 The Island of Orleans is situated between the Laurentian Plateau or Canadian Shield to the north and the Appalachian Mountains to the south.Its north-eastern point marks the boundary between the St. Lawrence River and its estuary (the largest in the world), where fresh water begins to mix with salt water.The island is separated from the mainland by 2 channels; to the north-west is the Île d'Orléans Channel and to the south-east is the Grands Voiliers Channel.