Formed by the progressive uprising of an ancient atoll, Lifou Island in the Province of the Loyalty Islands is made of massive limestone rocks (calcitic and dolomitic karsts) of coral origin. It has a large central plateau in a 8-shape which corresponds to the bottom of the ancient atoll i.e. the dried part of the lagoon. This forest-covered plateau is cut by a rocky isthmus and surrounded by a crown of cliffs, vestiges of the ancient barrier reef.