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. 

    Photo Credit: Alan Pryke

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

    Photo Credit: Alan Pryke

    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.  

    Photo Credit: Alan Pryke

    “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. 

    Photo Credit: Alan Pryke

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

    Photo Credit: Alan Pryke

    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. 

    Photo Credit: Alan Pryke

    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”. 

    Photo Credit: Alan Pryke

    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. 

    Photo Credit: Alan Pryke

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

    Photo Credit: Alan Pryke

    Cavers relaxing at Old Homestead Cave’s hut. 

    Photo Credit: Alan Pryke

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

    Photo Credit: Alan Pryke

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

     

    Photo Credit: Alan Pryke

    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. 

    Photo Credit: Alan Pryke

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

    Photo Credit: Alan Pryke

    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). 

    Photo Credit: Alan Pryke

Nullarbor Caves: Australia’s hidden world

By AG STAFF | November 23, 2015

The ­Nullarbor Plain, the world’s largest limestone karst landscape, is tens of millions of years old. The Nullarbor – a dry, flat, 200,000sq.km savannah – stretches 1100km along the southern coast of Australia from Balladonia east of Norseman, WA, to north of Yalata in SA. Above ground it is famously featureless. Edward John Eyre, the first European to cross the Nullarbor in 1840–1841, described it as the “sort of place one gets into in bad dreams”. But beneath the surface is a complex world of tunnels within a vast slab of limestone. Much of southern Australia is also riddled with smaller blocks of limestone. Find the full story in the Jan/Feb issue (#130) of Australian Geographic.