Evidence of huge impact event found in Australia: What did it mean for life on earth?

Australian scientists announced they have discovered a twin asteroid impact crater in the Central Australia that may be the largest ever found. The question is, does it correspond to a major extinction event. Maybe, but it’s not clear yet as the age is questionable.

World’s largest asteroid impacts found in central Australia | ANU.

A 400 kilometre-wide impact zone from a huge meteorite that broke in two moments before it slammed into the Earth has been found in Central Australia.

The crater from the impact millions of years ago has long disappeared. But a team of geophysicists has found the twin scars of the impacts – the largest impact zone ever found on Earth – hidden deep in the earth’s crust.

Lead researcher Dr Andrew Glikson from the ANU School of Archaeology and Anthropology said the impact zone was discovered during drilling as part of geothermal research, in an area near the borders of South Australia, Queensland and the Northern Territory.

“The two asteroids must each have been over 10 kilometres across – it would have been curtains for many life species on the planet at the time,” said Dr Glikson, who is also affiliated with the ANU Planetary Science Institute.

asteroid_7The age of the rocks disturbed by the asteroid (which appears to have split into two before impacting) is 300-600 million years old. Therefore, the impact occurred at least 300 million years ago. But no widespread sediment layer resulting from the impact has been correlated to this event. The researchers think that the impact may be slightly older than 300 million years.

There are 5 recognized major extinction events in Earth’s history. The most popularly known is the K-Pg (Cretaceous-Paleogene [formerly known as the K-T boundary]) event that took out the non-avian dinosaurs, pterosaurs, and marine reptiles making way for the radiation of mammals and birds. That events is thought to be related to the Chicxulub impact crater in Mexico dated 65 million years ago.

Before the dinosaurs, the end Permian extinction is recognized as the largest in Earth’s history with 75% to 96% of all species on earth eliminated at that time. That event would not correspond to this new Australian find since it is 252 million years ago – still too young. It is not clear what triggered this mass extinction.

Two other extinction event in earth’s history remain causally unclear: end Ordovician about 443.7 mya and Late Devonian sometime before 358 mya. Both extinctions severely affected marine invertebrates (the major large life forms at the time).

Current thinking is that there were multiple causes for the Ordovician extinction due to climate, glaciation, sea level changes, volcanism, and plate tectonics. The same thinking goes for the late Devonian extinction which also is more complicated than just a single catastrophic event. Most extinctions seem to be pulsed events over millions of years possibly a result of feedback mechanisms from one cause creating another. Showing cause and effect is difficult. But large impacts must certainly have had some effect on the earth’s life forms. See this comprehensive piece for more.

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Extinction events across earth’s history are complex events possibly related to impacts and volcanism as well as climate. This chart shows the diameter of known impact craters along with major volcanism events correlated to extinction intensity. The new Australian crater is NOT on this chart. From G. Keller Australian Journal of Earth Sciences (2005) 52, (725 – 757)

 

This latest find from the Warburton Basin in Australia is extremely interested and will certainly serve to spark increasing exploration of the effects from such an event. Hopefully, that may give us better answers about the relationship between impacts and extinction events.

  4 comments for “Evidence of huge impact event found in Australia: What did it mean for life on earth?

  1. fredthechemist
    March 24, 2015 at 10:50 AM

    While I understand that it is difficult to estimate the “extinction intensity” (plot A) some error bars on these values would be very helpful in judging the significance of the correlations.

  2. Angela
    March 24, 2015 at 11:49 AM

    I have a break coming up in a few days and I am going to enjoy looking deeper into the added links. Fascinating stuff. *side note–I really wish I had paid closer attention to things in school that I am interested in now. I’m often playing catch-up. A point I try to bring home to my children as often as possible.

  3. Ronald H. Pine
    March 24, 2015 at 1:27 PM

    Has anyone seen a map of Australia, with the outlines of these former huge craters drawn on it? I’ve had a special interest in Australian impact craters ever since I visited the Gosse’s Bluff impact site. There I saw really impressive shatter cone structures.

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