During the last ice age almost all of Canada, along with parts of Europe and Asia, were buried beneath one to two miles of ice. At the same time, sea levels stood 350 to 400 feet lower than today. Sea levels were so low that the entire continental shelf, at least in eastern North America, was above water. Many states on the eastern seaboard were twice as big as today. New Jersey’s shoreline, for example, stood 60 to 100 miles east of its present location. Same in the west. The land between Alaska and Asia rose out of the sea...