How did the Great Barrier come to be?

Dated back to the 1700's, it is a track of Captain Cooks first voyage. (1768-1771)

History... 

It is believed that the east coast of Australia was first sighted near the early 1520’s, by the Portuguese expedition—led likely by Cristovao de Mendonca. The earliest Europeans to sight the Great Barrrier Reef first were, the French.  On the 6^th of June 1768, Louis de Bougainville approached Australia from, Bougainville Reef (near Cooktown). The sailors confronted various different hardships including a rough surf and big shortage of food. Later Bougainville turned north toward Asia along New Guinea.

These fleeting glimpses were only beginning to become popular. In August of 1770, James Cook sailed the length of the Great Barrier Reef. On June 11^th, Cook’s party became familiar with Endeavour Reef, north of Cape Shore in what is now Cooktown.

Its Formation…

All reefs require an adequate amount of sunlight, and grow only in shallow, clean water. A reef can develop from three different substances, this includes: sand, rock and coral. The appropriate temperature that is favorable for its formation and growth is between, 18 degrees Celsius and 30 degrees Celcius.

Next there are sea animals called polyps form colonies that make the reefs. A coral polyp resembles a sea anemone. This animal has many tentacles around its mouth. Many polyps join together to form a colony. The Barrier Reef is made of many coral reefs. Each coral polyp is associated with an alga. The photosynthesis by an alga helps the polyp to make a coral skeleton. The skeletons are made of aragonite, a form of calcium carbonate. These coral skeletons form quickly, creating the foundation of coral reefs. Two coral skeletons are sealed together by calcium carbonate produced by algae. The involvement between a specific sea animal and single-celled plant forms reefs like the Great Barrier Reef. (6)