What is the Manhattan prong?

The Manhattan Prong is one of two major metamorphic-igneous complexes in New England, the other being the Vermont Piedmont. It is a geologic feature in southeastern New York state, extending north-south for about 200 miles (320 km). The Manhattan Prong is also known geographically as the Lower Hudson Valley and Lower Hudson Valley Highlands, and geologically as the Manhattan Prong Belt and Manhattan Prong Terrane.