Sable Island is the last offshore remnant of land exposed when sea levels were much lower at the end of the last Ice Age, about 11,000 years ago. Some believe the pile of sand was pushed there by the ice - making Sable Island a terminal moraine. Sable Island survives because of the great reservoirs of sand on Sable Island Bank and the sand-binding trapping abilities of its plants, especially Marram grass.

The strongest current around Sable Island Bank flows along its outer edge. These are waters from the Labrador Current and Gulf of St. Lawrence. Some of this current branches off in a clockwise flow around the western tip (Western bank), leaving quieter waters over the bank shallows. Sand on the bank is not moved by slow, regular current. But storm-wind currents will move large amounts of sand, especially West to East. Sand is constantly replaced in the shallows around the island.

Storms waves and winds also fling sand onto the beaches of Sable Island, where strong winds carry it further onto the island. There it is trapped by plants. Some plants actually thrive on being partly smothered by nutrient rich sand.

Waves and wind can also tear up plants and return free sand to the sea.

Scientists do not agree about whether a natural balance of construction and destruction will keep the island in existance, especially with global warming and rising sea level.