This lecture has been cancelled because of the coronavirus outbreak. We hope to reschedule it for autumn 2020.
Professor Jenny Collier, Imperial College, London
For much of our pre-history, a permanent land bridge existed between Britain and France at the Dover Strait. How and when it was removed, however, was previously unknown. 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 observed 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 (see artist’s impression on front cover) 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. et al. 2007. Catastrophic flooding origin of the shelf valley systems in the English Channel, Nature, 448, pp. 342-345.
Collier, J.S. et al. 2015. Streamlined islands and the English Channel megaflood hypothesis, Global & Planetary Change, 135, pp. 190-206.
Gupta S., Collier J.S. et al. 2017. Two-stage opening of the Dover Strait and the origin of island Britain, Nature Communications, 8.
Collier, J.S. 2017: A megaflood in the English Channel. Astronomy & Geophysics, 58, 2.38-2.42.
Following her PhD at Cambridge, Jenny undertook post-doctoral studies and lecturing duties at Oxford, Leeds, Cambridge and Imperial College. She was appointed a senior lecturer in marine geophysics at Imperial in 2002, and became a professor in 2018. She is a former President of the British Geophysical Society.