Search results
The Great Barrier Reef is the world's largest coral reef system, [1] [2] composed of over 2,900 individual reefs [3] and 900 islands stretching for over 2,300 kilometres (1,400 mi) over an area of approximately 344,400 square kilometres (133,000 sq mi). [4] [5] The reef is located in the Coral Sea, off the coast of Queensland, Australia ...
- Overview
- Geography
Great Barrier Reef, complex of coral reefs, shoals, and islets in the Pacific Ocean off the northeastern coast of Australia that is the longest and largest reef complex in the world. The Great Barrier Reef extends in roughly a northwest-southeast direction for more than 1,250 miles (2,000 km), at an offshore distance ranging from 10 to 100 miles (1...
The reef actually consists of some 2,100 individual reefs and some 800 fringing reefs (formed around islands or bordering coastlines). Many are dry or barely awash at low tide; some have islands of coral sand, or cays; and others fringe high islands or the mainland coast. In spite of this variety, the reefs share a common origin: each has been formed, over millions of years, from the skeletons and skeletal waste of a mass of living marine organisms. The “bricks” in the reef framework are formed by the calcareous remains of the tiny creatures known as coral polyps and hydrocorals, while the “cement” that binds these remains together is formed in large part by coralline algae and bryozoans. The interstices of this framework have been filled in by vast quantities of skeletal waste produced by the pounding of the waves and the depredations of boring organisms.
European exploration of the reef began in 1770, when the British explorer Capt. James Cook ran his ship aground on it. The work of charting channels and passages through the maze of reefs, begun by Cook, continued during the 19th century. The Great Barrier Reef Expedition of 1928–29 contributed important knowledge about coral physiology and the ecology of coral reefs. A modern laboratory on Heron Island continues scientific investigations, and several studies have been undertaken in other areas.
The reef has risen on the shallow shelf fringing the Australian continent, in warm waters that have enabled the corals to flourish (they cannot exist where average temperatures fall below 70 °F [21 °C]). Borings have established that reefs were growing on the continental shelf as early as the Miocene Epoch (23.0 million to 5.3 million years ago). Subsidence of the continental shelf has proceeded, with some reversals, since the early Miocene.
Britannica Quiz
Wonders of the World Quiz
The water environment of the Great Barrier Reef is formed by the surface water layer of the southwestern Pacific Ocean. The reef waters show little seasonal variation: surface-water temperature is high, ranging from 70 to 100 °F (21 to 38 °C). The waters are generally crystal-clear, with submarine features clearly visible at depths of 100 feet (30 metres).
- The Editors of Encyclopaedia Britannica
Oct 19, 2023 · Learn about the biodiversity, threats, and conservation of the Great Barrier Reef, home to over 9,000 species of coral and algae. Find out how climate change, pollution, and pests affect the reef, and what you can do to help.
- Organ pipe coral. Tubipora musica. Size: Up to 1m across. Most soft corals have limestone spicules that provide some structural support by slightly stiffening the soft tissues.
- Flowerpot coral. Alveopora sp. Size: Polyps can grow up to 10cm long and 2cm wide. Flowerpot corals are made up of many individual polyps joined together at the base of their skeletons to form branches, columns or dome-shaped colonies.
- Smooth cauliflower coral. Stylophora pistillata. Size: Up to 30cm across. Common in shallow reef areas, particularly those that are exposed to strong wave action, although it can occur to a depth of about 15m.
- Hump coral. Porites densa. Size: Up to 15cm across. Common in shallow inner reefs, but also found less frequently on the outer reef. This small, stony coral grows in a rounded hump shape.
Learn about the Great Barrier Reef, the world's largest coral reef ecosystem with remarkable variety and beauty. Discover its outstanding universal value, superlative natural beauty, and globally significant biodiversity.
Apr 19, 2024 · Climate change is causing repeated coral bleaching and ecosystem transformation on the iconic reef, according to marine biologists. The report reveals that almost three-quarters of the reef is showing signs of bleaching and nearly 40% is showing high or extreme bleaching.
Apr 24, 2023 · Learn about corals, their types, colours, symbiotic algae and role in forming coral reefs. Find out what is coral bleaching and how it affects the Great Barrier Reef.
