The greatest impact on Earth

No, it’s not the one that made the dinosaurs extinct. There was another major event in the past. Tracks appear in southern New South Wales. It could have been the epicenter of the greatest impact on Earth. This is the structure of Deniliquin. It is up to 520 kilometers in diameter.

It thus exceeds the size of the Vredefort impact structure in South Africa. It is 300 km wide, considered until now the largest in the world. The history of the bombardment of Earth by asteroids is largely hidden. This is due to several reasons. The first is erosion. Gravity, wind, and water slowly wear away Earth’s materials over time.

The Deniliquin structure could be the largest impact on Earth.
The Deniliquin structure could be the largest impact on Earth.

The greatest of all

New geophysical discoveries are unearthing signs of impact structures formed by asteroids. They are pioneering discoveries of impact ‘ejecta’, which are materials thrown out of a crater during an impact. The oldest layers of these ejecta could mean the end of the Late Heavy Bombardment of Earth. The planets of the Solar System were subjected to intense bombardment by asteroids until about 3.2 billion years ago.

When a large asteroid hits Earth, the rebound produces a central dome. This may be the only thing preserved of the original impact structure. Famous examples are the Vredefort impact structure and the 170 km wide Chicxulub crater (Mexico). The latter represents the impact that caused the extinction of the dinosaurs.

Beneath the Murray Basin in New South Wales, there is evidence of a larger impact. There is a 520 km diameter structure with a seismically defined dome at its center. It has all the features you would expect from a large-scale impact structure.

The impact caused a mass extinction.
The impact caused a mass extinction.

Excavating the crater

To prove the impact, scientists will have to gather physical evidence of the crash. They must make deep holes in the structure. The greatest impact on Earth could trigger what is called the Hirnatian glaciation stage. This enormous glaciation and mass extinction eliminated about 85% of the planet’s species. It was more than double the impact of Chicxulub, which wiped out the dinosaurs.

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