The Pinelands is located in the Atlantic Outer Coastal Plain, a geological formation characterized by gently rolling terrain and sandy soils. Underlying much of the Pinelands is the Cohansey Aquifer. This formation of unconsolidated sand and gravel functions as a vast reservoir estimated to contain over 17 trillion gallons of some of the purest water in the country. The water in this shallow aquifer frequently lies at or near the surface, producing bogs, marshes, and swamps. The streams of the Pinelands are fed by this aquifer, and are characteristically acidic and nutrient poor. Natural organic contents leaching out of the soils are responsible for the dark tea color of the region's streams.