Although small, New Jersey has considerable topographic variety. In the extreme northwest corner of the state are the Appalachian Valley and the Kittatinny Ridge and Valley. This area contains High Point, the state's peak elevation, at 1,803 ft (550 m) above sea level. To the east and south is the highlands region, an area of many natural lakes and steep ridges, including the Ramapo Mountains, part of the Appalachian chain. East of the highlands is a flat area broken by the high ridges of the Watchungs and Sourlands and—most spectacularly—by the Palisades, a column of traprock rising some 500 ft (150 m) above the Hudson River. The Atlantic Coastal Plain, a flat area with swamps and sandy beaches, claims the remaining two-thirds of the state. Its most notable feature is the Pine Barrens, 760 sq mi (1,968 sq km) of pitch pines and white oaks. Sandy Hook, a peninsula more than 5 mi (8 km) long, extending northward into the Atlantic from Monmouth County, is part of the Gateway National Recreation Area.
Major rivers include the Delaware, forming the border with Pennsylvania, and the Passaic, Hackensack, and Raritan. The largest natural lake is Lake Hopatcong, about 8 mi (13 km) long. Some 550 to 600 million years ago, New Jersey's topography was the opposite of what it is now, with mountains to the east and a shallow sea to the west. Volcanic eruptions about 225 million years ago caused these eastern mountains to sink and new peaks to rise in the northwest; the lava flow formed the Watchung Mountains and the Palisades. The shoreline settled into its present shape at least 10,000 years ago.