On a clear day, it is possible to see the opposite coastline of England from France and vice versa with the naked eye, with the most famous and obvious sight being theWhite Cliffs of Dover from the French coastline and shoreline buildings on both coastlines, as well as lights on either coastline at night, as inMatthew Arnold's poem "Dover Beach".
Most maritime traffic between the Atlantic Ocean and the North Sea andBaltic Sea passes through the Strait of Dover, rather than taking the longer and more dangerous route around the north of Scotland. The strait is one of the busiestinternational seaways in the world, used by over 400 commercial vessels daily.[3] This has made traffic safety a critical issue, withHM Coastguard and theMaritime Gendarmerie maintaining a 24-hour watch over the strait and enforcing a strict regime ofshipping lanes.[5]
In addition to the intensive north-east to south-west traffic, the strait is crossed from north-west to south-east byferries linkingDover toCalais andDunkirk.[3] Until 1994 these provided the only route across it except for air transport. TheChannel Tunnel now provides an alternative route, crossing beneath the strait at an average depth of 45 m (148 ft) below the seabed.
The town of Dover gives its name to one of the sea areas of the BritishShipping Forecast.
Map showing the hypothetical extent of Doggerland (c. 10,000 BCE), which provided a land bridge between Great Britain and continental Europe
The formation of strait was through scouring byerosion. It had for many millennia (since the last warminterglacial) been a land bridge that linked theWeald in Great Britain to theBoulonnais in thePas de Calais. Though pitted by troughs and rivers, the English Channel was almost mainly land at the height of the last ice age.[6] The predominant geology of both and of the seafloor ischalk. Although somewhat resistant to erosion, erosion of both coasts has created the famouswhite cliffs of Dover in the UK and theCap Blanc Nez in France. TheChannel Tunnel was bored through solid chalk – compacted remains of sea creatures and marine-deposited, ground up calciferous rock/soil debris.
TheRhine (as theUrstrom) flows northeast into the North Sea as the sea (covering most of the Netherlands) fell during the start of the first of thePleistoceneIce Ages. The new ice unusually created a dam fromScandinavia to Scotland, and the Rhine, combined with theThames and drainage from much ofnorth Europe, created a vast lake behind the dam, which eventually spilled over the Weald into the English Channel. This overflow followed by further scouring became recognisably theShort Straits (an alternative name for this strait) about 425,000 years ago. A narrow deep channel along the middle of the strait is the remnants of the main (summer) outflow of the northern Ustrom glacial lake (a collect for other then-seasonal rivers, in winter iced up, such as the Thames and Weser) in thelast Ice Age. A deposit inEast Anglia marks the oldpreglacial northward course of the Urstrom-Thames when it also drainedDoggerland. The deep sea floor east ofLincolnshire andEast Yorkshire, connecting to theAtlantic via thePentland Firth in the last glaciation (of over 300,000 years) is a necessary pre-condition for the relatively late cutting through of the Strait to the south.
NASA Satellite image December 2002
Likewise, a 2007 study[7][8] concluded that the Strait was formed by erosion caused by two major floods. The first was about 425,000 years ago, when an ice-dammed lake in the southern North Sea overflowed and broke the Weald-Artois (Boulonnais) chalk range in a catastrophic erosion and flood event. Consequently the ice-age-muted flows from the Thames andScheldt flowed through the gap into the English Channel/Inlet, but theMeuse and Rhine still flowed without any significant link to the inlet (such as today'sIJssel distributary supports). In a second flood about 225,000 years ago supported by glaciers extending from areas then land such as theZuiderzee, the Meuse and Rhine were ice-dammed into a lake that broke catastrophically through a high weak barrier (perhaps chalk, or anend-moraine left by the ice sheet). Both floods cut massive flood channels in the dry bed of the English Channel, somewhat like theChanneled Scablands or theWabash River in the USA.A further update in 2017 attributed a series of previously described underwater holes in the Channel floor, "100m deep" and in places "several kilometres in diameter", to lake water plunging over a rock ridge causing isolated depressions orplunge pools.[9]The melting ice and rising sea levels submergedDoggerland, the area linking Britain to France, around 6,500–6,200 BCE.
The Lobourg strait, the deepest part the strait, runs its 6 km (4 mi)wide slash on a NNE–SSW axis. Nearer to the French coast than to the English, it borders theVarne sandbank (shoals) where it plunges to 68 m (223 ft) and further south, the Ridge bank (shoals) (French name "Colbart"[10]) with a maximum depth of 62 m (203 ft).[11]
The depth of the strait varies between 68 m (223 ft) at the Lobourg strait and 20 m (66 ft) at the highest banks. The seabed forms successions of three habitats:
rocky zones relatively deserted by ships wanting to spare their nets
The strong tidal currents of the strait at depth slow around its rocky masses as these stimulatecountercurrents and deep, calm pockets where many species can find shelter.[12] In these calmer lee zones, the water is clearer than in the rest of the strait; thusalgae can grow despite the 46 m (151 ft) average depth.[13] They help increase diversity in the local species – some of which areendemic to the strait.[13] Moreover, this is a transition zone for the species of the Atlantic Ocean and those of the southern part of the North Sea.[13]
This mix of various environments promotes a wide variety of wildlife.[13]
TheRidens de Boulogne, a 10–20 m (33–66 ft) deep[14] rocky shoal, partially sand-capped,15 nmi (28 km; 17 mi) west ofBoulogne, boasts the highest profusion ofmaerl in the strait.[14]
Thus some 682 km2 (263 sq mi) of the strait is classified as aNatura 2000 protection zone namedRidens et dunes hydrauliques du Pas de Calais (Ridens andsub-aqueous dunes of the Dover Strait). This includes thesub-aqueous dunes of Varne, Colbart, Vergoyer and Bassurelle, theRidens de Boulogne, and the Lobourg channel which provides calmer and clearer waters due to its depth reaching 68 m (223 ft).[15]
In the late 17th century during the "Little Ice Age", there were reports of severe winter ice in the English Channel[16][17] and Strait of Dover, including a case in 1684 of only aleague of open water remaining between Dover and Calais.[18]
^Crystal, David, ed. (1999). "English Channel".Cambridge Paperback Encyclopedia (3rd ed.). Cambridge University Press. p. 1080.ISBN978-0521668002.
^López Martín, Ana G. (2010).International Straits: Concept, Classification and Rules of Passage (Illustrated ed.). Springer Science & Business Media. p. 95 & 102.ISBN9783642129063.
^Van Dyke, Jon M. (2009). "Transit Passage Through International Strait". In Chircop, Aldo; McDorman, Ted; Rolstons, Susan (eds.).The Future of Ocean Regime-Building. Brill (1618). pp. 175–232.ISBN978-9004172678.
