Van Cortlandt Park

The characteristic sketch of Van Cortlandt Park—steep ridges, smooth hillsides, and open flats—was carved by glaciers. The most recent ice age began about 1.5 million years ago, at the advent of the Pleistocene Era, and lasted until around 10,000 years ago. At the beginning of the Pleistocene, global temperatures dropped dramatically. Huge masses of snow and ice formed in the Arctic, sometimes as thick as two miles. The tremendous weight and pressure of the ice sheet caused the snow underneath to solidify, providing a surface on which glaciers could travel. During the Pleistocene Epoch, there were four glacial advances, the most recent being the Wisconsin ice sheet, which had the greatest impact on the land beneath New York City.

The Wisconsin ice sheet began its southward journey from the Arctic around 100,000 years ago, reaching what is now New York roughly 50,000 years later. By this time, it had lost some of its bulk, although it was still 300 feet thick and stretched from Massachusetts to Montana. As the glacier moved through this region, it deepened the bed of the Hudson River, carved out such geologic features as the Great Lakes and the Finger Lakes basins, and left its mark on the valleys of the Adirondack mountains. The glacier also deposited tons of gravel and pebbles, moving boulders from the Palisades to Central Park, plowing up topsoil, and leveling the earth, filling in depressed areas with glacial till, and creating the dramatically varied landscape we see today.