48 Australian Geographic
LMOST EXACTLY 100KM west of the
Western Australia–South Australia border,
Graham Pilkington twists and clambers
down a fissure little wider than his body
into one of the first of Old Homestead
Cave system’s large passages.
Light from his head-torch pierces the blackness
as his hands grip a wet ladder made slippery by
condensation in 90 per cent humidity, before his
boots thump to the cave floor, raising a dull echo.
This low, wide entry passage sits below the
Nullarbor Plain, the world’s largest limestone karst
landscape, which 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.
The Old Homestead Cave – one of Australia’s
longest cave systems yet discovered – comprises about
34km of known tunnels and chambers across four
levels. These are filled with stalactites and stalagmites,
smooth flowstone and occasional curling tendrils of
gypsum crystals that grow out from the walls.
Some of the other equally impressive Nullarbor
cave systems are protected within the 28,730sq.km
Nullarbor National Park and Regional Reserve.
Another 9000sq.km falls within the Nullarbor
Wilderness Protection Area.
Karst topographies such as this are created when
water seeps through large expanses of soluble rocks,
such as limestone or dolomite, riddling them with
sinkholes and caves, like holes in Swiss cheese. Drip-
ping with stalactites, the chamber Graham is exploring
is beautiful but also packed with information. “We
think of the shape of the cave itself as nice to look at,but every shape also shows you the history of the cave,”
he says. A life member of the Cave Exploration Group
of SA, Graham is the expert on the Old Homestead
Cave. It’s been his passion to map this remote cavern
almost every year for more than three decades.
Exploring the caves that riddle Nullarbor has been
a lifelong obsession for a select group of cavers and
cave-divers. Among them are Andrew Wight, the AG
Society’s 1989 Spirit of Adventure awardee, who was
killed in a helicopter crash in 2012; and Ron Allum,
creator of the Deepsea Challenger submarine that in
2012 took Hollywood director James Cameron to the
bottom of the Mariana Trench. Indeed, James helped
produce Sanctum in 2011, a suspense-thriller based on
the true story of 15 cavers, including Andrew, who
became trapped in a Nullarbor cave in 1988 after the
entrance collapsed (AG 19).
All this limestone began to form more than
50 million years ago when the continent broke away
from Antarctica and the sea flooded into the subse-
quent gap. The calcium carbonate shells of tiny sea
creatures accumulated on the ocean floor, eventually
forming into a chalky layer of limestone. More recently,
the sea retreated and the southern part of Australia
tilted, lifting up the 100m-high sea cliffs that line the
southern coast of the Nullarbor today.
Ian Lewis, a karst geomorphologist based in
Adelaide, describes the Nullarbor as one of very few
places in the world where the limestone retains its
original shape – a vast, flat disk, hardly touched by the
grinding, breaking and buckling pressures generated
as tectonic plates collided.
“The southern end of Australia is geologically
peaceful,” he says. “That ancient sea floor has been
relatively untouched for millions of years.” If it had
been in the north of the continent, it would have been
scrunched up into mountains in New Guinea, or
pushed under the ocean floor, he adds.
There is a great variety of cave types under the
Nullarbor, but the plain’s most interesting features are
long, deep systems (such the Old Homestead Cave),Permits are required to access many of
the hundreds of subterranean caves that
dot the vast karst system of the Nullarbor
Plain, which covers 1100km of Australia’s
southern coast. Some caves are open to
the public, but only to those with extensive
caving experience. Permits are available for
the caves in each state from the WA Dept of
Parks and Wildlife and the SA Department of
Environment, Water and Natural Resources.A
Nullarbor Caves