The Great Lakes formed where they did 20,000 years ago thanks to a hotspot that sat under the supercontinent Pangaea 300 million years ago, before North America even existed.

NEW YORK — Scientists have identified a new pod of ancient hunter-gatherers who lived near the land bridge between North America and South America about 6,000 years ago.

“Seismic full-waveform tomography of active cratonic thinning beneath North America consistent with slab-induced dripping,” by Junlin Hua et al., Nature Geoscience, Vol. 18.