Nullarbor is the light tan semi-circular area near the coastline, 2002 Murrawijinie cave system seen from inside. It is a karst system, formed by water running through the limestone. Murrawijinie means "bloody hands": the caves were used by indigenous people who left their ochre hand stencils on the cave walls
Nullarbor Plain (Latin: nullus, "no", and arbor, "tree") is an area of flat, dry land in southern Australia on the coastline of the Great Australian Bight.
It is the world's largest single piece of limestone, and occupies an area of about 200,000 square kilometres (77,000sqmi). At its widest point, it stretches about 1,100 kilometres (684mi) from east to west between South Australia (SA) and Western Australia (WA).
As to what causes these huge and distinctive limestone areas, no-one knows. Perhaps it is significant that one of the best-known area, the Yukatan, was in or near a hit by a huge meteorite. As much as 50% of the world's hydrocarbon reserves are in carbonate rock, and much of this is in porous karst systems.
↑Ford, Derek 2007. Jovan Cvijić and the founding of karst geomorphology. Environmental Geology. 51 (5): 675–684.
Further reading
Bolam, Anthony Gladstone, 1893–1966. The trans-Australian wonderland Melbourne: Modern Printing, (many editions in the early 20th century)
Edmonds, Jack 1976. Nullarbor crossing: with panorama photographs by Brian Gordon. Perth. West Australian Newspapers, Periodicals Division. ISBN0-909699-09-7