Catastropic Flooding of the English Channel
A catastrophic megaflood separated Britain from France hundreds of thousands of years ago, changing the course of British history
The study has revealed spectacular images of a huge valley tens of kilometres wide and up to 50 metres deep carved into chalk bedrock on the floor of the English Channel.
We analysed a new regional bathymetric map of part of the English Channel derived from a compilation of both single- and multi-beam sonar data, which shows the morphology of the seabed in unprecedented detail. We observe a large bedrock-floored valley that contains a distinct assemblage of landforms, including streamlined islands and longitudinal erosional grooves, which are indicative of large-scale subaerial erosion by high-magnitude water discharges. Our observations support the megaflood model, in which breaching of a rock dam at the Dover Strait instigated catastrophic drainage of a large pro-glacial lake in the southern North Sea basin. This flow was one of the largest recorded megafloods in history and could have occurred 450,000 to 200,000 years ago. We suggest that megaflooding provides an explanation for the permanent isolation of Britain from mainland Europe during interglacial high-sea-level stands. The breaching likely affected patterns of early human occupation in Britain by creating a barrier to migration which possibly explains the complete absence of humans in Britain 100,000 years ago. The breach of the ridge, and subsequent flooding, also may have initiated the large-scale reorganisation of the river drainages in north-west Europe by re-routing the combined Rhine-Thames River through the English Channel to form the Channel River.
Gupta, S., Collier, J.S., Palmer-Felgate, A., & Potter G 2007. Catastropic flooding origin of the shelf valley systems in the English Channel, Nature, Vol 448, 342-345. PDF
UK Hydrographic Office (UKHO) and the Maritime Coastguard Agency (MCA)
Data collected by the MCA and archived by the UKHO was originally sourced for civil safety at sea.