ith the melting of ice masses and the slow emergence of the coastal shelf, rising water levels gradually flooded ancient shorelines. By about 6,000 years ago, Northumbria was breached, forming what is now Northumberland Strait, and cutting off Prince Edward Island from the mainland. This process continues today, and parts of the southern Maritimes are receding into the sea at a rate of about ten centimetres per century. This is not true for all of Atlantic Canada, however. Along the south shore of Labrador and parts of Newfoundland, the land is still rebounding and a new shoreline is emerging.