* Adirondack Mountains: This region is composed of Precambrian igneous and metamorphic rocks, some of which are over a billion years old. These rocks were formed deep within the Earth's crust and were later uplifted and exposed by erosion.
* Hudson Highlands: This region also contains Precambrian metamorphic rocks, specifically the highly resistant, hard, and durable rocks known as the Hudson River Formation. These rocks, like those in the Adirondacks, are incredibly ancient.
While other regions of New York State have older rocks below the surface, the Adirondacks and Hudson Highlands are the only regions where the oldest bedrock is exposed at the surface.
