" It concerns the growing body of evidence that 12,800 years ago a giant comet traveling on an orbit that took it through the inner solar system broke up into multiple fragments, and that many of these fragments, some more than a mile (2.4 kilometers) in diameter, hit the earth. It is believed that North America was the epicenter of the resulting cataclysm with several of the largest impacts on the North American ice cap causing floods and tidal waves and throwing a vast cloud of dust into the upper atmosphere that enshrouded the earth, preventing the sun’s rays from reaching the surface and thus initiating the sudden, mysterious global deep freeze that geologists call the Younger Dryas. We will go into the evidence for all this, and how it relates to “Bretz’s flood "

― Graham Hancock , Magicians of the Gods: The Forgotten Wisdom of Earth's Lost Civilization