When people first think of the country continent of Australia, they may immediately think of koala bears, kangaroos, and perhaps surfing. However, one of this countries greatest gifts to the world is the Great Barrier Reef. Located off the Northeastern coast of Australia, and bordering the Coral Sea that is part of the Pacific Ocean (Encarta). Not only is this reef arguably the most beautiful in the world, but is also the largest. The formation of any reef structure is a slow, and time-consuming process, and the Great Barrier Reef is no exception.
All coral reefs are made up of calcium-based corals. The corals found in the Great Barrier Reef may not all be reef builders, but are essential to the structure and survival of the reef. When reef-building corals come together, they form a deposit of calcium carbonate (limestone). This limestone eventually becomes the formation of the reef, and through time, sand and other sea particles fill in the gaps in the coral and form what is known as "live rock". This live rock is essential for the growth of a reef because of the calcium it contains. Over time, either other reef building "stony corals", or soft corals containing multicolored polyps begin to grow on the live rock. Eventually the rock becomes covered with corals and becomes a reef. .
The Great Barrier Reef is not a typical reef however, because it is a barrier reef. Barrier reefs run parallel to a coastline, and are always spaced by a shallow cove that separates the reef from the immediate coastline. Barrier reefs tend to serve the same purpose as a barrier beach. They protect the mainland from the harsh waves and ocean .
currents. This reef, although it is a barrier reef, is also broken down into many other subgroups. The northern most portion of the reef is considered a Ribbon Reef, which is a narrow wall of coral on the continental shelf. This is a key element of the reef because the wall is not continuous, with some of the holes being large enough for ships to pass through.