clipped from: news.bbc.co.uk   
Ice Age blast 'ravaged America'
Artist's impression of a comet strike, BBC
A space rock may have exploded in the air over North America
A controversial new idea suggests that a large space rock exploded over North America 13,000 years ago.
The blast may have wiped out one of America's first Stone Age cultures as well as the continent's big mammals such as the mammoth and the mastodon.
The blast, from a comet or asteroid, caused a major bout of climatic cooling which may also have affected human cultures emerging in Europe and Asia.

Scientists will outline their evidence this week at a meeting in Mexico.

Their impact theory shouldn't be dismissed; it deserves further investigation
Jeff Severinghaus, Scripps Institution of Oceanography
The evidence comes from layers of sediment at more than 20 sites across North America.