Wild sequences of color are unusual in the collection. Here they are used for specific reasons, to tell the story of the largest freshwater lake we know to have existed. It ponded up against the southern margins of its massive glacial dam, which was grounded in the shallow basins of Hudson and James Bays. Meltwater accumulated until it overtopped the passageways to the south, into the Mississippi and the St Lawrence river systems. The spill point is near the red-beige level, while the broadness of the red areas shows how steep (and constraining on ice-flow) were the approaches to these divides.