display showing traffic in the strait in 2006 Most maritime traffic between the Atlantic Ocean and the North Sea and
Baltic 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 busiest
international seaways in the world, used by over 400 commercial vessels daily. In addition to the intensive north-east to south-west traffic, the strait is crossed from north-west to south-east by
ferries linking
Dover to
Calais and
Dunkirk. The predominant geology of both and of 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 – compacted remains of sea creatures and marine-
deposited, ground up calciferous rock/soil debris. The
Rhine (as the
Urstrom) flows northeast into the North Sea as the sea (covering most of the Netherlands) fell during the start of the first of the
Pleistocene Ice Ages. The new ice unusually 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 followed by further scouring became recognisably the
Short 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 the
last Ice Age. A deposit in
East Anglia marks the old
preglacial northward course of the Urstrom-Thames when it also drained
Doggerland. The deep sea floor east of
Lincolnshire and
East Yorkshire, connecting to the
Atlantic via the
Pentland Firth in the last glaciation (of over 300,000 years) is a condition for the relatively late cutting through of the Strait to the south. A 2007 study by British geoscientists
Sanjeev Gupta and
Jenny Collier 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 and
Scheldt flowed through the gap into the English Channel/Inlet, but the
Meuse and Rhine still flowed without any significant link to the inlet (such as today's
IJssel distributary supports). In a second flood about 225,000 years ago supported by glaciers extending from areas then land such as the
Zuiderzee, 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 underwater holes in the Channel floor, "100 m 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, around 6,500–6,200 BCE. The Lobourg strait, the deepest part the strait, runs its wide slash on a NNE–SSW axis. Nearer to the French coast than to the English, it borders the
Varne sandbank (shoals) where it plunges to and further south, the Ridge bank (shoals) (French name "
Colbart") with a maximum depth of . == Marine wildlife ==