I mentioned on Coast to Coast AM with George Noory that many scientists now believe the Great Lakes were created in ten years around 13,000 years ago. You asked how that was possible. There's now a lot of evidence that an asteroid or comet exploded above--or perhaps partially on--the Laurentide Ice Sheet near where the Great Lakes now reside. This exploding extraterrestrial object would have generated enough heat to eventually eradicate much of that glacier, and its icemelt would have filled the Great Lakes in a shockingly short time period. This extraterrestrial explosion is known as "the Younger Dryas Extraterrestrial Impact Event" or sometimes "the Clovis Comet". Its impact markers are composed in part of n-type nanodiamonds, magnetized grains and microspherules, glassy carbon and polycyclic hydrocarbons. Many of these impact markers are found near or even at the bottom of the Great Lakes.