Why does the English Channel narrow toward the Strait of Dover?

The English Channel does not narrow toward the Strait of Dover due to a specific active geological process; rather, its tapering shape is a result of the region's long-term structural evolution and the history of sea-level changes.12

The contemporary English Channel formed through complex structural downfolding that began approximately 40 million years ago. The channel's current configuration is the result of rising sea levels following the last glacial period. Until about 8,000 years ago, a land bridge existed across what is now the Strait of Dover, connecting England to the European continent. As the ice sheets melted and global sea levels rose, this land bridge was submerged, creating the narrow passage that marks the junction between the English Channel and the North Sea. Consequently, the channel's width gradually decreases from 112 miles (180 km) at its western mouth to a minimum of about 21 miles at the strait.132