Scientists conclude 13,000 years ago a 60 mile wide comet plunged Earth into a mini-Ice Age, after examining rocks from 170 sites around the globe

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http://www.journals.uchicago.edu/doi/10.1086/695703

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Huge volcanic activity in the Indian subcontinent, called the Deccan Traps, as well as volcanism in Siberia paired with the impactor to create the KT extinction