The Palisades Sill is a Triassic, 200 Ma diabase intrusion. It extends through portions of New York and New Jersey. It is most noteworthy for The Palisades, the cliffs that rise steeply above the western bank of the Hudson River. The ideal location and accessibility of the sill, as well as its unique features, have generated much attention from nature enthusiasts, rock climbers, and geologists alike. Location The outcrop of the Palisades Sill is quite recognizable for its prominent cliffs above the Hudson River; it is easily seen from the western portions of Manhattan. The exposure is approximately long, most of it following the Hudson River. It first emerges in Staten Island in New York City. The sill then crosses the state line into New Jersey, where Jersey City, Union City, Fort Lee, and Englewood Cliffs all lie on it. The sill eventually crosses back into New York, following the Hudson River north until reaching Haverstraw. It is at this point that the sill makes a turn to the west, where it disappears near Pomona. At this turn, the sill cuts across local strata, making it a dike in that area, not a sill. It has been proposed that the sill reemerges in two locations in Pennsylvania (where the outcrops are also discordant with local strata), but this idea is not generally agreed upon, and discussion of the Palisades Sill is usually limited to the exposure in New York and New Jersey. A portion of the sill is also home to the Palisades Interstate Parkway, a stretch of road that passes through the park area preserved by John D. Rockefeller to protect its natural beauty. Geology The end of the Triassic Period saw large-scale rifting during the break-up of Pangaea. What is now eastern North America began to separate from what is now north-western Africa, creating the young Atlantic Ocean. Magma was generated through decompression melting, and a portion of it was intruded into the sandstones and arkoses of the Stockton Formation within the Newark Basin, one of the Eastern North America Rift Basins. The magma would eventually solidify and, after millions of years, the overlying rocks would be uplifted and eroded, exposing the Palisades Sill as we know it today. The composition of the sill is that of diabase, although its mineral assemblage is not uniform throughout the thickness of the body. The mineralogy of the sill consists principally