New Jersey is a small, almost peninsular state between the Hudson and Delaware rivers and the Atlantic Ocean, covering 22,591 km² (8,723 sq mi), the fourth-smallest of the 50 states. Its geography runs in four bands from northwest to southeast: the Kittatinny ridge and valley country, where High Point reaches the state’s highest elevation of 550 m (1,803 ft); the rocky New Jersey Highlands; the Piedmont lowland of the Newark Basin, with the Palisades and Watchung Mountains; and the flat, sandy Atlantic Coastal Plain of the south, which holds the Pine Barrens and the barrier islands of the Jersey Shore. The lowest point is sea level on the Atlantic. The Delaware River forms the western border, the Hudson the northeastern one, and the 130 km (80 mi) Passaic is the longest river wholly inside the state. Despite being the most densely populated state, New Jersey is about 45% forest.
Kittatinny Mountain and the Delaware Water Gap
The far northwest of New Jersey, mostly in Sussex and Warren counties, belongs to the Ridge and Valley province of the Appalachians. Its defining landform is Kittatinny Mountain, a long, narrow ridge running northeast to southwest; the name comes from a Lenape word usually translated as "endless hill". In Pennsylvania the same ridge is called Blue Mountain. Its crest carries the Appalachian Trail, and most of it is protected in High Point State Park, Stokes State Forest, Worthington State Forest and the Delaware Water Gap National Recreation Area.
The ridge reaches its highest point, and the state’s, at High Point in Montague and Wantage townships, 550 m (1,803 ft) above sea level. A 67 m (220 ft) obelisk, the High Point Monument, was built on the summit in 1930 as a war memorial, and from it New Jersey, New York and Pennsylvania are all visible. Just to the north, the Tri-States Monument marks the state’s northernmost point where the three states meet. West of Kittatinny, the Wallpack Valley and the lower Wallpack Ridge (283 m, 928 ft) drop to the Delaware River, while to the east lies the broad lowland of the Kittatinny Valley, separating the ridge from the Highlands.
At the ridge’s southwestern end, the Delaware River cuts straight through it at the Delaware Water Gap. The gap is nearly 400 m (1,300 ft) wide at river level and about 1.6 km (1 mi) wide between the summits on either side: Mount Tammany in New Jersey, at about 470 m (1,540 ft; some sources give 465 m), and Mount Minsi in Pennsylvania. The river runs at just 88 m (290 ft) above sea level, more than 370 m (1,200 ft) below the ridge top. The quartzite of the ridge was fractured during mountain building about 400 million years ago, and the Delaware was able to cut down through those cracks. Nearby Sunfish Pond, a glacial tarn on the ridge, is the southernmost of its kind along the Appalachian Trail. The river’s full course is covered in our Delaware River guide.
The New Jersey Highlands: Lake Hopatcong and Franklin’s zinc
Southeast of the Kittatinny Valley rises a belt of rounded, forested ridges built from much older rock. The New York–New Jersey Highlands are made mostly of Precambrian igneous and metamorphic rock, and they run from the Delaware River near Musconetcong Mountain northeast along Bearfort Ridge and the Ramapo Mountains into New York, where they end at the Hudson at Storm King Mountain. They form part of the Reading Prong, a subrange of the Appalachians. The state’s greatest topographic prominence, 272 m (892 ft), belongs to Kitty Ann Mountain in Morris County, in this belt.
Most of New Jersey’s significant lakes lie here or on the ridges to the northwest, many of them enlarged by dams. The largest is Lake Hopatcong, about 10 km² (4 sq mi), on the Morris–Sussex county line; it was created by damming two ponds known as Great Pond and Little Pond, and it feeds the Musconetcong River, which runs southwest to the Delaware. Greenwood Lake, 11 km (7 mi) long, is shared with New York, the Wanaque Reservoir supplies Newark, Paterson and neighbouring towns, and Round Valley Reservoir holds 208 million m³ (55 billion US gallons) for central New Jersey. At Lake Mohawk near Sparta the Wallkill begins its 142 km (88 mi) journey north, making it the longest river that rises in New Jersey.
The Highlands also carry mineral wealth. At Franklin and at the Sterling Hill Mine in Ogdensburg, zinc ores were mined on a large scale; digging at Sterling Hill began in the 1630s, when the ore was mistaken for copper. Sterling Hill, the last working underground mine in the state, closed in 1986 and is now a museum known for fluorescent minerals. Because these hills gather water for millions of people downstream, the state passed the Highlands Water Protection and Planning Act in 2004 to limit building on them.
The Newark Basin Piedmont: Palisades, Watchungs and the Great Falls
Below the Highlands, the land drops into a lowland of red sandstone and shale, the Newark Basin, where most of North Jersey’s cities stand. It is a rift basin that opened about 220 million years ago, in the late Triassic, when Pangaea began to break apart. Most of the rifts along this coast stalled before an ocean formed, and the Newark Basin is one of those failed rifts, filled with lake and river sediment. Molten rock pushed into and over those sediments, and its hard remains now make the region’s most striking landforms.
The Palisades are the eastern edge of a diabase sill that intruded into the sandstone about 200 million years ago and cooled underground; erosion stripped away the softer rock and left a line of columned cliffs along the west bank of the Hudson. They run about 32 km (20 mi) north from Jersey City to near Nyack, New York, rising from about 90 m (300 ft) at Weehawken to 160 m (540 ft) near their northern end. The Lenape phrase for them, "rocks that look like rows of trees", gave Weehawken its name. North of Fort Lee they are protected in Palisades Interstate Park, and the state’s easternmost point, Station Rock, sits at their base in Alpine. Our Hudson River guide follows the river past them.
Further west, three long ridges of basalt lava flows, the Watchung Mountains, rise 120 to 150 m (400 to 500 ft) and run for more than 64 km (40 mi) from Somerville northeast. They long held back the spread of Newark’s suburbs. They also rerouted the Passaic River. At the end of the last ice age, a glacial moraine blocked the river’s old gap through the Watchungs near Summit, and meltwater pooled into Glacial Lake Passaic between about 19,000 and 14,000 years ago. The Great Swamp and the other Passaic Meadows are wetland remnants of that lake’s floor. Forced to find a new outlet, the river swung north and plunged over the basalt at Paterson, forming the 23 m (77 ft) Great Falls of the Passaic, whose water power drove New Jersey’s early industrial growth and is now the centrepiece of Paterson Great Falls National Historical Park.
The Piedmont ends along the fall line, where rivers drop from harder rock onto the soft sediments of the coastal plain. In New Jersey that line passes Trenton, at the old Falls of the Delaware, and New Brunswick on the Raritan, the river that drains most of central New Jersey into Raritan Bay.
The Atlantic Coastal Plain: Pine Barrens, barrier islands and Cape May
Southeast of the fall line, New Jersey is built of loose, unconsolidated sand, silt, gravel and clay, and the outer plain’s soils are sandy, acidic and dry. The only notable hill in South Jersey, Arneys Mount in Burlington County, reaches about 73 m (240 ft).
The interior of the southern coastal plain is the New Jersey Pine Barrens, a forest of pitch pine and oak on sandy, acidic, nutrient-poor soil that has always been agriculturally poor. In 1978 Congress made 1.1 million acres (4,500 km²) of it the Pinelands National Reserve, the first National Reserve in the country, and it was later named an international biosphere reserve. The sand soaks up rain into the Kirkwood–Cohansey aquifer, which holds about 64 billion m³ (17 trillion US gallons) of some of the purest water in the United States. Slow rivers drain it, the longest being the 82 km (51 mi) Mullica, which rises near Berlin and reaches the sea at Little Egg Harbor.
The outer edge of the plain is the Jersey Shore, about 227 km (141 mi) of ocean frontage from Perth Amboy to Cape May Point. Most of it is a chain of barrier islands and spits separated from the mainland by shallow bays. Sandy Hook, a barrier spit about 10 km (6 mi) long, guards the entrance to Lower New York Bay; Island Beach and the northern end of Long Beach Island enclose Barnegat Bay, about 68 km (42 mi) long; Long Beach Island itself is about 29 km (18 mi) long and just 320 m wide at Harvey Cedars; and Absecon Island carries Atlantic City. Hurricane Sandy in 2012 showed how exposed these islands are. At the southern tip, Cape May marks the state’s southernmost point, with Delaware Bay to the west. Because the state is nearly surrounded by water, the sun can be seen both rising and setting over the sea from different spots on the Shore. How these islands form and move is explained in our guide to what a barrier island is.