This is a vast, treeless, flat, limestone plain covering 270 000 square kilometres. It is 50 m - 200 m above sea level, extending for 2000 km across the southern parts of Western Australia and South Australia, south of the Great Victoria Desert, and adjacent to the Great Australian Bight. Its name is Latin for 'no trees'. About 25 million years ago it was the bed of a large sea, but has been uplifted by earth movements. It is also Australia's largest karst (weathered limestone) terrain, containing 200 000 km2 of various features caused by dissolution and weathering of limestone. In fact, it is the world's largest single piece of limestone, covering the plain with a 15 m - 60 m limestone layer.
The Transcontinental Railway stretches across the Nullarbor from Port Augusta in South Australia to Perth in Western Australia, and includes the longest section of straight railway track in the world (478 km). The Eyre Highway passes through the its southern-most area, and includes the longest straight section of tarred highway in the world (146.6 km). The highway passes five of the most spectacular lookouts on the Australian coastline, adjacent to towering, vertical, limestone cliffs washed by the Southern Ocean. The ocean flows into subterranean caves up to several hundreds of metres from the coast, (e.g. Murrawjinie Cave), some making blow holes. There are sand dunes between the highway and the coastline.
The Nullabor Plain has an arid to semi-arid climate, with 150 mm - 250 mm annual rainfall and 1200 mm - 2500 mm annual evaporation. The karst features include many dolines (collapsed sink holes) leading to deep cave systems. One such system, Cocklebiddy Cave, 12 km north of the Highway, has about 4 km of flooded passages which require scuba equipment to explore. Many other cave systems are extensive. For example, the Old Homestead Cave contains over 30 km of surveyed passages. Some cave systems are deep enough to reach the water table and contain lakes of blue-green saline water. Weebubbie Lake is a spectacular example, at a depth of 100 m below the surface, and is over 150 m in length.
The caves contain formations of gypsum and calcite (including abundant dark-brown to black varieties coloured by organic compounds), as well as salt deposits (halite).
Copyright © Australian Museum, 2004