Rapid changes may happen by huge lakes breaking through into seas. This has happened on a number of occasions. When the latest ice age was ending, melting caused huge lakes in central North America. This eventually broke through into the Atlantic. Melting ice in the North Sea are also broke through into the English Channel. The largest known example of marine flooding was when the Atlantic breached the Strait of Gibraltar about 5.2 million years ago. This restored Mediterranean sea levels, which had dried up.