![]() ![]() ![]() High tide (left) and low tide (right) on Heron Island (picture taken from the same location in both images). At low tide the baggage and supplies could be retrieved without any chance of it getting soaked. This view from Heron Island at high tide shows the structure used to hoist baggage and supplies out of the boats at high tide while people waded ashore. People used to row across the reef before the harbor was built on Heron Island. High tide (left) and low tide (right) on Heron Island. There is a marine lab and a resort on this tiny island. Heron Island has been quite stable for a long time and has a lot of plant growth on it contributing to its stabilization. Unaware of the spectacular reef below, visitors approaching the cay, called Heron Island, are in for a treat. Each reef is unique - many are table reefs (like Wistari) but some are long, thin, ribbon reefs. Their tops were "mowed down" by waves, tides and storms so they remained just under the surface of the water but expanded in width (just as you saw Wistari Reef in the foreground of the last image). About 2,000 of these grew fast enough to keep the upper (living) part of the reef in the lighted surface waters so the symbiotic zooxanthellae, in the coral animal's tissues, could live.Īs sea level stabilized these isolated individual reefs began to grow out. As the sea covered the coastal plain on Australia's northeast coast, many of the coral heads grew upward. Gradually, the glaciers melted and sea level rose to its present height where it stabilized about 6,500 years ago. Coral larvae, in the ocean, had settled along the edge of this plain and grown into coral heads as a reef (similar to the formation of a 'classical' fringing reef). The area that is now the Great Barrier Reef was a broad, flat, coastal plain then - land, not sea. These glaciers held a lot of Earth's water so that the oceans were some 300-400 feet lower than they are today. Its history began some 15,000 years ago when Earth was experiencing an ice age and much of North America was covered with glaciers. Each of the 2,000 reefs making up the Great Barrier Reef has its own particular shape and name.Īustralia is not a true barrier reef because it is a continental island (not volcanic) and is not sinking. These reefs are typical of the Great Barrier Reef. Part of Heron Reef filled in with debris (mostly broken coral) and a cay, knows as Heron Island, formed. Wistari Reef (left) is in the foreground and Heron Reef is in the background separated by a deep channel. Most of the Great Barrier Reef is almost entirely underwater. Heron reef has a very stable cay called Heron Island (right). Wistari and Heron reefs (left) are two of the reefs that make up the Great Barrier Reef. It is actually not a true barrier reef as defined by the 'classic' coral reef formation and originally described by Charles Darwin in the 1800's. The Great Barrier Reef is not one reef but a chain of over 2,000 reefs located anywhere from 10 to 150 miles off the northeastern coast of the territory of Queensland in Australia - extending some 1,250 miles from north to south. (Both maps from the Australian Tourist Commission) ![]() The Great Barrier Reef is a chain of reefs along the coastline ranging from a few miles to over 150 miles from the shore (right). It is the largest biological structure on Earth and one of the only naturally occurring structures that can be seen by satellite.Īustralia's northeast coastline is where the Great Barrier Reef is located (shadowed in blue on the left). One of Earth's wonders - the Great Barrier Reef - is located off the northeastern side of Australia. The continent of Australia, in the southern hemisphere, is about as big as the entire United States. The Great Barrier Reef in Australia is an immense and very unique coral reef.
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