Geography of Long Island

Long Island is in southeastern New York, United States, separated from the rest of the state by the East River and from Connecticut by Long Island Sound. Long Island contains four counties, of which the western two are boroughs (Queens and Brooklyn) of New York City, and the other two (Nassau and Suffolk) are mainly suburban.

Long Island, as part of the Outer Lands region, is formed largely of four spines of glacial moraine, with a large, sandy outwash plain northwesternward, towards its barrier islands and the Atlantic Ocean. These moraines consist of gravel and loose rock left behind during the two most recent pulses of Wisconsin glaciation some 21,000 years ago (19,000 BC). The northern moraine, which directly abuts the North Shore of Long Island at points, is known as the Harbor Hill moraine. The more southerly moraine, known as the Ronkonkoma moraine, forms the "backbone" of Long Island; it runs primarily through the very center of Long Island, roughly coinciding with the length of the Long Island Expressway.

The land to the south of this moraine to the South Shore is the outwash plain of the last glacier. Part of this, known as the Hempstead Plains, supported one of the few natural prairies to exist east of the Appalachian Mountains.

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