volcano in the south-east of Iceland. It is covered by the Mýrdalsjökull ice cap. Over 300 basaltic eruptions may have occurred in the Holocene.Larsen 2010 Summary The 1918 eruption was amongst the largest 20th century eruptions in Iceland.Larsen Janebo Guðmundsson 2021 p3 Geology This was a typical hydromagmatic basaltic eruption below the Mýrdalsjökull ice cap, although explosive silicic eruptions are known from the volcano.Larsen 2010 Introduction The eruption produced a bulk volume of tephra of up to 1.2 km3 and eruption cloud height of at least 14 km.Larsen Janebo Guðmundsson 2021 p1Larsen Guðmundsson 2019 Detailed Description:4. Eruption history and pattern: Frequency and duration of eruptions The total dry rock equivalent erupted was up to 0.9 km3.Larsen Janebo Guðmundsson 2021 p17Dry rock equivalent can not be assumed to be the same as dense-rock equivalent the more usual terminology. Events Seismic signs of unrest are reported to have started at about 11:30am local time on 12 October 1918 with ripples observed in a bucket of water and at about 1pm an earthquake was felt at Vík í Mýrdal.Larsen Janebo Guðmundsson 2021 p4 Observers in the Vestmannaeyjar Islands mention steam from the volcano about an hour before the eruptive column was sighted there.Larsen Janebo Guðmundsson 2021 p3The detailed sequence of events can only be speculated upon as they were not subjected to modern real time observation techniques. Timing was mainly based on where in the sky the sun was which at the time split daylight into 8 periods. The observation of prior steam is consistent with geothermal melting of ice before the eruption so one possibility is that the first phase jökulhlaup by relief of pressure triggered the major eruption. Against this is the observation of glacial surface jökulhlaup flow in the first phase jökulhlaup. There is no preferred interpretation in the literature. See the article jökulhlaup for more detail on this and other possibilities. The eruption column and initial flood were first noted locally at about 3pm taking observers by surprise, and with their immediate realisation that they would have to flee to high ground.Gísladóttir Bird Pagneux 2021 p76 Some described the evening and night after the initial eruption as pitch black with inability to see their hands due to the tephra fall,Gísladóttir Bird Pagneux 2021 p80 and also described "lightning was so severe that it looked like the middle of the day even though it was night."Gísladóttir Bird Pagneux 2021 p84 They could hear the surrounding flood waters but not see the flood.Gísladóttir Bird Pagneux 2021 p80 Tephra fall was very intense overnight on the 12th, and lasted through to the 14th. A second intense tephra fall occurred between 22 and 24 October. The final light tephra fall was on 1 November 1918. Larsen Janebo Guðmundsson 2021 p5-8 Eruptive activity is assumed to have continued until 18 October when the plume as not observed. On the 20th twin plumes, suggesting at least two separate vents were noted, and the plume was described two days later as more magnificent than before.Larsen Janebo Guðmundsson 2021 p4 The last day that steam was seen arising was 4 November.Larsen Janebo Guðmundsson 2021 p5 Jökulhlaups The jökulhlaup that inundated the largest area, with a peak flow of 300000 m3/s, occurred within minutes of the first eruptive events according to those nearby.Gísladóttir Bird Pagneux 2021 p82Larsen Janebo Guðmundsson 2021 p11 This first phase jökulhlaup lasted about 3 hours but was followed about 2 hours later by a more limited in area second phase jökulhlaup, that delivered much ice and sediment to the Mýrdalssandur flood plain east of the Múlakvísl river. This second phase jökulhlaup lasted about 5 hours. The flood flowed down the flood plain at a velocity of 20 km/hour and resulted in the temporary extension of southern coastline of Iceland by 4 km into the sea.Larsen Janebo Guðmundsson 2021 p13–14 Smaller jökulhlaups occurred from the 14th onward to the 18th on essentially a daily basis in the same area as the second phase jökulhlaup, but flooding had stopped by 26 October when the flood plain had mainly dried out. A jökulhlaup occurred on 28 October and after the eruption had stopped on 26 November.Larsen Janebo Guðmundsson 2021 p13–14 Impact Near Álftaver three farms were abandoned for good, and a local population of 129 people was reduced a year later by 17% and in 1920 by 23%.Gísladóttir Bird Pagneux 2021 p74 A bridge was swept away and communications disrupted across the Mýrdalssandur until the last jökulhlaup related to the eruption.Larsen Janebo Guðmundsson 2021 p13–14 Four farms (including those 3 abandoned) were seriously damaged by tephra falls and seventeen farms were damaged.Larsen Janebo Guðmundsson 2021 p11 Trout fishing was disrupted up to 70 km to the north.Larsen Janebo Guðmundsson 2021 p11 Notes References Citations 2 Katla 3720300 Eruptions 2024-06-22 Sources Catalogue of Icelandic Volcanoes:Katla Alternative name: Mýrdalsjökull Guðrún Larsen Magnús T. Guðmundsson https://icelandicvolcanoes.is/?volcano=KAT 22 June 2022 2019 Larsen G. Janebo M. Guðmundsson M.T. 2021 The explosive basaltic Katla eruption in 1918, south Iceland I: Course of events, tephra fall and flood routes 71 Jökull 1–20 0449-0576 10.33799/jokull2021.71.001 20.500.11815/3031 free Gísladóttir G. Bird D. Pagneux E. 2021 What can we learn from previous generations? Álftaver’s experience of the 1918 Katla eruption Jökull 71 71–90 10.5194/egusphere-egu22-12884 2022EGUGA..2412884G free http://www.earthice.hi.is/page/ies_katla1918 The Katla eruption in 1918 Institute of Earth Sciences University of Iceland 2024-06-23 dead http://wayback.vefsafn.is/wayback/20051102000000/http://www.earthice.hi.is/page/ies_katla1918 2 November 2005 Note this source has information updated by later studies. 3 Katla: Tephrochronology and Eruption History Developments in Quaternary Sciences 13 2010 23–49 Guðrún Larsen 10.1016/S1571-0866(09)01303-7 Note this source has information updated by later studies, some by same author. Category:Katla (volcano) Category:20th-century volcanic events Category:Volcanic eruptions in Iceland Category:Jökulhlaups Category:1910s disasters in Denmark