page_title: Strait of Dover
section_title: Geological formation
hierarchical_section_title: Strait of Dover / Geological formation
caption_attribution_description: NASA MODIS satellite imagery of the Strait of Dover, the narrowest part of the English Channel.
context_page_description: The Strait of Dover or Dover Strait, historically known as the Dover Narrows, is the strait at the narrowest part of the English Channel, marking the boundary between the Channel and North Sea, separating Great Britain from continental Europe. The shortest distance across the strait, 33.3 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. The entire strait is within the territorial waters of France and the United Kingdom, but a right of transit passage under the UNCLOS exists allowing unrestricted shipping.
  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".
context_section_description: The strait is believed to have been created by the erosion of a land bridge that linked the Weald in Great Britain to the Boulonnais in the Pas de Calais. The predominant geology on both the British and French sides and on the seafloor is chalk. Although somewhat resistant to erosion, erosion of both coasts has created the famous white cliffs of Dover in the UK and the Cap Blanc Nez in France. The Channel Tunnel was bored through solid chalk.
  The Rhine (as the Urstrom) flowed northwards into the North Sea as the sea level fell during the start of the first of the Pleistocene Ice Ages. The ice created a dam from Scandinavia to Scotland, and the Rhine, combined with the Thames and drainage from much of north Europe, created a vast lake behind the dam, which eventually spilled over the Weald into the English Channel. This overflow channel became the Strait of Dover about 425,000 years ago. A narrow deep channel along the middle of the strait was the bed of the Rhine in the last Ice Age. A geological deposit in East Anglia marks the old preglacial northward course of the Rhine.
  A 2007 study concluded that the English Channel 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 chalk range in a catastrophic erosion and flood event. Afterwards, the Thames and Scheldt flowed through the gap into the English Channel, but the Meuse and Rhine still flowed northwards. In a second flood about 225,000 years ago the Meuse and Rhine were ice-dammed into a lake that broke catastrophically through a high weak barrier (perhaps chalk, or an end-moraine left by the ice sheet). Both floods cut massive flood channels in the dry bed of the English Channel, somewhat like the Channeled Scablands or the Wabash 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 or plunge pools.
  The melting ice and rising sea levels submerged Doggerland, the area linking Britain to France 6,500–6,200 BCE.
  The Lobourg strait, a major feature of the strait's seafloor, runs its 6 km (4 mi) wide slash on a NNE–SSW axis. Nearer to the French coast than to the English coast, it runs along the Varne sandbank where it plunges to 68 m (223 ft) at its deepest, and along the latter's south-east neighbour the Ridge bank (French name "Colbart") with a maximum depth of 62 m (203 ft).
caption: NASA Satellite image
  December 2002
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