Stand on the gibber plains north of Eromanga and there is nothing to see. No rim, no bowl, no scar - just flat, red, unremarkable outback running to a flat horizon. Yet somewhere beneath your boots, sealed under nearly a kilometre of rock, lies one of the largest impact craters on the Australian continent. Tookoonooka is an astrobleme, a "star wound," and it is utterly hidden. Up to sixty-six kilometres across, it was punched into the earth roughly 125 million years ago and then buried so completely that humanity had no idea it existed until oil prospectors went looking for something else entirely.
Tookoonooka was not found by an explorer or a geologist tramping the surface. It was found by sound. In the 1980s, seismic surveys shot across the Eromanga Basin in the hunt for petroleum returned a strange, ring-shaped disturbance deep in the rock, and in 1989 the structure was reported in the scientific literature. Suspicion is not proof, and a buried ring could be many things. The clincher came from drill core: tiny grains of shocked quartz, their crystal structure deformed by pressures that only a hypervelocity impact or a nuclear blast can produce. Nature offered no other explanation. Something enormous had struck this spot, and the rock far below still remembered the blow.
When the meteorite fell, the Queensland outback did not exist. In its place lay the Eromanga Sea, a vast, shallow inland ocean that flooded much of the continent's interior during the Early Cretaceous. The impactor tore through that water and slammed into the seabed beneath, throwing up a curtain of debris that rained back across an astonishing expanse. Ejecta from Tookoonooka has since been identified in 31 separate wells spread over 400,000 square kilometres of the basin, a buried layer marking the moment of catastrophe across an area larger than Germany. Researchers have traced the signature of the tsunami that must have followed, churning the soft sea floor far from the point of impact.
Tookoonooka may not have come alone. About three hundred kilometres away lies another buried ring of almost exactly the same age, known as Talundilly, and many scientists suspect the two were made in a single event - a binary impact, perhaps from an asteroid that split in two before it arrived. Proving Talundilly is genuinely an impact crater would require drilling that has not yet been done, so the pairing remains a strong hypothesis rather than a settled fact. The idea is tantalising: two great wounds opened in the same shallow sea on the same terrible day, then sealed away beneath the slow accumulation of millions of years.
There is an irony buried with the crater. The very industry that discovered Tookoonooka now benefits from it: the shattered, fractured rock of the impact zone is associated with several small oil fields, the broken geology making natural traps for hydrocarbons. A cataclysm that would have annihilated everything for hundreds of kilometres has become, over deep time, a quiet asset. It is a useful reminder of how thoroughly the past can vanish. An impact powerful enough to reshape an inland sea now leaves no mark a traveller could ever find - only a ring in the seismic data and a few deformed grains of quartz, brought up from the dark a kilometre below the unremarkable plain.
The Tookoonooka structure is centred near 27.12 degrees south, 142.83 degrees east, in south-west Queensland - but there is nothing to see from the air, because the crater lies buried beneath up to 900 metres of sediment. The surface above is flat Channel Country gibber plain and floodplain, with no rim or depression marking the impact. Use it as a conceptual waypoint rather than a visual one. The nearest airfields are Quilpie (YQLP) to the north-east and Thargomindah (YTGM) to the south; Eromanga, Australia's most inland town, lies nearby to the north. Outback visibility is generally excellent, though only the imagination reveals what lies below.