New York City Geology
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To the right is a geologic map of New York City that is based on the map by Baskerville (see reference below). 
Click on the image to see a much larger scale Geologic Map of
New York City. NYC is primarily composed of sediments that were metamorphosed during the Taconic and Acadian orogenies roughly 500 - 400 million years ago. Garnets can be found in the rocks of the Hartland Formation and Manhattan Schist (view a NYC rock sample). It is in these hard rocks that the city skyscrapers have their foundations. During the Pleistocene epoch (the Ice Age: about 1.8 million years ago to 8,000 years ago), large ice sheets bulldozed the landscape. Rocks within the glaciers scraped and scratched the bedrock of Central Park producing long linear striations and grooves. Long Island is composed of rubble that the glacier left behind as it melted. The crust and part of the mantle of the Earth together form rigid plates called tectonic plates. Generally, earthquakes are located at the boundaries between plates where they collide, or grind past each other, or spread apart. New York City lies within the North American plate and the closest plate boundary is thousands of miles away in the middle of the Atlantic. Despite its intraplate location, the city has an unusually high number of earthquakes. However, it still has fewer earthquakes than plate boundaries and most of these tremors are quite small and cannot be felt.
For links to information about New York State geology, go to the NY geology resource page.
NYC Geology ExcursionsGeologist Sidney Horenstein leads classes, walking tours and cruises that focus on the rocks and geologic processes recorded in the NYC metropolitan area. Call (212) 769-5200 Mon-Fri 8 am to 6 pm, Sat 10 am to 6 pm for more information and to register. NYC Geology References
Links to General Geology Sites
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