New York Skyscrapers in an Ancient Sea

Submitted by Deborah Cramer

New York Skyscrapers in an Ancient Sea
Ancient seafloor exposed near the boathouse in New York’s Central Park
Photo © Betsy McCully

New York’s high skyscrapers are held up by hard bedrock, bedrock that used to be soft mud and clay lining an ancient sea. Approximately 460 million years ago, the continent that would become North America, Laurentia, rested by the Iapetus Ocean, the Atlantic’s predecessor. The Atlantic was named after Atlas; in Greek mythology, his father was the Titan Iapetus.

When Earth’s continents collided to form Pangaea (“all earth”), the Iapetus Ocean narrowed and closed. The process was violent and messy. During the Ordovician period, Iapetus seafloor was pushed deep into the earth, where it formed hard schist.

Where this rock approaches the surface, it holds up Manhattan’s towering skyscrapers. The city’s skyline drops where the rock is too deep to support really tall buildings – in Greenwich Village, for example. In some spots in Marcus Garvey and Central Park, this old seafloor is right at the surface, where you can see it, walk around it, and even sit on it. Bits of mica make it glitter.

References and more information

Manhattan schist in New York City
http://www.nycgovparks.org/parks/marcusgarveypark/highlights/12370
http://3dparks.wr.usgs.gov/nyc/parks/loc1.html
http://www.newyorkcitywalk.com/html/images_schist.html

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