Palisades Sill

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.

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.

[2] 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.

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 mineralogy of the sill consists principally of plagioclase feldspar, several varieties of pyroxenes, and olivine, with minor biotite, titanite, zircon and oxides.

These studies also concluded that the sill was emplaced in a position nearly identical to its current one (10-to-15-degree dip); this is further confirmed by the still-vertical orientation of the columnar jointing.

Each of these theories supported the idea of crystal fractionation playing a significant, if not total, role in the differentiation of the sill.