Off the Queensland coast the shelf broadens, its outer edge being lined by the seaward face of the Great Barrier Reef.
The Great Barrier Reef forms the prominent feature off the north-east coast of Australia; its extent from north to south is 1200 m., and it is therefore the greatest of all coral reefs.
The Great Barrier Reef of Australia can be traced more or less continuously round the Gulf of Papua and along the south-east coast to the extremity of the Louisiades.
The black coral (Antipathes abies), formerly abundant in the Persian Gulf, and for which India is the chief market, has a wide distribution and grows to a considerable height and thickness in the tropical waters of the Great Barrier Reef of Australia.
