Piedmont

Rivers winding through natural obstacles

Jesse Fried • Jun 14, 2017


NJ's Piedmont extends from the Hudson River and Raritan Bay to about twenty miles inland in North Jersey. Moving into Central Jersey, it widens, reaching all the way to the Delaware in Hunterdon and Mercer Counties, continuing on contiguously through other states as far as Alabama). A line running southwest from New Brunswick to Trenton marks the southeastern edge.

The landscape ranges from swamps, notably the Meadowlands, to rolling hills, to scattered low-relief but rugged mountain ridges such as the Palisades, the Watchung Mountains, Cushentuck Mountain and Sourland Mountain. The bedrock is Triassic and Jurassic in age. Predominantly a sequence of sedimentary red beds ranging from sandstone to mudstone, it is interrupted by volcanic and magmatic rocks that define some of the major topographic features of the region.

Geologically, the Piedmont is a rift basin formed during the break-up of the supercontinent Pangea and the opening of the Atlantic Ocean. Its sedimentary layers, and the igneous rocks sandwiched between them, dip relatively steeply due to rift faulting. In North Jersey, the dip is to the west. The steepest slopes in the area tend to face east and run roughly north-south for long distances. This north-south trend is also observable in the river drainages and indeed patterns of urbanization. In Central Jersey, the trend becomes less clear. The author has no clear explanation for phenomena like the the clockwise spiraling of the Watchung Mountains as one proceeds southwest, or the positions of Central Jersey's volcanic mountains (maybe revealing his North Jersey bias). Throughout the region, the volcanic and magmatic structures tend to form be long, flat-topped ridges with one steeper slope.

The Passaic, Hackensack and Rahway rivers drain most of the northern Piedmont, while the basin of the mighty Raritan River encompasses most of the central Piedmont

NJ's Highlands border the region along a series of faults to the northwest, the most dramatic being the Ramapo fault, with several hundred feet of relief along the escarpment of the Ramapo Mountains in northern Bergen County. Along the region's southwest border, the silt, sand and clay layers of the Coastal Plain overlie it.




Interpretation: