The crater, 400 kilometers in diameter, was formed between 300 and 600 million years ago, and though it presence on the planet’s surface has been obliterated by geological processes, the effect it had on the Earth’s crust is still very much visible. The two domes were formed when the Earth’s crust buckled under the impact, and pushed rock up from the mantle, which lies below the crust.
The impact zone is in fact the result of two asteroids slamming into the Earth, caused by a massive space rock splitting in two just before impact. In contrast, the asteroid that killed off the dinosaurs 66 million years ago was a bit of a juvenile. The Chicxulub crater it left under the Yucatán Peninsula in Mexico is about 180 kilometers in diameter, caused by an asteroid about 10 kilometers in diameter.
The newly discovered impact zone was caused by two asteroids, each about 10 kilometers wide. The impact zone is embedded 30 kilometers in the crust, and was discovered when a geothermal research project in 2013, drilled out rock that had been turned to glass, a sign of ancient impact. A research team led by Andrew Glikson, of the Australian National University, investigated the zone, and based on magnetic modeling of the crust, realized that there were bulges throughout the region, which were bruises left by the powerful impact.
“There are two huge, deep domes in the crust, formed by the Earth’s crust rebounding after the huge impacts, and bringing up rock from the mantle below,” Glikson said. The research was published in the journal Tectonophysics this month.
There is still a lot of mystery surrounding the impact though. When the Chicxulub asteroid struck, a plume of ash blanketed the atmosphere and settled on the land and sea throughout the globe, a layer visible in sediments even today. But nothing of the sort has been found in connection with the present impact crater. “It’s a mystery – we can’t find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” said Glikson. “Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought,” he added.
