Strait of Dover - Geological Formation

Geological Formation

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 sea floor is chalk. Although somewhat resistant to erosion, erosion of both coasts has created the famous white cliffs of Dover in 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 was gradually widened and deepened into the Strait of Dover. A narrow deeper channel along the middle of the strait was the bed of the Rhine in the last Ice Age. In East Anglia there is a geological deposit that marks the old preglacial northward course of the Rhine.

A 2007 study concluded 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.