On June 11, 1770, Captain James Cook ran his ship aground on a coral reef off the coast of Queensland, Australia. The reef was one of thousands of coral reefs that extended in a broken chain – more than 1,250 miles in length – along the northeastern Australian coast. Cook had discovered the Great Barrier Reef, the largest group of coral reefs in the world and the largest structure ever formed from living creatures.

Known for its vibrant beauty, the Great Barrier Reef lies offshore at distances ranging from 10 miles to more than 100 miles. A shallow lagoon, itself containing reefs and islands, connects the Great Barrier Reef with the Australian shore. The entire complex, encompassing 80,000 square miles, attracts scientific interest with its diverse geological features, birds, animals, and sea life. The area also draws vacationers, and some of its small islands have been developed into tourist havens.

The Great Barrier Reef owes its origin to marine organisms called “polyps,” each the approximate size of a pencil eraser. Over the course of millions of years, their hardened skeletal remains have formed the coral reefs. Today, billions of living polyps are attached to the Great Barrier Reef, combining with other sea creatures to provide the Reef with a variety of vivid colors.

PostScript: The Great Barrier Reef has faced a series of threats, from the crown-of-thorns starfish, which eats living polyps, to petroleum companies. Controls have been placed on drilling in the area, and collecting its coral has been made illegal.