Geologists from Evolution Mining, Australia's third largest mining company, have announced the discovery of a 5 km wide crater beneath the desert close to the town of Ora Banda in Western Australia. The structure, which is not visible at the surface, was discovered during geophysical surveys using gravity and electromagnetic surveying, methods that detect buried structures by measuring variations in density. The structure is thought to be an impact crater not just because of its circular structure, which can be caused in other ways, but due to the presence of a shatter cone beneath, a distinctive pattern of damage to underlying strata associated with impact craters and nuclear test sites.
The structure is thought to be about 100 million years old (Early Cretaceous), as no impact related features are found in overlying layers younger than this. A crater about 5 km wide is likely to have been caused by an object about 200 m in diameter. Such an impact would probably have caused climatic disturbances that lasted several years.
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