Near the end of the last ice age, 12,800 years ago (10800 BC), a giant comet that had entered the solar system from deep space thousands of years earlier broke into multiple fragments.
Some of these struck the Earth, causing a global cataclysm on a scale unseen since the extinction of the dinosaurs.
At least eight of the fragments hit the North American ice cap while further fragments hit the Northern European ice cap.
The impacts, from comet fragments a mile wide approaching at more than 60,000 miles an hour, generated huge amounts of heat that instantly liquidized millions of square kilometers of ice, destabilizing the Earth's crust and causing the global deluge that is remembered in myths all around the world.