"If 13,000 years ago you had stood on the high Palisades ridge opposite Manhattan, you would have found yourself on the crest of a long, narrow island. To the north is the glacier edge, falling away toward Canada, a receding wall of ice stretching from east to west as far as the eye can see. On opposite sides of your island are broad lakes filled with frigid water that leaks away from the melting ice. The meltwater outflow is here temporarily kept from flowing out across the still-dry continental shelf to the distant sea by ridges of resistant Triassic lava and heaps of glacial rubble."
-- Chet Raymo and Maureen E. Raymo, Written in Stone