NEW YORK’S GEOLOGY AND PLATE TECTONICS
Adapted from an article by Dr. Ed Landing

New York State has an array of geological features typical of a continent-sized land mass. Its geological heritage is particularly extensive in terms of the great age span of its rocks, the variety of geological features, and the long period of scientific research that it has received.

GEOLOGICAL SUBDIVISIONS
The ancient basement rocks exposed in the interior of continents is called the “shield”. Shields are dominated by metamorphic rocks (rocks resulting from the change of older rocks by heat, pressure, and fluids during deep burial) produced during ancient mountain building and have not been subjected to more recent mountain building. On top of the geologically stable shield are sedimentary rocks (older rock fragments or materials produced biologically, as fossil-rich limestones, or chemically, as salt deposits) that have not been folded, faulted, or metamorphosed by mountain building. These sedimentary rocks that commonly lie closer to the margins of continents are the craton.

New York State can be broadly divided into three geological regions:
1. The first is the ancient shield and overlying sedimentary rocks of the craton. The Adirondack Mountains are part of the Canadian Shield. The craton includes the sedimentary rocks that overlie the Adirondack basement and extend into Ontario, Quebec, and the Lake Champlain valley and that underlie all areas south of the Adirondacks and west of the Hudson-Wallkill River valley. The craton south of the Mohawk-Lake Ontario Lowlands lies at the north end of the Allegheny Plateau, an upland east of the Appalachians that extends to Alabama and into the Midwest.

2. Because of repeated episodes of folding and faulting by orogenic (mountain-building) processes, the craton changes east of the Wallkill-Hudson-Lake Champlain Lowlands into the Appalachian Mountain belt of easternmost New York State. This second geological region of the state features New England-type geology. In this area, Adirondack-type basement was uplifted on faults (Hudson Highlands), and deepwater, continent-martin rocks of the Taconic slate belt were pushed into New York from their original position in the Connecticut River Valley region.

3. The state’s third geological region is coastal New York. The southern end of the New England Appalachians is covered by relatively young, flat-lying coastal plain rocks deposited during the “Age of Dinosaurs,” 255-65 million years ago (mya). Similar coastal plain rocks extend south from Long Island and southeast Staten Island to Florida and along the Gulf of Mexico. Most New York State bedrock is mantled by late and postglacial sediments that rarely more than 20,000 years old. The black-dark gray colors of most of the state’s soils reflect a relatively recent origin following the northern retreat of continental ice sheets. From central Pennsylvania and further south, soils are red.

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