So discovery channel had this show on what really killed the dinosaurs. They started with the normal single impact iridium conventional theory. Then they brought up new findings that suggest it was not one, but two impacts that wiped out the dinosaurs.
Apparently two scientists found 8 meters below the iridium layer tiny rocks that were melted by the first impact commonly thought to have wiped out the dinosaurs, came back to Earth and settled. Then a layer of mud which would have taken thousands of years to form. Then a layer of sand, then another layer of mud which shows colonization by worms, then sand then the sandstone and iridium and molten rocks.
It would seem to incidate the yunctan impact wiped out most species, but the 2nd impact 300,000 or so years later finished off the dinos.
This of course shows that science can change and adapt.
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