Last updated December 4, 2019 at 5:46 pm
Researchers reveal that the Wolfe Creek Crater – the second largest crater on Earth – may be 180,000 years younger than we thought.
Why This Matters: Rewriting the history of Australia one impact at a time.
Situated on the edge of the Great Sandy Desert is the second largest crater on Earth in which meteorite fragments have been found, the Wolfe Creek Crater.
Perhaps best known for its appearance in the two Wolf Creek films and the TV show, Wolfe Creek crater is one of the best preserved craters in the world, measuring 880 metres across.
Known as Kandimalal by the local Djaru Aboriginal people, it was likely formed by a meteor about 15 metres in diameter, weighing around 14,000 tonnes.
However the age of the impact wasn’t really understood. Some unpublished data suggested the impact could have occurred around 300,000 years ago.
Piecing together the real age of Wolfe Creek Crater
In the study, published in the journal Meteoritics & Planetary Science, researchers from the University of Portsmouth, Australia and the USA calculated the new age of Wolfe Creek Crater using two geochronological dating techniques.
First, the researchers collected samples from around the crater rim and applied exposure dating, which estimates the length of time that a rock has been exposed at the Earth’s surface to cosmic radiation.
They were also able to determine the age through optically stimulated luminescence, (a dating technique used to measure how long ago sediment was last exposed to sunlight) on sand buried after the impact.
“The crater is located in a fortuitous situation where we can use two different techniques to determine its age,” says Portsmouth’s Tim Barrows, who led the research.
“The impact of the meteorite tilted and overturned the rock, exposing rock that was previously shielded from cosmic radiation. The newly formed crater also deflected the local wind field and created a new set of sand dunes.”
“Results from the two dating techniques mutually support each other within the same age range.”
The researchers were able to produce a new topographic survey of the crater using aerial photos by Ted Brattstrom, a school teacher from Hawaii. He flew over the crater in a light aircraft in 2007 and took pictures of the crater from all directions.
The resulting 3D model was used to create a digital elevation model of the crater. The researchers calculate that the maximum width of the crater is 946 metres in a NE-SW direction, reflecting the direction of the impact. The average diameter is 892 metres.
They also predict a crater depth of 178 metres and that it is filled by about 120 metres of sediment, mostly sand blown in from the desert.
Wolfe Creek Crater reveals how often crater-producing events occur
Wolfe Creek Crater is one of seven sets of impact craters in Australia dating to within the last 120,000 years. From this, the researchers were able to calculate as to how often these crater-producing events occur.
“Although the rate is only one large meteor hitting Australia every 17,000 years, it isn’t that simple. The craters are only found in the arid parts of Australia,” says Barrows.
In other parts of the world, craters are often destroyed by geomorphic activity – like river migration or slope processes in mountains.
However, due to Australia’s “excellent preservation record” with dated craters, Barrows says researchers can estimate a rate for the Earth as a whole.
“Taking into account that arid Australia is only about one percent of the surface, the rate increases to one hitting the Earth every 180 years or so. There have been two big objects hitting the atmosphere in the last century — Tunguska in 1908 and Chelyabinsk in 2013.
“This is a minimum estimate because some smaller impacts were probably covered by sand during the last ice age,” Barrows says.
“The number of large objects the atmosphere is probably 20 times this number because stony meteorites are far more common but not as many survive the fiery journey through the atmosphere or effectively make craters.”
Barrows also adds that these results can give researchers a better idea of how frequently these events occur.
Using the same geochronological dating techniques, the researchers were also able to recalculate the age of Meteor Crater. They found it is likely to be 61,000 years old, over 10,000 years older than previously thought.
The Indigenous story of Kandimalal
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Kandimalal is referred to in several stories, and is prominent in knowledge, art and song by the Djaru people.
One Dreamtime story, which is presented on signage in the area, tells the story of two rainbow snakes crossing the desert. These snakes formed Wolfe Creek and the nearby Sturt Creek. One of the snakes emerged from the ground, creating Kandimalal.
Another story, told by Djaru Elder Jack Jugarie to astronomer John Goldsmith involves a star crashing to the ground. The story had been passed down through generations – long before contact with Europeans.
One day, the crescent moon and the evening star, named “warda”, passed very close to each other. Warda became hot and fell to the ground. When it struck the Earth is caused an enormous explosion, flash, dust cloud and noise, shaking the country for long distances around.
This giant impact frightened the people and a long time passed before they ventured near the crater to see what had happened. When they did, they realised it was the place where the star had fallen to the Earth.
The story very closely resembles a modern scientific explanation for a large meteorite impact.