French Pas de Calais ancient Fretum Gallicum.
Channel separating southeastern England from northwestern France.
Connecting the English Channel with the North Sea , it is about 20 mi (32 km) wide at its narrowest point. Lined on the British side with the famous White Cliffs, which are composed of soft chalk, it is one of the world's busiest seaways; its chief ports include Dover and Folkestone in England and Calais and Boulogne in France. It was the scene of several historic naval battles, including the repulse by the English of the Spanish Dunkirk Evacuation crossed to Dover in 1940.