Gypsum crystals often develop when it’s too dry for stalactites and stalagmites and water is being drawn out of rock and clay through evaporation (i.e. not dripping through).

Here gypsum crystals curl out of clay. These small mineral structures are formed from the same minerals that created the giant 12m crystals in the famous Cave of the Crystals found near Mexico’s Naica Mine.

In other parts of the Nullarbor, these crystals grow into bigger structures, but nowhere near as big as the Mexican monsters. 

These “dali-esque” shapes were formed when water dissolved parts of the rock. 

Caves shaped by water-flow are more likely to be longer on the horizontal plane, whereas passages such as those found in “dissolved” caves in the Nullarbor can be much wider than they are long.  

“Popcorn” rock formations, such as the one that can be seen on the column to the right, form when water precipitates (cools to form solid drops from evaporation) on a surface. 

Cavers explore a large collapsed dome in Old Homestead Cave in Western Australia. 

Descent 100m underground to the bottom of Old Homestead Cave in Western Australia involved a long metal ladder and a narrow man-made hole cut by early farmers looking for water. 

The first European to record crossing the Nullarbor was explorer Edward John Eyre who travelled across in 1841. Featureless for almost 2000km, he described it as “the sort of place one gets into in bad dreams”. 

Helictite-covered stalagmite. These rock formations are the result of water dripping through cracks in the limestone rock that forms the cave. The water deposits calcite as it drips, slowly forming the stalactite spike that drops from the roof. Stalagmites, which spike up from the ground, form when water drips off the end of a stalagtite onto the ground. 

Many of the Nullarbor’s cave locations are kept secret by cavers, because of their easily damaged formations. 

Cavers relaxing at Old Homestead Cave’s hut. 

“Soda straws” such as these form when water is dripping very, very slowly. They are among the most delicate cave formations. 

Columns formed at Stegamite Cave when a salactite and a stalagmite joined to form a single entity. 

A shed near the entrance of WA’s Old Homestead Cave acts as a base for cavers who visit annually. From far away it’s the only clue to the hidden world of caves underneath this flat land. 

Here a cave roof is festooned with helictites (eccentric formations). 

Ann-Marie Meredith (left) and Graham Pilkington are dedicated cavers from Western Australia and stand in a cave that show signs of wetter times. The cracked clay here in Old Homestead has probably been there for a long time. In fact, in places these cracks have continued to deepen until they are 2m deep (taller than most humans).