We will see the Great Australian Bight from the Bunda Cliffs.
The Great Australian Bight, (Bight being a bend in the coast that forms an open bay) the largest indentation on the Australian coast, is said to be the longest line of seacliffs in the world. The white coloured rock near the base of the cliffs is known to geologists as Wilson Bluff Limestone and it was formed on the seabed between 38 and 42 million years ago.
Aboriginals have lived on its shores since time immemorial. Europeans first explored it in the nineteenth century, with whalers, sealers, farmers and government surveyors entering the region following initial surveys by Matthew Flinders and Edward Eyre.
Most Australians consider the Great Australian Bight to be the curve extending from Cape Pasley, in the west, to Cape Carnot, near Port Lincoln, a distance of 1160kms. However, according to the definition laid down by the International Hydrographic Bureau in 1953, the Bight commences in the west at West Cape Howe and stretches to South West Cape in Tasmania.
The shallow continental shelf in the Bight is very wide. In some places the shelf break, where the water is around 200 metres deep, is over 100 nautical miles (or around 190 kilometres) away from the coastline. Beyond the shelf break the seabed slopes down gradually to the abyssal plain, where the water is around 4,000 metres (4 kilometres) deep.
The seabed of the Bight is made of layers of sediment like mud and sand. Deep below the seabed the sediment has been pressed into sedimentary rocks. These sedimentary rocks can tell us about how the climate has changed in the past and how the southern edge of Sahul (the ancestor of the Australian continent) formed by rifting from Antarctica.
The Great Australian Bight is an unusual environment. The coastline is aligned with the equator, meaning that it runs mostly from east to west instead of from north to south. It is the longest ice-free coastline running in this direction in the Southern Hemisphere.
Little rain falls on the Nullarbor Plain and no major rivers flow into the Bight. Very little sediment has washed from the land onto the continental shelf. Instead the sediments on the seabed build up mainly from particles such as seashells settling out of the seawater. This has helped to protect and build up layers of sedimentary rocks that can tell us about what the climate was like in the past.
In many parts of central Australia it is possible to find springs of underground or artesian fresh water. There are probably springs of artesian water beneath the Great Australian Bight.
Like the Southern Ocean, strong winds drive across the Great Australian Bight and the sea is usually very rough. In the summer hot, dry winds blow from the deserts of central Australia over the Bunda Cliffs, which form the northern coastline of the Bight. They help evaporate more water from the sea surface, increasing the amount of salt in the surface waters. Often the winds blow from the right direction to force cold water to well up from the bottom to the surface near the Eyre Peninsula, which forms the eastern coastline of the Bight. This brings nutrients near the surface where marine plants can grow and support food chains.
The Bight is a place where different types of seawater mix. Strictly speaking it is part of the south-east Indian Ocean, but most people think of it as being part of the Southern Ocean. Strong winds affect the patterns of flow in the Bight, which are also influenced by several important currents. Near the coastline the main current is close to the surface and flows from west to east. During the winter it extends the Leeuwin Current, which wraps around south-western Australia and brings warm tropical waters from the Timor Sea to the northern part of the Bight. Sometimes tropical animals like turtles are washed into the Bight. Further offshore the main current is deeper and flows from east to west. This current is called the Flinders Current. It brings cooler waters and nutrients into the southern part of the Bight. The cool waters are channelled upwards along underwater canyons and carry nutrients onto the southern edge of the continental shelf where they encourage plants and animals to grow. In turn these plants and animals can support food chains. In addition, large eddies and gyres are common and cold surface water from the Southern Ocean mixes with the waters in the Bight.
Many large animals live in or visit the Great Australian Bight. The most famous are the southern right whale, the Australian sea lion, the great white shark, and the southern bluefin tuna.
There could not be a better family experience than seeing one of Australia's most outstanding wildlife spectacles than the winter gathering of Southern Right Whales. A cliff top platform at the Head of the Bight will give you first class views of whales in the waters beyond. Some day try to enjoy this unique experience.
There are also many kinds of seabirds, fish and marine mammals live in or visit the Great Australian Bight. Blue whales, humpback whales and sperm whales travel through the Bight. New Zealand fur seals feed in the Bight, as do dolphins and other toothed whales. Squid, octopus and cuttlefish are important food for these animals.
There are also many other species in the Bight that are important as food for humans, especially southern rock lobster, king crab, abalone, school shark, gummy shark, deepwater flathead, Bight redfish and orange roughy. Every year school and gummy sharks travel into the shallow waters at the northern end of the Bight to give birth to pups.
The seabed of the continental shelf in the Great Australian Bight is home to a wide variety of plants and animals. Many of them are found nowhere else in the world. In fact, the Great Australian Bight has some of the highest levels of marine diversity and endemism (occurring nowhere else in the world) in Australia. There are large numbers of species of red algae (sea weed), ascidians (sea squirts), bryozoans (similar to corals), molluscs (shellfish) and echinoderms (sea urchins and sea stars). Scientists find new species almost every time they set up a voyage to sample the seabed in the Bight.