Coral cays are the islands that form on coral reefs through sedimentation, and the build up of rubble on the reef. Sandy coral cays are present on the leeward side of reefs, whereas rubble cays are formed on the inside, windward edge of the coral reef flat. It therefore is obvious that the wind and water currents play a vital role in coral cay formation. Heron Island is an example of a coral cay that has formed on an outer shelf reef, however coral cays do not always form on reefs. The adjoining reef to Heron Reef, Wistari Reef does not have any coral cay formation.
Coral cays are dynamic in that they move around, with time, as a result of wind and water motion.
It should also be noted that coral cays take a long time to form, with vegetation that colonises the island coming from either birds or floating in the water as seeds. For more information on Coral Reefs and there different components, go back to our Home page .