Right now, a wall of ice nearly two miles thick is covering the land where Chicago used to be. And it has been moving across the continent for 20,000 years without ever stopping. At the peak of the ...

The Holocene began around 11,700 years ago as the Pleistocene Ice Age faded and humans moved into a warmer, more stable world. With glaciers retreating and many megafauna disappearing, early humans ...