Every 18 years, the coastlines of France and England experience a rare phenomenon called a supertide. On Saturday, the supertide made its appearance and enveloped tidal island Mont Saint-Michel with over 40 feet of water, cutting the medieval abby off from land and flooding its paved causeway. The supertide is caused by a solar eclipse during a full-moon phase.
The waters around the UNESCO world heritage site rose quickly from low tide, reaching a height comparable to a four-story building and drawing thousands of visitors. The next supertide is predicted to occur in March 2033. Other areas of the world that experience the extreme shifts in tides are Canada’s Bay of Fundy, the Bristol Channel in Britain, Australia’s northern coast, and Tierra del Fuego in South America — but none of these locations boast the ancient fortifications of Mont Saint-Michel that date back to the 11th century.