| Summary: | The island of Britain is surrounded by a ‘moat’ of water, of which the English Channel and the North Sea are two major components. This talk described some major events that occurred to shape these seaways and, in particular, the evidence preserved on the Channel seabed. Here a system of valleys occurs that was carved by the westward-flowing Channel River. At its maximum in the last glacial period this river was larger than any other river in Europe today. It carried water not only from the rivers currently entering the Channel, but also from rivers flowing into the southern North Sea. Today the Holocene is characterised by limited glaciation and therefore high sea level. However, for much of the time, global sea level was lower, exposing shallow areas as dry land. Throughout the last 2–3Ma, the build-up and decay of ice sheets on the continents have driven spectacular changes of global sea level. Driven by climatic fluctuations, these sea-level changes resulted in cycles of emergence and submergence of the Channel floor. About 500,000 years ago the English Channel and North Sea were flooded, as they are today, but unlike today there was a substantial land barrier, the Weald–Artois ridge, that linked Britain to the European continent. During cold periods up to 500,000 years ago the two seas were drained by separate river systems: the Channel River, aligned along the Channel basin’s axis, drained towards the Atlantic Ocean, while in the North Sea the major rivers flowed northward. Although there were earlier events, the first major extension of a continental-scale ice sheet into lowland central Europe and Britain occurred c. 450,000 years ago (the Anglian advance). Critically, this ice advanced across the emergent North Sea floor from the mountains of southern Scandinavia and Scotland, blocking the northward-flowing rivers and causing an immense glacial lake to develop in the basin south of the ice front. Once dammed, the water that continued flowing from most of western Europe’s rivers caused the lake level to ...
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