Editing Storegga Slide

{{Short description|Prehistoric landslide off Norway}}
[[File:StoreggaFLCommonsZone.jpg|thumb|Map of ''Storegga Slides'']]

The three '''Storegga Slides''' ({{langx|no|Storeggaraset}}) are amongst the largest known [[submarine landslide]]s. They occurred at the edge of Norway's [[continental shelf]] in the [[Norwegian Sea]], approximately 6225–6170 [[Common Era|BCE]]. The collapse involved an estimated {{cvt|290|km|mi}} length of coastal shelf, with a total volume of {{cvt|3500|km3|cumi}} of debris, which caused a [[paleotsunami]] in the [[North Atlantic Ocean]].

==Description==
[[File:StoreggaFLCommonsZone2OK.jpg|thumb|The yellow numbers give the height of the tsunami wave as indicated by [[tsunamite]]s studied by researchers.<ref>[http://www.hse.gov.uk/research/othpdf/200-399/oth323.pdf P.C. Marrow, "Seismic Monitoring of the North Sea", Global Seismology Research Group, British Geological Society, HSE, 1992]</ref>]]
Storegga ([[Norwegian language|Norwegian]]: ''Great Edge'') is located at the edge of Norway's continental shelf in the Norwegian Sea, {{convert|100|km|mi|abbr=on}} north-west of the [[Møre og Romsdal|Møre]] coast. In around 6200 BCE, structural failures of the shelf caused three underwater [[landslide]]s, which triggered very large [[tsunami]]s in the North Atlantic Ocean. The collapses involved an estimated {{convert|290|km|mi|abbr=on}} length of coastal shelf, with a total volume of {{convert|3500|km3|cumi|abbr=on}} of debris.<ref name=stein>{{cite journal | first1 = S. | last1 = Bondevik | first2 = J. | last2 =Mangerud | first3 = S. | last3 = Dawson | first4 = A. | last4 = Dawson | first5 = Ø. | last5 = Lohne |date=5 August 2003 | title = Record-breaking Height for 8000-Year-Old Tsunami in the North Atlantic | journal = Eos, Transactions, American Geophysical Union | volume = 84 | issue = 31 | pages = 289, 293| doi=10.1029/2003EO310001 | bibcode=2003EOSTr..84..289B | hdl = 1956/729 | doi-access = free | hdl-access = free }}</ref> 

Based on [[carbon dating]] of plant material recovered from sediment deposited by the tsunamis, the latest incident occurred around 6225–6170 BCE.<ref>{{cite conference |author1=Bondevik, S |author2=Lovholt, F |author3=Harbitz, C |author4=Stormo, S |author5=Skjerdal, G | title=The Storegga Slide Tsunami – Deposits, Run-up Heights and Radiocarbon Dating of the 8000-Year-Old Tsunami in the North Atlantic | book-title=American Geophysical Union meeting | year=2006 | bibcode = 2006AGUFMOS34C..01B }}</ref><ref>{{cite journal |author1=Bondevik, S |author2=Stormo, SK |author3=Skjerdal, G | title=Green mosses date the Storegga tsunami to the chilliest decades of the 8.2 ka cold event | journal=Quaternary Science Reviews | volume=45 | year=2012 | pages=1–6 | doi=10.1016/j.quascirev.2012.04.020|bibcode=2012QSRv...45....1B }}</ref> In [[Scotland]], traces of the subsequent tsunami have been recorded, with deposited sediment being discovered in [[Montrose Basin]] and the [[Firth of Forth]] up to {{convert|29|km|mi|abbr=on}} inland and {{convert|4|m|ft|abbr=on}} above current normal tide levels.<ref name=brooks/>

==Possible mechanism==
The triggering mechanism is thought to have been an earthquake that induced a catastrophic expansion of [[methane clathrate]], a solid compound consisting of large amounts of methane suspended within a crystal water structure that forms in deep oceans under extremely high pressure. If removed from a high-pressure, low-temperature environment, one cubic metre of solid methane clathrate expands to 164 cubic metres of gaseous methane.<ref>{{cite journal|journal=Scientific American|first=Lisa|last=Margonellis|title=An Inconvenient Ice|publisher=Nature America|date =October 2014|volume=311|number=4|pages=82–89|doi=10.1038/scientificamerican1014-82|pmid=25314880|bibcode=2014SciAm.311d..82M}}</ref> If such an expansion occurred, it may have weakened the integrity of the surrounding rock sufficiently to trigger the slide.

A second theory states that over time, streams from melting glaciers had carried trillions of tons of sediment to the edge of the continental shelf, where it accumulated in many layers. In this case, a trigger such as an earthquake could have caused a large area of seafloor to collapse into the deep Norwegian sea, thus carrying the enormous volume of accumulated sediment along with it.<ref>[http://www.pnas.org/content/113/7/1675.full.pdf ''Skimming the surface of underwater landslides'' 2016]</ref>

==Impact on human populations==
[[File:Storegga tsunami deposits, Montrose basin (Maryton).jpg|thumb|Storegga tsunami deposits (grey upper layer), bracketed by peat (dark brown layers), taken at Maryton on the Montrose Basin, Scotland]]
At, or shortly before, the time of the Second Storegga Slide, a [[land bridge]] known to archaeologists and geologists as [[Doggerland]] linked [[Great Britain|Britain]], [[Denmark]] and the [[Netherlands]] across what is now the southern [[North Sea]].  This area is believed to have included a coastline of lagoons, marshes, mudflats and beaches, and to have been a rich hunting, fowling and fishing ground populated by [[Mesolithic]] human cultures.<ref>{{Cite web |url=https://humanities.exeter.ac.uk/archaeology/research/projects/title_89282_en.html |title=Bryony Coles, "Doggerland Project", University of Exeter Department of Archaeology |access-date=2014-05-04 |archive-date=2015-08-17 |archive-url=https://web.archive.org/web/20150817003759/http://humanities.exeter.ac.uk/archaeology/research/projects/title_89282_en.html |url-status=dead }}</ref><ref name=gaffney>[http://livebettermagazine.com/article/global-warming-and-lost-lands-understanding-the-effects-of-sea-level-rise/  Vincent Gaffney, "Global Warming and the Lost European Country"]</ref><ref>[http://www.channel4.com/programmes/time-team-specials/4od#3591277 Tony Robinson, "Britain's Stone Age Tsunami", ''Time Team specials'', Channel 4 Television, 30 May 2013]</ref>

Although Doggerland was permanently submerged through a gradual rise in sea level, it has been hypothesized that coastal areas of both Britain and mainland Europe, extending over areas which are now submerged, would have been temporarily inundated by a tsunami triggered by the Storegga Slide.  This event would have had a catastrophic impact on the Mesolithic population at the time.<ref>{{cite journal |last1=Bernhard Weninger |title=The catastrophic final flooding of Doggerland by the Storegga Slide tsunami |journal=Documenta Praehistorica |volume=35 |pages=1–24 |date=Dec 31, 2008 |doi=10.4312/dp.35.1 |url=http://sprint.clivar.org/soes/staff/ejr/Rohling-papers/2008-Weninger%20et%20al%20Documenta%20Praehistorica.pdf|archive-url=https://web.archive.org/web/20130325085427/http://sprint.clivar.org/soes/staff/ejr/Rohling-papers/2008-Weninger%20et%20al%20Documenta%20Praehistorica.pdf |archive-date=2013-03-25 |display-authors=etal|doi-access=free }}</ref><ref>{{cite news|last=Rincon|first=Paul|title=Prehistoric North Sea 'Atlantis' ht by 5m tsunami|url=https://www.bbc.com/news/science-environment-27224243|work=BBC News|date=May 2014|access-date=1 May 2014}}</ref><ref name="HillCollins2014">{{cite journal|last1=Hill|first1=Jon|last2=Collins|first2=Gareth S.|last3=Avdis|first3=Alexandros|last4=Kramer|first4=Stephan C.|last5=Piggott|first5=Matthew D.|title=How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?|journal=Ocean Modelling|volume=83|year=2014|pages=11–25|issn=1463-5003|doi=10.1016/j.ocemod.2014.08.007|bibcode=2014OcMod..83...11H|doi-access=free|hdl=10044/1/18934|hdl-access=free}}</ref> It is estimated that up to a quarter of the Mesolithic population of Britain lost their lives.<ref>{{cite news |title=How a giant tsunami devastated Britain's Atlantis |last=Keys |first=David |url=https://www.independent.co.uk/news/science/archaeology/tsunami-britain-atlantis-6200-bc-archaeology-a9622591.html |work=The Independent |date=16 July 2020}}</ref>

A 2021 study found that about {{Convert|370|miles|abbr=on|order=flip}} of Scotland's northern and eastern coastline were affected, with water encroaching {{Convert|18|miles|abbr=on|order=flip}} inland. With present-day populations and sea levels, a similar event today could devastate and destroy seafront and port areas of Arbroath, Stonehaven, Aberdeen, Inverness, Wick, and Montrose.<ref name=brooks>{{Cite news |title=Ancient tsunami could have wiped out Scottish cities today, study finds |last=Brooks |first=Libby |work=The Guardian |date=4 June 2021 |url= https://www.theguardian.com/world/2021/jun/04/ancient-tsunami-could-have-wiped-out-scottish-cities-today-study-finds}}</ref>

While the tsunami caused by the Second Storegga Slide would have been devastating for those within the run-in zone, ultimately the tsunami was neither universally catastrophic nor the reason behind the inundation of the last vestiges of Doggerland.<ref>{{Cite journal|last1=Walker|first1=James|last2=Gaffney|first2=Vincent|last3=Fitch|first3=Simon|last4=Muru|first4=Merle|last5=Fraser|first5=Andrew|last6=Bates|first6=Martin|last7=Bates|first7=Richard|date=2020|title=A great wave: the Storegga tsunami and the end of Doggerland?|journal=Antiquity|language=en|volume=94|issue=378|pages=1409–1425|doi=10.15184/aqy.2020.49|issn=0003-598X|doi-access=free|hdl=10454/18239|hdl-access=free}}</ref>

==Future slides==
Storegga has been thoroughly investigated as part of the preparation activities for the [[Ormen Lange (gas field)|Ormen Lange gas field]] off the coast of Norway. The prevalent conclusion is that the slide was caused by glacial deposits left behind after the previous [[ice age|glacial period]], making any recurrence only possible following a new glaciation.<ref name=stein/> After facts and arguments supporting this conclusion were published in 2004, the development of the Ormen Lange gas field was considered unlikely to increase the risk of triggering a new slide.<ref name=stein/>

==See also==
* [[Arctic methane release]]
* [[Tsunamis affecting the British Isles]]
* [[Submarine landslide#Prehistoric submarine landslides|Giant mass transport deposits]]

==References==
{{reflist|2}}

== Further reading ==
* {{Cite journal|last=Williams|first=Sarah C. P.|date=16 February 2016|title=News Feature: Skimming the surface of underwater landslides|journal=[[Proceedings of the National Academy of Sciences of the United States of America]]|volume=113|issue=7|pages=1675–78|doi=10.1073/pnas.1524012113|pmc=4763740|pmid=26884637|bibcode=2016PNAS..113.1675W|doi-access=free}}
*{{cite journal |last1=Walker |first1=James |last2=Gaffney |first2=Vincent |last3=Fitch |first3=Simon |last4=Muru |first4=Merle |last5=Fraser |first5=Andrew |last6=Bates |first6=Martin |last7=Bates |first7=Richard |title=A great wave: the Storegga tsunami and the end of Doggerland? |journal=Antiquity |date=2020|volume=94 |issue=378 |pages=1409–1425 |doi=10.15184/aqy.2020.49 |language=en |issn=0003-598X|doi-access=free |hdl=10454/18239 |hdl-access=free }}
*{{cite journal | last1=Woodroffe | first1=Sarah A. | last2=Hill | first2=Jon | last3=Bustamante-Fernandez | first3=Emmanuel | last4=Lloyd | first4=Jerry M. | last5=Luff | first5=Jake | last6=Richards | first6=Sarah | last7=Shennan | first7=Ian | title=On the varied impact of the Storegga tsunami in northwest Scotland | journal=Journal of Quaternary Science | date=2023 | volume=38 | issue=8 | pages=1219–1232 | issn=0267-8179 | doi=10.1002/jqs.3539| doi-access=free | bibcode=2023JQS....38.1219W }}

==External links==
* [https://www.bbc.co.uk/news/magazine-12244964  BBC: The moment Britain became an island, 14 February 2011]

{{Coord|64|52|N|1|18|E|display=title}}

[[Category:Historical geology]]
[[Category:Landslides in Norway]]
[[Category:Geology of Norway]]
[[Category:7th millennium BC]]
[[Category:Natural disasters in Scotland]]
[[Category:Tsunamis]]
[[Category:Norwegian Sea]]
[[Category:North Sea]]