Mega asteroid impact 3 bln yrs ago dwarfed dinosaur-extinction blast
Researchers have now determined the power and scale of a cataclysmic event some 3.26 billion years ago, which dwarfs dinosaur-extinction blast, and is thought to have created geological features found in a South African region known as the Barberton greenstone belt.
The huge impactor -- between 37 and 58 kilometers (23 to 36 miles) wide -- collided with the planet at 20 kilometers per second (12 miles per second). The jolt, bigger than a 10.8 magnitude earthquake, propelled seismic waves hundreds of kilometers through the Earth, breaking rocks and setting off other large earthquakes.
Tsunamis thousands of meters deep -- far bigger than recent tsunamis generated by earthquakes -- swept across the oceans that covered most of the Earth at that time.
Donald Lowe, a geologist at Stanford University and a co-author of the study, who discovered telltale rock formations in the Barberton greenstone a decade ago, thought their structure smacked of an asteroid impact.
The impact of the impactor would have turned the sky red hot, the atmosphere would have been filled with dust and the tops of oceans would have boiled, the researchers said. The impact sent vaporized rock into the atmosphere, which encircled the globe and condensed into liquid droplets before solidifying and falling to the surface, according to the researchers.
The impact may have been one of dozens of huge asteroids that scientists think hit the Earth during the tail end of the Late Heavy Bombardment period, a major period of impacts that occurred early in the Earth's history -- around 3 billion to 4 billion years ago.
The Barberton greenstone belt is an area 100 kilometers (62 miles) long and 60 kilometers (37 miles) wide that sits east of Johannesburg near the border with Swaziland. It contains some of the oldest rocks on the planet.
The research is set to be published in Geochemistry, Geophysics, Geosystems.
(Posted on 10-04-2014)