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A peninsula is a piece of land surrounded by water on three sides and joined to a larger body of land by an isthmus, or neck. A peninsula is a topographic high spot; a dry land range of hills or mountains created during the formation of the earth's crust. It is left visible when the low areas on both sides either subside and become submerged, or when the water level rises and floods the valleys. The coast of Maine and the Chesapeake Bay are excellent examples of shorelines of submergence. The Delmarva Peninsula, which forms the eastern section of the Chesapeake Bay, formed millions of years ago as the Susquehanna River eroded a river valley which was subsequently swamped when the sea level rose.

Because of their segregation from the primary body of land to which they are connected, peninsulas provide their inhabitants with relative isolation. During continental wars, peninsulas can be defended at the narrow isthmus. During peacetime, invasion by immigration tends to pass by because they lie off the main routes of travel. Thus, peninsulas can provide havens where humans and animals of ancient descent may still be found quite unadulterated. Examples are the Cornish and Welsh in peninsulas in western England; Australian aborigines of the Cape York Peninsula; and non Indo-European speaking people of the Indian peninsula.

During wars involving oceanic invasion, however, peninsulas are often targeted as the gateway to the continent. A rocky peninsula in Acadia National Park, Maine. JLM Visuals. Reproduced with permission. Two examples are the occupation of the Gallipoli Peninsula by Britain, from which they invaded Turkey during World War I, and the United States World War II entry into Europe through Italy's Calabrian Peninsula and France's Conetin Peninsula.

Because of this vulnerability, small peninsulas are often politically different from their mainland continent. For example, the Florida Peninsula for many years belonged to Spain. Conversely, large peninsulas often become independent from their continental neighbors—like the peninsulas of Sweden and Italy.

The world's largest peninsulas are Arabia (1,254,000 sq mi [2,017,686 km]); Southern India (800,000 sq mi [1,287,200 km]); Alaska (580,000 sq mi [933,220 km]); Labrador (502,000 sq mi [807,718 km]); Scandinavia (309,000 sq mi [497,181 km]); and the Iberian Peninsula (225,000 sq mi [339,525 km]).

Marie L. Thompson

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Science EncyclopediaScience & Philosophy: Pebi- to History of Philosophy - Indifferentism