A swamp is a wetland that features permanent inundation of large areas of land by shallow bodies of water, generally with a substantial number of hummocks, or dry-land protrusions. Swamps usually are regarded as including a large amount of woody vegetation. When a wetland area does not, it is usually termed a marsh.
Swamps are generally characterized by very slow-moving waters, often rich in tannins from decaying vegetation. They are usually associated with adjacent rivers or lakes. In some cases, rivers become swamps for a distance. Swamps are features of areas with very low topographic relief, although they may be surrounded by mountains.
The most famous swamps in the United States are the Okefenokee Swamp (home to the cartoon characters of Pogo, by Walt Kelly) and the Great Dismal Swamp. The Okefenokee is located in extreme southeastern Georgia and extends slightly into northeastern Florida. The Great Dismal Swamp lies in extreme southeastern Virginia and extreme northeastern North Carolina. Both are National Wildlife Refuges. Another swamp area, Reelfoot Lake of extreme western Tennessee, was created by the New Madrid earthquake of 1812. Caddo Lake, the Great Dismal and Reelfoot are swamps that are centered around around large lakes. Swamps are often called bayous in the southeastern United States.
Swamps are characterized by rich biodiversity and specialized organisms. For instance, southeastern U.S. swamps, such as those mentioned above, feature trees such as the Bald cypress and Water tupelo, which are adapted to growing in standing water, and animals such as the American alligator.
A common species name in biological nomenclature is the Latin palustris, meaning "of the swamp". Examples of this are Quercus palustris (pin oak) and Thelypteris palustris (marsh fern).