by Brooks Hays
Acton, Australia (UPI) May 16, 2016
Researchers in Australia recently found a collection of spherules, evidence of a massive asteroid that struck Earth as it was still forming.
Spherules are tiny glass beads formed from material vaporized in the intense heat of an asteroid impact. They were found in northwestern Australia by a team of geologists led by Andrew Glikson of the Australian National University.
The glass beads were found scattered among ancient ocean sediments dated to the middle of the Archean Eon -- 3.46 billion years ago. The spread of the spherules deposit suggests the impact would have left a crater between 12 and 18 miles in diameter.
Taken together, researchers believe their findings reveal the second oldest known impact and one of the largest in Earth's history.
"The impact would have triggered earthquakes orders of magnitude greater than terrestrial earthquakes, it would have caused huge tsunamis and would have made cliffs crumble," Glikson, a researcher with the ANU Planetary Institute, explained in a news release. "Material from the impact would have spread worldwide."
The impact corresponds with a time period when the moon was known to have been pelted by asteroids. The scars of the barrage can still be seen today in the lunar mare.
"Exactly where this asteroid struck the earth remains a mystery," Glikson said. "Any craters from this time on Earth's surface have been obliterated by volcanic activity and tectonic movements."
Glikson has spent the last two decades searching for ancient impacts. So far, he's found 17. But he's not done. Glikson believes there are likely hundreds -- their ancient signatures waiting to be unearthed.
"Asteroid strikes this big result in major tectonic shifts and extensive magma flows," Glikson said. "They could have significantly affected the way the Earth evolved."
Glikson and his colleagues recalled their latest discovery this week in the journal Precambrian Research.
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