Strait of Dover
The Strait of Dover or Dover Strait (French: Pas de Calais French pronunciation: [pɑ d(ə) kalɛ] - Strait of Calais)[1] is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and the North Sea, and separating Great Britain from continental Europe. The shortest distance across the strait, at approximately 20 miles (32 kilometres), is from the South Foreland, northeast of Dover in the English county of Kent, to Cap Gris Nez, a cape near to Calais in the French département of Pas-de-Calais. Between these points lies the most popular route for cross-channel swimmers.[2] The entire strait is within the territorial waters of France and the United Kingdom, but a right of transit passage under the United Nations Convention on the Law of the Sea allows vessels of other nations to move freely through the strait.[3][4][5]
Dover Strait
North Sea–English Channel (Atlantic Ocean)
France
United Kingdom
20 miles (32 km)
150 feet (46 m)
68 m (223 ft)
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 the White Cliffs of Dover from the French coastline and shoreline buildings on both coastlines, as well as lights on either coastline at night, as in Matthew Arnold's poem "Dover Beach".
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:
The strong tidal currents of the strait at depth slow around its rocky masses as these stimulate countercurrents and deep, calm pockets where many species can find shelter.[13] In these calmer lee zones, the water is clearer than in the rest of the strait; thus algae can grow despite the 46 m (151 ft) average depth.[14] They help increase diversity in the local species – some of which are endemic to the strait.[14] Moreover, this is a transition zone for the species of the Atlantic Ocean and those of the southern part of the North Sea.[14]
This mix of various environments promotes a wide variety of wildlife.[14]
The Ridens de Boulogne, a 10–20 m (33–66 ft) deep[15] rocky shoal, partially sand-capped,15 nmi (28 km; 17 mi) west of Boulogne, boasts the highest profusion of maerl in the strait.[15]
Thus some 682 km2 (263 sq mi) of the strait is classified as a Natura 2000 protection zone named Ridens et dunes hydrauliques du Pas de Calais (Ridens and sub-aqueous dunes of the Dover Strait). This includes the sub-aqueous dunes of Varne, Colbart, Vergoyer and Bassurelle, the Ridens de Boulogne, and the Lobourg channel which provides calmer and clearer waters due to its depth reaching 68 m (223 ft).[16]