The Newark Basin is a region in northern New Jersey defined by the boundaries of a sediment-filled rift basin. This basin was formed when the supercontinent Pangaea began to split approximately 220 million years ago, causing several large depressions to form due to extension, which then filled with sediment. The basin itself extends from Rockland County in the southern tip of New York to south-eastern Pennsylvania. It lies within the broader region known as the Piedmont, a crescent-shaped area characterized by smooth topography and large volumes of sediments. Like the Piedmont, the Newark Basin has gentle topography consisting of red bed clastic sediments with occasional igneous rock formations, such as the Palisades Sill and the Watchung basalt flows; these igneous features are responsible for the dramatic elevation changes observed in the region, such as The Palisades and the Watchung Mountains, respectively. The boundaries of the Newark Basin, as well as major highways, are shown on the map at left.