A Map of the Mile-Thick Ice Sheet That Made Modern Manhattan

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Think this polar vortex part deux is bad? Here's a little perspective, courtesy the wonderful PTAK Science Books: A map of the glacier that once covered New York City in thick ice some 20,000 odd years ago, carving out the landscape we know today.


It was called the Laurentide ice sheet, and it was part of the last glacial period in North America—the Wisconsin stage, which was one of three periods that carved out our continent in long, slow movements. Stretching across the Northern Hemisphere, the glacier shaped everything from the Great Lakes to the Niagara River, creating the famous falls.

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The Labrador Ice Sheet was a section of the Laurentide sheet. Image via.

It stretched down through New York, too, forming the city we know today, from Long Island—created by moraines and outwash from the glacier—to the archipelago of greater New York City, created by rising tides as the ice sheet melted. Even Central Park is littered with boulders left over from its movement. And see that dark line that cuts across Brooklyn? That's the where the march of the Laurentide came to a halt—leaving a ridge above the untouched southern flatlands that divides the borough today.

We still name our neighborhoods for this ancient ice event: Flatbush, for example, marks the point where the ice stopped and began to retreat, leaving low-lying neighborhoods like Canarsie and the outwash beaches, like Coney Island.

Amazingly, the Laurentide ice sheet still exists: You can visit its last remaining chunk, the Barnes Ice Cap, on Baffin Island. [PTAK]




"Maps of the ancient sea kings" (ISBN 978-0932813428) touches on this. Amongst other things, it discusses extremely old maps that show ice sheets covering most of the UK, the land bridge from England to France (where the Channel is now) and the ice sheet across what is now north america. The maps were produced in the 16th century but it's unclear how the mapmakers knew where the ice was 20,000 years ago. The same maps also show the coastline of Antarctica with rivers flowing - evidence of which has only just recently been re-discovered under the ice sheet down there. Bloody good book - raises some interesting questions.