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The Menai Strait was created by glacial erosion along a line of weakness associated with the Menai Strait Fault System. During a series of Pleistocene glaciations (that lasted from about 2,580,000 to 11,700 years ago) a succession of ice-sheets moved from northeast to southwest across Anglesey and neighbouring Arfon scouring the underlying rock creating a series of linear bedrock hollows. The deepest of these channels eventually became flooded by the sea as the ice sheets receded forming the Menai Strait.