The Great Barrier Reef is the largest coral reef in the world. It lies off the Pacific coast of tropical northeastern Australia stretching 1,430 miles (2,300 km) from about Brisbane to the Torres Strait between Australia and New Guinea.
The Great Barrier Reef is a vast complex assemblage of 3,000 separate coral reefs and 900 islands linked together in a chain of living coral rock. It gets its name because it acts as a barrier between the coast and the large waves of the Pacific Ocean. The reef is several miles offshore at the edge of Australia’s continental shelf. The water between the reef and the shore is relatively shallow; beyond the reef the ocean plunges to 3,280 feet (1,000 m) or more.
The organisms that created the reef consist of about 400 different types of hard corals. These organisms have been depositing the limestone that builds up the reef for thousands of years. Coral reefs are made up of many individual animals called polyps. A coral reef forms when a polyp attaches itself to a rock underwater. The polyp then divides again and again to form a colony. Some polyps secrete calcium carbonate which protects the polyp with a limestone exoskeleton. This exoskeleton is essentially a bionic rock. Coral reefs are massive bionic rocks. They are living structures.
The Great Barrier Reef is composed of billions of coral polyps. It is the world’s biggest single structure made by living organisms. The Great Barrier Reef covers 133,000 square miles (344,400 sq km). Besides being alive itself, the Great Barrier Reef supports a diversity of life, with more than 1,500 species of fish, 30 species of whales and dolphins, 17 species of sea snakes, and at least 5,000 species of mollusks living in its waters. The reef is visited by more than 200 species of birds.
Coral reefs increase in diameter by .39 to 1.18 inches (1-3 cm) per year and grow vertically by .39 to 9.84 inches (1-25 cm) per year. There is evidence that the Great Barrier Reef may have begun to form about 600,000 years ago and that the coral structure we see today is about 20,000 years old.
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