A study by an international team of researchers led by Professor Tim Barrows of the University of Wollongong has shed new light on the frequency with which large meteorites strike the Earth.
The research focused on Wolfe Creek Crater, one of the largest meteorite impact craters in Australia and the second largest on Earth from which meteorite fragments were recovered (the largest being the Meteor Crater in Arizona in the United States).
horror movie enthusiasts might recognize Wolfe Creek Crater from the 2005 film Wolf Creek .
Located in a remote part of Western Australia, on the edge of the Great Sandy Desert and about 1
The meteorite probably moved at a speed of 17 kilometers per second and hit TNT with a force of 0.54 megaton.
However, when this impact occurred, it was not known exactly.
The new study, published in The Journal Meteoritics & Planetary Science found that the effects most likely occurred about 120,000 years ago – much younger than the previous estimate of 300,000 years ago.
Space debris constantly bombards the Earth, but only the largest objects survive the journey through the atmosphere, hit the surface of the planet and leave a crater. With an exact age for the impact of the Wolfe Creek Crater, the researchers were able to calculate how often such impacts occur.
Including Wolfe Creek Crater, there are seven types of impact craters in Australia that have emerged within the last 120,000 years, says Professor Barrows. a Future Fellow at the School of Earth, Atmospheric and Life Sciences of UOW.
"Although the rate is only one big meteor striking Australia every 17,000 years, it's not that easy," he said.
"The craters are found only in the arid parts of Australia, and elsewhere craters are destroyed by geomorphic activities such as river migration or hillside mountain hibernation, Australia having an excellent conservation record with dated craters within the arid zone Extrapolate Rate for the Whole Earth.
"Considering the fact that Australia accounts for only about one percent of the surface, the rate rises to one every 180 years.
" This is a minimal estimate, as some smaller impacts during the period were likely covered by sand ice age. The number of large objects is probably 20 times that number, since stone meteorites are much more common, but not so many survive the fiery voyage through the atmosphere or effectively create craters.
"Our results give us a better idea of how common these events are."
Professor Barrows and his colleagues used two techniques to date the crater: exposure dating (the estimated length of time a rock was exposed) to the Earth's surface versus cosmic rays) and optically stimulated luminescence (which measures how long the sediment lasted) exposed to sunlight).
The researchers also created a new topographic 3D model of the crater using aerial photographs taken by Ted Brattstrom. a Hawaiian high school teacher who flew over the crater in 2007 and took pictures of him from different directions. They used this to calculate the dimensions of the crater.
"We calculate that the maximum width of the crater is 946 meters in a NE-SW direction, which reflects the direction of the impact, the average diameter is 892 meters, we predate a depth of 178 meters, and that with 120 meters of sediment, mostly sand from the desert, is filled, "said Professor Barrows.
Using the same geochronological dating techniques, the researchers were also able to recalculate the age of the meteor crater in Arizona. They found that it is probably 61,000 years old, more than 10,000 years older than previously thought.
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Timothy T. Barrows et al. The Age of Wolfe Creek Meteorite Crater (Kandimalal), Western Australia, Meteoritics & Planetary Science (2019). DOI: 10.1111 / maps.13378
New Study Unveils Secrets of Wolfe Creek Crater (2019, November 20)
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