Editing English Channel (section)

=== Geological origins ===
[[File:Weichsel-Würm-Glaciation.png|thumb|Europe during the [[Last Glacial Maximum]] ca. 20,000 years ago]]
The full English Channel connecting the [[North Sea]] to the [[Western Atlantic]] via the [[Strait of Dover]] is of geologically recent origin, having formed late in the [[Pleistocene]] period.<ref>{{Cite encyclopedia |title=English Channel {{!}} channel, Europe |encyclopedia=Encyclopædia Britannica |url=https://www.britannica.com/place/English-Channel |access-date=16 May 2017 |language=en |archive-url=https://web.archive.org/web/20170403222035/https://www.britannica.com/place/English-Channel |archive-date=3 April 2017 |url-status=live}}</ref> The English Channel first developed as an arm of the Atlantic Ocean during the [[Pliocene]] period (5.3-2.6 million years ago) as a result of differential [[tectonic uplift]] along pre-existing tectonic weaknesses during the [[Oligocene]] and [[Miocene]] periods. During this early period, the Channel did not connect to the North Sea,<ref>{{Cite journal |last1=Lagarde |first1=J. L. |last2=Amorese |first2=D. |last3=Font |first3=M. |last4=Laville |first4=E. |last5=Dugué |first5=O. |date=March 2003 |title=The structural evolution of the English Channel area |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.744 |journal=Journal of Quaternary Science |language=en |volume=18 |issue=3–4 |pages=201–213 |doi=10.1002/jqs.744 |bibcode=2003JQS....18..201L |issn=0267-8179}}</ref> with [[Great Britain|Britain]] and [[Ireland]] remaining part of [[continental Europe]], linked by an unbroken [[Weald-Artois Anticline|Weald–Artois anticline]], a ridge running between the Dover and Calais regions. During Pleistocene glacial periods this ridge acted as a natural dam holding back a large freshwater [[pro-glacial lake]] in the [[Doggerland]] region, now submerged under the [[North Sea]]. During this period, the North Sea and almost all of the British Isles were covered by ice. The lake was fed by meltwater from the Baltic and from the Caledonian and Scandinavian [[ice sheet]]s that joined to the north, blocking its exit. The sea level was about {{convert|120|m|ft|abbr=on}} lower than it is today. Then, between 450,000 and 180,000&nbsp;years ago, at least two catastrophic [[glacial lake outburst flood]]s breached the Weald–Artois anticline. These contributed to creating some of the deepest parts of the channel such as [[Hurd's Deep]].

The first flood of 450,000 years ago  would have lasted for several months, releasing as much as one million cubic metres of water per second.<ref name="Gupta Nature">{{Cite journal |last1=Gupta |first1=Sanjeev |last2=Jenny S. Collier, Andy Palmer-Felgate & Graeme Potter |last3=Palmer-Felgate |first3=Andy |last4=Potter |first4=Graeme |year=2007 |title=Catastrophic flooding origin of shelf valley systems in the English Channel |journal=[[Nature (journal)|Nature]] |volume=448 |issue=7151 |pages=342–345 |bibcode=2007Natur.448..342G |doi=10.1038/nature06018 |pmid=17637667 |s2cid=4408290}}
*{{cite news |author=Dave Mosher |date=18 July 2007 |title=Why the rift between Britain and France? |work=[[NBC News]] |url=https://www.nbcnews.com/id/wbna19833064}}</ref><ref name="PhysToday">{{Cite journal |last=Schwarzschild |first=Bertram |date=September 2007 |title=Sonar mapping suggests that the English Channel was created by two megafloods |url=http://www.qpg.geog.cam.ac.uk/research/projects/englishchannelfloods/physicstoday.pdf |url-status=live |journal=Physics Today |volume=60 |issue=9 |pages=24–27 |bibcode=2007PhT....60i..24S |doi=10.1063/1.2784673 |archive-url=https://web.archive.org/web/20111002162907/http://www.qpg.geog.cam.ac.uk/research/projects/englishchannelfloods/physicstoday.pdf |archive-date=2 October 2011 |access-date=27 April 2010}}</ref> The flood started with large but localised waterfalls over the ridge, which excavated depressions now known as the ''Fosses [[Louis Dangeard|Dangeard]]''. The flow eroded the retaining ridge, causing the rock dam to fail and releasing lake water into the Atlantic. After multiple episodes of changing sea level, during which the ''Fosses Dangeard'' were largely infilled by various layers of sediment, another catastrophic flood some 180,000 years ago carved a large bedrock-floored valley, the [[Lobourg Channel]], some 500 m wide and 25 m deep, from the southern North Sea basin through the centre of the [[Straits of Dover]] and into the English Channel.<ref name="PhysToday" /> It left streamlined islands, longitudinal erosional grooves, and other features characteristic of catastrophic [[megaflood]] events, still present on the sea floor and now revealed by high-resolution sonar.<ref>{{Cite journal |last1=Gupta |first1=Sanjeev |last2=Collier |first2=Jenny S. |last3=Garcia-Moreno |first3=David |last4=Oggioni |first4=Francesca |last5=Trentesaux |first5=Alain |last6=Vanneste |first6=Kris |last7=De Batist |first7=Marc |last8=Camelbeeck |first8=Thierry |last9=Potter |first9=Graeme |last10=Van Vliet-Lanoë |first10=Brigitte |last11=Arthur |first11=John C. R. |year=2017 |title=Two-stage opening of the Dover Strait and the origin of island Britain |journal=Nature Communications |volume=8 |pages=15101 |bibcode=2017NatCo...815101G |doi=10.1038/ncomms15101 |pmc=5382280 |pmid=28375202}}</ref><ref>{{Cite journal |last1=Gupta |first1=Sanjeev |last2=Collier |first2=Jenny S. |last3=Palmer-Felgate |first3=Andy |last4=Potter |first4=Graeme |year=2007 |title=Catastrophic flooding origin of shelf valley systems in the English Channel |journal=Nature |volume=448 |issue=7151 |pages=342–345 |bibcode=2007Natur.448..342G |doi=10.1038/nature06018 |pmid=17637667 |s2cid=4408290}}</ref><ref>{{Cite web |date=19 July 2007 |title=Catastrophic Flooding Changed the Course of British History |url=https://www.sciencedaily.com/releases/2007/07/070718140833.htm |url-status=live |archive-url=https://web.archive.org/web/20170703151736/https://www.sciencedaily.com/releases/2007/07/070718140833.htm |archive-date=3 July 2017 |access-date=28 February 2018 |website=Science Daily}}</ref> Through the scoured channel passed a river, the [[Channel River]], which drained the combined [[Rhine]] and [[Thames]] westwards to the Atlantic.

The flooding destroyed the ridge that connected Britain to [[continental Europe]], although a land connection across the southern [[North Sea]] would have existed intermittently at later times when periods of [[glaciation]] resulted in lowering of sea levels.<ref>{{Cite web |last=Bryony Coles |title=The Doggerland project |url=http://humanities.exeter.ac.uk/archaeology/research/projects/title,89282,en.html |url-status=dead |archive-url=https://web.archive.org/web/20200606132746/http://humanities.exeter.ac.uk/archaeology/research/projects/title_89282_en.html |archive-date=6 June 2020 |access-date=3 January 2011 |publisher=University of Exeter}}</ref>

During [[interglacial]] periods (when sea levels were high) between the initial flooding 450,000 years ago until around 180,000 years ago, the Channel would still have been separated from the North Sea by a land bridge to the north of the Strait of Dover (the Strait of Dover at this time formed part of a [[estuary]] fed by the Thames and [[Scheldt]]), restricting interchange of marine fauna between the Channel and the North Sea (except perhaps by occasional overtopping). During the [[Last Interglacial|Last Interglacial/Eemian]] (115–130,000 years ago) the connection between the North Sea and the English Channel was fully open as it is today, resulting in Britain being an island during this interval, before lowered sea levels reconnected it to the continent during the [[Last Glacial Period]].<ref>{{Cite journal |last1=Hijma |first1=Marc P. |last2=Cohen |first2=Kim M. |last3=Roebroeks |first3=Wil |last4=Westerhoff |first4=Wim E. |last5=Busschers |first5=Freek S. |date=January 2012 |title=Pleistocene Rhine–Thames landscapes: geological background for hominin occupation of the southern North Sea region |url=https://onlinelibrary.wiley.com/doi/10.1002/jqs.1549 |journal=Journal of Quaternary Science |language=en |volume=27 |issue=1 |pages=17–39 |doi=10.1002/jqs.1549 |bibcode=2012JQS....27...17H |issn=0267-8179}}</ref> From the end of the Last Glacial Period, to the beginning of the Holocene rising sea levels again resulted in the unimpeded connection between the North Sea and the English Channel resuming due to the sinking of [[Doggerland]], with Britain again becoming an island.<ref>{{Cite journal |last1=Bicket |first1=Andrew |last2=Tizzard |first2=Louise |date=December 2015 |title=A review of the submerged prehistory and palaeolandscapes of the British Isles |url=https://linkinghub.elsevier.com/retrieve/pii/S0016787815000978 |journal=Proceedings of the Geologists' Association |language=en |volume=126 |issue=6 |pages=643–663 |doi=10.1016/j.pgeola.2015.08.009|bibcode=2015PrGA..126..643B }}</ref>