The region has an arid to semi-arid climate with annual rainfall between 150 and 250mm, with a winter maximum. Relief is low, less than 5m, with slope angles of 1o-3o. The Nullarbor Plain has no surface drainage, but relict stream channels are found on the northern and western flanks of the plain. These have meandering traces and are infilled with alluvium and aeolian deposits.
Blowholes are very numerous, fed by deep solution pipes of complex origin.
The caves are extensive, much modified by salt wedging and collapse processes, and commonly descend gently to near-static pools and lakes of brackish to saline water. A low gradient watertable underlies the plain and its depth ranges from 30m in the north to 120m in the south. The flooded tunnels of Cocklebiddy Cave are in excess of four kilometres long - most of it only explorable by scuba diving. A particular feature of the Nullarbor caves is the abundance of halite which produces both speleothems and many weathering forms through wedging during recrystallisation. Gypsum speleothems are also abundant with calcite speleothems less obvious largely because of destruction through salt wedging.