central Alberta to Niagara

print size: 86 in x 101 in, 218 cm x 257 cm

file size: 1723MB, 36311 x 31094

number of images:

center location: N 48.5, W 90.1

approximate scale: 1 to 763,000

ground cell: 54.00 m, long side: 1958 km

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.