Tuesday, 25 February 2014

edge, bunda cliff, sea

Bunda Cliffs stretch for 200 kilometres along the Great Australian Bight between the Head of the Bight and the border with Western Australia. Bunda Cliffs are the southern edge of the limestone slab forming the Nullarbor Plain which extends far inland. 

The light coloured base is Wilson Bluff Limestone, this is white, chalky material formed as part of an ancient seabed when Australia began to separate from Antarctica 65 million years ago. This Wilson Limestone is up to 300 metres thick but only the upper portion is visible in Bunda Cliffs. 

The Bunda Cliffs are part of a larger scarp of the Eucla Basin that spreads across the south eastern corner of Western Australia and the far western part of South Australia The Bunda cliffs is an aboriginal name which has been used in South Australia for the name of the Nullarbor coastal cliffs.

 The usage is not included in national geographic name databases - but the usage is general in South Australia The Bunda cliffs extend for around 100 km along the Great Australian Bight near its northern extremity and are close to the Nullarbor Plain in a very sparsely settled area of Australia. The cliffs, which are some 60 to 120 metres high and sheer, can be viewed from several viewing points along the Eyre Highway east of Eucla and west of Nullarbor roadhouse, although could be better appreciated from the air. 

A view of the cliffs can be had at 31°57′0″S 130°14′0″E / 31.95000°S 130.23333°E. Geologically the cliffs are of Tertiary age and are composed of fossiliferous limestone. The same formation can be seen from Eucla to Madura, where it forms a scarp separating the Roe Plain from the Hampton Tableland, but in this section the coastline has moved away from the cliffs. The scarp in this area runs parallel to, and within sight of, the Eyre Highway.
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 c
urve 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.

Above the white Wilson Limestone are whitish, grey or brown layers of limestone or crystalline rock. Some layers incorporate marine fossils including worms and molluscs indicating their marine origin; other layers are made up entirely of marine sediment (foraminifera). The cliffs are capped by a hardened layer of windblown sand laid down between 1.6 million and 100,000 year ago.
The explorer John Edward Eyre was the first European explorer to come this way, in 1841. Although he was helped by local aboriginals to find water elsewhere on his trip, there is no water behind Bunda Cliffs and shortage of fresh water was a major impediment to his party. Many plants growing along the top of the cliff are adapted for survival in the very low rainfall of this region. 

The Eyre Highway runs less than a kilometre inland from the Bunda Cliffs. Over a distance of 85 kilometres there are five main lookouts on the cliffs with signed, gravel access roads from the highway. The western lookout is most favoured because it provides a vantage point looking along the cliffs to the east. This lookout is at 31° 34' 45"S, 130° 08' 39"E. 


Post a Comment