St George's Channel, strait separating south-east Ireland from Wales and joining the Atlantic Ocean to the Irish Sea in the north. The Channel measures between 80 and 145 km (50 and 90 mi) from west to east, meeting Cardigan Bay west of Wales, and about 160 km (100 mi) north to south. The Channel has shallow banks and was flooded by changing water levels relatively recently, at the end of the last Ice Age.