History: Central Park In The Early 1900s, Manhattan, New York City, United States

Geology
There are four different types of bedrock in Manhattan, two are exposed in various outcroppings in Central Park, Manhattan schist and Hartland schist (both are metamorphosed sedimentary rock); Fordham gneiss, an older deeper layer which does not surface in the park and Inwood marble (metamorphosed limestone) which overlays the gneiss are the others.
Fordham gneiss, which consists of metamorphosed igneous rocks, was formed a billion years ago, during what is known as the Grenville orogeny that occurred during the creation of an ancient super-continent. It is the oldest rock in the Canadian Shield, the most ancient part of the North American tectonic plate.