Britain becomes an island
A glacial lake bursts through the chalk ridge at Dover and carves the English Channel in two catastrophic floods.
- When
- —
- Duration
- 290 thousand years
- Known to
- ± 30 thousand years
- Era
- Middle Pleistocene, Quaternary
During the Anglian, ice and the Weald-Artois chalk ridge dam a vast lake in the southern North Sea. Around 450,000 years ago the ridge fails, and the lake discharges through the breach at rates estimated in the millions of cubic metres per second, scouring a deep valley system with streamlined islands and plunge pools still visible on the Channel floor today. A second breach around 160,000 years ago completes the work. Britain's separation from the continent — geographically, biologically and eventually politically — begins with a dam failure.